MODELING AND MANUFACTURING METHOD FOR REVERSIBLE PLOW POINT WITH CHARACTERISTICS OF LOW RESISTANCE AND BEING STRONG INSIDE AND HARD OUTSIDE

Description

TECHNICAL FIELD

The present invention relates to a method for modeling and manufacturing a reversible plow's plow point that has low resistance and internal strength with external hardness characteristics.

BACKGROUND TECHNOLOGY

Plowing is the most fundamental operation in agricultural cultivation. The main plow body, as the core component of a high-speed reversible plow, mainly comprises plow point, plow shovel, breast plate, and grille bar. Among them, the plow point mainly functions in breaking soil, and it is prone to wear and fracture failure during service due to long-term exposure to high-speed impacts and wear from soil, sand and gravel, and root blocks. In addition, due to the mismatch between the surface parameters and operating speed of the existing reversible plow components, the running resistance of the plow body increases, which further accelerates the wear process of the plow point and increases the energy consumption of the tractor. Therefore, designing and developing a flip plow point that combines low operating resistance, high strength and toughness, and high wear resistance has become one urgent task to accelerate the high-quality development of the flip plow industry.

In order to solve the above problems, the existing reversible plow mainly adopts the traditional optimization method of plow body surface parameters to reduce the running resistance of the plow body, and welds a hard alloy layer on the local area of the plow point to protect the plow point material. Among them, the parameter optimization of plow body surface generally adopts empirical design method, semi empirical design method (geometric formation line diagram method and analytical method), and plow body surface design method based on plowing process.

Although these methods can effectively perform qualitative and quantitative analysis of the local motion process of plow body surface, they ignore soil parameters and the interaction parameters between soil and plow body; which has a significant negative impact on the analysis of plow body operating resistance. advanced simulation calculation methods must be relied on to make the calculation results closer to reality and the design methods more effective. In order to solve the problem of insufficient wear resistance of plow point materials, the production of reversible plows generally adopts technologies such as plasma cladding, plasma welding, and argon arc cladding, to weld high hardness composite coatings such as Fe based, Ni based, and Fe Ni based high hardness composite coatings on the tip of the plow's plow point. However, limited by the structural design of the reversible plow point, if only the method of welding hard alloy layers is used to enhance its wear resistance, it is only applicable to a small area of the plow point tip, which will result in rapid wear of the parts of the plow point that have not been welded with hard alloy layers in high-speed service environments, making it difficult to meet the overall high wear resistance and high service life requirements of the plow point.

On the other hand, in recent years, with the continuous acceleration of the plow body's operating speed and the rapid development of new energy tractors, it has become an inevitable trend to reduce the plow body's resistance and energy consumption while maintaining the quality of high-speed reversible plowing. The main plow body, as the core component of the high-speed reversible plow, includes the plow point, plow shovel, breast plate and grille bars. Among them, the grille bar components play the role of turning over the soil, and often break and fail due to the high-speed impact of soil and stones. Therefore, the reversible plow grille bars in high-speed service environments not only require good surface parameter design to obtain lower running resistance, but also must meet high-strength and toughness matching performance to resist the impact of soil and stones.

So far, the horizontal straight line design method for the plow body surface is the most widely used method. The principle of the horizontal straight line method to form the plow body surface is to use a three-dimensional coordinate system, with the straight line moving along the directrix (trajectory line or guiding line), and always parallel to the XOY coordinate plane, and constantly changing the angle (line angle) between the straight line and the ZOX coordinate plane to form a surface. However, only using the horizontal straight line method to optimize the plow body surface parameters cannot effectively describe the actual soil turning process, and it is impossible to quantitatively analyze the optimized plow body working resistance due to the lack of interaction parameters between the soil and the plow body. In addition, for the boron steel widely used in high-speed reversible plow's grille bars, the reversible plow manufacturing companies generally use quenching-tempering process to strengthen it, and a reversible plow's grille bar component composed of a lath martensite structure with a content of more than 98% can be obtained. Therefore, only by optimizing the heat treatment process parameters (such as temperature and time) the phase structure composition of the boron steel used for the grille bars cannot be changed, and the improvement of the tensile strength, toughness and wear resistance of the grille bars is very limited. Therefore, the traditional horizontal straight line design method and heat treatment process parameter improvement method are obviously difficult to meet the requirements of low running resistance and high service performance (specifically high tensile strength, high toughness and high wear resistance) of the existing reversible plow under high-speed service environment.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention provides a modeling and manufacturing method for a reversible plow point with low resistance and strong inside and hard outside. This method changes the performance enhancement method of the traditional plow point and comprehensively adopts the plow point surface parameter optimization method, plow point material composition improvement method and manufacturing process improvement method.

First, the present invention determines the parameters of the plowshare angle λ₀, plow face angle ε, the angle between soil trace and plowshare edge η, and soil lifting angle θ with the lowest working resistance by combining mathematical modeling, 3D software modeling, and discrete element simulation analysis methods. Compared with the traditional plow body surface optimization method, the introduction of 3D modeling and discrete element simulation analysis methods fully considers more factors affecting the plow body operation process, which can greatly improve the feasibility of the optimization results.

Second, the present invention introduces appropriate amounts of Nb, V and Ni elements into the composition design of the existing 34MnCrB5 steel for the tip of the reversible plow, thereby obtaining a new type of 34MnCrB5-M steel with fine grains and uniform structure. The composite addition of Nb and V elements can refine the grains, improve the strength and toughness of the steel, reduce overheating sensitivity, and improve thermal stability. The Ni element can effectively reduce the ductile-to-brittle transition temperature of the 34MnCrB5-M steel and improve the service stability of the plow point components under low temperature conditions.

On this basis, the present invention improves the manufacturing process of the novel 34MnCrB5-M plow point, and the hardness and wear resistance of the surface layer are significantly improved by newly introduced carburizing process (die forging-annealing-machining-carburizing-quenching-tempering-shot peening-spraying plastics), and meanwhile, the core part still maintains new 34MnCrB5-M plow point with good strength and toughness matching. It is well known that increasing the content of C in steel is a high cost performance method for improving the hardness thereof. However, increasing the C content in the steel may also cause the toughness of the steel to be significantly reduced after heat treatment, which will cause the plow point to be easily broken due to sand impact during operation. In the present invention, this problem is effectively avoided by using a carburizing process, including obtaining a high-hardness and high-wear-resistance carburized layer with a thickness of about 2.5 mm on the surface of the novel 34MnCrB5-M plow point by using a carburizing process, while the core material still keeps the component of the substrate unchanged, so as to ensure that the plow point substrate has good strength and toughness matching performance to resist the impact of gravel.

In summary, the method of the present invention effectively ensures that the novel 34MnCrB5-M plow point can withstand high-speed impact of soil and stones and is not prone to failure, and can also achieve the purpose of reducing energy consumption by reducing the running resistance of the plow body. The technical method used in the present invention also has the characteristics of high feasibility, easy popularization and low cost, and is expected to be widely applied in the fields of agricultural machinery manufacturing, mining machinery manufacturing and the like.

According to another aspect of the present invention, there is provided a modeling and manufacturing method of a high-speed reversible plow's grille bar which can improve mechanical properties and reduce resistance.

First, according to the present invention, the optimal curved surface parameters of the low resistance grille bar are determined by means of horizontal straight line design, UG modeling and ANSYS simulation analysis. Compared with a traditional grille bar curved surface optimization method, the method comprehensively considers factors such as soil parameters, grille bar material parameters and contact relationships between a plow body and soil through UG modeling and ANSYS simulation analysis, and greatly improves the working efficiency of the plow body curved surface optimization process and the feasibility of the optimization scheme. On this basis, in the present invention, a proper amount of Al, Nb and Cu elements are added on the basis of the component design of the 28MnB5 steel for the existing reversible plow's grille bars, and the novel 28MnB5-M steel with fine grains and uniform distribution is obtained by smelting by using a vacuum induction melting furnace. In the novel 28MnB 5-M steel, the Al element may generate highly finely divided ultra-microscopic oxide particles dispersed in the steel to prevent grain growth. The Nb element can generate highly dispersed strong carbide NbC, which can further prevent grain growth. The Cu element not only can improve the harden ability of the steel by enhancing the stability of the austenite, but also can improve the corrosion resistance of the steel. The above-mentioned alloying idea effectively improves the defects of coarse grains and uneven distribution of the original 28MnB5 steel, and provides a high-quality raw material supply for the subsequent manufacturing of the high-strength reversible plow's grille bar. In addition, the present invention adds a thermoforming and normalizing process (machining-thermoforming- normalizing-quenching-tempering-shot peening-spraying plastics) to the grille bar member prepared on the basis of the low-resistance grille bar modeling scheme and the high-quality 28MnB5-M steel. The thermal forming is a process of synchronously using the stamping die to form the grille bar blank heated to the austenitizing state, so that the micro-crack defect of the large deformation part of the grille bar blank during cold machining can be effectively avoided, the workload of the press in the forming process of the grid strip blank can be greatly reduced, and the energy saving is better facilitated. In addition, the normalizing process may uniformly distribute the chemical elements in the 28MnB5-M steel to reduce component segregation, so as to further refine the structure of the 28MnB5-M steel and reduce the content of the strip-shaped tissue in the steel, so as to achieve good strength and toughness matching and high wear resistance of the reversible plow's grille bar component. The above technical method effectively realizes the manufacturing of the novel high-speed reversible plow's grille bar with low running resistance, high yield strength, high tensile strength, high toughness and high wear resistance, and is more beneficial to achieving the purpose of reducing the energy consumption of the tractor. The technical method used in the present invention is high in feasibility, easy to popularize and low in cost, and is expected to be widely applied in the field of agricultural machinery manufacturing.

Therefore, according to an aspect of the present invention, there is provided a method for manufacturing grille bars of a high-speed reversible plow that combines low resistance and internal strength with external hardness, characterized by comprising:

Step XE): preparing novel 28MnB5-M steel, including:

• • Step XE1): adding Nb with a mass fraction of 0.05%˜0.11% and Al with a mass fraction of 0.04%˜0.10% as shown in Table 1 to form the composition of 28MnB5-M steel. Use a vacuum induction furnace to melt the alloy, cast it into a 200 kg ingot, and forge it into a 500 mm×1000 mm×50 mm hot-rolled billet; The units in Table 5 are mass fraction %,

TABLE 5
28MnB5-M steel composition

Name	C	Si	Mn	Cr	Nb	Al	Cu	Ti	B
28MnB5-M	0.29	0.24	1.22	0.21	0.05~0.11	0.04~0.10	0.10~0.20	0.041	0.003

• • Step XE2): heating the hot rolled billet to 1100° C.˜1200° C., holding time 1.8 h˜2.0 h, after leaving the furnace for 3 passes rolling, with the final rolling temperature being 880° C.˜920° C., the thickness of the plate after rolling being 12 mm;
  • Step XE3): water-cooling the final rolled hot rolled sheet to a set coiling temperature of 500° C.˜600° C., and then putting into the heating furnace for holding temperature for 28 min˜30 min, then cooling with the furnace;

Step XF): performing grille bar machining, including:

• • Step XF1): cutting the 28MnB5-M hot rolled sheet from step XE3 into grille bars using an oxy-acetylene cutting method;
  • Step XF2): using a milling machine to finish the profile of the grille bars,
  • Step XF3): machining countersunk square holes in grille bar blanks using a drilling machine,

Step XG): performing hot forming-normalizing-quenching-tempering treatment of the grille bars, including:

• • Step XG1): heating the grille bars to 940° C.˜960° C. and keeping temperature for 1.0 h˜1.2 h;
  • Step XG2): at the end of the holding period, transferring the grille bar blanks into a stamping die to form it into a three-dimensional solid grille bar, which is placed in the air to cool to room temperature at the end of the molding process;
  • Step XG3): heating the grille bars again to 900° C.˜920° C., keeping temperature for 0.5 h˜0.7 h and then quenching to room temperature by immersion in water;
  • Step XG4): further transferring the quenched grille bars to a tempering furnace at a temperature of 180° C.˜200° C. for 2.0 h˜2.4 h, removing the grille bars from the furnace and air-cooling the grille bars.

The parameters of the grille bars of said three-dimensional entity are determined by the following steps:

Step XA): optimizing the grille bar curved surface using the horizontal rectilinear design method, including obtaining the key parameters of the reversible plow's grille bar curved surface based on the following equations (13)-(15):

l = C 1 ⁢ b ⁡ ( cos ⁢ Δ ⁢ ε - sin ⁢ ε ) , ( 13 ) h = l ⁡ ( cos ⁢ ε + sin ⁢ ε cos ⁢ Δ ⁢ ε - sin ⁢ ε ) , ( 14 ) ω = π 2 + ε - Δε , ( 15 )

wherein:

• • the width of the plow body b is taken as 640 mm˜700 mm,
  • the range of the plow shovel mounting angle ε is 20° to 30°,
  • the guide curve buckling angle Δ₂₄₉ takes values between 5° and 11°,
  • C₁ is a constant, taking a value between 1.0 and 1.8,
  • the value of the guide curve opening l determined by equations (1)-(3) is 308 mm˜458 mm,
  • the value of the guide curve height h is 550 mm˜870 mm, and the value of the tangent angle ω at the endpoint is 105°˜109°;

Step XB): using UG software to build a 3D model of the plow body, including:

• • XB1) selecting the reference plane to sketch the spar line and the guide curve, respectively;
  • XB2) combining the grille bar curved surface parameters from step XA and drawing horizontal straight meta-lines according to the meta-line number in Equation (16) and its corresponding meta-line angle calculation formula;
  • XB3) drawing the front view of the plow body curve, and projecting the front view of the plow body curve to get a closed space curve;
  • XB4) using the cut command to cut out the surface of the plow body, then using the stretch command to change the surface of the plow body into a 3D solid shape, and exporting the .stl model file;

θ n = ⁢ { θ 0 - 1 3 ⁢ n ⁡ ( θ 0 - θ m ) ( n = 0 , 1 , 2 , 3 ) θ m + ( θ max - θ min ) ⁢ 100 + [ Δ z ( n max - n min ) ] 2 [ Δ z ( n max - n min ) ] 2 × [ Δ z ( n max - n min ) ] 2 100 + [ Δ z ( n max - n min ) ] 2 ⁢ ( n = 4 , 5 , 6 ⁢ … ⁢ 15 ) , ( 16 )

wherein:

• • n is the meta-line number; θ is the meta-line angle; θ_m and θ_n are the meta-line angles when the meta-line number is m and n, respectively; θ₀ is the initial meta-line angle, which is generally taken to be 36°˜45°; θ_max and θ_min are the maximum meta-line angle and the minimum meta-line angle, respectively; and Δz is the distance between meta-lines.

According to a further aspect of the present invention, the above method of manufacturing a high-speed reversible plow grille bar further comprises:

Step XC): performing ANSYS simulation pre-preparation comprising:

• • setting the soil properties as: the soil density as 1.76˜1.78×10³ kg/m3, the elastic modulus as 4.3˜4.5×10⁷ Pa, the Poisson's ratio as 0.33˜0.35, the yield stress as 8.3˜8.5×10⁵ Pa, the tangent modulus as 1.0˜1.2×10⁶ Pa, the failure strain as 0.6˜0.8, and the strain rate as 4%˜6%;
  • setting the material properties of the reversible plow grille bars as: the density as 7.79˜7.81×10⁻⁶ kg/mm³, the elastic modulus as 2.2˜2.4×10⁵ N/mm², the Poisson's ratio as 0.2˜0.4;
  • setting the contact method between the plow body surface and the earthwork to automatic contact with face-to-face erosion;

Step XD): performing simulations, including:

• • importing the .stl model file in step XB into the ANSYS simulation environment built in step XC, and setting the running speed of the plow body parts to 0.36˜0.38 m/s, wherein the forward direction to be the X-axis positive direction;
  • entering the simulation settings and setting the time step and simulation time to a total of 10 s;

starting the simulation to obtain the average resistance values of the plow components.

According to a further aspect of the present invention, the above method of manufacturing a high-speed reversible plow grate further comprises performing after step XE3:

Step XE4): performing pickling to remove iron oxide from the surface of the hot rolled sheet.

According to a further aspect of the present invention, the above method of manufacturing a high-speed reversible plow grate further comprises performing after step XG4:

Step XG5): performing shot peening and plastic spraying to obtain high-speed reversible plow grille bar parts with low running resistance, high strength, high toughness and high wear resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flowchart of a preparation method according to an embodiment of the present invention;

FIG. 2 shows the carbon content in the thickness direction of carburized layer of a plow point component prepared according to Embodiment 1;

FIG. 3 shows a photomicrograph of a plow point component prepared according to Embodiment 1;

FIG. 4 shows a comparison of the mechanical properties of the plow point component prepared according to Embodiment 1 with an existing plow point component;

FIG. 5 shows the carbon content in the thickness direction of the carburized layer of the plow point component prepared according to Embodiment 2;

FIG. 6 shows a photomicrograph of a plow point component prepared according to Embodiment 2;

FIG. 7 shows a comparison of the mechanical properties of the plow point component prepared according to Embodiment 2 with an existing plow point component;

FIG. 8 shows the carbon content in the thickness direction of the carburized layer of the plow point component prepared according to Embodiment 3;

FIG. 9 shows a photomicrograph of a plow point component prepared according to Embodiment 3;

FIG. 10 shows a comparison of the mechanical properties of the plow point component prepared according to Embodiment 3 with an existing plow point component;

FIG. 11 shows an assembly diagram of a grille bar component according to an embodiment of the present invention;

FIG. 12 shows a micrograph of a high-speed reversible plow grille bar component prepared according to Embodiment 4 of the present invention;

FIG. 13 shows a comparison between mechanical properties of the high-speed reversible plow grille bar component prepared according to Embodiment 4 of the present invention and an existing grille bar;

FIG. 14 shows a micrograph of a high-speed reversible plow grille bar component prepared according to Embodiment 5 of the present invention;

FIG. 15 shows a comparison between mechanical properties of the high-speed reversible plow grille bar component prepared according to Embodiment 5 of the present invention and an existing grille bar;

FIG. 16 shows a micrograph of a high-speed reversible plow grille bar component prepared according to Embodiment 6 of the present invention;

FIG. 17 shows a comparison between mechanical properties of the high-speed reversible plow grille bar component prepared according to Embodiment 6 of the present invention and an existing grille bar.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention provides a modeling and manufacturing method of a reversible plow's plow point with low resistance and internal strength and external hard characteristics. First, according to the present invention, by combining a mathematical modeling-three-dimensional software modeling-discrete element simulation analysis method, a plowshare edge angle λ₀, a plowshare surface angle ε, a soil trace and plowshare edge angle η and a soil angle θ with the lowest working resistance are determined. Compared with traditional plow body curved surface optimization method, a three-dimensional modeling and discrete element simulation analysis method is introduced to fully consider more factors affecting the operation process of the plow body, so as to greatly improve the optimization effect.

Secondly, in the present invention, by introducing a proper amount of Nb, V, and Ni elements into the component design of the 34MnCrB5 steel used at the tip of the existing reversible plow, the novel 34MnCrB5-M steel with fine grains and uniform structure was obtained. The composite addition of the Nb and V elements can refine the grains, improve the strength and toughness of the steel, reduce the overheating sensitivity, and improve the thermal stability. The Ni element can effectively reduce the ductile-to-brittle transition temperature of the 34MnCrB5-M steel, and improve the service stability of the plow point component under a low-temperature condition.

On this basis, the present invention improves the manufacturing process of the novel 34MnCrB5-M plow point, so that a novel 34MnCrB5-M plow point is obtained, of which the hardness and wear resistance of the surface layer are remarkably improved by newly introducing the carburizing process (die forging-annealing-machining-carburizing-quenching-tempering-shot peening-plastic spraying) while the core part still keeps good high-toughness matching, thereby effectively ensuring that the novel 34MnCrB5-M plow point can bear high-speed impact of soil and stones and is not prone to failure, while the purpose of reducing energy consumption can be achieved by reducing the running resistance of the plow body.

A method for manufacturing a reversible plow point according to an embodiment of the present invention comprises:

• • Step 1: Determining basic parameters. As shown in Formula (1), the relationship between the plowshare edge angle λ₀ and the internal friction angle φ_t of the soil is established using parameter selection method, where the internal friction angle φ_t of the soil is usually less than 4 degrees. Thus, the value range of the plowshare angle λ₀ is usually 40-45 degrees.

π 4 - ϕ t 2 ≤ λ 0 ≤ π 4 . ( 1 )

Further, the relationship among the angle η between the soil trace and the plowshare edge and the plowshare surface angle ε and the soil lifting angle θ is established, as shown in Formula (2). Usually, for optimizing the parameters of the plow surface, in order to ensure the overall reliability of the plow surface, the angle η between the soil trace and the plowshare edge is generally set to 16-24 degrees, the plowshare surface angle ε is generally set to 30-40 degrees. Therefore, the range of soil lifting angle θ is 18-30 degrees.

tan ⁢ η = tan ⁢ θ ⁢ cos ⁢ ε ( 2 )

Step 2: Establishing three-dimensional model. According to the plowshare edge angle 20, the plowshare surface angle ε, the angle η between the soil trace and the plowshare edge and soil lifting angle θ determined in step 1, the main curve is generated using the curve construction command in the UG software, and then the overall structure is completed by trimming, connecting, smoothing, editing and the like of the curved surface, and .stl model file is exported.

Step 3: Early stage preparation of EDEM Discrete Element Simulation was performed. The plow body material properties were set as: the plow body material density was 7800 kg/m³, the shear modulus was 7.0×10¹⁰ Pa, and the Poisson's ratio was 0.3; soil properties were set as: the soil density was 2600 kg/m³, the shear modulus was 2.5×10⁷ Pa, the Poisson's ratio was 0.5, and the soil particle radius was 2 mm; setting interaction parameters between the soil particles and the plow body entry part as: the static friction coefficient between the soil particles was 0.40, the kinetic friction coefficient between the soil particles was 0.32, the coefficient of restitution between the soil particles was 0.11, the static friction coefficient between the soil particles and the plow body was 0.30, the kinetic friction coefficient between the soil particles and the plow body was 0.22, and the coefficient of restitution between the soil particles and the plow body was 0.18; and a particle factory was created to generate soil particles.

Step 4: Performing analog simulation. The .stl model file in step 2 was imported into the EDEM software, the running speed of the plow body component was set to be 3.6-3.8 m/s, and the advancing direction was the X-axis direction; entering the simulation setting, setting the time step length and the simulation time to be 10 s, and setting the cell-size to be 2.5 Rmin; and starting the simulation, and obtaining the average resistance value of the plow body component through simulation.

Step 5: Preparation of the novel 34MnCrB5-M Steel. On the basis of the component design of the existing 34MnCrB5 steel, Nb with a mass fraction of 0.1-0.3% and V element with a mass fraction of 0.1-0.3% were added, and an intermediate-frequency induction smelting furnace was used to smelt the alloy, which was casted into an ingot with a size of φ100 mm×500 mm; the ingot was heated to 920° C.-960° C., and was maintained in temperature for 1.0 h-1.2 h; after discharging the ingot, the ingot was formed into a 34MnCrB5-M rod with a size of g furnace 1380 mm after one initial rolling and two finishing rolling; the rod was cut into a plow point blank having a length of 340 mm-360 mm.

TABLE 1
Chemical Composition Comparison between New 34MnCrB5-M
Steel and Existing 33MnCrB5 Steel (Mass Fraction, %)

name	C	Si	Mn	P	S	Cr	Nb	V	Ni	Ti	B

34MnCrB5-M	0.35	0.21	1.22	0.01	0.01	0.26	0.1-0.3	0.1-0.3	0.1-0.3	0.037	0.004
34MnCrB5	0.35	0.21	1.22	0.01	0.01	0.26	—	—		0.037	0.004

Step 6: Die forging-annealing treatment of plow pointblank. The 34MnCrB5-M steel blank from step 5 was placed in a heating furnace and heated to 900° C.-950° C., and was kept in temperature for 1-2 hours before being removed from the furnace and transferred to a die forging machine, and, after die forging, was cooled to room temperature in air; the forged blank was transferred into an annealing furnace and was heated to 600° C.-650° C. and was kept in temperature for 1-2 hours, and was then cooled down to room temperature with the furnace; a hard alloy layer was built-up welded on the back of the plow point.

Step 7: Plow point machining. Based on the 3D model data of the plow point component in step 2, the plow point was precision machined using a computerized numerical control (CNC) machine according to the drawing requirements.

Step 8: Plow point carburizing-quenching-tempering treatment. The plow point in step 7 was placed into a gas carburizing furnace, the carburizing temperature was set to 910° C.-930° C., time was set to 9-10 h, and carbon potential was set to 1.0%-1.2%; after carburizing was completed, the plow point was quenched in quenching oil at a temperature of 45° C.-55° C.; after quenching, the plow point was transferred into a tempering furnace with a temperature of 180° C.-200° C. for 1.8 h to 2.0 h, and then was cooled in air to room temperature. Finally, shot peening and spraying plastics treatment were performed.

The advantages of the present invention include:

• • the invention provides a modeling and manufacturing method of a reversible plow's plow point with low resistance and internal strength and external hard characteristics, and the method changes a single performance strengthening mode of a traditional plow point, comprehensively adopts a plow point curved surface parameter optimization method, a plow point material component improvement method and a manufacturing process improvement method, and the method has the following advantages:

(1) On the basis of the traditional mathematical calculation and three-dimensional modeling combined plow surface optimization method, the present invention introduces the EDEM discrete element simulation analysis method to reasonably optimize the design parameters of the reversible plow's plow point component, fully considering the soil environment and the contact environment between the plow body and soil, effectively reducing the running resistance of the plow body, the wear of the plow point component, and the fuel consumption of the tractor.

(2) The present invention improves the composition design of 34MnCrB5 steel by composite addition of 0.1-0.3% Nb, 0.1-0.3% V, and 0.1-0.3% Ni elements in mass fraction to obtain a new type of 34MnCrB5-M steel. Nb and V, as strong carbide forming elements, mostly exist in the form of small and dispersed carbides in steel, which can effectively refine the grain size of 34MnCrB5-M steel, thereby improving the strength and toughness of the steel. Ni element can effectively reduce the ductile-to-brittle transition temperature of 34MnCrB5-M steel and improve the service stability of plow point components under low temperature conditions. At the same time, Nb, V, and Ni elements are environmentally friendly and inexpensive, making them one of the cost-effective means to improve the performance of the steel.

(3) The industrialization technology of the carburizing-quenching-tempering heat treatment process adopted in the present invention is mature, and the cost is lower than other surface strengthening technologies such as plasma spraying and surface re-melting. The plow point after carburizing-quenching-tempering treatment has the performance characteristics of “external hardness and internal toughness”, effectively ensuring that the new plow point can withstand high-speed impacts from soil and stones without easily failing. Therefore, the heat treatment process adopted in the present invention not only has a high cost-effectiveness, but also can be extended to the manufacturing field of wear-resistant parts for mining machinery, with broad application prospects.

In summary, the modeling and manufacturing method of a reversible plow's plow point provided by the present invention, which combines low resistance and strong internal and external hardness characteristics, not only effectively solves the problems of insufficient wear resistance and high resistance in the operation process of existing reversible plow points, but also has the characteristics of high cost-effectiveness and easy promotion. It has important and broad application prospects in the fields of agricultural machinery manufacturing and mineral machinery manufacturing.

In order to provide a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solution of the present invention will be described in detail with respect to embodiments, but the scope of the present invention is not limited to the following embodiments.

Embodiment 1

The operation steps include:

(1) The design and manufacturing of plow point, including:

Step 1: Establish a mathematical model. As shown in Equation 3, the relationship between the plowshare edge angle λ₀ and the internal friction angle φ_t of the soil is established using parameter selection method, where the internal friction angle φ_t of the soil is usually less than 4 degrees. Thus, the plow share edge angle λ₀ ranges 40-45 degrees; and in this embodiment, the value of the plow share edge angle λ₀ is set to 40 degrees.

π 4 - ϕ t 2 ≤ λ 0 ≤ π 4 . ( 3 )

Further, the relationship among the angle η between the soil trace and the plowshare edge and the plowshare surface angle ε and the soil lifting angle θ is established, as shown in Formula 4. Usually, for optimizing the parameters of the plow surface, in order to ensure the overall reliability of the plow surface, in the present embodiment the angle η between the soil trace and the plowshare edge is set to 16 degrees, and the plow share surface angle is set to 16 degrees, the plow surface angle ε is set to 30 degrees. Thus, the soil lifting angle θ is set to 18 degrees.

tan ⁢ η = tan ⁢ θcosε . ( 4 )

Step 2: Establishing 3-D model. According to the plowshare edge angle λ₀, the plowshare surface angle ε, the angle η between the soil trace and the plowshare edge and soil lifting angle θ determined in step 1, the main curve was generated using the curve construction command in the UG software, and then the overall structure was completed by trimming, connecting, smoothing, editing and the like of the curved surface, and .stl model file was exported.

Step 3: Early stage preparation of EDEM Discrete Element Simulation was performed. The plow body material properties were set as: the plow body material density was 7800 kg/m³, the shear modulus was 7.0×10¹⁰ Pa, and the Poisson's ratio was 0.3; soil properties were set as: the soil density was 2600 kg/m³, the shear modulus was 2.5×10⁷ Pa, the Poisson's ratio was 0.5, and the soil particle radius was 2 mm; setting interaction parameters between the soil particles and the plow body entry part as: the static friction coefficient between the soil particles was 0.40, the kinetic friction coefficient between the soil particles was 0.32, the coefficient of restitution between the soil particles was 0.11, the static friction coefficient between the soil particles and the plow body was 0.30, the kinetic friction coefficient between the soil particles and the plow body was 0.22, and the coefficient of restitution between the soil particles and the plow body was 0.18; and a particle factory was created to generate soil particles.

Step 4: Performing analog simulation. The .stl model file in step 2 was imported into the EDEM software, the running speed of the plow body component was set to be 3.6 m/s, and the advancing direction was the X-axis direction; entering the simulation setting, setting the time step length and the simulation time to be 10 s, and setting the cell-size to be 2.5 Rmin; the simulation was started, and the average resistance value of the plow body component was obtained through simulation as 5.63 kN.

Step 5: Preparing the novel 34MnCrB5-M Steel. On the basis of the component design of the existing 34MnCrB5 steel, Nb with a mass fraction of 0.1%, V element with a mass fraction of 0.1%, and Ni element with a mass fraction of 0.1% were added, and an intermediate-frequency induction smelting furnace was used to smelt the alloy, which was cast into an ingot with a size of resent invention will be described in detail mineral machinery manufacturing. The operation process of existing the ingot, the ingot was formed into a 34MnCrB5-M rod with a size of φ 60 mm×1380 mm after one initial rolling and two finishing rolling; the rod was cut into a plow point blank having a length of 340 mm.

TABLE 2
Chemical Composition Comparison between New 34MnCrB5-M
Steel and Existing 33MnCrB5 Steel (Mass Fraction, %)

Name	C	Si	Mn	P	S	Cr	Nb	V	Ni	Ti	B

34MnCrB5-M	0.35	0.21	1.22	0.01	0.01	0.26	0.1	0.1	0.1	0.037	0.004
34MnCrB5	0.35	0.21	1.22	0.01	0.01	0.26	—	—		0.037	0.004

Step 6: Die forging-annealing treatment of plow pointblank. The 34MnCrB5-M steel blank from step 5 was placed in a heating furnace and heated to 900° C., and was kept in temperature for 1 hour before being removed from the furnace and transferred to a die forging machine, and, after die forging, was cooled to room temperature in air; the forged blank was transferred into an annealing furnace and was heated to 600° C and was kept in temperature for 1 hour, and was then cooled down to room temperature with the furnace; a hard alloy layer was built-up welded on the back of the plow point.

Step 7: Plow point machining. Based on the 3D model data of the plow point component in step 2, the plow point was precision machined using a computerized numerical control (CNC) machine according to the drawing requirements.

Step 8: Plow point carburizing-quenching-tempering treatment. The plow point in step 7 was placed into a gas carburizing furnace, the carburizing temperature was set to 910° C., time was set to 9.0 h, and carbon potential was set to 1.0%; after carburizing was completed, the plow point was quenched in quenching oil at a temperature of 45° C.; after quenching, the plow point was transferred into a tempering furnace with a temperature of 180° C. for 1.8 h and then was cooled in air to room temperature. Finally, shot peening and spraying plastics treatment were performed.

(2) Alloy Testing

The variation of carbon content along the thickness direction in the carburized layer of the new 33MnCrB5-M plow point was tested using a SPECTRO direct reading spectrometer, and the test results are shown in FIG. 2. It can be seen that the carbon content of the new 33MnCrB5-M plow point carburized layer in this embodiment first decreases and then tends to remain unchanged with the increase of distance from the surface layer. The maximum carbon content near the surface layer is 0.70 wt. %, and the carbon content at the core is 0.34 wt. %.

The microstructure of the surface layer of the novel 33MnCrB5-M plow point was observed using FEI Nova Nano450 field emission scanning electron microscope and Leica optical microscope, as shown in FIG. 3. It can be seen that the surface layer of the 33MnCrB5-M plow point is composed of acicular martensite+residual austenite+carbides. The acicular martensite is small in size and evenly distributed, with an average length of about 5.4 μm.

The comparison of mechanical performance parameters between the new 33MnCrB5-M plow point of this embodiment and the existing plow point is shown in FIG. 4. It can be seen that the yield strength of the new 33MnCrB5-M plow point is 1347 MPa, and the tensile strength is 1814MPa; the surface hardness of the new 33MnCrB5-M plow point material is 59.7 HRC. Thanks to the high hardness of the plow point surface material, the surface wear of the new 33MnCrB5-M plow point is 0.8 mg; the impact energy absorption of the new 33MnCrB5-M plow point core material is 57.3 J, indicating that the core of the new 33MnCrB5-M plow point has achieved high toughness. In addition, compared with existing plow points, the new 33MnCrB5-M plow point of this embodiment not only significantly improves yield strength, tensile strength, hardness, wear resistance, and toughness, but also reduces operational resistance during operation.

Through the above tests and characterizations, it can be found that the new 33MnCrB5-M plow point of this embodiment maintains good strength and toughness matching of the core while also possessing high hardness and wear resistance on its surface. In addition, the new 33MnCrB5-M plow point with optimized surface design parameters also has low resistance characteristics and is expected to have important applications in agricultural machinery and advanced industry.

Embodiment 2

The operation steps include:
(1) The design and manufacturing of plow point, including:

• • Step 1: Establish a mathematical model. As shown in Equation 5, the relationship between the plowshare edge angle λ and the internal friction angle φ_t of the soil is established using parameter selection method, where the internal friction angle φ_t of the soil is usually less than 4 degrees. So the edge angle λ₀ ranges from 40 to 45 degrees, and in this embodiment, the value of the plowshare edge angle λ₀ is set to 42.5°.

π 4 - ϕ t 2 ≤ λ 0 ≤ π 4 . ( 5 )

Further, the relationship among the angle η between the soil trace and the plowshare edge and the plowshare surface angle ε and the soil lifting angle θ is established, as shown in Formula 6. For optimizing the parameters of the plow surface, in order to ensure the overall reliability of the plow surface, in the present embodiment the angle η between the soil trace and the plowshare edge is set to 20 degrees, the plowshare surface angle ε is generally set to 35°.

Therefore, the soil lifting angle θ is 24°.

tan ⁢ η = tan ⁢ θcosε . ( 6 )

Step 2: Establishing 3-D model. According to the plowshare edge angle λ₀, the plowshare surface angle ε, the angle η between the soil trace and the plowshare edge and soil lifting angle θ determined in step 1, the main curve was generated using the curve construction command in the UG software, and then the overall structure was completed by trimming, connecting, smoothing, editing and the like of the curved surface, and .stl model file was exported.

Step 3: Early stage preparation of EDEM Discrete Element Simulation was performed. The plow body material properties were set as: the plow body material density was 7800 kg/m³, the shear modulus was 7.0×10¹⁰ Pa, and the Poisson's ratio is 0.3; soil properties were set as: the soil density was 2600 kg/m³, the shear modulus was 2.5×10⁷ Pa, the Poisson's ratio was 0.5, and the soil particle radius was 2 mm; setting interaction parameters between the soil particles and the plow body entry part as: the static friction coefficient between the soil particles was 0.40, the kinetic friction coefficient between the soil particles was 0.32, the coefficient of restitution between the soil particles was 0.11, the static friction coefficient between the soil particles and the plow body was 0.30, the kinetic friction coefficient between the soil particles and the plow body was 0.22, and the coefficient of restitution between the soil particles and the plow body was 0.18; and a particle factory was created to generate soil particles.

Step 4: Performing analog simulation. The .stl model file in step 2 was imported into the EDEM software, the running speed of the plow body component was set to be 3.7 m/s, and the advancing direction was the X-axis direction; entering the simulation setting, setting the time step length and the simulation time to be 10 s, and setting the cell-size to be 2.5 Rmin; the simulation was started, and the average resistance value of the plow body component was obtained through simulation as 5.03 kN.

Step 5: Preparing the novel 34MnCrB5-M Steel. On the basis of the component design of the existing 34MnCrB5 steel, Nb with a mass fraction of 0.2%, V element with a mass fraction of 0.2%, and Ni element with a mass fraction of 0.2% were added, and an intermediate-frequency induction smelting furnace was used to smelt the alloy, which was casted into an ingot with a size of φ100 mm×500 mm; and the ingot was heated to 940° C., and was maintained in temperature for 1.1 h; after discharging the ingot, the ingot was formed into a 34MnCrB5-M rod with a size of φ60 mm×1380 mm after one initial rolling and two finishing rolling, the rod was cut into a plow point blank having a length of 350 mm.

TABLE 3
Chemical Composition Comparison between New 34MnCrB5-M
Steel and Existing 33MnCrB5 Steel (Mass Fraction, %)

Name	C	Si	Mn	P	S	Cr	Nb	V	Ni	Ti	B

34MnCrB5-M	0.35	0.21	1.22	0.01	0.01	0.26	0.2	0.2	0.2	0.037	0.004
34MnCrB5	0.35	0.21	1.22	0.01	0.01	0.26	—	—		0.037	0.004

Step 6: Die forging-annealing treatment of plow pointblank. The 34MnCrB5-M steel blank from step 5 was placed in a heating furnace and heated to 925° C., and was kept in temperature for 1.5 hour before being removed from the furnace and transferred to a die forging machine, and, after die forging, was cooled to room temperature in air; the forged blank was transferred into an annealing furnace and was heated to 625° C. and was kept in temperature for 1.5 hour, and was then cooled down to room temperature with the furnace; a hard alloy layer was built-up welded on the back of the plow point.

Step 7: Plow point machining. Based on the 3D model data of the plow point component in step 2, the plow point was precision machined using a CNC machine according to the drawing requirements.

Step 8: Plow point carburizing-quenching-tempering treatment. The plow point in step 7 was placed into a gas carburizing furnace, the carburizing temperature was set to 920°° C., time was set to 9.5 h, and carbon potential was set to 1.1%; after carburizing was completed, the plow point was quenched in quenching oil at a temperature of 50° C.; after quenching, the plow point was transferred into a tempering furnace with a temperature of 190°° C. for 1.9 h and then was cooled in air to room temperature. Finally, shot peening and spraying plastics treatment were performed.

(2) Alloy Testing

The variation of carbon content along the thickness direction in the carburized layer of the new 33MnCrB5-M plow point was tested using a SPECTRO direct reading spectrometer, and the test results are shown in FIG. 5. It can be seen that the carbon content of the new 33MnCrB5-M plow point carburized layer in this embodiment first decreases and then tends to remain unchanged with the increase of distance from the surface layer. The maximum carbon content near the surface layer is 0.73 wt. %, and the carbon content at the core is 0.34 wt. %.

The microstructure of the surface layer of the novel 33MnCrB5-M plow point was observed using FEI Nova Nano450 field emission scanning electron microscope and Leica optical microscope, as shown in FIG. 6. It can be seen that the surface layer of the 33MnCrB5-M plow point is composed of acicular martensite+residual austenite+carbides. The acicular martensite is small in size and evenly distributed, with an average length of about 5.0 μm.

The comparison of mechanical performance parameters between the new 33MnCrB5-M plow point of this embodiment and the existing plow point is shown in FIG. 7. It can be seen that the yield strength of the new 33MnCrB5-M plow point is 1393 MPa, and the tensile strength is 1871 MPa; the surface hardness of the new 33MnCrB5-M plow point material is 60.2 HRC. Thanks to the high hardness of the plow point surface material, the surface wear of the new 33MnCrB5-M plow point is 0.7 mg; the impact energy absorption of the new 33MnCrB5-M plow point core material is 58.2 J, indicating that the core of the new 33MnCrB5-M plow point has achieved high toughness. In addition, compared with existing plow points, the new 33MnCrB5-M plow point of this embodiment not only significantly improves yield strength, tensile strength, hardness, wear resistance, and toughness, but also reduces operational resistance during operation.

Through the above tests and characterizations, it can be found that the new 33MnCrB5-M plow point of this embodiment maintains good strength and toughness matching of the core while also possessing high hardness and wear resistance on its surface. In addition, the new 33MnCrB5-M plow point with optimized surface design parameters also has low resistance characteristics and is expected to have important applications in agricultural machinery and advanced industry.

Embodiment 3

The operation steps include:

(1) The design and manufacturing of plow point, including:

• • Step 1: Establish a mathematical model. As shown in Equation 7, the relationship between the plowshare edge λ₀ and the internal friction angle φ_t of the soil is established using parameter selection method, where the internal friction angle φ_t of the soil is usually less than 4 degrees, Thus, the plowshare edge angle λ₀ is usually 40-45 degrees, and in this embodiment, the value of the plowshare edge angle λ₀ is set to 45°.

π 4 - ϕ t 2 ≤ λ 0 ≤ π 4 . ( 7 )

Further, the relationship among the angle η between the soil trace and the plowshare edge and the plowshare surface angle ε and the soil lifting angle θ is established, as shown in Formula 8. For optimizing the parameters of the plow surface, in order to ensure the overall reliability of the plow surface, in the present embodiment the angle η between the soil trace and the plowshare edge is set to 24°, and the plowshare surface angle ε is set to 40 degrees. Thus, the soil lifting angle θ is set to 30°.

tan ⁢ η = tan ⁢ θcosε . ( 8 )

Step 2: Establishing 3-D model. According to the plowshare edge angle λ₀, the plowshare surface angle ε, the angle η between the soil trace and the plowshare edge and soil lifting angle θ determined in step 1, the main curve was generated using the curve construction command in the UG software, and then the overall structure was completed by trimming, connecting, smoothing, editing and the like of the curved surface, and .stl model file was exported.

Step 3: Early stage preparation of EDEM Discrete Element Simulation was performed. The plow body material properties were set as: the plow body material density was 7800 kg/m³, the shear modulus was 7.0×10¹⁰ Pa, and the Poisson's ratio is 0.3; soil properties were set as: the soil density was 2600 kg/m³, the shear modulus was 2.5×10⁷ Pa, the Poisson's ratio was 0.5, and the soil particle radius was 2 mm; setting interaction parameters between the soil particles and the plow body entry part as: the static friction coefficient between the soil particles was 0.40, the kinetic friction coefficient between the soil particles was 0.32, the coefficient of restitution between the soil particles was 0.11, the static friction coefficient between the soil particles and the plow body was 0.30, the kinetic friction coefficient between the soil particles and the plow body was 0.22, and the coefficient of restitution between the soil particles and the plow body was 0.18; and a particle factory was created to generate soil particles.

Step 4: Performing analog simulation. The .stl model file in step 2 was imported into the EDEM software, the running speed of the plow body component was set to be 3.8 m/s, and the advancing direction was the X-axis direction; entering the simulation setting, setting the time step length and the simulation time to be 10 s, and setting the cell-size to be 2.5 Rmin; and the simulation was started, and the average resistance value of the plow body component was obtained through the simulation 5.53 kN.

Step 5: Preparing the novel 34MnCrB5-M Steel. On the basis of the component design of the existing 34MnCrB5 steel, Nb with a mass fraction of 0.3%, V element with a mass fraction of 0.3%, and Ni element with a mass fraction of 0.3% were added, and an intermediate-frequency induction smelting furnace was used to smelt the alloy, which was casted into an ingot with a size of φ100 mm×500 mm; the ingot was heated to 960 were added, and an intermediate-frequency in 2 h; after discharging the ingot, the ingot was formed into a 34MnCrB5-M rod with a size of φ 60 mm×1380 mm after one initial rolling and two finishing rolling; the rod was cut into a plow point blank having a length of 360 mm.

TABLE 4
Chemical Composition Comparison between New 34MnCrB5-M
Steel and Existing 33MnCrB5 Steel (Mass Fraction, %)

Name	C	Si	Mn	P	S	Cr	Nb	V	Ni	Ti	B

34MnCrB5-M	0.35	0.21	1.22	0.01	0.01	0.26	0.3	0.3	0.3	0.037	0.004
34MnCrB5	0.35	0.21	1.22	0.01	0.01	0.26	—	—		0.037	0.004

Step 6: Die forging-annealing treatment of plow pointblank. The 34MnCrB5-M steel blank from step 5 was placed in a heating furnace and heated to 950° C., and was kept in temperature for 2 hour before being removed from the furnace and transferred to a die forging machine, and, after die forging, was cooled to room temperature in air; the forged blank was transferred into an annealing furnace and was heated to 650° C. and was kept in temperature for 2 hour, and was then cooled down to room temperature with the furnace; a hard alloy layer was built-up welded on the back of the plow point.

Step 7: Plow point machining. Based on the 3D model data of the plow point component in step 2, the plow point was precision machined using a CNC machine according to the drawing requirements.

Step 8: Plow point carburizing-quenching-tempering treatment. The plow point in step 7 was placed into a gas carburizing furnace, the carburizing temperature was set to 930° C., time was set to 10.0 h, and carbon potential was set to 1.2%; after carburizing was completed, the plow point was quenched in quenching oil at a temperature of 55° C.; after quenching, the plow point was transferred into a tempering furnace with a temperature of 200°° C. for 2.0 h and then was cooled in air to room temperature. Finally, shot peening and spraying plastics treatment were performed.

(2) Alloy Testing

The variation of carbon content along the thickness direction in the carburized layer of the new 33MnCrB5-M plow point was tested using a SPECTRO direct reading spectrometer, and the test results are shown in FIG. 8. It can be seen that the carbon content of the new 33MnCrB5-M plow point carburized layer in this embodiment first decreases and then tends to remain unchanged with the increase of distance from the surface layer. The maximum carbon content near the surface layer is 0.72 wt. %, and the carbon content at the core is 0.34 wt. %.

The microstructure of the surface layer of the novel 33MnCrB5-M plow point was observed using FEI Nova Nano450 field emission scanning electron microscope and Leica optical microscope, as shown in FIG. 9. It can be seen that the surface layer of the 33MnCrB5-M plow point is composed of acicular martensite+residual austenite+carbides. The acicular martensite is small in size and evenly distributed, with an average length of about 5.3 μm.

The comparison of mechanical performance parameters between the new 33MnCrB5-M plow point of this embodiment and the existing plow point is shown in FIG. 10. It can be seen that the yield strength of the new 33MnCrB5-M plow point is 1344 MPa, and the tensile strength is 1803 MPa; the surface hardness of the new 33MnCrB5-M plow point material is 59.1 HRC. Thanks to the high hardness of the plow point surface material, the surface wear of the new 33MnCrB5-M plow point is 0.8 mg; the impact energy absorption of the new 33MnCrB5-M plow point core material is 58.0 J, indicating that the core of the new 33MnCrB5-M plow point has achieved high toughness. In addition, compared with existing plow points, the new 33MnCrB5-M plow point of this embodiment not only significantly improves yield strength, tensile strength, hardness, wear resistance, and toughness, but also reduces operational resistance during operation.

Through the above tests and characterizations, it can be seen that the new 33MnCrB5-M plow point of this embodiment maintains good strength and toughness matching of the core while also possessing high hardness and wear resistance on its surface. In addition, the new 33MnCrB5-M plow point with optimized surface design parameters also has low resistance characteristics and is expected to have important applications in agricultural machinery and advanced industry.

According to another aspect of the present invention, in order to solve the problems of excessive resistance and insufficient service life of existing high-speed reversible plow's grille bar in service, the present invention provides a modeling and manufacturing method of a high- speed reversible plow's grille bar that improves mechanical properties and reduces resistance. First, according to the present invention, the optimal curved surface parameters of the low resistance grille bar are determined by means of horizontal straight line design, UG modeling and ANSYS simulation analysis. Compared with a traditional grille bar grid strip curved surface optimization method, the method comprehensively considers factors such as soil parameters, grid material parameters and contact relationships between a plow body and soil through UG modeling and ANSYS simulation analysis, and greatly improves the working efficiency of the plow body curved surface optimization process and the feasibility of the optimization scheme. On this basis, in the present invention, a proper amount of Al, Nb and Cu elements are added on the basis of the component design of the 28MnB steel for the existing reversible plow's grille bars, and the novel 28MnB5-M steel with fine grains and uniform distribution is obtained by smelting by using a vacuum induction melting furnace. In the novel 28MnB5-M steel, the Al element may generate highly finely divided ultra-microscopic oxide particles dispersed in the steel to prevent grain growth. The Nb element can generate highly dispersed strong carbide NbC, which can further prevent grain growth. The Cu element not only can improve the harden ability of the steel by enhancing the stability of the austenite, but also can improve the corrosion resistance of the steel. The above-mentioned alloying idea effectively improves the defects of coarse grains and uneven distribution of the original 28MnB5 steel, and provides a high-quality raw material supply for the subsequent manufacturing of the high-strength reversible plow's grille bar. In addition, the present invention adds a thermoforming and normalizing process (machining-thermoforming-normalizing-quenching-tempering-shot peening-spraying plastics) to the grid strip member prepared on the basis of the low-resistance grille bar modeling scheme and the high-quality 28MnB5-M steel. The thermal forming is a process of synchronously using the stamping die to form the grid strip blank heated to the austenitizing state, so that the micro-crack defect of the large deformation part of the gate strip blank during cold machining can be effectively avoided, the workload of the press in the forming process of the grid strip blank can be greatly reduced, and the energy saving is better facilitated. In addition, the normalizing process may uniformly distribute the chemical elements in the 28MnB5-M steel to reduce component segregation, so as to further refine the structure of the 28MnB5-M steel and reduce the content of the strip-shaped tissue in the steel, so as to achieve good strength and toughness matching and high wear resistance of the reversible plow's grille bar component.

The above technical methods effectively realize the manufacturing of a new type of high-speed reversible plow's grille bar with low operating resistance, good strength and toughness matching and high wear resistance, which is also more conducive to reducing the energy consumption of tractors. It is expected to provide a feasible technical solution for the safe and long-life service of agricultural machinery soil-engaging parts.

According to an aspect of the present invention, there is provided a method for manufacturing grille bars of a high-speed reversible plow that combines low resistance and internal strength with external hardness, characterized by comprising:

• • Step XA): Optimize the grille bar curved surface using the horizontal rectilinear design method. In order to improve the ability of the plow body to turn over the soil, reduce the friction between the grille bar and the soil, and reduce the loss of the plow body, the present invention calculates the key parameters of the curved surface of the grille bar of the reversible plow based on Formulas 1-3,
  • wherein, the plow width b is generally 640 mm˜700 mm; the value range of the plow shovel installation angle ε is 20°˜30°, the guide curve furrowing angle Δ_εis generally between 5°˜11°, and C₁ is a constant, generally between 1.0˜1.8. Through formula 1-3, the value range of guide curve opening l is 308 mm˜458 mm, the value range of the height h of the guide curve is 550 mm˜870 mm, and the value range of the tangent angle ω of the endpoint is 105°˜109°.

l = C 1 ⁢ b ⁡ ( cos ⁢ Δε - sin ⁢ ε ) , ( 9 ) h = l ⁡ ( cos ⁢ ε + sin ⁢ ε cos ⁢ Δε - sin ⁢ ε ) , ( 10 ) ω = π 2 + ε - Δε , ( 11 )

Step XB): Using UG software to build a 3D model of the plow body, including:

• • B1) Selecting the reference plane to sketch the spar line and the guide curve, respectively;
  • B2) Combining the grille bar curved surface parameters from step XA and drawing horizontal straight meta-lines according to the meta-line number in equations (12) and its corresponding meta-line angle calculation formula;
  • B3) Drawing the front view of the plow body curve, and projecting the front view of the plow body curve to get a closed space curve;
  • B4) Using the cut command to cut out the surface of the plow body, then using the stretch command to change the surface of the plow body into a 3D solid shape, and exporting the .stl model file;

θ n = { θ 0 - 1 3 ⁢ n ⁡ ( θ 0 - θ m ) ⁢ ( n = 0 , 1 , 2 , 3 ) θ m + ( θ max - θ min ) ⁢ 100 + [ Δ z ( n max - n min ) ] 2 [ Δ z ( n max - n min ) ] 2 × [ Δ z ( n - n min ) ] 2 100 + [ Δ z ( n - n min ) ] 2 ⁢ ( n = 4 , 5 , 6 ⁢ … ⁢ 15 ) , ( 12 )

where η is the meta-line number; θ is the meta-line angle; θ_m and θ_n are the meta-line angles when the meta-line number is m and n, respectively; θ₀ is the initial meta-line angle, which is generally taken to be 36°˜45°; θ_max and θ_min are the maximum meta-line angle and the minimum meta-line angle, respectively; and Δ_z is the distance between meta-lines.

Step XC): performing ANSYS simulation pre-preparation comprising:

• • Setting the soil properties as: the soil density as 1.76˜1.78×10³ kg/m³, the elastic modulus as 4.3˜4.5×10⁷ Pa, the Poisson's ratio as 0.33˜0.35, the yield stress was 8.3˜8.5×10⁵ Pa, the tangent modulus was 1.0˜1.2×10⁶ Pa, the failure strain was 0.6˜0.8, and the strain rate was 4%˜6%;
  • Setting the material properties of the reversible plow grille bars as: the density as 7.79˜7.81×10⁻⁶ kg/mm³, the elastic Modulus as 2.2˜2.4×10⁵ N/mm², the Poisson's ratio as 0.2˜0.4;
  • setting the contact method between the plow body surface and the earthwork to automatic contact by face-to-face erosion.

Step XD): perform simulations, including:

• • Import the .stl model file in step XB into the ANSYS simulation environment built in step XC, and set the running speed of the plow body parts to 0.36˜0.38 m/s, and the forward direction to be the X-axis positive direction;
  • Enter the simulation settings and set the time step and simulation time to a total of 10 s;

the simulation was initiated and the average resistance values of the plow components were obtained when the simulation was completed.

Step XE: Preparation of the novel 28MnB5-M Steel, including:

• • on the basis of the composition design of the existing 28MnB5 steel, Nb and Al elements with mass fractions of 0.05%˜0.11% and 0.04%˜0.10% were added (see Table 1 for details), and the alloy was melted in a vacuum induction furnace, and then cast into a 200 kg ingot, and then forged into a hot rolled billet with a capacity of 500 mm×1000 mm×50 mm;
  • the hot rolled billet was heated to 1100° C.˜1200° C. and kept for 1.8 h˜2.0 h. Three passes of rolling were carried out after discharge. The final rolling temperature was 880° C.˜920° C., and the thickness of the rolled plate was 12 mm.
  • the final rolled plate is cooled to the set coiling temperature of 500° C.˜600° C., and then placed in the heating furnace for 28 min˜30 min and cooled with the furnace; and
  • final pickling was carried out to remove iron oxide on the surface of the hot rolled plate.

TABLE 5
Chemical Composition Comparison between New 28MnB5-M
Steel and Existing 28MnB5 Steel (Mass Fraction, %)

Name	C	Si	Mn	Cr	Nb	Al	Cu	Ti	B

28MnB5-M	0.29	0.24	1.22	0.21	0.05~0.11	0.04~0.10	0.10~0.20	0.041	0.003
28MnB5	0.29	0.24	1.22	0.21	—	—	—	0.041	0.003

Step XF): Machining of grille bars, including:

• • the 28MnB5-M hot-rolled sheet in step XE was cut into a grille bar by oxygen-acetylene cutting method;
  • the milling machine was used to finish the shape of the grille bar; and
  • a drilling machine was used to process the countersunk square hole of the grille bar.

Step XG): the hot forming-normalizing-quenching-tempering treatment of the grid bar was carried out, including:

• • the grid billet in step XF was heated to 940° C.˜960° C. for 1.0 h˜1.2 h;
  • after the heat preservation, the grille bar was transferred into the stamping die to form the three-dimensional solid shape required in step XB. After the forming, it was cooled to room temperature in air;
  • the grid billet was heated again to 900° C.18 920° C. for 0.5 h˜0.7 h, and then immersed in water and quenched to room temperature;
  • the quenched grille bar was further transferred to a tempering furnace with a temperature of 180° C.˜ 200°° C. for 2.0 h˜2.4 h, and the furnace was air-cooled after the heat preservation; and
  • the high-speed reversible plow grille bar parts with low running resistance, high strength, high toughness and high wear resistance were obtained by shot peening and plastic spraying.

The advantages of the invention include:

• • The invention provides a modeling and manufacturing method for a high-speed reversible plow grille bar that can improve mechanical properties and reduce resistance. The horizontal straight line design method, UG modeling and ANSYS simulation analysis are used to determine the optimal surface parameters of the low-resistance grille bar. Then, the composition of 28MnB5 steel for grille bar and the manufacturing process of grille bar were improved. The advantages of the invention include:

(1) Different from the previous method of optimizing the grille bar surface merely by mathematical model calculation, the present invention combines the horizontal straight line design method, UG modeling and ANSYS simulation analysis method to reasonably optimize the design parameters of the high-speed reversible plow grille bar components. At the same time, the soil parameters, grille bar material parameters and the contact relationship between the plow body and the soil are introduced, which greatly improves the working efficiency of the plow body surface optimization process and the feasibility of the optimization scheme, effectively reduces the running resistance of the plow body, and further reduces the impact of the soil on the grille bar components and the fuel consumption of the tractor.

(2) The composition design of 28MnB5 steel is improved. A new type of 28MnB5-M steel is obtained by adding 0.05˜0.11% Nb, 0.04˜0.10% Al and 0.10˜0.20% Cu. The use of Nb and Al composite addition to generate highly fragmented oxides can prevent the grain growth of the steel during heating, and further improve the strength and toughness matching degree of the new 28MnB5-M steel after heat treatment. Cu element can not only improve the harden ability of steel by enhancing the stability of austenite, but also improve the corrosion resistance of steel. Compared with the method of adding expensive rare earth elements, the prices of Nb, Al and Cu elements used in this invention are significantly reduced, and the performance also meets the needs of the industry. It is one of the most economical and effective means to improve the performance of steel.

(3) The industrialization technology of thermoforming-normalizing-quenching-reheating heat treatment process used in the invention is mature, which can be realized on the basis of existing production equipment without adding other heat treatment equipment, and can greatly reduce the cost. At the same time, the microstructure size and uniformity of the grille bar parts after thermoforming-normalizing-quenching-tempering treatment are significantly better than those of the previous grille bar parts, which makes them have good strength and toughness matching performance, and effectively ensures that the grille bar can withstand the high-speed impact of soil and stone and is not easy to fail. Therefore, the heat treatment process adopted in the invention has high cost performance, and has broad application prospects in the field of plow body manufacturing.

In summary, the invention provides a modeling and manufacturing method of high-speed reversible plow grille bar that can improve mechanical properties and reduce resistance. It can not only effectively solve the problems of insufficient matching of strength and toughness and large resistance in the operation process of the existing high-speed reversible plow grille bar, but also has the characteristics of high cost performance. It has important and broad application prospects in the field of agricultural machinery manufacturing.

Embodiment 4

The operation steps include:

(1) The design and manufacturing of grille bar, including:

• • Step X1): Optimize the grille bar curved surface using the horizontal rectilinear design method. In order to improve the ability of the plow body to turn over the soil, reduce the friction between the grille bar and the soil, and reduce the loss of the plow body, the present invention calculates the key parameters of the curved surface of the grille bar of the reversible plow based on Formulas 5-7. Among them, the plow width b is 640 mm; the plow shovel installation angle ε is 20°, the guide curve furrowing angle Δ_ε is 5°, and C₁ is a constant with a value of 1.0. Through formula 5-7, the guide curve opening l is 308 mm, the height h of the guide curve is 550 mm, and the tangent angle ω of the endpoint is 105°.

l = C 1 ⁢ b ⁡ ( cos ⁢ Δε - sin ⁢ ε ) , ( 13 ) h = l ⁡ ( cos ⁢ ε + sin ⁢ ε cos ⁢ Δε - sin ⁢ ε ) , ( 14 ) ω = π 2 + ε - Δε . ( 15 )

• • Step X2): Using UG software to build a 3D model of the plow body.

First, selection was made of the reference plane to sketch the spar line and the guide curve, respectively; then, the grille bar curved surface parameters from step X1 and draw horizontal straight meta-lines were combined according to the meta-line number in equations (16) and its corresponding meta-line angle calculation formula; finally, the front view of the plow body curve was drawn, and the front view of the plow body curve was projected to get a closed space curve. On this basis, the cut command was used to cut out the surface of the plow body, then the stretch command was used to change the surface of the plow body into a 3D solid shape, and the .stl model file was projected.

θ n = { θ 0 - 1 3 ⁢ n ⁡ ( θ 0 - θ m ) ⁢ ( n = 0 , 1 , 2 , 3 ) θ m + ( θ max - θ min ) ⁢ 100 + [ Δ z ( n max - n min ) ] 2 [ Δ z ( n max - n min ) ] 2 × [ Δ z ( n - n min ) ] 2 100 + [ Δ z ( n - n min ) ] 2 ⁢ ( n = 4 , 5 , 6 ⁢ … ⁢ 15 ) . ( 16 )

In the formula: n is the meta-line number; θ is the meta-line angle; θ_m and θ_n are the meta-line angles when the meta-line number is m and n, respectively; θ₀ is the initial meta-line angle, which is generally taken to be 36°˜45°; θ_max and θ_min are the maximum meta-line angle and the minimum meta-line angle, respectively; and Δz is the distance between meta-lines.

Step X3): performing ANSYS simulation pre-preparation. Setting the soil properties as: the soil density as 1.76×10³ kg/m³, the elastic modulus as 4.3×10⁷ Pa, the Poisson's ratio as 0.33, the yield stress was 8.3×10⁵ Pa, the tangent modulus was 1.0×10⁶ Pa, the failure strain was 0.6, and the strain rate was 4%; Setting the material properties of the reversible plow grille bars as: the density as 7.79×10⁻⁶ kg/mm³, the elastic modulus as 2.2×10⁵ N/mm², the Poisson's ratio as 0.2; setting the contact method between the plow body surface and the earthwork to automatic contact by face-to-face erosion.

Step X4): perform simulations. The .stl model file in step X2 was imported into the ANSYS simulation environment built in step X3, and the running speed of the plow body parts was set to 0.36 m/s, with the forward direction to be the X-axis positive direction; the simulation settings were entered and the time step and simulation time were set to a total of 10 s; when the simulation was completed, the average resistance value of the plow part was obtained as 4.98 kN.

Step X5: Preparation of the novel 28MnB5-M Steel. On the basis of the composition design of the existing 28MnB5 steel, Nb, Al and Cu elements with mass fractions of 0.05%, 0.04% and 0.10% were added (see Table 2 for details), and the alloy was melted in a vacuum induction furnace, and then cast into a 200 kg ingot, and then forged into a hot rolled billet with a capacity of 500 mm×1000 mm×50 mm;

The hot rolled billet was heated to 1100° C. and kept for 1.8 h. Three passes of rolling were carried out after discharge. The final rolling temperature was 880° C., and the thickness of the rolled plate was 12 mm. The final rolled plate is cooled to the set coiling temperature of 500° C., and then placed in the heating furnace for 28 min and cooled with the furnace. Final pickling was performed to remove iron oxide on the surface of the hot rolled plate.

TABLE 6
Chemical Composition Comparison between New 28MnB5-M
Steel and Existing 28MnB5 Steel (Mass Fraction, %)

name	C	Si	Mn	Cr	Nb	Al	Cu	Ti	B

28MnB5-M	0.29	0.24	1.22	0.21	0.05	0.04	0.10	0.041	0.003
28MnB5	0.29	0.24	1.22	0.21	—	—	—	0.041	0.003

Step X6): Machining of grille bars. The 28MnB5-M hot-rolled sheet in step X5 was cut into a grille bar by oxygen-acetylene cutting method. The milling machine was used to finish the shape of the grille bar. A drilling machine was used to process the countersunk square hole of the grille bar

Step X7): The hot forming-normalizing-quenching-tempering treatment of the grid bar was carried out, including: The grid billet in step X6 was heated to 940° C. for 1.0 h. After the heat preservation, the grille bar was transferred into the stamping die to form the three-dimensional solid shape required in step X2. After the forming, it was cooled to room temperature in air. The grid billet was heated again to 900° C. for 0.5 h, and then immersed in water and quenched to room temperature. The quenched grille bar was further transferred to a tempering furnace with a temperature of 180° C. for 2.0 h and the furnace was air-cooled after the heat preservation. The high-speed reversible plow grille bar parts with low running resistance, high strength, high toughness and high wear resistance were obtained by shot peening and plastic spraying.

(2) Alloy Testing

The microstructure of the new 28MnB5-M grille bar was observed by FEI Nova Nano450 field emission scanning electron microscope and Leica optical microscope, as shown in FIG. 12. It can be seen that the microstructure of 28MnB5-M grille bar is mainly composed of lath martensite with fine size and uniform distribution, and its average length is about 4.6 μm.

At room temperature, the wear volume of the new 28MnB5-M grille bar is 1.5 mg tested by MFT-R4000 high-speed reciprocating friction and wear machine.

The comparison of the mechanical properties of the new 28MnB5-M grille bar and the existing grille bar is shown in FIG. 13. It can be seen that the yield strength of the new 28MnB5-M grille bar is 1308 MPa and the tensile strength is 1608 MPa. The impact absorption energy of the new 28MnB5-M grille bar is 56.0 J. Combined with the analysis of tensile strength data, it can be seen that the new 28MnB5-M grille bar achieves a good matching of strength and toughness. In addition, compared with the existing grid bars, the new 28MnB5-M grille bars in this implementation case are not only significantly higher in yield strength, tensile strength and toughness, but also lower in operating resistance.

Through the above test and characterization, it can be found that the new 28MnB5-M grille bar component of this embodiment has good strength and toughness matching performance. In addition, the new 28MnB5-M grille bar after optimizing the surface design parameters also has low resistance characteristics, and is expected to have important applications in agricultural machinery and advanced industries.

Embodiment 5

The operation steps include:

(1) The design and manufacturing of grille bar, including:

Step X1): Optimize the grille bar curved surface using the horizontal rectilinear design method. In order to improve the ability of the plow body to turn over the soil, reduce the friction between the grille bar and the soil, and reduce the loss of the plow body, the present invention calculates the key parameters of the curved surface of the grille bar of the reversible plow based on Formulas 9-11. Among them, the plow width b is 670 mm; the plow shovel installation angle ε is 25°, the guide curve furrowing angle Δ_ε is 8°, and C₁ is a constant with a value of 1.4. Through formula 9-11, the guide curve opening 1 is 383 mm, the height h of the guide curve is 710 mm, and the tangent angle ω of the endpoint is 107°.

l = C 1 ⁢ b ⁢ ( cos ⁢ Δε - sin ⁢ ε ) , ( 17 ) h = l ⁡ ( cos ⁢ ε + sin ⁢ ε cos ⁢ Δε - sin ⁢ ε ) , ( 18 ) ω = π 2 + ε - Δε . ( 19 )

Step X2): Using UG software to build a 3D model of the plow body. First, selection was made of the reference plane to sketch the spar line and the guide curve, respectively; then combination of the grille bar curved surface parameters from step X1 and draw horizontal straight meta-lines was made according to the meta-line number in equations (20) and its corresponding meta-line angle calculation formula; finally, drawing was made of the front view of the plow body curve and projection of the front view of the plow body curve was made to get a closed space curve; on this basis, use was made of the cut command to cut out the surface of the plow body, then use was made of the stretch command to change the surface of the plow body into a 3D solid shape, and the .stl model file was exported.

θ n = { θ 0 - 1 3 ⁢ n ⁡ ( θ 0 - θ m ) ⁢ ( n = 0 , 1 , 2 , 3 ) θ m + ( θ max - θ min ) ⁢ 100 + [ Δ z ( n max - n min ) ] 2 [ Δ z ( n max - n min ) ] 2 × [ Δ z ( n - n min ) ] 2 100 + [ Δ z ( n - n min ) ] 2 ⁢ ( n = 4 , 5 , 6 ⁢ … ⁢ 15 ) , ( 20 )

In the formula: n is the meta-line number; θ is the meta-line angle; θ_m and θ_n are the meta-line angles when the meta-line number is m and n, respectively; θ₀ is the initial meta-line angle, which is generally taken to be 36°˜45°; θ_max and θ_min are the maximum meta-line angle and the minimum meta-line angle, respectively; and Δ_z is the distance between meta-lines.

Step X3): performing ANSYS simulation pre-preparation. Setting the soil properties as: the soil density as 1.77×10³ kg/m³, the elastic modulus as 4.4×10⁷ Pa, the Poisson's ratio as 0.34, the yield stress was 8.4×10⁵ Pa, the tangent modulus was 1.1×10⁶ Pa, the failure strain was 0.7, and the strain rate was 5%; setting the material properties of the reversible plow grille bars as: the density as 7.80×10⁻⁶ kg/mm³, the elastic modulus as 2.3×10⁵ N/mm², the Poisson's ratio as 0.3; setting the contact method between the plow body surface and the earthwork to automatic contact by face-to-face erosion.

Step X4): performing simulations. The .stl model file in step X2 was imported into the ANSYS simulation environment built in step X3, and the running speed of the plow body parts was set to 0.37 m/s, with the forward direction to be the X-axis positive direction; the simulation settings was entered and the time step and simulation time were set to a total of 10 s; when the simulation was completed, the average resistance value of the plow part was obtained as 4.81 kN.

Step X5: Preparation of the novel 28MnB5-M Steel. On the basis of the composition design of the existing 28MnB5 steel, Nb, Al and Cu elements with mass fractions of 0.08%, 0.07% and 0.15% were added (see Table 3 for details), and the alloy was melted in a vacuum induction furnace, and then cast into a 200 kg ingot, and then forged into a hot rolled billet with a capacity of 500 mm×1000 mm×50 mm; the hot rolled billet was heated to 1150° C. and kept for 1.9 h. Three passes of rolling were carried out after discharge. The final rolling temperature was 900° C., and the thickness of the rolled plate was 12 mm. The final rolled plate was cooled to the set coiling temperature of 550° C., and then placed in the heating furnace for 29 min and cooled with the furnace. Final pickling was performed to remove iron oxide on the surface of the hot rolled plate.

TABLE 7
Chemical Composition Comparison between New 28MnB5-M
Steel and Existing 28MnB5 Steel (Mass Fraction, %)

name	C	Si	Mn	Cr	Nb	Al	Cu	Ti	B

28MnB5-M	0.29	0.24	1.22	0.21	0.08	0.07	0.15	0.041	0.003
28MnB5	0.29	0.24	1.22	0.21	—	—	—	0.041	0.003

Step X6): Machining of grille bars. The 28MnB5-M hot-rolled sheet in step X5 was cut into a grille bar by oxygen-acetylene cutting method. The milling machine was used to finish the shape of the grille bar. A drilling machine was used to process the countersunk square hole of the grille bar

Step X7): The hot forming-normalizing-quenching-tempering treatment of the grid bar was carried out, including: The grid billet in step X6 was heated to 950° C. for 1.1 h. After the heat preservation, the grille bar was transferred into the stamping die to form the three-dimensional solid shape required in step X2. After the forming, it was cooled to room temperature in air. The grid billet was heated again to 910° C. for 0.6 h, and then immersed in water and quenched to room temperature. The quenched grille bar was further transferred to a tempering furnace with a temperature of 190° C. for 2.2 h and the furnace was air-cooled after the heat preservation. The high-speed reversible plow grille bar parts with low running resistance, high strength, high toughness and high wear resistance were obtained by shot peening and plastic spraying.

(2) Alloy Testing

The microstructure of the new 28MnB5-M grille bar was observed by FEI Nova Nano450 field emission scanning electron microscope and Leica optical microscope, as shown in FIG. 14. It can be seen that the microstructure of 28MnB5-M grille bar is mainly composed of lath martensite with fine size and uniform distribution, and its average length is about 4.3 μm.

At room temperature, the wear volume of the new 28MnB5-M grille bar is 1.2 mg tested by MFT-R4000 high-speed reciprocating friction and wear machine.

The comparison of the mechanical properties of the new 28MnB5-M grille bar and the existing grille bar is shown in FIG. 15. It can be seen that the yield strength of the new 28MnB5-M grille bar is 1407 MPa and the tensile strength is 1691 MPa. The impact absorption energy of the new 28MnB5-M grille bar is 58.0 J. Combined with the analysis of tensile strength data, it can be seen that the new 28MnB5-M grille bar achieves a good matching of strength and toughness. In addition, compared with the existing grid bars, the new 28MnB5-M grille bars in this implementation case are not only significantly higher in yield strength, tensile strength and toughness, but also lower in operating resistance.

Through the above test and characterization, it can be found that the new 28MnB5-M grille bar component of this embodiment has good strength and toughness matching performance. In addition, the new 28MnB5-M grille bar after optimizing the surface design parameters also has low resistance characteristics, and is expected to have important applications in agricultural machinery and advanced industries.

Embodiment 6

The operation steps include:

(1) The design and manufacturing of grille bar, including:

Step X1): Optimize the grille bar curved surface using the horizontal rectilinear design method. In order to improve the ability of the plow body to turn over the soil, reduce the friction between the grille bar and the soil, and reduce the wear of the plow body, the present invention calculates the key parameters of the curved surface of the grille bar of the reversible plow based on Formulas 13-15. Among them, the plow width b is 700 mm; the plow shovel installation angle ε is 30°, the guide curve furrowing angle Δε is 11°, and C1 is a constant with a value of 1.8. Through formula 13-15, the guide curve opening l is 458 mm, the height h of the guide curve is 870 mm, and the tangent angle ω of the endpoint is 109°.

l = C 1 ⁢ b ⁡ ( cos ⁢ Δε - sin ⁢ ε ) , ( 21 ) h = l ⁡ ( cos ⁢ ε + sin ⁢ ε cos ⁢ Δε - sin ⁢ ε ) , ( 22 ) ω = π 2 + ε - Δε . ( 23 )

Step X2): Using UG software to build a 3D model of the plow body.

First, selection of the reference plane was made to sketch the spar line and the guide curve, respectively; then, the grille bar curved surface parameters from step X1 and draw horizontal straight meta-lines according to the meta-line number in equations (24) and its corresponding meta-line angle calculation formula were combined; finally, the front view of the plow body curve was drawn, and the front view of the plow body curve was projected to get a closed space curve; on this basis, the cut command was used to cut out the surface of the plow body, then the stretch command was used to change the surface of the plow body into a 3D solid shape, and the .stl model file was exported.

θ n = { θ 0 - 1 3 ⁢ n ⁡ ( θ 0 - θ m ) ⁢ ( n = 0 , 1 , 2 , 3 ) θ m + ( θ max - θ min ) ⁢ 100 + [ Δ z ( n max - n min ) ] 2 [ Δ z ( n max - n min ) ] 2 × [ Δ z ( n - n min ) ] 2 100 + [ Δ z ( n - n min ) ] 2 ⁢ ( n = 4 , 5 , 6 ⁢ … ⁢ 15 ) . ( 24 )

In the formula: n is the meta-line number; θ is the meta-line angle; θ_m and θ_n are the meta-line angles when the meta-line number is m and n, respectively; θ₀ is the initial meta-line angle, which is generally taken to be 36°˜45°; θ_max and θ_min are the maximum meta-line angle and the minimum meta-line angle, respectively; and Δ_z is the distance between meta-lines.

Step X3): performing ANSYS simulation pre-preparation. Setting the soil properties as: the soil density as 1.78×10³ kg/m³, the elastic modulus as 4.5×10⁷ Pa, the Poisson's ratio as 0.35, the yield stress was 8.5×10⁵ Pa, the tangent modulus was 1.2×10⁶ Pa, the failure strain was 0.8, and the strain rate was 6%; setting the material properties of the reversible plow grille bars as: the density as 7.81×10⁻⁶ kg/mm³, the elastic modulus as 2.4×10⁵ N/mm², the Poisson's ratio as 0.4; setting the contact method between the plow body surface and the earthwork to automatic contact by face-to-face erosion.

Step X4): performing simulations. The .stl model file in step X2 was imported into the ANSYS simulation environment built in step X3, and the running speed of the plow body parts was set to 0.38 m/s, and the forward direction was set to be the X-axis positive direction; the simulation settings were entered and the time step and simulation time were set to a total of 10 s; after the simulation was completed, the average resistance value of the plow part was obtained as 4.90 kN.

Step X5: Preparation of the novel 28MnB5-M Steel. On the basis of the composition design of the existing 28MnB5 steel, Nb, Al and Cu elements with mass fractions of 0.11%, 0.10% and 0.2% were added (see Table 4 for details), and the alloy was melted in a vacuum induction furnace, cast into a 200 kg ingot, and then forged into a hot rolled billet with a capacity of 500 mm×1000 mm×50 mm; the hot rolled billet was heated to 1200° C. and kept for 2.0 h. Three passes of rolling were carried out after discharge. The final rolling temperature was 920° C., and the thickness of the rolled plate was 12 mm. The final rolled plate was cooled to the set coiling temperature of 600° C., and then placed in the heating furnace for 30 min and cooled with the furnace. Finally, pickling was made to remove iron oxide on the surface of the hot rolled plate.

TABLE 8
Chemical Composition Comparison between New 28MnB5-M
Steel and Existing 28MnB5 Steel (Mass Fraction, %)

name	C	Si	Mn	Cr	Nb	Al	Cu	Ti	B

28MnB5-M	0.29	0.24	1.22	0.21	0.08	0.07	0.20	0.041	0.003
28MnB5	0.29	0.24	1.22	0.21	—	—	—	0.041	0.003

Step X6): Machining of grille bars. The 28MnB5-M hot-rolled sheet in step X5 was cut into a grille bar by oxygen-acetylene cutting method. The milling machine was used to finish the shape of the grille bar. A drilling machine was used to process the countersunk square hole of the grille bar.

Step X7): The hot forming-normalizing-quenching-tempering treatment of the grid bar was carried out, including: the grid billet in step X6 was heated to 960° C. for 1.2 h. After the heat preservation, the grille bar was transferred into the stamping die to form the three-dimensional solid shape required in step X2. After the forming, it was cooled to room temperature in air. The grid billet was heated again to 920° C. for 0.7 h, and then immersed in water and quenched to room temperature. The quenched grille bar was further transferred to a tempering furnace with a temperature of 200° C. for 2.4 h and the furnace was air-cooled after the heat preservation. High-speed reversible plow grille bar parts with low running resistance, high strength, high toughness and high wear resistance were obtained by shot peening and plastic spraying.

(2) Alloy Testing

The microstructure of the new 28MnB5-M grille bar was observed by FEI Nova Nano450 field emission scanning electron microscope and Leica optical microscope, as shown in FIG. 16. It can be seen that the microstructure of 28MnB5-M grille bar is mainly composed of lath martensite with fine size and uniform distribution, and its average length is about 4.5 μm.

At room temperature, the wear volume of the new 28MnB5-M grille bar was 1.6 mg tested by MFT-R4000 high-speed reciprocating friction and wear machine.

The comparison of the mechanical properties of the new 28MnB5-M grille bar and the existing grille bar is shown in FIG. 17. It can be seen that the yield strength of the new 28MnB5-M grille bar is 1317 MPa and the tensile strength is 1632 MPa. The impact absorption energy of the new 28MnB5-M grille bar is 57.0 J. Combined with the analysis of tensile strength data, it can be seen that the new 28MnB5-M grille bar achieves a good matching of strength and toughness. In addition, compared with the existing grid bars, the new 28MnB5-M grille bars in this embodiment are not only significantly higher in yield strength, tensile strength and toughness, but also lower in operating resistance.

Through the above test and characterization, it can be found that the new 28MnB5-M grille bar component of this embodiment has good strength and toughness matching performance. In addition, the new 28MnB5-M grille bar after optimizing the surface design parameters also has low resistance characteristics, and is expected to have important applications in agricultural machinery and advanced industries.