STEEL AND PROCESS FOR PRODUCTION, AND A METHOD OF PROCESSING THE STEEL

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application which claims the benefit of priority from European Patent Application No. 24 160 285.3 filed Feb. 28, 2024, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a steel, especially in the present context as steel sheet, which is suitable for processing by welding, in particular high-energy welding, and to a process for production and to a method of processing the steel.

In the case of such steels that are known through use, energy input in the course of welding in a region affected by the heat of welding worsens the mechanical properties, with a considerable reduction in toughness in particular. It is often the case even with an energy input of 2-5 KJ/mm that demands on mechanical properties that are typically made on such steels are not attainable.

SUMMARY AND DESCRIPTION OF THE INVENTION

It is an object of the invention to provide a steel of the type specified at the outset, which has sufficiently good mechanical properties after processing by welding, in particular high-energy welding.

This object is achieved in accordance with the invention by a steel of the following composition:

• • 0.02-0.1% by weight of C,
  • 0.01-0.1% by weight of Si,
  • 0.60-2.00% by weight of Mn,
  • >0 and ≤0.01% by weight of Al,
  • 0.01-0.30% by weight of Cu,
  • 0.01-0.60% by weight of Ni,
  • 0.01-0.30% by weight of Cr,
  • 0.005-0.050% by weight of Nb,
  • 0.005-0.050% by weight of Ti,
  • 0.0005-0.0050% by weight of S,
  • 0.0002-0.0050% by weight of Ca,
  • 0.0005-0.0050% by weight of O,
  • ≤0.010% by weight of N,
  • ≤0.02% by weight of P,
  • 0-0.0050% by weight of Mg
  • 0-0.0060% by weight of V
  • 0-0.15% by weight of Mo balance: Fe and production-related impurities.

The steel according to the invention has comparatively high toughness, especially notch impact resistance, up to an energy input of more than 20 KJ/mm. It has also been found that the steel, after welding, because of its chemical and microstructural characteristics in a region affected by the heat of welding, i.e. in a region in which the welding affects the mechanical properties of the steel, even in the case of high energy input, has a comparatively small number of martensite/austenite constituents and a comparatively small austenite grain size compared to known steels. Advantages of mechanical properties of the steel are manifested even from an energy input of >2 KJ/mm, especially >3.5 KJ/mm. The steel has been found to be particularly advantageous for processing at energy inputs of >5 KJ/mm, especially >8 KJ/mm, more preferably >10 KJ/mm.

The steel is appropriately a microalloyed steel produced by thermomechanical rolling, especially in the present context as steel sheet, typically referred to as “TM steel”.

In one configuration of the invention, the steel, after processing by welding with an energy input of 3.5 to 30 KJ/mm, preferably with an energy input of 3.5 to 25 kJ/mm, has a notch impact energy of at least 75 J, preferably at least 100 J. Appropriately, the steel, after processing by welding with an energy input of 3.5 to 7 KJ/mm, has a notch impact energy of at least 150 J, preferably at least 190 J.

Preferably, the steel, after processing by welding with an energy input of 7 to 15 KJ/mm, has a notch impact energy of at least 100 J, preferably at least 130 J.

In a particularly preferred embodiment of the invention, the steel, after processing by welding with an energy input of 15 to 25 KJ/mm, preferably of 15 to 30 KJ/mm, has a notch impact energy of at least 75 J, preferably at least 100 J.

All the above-reported values for the notch impact energies of the steels that have been processed by welding are based on a determination at a fusion line of the weld seam formed in the welding operation by the Charpy notch impact bending test at −40° C., especially according to the standard DIN EN ISO 148-1:2017. They are preferably each an average of results from at least 3 of the notch impact bending tests in each case.

In a particularly preferred embodiment of the invention, the weld which is provided in order to ascertain the above-reported notch impact energies is aligned longitudinally with respect to the rolling direction and is conducted at a preheating temperature of 125° C. to 250° C. Appropriately, the seam shape is provided as a single-bevel groove weld with a steep flank. The sample direction is preferably transverse to the rolling direction. Sample positions envisaged are preferably the top side of the sheet, the middle of the sheet or the underside of the sheet.

Submerged arc welding is appropriate, although a different welding method would also be conceivably employable. In particular, welding is effected according to the standard DIN EN 10225-1:2019, except that, in the present context, differently from the standard, an energy input of >5 KJ/mm2 may be provided.

The energy input is appropriately calculated by the formula

Q = k · U · I v · 10 - 3 ( Formula ⁢ 1 )

• • where
  • Q=introduction of heat [kJ/mm]
  • k=thermal efficiency,
  • U=arc voltage applied [V],
  • I=weld current [A],
  • v=weld speed [mm/s]

In a further configuration of the invention, the steel, after treatment by physical welding simulation of the coarse grain zone with an energy input of 3.5 to 30 kJ/mm, has a notch impact energy of at least 75 J, preferably at least 100 J.

Appropriately, the steel, after treatment by physical welding simulation of the coarse grain zone with an energy input of 3.5 to 7 KJ/mm, has a notch impact energy of at least 150 J, preferably at least 190 J.

Preferably, the steel, after treatment by physical welding simulation of the coarse grain zone with an energy input of 7 to 15 KJ/mm, has a notch impact energy of at least 100 J, preferably at least 130 J.

In a particularly preferred embodiment of the invention, the steel, after treatment by physical welding simulation of the coarse grain zone with an energy input of 15 to 30 KJ/mm, has a notch impact energy of at least 75 J, preferably at least 100 J.

All the above-specified values of the notch impact energies of the steels that have been treated by physical welding simulation of the coarse grain zone relate to a determination by the Charpy notch impact resistance test at −40° C. or −20° C., especially according to the standard DIN EN ISO 148-1:2017, wherein a determination is preferably effected at −40° C. for a welding simulation with just a single cycle and a determination at −20° C. instead for a welding simulation with two cycles.

Appropriately, for the welding simulation, a T_max=1350° C. is envisaged. In the case of performance of two cycles, the second cycle is effected at a T_max Of 750 to 775° C., preferably of 775° C. The welding simulation with just a single cycle serves for welding simulation of the coarse grain zone; the welding simulation with two cycles serves for welding simulation of the coarse grain zone superposed by the intercritical zone.

The notch impact energies are preferably each an average of results from at least 3 of the notch impact bending tests in each case.

In one embodiment of the invention, the above-reported values for the energy inputs relate to a treatment by physical welding simulation of the coarse grain zone by conversion of the desired energy input to a t8/5 time. For this purpose, the following two formulae are calculated and the higher value is used as the 18/5 time in order to enter the desired energy:

3 ⁢ D ⁢ heat ⁢ conduction : t 8 / 5 = 
 ( 6700 - 5 · T V ) · Q · ( 1 5 ⁢ 0 ⁢ 0 - T V - 1 8 ⁢ 0 ⁢ 0 - T V ) · F 3 ( Formula ⁢ 2 ) 2 ⁢ D ⁢ heat ⁢ conduction : t 8 / 5 = 
 ( 4300 - 4.3 · T V ) · 10 5 · Q 2 d 2 · ( ( 1 5 ⁢ 0 ⁢ 0 - T V ) 2 - ( 1 8 ⁢ 0 ⁢ 0 - T V ) 2 ) · F 2 , ( Formula ⁢ 3 )

• • where
  • T_v=preheating temperature [° C.],
  • F₃, F₂=seam factor in the case of three- or two-dimensional heat dissipation,
  • d=sheet thickness

The abovementioned formulae (1), (2) and 3 are given in the technical standard SEW 088:2017-10 (SEW 088 Annex 1:2017-10; SEW 088 Annex 2:2017-10 Weldable Non-Alloy and Low-Alloy Steel. Recommendations for Processing, in particular for Fusion Welding).

The temperature regime corresponding to the respective melting process was ascertained by the calculation method according to Hannerz:

Hannerz equation:

T - T 0 = A 3 ⁢ 0 ⁢ 0 * B * t * exp ⁢ ( - A 6 ⁢ 0 ⁢ 0 * e * B * ( T max - T 0 ) 2 * t ) , ( Formula ⁢ 4 )

• • where

A = t 8 / 5 * ( 5 ⁢ 0 ⁢ 0 - T 0 ) 2 ⁢ ( 8 ⁢ 0 ⁢ 0 - T 0 ) 2 , B = 13 ⁢ 0 ⁢ 0 - 2 ⁢ T 0 ,

• • T_max=peak temperature (° C.),
  • T₀=exit temperature (° C.),
  • e=Euler's number
  • t_8/5=cooling time from 800° C. to 500° C. (s)
  • (Source: Hannerz, N. E., “Idealized thermal cycle for weld heat affected zone simulation of steel”, Perdue Thermal Physical Property Handbook)

In order to avoid formation of embrittling martensite/austenite constituents, the steel is provided with a comparatively small content of silicon and aluminum.

Silicon is provided in such a content that oxygen, in spite of the low aluminum content and associated comparatively low Al deoxidation, is sufficiently bound by the silicon (Si deoxidation). The stated minimum content of 0.01% by weight of silicon is required to achieve sufficient Si deoxidation. Alternatively or additionally, it would be possible to provide for Mg, Ca or Ti deoxidation.

Since the aluminum and the silicon have high solubility in the ferrite, the carbon is increasingly displaced from the ferrite into the austenite in the phase transformation, and the driving force for cementite precipitation is considerably reduced.

Residual austenite is indirectly stabilized because of the elevated carbon content. For avoidance of martensite/austenite constituents, a maximum content of 0.01% by weight of aluminum and of 0.10% by weight of silicon is envisaged in the steel according to the invention.

Niobium in the steel serves in particular for avoidance of recrystallization at low rolling temperature via solute drag and/or deformation-induced precipitates. The envisaged minimum content of 0.005% by weight of niobium is provided in order that NbC is formed for deformation-induced precipitates. For avoidance of coarse primary precipitates, the alloy includes a maximum of 0.050% by weight of niobium.

Titanium leads to the formation of precipitates of high thermal stability, which withstand even high temperatures on welding and inhibit temperature-related growth of austenite grains in the heat-affected region (“pinning”). Appropriately, not more than 0.050% by weight of titanium is provided, in order to avoid coarse primary precipitates. The composition includes at least 0.005% by weight of titanium, in order to promote formation of complex particles and to ensure sufficient nitrogen binding, especially for avoidance of aging effects. Advantageously, the steel according to the invention, also because of the titanium content, meets the standard EN10025-4, which envisages different nitrogen-binding alloy elements in the case of a low aluminum content.

In the alloy according to the invention, at least 0.02% by weight of carbon and at least 0.60% by weight, preferably at least 1% by weight, of manganese are provided in order that the steel attains a required minimum strength. The steel includes not more than 0.1% by weight, preferably not more than 0.05% by weight, of carbon in order to avoid the formation of hard phase regions. Manganese is provided in a maximum content of 2.00% by weight, preferably 1.70% by weight, in order to prevent any austenite-stabilizing effect and avoid the formation of martensite/austenite constituents.

The minimum contents of 0.01% by weight of copper, 0.01% by weight of nickel and 0.01% by weight of chromium are provided for solid solution strengthening.

The maximum content of 0.3% by weight, preferably of 0.1% by weight, of copper and 0.6% by weight of nickel, preferably 0.4% by weight of nickel, more preferably 0.2% by weight of nickel, contributes to the reduction in austenite stabilization and hence to the avoidance of martensite/austenite constituents.

Chromium is provided in the steel in a maximum content of 0.30% by weight, preferably 0.10% by weight, in order to avoid the formation of Cr carbides, which have an embrittling effect.

The minimum contents of 0.0005% by weight, preferably of 0.001% by weight, of sulfur, of 0.0002% by weight of calcium and 0.0005% by weight of oxygen are provided for the formation of complex particles.

The maximum contents of 0.0050% by weight, preferably of 0.0040% by weight, of sulfur and of 0.0050% by weight of oxygen are provided for the compliance with a required purity. The envisaged maximum oxygen content also serves for castability.

Calcium is provided in a maximum content of 0.0050% by weight since it has an adverse effect on the mechanical properties after binding of the titanium and the oxygen.

A maximum nitrogen content of 0.010% by weight avoids aging effects.

Phosphorus is provided with a maximum amount of 0.02% by weight in order to avoid grain boundary fracture, especially temper embrittlement.

Magnesium may be provided in order to bring about the abovementioned Mg deoxidation. The maximum content of 0.0050% by weight of Mg is provided in order to avoid the formation of embrittling magnesium oxide particles.

The steel may contain vanadium as a microalloy element. In order to avoid formation of coarse primary precipitates, a maximum content of 0.0060% by weight of V is envisaged.

Molybdenum may be provided for solid solution strengthening. A maximum content of 0.15% by weight of Mo is provided in order to avoid the formation of embrittling carbides.

In one embodiment of the invention, the steel has a, preferably fine-grain, bainitic microstructure, preferably with an average grain size of <15 μm, preferably <14 μm, and/or a proportion of high-angle grain boundaries of >50%, preferably >60%. The specified grain sizes are appropriately grain sizes determined by REM-EBSD (backscattering electron diffraction in the scanning electron microscope), where the value is preferably based on the average of the area-weighted distribution of the circle-equivalent diameter at a tolerance angle of 5°.

The steel preferably has nonmetallic inclusions comprising CaTiO₃ compounds and Al₂O₃, MgO and/or MnS constituents. The inclusions comprise agglomerates in which the Al₂O₃, MgO and/or MnS constituents are incorporated into a matrix of the CaTiO₃ compound. The constituents of the inclusions are appropriately determined by REM-EDX (energy-dispersive x-ray spectroscopy in the scanning electron microscope).

The inclusions are appropriately present in a particle size of 0.5-5 μm.

Because of the agglomerates, the number of nonmetallic inclusions in the size range from 0.5 to 2 μm that are formed from the Al₂O₃, MgO and MnS constituents and are not incorporated into the agglomerates of the CaTiO₃ compound is considerably reduced and bound in few relatively large inclusions having sizes of 2 to 5 μm that are formed by the agglomerates of the CaTiO₃ compound.

In a particularly preferred embodiment of the invention, the ratio of the density of particles of nonmetallic inclusions of size 0.5 to 2 μm to the density of particles of nonmetallic inclusions of size 2 to 5 μm is less than 5, preferably less than 3.

The steel appropriately takes the form of a cast and preferably rolled semifinished product, preferably of a slab or a sheet.

In a particularly preferred embodiment of the invention, the steel is a welded construction steel, especially a steelwork construction steel and/or offshore construction steel, more preferably of a wind turbine. It is preferably part of a footing of an offshore wind turbine or an oil rig.

The steel is appropriately employed in a welded construction, especially a steelwork construction and/or offshore construction, preferably in a wind turbine.

The specified process for producing the steel is characterized by a process regime in which Si deoxidation is effected. The steel is appropriately cast by the continuous casting method. A semifinished product formed thereby, especially a slab, is preferably subjected to thermomechanical rolling.

In one embodiment of the invention, casting is effected in such a way that the semifinished product, especially the slab, is formed with a thickness of 300-600 mm, preferably of 450-550 mm. The semifinished product, especially the slab, is preferably formed with a length of 1000-5200 mm, more preferably of 2000-4500 mm.

Appropriately, the semifinished product, especially the slab, is reheated in a furnace to a temperature greater than the NbC solubility temperature. It is preferably reheated to a temperature between 1100 and 1250° C., preferably between 115° and 1200° C.

In one configuration of the invention, the semifinished product formed, especially the slab, is subjected to thermomechanical rolling in at least two rolling phases, where the degree of forming after the first rolling phase is preferably >0.20, more preferably >0.25.

A final rolling temperature is appropriately 750 to 850° C.

Preference is given to rolling to a final thickness of 60 to 200 mm, preferably 65 to 150 mm, more preferably 70 to 120 mm.

After rolling, in one embodiment of the invention, accelerated cooling is effected with a cooling rate of at least 2 K/s. Cooling is appropriately effected at the cooling rate to a temperature of at most 600° C., if appropriate down to room temperature.

In one configuration of the invention, the semifinished product formed, especially a sheet rolled from the slab, is welded, preferably while retaining sufficiently high notch impact resistance, especially the above-mentioned notch impact energy values. Welding is appropriately effected with an energy input of up to 30 KJ/mm, preferably an energy input of >3.5 KJ/mm, preferably >7 KJ/mm, more preferably an energy input of >15 kJ/mm. The semifinished product formed is of particularly good suitability in accordance with the invention even for welding with an energy input of >20 KJ/mm, especially >25 KJ/mm.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure.

EXAMPLES

The invention is elucidated in detail hereinafter by working examples and the appended tables.

Table 1 shows the composition of inventive steels A, B, C and D. Steels E, F and G have a conventional composition and serve as reference. The compositions are reported in % by weight.

Table 2 gives the rolling parameters with which the steels have been produced.

Mechanical properties of the sheets produced, namely results from tensile tests, hardness measurements, notch impact bending tests and for fracture mechanics (Crack Tip Opening Displacement, CTOD) are shown in table 3.

In order to test the steels, deposit welts have been conducted on steel sheets having a thickness of 80 mm. A submerged arc welding machine with which the real welds (deposit welts and multipass welds) have been conducted is composed of several components: a UniWeld welding unit with Subarc-5 controller as submerged-arc twin-head welding system with the power sources 1× OERLIKON TRE1004 AC and 1× SAF Starmatic 1000DC. The welds were performed with the OE SD3 electrode and the OP 121TT powder (both from LincolnElectric).

Table 4 shows results from a Charpy notch impact test according to DIN EN ISO 148-1, done as a standard test by pendulum impact instrument for determination of notch impact energy.

The notch impact test was conducted on a sheet metal surface at a fusion line of a weld seam of a deposit weld, in each case at −40° C. at different energy inputs that are stated in kJ/mm.

The energy input has been determined by means of the above formula 1. In the case of submerged arc welding, for example, the thermal efficiency is k=1.

For the sheets made from melt A, produced according to rolled plate 2, and for those made from melt E, produced according to rolled plate 9, several single-pass deposit welds have been undertaken with the different energy inputs given in table 4. Three measurements have been undertaken, the respective individual values from which are reported, and the average of the respective individual values is given.

The results show that the notch impact energies of the welded sheet that has been formed from the inventive melt A are much higher than those for the sheet made from reference melt E. The differences in the notch impact energies between the sheet made from the inventive steel compared to those made from the reference steel increase with rising energy input in the welding operation.

Table 5 shows results from notch impact bending tests on sheets with real multipass welds having an energy input of 5 kJ/mm along a weld seam formed in the multipass welding operations in the middle of the sheet at −80° C. Notch impact bending tests have been conducted on a sheet that has been produced from inventive melt A according to the rolled plate 2 and on a sheet of reference melt G that has been produced according to the rolled plate 10. The notch impact energies which for the sheet that has been produced from the inventive steel are much higher than those for the sheet made from the reference steel.

Table 5 also shows results of notch impact bending tests on sheets with real multipass welds having an energy input of 7 kJ/mm along a weld seam formed in the multipass welding operations in the middle of the sheet at −80° C. Notch impact bending tests have been conducted on a sheet that has been produced from inventive melt B according to the rolled plate 5 and on a sheet of reference melt F that has been produced according to the rolled plate 10. In the case of an energy input of 7 kJ/mm too, it is found that the notch impact energies which for the sheet that has been produced from the inventive steel are much higher than those for the sheet made from the reference steel.

Further notch impact energies were determined by a physical welding simulation of the coarse grain zone elucidated hereinafter.

In order to perform the Charpy notch impact test according to standard DIN EN ISO 148-1 on a material treated by a physical welding simulation, first of all, a sample blank having a length of at least 55 mm in the transverse direction of the sheet and a cross-sectional area of 10 mm×10 mm (rolling direction×normal direction) was taken from the layer of 1/4 sheet thickness of the material under examination. The welding simulations were effected with a Gleeble 3800 hot forming simulator and the QuickSim 2 software (version 2.5.8011.33152). For preparation, in the case of these notch impact blanks (normal sample without notch), a thermocouple pair was mounted by point welding methods on a lateral face at a distance of 27.5 mm from the end face. The samples thus prepared were inserted into the hot forming simulator and clamped with minimal stress between the copper dies provided for the purpose, and centered at the position of the thermocouple. During the experiment, the flow of current necessary for resistance heating was provided through these dies, and closed-loop control was exerted via the welded-on thermocouples.

The temperature regime corresponding to the respective welding process was determined by the abovementioned integrated calculation method according to Hannerz (formula 4).

The input parameters chosen for T_max=1350° C. (second cycle 775° C. or 750° C.) were T₀=100° C. and ta/s=40 s, 60 s, 200 s, 300 s or 500 s (then correspondingly proportionally if the second cycle is at T_max <800° C.). Closed-loop control upon cooling was effected at least down to a temperature of 350° C. After the welding simulation, the thermocouples were removed, a 2 mm-deep V-shaped notch was introduced at that point, and the length of the samples was shortened if necessary to 55 mm.

Finally, the weld-simulated samples were tested as standard by means of the pendulum tester to ascertain the notch impact energy.

The values given below for the energy inputs are based on a treatment by physical welding simulation of the coarse grain zone by conversion of the desired energy input to a 18/5 time using the formulae 2 and 3 shown above.

The preheating temperature T_V is appropriately assumed to be 200° C., and a welding factor of 0.9 (F₁ and F₂) for the simulation of a multipass weld. The sheet thickness d envisaged was 80 mm.

Tables 6 and 7 give results of notch impact bending tests on various sheets that have been produced from melts A to G and according to various ones of the rolled plates 1 to 11 and have been treated as elucidated above for welding simulation.

Table 6 shows the notch impact bending test results

• • with a 18/5 time of 500 s, corresponding to an energy input of 35 kJ/mm, for a cycle at 1350° C.,
  • with a 18/5 time of 300 s, corresponding to an energy input of 27 KJ/mm, for a cycle at 1350° C.,
  • with a 18/5 time of 200 s, corresponding to an energy input of 22 KJ/mm, both for one cycle at 1350° C. and for two cycles, with the first cycle conducted at 1350° C. and the second cycle at 775° C.

Table 7 shows the notch impact bending test results

• • with a 18/5 time of 60 s, corresponding to an energy input of 7 KJ/mm, both for one cycle at 1350° C. and for two cycles, with the first cycle conducted at 1350° C. and the second cycle at 750° C., and
  • with a 18/5 time of 40 s, corresponding to an energy input of 5 KJ/mm, both for one cycle at 1350° C. and for two cycles, with the first cycle conducted at 1350° C. and the second cycle at 775° C.

For the sheets that have been produced from the inventive steels, considerably greater notch impact energies are found for all energy inputs, both for one and for two cycles and for the averages from the tests.

Results of microstructure analyses are shown in table 8. The proportion of large-angle grain boundaries of the sheets made from the inventive steels, apart from the sheet made from melt C according to rolled plate 6, is lower than in the case of the sheets made from the reference steels, but >50% for all sheets. Moreover, the particle density of particles having a diameter of 0.5 μm-2 μm for the sheets made from the inventive steels is smaller than in the case of those made from the reference steels, and the particle density of particles having a diameter of 2 μm-5 μm in the case of the sheets made from the inventive steels is greater than in the case of those made from the reference steels. Accordingly, the ratio of the particle densities of particles having a diameter of 0.5 μm-2.0 μm to those having a diameter of 2 μm-5 μm for the sheets made from the inventive steels is smaller than for those made from the reference steels. These results show that, in the case of the sheets made from the inventive steel, because of the agglomerates, the number of nonmetallic inclusions in the size range of 0.5 to 2 μm that are formed from the Al₂O₃, MgO and MnS constituents and not incorporated into the agglomerates formed from the CaTiO₃ compound is reduced.

	TABLE 1
	C	Si	Mn	P	S	N	Al	Cu	Mo	Ni	Cr	V	Nb	Ti	Ca	O	Mg

A	0.046	0.056	1.46	0.009	0.0015	0.0020	0.002	0.03	0.01	0.07	0.04	0.001	0.018	0.008	0.0021	0.0017	—
B	0.050	0.034	1.48	0.010	0.0017	0.0024	0.001	0.03	0.01	0.05	0.03	0.002	0.017	0.009	0.0020	0.0024	0.0002
C	0.053	0.029	1.46	0.011	0.0019	0.0032	0.001	0.02	—	0.04	0.03	0.001	0.015	0.006	0.0014	0.0012	—
D	0.047	0.068	1.46	0.010	0.0008	0.0022	0.002	0.03	0.01	0.05	0.03	—	0.019	0.010	0.0020	0.0018	—
E	0.059	0.356	1.45	0.012	0.0006	0.0036	0.032	0.03	0.01	0.04	0.03	0.001	0.016	0.002	0.0017	0.0002	—
F	0.063	0.354	1.34	0.012	0.0012	0.0053	0.034	0.02	0.01	0.02	0.03	0.001	0.014	0.003	0.0020	0.0004	0.0011
G	0.056	0.414	1.59	0.013	0.0010	0.0044	0.033	0.27	0.02	0.52	0.23	0.001	0.001	0.008	0.0028	0.0004	—

	TABLE 2
	Dimensions in mm	Temperatures in ° C.

Number of

Finish

Slab

Interphase

Rolling

Cooling

Rolled

rolling

Exit

Interphase

phase

End

temper-

start

end temper-

Cooling

speed in

Melt

plate

phases

thickness

thickness

thickness

thickness

Length

Width

ature

ature

end

° C./s

A	1	3	490	215	145	80	13994	2199	1161	876	786	RT	—
A	2	3	490	215	145	80	13898	2199	1166	853	794	418	3.55
B	3	3	490	215	145	80	16612	2199	1180	871	788	453	3.36
B	4	3	490	215	145	80	16587	2199	1191	873	787	441	3.44
B	5	2	490	—	145	80	16625	2199	1203	—	791	423	3.38
B	6	2	490	—	145	80	16312	2199	1177	—	788	419	3.43
C	7	2	490	—	145	80	14216	2199	1219	—	786	430	3.52
D	8	2	490	—	145	80	14130	2199	1192	—	767	409	3.45
E	9	3	340	193	136	90	11187	3092	1146	866	797	506	3.07
F	10	2	390	—	157	80	24514	2205	1126	—	775	496	2.66
G	11	3	290	175	122	65	12055	2215	1083	804	769	463	6.73
indicates data missing or illegible when filed

	TABLE 3
	Notch impact bending test
	Quarter of sheet	CTOD

		Indiv.	Indiv.	Indiv.	Indiv.	Indiv.	Indiv.
	Hardness	value 1	value 2	value 3	value 1	value 2	value 3

Rolled

Transverse tensile test

HV10

−50° C.

−50° C.

−50° C.

−60° C.

−60° C.

−60° C.

Melt	plate	Rp0.2	Rm	A5	Averages	long.	long.	long.	transv.	transv.	transv.

A	1	390	484	29.2	156.7	348	349	350	2.98	2.92	—
A	2	385	471	31.0	150.8	366	367	369	2.88	2.64	—
B	3	384	471	30.8	163.8	309	327	329	0.77	0.57	0.85
B	4	388	472	28.6	168.3	356	362	364	0.90	0.91	1.06
B	5	392	476	28.3	160.0	308	323	325	0.90	0.42	0.91
B	6	391	475	28.8	165.5	356	360	375	0.97	1.02	0.99
C	7	394	468	33.8	149.3	309	321	323	0.71	0.71	0.71
D	8	393	476	32.9	148.3	347	353	353	1.06	0.58	0.47
E	9	408	499	27.1	—	308	324	324	—	—	—
F	10	383	490	32.9	168.3	293	295	306	1.08	2.07	1.62
G	11	428	524	31.3	—	—	—	—	—	—	—

TABLE 4
		1-pass deposit weld	1-pass deposit weld
		16 kJ/mm	12 kJ/mm
		Notch impact bending test	Notch impact bending test
		Sheet surface - Melt line	Sheet surface - Melt line

		Indiv. value 1	Indiv. value 2	Indiv. value 3	Average	Indiv. value 1	Indiv. value 2	Indiv. value 3	Average
	Rolled	−40° C.	−40° C.	−40° C.	−40° C.	−40° C.	−40° C.	−40° C.	−40° C.
	plate	transv.	transv.	transv.	transv.	transv.	transv.	transv.	transv.
A	2	203	132	179	171.3	174	161	181	172.0
E	9	50	51	53	51.3	58	51	169	92.7

		1-pass deposit weld	1-pass deposit weld
		8 kJ/mm	4 kJ/mm
		Notch impact bending test	Notch impact bending test
		Sheet surface - Melt line	Sheet surface - Melt line

		Indiv. value 1	Indiv. value 2	Indiv. value 3	Average	Indiv. value 1	Indiv. value 2	Indiv. value 3	Average
		−40° C.	−40° C.	−40° C.	−40° C.	−40° C.	−40° C.	−40° C.	−40° C.
		transv.	transv.	transv.	transv.	transv.	transv.	transv.	transv.
	A	172	204	69	148.3	218	44	158	140.0
	E	78	69	76	74.3	80	52	116	82.7
	indicates data missing or illegible when filed

	TABLE 5
	Real multipass weld	Real multipass weld
	7 kJ/mm	5 kJ/mm
	Notch impact bending test	Notch impact bending test
	Middle of sheet - Melt line	Middle of sheet - Melt line

		Indiv.	Indiv.	Indiv.		Indiv.	Indiv.	Indiv.
		value 1	value 2	value 3	Average	value 1	value 2	value 3	Average
	Rolled	−80° C.	−80° C.	−80° C.	−80° C.	−80° C.	−80° C.	−80° C.	−80° C.
Melt	plate	transv	transv.	transv.	transv.	transv	transv.	transv.	transv.

A	2	—	—	—	—	135	197	178	170.0
B	5	188	214	191	197.7	—	—	—	—
F	10	16	17	8	13.7	—	—	—	—
G	11	—	—	—	—	132	16	70	72.7

TABLE 6
		Gleeble: 1 cycle (1350° C.)	Gleeble: 1 cycle (1350° C.)
		t8/5 = 500 s --> 35 kJ/mm	t8/5 = 300 s --> 27 kJ/mm
		Notch impact bending test	Notch impact bending test
		Quarter of sheet - CG-HAZ simulation	Quarter of sheet - CG-HAZ simulation

		Indiv. value 1	Indiv. value 2	Indiv. value 3	Average	Indiv. value 1	Indiv. value 2	Indiv. value 3	Average
	Rolled	−40° C.	−40° C.	−40° C.	−40° C.	−40° C.	−40° C.	−40° C.	−40° C.
Melt	plate	transv.	transv.	transv.	transv.	transv.	transv.	transv.	transv.
A	1	—	—	—	—	—	—	—	—
A	2	—	—	—	—	—	—	—	—
B	3	—	—	—	—	—	—	—	—
B	4	—	—	—	—	—	—	—	—
B	5	22	23	16	20.3	12	266	23	100.3
B	6	—	—	—	—	—	—	—	—
C	7	9	17	9	11.7	—	—	—	—
D	8	10	19	14	14.3	8	182	245	145.0
E	9	—	—	—	—	—	—	—	—
F	10	—	—	—	—	—	—	—	—
G	11	—	—	—	—	—	—	—	—

		Gleeble: 1 cycle (1350° C.)	Gleeble: 2 cycles (1350° C., 775° C.)
		t8/5 = 200 s --> 22 kJ/mm	t8/5 = 200 s --> 22 kJ/mm
		Notch impact bending test	Notch impact bending test
		Quarter of sheet - CG-HAZ simulation	Quarter of sheet - ICRCG-HAZ simulation

		Indiv. value 1	Indiv. value 2	Indiv. value 3	Average	Indiv. value 1	Indiv. value 2	Indiv. value 3	Average
	Rolled	−40° C.	−40° C.	−40° C.	−40° C.	−20° C.	−20° C.	−20° C.	−20° C.
Melt	plate	transv.	transv.	transv.	transv.	transv.	transv.	transv.	transv.
A	1	239	242	259	246.7	243	220	215	226.0
A	2	275	245	230	250.0	367	322	367	352.0
B	3	223	9	237	156.3	269	9	7	95.0
B	4	—	—	—	—	11	256	231	166.0
B	5	15	254	232	167.0	242	279	8	176.3
B	6	300	12	8	106.7	7	23	363	131.0
C	7	207	13	29	83.0	239	288	208	245.0
D	8	20	244	262	175.3	307	219	258	261.3
E	9	26	16	7	16.3	75	121	136	110.7
F	10	7	8	192	69.0	13	180	105	99.3
G	11	12	10	16	12.7	19	23	21	21.0

TABLE 7
		Gleeble: 1 cycle (1350° C.)	Gleeble: 2 cycles (1350° C., 750° C.)
		t8/5 = 60 s --> 7 kJ/mm	t8/5 = 60 s --> 7 kJ/mm
		Notch impact bending test	Notch impact bending test
		Quarter of sheet - CG-HAZ simulation	Quarter of sheet - ICRCG-HAZ simulation

		Indiv.	Indiv.	Indiv.		Indiv.	Indiv.	Indiv.
		value 1	value 2	value 3	Average	value 1	value 2	value 3	Average
	Rolled	−40° C.	−40° C.	−40° C.	−40° C.	−20° C.	−20° C.	−20° C.	−20° C.
Melt	plate	transv.	transv.	transv.	transv.	transv.	transv.	transv.	transv.
A	1	—	—	—	—	—	—	—	—
A	2	—	—	—	—	—	—	—	—
B	5	276	328	9	204.3	343	366	364	357.7
E	9	—	—	—	—	—	—	—	—
F	10	22	15	20	19.0	301	18	14	111.0
G	11	65	71	175	103.7	—	—	—	—

		Gleeble: 1 cycle (1350° C.)	Gleeble: 2 cycles (1350° C., 775° C.)
		t8/5 = 40 s --> 5 kJ/mm	t8/5 = 40 s --> 5 kJ/mm
		Notch impact bending test	Notch impact bending test
		Quarter of sheet - CG-HAZ simulation	Quarter of sheet - ICRCG-HAZ simulation

		Indiv.	Indiv.	Indiv.		Indiv.	Indiv.	Indiv.
		value 1	value 2	value 3	Average	value 1	value 2	value 3	Average
	Rolled	−40° C.	−40° C.	−40° C.	−40° C.	−20° C.	−20° C.	−20° C.	−20° C.
Melt	plate	transv.	transv.	transv.	transv.	transv.	transv.	transv.	transv.
A	1	327	317	329	324.3	—	—	—	—
A	2	313	313	312	312.7	273	263	366	300.7
B	5	—	—	—	—	—	—	—	—
E	9	37	57	27	40.3	240	18	33	97.0
F	10	—	—	—	—	—	—	—	—
G	11	—	—	—	—	—	—	—	—

TABLE 8
							Ratio of particle
			Average grain	High-angle	Particle	Particle	densities
		Grain size	size in μm	grain boundaries	density mm−1	density mm−1	0.5 μm < d ≤ 2.0 μm
	Rolled	class	5° area fraction	proportion in %	0.5 μm < d ≤ 2.0 μm	2.0 μm < d ≤ 5.0 μm	divided by
Melt	plate	Light microscope	EBSD	EBSD	AsB + EDX	AsB + EDX	2.0 μm < d ≤ 5.0 μm

A	1	10.5	13.52	54.2	22.1	23.0	0.96
A	2	10.5	12.83	65.0	26.6	14.5	1.83
B	3	10.5	12.60	66.2	37.5	20.6	1.82
B	4	11	12.61	63.7	40.6	19.1	2.13
B	5	10.5	12.98	66.5	22.3	17.7	1.26
B	6	11	13.25	65.5	36.9	20.3	1.82
C	7	9	12.79	77.2	22.4	20.3	1.10
D	8	9.5	11.98	66.2	20.6	17.9	1.15
E	9	11	17.70	69.1	70.2	4.8	14.63
F	10	10.5	12.46	81.0	62.8	7.6	8.26
G	11	10.5	9.13	74.2	121.4	6.7	18.12