LOW-LEAD BRASS ALLOY

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Chinese patent application No. 201410247387.0, filed on Jun. 5, 2014. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a low-lead brass alloy, and particularly to a low-lead free-cutting brass alloy.

2. Background of the Invention

Copper has excellent electrical conductivity and environmental friendliness, and bacteria harmful to the human can't survive on its surface. Other elements are added into copper, so as to improve its performance. For example, the addition of lead into the brass alloy containing copper and zinc significantly improves the cutting performance of the brass. However, brass with a high lead content will pollute the environment during its application. Especially in various valves, faucets, or the like for a water supply system, lead tends to dissolve in the water, which has serious damage to human health.

In addition, the environmental problem is increasingly outstanding, and the working environment is becoming more serious. As a result, the surface strength of brass products is reduced, and the brass tube may even perforate. This greatly reduces the lifetime of brass products and causes problems in application.

Therefore, there is a need to provide an alloy formula for solving the above problems, which can replace the brass with a high lead content, is dezincification corrosion resistant, and further has excellent casting performance, forgeability, cutting performance, corrosion resistance and mechanical properties.

BRIEF SUMMARY OF THE INVENTION

It is an object of the invention to provide a brass alloy which exhibits excellent performance like tensile strength, elongation rate, dezincification resistance and cutting performance, which is suitable for cutting processed products that require high strength and wear resistance. The brass alloy of the invention can securely replace the alloy copper with a high lead content, and can completely meet the demands about restrictions on lead-containing products in the development of human society.

To achieve the above object, the inventors have proposed the following low-lead brass alloy.

A low-lead brass alloy (hereinafter referred to as the inventive product 1) comprises: by the total weight of the brass alloy, 59-61 wt % copper, 0-0.1 wt % lead, 0.5-1.3 wt % bismuth, and a balance of zinc.

In the inventive product 1, the content of lead is reduced to 0.1 wt % or less, the content of copper is maintained at 59-61 wt %, and bismuth is added to form cutoff points in the alloy structure, thus increasing cutting performance of the brass alloy. On one hand, bismuth can not play its role effectively if the content of bismuth is relatively low. On the other hand, thermal cracking is prone to occur during forging of the brass alloy when the content of bismuth is relatively high, which is not conducive for producing. Thus, the content of bismuth is maintained at 0.5-1.3 wt %.

A low-lead brass alloy (hereinafter referred to as the inventive product 2) comprises: by the total weight of the brass alloy, 59-61 wt % copper, 0-0.1 wt % lead, 0.5-1.3 wt % bismuth, one or more elements selected from the group consisting of 0-0.1 wt % iron, 0-0.05 wt % aluminum, 0-0.2 wt % tin, and 0-0.3 wt % nickel by the total weight of the brass alloy, and a balance of zinc.

As compared with the inventive product 1, the inventive product 2 is further added with 0-0.1 wt % iron, 0-0.05 wt % aluminum, 0-0.2 wt % tin, and/or 0-0.3 wt % nickel. Iron is added for the purpose of enhance toughness of the alloy. Aluminum and tin are added for the purpose of further improving cutting performance of the alloy. Besides, aluminum can also increase strength, wear resistance, cast flowability, and oxidation resistance at high temperature of the alloy. Nickel can prevent the alloy from rusting. It is noted that a relatively high content of iron, aluminum, tin, and nickel will affect polishing performance of the alloy. Therefore, in order to produce a brass alloy with excellent performance, the content of iron, aluminum, tin, and nickel is 0.1 wt %, 0.05 wt %, 0.2 wt %, and 0.3 wt % or less, respectively. Whether iron, aluminum, tin, and nickel is added depends on the requirements for performance during actual production.

Preferably, in the inventive product 2, a total content of iron, aluminum, tin, and/or nickel is not less than 0.1 wt % by the total weight of the brass alloy, thus producing the inventive product 3.

More preferably, a total content of iron, aluminum, tin, and/or nickel is not more than 0.5 wt % by the total weight of the brass alloy, thus producing the inventive product 4.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The technical solutions of the invention will be described expressly by referring to embodiments thereof.

It is not intended to limit the scope of the invention to the described exemplary embodiments. The modifications and alterations to features of the invention as described herein, as well as other applications of the concept of the invention (which will occur to the skilled in the art, upon reading the present disclosure) still fall within the scope of the invention.

In the invention, the wording “or more”, “or less” in the expression for describing values indicates that the expression comprises the relevant values.

The term “and/or” as used herein should be read as “any one or more” of the elements which are connected with this term. Namely, in some case these elements can exist separately.

The dezincification corrosion resistant performance measurement, as used herein, is performed according to AS-2345-2006 specification in the cast state, in which 12.8 g copper chloride is added into 1000 C.C deionized water, and the object to be measured is placed in the resulting solution for 24 hr to measure a dezincification depth.

⊚ indicates a dezincification depth of less than 350 μm; ◯ indicates a dezincification depth between 350 μm and 400 μm; and x indicates a dezincification depth larger than 400 μm.

The cutting performance measurement, as used herein, is performed in the cast state, in which the same cutting tool is adopted with the same cutting speed and feed amount. The cutting speed is 25 m/min (meter per minute), the feed amount is 0.2 mm/r (millimeter per number of cutting edge), the cutting depth is 0.5 mm, the measurement rod has a diameter of 20 mm, and C36000 alloy is taken as a reference. The relative cutting rate is derived by measuring the cutting resistance.

The relative cutting rate=cutting resistance of C36000 alloy/cutting resistance of the sample.

⊚ indicates a relative cutting rate larger than 85%; and ◯ indicates a relative cutting rate larger than 70%.

Both the tensile strength measurement and the elongation rate measurement, as used herein, are performed in the cast state at room temperature as an elongation measurement. The elongation rate refers to a ratio between the total deformation of gauge section after elongation ΔL and the initial gauge length L of the sample in percentage: δ=ΔL/L×100%. The reference sample is a lead-containing brass with the same state and specification, i.e., C36000 alloy.

According to measurement, the proportions for constituents of C36000 alloy mentioned above are listed as follow, in the unit of weight percentage (wt %):

	copper	zinc	bismuth	antimony	manganese	aluminum	tin	lead	iron
Material No.	(Cu)	(Zn)	(Bi)	(Sb)	(Mn)	(Al)	(Sn)	(Pb)	(Fe)
C36000 alloy	60.53	36.26	0	0	0	0	0.12	2.97	0.12

Embodiment 1

Table 1-1 lists inventive products 1 with 5 different constituents, which are respectively numbered as 1001-1005, each constituent being in the unit of weight percentage (wt %).

TABLE 1-1
No.	copper (Cu)	zinc (Zn)	lead (Pb)	bismuth (Bi)
1001	59.650	39.653	0.055	0.640
1002	60.305	39.093	0.100	0.500
1003	61.000	37.748	0.000	1.250
1004	59.000	39.618	0.080	1.300
1005	60.032	39.028	0.093	0.845

Measurements about cutting performance, dezincification corrosion resistant performance, tensile strength, and elongation rate are performed on alloys with the above constituents in the cast state at room temperature, and the reference sample is a lead-containing brass with the same state and specification, i.e., C36000 alloy.

Results of the measurements about tensile strength, elongation rate, cutting performance, and dezincification corrosion resistant performance are listed as follow:

	TENSILE	ELON-		RELATIVE
	STRENGTH	GATION	DEZINCIFICATION	CUTTING
No.	(N/mm2)	RATE (%)	LAYER	RATE

1001	297	10	⊚	⊚
1002	308	11	⊚	⊚
1003	293	10	⊚	⊚
1004	317	12	⊚	⊚
1005	310	12	⊚	⊚
C36000	394	9	◯	⊚
alloy

Embodiment 2

Table 2-1 lists inventive products 2 with 5 different constituents, which are respectively numbered as 2001-2005, each constituent being in the unit of weight percentage (wt %).

TABLE 2-1
				bis-		alu-
	copper	zinc	lead	muth	iron	minum	tin	Nickel
No.	(Cu)	(Zn)	(Pb)	(Bi)	(Fe)	(AL)	(Sn)	(Ni)
2001	60.340	38.858	0.100	0.500	0.000	0.050	0.150	0.000
2002	59.000	39.684	0.085	0.854	0.100	0.020	0.000	0.255
2003	60.221	38.286	0.000	1.110	0.051	0.000	0.200	0.130
2004	59.870	32.662	0.013	1.300	0.085	0.000	0.132	0.300
2005	61.000	37.438	0.050	0.995	0.080	0.040	0.143	0.252

Measurements about cutting performance, dezincification corrosion resistant performance, tensile strength, and elongation rate are performed on alloys with the above constituents in the cast state at room temperature, and the reference sample is a lead-containing brass with the same state and specification, i.e., C36000 alloy.

Results of the measurements about tensile strength, elongation rate, cutting performance, and dezincification corrosion resistant performance are listed as follow:

	TENSILE	ELON-		RELATIVE
	STRENGTH	GATION	DEZINCIFICATION	CUTTING
No.	(N/mm2)	RATE (%)	LAYER	RATE

2001	318	11	⊚	⊚
2002	307	12	⊚	⊚
2003	300	11	⊚	⊚
2004	299	10	⊚	⊚
2005	308	10	⊚	⊚
C36000	394	9	◯	⊚
alloy

Embodiment 3

Table 3-1 lists inventive products 3 with 5 different constituents, which are respectively numbered as 3001-3005, each constituent being in the unit of weight percentage (wt %).

TABLE 3-1
				bis-		alu-
	copper	Zinc	Lead	muth	Iron	minum	Tin	Nickel
No.	(Cu)	(Zn)	(Pb)	(Bi)	(Fe)	(AL)	(Sn)	(Ni)
3001	59.145	39.963	0.000	0.670	0.000	0.050	0.155	0.015
3002	59.000	40.104	0.006	0.500	0.054	0.034	0.000	0.300
3003	60.240	38.370	0.065	1.112	0.011	0.000	0.200	0.000
3004	61.000	37.081	0.100	1.300	0.100	0.050	0.112	0.255
3005	60.081	38.327	0.073	1.000	0.095	0.025	0.181	0.216

Measurements about cutting performance, dezincification corrosion resistant performance, tensile strength, and elongation rate are performed on alloys with the above constituents in the cast state at room temperature, and the reference sample is a lead-containing brass with the same state and specification, i.e., C36000 alloy.

Results of the measurements about tensile strength, elongation rate, cutting performance, and dezincification corrosion resistant performance are listed as follow:

	TENSILE	ELON-		RELATIVE
	STRENGTH	GATION	DEZINCIFICATION	CUTTING
No.	(N/mm2)	RATE (%)	LAYER	RATE

3001	295	10	⊚	⊚
3002	309	11	⊚	⊚
3003	308	10	⊚	⊚
3004	319	12	⊚	⊚
3005	320	12	⊚	⊚
C36000	394	9	◯	⊚
alloy

Embodiment 4

Table 4-1 lists inventive products 4 with 5 different constituents, which are respectively numbered as 4001-4005, each constituent being in the unit of weight percentage (wt %).

TABLE 4-1
				bis-		alu-
	copper	zinc	Lead	muth	Iron	minum	Tin	Nickel
No.	(Cu)	(Zn)	(Pb)	(Bi)	(Fe)	(AL)	(Sn)	(Ni)
4001	60.145	38.496	0.043	0.855	0.044	0.000	0.200	0.215
4002	61.000	38.039	0.000	0.500	0.100	0.004	0.055	0.300
4003	59.855	39.023	0.050	0.950	0.070	0.050	0.000	0.000
4004	59.000	39.368	0.032	1.300	0.085	0.013	0.100	0.100
4005	60.050	38.644	0.100	1.000	0.000	0.011	0.088	0.105

Measurements about cutting performance, dezincification corrosion resistant performance, tensile strength, and elongation rate are performed on alloys with the above constituents in the cast state at room temperature, and the reference sample is a lead-containing brass with the same state and specification, i.e., C36000 alloy.

Results of the measurements about tensile strength, elongation rate, cutting performance, and dezincification corrosion resistant performance are listed as follow:

	TENSILE	ELON-		RELATIVE
	STRENGTH	GATION	DEZINCIFICATION	CUTTING
No.	(N/mm2)	RATE (%)	LAYER	RATE

4001	302	29	⊚	⊚
4002	310	19	⊚	⊚
4003	303	10	⊚	⊚
4004	318	12	⊚	⊚
4005	319	11	⊚	⊚
C36000	394	9	◯	⊚
alloy

Although the invention has been described with respect to embodiments thereof, these embodiments do not intend to limit the invention. The ordinary skilled in the art can made modifications and changes to the invention without departing from the spirit and scope of the invention. Thus, the protection of the invention is defined by the appended claims.