CA2678074C - Dezincification-resistant copper alloy and method for producing product comprising the same - Google Patents
Dezincification-resistant copper alloy and method for producing product comprising the same Download PDFInfo
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Abstract
A dezincification-resistant copper alloy and a method for producing a product comprising the same are proposed by the present invention. The dezincification-resistant alloy of the present invention consists of 59.5 to 4 wt% of copper (Cu); 0.3 to 0.5 wt% of bismuth (Bi); 0.08 to 0.16 wt% of arsenic (As); 5 to 15 ppm of boron (B); 0.3 to 1.5 wt%
of tin (Sn); 0.1 to 0.7 wt% of zirconium (Zr); less than 0.05 wt% of lead (Pb); and zinc (Zn) in balance. The dezincification-resistant copper alloy of the present invention has excellent casting properties, good toughness and machinability, and can be corrosion-resistant. Thus, the alloy can reduce dezincification on the surfaces thereof.
of tin (Sn); 0.1 to 0.7 wt% of zirconium (Zr); less than 0.05 wt% of lead (Pb); and zinc (Zn) in balance. The dezincification-resistant copper alloy of the present invention has excellent casting properties, good toughness and machinability, and can be corrosion-resistant. Thus, the alloy can reduce dezincification on the surfaces thereof.
Description
DEZINCIFICATION-RESISTANT COPPER ALLOY AND METHOD FOR
PRODUCING PRODUCT COMPRISING THE SAME
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to dezincification-resistant copper alloys methods for producing a product comprising the same, and more particularly, to a dezincification-resistant low lead brass alloy and a method for producing a product 4.4 comprising the same.
PRODUCING PRODUCT COMPRISING THE SAME
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to dezincification-resistant copper alloys methods for producing a product comprising the same, and more particularly, to a dezincification-resistant low lead brass alloy and a method for producing a product 4.4 comprising the same.
2. Description of Related Art Brass comprises copper and zinc, as major ingredients, usually at a ratio of about 7:3 or 6:4. If the zinc content of brass exceeds 20 wt%, corrosion (such as dezincification) is likely to occur. For example, when a brass alloy article is employed in the environment, zinc present on the alloy surface is preferentially melted and copper contained in the alloy remains on the base metal, thereby causing corrosion in the form of porous, brittle copper. Generally, if the zinc content is less than 15 wt%, dezincification is not likely to occur. However, as the zinc content increases, the sensitivity to dezincification is increased. If the zinc content exceeds 30 wt%, dezincification corrosion is more apparent.
It has been reported in literatures that alloy compositions and environmental factors affect dezincification corrosion. In the context of alloy compositions, dezincification of brass with a single a phase and zinc content higher than 20 wt% gives porous copper, whereas dezincification of brass with double a+ji phases begins initially in 3 phase and later expands to a phase when 0 phase is completely converted into loosely-structured copper (referring to Kuaiji Wang et al., Chinese Journal of Materials Research, Vol.13, pages 1-8).
Because dezincification of brass severely damages the structures of brass alloys, the surface intensities of brass products produced from brass alloys are lowered such that porosity occurs on brass pipes. This significantly lowers the lifetimes of the brass products, thereby causing application problems. Particularly, under the conditions of a marine climate, the lifetimes of hot water products are directly affected.
Therefore, AS
2345, ISO 6509, etc. are used internationally by various countries to specify the dezincification resistance of brass products. Using the standard set forth in established in Australia as an example, the depth of a dezincification layer formed on the surface of a brass product shall not exceed 100 gm. However, there are also literatures reporting that common brass products are not likely to meet the high standard set forth in AS 2345 (referring to Casting Technology, 2007, volume 9, pages 1272-1274).
Hence, the industry continues to develop dezincification-resistant copper alloy.
Regarding the formulations of dezincification resistant brass alloys, with exceptions of copper and zinc as major ingredients, patents like US 4,417,929 discloses a formulation comprising iron, aluminum and silicon ingredients, US 5,507,885 and US
6,395,110 disclose formulations comprising phosphorus, tin and nickel ingredients, US
5,653,827 discloses a formulation comprising iron, nickel and bismuth ingredients, US
6,974,509 discloses a formulation comprising tin, bismuth, iron, nickel and phosphorus ingredients, US 6,787,101 discloses a formulation comprising phosphorus, tin, nickel, iron, aluminum, silicon and arsenic ingredients at the same time, and US
6,599,378 and US 5,637,160 discloses adding selenium and phosphorus ingredients in a brass alloy to achieve a dezincifying effect. CN 1906317 discloses a formulation comprising bismuth, tin, nickel and phosphorus ingredients. The alloy has excellent dezincification-resistant corrosion property even without performing a heat treatment, wherein specific conditions of the heat treatment are not disclosed. Alternately, there are also literatures disclosing adding boron, arsenic, etc. in a brass alloy to achieve a dezincifying effect (please refer to Kuaiji Wang et al., Chinese Journal of Materials Research, volume 13, pages 1-8).
Conventional dezincification-resistant brasses usually have higher lead contents (most in the range from 1 to 3 wt%), facilitating cold/thermal processing of brass materials. However, as the awareness of environmental protection increases and the impacts of heavy metals on human health and issues like environmental pollutions become major focuses, it is a tendency to restrict the usage of lead-containing alloys.
Various countries such as Japan, the United States of America, etc, have sequentially amended relevant regulations, putting intensive efforts to lower lead contents in the environment by particularly demanding that no molten lead shall leak from the lead-containing alloy materials used in products encompassing household electronic appliances, automobiles and water systems to drinking water and lead contamination shall be avoided during processing. Thus, the industry continues to develop a brass material, and to find an alloy formulation that can substitute for lead-containing brasses while possessing desirable properties like good casting and mechanical properties as well as corrosion resistance.
SUMMARY OF THE INVENTION
In order to attain the above, the present invention provides a dezincification-resistant copper alloy, consisting of 59.5 to 64 wt% of copper (Cu), 0.3 to 0.5 wt% of bismuth (Bi), 0.08 to 0.16 wt% of arsenic (As), 5 to 15 ppm of boron (B), 0.3 to 1.5 wta/o of tin (Sn), 0.1 to 0.7 wt% of zirconium (Zn), less than 0.05 wt% of lead (Pb)
It has been reported in literatures that alloy compositions and environmental factors affect dezincification corrosion. In the context of alloy compositions, dezincification of brass with a single a phase and zinc content higher than 20 wt% gives porous copper, whereas dezincification of brass with double a+ji phases begins initially in 3 phase and later expands to a phase when 0 phase is completely converted into loosely-structured copper (referring to Kuaiji Wang et al., Chinese Journal of Materials Research, Vol.13, pages 1-8).
Because dezincification of brass severely damages the structures of brass alloys, the surface intensities of brass products produced from brass alloys are lowered such that porosity occurs on brass pipes. This significantly lowers the lifetimes of the brass products, thereby causing application problems. Particularly, under the conditions of a marine climate, the lifetimes of hot water products are directly affected.
Therefore, AS
2345, ISO 6509, etc. are used internationally by various countries to specify the dezincification resistance of brass products. Using the standard set forth in established in Australia as an example, the depth of a dezincification layer formed on the surface of a brass product shall not exceed 100 gm. However, there are also literatures reporting that common brass products are not likely to meet the high standard set forth in AS 2345 (referring to Casting Technology, 2007, volume 9, pages 1272-1274).
Hence, the industry continues to develop dezincification-resistant copper alloy.
Regarding the formulations of dezincification resistant brass alloys, with exceptions of copper and zinc as major ingredients, patents like US 4,417,929 discloses a formulation comprising iron, aluminum and silicon ingredients, US 5,507,885 and US
6,395,110 disclose formulations comprising phosphorus, tin and nickel ingredients, US
5,653,827 discloses a formulation comprising iron, nickel and bismuth ingredients, US
6,974,509 discloses a formulation comprising tin, bismuth, iron, nickel and phosphorus ingredients, US 6,787,101 discloses a formulation comprising phosphorus, tin, nickel, iron, aluminum, silicon and arsenic ingredients at the same time, and US
6,599,378 and US 5,637,160 discloses adding selenium and phosphorus ingredients in a brass alloy to achieve a dezincifying effect. CN 1906317 discloses a formulation comprising bismuth, tin, nickel and phosphorus ingredients. The alloy has excellent dezincification-resistant corrosion property even without performing a heat treatment, wherein specific conditions of the heat treatment are not disclosed. Alternately, there are also literatures disclosing adding boron, arsenic, etc. in a brass alloy to achieve a dezincifying effect (please refer to Kuaiji Wang et al., Chinese Journal of Materials Research, volume 13, pages 1-8).
Conventional dezincification-resistant brasses usually have higher lead contents (most in the range from 1 to 3 wt%), facilitating cold/thermal processing of brass materials. However, as the awareness of environmental protection increases and the impacts of heavy metals on human health and issues like environmental pollutions become major focuses, it is a tendency to restrict the usage of lead-containing alloys.
Various countries such as Japan, the United States of America, etc, have sequentially amended relevant regulations, putting intensive efforts to lower lead contents in the environment by particularly demanding that no molten lead shall leak from the lead-containing alloy materials used in products encompassing household electronic appliances, automobiles and water systems to drinking water and lead contamination shall be avoided during processing. Thus, the industry continues to develop a brass material, and to find an alloy formulation that can substitute for lead-containing brasses while possessing desirable properties like good casting and mechanical properties as well as corrosion resistance.
SUMMARY OF THE INVENTION
In order to attain the above, the present invention provides a dezincification-resistant copper alloy, consisting of 59.5 to 64 wt% of copper (Cu), 0.3 to 0.5 wt% of bismuth (Bi), 0.08 to 0.16 wt% of arsenic (As), 5 to 15 ppm of boron (B), 0.3 to 1.5 wta/o of tin (Sn), 0.1 to 0.7 wt% of zirconium (Zn), less than 0.05 wt% of lead (Pb)
3 and zinc (Zn) in balance.
In the dezincification-resistant low lead brass alloy of the present invention, the copper content ranges from 59.5 to 64 wt%. In a preferred embodiment, the copper content ranges from 62 to 64 wt%. The range of the copper content can provide good toughness, so that subsequent processing of the alloy material is facilitated.
In the dezincification-resistant copper alloy of the present invention, the bismuth content ranges from 0.1 to 0.5 wt%. In a preferred embodiment, the bismuth content ranges from 0.3 to 0.5 wt%. Addition of bismuth is advantageous to maintenance of the machinability of brass.
In the dezincification-resistant copper alloy of the present invention, the arsenic content ranges from 0.08 to 0.16 wt%. In a preferred embodiment, the arsenic content ranges from 0.10 to 0.14 wt%. Addition of an adequate amount of arsenic can significantly increase the dezincification corrosion resistance of brass.
In the dezincification-resistant copper alloy of the present invention, the boron content ranges from 5 to 15 ppm. In a preferred embodiment, the boron content ranges from 7 to 13 ppm. Addition of an adequate amount of boron can refine the grains of the alloy material, thereby improving the properties of the alloy material.
In the dezincification-resistant copper alloy of the present invention, the tin content ranges from 0.3 to 1.5 wt%. In a preferred embodiment, the tin content ranges from 0.3 to 0.8 wt%. Addition of an adequate amount of tin can increase the intensity and the corrosion resistance of the alloy material.
In the dezincification-resistant copper alloy of the present invention, the zirconium content ranges from 0.1 to 0.7 wt%. In a preferred embodiment, the zirconium content ranges from 0.3 to 0.5 wt%. Addition of an adequate amount of zirconium can refine the grains of the alloy material, thereby increasing the mechanical property of the alloy
In the dezincification-resistant low lead brass alloy of the present invention, the copper content ranges from 59.5 to 64 wt%. In a preferred embodiment, the copper content ranges from 62 to 64 wt%. The range of the copper content can provide good toughness, so that subsequent processing of the alloy material is facilitated.
In the dezincification-resistant copper alloy of the present invention, the bismuth content ranges from 0.1 to 0.5 wt%. In a preferred embodiment, the bismuth content ranges from 0.3 to 0.5 wt%. Addition of bismuth is advantageous to maintenance of the machinability of brass.
In the dezincification-resistant copper alloy of the present invention, the arsenic content ranges from 0.08 to 0.16 wt%. In a preferred embodiment, the arsenic content ranges from 0.10 to 0.14 wt%. Addition of an adequate amount of arsenic can significantly increase the dezincification corrosion resistance of brass.
In the dezincification-resistant copper alloy of the present invention, the boron content ranges from 5 to 15 ppm. In a preferred embodiment, the boron content ranges from 7 to 13 ppm. Addition of an adequate amount of boron can refine the grains of the alloy material, thereby improving the properties of the alloy material.
In the dezincification-resistant copper alloy of the present invention, the tin content ranges from 0.3 to 1.5 wt%. In a preferred embodiment, the tin content ranges from 0.3 to 0.8 wt%. Addition of an adequate amount of tin can increase the intensity and the corrosion resistance of the alloy material.
In the dezincification-resistant copper alloy of the present invention, the zirconium content ranges from 0.1 to 0.7 wt%. In a preferred embodiment, the zirconium content ranges from 0.3 to 0.5 wt%. Addition of an adequate amount of zirconium can refine the grains of the alloy material, thereby increasing the mechanical property of the alloy
4 material.
The dezincification-resistant copper alloy of the present invention comprises an extremely low lead content (i.e., less than 0.05 wt%) or even no lead. As compared with conventional brass alloys, the lead content is substantially lowered, thereby facilitating environmental protection. The alloy can possibly have impurities therein. The content of the unavoidable impurities is less than 0.1 wt%.
The dezincification-resistant copper alloy of the present invention has excellent casting properties, toughness, machinability, and corrosion resistance (which lowers dezincification of surfaces).
The present invention further provides a method for producing a product comprising a copper alloy, comprising the steps of (a) melting a brass tablet comprising a dezincification-resistant copper alloy of the present invention and scarp returns to boiling to form a molten copper liquid;
(b) casting the molten copper liquid into a mold;
(c) cooling the mold to allow the molten copper liquid to form a casting product, and releasing the casting product from the mold;
(d) heat treating the casting product to a temperature ranging from 5601C to 620'C, and holding at the temperature for a period of time (e.g., 4 to 6 hours); and (e) naturally cooling the casting product.
In the method, the brass tablet in step (a) comprises 70 to 90 wto/u of the dezincification-resistant copper alloy of the present invention and 10 to 30 wt% of the scrap returns. In a preferred embodiment, the brass tablet comprises 75 to 85 wt% of the dezincification-resistant copper alloy of the present invention and 15 to 25 wt% of the scrap returns. In an embodiment, 80 wt% of a dezincification-resistant brass alloy and 20 wt% of the scrap returns are placed in an induction furnace for smelting and then tableting into a brass tablet. "Scrap returns" is a technological term that is conventionally used in the art. In the specification of the present invention, the residual metal scraps obtained after performing processes like casting processing on the dezincification-resistant copper alloy of the present invention can be recycled for re-use in casting processes.
In the embodiment, the brass tablet and the scrap returns are preheated to a temperature ranging from 4000 to 500'C, and then melting the brass tablet and the scrap returns mixed at a weight ratio ranging from 3:1 to 5:1 to boiling to form the molten copper liquid. In a preferred embodiment, the brass tablet and the scrap returns are mixed at a weight ratio of 4:1. A sand cleaning treatment is performed on the scrap returns before they are being preheated, so as to remove sand and iron wires from the scrap returns.
Then, a mold is provided. The mold can be preheated to 200'C, following by casting the molten copper liquid into the mold. The casting step can be achieved by gravity casting. The casting temperature is controlled to between 1010 to 1060'C.
The casting product is released from the mold at 10 to 15 seconds after completing the casting or when the casting product is not red and hot. After the casting product is released, a heat treatment can be performed on the casting product by using a resistance furnace at a heating rate of I to 51C/min, and preferably at a heating rate of 2 to 31C/min.
The casting product is heated to a temperature ranging from 560'C to 620C, and held at the temperature for up to 4 hours. Then, the heat treatment is terminated, and casting product cools down naturally.
In the method of the present invention, a heat treatment is performed on the casting product for a period of time at a temperature ranging from 560C to 620C, so as to reduce the residual stress and defects in alloy grains. If the heat treatment is performed at a temperature lower than 400 C, the residual stress cannot be completely eliminated and the number of point defects cannot be reduced. However, if the heat treatment is performed at a temperature higher than 560 C, the defects (such as dislocation) in the alloy grains can be reduced in addition to eliminating the point defects and residual stress.
Accordingly, the dezincification resistance of the copper alloy can be increased, thereby decreasing the depth of dezincification corrosion. On the other hand, if the heat treatment is performed at a temperature higher than 620 C, bismuth comprised in the copper alloy is likely to segregate on the grain boundary to form a thin film. This increases the brittleness of the material, and lowers the inhibitory effect on the diffusion of zinc through the grain boundary, thereby decreasing the dezincification resistance of the copper alloy. It should be noted that dezincification resistance of a copper alloy decreases over increasing temperatures..
By employing the method of the present invention, a heat treatment, a holding temperature and cooling are used to process the casting product, so as to lower the toughness of the alloy material of the present invention and increase the plasticity and machinability thereof. Further, the residual stress of the alloy material is reduced, thereby lowering the stress corrosion. The dezincification resistance of the alloy material is also increased.
According to an aspect of the invention, there is provided a dezincification-resistant copper alloy, comprising: 59.5 to 64 wt% of copper; 0.1 to 0.5 wt% of bismuth;
0.08 to 0.16 wt% of arsenic; 5 to 15 ppm of boron; 0.3 to 1.5 wt% of tin; 0.1 to 0.7 wt% of zirconium; less than 0.05 wt% of lead; and zinc in balance.
According to a further aspect of the invention, there is provided a method for producing a copper alloy product, comprising the steps of. (a). melting a brass tablet comprising the - 7a -dezincification-resistant copper alloy of claim I and scarp returns to boiling to form a molten copper liquid; (b). casting the molten copper liquid into a mold; (c). cooling the mold to allow the molten copper liquid to form a casting product, and releasing the casting product from the mold; (d). heat treating the casting mold to a temperature ranging from 560 C
to 620 C; and (e). naturally cooling the casting product.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. IA is a metallographic structural distribution of a specimen of a dezincification-resistant copper alloy of the present invention in example 1 after a heat treatment is performed at 560 C;
FIG. 113 is a metallographic structural distribution of a specimen of a dezincification-resistant copper alloy of the present invention in example 1 after a heat treatment is performed at 6201C;
FIG. 2A is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example 2 after a heat treatment is performed at 560C;
FIG. 2B is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example 2 after a heat treatment is performed at 620'C;
FIG. 3A is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example 1 after a test of dezincification corrosion resistance following a heat treatment at 560'C was performed;
FIG. 3B is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example 1 after a test of dezincification corrosion resistance following a heat treatment at 620C was performed;
FIG. 3C is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example I
after a test of dezincification corrosion resistance following a heat treatment at 4000 was performed;
FIG. 4A is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example 2 after a test of dezincification corrosion resistance following a heat treatment at 560C was performed;
FIG 4B is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example 2 after a test of dezincification corrosion resistance following a heat treatment at 620'C was performed;
FIG. 4C is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example 2 after a test of dezincification corrosion resistance following a heat treatment at 400C was performed;
FIG. 5A is a metallographic structural distribution of a specimen of a CW602N
copper after a test of dezincification corrosion resistance following a heat treatment at 560'C was performed;
FIG. 5B is a metallographic structural distribution of a specimen of the copper after a test of dezincification corrosion resistance following a heat treatment at 6201C was performed;
FIG. 5C is a inetallographic structural distribution of a specimen of the copper after a test of dezincification corrosion resistance following a heat treatment at 400C was performed;
FIG. 5D is a metallographic structural distribution of a specimen of the copper after a test of dezincification corrosion resistance following a heat treatment at 700C was performed;
FIG. 6 is a metallographic structural distribution of a specimen of a lead-free bismuth copper after a test of dezincification corrosion resistance following a heat treatment at 560C was performed; and FIG. 7 is a metallographic structural distribution of a specimen of the CW602N
copper after a test of dezincification corrosion resistance following a heat treatment at 560 C was performed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The detailed description of the present invention is illustrated by the following specific examples. Persons skilled in the art can conceive the other advantages and effects of the present invention based on the disclosure contained in the specification of the present invention.
Unless otherwise specified, the ingredients comprised in the dezincification-resistant copper alloy of the present invention, as discussed herein, are all based on the total weight of the alloy, and are expressed in weight percentages (wt%).
In an embodiment, the dezincification-resistant copper alloy of the present invention comprises 59.5 to 64 wt% of copper, 0.1 to 0.5 wt=%o of bismuth, 0.08 to 0.16 wt% of arsenic, 5 to 15 ppm of boron, 0.3 to 1.5 wt% of tin, 0.1 to 0.7 wt% of zirconium and zinc in balance. The copper alloy may or may not comprise lead. If the copper alloy comprises lead, the lead content is less than 0.5 wt%.
In an embodiment, the dezincification-resistant copper alloy comprises 59.5 to wt% of copper, 0.1 to 0.5 wt% of bismuth, 0.08 to 0.16 wt% of arsenic, 5 to 15 ppm of boron, 0.3 to 1.5 wt% of tin, 0.1 to 0.7 wt% of zirconium, less than 0.05 wt%
of lead, less than 0.1 wt% of unavoidable impurities and zinc in balance.
In an embodiment, the dezincification-resistant copper alloy of the present invention comprises 62 to 64 wto/o of copper, 0.3 to 0.5 wt% of bismuth, 0.10 to 0.14 wt% of arsenic, 7 to 13 ppm of boron, 0.3 to 0.8 wt% of tin, 0.3 to 0.5 wt% of zirconium, less than 0.1 wt% of unavoidable impurities and zinc in balance.
The dezincification-resistant low lead copper alloy according to the present invention can achieve the material properties (such as machinability) possessed by conventional lead brasses or dezincification-resistant brasses. Further, this type of dezincification-resistant low lead copper alloy material is not prone to generate product defects like cracks and slag inclusions, and complies with the dezincification requirement set forth in AS-2345. Also, the copper alloy formulation of the present invention is effective in lowering the production cost of a dezincification-resistant low lead copper alloy, and is extremely advantageous to commercial-scale productions and applications.
Moreover, the dezincification-resistant copper alloy formulation of the present invention can lower the lead content to less than 0.05 wt%. Therefore, the alloy formulation facilitates manufacturing of faucets and laboratory components, water pipelines for supplying tap water, water supply systems, etc.
The present invention is illustrated by the following exemplary examples.
The ingredients of the dezincification-resistant copper alloy of the present invention used in the following test examples are described below, wherein each of the ingredients is added at a proportion based on the total weight of the alloy.
Example 1 :
Cu : 63.3 wt% Bi : 0.375 wt%
As : 0.122 wt% B : 10 ppm Sn : 0.837 wt% Zr : 0.362 wt%
Pb : 0.013 wt% Zn : in balance Example 2 :
Cu : 63.06 wt% Bi : 0.335 wt%
As : 0.107 wt% B : 8 ppm Sn : 0.632 wt% Zr : 0.433 wt%
Pb : 0.007 wt% Zn : in balance Example 3 :
Cu : 62.6 wt% Bi : 0.413 wt%
As : 0.138 wt% B : 12 ppm Sn : 0.431 wt% Zr : 0.487 wt%
Pb : 0.009 wt% Zn : in balance Test example 1:
The dezincification-resistant low lead brass alloy of the present invention and scrap returns were preheated for 15 minutes to reach a temperature higher than 400'C, and the two were mixed at a weight ratio of 7:1, along with addition of 0.2 wt% of refining slag, for melting in an induction furnace until the brass alloy reached a certain molten state (hereinafter referred to as "molten copper liquid"). A metallic gravity casting machine coupled with sand core and gravity casting products to perform casting, and a temperature monitoring system further controlled the temperature so as to maintain the casting temperature to between 1010 and 1060 C. Casting was performed in batches. In each batch, the feed amount was preferably between 1 and 2 kg, and the casting time was controlled to a between 3 and 8 seconds.
After the molds were cooled, the molds were opened and the casting heads were cleaned. The mold temperatures were monitored so as to control the mold temperatures to between 200 and 2201C to form casting parts. Then, the casting parts were released from the molds. Then, the molds were cleaned to ensure that the sites of the core head were clean. A graphite liquid was spread on the surface of the molds following by cooling by immersion. The temperature of the graphite liquid for cooling the mold was preferably maintained at between 30 and 361C, and the specific weight of the graphite liquid ranged from 1.05 to 1.06.
Self-checking was performed on the cooled casting parts, and the casting parts were sent in a sand cleaning drum for performing a sand cleaning treatment. Then, a heat treatment was performed on as-cast to distress annealing, thereby eliminating the internal stress generated by casting. The heat treatment was performed using a resistance furnace at a heating rate of 2'C/min, to heat the as-casts to a temperature ranging from 560'C to 620 *C and then held at the temperature for 4 hours. Then, the heat treatment is terminated, and the as-casts naturally cooled down. The as-casts were subsequently mechanically processed and polished, so that no sand, metal powder or other impurities adhered to the cavity of the casting parts. A quality inspection analysis was performed, and the overall production yield was calculated by the following equation.
overall production yield = the number of non-defective products/the total number of products x 100%
The overall production yield reflects the qualitative stability of production processes.
High qualitative stability of production processes ensures normal production.
Moreover, a conventional CW602N dezincification-resistant brass (which is sometimes abbreviated as DR brass, and certified as a dezincification-resistant brass according to AS2345-2006) and a commercially available lead-free bismuth brass were used in comparative examples in which products were produced by the same process as described above. The ingredients, processing characteristics and the overall production yield of each of the alloys are shown in FIG. 1.
Table 1. Ingredients, processing characteristics and total non-defectiveness in production of the alloys y ~ O O O O C .. ~
p~ O
o td R O M O M M 00 y M O 00 d; ~D N
M t~ O ~ M a0 .~-. M .-r O O O G O '~
oo OD 00 O\ o 0C!
I o, CI
o a I I o~
o o `p .o u u ~ I o I I ` v + 'O c > v to 00 U, N N
a N q I a I I '^ a > M
,~ N O O e I I I v - ~; N
C N O
N
N
U a. ~ I ~o ( I In != B d N o a M
~M I 09 I N ~N
W O C
(~ a iYl a Q a e a. N ~ e~ .S v v =O v =~L v 'O .r _0. v 'g v u u 7 u C o C u ao I
" - is represents absence of the ingredient or comprises the ingredient at a content lower than a measured value; wherein the lower limit of the measured value of each of the ingredients are as follows: Bi: 0.006%, As: 0.0005%, B: 1 ppm and Zr: 0.0005%.
It is known from Table 1 that the test group in which dezincification-resistant copper alloy according to the present invention was used a raw material had an overall production yield higher than 90%. The yield of the alloy of the present invention was comparable to that of conventional DR brass (i.e., CW602N), and was significantly higher than that of the lead-free bismuth brass. Thus, the alloy of the present invention can indeed be a substitute brass material. Further, the dezincification-resistant copper alloy of the present invention can significantly decrease the lead content of the alloy, effectively avoid the lead contamination occurred during processes, and lower the amount of lead leached when using the casting parts. This allows the alloy of the present invention to possess material characteristics while meeting the environmental requirements.
Test example 2:
Except that the temperature applied in the heat treatment is different (i.e., 560 C or 620 C), the alloy formulations in examples 1 and 2 were prepared into brass specimens according to the process described in test example 1. The specimens were placed under an optical metallographic microscope, and magnified at 100X to examine the structural distributions of the materials.
The results of example 1 are shown in FIG. 1, wherein FIG. I A shows results of the specimens being heat treated at 560 C, and FIG. lB shows results of the specimens being heat treated at 620 C . The results of example 2 are shown in FIG. 2, wherein FIG.
2A shows results of the specimens being heat treated at 560 C, and FIG. 2B
shows results of the specimens being heat treated at 620 C . As shown in FIGs. I and 2, the structure of the dezincification-resistant copper alloy being heat treated is similar to a single a phase brass. The dezincification-resistant copper alloy has good dezincification resistance.
Test example 3:
Except that the temperature applied in the heat treatment is different, the alloy formulations in examples 1 and 2 and comparative examples 1, 4 and 5 were prepared into brass specimens according to the process described in test example 1, wherein the temperature conditions in the heat treatment are listed in Table 2.
A dezincification test was performed on the above brass specimens to test the corrosion resistance of the brasses. The dezincification test was performed according to the Australian standard AS2345-2006 "Dezincification resistance of copper alloys".
Before the corrosion experiment was performed, a novolak resin was used to make the exposed area of each of the specimens to be 100 mm2. The specimens were ground flat using a 600# metallographic abrasive paper, following by washing using distilled water.
Then, the specimens were baked dry. The test solution was 1% CuCI2 solution prepared before use, and the testing temperature was 75 2 C. The specimens and the CuC12 solution were placed in a temperature-controlled water bath to react for 24 0.5 hours.
The specimens were removed from the water bath, and cut along the vertical direction.
The cross-sections of the specimens were polished, and then the corrosion depths of the specimens were measured. Results are shown in FIG. 2. The dezincification of the brass alloy specimens were observed under a digital metallographic electronic microscope, and results are shown in FIGs. 3 to 7.
Table 2. Summary of the heating conditions and the average depths of dezincification corrosion in examples I and 2 and comparative examples 1, 4 and 5 Comparative Comparative Comparative Alloy fonnulation Example I Example 2 example I example 4 example 5 Heating conditions 560C 620C 4000 560 C 620 C 7001C 560C 620C 560'C 560C
Average depth o dezincification 12.6 9.6 180.6 12.4 14.3 132.1 91.3 82.1 324.1 781.1 corrosion (}un) As shown in Table 2 and FIGs. 3 to 7, when no heat treatment was performed, the depth of the dezincification layer of the dezincification-resistant copper alloy of the present invention was less than 200 pm, and the depth of the dezincification layer of the conventional CW602N brass exceeded 300 m. When the heat treatment was performed at 700 C, the depth of the dezincification layer of the dezincification-resistant copper alloy of the present invention was less than 150 m, and the depth of the dezincification layer of the conventional CW602N brass still exceeded 200 m.
It was further found that when the heat treatment was performed at a temperature ranging from 520 to 620 C , the depths of dezincification layers of the dezincification-resistant copper alloy of the present invention and the conventional CW602N brass could both be less than 100 gm. Hence, the dezincification-resist copper alloy of the present invention and the conventional CW602N brass met the standard of dezincification resistance (i.e., the depth of a dezincification layer formed on the surface of a brass product shall not exceed 100 gm) set forth in AS2345. This corroborated that by employing the method of the present invention to perform casting of products, the dezincification resistance of brass alloys were indeed improved. The dezincification resistance of the lead-free bismuth brass was the poorest among the tested samples.
Specifically, even after the heat treatment was performed, the depth of the dezincification layer of the lead-free bismuth brass still exceeded 300 gm.
Moreover, by using the dezincification-resistant copper alloy formulation of the present invention, along with a heat treatment applied at a temperature ranging from 520 to 620 C, the depth of the dezincification layer can be less than 15 m, thereby substantially increasing the dezincification resistance.
In conclusion, the dezincification-resistant brass alloy material of the present invention has excellent dezincification resistance, and can be coupled with suitable heat treatment conditions to further enhance the dezincification resistance of casting products produced therefrom. The dezincification-resistant brass alloy of the present invention has advantages like having good toughness and machinability, low production cost, high overall production yield and environmental friendliness while possessing properties essential for industrial productions.
The invention has been described using exemplary preferred embodiments.
However, it is to be understood that the scope of the invention is not limited to the disclosed arrangements. The scope of the claims, therefore, should be accorded the broadest interpretation, so as to encompass all such modifications and similar arrangements.
l8
The dezincification-resistant copper alloy of the present invention comprises an extremely low lead content (i.e., less than 0.05 wt%) or even no lead. As compared with conventional brass alloys, the lead content is substantially lowered, thereby facilitating environmental protection. The alloy can possibly have impurities therein. The content of the unavoidable impurities is less than 0.1 wt%.
The dezincification-resistant copper alloy of the present invention has excellent casting properties, toughness, machinability, and corrosion resistance (which lowers dezincification of surfaces).
The present invention further provides a method for producing a product comprising a copper alloy, comprising the steps of (a) melting a brass tablet comprising a dezincification-resistant copper alloy of the present invention and scarp returns to boiling to form a molten copper liquid;
(b) casting the molten copper liquid into a mold;
(c) cooling the mold to allow the molten copper liquid to form a casting product, and releasing the casting product from the mold;
(d) heat treating the casting product to a temperature ranging from 5601C to 620'C, and holding at the temperature for a period of time (e.g., 4 to 6 hours); and (e) naturally cooling the casting product.
In the method, the brass tablet in step (a) comprises 70 to 90 wto/u of the dezincification-resistant copper alloy of the present invention and 10 to 30 wt% of the scrap returns. In a preferred embodiment, the brass tablet comprises 75 to 85 wt% of the dezincification-resistant copper alloy of the present invention and 15 to 25 wt% of the scrap returns. In an embodiment, 80 wt% of a dezincification-resistant brass alloy and 20 wt% of the scrap returns are placed in an induction furnace for smelting and then tableting into a brass tablet. "Scrap returns" is a technological term that is conventionally used in the art. In the specification of the present invention, the residual metal scraps obtained after performing processes like casting processing on the dezincification-resistant copper alloy of the present invention can be recycled for re-use in casting processes.
In the embodiment, the brass tablet and the scrap returns are preheated to a temperature ranging from 4000 to 500'C, and then melting the brass tablet and the scrap returns mixed at a weight ratio ranging from 3:1 to 5:1 to boiling to form the molten copper liquid. In a preferred embodiment, the brass tablet and the scrap returns are mixed at a weight ratio of 4:1. A sand cleaning treatment is performed on the scrap returns before they are being preheated, so as to remove sand and iron wires from the scrap returns.
Then, a mold is provided. The mold can be preheated to 200'C, following by casting the molten copper liquid into the mold. The casting step can be achieved by gravity casting. The casting temperature is controlled to between 1010 to 1060'C.
The casting product is released from the mold at 10 to 15 seconds after completing the casting or when the casting product is not red and hot. After the casting product is released, a heat treatment can be performed on the casting product by using a resistance furnace at a heating rate of I to 51C/min, and preferably at a heating rate of 2 to 31C/min.
The casting product is heated to a temperature ranging from 560'C to 620C, and held at the temperature for up to 4 hours. Then, the heat treatment is terminated, and casting product cools down naturally.
In the method of the present invention, a heat treatment is performed on the casting product for a period of time at a temperature ranging from 560C to 620C, so as to reduce the residual stress and defects in alloy grains. If the heat treatment is performed at a temperature lower than 400 C, the residual stress cannot be completely eliminated and the number of point defects cannot be reduced. However, if the heat treatment is performed at a temperature higher than 560 C, the defects (such as dislocation) in the alloy grains can be reduced in addition to eliminating the point defects and residual stress.
Accordingly, the dezincification resistance of the copper alloy can be increased, thereby decreasing the depth of dezincification corrosion. On the other hand, if the heat treatment is performed at a temperature higher than 620 C, bismuth comprised in the copper alloy is likely to segregate on the grain boundary to form a thin film. This increases the brittleness of the material, and lowers the inhibitory effect on the diffusion of zinc through the grain boundary, thereby decreasing the dezincification resistance of the copper alloy. It should be noted that dezincification resistance of a copper alloy decreases over increasing temperatures..
By employing the method of the present invention, a heat treatment, a holding temperature and cooling are used to process the casting product, so as to lower the toughness of the alloy material of the present invention and increase the plasticity and machinability thereof. Further, the residual stress of the alloy material is reduced, thereby lowering the stress corrosion. The dezincification resistance of the alloy material is also increased.
According to an aspect of the invention, there is provided a dezincification-resistant copper alloy, comprising: 59.5 to 64 wt% of copper; 0.1 to 0.5 wt% of bismuth;
0.08 to 0.16 wt% of arsenic; 5 to 15 ppm of boron; 0.3 to 1.5 wt% of tin; 0.1 to 0.7 wt% of zirconium; less than 0.05 wt% of lead; and zinc in balance.
According to a further aspect of the invention, there is provided a method for producing a copper alloy product, comprising the steps of. (a). melting a brass tablet comprising the - 7a -dezincification-resistant copper alloy of claim I and scarp returns to boiling to form a molten copper liquid; (b). casting the molten copper liquid into a mold; (c). cooling the mold to allow the molten copper liquid to form a casting product, and releasing the casting product from the mold; (d). heat treating the casting mold to a temperature ranging from 560 C
to 620 C; and (e). naturally cooling the casting product.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. IA is a metallographic structural distribution of a specimen of a dezincification-resistant copper alloy of the present invention in example 1 after a heat treatment is performed at 560 C;
FIG. 113 is a metallographic structural distribution of a specimen of a dezincification-resistant copper alloy of the present invention in example 1 after a heat treatment is performed at 6201C;
FIG. 2A is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example 2 after a heat treatment is performed at 560C;
FIG. 2B is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example 2 after a heat treatment is performed at 620'C;
FIG. 3A is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example 1 after a test of dezincification corrosion resistance following a heat treatment at 560'C was performed;
FIG. 3B is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example 1 after a test of dezincification corrosion resistance following a heat treatment at 620C was performed;
FIG. 3C is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example I
after a test of dezincification corrosion resistance following a heat treatment at 4000 was performed;
FIG. 4A is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example 2 after a test of dezincification corrosion resistance following a heat treatment at 560C was performed;
FIG 4B is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example 2 after a test of dezincification corrosion resistance following a heat treatment at 620'C was performed;
FIG. 4C is a metallographic structural distribution of a specimen of the dezincification-resistant copper alloy of the present invention in example 2 after a test of dezincification corrosion resistance following a heat treatment at 400C was performed;
FIG. 5A is a metallographic structural distribution of a specimen of a CW602N
copper after a test of dezincification corrosion resistance following a heat treatment at 560'C was performed;
FIG. 5B is a metallographic structural distribution of a specimen of the copper after a test of dezincification corrosion resistance following a heat treatment at 6201C was performed;
FIG. 5C is a inetallographic structural distribution of a specimen of the copper after a test of dezincification corrosion resistance following a heat treatment at 400C was performed;
FIG. 5D is a metallographic structural distribution of a specimen of the copper after a test of dezincification corrosion resistance following a heat treatment at 700C was performed;
FIG. 6 is a metallographic structural distribution of a specimen of a lead-free bismuth copper after a test of dezincification corrosion resistance following a heat treatment at 560C was performed; and FIG. 7 is a metallographic structural distribution of a specimen of the CW602N
copper after a test of dezincification corrosion resistance following a heat treatment at 560 C was performed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The detailed description of the present invention is illustrated by the following specific examples. Persons skilled in the art can conceive the other advantages and effects of the present invention based on the disclosure contained in the specification of the present invention.
Unless otherwise specified, the ingredients comprised in the dezincification-resistant copper alloy of the present invention, as discussed herein, are all based on the total weight of the alloy, and are expressed in weight percentages (wt%).
In an embodiment, the dezincification-resistant copper alloy of the present invention comprises 59.5 to 64 wt% of copper, 0.1 to 0.5 wt=%o of bismuth, 0.08 to 0.16 wt% of arsenic, 5 to 15 ppm of boron, 0.3 to 1.5 wt% of tin, 0.1 to 0.7 wt% of zirconium and zinc in balance. The copper alloy may or may not comprise lead. If the copper alloy comprises lead, the lead content is less than 0.5 wt%.
In an embodiment, the dezincification-resistant copper alloy comprises 59.5 to wt% of copper, 0.1 to 0.5 wt% of bismuth, 0.08 to 0.16 wt% of arsenic, 5 to 15 ppm of boron, 0.3 to 1.5 wt% of tin, 0.1 to 0.7 wt% of zirconium, less than 0.05 wt%
of lead, less than 0.1 wt% of unavoidable impurities and zinc in balance.
In an embodiment, the dezincification-resistant copper alloy of the present invention comprises 62 to 64 wto/o of copper, 0.3 to 0.5 wt% of bismuth, 0.10 to 0.14 wt% of arsenic, 7 to 13 ppm of boron, 0.3 to 0.8 wt% of tin, 0.3 to 0.5 wt% of zirconium, less than 0.1 wt% of unavoidable impurities and zinc in balance.
The dezincification-resistant low lead copper alloy according to the present invention can achieve the material properties (such as machinability) possessed by conventional lead brasses or dezincification-resistant brasses. Further, this type of dezincification-resistant low lead copper alloy material is not prone to generate product defects like cracks and slag inclusions, and complies with the dezincification requirement set forth in AS-2345. Also, the copper alloy formulation of the present invention is effective in lowering the production cost of a dezincification-resistant low lead copper alloy, and is extremely advantageous to commercial-scale productions and applications.
Moreover, the dezincification-resistant copper alloy formulation of the present invention can lower the lead content to less than 0.05 wt%. Therefore, the alloy formulation facilitates manufacturing of faucets and laboratory components, water pipelines for supplying tap water, water supply systems, etc.
The present invention is illustrated by the following exemplary examples.
The ingredients of the dezincification-resistant copper alloy of the present invention used in the following test examples are described below, wherein each of the ingredients is added at a proportion based on the total weight of the alloy.
Example 1 :
Cu : 63.3 wt% Bi : 0.375 wt%
As : 0.122 wt% B : 10 ppm Sn : 0.837 wt% Zr : 0.362 wt%
Pb : 0.013 wt% Zn : in balance Example 2 :
Cu : 63.06 wt% Bi : 0.335 wt%
As : 0.107 wt% B : 8 ppm Sn : 0.632 wt% Zr : 0.433 wt%
Pb : 0.007 wt% Zn : in balance Example 3 :
Cu : 62.6 wt% Bi : 0.413 wt%
As : 0.138 wt% B : 12 ppm Sn : 0.431 wt% Zr : 0.487 wt%
Pb : 0.009 wt% Zn : in balance Test example 1:
The dezincification-resistant low lead brass alloy of the present invention and scrap returns were preheated for 15 minutes to reach a temperature higher than 400'C, and the two were mixed at a weight ratio of 7:1, along with addition of 0.2 wt% of refining slag, for melting in an induction furnace until the brass alloy reached a certain molten state (hereinafter referred to as "molten copper liquid"). A metallic gravity casting machine coupled with sand core and gravity casting products to perform casting, and a temperature monitoring system further controlled the temperature so as to maintain the casting temperature to between 1010 and 1060 C. Casting was performed in batches. In each batch, the feed amount was preferably between 1 and 2 kg, and the casting time was controlled to a between 3 and 8 seconds.
After the molds were cooled, the molds were opened and the casting heads were cleaned. The mold temperatures were monitored so as to control the mold temperatures to between 200 and 2201C to form casting parts. Then, the casting parts were released from the molds. Then, the molds were cleaned to ensure that the sites of the core head were clean. A graphite liquid was spread on the surface of the molds following by cooling by immersion. The temperature of the graphite liquid for cooling the mold was preferably maintained at between 30 and 361C, and the specific weight of the graphite liquid ranged from 1.05 to 1.06.
Self-checking was performed on the cooled casting parts, and the casting parts were sent in a sand cleaning drum for performing a sand cleaning treatment. Then, a heat treatment was performed on as-cast to distress annealing, thereby eliminating the internal stress generated by casting. The heat treatment was performed using a resistance furnace at a heating rate of 2'C/min, to heat the as-casts to a temperature ranging from 560'C to 620 *C and then held at the temperature for 4 hours. Then, the heat treatment is terminated, and the as-casts naturally cooled down. The as-casts were subsequently mechanically processed and polished, so that no sand, metal powder or other impurities adhered to the cavity of the casting parts. A quality inspection analysis was performed, and the overall production yield was calculated by the following equation.
overall production yield = the number of non-defective products/the total number of products x 100%
The overall production yield reflects the qualitative stability of production processes.
High qualitative stability of production processes ensures normal production.
Moreover, a conventional CW602N dezincification-resistant brass (which is sometimes abbreviated as DR brass, and certified as a dezincification-resistant brass according to AS2345-2006) and a commercially available lead-free bismuth brass were used in comparative examples in which products were produced by the same process as described above. The ingredients, processing characteristics and the overall production yield of each of the alloys are shown in FIG. 1.
Table 1. Ingredients, processing characteristics and total non-defectiveness in production of the alloys y ~ O O O O C .. ~
p~ O
o td R O M O M M 00 y M O 00 d; ~D N
M t~ O ~ M a0 .~-. M .-r O O O G O '~
oo OD 00 O\ o 0C!
I o, CI
o a I I o~
o o `p .o u u ~ I o I I ` v + 'O c > v to 00 U, N N
a N q I a I I '^ a > M
,~ N O O e I I I v - ~; N
C N O
N
N
U a. ~ I ~o ( I In != B d N o a M
~M I 09 I N ~N
W O C
(~ a iYl a Q a e a. N ~ e~ .S v v =O v =~L v 'O .r _0. v 'g v u u 7 u C o C u ao I
" - is represents absence of the ingredient or comprises the ingredient at a content lower than a measured value; wherein the lower limit of the measured value of each of the ingredients are as follows: Bi: 0.006%, As: 0.0005%, B: 1 ppm and Zr: 0.0005%.
It is known from Table 1 that the test group in which dezincification-resistant copper alloy according to the present invention was used a raw material had an overall production yield higher than 90%. The yield of the alloy of the present invention was comparable to that of conventional DR brass (i.e., CW602N), and was significantly higher than that of the lead-free bismuth brass. Thus, the alloy of the present invention can indeed be a substitute brass material. Further, the dezincification-resistant copper alloy of the present invention can significantly decrease the lead content of the alloy, effectively avoid the lead contamination occurred during processes, and lower the amount of lead leached when using the casting parts. This allows the alloy of the present invention to possess material characteristics while meeting the environmental requirements.
Test example 2:
Except that the temperature applied in the heat treatment is different (i.e., 560 C or 620 C), the alloy formulations in examples 1 and 2 were prepared into brass specimens according to the process described in test example 1. The specimens were placed under an optical metallographic microscope, and magnified at 100X to examine the structural distributions of the materials.
The results of example 1 are shown in FIG. 1, wherein FIG. I A shows results of the specimens being heat treated at 560 C, and FIG. lB shows results of the specimens being heat treated at 620 C . The results of example 2 are shown in FIG. 2, wherein FIG.
2A shows results of the specimens being heat treated at 560 C, and FIG. 2B
shows results of the specimens being heat treated at 620 C . As shown in FIGs. I and 2, the structure of the dezincification-resistant copper alloy being heat treated is similar to a single a phase brass. The dezincification-resistant copper alloy has good dezincification resistance.
Test example 3:
Except that the temperature applied in the heat treatment is different, the alloy formulations in examples 1 and 2 and comparative examples 1, 4 and 5 were prepared into brass specimens according to the process described in test example 1, wherein the temperature conditions in the heat treatment are listed in Table 2.
A dezincification test was performed on the above brass specimens to test the corrosion resistance of the brasses. The dezincification test was performed according to the Australian standard AS2345-2006 "Dezincification resistance of copper alloys".
Before the corrosion experiment was performed, a novolak resin was used to make the exposed area of each of the specimens to be 100 mm2. The specimens were ground flat using a 600# metallographic abrasive paper, following by washing using distilled water.
Then, the specimens were baked dry. The test solution was 1% CuCI2 solution prepared before use, and the testing temperature was 75 2 C. The specimens and the CuC12 solution were placed in a temperature-controlled water bath to react for 24 0.5 hours.
The specimens were removed from the water bath, and cut along the vertical direction.
The cross-sections of the specimens were polished, and then the corrosion depths of the specimens were measured. Results are shown in FIG. 2. The dezincification of the brass alloy specimens were observed under a digital metallographic electronic microscope, and results are shown in FIGs. 3 to 7.
Table 2. Summary of the heating conditions and the average depths of dezincification corrosion in examples I and 2 and comparative examples 1, 4 and 5 Comparative Comparative Comparative Alloy fonnulation Example I Example 2 example I example 4 example 5 Heating conditions 560C 620C 4000 560 C 620 C 7001C 560C 620C 560'C 560C
Average depth o dezincification 12.6 9.6 180.6 12.4 14.3 132.1 91.3 82.1 324.1 781.1 corrosion (}un) As shown in Table 2 and FIGs. 3 to 7, when no heat treatment was performed, the depth of the dezincification layer of the dezincification-resistant copper alloy of the present invention was less than 200 pm, and the depth of the dezincification layer of the conventional CW602N brass exceeded 300 m. When the heat treatment was performed at 700 C, the depth of the dezincification layer of the dezincification-resistant copper alloy of the present invention was less than 150 m, and the depth of the dezincification layer of the conventional CW602N brass still exceeded 200 m.
It was further found that when the heat treatment was performed at a temperature ranging from 520 to 620 C , the depths of dezincification layers of the dezincification-resistant copper alloy of the present invention and the conventional CW602N brass could both be less than 100 gm. Hence, the dezincification-resist copper alloy of the present invention and the conventional CW602N brass met the standard of dezincification resistance (i.e., the depth of a dezincification layer formed on the surface of a brass product shall not exceed 100 gm) set forth in AS2345. This corroborated that by employing the method of the present invention to perform casting of products, the dezincification resistance of brass alloys were indeed improved. The dezincification resistance of the lead-free bismuth brass was the poorest among the tested samples.
Specifically, even after the heat treatment was performed, the depth of the dezincification layer of the lead-free bismuth brass still exceeded 300 gm.
Moreover, by using the dezincification-resistant copper alloy formulation of the present invention, along with a heat treatment applied at a temperature ranging from 520 to 620 C, the depth of the dezincification layer can be less than 15 m, thereby substantially increasing the dezincification resistance.
In conclusion, the dezincification-resistant brass alloy material of the present invention has excellent dezincification resistance, and can be coupled with suitable heat treatment conditions to further enhance the dezincification resistance of casting products produced therefrom. The dezincification-resistant brass alloy of the present invention has advantages like having good toughness and machinability, low production cost, high overall production yield and environmental friendliness while possessing properties essential for industrial productions.
The invention has been described using exemplary preferred embodiments.
However, it is to be understood that the scope of the invention is not limited to the disclosed arrangements. The scope of the claims, therefore, should be accorded the broadest interpretation, so as to encompass all such modifications and similar arrangements.
l8
Claims (14)
1. A dezincification-resistant copper alloy, consisting of:
59.5 to 64 wt% of copper;
0.3 to 0.5 wt% of bismuth;
0.08 to 0.16 wt% of arsenic;
to 15 ppm of boron;
0.3 to 1.5 wt% of tin;
0.1 to 0.7 wt% of zirconium;
less than 0.05 wt% of lead; and zinc in balance.
59.5 to 64 wt% of copper;
0.3 to 0.5 wt% of bismuth;
0.08 to 0.16 wt% of arsenic;
to 15 ppm of boron;
0.3 to 1.5 wt% of tin;
0.1 to 0.7 wt% of zirconium;
less than 0.05 wt% of lead; and zinc in balance.
2. The dezincification-resistant copper alloy of claim 1, wherein the copper is in an amount ranging from 62 to 64 wt%.
3. The dezincification-resistant copper alloy of claim 1, wherein the arsenic is in an amount ranging from 0.10 to 0.14 wt%.
4. The dezincification-resistant copper alloy of claim 1, wherein the boron is in an amount ranging from 7 to 13 ppm.
5. The dezincification-resistant copper alloy of claim 1, wherein the tin is in an amount ranging from 0.3 to 0.8 wt%.
6. The dezincification-resistant copper alloy of claim 6, wherein the zirconium is in an amount ranging from 0.3 to 0.5 wt%.
7. A method for producing a copper alloy product, comprising the steps of:
(a) melting a brass tablet comprising the dezincification-resistant copper alloy of claim 1 and scrap returns to boiling to form a molten copper liquid;
(b) casting the molten copper liquid into a mold;
(c) cooling the mold to allow the molten copper liquid to form a casting product, and releasing the casting product from the mold;
(d) heat treating the casting product to a temperature ranging from 560°C to 620°C;
and (e) naturally cooling the casting product.
(a) melting a brass tablet comprising the dezincification-resistant copper alloy of claim 1 and scrap returns to boiling to form a molten copper liquid;
(b) casting the molten copper liquid into a mold;
(c) cooling the mold to allow the molten copper liquid to form a casting product, and releasing the casting product from the mold;
(d) heat treating the casting product to a temperature ranging from 560°C to 620°C;
and (e) naturally cooling the casting product.
8. The method of claim 8, wherein the brass tablet comprises 70 to 90 wt% of the dezincification-resistant copper alloy and 10 to 30 wt% of the scrap returns.
9. The method of claim 9, wherein the brass tablet is prepared by smelting and tableting the dezincification-resistant copper alloy and the scrap returns
10. The method of claim 8, wherein the brass tablet and the scrap returns are at a weight ratio ranging from 3:1 to 5:1.
11. The method of claim 8, wherein the step (b) is performed by using gravity casting.
12. The method of claim 8, wherein the step (d) is performed by using a resistance furnace.
13. The method of claim 8, wherein the step (d) is performed at a heating rate of 1 to 5°C
/minute until the casting product reaches a temperature ranging from 560 to 620°C.
/minute until the casting product reaches a temperature ranging from 560 to 620°C.
14. The method of claim 8, further comprising: after the step (d), holding at the temperature for 4 to 6 hours.
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| TW098127416A TWI398531B (en) | 2009-08-14 | 2009-08-14 | Dezincification resistant brass alloy and manufacture of an article comprising thereof |
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| CN105723007A (en) * | 2013-11-13 | 2016-06-29 | 北欧古苏姆冶金公司 | Brass alloy comprising ceramic nanoparticles and having improved machinability |
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| DE102020101697A1 (en) * | 2020-01-24 | 2021-07-29 | Lixil Corporation | Process for the additive manufacture of a dezincification-resistant brass component for a sanitary fitting |
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| US5330712A (en) * | 1993-04-22 | 1994-07-19 | Federalloy, Inc. | Copper-bismuth alloys |
| JP2004244672A (en) * | 2003-02-13 | 2004-09-02 | Dowa Mining Co Ltd | Copper-base alloy with excellent dezincification resistance |
| JP4951517B2 (en) * | 2005-09-30 | 2012-06-13 | 三菱伸銅株式会社 | Melt-solidified product, copper alloy material for melt-solidification, and method for producing the same |
| TWI577931B (en) * | 2015-05-28 | 2017-04-11 | 建準電機工業股份有限公司 | Motor of ceiling fan with illuminating module |
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| CN105723007B (en) * | 2013-11-13 | 2018-09-11 | 北欧古苏姆冶金公司 | Brass alloys containing ceramic nanoparticle and with improved machining property |
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