Patent Application
20110142715
1. Field of the Invention
The present invention relates to copper alloys, and more particularly, to an environment friendly brass alloy.
2. Description of Related Art
A brass includes copper and zinc, as major ingredients, usually in a ratio of about 7:3 or 6:4. In addition, a brass usually includes a small amount of impurities. In order to improve the properties of a brass, a conventional brass contains lead (mostly in the range of 1 to 3 wt %) to achieve the desired mechanical properties for use in the industry, thereby becoming an important industrial material that is widely applicable to metallic devices and valves for use in pipelines, faucets and water supply and discharge systems.
However, as awareness of the importance of environmental protection increases and the impact of heavy metals on human health becomes better understood, it is a trend to restrict the use of lead-containing alloys. Various countries, such as Japan and the United States, have progressively amended relevant regulations in an intensive effort to lower the lead content in the environment by particularly requiring that no lead shall leach from lead-containing alloys used in products ranging from household appliances and automobiles to residential water pipes and municipal water systems, while also requiring that lead contamination shall be avoided during processing. Hence, there is a need to develop lead-free brass with good properties for casting, cutting, corrosion-resisting and mechanical processing.
Currently, there are many formulations of lead-free copper alloy. For example, Taiwanese Patent No. 421674, U.S. Pat. No. 7,354,489, and US Patent Application Publication Nos. 20070062615, 20060078458 and 2004023441 disclose adding silicon (Si) in a brass alloy instead of lead. However, the alloys made from these formulations have poor property for cutting. In addition, Chinese Patent Application Publication No. 10144045 discloses aluminum, silicon and phosphorous as main components of a lead-free copper alloy. This lead-free copper alloy can be used for casting, but has poor property for cutting and much lower processing efficiency than lead-containing brass. Chinese Patent Application Publication Nos. 101285138 and 101285137 disclose phosphorous as main component in an alloy; however, cracks are easily formed while casting this alloy.
In addition, U.S. Pat. Nos. 7,297,215, 6,974,509, 6,955,378, 6,149,739, 5,942,056, 5,637,160, 5,653,827, 5,487,867 and 5,330,712, and US Patent Application Publication Nos. 20060005901, 20040094243 and 20070039667, etc., disclose lead-free or low-lead bismuth-containing brass alloy formulations, wherein the bismuth content of the formulations ranges from 0.5 wt % to 7 wt %. Further, U.S. Pat. No. 6,413,330 discloses a lead-free copper alloy containing bismuth, silicon and other components. Chinese Patent Application Publication No. 101440444 also discloses a lead-free brass alloy having high content of zinc and silicon, but this brass ally has high content of silicon and low content of copper, such that the fluidity of the melt alloy is poor to fill the cavity while casting, resulting in disadvantages such as misrun, etc. Chinese Patent Application Publication No. 101403056 discloses bismuth and manganese in a lead-free brass alloy instead of lead. However, high bismuth content is likely to cause defects like cracks and slag inclusions, leading to low processing efficiencies. On the other hand, low bismuth content and high manganese content cause less cracks, but have poor cutting property.
Due to rare resource and expensive cost, high bismuth content instead of lead results in high fabrication cost of a lead-free brass. Further, the above-mentioned brass alloys have drawbacks such as poor casting property, easily forming cracks, etc.
Moreover, there are literatures disclosing the improvement of a fabrication of a lead-free copper alloy or a lead removal process. For example, U.S. Pat. No. 5,904,783 discloses treating a brass alloy with the sodium and potassium solution at a high temperature for reducing lead leaching into a fluid supply. Taiwanese Patent No. 491897 discloses a method for fabricating a brass alloy having 1-2.6 wt % of bismuth. However, the conventional lead removal process is used for reducing lead, which is in contact with water, leaching when the lead-containing product is immersed in water, but fails to reduce the lead content to less than 0.3 wt % in a material.
The present invention provides an environmental friendly brass alloy.
The environmental friendly brass alloy includes 0.4 to 0.8 wt % of aluminum; 0.6 to 1.6 wt % of nickel; 0.8 to 2.0 wt % of tin; more than 95.6 wt % of copper and zinc; and less than 0.1 wt % of iron, lead, phosphorous and impurities, wherein the copper is in an amount ranging from 60 to 68 wt %.
In the environmental friendly brass alloy of the present invention, the copper and zinc are present in an amount more than 95.6 wt %. In an aspect, the copper is present in an amount ranging from 60 to 68 wt % of the environmental friendly brass alloy, so as to provide toughness and to facilitate subsequent processes. In a preferred embodiment, the copper is in an amount ranging from 61 to 64 wt %.
In the environmental friendly brass alloy of the present invention, the aluminum is present in an amount ranging from 0.4 to 0.8 wt %. In a preferred embodiment, the aluminum is present in an amount ranging from 0.5 to 0.6 wt %, in which the addition of aluminum increases the fluidity of melt copper and improves casting property of the brass alloy.
In the environmental friendly brass alloy of the present invention, the nickel is present in an amount ranging from 0.6 to 1.6 wt %. In a preferred embodiment, the nickel is present in an amount ranging from 0.8 to 1.4 wt %, in which the addition of nickel improves the mechanical property and corrosion-resistance of the brass alloy.
In the environmental friendly brass alloy of the present invention, the tin is present in an amount ranging from 0.8 to 2.0 wt %. In a preferred embodiment, the tin is present in an amount ranging from 1.2 to 1.6 wt %, in which the addition of tin increases the corrosion-resistance of the brass alloy to the environment with high chloride (such as sea water) and increases the strength of the brass alloy.
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 environmental friendly brass alloy of the present invention, as discussed herein, are all based on the total weight of the brass alloy, and are expressed in weight percentages (wt %).
The environmental friendly brass alloy according to the present invention has the lead content less than 0.05 wt %, to comply with the international standards for lead content in pipeline materials in contact with water. Therefore, the environmental friendly brass alloy of the present invention is suitable for applications to faucets and lavatory components, pipelines for tap water, water supply systems, etc.
The environmental friendly brass alloy of the present invention includes 0.4 to 0.8 wt % of aluminum; 0.6 to 1.6 wt % of nickel; 0.8 to 2.0 wt % of tin; more than 95.6 wt % of copper and zinc; and less than 0.1 wt % of iron, lead, phosphorous and impurities, wherein the copper is present in an amount ranging from 60 to 68 wt %.
In the environmental friendly brass alloy of the present invention, the copper and zinc are present in an amount more than 95.6 wt %, wherein the copper is present in an amount ranging from 60 to 68 wt % of the environmental friendly brass alloy. Preferably, the copper is in an amount ranging from 61 to 64 wt %.
In the environmental friendly brass alloy of the present invention, the aluminum is present in an amount ranging from 0.4 to 0.8 wt %. In a preferred embodiment, the aluminum is present in an amount ranging from 0.5 to 0.6 wt %. The addition of aluminum increases the fluidity of melt copper and improves casting property of the brass alloy. Further, in the environmental friendly brass alloy of the present invention, the nickel is present in an amount ranging from 0.6 to 1.6 wt %. In a preferred embodiment, the nickel is present in an amount ranging from 0.8 to 1.4 wt %. The addition of nickel improves the mechanical property, corrosion-resistance and dezincification-resistance of the brass alloy. In the environmental friendly brass alloy of the present invention, the tin is present in an amount ranging from 0.8 to 2.0 wt %. In a preferred embodiment, the tin is present in an amount ranging from 1.2 to 1.6 wt %. The addition of tin increases the corrosion-resistance of the brass alloy to the environment with high chloride (such as sea water) and increases the strength of the brass alloy.
The present invention provides the detailed illustrations in the following examples. The ingredients of the environmental brass alloy of the present invention used in the following test examples are described as follows, wherein each ingredient is added at a proportion based on the total weight of the brass alloy.
The environmental friendly brass alloy (Embodiments 1-3), lead-free bismuth brass (Comparative examples 1-3) and C85710 lead brass (Comparative examples 4-5) are used for casting under the same process and operation condition. The processing characteristics and yields of these brass alloys are shown in Table 1. The overall production yield was calculated by the following equation:
O. P. Yield=Number of Non-Defective Products/Total Number of Products×100%
The overall production yield (O. P. Yield) reflects the qualitative stability of production processes. High qualitative stability of production processes ensures normal production.
As shown in Table 1, the products made of the lead-free bismuth brass alloy have more defects, and have the yield less than 70%, wherein more bismuth content results in the fewer yield. The casting product of the lead-free bismuth brass has the drawbacks such pores, cracks, slag entrapment, misrun and loose. Specifically, the melt copper of the lead-free bismuth brass has poor fluidity and poor filling in a mold, resulting in the misrun. Further, the casting products easily form crack, which are usually found while polishing. Moreover, the casting products easily form slag entrapment and pores.
As shown in Table 1, the products made from the environmental friendly brass alloy in the present invention had the best yield (more than 85%), and had the fluidity close to the conventional C85710 lead brass. Further, upon optimization of the casting products, the casting product formed the isometric crystal structures after solidification, so as to eliminate the formation of cracks and to meet the requirement of production.
It is shown in
In Embodiment 3 of the present invention, the environmental friendly brass alloy included 63.64 wt % of Cu, 0.564 wt % of Al, 0.0036 wt % of Pb, 1.167 wt % of Ni and 1.548 wt % of Sn, and has the structural distribution as shown in
Upon casting, the lead-free high bismuth brass in Comparative example 1 had the crack as shown in
The tests on the mechanical properties of the brass alloys in Embodiment 3 and Comparative example 5 were performed according to the standard set forth in ISO6998-1998, “Tensile experiments on metallic materials at room temperature.” The results are shown in Table 2.
As shown in Table 2, the environmental friendly brass alloy in the present invention had the tensile strength higher than the conventional C85710 lead brass, and had the elongation comparable to the conventional C85710 lead brass. Hence, the environmental friendly brass alloy in the present invention has the mechanical properties comparable to the C85710 lead brass, and can indeed substitute for the C85710 lead brass in manufacturing of products.
The tests were performed according to the standard set forth in NSF 61-2007a SPAC for the allowable precipitation amounts of metals in products, to examine the amounts of the metal precipitations of the brass alloys in an aqueous environment in Embodiment 3 and Comparative example 5. The results are shown in Table 3.
As shown in Table 3, the precipitation amounts of metals from the environmental friendly brass alloy in the present invention were all much lower than the upper limit of the standard values, so as to meet the requirement of NSF 61-2007a SPAC. Moreover, the amounts of heavy metal precipitations from the environmental friendly brass alloy in the present invention were significantly lower than the C85710 lead brass and significantly lower than the a lead-stripping treated C85710 lead brass. Hence, the brass alloy of the present invention is more environmentally friendly and has less risk to human health.
The environmental friendly brass alloy of the present invention has the mechanical properties (such as cutting properties) comparable to the C85710 lead brass, and even better properties (such as tensile strength) than the C85710 lead brass. The casting products made from the environmental friendly brass alloy of the present invention have great yield, and also the yield of mechanical processing is excellent. Furthermore, the environmental friendly brass alloy of the present invention reduces the amount of lead precipitations, and can substitute for the conventional brass.
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.
