Metal treatment – Stock – Copper base
Reexamination Certificate
2000-11-28
2002-07-16
Ip, Sikyin (Department: 1742)
Metal treatment
Stock
Copper base
C420S472000
Reexamination Certificate
active
06419766
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of The Invention
This invention relates to cutting-free bronze alloys which are substantially free of lead and which exhibit good castability and a good corrosion resistance. The alloys are adapted for use in various fields such as of plumbing faucets and fixtures for water supply for general-purpose pipings, and sliding members employed in a corrosive atmosphere such as of fresh water or sea water. The alloys are also suitable as a material which is employed when it is desirable to improve machinability, soundness in texture, pressure resistance and anti-seizing property while eliminating the injury from lead.
2. Description of the Prior Art
In general, characteristic requirements for constituent materials of plumbing faucets and fixtures for water supply for general-purpose pipings (hereinafter referred to generically as cock fixtures) include (1) good flowability because of the adoption of a casting method which is used to make complicated shapes, (2) good soundness in texture for preventing detrimental porosity which is liable to occur owing to the possible irregularity in thickness, (3) high mechanical strength and a good pressure resistance since no water leakage is permitted on use as a cock fixture, (5) good machinability because of a great number of portions to be worked, and (6) a good resistance to corrosion through dezincification since the fixture is employed in contact with water supply, waters or sea water and should thus have a good corrosion resistance. Moreover, when used as sliding members which are used in contact with fresh water or sea water and should have a good corrosion resistance, such a constituent material should effectively prevent corrosion through dezincification. The constituent material should also have a good anti-seizing property in order to ensure good sliding characteristics. In order to almost satisfy these requirements, usual practice is to use brass or bronze materials.
However, the conventionally employed materials as mentioned above have the following problems which should be overcome. Brass materials utilized for the plumbing faucets and fixtures include, for example, JIS.H.3250.C3604, C3771 (cutting-free brasses), which contain large amounts of lead. Thus, the injury from lead is not avoidable. In fact, when they are in contact with water, corrosion through dezincification inevitably takes place. Another type of brass material such as JIS.H.3250.C4641 is known as preventing corrosion through dezincification. This brass material contains no lead, so that the machinability is not satisfactory. Although cutting-free brass materials which prevent corrosion through dezincification are commercially sold, they contain lead, thereby causing injury from lead. In addition, cutting-free brass materials wherein lead is substituted with bismuth are known. However, no tin is added to the materials, so that the corrosion through dezincification is liable to occur, coupled with another problem that the materials contain a misch metal and is thus expensive (Japanese Laid-open Patent Application No. 5-255778).
Moreover, U.S. Pat. No. 5167726 discloses a cutting-free brass wherein lead is substituted with bismuth, but expensive indium is also contained therein, resulting in high costs. A further type of brass which contains phosphorus in place of indium is known. However, phosphorus reacts with iron in the starting materials, thereby creating hard spots in the resultant brass. This, in turn, requires the use of starting materials which have to be substantially free of any metals adversely influencing the brass alloy, thus inviting a rise in cost. On the other hand, bronze materials which are utilized as a plumbing faucet and fixture include, for example, JIS.H.5111.BC1, BC6 and BC7. These materials have good castability, soundness in texture and machinability along with a satisfactory pressure resistance. However, the bronze materials contain a large amount of lead, thereby presenting the problem of injury from lead. Moreover, other types of bronze materials are known including, for example, JIS.H.5111.BC2, BC3. Although these types of materials contain not larger than 1 wt. % of lead, lead is not positively incorporated as an additive element. More particularly, the content of lead in these materials is less than that of lead-containing bronzes, thus leading to poorer machinability. Japanese Patent Publication No. 5-63536 discloses a material wherein lead in lead bronzes is replaced by bismuth to prevent injury from lead and improve the machinability and castability. However, a multitude of pores are formed at the time of casting, thereby impeding the soundness in texture. In addition, this material is poorer in pressure resistance and mechanical strength than lead-containing bronzes. Hence, limitation is placed on the use of the material as articles which are simple in shape and which are relatively uniform in thickness. Furthermore, the material disclosed in Japanese Patent Publication No. 5-279771 has a similar problem as in Japanese Patent Publication No. 5-63536, coupled with another problem that it contains a misch metal and is thus expensive.
Next, the materials utilized as sliding members include, for example, aluminium bronze materials such as JIS.H.5114.AlBC1, AlBC2 and AlBC3. These materials undergo corrosion through dealuminization and are low in anti-seizing property and poor in machinability. In contrast, brass which is set out, for example, in Japanese Laid-open Patent Application No. 63-16456 is admixed with 0.5 to 2 wt % of tin in order not to cause corrosion through dezincification and further with bismuth in place of lead thereby improving machinability. Moreover, in order to improve a wear resistance, 1.0 to 10.0 wt % of graphite is added. For the uniform dispersion of the graphite, a mold has to be used, which places limitation on the shape of articles along with an additional cost of the mold. On the other hand, phosphorus bronze is known including JIS.H.5113.PBC2. This bronze does not cause any corrosion through dezincification and has a satisfactory wear resistance. Because neither lead nor bismuth is added to the material, it is poor in machinability and is worse in anti-seizing property than similar bronze alloys containing lead. Moreover, a material called CDA915, wherein nickel and lead are added to the phosphorus bronze material, is known and has been in wide use as a material for gears. This material is excellent in wear resistance and corrosion resistance through dezincification but is injured from lead owing to the presence thereof.
The term “injury from lead” used herein is intended to mean injuries of human body or environments caused from lead. More particularly, the problems involved at the time of fabrication of articles during the course of high temperature working operations such as liquation or dissolution, casting and welding include the formation of metallic fumes containing lead. Likewise, the problems caused during the course of working processes such as cutting, polishing and the like include the formation of metallic dust or powder. In the use of the resultant articles, another problem is involved in that lead is liable to dissolve out from portions contacting with water and that worn dust is inevitably produced at sliding portions.
As is apparent from the above, most of the alloys produced in the prior art contain lead, and thus, present injurious problems of lead to the human body and environment. If, however, alloys which are free of any lead in order to prevent injury from lead are used, machinability, anti-seizing property and pressure resistance become poorer than those of lead-containing alloys. This places limitations on the types of articles to be fabricated or utilized. The substitution of lead with bismuth can solve these disadvantages and will make it possible to improve the machinability and anti-seizing property to an extent comparable to those of lead-containing materials. However, such materials have a great number of pores produced at the time of cast
Hosoda Masao
Ikemiya Yukinori
Inagaki Kazuyuki
Nakashima Kunio
Sugiyama Kenji
Flynn ,Thiel, Boutell & Tanis, P.C.
Ip Sikyin
Tabuchi Corp.
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