Metal treatment – Stock – Copper base
Reexamination Certificate
2000-05-08
2002-10-01
Ip, Sikyin (Department: 1742)
Metal treatment
Stock
Copper base
C148S681000, C148S682000, C148S685000
Reexamination Certificate
active
06458222
ABSTRACT:
1. TECHNICAL FIELD
This invention relates to a metal material, mainly to a copper-zinc alloy, i.e., brass, and processes for preparing the same, but the principle of the present invention to be applied is not limited only to brass.
2. BACKGROUND ART
Brass is generally excellent in machinability, good in corrosion resistance and easy in plastic working so that it has been used in an extremely wide field. Among these, a two-phase alloy of &agr;+&bgr; show a large ductility in a hot region (650 to 750° C.), and a modification resistance thereof belongs to the lowest group among the metal materials provided for forging.
However, in the characteristics inherently possessed by the material, it cannot be said that research and development of the material itself have been earnestly studied whereas it has an extremely old history. Recently, only a report about ultra-plasticity at brittleness temperature region of an &agr;-type brass has been found. [Tuyoshi Muto et. al.: Nippon Kinzoku Gakkai-shi, 59 (1995), 28]
The present invention has been done in view of the above-mentioned circumstances, and an object thereof is to provide a metal material, brass and a preparation thereof improved in hot working property.
Also, another object of the present invention is to improve hot working property in a plastic working method of a brass material which is representative as metal materials.
Also, another object of the present invention is to provide brass improved in forging property at a low temperature region of 450° C. or less and a process for preparing the same, and a plastic working method of a brass material.
3. DISCLOSURE OF THE INVENTION
A metal material according to the first embodiment of the present invention is a metal material having a microstructure which is formed by dispersing strain by deformation when an external force is received, and said strain energy by the above-mentioned deformation becomes an energy source of recrystallization of said metal microstructure, characterized in that said microstructure contains the first to the third crystals or phases different in hardness. Thus, in the metal material, as compared with microstructure with two-phases, an amount of an interface between different phases increases so that slipping at the interface between different phases effectively acts. According to this, strain is not locally concentrated but dispersed so that a large amount of strain energy is applied to an energy source for recrystallization whereby high hot ductility can be obtained.
It is suitably desired that the above-mentioned first to third crystals are sufficiently made fine so as to disperse the strain caused at the first crystal which is the softest crystal by slipping at the interface between different phases when an external force is applied thereto. When such a constitution is employed, strain can be easily dispersed in cooperation with the slipping at the interface between different phases.
Brass according to the second embodiment of the present invention comprises an apparent Zn content of 37 to 46 wt % and contains Sn of 1.7 to 2.2 wt %. That is, by firstly making the apparent Zn content 37 to 46 wt %, area ratios of &bgr; and &ggr; phases at the recrystallization temperature region can be ensured with certain extents. Here, when the Zn content alone is increased, whereas the &bgr; and &ggr; phases can be ensured, an &agr; phase cannot be ensured.
Thus, in the brass according to the second embodiment, by adding Sn which is an element having a large Zn equivalent, while ensuring the &bgr; and &ggr; phases at the recrystallization temperature region, the &agr; phase is also ensured sufficiently whereby an interface slipping between the different phases according to the three phases effectively acts. And it is preferred that the Sn amount is regulated to in the range of 1.7 to 2.2 wt %.
Here, the term “an apparent Zn content” is used in the meaning of “{(B+txQ)/(A+B+txQ)}×100” wherein A is a Cu content [wt %], B is a Zn content [wt %], t is a Zn equivalent of the third element (e.g., Sn), and Q is a content of the third element [wt %].
Brass according to the third embodiment of the present invention is brass as a material for effecting plastic working which comprises an apparent Zn content of 37 to 50 wt %, and contains Sn of 1.5 to 7 wt %. Also, more preferably, it is the brass as a material for effecting plastic working comprising an apparent Zn content of 45 to 50 wt %, and containing Sn of 1.5 to 7 wt %.
Brass according to the fourth embodiment of the present invention is brass as a material for effecting plastic working which comprises an apparent Zn content of 37 to 50 wt %, and contains Sn of 3.5 to 7 wt %.
Brass according to the fifth embodiment of the present invention comprises satisfying all the requirements that the microstructure when it is plastic deformed by receiving an external force is a three-phase of &agr;+&bgr;+&ggr;, an area ratio of the &agr; phase is 44 to 65%, an area ratio of the &bgr; phase is 10 to 55%, an area ratio of the &ggr; phase is 1 to 25%, average crystal grain sizes of the &agr;, &bgr; and &ggr; phases are 15 &mgr;m or less, preferably 10 &mgr;m or less, and the above &agr; and &ggr; phases are present in dispersed states.
Here, when it is a two-phase of &agr;+&bgr;, external force-absorption by deformation does not effectively act if the area ratio of the &bgr; phase becomes lower than 30%. However, in the present invention, when the area ratio of the &bgr; phase is lower than 30%, it is defined to be necessarily a three-phase of the &agr;, &bgr; and &ggr; phases. Thus, in this case, slipping at the interface between the different phases effectively acts to realize high ductility.
On the other hand, when the area ratio of the &bgr; phase exceeds 80%, growth and coarsening of crystal grains occur whereby ductility is lowered. In the temperature region coexisting the &agr;, &bgr; and &ggr; phases as in the present invention, the area ratio of the &bgr; phase does not become to such a large value. Also, when the area ratio of the &ggr; phase exceeds 25%, brittleness of the &ggr; phase becomes dominant whereby ductility is lowered. If the area ratio of the &agr; phase exceeds 65%, optimum ratios of the &bgr; and &ggr; phases cannot be difficultly ensured.
Moreover, the reason why the average crystal grain sizes of the &agr;, &bgr; and &ggr; phases are made 15 &mgr;m or less, preferably 10 &mgr;m or less, and the above &agr; and &ggr; phases are present by dispersing is not to concentrated locally but to disperse the strain generated at the &bgr; phase
Brass according to the sixth embodiment of the present invention comprises satisfying all the requirements that the brass has a microstructure of &agr;+&bgr;+&ggr; at the recrystallization temperature region, an area ratio of the &agr; phase at the recrystallization temperature region is 44 to 65%, an area ratio of the &bgr; phase is 10 to 55%, an area ratio of the &ggr; phase is 1 to 25%, average crystal grain sizes of the &agr;, &bgr; and &ggr; phases are 15 &mgr;m or less, preferably 10 &mgr;m or less, and the above &agr; and &ggr; phases are present in dispersed states.
Brass according to the seventh embodiment of the present invention comprises satisfying all the requirements that the brass has a microstructure of &agr;+&bgr;+&ggr; at the temperature region of 300 to 550° C., preferably 400 to 550° C., an area ratio of the &agr; phase at the temperature region is 44 to 65%, an area ratio-of the &bgr; phase is 10 to 55%, an area ratio of the &ggr; phase is 1 to 25%, average crystal grain sizes of the &agr;, &bgr; and &ggr; phases are 15 &mgr;m or less, preferably 10 &mgr;m or less, and the above &agr; and &ggr; phases are present in dispersed states.
The brass according to the fifth embodiment of the present invention is brass as a material for effecting plastic working which comprises having at least the &ggr; phase microstructure.
Also, in the brass according to t
Ashie Nobuyuki
Matsubara Ryuji
Nakamura Katsuaki
Frishauf Holtz Goodman & Chick P.C.
Ip Sikyin
Toto Ltd.
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