Alloys or metallic compositions – Aluminum base – Copper containing
Reexamination Certificate
2002-05-31
2003-01-28
Wyszomierski, George (Department: 1742)
Alloys or metallic compositions
Aluminum base
Copper containing
C420S538000, C420S554000
Reexamination Certificate
active
06511633
ABSTRACT:
RELATED U.S. APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
REFERENCE TO MICROFICHE APPENDIX
Not applicable.
FIELD OF THE INVENTION
The present invention relates to a eutectic Al—Si alloy having excellent free machinability and abrasion resistance. In the present invention, the free machinability means that machinability is excellent.
The inventive eutectic Al—Si alloy can be applied to parts requiring formability, workability and abrasion resistance, such as scrolls or pistons of compressors for air conditioners in automobiles or appliances.
BACKGROUND OF THE INVENTION
Lubricants should be continuously fed to friction face of scrolls or pistons. Otherwise, seizure between friction metals occurs. So, metal materials having excellent abrasion resistance as well as formability and workability are suitable for use in such parts.
On the other hand, in order to manufacture lightweight automobiles or appliances, metals having low specific gravity are used. Also, even though metals are excellent in abrasion resistance and have low specific gravity, if they have poor workability including machinability, preparation cost becomes high. Metals, such as cast iron or bronze, have the advantage of excellent machinability but suffer from the disadvantage of high specific gravity. Therefore, in recent years, Al-based alloys are widely used. Excellent ductility of these metals results in improved formability.
Typically, there is a representative eutectic Al—Si alloy having excellent abrasion resistance, lightweight property, and relatively superior formability and workability, as shown in the following
TABLE 1
Composition of Conventional Eutectic Al-Si Alloy
Composition Component
Composition Ratio (wt %)
Si
11.0-1.35
Cu
0.5-1.3
Fe
1.0 or less
Mg
0.8-1.3
Cr
0.10 or less
Ni
0.5-1.3
Al
Balance
Such alloy is called A4032 alloy in the related fields.
In alloys comprising two or more metals, the metals which are able to produce a congruent compound are used stoichiometrically, in which the congruent compound refers to that one metal of solid phase which is melted in the other metal of liquid phase at melted state or solid solution state. The alloy forming the congruent compound appears to be in equilibrium state.
The alloy which consists of compositions forming the congruent compound is called a eutectic alloy, in which the eutectic alloy exists at the eutectic point in equilibrium diagrams of alloys. Alloys which are positioned at the left side of eutectic point in the equilibrium diagram are referred to as hypo-eutectic alloys, and alloys located at the right side of eutectic point in the diagram are called hyper-eutectic alloys.
As for Al—Si alloy, alloys having 12.5 wt % of Si correspond to congruent compounds. Commonly, if Si content ranges from 11 to 13 wt % , such alloy is called a eutectic alloy. On the other hand, hypo-eutectic alloys have Si content less than said range and hyper-eutectic alloys have Si content higher than said range.
In the case of applying to pistons in compressors for automobile air conditioners, conventional A4032 eutectic alloys representatively used in this field are subject to surface-treatment, such as anodizing or Sn plating, to improve abrasion resistance. Such conventional alloy is disadvantageous in that, unless lubricants are smoothly fed onto friction faces, seizure between the metals occurs. As well, cutting workability becomes poor and abrasion ratio of cutting tools is very high, thus increasing preparation cost.
There is thus a widely recognized need for materials having superior machinability and abrasion resistance to conventional A4032 alloy.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a eutectic Al—Si alloy, which is excellent in free-machinability and abrasion resistance and maintains high strength through heat treatment.
The intensive and thorough research on a eutectic Al—Si alloy, carried outby the present inventors aiming to avoid the problems encountered in the prior arts, resulted in the finding that, on preparation of a eutectic Al—Si alloy, Sb, not reactive with Bi, is added, along with Bi, under conditions that Sr, strongly reactive with Bi, is not used, and amounts of Mg, Mn and Ni to be added are minimized, yielding Al—Si—Cu—Bi alloy, whereby eutectic Al—Si alloys which have superior free-machinability, abrasion resistance and ductility to conventional eutectic Al—Si alloys, and maintain high strength though heat treatment, can be obtained.
As for conventional eutectic Al—Si alloys, there was no alloy containing Sb as a component.
REFERENCES:
patent: 5122207 (1992-06-01), Alabi
“Internation Alloy Designations and Chemical Composition limits for Wrought Aluminum and Wrought Aluminum Alloys”, The Aluminum Association, 1997.
Combs-Morillo Janelle
Foosung Precision Ind., Co., Ltd.
Harrison & Egbert
Wyszomierski George
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