| 摘要 |
<p>A free machining cold formable austenitic stainless steel alloy and articles made therefrom which contains in weight percent about < IMG > with the balance iron and preferably no more than 2 w/o manganese, 1 w/o silicon, 0.04 w/o phosphorus, 0.08 w/o nitrogen. Also, the alloy preferably contains 1.4-2.0 w/o copper and the free machining additive is 0.08-0.14 w/o sulfur. SPECIFICATION This invention relates to austenitic stainless steel and, more specifically, to an austenitic stainless steel having a unique combination of good cold formability and machinability It has long been recognized that austenitic chromiumnickel stainless steels not only have generally poor cold workability, but they are also characterized by wide variations in how they respond to cold forming. Bloom et al, 39 ASM 843-867 (1947), demonstrated that increasing carbon from about 0.03% by as little as 0.01% sharply increased the cold work hardening rate of 18Cr-8Ni stainless until about 0.10% carbon content was reached. They also brought out that increasing nickel from 8% to 12% effectively rendered the steel insensitive to increases in carbon content insofar as cold work hardening was concerned. U.S. patent No. 2,697,035, granted December 14, 1954 to W. C. Clarke, Jr., relates to free machining austenitic chromium-nickel stainless steel containing 12-20% chromium, 6.5-15% nickel, 1 to about 5.0% copper, 0.1-0.5% sulfur and/or selenium, up to 0.5% phosphorus and the remainder iron. When Clarke characterizes his alloy in claim 4 as having an improved surface finish, the just-mentioned composition is restricted to a range of 2.5 to about 5.0% copper. The alloys disclosed by Clarke in the tablet Col. 3, have left much to be desired both with regard to their cold working properties and machinability as represented by surface finish. The present invention is based upon the discovery that a unique combination of cold formability and machinability</p> |
