GB473331A - Improvements in and relating to the heat treatment of austenitic nickel-chromium steels - Google Patents

Abstract

To render austenitic steel alloys containing 6-50 per cent of nickel, 10-40 of chromium and not more than 0,25 of carbon resistant to corrosion at temperatures of in the range 800-1500 DEG F., and at below 800 DEG F. after heating at that range, slip bands are formed in the alloys by cold working below the temperature of carbide precipitation and the precipitation of carbides in the slip bands is produced by heating the alloys within the carbide precipitation range, but below 1500 DEG F. and below the recrystallization range, whichever is the lower, for a time at least sufficient to effect a precipitation of substantially all the carbon in excess of the solubility limit at the temperature of heating and at least sufficient to effect substantially uniform redistribution of the chromium throughout the said alloy but not sufficient to cause substantial recrystallization. The cold working may be carried out at atmospheric temperature or such as result from cold working without heating the alloy. Reduction of cross-section of the alloys up to 60 per cent is referred to. In an example, wire stock made of an alloy steel containing 18 per cent of chromium, 8 of nickel, and 0,05 of carbon is heated for 16 hours at 1200 DEG F., after being subjected to cold working to produce a 50 per cent reduction in cross-section.