GB447606A - Improvements in processes for improving the physical properties of austenitic alloy steels - Google Patents

Abstract

In a process for improving the properties of austenitic alloy steels containing a precipitation hardening agent such as titanium or niobium, the alloy steel is quenched from a temperature above the recrystallization to normal temperature, strain-hardened, e.g. by cold working, and then subjected to a precipitation-hardening heat-treatment below the recrystallization temperature. The precipitation-hardening temperature is carried out at 600-1200 DEG F., preferably at 850 DEG F. for an alloy steel containing niobium, and may be of an hour's duration. The alloy steels treated may be chromium-nickel steels, chromium-nickel-manganese steels or chromium-manganese steels, and the content of titanium 0,2-1,0 per cent and of niobium up to 3 per cent. In an example, an alloy steel treated contains 18 per cent of chromium, 8 of nickel, not more than 0,2 of carbon and titanium 0,2-1,0, the latter content being preferably 5 times that of the carbon. Beryllium, copper, silicon and tantalum may also be used as precipitation hardening agents and in amounts up to 3 per cent or a total of 3 per cent when more than one is used. In an example, an alloy steel treated contains 18 per cent of chromium, 8 of nickel, ,05 of carbon, ,40 of titanium, ,03 of sulphur, ,03 of phosphorus, ,7 of manganese and ,5 of silicon. In the Specification as open to inspection under Sect. 91, cobalt, molybdenum, tungsten and vanadium may be used as precipitation hardening agents and also it is stated that the strain-hardening and the precipitation-hardening treatments may not be carried out in a single stage. This subject-matter does not appear in the Specification as accepted.