GB722427A - Improvements in or relating to corrosion resistant steel springs and spring materialand methods for making same - Google Patents

Abstract

Steel springs and spring material having good corrosion resistance and high elastic modulus and tensile strength are manufactured by quench-annealing an unstable austenitic alloy from 950-1200 DEG C., the alloy containing Fe as its principal constituent, 6-10 per cent of Ni, 12-20 per cent Cr, at least one of the ferrite-forming elements Si up to 2 per cent and Mo up to 3 per cent, there being present at least 0.8 per cent Si and/or at least 0.4 per cent Mo, cold working in a number of steps without intermediate annealing with a total cross-sectional reduction of at least 70 per cent and tempering the alloy at 350-550 DEG C. to achieve the spring properties, the proportion of austenite-forming elements to ferrite-forming elements being such as to effect substantially no transformation of austenite below 70 per cent reduction but a substantial transformation to a ferro-magnetic phase thereabove. The alloy may also contain C up to 0.3 per cent, Ti 0.4-30 per cent, one or more of Nb, Ta, V, W, Cu, Co up to 1.5 per cent each and Mn up to 3.0 per cent. The following ranges of alloys are referred to: C 0.07-0.25, Si 0.8-1.3, No 0.8-0.3, Mn 0.7-3.0, Cr 17.0-19.0, Ni 7.0-9.0, Fe remainder; C 0.1-0.2, Si 1.1-1.2, Mo 0.8-0.9, Mn 0.9-1.0, Cr 18.0-19.0, Ni 8.0-9.0, Fe remainder and C 0.1-0.2, Si 0.4-0.5, Mo 1.0-2.0, Mn 0.1-0.2, Cr 17.0-18.0, Ni 9.0-10.0, Fe remainder, all proportions being per cent by weight.