US 4,378,246 AGranted

Precipitation hardening type stainless steel for spring

AssigneeNisshin Steel Co., Ltd.

InventorsKazuo Hoshino, Sadao Hirotsu, Masahiro Nishimura, Teruyoshi Iida

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Abstract

Precipitation hardening type stainless steel comprising in % by weight, 0.03<C.ltoreq.0.08, 0.3.ltoreq.Si.ltoreq.2.5, Mn.ltoreq.4.0, 5.0.ltoreq.Ni.ltoreq.9.0, 12.0.ltoreq.Cr.ltoreq.17.0, 0.1.ltoreq.Cu.ltoreq.2.5, 0.2.ltoreq.Ti.ltoreq.1.0, and Al.ltoreq.1.0, the balance being Fe and impurities, the elements being further adjusted so that A'=17.times.(C/Ti)+0.70.times.(Mn)+1.times.(Ni)+0.60.times.(Cr)+0.76.times. (Cu)-0.63.times.(Al)+20.871 is less than 42.0, ##EQU1## is not more than 2.7, and .DELTA.Hv=205.times.[Ti-3.times.(C+N)]+205.times.[Al-2.times.(N)]+57.5.time s.(Si)+20.5.times.(Cu)+20 is within the range between 120 and 210, said steel as solution treated and optionally slightly cold worked having a substantial martencite structure. The steel has a good mechanical workability before aging, and when age hardened, it develops improved hardness and toughness as well as an isotropic and improved spring performance.

Claims2

Dependent claims

A precipitation hardening type stainless steel for spring comprising in % by weight more than 0.03% but not more than 0.08% of C, 0.3 to 2.5% of Si, not more than 4.0% of Mn, 5.0 to 9.0% of Ni, 12.0 to 17.0% of Cr, 0.1 to 2.5% of Cu, 0.2 to 1.0% of Ti and not more than 1.0% of Al, the balance being Fe and unavoidable impurities, the contents of the elements being further adjusted so that the A' value defined by the equation

A'=17.times.(C%/Ti%)+0.70.times.(Mn%)+1.times.(Ni%)+0.60.times.(Cr%)+0.76.t imes.(Cu%)-0.63.times.(Al%)+20.871
is less than 42.0, the ratio of Cr equivalents to Ni equivalents defined by the equation ##EQU4## is not more than 2.7, and .DELTA.Hv value defined by the equation
.DELTA.Hv=205.times.[Ti%-3.times.(C%+N%)]+205.times.[Al%-2.times.(N%)]+57.5 .times.(Si%)+20.5.times.(Cu%)+20
is within the range between 120 and 210, said steel having a substantial martensitic structure at the state of having been solution treated or at the state of having been solution treated and then cold worked with a rolling reduction of not more than 50%.

1 more element

Dependencies are inferred from the claim text.