The carriage rail part null mass which is used for the common rail system which consists of fatigue strength and the non heat treated steel and the said non heat treated steel which for ferrite - pearlite die hot forging are superior in cutting

摘要

PROBLEM TO BE SOLVED: To provide a ferrite-pearlite type non-heat treated steel for hot forging, which maintains cutting workability such as super-hard drilling without adding free-cutting elements such as Ca, and having improved fatigue strength without using expensive alloy elements as much as possible.;SOLUTION: The ferrite-pearlite type non-heat treated steel for hot forging has a composition comprising, by mass, 0.30 to 0.50% C, 0.40 to 1.00% Si, 1.00 to 1.60% Mn, ≤0.035% P, 0.005 to 0.035% S, 0.005 to 0.050% Al, 0.10 to 0.30% V, ≤0.0300% N and ≤0.0080% O, and the balance Fe with inevitable impurities, and in which carbon equivalent C_eq satisfies 0.70≤C_eq≤1.05, and has a ferrite-pearlite type structure where, after hot rolling or hot forging, in an air-cooled state, 0.2% proof stress is ≥550 MPa and a proof stress ratio as the ratio of 0.2% proof stress to tensile strength satisfies ≥62%.;COPYRIGHT: (C)2011,JPO&INPIT