SHOT PEENING METHOD

摘要

Disclosed is a shot peening method that, while suppressing cutting of a steel product to be treated, can apply a higher compressive residual stress than that in the conventional technique. A projection material having Vickers hardnesses HV (m), which are represented by formulae (1) to (3) and are higher than the hardnesses HV (m) of a steel product to be treated by a value in the range of 50 HV to 250 HV, is projected against the steel product having a hardness of not less than 750 HV to be treated to reduce the cutting level of the steel product to not more than 5 µm. HV(m1) = {f(C) - f(T, t)}(1 - ?R/100) + 400 × ?R/100 Formula (1) f(C) = -660C2 + 1373C + 278 Formula (2) f(T, t) = 0.05T(logt + 17) - 318 Formula (3) where C: C (carbon) concentration of carburized surface layer, % by mass T: tempering temperature, K t: tempering holding time, hr ?R: amount of residual austenite (% by volume)