1996 Volume 82 Issue 4 Pages 309-314
As the hardness of high carbon martensitic stainless steels is very high, they are used for cutlery and bearings, etc. However, as huge Cr carbides larger than 20 μm in diameter are formed in these steels, knife edges are easily chipped and fatigue cracks during rolling are initiated from these huge Cr carbides.
In this paper, the effect of nitrogen addition to obtain fine Cr carbides in SUS440A (Fe-16.5%Cr-0.65%C) has been studied, and the effect of nitrogen content on both mechanical properties and the corrosion resistance has been investigated. The main results are summarized as follows : The addition of nitrogen more than 0.25% supresses the crystallization of eutectic Cr carbides during casting, and fine Cr carbides can precipitate after hardening heat treatment. As a result, the impact toughness of hardened and tempered sheets is improved, the maximum hardness shows more than HRC60, and the cold workability, the resistance to temper softening and the corrosion resistance are comparable to conventional low nitrogen steels.
