鋼の 700∿1300℃における間欠引張変形による応力緩和と高温延性

概要

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In order to understand the effects of straightening points of continuous caster on the surface cracking susceptibility of the slabs, stress relaxation during hot deformation of low alloy steel austenite and austenitic steels has been studied by means of intermittent tensile testing at temperatures ranging from 700 to 1300℃. The processes of deformation to given strains at a slow strain rate of 4×10^<-4>s^<-1> and subsequent stress relaxation for 3 min were repeated. Stress relaxation is largely suppressed by lowering the deformation temperature especially in Nb steels because of the dynamic precipitation of NbC. Although the carbonitride precipitates nucleating dynamically can grow into considerably coarser particles in the subsequent relaxation process, the dynamic precipitetion introducing the ductility loss can occur in the next deformation. Thus the ductility in the intermittent deformation is completely the same as in the continuous deformation, indicating that increasing the straightening points will enhance the dynamic precipitation because of lowering the average strain rate, resulting in significant enhancement effect on the surface cracking frequency. While at higher temperatures, since the stress relaxation can occur much easily, the multipoint straightenng could give considerable improvement effect on internal cracking which is usually formed at temperatures close to the solidus.
社団法人日本鉄鋼協会の論文
1987-07-01