2009 Volume 95 Issue 4 Pages 369-377
The recycling of scrap steels is a global issue due to the environmental problem. Tramp elements such as Cu and Sn that they can contain cause surface cracking of steels during hot rolling process (i.e., the liquid embrittlement by Cu). This paper describes the influence of shot peening on the surface hot shortness of x% Cu (x50, 0.4 and 0.6) containing low carbon–Nb–V steel. These materials were shot peened by Al2O3 at room temperature and they were subjected to 1100°C oxidation in air or in water vapor contained atmosphere followed by tensile strain or compression strain. Surface hot shortness was assessed by measuring the number and depth of surface cracks occurring in the specimens. It was found that shot peening largely changed the oxidized scale structure such as Fe2O3/Fe3O4 and Fe3O4/FeO interfaces, the volume fraction of voids in the scale, and the distribution of Cu enriched alloy at the interface of scale/steel, thereby suppressing the hot shortness of Cu steels.
The authors discussed this mechanism by macroscopically homogenous and microscopically heterogeneous oxidation due to the introduction of defects such as dislocations and lattice distortions into surface layer of Cu steels by shot peening. It was concluded that shot peening is high potentialities for suppressing the hot shortness of Cu containing steel as a new method other than using expensive nickel.