Hot ductility of Ti-added ultra low carbon steels has beenstudied with particular emphasis on the bahavior of TiS. Hot ductility of low Mn low carbon steels initially solution-treated in the high temperature y region is reduced with intergranular fracture by high strain rate deformation at temperatures ranging from 900 to 1 100'C. This can be explained by the fact that hardening due to dynamic precipitation of Fe-rich sulfide within the matrix accelerates the void initiation at interface of

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... n boundary precipitate/matrix. In Ti-added steels, the ductility loss is considerably smaller comparedto that of Ti-free low Mn steels, since Ti has a role of trapping Satoms as TiS particles in the samewayas Mn. However, nitrogenation due to heating in the nitrogen gas atmosphere or in air changesTiS into the more stable TiN especial]y in the surface layer. As a result, the extra free Satoms formed by this reaction leads to hot embrittlement by the same mechanism.