Influence of hot rolling temperature and reduction on mechanical properties of Ti-bearing extra low carbon hot-rolled steel sheets

The effects of hot rolling temperature and rolling reduction on the mechanical properties of Ti-bearing extra low carbon steel sheets have been studied. Conclusions obtained are as follows: 1. The elongation of as-rolled steel sheet through conventional reduction decreased when the finishing rolling temperature was under 830 degreesC. But the elongation, tensile strength and yield strength of the steel sheet after annealing had little change in the range of 650 similar to 850 degreesC. 2. The difference of tensile strength between as-rolled and annealed steel sheet was thought to be due to the substantial strain energy which was stored by hot rolling. The substantial strain energy of the steel sheet rolled at 650 degreesC through conventional reduction corresponds to about 37% cold reduction. 3. The (r) over bar -value of the annealed steel sheet rolled at 650 degreesC was 0.8. But it increased to 1.14 by surface shaving. This value is approximately equal to that of about 37% cold reduction steel sheet. In these circumstances. the cause of the low (r) over bar -value of steel sheet rolled in the ferrite region is the influence of surface shear strain. 4. In the case of heating at 1250 degreesC, average (r) over bar -value of Ti-bearing exrta low carbon steel sheet is approximately 1.0. when the high-reduction rolling is achieved in the final three stands with a reduction more than 50% near the Ar-3 temperature at each rolling pass.