Ti添加極低炭素熱延鋼板の材質に及ぼす熱延温度,圧下条件の影響

抄録

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 840°C. But the elongation, tensile strength and yield strength of the steel sheet after annealing had little change in the range of 650850°C.
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°C through conventional reduction corresponds to about 37% cold reduction.
3. The r-value of the annealed steel sheet rolled at 650°C 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-value of steel sheet rolled in the ferrite region is the influence of surface shear strain.
4. In the case of heating at 1250°C, average r-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 Ar₃ temperature at each rolling pass.