NUNTAWAT Chokchaithananan Sahaviriya Steel Industry

Spoluautoři TAKATERU Umeda

The Thailand automotive industry and electrical appliance are growth continuously in the last decent. For this reason, a demand of high formability low carbon hot rolled steel strip has ever-increasing. One is boron added low carbon steel. Added 20-40 ppm can increase elongation while tensile strength and yield strength are slightly decreased. However, hot rolling of boron added steel caused some difficulties in rolling practice due to high rolling load at finishing mill. To success the development, continuous cooling transformation and high temperature deformation was investigated by using deformable dilatometer. Flow stress of both steels was determined by hot compression test at temperature range of 850 to 1050 °C under strain rate of 10 s-1. The results show that transformation start temperature of boron-added steel is lower than that of boron-free steel. Hot compression test results show that flow stress of boron-added steel is higher than that of boron-free steel. Especially at 1,000 – 1,050 oC, boron free steel exhibit work softening after strain of 0.35 can be observed, representing the dynamic recrystallization occurs but boron added steel does not occur that may cause of high rolling load at finishing mill stand. From this fundamental data, the developed steel success to increase 15 % elongation and higher forming limit curve than boron free low carbon steel

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