EFFECTS OF CU, NI, CR AND SN ON MECHANICAL-PROPERTIES OF TI ADDED EXTRA LOW C-STEEL SHEET

The effects of Cu, Ni, Cr and Sn addition on the mechanical properties of Ti-added extra low carbon continuously annealed steel sheet were studied. Following results were obtained: (1)Cu or Cr addition up to around 0.2% raised tensile strength, and decreased total elongation and r value. (2)When slab reheating temperature was lowered to 1050-degrees-C, tensile strength was decreased and total elongation and r value were increased at the same 0.2% Cu or 0.2% Cr content. (3)Ni addition up to 0.12% did not give a significant effect on tensile properties or r value. (4)Sn addition up to 0.085% increased tensile strength, and decreased total elongation and r value. In the case of Sn, lowering slab reheating temperature did not improve total elongation and r value. (5)The effects of Cu, Ni, Cr and Sn content on mechanical properties are proportional to the difference in atomic radius between iron and those impurities. (6)The effect of impurity content on r value is different between the group of Cu, Ni and Cr, and Sn. In the case of Cu, Ni and Cr whose atomic radius are slightly bigger than that of iron, r value can be improved with lowering slab reheating temperature. However, in the case of Sn whose atomic radius is significantly bigger than that of iron, the effect of slab reheating temperature is very small.