| 摘要 |
PURPOSE: To continuously cast an Ni-contg. steel slab free from internal crack by specifying the contents of P and S to prescribed values and specifying the internal solidification boundary strain rate in the region where the thickness of a solidified shell attains the prescribed value with the thickness of the slab to a prescribed value. CONSTITUTION: The molten steel is smelted by confining the contents to be incorporated into the steel to <=0.01% P and <=0.005% S from the results obtd. by finding the presence of a correlation among the internal crack of the slab, the thickness of the solidified shell of the slab and the internal solidification boundary strain rate. The molten steel is cast into a continuous casting machine. The internal solidification boundary strain rateεcalculated from equations I, II and IV or equations I, III and IV is confined to <=0.7×10<-2> in the region where the thickness of the solidified shell on the front and rear surfaces of the slab attains the thickness of >=1/4 the thickness of the slab in the continuous casting machine, by which the continuous casting of the slab contg. 5 to 10% Ni free from the internal crack is made possible. In the equations,εN: the distortion by straightening of bending,εB: a bulging distortion, D: the thickness (cm) of the slab, d, dn : the thickness (cm) of the solidified shell, R, Rn-1 , Rn : the bending radius (cm), P: the static pressure (kg/cm<2> ) of the molten metal, l: the distance between rolls (cm), E: 0.3×10<6> (kg/cm<2> ).
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