CAST STEEL PIECE WITH FINE SOLIDIFICATION STURCTURE AND EXCELLENT FORMING CHARACTERISTICS AND STEEL PRODUCT AND SEAMLESS STEEL PIPE PRODUCED BY USING THE SAME

摘要

A cast steel piece excellent in forming characteristics, characterized in that 60 % or more of the total cross section is constituted by equiaxial grains satisfying the following formula: D < 1.2 X 1/3 + 0.75 wherein D represents a diameter(mm) of an equiaxial grain as a structure having same orientation of crystal and X represents a distance from the surface (mm) of the cast steel piece. The cast steel piece and a steel product produced by forming the cast steel piece is extremely reduced in the amount of surface and internal defects.