CAST SLAB EXCELLENT IN QUALITY AND WORKING CHARACTERISTIC AND STEEL MATERIAL WORKED FROM THIS SLAB

摘要

PROBLEM TO BE SOLVED: To obtain a cast slab having fine and uniform solidified structure, and restraining the surface and the internal defects such as crack, dent flaw, center segregation and excellent in the quality and the workability by containing specified pieces of inclusions having a specified ratio or lower of a lattice coherency with δ-ferrite formed at the solidifying time from molten steel. ;SOLUTION: This steel material is the one applying the working of rolling, etc., after heating a cast slab, in which ≥100 pieces/cm2 of the inclusion having ≤6% lattice coherency with the δ-ferrite formed at the solidifying time from the molten steel is contained. Since this steel material works the cast slab having uniform and fine solidified structure, the surface and internal defects thereof caused by the solidified structure are reduced, and this cast slab is easily deformed in the rolling reduction direction and the workability of rolling, etc., can be improved. Further, the surface defects of slab, crack, etc., and the surface and internal defect of porosity, center segregation, etc., generated in the steel material after working can be restrained. Then, in the inclusion contained in the cast slab, it is desirable to contain ≥100/cm2 inclusion having ≤10 μm size.;COPYRIGHT: (C)2000,JPO