Continuously cast slab

Abstract

A continuously cast slab prevents cracking during a cooling process therefor even if such a slab is a high-alloy slab with low toughness. Specifically, a continuously cast slab for high-strength steel features the average prior austenite grain size at a position 10 mm from the surface layer of the continuously cast slab in the range of 100 μm to 0.5 mm; and in the microstructure of the slab, the area ratio of ferrite is 10% or more, the area ratio of pearlite is 10% or more, and the area ratio of bainite is in the range of 1% to 30%. The continuously cast slab preferably contains, in mass %, C: 0.10 to 0.40%, Si: 0.10 to 2.50%, and Mn: 1.00 to 5.00%.

1 . A continuously cast slab for high-strength steel, wherein
 an average prior austenite grain size at a position 10 mm from a surface layer of the continuously cast slab is in a range of 100 μm to 0.5 mm, and   in a microstructure, an area ratio of ferrite is 10% or more, an area ratio of pearlite is 10% or more, and an area ratio of bainite is in a range of 1% to 30%.   
     
     
         2 . The continuously cast slab according to  claim 1 , comprising, in mass %:
 C: in a range of 0.10 to 0.40%;   Si: in a range of 0.10 to 2.50%; and   Mn: in a range of 1.00 to 5.00%.