Patent ID: 7170073

Claim:
A stainless steel slab containing B, wherein a protecting material made of a stainless steel containing B of 0.3 mass % or less is joined onto at least two faces across the bloom from each other, excluding a working plane, in a stainless steel bloom containing B of 0.3–2.5 mass %, being integrated into one-piece by forming a weld metal comprising a stainless steel with chemical composition that satisfies the relationship expressed by formulas (1)–(4) as below; 15≦Cr eq≦ 30 (1) 4≦Cr eq −Ni eq≦ 17 (2) where, Cr eq =Cr+1.5×Si+Mo−5×B (3) Ni eq =Ni+30×(C+N)+0.5×Mn (4) Herein, each symbol of a chemical element designates the content (mass %) of relevant chemical element contained in steel.