Patent ID: 8607941

Claim:
A steel sheet for a brake disc, comprising, on a mass percent basis: 0.02% or more and less than 0.10% C, 0.6% or less Si, more than 0.5% and 2.0% or less Mn, 0.06% or less P, 0.01% or less S, 0.05% or less Al, 11.0% to 13.5% Cr, 0.01% to 0.30% Ni, 0.10% to 0.60% Nb, 0.03% or more and less than 0.10% N, more than 0.0016% and 0.0060% or less B, and the balance being Fe and incidental impurities, wherein the steel sheet after quenching has a hardness of 32 HRC to 40 HRC on a Rockwell hardness scale C (HRC), and the steel sheet satisfies expressions (1) to (3): 420C+470N+23Ni+9Cu+7Mn−11.5Cr−11.5Si−12Mo−47Nb−52Al−49Ti−23V+189≧85 (1) 0.04≦C+N−13(Nb/93+Ti/48+Zr/91+V/51)−14B/11≦0.09 (2) C−12(Nb/93+Ti/48+Zr/91+V/51+Mo/96+Ta/181+/184)≦0.045 (3)