BRAKE DISC HAVING HIGH TEMPER SOFTENING RESISTANCE

摘要

A brake disc that has appropriate hardness, exhibiting a high temper softening resistance. In particular, there is provided a brake disc having a high temper softening resistance, characterized in that it has a component composition comprising 0.1 mass% or less C, 1.0 mass% or less Si, 2.0 mass% or less Mn, 10.5 to 15.0 mass% Cr, 2.0 mass% or less Ni, over 0.5 to 4.0 mass% Cu, 0.02 to 0.3 mass% Nb and 0.1 mass% or less N, further comprising C, N, Nb, Cr, Si, Ni, Mn, Mo and Cu in amounts satisfying the formulae: 5Cr+10Si+15Mo+30Nb-9Ni-5Mn-3Cu-225N-270C<45 (1), and 0.03={C+N-(13/93)Nb}=0.09 (2), and still further comprising the balance Fe and unavoidable impurities, and that the brake disc has a martensite structure wherein the average diameter of former austenite grains is 8 µm or greater, and that the hardness thereof is in the range of 32 to 38 in terms of HRC.