| 摘要 |
A martensitic stainless steel for a disc brake, which comprises, in mass %, less than 0.050 % of C, less than 0.09 % of N, 1.0 % or less of Si, 2.0 % or less of Mn, 0.04 % or less of P, 0.010 % or less of S, 0.2 % or less of Al, more than 11.5 % and not more than 15.0 % of Cr, 0.5 to 2. 0 % of Ni, more than 0.50 % and not more than 4.0 % of Cu, more than 0.08 % and not more than 0.6 % of Nb, with the proviso that the contents of C, N, Nb, Cr, Si, Ni, Mn and Cu satisfy the following formulae (1) and (2): 0.03 <= [C] + [N] - 13/93 X [Nb] <= 0.09 (1) 5 X [Cr] + 10 X [Si] + 30 X [Nb] - 9 X [Ni] - 5 X [Mn] - 3 X [Cu] - 225 X [N] - 270 X [C] <= 40 (2). The martensitic stainless steel is not significantly softened even after it has been kept at a temperature higher than 600°C. For example, it exhibits a HRC hardness of 32 or more after the temering at 650°C for 1 hr and a HRC hardness of 30 or more after the temering at 670°C for 1 hr.
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