Steel sheet for disk brake with improved anti-warp property and disk made thereof

Abstract

A steel sheet for disk brake with improved anti-warp property has a chemical composition comprising, in mass percent, 0.05-0.15% of C, not more than 1.0% of Si, not more than 2.0% of Mn, not more than 1.0% of Ni, 9.0-15.0% of Cr, 0.5-4.0% of Cu, 0.10-2.0% of Mo, not more than 0.10% of N, 0.05-1.0% of Nb, and the balance of Fe and unavoidable impurities and having a γmax value defined by: γmax=420C+470N+23Ni+7Mn+9Cu−11.5Cr−11.5Si−12Mo−3.5Nb+189 of not greater than 80. A brake disk obtained from the steel sheet keeps disk periphery warp height within 0.3 mm when the disk is subjected to 500 cycles of repeated heating/cooling each consisting of [Temperature increase at a rate of 5-20° C./sec up to 600° C. Maintaining at 600° C. during 10 sec Water cooling].

What is claimed is:  
     
         1 . A steel sheet for disk brake with improved anti-warp property having a chemical composition comprising, in mass percent, 0.05-0.15% of C, not more than 1.0% of Si, not more than 2.0% of Mn, not more than 1.0% of Ni, 9.0-15.0% of Cr, 0.5-4.0% of Cu, 0.10-2.0% of Mo, not more than 0.10% of N, 0.05-1.0% of Nb, and the balance of Fe and unavoidable impurities and having a γmax value defined by:  
       γmax=420C+470N+23Ni+7Mn+9Cu−11.5Cr−11.5Si−12Mo−3.5Nb+189  
       of not greater than 80.  
     
     
         2 . A steel sheet according to  claim 1 , further comprising not more than 0.50% of Ti.  
     
     
         3 . A steel sheet according to  claim 1  or  2 , further comprising not more than 0.2% of Al.  
     
     
         4 . A steel sheet according to any of  claims 1  to  3 , further comprising not more than 0.015% of B.  
     
     
         5 . A steel sheet according to any of  claims 1  to  4 , further comprising one or more of not more than 0.2% of REM, not more than 0.2% of Y, not more than 0.1% of Ca and not more than 0.1% of Mg.  
     
     
         6 . A steel sheet according to any of  claims 1  to  5  that is a steel sheet for a two-wheeled vehicle disk brake.  
     
     
         7 . A quenched brake disk obtained from a steel sheet having a chemical composition comprising, in mass percent, 0.05-0.15% of C, not more than 1.0% of Si, not more than 2.0% of Mn, not more than 1.0% of Ni, 9.0-15.0% of Cr, 0.5-4.0% of Cu, 0.10-2.0% of Mo, not more than 0.10% of N, 0.05-1.0% of Nb, and the balance of Fe and unavoidable impurities and having a γmax value defined by:  
       γmax=420C+470N+23Ni+7Mn+9Cu−11.5Cr−11.5Si−12Mo−3.5Nb+189  
       of not greater than 80,  
       which brake disk exhibits excellent anti-warp property of keeping disk periphery warp height within 0.3 mm when the disk is subjected to 500 cycles of repeated heating/cooling each consisting of [Temperature increase at a rate of 5-20° C./sec up to 600° C. Maintaining at 600° C. during 10 sec Water cooling].