Maraging steel

Abstract

Provided is maraging steel with which maraging steel that has been subjected to nitriding treatment has excellent fatigue strength and stable high strength. Maraging steel that has been subjected to nitriding treatment to a thickness of 0.5 mm or less and comprises, by mass %, 0.008% or less of C, 0.5% or less of Si, 0.5% or less of Mn, 0.5 to 1.5% of Cr, 16.0 to 22.0% of Ni, 3.0 to 7.0% of Co, and 3.0 to 7.0% of Mo is maraging steel further comprising, by mass %, 0.6 to 1.3% of Al and Fe and impurities as the balance, wherein the impurities are maintained at 0.01% or less of Ti, 0.01% or less of Nb, 0.01% or less of Ta, and 0.01% or less of W, the ratio of Al and Ti is Al/Ti>250, and by Vickers hardness, the surface hardness of the maraging steel is 800 to 1,050 HV and internal hardness of the maraging steel is 570 HV or less.

1 . Maraging steel subjected to nitriding treatment, the maraging steel containing 0.008% or less of C, 0.5% or less of Si, 0.5% or less of Mn, 0.5 to 1.5% of Cr, 16.0 to 22.0% of Ni, 3.0 to 7.0% of Co, and 3.0 to 7.0% of Mo by mass % and having a thickness of 0 5 mm or less, wherein
 the maraging steel further contains 0.6 to 1.3% of Al by mass %, and the balance consisting of Fe and impurities, the impurities are restricted to 0.01% or less of Ti, 0.01% or less of Nb, 0.01% or less of Ta, and 0.01% or less of W, a ratio of Al to Ti satisfies Al/Ti≧250, and a surface hardness of the maraging steel is 800 to 1,050 HV and an internal hardness of the maraging steel is 570 HV or less by Vickers hardness.   
     
     
         2 . The maraging steel according to  claim 1 , wherein the Al content is 0.7 to 1.2% by mass %. 
     
     
         3 . The maraging steel according to  claim 1 , wherein the maraging steel further contains, in addition to said compositions, either 0.0001 to 0.0030% of Mg or 0.0001 to 0.0030% of Ca, or both thereof, by mass %. 
     
     
         4 . The maraging steel according to  claim 1 , wherein the maraging steel further contains, in addition to said compositions, 0.0001 to 0.0030% of B.