摘要:
Provided is a maraging steel excellent in fatigue characteristics, including, in terms of % by mass: C: ≤0.015%, Ni: from 12.0 to 20.0%, Mo: from 3.0 to 6.0%, Co: from 5.0 to 13.0%, Al: from 0.01 to 0.3%, Ti: from 0.2 to 2.0%, O: ≤0.0020%, N: ≤0.0020%, and Zr: from 0.001 to 0.02%, with the balance being Fe and unavoidable impurities.
摘要:
Disclosed is a heat resistant alloy for exhaust valves, in which Ni-content is constrained to at maximum 62% due to the material cost, while the strength is maintained equal or better to those of conventional alloys and the strength is kept even after use at high temperature for a long period of time. The alloy has the composition essentially consisting of, by weight %, C: 0.01-0.2%, Si: up to 1.0%, Mn: up to 1.0%, P: up to 0.02%, S: up to 0.01%, Ni: 30-62%, Cr: 13-20%, W: 0.01-3.00%, Mo: up to 2.0%, provided that Mo+0.5W: 1.0-2.5%, Al: 0.7% or higher and less than 1.6%, Ti: 1.5-3.0%, Nb: 0.5-1.5%, B: 0.001-0.010%, provided that [%Ti]/[%Al]: 1.6 or more to less than 2.0, and the balance of Fe and inevitable impurities. Optional components are I) at least one of Mg: 0.001-0.030%, Ca: 0.001-0.030% and Zr: 0.001-0.100%, II) Cu: up to 2.0%, and III) V: 0.005-1.00%.