| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a new high-strength steel for a machine structure, which is superior in a recycling property because of having a simple composition, does not require complex processing and heat treatment, and is superior in delayed fracture resistance. SOLUTION: The high-strength steel for the machine structure has a composition of, by wt.%, 0.2-0.7% C, 0.2-2.5% Si, 0.05-1.0% Mn, 0.2-1.5% Cr, and 0.3-1.5% Mo, has a total amount of alloy elements, which satisfies Si+Mn+Cr+Mo <=5 wt.%, includes the balance Fe with unavoidable impurities, is tempered in a range of 500 deg.C to Ae1 temperature or lower, and in a condition that a tempering parameter,λ, satisfiesλ=T(20+logt)>=15,800, (where T indicates a temperature (K), and t indicates a time (h)), and has tensile strength of 1,800 MPa or higher.</p> |
