研究了淬火温度和回火温度对中碳铬-镍-钼系超高强度钢屈强比的影响,分析了超低屈强比现象产生的原因.结果表明:在淬火后200 ℃回火条件下,屈强比随淬火温度的升高先下降,至950~1 000 ℃淬火时仅约为0.45,尔后又升高;900 ℃淬火、165~180 ℃回火后,其屈强比较低(约为0.45),而抗拉强度大于2 200 MPa.超低屈强比现象主要与残余奥氏体及其中的可动位错和淬回火后的残余应力有关.

The effects of quenching temperature and tempering temperature on the ratio of yield strength to tensile strength (yield ratio) in a medium carbon Cr-Ni-Mo ultra high strength steel have been investigated.After quenching and tempering at 200 ℃,the yield ratio first decreases and then increases with the increase of quenching temperature,being the lowest of about 0.45 at 950-1 000 ℃ quenching.When the quenching temperature was 900 ℃ and the tempering temperature was 165-180 ℃,the yield ratio was as low as 0.45 while the tensile strength was more than 2 200 MPa.The phenomenon of ultra low yield ratio correlated with the presence of retained austenite,large amounts of movable dislocations in retained austenite,and residual stress after quenching and tempering.