回火温度对1500MPa级Nb-Ti低合金直接淬火钢组织与性能的影响

Effects of tempering temperature on microstructure and mechanical properties of 1500 MPa grade Nb-Ti low alloyed directly quenched steel

通过低成本成分设计,在控制轧制的基础上,应用直接淬火+回火工艺制得抗拉强度1 500 MPa级经济型低合金高强高韧钢,测定了该合金成分体系的连续冷却转变曲线,研究了不同回火温度对直接淬火钢组织与力学性能的影响.结果表明:随着回火温度的升高,试验钢抗拉强度逐渐下降,屈服强度先升高后降低,-40℃冲击功则呈现出先升高、后降低、再升高的趋势.回火温度为200℃时,试验钢获得了最优的综合力学性能,抗拉强度达到1 730 MPa,屈服强度为1 400 MPa,-40℃冲击功为43 J.

Based on the chemical composition design of low cost and controlled rolling,an economical high strength and high toughness low alloy steel with tensile strength of 1 500 MPa grade was obtained by using direct quenching ＋ tempering.The continuous-cooling-temperature（CCT） curve was measured.And the effects of tempering temperature on the microstructure and mechanical properties of the directly-quenched steel were also investigated.The results showed that with the increasing of tempering temperature,the tensile strength continuously reduced while the yield strength gradually increased first and then decreased.However,-40 ℃ Charpy impact energy firstly increased,then decreased and increased again as the tempering temperature was increased.The best mechanical properties of the steel can be obtained when tempered at 200 ℃,the tensile strength is 1 730 MPa,the yield strength is 1 400 MPa and the-40 ℃ Charpy impact energy is 43 J.