冷却速度对微合金化中碳非调质钢组织和性能的影响

通过热处理试验模拟了曲轴用微合金化中碳非调质钢经过小变形量条件的闭式模锻后获得的粗大组织,并进行相应的力学性能测试,研究了冷却速度和微合金元素Ti、Nb对中碳非调质V钢组织和力学性能的影响。结果表明,V-Ti-Nb钢炉冷后的综合力学性能最佳,抗拉强度达到960.6 MPa、屈服强度达到672.1 MPa、断后伸长率达到17.5%、冲击吸收能量达到22.9 J。冷却速度的增加使得V钢的抗拉强度和屈服强度均提高了近120 MPa,由于贝氏体这类硬相的存在,导致塑性下降,但是由于原始奥氏体晶粒尺寸的细化,使得冲击性能没有发生明显变化。Ti和Nb的加入,V-Ti-Nb钢由于珠光体片层间距的细化及(V, Ti, Nb)(C, N)的析出强化,屈服强度提升了76.5 MPa;珠光体片层间距和原始奥氏体晶粒尺寸的细化是V-Ti-Nb钢冲击性能改善的主要原因。

Effect of cooling rate on microstructure and properties of microalloyed medium carbon non-quenched and tempered steel

Heat treatment was adopted to simulate the coarse microstructure of microalloyed medium carbon non-quenched and tempered steel for crankshaft after closed-die forging with small deformation amount, the corresponding mechanical properties were tested, and the effects of cooling rate and microalloying elements Ti, Nb on microstructure and mechanical properties of the tested steels was studied. The results show that the comprehensive mechanical properties of V-Ti-Nb steel after furnace cooling are the best: the tensile strength, yield strength, elongation and impact absorbed energy are 960.6 MPa, 672.1 MPa, 17.5% and 22.9 J, respectively. With the increase of cooling rate, the tensile strength and yield strength are increased by nearly 120 MPa, the plasticity is decreased due to the existence of bainite, but the impact property is nearly unchanged due to the refinement of prior austenite grain size. With the addition of Ti and Nb, the yield strength is increased by 76.5 MPa due to the precipitation strengthening of (V, Ti, Nb)(C, N) and the refinement of pearlite interlamellar spacing, and in addition, the impact property of the V-Ti-Nb steel is improved mainly due to the refinement of both the pearlite interlamellar spacing and the prior austenite grain size.