正火温度对胀断连杆用36MnVS4和46MnVS5钢组织及性能的影响

Effect of normalizing temperature on microstructure and mechanical properties of 36MnVS4 and 46MnVS5 steels for fracture splitting connecting rod

以目前广泛用于汽车胀断连杆的中碳非调质钢36MnVS4和46MnVS5钢为对象,对比研究了其不同正火温度下的力学性能差异和组织转变规律,并分析了强化机理。结果表明,随着正火温度的升高,36MnVS4钢和46MnVS5钢的屈服强度、抗拉强度和硬度均逐渐增加,且46MnVS5钢的抗拉强度和硬度均大于36MnVS4钢。当在990℃以下正火时,46MnVS5钢的屈服强度大于36MnVS4钢,而在990℃以上正火时,46MnVS5钢的屈服强度小于36MnVS4钢。1140℃以上正火时,36MnVS4钢断面收缩率和伸长率较46MnVS5钢更高,韧性较好。36MnVS4钢和46MnVS5钢力学性能上的差异主要是由于36MnVS4钢中先共析铁素体含量多于46MnVS5钢,且1200℃正火后的先共析铁素体中析出强化相V(C,N)也多于46MnVS5钢,因此36MnVS4钢的塑性更好。但从胀断连杆的生产工艺及性能要求出发,由于韧性的提高对连杆的胀断加工不利,而46MnVS5钢具有良好的综合力学性能且较36MnVS4钢更具成本优势,因此胀断连杆用钢宜选择46MnVS5钢。

Mechanical properties and microstructure evolution of two medium carbon non-quenched and tempered steels 36MnVS4 and 46MnVS5 widely used for automotive fracture splitting connecting rod at different normalizing temperatures were compared and studied,and the strengthening mechanism was analyzed.The results show that with the increase of normalizing temperature,the yield strength,tensile strength and hardness of both the 36MnVS4 and 46MnVS5 steels increase gradually,and the tensile strength and hardness of the 46MnVS5 steel are higher than those of the 36MnVS4 steel.When normalized below 990℃,the yield strength of the 46MnVS5 steel is higher than that of the 36MnVS4 steel,while normalized above 990℃,the yield strength of the 46MnVS5 steel is lower.When normalized above 1140℃,the elongation and percentage reduction of area of the 36MnVS4 steel are higher than that of the 46MnVS5 steel,and the toughness is better.The difference in mechanical properties between the two steels is mainly due to both the content of proeutectoid ferrite and the precipitated strengthening phase V(C,N)in proeutectoid ferrite after normalizing at 1200℃ of the 36MnVS4 steel are more than that in 46MnVS5 steel,so the plasticity of 36MnVS4 steel is better.However,considering the production process and properties requirements of the fracture splitting connecting rod,the improvement of toughness is unfavorable to the fracture splitting processing of the connecting rod,and the 46MnVS5 steel has good comprehensive mechanical properties and more cost advantages than the 36MnVS4 steel.Therefore,the 46MnVS5 steel is better to be selected for the fracture splitting connecting rod.