滚压强化对连杆用42CrMo4钢疲劳性能的影响

Effect of Rolling Strengthening on Fatigue Properties of 42CrMo4 Steel for Connecting Rod

为了提高42CrMo4钢材料的柴油机连杆的使用寿命和服役质量,采用滚压强化工艺对其进行处理,研究不同滚压参数(滚压应力、进给量、滚压次数和滚压速度)对表面粗糙度和表层显微硬度的影响并对比喷丸试样和滚压试样的高周疲劳性能。试验结果表明:试样表面粗糙度随着滚压次数的增加先降低后升高,随着滚压速度的增加先升高后降低;表面显微硬度随滚压应力、进给量和滚压次数的增加先降低后增加,随滚压速度的增加先增加后降低;经R5滚压处理后,材料的疲劳强度从673.80 MPa升高到752.17 MPa,R5滚压工艺对材料高周疲劳寿命的强化效果明显高于喷丸强化;不同滚压工艺的试样主要断裂机制为延性断裂,由于滚压强化的作用,试样内部的夹杂物和基体界面的二次裂纹萌生成为了主要裂纹起始源。

In order to improve the service life and service quality of 42CrMo4 steel for diesel engine connecting rod,the rolling strengthening process was adopted.The influence of different rolling parameters(rolling stress,feed rate,rolling times and rolling speed)on surface roughness and surface micro-hardness was studied and the high cycle fatigue performance of shot peened and rolled specimens was compared.The experimental results show that:The surface roughness of the sample decreases first and then increases with the increase of rolling times,and increases first and then decreases with the increase of rolling speed;The surface micro-hardness decreases first and then increases with the increase of rolling stress,feed rate,and rolling times,and increases first and then decreases with the increase of rolling speed;After R5 rolling treatment,the fatigue strength of the material increased from 673.80 MPa to 752.17 MPa,which means the strengthening effect of R5 rolling process on the high cycle fatigue life of the material is significantly higher than that of shot peening strengthening;The main fracture mechanism of samples with different rolling processes is ductile fracture,and due to the strengthening effect of rolling,the secondary crack initiation at the interface between the inclusions inside the specimen and the matrix is the main source of crack initiation.