调质处理对34CrNiMo6钢连杆锻件组织与硬度的影响

Effect of quenching and tempering on microstructure and hardness of 34CrNiMo6 steel forged connecting rods

通过微观组织表征、显微硬度测试及相图计算,研究了调质处理对34CrNiMo6钢连杆锻件微观组织与显微硬度的影响,同时基于微观组织演变规律,揭示了连杆锻件调质前后近表面和内部显微硬度变化的机制。结果表明,连杆锻件组织为珠光体和索氏体,表面有轻微脱碳。调质处理后,连杆锻件晶粒尺寸降低,局部应变均匀性变好,在近表面同时存在不显著脱碳层和弥散碳化物颗粒,硬度起伏变化明显;内部组织为均匀回火索氏体,显微硬度均值虽然较热处理前有所降低,但均匀组织降低了硬度的分散性。

Effect of quenching and tempering on microstructure and microhardness of 34CrNiMo6 steel forged connecting rods was studied by means of microstructure characterization,microhardness testing and phase diagram calculation.Based on the evolution of microstructure,the change regulation of surface and internal microhardness before and after quenching and tempering of the forged connecting rods was revealed.The results show that the forged connecting rod is composed of pearlite and sorbite,with slight decarburization on the surface.After quenching and tempering,the grain size of the forged connecting rod decreases and its local strain uniformity gets well.There is a nonsignificant decarburization layer and dispersed carbide particles on the near surface,thus the hardness variation of the near surface is obvious.Although the average micro-hardness after heat treatment is lower than that before heat treatment,the internal microstructure is uniform tempered sorbite,which reduces the dispersion of hardness.