48MnV钢曲轴磁粉探伤不合格原因分析

UNQUALIFIED REASON ANALYSIS FOR MAGNETIC PARTICLE TEST OF 48MnV STEEL CRANKSHAFT

某厂在对48MnV钢曲轴进行磁粉探伤时,发现曲轴的连杆轴颈上存在线状磁痕,此类磁痕是曲轴磁粉探伤中不允许存在的缺陷。利用直读光谱仪(OES)、光学显微镜(OM)和扫描电子显微镜(SEM)等观察分析手段,研究了48MnV钢曲轴磁粉探伤存在磁痕的原因。结果表明:钢材内部夹渣在锻造过程中迁移至连杆轴颈近表面,夹渣与钢的磁导率差异使磁粉探伤时出现磁痕。针对此类磁痕,提出了相应的改进措施。

During the magnetic particle test of the 48MnV steel crankshaft produced in a factory,it was found that there were linear magnetic marks on the crank pin of the crankshaft,which was not allowed in the magnetic particle test of the crankshaft.The cause of unqualified magnetic particle test of 48MnV steel crankshaft was studied by means of optical emission spectrometer(OES),optical microscope(OM)and scanning electron microscopy(SEM).The results showed that the internal slag of steel is transferred to the surface of the connecting rod shaft neck during forging process and the difference between the slag and the steel's magnetic conductivity causes the magnetic mark to appear when the magnetic powder is tested.Corresponding technical improvement measures were proposed for such magnetic marks.