30CrMnSiNi2A钢螺纹零件局部感应回火工艺

Local induction tempering process of 30CrMnSiNi2A steel threaded parts

对30CrMnSiNi2A钢螺纹试验件进行了局部感应回火工艺研究,对比研究了不同预处理(等温淬火+低温回火和真空油淬+低温回火)和不同感应回火工艺(单段式加热、两段式加热、两段式加热+移动补温)对工件回火后硬度分布的影响。结果表明,等温淬火+低温回火和真空油淬+低温回火后试验件的硬度和显微组织差别不大。由于集肤效应和端部效应,单段式感应加热会使试验件内部产生较大的径向和轴向硬度梯度,而两段式加热法可通过增设一段均温时间以消除集肤效应所造成的径向硬度梯度,通过感应器移动补温可消除端部效应所导致的轴向硬度梯度。两段式加热+移动补温的感应回火工艺可使试验件螺纹端头的硬度达到要求,并获得均匀的硬度分布。

Local induction tempering process of 30CrMnSiNi2A steel threaded specimen was studied.The effects of different pre-treatment(isothermal quenching+low temperature tempering and vacuum oil quenching+low temperature tempering)and different induction tempering processes(single-stage heating,two-stage heating and two-stage heating+temperature compensation by moving)on the hardness distribution of the specimen after tempering were investigated.The results show that the difference of hardness and microstructure of the specimen pre-treated by isothermal quenching plus low temperature tempering and vacuum oil quenching plus low temperature tempering are not obvious.Due to the skin effect and end effect,large radial and axial hardness gradients is produced in the specimens by single-stage induction heating.The two-stage heating can eliminate the radial hardness gradient caused by skin effect by adding a uniform temperature time,and the axial hardness gradient caused by end effect can be eliminated through temperature compensation by moving the sensor.The hardness at the thread end of the specimen uniformly distributed within the required range can be obtained by the induction tempering process of two-stage heating+temperature compensation by moving.