感应回火工艺研究

Research on Induction Tempering Technology

与传统的炉内回火相比,感应回火具有生产效率高、节能等优点。对含0.53%C、0.20%Si、0.71%Mn和0.11%Cu(质量分数)的UC1钢外星轮进行了感应淬火和在170℃、210℃和260℃以50 kW、66 kW和85 kW功率及3.5 kHz频率感应回火180 s。随后检测了工件的表面硬度及硬化层的深度、硬度梯度、显微组织和静扭扭矩。结果表明:在170℃以50 kW的功率感应回火的外星轮表面硬度接近技术要求的中间值,硬度梯度较平缓,硬化层较深,硬化层组织为回火马氏体和极少量的残留奥氏体;在210℃以66 kW的功率感应回火的外星轮静扭扭矩最高,在170℃以50 kW的功率感应回火的外星轮次之。感应回火既需要温度合适,也需要加热均匀,使硬化层由表及里充分回火。

Compared with furnace tempering, induction tempering is higher in effectiveness and lower in energy consumption. The UC1 steel outer sprocket containing 0.53%C,0.20%Si, 0.71%Mn and 0.11%Cu by mass was induction hardened and then induction tempered at 170 ℃, 210 ℃ and 260 ℃at powers of 50 kW,66 kW and 85 kW and frequency of 3.5 kHz for 180 s. After this, the outer sprocket was tested for surface hardness, as well as for depth, hardness gradient, microstructure and static torsional strength of hardening case. The results demonstrated that(a)the outer sprocket induction tempered at 170 ℃at power of 50 kW exhibited surface hardness approximate to intermediate value of the specification, gentler hardness gradient, deeper hardening case, and microstructure consisting of tempered martensite and extre-small amount of retained austenite;and(b) the outer sprocket induction tempered at 210 ℃at power of 66 kW had the highest static torsional strength, followed by the outer sprocket induction tempered at 170 ℃at power of 50 kW. Induction tempering requires both a suitable temperature and uniformly heating workpiece, causing the hardening case to be sufficiently tempered from surface to interior.