拉丝机塔轮轴用40Cr钢热处理工艺优化

Optimization of heat treatment of 40Cr steel for wire drawing machine tower axle

通过正交设计探究不同调质工艺下40Cr钢的组织和力学性能的变化规律,确定拉丝机塔轮轴用40Cr钢的最佳工艺,并与断轴试样和正常试样进行对比分析。结果表明,拉丝机塔轮轴用40Cr钢最优调质工艺为850℃保温1 h淬火,630℃下保温1 h回火。在最优工艺条件下组织为具有特定位向、细小的回火索氏体和极少量铁素体,硬度为283.5 HBW,冲击韧度为211.3 J/cm2。40Cr钢硬度影响因素依次为回火温度、淬火保温时间、回火保温时间和淬火温度。组织分布不均和冷速不当是导致硬度不均匀的主要原因。40Cr钢冲击性能影响因素依次是淬火温度、回火保温时间、淬火保温时间和回火温度。断口纤维区主要为小且浅的等轴韧窝;剪切唇区主要为大且深的剪切韧窝。

Orthogonal experiments were designed for 40Cr steel. Transformation laws of microstructure and mechanical properties were studied after different quenching and tempering. Optimum process of heat treatment was determined and was compared with the failure axle specimen and the normal specimen. The results show that the optimal heat treatment process of 40Cr steel for wire drawing machine tower axle is quenching at 850 ℃ for 1 h and tempering at 630 ℃ for 1 h, and the microstructure are fine tempering sorbites with some specific orientations and a small amount of ferrites, the hardness and impact toughness are 283. 5 HBW and 211. 3 J/cm2 . The sequence influencing factors on hardness of 40Cr steel is as follows tempering temperature, quenching holding time, tempering holding time and quenching temperature. Inhomogeneity structure distribution and improper cooling rate are main causes of uneven hardness. The sequence influencing factors on impact toughness is as follows quenching temperature, tempering holding time, quenching holding time and tempering temperature. The small and shallow equiaxed dimples are mainly in the fiber region, and the large and deep shear dimples are mainly in shear lips region.