推土机终传动的花键轴使用过程中曾发生过多起断裂事故。断裂的原因是工况恶劣、热处理工艺不合理。要求花键轴应有足够的抗弯、抗扭、抗疲劳强度以及较好的耐磨性和韧性。花键轴的材质为42CrMo合金结构钢,要求整体淬火,硬度达到HRC48～55。存在的问题是,42 CrMo淬透性较高,油淬临界直径最大可达106 mm,花键轴整个截面都可能会淬透,不仅造成零件表面产生拉应 Bulldozer end of the transmission spline shaft used in the process of excessive occurrence of fracture accident. Fracture is due to poor working conditions, heat treatment process unreasonable. Requires spline shaft should be sufficient bending, torsion, fatigue strength and good wear resistance and toughness. Spline shaft material is 42CrMo alloy structural steel, requiring the overall quenching, hardness HRC48 ~ 55. The existing problems are that the hardenability of 42 CrMo is higher and the critical diameter of oil quenching can reach as large as 106 mm. The entire cross-section of the spline shaft may be hardened, which not only causes the tensile strength of the part surface