我们经常碰到一些形状复杂、厚薄悬殊而又要求有一定硬度的碳素结构钢零件,如何保证零件的硬度而又能减少变形、防止开裂是这种零件热处理的重要课题。为此在生产实践中曾采用过等温处理、预冷淬火、双液或三液淬火等各种不同的淬火方法,以减少在淬火过程中所产生的内应力,从而比较有效地解决开裂问题。但是对某些特殊形状的零件尽管采用了上述方法,还是不能完全满足要求。例如附图中的顶盖,材料为45钢,要求硬度为HRC40～45,该零件既有厚薄悬殊的截面,又有孔端平面。在采用一般加热淬火后,肩部全开裂,而且在 We often encounter some complex shapes, thickness and require a certain degree of hardness of carbon structural steel parts, how to ensure the hardness of the part but also to reduce deformation and prevent cracking is an important issue of heat treatment of such parts. To this end in production practice has been used isothermal treatment, pre-cooling quenching, two-liquid or three-liquid quenching and other quenching methods to reduce the internal stress generated in the quenching process, so as to solve the cracking problem more effectively. However, some special shapes of parts despite the use of the above method, still can not fully meet the requirements. For example, the cap shown in the figure, the material is 45 steel, the required hardness of HRC40 ~ 45, the part has both thickness and thickness of the cross section, but also hole end plane. After using the general heating quenching, shoulder full cracking, but also