摘要
对42CrMo螺杆两种形态的裂纹进行了宏观断口及显微组织分析。结果表明,内六方处裂纹是由于热冲内六方后未经正火,原材料中存在带状偏析及粗大的魏氏体组织,在淬火加热和冷却时,原魏氏体组织遗传引起过热及带状偏析使马氏体相变产生不等时性,使工件产生了较大的组织应力而开裂。螺纹处开裂是由于工件在热镀锌酸洗时,氢渗入工件产生氢脆和水曝应力所致,并对氢脆裂纹产生的原因进行了试验和分析。提出了增加正火、机械抛丸和水曝光后150℃消除应力工序,上述两种形态的裂纹得到了彻底根除。
Two cracking patterns of screw rod made of 42CrMo steel were investigated by macrostructure and microstructure analyses, the effective methods for avoiding cracks were proposed. The results show that the reasons which cause the crack in inner hexagon are as follows. Firstly, the rod is not normalized after hot blanking. Secondly, the banded structure （segregation） and large widmanstatten structure exist in raw materials. When the rod is heated to high temperature, the structure inheritance caused by widmanstatten structure results in overheat, when the rod is quenched, the martensite deformation occurs nonsynchronously because of bend segregation, so that the crack occurred by structure stress. When the rod was pickled before hot dip galvanizing, cracks on screw occurred. The reason causing crack is that when being pickling, the hydrogen atom penetrates into the screw, then the surface is brittled. The stress resulted from water blasting can also cause crack on the screw. In order to avoid the cracks, normalizing is added after hot blanking. The shot blasting is used instead of pickling and 150 ℃ stress relief is recommended.
出处
《金属热处理》
CAS
CSCD
北大核心
2008年第4期105-108,共4页
Heat Treatment of Metals
