42CrMo钢曲轴锻件表面裂纹形成机理分析和工艺改进

Analysis on Surface Crack Formation Mechanism for Crankshaft Forgings of Steel 42CrMo and Process Improvement

对865℃1.5 h油淬+640℃4 h回火、水冷的42CrMo钢(/%:0.43C,0.77Mn,0.24Si,0.014P,0.007S,1.08Cr,0.17Mo,0.01Cu)曲轴锻件表面裂纹形成进行了分析。结果表明,曲轴锻件表面裂纹为淬火裂纹,回火时间不足(4 h)和锻件存在较严重的带状组织(3级)是该曲轴产生淬火裂纹的主要原因。通过将回火时间延长至5 h,控制带状组织≤2级,曲轴调质后未发现裂纹,产品合格率达100%。

An analysis on the surface crack formation for crankshaft forgings of steel 42CrMo （/% ： 0.43C, 0. 77Mn, 0. 24Si, 0. 014P, 0. 007S, 1.08Cr, 0. 17Mo, 0. 01Cu） with 865 ℃ 1.5 h oil quenching ＋640 ℃ 4 h tempering, water cooling has been carried out. Results show that the surface cracks of crankshaft forgings are quenching cracks, and the main causes for quenching cracks of crankshaft are insufficient tempering holding time （4 h） and more serious banded ori- entation structure exiting in forgings （ rating 3）. With prolonging the tempering time to 5 h and controlling the banded ori- entation structure in forgings ≤ rating 2, the cracks are not found in quenched and tempered crankshaft forgings and the qualified products are up to 100%.