曲轴齿轮感应淬火后齿根开裂原因分析

某大型柴油机42CrMoA钢曲轴齿轮在中频感应淬火后数小时内齿根出现裂纹。分析表明,齿根延迟开裂是由于先淬火的主轴颈受到后来轮齿淬火加热时的热影响而使齿根产生过大拉应力所致。采取轴颈淬火和磨削后、轮齿淬火前进行240℃×4 h去应力退火,在轮齿淬火加热时对已经淬火的主轴颈进行补充冷却,以及主轴颈与轮齿侧面连接的圆角处不予淬火等措施后,齿根开裂问题得到了解决。

Analysis on Root Cracking of Crankshaft Gear after Induction Hardening

In a few hours after being medium-frequency induction hardened , the cracks were found in root of crankshaft gear made of 42CrMoA steel of some type of heavy-duty diesel engine. The analysis shows that the delayed cracking of the root is attributed to excessive tensile stress which originated from the effect of heat producing during afterwards hardening of the teeth on king journal early hardened. The root cracking has been avoided by adopting several measures which are as follows： （a） the king journal is stress relieved by heating to 240 ℃ for 4 h after being hardened and grinded and before the teeth being hardened ; （b） the hardened king journal is additionally cooled during hardening of the teeth ; （c） the round joint of king journal and tooth side is not hardened.