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我厂的汽车万向节叉是用40MnB制成,要求调质处理,调质硬度为dB3.9～4.2。该零件截面变化较大,形状较为复杂。采用热水淬火时,淬火裂纹较多,最高时达20～30％,无法进行生产。后改用油作淬火介质,虽淬火裂纹现象基本消除,但产量下降,成本增加,工人劳动强度增大,劳动条件变差,并容易引起火灾。为此,我们根据万向节叉配套使用的是一个铸造件,强度储备比较富裕,以及零件本身硬度要求低的特点,决定用正火工艺代替调质工艺。
Our car universal joint fork is made of 40MnB, quenching and tempering requirements, quenching and tempering hardness dB3.9 ~ 4.2. The part changes larger, the shape is more complicated. Quenching with hot water, quenching cracks more, up to 20 to 30%, can not be produced. After the switch to oil for quenching medium, although the phenomenon of quenching and cracking basically eliminated, but the decline in production, increased costs, increased labor intensity, poor working conditions, and easily lead to fire. To this end, according to the universal joint supporting the use of a cast, strength reserves more affluent, and the low hardness of the part itself, the characteristics of the decision to use normalizing process instead of quenching and tempering process.