(1) Material and technical requirements of lock spring
The material of lock spring is 65Mn steel, and the hardness is hrc40 ~ 48, and the unevenness is less than 0.3mm. Finally, the process of plate forming, quenching and tempering is as follows. The lock spring is shown in Fig. 6-10. The heat treatment process of lock spring is shown in Fig. 6-11.
(2) Key points of heat treatment process for lock spring
In order to reduce the deformation and improve the strength of the lock spring, bainite austempering should be adopted
1) The lock spring is heated to 840 ℃± 10 ℃ in salt bath furnace after being installed with spreader and kept for 10 ~ 15min, then it is moved into the nitrate furnace at 340 ~ 380 ℃ for 15 ~ 30min, and then it is cooled by air.
2) The lock spring was Austempered in a salt bath at 380 ℃ for another time. The tempering holding time is 30min.
3) After tempering, the lock spring is cleaned in hot water at 60 ~ 80 ℃ and then dried in oven at 100 ~ 150 ℃.