There are many methods used in the crankshaft machining process. Today, we have a simple analysis of the crankshaft thrust surface grinding process.
When grinding the quenched steel crankshaft thrust surface, the following three types of burns may occur:
Tempering burn
If the temperature in the grinding zone does not exceed the phase transition temperature of the hardened steel, but the transformation temperature of the martensite has been exceeded, the tempered martensite structure of the surface metal of the thrust surface will be converted into a tempered structure with a lower hardness (Soch Body or tortoise), this burn is called temper burn.
2. Quenching burns
If the temperature of the grinding zone exceeds the phase transition temperature, and the quenching effect of the coolant, the surface metal is quenched twice, causing the surface metal to have a secondary quenched martensite structure, the hardness of which is higher than that of the original tempered martensite. High, in its lower layer, due to slower cooling, there is a tempering structure (sordonite or tonite) with a lower hardness than the original tempered martensite. This type of burn is called quenching burn.
3. Annealing burns
If the temperature in the grinding zone exceeds the phase transition temperature and no coolant enters in the grinding zone, the surface metal will produce an annealed structure and the surface hardness will drop sharply. This burn is called an annealed burn. In the crankshaft forming grinding, it is mostly such a burn.
Improve the way to burn burns:
Grinding heat is the root cause of grinding burns, so there are two ways to improve the grinding burn: one is to reduce the generation of grinding heat as much as possible; the other is to improve the cooling conditions and try to make less heat generated into the workpiece.