The main rotating parts of the engine, after installing the connecting rod, can undertake the up-down (reciprocating) motion of the connecting rod and turn it into a circular (rotary) motion. It is an important part of the engine. Its material is made of carbon structural steel or nodular cast iron. It has two important parts: main journal, connecting rod journal, (and others). The main journal is installed on the cylinder block. The connecting rod journal is connected with the big end hole of the connecting rod, and the small end hole of the connecting rod is connected with the cylinder piston. The lubrication of crankshaft mainly refers to the lubrication of connecting rod big end bearing bush and crankshaft connecting rod journal as well as the lubrication of two fixed points. The rotation of crankshaft is the power source of engine. It is also the source power of the whole mechanical system.

HCVAC used in crankshaft coating and heat treatment can reduce fuel consumption, improve wear resistance and achieve compact design, improve wear resistance and service life of components, so as to extend maintenance interval and reduce the demand for spare parts, reduce the friction loss in the engine, and improve the efficiency of the overall transmission system.