(1) Selection of raw materials
Carbon spring steel due to quenching permeability is low, less use in the car; manganese steel hardenability, quenching cracks but easy to produce, and temper brittleness. Therefore, silico-manganese steel to be used in China is more extensive.
(2) raw material defects
The ① impurities greatly reduce the fatigue strength of automobile spring;
② banded structure severely degrade the mechanical properties of the steel.
(3) heat treatment defects
The surface decarburization quenching due to thermal organizations, the feathery organizations, etc. will reduce the fatigue strength of automobile spring.
(4) the quality of the shot peening
Shot peening is not only to make the spring surface the strengthening layer, but also to remove the the tiny spring surface defects and decarburization phenomenon, reduce stress concentration. One of the reasons peening quality difference is caused by differences in the useful life of the leaf spring.
(5) the use of the level of
The careful driver operates the vehicle, the life of the leaf spring is far higher than the poor road conditions, overloading serious, the driver rude driving a vehicle leaf spring.