Shot peening is generally used in the processing of automobile spring steel plates. It is to reduce the plastic deformation of the processed material.
Shot peening is divided into general shot peening and stress shot peening. In general processing, the steel plate is in a free state, and high-speed steel shot is used to hit the inside of the steel plate to generate pre-compression stress on the surface. To reduce the tensile stress on the surface of the steel plate during work, increase Service life. Stress shot peening is to pre-bend the steel plate under a certain force, and then perform shot peening.
Shot peening is a cold working method that accelerates the pellets with a proper acceleration device and sprays them to the workpiece in a proper way.
Shot peening is used to plastically deform the surface layer and form a strained layer, in which the transformation ratio of the structure and residual stress occurs. Properly controlling these changes in the strain layer can improve the fatigue fracture resistance and stress corrosion cracking resistance of the parts.
Springs are one of the earliest parts in the production of shot peening, especially those compression coil springs, leaf springs and torsion bar springs that are subject to cyclic loads and are prone to fatigue damage. They must be shot peened.
Shot peening is arranged after spring forming and heat treatment. Using small metal balls or metal particles, sprayed on the surface of the spring countless times at a speed of tens of meters per second to produce many small pressure pits, which are uniformly bulging, covering the surface layer of the spring and on the surface layer It produces work hardening, and at the same time it can reduce or eliminate the harmful effects of spring surface defects (such as small cracks, uneven gaps and decarburized layers, etc.), thereby effectively improving the fatigue life of the spring.
Pay attention to the shot peening operation: ①Select the type and specification of the shot correctly, avoid using sharp-edged shots to damage the surface of the spring; ②Select a shot blasting machine reasonably, requiring high injection speed; ③The shot blasting time is required when the conditions are possible Properly longer, so that although the strength of the spring cannot continue to be improved, it can increase the coverage of shot peening and also increase the fatigue life.
The ratio between the area occupied by the bullet marks and the area required for shot peening on the specified parts of the surface of the shot peened part is called the surface coverage. The surface coverage is expressed as a percentage.