The smaller the surface roughness is, the smaller the stress is and the higher the fatigue strength is. The damage of surface roughness on fatigue limit of material surface. With the increase of surface roughness, the fatigue limit decreases. Under the condition of the same surface roughness, different steel brands and different production methods have different fatigue limit reduction levels. For example, the reduction level of cold rolled coil spring is smaller than that of hot coil spring. Because the steel hot rolled coil spring and heat treatment process heating, because the air oxidation makes the surface of the spring material become not smooth and cause carburizing condition, so as to reduce the fatigue strength of the spring.

On the surface of the material to carry out cutting, air brake, shot rusting and extrusion molding. Can improve the fatigue strength of the spring.

The larger the size of the material, the higher the probability of defects caused by various cold drawing and hot working, and the greater the probability of surface defects, which will result in the reduction of fatigue characteristics. Therefore, the hazard of gauge utility should be taken into account when estimating the fatigue strength of spring.

Metallurgical industrial defects Metallurgical industrial defects refers to the non-metallic materials in materials including debris, bubbles, corrugated spring elements of shrinkage, these. The reference material on the surface is the stress source, will cause the reference material and the base material in the middle of the page forced to cause fatigue cracks. The selection of vacuum pump smelter, vacuum pouring and other countermeasures can further improve the quality of stainless steel plate.