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Henan Friend Metal Products Co.,Ltd

Spring Steel Material Should Have The Performance

1) high strength: in order to improve the fatigue resistance and anti relaxation ability of spring, the spring material should have a certain yield strength, s and elastic limit e, especially the high yield strength ratio (S/ B). In general, the elastic limit of the material and the yield strength is proportional to the spring design and manufacture always hope that the material with high yield strength, and ultimate tensile strength of spring materials B and S are relatively close to the yield strength, such as cold drawn carbon steel wire is about S sigma sigma B 90%. As tensile strength is easier to measure than yield strength, tensile strength is provided in the delivery of materials, so tensile strength is generally used as the basis for design and manufacture. But the tensile strength of the material is not the higher the better, the high strength will reduce the plasticity and toughness of the material, increase the brittleness tendency. The tensile strength of the material is related to its chemical composition, microstructure, heat treatment, cold working (drawing or rolling) degree and other strengthening processes. Tensile strength and fatigue strength also have a certain relationship. When the material's sigma B is below 1600Mpa, its fatigue strength increases with the increase of tensile strength. The relationship between fatigue strength and tensile strength of the materials on the follow is: O -1 = (0.35 ~ 0.55) B (sigma Sigma -1 for the material in the symmetrical cycle (such as alternating load) fatigue strength).

2) good plasticity and toughness: in the process of spring manufacturing, the material needs to undergo varying degrees of processing deformation, so the material has a certain plasticity. For example, the hook ring and torsion arm with complex shape of stretching and torsion spring, when the radius of curvature is very small, the spring material can not crack, fold and other defects when processing, winding or stamping bending forming. At the same time, the spring should bear good toughness under the impact load or variable load, so that the service life of the spring can be obviously improved.

3) excellent surface state and fatigue properties of spring work surface under the maximum stress and fatigue failure are often started from the surface of the wire, the spring used on important occasions, such as the car engine valve spring general requirements of fatigue life of 2.3 * 107 ~ 3 * 107 times, in the high-end car suspension spring 2 x 106 to 5 x 106 or even longer fatigue life, which made very high demands on fatigue properties of materials. There are many factors affecting the fatigue properties of materials, such as the chemical composition, hardness, purity of steel, surface quality and metallographic structure, etc., especially the surface quality of materials. Surface defects, such as cracks, folds, scales, corrosion, pits, scratches and indentation, are easy to cause stress concentration in the process of spring. The location of stress concentration is often the fatigue source causing fatigue failure. The fatigue source is easy to occur first on the surface of decarburization. Therefore, it is an important quality index to strictly control the depth of decarburization layer. In order to improve the surface quality of spring material, the surface of the material can be polished or polished. Peeling off the surface of a layer of material by peeling process before wire drawing can remove most of the surface defects. Heat treatment or vacuum heat treatment can be used to prevent surface decarburization and oxidation during spring heat treatment.

4) precision strict: many spring has higher requirements on the accuracy of the load, such as valve spring load deviation shall not exceed the specified load of 5% to 6%, the tension and compression spring as an example by using round steel wire, steel wire diameter if the deviation is 1%, the load will produce deviation of about 4%. Thus, strict dimensional accuracy is also very important to ensure the quality of spring.

5) good uniformity: the requirement for uniformity of material means that the chemical composition, mechanical properties, size deviation and other indicators of the material require uniform and stable consistency. If the material performance is inconsistent, it will bring great difficulties to the production of spring, resulting in product geometric size, hardness, load and other parameters of discrete, serious inhomogeneity even cause waste.

6) in order to meet the performance requirements of spring steel must have excellent metallurgical quality, including chemical composition, strict control of high purity, low impurity content, low content of nonmetallic inclusions, and control the morphology, size and distribution. In addition, the uniformity and stability of the steel are also required. Spring steel should also have a good surface quality (including surface decarburization) and high precision shape and size.

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