Original genuine SUP9 spring steel wire-high elastic spring steel

1) High strength: In order to improve the spring's ability to resist fatigue damage and relaxation, the spring material should have a certain yield strength σs and elastic limit σe, especially a high yield strength. Stronger than (σS/σb). Under normal circumstances, the elastic limit of a material is proportional to the yield strength, so spring designers and manufacturers always hope that the material has a high yield strength, and the tensile strength σb and yield strength σS of the spring material are close, For example, the σS of cold-drawn carbon steel wire is about 90% of the σb. Since tensile strength is easier to measure than yield strength, tensile strength is provided in material delivery, so tensile strength is generally used as the basis for design and manufacturing. However, the tensile strength of the material is not as high as possible. Excessive strength will reduce the plasticity and toughness of the material and increase the brittleness tendency. The tensile strength of a material is related to factors such as its chemical composition, metallographic structure, heat treatment conditions, degree of cold working (drawing or rolling) and other strengthening processes. There is also a certain relationship between tensile strength and fatigue strength. When the σb of a material is below 1600Mpa, its fatigue strength increases with the increase of tensile strength. Generally speaking, the relationship between the fatigue strength and tensile strength of materials is: σ-1≈ (0.35~0.55) σb (where σ-1 is the fatigue strength of the material under symmetrical cycles (such as alternating loads)) .

2) Good plasticity and toughness: During the spring manufacturing process, the material needs to undergo varying degrees of processing deformation, so the material is required to have a certain degree of plasticity. For example, when the shackles and torsion arms of complex-shaped tension and torsion springs have a small radius of curvature, the spring materials must not have defects such as cracks or breakage during processing of winding or stamping and bending. At the same time, when the spring is subjected to impact load or variable load, the material should have good toughness, which can significantly increase the service life of the spring.

3) Excellent surface condition and fatigue performance: The surface of the spring bears the greatest stress when it is working, and fatigue damage often starts from the surface of the steel wire. For springs used in important occasions, such as car engine valve springs Generally, the fatigue life is required to be 2.3×107 times to 3.0×107 times. The suspension springs of mid- to high-end cars generally require a fatigue life of 2.0×106 times to 5.0×106 times or even longer. This puts forward the fatigue performance of the material. met very high demands. There are many factors that affect the fatigue performance of materials, such as the chemical composition, hardness, purity of steel, surface quality and metallographic structure of the material. The most important thing is the surface quality of the material. Material surface defects, such as cracks, folds, scales, rust, pits, scratches and indentations, can easily cause stress concentration in the spring during operation. The areas where stress is concentrated are often fatigue sources that cause fatigue damage. Fatigue sources are also likely to occur first at the surface decarburization site, so strictly controlling the depth of the decarburization layer is also a very important quality indicator. In order to improve the surface quality of the spring material, the surface of the material can be ground or polished, and a peeling process is used to remove a layer of material skin before wire drawing, so that most surface defects can be removed. Controlled atmosphere or vacuum heat treatment can be used during spring heat treatment to prevent surface decarburization and oxidation.

4) Strict dimensional accuracy: Many springs have high requirements for load accuracy. For example, the load deviation of the valve spring must not be greater than 5% to 6% of the specified load, so the tension and compression of round steel wires are used. Taking a spring as an example, if the wire diameter deviation is 1%, the load will produce a deviation of about 4%. It can be seen that strict dimensional accuracy is also very important to ensure the quality of springs.

5) Good uniformity: The requirement for material uniformity refers to the requirements for the material’s chemical composition, mechanical properties, dimensional deviation and other indicators to be uniform and stable. If the properties of materials are inconsistent in all aspects, it will bring great difficulties to spring production, resulting in discrete product parameters such as geometric size, hardness, load, etc. Serious inhomogeneity may even result in scraps.

6) In order to meet the above performance requirements, spring steel must have excellent metallurgical quality, including strictly controlled chemical composition, high purity, low impurity content, low non-metallic inclusion content, and Control its morphology, particle size and distribution. In addition, the uniformity and stability of the steel are also required. Spring steel should also have good surface quality (including surface decarburization) and high-precision shape and size.