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Industry analysis spring material performance research

    Industry analysis spring material performance research:

    With the development of the automobile industry, weight reduction and energy saving have become the current development direction of heavy-duty vehicles. Heavy-duty vehicles use small-piece variable-section leaf springs to reduce the weight of the spring assembly by 30-50%. Foreign heavy-duty vehicles have been widely used in small pieces Variable-section leaf springs, such as VOLVOS35, use the structure of 2 front springs and 3 rear springs.

    In order to understand the application status of foreign heavy-duty vehicle small-piece variable-section leaf springs, the material properties and shot peening performance of VOLVOS35 variable-section leaf springs for vehicles are studied.

    A tensile specimen with a diameter of 10mm and a U-notch impact specimen with a diameter of 55mm×10mm×10mm were prepared on the VOLVOS35 vehicle leaf spring. The tensile test was carried out at room temperature, and the impact test was carried out at room temperature and low temperature (-40℃). ). At the same time, the hardness of the VOLVOS35 automotive leaf spring was tested, and its hardness was 420-432HB. Microstructure analysis found that its metallographic structure was fine tempered sorbite with a grain size of 8.

    In response to the development needs of leaf spring performance, the steel for leaf springs is required to have: high tensile strength, elastic limit and fatigue strength; suitable hardenability, and the core of the leaf spring should obtain more than 80% martensite structure after quenching; High purity and suitable grain size, in addition, also require suitable shot peening performance.

    In order to adapt to the development of the long life of automobile leaf springs, the steel for leaf springs is required to have high purity. While reducing the content of impurity elements and controlling the total amount of inclusions, it should also control its shape to make it a low melting point and easy to deform inclusion. The analysis results of the VOLVOS35 leaf spring show that its O2 content is 15×10-6, Ti content is 27×10-6, alumina content is low, and there is no titanium oxide inclusions, indicating that the steel has high purity and has Higher fatigue strength and life.

    The analysis results of the VOLVOS35 vehicle leaf spring show that the material of the leaf spring is the traditional European 50CrV4 spring steel, which is equivalent to China’s CrMnV steel. The main elements C, Mn, and Cr of the VOLVOS35 leaf spring steel are controlled to the required composition The upper limit, and the appropriate amount of V, Al, etc., are added to maximize the effect of C, Mn, Cr and microalloying elements to improve the performance of the steel. VOLVOS35 steel plate springs optimize the ratio of C, Mn, and Cr elements , So that the end hardenability of the steel reaches the upper limit of 50CrV4 spring steel, and the hardenable thickness of the leaf spring reaches 35mm.

    The appropriate amount of C and Al precipitate carbon and nitride in the steel, so that the VOLVOS35 leaf spring steel produces precipitation strengthening and fine The grains of chemical steel make the grain size reach 8. After tempering and heat treatment, the matrix phase α solid solution (troostite) has a higher dislocation density, and there is a large amount of dispersed and uniformly distributed carbon in the matrix. Nitrided material points meet the requirements for high tensile strength and good toughness and plasticity of the material.