General characteristics of spring steel:
Spring is an important part of various machinery and instruments. It mainly uses the energy stored during elastic deformation to relieve mechanical vibration and impact, and also uses the stored energy of elastic deformation to work. Because springs are generally under dynamic load Therefore, it is required that spring steel must first have high elastic limit a, high resistance strength b, high flexural strength (s/b), high fatigue strength r (especially notched fatigue strength), and Sufficient plasticity and toughness and good surface quality, while also requiring good hardenability and low decarburization sensitivity, easy to process and form in hot and cold conditions.
The chemical composition characteristics of spring steel:
In order to obtain the required performance of the spring, the carbon content of spring steel is higher than that of quenched and tempered steel, and carbon spring steel is usually in the range of 0.6% to 0.75% C. Due to the hardening of carbon spring steel (such as 65, 75 steel, etc.) The performance is poor. When the cross-sectional size exceeds 12mm, it cannot be quenched in oil. If it is quenched with water, cracks are prone to occur. Therefore, the springs with larger cross-sectional sizes and heavy loads are made of alloy spring steel.
The carbon content of alloy spring steel is generally between 0.46% and 0.70%. The alloying elements contained in alloy spring steel often include Si, Mn, Cr, V, etc., and their main function is to improve the hardenability and tempering of steel. Stability, ferrite strengthening and grain refinement, thereby effectively improving the mechanical properties of spring steel, increasing the elastic limit and yield ratio. Si and Mn mainly improve the hardenability, but also improve the yield ratio, and are better than Si The most prominent role, but it promotes surface decarburization during heat treatment, and Mn makes steel easy to overheat.
Therefore, spring steel for important uses must be added with elements such as Cr, V, W, such as Si-Cr spring steel, which is not easy to decarburize. ;Cr-V spring steel is not easy to overheat, has fine grains, is not easy to grow and coarsen, has good impact resistance, and high temperature strength. Among them, Cr and V are also conducive to improving the high temperature strength of spring steel.