The spring steel is the material of the main structural components designed to create a variety of springs and elastic components or similar performance requirements. 
 A. Performance requirements ① high elastic limit σe and yield strength σs of / σb to ensure excellent elastic properties, and to absorb a large amount of flexibility can not produce plastic deformation; ② high fatigue limit, fatigue is the spring the most important failure modes. fatigue performance addition to the related to the composition of the steel structure, mainly by the metallurgical quality of the steel (such as non-metallic inclusions) and spring surface quality (such as decarburization); the ③ sufficient plasticity and toughness to prevent impact fracture; ④ Other properties, such as heat treatment and plastic processing performance, the special conditions of heat resistance or corrosion resistance requirements. 

 Two. Compositional characteristics of steel, carbon and alloying element content and the role is to: (1), generally high-carbon, carbon spring steel wc = 0.6% ~ 0.9%, alloy spring steel wc = 0.45% ~ 0.70%, after quenching temperature tempering after tempered care Golgi organizations can better ensure the performance requirements of the spring. (2) The general purpose of the alloying elements of alloy spring steel is generally low alloy steel. Main elements of Si, Mn, Cr, its main role is to improve the hardenability and solid solution strengthening of the matrix and improve the tempering stability; auxiliary plus elements of Mo, W, V strong carbide forming elements, the main role prevent decarburization defects caused by Si and Mn-caused overheating defects and improve the tempering stability and heat resistance. 

 3. 12-10 commonly used spring steel sheet of commonly used spring steel grades, performance characteristics and main uses of the composition, heat treatment and mechanical properties can refer to the relevant national standards (GB1222-1984). 12-10 commonly used spring steel grades the performance characteristics and use types of steel performance characteristics of production to use ordinary Mn content of carbon spring steel 65 of hardness, strength, yield strength is high, but the hardenability, heat resistance is not good. under dynamic loading and fatigue loading capacity and low price, and more used in the operating temperature of small Spring <12mm or larger unimportant spring 7085 high Mn content 65Mn hardenability, the mechanical properties superior to carbon steel, but more sensitive to lower prices of overheating, a large amount of Si-Mn system, the manufacture of various cross-section <15mm flat spring, spring, shock absorbers and clutch springs, brake axle alloy spring steel 55Si2Mn strength, good elasticity temper resistance; but easy to decarburization and graphitization. Containing B steel hardenability significantly improve the main spring steel class, very versatile and can produce a variety of medium cross-section <25mm springs, such as good the Department of 60Si2Mn55Si2MnB55SiMnVBCr, cars, tractors, leaf springs, helical springs 50CrVA hardenability, tempering high stability, low decarburization and graphitization tendency; good comprehensive mechanical properties, corrosion resistance, containing V, Mo, W and other elements of the spring has a certain temperature resistance; are high quality steel, so the fatigue further improve the performance for the manufacture of load large heavy-duty large size (50 ~ 60mm) springs, such as engine valve springs, conventional weapons to take the bomb hook spring crusher spring; heat-resistant springs, such as boiler safety valve springs, fuel injectors spring cylinder expansion ring 60CrMnA60CrMnBA60CrMnMoA60Si2CrA60Si2CrVA1 of and) carbon spring steel (ie, non-alloy spring steel) cheap but poor hardenability, suitable for smaller section size of the non-important spring, which is the most commonly used 65,65 Mn. 2) Alloy spring steel according to the main alloy element types can be divided into two categories: the Si-Mn spring steel and Cr spring steel. The former quenching permeability compared with high-carbon steel, the price is not very expensive, it is the most widely used, mainly for the cross-sectional dimension greater than 25mm of various types of spring, 60Si2Mn typical representative; latter hardenability better comprehensive mechanical high-performance, spring surface is not easy decarburization, but the price is relatively high, generally used for the cross-section of a larger size spring, 50CrVA is a typical representative. 

 4. Heat treatment characteristics of spring steel heat treatment depends on the processing of the spring forming method, generally can be divided into forming hot springs and cold forming two spring classes: 1) hot forming spring section size> 10mm a variety of large and complex shape of the spring are used to heat forming (such as hot-rolled, hot rolled), such as automobiles, tractors, trains leaf spring and coil spring. Concise processing line as follows: flat or round material → heat bending or winding → quenching-tempering → surface shot peening treatment, the use of the state organization's body tempering care. Shot peening can enhance the surface and improve the quality of spring surface, significantly improved fatigue properties. 2) cold forming spring-section size of <10mm small spring can be cold formed (such as cold rolled, cold rolled), such as instrument in the coil spring, spring and spring. The first cold pull (cold), quenching temperature tempering or lead bath temperature after quenching, cold drawn (rolled) to strengthen the forming of such spring; then cold forming, this process will further strengthen the metal, but also produced large internal stresses and brittle, so in the following should be carried out low temperature stress relief annealing (typically 200 to 400 ° C).