70mn 70mn-performance spring steel wire spring steel wire

 Spring process performance under impact, vibration or stress in the long-term use of cross, it requires a high spring steel tensile strength, elastic limit, a high fatigue strength. In the process requires a certain degree of spring steel hardenability, easy removal, good surface quality carbon spring steel that is the carbon content of WC within 0.6% -0.9% range of high-quality carbon structural steel. Silicomanganese alloy spring steel is mainly the Department of steel, their lower carbon content, mainly by increasing silicon content Wsi improve performance; in addition to Ge, tungsten, vanadium alloy spring steel. In recent years, with China's resources, and designed according to the requirements of new technology cars, tractors, developed a boron, niobium, molybdenum and other elements on the basis of in silico-manganese steel new steel to extend the spring of life and improve the quality of the spring . Performance requirements for use in the spring under the impact, vibration, or long-term cross-stress, it requires a high spring steel tensile strength, elastic limit, high fatigue strength. In the process requires a certain degree of spring steel hardenability, easy removal, good surface quality carbon spring steel that is the carbon content of WC within 0.6% -0.9% range of high-quality carbon structural steel. Silicomanganese alloy spring steel is mainly the Department of steel, their lower carbon content, mainly by increasing silicon content Wsi improve performance; in addition to Ge, tungsten, vanadium alloy spring steel. In recent years, with China's resources, and designed according to the requirements of new technology cars, tractors, developed a boron, niobium, molybdenum and other elements on the basis of in silico-manganese steel new steel to extend the spring of life and improve the quality of the spring . Production process is generally available spring steel furnace, open-hearth, or oxygen converter production; better quality or have special properties of high-quality spring steel, electric furnace or vacuum furnace slag refining. The main provisions of spring steel elements carbon, manganese, silicon and other content narrower, must strictly control the chemical composition of smelting. Easy to form bubbles and other defects at higher silicon content, after cooling wrought ingot was not easy to produce white spots. Therefore, the smelting of raw materials must be dry, try to remove gas and inclusions, but also to avoid superheat. Spring steel surface decarburization and pay special attention to the quality of the rolling process. When the steel surface decarbonization serious, it will significantly reduce the fatigue limit of steel. For high-silicon spring steel as 70Si3MnA, should be taken to avoid graphitization. Thus, when the thermal processing temperature should not stop rolling low (≥850 ℃), easier to avoid the formation of graphitization temperature range (650 ~ 800 ℃) long residence time. Rear springs made by shot peening make spring surface residual compressive stresses to offset part of the work on the surface stress, inhibit the formation of surface cracks, which can significantly increase the fatigue limit of the spring. Heat-treated spring steel require high strength and fatigue limit, usually in the quenching and tempering of state used in order to obtain a high elastic limit. Heat treatment technology to the intrinsic quality of the spring has a crucial impact. So, how to further improve the fatigue life of the spring, further research is needed, especially chemical surface modification heat treatment, shot peening and so have a major impact on the spring fatigue life. To further strengthen the valve spring surface strength, increased stress, improve fatigue life, after forming the valve spring, to further after nitriding, carbonitriding or cryogenic liquid sulfur and nitrogen permeation, and then by shot peening. For example, Japan will f4mm of si-cr oil quenched steel wire 450 ℃ × 4.5h hypothermic carbonitriding and after 400 ℃ × 15min tempering comparison, the fatigue limit can be increased 240mpa. Nitrogen infiltration, not only to eliminate the adverse effects of decarbonization, but also improve the residual compressive stress, while low-temperature liquid nitriding and carbonitriding temperature strength valve springs increase the amount of deformation at 150 ℃ 0.2% (provision of 0.5%), the amount of deformation 250 ℃ 0.56%, increased valve spring thermal stability and resistance to relaxation stability, but liquid nitriding and carbonitriding time should be strictly controlled, otherwise it will form a network sulfide and net nitride, but it will reduce its fatigue strength.