The development of spring application technology puts forward higher requirements for materials. Mainly under high stress to improve fatigue life and relaxation performance; followed by different uses, requiring corrosion resistance, non-magnetic, electrical conductivity, wear resistance, heat resistance and so on. For this reason, in addition to the development of new varieties of spring materials, in addition to strictly control the chemical composition, reduce non-metallic inclusions, improve the surface quality and dimensional accuracy, etc. have also achieved beneficial results.
1. Development of alloy steel wire
Si-Cr steel has been widely used for valve springs and suspension springs. In order to improve fatigue life and relaxation resistance, V and Mo were added to Si-Cr steel. At the same time, Si-Cr drawn steel wire was developed. Its resistance to relaxation at high temperatures is better than that of steel wire. With the miniaturization of high-speed engines, Ti alloys with good vibration resistance, light weight, and low elastic modulus have been widely used, and their strengths can reach 2000 MPa.
2. Stainless steel wire development
1) The austenitic stainless steel wire has better strength than ferrite and its corrosion resistance is better than that of martensite. Therefore, the application range is expanding.
2) Low temperature wire drawing or low temperature nitrogen wire drawing can increase wire strength. When the martensite is heated, the structure is not stable, and wire drawing in the low-temperature liquid nitrogen can form latent acicular martensite, and hot high strength can be obtained. This kind of steel wire has many applications in the United States and Japan, but at present it can only handle steel below 1mm.
3) The precision springs in electronic equipment require non-magnetic properties, and such wire cannot produce latent acicular martensite during drawing. To this end, add N, Mn, Ni and other elements. In order to meet this demand, the United States developed AUS205 (0.15C-17Cr-1Ni-15Mn-0.3N) and YUS (0.17C-21Cr-5Ni-10Mn-0.3N). Due to the increase of Mn content, latent acicular martensite is not produced during processing. After solution treatment, the strength can reach 2000MPa, and the fatigue performance is higher than SUS 304.