The development of the spring material
The the spring application technology development, the material put forward higher requirements. mainly to improve fatigue life and under high stress relaxation properties; secondly is required to have corrosion resistance, non-magnetic, electrical conductivity, abrasion resistance, heat resistance, etc. according to different application. To this end, the spring material in addition to the development of new varieties, the other strictly control the chemical composition to reduce the non-metallic inclusions to improve the surface quality and dimensional accuracy also made beneficial effects.
1.The development of Alloy steel
In order to improve the fatigue life and anti-relaxation properties,Valve springs and suspension springs has been widely applied to the Si-Cr steel.V, Mo is added to the Si-Cr steel.While developing the Si-Cr drawn steel wire.the Anti-relaxation properties of the work at high temperatures than the music wire.With the engine speed miniaturization ,perfect Anti-flutter performance.The light weight, small elastic modulus of Ti alloys has been more widely used, strength up 2000Mpa.
2.the development of stainless steel.
1)Austenite structure stainless steel wire strength than ferritic organization, its corrosion resistance is also superior to the martensite structure, expanding range of applications due to surface.
2)Low temperature of candied or low temperature nitride caramelized increase wire strength.Martensite organization unstable when heated ,Roberts implicit acicular martensite is formed in the cryogenic liquid nitrogen.The availability of the high intensity of the thermal state. Such wire in the United States and Japan have a lot of applications, but can only handle less than 1mm wire.
3)Precision springs in electronic equipment requires a non-magnetic,Such steel wire in drawing processing can not generate implicit acicular martensite.N, Mn, Ni, and other elements for this to be added.In order to meet this demand, the United States developed AUS205 (0.15C-17Cr-1Ni-15Mn-0.3N) YUS (0.17C-21Cr-5Ni-10Mn-0.3N).As the Mn content is increased, the processing does not generate implicit acicular martensite. After solution treatment, the strength up 2000Mpa, high fatigue performance, superior to SUS304.
3.Improve the purity of the material
The high strength material, and strict control of inclusions, to increase the purity in order to ensure its performance. Such as the oxygen content of the material of the valve spring, and currently has 20 × 10 ¯ 6 development
4.Improve the surface quality.
The quality of the material surface have a great influence on fatigue performance.0.1mm surface peeling process in order to ensure that the surface quality of materials with special requirements.0.5mm depth defects using eddy current testing.Generating irregularities on the surface of the wire drawing process, the available electrolytic polishing make the surface roughness falls Ra = 6.5 to 3.4μm.
5. Plated steel wire in exceptional circumstances, in addition to the requirements of the spring characteristics.Also requires additional properties such as corrosion resistance, electrical conductivity, most of process are used the electroplating to solve.
The corrosion resistance of stainless steel wire and music steel wire equivalent galvanized corrosion resistance,And coated with a layer of ZnAl (5%) of the alloy, the corrosion resistance can be increased to about 3 times.
For stainless steel or music steel ,having resistance performance requirements,Can be plated copper wire diameter less than 0.4mm,Greater than 0.4mm can be used internally is copper,External stainless steel material.Usually music steel wire plated 5μm thick Ni, its conductivity can be improved.
In general, make the surface hardening of the formation process (such as shot peening and surface nitriding, etc.) can improve the fatigue strength of the residual stress.Currently being studied No-electroless plating Ni,By heating (300 to 500 ° C) 7% of the P can be precipitated in PNi,Vickers hardness can be increased up to HV500.after peening,below 300 ℃ heating and plated Ni.can improve the hardness of 10%.
6.Development of shape memory alloy
The one-way shape memory alloy, the spring application promising 50Ti-50Ni performance best. A spring made of a shape memory alloy, the temperature effect can be telescopic. Mainly used for constant temperature, constant load, constant amount of deformation of the control system. Executing agency driven by a spring retractable spring of work stress.
7.The application of ceramic
with high elastic modulus, low fracture strength, ceramic suitable for little change in the local. Currently being developed with heat resistance, abrasion resistance, and good insulating ceramic; application the a superplastic zinc alloy (SPZ), and having a high strength at room temperature. In addition, there is a high strength, silicon nitride, can withstand high temperatures up to 1000 ° C. Ceramic spring does not apply to work under impact loading.
8.Fiber-reinforced plastic in the spring
The glass fiber reinforced plastics (GFRP) plate spring in Britain, the United States and Japan and other countries have widely used.In addition for Tap suspension, can also be used for special light-duty vehicles, such as car racing longitudinally mounted suspension.Currently has developed successful suspension spring of carbon fiber reinforced plastics (CFRP) lighter than the metal leaf spring 20%.