There is a big gap between my country’s automobile suspension spring industry and foreign countries in terms of labor productivity, technical equipment level, materials and product research and development. Especially after my country’s accession to the WTO, automobile suspension springs are not among the products to be protected. The tariff reduction is in place once, and the price advantage of our products is gradually lost. With the upgrading of the main engine models, the technology and quality indicators of suspension spring products will be improved simultaneously. At that time, if the company still produces new products with current materials, equipment, technology and testing methods, it may be difficult to meet the requirements. Therefore, how to change the backward situation is an urgent issue for many automobile suspension spring manufacturers in our country. In particular, we should pay close attention to the development trend of foreign suspension spring technology in order to shorten the gap as soon as possible.
From the perspective of the research and development of new materials for automobile suspension springs, Japan is at the forefront. Mitsubishi Steel, Datong Special Steel, Kobe Steel and other companies have conducted a lot of research on suspension spring materials used under high stress conditions and developed HDS12, HDS13, UHS1900, UHS2000 and other new materials are used in the production of suspension springs with stresses of 1200MPa and 1300MPa respectively. These materials still have good plasticity and toughness when the tensile strength is greater than 2000MPa, even in the case of 2100~2200MPa, and maintain good corrosion fatigue resistance. However, the prices of these new materials have risen much more than before, and they are not supplied to markets outside of Japan.
The shape of the spring has also changed. In addition to the usual cylindrical spiral shape, there are truncated cones, banana shapes, non-circular shapes and S shapes. In particular, the S-shaped suspension spring is conducive to improving shock absorption. It is an invention patent of the German Bend company. The suspension springs of Polo and Bora launched in the Chinese market all use this design.
From the perspective of the spring manufacturing process: First of all, in order to adapt to the large wire diameter and high-strength materials, the German WAFIOS company has developed a suspension spring coiling machine that can coil up to Φ17mm and the material strength can reach 2100~2200MPa. ; The hot coil forming is the development of intermediate frequency heating. Because of its fast heating speed, high thermal efficiency, fine grains, and no decarburization, it is an ideal heating method for hot coil springs. Secondly, in terms of shot peening technology, multiple shot peening for high-stress springs is now common; warm shot peening (around 200℃) technology has also been officially used in production; stress shot peening has solved the problem of automatic spring clamping after years of research. , Stress shot peening machine has been put on the market. In terms of pellets, steel wire cut pellets must be used for high-stress suspension springs. The hardness of the pellets has been increased from HV560 and HV640 to HV720 or even HV800. Third, the requirements for surface coating of suspension springs have now been increased to 720h or even 1000h. In order to prevent surface bumps and the intrusion of corrosive media during use of the spring, in addition to the salt spray test, test items such as warm heat, bonding force, stone impact, and low temperature impact must be added. These stringent requirements, except for a few domestic enterprises , It is difficult to do it all. Fourth, in the fatigue test, the OEM is no longer satisfied to test the fatigue life of the suspension spring by the up and down vibration, and requires the manufacturer to imitate the working conditions for the test, such as diagonal beating, accordion-style beating, and salt spray conditions. At present, only a few domestic enterprises can meet such test conditions.