Research progress of automotive gear steel

Automobile gear is an important transmission part, which plays the role of transmitting power and changing speed and direction. Due to the complex working conditions of automobile gears, they often need to work under large load and have large wear; The tooth root is subjected to the impact load of sudden load change and the bending load of periodic change, which is easy to cause the brittle fracture or bending fatigue failure of the tooth; The tooth surface bears large compressive stress and friction, and pitting contact fatigue failure and deep peeling often occur.

Therefore, in the production of automobile industry, gears are required to have not only excellent wear resistance, but also high resistance to contact fatigue and bending fatigue. The quality of gears largely depends on the gear materials and their heat treatment process. At present, forged steel, cast steel, cast iron, non-ferrous metals and non-metallic materials can be used to manufacture gears, mainly carburized gear steel. In order to meet the development trend of lightweight, high performance, long service life and environmental protection of gear steel, higher requirements are put forward for the performance of gear steel.

As energy conservation, environmental protection, safety and economy will account for an increasing proportion in automobile production, higher requirements are put forward for automobile gear materials. The localization of gear steel imported from Germany, Japan, the United States and other countries by domestic automobile gear production lines is also urgent. Now the new gear steel that can be mass produced includes Cr Mo, Mn-Cr, mn-cr-b, Cr Ni Mn, Cr Ni Mo series steel. In recent years, with the continuous demand for high-performance gear steel for medium and high-grade vehicles, new types of gear steel and new products in China are increasing, such as 20CrMo, 20crni2m o, 17CrNiMo6 and other new types of steel developed successively, as well as 17cr2m n2tih, 20cr2ni4 carburized gear steel, 28m ncr5 gear steel, Nb-V-Ti composite microalloyed steel for heavy-duty vehicles. The continuous improvement of gear steel smelting process and heat treatment process will gradually improve the comprehensive properties of gears, such as continuous casting process and American gearbox gear sae4047 and sae4047m steel developed by carbonitriding process.

With the need of automobile lightweight, the application prospect of polymer fiber reinforced metal matrix composites in gears will be more extensive. Bayer’s “all plastic automobile” at the 2008 Shanghai International Rubber and plastic exhibition is a good start.

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