Metallurgical quality of steel for truck gear

The metallurgical quality of steel for truck gear has the following requirements:

1.End hardenability

At present, the bandwidth control of truck gear steel in China is as follows: Guqian enterprise is controlled by two points, generally 6-8hrc at JG and 6-10hrc at j15; General enterprise requirements are to comply with GB / t3077-1999 or single point control. In foreign countries, the hardenability bandwidth of truck gear steel is generally controlled at 4 ~ 7hrc.


At present, the requirement of truck gear steel in China is less than 20ppm, and that in foreign countries is generally less than 15ppm. Non metallic inclusions are rated according to JK series standard rating chart, with general requirements of Grade A (sulfide) ≤ 2.5, B (alumina) ≤ 2.5, C (silicate) ≤ 2.0 and D (spherical oxide) ≤ 2.5.

3.Grain size

Austenite grain size is another important index for the quality requirements of truck gear steel. Fine and uniform austenite grain size can stabilize the end hardenability, reduce heat treatment deformation and improve the brittle fracture resistance of carburized steel. At present, the austenite grain size grade of truck gear steel in China is generally required to be less than or equal to grade 5.

4.Trace elements

In order to ensure the processing performance of truck gear steel, there are certain requirements for trace elements of truck gear steel at home and abroad. For example, in order to ensure the grain size, Al content is required to be 0.020% ~ 0.040%; In order to improve the cutting performance, the s content is required to be 0.025% ~ 0.040%.

5.Surface quality

Truck gear steels are all top forging steels, which have strict requirements on the surface quality of steel. Whether it is GB / t3077-1999 standard or the technical conditions of vehicle gear steel recently formulated by China gear professional association, there are strict requirements for this. There is still a big gap between the current surface quality of truck gear steel in China and the foreign advanced level.

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