The bearings loaded into automobile, industrial machinery, household appliances, information machinery and other mechanical devices not only require lightweight, compact, but also require to improve the performance of the bearings to adapt to the use of too harsh environment.To meet this demand, materials, heat treatment processes, shapes and sizes must be optimized, and the integration of the surrounding components with the users of the materials must be sought.
Datong has been developing bearing materials suitable for use in particularly harsh environments and heat treatment processes suitable for this material.The following is a brief introduction of the high temperature bearing steel which has been developed jointly with the bearing manufacturers and has been put into practical use, and the foreign body resistant bearing steel developed by the company alone.
1. High temperature bearing steel STJ2
With the continuous improvement of the output power of automobile engines and the industrial machinery high-speed and closure, the ambient temperature of bearing use rises.It is desirable to develop bearings that maintain performance at temperatures between 473 and 523K.At this temperature range, if the use of tempered SUJ2, the hardness will be reduced, rolling life characteristics will be worse.On the other hand, although the precipitated hardened alloy steel-m50 used in jet engines has a full rolling life in the same temperature range, the alloy contains about 10% of Cr, Mo, V and other alloy elements, so the material cost is high, the heat treatment is complex, and the lack of universality.Therefore, it is effective to improve tempering resistance and softening to prevent the softening under the high temperature condition to develop the high-temperature bearing bearing with steel as the working target for the consideration of heat treatment and processing.
The company investigated the influence of alloying elements on quenching hardness and tempering hardness, using element C to improve quenching hardness and element Si to improve tempering resistance.Therefore, for the bearing steel SUJ2 for comparison, the material STJ2, which increases the content of C and Si to prevent the hardness from decreasing at high temperature and maintains the rolling characteristics by adding Ni elements, is developed as the steel for high temperature bearing.
2. Foreign body resistant bearing steel DCJ2
For automotive transmission and differential bearings, because oil mixed with foreign bodies (silt, cutting powder), once the foreign bodies bite into the rolling surface of the bearing will produce indentation caused early peeling of the rolling surface, for this purpose, the development of foreign body bearing steel.
In order to improve the service life of the bearing in the mixed foreign body environment, it is effective to improve the residual austenite volume on the surface and the surface hardness or the toughness of the matrix.
Development to add more than 2% of the Mn's resistance to foreign body bearing steel DCJ2 in quenched and tempered condition of foreign body fatigue life of rolling resistance and rolling fatigue life compared with SUJ2 clean oil, its residual austenite volume is high, under the condition of the foreign bodies with shows like in clean oil, excellent rolling fatigue life has clear DCJ2 nitrocarburizing treatment steel excellent resistance to foreign life.
Datong special steel company has carried out the research on the surface hardening treatment of STJ2 and DCJ2, which are high temperature bearing steel and foreign body bearing steel.In addition, the surface hardened steel with added Mn, which has better life characteristics than carburizing and nitriding treatment, has been developed and applied to bearing manufacturers in Japan, the United States and Europe.