INA non-standard bearing parts heat treatment technology application effect appraisal method

In repairing imported bearing, the commonly used heat treatment method has three such as quenching, tempering, annealing, tool is alcohol lamp and torch, although the method is simple, but very practical. General to quenching by the file system of parts, in order to improve the hardness of the parts, lays the foundation for grinding and polishing. Quenching method is to wet file system of the steel, the surface dip in on some of borax, the alcohol lamp L in torch burning red, into the oil. Parts surface decarburization phenomenon of borax in order to prevent the purpose of the parts. The broken parts to the fire for a layer on the surface of borax, in black. Must be removed before tempering. The method is to take parts borax copper container that is put in the water and in alcohol lamp heating boiling, borax automatically fall off from the parts. After quenching parts hardness is very high, very brittle, tempering treatment, must be conducted to suitable hardness. Usually put the quenching of the parts on the copper plate, on the alcohol lamp heating, stop the heating parts after brown, natural cooling in air. After tempering hardness of parts is in commonly R C55 - rockwell hardness 62. Imported bearing machine parts (heart Steel) Recommend in appendix nv hardness requirements. ( 1) To expand the application range of GCr15 steel, M generally GCr15 steel quenching ring effective wall thickness under 12 mm, but the BL quenching by nitrate cooling ability is strong, if use the measures, such as stirring, string move, add water ring effective wall thickness can be expanded to about 28 mm. ( 2) Hardness is stable, good uniformity of the BL change is a slow process, generally GCr15 steel 4 h, GCr18Mo steel need 5 h, ring in long isothermal nitrate, on the surface of the core organization transformation almost simultaneously, so the hardness of stability, uniformity, good general BL GCr15 steel after quenching hardness in 59 ~ 61 HRC, uniformity of 1 or less HRC, unlike M quenching ring wall thickness slightly bigger when there is low hardness, soft point, poor uniformity. ( 3) Reduce the quenching and grinding cracks in railway, non-standard bearing production, because the ring size, weight, oil quenching M the organization brittleness is big, to obtain high hardness after quenching is often strong cooling measures, resulting in quenching cracks; And BL quenching, because is much better than M BL organization toughness, surface formed up to at the same time 400 - - 500 mpa compressive stress, greatly reducing the quenching crack tendency [ 19] ; When grinding surface compressive stress to offset some of the stress, makes the overall stress level drops, greatly reducing the grinding crack. ( 4) Improve the service life of bearing to bear large impact load of railroad, non-standard bearings, etc. , after M quenching when using main failure forms is: inner sleeve cracking when assembling, use in the process of impact outer ring, inner ring fracture, falling guard and isothermal quenching bearing with good impact toughness, surface compressive stress, whatever the assembly inner sleeve craze, or using Chinese and foreign set of guard metal shed and inner sleeve fracture tendency is greatly reduced, and can reduce the edge stress concentration of roller. Therefore, after isothermal quenching than M after quenching the average life expectancy and improve reliability.