TIMKEN bearing components for heat treatment has its reason

TIMKEN bearing structure characteristics and working condition requirements of TIMKEN bearing materials must have high hardness, high wear resistance, high contact fatigue strength, high elastic limit, good impact toughness, good fracture toughness and good dimensional stability, good rust resistance and good heat and cold processing performance, etc. In order to guarantee the performance requirements, TIMKEN bearing steel metallurgy quality must ensure that the chemical composition of strict, especially high purity ( Low-level non-metallic inclusions) , low oxygen content and residual element content, strict macrostructure and microstructure ( Microscopic) Organization, strict carbide inhomogeneity, strict surface decarburization layer and internal loose, segregation, and microscopic pore requirements; Don't allow there are cracks, slag inclusion, burr, folding, scarring, scale, shrinkage cavity, bubble, since the point and burnt surface and internal defects. In order to ensure the machining performance, the precision of the size of steel also has strict requirements. TIMKEN bearing steel quality is the most demanding of all the alloy steel and steel grade of inspection items at most. Recognized in the world, and the level of the TIMKEN bearing steel is a sign of a national level of metallurgy. The latest metallurgical technology generally first on the development and production of TIMKEN bearing steel applications. Calcined fire crack TIMKEN bearing components in the process of cooling calcined fire fire burnt for crack formed by the internal stress of the crack. Of the cause of the crack are: because of the calcined fire heating temperature is too high or cooling, the thermal stress and quality of metal volume change of the organization stress is greater than the fracture strength of steel; The original defects on the surface of the work ( Such as surface microcrack or scratches) Or steel internal defects ( The non-metallic inclusions such as slag, serious, white spots, shrinkage residual, etc. ) When the fire burnt form stress concentration; TIMKEN bearing serious surface decarbonization and carbide segregation; Component calcined fire insufficient tempering or failed to timely after tempering; The previous process caused by salt stress, cold forging folding, deep turning tool and the oil groove sharp edges, etc. In short, the cause of calcined fire crack could be one or more of the above factors, the existence of internal stress is the main reason for the formation of calcined fire crack. Fractures in the calcined fire crack deep and long and thin, flat and broken section without oxidation color. It's on the TIMKEN bearing ring is often on the longitudinal straight crack or annular crack; On the TIMKEN bearing steel ball shape with s-shaped, TIMKEN bearing components in the process of heat treatment, if they are in oxidizing medium heat, TIMKEN bearing surface oxidation happens reduce component on the surface of carbon mass fraction, causing surface decarburization. The depth of the surface decarburization layer over the last machining allowance will make component scrap. The determination of surface decarburization layer depth is available in the metallographic examination metallography and microhardness method. The surface microhardness distribution curve measurement shall prevail, to do the arbitration criterion. TIMKEN bearings components after heat treatment of the common quality defects are: fire burnt microstructure overheating, less heat, quenching crack, hardness is not enough, the heat treatment deformation, surface decarburization, soft point etc, TIMKEN bearing maintenance and repair methods. Overheating from the mouth of the TIMKEN bearing components rough can observe the microstructure after calcined fire from overheating. The importance of TIMKEN bearings, means that when the damage cause of equipment downtime, so this type of TIMKEN bearings shall be mounted to the best temperature detector. Under normal circumstances, TIMKEN bearings in just after the grease or lubricant will be a natural temperature rise and the last one to two days. Usually, working temperature over 150 ° use TIMKEN bearing called heat TIMKEN bearing, due to chromium TIMKEN bearing steel in the use of temperature over 150 °, the hardness will fell sharply, size is not stable, TIMKEN bearing cannot work normally. So for the working temperature at 150 ° to 350 ° work under the conditions of TIMKEN bearings, if rings and rolling body still choose ordinary high carbon chromium TIMKEN bearing steel manufacturing, it must be to special tempering treatment of TIMKEN bearing components, shall generally be higher than working temperature tempering under 50 °. After tempering treatment according to the requirements of the TIMKEN bearing steel, can be used in normal working temperature. But after tempering hardness decreased, TIMKEN bearing life. When the TIMKEN bearing operating temperature higher than 350 °, must use high temperature resistant TIMKEN bearing steel manufacturing. TIMKEN bearing temperature is too high: 1, TIMKEN bearing lubricating oil quality, high viscosity lubricating oil; 2, assemble is too tight, the gap is insufficient; 3, TIMKEN bearing assembly too tight; 4, TIMKEN bearing race in internal rotation shaft or housing; 5, TIMKEN bearing heavy load; 6, TIMKEN bearing cage or rolling body fracture.