To be exact judge its overheating degree must observe the microstructure. If in GCr15 steel quenching organization acicular martensites appear coarse, the quenching overheating organization. Formation reasons may be quench heating temperature is too high or heat insulation for too long a time of comprehensive cause overheating; May also be a primitive organization ribbon carbide serious, in between the two take.

Quenching cracking bearing parts in the quenching process for internal stress by the formation of the crack says quenching cracks. The reason cause the crack: due to quench heating temperature is too high or cooling too quickly, thermal stress and metal quality volume change the organization when stress is more than steel resistance of the fracture strength; The original work surface defects (such as surface imperceptible crack or scratch) or steel internal defects (such as slag, serious non-metallic inclusions, white, shrinkage residual, etc) in the hardened form stress concentration; The surface of the serious TIMKEN bearing the decarburization and carbide segregation; Parts after quenching insufficient or not seasonable tempering tempering; The cold front process caused by blunt stress, forging fold, deep turning point, oil groove sharp edges, etc. In short, cause the quenching cracking reason may be the above factors of one or more, the existence of the internal stress is the main cause of quenching cracks formation.
 
Quenching cracking deep and slender, fracture with broken section without oxidation color. It is often the front-runners in bearing the longitudinal crack or flat ring crack; In the shape of the steel ball bearings on a S form,

Bearing parts in heat treatment process, if it was in oxidizing medium heat, TIMKEN bearing surface oxidation happens the parts in the quality of the surface carbon scores decline, resulting in the decarburization surface. The depth of the decarburization layer surface more than the last processing will make allowance for scrap parts. The surface of the decarburization layer depth in determination of metallographic composition metallographic method and available in the micro hardness method. Surface layer microhardness distribution curve to measure method shall prevail, to do the arbitration criterion. TIMKEN bearings components after heat treatment by the common quality defects are: quenching microstructure overheating, owe hot, quenching cracks, hardness is not enough, heat treatment deformation, surface decarburization, soft spots, TIMKEN bearing maintenance and overhaul method. Overheating from bearing parts rough mouth can be observed in hardened microstructure overheating.

The importance of the TIMKEN bearing, means that when the damage, can cause equipment of down, so this kind of bearing should be the best temperature probe. Normally, TIMKEN bearing in just lubrication or again after the lubrication can have natural temperature rise and last for one to two days.

Often, working temperature in the 150 ° above the use of bearing called heat TIMKEN bearing, because chrome bearing steel in the use of temperature is more than 150 °, its hardness fell sharply, size is not stable, make TIMKEN bearing can't work normally. So for the working temperature 150 ° to 350 ° in under the working conditions of TIMKEN bearing, if rings and rolling body still choosing normal high carbon chromium bearing steel manufacturing, it must be on the bearing parts special tempering treatment, should be generally higher than 50 ° working temperature under tempering. According to the above requirements after the tempering treatment TIMKEN bearing steel, can work under the temperature in normal use. But because after tempering hardness declined, TIMKEN bearing life is reduced. When bearings working temperature higher than 350 °, it must use high temperature resistant
 
TIMKEN bearing steel manufacturing.

The cause of the high temperature TIMKEN bearing:

1, bearing grease quality not line, high viscosity lubricating oil;

2, the agency assembly is too tight, clearance is insufficient;

3, TIMKEN bearing assembly too tightly;

4, TIMKEN circle in the bearing shaft or shell and rotation;

5, bearing load too big,

6, TIMKEN bearing maintains a or rolling body break.




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