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Hardening hardness of bearing steel

Hardening hardness of bearing steel

2020-05-25

The ferrules and rollers made of GCr15 and ZGCr15 are HRc61~65, and the steel balls are HRc62~66.The rings and rollers made of GCr15SiMn and ZGCr15SiMn are HRc60~64, and the steel balls are HRc60~66.

Bearings made of high carbon steel chromium bearing steel are generally suitable for operating temperature range of -40~130 degrees, oil and grease lubrication is normal.Can meet the general mechanical requirements.High carbon chromium bearing steel bearing parts after high temperature fire, it can adapt to the operating temperature of up to 250 degrees.

Ring and rolling body made of carburized bearing steel, its hardness is: ring and rolling body are HRc60~64, generally suitable for working temperature range of -40~140 ℃, oil and grease lubrication is normal, can be used under the condition of greater impact and vibration, such as locomotive and rolling mill bearings, but the heat treatment process of this steel is more complex.

With 910℃ quenching and 180℃ secondary tempering, the material properties of bearing steel can reach hardness HRC 45.2, tensile strength Rm is 1 450MPa, yield strength ReL is 1 240MPa,AKU is 105J, and the volume fraction of residual austenite is controlled below 1%.The good fit of strength and toughness of the test steel mainly comes from the refinement of grain, the precipitation of ultrafine martensite and uniform dispersed fine carbide.The effect of dimensional stability is mainly the control of the residual austenitic volume.

The contact fatigue life of bearing is very sensitive to the uniformity of steel structure.The contact fatigue life of bearing steel can be improved by improving the cleanliness (reducing the content of impurity elements and inclusions in steel) and promoting the fine and even distribution of non-metallic inclusions and carbides in steel.The structure of bearing steel in service state should be evenly distributed with small carbide particles on tempered martensite matrix, which can give the required performance of bearing steel.The main alloying elements in high carbon bearing steel are carbon, chromium, silicon, manganese, vanadium, etc. 

How to obtain the spheroidized structure is an important problem in the production of bearing steel.The net carbide can be eliminated by controlled rolling or fast cooling after rolling, and the suitable preparation structure can be obtained, which can shorten the annealing time of bearing steel spherification, refine carbide and improve fatigue life.In recent years, Russia and Japan have adopted low temperature controlled rolling (800 ℃ ~ 850 ℃), after which air cooling and short annealing are adopted, or the spheroidal annealing process is completely eliminated, qualified bearing steel structure can be obtained.Bearing steel processing at 650℃ temperature is also a new technology.If the eutectoid steel or high carbon steel have fine grain structure or can form fine grain in the processing process before hot processing, it will show superplasticity within the melting temperature range (0.4 ~ 0.6) and under a certain strain rate.The us naval research institute (NSP) has conducted processing tests on 5 2100 steel at a temperature of 650 ° c, indicating that the true strain 2.5 does not fracture at 650 ° c.Therefore, it is possible to use 650℃ temperature processing instead of high temperature processing and combine it with spheroidal annealing process, which is of great significance to simplify equipment and processes, save energy and improve quality.


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