Selection principle of rolling bearing steel

When designing and manufacturing rolling bearings, the bearing materials are generally selected according to the following principles.

First, according to the working conditions of the bearing
1. Operating temperature
Bearings operating at room temperature are made of chrome bearing steel. Chromium bearing steels are also used at operating temperatures above 150 ° C and below 250 ° C, but subjected to special heat treatment (requires tempering at 200 ° C or 300 ° C).
2. The magnitude of the impact load
Bearings with strong impact loads are generally not made of chrome bearing steel, and most of them are made of high-quality carburized structural steel, impact-resistant tool steel or quenched and tempered structural steel.
3. Contact medium
Bearings used in corrosive media must be made of corrosion-resistant steel or alloy steel with good corrosion resistance.

Second, according to the type of structure of the bearing
The structure of the bearing parts is more complicated. For example, when the outer ring is equipped with a rib, and the high impact load is required, the carburized steel with good processing performance should be used; the outer ring of the rolled needle bearing can be made of 08 and 10 low carbon steel (good plasticity) Suitable for cold stamping); the joint bearing used in the swing mechanism or the operating mechanism can be cold extruded by using GCr15, 9Cr18, 9Cr8Mo and alloy structural steel with excellent cold plastic deformation properties.

Third, according to bearing fatigue life and reliability requirements
Bearing fatigue life and reliability depend to some extent on the purity and uniformity of the steel. For general use, use ordinary bearing steel smelted in acid open hearth furnace or alkaline electric furnace. With the continuous improvement of the smelting method, new smelting methods such as current remelting, vacuum smelting, and electron beam furnace smelting have been produced, and the bearing made of the bearing steel made by the above method has a correspondingly improved life. Suitable for bearings with special requirements for fatigue life and reliability, such as axlebox bearings for railway vehicles, aerospace engine spindle bearings and navigation system bearings.
In addition, in the selection of steel grades should also consider the processing properties of steel, supply of goods and domestic resources.

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The role of alloying elements in precision bearing rolling bearing steel

China Bearing Network Summary Precision alloy rolling bearing steel alloy elements are mainly silicon and chromium, what are the two roles? Introduced as follows:

1. The role of silicon in GCr15 bearing steel

It is beneficial to the formation of the body-centered cubic ferrite structure. It does not form carbides in the steel. It is on the left side of the iron in the periodic table and is mainly dissolved in iron. It has little effect on the diffusion coefficient of carbon in austenite, and has no effect on the formation rate of austenite. It can raise the A1 point and relatively slow the formation of austenite. If the austenite grain size is slightly hindered or ineffective during heating, the pearlite phase transformation can be delayed to shift the C curve to the right, so that the nose on the C curve moves to a high temperature region, which lowers the Ms point and improves the supercooled austenite. The stability of the body, thereby reducing the quenching critical cooling rate and improving the hardenability of the steel. It can significantly slow down the decomposition of martensite at lower temperature, but does not slow down the decomposition of martensite at tempering at 400-500 °C, significantly hindering the accumulation of carbides, hindering the elimination of various types of distortion in steel during tempering. The effect, and generally delays the recovery, recrystallization and carbide aggregation process of the α phase of the quenched steel, thereby inhibiting the reduction of the hardness and strength of the steel and enhancing the tempering stability of the steel. The recrystallization temperature of the α phase can be increased, the temper brittleness of the steel can be significantly enhanced, the phase structure of the steel can be changed, and the amount of pearlite can be increased. The main purpose is to increase the hardenability of the steel. All the hardened parts can obtain high and uniform comprehensive mechanical properties after high temperature tempering, especially the high yield ratio, which significantly strengthens the ferrite and is more than a certain range. Can improve the toughness of steel.

2. The role of chromium in GCr15 bearing steel

The element of the γ phase region can be blocked. When the content reaches a certain amount, the γ phase region is blocked, even if the γ region on the phase diagram shrinks to a small range, and the γ to α phase transformation occurs in the alloy beyond this content, which is beneficial to the body center. Formation of cubic ferrite structure. Carbide can be formed in steel, which is a transitional over-group element. It is located on the left side of iron in the periodic table, which can reduce the carbon content of the steel at the eutectoid point and the maximum solid solubility of carbon in γ. The phase region disappears and all ferrite structures are obtained. It is a strengthening element forming element, which reduces the diffusion coefficient of carbon in austenite, thus greatly delaying the transformation process of pearlite to austenite. In the steel, the formation of special carbides is not easy to dissolve, which will reduce the austenite formation speed. Slow, can raise the A1 point, relatively slowing the formation of austenite. Significantly, the recrystallization temperature of the α phase is pushed to a high temperature, so that temper brittleness is apparent in the steel, and the further development of martensite decomposition is strongly prevented, and the phase structure of the steel can be changed to increase the amount of pearlite. Increasing the hardenability of the steel, all the hardened parts can obtain high and uniform comprehensive mechanical properties after high temperature tempering, especially the high yield ratio, significantly strengthening the ferrite, and increasing the steel in a certain range. Resilience. If a special carbide which is difficult to dissolve is formed, if the holding time is insufficient during heating, austenite having extremely uneven composition will be obtained. It has a moderate hindrance to the austenite grain size during heating, which can delay the pearlite phase transformation, reduce the Ms point, improve the stability of the supercooled austenite, thereby reducing the quenching critical cooling rate and improving the hardenability of the steel. Significantly hinder the accumulation of carbides, hinder the steel from eliminating various types of distortion during tempering, and generally delay the recovery, recrystallization and carbide aggregation of the α phase of the quenched steel, thereby inhibiting the reduction of hardness and strength of the steel. Enhance the role of manganese in 5.3 GCr15 bearing steel.https://www.supplyforever.com/