The role of alloying elements in precision bearing rolling bearing steel
2019-05-20
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
The γ phase region can be turned on, and if a certain amount is reached, the occurrence of the α phase region can be completely suppressed, and the γ phase is replaced, so if the r region is quenched to room temperature, austenite is easily obtained. The recrystallization temperature of the α phase can be increased, and temper brittleness is apparent in the steel, and the phase structure of the steel can be changed to increase the number of pearlite. Carbides can be formed in steel, which are transitional transitional elements. On the left side of the iron in the periodic table, A3 and A1 can be lowered. After a large amount of addition, A3 can be lowered to below room temperature, and the steel still has a temperature at room temperature. The structure of the austenite can change the transformation temperature of the electrolysis, reduce the A1 point and increase the superheat degree relatively, which increases the formation speed of austenite, can make the pearlite refine, and is beneficial to the formation of austenite. The austenite grain size is helpful. The pearlite phase transformation can be postponed to lower the Ms point and improve the stability of the supercooled austenite, thereby reducing the quenching critical cooling rate and improving the hardenability of the steel. In order to increase the hardenability of steel, all hardened parts can obtain high and uniform comprehensive mechanical properties after high temperature tempering, especially high yield ratio, which significantly strengthens ferrite and can be improved in a certain range. The toughness of steel.
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