The Role Of Alloying Elements In Rolling Bearing Steel For Precision Bearings

1. The role of silicon in GCr15 bearing steel
It is conducive to the formation of body-centered cubic ferrite structure, no carbide is formed in steel, it is on the left side of iron in the periodic table, and it is mainly dissolved in iron. It has little effect on the diffusion coefficient of carbon in austenite, and has little effect on the formation rate of austenite. It can increase the A1 point and relatively slow down the formation rate of austenite. Slightly hinder or have no effect on the size of austenite grains during heating, it can delay the pearlite phase transformation, move the C curve to the right, make the nose on the C curve move to the high temperature area, reduce the Ms point, and improve the supercooled austenite The stability of the body, thereby reducing the critical cooling rate of quenching and improving the hardenability of the steel. Can significantly slow down the decomposition of martensite at lower temperatures, but does not slow down the decomposition of martensite during tempering at 400-500°C, significantly hinders the aggregation of carbides, and hinders the elimination of various distortions of steel during tempering The effect, and generally delay 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. It can increase the recrystallization temperature of α phase, significantly enhance the temper brittleness of steel, change the structure of each phase of steel, and increase the number of pearlite. The main purpose is 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 can significantly strengthen ferrite. Can improve the toughness of steel.

2. The role of chromium in GCr15 bearing steel
Elements that can seal the γ-phase region, when the content reaches a certain amount, the γ-phase region will be closed, even if the γ-region on the phase diagram shrinks to a small range, the alloy will undergo a γ-to-α phase transition beyond this content, which is beneficial to the body center Cubic ferrite formation. Carbide can be formed in steel, which is a transition group element, located on the left side of iron in the periodic table, which can reduce the carbon content of the eutectoid point of steel and the maximum solid solubility of carbon in γ, adding a large amount can make γ The phase area disappears, and the whole ferrite structure is obtained. It is a strengthening element that reduces the diffusion coefficient of carbon in austenite, thus greatly delaying the transformation process from pearlite to austenite. In steel, the formation of special carbides is not easy to dissolve, which will slow down the formation rate of austenite. Slow, the A1 point can be raised, which relatively slows down the formation speed of austenite. Significantly push the recrystallization temperature of α phase to high temperature, make temper brittleness obviously appear in steel, strongly prevent the further development of martensite decomposition, change the structure of each phase of steel, and increase the number of pearlite. Increase the hardenability of steel, and all hardened parts can obtain high and uniform comprehensive mechanical properties after high-temperature tempering, especially high yield ratio, which can significantly strengthen ferrite, and the ratio of steel can also be improved within a certain range. toughness. If special insoluble carbides are formed, austenite with extremely uneven composition will be obtained if the holding time is insufficient during heating. It has a moderate hindering effect on the size of austenite grains during heating, can delay the pearlite phase transformation, reduce the Ms point, improve the stability of supercooled austenite, thereby reducing the critical cooling rate of quenching and improving the hardenability of steel. Significantly hinder the aggregation of carbides, hinder the elimination of various distortions of steel during tempering, and generally delay the recovery, recrystallization and carbide aggregation process of quenched steel α phase, thereby inhibiting the reduction of hardness and strength of steel , to enhance the role of manganese in 5.3 GCr15 bearing steel
The γ-phase region can be opened. If it reaches a certain amount, the appearance of the α-phase region can be completely suppressed and replaced by the γ-phase region. Therefore, if the r region is quenched to room temperature, it is easy to obtain austenite. It can increase the recrystallization temperature of α phase, make temper brittleness obviously appear in steel, change the structure of each phase of steel, and increase the number of pearlite. Carbide can be formed in steel, which is a transition group element, which is located on the left side of iron in the periodic table, and can reduce A3 and A1. After a large amount of addition, A3 can even be lowered below room temperature, and the steel still has austenitic properties at room temperature. Tenite structure can change the work-analysis transformation temperature, and lowering the A1 point relatively increases the degree of superheat, which also increases the formation speed of austenite, which can refine the pearlite, which is beneficial to the formation of austenite, and is beneficial to heating. When the austenite grain size is helpful. It can delay the pearlite phase transformation, reduce the Ms point, improve the stability of supercooled austenite, thereby reducing the critical cooling rate of quenching and improving the hardenability of 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 can significantly strengthen ferrite, and the ratio can be improved within a certain range. toughness of steel.