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Mechanical Engineering Information: Rolling Bearing Steel
Source: China Bearing Network Time: 2014-09-09
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High carbon chromium bearing steel was first introduced in Europe in 1901. In 1913, the United States listed it as a standard steel grade. For more than 70 years, many countries have developed many new technologies for improving the purity of bearing steel and improving carbide non-uniformity. The skills such as the essence of gas p furnace have been widely used in the production of bearing steel o and the production of ferrules with bearing steel pipe o further improved the steel utilization rate and bearing life. China began production of bearing steel in 1951.
Type p function p used in modern rolling bearing steel can be divided into high carbon chromium bearing steel p carburized chromium bearing steel p stainless bearing steel and high temperature bearing steel four categories. In the bearing manufacturing industry, the use of a wide range of p A large amount of high carbon chromium bearing steel.
The high degree of pureness of the alloying elements and the outstanding uniform arrangement are the primary quality indicators of the bearing steel. Therefore, the non-metallic inclusions and the carbide non-uniformity in the bearing steel are all based on different conditions in the steel specification. Qualified grade.
Carbon is the primary strengthening element in bearing steel. Bearing steel usually has a high carbon content. The use of cryptocrystalline needles and fine-grained needle-shaped martensite as the base is to preserve a certain amount of quenched and undissolved carbides in the arrangement. Improve the wear resistance of steel. Appropriately reduce the carbon content in steel. Add the solubility of alloying elements in the matrix. Although the amount of hardened undissolved carbide is reduced, the hardenability and touch fatigue strength of steel are improved. The addition of carbon content is beneficial to the wear resistance of the steel. Therefore, the carbon content in the bearing steel is determined according to the different uses o is usually controlled in the range of 0.8 to 1.2%.
Chromium is the primary element of carbide formation. High carbon chromium steel constitutes MC type carbide under various heat treatment conditions (M indicates metal). Chromium can improve the mechanical function of steel, p hardenability and arrangement uniformity. The corrosion resistance of the added steel. The chromium content in the steel usually does not exceed 2. 0% of can replace the chromium in the steel. The hardenability of the added steel is stronger than that of chromium. Therefore, high hardenability has been carried out. Containing f high carbon chromium bearing steel.
Silicon p-manganese can improve hardenability in bearing steel. The typical steel grade of silicon p-manganese is GCr15SiMn. Manganese can also form stable MnSo sulfide with sulfur in steel. The composite inclusions in the center o reduce the damage effect of oxides on steel.
Production process bearing steel is usually operated by inert electric furnace o can also be added outside the furnace vacuum degassing treatment or ladle vacuum essence. Bearing steel ingot process and ingot type depiction of non-metallic inclusions and carbide dispersion in steel Great influence. Bearing steel has a simple white point o, so steel ingots and billets should be slow. Aerospace high-quality bearing steel needs special methods such as electroslag remelting or vacuum self-consumption remelting.
Bearing steel ingots are usually subjected to long-term dispersion annealing at a high temperature of 1200 to 1250 to improve carbide segregation. The atmosphere in the furnace should be controlled during hot processing. The heating temperature of the billet should not be too high. The holding time should not be too long to avoid severe decarburization. The final rolling (forging) temperature is usually between 800 and 900. If it is too high, it will be coarse and coarse mesh carbide. If it is too low, it will form a rolling (forging) crack. The rolled (forged) product should be cooled to 650o to avoid cementite. In the grain boundary, it is divided into meshes. When there are conditions, the control can be used.
In order to obtain outstanding machinability and pre-arrangement before quenching, the cold-working bearing steel should be thoroughly spheroidized. The annealing temperature is usually 780-800o. Avoid annealing when annealing. If the rolled steel has excessive coarse mesh permeability Carbon body o should be normalized before annealing. Chromium bearing steel is usually heated between 830 and 860 o oil quenching o150 ~ 180 tempering. In the arrangement of fine bearings, the amount of retained austenite should be reduced or The remaining austenite remains stable during the application process, so it is often necessary to carry out -80 (or lower temperature) cold treatment after quenching and long-term stability treatment at 120-140.
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