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Analysis: Basic requirements for the quality of bearing steel
Source: Bearing network time: 2014-10-06
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1. Strict chemical composition requirements Generally, the bearing steel is mainly high carbon chromium bearing steel; that is, the carbon content is about 1%; the chromium is involved in about 1.5%; and the hypereutectic steel is rich in a few manganese and silicon elements. Chromium can improve heat treatment function, improve hardenability, arrange uniformity, tempering stability; and can improve the anti-rust function and grinding function of steel. But when the chromium content exceeds 1.65%; steel will be added after quenching Remaining austenite; reduced hardness and dimensional stability; added carbide non-uniformity; reduced steel impact toughness and fatigue strength. For this reason; chromium content in high carbon chromium bearing steel is usually controlled at 1; 65% The following. As long as the chemical composition of the bearing steel is strictly controlled; the arrangement and hardness of the satisfactory bearing function can be obtained through the heat treatment process.
Second, high-precision scale requirements Steel for rolling bearings requires high dimensional accuracy; this is because most bearing parts must be formed by pressure. In order to save data and improve labor productivity; most bearing rings are formed by casting The steel ball is formed by cold heading or hot rolling; the small-scale roller is also formed by cold heading. If the dimensional accuracy of the steel is not high; the cutting scale and component cannot be accurately calculated; the product quality of the bearing parts cannot be ensured. Also, it is easy to form damage to equipment and molds.
Third, the unique and strict purity requirements The purity of steel refers to the number of non-metallic inclusions in the steel; the higher the purity; the less non-metallic inclusions in the steel. The oxides and silicates in the bearing steel The harmful inclusions are the main reason for the early fatigue loss of the bearing and the significant decrease in bearing life. The unique is that the brittle inclusions are the most damaged; because it is simply detached from the metal substrate during the processing; the appearance of the bearing parts after finishing is severely affected. Quality. Therefore; in order to improve the life and reliability of the bearing; it is necessary to reduce the content of inclusions in the bearing steel.
Fourth, strict low-order arrangement and microscopic (high-power) arrangement requirements Low-order arrangement of bearing steel refers to usually loose, intermediate loose and flat analysis; microscopic (high-power) arrangement includes steel annealing arrangement, carbide mesh, belt Carbide liquid analysis is hard and brittle; its damaging is the same as brittle inclusions. Reticulated carbides reduce the impact toughness of steel; and make it unevenly arranged; simple deformation and cracking during quenching. Carbide affects the annealing and quenching tempering arrangement and the fatigue strength of the touch. The low and high times arrangement has a great influence on the function and service life of the rolling bearing; therefore, the low and high magnification arrangements are severe in the bearing data specification. Demand.
5. Unique and severe external defects and internal defects are required for bearing steel; external defects include cracks, slag inclusions, burrs, crusting, oxide scales, etc.; internal defects include shrinkage cavities, bubbles, white spots, severe looseness and segregation Etc. These shortcomings have a great influence on the processing of the bearing, the function of the bearing and the lifespan; clear rules in the bearing data specification do not allow these shortcomings to be presented.
Sixth, the unique and strict carbide non-uniformity requirement is in the bearing steel; if the severe carbide dispersion is uneven, the arrangement and hardness unevenness are simply formed in the heat treatment process; the arrangement unevenness of the steel is touched The fatigue strength has a greater impact. Others; severe carbide inhomogeneity also makes the bearing parts crack when quenching and cooling; carbide inhomogeneity will also lead to a decrease in the life of the bearing; therefore, in the bearing data specification There are clear and unique requirements for different specifications of steel.
VII. Unique and strict appearance of decarburization layer requirements There are strict rules on the decarburization layer of steel in the bearing data specification; if the outer decarburization layer exceeds the normative rule scale; and it is not in the processing process before heat treatment Cleared; in the heat treatment quenching process, quenching cracks occur simply; the formation of parts is invalid.
Eight, other requirements in the bearing steel data specifications also on the bearing steel training methods, oxygen content, annealing hardness, fracture, residual elements, spark inspection, delivery status, signs, etc. have severe demand.
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