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The rolling bearing service life and reliability largely bearing steel smelting quality is closely related to. Due to the characteristics of bearing steel, smelting quality than general industrial steel to much more stringent, such as steel chemical composition, purity, organization and uniformity.
1, strict chemical requirements
The ships bearing steel is a high carbon chromium bearing steel, i.e. carbon content of about 1%, about 1.5% chromium, and contain small amounts of manganese, silicon element eutectoid steel. Chromium can improve the heat treatment performance, improve the hardenability, homogeneous, tempering stability, but also can improve the rust resistance of the steel and the grinding performance. But when the chromium content exceeds 1.65%, after quenching increases the retained austenite in steel, to reduce the hardness and dimensional stability, to increase the unevenness of the carbides, and to reduce the impact toughness and fatigue strength. For this reason, the amount of chromium in the carbon chromium bearing steel general control of 1,65%. Only by strict control of the chemical composition of the bearing steel, obtained by the heat treatment step in order to meet the microstructure and hardness of the bearing performance.
2, high-precision size requirements
Rolling steel steel high dimensional accuracy requirements This is because most of the bearing parts to go through the pressure molding. In order to save material and improve labor productivity, most bearing rings are forged molding, ball after cold heading or hot forming, the small size of the roller after cold heading molding. If the accuracy of the size of the steel is not high, you can not accurately calculate the sizes of materials and weight bearing parts, but can not guarantee product quality, are likely to cause damage to the equipment and tooling.
Particularly stringent purity requirements
The purity of the steel is defined as the number of non-metallic inclusions contained in the steel, the higher the degree of purity, and fewer nonmetallic inclusions in the steel. Bearing steel, oxides, silicates, and other harmful inclusions lead to premature bearing fatigue spalling, mainly due to significantly reduced bearing life. Especially brittle inclusions hazards seriously affect the surface quality of the finishing of the bearing parts come off easily from the metal substrate during processing. Therefore, in order to improve bearing life and reliability, it is necessary to reduce the content of inclusions in bearing steel.
4, strict macrostructure and microstructure (high power) organization requirements
Bearing steel low magnification is generally loose, center porosity and flat analysis, microscopy (high power) organization Annealing of steel, carbide mesh, ribbon and liquid analysis. Carbide liquation hard and brittle, and its harmfulness and brittle inclusions. Carbide network to reduce the impact toughness, and uneven, easy to deformation and cracking during quenching. Banded carbide affect annealing and quenching and tempering organizations, as well as contact fatigue strength. Low, the pros and cons of high-powered organization has a great influence on the performance and service life of rolling bearings, bearing material standards for low-, high-powered organizations have strict requirements.
5, particularly stringent surface and internal defects requirements
Bearing steel, the surface defects including cracks, slag, burrs, scarring, oxide, the internal defects include shrinkage, bubbles, white spots, severe osteoporosis and segregation. These defects for the machining of the bearing, the bearing performance and life are greatly affected, these defects are not allowed in the bearing material standards specified.
6, particularly strict carbide requirements
In bearing steel, if there is a serious carbide uneven distribution is likely to cause non-uniformity of the microstructure and hardness in the heat treatment process, the inhomogeneity of the steel has a greater impact on the contact fatigue strength. In addition, severe carbide heterogeneity is also easy to make the bearing parts in the quenching cracks, carbide heterogeneity also lead to a decrease in the life of the bearing Accordingly, in the standard of bearing materials, steel of different specifications are clearly special requirements.
7, particularly stringent surface decarburization layer requirements
Bearing material standard has strict rules on the steel surface decarburization, surface decarburization beyond the standard specified range, and before the heat treatment process and not all of its removed, heat treatment and quenching process prone to quenching cracks, resulting in scrapped parts.
8, other requirements
Bearing steel standard bearing steel smelting, oxygen content, annealing hardness, fracture, residual elements, sparks inspection, delivery status, logos and other stringent requirements.
| Product Model | Inside Diameter | Outside Diameter | Thickness |
| NNU4934MBKRCC1P4 NSK | 170 | 230 | 60 |
| NN4934MBKRCC1P4 NSK | 170 | 230 | 60 |