Bearing steel refers to hot or cold (cold drawn) seamless steel tubes for the manufacture of ordinary bearing rings with.outer diameter of Pipe of 25-180 mm, wall thickness of 3.5-20 mm, divided into sub-normal precision and high precision.Bearing steel is used to make the balls, rollers and bearing rings of steel. Bearing in the work is under immense pressure and friction, it is required bearing steel has high and uniform hardness and wear resistance, and high elastic limit. On the chemical composition of bearing steel uniformity, non-metallic inclusion content and distribution, carbide distribution requirements are very strict, is one of the most stringent of all kinds of steel production requirements.
The physical properties of bearing steel microstructure mainly to check, decarburization, non-metallic inclusions, low magnification as the master. Under normal circumstances are annealed hot-rolled, cold drawn annealed delivery. Delivery status should be specified in the contract. Steel low magnification must be free of shrinkage, subcutaneous bubbles, white point and microscopic pores. Center porosity, generally can not be more than 1.5 osteoporosis, segregation may not exceed 2 levels. Steel annealing organization should be evenly distributed fine granular pearlite. Decarburization depth, non-metallic inclusions and carbide of shall comply with the relevant national standards.
Under normal circumstances, less than 20mm in diameter to package delivery, greater than 20mm can bare delivery.Specific packaging requirements, depending on the requirements of the contract signed by both parties may be, eg, hexagonal package, the length difference, exports generally plus packaging and the like. Of cold drawn steel should be coated with anti-rust oil, some domestic manufacturers urgently needed goods can not rust, otherwise it done in degreasing processing complete sets of ring-out. Quality assurance should be attached, indicating the steel, heat number, weight, size, chemical composition, inspection standards and test results, etc. before the goods are shipped.
Bearing steel smelting technology
Bearing steel is mainly used for the manufacture of rolling bearing rolling elements and rings.
Since the bearing should have a long life, high-precision, low heat, high speed, high rigidity, low noise, high wear resistance and other characteristics, thus requiring bearing steel should have: high hardness, uniform hardness, high elastic limit, high contact fatigue strength and toughness necessary, certain hardenability, in the atmosphere of the lubricant in the corrosion resistance. To achieve the above performance requirements, chemical composition uniformity, and the type of content of nonmetallic inclusions, carbide size and distribution of the bearing steel, carbon and other demanding off. Bearing steel to the development of high quality, high performance and multi-species direction as a whole. Bearing steel according to characteristics and application environments are divided into: high carbon chromium bearing steel, carburizing bearing steel, high temperature bearing steel, stainless steel and special bearing special bearing materials.
To meet the high-temperature, high-speed, high load, corrosion, anti-radiation requirements, the need to develop a series of new bearing steel with special properties. In order to reduce the oxygen content of bearing steel tubes, the development of vacuum smelting, remelting, electron beam remelting bearing steel smelting technology. The large quantities of bearing steel smelting by the arc melting, develop into various types of foreign First Canadian refining furnace.Currently, the use of early capacity greater than 60 tons furnace + LF / VD or RH + + continuous casting and rolling bearing steel production process, in order to achieve high-quality, high efficiency, low energy consumption purposes. In terms of the heat treatment process by car bottom furnace, bell furnace developed into a continuous annealing furnace controlled atmosphere heat treatment. Currently, continuous heat treatment furnace up to 150m, processing and production of steel ball bearings of organizational stability and uniformity, small decarburization, low energy consumption.