Bearing steel tube is hot-rolled or cold-rolled (cold-drawn) seamless steel tube for the manufacture of ordinary rolling bearing rings. The outer diameter of the steel tube is 25-180 mm, and the wall thickness is 3.5-20 mm. Bearing steel is used to make ball, roller and bearing ring steel. Bearing at work is under great pressure and friction, so the requirements of bearing steel has high and uniform hardness and wear resistance, as well as high elastic limit. It has strict requirements on the uniformity of the chemical composition of bearing steel, the content and distribution of non-metallic inclusions, and the distribution of carbide.
The physical properties of bearing steel are mainly to check the microstructure, decarburization layer, non-metallic inclusions and low-power structure.
Generally, hot rolling annealing and cold drawing annealing are used for delivery. The status of delivery shall be stated in the contract. The microstructure of steel must be free of shrinkage, subcutaneous bubbles, white spots and microscopic pores. Center loose, general loose must not exceed 1.5 grade, segregation must not exceed 2 grade.
The annealed structure of steel should be fine granular pearlite with uniform distribution. The depth of decarburization layer, non-metallic inclusion and non-uniformity of carbide should accord with relevant national standards.
Generally, if the diameter is less than 20mm, the goods shall be packed and delivered. If the diameter is larger than 20mm, the goods can be delivered naked. Specific pack requirement, inspect the contract requirement that both sides signs and decide, be like, hexagon pack, length is poor, exit should add outer packing commonly.
Cold drawn steel should be coated with anti-rust oil, some domestic manufacturers need goods, can not prevent rust, otherwise its processing into a ring when doing in addition to oil treatment. Before leaving the factory, the goods shall be accompanied with quality guarantee certificate, indicating steel number, furnace number, weight, specification, chemical composition, inspection standard and inspection result, etc.