Rolling method controlling network carbide precipitation of large-section GCr15 bearing steel

Abstract

The invention discloses a rolling method controlling network carbide precipitation of large-section GCr15 bearing steel. According to the method, GCr15 continuous casting billet serves as raw materials; and the following working procedures of heating, decaling, rough rolling, intermediate rolling, pre-finish-rolling, first time of water penetrating cooling, finish rolling of a rod reducing and sizing mill, second time of water penetrating cooling, cooling of a cooling bed and final obtaining of finished product rods are sequentially included. By means of the method, the level of the obtained network carbide of the large-section GCr15 bearing steel is reduced to be smaller than or equal to level 2 from the original level larger than or equal to level 3, the comprehensive mechanical performance of high-carbon-chromium bearing steel is improved, the service life of a bearing is prolonged, besides, the production cost is reduced, and the market competitiveness of the bearing steel is improved.

Description

technical field [0001] The invention belongs to the field of special steel production and processing in the metallurgical industry, and relates to a rolling process, in particular to a rolling method for controlling the precipitation of reticular carbides in large-section GCr15 bearing steel. Background technique [0002] In recent years, my country's bearing industry has developed rapidly, and the bearing market has expanded rapidly, thereby driving a strong demand for bearing steel, making bearing steel a bright spot in my country's special steel market. Among the total amount of bearing steel, GCr15 bearing steel occupies most of the market, and it is widely used in the fields of automobile industry, machinery manufacturing, military industry, railway, aerospace and so on. However, due to the uneven distribution of carbides in GCr15 bearing steel, especially The existence of network carbides will increase the brittleness of steel and reduce the fatigue life of bearings, s...

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Problems solved by technology

[0009] (1) At present, the domestic control of GCr15 bearing steel reticulated carbide precipitation is mainly focused on ≤ The patented technology of network carbide control for the online rolling of large-section GCr15 bearing steel with specifications of Φ50~Φ90mm has never been reported.

[0010] (2) The heat treatment process (normalizing treatment) is an effective method for improving network carbides for small-sized bearing steel bars, but the effect of controlling network carbides for large-section bearing steel bars is not obvious, and increases the cost , not conducive to energy saving and environmental protection

[0011] (3) The large-section GCr15 bearing steel reticulated carbide controlled rolling and controlled cooling process is completely different from the small-sized GCr15 bearing steel reticulated carbide controlled rolling and controlled cooling process: first, the small-sized bearing steel has a small cross-section, and the core The surface temperature gradient is small, so the heat of the bearing steel can be taken away during rapid cooling, thereby suppressing the reticulated carbides of the bearing steel; for large-sized bearings, due to the large cross-section, the temperature difference between the core and the surface is large, even if the core is cooled rapidly, the core The influence of temperature is also small, and due to the latent heat of phase change, it is more difficult to suppress the reticular carbides in the core of large-section bearing steel due to the large heat; For large-size bearings, if the cooling rate after rolling is too small, it will not be able to break the mesh and refine the grains of the bearing steel core. If the cooling rate after rolling is too high, the bearing The surface of the steel is easy to form martensitic structure, leading to surface cracks; third, the research on the mesh controlled rolling and controlled cooling process for small-sized bearing steel has been mature and widely used in the steel industry, while for large-sized bearing steel mesh controlled The controlled rolling and controlled cooling process is still in the experimental stage and has not been applied and promoted.

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