Back-up Rolls and Its Manufacturing Process for Wide and Heavy Plate Rolling Mills Over 4200mm

Abstract

The invention relates to a bearing roller of a 4200 mm or above wide and thick plate rolling mill and a manufacturing process of the bearing roller, and belongs to the technical field of forging. Thebearing roller comprises, by mass percent, 0.50 to 0.65% of C, 0.17 to 0.50% of Si, 0.80 to 2.0% of Mn, 0.30 to 0.70% of Ni, 1.60 to 2.5% of Cr, 0.30 to 1.00% of Mo, 0.10 to 0.35% of V, not larger than 0.020% of P, not larger than 0.010% of S, not larger than 0.15% of Cu, not large than 1.0 ppm of H, and the balance iron and inevitable impurities. The carton content of a new material of the super-huge type forged steel bearing roller is low, alloy elements of chromium, nickel and vanadium are added, the microstructure comprises bainite and pearlite, the strength and toughness of the material are improved, the solidification segregation of a large steel ingot is reduced, the comprehensive performance is good, and the service life is long.

Description

technical field [0001] The invention relates to a back-up roll and its manufacturing process, in particular to a back-up roll of a 4200mm thick plate rolling mill and its manufacturing process, and belongs to the technical field of forging. Background technique [0002] Wide and thick plates are important strategic materials, widely used in large ships over 100,000 tons, large-diameter oil and gas longitudinal welded pipes, and weapon armor, structural steel for giant bridges, structural steel for offshore drilling platforms, containment shells for nuclear power plants, large dam gates, and high-pressure boilers Steel plates, steelmaking blast furnace shells, large oil and gas storage tanks, large mechanical structural steels, die steels, super high-rise buildings and other fields, especially in the field of military shipbuilding, large single-weight wide and thick plates are indispensable. [0003] Back-up rolls are key stress-bearing parts and consumable spare parts on wid...

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Problems solved by technology

[0005] At present, there are very few manufacturers of extra-large backup rolls in the world. The carbon content of the traditional steel materials used is 0.70% to 1%, the chromium content is 0.9 to 1.6, and it does not contain vanadium. There is no requirement for the hydrogen content in the steel. Therefore, there are the following defects: (1) Since the steel ingot used for the extra-large backup roll is 340t to 450t, the carbon content of this material is very high. With the increase in size of the steel ingot, the segregation of carbon elements is quite serious. The carbon content can reach more than 1.5%, and large block carbides and severe network carbides are formed in the material, which are not easy to eliminate, so that the back-up roll often breaks during heat treatment and use; (2) Due to the low content of alloy elements in the material, The microstructure is pearlite, the hardness of the surface of the roller body and the working layer is low, HS45~HS50, the wear resistance is poor, pits and early peeling often appear on the roller surface, the consumption of the backup roller is large, and the service life is short; (3) due to the Large block carbides and severe network carbides are formed, the toughness is poor, and fatigue cracks often appear on the surface during use; (4) Due to the relatively low strength and hardness of pearlite materials, lower hardness must be used in heat treatment for performance. Tempering at a high temperature increases the residual stress of the back-up roll, and there is no requirement for the hydrogen content in the steel, often resulting in white spots or fractures in the back-up roll due to excessive stress and high hydrogen content

[0006] Wang Lidi. Analysis on the manufacturing of back-up rolls for wide and heavy plate mills[J]. Yizhong Technology, 2008(4):56-58 disclosed that the material 70Cr3Mo and 70Cr3NiMo steel ingots are seriously segregated, which reduces the toughness of the center of the back-up rolls and the ability to resist accidents.

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