The original composition design of A572 Gr.50 steel plate contains carbon, silicon, manganese, niobium and other elements. The silicon element is dissolved in ferrite and austenite, which improves the hardness and strength of steel, but reduces the plasticity and toughness of A572 Gr.50 steel plate. Manganese is dissolved in ferrite, which plays the role of solid solution strengthening and improves the performance of hot working. Niobium can increase the recrystallization temperature of A572 Gr.50 steel plate, reserve a lot of distortion energy for nucleation and grain growth, and has the effect of refining grain.
This composition design adjustment is in accordance with customer requirements to add Cr not added in the original composition,Cr increases the hardenability of A572 Gr.50 steel plate, has the effect of secondary hardening, can improve the hardness and wear resistance of A572 Gr.50 steel plate, while not making A572 Gr.50 steel plate brittle.
According to customer requirements, the design components were optimized, and trial production was organized according to scheme 1 and Scheme 2. The thickness of the trial production A572 Gr.50 steel plate was 4 mm and 6 mm respectively. The mechanical properties of 6mm thick steel coil with the highest similarity of chemical composition and rolling temperature were compared after inquiring the actual chemical composition and process parameters of sampling position.
According to the technical conditions proposed by the customer, combined with the actual situation of steelmaking and 2250mm hot rolling line, the A572 Gr.50 steel plate designed for trial production by two schemes meets the standard requirements, but scheme 2 is closer to the customer's requirements, and the results of small batch trial production are better than the original chemical composition design. The optimized product is used by users, and the A572 Gr.50 steel plate has good surface quality and stable performance.
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