Cooling after rolling method for low-alloy hot-rolled H-steel with yield strength up to 500MPa

Abstract

The invention discloses a cooling after rolling method for low-alloy hot-rolled H-steel with yield strength up to 500MPa. The low-alloy hot-rolled H-steel with the yield strength up to 500MPa comprises the following components in weight percentage: 0.08-0.14 percent of C, 0.30-0.50 percent of Si, 1.20-1.40 percent of Mn, not greater than of 0.025 percent of P, not greater than 0.020 percent of S, 0.025-0.050 percent of Nb, 0.003-0.030 percent of Als and the balance of ferrum and residual trace impurities. An H-steel rolling process comprises the following steps of: heating a casting blank in a heating furnace, rolling by a roughing mill, rolling by a universal rolling mill, and performing two-stage rapid cooling after rolling is ended. According to the cooling after rolling method for the low-alloy hot-rolled H-steel with the yield strength up to 500MPa, through adopting a two-stage rapid cooling method after hot rolling is performed on the H-steel, the H-steel with higher temperature can be cooled to the proper temperature in a short time. By adopting the cooling after rolling method, an H-steel texture with fine grains and a multiphase structure can obtained, thereby, the additive amount of alloying elements is greatly reduced; and while the high-strength performance requirement is met, the production cost can be obviously reduced, the welding performance of the steel is improved, and the production efficiency is also increased.

Description

technical field [0001] The invention relates to the field of low-alloy steel, in particular to a post-rolling cooling method for low-alloy hot-rolled H-shaped steel with a yield strength of 500 MPa. Background technique [0002] Hot-rolled H-shaped steel is an economical cross-section profile with excellent mechanical properties and superior performance. The main performances are: 1) The section modulus is large, and it can save 10-15% of metal under the same load conditions, thereby reducing the cost ; 2) Beautiful appearance, easy processing, its flange inside and outside are parallel, various H-beams of different specifications can be easily combined into many components of different shapes and sizes, easy to connect, easy to machine, can improve production efficiency and Reduce the labor intensity of producers; 3) Improve the structural strength. Compared with ordinary I-beams, when the cross-sectional area or weight is roughly the same, its bending resistance and compre...

AI Technical Summary

Problems solved by technology

[0004] At present, my country's H-beam manufacturers have developed 420MPa, 460MPa and other H-beams, but they are all produced by hot rolling with the addition of alloying elements, and the amount of alloying elements is relatively high, such as BS 55C with a yield strength of 420MPa Hot-rolled H-shaped steel adopts Nb and V composite microalloying, the V content is 0.08-0.12wt%, and the Nb content is 0.040-0.060wt%. The production of 500MPa-level H-shaped steel has higher alloying element content, which leads to steelmaking costs. High; and due to high alloying element content, carbon content, etc., the weldability deteriorates; in addition, in order to obtain better impact toughness, a very low final rolling temperature is required, which increases the load and energy consumption of the rolling mill. reduced production efficiency