Method for cooling low-alloy hot-rolled H-shaped steel with yield strength of 550MPa after rolling

Abstract

The invention discloses a method for cooling a low-alloy hot-rolled H-shaped steel with yield strength of 550MPa after rolling, wherein the low-alloy hot-rolled H-shaped steel with the yield strength of 550MPa comprises following components by mass: 0.13-0.18% of C, 0.30-0.50% of Si, 1.40-1.60% of Mn, not more than 0.025% of P, not more than 0.025% of S, 0.10-0.12% of V, 0.010-0.014% of N, 0.003-0.030% of Als, and the balance of iron and residual trace impurities; a rolling process of the H-shaped steel is as follows: heating casting blank in a heating furnace, performing rolling by a cogging mill, performing rolling by a universal rolling mill and quickly cooling the steel in two-stage manner after rolling; the method adopts the two-stage quick cooling method after the H-shaped steel is hot-rolled, so that the high-temperature H-shaped steel is cooled to proper temperature at short time; by using the cooling method after colling, texture state of the H-shaped steel with fine crystal particles and complex phase texture is obtained, adding amount of the alloy elements is drastically reduced, production cost is notably reduced when requirement of high-strength performance is satisfied, and welding performance of the steel and production efficiency are improved.

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 550 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 The 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 550MPa grade H-shaped steel has not been developed yet. If it is also produced by this method, its alloy The element content will be higher, resulting in high steelmaking costs; and due to the high alloy element content, carbon content, etc., the weldability will deteriorate; in addition, in order to obtain better impact toughness, a very low final rolling temperature is required, which is both Increase the load and energy consumption of the rolling mill, and reduce the production efficiency