Cooling after rolling method for high-weather fastness hot-rolled H-steel with yield strength up to 550MPa

Abstract

The invention discloses a cooling after rolling method for high-weather fastness hot-rolled H-steel with yield strength up to 550MPa. The high-weather fastness hot-rolled H-steel with the yield strength up to 550MPa comprises the following components in weight percentage: 0.06-0.12 percent of C, 0.30-0.60 percent of Si, 1.25-1.50 percent of Mn, 0.010-0.030 percent of P, 0.001-0.015 percent of S, 0.20-0.35 percent of Cu, 0.20-0.40 percent of Cr, 0.15-0.30 percent of Ni, 0.10-0.12 percent of V, 0.008-0.014 percent of N, 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 high-weather fastness hot-rolled H-steel with the yield strength up to 550MPa, through adopting a two-stage rapid cooling method after hot rolling is performed on the H-steel and by utilizing a refined crystalline strengthening mechanism, a precipitation strengthening mechanism and a phase change strengthening mechanism, an H-steel texture which is provided with single-phase bainite on the surface layer, is of a multiphase structure inside and has fine grains is obtained, thereby, the additive amount of alloying elements is reduced, the production cost is obviously reduced, the welding performance of the steel is improved, and the production efficiency is increased.

Description

technical field [0001] The invention relates to the field of low-alloy steel, in particular to a post-rolling cooling method for hot-rolled H-shaped steel with a yield strength of 550 MPa and high weather resistance. Background technique [0002] Hot-rolled H-section steel is an economical cross-section profile with excellent mechanical properties and superior performance. It can be widely used in construction, transportation, electric power, water conservancy, energy, chemical and manufacturing industries. Among them, weather-resistant H-beams are mainly used in the manufacture of high-speed train carriages and bridges, which play an important role in reducing weight, prolonging service life, increasing speed, increasing freight volume and reducing logistics costs. Especially with the rapid development of the national economy, the railway transportation industry is moving towards high-speed, heavy-duty, and long-life directions, and there is an urgent need for hot-rolled H-...

AI Technical Summary

Problems solved by technology

For example, the V content of Q420NQR1 hot-rolled H-beam with a yield strength of 420MPa is as high as 0.10-0.14wt%, and the Mn content is as high as 1.40-1.60wt%, which leads to an increase in production costs; and because its structure is ferrite + pearlite, the structure is uniform Compared with ordinary Q345B steel, the relative corrosion rate can only reach 50-55%; at the same time, due to the high content of alloy elements, the welding performance deteriorates

If this method is used to produce 550MPa weather-resistant H-shaped steel, the content of alloy elements will be higher, resulting in high production costs and poor welding performance, and its weather resistance is equivalent to that of Q420NQR1 hot-rolled H-shaped steel

In addition, in order to obtain better impact toughness, a very low final rolling temperature is required, which not only increases the load and energy consumption of the rolling mill, but also reduces the production efficiency.