Cooling-after-rolling method of high-weather resistance hot-rolling H-shaped steel with yield strength of 500MPa

Abstract

The invention discloses a cooling-after-rolling method of high-weather resistance hot-rolling H-shaped steel with yield strength of 500MPa. The high-weather resistance hot-rolling H-shaped steel with yield strength of 500MPa comprises the following components in percentage by mass: 0.06-0.12% of C, 0.30-0.60% of Si, 0.80-1.20% of Mn, 0.010-0.030% of P, 0.001-0.015% of S, 0.20-0.35% of Cu, 0.20-0.40% of Cr, 0.15-0.30% of Ni, 0.040-0.060% of Nb, 0.003-0.030% of Als, and the balance of iron and residual trace impurities. The H-shaped steel rolling technology comprises the steps of: heating with a casting blank heating furnace, rolling with a cogging mill, rolling with a universal mill and two-segment quick cooling after the rolling. In the invention, by adopting a two-segment quick cooling method after the hot rolling of the H-shaped steel and by use of a refined crystalline strengthening, precipitation strengthening and phase change strengthening mechanism, the H-shaped steel organization state with single-phase bainite on the surface layer and complex-phase organization inside and with small grains is obtained, the addition of the alloy elements is obviously reduced, the productioncost is lowered, the weather resistance of the H-shaped steel is improved, the welding performance of the steel is enhanced, 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 500 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 500MPa 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.