Method for preventing surface of flange steel from cracking

Abstract

The invention discloses a method for preventing the surface of flange steel from cracking. The method includes the steps that smelting is performed through an electric furnace; refinement is performed through an LF refining furnace; refinement is performed through a VD refining furnace, wherein after being refined in the LF refining furnace, molten steel is then placed in the VD refining furnace for refinement, and the soft blow time of the molten steel in the VD refining furnace is larger than or equal to 20 min; continuous casting is performed, wherein the degree of superheat of a tundish is smaller than or equal to 30 DEG C, the average casting speed is controlled between 0.78 m / min and 0.82 m / min, and secondary cooling distributed water is controlled at 0.20 L / Kg; the tension leveling temperature is designed to meet the condition that the tension leveler entry temperature is higher than or equal to 930 DEG C and the after-straightening temperature is higher than 870 DEG C; a heating furnace is adopted, wherein cast blank heating temperature increase curve is made and based on the cast blank heating temperature increase curve, heating temperature increase is performed; high-pressure water is used for removing scale, wherein the scale removing pressure is 1.8 MPa, and it is guaranteed that the scale removing rate of the surface of a cast blank is larger than or equal to 99%; and cogging rolling, finish rolling, sawing, quick moving cooling bed adoption and slow cooling pit slow cooling are performed, wherein a chain structure and frequency conversion control are adopted for a quick moving cooling bed to achieve round steel pit entry acceleration, and it is guaranteed that the round steel pit entry temperature is higher than or equal to 570 DEG C.

Description

technical field [0001] The invention relates to the field of iron and steel smelting, in particular to a method for avoiding cracks on the steel surface for flanges. Background technique [0002] S355J0 belongs to the surface crack sensitive steel grade. As a low-carbon steel, peritectic reaction is prone to occur when it is cooled from the liquid phase, and the temperature range of the third brittle zone of this steel is relatively large, which may easily lead to tensile cracks in the casting billet during the production process (exposed on the surface of the steel after rolling) ); during the rolling process, S355J0 is also prone to surface cracks due to improper operations such as heating, descaling, slow cooling and hydrogen expansion. The generation of cracks increases the finishing difficulty and grinding cost of the steel, and in severe cases, the whole round steel will be scrapped, which greatly affects the yield of the round steel. [0003] S355J0 is used to make ...

AI Technical Summary

Problems solved by technology

As a low carbon steel, peritectic reaction is prone to occur when it is cooled from the liquid phase, and the temperature range of the third brittle zone of this steel is relatively large, which is easy to cause tensile cracks in the casting billet during the production process (exposed on the surface of the steel after rolling) ); during the rolling process, S355J0 is also prone to surface cracks due to improper operations such as heating, descaling, slow cooling and hydrogen expansion

The generation of cracks increases the difficulty of steel finishing and the cost of grinding, and in severe cases, the entire round steel will be scrapped, which greatly affects the yield of round steel