Research And Improvement Of Slab Quality In Wide And Thick Slab Continuous Caster

Following the society and national economy development, the wide and thick plate steel products are widely used in some important fields, such as ship building,bridge project, pressure container, nuclear power, high-rise building and so on,meanwhile, requirements on the quality of casting slab are more stringent.Since the 2300 mm wide and thick slab continuous caster of Ansteel starting up,three kinds of slab quality problem are outstanding,such as high surface longitudinal crack incidence rate, low detection qualified rate of the head and tail slab by rolled,and the subsurface blowhole defect of high carbon steel grade. These quality defects of product not only cause customers and corporation economic losses, but also hurt customers' feeling and satisfaction, more important influence the corporation image and market share of products.Based on the productive practice of 2300 mm wide and thick slab continuous caster of Ansteel in recent years, the three kinds of slab quality defect during the production process are researched and controlled in this article. The main research contents and results of the article are as follows:(1) Through researching the morphology, characteristic and cause of slab surface longitudinal crack, by taking measures to adjust the composition of steel, optimize the flow field and heat transfer of mold, improve process system and operation, the incidence rate of slab surface longitudinal crack of Q345 B steel grade and so on is controlled lower than 0.60%.(2) Through analyzing the plate sample parts of detection disqualification, the measures of controlling hydrogen content in steel and improving the steel purity are researched, and by optimizing dynamic soft reduction system of the sector segment,the qualified rate of ultrasonic flaw detection increases from about 60% to more than90%.(3) Through analyzing the relationship between the test of blowing argon and blowhole defect, it is determined that the blowhole defect of high carbon steel grade is caused by blowing argon. By taking measure to cast slab without argon, the blowhole defect of high carbon steel grade is eliminated. At the same time, by optimizing the SEN structure and adjusting the mold powder property, the slab quality of high carbon steel grade is further improved.