Requirements for Ladle Chemical Composition of Thick Slab Continuous Casting Steel
Continuous casting of steel is a kind of modern production process with high efficiency and good quality. In this process, the key point that affects the slab quality is to control the chemical composition of the steel in the ladle. Therefore, it is important to control the ladle chemical composition of the thick slab continuously cast steel in the production process.
First of all, when controlling the ladle chemical composition of thick slab continuous casting steel, the sulfur content and phosphorus content of steel should be strictly controlled. Generally, the sulfur content of steel should be controlled at 0.02-0.030%, the phosphorus content at 0.015-0.025%, and the total sulfur and phosphorus content should be controlled at ≤ 0.040%. The purpose of this is to ensure the desulfurization efficiency of steel, prevent hot crack and cold crack of steel, and reduce the inclusions in steel.
Secondly, the molten steel of the ladle should be as pure as possible, and the oxygen content should not exceed. 0.05%. If the oxygen content is too high, it will make steel excessively refined, resulting in poor tensile, yield and elongation properties. Excessive oxygen content will also increase the risk of steel cold crack. Moreover, the oxygen content of steel should not be too low, otherwise, it will increase the oxygen content in the steel ingot, leading to the appearance of large inclusions in the ingot.
Besides, the ladle alloy elements should also be controlled within the specified range. Cr-Mo type alloy is generally used for ladle alloy. During steelmaking, when the amount of ladle alloy is appropriately increased, the content of Mn and Si in the steel will be reduced, which can effectively reduce the risk of segregation. Too much or too little addition of Ladle alloy will lead to instability of steel composition and even steel hot crack.
Finally, Temperature control is very important for controlling the ladle chemical composition of thick slab continuous casting steel. The temperature of molten steel should be properly controlled during the continuous casting process. The temperature of the steel should not be too high or too low, too low temperature causes the steel to solidify easily, leading to cold crack, while too high temperature will make steel exaggerate and reduce the strength. Therefore, it is necessary to accurately control the temperature of steel to ensure the quality of steel.
In summary, it is important to control the chemical composition of the ladle of thick slab continuous casting steel. Sulfur and phosphorus content should be strictly controlled, oxygen content should not be too low or too high, Ladle alloy addition should be appropriate, and temperature control should be carried out in production process. All of these requirements are the key factors for ensuring the continuous casting quality of thick slab steel.
