Erosion prevention measures for monoblock stopper

1.Strictly control on ladle slag

The main sources of slag in the casting zone are ladle refining slag, tundish covering agent and molten steel inclusions floating into slag layer. Among them, the slag of low silicon and aluminum sedated steel with more serious plug erosion is the high alkalinity refining slag system, and the CaO content in the slag is controlled at 55%~65%. The slag under ladle of each furnace will form refining slag enrichment in the middle ladle injection point area. When the slag surface of the injection point area is impacted by the steel flow in the subladle process and the pouring process, refining slag will enter the pouring area and cause erosion to the plug rod.

Therefore, it is necessary to strictly control the ladle slag and use the automatic control of slag detection to avoid a large amount of slag at the end of pouring. At the same time, the tundish slagging operation should be adopted. The slagging operation should be carried out at the lift level of the middle ladle when the ladle continuously pours 5~7 furnaces of molten steel, and the thickness of the slag layer in the injection point area should be controlled appropriately.

2. Control the overheat of the tundish

The liquid phase of the steel is 1535℃, and the superheat is controlled by 25~45℃. From the actual production process, when the average superheat of the ladle reaches 45℃(the ladle temperature is 1580℃), slag line erosion breaks in all cases. When the average superheat of the plug was reduced by 15℃ and the actual average temperature of the plug was reduced to about 1560-1565 ℃, the slag line erosion condition could be significantly improved, and the slag line erosion rate of the plug rod could be stabilized within 20%.

3. Optimize the composition of water covering agent for intermediate cladding steel

In view of the reaction between tundish slag and monoblock stopper slag line, the problems of refining slag entering the pouring zone and high superheat of tundish cannot be completely avoided in the actual production process. Therefore, the composition of water covering agent for intermediate steel is optimized, and Mg-Ca-Al-Si multi-compound is formed in the tundish slag layer by increasing the content of MgO in the covering agent according to the condition of medium ladle temperature for different kinds of steel. The melting point is above 1600℃, and the protective layer is formed in the slag line of the plug rod, which slows down the erosion of the bar body resistant material by the intermediate slag.

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