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Analysis of working conditions of VOD furnace lining

[11/30/2021]


The VOD furnace is a device that must be used in conjunction with the ladle, so the ladle has become an indispensable device for the VOD furnace. Furthermore, the quality of the refractory equipment in the ladle is related to the smooth progress of the entire VOD refining process. After adopting the VOD method, the task of the ladle is obviously aggravated, so the erosion of the refractory material brick will be more severe. Liu Guoping summarized the working conditions of the refined ladle:
1) Alkaline slag is corrosive to refined ladle, and its own alkalinity varies widely:
The LF furnace uses lime, calcium carbide and fluorite as raw materials to produce synthetic slag as the refining slag. The highly corrosive CaF and CaAlO3 will form liquid slag, so the composition of the slag will be greatly changed: the alkalinity will be 0.6-4, and the strongest is 0.3. The strongly acidic slag has strong fluidity and high temperature. High, the slag line part is constantly eroded and scoured; in the initial stage of oxidation, oxygen is blown from the top to remove carbon. This period accounts for about 80% of the entire refining cycle, and the slag alkalinity is very small during this period. Acidic slag affects the refractory bricks There is serious erosion and erosion, which directly affects the service life of refractory bricks.
2) High vacuum degree:
In the VOD method, a strong vacuum degree of about 133.3Pa will be applied, which will volatilize some components of the refractory brick. At this time, the acidic molten slag will corrode into the fire bricks along with the molten steel, and the refractory brick’s address will be further deteriorated.
3) The blowing and stirring in the ladle is very strong:
In order to remove the carbon monoxide produced by the reaction of oxygen and carbon and the impurity gases in the ladle, high-pressure argon must be blown in during refining to reduce the partial pressure of carbon monoxide. The molten steel will therefore boil, causing the slag line to become hot. Refractory bricks are strongly scoured.
4) The required heat preservation time is too long:
After the entire refining and cooling, the reheating time reaches about four and a half hours, and the temperature of the furnace lining will increase as a result. It will also cause the refractory bricks to be more severely corroded and penetrated.
5) Intermittent operation results in a strong thermal shock effect:
During smelting, the furnace lining will undergo rapid cooling and heating changes, causing damage to the charge due to explosion and thermal spalling.
6) High temperature:
The application of submerged arc heating makes the refractory bricks in the slag line part have a much higher temperature than other parts. The fluidity of the slag, the erosion of the acid slag on the refractory bricks and the high temperature operation will bring huge damage to the refractory bricks. . Because of the instability of the submerged arc heating method, sometimes "hot spots" appear on the sidewall of the ladle.
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