Four main reasons for damage to ladle purging plug

 There are four main reasons for the damage of ladle purging plug as follows:

1. The role of thermal stress

The refractory materials on the working surface of the purging plug, especially the refractory materials around the air outlet, are directly in contact with the high-temperature molten steel, and are affected by the high-temperature molten steel and the continuous outflow of cold airflow, resulting in a large temperature gradient. The rapid cooling and heating effect is great, especially the parts close to the air outlet are subjected to greater thermal stress, which is prone to cracks.

2. The effect of mechanical wear

During the tapping process, the high-speed and strong scouring of the molten steel against the bottom of the steel tank accelerates the corrosion of the ventilating brick; Some people have studied the damage of the ventilating brick through hydraulic model tests and found that: when a low-speed flow of air is injected into the liquid-phase molten pool. When the airflow hits back and hits the front of the ventilating brick, it gives a certain impact force to the refractory around the air port. When the gas flow rate is further increased, the reverse pulse frequency is reduced, but the reverse impact strength is further increased; In addition, when the argon is blown into the normal spray state, the strong bubbles form a gas jet, which strengthens the stirring at the bottom of the steel tank , The liquid phase movement at the bottom of the steel tank is intensified, and the two-phase plume causes the ventilating brick to be subjected to strong shear and impact stress. When the air-permeable brick is higher than the seat brick, the shear and erosion of this kind of plume are particularly obvious. The part higher than the seat brick is generally washed away after one use; In addition, if the valve is quickly closed after the refining is completed, the molten steel will be reversed. The impact will also accelerate the damage of the breathable brick.

3. Chemical attack

The working face of ventilated bricks has a long contact time with slag and molten steel, and the molten slag continuously infiltrates and penetrates into the bricks during the entire package service. The oxides MnO, MgO, SiO2, FeO, Fe2O3, etc. in the molten steel and slag react with the bricks, and the resulting FeO·Al2O3, 2(MnO)·SiO2·Al2O3, 12CaO·7Al2O3 and other low-melting substances are washed away, causing the ladle permeable brick to be washed away erosion.

4. The role of mechanical stress

The working surface of the refractory material at the bottom of the ladle is in direct contact with the high-temperature molten steel, and the temperature of the non-working surface of the refractory material at the bottom of the ladle is relatively low. The temperature of the ladle has been changing during the cycle of using molten steel → molten steel pouring → hot repair of the ladle → molten steel. , The volume of the bottom refractory material changes accordingly. Due to the existence of the temperature gradient of the bottom refractory material and the different expansion coefficients of the metamorphic layer of the bottom refractory material and the original layer, the corresponding volume of each layer of the bottom refractory material from the working surface to the non-working surface The changes are different, which generates shearing force on the ventilating bricks, causing the ventilating bricks to produce horizontal cracks, and even causing the ventilating bricks to appear horizontally fractured. During the baking process of the ladle integrally poured at the bottom of the ladle, the heating speed is too fast, and the temperature gradient of the refractory material at the bottom of the ladle is too large, and the same phenomenon will occur in the purging plug.

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Article Source:Four main reasons for damage to ladle purging plug
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