This article describes the damage mechanism of carbon-containing refractory materials used in ladles, explains the erosion of slag on magnesia-carbon bricks and the influence of carbon oxidation and pores of magnesia-carbon bricks.
Key words: magnesia carbon brick, erosion mechanism, ladle
Damage of carbon-containing refractories for steel ladles
The erosion mechanism of refractory materials is related to the viscosity and temperature of slag and the reaction speed with refractory materials. The slag stays in the ladle for a long time, and the damage to the carbon-containing refractory is relatively large; the slag mainly penetrates through the pores and liquid phases in the refractory, which changes the structure and composition of the material, resulting in spalling and accelerating the damage of the refractory ; Therefore, the degree of corrosion of the refractory material varies with its structure and performance, which in turn affects the service life of the ladle.
The damage of carbon-containing refractories (magnesia-carbon bricks, aluminum-magnesia bricks, low-carbon magnesia-carbon bricks) for ladles is firstly due to the oxidation of carbon. The decarburization layer is formed, resulting in loose structure and reduced strength. After physical erosion by slag, the material is gradually eroded and peeled off. The corrosion mechanism of steel slag on magnesia carbon bricks, domestic and foreign researches generally believe that the main reason is the dissolution of MgO by slag and the oxidation of carbon.
Corrosion of slag on magnesia carbon bricks
The erosion of magnesia carbon bricks is mainly due to the oxidation of carbon and the dissolution of magnesia, and they are interconnected and affect each other.
① The slag alkalinity has a very obvious effect on the erosion. When the alkalinity increases, the FeO activity decreases, and the erosion rate of the slag on the refractory material slows down.
②The damage of magnesia is also related to the degree of slag erosion; the MgO content in the LF slag line brick reaction layer is higher, while the slag erosion degree with low MgO content is greater, and the erosion is aggravated as the alkalinity decreases.
③The increase of Al2O3 content in the slag reduces the melting point of the slag, and the generated aluminate will enter the interior of the material along the pores and cracks, thereby destroying the structure of the brick;
④ The MgO in the magnesia-iron brick can solid-dissolve the FeO in the slag to form magnesia futenite. Foreign studies believe that the degree of brick erosion is related to Fe.
Influence of Carbon Oxidation and Porosity of Magnesia Carbon Bricks
The working face of the magnesia carbon brick is in contact with the slag, the O2 in the air and the oxides in the slag will oxidize the carbon, and a decarburization layer is formed on the surface, and the slag liquid phase penetrates into the pores or cracks of the decarburization layer at high temperature In the process, the surface structure of the brick changes, and it falls off under the physical washing of the slag, resulting in the destruction of the magnesia carbon brick. The open pores in the magnesia carbon brick have an important influence on the damage of the brick. C in magnesia-carbon bricks is mainly oxidized through pores, which accelerates the erosion of slag. The existence of open pores allows air to enter, and the O2 in the air reacts with C to form CO, which increases the porosity; at the same time, the phenolic resin binder used in the magnesia carbon brick will decompose at high temperature and produce pores to be discharged, which will also increase the porosity. , is not conducive to the corrosion resistance of bricks, promotes the oxidation of carbon and the erosion of slag and magnesia, causing the surface structure of magnesia carbon bricks to become loose and fall off, reducing the service life of bricks.