Magnesia-carbon bricks in China have been documented from raw materials, production (process and facilities) to performance and wear issues in the ladle. Magnesia-carbon bricks made of ordinary fused magnesia is the prevailing material used in the slagline of the ladle, but its service life is substantially lower than the bricks based on large-periclase-crystal fused magnesia. In two types of fused magnesia, the average values of periclase crystal size are in double for their difference. It is suggested that large-periclase-crystal fused magnesia should be used for manufacturing magnesia-carbon bricks for the slagline of the ladle by abandoning ordinary fused magnesia, in order to have a prolonged service life, increase the availability of the ladle and reduce the number of downtimes of the ladle. Free phenol in resin produced in China should be as low as that of resin made in Europe, to improve production environment and reduce smoke emission during the ladle preheating. There are large spaces to promote the productivity of magnesia-carbon bricks in China, with high intensity mixers and hydraulic presses. Expansion controlled magnesia-carbon bricks in the ladle depend on the optimized combination of sintered magnesia, Carbores and antioxidants as the matrix, to minimize the premature wear of vertical cracks and joint opening formed in the ladle lining.
Title：Magnesia-carbon Bricks for Steelmaking Process in ladle
Keywords：magnesia-carbon brick; ladle; fused magnesia
The production of fused magnesia (FM) from macrocrystalline magnesite has been documented into four routes in China. The commonest route is that natural magnesite lumps, directly as raw materials, molten and crystallized in melting furnaces. The second route is to melt the briquettes of caustic calcined magnesia (CCM) made in reverberatory furnaces. The floated magnesite concentrates, mixed with 20%-30% CCM, are briquetted and then molten, which is called as the hybrid route. The sustainable route collects all heat dissipation to preheat raw magnesite in order toreduce the entire energy consumption in the melting process. Taking fused magnesia made directly from raw magnesite and also CCM briquettes in their production, some parameters and performance of magnesia-carbon bricks are listed in Table 1.
Table 1 Distinctions of magnesia-carbon bricks for slagline of ladles oxidant additives.
The lining failure of ladle due to spalling and premature joint wear occurs occasionally. Temperature cycling in ladle operation causes vertical cracking and joint opening due to thermal expansion and irreversible plastic deformation on the hot face, as shown in Fig. 11. The typical appearance is a ladle bricklining where the vertical joints are linked by vertical cracks. The infiltration of molten steel through cracks and joint openings could bring about severe circulation of spalling. As a result, the working lining cannot perform to the minimum residual thickness to avoid the risk of leakage of steel liquid, being removed out of ladle. The regular service life of magnesia-carbon bricks cannot reach as in normal ladle operation.
Magnesia-carbon bricks based on ordinary fused magnesia are the prevailing material used in the slagline of the ladle but its service life is substantially lower than those bricks based with large-periclase-crystal fused magnesia. It is suggested that large-periclase-crystal fused magnesia should be used for manufacturing magnesia-carbon bricks for the ladle by abandoning ordinary fused magnesia, in order to reduce the number of downtimes of a ladle. Free phenol in resin produced in China is supposed to be as low as that of resin made in Europe.There are large spaces to promote the productivity of magnesia-carbon bricks in China, with high intensity mixer and high pressure hydraulic press. Expansion controlled magnesiacarbon bricks in ladles depends on the optimization of the matrix of sintered magnesia, Carbores and antioxidants, so to minimize the premature wear of vertical cracks and joint opening formed in a ladle lining.