Magnesia-carbon bricks are made of high melting point alkaline oxide magnesia (melting point 2800°C) and high melting point carbon materials that are difficult to be infiltrated by slag as raw materials, and various non-oxide additives are added. Non-burning carbon composite refractory material combined with carbon binder.
Magnesia-carbon bricks are mainly used for the lining of converters, AC electric arc furnaces, DC electric arc furnaces, and the slag line of ladle.
As a composite refractory material, magnesia-carbon brick effectively utilizes the strong slag erosion resistance of magnesia and the high thermal conductivity and low expansion of carbon, which compensates for the biggest disadvantage of poor spalling resistance of magnesia.
Its main features are: good high temperature resistance, strong slag resistance, good thermal shock resistance, and low high temperature creep.
The refractory materials used in the early ladle slag line were directly combined with magnesia-chrome bricks, electrofused and then combined with high-quality alkaline bricks such as magnesia-chrome bricks. After the MgO-C brick was successfully used in the converter, the MgO-C brick was also used in the refining ladle slag line, and good results were obtained. China and Japan generally use resin-bonded MgO-C bricks with a carbon content of 12% to 20%, while Europe mostly uses asphalt-bonded MgO-C bricks, and the carbon content is generally around 10%.
The Kokura Steel Plant of Sumitomo Metal Corporation of Japan uses MgO-C bricks with MgO content of 83% and C content of 14-17% in the VAD slag line instead of directly bonded magnesia-chrome bricks. The life of the slag line is increased from 20 times to 30 times. -32 times.
Japan Sendai Iron and Steel Plant LF refining ladle, using MgO-C bricks instead of magnesia-chrome bricks, the life of the slag line has been increased from 20-25 times to 40 times, and good results have been achieved.
Since the use of MgO-C bricks instead of magnesia-chrome bricks for China’s refined ladle slag line bricks, the comprehensive use effect is obvious. The 300t ladle slag line of Baosteel Co., Ltd. has been using MT-14A magnesia-carbon bricks since July 1989, and the life of the slag line is maintained at more than 100 times; the 150t electric furnace ladle slag line uses low-carbon magnesia-carbon bricks to smelt cord steel. 1600 ℃ ~ 1670 ℃, and achieved obvious results.
After research, the MgO-C brick made of the mixture of fused magnesia and sintered magnesia, plus 15% phosphorus flake graphite and a small amount of magnesium aluminum alloy as antioxidant, has a very good use effect, and the capacity is 100 tons of LF. Compared with MgO-C bricks with a C content of 18% without antioxidants, the damage rate is reduced by 20-30%, and the average erosion rate is 1.2-1.3mm/furnace.