PN series of magnesia-alumina-carbon bricks adopt super bauxite or corundum as aggregate, with emphasis on strengthening matrix, phenolic resin as binder, and press forming. They have the characteristics of anti-erosion, anti-spalling and high strength. They are suitable for ladle bottom and ladle wall. Regenerative brick
PN series magnesia-alumina-carbon bricks are based on alumina-magnesia-carbon bricks. The process and technology have been adjusted to enhance the corrosion resistance and spalling resistance of the materials. They are suitable for the bottom and wall of ladle, and can significantly improve the service life of ladle. Carbon has been widely used in refractories in metallurgical industry. In the past, many new products have been developed to adapt to the development of new metallurgical processes and refractory technology. Refractories experts have long known the excellent properties of magnesia-alumina-carbon bricks with different forms of carbon in refractories. In refractory oxides, carbon can reduce the wettability of slag, molten steel and refractories, increase their thermal conductivity and reduce their expansion, so that refractories have excellent thermal shock resistance. In addition, carbon has high thermal stability, and its sublimation temperature is about 4000 C. Under the pressure of 110-140 bar, the three-phase point (solid/liquid/gas) of carbon in the phase diagram is close to 4020 C. Therefore, when the pressure is less than 110 bar, the carbon sublimates and does not melt. Because carbon is oxidized at high temperature, the above results can only be applied under specific conditions.
At present, the most important application fields of carbon-containing refractories are:
1. Converter, Electric Furnace and Ladle Working Lining
2. Crucibles for smelting metals
3. Key Components for Continuous Casting
4. Refractories for Blast Furnace Ironmaking
5. By adding carbon, many kinds of refractory bricks can be produced, especially magnesia-carbon high-grade alkaline refractories.
There are many ways to add carbon to refractories:
1. Magnesium Aluminum Carbon Bricks Impregnated with Tar Asphalt or Synthetic Resin
The open porosity of sintered oxide refractories is about 12%, most of which can be filled by tar pitch or resin. Due to the relatively low volatilization and density of volatiles, the residual carbon rate of these products is about 2%~3%. Aluminum-magnesia-carbon bricks with super bauxite clinker, fused magnesia, phenolic resin and high purity graphite as main raw materials and various additives have been used in 80 tons converter ladle of Xuanhua Iron and Steel Works. Good results have been achieved and production requirements have been met. 1. Wet spraying is to mix refractory aggregates, binders, additives and water into slurry with a certain consistency, and then compressed air is used by spraying machine. A method of spraying mud onto the spraying surface by air-magnesium-alumina-carbon bricks. Its characteristics are simple operation, high adhesion and rapid sintering. However, because of the large water content and the finer grain size, the shrinkage is also larger. At the same time, due to the thin spray layer, the durability is not very good.
2. Semi-dry spraying is a method of mixing refractory aggregate, binder, additives, etc. with water through the water ring hole at the spraying end and injecting compressed air onto the spraying surface. The amount of water can be adjusted at any time according to the spraying condition, and generally fluctuates between 10% and 20%, which is much lower than that of wet spraying. Therefore, the spraying layer has large volume density and small shrinkage, and can obtain a thicker spraying layer with better durability, but the springback is slightly higher than that of wet spraying method. This spraying method is widely used.
3. Flame spraying is a method of repairing refractory aggregate, flux or heating agent by compressed oxygen, which is conveyed to the nozzle, combusts with high calorific value fuel and instantaneously heats the surface of magnesia-alumina-carbon brick aggregate particles to the state of melting or semi-melting, and then sprays and adheres to the lining of the furnace. The spraying layer obtained by this method is compact in structure, high in strength, corrosion resistance and impact resistance. Strong brushing ability, solid and durable. However, flame spraying equipment is expensive, complex in technology and energy-consuming in construction.