Brief introduction of refractories for EAF

The magnesia zirconia brick has a high fire resistance. The melting point of zirconia is 2715 ℃ and the temperature is higher than 1660 ℃. The other characteristic of zirconia particles is the formation of microcracks around the particles, which can absorb the external stress. Under the hot and cold conditions, it has higher fracture strength. It has obvious advantages in corrosion resistance of clinker liquid phase, its influence before redox atmosphere and compressive strength. The thermal conductivity of early magnesia zirconia brick is higher than that of spinel brick, which has been improved. Magnesia zirconia brick has excellent performance. It can be used in the cement kiln with harsh working conditions. It can further improve the performance and maintain the excellent gas quality. It can reduce the production cost and is easy to be popularized and applied.

Magnesia chrome brick

The direct bonded magnesia chrome brick has good high temperature resistance, resistance to SiO2 corrosion and oxidation reduction. At the same time, it has high high temperature strength, mechanical stress resistance and good performance of hanging kiln skin, which is widely used in firing zone.

It is generally believed that Cr2O3 dispersed in the liquid phase can improve the viscosity of the liquid phase and inhibit the liquid phase from penetrating into the deep part of the brick. Therefore, in the high temperature zone of the cement rotary kiln firing zone, most of the magnesia chrome bricks are used. But at high temperature, the cement clinker contacts with the brick directly, which makes the magnesia react with the cement clinker to form CMS when the brick is melted, which accelerates the damage of the brick.

When magnesia chrome brick is used in cement kiln, under the action of alkali, When the content of chromium compounds in the air exceeds 10 mg / m3 and the content of chromium in aqueous solution exceeds 0.5 mg / L, it will cause extremely serious harm to human body. Since the mid-1980s, industrialized countries have formulated a series of environmental protection and health standards, and the use of magnesium chromium bricks has been restricted.

First of all, let's understand what kind of furnace the electric arc furnace is. The industrial furnace that generates electric arc heating by metal electrode or nonmetal electrode is called electric arc furnace. According to the form of arc, EAF can be divided into three-phase EAF, consumable EAF, single-phase EAF and resistance EAF. The furnace body of EAF is composed of furnace cover, furnace door, tapping trough and furnace body

Refractory or acid refractory masonry. According to the transformer capacity per ton of furnace capacity, EAF is divided into ordinary power EAF, high power EAF and UHP EAF. Electric arc furnace steelmaking is to input electric energy into EAF through graphite electrode, which is generated between electrode end and furnace charge

Arc is the heat source for steelmaking. Electric energy is the heat source of EAF, and the atmosphere in EAF can be adjusted, which is very beneficial to smelting steel with more oxidizable elements. Soon after the invention of EAF steelmaking, it was used to smelt alloy steel and got great development.

With the improvement of electric arc furnace equipment and smelting technology, and the development of electric power industry, the cost of electric arc furnace steelmaking is decreasing. Now EAF steelmaking is not only used to produce alloy steel, but also a large number of ordinary carbon steel. The proportion of its output in the total steel production of major industrial countries is rising. Refractories used in building electric arc furnaces. Electric arc furnace (EAF) is a kind of equipment which uses the electric arc between the electrode end and the charge as the heat source for electric dial steelmaking. The development of EAF technology is to develop DC EAF, bottom gas mixing and bottom tapping on the basis of adopting high power. These technical achievements are inseparable from the development and application of new refractories. At the same time, the consumption of refractories is also reduced, and it is easy to control automatically. The electric arc furnace is composed of furnace top, furnace wall, furnace bottom and tapping trough.

Good sintered magnesia or fused magnesia shall be selected for knotting lining. During construction, attention shall be paid to the connection and occlusion of each layer, and the thickness and density of each layer shall be kept consistent. In the early 1990s, the service life of 150t UHP EAF in China reached 239 heats. There are working lining and lining under the ramming layer. The working lining is made of tar pitch combined with magnesia brick, and the long lining is generally made of magnesia brick. At the slag line of the upper part of the dike slope, due to the serious slag erosion, the lining bricks which are the same as or similar to the hot spots of the furnace wall, such as fused cast magnesia chrome bricks or combined magnesia chrome bricks, are often used. The effect is better when magnesia carbon brick is used, and the service life can be as high as 100 ~ 200 heats.