Electric furnace bottom blowing Porous plug
The bottom blowing system of electric furnace is divided into two types: direct stirring system and indirect stirring system. Porous plug are generally used in UHP electric arc furnaces and are placed near the steel outlet at the bottom of the furnace or other locations.
The Porous plug of the gas supply components of the direct stirring system are in direct contact with the molten steel. Similar to the converter, the segmented combined air bricks formed by high pressure molding or isostatic pressing of MgO-C are used. However, according to the operating characteristics of the electric furnace, the aperture of the air channel in the gas supply component should be small. The air bricks of a 70t UHP electric furnace of a domestic steel company are 750mm long, of which the air chamber is 50mm. There are 19 3mm steel pipes and 1 use limit safety alarm air pipe 300mm long from the bottom of the air chamber.
The air bricks of the indirect mixing system air supply element are not in direct contact with the molten steel, but are covered by the surface permeable ramming material.
Ladle bottom blowing air brick
Gas supply components are most widely used in off-furnace refining, and the amount used is also the largest. This type of gas supply components is collectively called air-permeable bricks in China. At present, all electric furnace steel and most converter steel in my country must be processed by off-furnace refining process. The off-furnace refining process has the highest requirements for air-permeable bricks, which not only require good performance and high service life, but also high blow-through rate.
The air bricks used for ladle furnace refining include dispersion type, straight hole type and labyrinth type. These types of air bricks have poor corrosion resistance, low blow-through rate and complex molding, so they have been replaced by slit type or core plate assembly type air bricks.
The argon bubbles entering the molten steel from the bottom blowing argon are fine and dispersed, the flow field in the ladle is reasonable and the dead zone is eliminated, and the slag on the surface of the molten steel is well covered, so the mechanical properties of the steel are improved and the argon utilization is high. However, when the argon is blown from the top, the argon bubbles are large and concentrated, and the argon gun head cannot be inserted into the bottom of the ladle, so the argon utilization rate is low and the stirring effect is not good. The slag on the surface of the molten steel rolls severely, causing the slag to absorb air, and the refractory material of the argon gun pollutes the molten steel. Bottom blowing argon is superior to top blowing argon in terms of steel quality and cost.
Slit type air brick
At present, the most widely used domestically are the slit-type air-permeable bricks that are cast and fired at high temperature. The materials are chrome corundum and corundum-spinel. There are also mullite-corundum ones abroad. The slits are formed by the preset burnt objects. The air-permeable plug is used in conjunction with the seat brick. Its appearance structure includes two forms: external and internal integral structures. The ventilation volume of the air-permeable brick is generally in the range of 100 to 700L·min-1 (0.4MPa) to meet the needs of different smelting processes for stirring intensity.
The external air brick is composed of a seat brick, a sleeve brick and a breathable plug. This structure is suitable for refining furnaces such as LF and LF-VD that have high requirements for the blowing rate. When the air brick has poor air permeability or erosion is too fast due to unexpected reasons, the air brick can be replaced in time to accelerate the turnover of the ladle and improve production efficiency. The internal integral structure is composed of a seat brick and a breathable brick. The breathable brick and the seat brick are pre-assembled into one and then put into use, which can increase the safety of operation. This structure is suitable for the situation where the service life of the air brick is synchronized with the furnace bottom or with the minor repair of the furnace bottom.
Core plate assembled air brick
The core board used in the core board assembly method is formed by machine pressing, and the slits are reserved during the forming process or machined after the core board is fired, and the core board is wrapped with castables. The assembled air brick has a good buffer stress structure and is not easy to break during use, which is conducive to improving the service life and blowing rate. In addition to the traditional chrome corundum and corundum-spinel materials, the core board material also has non-oxide combined corundum, such as SiAlON combined corundum, etc.
Tundish bottom blowing air brick
As the last container that contacts the molten steel in steelmaking, the tundish plays a key role in the production of clean steel. Among a series of tundish metallurgical technologies, bottom argon blowing technology is a simple and effective measure with low investment and obvious effect.
According to reports from Nippon Steel and other steel mills in Japan, by installing permeable bricks near the slag weir of the tundish and blowing argon, the inclusion content is reduced by more than 20% compared with the case without argon blowing. This technology uses the addition of dispersed small argon bubbles to the molten steel in the tundish to increase the collision probability of inclusions, so that the tiny inclusions suspended in the molten steel gather and grow and are then removed. Compared with other methods that can only eliminate larger inclusions, the tundish argon blowing technology plays a special and important role in removing tiny inclusions of about 50μm, so as to ensure the quality of special thin steel sheets (such as automobile steel sheets).
The argon blowing technology of the tundish requires that the bubbles produced by the permeable bricks are tiny and continuously dispersed. When the gas carries inclusions to float up, the protective slag is not blown away. Therefore, the airway structure and operation method of the brick body are very different from the permeable bricks used for refining outside the furnace and the gas supply components used for the converter.
Air bricks for torpedo tanks
Many steel mills have adopted the process of pre-treating molten iron in torpedo tanks: dephosphorization and desulfurization agents are sprayed into the molten iron through the top gun, and the sulfur and phosphorus elements in the molten iron react with them to form slag that floats up. However, due to the special shape of the torpedo tank, under operating conditions, dead zones are formed at both ends of the torpedo tank, which seriously affects the efficiency and uniformity of desulfurization and dephosphorization, and further affects the realization of subsequent process smelting technology. By adding ventilation devices at both ends, the dead zones at both ends of the torpedo tank can be eliminated, the movement of molten iron can be strengthened, and the uniformity and efficiency of desulfurization and dephosphorization can be improved.
