Contains the inner lining of liquid molten iron, liquid molten steel container and related furnace protection and insulation materials. Specifically, it can be divided into iron ladle lining, converter lining, ladle lining and tundish lining and related supporting taps, sliding There are more than 130 kinds of shaped refractory materials such as nozzles and three continuous casting pieces and unshaped bulk materials such as refractory mud, dry materials, casting materials, drainage sand, covering agents, protective slag, etc.
Hot metal ladle
The iron ladle undertakes the task of receiving molten iron from the tap hole of the blast furnace and converting the molten iron into the converter for smelting. The usual temperature range of molten iron is about 1200～1370℃, and its service process has to withstand the impact of extreme cold and heat. Therefore, the iron ladle refractory material is required to withstand frequent changes in cold and heat, and the lining must remain rigid and not resistant to cooling and heating. Material disintegrates or creates gaps.
1.1 Brick lining iron ladle
The main refractory material used for the working layer of the brick lining iron ladle is low-aluminum silicon carbide carbon bricks, and the permanent layer is three-layer clay bricks. The low-aluminum silicon carbide carbon bricks have the properties of erosion resistance and non-sticking slag. Bricks have lower prices and better performance, and brick-lined iron ladle is mainly used for railway transportation of molten iron.
1.2 Integral cast iron ladle
The iron ladle used for molten iron in the workshop is integrally cast with castable. The cast material is Al-SiC. Its working cycle is compact, and the degree of endurance of hot and cold is lower than that of iron ladle transported on railway lines. The life span is longer than that on the railway line. In recent years, the thickness of the impact zone at the bottom of the iron ladle has been thickened to extend the life, and anti-sticking slag agent is applied to the iron ladle mouth to reduce the impact of the slag sticking treatment on the iron ladle life. The life of the iron ladle is increasing year by year.
The ladle is responsible for the dual tasks of carrying molten steel and refining outside the furnace. The temperature range of molten steel in the ladle is about 1550～1620℃, and the ladle has to withstand the impact of extreme cold and heat during service. Due to the extremely harsh use conditions of the refined ladle, the arc erodes the slag line and the cladding wall very seriously, leading to the advanced damage of the refractory material, which is the main reason that restricts its service life. Therefore, the requirement for the lining of the ladle brick is higher than that of the iron-clad brick lining.
2.1 Permanent lining of ladle
The castable for the ladle is corundum-spinel castable, which has good slag erosion resistance and permeability resistance and excellent spalling resistance, which can resist the above corrosion damage well. At present, the permanent lining of the steel ladle has a service cycle of about 1.5 years.
2.2 Ladle working lining
The ladle working lining is mainly made of aluminum-magnesium (carbon) refractory materials. In order to improve the life of the ladle, the refractory materials in key parts such as ladle slag line bricks, breathable bricks, sliding plates and nozzle bricks should be kept synchronized with the life of the ladle lining.
2.3 Bottom blown and breathable brick
The air-permeable bricks are embedded at the bottom of the ladle to effectively homogenize the temperature and composition of the molten steel through the stirring effect of argon, and make non-metallic inclusions float smoothly. Sangang Minguang adopts slit-type air-permeable bricks, which can be replaced within the service life of a ladle 2 A breathable brick.
2.4 Ladle nozzle and skateboard
The upper nozzle of the ladle is the channel through which the molten steel in the ladle flows into the tundish, and the sliding plate controls the amount of molten steel flowing into the tundish. The material is magnesium-carbon, and the life is not up to the process requirements and needs to be replaced.
The temperature of molten steel in the tundish is about 1470～1560℃, because the tundish has to leave a certain thickness of residual steel after the casting is completed, and the stopper rod and the residual steel are frozen in the tundish when the tundish is off-line, and the off-line tundish continues to work after cooling When the lining is removed together, the working lining is scrapped after one-time service, so the requirements for the working lining of the tundish are not as high as that of the ladle.
3.1 Permanent lining casting material
The permanent lining of the tundish usually uses aluminum-silicon castable. According to the use conditions of the tundish, the castable should have good strength, volume stability and thermal shock resistance. Sangang Minguang tundish adopts D57 casting material and has a service life of about 700-800 furnaces.
3.2 Working lining dry material
Tundish magnesium dry working lining has the advantages of simple construction, high baking thermal efficiency, easy separation of steel slag and permanent lining, fast tundish turnover, improved molten steel quality, and long service life. It has been widely used. Its main raw material is fused magnesium Sand is controlled by 10-40 furnaces according to the different tundish ages of steel types.
Table 3 Service life of tundish in recent years (Figure 4)
Three pieces of continuous casting
Long nozzle, stopper rod and immersion nozzle are the key functional refractory materials for continuous casting, and their performance directly affects continuous casting efficiency and billet quality.
4.1 Large bag long nozzle
The main function of the shroud is to cut off the air during the molten steel pouring process to prevent the secondary oxidation of the molten steel and the inhalation of nitrogen. The material of the shroud is aluminum and carbon. The life of ordinary steel is 9 to 10 furnaces, and the variety of steel is 2 to 6 furnaces. control.
The integral stopper is a key component to control the flow of molten steel injected into the mold in the tundish and ensure continuous casting production. Stopper rods are made of magnesium-carbon and aluminum-carbon, which are used in aluminum-containing steel and ordinary carbon steel, respectively. The service life is controlled between 10 and 40 furnaces due to the steel type.
4.3 Upper nozzle
In the stopper rod controlled flow casting system, the tundish upper nozzle is a distributor for molten steel to flow into the mold. The outer layer is aluminum carbon and the inner layer is inlaid with high melting point ZrO2. Its corrosion resistance, slow expansion, and other Compared with the material of the nozzle, it can significantly increase the continuous pouring time of a single tundish.
4.4 Immersion nozzle
The main function of the immersion nozzle is to prevent secondary oxidation of molten steel, control the flow state of molten steel, promote the floating of inclusions and prevent mold slag from being involved in molten steel, whether it is slab or billet immersion nozzle. Use aluminum carbon.
In addition to the “three major pieces” of continuous casting, the stopper rod and the tundish nozzle must be synchronized with the life of the tundish. The long nozzle and immersion nozzle of the large bag can be synchronized with the life of the tundish by changing the slag line or replacing it with a new one.
Table 4 In recent years, the service life of the “three major parts” of continuous casting (Figure 5)
shaped refractories also include the impact bricks of the iron ladle, the impact bricks and seat bricks at the bottom of the ladle, and the impact bricks, impact plates, retaining walls, dams, seat bricks, shaped billets, and clay billets of the tundish.