Configuration Plan of Refractory Materials for Steelmaking

Refractory materials used in the steel industry include the linings of liquid iron and liquid steel containers and related furnace protection and insulation materials. Specifically, it can be divided into iron ladle lining, converter lining, ladle lining, tundish lining, and related supporting shaped refractory materials such as taphole, sliding nozzle, and continuous casting. There are more than 130 kinds of amorphous bulk materials such as repairing materials, refractory mud, dry materials, casting materials, drainage sand, covering agents, protective slag, etc.

1. Iron Ladle

The iron ladle is responsible for receiving the molten iron from the blast furnace taphole and mixing 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 severe cold and heat. Therefore, the iron-clad refractory material is required to withstand frequent hot and cold changes, and the lining must remain rigid. The refractory material shall not disintegrate or create gaps due to cooling and heating.

1.1 Brick-lined iron cladding

The main refractory material of the working layer used in the brick-lined 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-stick slag. Magnesia-carbon bricks have a lower price and better performance than ladle-lined iron ladles. Brick-lined iron ladles are mainly used for railway transportation of molten iron.

1.2 Integral cast iron ladle

The iron ladle used for mixing molten iron in the factory is integrally cast with castables. The casting material is Al-SiC, which has a compact working cycle and can withstand severe cold and heat to a lower extent than the iron cladding transported on the railway line, so its lifespan 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 designed to extend its life. Apply an anti-slag agent to the ladle mouth to reduce the impact of slag sticking treatment on the life of the iron ladle. The life of the iron ladle increases year by year.

2. Ladle

The ladle is responsible for the dual tasks of carrying molten steel and refining outside the furnace. The temperature of the molten steel in the ladle ranges from about 1550 to 1620°C, and the ladle must withstand the impact of severe cold and heat during service. Due to the extremely harsh operating conditions of the refining ladle, arc erosion of the slag line and ladle wall is very serious. This leads to premature damage of the refractory material and becomes the main reason restricting its service life. Therefore, the requirements for steel-clad brick lining are higher than those for iron-clad brick lining.

2.1 Ladle permanent lining

The castable for the ladle is corundum-spinel castable, which has good resistance to slag erosion and penetration as well as excellent spalling resistance. Can resist the above-mentioned erosion very well. At present, the service life of the permanent lining of a steel ladle is about 1.5 years.

2.2 Ladle working lining

The working lining of the ladle is mainly aluminum magnesium (carbon) refractory material. To improve the service life of the ladle, refractory materials are used in key parts such as ladle slag line bricks, breathable bricks, sliding plates, and nozzle bricks. It should be kept in sync with the molten steel lining life.

2.3 Bottom-blown breathable bricks

Breathable bricks are embedded at the bottom of the ladle. The temperature and composition of molten steel are effectively homogenized through the stirring effect of argon gas, and non-metallic inclusions are smoothly floated up. A steel plant uses gap-type breathable bricks, and two breathable bricks are replaced during the service life of a steel ladle.

2.4 Ladle nozzle and sliding plate

The ladle upper nozzle 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 materials are all magnesium carbon and need to be replaced when their service life cannot meet the process requirements.

3. Tundish

The temperature of the molten steel in the tundish is about 1470~1560℃. Because a certain thickness of remaining steel must be left in the tundish after casting, and the plug rod and remaining steel are frozen in the tundish when it is off-line, the off-line tundish will be removed together with the working lining after cooling. The working lining will be scrapped after one-time service, so the requirements for the working lining of the tundish are not as high as those of the steel ladle.

3.1 Permanent lining casting material

The permanent lining of the tundish usually uses aluminum-silicon castables. According to the usage conditions of the tundish, the castable should have good strength, volume stability, and thermal shock resistance. The tundish of a steel plant uses D57 casting material, with a service life of about 700 to 800 furnaces.

3.2 Working lining dry material

The magnesium dry working lining of the tundish is easy to construct, has high baking thermal efficiency, and is easy to separate from the steel slag and the permanent lining. The tundish has the advantages of fast turnover, improved molten steel quality, and long service life and has been widely used. The main raw material is fused magnesia, and the tundish age is controlled from 10 to 40 furnaces according to different steel types.

4. Three major parts of continuous casting

The long nozzle, plug rod, and immersed nozzle are key functional refractory materials for continuous casting, and their performance directly affects the continuous casting efficiency and billet quality.

5. Others

Shaped refractory materials also include impact bricks for iron ladles, impact bricks, and seat bricks at the bottom of the ladles. Tundish impact bricks, impact plates, retaining walls, retaining dams, seat bricks, profiled blanks, clay bricks, etc.