What are the functions of the tundish? What are the requirements for refractory materials?
(1) The tundish is a container that mainly receives, stores and redistributes ladle water. Tundish metallurgical technologies such as adjusting temperature, adjusting trace alloy elements, and improving inclusions are now gradually developed.
(2) The requirements for refractory materials are that the refractoriness is not high, but it is required to be resistant to erosion by molten steel, steel slag and slag, have good thermal shock resistance, small thermal conductivity, good thermal insulation performance, no pollution to molten steel, and easy to build and disassemble.
What types of refractory materials are used in the middle?
(1) The refractory materials used for the tundish lining include clay bricks, lightly fired high-alumina bricks, high-alumina castables, unfired high-alumina seat bricks, and magnesium coatings.
(2) The refractory materials used for the tundish system include alumina-carbon long nozzles, integral stopper rods, and submerged nozzles.
What should be paid attention to when using high-alumina castables for the intermediate integral lining?
(1) The mixing sequence is loading, dry mixing for 2 minutes, adding water for 2 minutes, wet mixing for 6 minutes, and discharging.
(2) The amount of water added is strictly controlled at 6-8%, and the mixing is required to be uniform and can be kneaded into a ball by hand.
(3) Use multiple vibrating rods to vibrate, increase the insertion points, and insert and pull out the rods slowly and steadily to ensure that the casting layer is dense and complete.
(4) Layered and block-by-block staggered construction, one-time casting construction.
(5) In order to facilitate demoulding, a layer of engine oil should be applied to the outer wall of the mold before construction.
(6) Natural protection, demoulding in 8-12 hours in summer and 20-24 hours in winter.
What are the requirements for baking the integral tundish lining?
(1) In the 110-150°C stage, a large amount of free water can be removed. The temperature needs to be raised slowly, and low-temperature and steady-temperature baking operations are adopted.
(2) In the 300-400°C stage, more than 80% of the cement hydration crystal water is removed, and slight shrinkage occurs. Medium temperature is required, and the temperature needs to be raised slowly to prevent cracking.
What are the functions and types of intermediate coatings?
(1) The tundish coating is mainly used as a working lining, which can resist the erosion of molten steel slag, has a long service life, and can ensure continuous casting of multiple furnaces.
(2) It is required to be easy to construct, quick to replace, easy to clean, and not to damage the permanent lining.
(3) The types of special steel tundish coatings include magnesium coatings with a MgO content greater than 88%, and magnesium-chromium coatings with a MgO content of 65-75% and Cr2O36-8%.
What are the functions and masonry methods of the tundish lining slag retaining wall?
(1) The function of the slag retaining wall is to retain slag, further remove inclusions in the molten steel, and improve the cleanliness of the molten steel. The slag retaining wall can be a single wall or a double wall.
(2) The slag retaining wall can be built manually with high-aluminum bricks or prefabricated blocks made of high-aluminum castables and manually inserted.
(3) Ceramic foam filters, or porous filter plates and filter tubes can be placed in the steel flow holes of the slag retaining wall to remove trace non-metallic inclusions in the steel and obtain ultra-clean molten steel.
What are the functions of refractory materials in continuous casting tundish steel pouring system?
1) The long nozzle is also called the protective sleeve. It is mainly used between the ladle and the tundish. Its function is to prevent the molten steel from being secondary oxidized and splashing. It is installed with a lever-type fixing device.
(2) The integral stopper rod is mainly used in the tundish. It plays an opening and closing role, controls and adjusts the flow of molten steel entering the crystallizer, and can also pass argon to prevent the nozzle from being blocked.
(3) The submerged nozzle is mainly used in the crystallizer. The molten steel in the tundish flows into the crystallizer through the gap between the stopper rod and the submerged nozzle. The key to multi-furnace continuous casting of special steel is currently the quality of the submerged nozzle.’`23
What are the requirements for the materials of refractory materials used in continuous casting steel systems?
(1) The refractory materials used in the continuous casting steel pouring system are all aluminum carbon refractory materials, which are mainly made of corundum and graphite as raw materials, resin combined with isostatic pressing, fired in a reducing atmosphere, fine-processed on a lathe, and coated with an anti-oxidation layer to make the product.
(2) The characteristics of aluminum carbon materials are strong adaptability to steel types, especially suitable for casting special steels, and no pollution to molten steel.
(3) For the slag line of the submerged nozzle and the key parts of the gate, a layer of highly erosion-resistant and erosion-resistant zirconium carbon refractory material can also be compounded to increase the life of the submerged nozzle.
What should be paid attention to when baking the tundish before pouring steel?
(1) Within 1 to 2 hours before the continuous casting tundish is poured, it should be quickly baked to 1000-1100, and it is better to pour steel immediately.
(2) If baked for a long time, the carbon in the aluminum carbon product is easy to oxidize, the strength is reduced, the surface is loose, and the service life is reduced. For the immersion nozzle with thin wall thickness, the quality of use mainly depends on whether its surface is oxidized.
(3) After long-term baking without pouring steel, the magnesium coating lining is easy to crack, the surface is loose after moisture absorption, and the strength is reduced. If used again, the inclusions in the molten steel are very likely to increase, and some loose coatings will be mixed into the molten steel.
What are the causes of damage to aluminum carbon immersion nozzles?
(1) The internal quality of the submerged nozzle. The SiO2 content and graphite quality in the product largely determine its anti-corrosion performance. (2) The corrosion of the protective slag on the slag line. The basicity of the protective slag should not be too large. It is generally best to control it at about 1%.
(3) Baking reasons. Poor preheating or long-term baking will cause the submerged nozzle to have low strength, severe oxidation, and easy to burst.
(4) Mechanical damage during transportation and installation, internal cracks caused during the manufacturing process, etc.
What are the main problems with refractory materials used in tundish linings?
(1) The tundish lining is a working lining for pouring, not an emergency lining. After pouring, the residual steel and slag must be turned over immediately. Avoid cold steel sticking to the bottom of the tundish and damaging the permanent lining during cleaning.
(2) Select the best supplier to improve the overall structural strength of the permanent lining castable, strive to achieve a permanent lining that does not crack, loosen, or stick to slag during use, and increase the service life of the permanent lining.
(3) Use an integral slag retaining wall to facilitate cleaning and pouring.
What are the ways to reduce the consumption of refractory materials in the continuous casting tundish steel pouring system?
(1) Perform duties diligently, carry and install carefully to avoid unnecessary damage. Bake and use strictly according to the regulations.
(2) Increase the number of continuous castings. With each additional casting, the consumption of refractory materials in the continuous casting system per ton of steel will be reduced exponentially.
(3) Adopt new technologies, promote competition among multiple companies, and select refractory suppliers with good quality, long service life and reasonable prices.
(4) Study the erosion mechanism of refractory materials in the tundish casting steel system, explore its corrosion law, improve the use conditions of continuous casting refractory materials, and continuously improve the service life of continuous casting refractory materials.