CN-121990814-A - Tundish coating for rare earth steel

Abstract

The invention discloses a tundish coating for rare earth steel, which comprises, by mass, 90-95wt% of sintered magnesia, 1-5wt% of activated alumina, 1-4wt% of rare earth oxide and 1-4wt% of a magnesium aluminate binder, and an additive comprising a water reducer, a plasticizer and explosion-proof fibers. Not only obtains good compactness and thermal shock resistance, but also greatly improves the rare earth erosion resistance of the tundish coating, is particularly suitable for smelting rare earth-containing steel, and solves the problems that the existing magnesia coating has higher SiO 2 content and is easy to react with rare earth, thereby reducing the high-temperature service performance of the coating and the purity of molten steel.

Inventors

• WU QINXIN
• GAN FEIFANG
• GAO HUA

Assignees

• 宝山钢铁股份有限公司

Dates

Publication Date

20260508

Application Date

20241105

Claims (10)

1. 1. A tundish coating for rare earth steel is characterized by comprising raw materials and an additive, wherein, The raw materials comprise 90-95wt% of sintered magnesia, 1-5wt% of active alumina, 1-4wt% of rare earth oxide and 1-4wt% of magnesium aluminate binder.
2. 2. The tundish coating for rare earth steel according to claim 1, wherein MgO in the sintered magnesia is not less than 94.5wt%.
3. 3. The tundish coating for rare earth steel according to claim 1 or 2, wherein the sintered magnesia has a coarse particle size of 1-3 mm accounting for 38-45 wt%, the sintered magnesia fine particle size of 0.088mm < 1mm < accounting for 45-50 wt%, and the sintered magnesia fine powder of 0.088mm < 5-10 wt%.
4. 4. Tundish coating for rare earth steel according to claim 1, characterized in that Al 2 O 3 ≥99.5wt％,d 50 = 1.0-3.0 μm, preferably d 50 = 1.67 μm in the activated alumina.
5. 5. The tundish coating for rare earth steel according to claim 1, wherein the rare earth oxide is one or two of CeO 2 、La 2 O 3 , d 50 =30-60 nm, preferably d 50 =50nm。
6. 6. The tundish coating for rare earth steel according to claim 1, wherein MgO is not less than 45wt% and Al 2 O 3 is not less than 15wt% in the magnesium aluminate binder.
7. 7. The tundish coating for rare earth steel according to claim 1, wherein the additive comprises a water reducing agent, a plasticizer and an explosion-proof fiber.
8. 8. The tundish coating for rare earth steel according to claim 7, wherein the addition amount of the water reducer is 0.15-0.5% of the total weight of the raw materials, the water reducer is sodium tripolyphosphate and sodium hexametaphosphate, and the mass percentage of the sodium tripolyphosphate and the sodium hexametaphosphate is 1-3:1-3.
9. 9. The tundish coating for rare earth steel according to claim 7, wherein the addition amount of the plasticizer is 0.1-0.5% of the total weight of the raw materials, and the plasticizer is one or two of sodium methylcellulose and dextrin.
10. 10. The tundish coating for rare earth steel according to claim 7, wherein the addition amount of the explosion-proof fiber is 0.05-0.1% of the total weight of the raw materials.

Description

Tundish coating for rare earth steel Technical Field The invention belongs to the technical field of refractory materials, and particularly relates to a tundish coating for rare earth steel. Background The tundish is the last smelting container before molten steel becomes a casting blank, and is an important procedure for ensuring the purity of molten steel. The working lining of the tundish is generally made of fire-resistant paint, and the paint has the advantages of convenient construction, convenient storage and the like. Magnesium paint is widely used in tundish paint due to its excellent erosion and permeation resistance. Rare earth steel is obtained by adding rare earth in the form of an alloy to molten steel, and it is desired to change the morphology of inclusions and improve the properties of the steel. The rare earth element has low melting point and is easy to oxidize, and the rare earth element is easy to react with slag, refractory materials and air in the smelting process. Rare earth elements are easily oxidized in molten steel to form high-melting-point rare earth oxides (RE 2O3) and oxysulfides (RE 2O2 S). The chemical components of the magnesium coating used in the tundish are more than or equal to 60 percent of MgO and less than or equal to 10 percent of SiO 2, wherein SiO 2 mainly exists in the form of fine powder. The rare earth reacts with SiO 2 to form rare earth silicate (RESiO 4) and a high-viscosity glass phase, and the reaction can erode and destroy the bonding matrix of the magnesium coating, so that the coating has melting loss, peeling and cracking phenomena in the use process, the high-temperature use performance is reduced, and the risk of steel seepage and steel leakage can be caused. Chinese patent CN115246733a discloses a high durability tundish coating and its application, wherein the main raw materials are magnesia and silica micropowder, and magnesium aluminate is used as binder. Although the technology has strong anti-corrosion capability, is favorable for improving the purity of molten steel and the service life of a tundish, the technology is only suitable for common steel types, and can not effectively resist the corrosion of paint caused by the reaction of rare earth and SiO 2 because the fine powder is mainly silicon powder. Chinese patent CN111484343a discloses a hydration-resistant magnesia-calcia tundish coating and its preparation method, which uses dead burned magnesia and dolomite as raw materials. The patent effectively solves the problem of hydration of CaO by adopting a method of compounding a calcium source, but the magnesium-calcium refractory material still has the problem of difficult sintering. Chinese patent CN104803687A discloses an ultralow-silicon coating capable of reducing the oxygen content of a tundish, which is prepared by taking 70-80wt% of high-purity magnesia and 10-20wt% of high-purity calcium hydroxide as raw materials and zirconium oxychloride as a binding agent. In the patent, the SiO 2 content is extremely low, the oxygen content of the tundish can be effectively reduced, but calcium hydroxide and zirconium oxychloride used by raw materials can be decomposed into CaO and ZrO 2 at high temperature, and the coefficients of thermal expansion of the calcium hydroxide and the zirconium oxychloride are large, so that the volume expansion of the coating can be caused to generate cracks, and the production safety of the tundish is influenced. In summary, the content of SiO 2 in the conventional magnesium coating is high, rare earth is easy to react with SiO 2 to form rare earth silicate and high-melting glass phase, and the high-temperature service performance of the coating and the purity of molten steel are reduced. Therefore, if the SiO 2 content in the magnesium coating can be reduced by adjusting the components, the improvement of the corrosion resistance of rare earth is a problem to be solved. Disclosure of Invention The invention aims to provide a tundish coating for rare earth steel, which solves the problems that the existing magnesia coating has higher SiO 2 content and is easy to react with rare earth, thereby reducing the high-temperature service performance and the molten steel purity of the coating, can effectively resist the melting loss and erosion of rare earth to the tundish coating, and is beneficial to improving the continuous casting furnace number and the molten steel purity of the rare earth steel. In order to achieve the above purpose, the technical scheme of the invention is as follows: A tundish coating for rare earth steel comprises raw materials and an additive, wherein, The raw materials comprise 90-95wt% of sintered magnesia, 1-5wt% of active alumina, 1-4wt% of rare earth oxide and 1-4wt% of magnesium aluminate binder. Preferably, mgO in the sintered magnesia is more than or equal to 94.5wt%. Preferably, coarse sintered magnesia particles with the particle size of 1-3 mm account for 38-45 wt%, fine sintered mag