A method of continuous casting of high-aluminium steel

Abstract

The application discloses a high-aluminum steel continuous casting method, which adopts zirconium drainage sand in a ladle to reduce the reaction between the drainage sand and molten steel, and adopts a tundish cover argon blowing technology to blow argon on the tundish cover hole or in the tundish cover refractory, so that the oxygen content of the atmosphere in the tundish is reduced from 17-21% to below 0.1%, and a large amount of secondary oxidation caused by air in the first furnace opening and the subsequent continuous casting process is avoided. The method greatly reduces the reaction between aluminum in the high-aluminum steel and the drainage sand and air, reduces the alloy element burning loss, reduces the Al2O3 inclusions, is beneficial to improving the quality of the final product, greatly reduces the nozzle clogging rate, makes the production more stable, increases the continuous casting furnace number, reduces the contact between the molten steel and air, and significantly reduces the nitrogen increase.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a method for continuous casting of high-alumina steel. Background Technology

[0002] With my country's economic development and industrial structure upgrading, high-aluminum steel (Al≥0.2%) has been widely used in key sectors such as automobiles, energy, and power due to its high strength, high toughness, low density, and low cost. Hot-stamped steel possesses high strength, good elongation, and fracture strain, giving components excellent resistance to impact deformation and fracture, and has become the most important material for automotive body structural components. However, with continuous product upgrades, production technology and quality issues are becoming increasingly prominent.

[0003] Due to its high aluminum content, this steel grade is prone to secondary oxidation during continuous casting (especially before the addition of the tundish covering agent in the first heat), forming a large amount of alumina inclusions and causing blockage of the nozzle. On the other hand, high-alumina steel easily reacts with chromium oxide in the tundish guide sand, causing it to be significantly reduced, resulting in aluminum burn-off. At the same time, Al2O3 is generated and enters the slag, affecting the adsorption of alumina inclusions.

[0004] In the prior art, patent CN 113927025 B provides a method for preparing and using chromium-based ladle guide sand for high-manganese and high-alumina steel. The mass percentage of each component in the guide sand is Cr2O3 30-40%, Al2O3 25-35%, SiO2 5-10%, Fe2O3 15-25%, and MgO 5-10%. Alumina is used to replace part of the silicon oxide, reducing the reaction between the guide sand and the aluminum in the steel. However, the content of chromium oxide and silicon oxide is still 35-50%, which will still cause secondary oxidation of the molten steel. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention uses zirconium-based guiding sand in the ladle to reduce the reaction between the guiding sand and the molten steel, and employs argon blowing through the tundish cover and other technical measures for continuous casting of high-alumina steel. This reduces the loss of alloying elements, reduces the amount of inclusions produced, improves the quality of molten steel, and enhances the castability of molten steel.

[0006] To achieve the above-mentioned objective, the present invention provides a method for continuous casting of high-alumina steel, the method comprising the following steps:

[0007] ① Control the casting temperature in the tundish of continuous casting to be 1525~1540℃, and the casting speed of the casting machine to be 0.8~1.1m / min.

[0008] ② After the ladle slide is closed, add 50-200 kg of zirconium-based guiding sand; then add molten steel. Using zirconium-based guiding sand can reduce the reaction between the guiding sand and the molten steel.

[0009] ③ Argon blowing technology is adopted for the intermediate ladle cover: After the intermediate ladle car is driven above the crystallizer and baked, argon gas is blown into the impact zone, pouring zone and sampling hole of the intermediate ladle cover while waiting for the main ladle to be poured. This reduces the oxygen content in the atmosphere inside the intermediate ladle from 17-21% to below 0.1%, avoiding a large amount of secondary oxidation caused by air during the first pouring of the intermediate ladle and subsequent continuous pouring.

[0010] ④ After casting begins, when the weight of molten steel in the tundish reaches 30t, start adding tundish covering agent; after the tundish liquid level stabilizes at the highest level, reduce the argon gas flow rate and maintain it until the continuous casting is completed.

[0011] In the above technical solution, the zirconium diverting sand has the following composition by mass percentage: ZrO2 19-28%, Cr2O3 19-22%, SiO2 16-33%, Al2O3 8-22%; the remaining components are impurities.

[0012] Furthermore, the refractoriness of the zirconium diverting sand is 1700–1800℃.

[0013] Furthermore, in step ③, before pouring, the argon gas flow rate is 3 to 4 times the steel bath capacity, and the argon blowing time is 3 to 4 minutes; for example, for a 70t tundish, the argon gas flow rate is 210 to 280 m³ / h. 3 / h.

[0014] Furthermore, in step ④, the argon gas flow rate during steady-state casting is 1 to 2 times the volume of the intermediate ladle; for example, for a 70t intermediate ladle, the argon gas flow rate is 70 to 140m³. 3 / h.

[0015] Application of the above-mentioned continuous casting method for high-alumina steel in the smelting of molten steel with an Al content of 0.2 to 10.05 wt%.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1) Significantly reduces the reaction between aluminum and the guiding sand and air in high-aluminum steel, reducing the loss of alloying elements;

[0018] 2) The reduction of Al2O3 inclusions is beneficial to improving the quality of the final product;

[0019] 3) The sprue blockage rate has been significantly reduced, production is more stable, and the number of consecutive casting furnaces has increased;

[0020] 4) Reducing the contact between molten steel and air significantly reduces the amount of nitrogen added. Detailed Implementation

[0021] The present invention will be further described below with reference to specific embodiments, but this does not limit the invention in any way. To avoid redundancy, unless otherwise specified, the raw materials used in the following embodiments are all commercially available products, and the methods used are all conventional methods unless otherwise specified.

[0022] Example 1

[0023] According to the steel grade composition requirements, the Al content in the molten steel should be controlled between 10% and 10.05%.

[0024] A method for continuous casting of high-alumina steel, the method comprising the following steps:

[0025] ① Control the casting temperature of the tundish in continuous casting to 1530~1540℃, and the casting machine speed to 0.8m / min. The ladle capacity is 210t, and the tundish capacity is 70t.

[0026] ②After the ladle slide is closed, add 100kg of zirconium distillate sand; then fill with molten steel.

[0027] The zirconium diverting sand has the following composition by mass percentage: ZrO2 19%, Cr2O3 19%, SiO2 33%, Al2O3 8%, with the remainder being impurities; the zirconium diverting sand has a refractoriness of 1700℃.

[0028] ③ Argon blowing technology using the tundish cap: After the tundish car moves above the crystallizer and is baked, while waiting for the main ladle to be poured, argon gas is blown into the impact zone, pouring zone, and sampling port of the tundish cap. The argon gas flow rate is 210 m³ / h. 3 / h, argon blowing time is 3min; to reduce the oxygen content in the atmosphere inside the intermediate package to 0.1%.

[0029] ④ After pouring begins, when the weight of molten steel in the tundish reaches 30t, start adding tundish covering agent; after the tundish liquid level stabilizes at the highest level, reduce the argon gas flow rate to 100m³. 3 / h, and maintain until the continuous casting is finished.

[0030] Example 1 yielded a steel composition that meets the requirements of this invention, with an Al content of 10.02% and an aluminum loss of 0.02%. The produced high-alumina steel fully meets national standards and user requirements. After three heats of continuous casting, 30% of the sprue was clogged, meeting the requirements for multi-heat continuous casting. Nitrogen was added by 3 ppm during continuous casting.

[0031] Example 2

[0032] According to the steel grade composition requirements, the Al content in the molten steel should be controlled between 0.2% and 0.25%.

[0033] A method for continuous casting of high-alumina steel, the method comprising the following steps:

[0034] ① Control the casting temperature of the tundish in continuous casting to 1525~1540℃, and the casting machine speed to 1.1m / min. The ladle capacity is 120t, and the tundish capacity is 40t.

[0035] ②After the ladle slide is closed, add 100kg of zirconium distillate sand; then fill with molten steel.

[0036] The zirconium diverting sand has the following composition by mass percentage: ZrO2 28%, Cr2O3 22%, SiO2 16%, Al2O3 22%, with the remainder being impurities; the zirconium diverting sand has a refractoriness of 1800℃.

[0037] ③ Argon blowing technology using the tundish cap: After the tundish car moves above the crystallizer and is baked, while waiting for the main ladle to be poured, argon gas is blown into the impact zone, pouring zone, and sampling port of the tundish cap. The argon gas flow rate is 120 m³ / h. 3 / h, argon blowing time is 4min; to reduce the oxygen content in the atmosphere inside the intermediate package to 0.05%.

[0038] ④ After pouring begins, when the weight of molten steel in the tundish reaches 30t, start adding tundish covering agent; after the tundish liquid level stabilizes at the highest level, reduce the argon gas flow rate to 60m³ / h. 3 / h, and maintain until the continuous casting is finished.

[0039] Example 2 yielded a steel composition that meets the requirements of this invention, with an Al content of 0.21% and an aluminum loss of 0.025%. The produced high-alumina steel fully meets national standards and user requirements. After five heats of continuous casting, 35% of the nozzles were clogged, meeting the requirements for multi-heat continuous casting. Nitrogen was added by 4 ppm during continuous casting.

[0040] Comparative Example 1

[0041] According to the steel grade composition requirements, the Al content in the molten steel should be controlled between 10% and 10.05%.

[0042] The continuous casting tundish pouring temperature is 1530~1540℃, the casting machine speed is 1.0m / min, the ladle capacity is 210t, and the tundish capacity is 70t. Finally, molten steel is poured in.

[0043] After the ladle slide is closed, 100 kg of chromium-based diversion sand is added. The main components are: Cr2O3 37%, SiO2 18%, and Al2O3 13%.

[0044] Once the tundish car reaches above the crystallizer and casting begins, the molten steel in the tundish reaches 30 tons, at which point the tundish covering agent is added. The tundish level remains stable at its maximum level until the continuous casting process is complete. The oxygen content in the air inside the tundish is 18%.

[0045] The steel composition required by the above method cannot meet the requirements of this invention. The finished product has an Al content of 9.98% and an aluminum burn-off of 0.06%. Furthermore, after one heat of casting, 70% of the sprue is blocked, making continuous casting of multiple heats impossible. Nitrogen content increases by 10 ppm during continuous casting.

[0046] For anyone skilled in the art, many possible variations and modifications can be made to the technical solutions of this invention, or equivalent embodiments can be modified based on the disclosed technical content, without departing from the scope of the technical solutions of this invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this invention without departing from the content of the technical solutions of this invention should still fall within the protection scope of the technical solutions of this invention.

Claims

1. A method for continuous casting of high-alumina steel, characterized in that, The method includes the following steps: ① Control the casting temperature of the tundish in continuous casting to 1525~1540℃, and the casting machine speed to 0.8~1.1m / min; ② After the ladle slide is closed, add 50-200 kg of zirconium distillate sand; then pour in molten steel. ③ Argon blowing technology is adopted for the tundish cover: After the tundish car is driven above the crystallizer and the baking is completed, while waiting for the ladle to be poured, argon gas is blown into the impact zone, pouring zone and sampling hole of the tundish cover respectively; so that the oxygen content in the atmosphere inside the tundish is reduced to below 0.1%; ④ After casting begins, when the weight of molten steel in the tundish reaches 30t, start adding tundish covering agent; after the tundish liquid level stabilizes at the highest level, reduce the argon gas flow rate and maintain it until the continuous casting is completed; The zirconium-based diverting sand has the following composition by mass percentage: ZrO2 19-28%, Cr2O3 19-22%, SiO2 16-33%, Al2O3 8-22%; the remaining components are impurities.

2. The continuous casting method according to claim 1, characterized in that, The refractoriness of the zirconium diverting sand is 1700~1800℃.

3. The continuous casting method according to claim 1, characterized in that, Step ③ Before pouring, the flow rate of argon gas should be 3 to 4 times the capacity of the steel container, and the blowing time should be 3 to 4 minutes.

4. The continuous casting method according to claim 1, characterized in that, Step 4: The argon gas flow rate during steady-state casting is 1 to 2 times the intermediate containment volume.

5. The continuous casting method according to claim 1, characterized in that, The high-aluminum steel is steel with an Al content of 0.2~10.05wt%.