Method for refining HRB500E molten steel by using slag steel particle slagging process in LF (ladle furnace)

Abstract

The invention discloses a method for refining HRB500E molten steel in an LF (ladle furnace) by adopting a slag steel particle slagging process. According to the method, the total slag amount needed by LF refining temperature rise is increased by adding a proper amount of slag steel particles into the LF furnace, the total slag amount needed by LF refining temperature rise is guaranteed by adding a large amount of active lime for slagging in LF refining of HRB500E molten steel, and 2.0-3.0 kg of active lime added for slagging in the LF furnace is effectively reduced for each ton of steel. The method solves the problems that slag steel particles obtained after magnetic separation of slag steel in a steel plant return to the sintering process, the number of treatment processes is large, the recycling economic benefit is poor, and the converter smelting metal Fe recovery rate is low, solves the problem that the submerged arc temperature rising effect is poor in the early stage of HRB500E refining, shortens the power supply time of LF refining lower electrode temperature rising, and improves the production efficiency. And the quantity of active lime and pre-melted refining slag added for LF furnace slagging is effectively reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of steel smelting, and particularly relates to a method for refining HRB500E molten steel by using a slag steel particle slag making process in an LF furnace. Background Art

[0002] The metallic iron and its oxides contained in steel slag produced by converter smelting are a high-value-added renewable resource. The iron content of steel slag is approximately 20% to 30%, typically in the form of metallic iron and iron-containing minerals such as RO solid solution, calcium ferrite phase (C2F), magnetite (Fe3O4), or fusite (FeO). Currently, the primary method for recovering iron from steel slag is magnetic separation. After crushing, screening, and magnetic separation, the final separated bulk slag steel, primary magnetically separated slag steel, and purified slag steel are returned to the converter for scrap use. The slag steel pellets and slag steel powder separated by magnetic separation are returned to the sintering process or used as coolant in the converter smelting process. However, the return of magnetically separated slag steel pellets to the sintering process is economically inefficient due to their low and highly volatile total iron grade, and the fact that they must undergo multiple processing steps, including batching, sintering, and blast furnace smelting, before being converted into molten iron for transport to steelmaking. The slag steel particles after magnetic separation are returned to the steelmaking converter for smelting. Due to their small particles, lower density than molten iron, high iron oxide content and large slag volume, a large amount of iron oxide in the slag steel particles is retained in the converter slag, resulting in a large amount of converter slag and severe foaming. The probability of splashing increases during the converter smelting process, resulting in a metal Fe recovery rate of only about 40% for the slag steel particles after converter smelting, and the recycling value is also relatively low.

[0003] In view of the above problems, the present invention aims to provide a method for refining HRB500E using a slag and steel pellet slag-making process in an LF furnace, so as to solve the problems of low economic benefits of returning steelmaking slag and steel pellets to the sintering process or low recovery rate of metal Fe when returning them to the converter for smelting, and slow slag formation and poor submerged arc heating effect when a large amount of active lime is added in the early stage of LF refining of HRB500E molten steel. Summary of the Invention

[0004] The object of the present invention is to provide a method for refining HRB500E molten steel by adopting a slag and steel particle slag making process in an LF furnace.

[0005] The object of the present invention is achieved by a method for refining HRB500E molten steel using a slag steel pellet slag making process in an LF furnace, which is achieved by the following steps: A. Converter smelting: molten iron, scrap steel and pig iron are added to an LD converter and subjected to conventional top and bottom composite blowing. Lime and light-burned dolomite are added in conventional amounts to form slag, and the endpoint carbon content is controlled to be 0.06-0.12wt% and the tapping temperature is 1590-1620°C. After tapping, the molten steel is hoisted to an argon station processing station, the molten steel is temperature-measured, sampled and hoisted to an LF furnace, and the temperature of the molten steel entering the argon station is controlled to be 1520-1550°C. The chemical composition of the molten iron is: C 4.1-4.6wt%, Si 0.20-0.70wt%, Mn 0.20-0.45wt%, P 0.050-0.090wt%, S ≤ 0.050wt%, and the remainder is Fe and unavoidable impurities. B. Adding the first batch of steel to the LF furnace: The molten steel from step A is hoisted to the LF furnace for refining. Argon is blown at a rate of 150-250 NL / min for 2 minutes. Then, the argon is blown at a rate of 3.0-5.0 kg / t. 钢 , 2.0~4.0kg / t 钢 Slag steel particles and active lime are added to the ladle in sequence, wherein the slag steel particles have a particle size of 1-10 mm and a chemical composition of: TFe 45.0-70.0 wt%, FeO 10.0-25.0 wt%, Fe2O3 50.0-75.0 wt%, SiO2 11.0-15.0 wt%, CaO 22.0-31.0 wt%, MgO 6.0-9.0 wt%, Al2O3 2.0-4.5 wt%, MnO 3.5-4.5 wt%, MFe 45.0-60.0 wt%, S≤0.140 wt%, P≤1.200 wt%, and the remainder is Fe and unavoidable impurities; the temperature of the molten steel entering the LF furnace is controlled to be 1510-1540° C.; C. LF power supply temperature increase and composition adjustment: In step B, the electrode under the molten steel is set to gear 3 to 6 to slag; after 5-10 minutes of power on, lift the electrode to observe the slag in the furnace, then measure the temperature and take samples; if the slag is too thin, add 1.0-2.0 kg / t of lime 钢 The slag basicity (binary basicity, R) is controlled at 1.3-2.3. If it is too low, refined slag and fluorite are added to adjust the slag fluidity. After the steel sample analysis results are available, alloys are added based on the results to adjust the molten steel's chemical composition to acceptable levels. The molten steel is then heated to 1565-1585°C before being hoisted to the casting station. The total power supply time for the lower electrode to heat the molten steel is 12-16 minutes. The slag mass composition after LF refining is: TFe 2.0-2.5wt%, SiO2 20.0-28wt%, CaO 36.0-46.0wt%, with the remainder being unavoidable impurities.

[0006] D. Molten steel casting: The tundish temperature is 1525-1545℃, the casting speed is 2.6-2.8m / min, and the water volume in the crystallizer is 145-160m3 / h, and the secondary cooling water rate is 1.5~1.7L / kg, the molten steel in step C is cast into square billets with a cross-section of 165mm×165mm.

[0007] The present invention increases the total slag amount required for LF refining and heating by adding an appropriate amount of slag and steel particles into the LF furnace, solving the problem that the LF refining of HRB500E molten steel relies on adding a large amount of active lime to make slag to ensure the total slag amount required for LF refining and heating, and effectively reduces the active lime added in the LF furnace slag making by 2.0-3.0 kg / t. 钢 .

[0008] The present invention makes full use of the silicon dioxide, iron oxide, manganese oxide, aluminum oxide and other substances contained in slag steel particles to play a role in rapid slagging, replacing the slagging effect of pre-melted refined slag, and effectively reducing the amount of pre-melted refined slag added in LF refining slag making by 1.0-2.0 kg / t. 钢 .

[0009] This invention leverages the favorable reducing atmosphere of the LF refining furnace to reduce the iron oxide in the slag steel pellets to Fe, which is then incorporated into the molten steel. This also avoids the significant splashing losses during the return of the slag steel pellets to the converter for smelting, significantly improving the Fe recovery rate in the slag steel pellets. The Fe recovery rate of the slag steel pellets after magnetic separation reaches 70% to 80% when they are returned to the LF refining furnace for slag making, a 30% to 40% increase compared to the Fe recovery rate when they are returned to the converter for smelting. This also avoids the long processing cycle and low economic benefits of returning the slag steel pellets to the sintering process.

[0010] The present invention makes full use of the silicon dioxide, iron oxide, manganese oxide, aluminum oxide and other substances contained in slag steel particles to quickly deslagging during the LF refining process, thereby increasing the submerged arc temperature rise rate in the early stage of LF refining and shortening the lower electrode heating power supply time by 1-2 minutes per furnace of molten steel.

[0011] The present invention effectively improves the Fe recovery rate of slag steel smelting by adding an appropriate amount of slag steel particles to the LF furnace, accelerates the slag reduction rate, achieves a good submerged arc heating effect in the early stage of LF refining, shortens the power supply heating time, improves the technical and economic indicators of steelmaking, and reduces the steelmaking cost by 5 yuan / t. 钢 above. DETAILED DESCRIPTION

[0012] The present invention will be further described in detail below with reference to the embodiments, but the present invention is not limited in any way. Any changes or improvements made based on the teachings of the present invention fall within the scope of protection of the present invention.

[0013] The present invention provides a method for refining HRB500E molten steel in an LF furnace using a slag steel particle slag making process, which is achieved by the following steps: A. Converter smelting: molten iron, scrap steel and pig iron are added to an LD converter and subjected to conventional top and bottom composite blowing. Lime and light-burned dolomite are added in conventional amounts to form slag, and the endpoint carbon content is controlled to be 0.06-0.12wt% and the tapping temperature is 1590-1620°C. After tapping, the molten steel is hoisted to an argon station processing station, the molten steel is temperature-measured, sampled and hoisted to an LF furnace, and the temperature of the molten steel entering the argon station is controlled to be 1520-1550°C. The chemical composition of the molten iron is: C 4.1-4.6wt%, Si 0.20-0.70wt%, Mn 0.20-0.45wt%, P 0.050-0.090wt%, S ≤ 0.050wt%, and the remainder is Fe and unavoidable impurities. B. Adding the first batch of steel to the LF furnace: The molten steel from step A is hoisted to the LF furnace for refining. Argon is blown at a rate of 150-250 NL / min for 2 minutes. Then, the argon is blown at a rate of 3.0-5.0 kg / t. 钢 , 2.0~4.0kg / t 钢 Slag steel particles and active lime are added to the ladle in sequence, wherein the slag steel particles have a particle size of 1-10 mm and a chemical composition of: TFe 45.0-70.0 wt%, FeO 10.0-25.0 wt%, Fe2O3 50.0-75.0 wt%, SiO2 11.0-15.0 wt%, CaO 22.0-31.0 wt%, MgO 6.0-9.0 wt%, Al2O3 2.0-4.5 wt%, MnO 3.5-4.5 wt%, MFe 45.0-60.0 wt%, S≤0.140 wt%, P≤1.200 wt%, and the remainder is Fe and unavoidable impurities; the temperature of the molten steel entering the LF furnace is controlled to be 1510-1540° C.; C. LF power supply temperature increase and composition adjustment: In step B, the electrode under the molten steel is set to gear 3 to 6 to slag; after 5-10 minutes of power on, lift the electrode to observe the slag in the furnace, then measure the temperature and take samples; if the slag is too thin, add 1.0-2.0 kg / t of lime 钢 The slag basicity (binary basicity, R) is controlled at 1.3-2.3. If it is too low, refined slag and fluorite are added to adjust the slag fluidity. After the steel sample analysis results are available, alloys are added based on the results to adjust the molten steel's chemical composition to acceptable levels. The molten steel is then heated to 1565-1585°C before being hoisted to the casting station. The total power supply time for the lower electrode to heat the molten steel is 12-16 minutes. The slag mass composition after LF refining is: TFe 2.0-2.5wt%, SiO2 20.0-28wt%, CaO 36.0-46.0wt%, with the remainder being unavoidable impurities.

[0014] D. Molten steel casting: The tundish temperature is 1525-1545℃, the casting speed is 2.6-2.8m / min, and the water volume in the crystallizer is 145-160m3 / h, and the secondary cooling water rate was 1.5~1.7L / kg, and the molten steel in step C was cast into square billets with a cross-section of 165mm×165mm.

[0015] In step A, the chemical composition of the scrap steel is: C 0.10-0.26 wt%, Si 0.20-0.80 wt%, Mn 0.35-1.60 wt%, P ≤ 0.045 wt%, S ≤ 0.045 wt%, and the remainder is Fe and unavoidable impurities; The chemical composition of the pig iron is: C 3.5-4.4wt%, Si≤1.60wt%, Mn≤1.60wt%, P≤0.150wt%, S≤0.060wt%, and the rest is Fe and inevitable impurities.

[0016] In step B, the active lime has a particle size of 10-50 mm and a chemical composition of CaO 88.7%, SiO2 1.85%, MgO 3.45%, P 0.085%, S 0.065%, and the remainder being unavoidable impurities.

[0017] In step D, the secondary cooling water distribution adopts the full water cooling mode.

[0018] In step D, R9m7 7-strand billet continuous casting machine is used for casting.

[0019] Example 1 A. Converter smelting: molten iron (chemical composition: C 4.1wt%, Si 0.20wt%, Mn 0.20wt%, P 0.050wt%, S 0.030wt%, the rest are Fe and inevitable impurities), scrap steel (chemical composition: C 0.10wt%, Si 0.20wt%, Mn 0.35wt%, P 0.030wt%, S 0.030wt%, the rest are Fe and inevitable impurities) and pig iron (chemical composition: C 3.5wt%, Si 0.50wt%, Mn 0.30wt%, P 0.080wt%, S 0.030wt%, the rest being Fe and unavoidable impurities) is added into the LD converter for conventional top and bottom combined blowing, lime and light-burned dolomite are added in conventional amounts to form slag, the end point carbon content is controlled to be 0.06wt%, and the tapping temperature is controlled at 1590℃; after the molten steel from the converter is tapped, it is towed to the argon blowing station by a ladle car, the temperature of the molten steel is measured, samples are taken and hoisted to the LF furnace, and the temperature of the molten steel at the argon station is controlled to be 1520℃.

[0020] B. Adding the first batch of material to the LF furnace: Control the temperature of the molten steel entering the LF furnace in step A to 1510℃, lift the molten steel from the converter from the argon blowing station to the LF furnace refining station, connect the argon belt, turn on the argon gas and blow it at a rate of 150NL / min for 2 minutes, and add the following materials to the ladle in sequence: 钢 The amount of slag steel particles with a particle size of 1-10mm is added in the following mass ratio: TFe45.0wt%, FeO10.0wt%, Fe2O350.0wt%, SiO211.0wt%, CaO22.0wt%, MgO 6.0wt%, Al2O32.0wt%, MnO3.5wt%, MFe 45.0wt%, S0.080wt%, P 0.700wt%, and the rest is Fe and unavoidable impurities; at 4.0kg / t 钢 The amount of active lime with a particle size of 10-50 mm and the following mass ratio is added: CaO 88.7%, SiO21.85%, MgO3.45%, P 0.085%, S 0.065%, and the rest are unavoidable impurities.

[0021] C. Power supply LF to increase temperature and adjust composition of molten steel: Set the lower electrode of molten steel in step B to level 3 for slagging; power on for 10 minutes, lift the electrode to observe the slagging situation in the furnace, then measure the temperature and take samples; if the slag is too thin, add 1.0kg / t of lime 钢 The slag basicity (R) is controlled at 1.3. If it is below this level, refined slag and fluorite are added to adjust the slag fluidity. Upon steel sample analysis, alloys are added based on the results to adjust the molten steel's chemical composition to meet acceptable standards. The molten steel is then heated to 1565°C and hoisted to the casting station. The total power supply time for the lower electrode in this furnace to heat the molten steel is 12 minutes. The slag mass composition after LF refining is: TFe 2.3wt%, SiO2 28.0wt%, CaO 36.0wt%, with the remainder being unavoidable impurities.

[0022] D. Molten steel casting: The tundish temperature is 1525℃, the casting speed is 2.8m / min, and the water volume in the crystallizer is 160m 3 / h control, the secondary cooling water distribution adopts full water cooling mode, the water volume is controlled at 1.5L / kg, and the R9m7 machine 7-strand billet continuous casting machine is used to cast the molten steel in step C into billets with a cross-section of 165mm×165mm.

[0023] Example 2 A. Converter smelting: molten iron (chemical composition: C 4.4wt%, Si 0.50wt%, Mn 0.38wt%, P 0.070wt%, S 0.040wt%, the rest are Fe and inevitable impurities), scrap steel (chemical composition: C 0.19wt%, Si 0.50wt%, Mn 1.00wt%, P 0.040wt%, S 0.040wt%, the rest are Fe and inevitable impurities) and pig iron (chemical composition: C 3.9wt%, Si 1.00wt%, Mn 1.00wt%, P 0.120wt%, S 0.040wt%, the rest being Fe and unavoidable impurities) is added to the LD converter for conventional top and bottom combined blowing, lime and light-burned dolomite are added in conventional amounts to form slag, the end point carbon content is controlled to be 0.09wt%, and the tapping temperature is controlled at 1605℃; after the molten steel from the converter is tapped, it is towed to the argon blowing station by a ladle car, the temperature of the molten steel is measured, samples are taken and hoisted to the LF furnace, and the temperature of the molten steel at the argon station is controlled to be 1535℃.

[0024] B. Adding the first batch of material to the LF furnace: Control the temperature of the molten steel entering the LF furnace in step A to 1525℃, lift the molten steel from the converter from the argon blowing station to the LF furnace refining station, connect the argon belt, turn on the argon gas and blow it at a rate of 200NL / min for 2 minutes, and add the following materials to the ladle in sequence: 钢 The amount of slag steel particles with a particle size of 1-10 mm is added in the following mass ratio: TFe 58.0wt%, FeO 18.0wt%, Fe2O3 62.0wt%, SiO2 13.0wt%, CaO 25.0wt%, MgO 7.5wt%, Al2O3 3.2wt%, MnO 4.0wt%, MFe 52.0wt%, S 0.100wt%, P 0.900wt%, and the rest is Fe and unavoidable impurities; at 3.0kg / t 钢 The amount of active lime with a particle size of 10-50 mm and the following mass ratios: CaO 88.7%, SiO2 1.85%, MgO 3.45%, P 0.085%, S 0.065%, and the rest are unavoidable impurities.

[0025] C. Power supply to LF to increase temperature and adjust composition of molten steel: Set the electrode under the molten steel in step B to level 4 for slagging; power on for 7 minutes, lift the electrode to observe the slagging situation in the furnace, then measure the temperature and take samples; if the slag is too thin, add 1.5kg / t lime 钢The slag basicity (R) is controlled at 1.8. If it is below this level, refined slag and fluorite are added to adjust the slag fluidity. Upon steel sample analysis, alloys are added based on the results to adjust the molten steel's chemical composition to acceptable levels. The molten steel is then heated to 1575°C and hoisted to the casting station. The total power supply time for the lower electrode in this furnace to heat the molten steel is 14 minutes. The slag mass composition after LF refining is: TFe 2.3wt%, SiO2 24.0wt%, CaO 43.0wt%, with the remainder being unavoidable impurities.

[0026] D. Molten steel casting: The tundish temperature is 1535℃, the casting speed is 2.7m / min, and the water volume in the crystallizer is 160m 3 / h control, the secondary cooling water distribution adopts full water cooling mode, the water volume is controlled at 1.6L / kg, and the R9m7 machine 7-strand billet continuous casting machine is used to cast the molten steel in step C into billets with a cross-section of 165mm×165mm.

[0027] Example 3 A. Converter smelting: molten iron (chemical composition: C 4.6wt%, Si 0.70wt%, Mn 0.45wt%, P 0.090wt%, S 0.050wt%, the rest are Fe and inevitable impurities), scrap steel (chemical composition: C 0.26wt%, Si 0.80wt%, Mn 1.60wt%, P 0.045wt%, S 0.045wt%, the rest are Fe and inevitable impurities) and pig iron (chemical composition: C 4.4wt%, Si 1.60wt%, Mn 1.60wt%, P 0.150wt%, S 0.060wt%, the rest being Fe and unavoidable impurities) is added into the LD converter for conventional top and bottom combined blowing, lime and light-burned dolomite are added in conventional amounts to form slag, the end point carbon content is controlled to be 0.12wt%, and the tapping temperature is controlled at 1620℃; after the molten steel from the converter is tapped, it is towed to the argon blowing station by a ladle car, the temperature of the molten steel is measured, samples are taken and hoisted to the LF furnace, and the temperature of the molten steel at the argon station is controlled to be 1550℃.

[0028] B. Adding the first batch of material to the LF furnace: Control the temperature of the molten steel entering the LF furnace at 1540℃ in step A, lift the molten steel from the converter from the argon blowing station to the LF furnace refining station, connect the argon belt, turn on the argon gas and blow it at a rate of 250NL / min for 2 minutes, and add the following materials to the ladle in sequence: 钢The amount of slag steel particles with a particle size of 1-10 mm is added in the following mass ratio: TFe 70.0wt%, FeO25.0wt%, Fe2O375.0wt%, SiO215.0wt%, CaO31.0wt%, MgO 9.0wt%, Al2O34.5wt%, MnO4.5wt%, MFe 60.0wt%, S0.140wt%, P 1.200wt%, and the rest is Fe and unavoidable impurities; at 2.0kg / t 钢 The amount of active lime with a particle size of 10-50 mm and the following mass ratio is added: CaO 88.7%, SiO21.85%, MgO3.45%, P 0.085%, S 0.065%, and the rest are unavoidable impurities.

[0029] C. Power supply to LF to increase temperature and adjust composition of molten steel: Set the electrode under the molten steel in step B to level 6 for slagging; power on for 5 minutes, lift the electrode to observe the slagging situation in the furnace, then measure the temperature and take samples; if the slag is too thin, add 2.0kg / t of lime 钢 The slag basicity (R) is controlled at 2.3. If the slag basicity is below 2.3, refined slag and fluorite are added to adjust the slag fluidity. After the steel sample analysis results are available, alloys are added based on the results to adjust the chemical composition of the molten steel to meet the required standards. The molten steel is then heated to 1585°C and hoisted to the casting station. The total power supply time for the lower electrode of the furnace to heat the molten steel is 12 minutes. The slag mass composition after LF refining is: TFe 2.5wt%, SiO2 20.0wt%, CaO 46.0wt%, with the remainder being unavoidable impurities.

[0030] D. Molten steel casting: The tundish temperature is 1545℃, the casting speed is 2.6m / min, and the water volume in the crystallizer is 160m 3 / h control, the secondary cooling water distribution adopts full water cooling mode, the water volume is controlled at 1.7L / kg, and the R9m7 machine 7-strand billet continuous casting machine is used to cast the molten steel in step C into billets with a cross-section of 165mm×165mm.

[0031] Comparative Example 1 A. Converter smelting: molten iron (chemical composition: C 4.6wt%, Si 0.70wt%, Mn 0.45wt%, P 0.090wt%, S 0.050wt%, the rest are Fe and inevitable impurities), scrap steel (chemical composition: C 0.26wt%, Si 0.80wt%, Mn 1.60wt%, P 0.045wt%, S 0.045wt%, the rest are Fe and inevitable impurities) and pig iron (chemical composition: C 4.4wt%, Si 1.60wt%, Mn 1.60wt%, P 0.150wt%, S 0.060wt%, the rest being Fe and unavoidable impurities) is added into the LD converter for conventional top and bottom combined blowing, lime and light-burned dolomite are added in conventional amounts to form slag, the end point carbon content is controlled to be 0.12wt%, and the tapping temperature is controlled at 1620℃; after the molten steel from the converter is tapped, it is towed to the argon blowing station by a ladle car, the temperature of the molten steel is measured, samples are taken and hoisted to the LF furnace, and the temperature of the molten steel at the argon station is controlled to be 1550℃.

[0032] B. Adding the first batch of material to the LF furnace: Control the temperature of the molten steel entering the LF furnace at 1540℃ in step A, lift the molten steel from the converter from the argon blowing station to the LF furnace refining station, connect the argon belt, turn on the argon gas and blow it at a rate of 250NL / min for 2 minutes, and add the following materials to the ladle in sequence: 钢 The amount of active lime with a particle size of 10-50 mm and the following mass ratio: CaO 88.7%, SiO21.85%, MgO3.45%, P 0.085%, S 0.065%, the rest are inevitable impurities; at 2.0 kg / t 钢 The amount of pre-melted refined slag with a particle size of 10-50 mm is added in the following mass ratio: SiO23.0wt%, CaO41.0wt%, MgO 3.0wt%, Al2O335.1wt%, FeO0.30wt%, and the rest are inevitable impurities.

[0033] C. Power supply to LF to increase temperature and adjust composition of molten steel: Set the lower electrode of molten steel in step B to level 6 for slagging; power on for 7 minutes, lift the electrode to observe the slagging situation in the furnace, then measure the temperature and take samples; if the slag is too thin, add 2.0kg / t of lime 钢 The slag basicity (R) is controlled at 2.3. If the slag basicity is too low, refined slag and fluorite are added to adjust the slag fluidity. Upon steel sample analysis, alloys are added based on the results to adjust the molten steel's chemical composition to acceptable levels. The molten steel is then heated to 1585°C and hoisted to the casting station. The total heating time for the lower electrode in this furnace is 14 minutes. The slag mass composition after LF refining is: TFe 2.5wt%, SiO2 20.0wt%, CaO 46.0wt%, with the remainder being unavoidable impurities.

[0034] D. Molten steel casting: The tundish temperature is 1545℃, the casting speed is 2.6m / min, and the water volume in the crystallizer is 160m 3 / h control, the secondary cooling water distribution adopts full water cooling mode, the water volume is controlled at 1.7L / kg, and the R9m7 machine 7-strand billet continuous casting machine is used to cast the molten steel in step C into billets with a cross-section of 165mm×165mm.

Claims

1. A method for refining HRB500E molten steel using a slag steel pellet slag making process in an LF furnace, characterized in that: To do this, follow these steps: A. Converter smelting: molten iron, scrap steel and pig iron are added to an LD converter and subjected to conventional top and bottom composite blowing. Lime and light-burned dolomite are added in conventional amounts to form slag, and the endpoint carbon content is controlled to be 0.06-0.12wt% and the tapping temperature is 1590-1620°C. After tapping, the molten steel is hoisted to an argon station processing station, the molten steel is temperature-measured, sampled and hoisted to an LF furnace, and the temperature of the molten steel entering the argon station is controlled to be 1520-1550°C. The chemical composition of the molten iron is: C 4.1-4.6wt%, Si 0.20-0.70wt%, Mn 0.20-0.45wt%, P 0.050-0.090wt%, S ≤ 0.050wt%, and the remainder is Fe and unavoidable impurities. B. Adding the first batch of steel to the LF furnace: The molten steel from step A is hoisted to the LF furnace for refining. Argon is blown at a rate of 150-250 NL / min for 2 minutes. Then, the argon is blown at a rate of 3.0-5.0 kg / t. 钢 , 2.0~4.0kg / t 钢 Slag steel particles and active lime are added to the ladle in sequence, wherein the slag steel particles have a particle size of 1-10 mm and a chemical composition of: TFe 45.0-70.0 wt%, FeO 10.0-25.0 wt%, Fe2O3 50.0-75.0 wt%, SiO2 11.0-15.0 wt%, CaO 22.0-31.0 wt%, MgO 6.0-9.0 wt%, Al2O3 2.0-4.5 wt%, MnO 3.5-4.5 wt%, MFe 45.0-60.0 wt%, S≤0.140 wt%, P≤1.200 wt%, and the remainder is Fe and unavoidable impurities; the temperature of the molten steel entering the LF furnace is controlled to be 1510-1540° C.; C. LF power supply temperature increase and composition adjustment: In step B, the electrode under the molten steel is set to gear 3 to 6 to slag; after 5-10 minutes of power on, lift the electrode to observe the slag in the furnace, then measure the temperature and take samples; if the slag is too thin, add 1.0-2.0 kg / t of lime 钢 , control the binary basicity R of the slag to 1.3-2.3, otherwise add refined slag and fluorite to adjust the fluidity of the slag liquid; after the steel sample analysis results are available, add alloys according to the steel sample analysis results to adjust the chemical composition of the molten steel to meet the requirements; then heat the molten steel to 1565-1585℃ and hoist it to the casting station; the total power supply time for the lower electrode of the molten steel to heat up is 12-16 minutes; the mass ratio of the slag after LF refining is: TFe2.0-2.5wt%, SiO2 20.0-28wt%, CaO 36.0-46.0wt%, and the rest are unavoidable impurities; D. Molten steel casting: The tundish temperature is 1525-1545℃, the casting speed is 2.6-2.8m / min, and the water volume in the crystallizer is 145-160m 3 / h, and the secondary cooling water rate is 1.5~1.7L / kg, the molten steel in step C is cast into square billets with a cross-section of 165mm×165mm.

2. The method for refining HRB500E molten steel by using slag steel pellet slag making process in LF furnace according to claim 1, characterized in that: In step A, the chemical composition of the scrap steel is: C 0.10-0.26wt%, Si 0.20-0.80wt%, Mn 0.35-1.60wt%, P ≤0.045wt%, S ≤0.045wt%, and the remainder is Fe and inevitable impurities; The chemical composition of the pig iron is: C 3.5-4.4wt%, Si ≤1.60wt%, Mn ≤1.60wt%, P ≤0.150wt%, S ≤0.060wt%, and the rest is Fe and inevitable impurities.

3. The method for refining HRB500E molten steel by using slag steel pellet slag making process in LF furnace according to claim 1, characterized in that: In step B, the active lime has a particle size of 10-50 mm and a chemical composition of CaO 88.7%, SiO2 1.85%, MgO 3.45%, P 0.085%, S 0.065%, and the remainder is unavoidable impurities.

4. The method for refining HRB500E molten steel by using slag steel pellet slag making process in LF furnace according to claim 1, characterized in that: In step D, the secondary cooling water distribution adopts the full water cooling mode.

5. The method for refining HRB500E molten steel by using slag steel pellet slag making process in LF furnace according to claim 1, characterized in that: In step D, R9m7 7-strand billet continuous casting machine is used for casting.