A method for smelting DC04 steel in an electric arc furnace and an oxygen lance device for the electric arc furnace.

Abstract

This application provides a method for smelting DC04 steel in an electric arc furnace and an oxygen lance device for the electric arc furnace, relating to the metallurgical field. The method for smelting DC04 steel in an electric arc furnace includes: a raw material feeding stage, a pre-melting stage of raw material melting, a post-melting stage of raw material melting, an oxidation and heating stage after the raw material is saturated, a tapping stage, an RH refining stage, a stage after the pure circulation treatment is completed, and a steel casting stage. The method provided in this application achieves multi-functional rapid switching through a single lance body, solving the problems of traditional oxygen lances having single functions and complex switching. It can effectively shorten the smelting cycle, reduce power consumption per ton of steel, and improve the efficiency of metallurgical reactions such as dephosphorization. It is applicable to multi-stage smelting processes in electric arc furnaces of different capacities, and in particular, can meet the stringent control requirements for phosphorus and carbon content in the tapped steel of DC04 steel.

Description

Technical Field

[0001] This application relates to the field of metallurgy, and more particularly to a method for smelting DC04 steel in an electric arc furnace and an oxygen lance apparatus for the electric arc furnace. Background Technology

[0002] Electric arc furnace (EAF) short-process smelting is one of the core technological routes for producing DC04 ultra-low carbon automotive steel. DC04 steel requires a carbon content ≤0.0025%, a phosphorus content ≤0.005%, and a nitrogen content ≤0.0030%, and demands extremely high purity in the molten steel. As the primary smelting stage in this process, the EAF plays a crucial role in scrap melting, primary decarburization, and deep dephosphorization. Its smelting efficiency and energy consumption are directly constrained by the performance of the oxygen supply equipment and the kinetic conditions of the slag-forming and dephosphorization process.

[0003] With the widespread use of multi-source furnace charges such as scrap steel, molten iron, and direct reduced iron (DRI) in electric arc furnaces, the complexity of the furnace charge structure places higher demands on oxygen injection equipment. In existing technologies, electric arc furnace slag formation and dephosphorization often employs slag-forming materials such as block lime. Block lime needs to penetrate the slag layer to fully contact the molten steel and oxidizing components. Its slag formation process relies on oxides gradually penetrating from the outside in, resulting in a long mass transfer path and slow reaction interface renewal, thus prolonging the slag formation and dephosphorization cycle. Even with the addition of supersonic oxygen jets to agitate the steel-slag interface, the block slag-forming material still needs to be repeatedly entrained into the interface region under the jet's action to gradually complete the dephosphorization reaction, limiting interface renewal efficiency and reaction rate. For DC04 steel, which requires a phosphorus content ≤0.005% and a carbon content ≤0.05%, deep dephosphorization must be completed within the electric arc furnace. However, existing slag-forming methods struggle to achieve stable and efficient dephosphorization results in a short time. Especially when the furnace charge contains a high proportion of direct reduced iron (DRI), because DRI has a low density and easily floats on the surface of the slag layer, it is prone to forming incompletely melted agglomerates, hindering heat transfer to the molten pool and further prolonging the melting stage. This "iceberg effect" not only exacerbates the fluctuations in the smelting cycle but also increases the difficulty of controlling the homogenization of the molten pool, adversely affecting the stable control of phosphorus content in DC04 steel.

[0004] As the core equipment for oxygen injection, enhanced molten pool stirring, and mass and heat transfer in electric arc furnaces, the oxygen lance's injection capability directly affects slag formation efficiency and dephosphorization kinetics. However, existing oxygen lances mostly use supersonic oxygen jet injection, which is insufficient in carrying and accelerating solid powders (such as lime powder). They generally suffer from the following technical defects: poor gas-solid two-phase synergy, large divergence angle and low effective kinetic energy of the powder in the jet, making it difficult to efficiently penetrate the slag layer and accurately inject it into the reaction interface, resulting in low lime powder utilization and limited dephosphorization efficiency; low functional integration, with most devices having a single function, making it difficult to achieve coordinated switching between supersonic oxygen jet, gas-solid two-phase jet, and oxygen burner (heating / flushing) modes on the same equipment, failing to meet the differentiated needs for oxygen supply and slag formation at different stages of DC04 steel smelting; and weak adaptability to operating conditions, lacking the ability to quickly and reliably switch between different smelting stages, making it difficult to meet the diverse process requirements such as scrap preheating, DRI rapid melting, enhanced dephosphorization, and heating stirring.

[0005] Analysis of existing patent literature, such as CN2406204Y, CN201548065U, and CN105950824A, primarily involves oxygen lance injection or multi-functional lance structures. However, these solutions are generally based on conventional injection and lack an integrated and efficient switching system solution for supersonic oxygen jets, high-efficiency gas-solid injection, and oxygen burner operation. For the production of DC04 steel, electric arc furnace tapping requires carbon content control at 0.03%-0.05% and phosphorus content ≤0.005%. This necessitates differentiated oxygen supply and slag-forming strategies at different stages, including melting, dephosphorization, and decarburization. Existing oxygen lance equipment suffers from low functional integration and slow switching response, making smooth transitions between stages difficult, leading to prolonged smelting cycles and increased compositional fluctuations.

[0006] In summary, existing oxygen lance equipment has significant shortcomings in handling complex multi-source furnace materials, improving dephosphorization efficiency, and shortening the smelting cycle. It struggles to meet the stringent requirements of DC04 ultra-low carbon automotive steel for phosphorus content, carbon content, and smelting pace in electric arc furnaces. There is an urgent need for a multi-functional oxygen lance that integrates supersonic oxygen jet, supersonic gas-solid jet, and oxygen burner functions, with the ability to rapidly switch between multiple modes, and its efficient injection method. This would enable multi-mode synergistic injection, improve powder utilization and slag dephosphorization efficiency, and meet the process requirements for rapid and efficient smelting of high-grade steels such as DC04 in electric arc furnaces under complex raw material conditions. Summary of the Invention

[0007] The purpose of this application is to provide a method for smelting DC04 steel in an electric arc furnace and an oxygen lance apparatus for an electric arc furnace, so as to solve the above-mentioned problems.

[0008] To achieve the above objectives, this application adopts the following technical solution: A method for smelting DC04 steel in an electric arc furnace includes: S1: During the stage of adding raw materials, including one or more of scrap steel, molten iron, and direct reduced iron, to the electric arc furnace, the oxygen lance of the electric arc furnace is controlled to be in oxygen combustion nozzle injection mode; the oxygen lance includes an oxygen lance shell body, a Raoul nozzle sleeved in the oxygen lance shell body, a pull-out central gas-solid nozzle sleeved in the Raoul nozzle, and a flow-around oxygen channel, an annular gap gas channel, and an annular gap oxygen channel. The outlet end of the trolley-type central gas-solid nozzle is far from the throat of the Raoult nozzle; S2: In the early stage of the raw material melting, the oxygen lance is in supersonic gas-solid jet mode, and the outlet end of the pump-type central gas-solid nozzle is advanced to the throat of the Raoul nozzle. S3: In the later stage of the raw material melting, the oxygen lance is in supersonic gas-solid jet mode, and the outlet end of the pump-type central gas-solid nozzle is kept at the throat of the Raoul nozzle. S4: The oxidation and heating stage after the raw material is dissolved and cleared, wherein the oxygen lance is in supersonic gas-solid jet mode; S5: Rapid heating stage, the temperature of molten steel is rapidly raised to the tapping temperature of the target steel grade within 2-5 minutes. The oxygen lance is in supersonic oxygen jet mode, and the outlet end of the pump-type central gas-solid nozzle is pulled out from the throat of the Raoult nozzle. S6: During the electric arc furnace tapping stage, the molten steel reaches the tapping temperature of the target steel grade. The oxygen lance is in supersonic oxygen jet mode, and the outlet end of the pump-type central gas-solid nozzle is kept away from the throat of the Raoult nozzle. S7: RH refining stage, start the vacuum pump and reduce the vacuum chamber pressure to 80Pa within 5 minutes; circulate argon gas at the first flow rate, and perform vacuum decarburization to reduce the carbon content; then add aluminum particles for deoxidation, and after deoxidation, add titanium-iron alloy for pure circulation at the second flow rate. S8: After the pure circulation process is completed, the vacuum pump is turned off, and argon or nitrogen is introduced into the vacuum chamber to break the air. After breaking the air, the temperature of the molten steel is measured and samples are taken to test the temperature, carbon content, nitrogen content and oxygen activity of the molten steel. After the test is qualified, the ladle is hoisted to the continuous casting process for casting. S9: Steel casting stage; control the temperature of the ladle entering the station, preheat the tundish and perform argon blowing and oxygen removal treatment, add calcium line to the tundish for the first furnace to prevent nozzle blockage; molten steel is injected into the tundish through the long nozzle argon seal, and the temperature and liquid level fluctuation range of the molten steel in the tundish are controlled. Molten steel is injected into the crystallizer through an immersion nozzle. The fluctuation range of the liquid level in the crystallizer is controlled by non-sinusoidal vibration, electromagnetic stirring is applied to the crystallizer, and water cooling is carried out simultaneously.

[0009] Preferably, in step S1, the oxygen flow rate of the pump-type central gas-solid nozzle is 500-1000 m³ / h. 3 The flow rate of lime powder is 0 kg / min, and the oxygen flow rate of the oxygen channel is 500-1000 m³ / h. 3 / h, the gas flow rate of the annular joint gas channel is 150-250m³ / h. 3 The oxygen flow rate of the annular oxygen channel is 300-550 m³ / h. 3 / h.

[0010] Preferably, in step S2, the oxygen flow rate of the pump-type central gas-solid nozzle is 800-1000 m³ / h. 3 The flow rate of lime powder is 30-45 kg / min, and the oxygen flow rate of the oxygen channel is 1000-1500 m³ / h. 3 / h, the gas flow rate of the annular joint gas channel is 150-300m³ / h. 3 / h, the oxygen flow rate of the annular oxygen channel is 300-600 m³ / h. 3 / h.

[0011] Preferably, in step S3, the oxygen flow rate of the pump-type central gas-solid nozzle is 800-1200 m³ / h. 3 The flow rate of lime powder is 30-45 kg / min, and the oxygen flow rate of the oxygen channel is 1200-1800 m³ / h. 3 / h, the gas flow rate of the annular joint gas channel is 200-300m³ / h. 3 / h, the oxygen flow rate of the annular oxygen channel is 400-600 m³ / h. 3 / h.

[0012] Preferably, in step S4, the outlet end of the traction-type central gas-solid nozzle is maintained at the throat of the Raoult nozzle; the oxygen flow rate of the traction-type central gas-solid nozzle is 800-1200 m³ / h. 3 The flow rate of lime powder is 60-120 kg / min, and the oxygen flow rate of the oxygen channel is 1600-2000 m³ / h. 3 / h, the gas flow rate of the annular joint gas channel is 200-300m³ / h. 3 / h, the oxygen flow rate of the annular oxygen channel is 400-600 m³ / h. 3 / h.

[0013] Preferably, in step S5, the oxygen flow rate of the pump-type central gas-solid nozzle is 800-1200 m³ / h. 3 The flow rate of lime powder is 0 kg / min, and the oxygen flow rate of the oxygen channel is 1600-2000 m³ / h. 3 / h, the gas flow rate of the annular joint gas channel is 200-300m³ / h. 3 / h, the oxygen flow rate of the annular oxygen channel is 400-600 m³ / h. 3 / h.

[0014] Preferably, in step S6, the oxygen flow rate of the pump-type central gas-solid nozzle is 100-200 m³ / h. 3 The flow rate of lime powder is 0 kg / min, and the oxygen flow rate of the oxygen channel is 50-100 m³ / h. 3 / h, the gas flow rate of the annular gas channel is 25-50m³ / h. 3 / h, the oxygen flow rate of the annular oxygen channel is 50-100 m³ / h. 3 / h.

[0015] Preferably, the method for smelting DC04 steel in an electric arc furnace satisfies one or more of the following conditions: (1) The first flow rate is 1500-2000 m³ / h 3 / h, the second flow rate is 1000-1500 Nm 3 / h; (2) The temperature of the ladle entering the station is 1580-1610℃; (3) The intermediate ladle is preheated to 1100-1200℃; (4) The argon flow rate of the argon seal is 100-200 L / min; (5) The temperature of the molten steel in the tundish is 1550-1580℃; (6) The liquid level fluctuation in the intermediate tundish is controlled within ±5mm; (7) The depth to which the immersion nozzle is inserted into the crystallizer is 120-150 mm; (8) The liquid level fluctuation in the crystallizer is controlled within ±3mm; (9) The frequency of the non-sinusoidal vibration is 120-180 times / min, and the amplitude is 3-6 mm; (10) The parameters of the electromagnetic stirring are 300-500A and 2-5Hz; (11) The consumption of protective slag in the crystallizer is 0.4-0.6 kg / m³. 2 .

[0016] This application also provides an electric arc furnace oxygen lance apparatus for performing the method of smelting DC04 steel in an electric arc furnace.

[0017] Preferably, the electric arc furnace oxygen lance device satisfies one or more of the following conditions: (1) The outer shell diameter of the electric arc furnace oxygen lance device is 150-250 mm; (2) The diameter of the pump-type central gas-solid nozzle is 10-20 mm and the wall thickness is 3-5 mm; (3) The electric arc furnace oxygen lance device also includes an inlet and outlet water cooling device for conveying cooling water, with a cooling water pressure of 0.2-0.8 MPa; (4) The pressure of the oxygen flow channel is 0.6-1.5 MPa, and the pressure of the pump-type central gas-solid injection pipeline is 0.7-1.6 MPa.

[0018] Compared with the prior art, the beneficial effects of this application include: The method for smelting DC04 steel in an electric arc furnace provided in this application is intended to serve the production and efficient smelting of DC04 steel in 50-220t electric arc furnaces. Its application scenarios are particularly suitable for the smelting process of DC04 steel in electric arc furnaces with complex steelmaking raw material composition. The electric arc furnace oxygen lance device provided in this application features a retractable central gas-solid nozzle, which allows for adjustment of the supersonic gas-solid injection mode, supersonic oxygen injection mode, and oxygen combustion nozzle mode by changing the outlet position of the retractable central gas-solid nozzle. Compared with traditional electric arc furnace steelmaking processes, the multi-functional oxygen lance and its efficient injection method in this application can achieve alternating supersonic oxygen jet, supersonic gas-solid jet, and oxygen-fuel jet, increasing oxygen lance life by 20-60%, reducing lime consumption per ton of steel by more than 10%, increasing dephosphorization rate by 5-10%, increasing metal yield by more than 2%, shortening the smelting cycle by 3-8 minutes, and reducing power consumption per ton of steel by 3-10 kWh. This invention can efficiently produce DC04 steel, which has stringent requirements for phosphorus and carbon content. While ensuring the production of high-quality steel, it significantly improves smelting efficiency and has good industrial application prospects. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0020] Figure 1 This is a cross-sectional schematic diagram of the electric arc furnace oxygen lance device provided in Example 1; Figure 2 This is a schematic diagram of the AA-direction cross-section of the electric arc furnace oxygen lance device provided in Example 1.

[0021] Figure label: 1-Oxygen lance outer shell; 2-Raoult nozzle; 3-Pull-out central gas-solid nozzle; 4-Oxygen flow channel; 5-Annular slit gas flow channel; 6-Annular slit oxygen flow channel; 7-Cooling water inlet channel; 8-Cooling water return channel; 9-Oxygen flow outlet; 10-Central powder gas flow outlet; 11-Annular slit oxygen outlet; 12-Annular slit gas flow outlet. Detailed Implementation

[0022] To better illustrate the technical solution provided in this application, the technical solution will be described in its entirety before the embodiments, as follows: A method for smelting DC04 steel in an electric arc furnace includes: S1: During the stage of adding raw materials, including scrap steel, molten iron, and direct reduced iron, to the electric arc furnace, the oxygen lance of the electric arc furnace is controlled to be in oxygen combustion nozzle injection mode; the oxygen lance includes an oxygen lance shell body, a Raoult nozzle (used for gas acceleration and forming an enveloping structure, a key part for forming an enveloping jet, with a Mach number designed between 1.6 and 2.2) sleeved in the Raoult nozzle, a pull-out central gas-solid nozzle, and a flow-around oxygen channel, an annular gap gas channel, and an annular gap oxygen channel; The outlet end of the trolley-type central gas-solid nozzle is far from the throat of the Raoult nozzle; S2: In the early stage of the raw material melting, the oxygen lance is in supersonic gas-solid jet mode, and the outlet end of the pump-type central gas-solid nozzle is advanced to the throat of the Raoul nozzle. S3: In the later stage of the raw material melting, the oxygen lance is in supersonic gas-solid jet mode, and the outlet end of the pump-type central gas-solid nozzle is kept at the throat of the Raoul nozzle. S4: The oxidation and heating stage after the raw material is dissolved and cleared, wherein the oxygen lance is in supersonic gas-solid jet mode; S5: Rapid heating stage, the temperature of molten steel is rapidly raised to the tapping temperature of the target steel grade within 2-5 minutes. The oxygen lance is in supersonic oxygen jet mode, and the outlet end of the pump-type central gas-solid nozzle is pulled out from the throat of the Raoult nozzle. S6: During the electric arc furnace tapping stage, the molten steel reaches the tapping temperature of the target steel grade. The oxygen lance is in supersonic oxygen jet mode, and the outlet end of the pump-type central gas-solid nozzle is kept away from the throat of the Raoult nozzle. S7: RH refining stage, start the vacuum pump and reduce the vacuum chamber pressure to 80Pa within 5 minutes; circulate argon gas at the first flow rate, and perform vacuum decarburization to reduce the carbon content; then add aluminum particles for deoxidation, and after deoxidation, add titanium-iron alloy for pure circulation at the second flow rate. S8: After the pure circulation process is completed, the vacuum pump is turned off, and argon or nitrogen is introduced into the vacuum chamber to break the air. After breaking the air, the temperature of the molten steel is measured and samples are taken to test the temperature, carbon content, nitrogen content and oxygen activity of the molten steel. After the test is qualified, the ladle is hoisted to the continuous casting process for casting. S9: Steel casting stage; control the temperature of the ladle entering the station, preheat the tundish and perform argon blowing and oxygen removal treatment, add calcium line to the tundish for the first furnace to prevent nozzle blockage; molten steel is injected into the tundish through the long nozzle argon seal, and the temperature and liquid level fluctuation range of the molten steel in the tundish are controlled. Molten steel is injected into the crystallizer through an immersion nozzle. The fluctuation range of the liquid level in the crystallizer is controlled. Non-sinusoidal vibration is used, and electromagnetic stirring is applied to the crystallizer. At the same time, water cooling is carried out (for example, following the principle of weak cooling, by controlling the flow rate of cooling water in the range of 6.0-8.0 m / s, the latent heat of solidification of the molten steel is removed to form a uniform initial shell).

[0023] In an optional embodiment, in step S1, the oxygen flow rate of the pump-type central gas-solid nozzle is 500-1000 m³ / h. 3 / h (can be 500m) 3 / h, 600m 3 / h, 700m 3 / h、800m 3 / h、900m 3 / h, 1000m 3 / h or 500-1000m 3 The flow rate of lime powder is 0 kg / min, and the oxygen flow rate of the oxygen channel is 500-1000 m³ / h (any value between / h). 3 / h (can be 500m) 3 / h, 600m 3 / h, 700m 3 / h、800m 3 / h、900m 3 / h, 1000m 3 / h or 500-1000m 3 The gas flow rate of the annular gas passage is 150-250 m³ / h (any value between / h). 3 / h (can be 150m) 3 / h、200m 3 / h, 250m 3 / h or 150-250m 3 The oxygen flow rate of the annular oxygen channel is 300-550 m³ / h (any value between / h). 3 / h (can be 300m) 3 / h, 350m 3 / h, 400m 3 / h, 450m 3 / h, 500m 3 / h, 550m 3 / h or 300-550 m 3 (any value between / h).

[0024] In step S1, large pieces of scrap steel are rapidly cut and preheated by a high-temperature combustion flame, accelerating the melting of the scrap steel.

[0025] In an optional embodiment, in step S2, the oxygen flow rate of the pump-type central gas-solid nozzle is 800-1000 m³ / h. 3 / h (can be 800m) 3 / h、900m 3 / h, 1000m 3 / h or 800-1000m 3 The flow rate of lime powder is 30-45 kg / min (can be any value between 30 kg / min, 35 kg / min, 40 kg / min, 45 kg / min or any value between 30-45 kg / min), and the oxygen flow rate of the surrounding oxygen channel is 1000-1500 m³ / min. 3 / h (can be 1000m) 3 / h、1100m 3 / h, 1200m 3 / h, 1300m 3 / h, 1400m 3 / h, 1500m 3 / h or 1000-1500m 3 The gas flow rate of the annular gas passage is 150-300 m³ / h (any value between / h). 3 / h (can be 150m) 3 / h、200m 3 / h, 250m 3 / h, 300m 3 / h or 150-300m 3 The oxygen flow rate of the annular oxygen channel is 300-600 m³ / h (any value between / h). 3 / h (can be 300m) 3 / h, 400m 3 / h, 500m 3 / h, 600m 3 / h or 300-600 m 3 (any value between / h).

[0026] In the early stage of steelmaking raw material melting, the process mainly relies on electrical and chemical energy (oxygen supply) for heating and melting, and the ferrous oxide content in the slag gradually increases. By spraying a small amount of lime powder into the high-temperature reaction zone, foamy slag can be quickly formed to cover the molten pool, reducing heat loss.

[0027] In an optional embodiment, in step S3, the oxygen flow rate of the pump-type central gas-solid nozzle is 800-1200 m³ / h. 3 / h (can be 800m) 3 / h、900m 3 / h, 1000m 3 / h、1100m 3 / h, 1200m 3 / h or 800-1200m 3 The flow rate of lime powder is 30-45 kg / min (can be any value between 30 kg / min, 35 kg / min, 40 kg / min, 45 kg / min or any value between 30-45 kg / min), and the oxygen flow rate of the surrounding oxygen channel is 1200-1800 m³ / min. 3 / h (can be 1200m) 3 / h, 1300m 3 / h, 1400m 3 / h, 1500m 3 / h, 1600m 3 / h, 1700m 3 / h, 1800m 3 / h or 1200-1800m 3 The gas flow rate of the annular gas passage is 200-300 m³ / h (any value between / h). 3 / h (can be 200m) 3 / h, 250m 3 / h, 300m 3 / h or 200-300m 3 The oxygen flow rate of the annular oxygen channel is 400-600 m³ / h (any value between / h). 3 / h (can be 400m) 3 / h, 500m 3 / h, 600m 3 / h or 400-600 m 3 (any value between / h).

[0028] The later stage of steelmaking raw material melting is one of the important stages of dephosphorization. During this stage, the increased flow rate of lime powder, combined with the high-speed jet of oxygen, can quickly slag and accelerate the dephosphorization process, effectively increasing the phosphorus capacity of the molten slag.

[0029] In an optional embodiment, in step S4, the outlet end of the traction-type central gas-solid nozzle is maintained at the throat of the Raoult nozzle; the oxygen flow rate of the traction-type central gas-solid nozzle is 800-1200 m³ / h. 3 / h (can be 800m) 3 / h、900m 3 / h, 1000m 3 / h、1100m 3 / h, 1200m 3 / h or 800-1200m 3 The flow rate of lime powder is 60-120 kg / min (can be 60 kg / min, 70 kg / min, 80 kg / min, 90 kg / min, 100 kg / min, 110 kg / min, 120 kg / min or any value between 60-120 kg / min), and the oxygen flow rate of the surrounding oxygen channel is 1600-2000 m³ / min. 3 / h (can be 1600m) 3 / h, 1700m 3 / h, 1800m 3 / h, 1900m 3 / h、2000m 3 / h or 1600-2000m 3 The gas flow rate of the annular gas passage is 200-300 m³ / h (any value between / h). 3 / h (can be 200m) 3 / h, 250m 3 / h, 300m 3 / h or 200-300m 3 The oxygen flow rate of the annular oxygen channel is 400-600 m³ / h (any value between / h). 3 / h (can be 400m) 3 / h, 500m 3 / h, 600m 3 / h or 400-600m 3 (any value between / h).

[0030] The oxidation heating stage after melting and clearing is one of the main dephosphorization stages in the molten pool. During this stage, the ferrous oxide in the slag increases significantly. The injection of a large amount of lime powder can quickly melt in the impact zone and be used in the dephosphorization process, accelerating the dephosphorization reaction. In addition, the lime powder increases the jet kinetic energy, thereby increasing the oxygen decarburization rate.

[0031] In an optional embodiment, in step S5, the oxygen flow rate of the pump-type central gas-solid nozzle is 800-1200 m³ / h. 3 / h (can be 800, 900, 1000, 1100, 1200 or 800-1200m) 3 The flow rate of lime powder is 0 kg / min, and the oxygen flow rate of the oxygen channel is 1600-2000 m³ / h (any value between / h). 3 / h (can be 1600m) 3 / h, 1700m 3 / h, 1800m 3 / h, 1900m 3 / h、2000m 3 / h or 1600-2000m 3 The gas flow rate of the annular gas passage is 200-300 m³ / h (any value between / h). 3 / h (can be 200m) 3 / h, 250m 3 / h, 300m 3 / h or 200-300m 3 The oxygen flow rate of the annular oxygen channel is 400-600 m³ / h (any value between / h). 3 / h (can be 400m) 3 / h, 500m 3 / h, 600m 3 / h or 400-600 m 3 (any value between / h).

[0032] In this stage, the multi-functional oxygen lance mainly serves to oxidize and heat up, rapidly decarburize, and stir the molten pool evenly.

[0033] In an optional embodiment, in step S6, the oxygen flow rate of the pump-type central gas-solid nozzle is 100-200 m³ / h. 3 / h (can be 100m) 3 / h, 150m 3 / h、200m 3 / h or 100-200m 3 The flow rate of lime powder is 0 kg / min, and the oxygen flow rate of the oxygen channel is 50-100 m³ / h (any value between / h). 3 / h (can be 50m) 3 / h、60m 3 / h、70m 3 / h、80m 3 / h、90m 3 / h, 100m 3 / h or 50-100m 3 The gas flow rate of the annular gas passage is 25-50 m³ / h (any value between / h). 3 / h (can be 25m) 3 / h, 30m 3 / h, 35m 3 / h, 40m 3 / h, 45m 3 / h, 50m 3 / h or 25-50m 3 The oxygen flow rate of the annular oxygen channel is 50-100 m³ / h (any value between / h). 3 / h (can be 50m) 3 / h、60m 3 / h、70m 3 / h、80m 3 / h、90m 3 / h, 100m 3 / h or 50-100m 3 (any value between / h).

[0034] The low-flow gas supply to each gas channel during this stage is to prevent slag splashing and clogging of the nozzle.

[0035] In an optional embodiment, the method for smelting DC04 steel in an electric arc furnace satisfies one or more of the following conditions: (1) The first flow rate is 1500-2000 m³ / h 3 / h (can be 1500m) 3 / h, 1600m 3 / h, 1700m 3 / h, 1800m 3 / h, 1900m 3 / h、2000m 3 / h or 1500-2000m 3 (any value between / h), the second flow rate is 1000-1500 Nm 3 / h (can be 1000 Nm) 3 / h, 1100 Nm 3 / h, 1200 Nm 3 / h, 1300 Nm 3 / h, 1400 Nm 3 / h, 1500 Nm 3 / h or 1000-1500Nm 3 / h); (2) The ladle temperature entering the station is 1580-1610℃ (which can be any value between 1580℃, 1590℃, 1600℃, 1610℃ or 1580-1610℃). (3) The intermediate ladle is preheated to 1100-1200℃ (which can be any value between 1100℃, 1110℃, 1120℃, 1130℃, 1140℃, 1150℃, 1160℃, 1170℃, 1180℃, 1190℃, 1200℃ or 1100-1200℃). (4) The argon flow rate of the argon seal is 100-200 L / min (which can be any value between 100 L / min, 110 L / min, 120 L / min, 130 L / min, 140 L / min, 150 L / min, 160 L / min, 170 L / min, 180 L / min, 190 L / min, 200 L / min or 100-200 L / min). (5) The temperature of the molten steel in the tundish is 1550-1580℃ (which can be any value between 1550℃, 1560℃, 1570℃, 1580℃ or 1550-1580℃). (6) The liquid level fluctuation in the intermediate tundish is controlled within ±5mm; (7) The depth to which the immersion nozzle is inserted into the crystallizer is 120-150 mm (it can be any value between 120 mm, 130 mm, 140 mm, 150 mm or 120-150 mm). (8) The liquid level fluctuation in the crystallizer is controlled within ±3mm; (9) The frequency of the non-sinusoidal vibration is 120-180 times / min (which can be any value between 120 times / min, 130 times / min, 140 times / min, 150 times / min, 160 times / min, 170 times / min, 180 times / min or 120-180 times / min), and the amplitude is 3-6 mm (which can be any value between 3 mm, 4 mm, 5 mm, 6 mm or 3-6 mm). (10) The parameters of the electromagnetic stirring are 300-500A (can be any value between 300A, 400A, 500A or 300-500A) and 2-5Hz (can be any value between 2Hz, 3Hz, 4Hz, 5Hz or 2-5Hz). (11) The consumption of protective slag in the crystallizer is 0.4-0.6 kg / m³. 2 (can be 0.4kg / m) 2 0.5kg / m 2 0.6kg / m 2 Or 0.4-0.6 kg / m 2 (any value between).

[0036] This application also provides an electric arc furnace oxygen lance apparatus for performing the method of smelting DC04 steel in an electric arc furnace.

[0037] This multi-functional oxygen lance integrates three working modes: supersonic gas-solid jet mode, supersonic oxygen jet mode, and oxygen burner mode. Its structure includes an oxygen lance housing, a retractable central gas-solid nozzle, a Raoult nozzle assembly, an annular gas injection pipe, an annular oxygen injection pipe, a multi-functional oxygen lance nozzle, and inlet and outlet water pipes. The core of this invention lies in the axial relative displacement of the retractable central gas-solid nozzle, combined with independent control of the flow rate and pressure of the surrounding oxygen, central powder, annular gas, and annular oxygen, enabling flexible switching between the three working modes. In supersonic gas-solid jet mode: the retractable nozzle outlet moves to the Raoult nozzle throat, where the central powder gas flow is entrained and accelerated to supersonic speed by the surrounding oxygen. The formation of surrounding oxygen not only significantly improves the jet's cohesion and impact force but also isolates the lime powder from the throat wall. The wear of the lime powder on the nozzle's contraction and expansion sections significantly extends the nozzle's service life. Supersonic Oxygen Injection Mode: The withdrawable nozzle is pulled back from the Raoult nozzle, forming a supersonic oxygen jet channel to enhance oxygen supply and agitation of the molten pool. At this time, only pure oxygen passes through the Raoult nozzle, completely avoiding wear on the throat from high-speed powder. Oxygen Combustion Nozzle Mode: A flat, high-temperature flame is formed through the mixing and combustion of combustion gases and oxygen in the annular gap, used for scrap steel cutting, melting, and heat compensation. Compared with existing technologies, this invention achieves multi-functional rapid switching through a single lance body, solving the problems of single function and complex switching in traditional oxygen lances. It can effectively shorten the smelting cycle, reduce power consumption per ton of steel, and improve the efficiency of metallurgical reactions such as dephosphorization. It is suitable for multi-stage smelting processes in electric arc furnaces of different capacities, and can especially meet the stringent control requirements for phosphorus and carbon content in the production of DC04 steel. The multi-functional oxygen lance and efficient injection method for electric arc furnaces described in this application enable alternating injection of supersonic oxygen jets, supersonic gas-solid jets, and oxygen-fuel jets in multiple modes. This increases oxygen lance lifespan by 20-60%, reduces lime consumption per ton of steel by over 10%, increases dephosphorization rate by 5-15%, increases metal yield by over 2%, shortens the smelting cycle by 3-8 minutes, and reduces power consumption per ton of steel by 3-10 kW•h. Through the coordinated switching and precise injection of the multi-functional oxygen lance, this invention achieves precise control of phosphorus and carbon content in DC04 steel produced from electric arc furnaces, significantly improving smelting efficiency while ensuring high-quality steel production, and has promising prospects for industrial application.

[0038] In an optional implementation, the electric arc furnace oxygen lance device satisfies one or more of the following conditions: (1) The outer diameter of the electric arc furnace oxygen lance device is 150-250mm (it can be any value between 150mm, 200mm, 250mm or 150-250mm). (2) The diameter of the pump-type central gas-solid nozzle is 10-20mm (which can be any value between 10mm, 15mm, 20mm or 10-20mm), and the wall thickness is 3-5mm (which can be any value between 3mm, 4mm, 5mm or 3-5mm). (3) The electric arc furnace oxygen lance device also includes an inlet and outlet water cooling device for conveying cooling water, with a cooling water pressure of 0.2-0.8MPa (which can be any value between 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa or 0.2-0.8MPa). (4) The pressure of the oxygen flow channel is 0.6-1.5MPa (which can be any value between 0.6MPa, 0.7MPa, 0.8MPa, 0.9MPa, 1.0MPa, 1.1MPa, 1.2MPa, 1.3MPa, 1.4MPa, 1.5MPa or 0.6-1.5MPa), and the pressure of the pump-type central gas-solid injection pipeline is 0.7-1.6MPa (which can be any value between 0.7MPa, 0.8MPa, 0.9MPa, 1.0MPa, 1.1MPa, 1.2MPa, 1.3MPa, 1.4MPa, 1.5MPa, 1.6MPa or 0.7-1.6MPa).

[0039] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0040] Example 1 like Figure 1 As shown, this embodiment provides an oxygen lance device for an electric arc furnace, including an oxygen lance housing body 1, a Raoult nozzle 2 sleeved within the oxygen lance housing body 1, a retractable central gas-solid nozzle 3 sleeved within the Raoult nozzle 2, and an surrounding oxygen channel 4, an annular gas combustion channel 5, an annular oxygen channel 6, a cooling water inlet channel 7, and a cooling water return channel 8. Figure 2 As shown, the oxygen lance cross-section includes an oxygen outlet 9 around the flow, a central powder gas outlet 10, an annular oxygen outlet 11, and an annular gas outlet 12.

[0041] The Raoult nozzle 2 is used to accelerate the gas and form an enveloping structure, a key component in creating the enveloping jet. The withdrawable central gas-solid nozzle 3 allows adjustment of the gas-solid injection mode, oxygen supply mode, and oxygen burner mode by changing the nozzle's outlet position. The oxygen lance housing 1 has a diameter of 180mm, and the withdrawable central gas-solid nozzle 3 has a diameter of 15mm and a wall thickness of 5mm. Cooling water inlet channel 7 and cooling water return channel 8 are used to transport cooling water at a pressure of 0.5MPa, reducing the temperature of the oxygen lance head and Raoult nozzle, ensuring the service life of the supersonic gas-solid oxygen lance. The pressure in the surrounding oxygen channel 4 is 1.4MPa, and the pressure in the withdrawable central gas-solid nozzle 3 is 1.5MPa.

[0042] Example 2 This embodiment provides a method for smelting DC04 steel in an electric arc furnace. The smelting is carried out using a 150t electric arc furnace including the oxygen lance device provided in Embodiment 1, with an oxygen lance designed flow rate of 3200 m³ / h. 3 The oxygen flow rate is 1.0 liters per hour, Mach number 2.1, with a central circular tube diameter of Ф15 mm × 3 mm. The main oxygen pipeline is made of Ф50 × 5 mm wear-resistant stainless steel. The powder is mainly fed into the compression section (throat) of the Raoult nozzle 2 through a pump-operated central gas-solid nozzle 3, where it mixes with the surrounding oxygen and is accelerated. The main oxygen pipeline pressure is 1.4 MPa, and the pressure of the pump-operated central gas-solid nozzle 3 is 1.6 MPa. The slag-forming material is lime powder with a particle size of 200 mesh.

[0043] Specifically, the following steps are included: S1: During the stage of adding 65% scrap steel and 35% molten iron, the multi-functional oxygen lance is in oxygen combustion nozzle injection mode, with a centrally operated pull-out gas-solid nozzle and a Raoult nozzle. The oxygen flow rate of the pull-out central gas-solid nozzle is 750 m³ / h. 3 / h, powder flow rate is 0 kg / min, and oxygen flow rate around the flow is 750 m³ / h. 3 / h, annular gas flow rate is 250m³ / h 3 / h, oxygen flow rate at the annular gap is 550m³ / h 3 / h, through full combustion to generate high-temperature flames to quickly cut and preheat large pieces of scrap steel, accelerating the melting of the scrap steel.

[0044] S2: The initial stage of steelmaking raw material melting. This stage mainly relies on electrical energy and chemical energy (oxygen supply) for heating and melting, and the ferrous oxide content in the slag gradually increases. The electric arc furnace's multi-functional oxygen lance is a supersonic gas-solid jet mode, with a pump-operated central gas-solid nozzle propelled to the throat, and its oxygen flow rate is 800 m³ / s. 3 / h, powder flow rate is 30 kg / min, and oxygen flow rate around the flow is 1200 m³ / min. 3 / h, annular gap gas flow rate 150 m 3 / h, the oxygen flow rate in the annular gap is 300 m³ / h. 3 / h, by spraying a small amount of lime powder into the high-temperature reaction zone, foam slag can be quickly formed to cover the molten pool, reducing heat loss.

[0045] S3: The later stage of steelmaking raw material melting, which is one of the important stages of dephosphorization. The electric arc furnace multi-functional oxygen lance is a supersonic gas-solid jet mode, and the oxygen flow rate of the pull-out central gas-solid nozzle is 1000 m³ / s. 3 / h, powder flow rate is 45 kg / min, and oxygen flow rate around the flow is 1500 m³ / min. 3 / h, annular gap gas flow rate 250 m 3 / h, the oxygen flow rate in the annular gap is 500 m³ / h. 3 / h, at this stage, the increased flow rate of lime powder, combined with the high-speed jet of oxygen, can quickly slag and accelerate the dephosphorization process, and effectively increase the phosphorus capacity of the molten slag. S4: The oxidation and heating stage following melt cleaning is one of the main dephosphorization stages in the molten pool. The electric arc furnace's multi-functional oxygen lance operates in supersonic gas-solid jet mode, with a centrally operated, withdrawable gas-solid nozzle providing an oxygen flow rate of 1200 m³ / s. 3 / h, powder flow rate is 60 kg / min, and oxygen flow rate around the flow is 1800 m³ / min. 3 / h, the gas flow rate in the annular gap is 200 m³ / h. 3 / h, the oxygen flow rate in the annular gap is 400m³ / h. 3 / h, during this stage, the ferrous oxide in the slag increases significantly. The injection of a large amount of lime powder can quickly melt in the impact zone and be used in the dephosphorization process, accelerating the dephosphorization reaction. In addition, the lime powder increases the jet kinetic energy, thereby increasing the oxygen decarbonization rate.

[0046] S5: Rapid heating stage, rapidly raising the molten steel temperature to the tapping temperature of the target steel grade within minutes. The electric arc furnace multi-functional oxygen lance operates in supersonic oxygen jet mode, with a pull-out central gas-solid nozzle and a Raoult nozzle, and its oxygen flow rate is 1200 m³ / s. 3 / h, powder flow rate is 0 kg / min, and oxygen flow rate around the flow is 2000 m³ / min. 3 / h, the gas flow rate in the annular gap is 300m³ / h. 3 / h, the oxygen flow rate at the annular gap is 540 m³ / h. 3 / h, during this stage, the multi-functional oxygen lance mainly serves to oxidize and heat up, rapidly decarburize, and stir the molten pool.

[0047] S6: During the tapping stage of the electric arc furnace, the molten steel reaches the tapping temperature of the target steel grade. The multi-functional oxygen lance of the electric arc furnace is in supersonic oxygen jet mode, and the oxygen flow rate of the expedited central gas-solid nozzle is 100 m³ / s. 3 / h, powder flow rate is 0 kg / min, oxygen flow rate around the flow is 50 m³ / h. 3 / h, annular gas flow rate 25 m 3 / h, oxygen flow rate at the annular gap is 50 m³ / h 3 / h, the gas supply to each gas channel at this stage is to prevent steel slag splashing and causing the nozzle to become clogged.

[0048] S7: RH refining stage, start the vacuum pump and reduce the vacuum chamber pressure to 80 Pa within 5 minutes. The circulating argon flow rate is 1800 m³ / s. 3 After vacuum decarburization for 15 minutes, the carbon content was reduced to 0.0022%. Then, 180 kg of aluminum granules were added for deoxidation in three batches, with a 1.5-minute interval between each batch. After deoxidation, titanium-iron alloy was added to adjust the titanium content to 0.06%. Pure circulation treatment was performed for 9 minutes, with the circulating gas flow rate adjusted to 1000 Nm³. 3 / h. After the cavitation system is broken, temperature is measured and samples are taken. Once the temperature and composition meet the standards, the sample is sent out of the station to the continuous casting plant.

[0049] S8: During the RH tapping stage, after the pure circulation process is completed, the vacuum pump is shut off, and argon or nitrogen is introduced into the vacuum chamber to break the cavitation. After breaking the cavitation, the molten steel is temperature-measured and sampled to test its temperature, carbon content, nitrogen content, and oxygen activity. After passing the tests, the ladle is hoisted to the continuous casting process for casting.

[0050] S9: During the steel pouring stage, the ladle temperature is controlled at 1605℃. The tundish is preheated to 1150℃ and subjected to argon blowing and oxygen removal. For the first heat, calcium wire is added to the tundish to prevent nozzle blockage. Molten steel is injected into the tundish through a long nozzle with argon sealing (argon flow rate 150L / min). The tundish steel temperature is controlled at 1565℃, with liquid level fluctuations within ±5mm. Molten steel is then injected into the crystallizer through a submerged entry nozzle to a depth of 130mm. Liquid level fluctuations in the crystallizer are controlled within ±3mm. Non-sinusoidal vibration (frequency 150 times / min, amplitude 4mm) is used, and electromagnetic stirring (450A, 3Hz) is applied. The protective slag consumption is 0.5kg / m³. 2 .

[0051] Experimental results show that when using a multi-functional oxygen lance and its efficient injection method in a 150t electric arc furnace, the phosphorus content of the steel tapped from the electric arc furnace is reduced to below 0.005%, and the carbon content is controlled at 0.05%, meeting the production requirements of DC04 steel. The plastic strain ratio is increased by 50% (strong resistance to thinning, a core indicator for deep drawing performance), and the elongation after fracture increases to 35% (compared to approximately 25% for ordinary steel grades). Furthermore, the dephosphorization rate is increased by 8% compared to the original process, the service life of the multi-functional oxygen lance is extended by 30%, lime consumption per ton of steel is reduced by 12%, metal yield is increased by 3%, the smelting cycle is shortened by 4 minutes, and power consumption per ton of steel is reduced by 5 kW•h, effectively lowering the production cost of DC04 steel.

[0052] Example 3 This embodiment provides a method for smelting DC04 steel in an electric arc furnace. The smelting is carried out using a 150t electric arc furnace including the oxygen lance device provided in Embodiment 1. The oxygen lance is designed to have a flow rate of 2600 m³ / h, a Mach number of 2.0, and a central circular tube diameter of Ф12mm×3mm. The main oxygen pipeline is made of Ф50×5 mm wear-resistant stainless steel. The powder is mainly fed into the compression section of the nozzle through the central pipeline, where it mixes with the surrounding oxygen and is accelerated. The pressure in the main oxygen pipeline is 0.6-1.4 MPa, the pressure in the expedited central gas-solid injection pipeline is 0.6-1.4 MPa, and the slag-forming material is lime powder with a particle size of 200 mesh.

[0053] The method includes the following steps: S1: During the stage of adding 65% scrap steel + 35% direct reduced iron, the multi-functional oxygen lance is in oxygen combustion nozzle injection mode, and the oxygen flow rate of the pull-out central gas-solid nozzle is 600 m³ / s. 3 / h, powder flow rate is 0 kg / min, and oxygen flow rate around the flow is 600 m³ / min. 3 / h, annular gap gas flow rate 250 m 3 / h, oxygen flow rate in the annular gap is 550 m³ / h 3 / h, through full combustion to generate high-temperature combustion flames to quickly cut and preheat large pieces of scrap steel, accelerating the melting of the scrap steel.

[0054] S2: The initial stage of steelmaking raw material melting. This stage mainly relies on electrical energy and chemical energy (oxygen supply) for heating and melting, and the ferrous oxide content in the slag gradually increases. The electric arc furnace's multi-functional oxygen lance operates in supersonic gas-solid jet mode, with a pump-operated central gas-solid nozzle and an oxygen flow rate of 900 m³ / s. 3 / h, powder flow rate is 30 kg / min, and oxygen flow rate around the flow is 1300 m³ / min. 3 / h, annular gap gas flow rate 250 m 3 / h, the oxygen flow rate in the annular gap is 500 m³ / h. 3 / h, by spraying a small amount of lime powder into the reaction zone, foamy slag can be quickly formed to cover the molten pool, reducing heat loss.

[0055] S3: The later stage of melting, which is one of the important stages of dephosphorization. The electric arc furnace multi-functional oxygen lance is a supersonic gas-solid jet mode, and the oxygen flow rate of the traction-type central gas-solid nozzle is 800 m³ / s. 3 / h, powder flow rate is 45 kg / min, and oxygen flow rate around the flow is 1600 m³ / min. 3 / h, the gas flow rate in the annular gap is 200 m³ / h. 3 / h, the oxygen flow rate in the annular gap is 400 m³ / h. 3 / h, at this stage, the increased flow rate of lime powder, combined with the high-speed jet of oxygen, can quickly melt and form foam slag, thus accelerating the dephosphorization process. S4 (Oxidation Heating Period): This is the oxidation heating stage after melting and is one of the main dephosphorization stages in the molten pool. The electric arc furnace's multi-functional oxygen lance operates in supersonic gas-solid jet mode, with a 900 m³ / h oxygen flow rate from the withdrawable central gas-solid nozzle. 3 / h, powder flow rate is 60 kg / min, and oxygen flow rate around the flow is 1600 m³ / min. 3 / h, the gas flow rate in the annular gap is 200 m³ / h. 3 / h, the oxygen flow rate in the annular gap is 400 m³ / h. 3 At this stage, the ferrous oxide content in the slag increases significantly, and the injection of a large amount of lime powder can quickly melt in the impact zone and be used in the dephosphorization process, thus accelerating the dephosphorization reaction.

[0056] S5: Rapid heating stage, rapidly raising the molten steel temperature to the tapping temperature of the target steel grade within 2-5 minutes. The electric arc furnace multi-functional oxygen lance operates in supersonic oxygen jet mode, with an oxygen flow rate of 900 m³ / s using a pull-out central gas-solid nozzle. 3 / h, powder flow rate is 0 kg / min, and oxygen flow rate around the flow is 1700 m³ / min. 3 / h, annular gap gas flow rate 250 m 3 / h, oxygen flow rate in the annular gap is 550 m³ / h 3 / h, at this stage, the multi-functional oxygen lance mainly serves to oxidize, heat up, and stir the molten pool.

[0057] S6: During the tapping stage of the electric arc furnace, the molten steel reaches the tapping temperature of the target steel grade. The multi-functional oxygen lance of the electric arc furnace is in supersonic oxygen jet mode, and the oxygen flow rate of the expedited central gas-solid nozzle is 100 m³ / s. 3 / h, powder flow rate is 0 kg / min, oxygen flow rate around the flow is 50 m³ / h. 3 / h, annular gas flow rate 25 m 3 / h, oxygen flow rate at the annular gap is 50 m³ / h 3 / h, the gas supply to each gas channel at this stage is to prevent steel slag splashing and causing the nozzle to become clogged.

[0058] S7: RH refining stage, start the vacuum pump and reduce the vacuum chamber pressure to 80 Pa within 5 minutes. The circulating argon flow rate is 1550 m³ / min. 3 After vacuum decarburization for 15 minutes, the carbon content was reduced to 0.0022%. Then, 180 kg of aluminum granules were added for deoxidation in three batches, with a 1.5-minute interval between each batch. After deoxidation, titanium-iron alloy was added to adjust the titanium content to 0.06%. Pure circulation treatment was performed for 9 minutes, with the circulating gas flow rate adjusted to 900 Nm³. 3 / h. After the cavitation system is broken, temperature is measured and samples are taken. Once the temperature and composition meet the standards, the sample is sent out of the station to the continuous casting plant.

[0059] S8: After the pure circulation process is completed, the vacuum pump is turned off, and argon or nitrogen is introduced into the vacuum chamber to break the vacuum. After breaking the vacuum, the molten steel is temperature-measured and sampled to test the temperature, carbon content, nitrogen content, and oxygen activity. After passing the tests, the ladle is hoisted to the continuous casting process for casting.

[0060] S9: During the steel pouring stage, the ladle temperature is controlled at 1605℃ upon arrival at the plant. The tundish is preheated to 1150℃ and subjected to argon blowing and oxygen removal. For the first heat, calcium wire is added to the tundish to prevent nozzle blockage. Molten steel is injected into the tundish through a long nozzle with argon sealing (argon flow rate 130L / min). The tundish steel temperature is controlled at 1570℃, with liquid level fluctuations within ±5mm. Molten steel is then injected into the crystallizer through a submerged entry nozzle to a depth of 130mm. Liquid level fluctuations in the crystallizer are controlled within ±3mm. Non-sinusoidal vibration (frequency 150 times / min, amplitude 4mm) is used, and electromagnetic stirring (400A, 3Hz) is applied. The protective slag consumption is 0.4kg / m³. 2 .

[0061] Experimental results show that when using a multi-functional oxygen lance and its efficient injection method in a 115t electric arc furnace, the phosphorus content of the steel tapped from the electric arc furnace is reduced to below 0.005%, and the carbon content is 0.04%, meeting the requirements for producing DC04 steel. The plastic strain ratio is increased by 55% (strong resistance to thinning, a core indicator for deep drawing performance), and the elongation after fracture increases to 38% (compared to approximately 25% for ordinary steel grades). Furthermore, the dephosphorization rate is increased by 15% compared to the original process, the service life of the multi-functional oxygen lance is extended by 25%, lime consumption per ton of steel is reduced by 15%, metal yield is increased by 2.5%, the smelting cycle is shortened by 5 minutes, and power consumption per ton of steel is reduced by 6 kW•h, effectively lowering the production cost of DC04 steel.

[0062] Comparative Example 1 This case study is a comparison with Example 1. The difference between Example 2 and Example 2 is that the oxygen lance used is a wall-mounted cluster oxygen lance (traditional cluster oxygen lance) for an electric arc furnace. Structurally, it lacks a central gas-solid nozzle and a combustion injection mode. It uses oxygen as the carrier gas for lime powder injection and can only perform gas-solid injection and pure oxygen injection, with an oxygen flow rate of 3200 m³ / h. 3 / h.

[0063] The method includes the following steps: S1: During the electric arc furnace smelting process, when 65% scrap steel and 30% molten iron are added, the supersonic gas-oxygen lance is in protective gas mode with a flow rate of 2000 m³ / h. 3 / h, stirring the entire molten pool, eliminating the low-temperature zone, and allowing the difficult-to-melt furnace charge to quickly integrate into the molten steel.

[0064] S2: The entire melting stage of 65% scrap steel + 30% molten iron raw materials for steelmaking. This stage mainly relies on electrical energy and chemical energy (oxygen supply) for heating and melting, and the ferrous oxide content in the slag gradually increases. The furnace wall-mounted cluster oxygen lance operates in gas-solid injection mode, with a lime powder flow rate of 60 kg / min and a gas flow rate of 1800 m³ / min. 3 / h, and simultaneously, depending on the on-site smelting conditions, some blocky slag-forming materials can be added to the silo. In the early stages of melting, use a low flow rate (powder flow rate 50 kg / min, oxygen flow rate 1300 m³ / min). 3 / h, first epoxy channel flow rate 65 m³ / h 3 / h, 130 m³ / h, cyclic combustion channel flow rate 3 / h, second epoxy channel flow rate 65 m³ / h 3 / h).

[0065] S3: The later stage of melting is the main period for dephosphorization. During this stage, a high flow rate (powder flow rate 60 kg / min, oxygen flow rate 3200 m³ / min) is used. 3 / h, first epoxy channel flow rate 160 m³ / h 3 / h, 320 m³ / h, cyclic combustion channel flow rate 3 / h, second epoxy channel flow rate 160 m³ / h 3 / h) Supersonic gas-solid injection is used for deep dephosphorization, and lime powder is injected to quickly form slag and remove phosphorus.

[0066] S4: Oxidation Heating Period: In the early stage of oxidation heating, when the dephosphorization temperature is reached, continue to maintain a high flow rate (powder flow rate 60 kg / min, oxygen flow rate 3200 m³ / min). 3 / h, first epoxy channel flow rate 160 m³ / h 3 / h, 320 m³ / h, cyclic combustion channel flow rate 3 / h, second epoxy channel flow rate 160 m³ / h 3 ( / h) Injection and stirring continue for dephosphorization.

[0067] S5: After entering the later stage of oxidation and heating, the dephosphorization reaction is less or no longer occurring. The slag mainly serves as a submerged arc for insulation. During this stage, the lime powder flow rate during gas-solid injection into the furnace wall oxygen lance can be appropriately reduced, controlled at 50 kg / min. Simultaneously, some blocky slag-forming materials can be added according to the smelting situation. After the slag-forming and dephosphorization stage is completed, the powder injection tank stops feeding powder, and the furnace wall oxygen lance switches to gas supply mode with an oxygen flow rate of 3200 m³ / min. 3 / h, first epoxy channel flow rate 160 m³ / h 3 / h, 320 m³ / h, cyclic combustion channel flow rate 3 / h, second epoxy channel flow rate 160 m³ / h 3 / h.

[0068] S6: Tapping Stage: Once the molten steel reaches the expected temperature, oxygen supply is stopped, oxygen is removed from the slag, and the protective gas mode is activated with an oxygen flow rate of 150 m³ / h. 3 / h, the smelting of molten steel ends, and the steel is tapped.

[0069] S7: RH refining stage, start the vacuum pump and reduce the vacuum chamber pressure to 80 Pa within 5 minutes. The circulating argon flow rate is 1550 m³ / min. 3 After vacuum decarburization for 15 minutes, the carbon content was reduced to 0.0022%. Then, 180 kg of aluminum granules were added for deoxidation in three batches, with a 1.5-minute interval between each batch. After deoxidation, titanium-iron alloy was added to adjust the titanium content to 0.06%. Pure circulation treatment was performed for 9 minutes, with the circulating gas flow rate adjusted to 900 Nm³. 3 / h. After the cavitation system is broken, temperature is measured and samples are taken. Once the temperature and composition meet the standards, the sample is sent out of the station to the continuous casting plant.

[0070] S8: After the pure circulation process is completed, the vacuum pump is turned off, and argon or nitrogen is introduced into the vacuum chamber to break the vacuum. After breaking the vacuum, the molten steel is temperature-measured and sampled to test the temperature, carbon content, nitrogen content, and oxygen activity. After passing the tests, the ladle is hoisted to the continuous casting process for casting.

[0071] S9: During the steel pouring stage, the ladle temperature is controlled at 1600℃ upon arrival at the plant. The tundish is preheated to 1150℃ and subjected to argon blowing and oxygen removal. For the first heat, calcium wire is added to the tundish to prevent nozzle blockage. Molten steel is injected into the tundish through a long nozzle with argon sealing (argon flow rate 140L / min). The tundish steel temperature is controlled at 1565℃, with liquid level fluctuations within ±5mm. Molten steel is then injected into the crystallizer through a submerged entry nozzle to a depth of 135mm. Liquid level fluctuations in the crystallizer are controlled within ±3mm using non-sinusoidal vibration (frequency 145 times / min, amplitude 4mm), with electromagnetic stirring applied (400A, 3Hz). The protective slag consumption is 0.5kg / m³. 2 .

[0072] Experimental results show that when a 150-ton electric arc furnace is used for steelmaking with a furnace wall-mounted oxygen lance and a traditional injection process, the phosphorus content of the steel produced is between 0.015% and the carbon content is 0.11%, which does not meet the requirements for electric arc furnace steelmaking when producing DC04 steel. Compared with Example 2, the lime powder consumption per ton of steel increases by 6 kg, the smelting cycle is 5 minutes longer, and the smelting power consumption, raw material consumption, and carbon and phosphorus content of the steel produced are all higher than those in Examples 2 and 3.

[0073] Comparative Example 2 This case study is a comparison with Example 3. The difference is that the oxygen lance used is a wall-mounted cluster oxygen lance (traditional cluster oxygen lance) for an electric arc furnace. Structurally, it lacks a central gas-solid nozzle and a combustion injection mode. It uses oxygen as the carrier gas for lime powder injection and can only perform gas-solid injection and pure oxygen injection, with an oxygen flow rate of 600-2600 m³ / h. 3 / h.

[0074] The method includes the following steps: S1: During the electric arc furnace smelting process, in the stage of adding scrap steel and molten iron, the supersonic gas oxygen lance is in protective gas mode with a flow rate of 1500 m³ / h. 3 / h, stirring the entire molten pool, eliminating the low-temperature zone, and allowing the difficult-to-melt furnace charge to quickly integrate into the molten steel.

[0075] S2: In the entire melting stage of 65% scrap steel + 35% direct reduced iron, the heating and melting are mainly carried out by electrical energy and chemical energy (oxygen supply), and the ferrous oxide content in the slag gradually increases. The furnace wall-mounted cluster oxygen lance operates in gas-solid injection mode, with an oxygen flow rate of 2500 m³ / h. 3 The lime powder flow rate is 45 kg / min, and the gas flow rate is 600-2500 m³ / h. 3 / h, and simultaneously, depending on the on-site smelting conditions, some blocky slag-forming materials can be added to the silo. In the early stages of melting, use a low flow rate (powder flow rate 40 kg / min, oxygen flow rate 1000 m³ / min). 3 / h, first epoxy channel flow rate 50 m³ / h 3 / h, 100 m³ / h flow rate in the ignition channel 3 / h, second epoxy channel flow rate 50 m³ / h 3 / h).

[0076] S3: The later stage of melting is the main period for dephosphorization. During this stage, a high flow rate (powder flow rate 50 kg / min, oxygen flow rate 2500 m³ / min) is used. 3 / h, first epoxy channel flow rate 125 m³ / h 3 / h, 250 m³ / h, cyclic combustion channel flow rate 3 / h, second epoxy channel flow rate 125 m³ / h 3 / h) Supersonic gas-solid injection is used for deep dephosphorization, and lime powder is injected to quickly form slag and remove phosphorus.

[0077] S4: Oxidation Heating Period: In the early stage of oxidation heating, when the dephosphorization temperature is reached, continue to maintain a high flow rate (powder flow rate 60 kg / min, oxygen flow rate 2500 m³ / min). 3 / h, first epoxy channel flow rate 125 m³ / h 3 / h, 250 m³ / h, cyclic combustion channel flow rate 3 / h, second epoxy channel flow rate 125 m³ / h 3( / h) Injection and stirring continue for dephosphorization.

[0078] S5: After entering the later stage of oxidation and heating, the dephosphorization reaction is less or no longer occurring. The slag mainly serves as a submerged arc for insulation. During this stage, the lime powder flow rate during gas-solid injection into the furnace wall oxygen lance can be appropriately reduced, controlled at 45 kg / min. Simultaneously, some blocky slag-forming materials can be added according to the smelting situation. After the slag-forming and dephosphorization stage is completed, the powder injection tank stops feeding powder, and the furnace wall oxygen lance switches to gas supply mode with an oxygen flow rate of 2500 m³ / min. 3 / h, first epoxy channel flow rate 125 m³ / h 3 / h, 250 m³ / h, cyclic combustion channel flow rate 3 / h, second epoxy channel flow rate 125 m³ / h 3 / h.

[0079] S6: Electric Arc Furnace Tapping Stage: Once the molten steel reaches the expected temperature, oxygen supply is stopped, oxygen is removed from the slag, and the protective gas mode is activated with an oxygen flow rate of 100 m³ / h. 3 / h, the smelting of molten steel ends, and the steel is tapped.

[0080] Experimental results show that: when using a furnace wall-mounted oxygen lance and traditional injection process in the 115 t electric arc furnace steelmaking, the phosphorus content of the steel produced by the electric arc furnace is 0.015% and the carbon content is 0.12%, which does not meet the requirements for electric arc furnace steelmaking when producing DC04 steel. Compared with Example 2, the lime powder consumption per ton of steel increases by 5 kg, the smelting cycle is 4 minutes longer, and the smelting power consumption, raw material consumption, and carbon and phosphorus content of the steel produced are all higher than those in Examples 2 and 3.

[0081] Comparative Example 3 This comparative example uses the same smelting raw materials as in Example 1 and ensures that the oxygen supply and lime addition are consistent. However, the supersonic gas-solid injection mode of the S3 stage is missing, and only the oxygen supply intensity is maintained. The lime is added in block form through the silo.

[0082] The results showed that the phosphorus content of the tapped steel was 0.015% and the carbon content was 0.12%, which did not meet the requirements of the electric arc furnace tapped steel for DC04 steel grade. The lime consumption per ton of steel increased by 6 kg, the smelting cycle was extended by 5 minutes, the smelting power consumption increased by 6 kW•h, and the production cost of DC04 steel increased.

[0083] Comparative Example 4 This comparative example uses the same smelting raw materials as in Example 2 and ensures that the oxygen supply and lime addition are consistent. However, the supersonic gas-solid injection mode of the S4 stage is missing, and only the oxygen supply intensity is maintained. The lime is added in block form through the silo.

[0084] The results showed that the phosphorus content of the tapped steel was 0.010% and the carbon content was 0.09%, which did not meet the requirements of the electric arc furnace tapped steel for DC04 steel grade. The lime consumption per ton of steel increased by 3 kg, the smelting cycle was extended by 3 minutes, the smelting power consumption increased by 2 kW•h, and the production cost of DC04 steel increased.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for smelting DC04 steel in an electric arc furnace, characterized in that, include: S1: During the stage of adding raw materials, including one or more of scrap steel, molten iron, and direct reduced iron, to the electric arc furnace, the oxygen lance of the electric arc furnace is controlled to be in oxygen combustion nozzle injection mode; the oxygen lance includes an oxygen lance shell body, a Raoul nozzle sleeved in the oxygen lance shell body, a pull-out central gas-solid nozzle sleeved in the Raoul nozzle, and a flow-around oxygen channel, an annular gap gas channel, and an annular gap oxygen channel. The outlet end of the trolley-type central gas-solid nozzle is far from the throat of the Raoult nozzle. S2: In the early stage of the raw material melting, the oxygen lance is in supersonic gas-solid jet mode, and the outlet end of the pump-type central gas-solid nozzle is advanced to the throat of the Raoul nozzle. S3: In the later stage of the raw material melting, the oxygen lance is in supersonic gas-solid jet mode, and the outlet end of the pump-type central gas-solid nozzle is kept at the throat of the Raoul nozzle. S4: The oxidation and heating stage after the raw material is dissolved and cleared, wherein the oxygen lance is in supersonic gas-solid jet mode; S5: Rapid heating stage, the temperature of molten steel is rapidly raised to the tapping temperature of the target steel grade within 2-5 minutes. The oxygen lance is in supersonic oxygen jet mode, and the outlet end of the pump-type central gas-solid nozzle is pulled out from the throat of the Raoult nozzle. S6: During the electric arc furnace tapping stage, the molten steel reaches the tapping temperature of the target steel grade. The oxygen lance is in supersonic oxygen jet mode, and the outlet end of the pump-type central gas-solid nozzle is kept away from the throat of the Raoult nozzle. S7: RH refining stage, start the vacuum pump and reduce the vacuum chamber pressure to 80Pa within 5 minutes; circulate argon gas at the first flow rate, and perform vacuum decarburization to reduce the carbon content; then add aluminum particles for deoxidation, and after deoxidation, add titanium-iron alloy for pure circulation at the second flow rate. S8: After the pure circulation process is completed, the vacuum pump is turned off, and argon or nitrogen is introduced into the vacuum chamber to break the air. After breaking the air, the temperature of the molten steel is measured and samples are taken to test the temperature, carbon content, nitrogen content and oxygen activity of the molten steel. After the test is qualified, the ladle is hoisted to the continuous casting process for casting. S9: Steel casting stage; control the temperature of the ladle entering the station, preheat the tundish and perform argon blowing and oxygen removal treatment, add calcium line to the tundish for the first furnace to prevent nozzle blockage; molten steel is injected into the tundish through the long nozzle argon seal, and the temperature and liquid level fluctuation range of the molten steel in the tundish are controlled. Molten steel is injected into the crystallizer through an immersion nozzle. The fluctuation range of the liquid level in the crystallizer is controlled by non-sinusoidal vibration, electromagnetic stirring is applied to the crystallizer, and water cooling is carried out simultaneously.

2. The method for smelting DC04 steel in an electric arc furnace according to claim 1, characterized in that, In step S1, the oxygen flow rate of the pump-type central gas-solid nozzle is 500-1000 m³ / h. 3 The flow rate of lime powder is 0 kg / min, and the oxygen flow rate of the oxygen channel is 500-1000 m³ / h. 3 / h, the gas flow rate of the annular joint gas channel is 150-250m³ / h. 3 The oxygen flow rate of the annular oxygen channel is 300-550 m³ / h. 3 / h.

3. The method for smelting DC04 steel in an electric arc furnace according to claim 1, characterized in that, In step S2, the oxygen flow rate of the pump-type central gas-solid nozzle is 800-1000 m³ / h. 3 The flow rate of lime powder is 30-45 kg / min, and the oxygen flow rate of the oxygen channel is 1000-1500 m³ / h. 3 / h, the gas flow rate of the annular joint gas channel is 150-300m³ / h. 3 / h, the oxygen flow rate of the annular oxygen channel is 300-600 m³ / h. 3 / h.

4. The method for smelting DC04 steel in an electric arc furnace according to claim 1, characterized in that, In step S3, the oxygen flow rate of the pump-type central gas-solid nozzle is 800-1200 m³ / h. 3 The flow rate of lime powder is 30-45 kg / min, and the oxygen flow rate of the oxygen channel is 1200-1800 m³ / h. 3 / h, the gas flow rate of the annular joint gas channel is 200-300m³ / h. 3 / h, the oxygen flow rate of the annular oxygen channel is 400-600 m³ / h. 3 / h.

5. The method for smelting DC04 steel in an electric arc furnace according to claim 1, characterized in that, In step S4, the outlet end of the traction-type central gas-solid nozzle is maintained at the throat of the Raoult nozzle; the oxygen flow rate of the traction-type central gas-solid nozzle is 800-1200 m³ / h. 3 The flow rate of lime powder is 60-120 kg / min, and the oxygen flow rate of the oxygen channel is 1600-2000 m³ / h. 3 / h, the gas flow rate of the annular joint gas channel is 200-300m³ / h. 3 / h, the oxygen flow rate of the annular oxygen channel is 400-600 m³ / h. 3 / h.

6. The method for smelting DC04 steel in an electric arc furnace according to claim 1, characterized in that, In step S5, the oxygen flow rate of the pump-type central gas-solid nozzle is 800-1200 m³ / h. 3 The flow rate of lime powder is 0 kg / min, and the oxygen flow rate of the oxygen channel is 1600-2000 m³ / h. 3 / h, the gas flow rate of the annular joint gas channel is 200-300m³ / h. 3 / h, the oxygen flow rate of the annular oxygen channel is 400-600 m³ / h. 3 / h.

7. The method for smelting DC04 steel in an electric arc furnace according to claim 1, characterized in that, In step S6, the oxygen flow rate of the pump-type central gas-solid nozzle is 100-200 m³ / h. 3 The flow rate of lime powder is 0 kg / min, and the oxygen flow rate of the oxygen channel is 50-100 m³ / h. 3 / h, the gas flow rate of the annular gas channel is 25-50m³ / h. 3 / h, the oxygen flow rate of the annular oxygen channel is 50-100 m³ / h. 3 / h.

8. The method for smelting DC04 steel in an electric arc furnace according to any one of claims 1-7, characterized in that, One or more of the following conditions must be met: (1) The first flow rate is 1500-2000 m³ / h 3 / h, the second flow rate is 1000-1500 Nm 3 / h; (2) The temperature of the ladle entering the station is 1580-1610℃; (3) The intermediate ladle is preheated to 1100-1200℃; (4) The argon flow rate of the argon seal is 100-200 L / min; (5) The temperature of the molten steel in the tundish is 1550-1580℃; (6) The liquid level fluctuation in the intermediate tundish is controlled within ±5mm; (7) The depth to which the immersion nozzle is inserted into the crystallizer is 120-150 mm; (8) The liquid level fluctuation in the crystallizer is controlled within ±3mm; (9) The frequency of the non-sinusoidal vibration is 120-180 times / min, and the amplitude is 3-6 mm; (10) The parameters of the electromagnetic stirring are 300-500A and 2-5Hz; (11) The consumption of protective slag in the crystallizer is 0.4-0.6 kg / m³. 2 .

9. An oxygen lance device for an electric arc furnace, characterized in that, The method for smelting DC04 steel in an electric arc furnace according to any one of claims 1-8.

10. The electric arc furnace oxygen lance device according to claim 9, characterized in that, One or more of the following conditions must be met: (1) The outer shell diameter of the electric arc furnace oxygen lance device is 150-250 mm; (2) The diameter of the pump-type central gas-solid nozzle is 10-20 mm and the wall thickness is 3-5 mm; (3) The electric arc furnace oxygen lance device also includes an inlet and outlet water cooling device for conveying cooling water, with a cooling water pressure of 0.2-0.8 MPa; (4) The pressure of the oxygen flow channel is 0.6-1.5 MPa, and the pressure of the pump-type central gas-solid injection pipeline is 0.7-1.6 MPa.

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