A smelting process for preparing 38CrMoAlA high-aluminum steel based on ecological electric furnace short process

Abstract

This invention relates to the field of metallurgical technology, specifically to a short-process smelting technology for preparing 38CrMoAlA high-aluminum steel using an eco-friendly electric furnace. The smelting process is as follows: eco-friendly electric furnace smelting → LF refining → RH vacuum degassing → continuous casting. This invention provides a method for producing high-quality 38CrMoAlA steel using an electric furnace-refining furnace-RH furnace-round billet continuous casting machine. This method produces high-quality 38CrMoAlA steel without requiring additional processes, shortening the smelting cycle and facilitating production organization. Furthermore, it allows for a stable continuous casting cycle of 8-10 heats, with no turbulence or stopper rod level rise during casting, significantly reducing the production cost of 38CrMoAlA steel. The Al alloying yield is high and stable, and the finished product has low levels of various inclusions, achieving a leading domestic product quality.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a smelting process for preparing 38CrMoAlA high-aluminum steel based on a short process using an eco-friendly electric furnace. Background Technology

[0002] High-alumina steel is one of the steel grades with high demand in many fields such as energy, transportation, electromechanical, and military industries. Although 38CrMoAlA steel has a wide range of applications and a large market demand, there are relatively few domestic manufacturers of 38CrMoAlA steel. The main reason is that 38CrMoAlA steel has a high Al content, reaching 0.9%-1.0%, which is far higher than other conventional Al-containing steels. During continuous casting production, when the Al content in the steel is greater than 0.02%, tundish nozzle blockage is likely to occur. The aluminum content of high-alumina steel is dozens of times that of ordinary aluminum-killed steel, making the tendency for immersion nozzle blockage even more serious, resulting in very low castability and even making it difficult to ensure normal production. In addition, the contact between SiO2 in the tundish covering agent and the mold flux and Al in the molten steel will also cause redox reactions, leading to the deterioration of the steel quality and the performance of the mold flux, which in turn affects the quality of the billet and the smooth operation of continuous casting production, and may even cause accidents such as steel leakage leading to casting interruption. Moreover, it is difficult to control the steelmaking composition, the aluminum recovery rate is low, the number of consecutive castings is low, and the production cost is high, generally less than 5 castings.

[0003] Eco-friendly electric arc furnaces, as a new type of electric furnace with advanced energy recovery and environmental protection technologies, have unparalleled advantages over other electric furnaces in reducing dioxin emissions and saving energy. The products they produce can be called "green steel," and they have broad development prospects. Furthermore, compared to electric furnaces, converter smelting of high-alumina steel is more prone to slag buildup, and silicon in the molten steel easily reacts with Al2O3 in the slag, resulting in lower alloy element yields, higher alloy addition amounts, and decreased steel purity, among other disadvantages. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a smelting process for preparing 38CrMoAlA high-alumina steel using a short-process ecological electric furnace. This process utilizes electric furnace endpoint control, alloy baking, optimized LF slagging regime, RH vacuum circulation degassing, optimized tundish baking process, and electromagnetic stirring at the crystallizer and solidification end to produce 38CrMoAlA high-alumina steel. This enables continuous casting in multiple furnaces, achieving excellent comprehensive performance and improving the quality of high-alumina steel products and the economic benefits for enterprises.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] This invention provides a smelting process for preparing 38CrMoAlA high-aluminum steel based on a short process using an eco-friendly electric furnace. The smelting process is as follows: eco-friendly electric furnace smelting → LF refining → RH vacuum degassing → continuous casting.

[0007] The process of the eco-electric furnace smelting is as follows: The ECOARC eco-electric furnace uses continuous scrap steel feeding at a rate of 90-120t. The scrap steel is preheated to 600-800℃ by the flue gas in the furnace before entering the smelting area. Lime and dolomite are added, and carbon powder is injected. When the tapping conditions meet the requirements of carbon greater than 0.05%, P ≤ 0.01%, and temperature 1600-1630℃, tapping begins, and the tapping time is controlled within 3-5 minutes. The process of the LF refining is as follows: Molten steel after leaving the station is sent to the LF furnace for refining. The LF arrival temperature is 1520-1570℃. After initial power supply for 2-3 minutes to form liquid slag, carbon powder is added to begin carbonization. The entire process is white slag operation. When the temperature reaches 1560-1600℃, a full analysis sample is taken. Then, alloys and slag materials are added to adjust the composition. The SiO2 content of the final slag in the LF furnace is less than 2wt%.

[0008] The RH vacuum degassing process is as follows: After the ladle is placed on the ladle car, argon gas is turned on and blown in at a flow rate of 300-450 NL / min. After entering the working position, the lifting operation is started, the impregnation tube is inserted to a depth greater than 400 mm, the argon gas is turned off, the vacuum degree is <100 Pa, and the duration is >10 min. After the vacuum is broken, argon blowing is started, 170-220 m of silicon-calcium wire is fed in per furnace, and 60-90 kg of covering agent is fed in per furnace. The static argon blowing time is >15 min.

[0009] The continuous casting process is as follows: the superheat of the molten steel is controlled to be less than 45°C, and oxygen and coal gas are mixed for baking. After baking, the remaining oxygen content does not exceed 3%.

[0010] In the above technical solution, furthermore, in the ecological electric furnace smelting process, the amount of lime added is 30.0-41.0 kg / t, the amount of dolomite added is 22.0-26.0 kg / t, and the amount of carbon powder added is 22.0-32.0 kg / t.

[0011] In the above technical solution, further, in the ecological electric furnace smelting process, when 15-20t of steel is produced, the baked alloy and lime are added in sequence at a baking temperature of 600-800℃, including 21-24.0kg / t of high-carbon ferrochrome, 1.09kg / t-1.27kg / t of aluminum wire, 14.0-16.0kg / t of high-carbon ferromanganese, and 600kg / furnace of lime.

[0012] In the above technical solution, furthermore, during the ecological electric furnace smelting process, argon gas is supplied throughout the steel tapping process, with a flow rate of 600-750 NL / min.

[0013] In the above technical solution, further, in the LF refining process, the amount of slag added is: 5.0-10.0 kg / t of quicklime, and the amount of alloy added is: 0.6-1.0 kg / t of ferrosilicon, 2-5 kg / t of high-carbon ferrochrome, 1-4 kg / t of high-carbon ferromanganese, 1.5-4 kg / t of ferromolybdenum, and 1.0-4.0 kg / t of alumina balls.

[0014] In the above technical solution, the chemical composition of the high-aluminum steel, by weight percentage, is as follows: C: 0.36%–0.40%, Si: 0.25%–0.40%, Mn: 0.32%–0.50%, P≤0.019%, S≤0.015%, Alt: 0.8%–1.0%, Cr: 1.37%–1.55%, Mo: ≤0.16%–0.23%, Ni≤0.25%, Cu≤0.15%, V: ≤0.01%, Ti: ≤0.01%, with the balance being iron and unavoidable impurities.

[0015] The beneficial effects of this invention are as follows:

[0016] 1. This invention provides a method for producing high-quality 38CrMoAlA steel using an electric furnace-refining furnace-RH furnace-round billet continuous casting machine. This method produces high-quality 38CrMoAlA steel without requiring additional processes, shortening the smelting cycle and facilitating production organization. Furthermore, it allows for a stable continuous casting cycle of 8-10 heats, with no turbulence or stopper rod level rise during casting, significantly reducing the production cost of 38CrMoAlA steel. The Al alloying yield is high and stable, and the finished product has low levels of various inclusions, achieving a leading domestic product quality.

[0017] 2. This invention uses an ECOARC eco-friendly electric furnace for smelting, which reduces energy consumption and emissions of carbon dioxide and dioxins.

[0018] 3. The smelting process mentioned in this invention produces 38CrMoAlA steel with extremely low SiO2 content in the refining slag system, which can effectively avoid the generation of a large amount of Al2O3 due to the reduction of SiO2 during Al alloying.

[0019] 4. In the RH vacuum degassing process of this invention, the RH soft blowing flow rate is reduced and the static blowing time is increased. Al is not adjusted in the later stage, and the inclusions float to the surface in the early stage, resulting in a lower grade of various inclusions in the finished product.

[0020] 5. In the continuous casting process of this invention, Al loss is reduced by increasing the air-coal ratio (CO:O). Detailed Implementation

[0021] The following examples are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0022] This invention provides a smelting process for preparing 38CrMoAlA steel based on a short process using an eco-electric furnace: eco-electric furnace smelting → LF refining → RH vacuum degassing → continuous casting of 390×480 large square billets.

[0023] The process of eco-friendly electric arc furnace smelting is as follows: The ECOARC eco-friendly electric arc furnace adopts a continuous scrap steel feeding, vertical furnace preheating, and molten pool steel retention mode for smelting. The secondary system of the electric arc furnace adds one carload of scrap steel to the vertical furnace every 3-5 minutes, for a total of 10 cars (90-120 tons) throughout the smelting process. The scrap steel is preheated to 600-800℃ by the flue gas in the furnace before entering the smelting area. Lime (30.0-41.0 kg / t), dolomite (22.0-26.0 kg / t), and carbon powder (22.0-32.0 kg / t) are added. The final tapping conditions are: carbon > 0.05%, P ≤ 0.01%, and temperature... When the temperature reaches 1600-1630℃, tapping begins. Argon gas is supplied throughout the tapping process at a flow rate of 600-750 NL / min. The tapping is controlled to be a circular flow, and the molten steel is prohibited from spreading. The tapping time is controlled to be 3-5 minutes. When 15-20 tons of steel have been tapped, the baked alloy is added sequentially at a baking temperature of 600-800℃ to reduce the entry of external gases into the molten steel. The alloys are: 21-24.0 kg / t of high-carbon ferrochrome, 1.09-1.27 kg / t of aluminum wire segments (Φ10mm-Φ16mm), and 14.0-16.0 kg / t of high-carbon ferromanganese. 600 kg / furnace of lime is also added.

[0024] The LF refining process is as follows: molten steel after leaving the station is sent to the LF furnace for refining. The LF arrival temperature is 1520-1570℃. The LF furnace cover is kept in close contact with the ladle, and a slight positive pressure is maintained inside the furnace. Submerged arc heating is used to prevent arc leakage. During the refining process, the argon flow rate is continuously adjusted, and excessive argon blowing is prohibited to prevent nitrogen absorption. After initial power supply for 2-3 minutes to form liquid slag, carbon powder is added to begin carbonization. The entire process is white slag operation. When the temperature reaches 1560-1600℃, a full analysis sample is taken. Then, 5.0-10.0 kg / t of quicklime, 0.6-1.0 kg / t of ferrosilicon, 2-5 kg / t of high-carbon ferrochrome, 1-4 kg / t of high-carbon ferromanganese, 1.5-4 kg / t of ferromolybdenum for special steel, and 1.0-4.0 kg / t of alumina balls are added to adjust the composition. During the ladle transfer after refining, the liquid surface must not be exposed. The SiO2 content of the final LF furnace slag is less than 2 wt%.

[0025] The RH vacuum degassing process is as follows: After the ladle is placed on the ladle car, argon gas is turned on and blown in at a flow rate of 300-450 NL / min. After entering the working position, the lifting operation is started, the impregnation tube is inserted to a depth of more than 400 mm, the argon gas is turned off, the vacuum degree is <100 Pa, and the duration is >10 min. After the vacuum is broken, argon blowing is started, 170-220 m of silicon-calcium wire is fed in per furnace, and 60-90 kg of covering agent is fed in per furnace. The static argon blowing time is >15 min.

[0026] The continuous casting process is as follows: the molten steel after vacuum degassing is hoisted to the casting position, the superheat of the molten steel is controlled to be less than 45°C, the continuous casting ladle adopts a continuous slag detection device to prevent slag from falling into the ladle, oxygen and coal gas are mixed for baking, the residual oxygen after baking does not exceed 3%, and there is no excess oxygen in the ladle. The argon blowing sealing sleeve is connected, and argon gas is supplied to seal the connection of the long nozzle (argon pressure: 0.2-0.4Mpa, flow rate 50-90NL / min), so that the tundish does not expose the molten steel surface. The long nozzle and submerged entry nozzle of the ladle are used after baking. The submerged entry nozzle needs to be sealed with a sealing gasket. The electromagnetic stirring parameters are shown in Table 1. Low carbon titanium steel protective slag is used.

[0027] Table 1 Electromagnetic stirring parameters

[0028]

[0029] Different drawing speeds are set according to the different superheats of the molten steel, and the control targets are shown in Table 2.

[0030] Table 2. Pulling Speed ​​Control Targets

[0031] Superheat (°C) billet shape <15 15～20 20～30 30～35 35～40 ＞40 Pulling speed (m / min) 390×480 0.50 0.50 0.48 0.45 0.45 0.43

[0032] Example 1

[0033] Example 1 of this invention is a 390×480 large square billet. The chemical composition is shown in Table 3, the electric furnace smelting process parameters are shown in Table 4, the LF refining process parameters are shown in Table 5, the RH vacuum degassing process parameters are shown in Table 6, and the continuous casting process parameters are shown in Table 7.

[0034] Table 3 Chemical composition (%) of Example 1

[0035] Example C Si Mn P S Cr Mo Ni Cu Alt 1 0.38 0.30 0.40 0.015 0.010 1.45 0.18 0.05 0.05 0.9

[0036] Table 4 Example 1 Electric Furnace Smelting Process

[0037]

[0038] Table 5 Example 1 LF Refining Process

[0039]

[0040] Table 6 Example 1 RH Vacuum Degassing Process

[0041] Example Calcium silicate wire / m Covering agent / kg Vacuuming time / min Argon blowing time / min 1 250 60 15 20

[0042] Table 7 Example 1 Continuous Casting Process

[0043]

[0044] Table 8 Non-metallic inclusion index in Example 1

[0045]

[0046] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A smelting process for the production of 38CrMoAlA high-aluminum steel based on an ecological electric furnace short process, characterized by, The smelting process is as follows: ecological electric furnace smelting → LF refining → RH vacuum degassing → continuous casting; The process of the eco-friendly electric furnace smelting is as follows: The ECOARC eco-friendly electric furnace adopts continuous feeding of scrap steel, with an addition amount of 90-120t. The scrap steel is preheated to 600-800℃ by the flue gas in the furnace and then enters the smelting area in the furnace. Lime and dolomite are added, and carbon powder is injected. When the tapping conditions meet the final carbon content of greater than 0.05%, P ≤ 0.01%, and temperature of 1600-1630℃, tapping begins, and the tapping time is controlled within 3-5 minutes. The LF refining process is as follows: molten steel after leaving the station is sent into the LF furnace for refining. The LF arrival temperature is 1520-1570℃. After initial power supply for 2-3 minutes to form liquid slag, carbon powder is added to start carbonization. The entire process is white slag operation. When the temperature reaches 1560-1600℃, a full analysis sample is taken. Then, alloys and slag materials are added to adjust the composition. The SiO2 content of the final slag in the LF furnace is less than 2wt%. The RH vacuum degassing process is as follows: After the ladle is placed on the ladle car, argon gas is turned on and blown in at a flow rate of 300-450 NL / min. After entering the working position, the lifting operation is started, the impregnation tube is inserted to a depth greater than 400 mm, the argon gas is turned off, the vacuum degree is <100 Pa, and the duration is >10 min. After the vacuum is broken, argon blowing is started, 170-220 m of silicon-calcium wire is fed in per furnace, and 60-90 kg of covering agent is fed in per furnace. The static argon blowing time is >15 min. The continuous casting process is as follows: the superheat of the molten steel is controlled to be less than 45°C, and oxygen and coal gas are mixed for baking. After baking, the remaining oxygen content does not exceed 3%.

2. The smelting process for the production of 38CrMoAlA high-aluminum steel based on an eco-electric furnace short process according to claim 1, characterized in that, In the ecological electric furnace smelting process, the amount of lime added is 30.0-41.0 kg / t, the amount of dolomite added is 22.0-26.0 kg / t, and the amount of carbon powder added is 22.0-32.0 kg / t.

3. The smelting process for the production of 38CrMoAlA high-aluminum steel based on an eco-electric furnace short process according to claim 1, characterized in that, In the ecological electric furnace smelting process, when 15-20t of steel is produced, the baked alloy and lime are added in sequence at a baking temperature of 600-800℃. The high-carbon ferrochrome is 21-24.0kg / t, aluminum wire is 1.09kg / t-1.27kg / t, high-carbon ferromanganese is 14.0-16.0kg / t, and lime is 600kg / furnace.

4. The smelting process for preparing 38CrMoAlA high-aluminum steel based on a short-process ecological electric furnace according to claim 1, characterized in that, In the ecological electric furnace smelting process, argon gas is supplied throughout the steel tapping process, with a flow rate of 600-750 NL / min.

5. The smelting process for preparing 38CrMoAlA high-aluminum steel based on a short-process ecological electric furnace according to claim 1, characterized in that, In the LF refining process, the amount of slag added is: 5.0-10.0 kg / t of quicklime, and the amount of alloy added is: 0.6-1.0 kg / t of ferrosilicon, 2-5 kg / t of high-carbon ferrochrome, 1-4 kg / t of high-carbon ferromanganese, 1.5-4 kg / t of ferromolybdenum, and 1.0-4.0 kg / t of alumina balls.

6. The smelting process for the production of 38CrMoAlA high-aluminum steel based on an eco-electric furnace short process according to claim 1, characterized in that, The chemical composition of the high-aluminum steel, by weight percentage, is as follows: C: 0.36%–0.40%, Si: 0.25%–0.40%, Mn: 0.32%–0.50%, P≤0.019%, S≤0.015%, Alt: 0.8%–1.0%, Cr: 1.37%–1.55%, Mo: ≤0.16%–0.23%, Ni≤0.25%, Cu≤0.15%, V: ≤0.01%, Ti: ≤0.01%, with the balance being iron and unavoidable impurities.

Images