A method for producing a steel bar for an ecological electric furnace automobile axle sleeve

Abstract

This invention discloses a method for producing steel bars for automotive axle sleeves using an eco-friendly electric furnace. The steel bars, by mass percentage, consist of: C: 0.18%–0.23%, Si: 0.20%–0.35%, Mn: 0.42%–0.60%, P: ≤0.015%, S: ≤0.010%, Cr: 0.82%–1.00%, Ni: ≤0.25%, Mo: 0.41%–0.53%, Cu: ≤0.15%, with the balance being iron and unavoidable impurities. This invention employs an eco-friendly electric furnace smelting process → LF refining → RH refining → continuous casting → heating → rolling, achieving a breakthrough in the mass production of steel bars for automotive axle sleeves using an eco-friendly electric furnace continuous casting process.

Description

Technical Field

[0001] This invention relates to the field of special steel, specifically to a method for producing steel bars for automotive axle bushings using an eco-friendly electric furnace. Background Technology

[0002] As a flexible connecting element between automotive components, automotive bushings can improve product comfort, handling stability, and noise control. Different vehicle models have varying requirements for the stiffness and performance of bushings; therefore, the structure of the bushing product should be determined based on these specific needs.

[0003] Automotive bushings possess excellent wear resistance, tensile strength, temperature resistance, and corrosion resistance. Furthermore, they should also exhibit good fatigue resistance, impact resistance, and vibration resistance to ensure the normal operation of the vehicle. As a crucial component of the transmission system, automotive bushings have stringent quality requirements.

[0004] The quality of the steel used for automotive bushings directly affects the service life and wear resistance of the transmission system, and even the safety of the entire transmission system during operation.

[0005] Therefore, it is essential to develop automotive axle sleeve steel with excellent mechanical properties, high hardness, and high steel purity to meet the requirements of high-end products. Summary of the Invention

[0006] The purpose of this invention is to provide a manufacturing process for steel bars used in automotive axle sleeves. This method employs an ECOARC eco-friendly electric furnace + LF + RH + continuous casting smelting process to produce steel bars for automotive axle sleeves, meeting high-end application requirements. It represents a breakthrough in the mass production of automotive axle sleeve steel bars using the eco-friendly electric furnace continuous casting process, ensuring both the mechanical properties, high hardness, and high steel purity of the finished steel bars, as well as the surface quality of the automotive axle sleeve steel bars.

[0007] To achieve the aforementioned objectives, this invention provides a manufacturing process for steel bars used in automotive axle sleeves, including composition and process design. The specific steps are: ECOARC eco-friendly electric furnace + LF + RH + continuous casting billet → heating → rolling process. This method meets the quality requirements for steel bars used in automotive axle sleeves, and also achieves the required standards for mechanical properties, high hardness, and high steel purity.

[0008] A steel bar for automotive bushings has the following chemical composition by mass percentage: C: 0.18%–0.23%, Si: 0.20%–0.35%, Mn: 0.42%–0.60%, P: ≤0.015%, S: ≤0.010%, Cr: 0.82%–1.00%, Ni: ≤0.25%, Mo: 0.41%–0.53%, Cu: ≤0.15%, with the balance being iron and unavoidable impurities.

[0009] A method for producing steel bars for automobile axle sleeves by smelting in an eco-electric furnace, wherein the process route is: eco-electric furnace smelting → LF refining → RH refining → continuous casting → heating furnace heating process → rolling process.

[0010] The eco-friendly electric furnace smelting process involves: using scrap steel, with scrap steel comprising 100% by mass; a scrap steel loading of 116–122 t; a tapping temperature of 1655–1665℃; a carbon content of 0.08–0.10% and a phosphorus content of ≤0.010% at tapping; the addition of auxiliary materials and alloys when 1 / 4–1 / 3 of the steel has been tapped; a tapping volume of 107–112 t; and a smelting cycle of 45–55 min. The alloy addition per ton of steel is as follows: silicon manganese 4.3–4.4 kg / t, low-carbon ferrochrome 11–11.5 kg / t, coke particles (Φ20–Φ60 mm) 17–17.2 kg / t, aluminum ferrochrome (Φ40–70 mm) 2–2.2 kg / t, and heavy scrap steel (≥800 mm * 600 mm) 930–940 kg / t. Auxiliary material addition per ton of steel: Dolomite (Φ20~70mm) 20~21Kg / t, active lime (Φ10~70mm) 43~44Kg / t, steel ladle lime 6~6.2Kg / t.

[0011] Based on the above technical solution, the LF furnace refining process further involves: using a high current of 20,000–25,000 A to heat and slag; when the slag surface fluctuates and the molten steel and electric arc are not exposed, adding active lime; taking a sample for the first time to analyze the chemical composition after 5 minutes; and adding alloys and silicon carbide according to the target chemical composition values. The alloys and silicon carbide should be added to the argon gas flow to promote rapid melting and homogenization of the alloys and silicon carbide. When the molten steel temperature reaches 1590-1600℃, add 2-3 kg / t of diffusion deoxidizer for diffusion deoxidation. Close the furnace door for 10-12 minutes. When the molten steel temperature reaches 1620-1630℃, take a second sample to analyze the chemical composition to confirm the deviation of the content of each chemical element from the target value. After the second sample is taken, after a smelting cycle of 45-55 minutes, add the following alloys per ton of steel: ferrosilicon 3.4-3.5 kg / t, high-carbon ferromanganese 1.9-2.0 kg / t, high-carbon ferrochrome 0.5-0.55 kg / t, alumina balls (Φ10-15mm) 1.8-1.9 kg / t, coke particles (Φ20-60mm) 0.35-0.36 kg / t, ferromolybdenum (FeMo60-B) 6.6-6.7 kg / t, and aluminum wire (Φ10-Φ12mm) 1-1.1 m / t. Additional auxiliary materials per ton of steel: 6-6.2 kg / t of active lime (Φ10~70mm) and 1-1.1 kg / t of silicon carbide (Φ2~Φ5mm).

[0012] The RH refining process is as follows: inlet temperature 1675-1685℃, operation time 28-32 minutes, argon pressure controlled at 0.1-0.3 MPa before vacuum pump starts, ensuring the molten steel is not exposed by slight slag surface movement, start timing when vacuum reaches 100-110 Pa, maintain for 10-15 minutes, and simultaneously adjust argon pressure to 0.3-0.5 MPa. After static argon blowing, add 2-2.1 meters of silicon-calcium alloy cored wire (Φ12-Φ14mm) per t of steel, and 0.6-0.7 kg of covering agent per t of steel, and outlet temperature 1625-1635℃.

[0013] Based on the above technical solution, the continuous casting is further described as follows: the ladle temperature is 1620-1630℃, the molten steel volume is 95-103t, the H in the tundish is controlled to be ≤2ppm, the casting is protected throughout the process, and medium carbon steel protective slag is used for the crystallizer.

[0014] The heating process is as follows: the furnace inlet temperature is 350℃~550℃; the preheating section temperature is required to be 650℃~700℃ for 1.3~1.5h; the second heating section temperature is required to be 840℃~860℃ for 1.3~1.5h; the first heating section temperature is required to be 1190℃~1220℃ for 1.3~1.5h; the soaking section temperature is required to be 1180℃~1210℃ for 1.3~1.5h; and the tapping temperature is 1180℃~1190℃.

[0015] Based on the above technical solution, the further rolling process is as follows: initial rolling temperature 1100~1130℃, final rolling temperature 850~950℃; the rolling process includes primary rolling mill rolling → continuous rolling mill rolling, specifically:

[0016] BD continuous casting billet opening process: 9 rolling passes, rolling reduction: Turning steel → 1st pass reduction 65~65.1mm → 2nd pass reduction 70~70.1mm → Turning steel → 3rd pass reduction 64~64.1mm → 4th pass reduction 90~90.1mm → Turning steel → 5th pass reduction 42~42.1mm → 6th pass reduction 40~40.1mm → 7th pass reduction 35~35.1mm → 8th pass reduction 34~34.1mm → Turning steel → 9th pass reduction 82~82.1mm. After passing through 3 850mm rolling mills and 1 735mm rolling mill, it enters an 8-stand continuous rolling mill group for rolling.

[0017] Rolling process for Φ180mm raw material: 6 rolling passes. Pass 1: Height 229-229.1mm, width 245-245.1mm; Pass 2: Height 192-192.1mm, width 235-235.1mm; Pass 3: Height 200-200.1mm, width 195-195.1mm; Pass 4: Height 173-173.1mm, width 205-205.1mm; Pass 5: Height 182.4-182.5mm, width 182.4-182.5mm; Pass 6: Height 182.4-182.5mm, width 182.4-182.5mm; Finished product after 6 passes.

[0018] Based on the above technical solution, the rolled steel is further subjected to heat preservation. The heat preservation process is as follows: the temperature of the lower heat preservation pit is ≥600℃, the heat preservation time is 48~55h, and the temperature of the steel exiting the pit is ≤150℃.

[0019] Based on the above technical solution, the dimensions of the continuously cast billet are further defined as 390mm*480mm.

[0020] Furthermore, the process route includes heat preservation followed by finishing, inspection, packaging and warehousing, and then shipment.

[0021] Based on the above technical solution, further, samples of the insulated steel are taken for heat treatment, which includes the following steps:

[0022] 1) Quenching: 870~890℃, hold for 0.8~1.2h, oil cooling;

[0023] 2) Tempering: 490~510℃, hold for 1.6~2.0h, water cooling.

[0024] Based on the above technical solution, further, a 25mm diameter blank is drilled from the insulated steel for heat treatment.

[0025] The beneficial effects of this invention are:

[0026] (1) 38CrSiA steel bars for automotive drive shafts are produced using the ECOARC eco-friendly electric furnace + LF + RH + 390mm*480mm smelting and rolling processes. The production specification is Φ150mm, which meets the mechanical performance requirements and ensures the purity of the steel.

[0027] (2) Reasonable composition design and production process ensure surface quality and impact performance.

[0028] (3) The low magnification structure, non-metallic inclusions and mechanical properties of the finished steel meet the requirements of high-end products. Detailed Implementation

[0029] The following non-limiting embodiments 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.

[0030] Example 1

[0031] 1Chemical composition

[0032] The chemical composition by mass percentage is: C: 0.20%, Si: 0.28%, Mn: 0.49%, P: 0.010%, S: 0.003%, Cr: 0.90%, Ni: 0.05%, Mo: 0.48%, Cu: 0.05%, with the balance being iron and unavoidable impurities.

[0033] 2. Production processes of electric furnace continuous casting of steel bars for automobile axle sleeves

[0034] Process route: ECOARC eco-friendly electric furnace + LF + RH + continuous casting billet → heating furnace heating → rolling → holding → finishing → inspection → packaging and warehousing → shipment. Among them:

[0035] (1) Ecological electric furnace smelting

[0036] Scrap steel accounts for 100%; the scrap steel loading is 118t, the tapping temperature is 1660℃, the carbon content at tapping is 0.08%, and the phosphorus content is 0.008%. Auxiliary materials and alloys are added when 1 / 4 of the steel has been tapped, the tapping volume is 110t, and the smelting cycle is 50min. Alloy addition per ton of steel: silicon manganese 4.3Kg / t, low-carbon ferrochrome 11Kg / t, coke granules (Φ50mm) 17Kg / t, aluminum ferrochrome (Φ50mm) 2Kg / t, heavy scrap steel (800mm*600mm) 934Kg / t. Auxiliary material addition per ton of steel: dolomite (Φ50mm) 20Kg / t, active lime (Φ40mm) 43Kg / t, ladle ash 6Kg / t.

[0037] (2) LF furnace refining

[0038] A high current of 23000A is used to heat and slag. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime is added. After 5 minutes, the first sample is taken to analyze the chemical composition. Alloy and silicon carbide are added according to the target chemical composition value. Alloy and silicon carbide should be added to the argon gas flow to promote the rapid melting and homogenization of alloy and silicon carbide. When the molten steel temperature reaches 1595℃, add 2.5 kg / t of diffusion deoxidizer for diffusion deoxidation. Close the furnace door for 10 minutes. When the molten steel temperature reaches 1625℃, take a second sample to analyze the chemical composition to confirm the deviation of each chemical element content from the target value. After the second sample is taken, the smelting cycle is 48 minutes. The following alloys are added per ton of steel: ferrosilicon 3.4 kg / t, high-carbon ferromanganese 1.9 kg / t, high-carbon ferrochrome 0.52 kg / t, alumina balls (Φ10mm) 1.8 kg / t, coke particles (Φ50mm) 0.35 kg / t, ferromolybdenum (FeMo60-B) 6.6 kg / t, and aluminum wire (Φ10mm) 1.0 m / t. The following auxiliary materials are added per ton of steel: active lime (Φ40mm) 6 kg / t and silicon carbide (Φ4mm) 1 kg / t.

[0039] (3) RH refining

[0040] The inlet temperature is 1679℃, the operation time is 30min, the argon pressure is controlled at 0.15MPa before the vacuum pump is started, so that the molten steel is not exposed when the slag surface moves slightly. When the vacuum degree reaches 100Pa, the timing starts and is maintained for 15min. At the same time, the argon pressure is adjusted to 0.4MPa. After the static argon blowing is completed, 2m / t of silicon-calcium alloy cored wire (Φ14mm) and 0.6kg / t of covering agent are added. The outlet temperature is 1629℃.

[0041] (4) Continuous casting

[0042] The ladle temperature upon arrival is 1625℃, with a steel volume of 98t. The tundish H is controlled at 1.4ppm. The entire casting process is protected, and medium carbon steel protective slag is used in the crystallizer.

[0043] (5) Heating process

[0044] Heating process: Inlet temperature of 450℃, preheating zone temperature requirement of 680℃, time 1.3h; heating zone 2 temperature requirement of 840℃, time 1.4h; heating zone 1 temperature requirement of 1198℃, time 1.4h; soaking zone temperature requirement of 1195℃, time 1.4h; tapping temperature of 1185℃.

[0045] (6) Rolling process

[0046] Rolling process: initial rolling temperature 1100℃, final rolling temperature 880℃;

[0047] 390mm*480mm continuous casting billet BD billet opening process: 9 rolling passes, rolling reduction: turn steel → 1st pass reduction 65mm → 2nd pass reduction 70mm → turn steel → 3rd pass reduction 64mm → 4th pass reduction 90mm → turn steel → 5th pass reduction 42mm → 6th pass reduction 40mm → 7th pass reduction 35mm → 8th pass reduction 34mm → turn steel → 9th pass reduction 82mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, and then entering an 8-stand continuous rolling mill group for rolling.

[0048] The rolling process for the Φ180mm raw material is as follows: 6 rolling passes. The first pass is 229mm high and 245mm wide; the second pass is 192mm high and 235mm wide; the third pass is 200mm high and 195mm wide; the fourth pass is 173mm high and 205mm wide; the fifth pass is 182.4mm high and 182.4mm wide; the sixth pass is 182.4mm high and 182.4mm wide; the finished product is produced after 6 passes.

[0049] (7) Thermal Insulation Process

[0050] Insulation process: steel insulation, temperature of the lower insulation pit is 650℃, insulation time is 53 hours, and the temperature of the lower insulation pit is 110℃.

[0051] Example 2

[0052] 1Chemical composition

[0053] The chemical composition by mass percentage is: C: 0.19%, Si: 0.28%, Mn: 0.48%, P: 0.011%, S: 0.004%, Cr: 0.88%, Ni: 0.04%, Mo: 0.49%, Cu: 0.03%, with the balance being iron and unavoidable impurities.

[0054] 2. Production processes of electric furnace continuous casting of steel bars for automobile axle sleeves

[0055] Process route: ECOARC eco-friendly electric furnace + LF + RH + continuous casting billet → heating furnace heating → rolling → holding → finishing → inspection → packaging and warehousing → shipment. Among them:

[0056] (1) Ecological electric furnace smelting

[0057] Scrap steel accounts for 100%; the scrap steel loading is 118t, the tapping temperature is 1660℃, the carbon content at tapping is 0.09%, and the phosphorus content is 0.008%. Auxiliary materials and alloys are added when 1 / 4 of the steel has been tapped, resulting in a tapping volume of 109t and a smelting cycle of 50 minutes. Alloy additions per ton of steel: silicon manganese 4.3Kg / t, low-carbon ferrochrome 11.2Kg / t, coke granules (Φ50mm) 17Kg / t, aluminum ferrochrome (Φ50mm) 2Kg / t, heavy scrap steel 935Kg / t. Auxiliary material additions per ton of steel: dolomite (Φ40mm) 20Kg / t, quicklime (Φ50mm) 43Kg / t, ladle ash 6Kg / t.

[0058] (2) LF furnace refining

[0059] A high current of 22000A is used to heat and slag. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime is added. After 5 minutes, the first sample is taken to analyze the chemical composition. Alloy and silicon carbide are added according to the target chemical composition value. Alloy and silicon carbide should be added to the argon gas flow to promote the rapid melting and homogenization of alloy and silicon carbide. When the molten steel temperature reaches 1596℃, add 2.6 kg / t of diffusion deoxidizer for diffusion deoxidation. Close the furnace door for 10 minutes. When the molten steel temperature reaches 1626℃, take a second sample to analyze the chemical composition to confirm the deviation of each chemical element content from the target value. After the second sample is taken, the smelting cycle is 49 minutes. The following alloys are added per ton of steel: ferrosilicon 3.4 kg / t, high-carbon ferromanganese 1.9 kg / t, high-carbon ferrochrome 0.52 kg / t, alumina balls 1.8 kg / t, coke particles (Φ50mm) 0.35 kg / t, ferromolybdenum (FeMo60-B) 6.6 kg / t, and aluminum wire (Φ10mm) 1 m / t. The following auxiliary materials are added per ton of steel: active lime (Φ50mm) 6 kg / t and silicon carbide (Φ4mm) 1 kg / t.

[0060] (3) RH refining

[0061] The inlet temperature is 1680℃, the operation time is 30min, the argon pressure is controlled at 0.16MPa before the vacuum pump is started, so that the molten steel is not exposed when the slag surface moves slightly. When the vacuum degree reaches 100Pa, the timing starts and is maintained for 12min. At the same time, the argon pressure is adjusted to 0.4MPa. After the static argon blowing is completed, 2m / t of silicon-calcium alloy cored wire (Φ14mm) and 0.6kg / t of covering agent are added. The outlet temperature is 1629℃.

[0062] (4) Continuous casting

[0063] The ladle temperature upon arrival was 1626℃, with a steel volume of 98t. The tundish H was controlled at 1.5ppm. The entire casting process was protected, and medium carbon steel protective slag was used in the crystallizer.

[0064] (5) Heating process

[0065] Heating process: Inlet temperature to the heating furnace is 480℃; preheating zone temperature is required to be 680℃ for 1.4 hours; heating zone 2 temperature is required to be 840℃ for 1.4 hours; heating zone 1 temperature is required to be 1200℃ for 1.4 hours; soaking zone temperature is required to be 1195℃ for 1.4 hours; tapping temperature is 1185℃.

[0066] (6) Rolling process

[0067] Rolling process: initial rolling temperature 1110℃, final rolling temperature 890℃;

[0068] 390mm*480mm continuous casting billet BD billet opening process: 9 rolling passes, rolling reduction: turn steel → 1st pass reduction 65mm → 2nd pass reduction 70mm → turn steel → 3rd pass reduction 64mm → 4th pass reduction 90mm → turn steel → 5th pass reduction 42mm → 6th pass reduction 40mm → 7th pass reduction 35mm → 8th pass reduction 34mm → turn steel → 9th pass reduction 82mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, and then entering an 8-stand continuous rolling mill group for rolling.

[0069] The rolling process for the Φ180mm raw material is as follows: 6 rolling passes. The first pass is 229mm high and 245mm wide; the second pass is 192mm high and 235mm wide; the third pass is 200mm high and 195mm wide; the fourth pass is 173mm high and 205mm wide; the fifth pass is 182.4mm high and 182.4mm wide; the sixth pass is 182.4mm high and 182.4mm wide; the finished product is produced after 6 passes.

[0070] (7) Thermal Insulation Process

[0071] Insulation process: steel insulation, temperature in the lower insulation pit is 630℃, insulation time is 50h, and the temperature after exiting the pit is 90℃.

[0072] Example 3

[0073] 1Chemical composition

[0074] The chemical composition by mass percentage is: C: 0.20%, Si: 0.27%, Mn: 0.50%, P: 0.009%, S: 0.003%, Cr: 0.90%, Ni: 0.05%, Mo: 0.48%, Cu: 0.05%, with the balance being iron and unavoidable impurities.

[0075] 2. Production processes of electric furnace continuous casting of steel bars for automobile axle sleeves

[0076] Process route: ECOARC eco-friendly electric furnace + LF + RH + continuous casting billet → heating furnace heating → rolling → holding → finishing → inspection → packaging and warehousing → shipment. Among them:

[0077] (1) Ecological electric furnace smelting

[0078] Scrap steel accounts for 100%; the scrap steel loading is 118t, the tapping temperature is 1659℃, the carbon content at tapping is 0.08%, and the phosphorus content is 0.009%. Auxiliary materials and alloys are added when 1 / 4 of the steel has been tapped, the tapping volume is 109t, and the smelting cycle is 49min. Alloy addition per ton of steel: silicon manganese 4.3Kg / t, low-carbon ferrochrome 11.2Kg / t, coke granules (Φ40mm) 17Kg / t, aluminum ferro (Φ60mm) 2Kg / t, heavy scrap steel 936Kg / t. Auxiliary material addition per ton of steel: dolomite (Φ40mm) 20Kg / t, quicklime (Φ5mm) 43Kg / t, ladle ash 6Kg / t.

[0079] (2) LF furnace refining

[0080] A high current of 23000A is used to heat and slag. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime is added. After 5 minutes, the first sample is taken to analyze the chemical composition. Alloy and silicon carbide are added according to the target chemical composition value. Alloy and silicon carbide should be added to the argon gas flow to promote the rapid melting and homogenization of alloy and silicon carbide. When the molten steel temperature reaches 1596℃, add 2.4 kg / t of diffusion deoxidizer for diffusion deoxidation. Close the furnace door for 12 minutes. When the molten steel temperature reaches 1625℃, take a second sample to analyze the chemical composition to confirm the deviation of each chemical element content from the target value. After the second sample is taken, the smelting cycle is 49 minutes. The following alloys are added per ton of steel: ferrosilicon 3.4 kg / t, high-carbon ferromanganese 1.9 kg / t, high-carbon ferrochrome 0.52 kg / t, alumina balls 1.8 kg / t, coke particles (Φ40mm) 0.35 kg / t, ferromolybdenum (FeMo60-B) 6.6 kg / t, and aluminum wire (Φ10mm) 1 m / t. The following auxiliary materials are added per ton of steel: active lime (Φ50mm) 6 kg / t and silicon carbide (Φ3mm) 1 kg / t.

[0081] (3) RH refining

[0082] The inlet temperature is 1680℃, the operation time is 30min, the argon pressure is controlled at 0.18MPa before the vacuum pump is started, so that the molten steel is not exposed when the slag surface moves slightly. When the vacuum degree reaches 100Pa, the timing starts and is maintained for 13min. At the same time, the argon pressure is adjusted to 0.4MPa. After the static argon blowing is completed, 2m / t of silicon-calcium alloy cored wire (Φ14mm) and 0.6kg / t of covering agent are added. The outlet temperature is 1629℃.

[0083] (4) Continuous casting

[0084] The ladle temperature upon arrival was 1627℃, with a steel volume of 98t. The tundish H was controlled at 1.3ppm. The entire casting process was protected, and medium carbon steel protective slag was used in the crystallizer.

[0085] (5) Heating process

[0086] Heating process: Inlet temperature to the heating furnace: 440℃; Preheating section temperature: 670℃; Time: 1.4h; Heating section 2 temperature: 850℃; Time: 1.3h; Heating section 1 temperature: 1198℃; Time: 1.4h; Soaking section temperature: 1195℃; Time: 1.4h; Tap-out temperature: 1186℃.

[0087] (6) Rolling process

[0088] Rolling process: initial rolling temperature 1105℃, final rolling temperature 885℃;

[0089] 390mm*480mm continuous casting billet BD billet opening process: 9 rolling passes, rolling reduction: turn steel → 1st pass reduction 65mm → 2nd pass reduction 70mm → turn steel → 3rd pass reduction 64mm → 4th pass reduction 90mm → turn steel → 5th pass reduction 42mm → 6th pass reduction 40mm → 7th pass reduction 35mm → 8th pass reduction 34mm → turn steel → 9th pass reduction 82mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, and then entering an 8-stand continuous rolling mill group for rolling.

[0090] The rolling process for the Φ180mm raw material is as follows: 6 rolling passes. The first pass is 229mm high and 245mm wide; the second pass is 192mm high and 235mm wide; the third pass is 200mm high and 195mm wide; the fourth pass is 173mm high and 205mm wide; the fifth pass is 182.4mm high and 182.4mm wide; the sixth pass is 182.4mm high and 182.4mm wide; the finished product is produced after 6 passes.

[0091] (7) Thermal Insulation Process

[0092] Insulation process: steel insulation, temperature in the insulation pit is 640℃, insulation time is 52 hours, and the temperature after exiting the pit is 80℃.

[0093] Example 4

[0094] 1Chemical composition

[0095] The chemical composition by mass percentage is: C: 0.21%, Si: 0.28%, Mn: 0.50%, P: 0.008%, S: 0.005%, Cr: 0.90%, Ni: 0.05%, Mo: 0.50%, Cu: 0.05%, with the balance being iron and unavoidable impurities.

[0096] 2. Production processes of electric furnace continuous casting of steel bars for automobile axle sleeves

[0097] Process route: ECOARC eco-friendly electric furnace + LF + RH + continuous casting billet → heating furnace heating → rolling → holding → finishing → inspection → packaging and warehousing → shipment. Among them:

[0098] (1) Ecological electric furnace smelting

[0099] Scrap steel accounts for 100%; the scrap steel loading is 118t, the tapping temperature is 1659℃, the carbon content at tapping is 0.08%, and the phosphorus content is 0.006%. Auxiliary materials and alloys are added when 1 / 4 of the steel has been tapped, the tapping volume is 108t, and the smelting cycle is 48min. Alloy addition per ton of steel: silicon manganese 4.3Kg / t, low-carbon ferrochrome 11.3Kg / t, coke granules (Φ40mm) 17Kg / t, aluminum ferro (Φ60mm) 2Kg / t, heavy scrap steel 935Kg / t. Auxiliary material addition per ton of steel: dolomite (Φ50mm) 20Kg / t, active lime (50mm) 43Kg / t, ladle ash 6Kg / t.

[0100] (2) LF furnace refining

[0101] A high current of 22000A is used to heat and slag. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime is added. After 5 minutes, the first sample is taken to analyze the chemical composition. Alloy and silicon carbide are added according to the target chemical composition value. Alloy and silicon carbide should be added to the argon gas flow to promote the rapid melting and homogenization of alloy and silicon carbide. When the molten steel temperature reaches 1597℃, add 2.3 kg / t of diffusion deoxidizer for diffusion deoxidation. Close the furnace door for 10 minutes. When the molten steel temperature reaches 1628℃, take a second sample to analyze the chemical composition to confirm the deviation of each chemical element content from the target value. After the second sample is taken, the smelting cycle is 49 minutes. The following alloys are added per ton of steel: ferrosilicon 3.4 kg / t, high-carbon ferromanganese 1.9 kg / t, high-carbon ferrochrome 0.53 kg / t, alumina balls 1.8 kg / t, coke particles (Φ50mm) 0.35 kg / t, ferromolybdenum (FeMo60-B) 6.6 kg / t, and aluminum wire (Φ10mm) 1 m / t. The following auxiliary materials are added per ton of steel: active lime (Φ50mm) 6 kg / t and silicon carbide (Φ4mm) 1 kg / t.

[0102] (3) RH refining

[0103] The inlet temperature is 1682℃, the operation time is 30min, the argon pressure is controlled at 0.15MPa before the vacuum pump is started, so that the molten steel is not exposed when the slag surface moves slightly. When the vacuum degree reaches 100Pa, the timing starts and is maintained for 13min. At the same time, the argon pressure is adjusted to 0.3MPa. After the static argon blowing is completed, 2m / t of silicon-calcium alloy cored wire (Φ14mm) and 0.6kg / t of covering agent are added. The outlet temperature is 1628℃.

[0104] (4) Continuous casting

[0105] The ladle temperature upon arrival was 1625℃, with a steel volume of 98t. The tundish H was controlled at 1.3ppm. The entire casting process was protected, and medium carbon steel protective slag was used in the crystallizer.

[0106] (5) Heating process

[0107] Heating process: Inlet temperature of 530℃, preheating zone temperature requirement of 660℃, time 1.4h; heating zone 2 temperature requirement of 850℃, time 1.4h; heating zone 1 temperature requirement of 1198℃, time 1.4h; soaking zone temperature requirement of 1195℃, time 1.4h; tapping temperature of 1185℃.

[0108] (6) Rolling process

[0109] Rolling process: initial rolling temperature 1100℃, final rolling temperature 884℃;

[0110] 390mm*480mm continuous casting billet BD billet opening process: 9 rolling passes, rolling reduction: turn steel → 1st pass reduction 65mm → 2nd pass reduction 70mm → turn steel → 3rd pass reduction 64mm → 4th pass reduction 90mm → turn steel → 5th pass reduction 42mm → 6th pass reduction 40mm → 7th pass reduction 35mm → 8th pass reduction 34mm → turn steel → 9th pass reduction 82mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, and then entering an 8-stand continuous rolling mill group for rolling.

[0111] The rolling process for the Φ180mm raw material is as follows: 6 rolling passes. The first pass is 229mm high and 245mm wide; the second pass is 192mm high and 235mm wide; the third pass is 200mm high and 195mm wide; the fourth pass is 173mm high and 205mm wide; the fifth pass is 182.4mm high and 182.4mm wide; the sixth pass is 182.4mm high and 182.4mm wide; the finished product is produced after 6 passes.

[0112] (7) Thermal Insulation Process

[0113] Insulation process: steel insulation, temperature in the lower insulation pit is 630℃, insulation time is 50h, and the temperature after exiting the pit is 80℃.

[0114] Example 5

[0115] 1Chemical composition

[0116] The chemical composition by mass percentage is: C: 0.19%, Si: 0.28%, Mn: 0.48%, P: 0.010%, S: 0.004%, Cr: 0.90%, Ni: 0.04%, Mo: 0.48%, Cu: 0.04%, with the balance being iron and unavoidable impurities.

[0117] 2. Production processes of electric furnace continuous casting of steel bars for automobile axle sleeves

[0118] Process route: ECOARC eco-friendly electric furnace + LF + RH + continuous casting billet → heating furnace heating → rolling → holding → finishing → inspection → packaging and warehousing → shipment. Among them:

[0119] (1) Ecological electric furnace smelting

[0120] Scrap steel accounts for 100%; the scrap steel loading is 119t, the tapping temperature is 1659℃, the carbon content at tapping is 0.08%, and the phosphorus content is 0.007%. Auxiliary materials and alloys are added when 1 / 4 of the steel has been tapped, the tapping volume is 110t, and the smelting cycle is 49min. Alloy addition per ton of steel: silicon manganese 4.3Kg / t, low-carbon ferrochrome 11.3Kg / t, coke granules (Φ50mm) 17Kg / t, aluminum ferrochrome (Φ50mm) 2Kg / t, heavy scrap steel 935Kg / t. Auxiliary material addition per ton of steel: dolomite (Φ50mm) 20Kg / t, quicklime (Φ50mm) 43Kg / t, ladle ash 6Kg / t.

[0121] (2) LF furnace refining

[0122] A high current of 23000A is used to heat and slag. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime is added. After 5 minutes, the first sample is taken to analyze the chemical composition. Alloy and silicon carbide are added according to the target chemical composition value. Alloy and silicon carbide should be added to the argon gas flow to promote the rapid melting and homogenization of alloy and silicon carbide. When the molten steel temperature reaches 1595℃, add 2.5 kg / t of diffusion deoxidizer for diffusion deoxidation. Close the furnace door for 10 minutes. When the molten steel temperature reaches 1626℃, take a second sample to analyze the chemical composition to confirm the deviation of each chemical element content from the target value. After the second sample is taken, the smelting cycle is 52 minutes. The following alloys are added per ton of steel: ferrosilicon 3.4 kg / t, high-carbon ferromanganese 1.9 kg / t, high-carbon ferrochrome 0.53 kg / t, alumina balls 1.8 kg / t, coke particles (Φ50mm) 0.35 kg / t, ferromolybdenum (FeMo60-B) 6.6 kg / t, and aluminum wire (Φ10mm) 1 m / t. The following auxiliary materials are added per ton of steel: active lime (50mm) 6 kg / t and silicon carbide (Φ4mm) 1 kg / t.

[0123] (3) RH refining

[0124] The inlet temperature is 1682℃, the operation time is 29min, the argon pressure is controlled at 0.2MPa before the vacuum pump is started, so that the molten steel is not exposed when the slag surface moves slightly. When the vacuum degree reaches 100Pa, the timing starts and is maintained for 12min. At the same time, the argon pressure is adjusted to 0.3MPa. After the static argon blowing is completed, 2m / t of silicon-calcium alloy cored wire (Φ14mm) and 0.6kg / t of covering agent are added. The outlet temperature is 1628℃.

[0125] (4) Continuous casting

[0126] The ladle temperature upon arrival was 1627℃, with a steel volume of 98t. The tundish H was controlled at 1.5ppm. The entire casting process was protected, and medium carbon steel protective slag was used in the crystallizer.

[0127] (5) Heating process

[0128] Heating process: Inlet temperature to the heating furnace is 420℃; preheating zone temperature is required to be 660℃ for 1.3 hours; heating zone 2 temperature is required to be 850℃ for 1.3 hours; heating zone 1 temperature is required to be 1198℃ for 1.3 hours; soaking zone temperature is required to be 1198℃ for 1.3 hours; tapping temperature is 1186℃.

[0129] (6) Rolling process

[0130] Rolling process: initial rolling temperature 1100℃, final rolling temperature 880℃;

[0131] 390mm*480mm continuous casting billet BD billet opening process: 9 rolling passes, rolling reduction: turn steel → 1st pass reduction 65mm → 2nd pass reduction 70mm → turn steel → 3rd pass reduction 64mm → 4th pass reduction 90mm → turn steel → 5th pass reduction 42mm → 6th pass reduction 40mm → 7th pass reduction 35mm → 8th pass reduction 34mm → turn steel → 9th pass reduction 82mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, and then entering an 8-stand continuous rolling mill group for rolling.

[0132] The rolling process for the Φ180mm raw material is as follows: 6 rolling passes. The first pass is 229mm high and 245mm wide; the second pass is 192mm high and 235mm wide; the third pass is 200mm high and 195mm wide; the fourth pass is 173mm high and 205mm wide; the fifth pass is 182.4mm high and 182.4mm wide; the sixth pass is 182.4mm high and 182.4mm wide; the finished product is produced after 6 passes.

[0133] (7) Thermal Insulation Process

[0134] Insulation process: steel insulation, temperature of the lower insulation pit is 650℃, insulation time is 54 hours, and the temperature of the lower insulation pit is 90℃.

[0135] Inspection results of finished products in Examples 1-5

[0136] (1) Low magnification structure of Φ180mm steel

[0137] Serial Number Generally loose Central loose Ingot segregation General speckled segregation Edge spot-like segregation standard ≤1.5 ≤1.5 ≤1.5 ≤1.0 ≤1.0 Example 1 0.5 0.5 0.5 0 0 Example 1 0.5 0.5 0.5 0 0 Example 2 0.5 0.5 0.5 0 0 Example 2 0.5 0.5 0.5 0 0 Example 3 0.5 0.5 0.5 0 0 Example 3 0.5 0.5 0.5 0 0 Example 4 0.5 0.5 0.5 0 0 Example 4 0.5 0.5 0.5 0 0 Example 5 0.5 0.5 0.5 0 0 Example 5 0.5 0.5 0.5 0 0

[0138] (2) Non-metallic inclusions in Φ180mm steel

[0139]

[0140] (3) Mechanical properties of Φ180mm steel

[0141]

[0142] For anyone skilled in the art, many possible variations and modifications can be made to the technical solutions of this invention, or equivalent embodiments can be modified based on the disclosed technical content, without departing from the scope of the technical solutions of this invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this invention without departing from the content of the technical solutions of this invention should still fall within the protection scope of the technical solutions of this invention.

Claims

1. A method for smelting steel for automobile bushings using an ecological electric furnace, characterized in that, The automobile axle sleeve steel contains, by mass, C: 0.18-0.23%, Si: 0.20-0.35%, Mn: 0.42-0.60%, P: ≤0.015%, S: ≤0.010%, Cr: 0.82-1.00%, Ni: ≤0.25%, Mo: 0.41-0.53%, Cu: ≤0.15%, and the balance of iron and inevitable impurities; The method comprises: ecological electric furnace smelting, LF refining, RH refining, continuous casting, heating furnace heating process and rolling process; The ecological electric furnace smelting is: using scrap steel smelting, scrap steel loading amount is 116-122 t, tapping temperature is 1655-1665 DEG C, C is 0.08-0.10% when tapping, P is ≤0.010%, auxiliary materials and alloys are added when tapping 1 / 4-1 / 3, tapping amount is 107-112 t, smelting period is 45-55 min; alloy ton steel adding amount: silicon manganese 4.3-4.4 kg / t, low-carbon chromium iron 11-11.5 kg / t, coke particles 17-17.2 kg / t, aluminum iron 2-2.2 kg / t, heavy scrap steel 930-940 kg / t; auxiliary material ton steel adding amount: dolomite 20-21 kg / t, active lime 43-44 kg / t, ladle ash 6-6.2 kg / t; The LF furnace refining is: using 20000-25000A large current to heat and slag, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, active lime is supplemented, the first sampling analysis of chemical components is carried out after 5 min, and alloys and silicon carbide are supplemented according to the target value of the chemical components; when the molten steel temperature reaches 1590-1600 DEG C, diffusion deoxidizer 2-3 kg / t steel is added for diffusion deoxidation, the furnace door is closed for 10-12 min, the second sampling analysis of chemical components is carried out when the molten steel temperature reaches 1620-1630 DEG C, so as to confirm the deviation value of each chemical element content from the target value, after the second sampling is taken away, the smelting period is 45-55 min; the alloy ton steel adding amount for supplementing: silicon iron 3.4-3.5 kg / t, high-carbon manganese iron 1.9-2.0 kg / t, high-carbon chromium iron 0.5-0.55 kg / t, aluminum oxide ball 1.8-1.9 kg / t, coke particles 0.35-0.36 kg / t, molybdenum iron 6.6-6.7 kg / t, aluminum wire 1-1.1 m / t; the auxiliary material ton steel adding amount for supplementing: active lime 6-6.2 kg / t, silicon carbide 1-1.1 kg / t; The RH refining is: the entering station temperature is 1675-1685 DEG C, the operation time is 28-32 min, the argon pressure is controlled to 0.1-0.3 MPa before the vacuum pump starts, the slag surface slightly moves the molten steel and is not exposed, the timing is started when the vacuum degree reaches 100-110 Pa, the holding time is 10-15 min, the argon pressure is adjusted to 0.3-0.5 MPa at the same time, after the static argon blowing is finished, the silicon calcium alloy cored wire 2-2.1 m / t steel is added, the covering agent 0.6-0.7 kg / t steel is added, and the leaving station temperature is 1625-1635 DEG C.

2. The method of claim 1, wherein, The continuous casting is: continuous casting of 1620-1630 DEG C with ladle to station temperature, 95-103 tons of molten steel, H control of tundish is less than or equal to 2 ppm, whole process protection casting, and crystallizer protection slag is medium carbon steel protection slag.

3. The method of claim 1, wherein, The heating process is: 350 DEG C-550 DEG C into heating furnace, 650 DEG C-700 DEG C in preheating section, 1.3-1.5 h, 840 DEG C-860 DEG C in heating 2 section, 1.3-1.5 h, 1190 DEG C-1220 DEG C in heating 1 section, 1.3-1.5 h, 1180 DEG C-1210 DEG C in soaking section, 1.3-1.5 h, and 1180 DEG C-1190 DEG C out of steel.

4. The method of claim 1, wherein, The rolling process is: The BD breakdown process is: 9 passes, rolling reduction: turning over steel - 65-65.1 mm of the first pass reduction - 70-70.1 mm of the second pass reduction - turning over steel - 64-64.1 mm of the third pass reduction - 90-90.1 mm of the fourth pass reduction - turning over steel - 42-42.1 mm of the fifth pass reduction - 40-40.1 mm of the sixth pass reduction - 35-35.1 mm of the seventh pass reduction - 34-34.1 mm of the eighth pass reduction - turning over steel - 82-82.1 mm of the ninth pass reduction, through 3 sets of 850 mm rolling mill, 1 set of 735 mm rolling mill, and then into 8 sets of continuous rolling mill group for rolling; The rolling process of the product specification is: 6 passes, 229-229.1 mm of the first pass height, 245-245.1 mm of the first pass width, 192-192.1 mm of the second pass height, 235-235.1 mm of the second pass width, 200-200.1 mm of the third pass height, 195-195.1 mm of the third pass width, 173-173.1 mm of the fourth pass height, 205-205.1 mm of the fourth pass width, 182.4-182.5 mm of the fifth pass height, 182.4-182.5 mm of the fifth pass width, 182.4-182.5 mm of the sixth pass height, and 182.4-182.5 mm of the sixth pass width, and the finished product is discharged after 6 passes.

5. The method of claim 4, wherein, The rolling temperature of the rolling process is 1100-1130 DEG C, and the finish rolling temperature is 850-950 DEG C.

6. The method of claim 1, wherein, The rolled steel is subjected to heat preservation, and the heat preservation process is: steel heat preservation, the temperature of the lower heat preservation pit is greater than or equal to 600 DEG C, the heat preservation time is 48-55 h, and the pit temperature is less than or equal to 150 DEG C.

7. The method of claim 1, wherein, The diameter of the coke particles is 20-60 mm, the diameter of the aluminum-iron is 40-70 mm, the specification of the heavy scrap steel is greater than or equal to 800 mm*600 mm, the diameter of the dolomite is 20-70 mm, the diameter of the active lime is 10-70 mm, the diameter of the alumina ball is 10-15 mm, the molybdenum iron is FeMo60-B, the diameter of the aluminum wire is 10-12 mm, the diameter of the silicon carbide is 2-5 mm, and the diameter of the silicon-calcium alloy cored wire is 12-14 mm.

8. The method of claim 6, wherein, The heat treated steel is subjected to heat treatment, and the heat treatment comprises the following steps: 1) quenching: 870-890 DEG C, heat preservation for 0.8-1.2 h, and oil cooling; 2) tempering: 490-510 DEG C, heat preservation for 1.6-2.0 h, and water cooling.

Images