Method for producing and preparing steel bar for automobile shaft sleeve by means of ecological electric furnace

Abstract

A method for producing and preparing a steel bar for an automobile shaft sleeve by means of an ecological electric furnace. The steel bar comprises, in percentage 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%, and Cu: ≤0.15%, with the balance being iron and inevitable impurities. By means of smelting in an ecological electric furnace, LF refining, RH refining, continuous casting, a heating process and a rolling process, the method achieves a breakthrough in batch production of the steel bar for an automobile shaft sleeve by means of a continuous casting procedure using the ecological electric furnace.

Description

A method for producing steel bars for automobile shaft sleeves in an ecological electric furnace Technical Field

[0001] The present invention relates to the field of special steel, and in particular to a method for producing steel bars for automobile shaft sleeves in an ecological electric furnace. Background Art

[0002] As flexible connectors between vehicle components, automotive bushings can improve vehicle comfort, handling stability, and noise control. Different vehicle models have varying stiffness requirements for bushings, and the bushing structure should be tailored to meet these diverse needs.

[0003] Automobile bushings must possess excellent wear resistance, tensile strength, temperature resistance, and corrosion resistance. Furthermore, they must exhibit excellent fatigue resistance, impact resistance, and vibration resistance to ensure the normal operation of the vehicle. As an essential component of the transmission system, automobile bushings are subject to stringent quality requirements.

[0004] The quality of steel used in automobile bushings directly affects the service life and wear resistance of the transmission device, and even affects the safety of the entire transmission working process.

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

[0006] Summary of the Invention

[0007] The purpose of the present invention is to provide a production process and preparation method for steel bars for automobile axle sleeves. The method adopts the ECOARC ecological electric furnace + LF + RH + continuous casting smelting process to produce steel bars for automobile axle sleeves, which meets high-end usage requirements and achieves a breakthrough in the batch production of steel bars for automobile axle sleeves using the ecological electric furnace continuous casting process. It not only ensures the mechanical properties, high hardness and high steel purity of the finished steel bars for automobile axle sleeves, but also ensures the surface quality level of the steel bars for automobile axle sleeves.

[0008] To achieve the aforementioned objectives, the present invention provides a production process for steel bars for automotive axle sleeves, including component and process design. Specifically, the process involves an ECOARC electric furnace, LF furnace, RH furnace, continuous casting, heating, and rolling. This method meets the quality requirements for automotive axle sleeve steel bars, while also meeting standard specifications for mechanical properties, high hardness, and high steel purity.

[0009] A steel bar for automobile axle sleeves has the following chemical compositions, 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%, and the balance being iron and unavoidable impurities.

[0010] A production process and preparation method of the above-mentioned automobile axle sleeve steel bar by smelting in an ecological electric furnace, wherein the process route is: ecological electric furnace smelting → LF refining → RH refining → continuous casting → heating furnace heating process → rolling process;

[0011] The ecological electric furnace smelting process utilizes scrap steel, with scrap accounting for 100% by mass. The scrap charge is 116-122 tons, the tapping temperature is 1655-1665°C, the tapping temperature is 0.08-0.10%, and P is ≤0.010%. Auxiliary materials and alloys are added when 1 / 4-1 / 3 of the steel is tapped, resulting in a tapping volume of 107-112 tons. The smelting cycle is 45-55 minutes. Alloy additions per ton of steel include: 4.3-4.4 kg / t of silicon-manganese, 11-11.5 kg / t of low-carbon ferrochrome, 17-17.2 kg / t of coke pellets (Φ20-Φ60 mm), 2-2.2 kg / t of ferroaluminum (Φ40-70 mm), and 930-940 kg / t of heavy scrap steel (≥800 mm x 600 mm). The amount of auxiliary materials added per ton of steel: dolomite (Φ20~70mm) 20~21Kg / t, active lime (Φ10~70mm) 43~44Kg / t, ladle dust 6~6.2Kg / t.

[0012] Based on the above technical solution, further, the LF furnace refining is as follows: a large current of 20,000 to 25,000 A is used to heat and melt the slag; when the slag surface fluctuates and the molten steel and the arc are not exposed, active lime is added; after 5 minutes, the chemical composition is analyzed for the first time; alloy and silicon carbide are added according to the target chemical composition value; the alloy and silicon carbide should be added to the argon flow to promote rapid melting and homogenization of the alloy and silicon carbide. When the temperature of the molten steel reaches 1590-1600℃, 2-3kg / t of diffusion deoxidizer is added for diffusion deoxidation, and the furnace door is closed for 10-12 minutes. When the temperature of the molten steel reaches 1620-1630℃, the chemical composition is analyzed for the second time to confirm the deviation of the content of each chemical element from the target value. After the second sample is taken, the smelting cycle is 45-55 minutes. The additional alloy addition per ton of steel is: 3.4-3.5kg / t of ferrosilicon, 1.9-2.0kg / t of high carbon ferromanganese, 0.5-0.55kg / t of high carbon ferrochromium, 1.8-1.9kg / t of alumina balls (Φ10-15mm), 0.35-0.36kg / t of coke particles (Φ20-60mm), 6.6-6.7kg / t of ferromolybdenum (FeMo60-B), and 1-1.1m / t of aluminum wire (Φ10-Φ12mm). The amount of supplementary materials added per ton of steel: active lime (Φ10~70mm) 6~6.2Kg / t, silicon carbide (Φ2~Φ5mm) 1~1.1Kg / t.

[0013] The RH refining is as follows: the station entry temperature is 1675-1685°C, the operation time is 28 minutes to 32 minutes, the argon pressure is controlled at 0.1-0.3 MPa before the vacuum pump is started, so that the slag surface is slightly moved and the molten steel is not exposed. When the vacuum degree reaches 100-110 Pa, the timing is started and the time is maintained for 10-15 minutes. At the same time, the argon pressure is adjusted to 0.3-0.5 MPa. After the static argon blowing is completed, 2-2.1 meters / t of silicon-calcium alloy cored wire (Φ12-Φ14mm) and 0.6-0.7kg / t of steel of covering agent are added. The station exit temperature is 1625-1635°C.

[0014] Based on the above technical solution, the continuous casting is further as follows: the ladle arrival temperature is 1620-1630°C, the molten steel volume is 95-103t, the H in the tundish is controlled to be ≤2ppm, the whole process is protected casting, and the crystallizer protection slag uses medium carbon steel protection slag.

[0015] The heating process is as follows: the temperature entering the heating furnace is 350℃~550℃, the temperature of the preheating section is required to be 650℃~700℃, and the time is 1.3~1.5h; the temperature of the heating section 2 is required to be 840℃~860℃, and the time is 1.3~1.5h; the temperature of the heating section 1 is required to be 1190℃~1220℃, and the time is 1.3~1.5h; the temperature of the soaking section is required to be 1180℃~1210℃, and the time is 1.3~1.5h; the steel tapping temperature is 1180℃~1190℃.

[0016] Based on the above technical solution, further, the rolling process is: the starting rolling temperature is 1100-1130°C, and the finishing rolling temperature is 850-950°C; the rolling process includes rolling in the blooming mill → rolling in the tandem rolling mill, specifically:

[0017] BD blooming process for continuous casting billet: 9 rolling passes, rolling reduction: steel turning → 1st pass reduction 65~65.1mm → 2nd pass reduction 70~70.1mm → steel turning → 3rd pass reduction 64~64.1mm → 4th pass reduction 90~90.1mm → steel turning → 5th pass reduction 42~42.1mm → 6th pass reduction 40~40.1mm → 7th pass reduction 35~35.1mm → 8th pass reduction 34~34.1mm → steel turning → 9th pass reduction 82~82.1mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, and then entering 8 continuous rolling mill groups for rolling.

[0018] Product specification Φ180mm rolling process: 6 rolling passes, the first pass is 229~229.1mm high and 245~245.1mm wide; the second pass is 192~192.1mm high and 235~235.1mm wide; the third pass is 200~200.1mm high and 195~195.1mm wide; the fourth pass is 173~173.1mm high and 205~205.1mm wide; the fifth pass is 182.4~182.5mm high and 182.4~182.5mm wide; the sixth pass is 182.4~182.5mm high and 182.4~182.5mm wide; the finished product is produced after 6 passes.

[0019] Based on the above technical solution, further, the rolled steel is insulated, and the insulation process is: steel insulation, the temperature of the lower insulation pit is ≥600°C, insulation is 48-55h, and the exit temperature is ≤150°C.

[0020] Based on the above technical solution, further, the size of the continuous casting billet is 390mm*480mm.

[0021] Furthermore, the process route includes the following steps: heat preservation, finishing, inspection, packaging, storage, and shipment.

[0022] Based on the above technical solution, further, the steel sample after insulation is sampled and heat treated, and the heat treatment includes the following steps:

[0023] 1) Quenching: 870-890℃, holding time 0.8-1.2h, oil cooling;

[0024] 2) Tempering: 490-510℃, keep warm for 1.6-2.0h, water cooling.

[0025] Based on the above technical solution, further, the insulated steel is drilled to obtain a 25 mm diameter blank for heat treatment.

[0026] Beneficial effects of the present invention:

[0027] (1) The ECOARC ecological electric furnace + LF + RH + 390mm*480mm smelting process and rolling process are used to produce 38CrSiA steel bars for automobile drive shafts. The production specification is Φ150mm, which meets the mechanical performance requirements and ensures the purity of the steel.

[0028] (2) Reasonable component design and production process ensure surface quality and impact performance.

[0029] (3) The macrostructure, non-metallic inclusions and mechanical properties of the finished steel meet the requirements of high-end products. DETAILED DESCRIPTION

[0030] The following non-limiting examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0031] Example 1

[0032] 1Chemical composition

[0033] 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%, and the balance is iron and inevitable impurities.

[0034] 2. Electric furnace continuous casting production processes for automobile axle sleeve steel bars

[0035] Process route: ECOARC ecological electric furnace + LF + RH + continuous casting → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery.

[0036] (1) Ecological electric furnace smelting

[0037] Scrap steel accounts for 100% of the total steel production; the scrap charge is 118 tons, the tapping temperature is 1660°C, the carbon content is 0.08%, and the phosphorus content is 0.008%. Auxiliary materials and alloys are added when 1 / 4 of the steel is tapped. The tapping volume is 110 tons, and the smelting cycle is 50 minutes. Alloy additions per ton of steel include: 4.3 kg / t of silicon-manganese, 11 kg / t of low-carbon ferrochrome, 17 kg / t of coke pellets (Φ50mm), 2 kg / t of ferroaluminum (Φ50mm), and 934 kg / t of heavy scrap steel (800mm*600mm). Auxiliary material additions per ton of steel include: 20 kg / t of dolomite (Φ50mm), 43 kg / t of active lime (Φ40mm), and 6 kg / t of ladle dust.

[0038] (2) LF furnace refining

[0039] A high current of 23,000A is used to heat and melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, active lime is added. The chemical composition is analyzed for the first time after 5 minutes. Alloy and silicon carbide are added according to the target chemical composition values. The alloy and silicon carbide should be added to the argon flow to promote rapid melting and homogenization of the alloy and silicon carbide. When the molten steel temperature reaches 1595°C, 2.5 kg / t of diffusion deoxidizer is added for diffusion deoxidation. The furnace door is closed for 10 minutes. When the molten steel temperature reaches 1625°C, a second sample is taken for chemical composition analysis to confirm the deviation of the content of each chemical element from the target value. After the second sample is taken, the smelting cycle is 48 minutes. The following alloy additions per ton of steel are added: 3.4 kg / t of ferrosilicon, 1.9 kg / t of high-carbon ferromanganese, 0.52 kg / t of high-carbon ferrochromium, 1.8 kg / t of alumina balls (Φ10 mm), 0.35 kg / t of coke pellets (Φ50 mm), 6.6 kg / t of ferromolybdenum (FeMo60-B), and 1.0 m / t of aluminum wire (Φ10 mm). The following auxiliary materials are added per ton of steel: 6 kg / t of active lime (Φ40 mm) and 1 kg / t of silicon carbide (Φ4 mm).

[0040] (3)RH refining

[0041] The inlet temperature is 1679℃, the operation time is 30min, and the argon pressure is controlled at 0.15MPa before the vacuum pump is started, so that the slag surface moves slightly and the molten steel is not exposed. When the vacuum degree reaches 100Pa, the timing starts and the maintenance time is 15min. At the same time, the argon pressure is adjusted to 0.4MPa. After the static argon blowing is completed, 2 meters / t of silicon-calcium alloy cored wire (Φ14mm) and 0.6kg / t of covering agent are added. The outlet temperature is 1629℃.

[0042] (4) Continuous casting

[0043] The temperature of the ladle at the station for continuous casting is 1625℃, the amount of molten steel is 98t, the H in the tundish is controlled at 1.4ppm, the casting is protected throughout the process, and the crystallizer protection slag uses medium carbon steel protection slag.

[0044] (5) Heating process

[0045] Heating process: The temperature entering the heating furnace is 450℃, the preheating section temperature is required to be 680℃, and the time is 1.3h; the temperature of the heating section 2 is required to be 840℃, and the time is 1.4h; the temperature of the heating section 1 is required to be 1198℃, and the time is 1.4h; the temperature of the soaking section is required to be 1195℃, and the time is 1.4h; the steel tapping temperature is 1185℃.

[0046] (6) Rolling process

[0047] Rolling process: starting rolling temperature 1100℃, finishing rolling temperature 880℃;

[0048] BD billet opening process for 390mm*480mm continuous casting billet: 9 rolling passes, rolling reduction: steel turning → 1st pass reduction 65mm → 2nd pass reduction 70mm → steel turning → 3rd pass reduction 64mm → 4th pass reduction 90mm → steel turning → 5th pass reduction 42mm → 6th pass reduction 40mm → 7th pass reduction 35mm → 8th pass reduction 34mm → steel turning → 9th pass reduction 82mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, and then entering the 8-pass continuous rolling mill group for rolling.

[0049] The product specification is Φ180mm rolling process: 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.

[0050] (7) Insulation process

[0051] Insulation process: Steel insulation, lower insulation pit temperature 650℃, insulation 53h, exit pit temperature 110℃.

[0052] Example 2

[0053] 1Chemical composition

[0054] 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%, and the balance is iron and inevitable impurities.

[0055] 2. Electric furnace continuous casting production processes for automobile axle sleeve steel bars

[0056] Process route: ECOARC ecological electric furnace + LF + RH + continuous casting → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery.

[0057] (1) Ecological electric furnace smelting

[0058] Scrap steel accounts for 100% of the total steel production; the scrap charge is 118 tons, the tapping temperature is 1660°C, the carbon content is 0.09% and the phosphorus content is 0.008% at tapping, auxiliary materials and alloys are added when 1 / 4 of the steel is tapped, the tapping volume is 109 tons, and the smelting cycle is 50 minutes. Alloy additions per ton of steel include: 4.3 kg / t of silicon manganese, 11.2 kg / t of low-carbon ferrochrome, 17 kg / t of coke pellets (Φ50mm), 2 kg / t of ferroaluminum (Φ50mm), and 935 kg / t of heavy-duty scrap steel. Auxiliary material additions per ton of steel include: 20 kg / t of dolomite (Φ40mm), 43 kg / t of active lime (Φ50mm), and 6 kg / t of ladle dust.

[0059] (2) LF furnace refining

[0060] A high current of 22000A is used to heat and melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, active lime is added. The chemical composition is analyzed for the first time after 5 minutes. Alloy and silicon carbide are added according to the target chemical composition values. The alloy and silicon carbide should be added to the argon flow to promote rapid melting and homogenization of the alloy and silicon carbide. When the molten steel temperature reached 1596°C, 2.6 kg / t of diffusion deoxidizer was added for diffusion deoxidation. The furnace door was closed for 10 minutes. When the molten steel temperature reached 1626°C, a second sample was taken for chemical composition analysis to confirm the deviation of the content of each chemical element from the target value. After the second sample was taken, the smelting cycle lasted 49 minutes. The following alloy additions per ton of steel were added: 3.4 kg / t of ferrosilicon, 1.9 kg / t of high-carbon ferromanganese, 0.52 kg / t of high-carbon ferrochromium, 1.8 kg / t of alumina balls, 0.35 kg / t of coke pellets (Φ50 mm), 6.6 kg / t of ferromolybdenum (FeMo60-B), and 1 m / t of aluminum wire (Φ10 mm). The following auxiliary materials were added per ton of steel: 6 kg / t of active lime (Φ50 mm) and 1 kg / t of silicon carbide (Φ4 mm).

[0061] (3)RH refining

[0062] The inlet temperature is 1680℃, the operation time is 30min, and the argon pressure is controlled at 0.16MPa before the vacuum pump is started, so that the slag surface moves slightly and the molten steel is not exposed. When the vacuum degree reaches 100Pa, the timing starts and the maintenance time is 12min. At the same time, the argon pressure is adjusted to 0.4MPa. After the static argon blowing is completed, 2 meters / t of silicon-calcium alloy cored wire (Φ14mm) and 0.6kg / t of covering agent are added. The outlet temperature is 1629℃.

[0063] (4) Continuous casting

[0064] The temperature of the ladle at the station for continuous casting is 1626℃, the amount of molten steel is 98t, the H in the tundish is controlled at 1.5ppm, the casting is protected throughout the process, and the crystallizer protection slag uses medium carbon steel protection slag.

[0065] (5) Heating process

[0066] Heating process: The temperature entering the heating furnace is 480℃, the preheating section temperature is required to be 680℃, and the time is 1.4h; the temperature of the heating section 2 is required to be 840℃, and the time is 1.4h; the temperature of the heating section 1 is required to be 1200℃, and the time is 1.4h; the temperature of the soaking section is required to be 1195℃, and the time is 1.4h; the steel tapping temperature is 1185℃.

[0067] (6) Rolling process

[0068] Rolling process: starting rolling temperature 1110℃, finishing rolling temperature 890℃;

[0069] BD billet opening process for 390mm*480mm continuous casting billet: 9 rolling passes, rolling reduction: steel turning → 1st pass reduction 65mm → 2nd pass reduction 70mm → steel turning → 3rd pass reduction 64mm → 4th pass reduction 90mm → steel turning → 5th pass reduction 42mm → 6th pass reduction 40mm → 7th pass reduction 35mm → 8th pass reduction 34mm → steel turning → 9th pass reduction 82mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, and then entering the 8-pass continuous rolling mill group for rolling.

[0070] The product specification is Φ180mm rolling process: 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.

[0071] (7) Insulation process

[0072] Insulation process: Steel insulation, lower insulation pit temperature 630℃, insulation 50h, exit pit temperature 90℃.

[0073] Example 3

[0074] 1Chemical composition

[0075] 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%, and the balance is iron and inevitable impurities.

[0076] 2. Electric furnace continuous casting production processes for automobile axle sleeve steel bars

[0077] Process route: ECOARC ecological electric furnace + LF + RH + continuous casting → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery.

[0078] (1) Ecological electric furnace smelting

[0079] Scrap steel accounts for 100% of the total steel production; the scrap charge is 118 tons, the tapping temperature is 1659°C, the carbon content is 0.08%, and the phosphorus content is 0.009%. Auxiliary materials and alloys are added when 1 / 4 of the steel is tapped, resulting in a tapping volume of 109 tons and a smelting cycle of 49 minutes. Alloy additions per ton of steel include: 4.3 kg / t of silicon-manganese, 11.2 kg / t of low-carbon ferrochrome, 17 kg / t of coke pellets (Φ40mm), 2 kg / t of ferroaluminum (Φ60mm), and 936 kg / t of heavy-duty scrap. Auxiliary material additions per ton of steel include: 20 kg / t of dolomite (Φ40mm), 43 kg / t of active lime (Φ5mm), and 6 kg / t of ladle dust.

[0080] (2) LF furnace refining

[0081] A high current of 23,000A is used to heat and melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, active lime is added. The chemical composition is analyzed for the first time after 5 minutes. Alloy and silicon carbide are added according to the target chemical composition values. The alloy and silicon carbide should be added to the argon flow to promote rapid melting and homogenization of the alloy and silicon carbide. When the molten steel temperature reached 1596°C, 2.4 kg / t of diffusion deoxidizer was added for diffusion deoxidation. The furnace door was closed for 12 minutes. When the molten steel temperature reached 1625°C, a second sample was taken for chemical composition analysis to confirm the deviation of the content of each chemical element from the target value. After the second sample was taken, the smelting cycle lasted 49 minutes. The following alloy additions per ton of steel were added: 3.4 kg / t of ferrosilicon, 1.9 kg / t of high-carbon ferromanganese, 0.52 kg / t of high-carbon ferrochromium, 1.8 kg / t of alumina balls, 0.35 kg / t of coke pellets (Φ40 mm), 6.6 kg / t of ferromolybdenum (FeMo60-B), and 1 m / t of aluminum wire (Φ10 mm). The following auxiliary materials were added per ton of steel: 6 kg / t of active lime (Φ50 mm) and 1 kg / t of silicon carbide (Φ3 mm).

[0082] (3)RH refining

[0083] The inlet temperature is 1680℃, the operation time is 30min, and the argon pressure is controlled at 0.18MPa before the vacuum pump is started, so that the slag surface moves slightly and the molten steel is not exposed. When the vacuum degree reaches 100Pa, the timing starts and the holding time is 13min. At the same time, the argon pressure is adjusted to 0.4MPa. After the static argon blowing is completed, 2 meters / t of silicon-calcium alloy cored wire (Φ14mm) and 0.6kg / t of covering agent are added. The outlet temperature is 1629℃.

[0084] (4) Continuous casting

[0085] The temperature of the ladle at the arrival station for continuous casting is 1627℃, the amount of molten steel is 98t, the H in the tundish is controlled at 1.3ppm, the casting is protected throughout the process, and the crystallizer protection slag uses medium carbon steel protection slag.

[0086] (5) Heating process

[0087] Heating process: The temperature entering the heating furnace is 440℃, the temperature of the preheating section is required to be 670℃, and the time is 1.4h; the temperature of the heating section 2 is required to be 850℃, and the time is 1.3h; the temperature of the heating section 1 is required to be 1198℃, and the time is 1.4h; the temperature of the soaking section is required to be 1195℃, and the time is 1.4h; the steel tapping temperature is 1186℃.

[0088] (6) Rolling process

[0089] Rolling process: starting rolling temperature 1105℃, finishing rolling temperature 885℃;

[0090] BD billet opening process for 390mm*480mm continuous casting billet: 9 rolling passes, rolling reduction: steel turning → 1st pass reduction 65mm → 2nd pass reduction 70mm → steel turning → 3rd pass reduction 64mm → 4th pass reduction 90mm → steel turning → 5th pass reduction 42mm → 6th pass reduction 40mm → 7th pass reduction 35mm → 8th pass reduction 34mm → steel turning → 9th pass reduction 82mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, and then entering the 8-pass continuous rolling mill group for rolling.

[0091] The product specification is Φ180mm rolling process: 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.

[0092] (7) Insulation process

[0093] Insulation process: Steel insulation, lower insulation pit temperature 640℃, insulation 52h, exit pit temperature 80℃.

[0094] Example 4

[0095] 1Chemical composition

[0096] 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%, and the balance is iron and inevitable impurities.

[0097] 2. Electric furnace continuous casting production processes for automobile axle sleeve steel bars

[0098] Process route: ECOARC ecological electric furnace + LF + RH + continuous casting → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery.

[0099] (1) Ecological electric furnace smelting

[0100] Scrap steel accounts for 100% of the total steel production; the scrap charge is 118 tons, the tapping temperature is 1659°C, the carbon content is 0.08%, and the phosphorus content is 0.006%. Auxiliary materials and alloys are added when 1 / 4 of the steel is tapped, resulting in a tapping volume of 108 tons, and a smelting cycle of 48 minutes. Alloy additions per ton of steel include: 4.3 kg / t of silicon-manganese, 11.3 kg / t of low-carbon ferrochrome, 17 kg / t of coke pellets (Φ40mm), 2 kg / t of ferroaluminum (Φ60mm), and 935 kg / t of heavy-duty scrap. Auxiliary material additions per ton of steel include: 20 kg / t of dolomite (Φ50mm), 43 kg / t of active lime (50mm), and 6 kg / t of ladle dust.

[0101] (2) LF furnace refining

[0102] A high current of 22000A is used to heat and melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, active lime is added. The chemical composition is analyzed for the first time after 5 minutes. Alloy and silicon carbide are added according to the target chemical composition values. The alloy and silicon carbide should be added to the argon flow to promote rapid melting and homogenization of the alloy and silicon carbide. When the molten steel temperature reached 1597°C, 2.3 kg / t of diffusion deoxidizer was added for diffusion deoxidation. The furnace door was closed for 10 minutes. When the molten steel temperature reached 1628°C, a second sample was taken for chemical composition analysis to confirm the deviation of the content of each chemical element from the target value. After the second sample was taken, the smelting cycle lasted 49 minutes. The following alloy additions per ton of steel were added: 3.4 kg / t of ferrosilicon, 1.9 kg / t of high-carbon ferromanganese, 0.53 kg / t of high-carbon ferrochromium, 1.8 kg / t of alumina balls, 0.35 kg / t of coke pellets (Φ50 mm), 6.6 kg / t of ferromolybdenum (FeMo60-B), and 1 m / t of aluminum wire (Φ10 mm). The following auxiliary materials were added per ton of steel: 6 kg / t of active lime (Φ50 mm) and 1 kg / t of silicon carbide (Φ4 mm).

[0103] (3)RH refining

[0104] The inlet temperature is 1682℃, the operation time is 30min, and the argon pressure is controlled at 0.15MPa before the vacuum pump is started, so that the slag surface moves slightly and the molten steel is not exposed. When the vacuum degree reaches 100Pa, the timing starts and the maintenance time is 13min. At the same time, the argon pressure is adjusted to 0.3MPa. After the static argon blowing is completed, 2 meters / t of silicon-calcium alloy cored wire (Φ14mm) and 0.6kg / t of covering agent are added. The outlet temperature is 1628℃.

[0105] (4) Continuous casting

[0106] The temperature of the ladle at the station for continuous casting is 1625℃, the amount of molten steel is 98t, the H in the tundish is controlled at 1.3ppm, the casting is protected throughout the process, and the crystallizer protection slag uses medium carbon steel protection slag.

[0107] (5) Heating process

[0108] Heating process: The temperature entering the heating furnace is 530℃, the preheating section temperature is required to be 660℃, and the time is 1.4h; the temperature of the heating section 2 is required to be 850℃, and the time is 1.4h; the temperature of the heating section 1 is required to be 1198℃, and the time is 1.4h; the temperature of the soaking section is required to be 1195℃, and the time is 1.4h; the steel tapping temperature is 1185℃.

[0109] (6) Rolling process

[0110] Rolling process: starting rolling temperature 1100℃, finishing rolling temperature 884℃;

[0111] BD blooming process for 390mm*480mm continuous casting billet: 9 rolling passes, rolling reduction: steel turning → 1st pass reduction 65mm → 2nd pass reduction 70mm → steel turning → 3rd pass reduction 64mm → 4th pass reduction 90mm → steel turning → 5th pass reduction 42mm → 6th pass reduction 40mm → 7th pass reduction 35mm → 8th pass reduction 34mm → steel turning → 9th pass reduction 82mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, and then entering the 8-pass continuous rolling mill group for rolling.

[0112] The product specification is Φ180mm rolling process: 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.

[0113] (7) Insulation process

[0114] Insulation process: Steel insulation, lower insulation pit temperature 630℃, insulation 50h, exit pit temperature 80℃.

[0115] Example 5

[0116] 1Chemical composition

[0117] 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%, and the balance is iron and inevitable impurities.

[0118] 2. Electric furnace continuous casting production processes for automobile axle sleeve steel bars

[0119] Process route: ECOARC ecological electric furnace + LF + RH + continuous casting → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery.

[0120] (1) Ecological electric furnace smelting

[0121] Scrap steel accounts for 100% of the total steel production; the scrap charge is 119 tons, the tapping temperature is 1659°C, the carbon content is 0.08%, and the phosphorus content is 0.007%. Auxiliary materials and alloys are added when 1 / 4 of the steel is tapped. The tapping volume is 110 tons, and the smelting cycle is 49 minutes. Alloy additions per ton of steel include: 4.3 kg / t of silicon manganese, 11.3 kg / t of low-carbon ferrochrome, 17 kg / t of coke pellets (Φ50mm), 2 kg / t of ferroaluminum (Φ50mm), and 935 kg / t of heavy-duty scrap steel. Auxiliary material additions per ton of steel include: 20 kg / t of dolomite (Φ50mm), 43 kg / t of active lime (Φ50mm), and 6 kg / t of ladle dust.

[0122] (2) LF furnace refining

[0123] A high current of 23,000A is used to heat and melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, active lime is added. The chemical composition is analyzed for the first time after 5 minutes. Alloy and silicon carbide are added according to the target chemical composition values. The alloy and silicon carbide should be added to the argon flow to promote rapid melting and homogenization of the alloy and silicon carbide. When the molten steel temperature reaches 1595°C, 2.5 kg / t of diffusion deoxidizer is added for diffusion deoxidation. The furnace door is closed for 10 minutes. When the molten steel temperature reaches 1626°C, a second sample is taken for chemical composition analysis to confirm the deviation of the content of each chemical element from the target value. After the second sample is taken, the smelting cycle is 52 minutes. The following alloy additions per ton of steel are added: 3.4 kg / t of ferrosilicon, 1.9 kg / t of high-carbon ferromanganese, 0.53 kg / t of high-carbon ferrochromium, 1.8 kg / t of alumina balls, 0.35 kg / t of coke pellets (Φ50mm), 6.6 kg / t of ferromolybdenum (FeMo60-B), and 1 m / t of aluminum wire (Φ10mm). The following auxiliary materials are added per ton of steel: 6 kg / t of active lime (50mm), and 1 kg / t of silicon carbide (Φ4mm).

[0124] (3)RH refining

[0125] The inlet temperature is 1682℃, the operation time is 29min, and the argon pressure is controlled at 0.2MPa before the vacuum pump is started, so that the slag surface moves slightly and the molten steel is not exposed. When the vacuum degree reaches 100Pa, the timing starts and the maintenance time is 12min. At the same time, the argon pressure is adjusted to 0.3MPa. After the static argon blowing is completed, 2 meters / t of silicon-calcium alloy cored wire (Φ14mm) and 0.6kg / t of covering agent are added. The outlet temperature is 1628℃.

[0126] (4) Continuous casting

[0127] The temperature of the ladle at the station for continuous casting is 1627℃, the amount of molten steel is 98t, the H in the tundish is controlled at 1.5ppm, the casting is protected throughout the whole process, and the crystallizer protection slag uses medium carbon steel protection slag.

[0128] (5) Heating process

[0129] Heating process: The temperature entering the heating furnace is 420℃, the preheating section temperature is required to be 660℃, and the time is 1.3h; the temperature of the heating section 2 is required to be 850℃, and the time is 1.3h; the temperature of the heating section 1 is required to be 1198℃, and the time is 1.3h; the temperature of the soaking section is required to be 1198℃, and the time is 1.3h; the steel tapping temperature is 1186℃.

[0130] (6) Rolling process

[0131] Rolling process: starting rolling temperature 1100℃, finishing rolling temperature 880℃;

[0132] BD billet opening process for 390mm*480mm continuous casting billet: 9 rolling passes, rolling reduction: steel turning → 1st pass reduction 65mm → 2nd pass reduction 70mm → steel turning → 3rd pass reduction 64mm → 4th pass reduction 90mm → steel turning → 5th pass reduction 42mm → 6th pass reduction 40mm → 7th pass reduction 35mm → 8th pass reduction 34mm → steel turning → 9th pass reduction 82mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, and then entering the 8-pass continuous rolling mill group for rolling.

[0133] The product specification is Φ180mm rolling process: 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.

[0134] (7) Insulation process

[0135] Insulation process: Steel insulation, lower insulation pit temperature 650℃, insulation 54h, exit pit temperature 90℃.

[0136] Test results of finished products of Examples 1 to 5

[0137] (1) Macrostructure of Φ180mm steel

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

[0139] (3) Mechanical properties of Φ180mm steel

[0140] Anyone skilled in the art will be able to utilize the above-disclosed technical content to make many possible changes and modifications to the technical solution of the present invention, or to modify it into equivalent embodiments with equivalent changes, without departing from the scope of the technical solution of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention that do not depart from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A steel for automobile axle sleeve, characterized in that: In terms of 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%, and the balance is iron and unavoidable impurities.

2. A method for smelting the automobile axle sleeve steel according to claim 1 using an ecological electric furnace, characterized in that: The method comprises: ecological electric furnace smelting→LF refining→RH refining→continuous casting→heating furnace heating process→rolling process; Among them, the ecological electric furnace smelting is: using scrap steel smelting, the scrap steel loading amount is 116~122t, the steel tapping temperature is 1655~1665℃, the C at steel tapping time is 0.08~0.10%, P≤0.010%, auxiliary materials and alloys are added when 1 / 4~1 / 3 of the steel is tapped, the steel tapping amount is 107~112t, and the smelting cycle is 45~55min; the amount of alloy added per ton of steel: silicon manganese 4.3~4.4kg / t, low carbon ferrochrome 11~11.5kg / t, coke particles 17~17.2kg / t, aluminum iron 2~2.2kg / t, heavy scrap steel 930~940kg / t; the amount of auxiliary materials added per ton of steel: dolomite 20~21kg / t, active lime 43~44kg / t, ladle ash 6~6.2kg / t.

3. The method according to claim 2, characterized in that The LF furnace refining is as follows: using a large current of 20000-25000A to heat and melt the slag, when the slag surface fluctuates and the molten steel and the arc are not exposed, adding active lime, taking a first sample for chemical composition analysis after 5 minutes, adding alloy and silicon carbide according to the target value of the chemical composition; when the temperature of the molten steel reaches 1590-1600°C, adding 2-3kg / t of diffusion deoxidizer for diffusion deoxidation, closing the furnace door for 10-12 minutes, and taking a second sample for chemical composition analysis when the temperature of the molten steel reaches 1620-1630°C to confirm that the content of each chemical element is within the range of the target value. The deviation value required by the target value, after the secondary sample is taken away, the smelting cycle is 45min~55min; the amount of additional alloy added per ton of steel: ferrosilicon 3.4~3.5kg / t, high carbon ferromanganese 1.9~2.0kg / t, high carbon ferrochrome 0.5~0.55kg / t, alumina balls 1.8~1.9kg / t, coke particles 0.35~0.36kg / t, ferromolybdenum 6.6~6.7kg / t, aluminum wire 1~1.1m / t; the amount of additional auxiliary materials added per ton of steel: active lime 6~6.2Kg / t, silicon carbide 1~1.1Kg / t; The RH refining is as follows: the inlet temperature is 1675-1685°C, the operation time is 28min-32min, the argon pressure is controlled at 0.1-0.3MPa before the vacuum pump is started, so that the molten steel is not exposed when the slag surface moves slightly, the timing starts when the vacuum degree reaches 100-110Pa, and the holding time is 10-15min. At the same time, the argon pressure is adjusted to 0.3-0.5MPa. After the static argon blowing is completed, 2-2.1 meters / t of silicon-calcium alloy cored wire and 0.6-0.7kg / t of covering agent are added, and the outlet temperature is 1625-1635°C.

4. The method according to claim 2, characterized in that: The continuous casting is as follows: the continuous casting temperature of the ladle at the station is 1620-1630°C, the amount of molten steel is 95-103t, the H of the tundish is controlled to be ≤2ppm, the whole process is protected casting, and the crystallizer protection slag uses medium carbon steel protection slag.

5. The method according to claim 2, characterized in that: The heating process is as follows: the temperature entering the heating furnace is 350°C to 550°C, the temperature of the preheating section is required to be 650°C to 700°C, and the time is 1.3 to 1.5 hours; the temperature of the heating section 2 is required to be 840°C to 860°C, and the time is 1.3 to 1.5 hours; the temperature of the heating section 1 is required to be 1190°C to 1220°C, and the time is 1.3 to 1.5 hours; the temperature of the soaking section is required to be 1180°C to 1210°C, and the time is 1.3 to 1.5 hours; and the steel tapping temperature is 1180°C to 1190°C.

6. The method according to claim 2, characterized in that The rolling process is: BD billeting process: 9 rolling passes, rolling reduction: steel turning → 1st pass reduction 65~65.1mm → 2nd pass reduction 70~70.1mm → steel turning → 3rd pass reduction 64~64.1mm → 4th pass reduction 90~90.1mm → steel turning → 5th pass reduction The steel is rolled from 42 to 42.1 mm in the 6th pass, 40 to 40.1 mm in the 6th pass, 35 to 35.1 mm in the 7th pass, 34 to 34.1 mm in the 8th pass, turning the steel, and 82 to 82.1 mm in the 9th pass. The steel is then rolled through 3 850 mm rolling mills and 1 735 mm rolling mill. Product specifications rolling process: 6 passes, the 1st pass is 229-229.1mm high and 245-245.1mm wide; the 2nd pass is 192-192.1mm high and 235-235.1mm wide; the 3rd pass is 200-200.1mm high and 195-195.1mm wide; the 4th pass is 173-173.1mm high and 205-205.1mm wide; the 5th pass is 182.4-182.5mm high and 182.4-182.5mm wide; the 6th pass is 182.4-182.5mm high and 182.4-182.5mm wide; the finished product is produced after 6 passes.

7. The method according to claim 6, characterized in that The starting rolling temperature of the rolling process is 1100-1130°C, and the final rolling temperature is 850-950°C.

8. The method according to claim 2, characterized in that: The rolled steel is insulated, and the insulation process is as follows: the steel is insulated, the temperature of the lower insulation pit is ≥600°C, the insulation is 48-55h, and the exit temperature is ≤150°C.

9. The method according to claim 3, characterized in that: The diameter of the coke particles is 20-60mm, the diameter of the aluminum iron is 40-70mm, the specification of the heavy scrap steel is ≥800mm*600mm, the diameter of the dolomite is 20-70mm, the diameter of the active lime is 10-70mm, the diameter of the alumina ball is 10-15mm, the ferromolybdenum is FeMo60-B, the diameter of the aluminum wire is 10-12mm, the diameter of the silicon carbide is 2-5mm, and the diameter of the silicon-calcium alloy cored wire is 12-14mm.

10. The method according to claim 8, characterized in that The steel after heat preservation is heat treated, and the heat treatment includes the following steps: 1) Quenching: 870-890℃, keeping warm for 0.8-1.2h, oil cooling; 2) Tempering: 490-510℃, keep warm for 1.6-2.0h, water cooling.

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