Production and preparation method of high-temperature-resistant steel bar for automobile axle

Abstract

The invention discloses a production and preparation method of a high-temperature-resistant steel bar for an automobile axle, and the high-temperature-resistant steel bar comprises the following chemical components in percentage by mass: 0.39-0.42% of C, 0.22-0.30% of Si, 1.45-1.70% of Mn, less than or equal to 0.015% of P, less than or equal to 0.006% of S, less than or equal to 0.20% of Cr, less than or equal to 0.20% of Ni, less than or equal to 0.05% of Mo, less than or equal to 0.10% of Cu and the balance of iron and inevitable impurities. Comprising the steps of ecological electric furnace smelting, LF refining, RH refining, continuous casting, annealing process, heating process, rolling process and heat preservation process. The quality requirement of the steel bar for the automobile axle is met, and the indexes such as the mechanical property and the high steel purity can also meet the standard requirement.

Description

Technical Field

[0001] The invention relates to the field of special steel, and in particular to a method for producing a high-temperature resistant steel bar for automobile axles. Background Art

[0002] As a transmission shaft, the automobile axle is a vital component of the vehicle. It transmits power from one part to another and realizes different forms of energy conversion. The quality of automobile axle steel is related to the safety of power transmission. Therefore, the high temperature resistance, wear resistance, mechanical properties, fatigue life and steel purity of automobile axle steel are very high, so as to ensure the normal and safe operation of the axle force transmission process.

[0003] Therefore, it is necessary to develop steel bars for automobile axles with excellent mechanical properties and high steel purity to meet the requirements of high-end products. Summary of the invention

[0004] The purpose of the present invention is to provide a production process preparation method for high-temperature resistant steel bars for automobile axles. The method adopts ecological electric furnace smelting + LF refining + RH refining + continuous casting process smelting, as well as rolling process, to produce steel bars for automobile axles. It not only ensures the mechanical properties of the finished steel and high steel purity of the steel bars for automobile axles, but also ensures the surface quality level of the steel bars for automobile axles, meets high-end use requirements, and achieves a breakthrough in the mass production of steel bars for automobile axles by the ecological electric furnace continuous casting process.

[0005] In order to achieve the above invention purpose, the present invention provides a production process and preparation method of high temperature resistant automobile axle steel bars, including composition design and process design, and specific steps: ecological electric furnace + LF refining + RH refining + continuous casting → annealing → heating → rolling process. It meets the quality requirements of automobile axle steel bars, and the mechanical properties and high steel purity and other indicators can also meet the standard requirements.

[0006] A high temperature resistant steel bar for automobile axles, the chemical composition of which, by mass percentage, is C: 0.39%-0.42%, Si: 0.22%-0.30%, Mn: 1.45%-1.70%, P: ≤0.015%, S: ≤0.006%, Cr: ≤0.20%, Ni: ≤0.20%, Mo: ≤0.05%, Cu: ≤0.10%, and the balance is iron and unavoidable impurities.

[0007] The specification of the high temperature resistant steel bar for automobile axles of the present invention is Φ100mm.

[0008] The above-mentioned production process preparation method of steel bars for automobile axle sleeves, the process route is: ecological electric furnace smelting → LF refining → RH refining → continuous casting → annealing process → heating furnace heating process → rolling process → insulation.

[0009] The ecological electric furnace smelting is as follows: according to the mass fraction, 100% of all scrap steel is used for smelting, of which 80% to 90% is heavy scrap steel and 10% to 20% is alloy structural steel cutting head; the steel tapping temperature is 1640 to 1650°C, C is 0.10 to 0.15% when tapping, P≤0.010%, auxiliary materials and alloys are added when 1 / 4 to 1 / 3 of the steel is tapped, the smelting cycle is 55 to 65 minutes, and the furnace oxygen consumption is 21 to 22 m 3 / t steel. The amount of alloy added per ton of steel: high carbon ferromanganese 16.5~17.5Kg / t, aluminum iron (Φ40-70mm) 1.9~2.1Kg / t. The amount of auxiliary materials added per ton of steel: graphite pellets 7.8~8.2Kg / t, coke particles 35~36Kg / t, ladle ash 5.8~6.3Kg / t, active lime (Φ10-70mm) 40~41Kg / t, dolomite (Φ20-70mm) 29~31Kg / t.

[0010] The LF furnace refining is as follows: the LF inlet temperature is 1540-1550°C, a high current of 35000-36000A is used to heat and melt the slag, active lime is added when the slag surface fluctuates and the molten steel and the arc are not exposed, the chemical composition is first sampled and analyzed after 5-6 minutes, alloy and silicon carbide are added according to the target value of the chemical composition, and coke particles are added for carbon increase, and the alloy, silicon carbide and coke particles should be added to the argon gas flow to promote rapid melting and homogenization of the alloy, silicon carbide and coke. When the temperature of molten steel reaches 1600-1610℃, add diffusion deoxidizer (aluminum particles) 1.4-1.5kg / t steel for diffusion deoxidation, close the furnace door for 10-13min, and take a second sample to analyze the chemical composition when the temperature of molten steel reaches 1630-1640℃ to confirm the deviation of the content of each chemical element from the target value. After the second sample is taken, leave the station when the temperature of molten steel reaches 1650-1660℃, and the LF smelting cycle is 100min-110min. Addition of alloy to steel: ferrosilicon 2.3-2.4kg / t, high carbon ferromanganese 3.5-3.6kg / t, alumina balls 1.4-1.5kg / t, aluminum wire (Φ10-14mm) 0.4-0.6kg / t. The amount of supplementary materials added per ton of steel: active lime (Φ10-70mm) 4~4.2Kg / t, silicon carbide (Φ2-5mm) 1.1~1.2kg / t, coke particles 0.5~0.6kg / t.

[0011] The RH refining is as follows: the station entry temperature is 1630-1640°C, the operation time is 35min-45min, the argon pressure is controlled at 0.1-0.3Mpa before the vacuum pump is started, so that the slag surface moves slightly and the molten steel is not exposed, 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, 0.5-0.6kg / t steel of covering agent (carbonized rice husk) is added, and the station exit temperature is 1585-1595°C.

[0012] The continuous casting is as follows: the ladle arrival temperature is 1580-1590° C., the H in the middle ladle is controlled to be ≤2ppm, the casting time is 35min-45min, the superheat is 25-30° C., the pulling speed is 0.4-0.42m / min, the whole process is protected casting, and the crystallizer protection slag uses medium carbon steel protection slag.

[0013] The annealing process is: annealing in an annealing furnace at a temperature of 580-620° C. for more than 32 hours.

[0014] Furthermore, the heating process is as follows: the temperature entering the heating furnace is 500℃~540℃, the temperature of the preheating section is required to be 650℃~680℃, and the time is 1.3~1.5h; the temperature of the heating section 2 is required to be 860℃~880℃, and the time is 1.3~1.5h; the temperature of the heating section 1 is required to be 1210℃~1220℃, and the time is 1.3~1.5h; the temperature of the soaking section is required to be 1200℃~1210℃, and the time is 1.3~1.5h; the steel tapping temperature is 1190℃~1198℃.

[0015] Furthermore, the rolling process includes a primary rolling process and a continuous rolling process, specifically:

[0016] Initial rolling process: 9 passes; specifically: steel turning → 1st pass width 408 ~ 408.01mm, height 421 ~ 421.01mm, reduction 65 ~ 65.01mm → 2nd pass width 426 ~ 426.01mm, height 351 ~ 351.01mm, reduction 70 ~ 70.01mm → steel turning → 3rd pass width 370 ~ 370.01mm, height 362 ~ 362.01mm, reduction 64 ~ 64.01mm → 4th pass width 397 ~ 397.01mm, height 272 ~ 272.01mm, reduction 90 ~ 90.01mm → steel turning → 5th pass width 285 ~ 285.01mm, height 355 ~ 355.01 mm, reduction 42~42.01mm→the 6th pass width 297~297.01mm, height 315~315.01mm, reduction 40~40.01mm→the 7th pass width 307~307.01mm, height 280~280.01mm, reduction 35~35.01mm→the 8th pass width 317~317.01mm, height 246~246.01mm, reduction 34~34.01mm→steel turning→the 9th pass width 271~271.01mm, height 235~235.01mm, reduction 82~82.01mm, passes through 3 850mm rolling mills and 1 735mm rolling mill, and then enters the continuous rolling mill group for rolling.

[0017] Continuous rolling product rolling process: 11 passes; specifically: the first pass is 229-229.01mm high and 245-245.01mm wide; the second pass is 192-192.01mm high and 235-235.01mm wide; the third pass is 200-200.01mm high and 195-195.01mm wide; the fourth pass is 160-160.01mm high and 214.7-214.71mm wide; the fifth pass is 164-164.01mm high and 174.6-174.61mm wide; the sixth pass is 121-121. 01mm, width 187.6~187.61mm; the 7th pass is 139~139.01mm high, 138.5~138.51mm wide; the 8th pass is 106~106.01mm high, 152~152.01mm wide; the 9th pass is 118~118.01mm high, 121~121.01mm wide; the 10th pass is 91~91.01mm high, 130.2~130.21mm wide; the 11th pass is 101.4~101.41mm high, 101.4~101.41mm wide; the finished product is produced after 11 passes.

[0018] Furthermore, the insulation process is: steel insulation, lower insulation pit temperature ≥ 560°C, insulation 48 to 55 hours, pit exit temperature ≤ 120°C.

[0019] Furthermore, the process route includes the following steps: heat preservation, finishing, inspection, packaging, storage, and shipment.

[0020] Furthermore, the steel material after heat preservation is subjected to heat treatment, and the heat treatment comprises the following steps:

[0021] 1) Quenching: 830-850℃, insulation 0.8-1.2h, oil cooling;

[0022] 2) Tempering: 530-550℃, keep warm for 1.8-2.2h, water cooling.

[0023] Beneficial effects of the present invention:

[0024] (1) The ecological electric furnace smelting + LF refining + RH refining + continuous casting and rolling process is used to produce steel bars for automobile axles, which meets the mechanical property requirements and ensures the purity of the steel.

[0025] (2) Reasonable component design and production process ensure surface quality and mechanical properties.

[0026] (3) The macrostructure and non-metallic inclusions of the finished steel meet the requirements of high-end products.

[0027] (4) The finished steel has good high temperature resistance (400-600℃). DETAILED DESCRIPTION

[0028] The following non-limiting embodiments may enable a person skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0029] Example 1

[0030] 1Chemical composition

[0031] The chemical composition, by mass percentage, is C: 0.40%, Si: 0.26%, Mn: 1.55%, P: 0.010%, S: 0.005%, Cr: 0.08%, Ni: 0.05%, Mo: 0.02%, Cu: 0.01%, and the balance is iron and inevitable impurities.

[0032] 2. Electric furnace continuous casting production processes for automobile axle steel bars

[0033] Process route: ecological electric furnace + LF refining + RH refining + continuous casting → annealing → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery. Among them:

[0034] (1) Ecological electric furnace smelting

[0035] Scrap steel and molten iron are used for smelting. 100% scrap steel is used by mass, including 85% heavy scrap steel and 15% alloy structural steel cuttings. The tapping temperature is 1646℃, C is 0.12% and P is 0.008% when tapping. Auxiliary materials and alloys are added when 1 / 4 of the steel is tapped. The smelting cycle is 60min and the furnace oxygen consumption is 21m 3 / t steel. Alloy addition per ton of steel: high carbon ferromanganese 16.8Kg / t, aluminum iron (Φ50mm) 2Kg / t. Auxiliary materials addition per ton of steel: graphite pellets 8Kg / t, coke particles 35Kg / t, ladle ash 5.9Kg / t, active lime (Φ35mm) 40Kg / t, dolomite (Φ40mm) 30Kg / t.

[0036] (2) LF furnace refining

[0037] The LF station temperature is 1547℃, and the 35600A high current is used to heat and melt the slag. When the slag surface fluctuates, the molten steel and the arc are not exposed, active lime is added. After 5 minutes, the first sampling is performed to analyze the chemical composition. According to the target value of the chemical composition, alloy and silicon carbide are added, and coke particles are added for carbon increase. The alloy, silicon carbide and coke particles are quickly melted and homogenized. When the molten steel temperature reaches 1604℃, 1.4kg / t of diffusion deoxidizer (aluminum particles) is added for diffusion deoxidation. The furnace door is closed for 11 minutes. When the molten steel temperature reaches 1635℃, the chemical composition is analyzed for the second time to confirm the deviation value of the content of each chemical element from the target value. After the second sample is taken away, the station is left when the molten steel temperature reaches 1657℃. The LF smelting cycle is 104 minutes. The amount of alloy added to each ton of steel is: 2.3kg / t of ferrosilicon, 3.5kg / t of high carbon ferromanganese, 1.4kg / t of alumina balls, and 0.5kg / t of aluminum wire (Φ10mm). Supplementary materials added per ton of steel: Active lime (Φ35mm) 4Kg / t, Silicon carbide (Φ3mm) 1.1kg / t, Coke particles 0.5kg / t.

[0038] (3) RH refining

[0039] The inlet temperature is 1636℃, the operation time is 42min, and the argon pressure is controlled at 0.1MPa 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 102Pa, the timing starts and the holding time is 11min. At the same time, the argon pressure is adjusted to 0.4MPa. After the static argon blowing is completed, 0.5kg / t of covering agent (carbonized rice husk) is added, and the leaving station temperature is 1588℃.

[0040] (4) Continuous casting

[0041] The temperature of the ladle arriving at the station is 1586℃, the H content of the tundish is controlled at 1.5ppm, the casting time is 41min, the superheat is 27℃, the pulling speed is 0.4m / min, the whole process is protected casting, and the crystallizer protection slag uses medium carbon steel protection slag.

[0042] (5) Annealing process

[0043] Annealing was carried out in an annealing furnace at a temperature of 600°C for 35 hours.

[0044] (6) Heating process

[0045] Heating process: the temperature entering the heating furnace is 520℃, the temperature of the preheating section is required to be 660℃, and the time is 1.4h; the temperature of the heating section 2 is required to be 870℃, and the time is 1.3h; the temperature of the heating section 1 is required to be 1216℃, and the time is 1.3h; the temperature of the soaking section is required to be 1205℃, and the time is 1.5h; the steel tapping temperature is 1195℃.

[0046] (7) Rolling process

[0047] Primary rolling process: 9 passes, steel turning → 1st pass width 408mm, height 421mm, reduction 65mm → 2nd pass width 426mm, height 351mm, reduction 70mm → steel turning → 3rd pass width 370mm, height 362mm, reduction 64mm → 4th pass width 397mm, height 272mm, reduction 90mm → steel turning → 5th pass width 285mm, height 355mm, reduction 42mm→The 6th pass is 297mm wide, 315mm high, and 40mm reduction→The 7th pass is 307mm wide, 280mm high, and 35mm reduction→The 8th pass is 317mm wide, 246mm high, and 34mm reduction→Steel turning→The 9th pass is 271mm wide, 235mm high, and 82mm reduction, passes through 3 850mm rolling mills and 1 735mm rolling mill, and then enters the continuous rolling mill for rolling.

[0048] Continuous rolling product rolling process: 11 passes, the 1st pass is 229mm high and 245mm wide; the 2nd pass is 192mm high and 235mm wide; the 3rd pass is 200mm high and 195mm wide; the 4th pass is 160mm high and 214.7mm wide; the 5th pass is 164mm high and 174.6mm wide; the 6th pass is 121mm high and 187.6mm wide; the 7th pass is 139mm high and 138.5mm wide; the 8th pass is 106mm high and 152mm wide; the 9th pass is 118mm high and 121mm wide; the 10th pass is 91mm high and 130.2mm wide; the 11th pass is 101.4mm high and 101.4mm wide; the finished product is produced after 11 passes.

[0049] (8) Insulation process

[0050] Insulation process: Steel insulation, lower insulation pit temperature 580℃, insulation 52h, exit pit temperature 100℃.

[0051] (9) Heat treatment process

[0052] The steel after heat preservation is heat treated, and the heat treatment includes the following steps:

[0053] 1) Quenching: 840℃, holding time 1.0h, oil cooling;

[0054] 2) Tempering: 540℃, keep warm for 2.0h, water cooling.

[0055] Example 2

[0056] 1Chemical composition

[0057] The chemical composition by mass percentage is C: 0.39%, Si: 0.26%, Mn: 1.52%, P: 0.010%, S: 0.004%, Cr: 0.06%, Ni: 0.02%, Mo: 0.01%, Cu: 0.01%, and the balance is iron and inevitable impurities.

[0058] 2. Electric furnace continuous casting production processes for automobile axle steel bars

[0059] Process route: ecological electric furnace + LF refining + RH refining + continuous casting → annealing → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery. Among them:

[0060] (2) Ecological electric furnace smelting

[0061] Scrap steel and molten iron are used for smelting. 100% scrap steel is used by mass, including 84% heavy scrap steel and 16% alloy structural steel cutting heads. The tapping temperature is 1646℃, C is 0.12% and P is 0.007% when tapping. Auxiliary materials and alloys are added when 1 / 4 of the steel is tapped. The smelting cycle is 60min and the furnace oxygen consumption is 21m 3 / t steel. Alloy addition per ton of steel: high carbon ferromanganese 16.9Kg / t, aluminum iron (Φ50mm) 1.9Kg / t. Auxiliary materials addition per ton of steel: graphite pellets 7.9Kg / t, coke particles 35Kg / t, ladle ash 6.0Kg / t, active lime (Φ35mm) 40Kg / t, dolomite (Φ40mm) 30Kg / t.

[0062] (2) LF furnace refining

[0063] The LF station temperature is 1547℃, and the 35400A high current is used to heat and melt the slag. When the slag surface fluctuates, the molten steel and the arc are not exposed, active lime is added. After 5 minutes, the first sampling is performed to analyze the chemical composition. According to the target value of the chemical composition, alloy and silicon carbide are added, and coke particles are added for carbon increase. The alloy, silicon carbide and coke particles are quickly melted and homogenized. When the molten steel temperature reaches 1606℃, 1.4kg / t of diffusion deoxidizer (aluminum particles) is added for diffusion deoxidation. The furnace door is closed for 12 minutes. When the molten steel temperature reaches 1635℃, the chemical composition is analyzed for the second time to confirm the deviation value of the content of each chemical element from the target value. After the second sample is taken away, the station is left when the molten steel temperature reaches 1655℃. The LF smelting cycle is 105 minutes. The amount of alloy added to each ton of steel is: 2.3kg / t of ferrosilicon, 3.5kg / t of high carbon ferromanganese, 1.4kg / t of alumina balls, and 0.5kg / t of aluminum wire (Φ10mm). Supplementary materials added per ton of steel: Active lime (Φ35mm) 4Kg / t, Silicon carbide (Φ3mm) 1.1kg / t, Coke particles 0.5kg / t.

[0064] (3) RH refining

[0065] The inlet temperature is 1637℃, the operation time is 42min, and the argon pressure is controlled at 0.1MPa 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 104Pa, the timing starts and the holding time is 12min. At the same time, the argon pressure is adjusted to 0.3MPa. After the static argon blowing is completed, 0.5kg / t of covering agent (carbonized rice husk) is added, and the leaving station temperature is 1592℃.

[0066] (4) Continuous casting

[0067] The temperature of the ladle arriving at the station is 1585℃, the H content of the tundish is controlled at 1.5ppm, the casting time is 40min, the superheat is 27℃, the casting speed is 0.4m / min, the whole process is protected casting, and the crystallizer protection slag uses medium carbon steel protection slag.

[0068] (5) Annealing process

[0069] Annealing was carried out in an annealing furnace at a temperature of 600°C for 34 hours.

[0070] (6) Heating process

[0071] Heating process: the temperature entering the heating furnace is 520℃, the temperature of the preheating section is required to be 660℃, and the time is 1.3h; the temperature of the heating section 2 is required to be 870℃, and the time is 1.4h; the temperature of the heating section 1 is required to be 1214℃, and the time is 1.3h; the temperature of the soaking section is required to be 1204℃, and the time is 1.3h; the steel tapping temperature is 1195℃.

[0072] (7) Rolling process

[0073] Primary rolling process: 9 passes, steel turning → 1st pass width 408mm, height 421mm, reduction 65mm → 2nd pass width 426mm, height 351mm, reduction 70mm → steel turning → 3rd pass width 370mm, height 362mm, reduction 64mm → 4th pass width 397mm, height 272mm, reduction 90mm → steel turning → 5th pass width 285mm, height 355mm, reduction 42mm→The 6th pass is 297mm wide, 315mm high, and 40mm reduction→The 7th pass is 307mm wide, 280mm high, and 35mm reduction→The 8th pass is 317mm wide, 246mm high, and 34mm reduction→Steel turning→The 9th pass is 271mm wide, 235mm high, and 82mm reduction, passes through 3 850mm rolling mills and 1 735mm rolling mill, and then enters the continuous rolling mill for rolling.

[0074] Continuous rolling product rolling process: 11 passes, the 1st pass is 229mm high and 245mm wide; the 2nd pass is 192mm high and 235mm wide; the 3rd pass is 200mm high and 195mm wide; the 4th pass is 160mm high and 214.7mm wide; the 5th pass is 164mm high and 174.6mm wide; the 6th pass is 121mm high and 187.6mm wide; the 7th pass is 139mm high and 138.5mm wide; the 8th pass is 106mm high and 152mm wide; the 9th pass is 118mm high and 121mm wide; the 10th pass is 91mm high and 130.2mm wide; the 11th pass is 101.4mm high and 101.4mm wide; the finished product is produced after 11 passes.

[0075] (8) Insulation process

[0076] Insulation process: Steel insulation, lower insulation pit temperature 600℃, insulation 49h, exit pit temperature 100℃.

[0077] (9) Heat treatment process

[0078] The steel after heat preservation is heat treated, and the heat treatment includes the following steps:

[0079] 1) Quenching: 840℃, holding time 1.0h, oil cooling;

[0080] 2) Tempering: 540℃, keep warm for 2.0h, water cooling.

[0081] Example 3

[0082] 1Chemical composition

[0083] The chemical composition by mass percentage is C: 0.41%, Si: 0.26%, Mn: 1.55%, P: 0.010%, S: 0.005%, Cr: 0.05%, Ni: 0.03%, Mo: 0.01%, Cu: 0.01%, and the balance is iron and inevitable impurities.

[0084] 2. Electric furnace continuous casting production processes for automobile axle steel bars

[0085] Process route: ecological electric furnace + LF refining + RH refining + continuous casting → annealing → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery. Among them:

[0086] (1) Ecological electric furnace smelting

[0087] Scrap steel and molten iron are used for smelting. 100% scrap steel is used by mass, including 86% heavy scrap steel and 14% alloy structural steel cutting heads. The tapping temperature is 1646℃, C is 0.12% and P is 0.008% when tapping. Auxiliary materials and alloys are added when 1 / 4 of the steel is tapped. The smelting cycle is 65min and the furnace oxygen consumption is 21m 3 / t steel. Alloy addition per ton of steel: high carbon ferromanganese 16.8Kg / t, aluminum iron (Φ50mm) 2.0Kg / t. Auxiliary materials addition per ton of steel: graphite pellets 8.0Kg / t, coke particles 35Kg / t, ladle ash 6.0Kg / t, active lime (Φ35mm) 40Kg / t, dolomite (Φ40mm) 30Kg / t.

[0088] (2) LF furnace refining

[0089] The LF station temperature is 1546℃, and the 35400A high current 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. After 5 minutes, the chemical composition is analyzed for the first time. According to the target value of the chemical composition, alloy and silicon carbide are added, and coke particles are added for carbon increase. The alloy, silicon carbide and coke particles are quickly melted and homogenized. When the molten steel temperature reaches 1604℃, 1.4kg / t of diffusion deoxidizer (aluminum particles) is added for diffusion deoxidation. The furnace door is closed for 10 minutes. When the molten steel temperature reaches 1635℃, the chemical composition is analyzed for the second time to confirm the deviation value of the content of each chemical element from the target value. After the second sample is taken away, the station is left when the molten steel temperature reaches 1656℃. The LF smelting cycle is 104min. The amount of alloy added to each ton of steel is: 2.3kg / t of ferrosilicon, 3.5kg / t of high carbon ferromanganese, 1.4kg / t of alumina balls, and 0.4kg / t of aluminum wire (Φ10mm). Supplementary materials added per ton of steel: Active lime (Φ35mm) 4Kg / t, Silicon carbide (Φ3mm) 1.1kg / t, Coke particles 0.5kg / t.

[0090] (3) RH refining

[0091] The station entry temperature is 1635℃, the operation time is 40min, and the argon pressure is controlled at 0.1MPa 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 104Pa, 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, 0.5kg / t of covering agent (carbonized rice husk) is added, and the station exit temperature is 1590℃.

[0092] (4) Continuous casting

[0093] The temperature of the ladle arriving at the station is 1585℃, the H content of the tundish is controlled at 1.5ppm, the casting time is 40min, the superheat is 27℃, the casting speed is 0.4m / min, the whole process is protected casting, and the crystallizer protection slag uses medium carbon steel protection slag.

[0094] (5) Annealing process

[0095] Annealing was carried out in an annealing furnace at a temperature of 600°C for 36 hours.

[0096] (6) Heating process

[0097] Heating process: the temperature entering the heating furnace is 520℃, the temperature of the preheating section is required to be 660℃, and the time is 1.5h; the temperature of the heating section 2 is required to be 870℃, and the time is 1.3h; the temperature of the heating section 1 is required to be 1214℃, and the time is 1.3h; the temperature of the soaking section is required to be 1204℃, and the time is 1.3h; the steel tapping temperature is 1195℃.

[0098] (7) Rolling process

[0099] Primary rolling process: 9 passes, steel turning → 1st pass width 408mm, height 421mm, reduction 65mm → 2nd pass width 426mm, height 351mm, reduction 70mm → steel turning → 3rd pass width 370mm, height 362mm, reduction 64mm → 4th pass width 397mm, height 272mm, reduction 90mm → steel turning → 5th pass width 285mm, height 355mm, reduction 42mm→The 6th pass is 297mm wide, 315mm high, and 40mm reduction→The 7th pass is 307mm wide, 280mm high, and 35mm reduction→The 8th pass is 317mm wide, 246mm high, and 34mm reduction→Steel turning→The 9th pass is 271mm wide, 235mm high, and 82mm reduction, passes through 3 850mm rolling mills and 1 735mm rolling mill, and then enters the continuous rolling mill for rolling.

[0100] Continuous rolling product rolling process: 11 passes, the 1st pass is 229mm high and 245mm wide; the 2nd pass is 192mm high and 235mm wide; the 3rd pass is 200mm high and 195mm wide; the 4th pass is 160mm high and 214.7mm wide; the 5th pass is 164mm high and 174.6mm wide; the 6th pass is 121mm high and 187.6mm wide; the 7th pass is 139mm high and 138.5mm wide; the 8th pass is 106mm high and 152mm wide; the 9th pass is 118mm high and 121mm wide; the 10th pass is 91mm high and 130.2mm wide; the 11th pass is 101.4mm high and 101.4mm wide; the finished product is produced after 11 passes.

[0101] (8) Insulation process

[0102] Insulation process: Steel insulation, lower insulation pit temperature 580℃, insulation 52h, exit pit temperature 110℃.

[0103] (9) Heat treatment process

[0104] The steel after heat preservation is heat treated, and the heat treatment includes the following steps:

[0105] 1) Quenching: 840℃, holding time 1.0h, oil cooling;

[0106] 2) Tempering: 540℃, keep warm for 2.0h, water cooling.

[0107] Example 4

[0108] 1Chemical composition

[0109] The chemical composition by mass percentage is C: 0.40%, Si: 0.26%, Mn: 1.53%, P: 0.010%, S: 0.005%, Cr: 0.06%, Ni: 0.02%, Mo: 0.01%, Cu: 0.01%, and the balance is iron and inevitable impurities.

[0110] 2. Electric furnace continuous casting production processes for automobile axle steel bars

[0111] Process route: ecological electric furnace + LF refining + RH refining + continuous casting → annealing → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery. Among them:

[0112] (3) Ecological electric furnace smelting

[0113] Scrap steel and molten iron are used for smelting. 100% scrap steel is used by mass, including 85% heavy scrap steel and 15% alloy structural steel cuttings. The tapping temperature is 1645℃, C is 0.11% and P is 0.007% when tapping. Auxiliary materials and alloys are added when 1 / 4 of the steel is tapped. The smelting cycle is 65min and the furnace oxygen consumption is 21m3 / t steel. Alloy addition per ton of steel: high carbon ferromanganese 16.8Kg / t, aluminum iron (Φ50mm) 2.0Kg / t. Auxiliary materials addition per ton of steel: graphite pellets 7.9Kg / t, coke particles 35Kg / t, ladle ash 6.0Kg / t, active lime (Φ35mm) 40Kg / t, dolomite (Φ40mm) 30Kg / t.

[0114] (2) LF furnace refining

[0115] The LF station temperature is 1545℃, and the 35500A high current 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. After 5 minutes, the chemical composition is analyzed for the first time. According to the target value of the chemical composition, alloy and silicon carbide are added, and coke particles are added for carbon increase. The alloy, silicon carbide and coke particles are quickly melted and homogenized. When the molten steel temperature reaches 1604℃, 1.4kg / t of diffusion deoxidizer (aluminum particles) is added for diffusion deoxidation. The furnace door is closed for 10 minutes. When the molten steel temperature reaches 1635℃, the chemical composition is analyzed for the second time to confirm the deviation value of the content of each chemical element from the target value. After the second sample is taken away, the station is left when the molten steel temperature reaches 1657℃. The LF smelting cycle is 102min. The amount of alloy added to each ton of steel is: 2.3kg / t of ferrosilicon, 3.5kg / t of high carbon ferromanganese, 1.4kg / t of alumina balls, and 0.5kg / t of aluminum wire (Φ10mm). Supplementary materials added per ton of steel: Active lime (Φ35mm) 4Kg / t, Silicon carbide (Φ3mm) 1.1kg / t, Coke particles 0.5kg / t.

[0116] (3) RH refining

[0117] The station entry temperature is 1635℃, the operation time is 41min, and the argon pressure is controlled at 0.1MPa 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 103Pa, the timing starts and the holding time is 10min. At the same time, the argon pressure is adjusted to 0.3MPa. After the static argon blowing is completed, 0.5kg / t of covering agent (carbonized rice husk) is added, and the station exit temperature is 1588℃.

[0118] (4) Continuous casting

[0119] The temperature of the ladle arriving at the station is 1586℃, the H content of the tundish is controlled at 1.5ppm, the casting time is 40min, the superheat is 26℃, the pulling speed is 0.4m / min, the whole process is protected casting, and the crystallizer protection slag uses medium carbon steel protection slag.

[0120] (5) Annealing process

[0121] Annealing was carried out in an annealing furnace at a temperature of 600°C for 35 hours.

[0122] (6) Heating process

[0123] Heating process: the temperature entering the heating furnace is 520℃, 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 870℃, and the time is 1.5h; the temperature of the heating section 1 is required to be 1215℃, and the time is 1.3h; the temperature of the soaking section is required to be 1204℃, and the time is 1.4h; the steel tapping temperature is 1194℃.

[0124] (7) Rolling process

[0125] Primary rolling process: 9 passes, steel turning → 1st pass width 408mm, height 421mm, reduction 65mm → 2nd pass width 426mm, height 351mm, reduction 70mm → steel turning → 3rd pass width 370mm, height 362mm, reduction 64mm → 4th pass width 397mm, height 272mm, reduction 90mm → steel turning → 5th pass width 285mm, height 355mm, reduction 42mm→The 6th pass is 297mm wide, 315mm high, and 40mm reduction→The 7th pass is 307mm wide, 280mm high, and 35mm reduction→The 8th pass is 317mm wide, 246mm high, and 34mm reduction→Steel turning→The 9th pass is 271mm wide, 235mm high, and 82mm reduction, passes through 3 850mm rolling mills and 1 735mm rolling mill, and then enters the continuous rolling mill for rolling.

[0126] Continuous rolling product rolling process: 11 passes, the 1st pass is 229mm high and 245mm wide; the 2nd pass is 192mm high and 235mm wide; the 3rd pass is 200mm high and 195mm wide; the 4th pass is 160mm high and 214.7mm wide; the 5th pass is 164mm high and 174.6mm wide; the 6th pass is 121mm high and 187.6mm wide; the 7th pass is 139mm high and 138.5mm wide; the 8th pass is 106mm high and 152mm wide; the 9th pass is 118mm high and 121mm wide; the 10th pass is 91mm high and 130.2mm wide; the 11th pass is 101.4mm high and 101.4mm wide; the finished product is produced after 11 passes.

[0127] (8) Insulation process

[0128] Insulation process: Steel insulation, lower insulation pit temperature 580℃, insulation 52h, exit pit temperature 100℃.

[0129] (9) Heat treatment process

[0130] The steel after heat preservation is heat treated, and the heat treatment includes the following steps:

[0131] 1) Quenching: 840℃, holding time 1.0h, oil cooling;

[0132] 2) Tempering: 540℃, keep warm for 2.0h, water cooling.

[0133] Example 5

[0134] 1Chemical composition

[0135] The chemical composition by mass percentage is C: 0.41%, Si: 0.25%, Mn: 1.52%, P: 0.011%, S: 0.005%, Cr: 0.06%, Ni: 0.02%, Mo: 0.01%, Cu: 0.01%, and the balance is iron and inevitable impurities.

[0136] 2. Electric furnace continuous casting production processes for automobile axle steel bars

[0137] Process route: ecological electric furnace + LF refining + RH refining + continuous casting → annealing → heating in heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery. Among them:

[0138] (1) Ecological electric furnace smelting

[0139] Scrap steel and molten iron are used for smelting. 100% scrap steel is used by mass, including 86% heavy scrap steel and 14% alloy structural steel cutting heads. The tapping temperature is 1645℃, C is 0.10% and P is 0.007% when tapping. Auxiliary materials and alloys are added when 1 / 4 of the steel is tapped. The smelting cycle is 65min and the furnace oxygen consumption is 21m 3 / t steel. Alloy addition per ton of steel: high carbon ferromanganese 16.8Kg / t, aluminum iron (Φ50mm) 2.0Kg / t. Auxiliary materials addition per ton of steel: graphite pellets 8.0Kg / t, coke particles 35Kg / t, ladle ash 6.0Kg / t, active lime (Φ35mm) 40Kg / t, dolomite (Φ40mm) 30Kg / t.

[0140] (2) LF furnace refining

[0141] The LF station temperature is 1546℃, and the 35400A high current is used to heat and melt the slag. When the slag surface fluctuates, the molten steel and the arc are not exposed, active lime is added. After 5 minutes, the first sampling is performed to analyze the chemical composition. According to the target value of the chemical composition, alloy and silicon carbide are added, and coke particles are added for carbon increase. The alloy, silicon carbide and coke particles are quickly melted and homogenized. When the molten steel temperature reaches 1605℃, 1.4kg / t of diffusion deoxidizer (aluminum particles) is added for diffusion deoxidation. The furnace door is closed for 11 minutes. When the molten steel temperature reaches 1635℃, the chemical composition is analyzed for the second time to confirm the deviation value of the content of each chemical element from the target value. After the second sample is taken away, the station is left when the molten steel temperature reaches 1655℃. The LF smelting cycle is 104min. The amount of alloy added to each ton of steel is: 2.3kg / t of ferrosilicon, 3.5kg / t of high carbon ferromanganese, 1.4kg / t of alumina balls, and 0.5kg / t of aluminum wire (Φ10mm). Supplementary materials added per ton of steel: Active lime (Φ35mm) 4Kg / t, Silicon carbide (Φ3mm) 1.1kg / t, Coke particles 0.5kg / t.

[0142] (3) RH refining

[0143] The station entry temperature is 1636℃, the operation time is 40min, and the argon pressure is controlled at 0.1MPa 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 102Pa, the timing starts and the holding time is 13min. At the same time, the argon pressure is adjusted to 0.3MPa. After the static argon blowing is completed, 0.5kg / t of covering agent (carbonized rice husk) is added, and the station exit temperature is 1589℃.

[0144] (4) Continuous casting

[0145] The temperature of the ladle at the station is 1585℃, the H content of the tundish is controlled at 1.5ppm, the casting time is 40min, the superheat is 26℃, the pulling speed is 0.4m / min, the whole process is protected casting, and the crystallizer protection slag uses medium carbon steel protection slag.

[0146] (5) Annealing process

[0147] Annealing was carried out in an annealing furnace at a temperature of 600°C for 35 hours.

[0148] (6) Heating process

[0149] Heating process: the temperature entering the heating furnace is 520℃, the temperature of the preheating section is required to be 660℃, and the time is 1.4h; the temperature of the heating section 2 is required to be 870℃, and the time is 1.3h; the temperature of the heating section 1 is required to be 1215℃, and the time is 1.4h; the temperature of the soaking section is required to be 1203℃, and the time is 1.3h; the steel tapping temperature is 1194℃.

[0150] (7) Rolling process

[0151] Primary rolling process: 9 passes, steel turning → 1st pass width 408mm, height 421mm, reduction 65mm → 2nd pass width 426mm, height 351mm, reduction 70mm → steel turning → 3rd pass width 370mm, height 362mm, reduction 64mm → 4th pass width 397mm, height 272mm, reduction 90mm → steel turning → 5th pass width 285mm, height 355mm, reduction 42mm→The 6th pass is 297mm wide, 315mm high, and 40mm reduction→The 7th pass is 307mm wide, 280mm high, and 35mm reduction→The 8th pass is 317mm wide, 246mm high, and 34mm reduction→Steel turning→The 9th pass is 271mm wide, 235mm high, and 82mm reduction, passes through 3 850mm rolling mills and 1 735mm rolling mill, and then enters the continuous rolling mill for rolling.

[0152] Continuous rolling product rolling process: 11 passes, the 1st pass is 229mm high and 245mm wide; the 2nd pass is 192mm high and 235mm wide; the 3rd pass is 200mm high and 195mm wide; the 4th pass is 160mm high and 214.7mm wide; the 5th pass is 164mm high and 174.6mm wide; the 6th pass is 121mm high and 187.6mm wide; the 7th pass is 139mm high and 138.5mm wide; the 8th pass is 106mm high and 152mm wide; the 9th pass is 118mm high and 121mm wide; the 10th pass is 91mm high and 130.2mm wide; the 11th pass is 101.4mm high and 101.4mm wide; the finished product is produced after 11 passes.

[0153] (8) Insulation process

[0154] Insulation process: Steel insulation, lower insulation pit temperature 590℃, insulation 52h, exit pit temperature 100℃.

[0155] (9) Heat treatment process

[0156] The steel after heat preservation is heat treated, and the heat treatment includes the following steps:

[0157] 1) Quenching: 840℃, holding time 1.0h, oil cooling;

[0158] 2) Tempering: 540℃, keep warm for 2.0h, water cooling.

[0159] Test results of finished products of Examples 1 to 5

[0160] (1) Macrostructure of Φ100mm steel (finished steel obtained by heat preservation process)

[0161] Serial number Generally loose Loose center Ingot segregation General spot segregation Edge spot 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

[0162] (2) Non-metallic inclusions in Φ100mm steel (finished steel obtained by thermal insulation process)

[0163]

[0164]

[0165] (3) Mechanical properties of Φ100mm steel (finished steel after heat treatment)

[0166] Serial number Quenching / ℃ Insulation time Tempering / ℃ Insulation time Rm / MPa Rel / MPa A / ％ z / ％ KU2 / J standard 840, oil cooling 0.8～1.2h 540, water cooling 1.8～2.2h ≥885 ≥735 ≥12 ≥45 ≥47 Example 1 840, oil cooling 1h 540, water cooling 2h 920 785 18 67 58 Example 1 840, oil cooling 1h 540, water cooling 2h 935 790 17 65 60 Example 2 840, oil cooling 1h 540, water cooling 2h 930 780 17 59 59 Example 2 840, oil cooling 1h 540, water cooling 2h 928 782 18 61 57 Example 3 840, oil cooling 1h 540, water cooling 2h 932 875 16 64 62 Example 3 840, oil cooling 1h 540, water cooling 2h 926 790 17 65 58 Example 4 840, oil cooling 1h 540, water cooling 2h 930 784 18 64 61 Example 4 840, oil cooling 1h 540, water cooling 2h 925 770 19 63 60 Example 5 840, oil cooling 1h 540, water cooling 2h 933 788 18 60 55 Example 5 840, oil cooling 1h 540, water cooling 2h 927 776 16 62 58

Claims

1. A high temperature resistant steel bar for automobile axles, characterized in that: In terms of mass percentage, C: 0.39% to 0.42%, Si: 0.22% to 0.30%, Mn: 1.45% to 1.70%, P: ≤0.015%, S: ≤0.006%, Cr: ≤0.20%, Ni: ≤0.20%, Mo: ≤0.05%, Cu: ≤0.10%, and the balance is iron and unavoidable impurities.

2. The method for preparing the high temperature resistant steel bar for automobile axles according to claim 1, characterized in that: The process includes the following steps: ecological electric furnace smelting → LF refining → RH refining → continuous casting → annealing process → heating process → rolling process → insulation process; The ecological electric furnace smelting is as follows: using scrap steel for smelting, the tapping temperature is 1640-1650℃, C is 0.10-0.15% when tapping, P≤0.010%, auxiliary materials and alloys are added when 1 / 4-1 / 3 of the steel is tapped, the smelting cycle is 55-65min, and the furnace oxygen consumption is 21-22m 3 / t steel; The LF refining is as follows: the LF inlet temperature is 1540-1550°C, a high current of 35000-36000A is used to heat and melt the slag, active lime is added when the slag surface fluctuates and the molten steel and the arc are not exposed, and the chemical composition is first sampled and analyzed after 5-6 minutes, and alloy and silicon carbide are added according to the target value of the chemical composition, and coke particles are added for carbon increase; when the molten steel temperature reaches 1600-1610°C, 1.4-1.5kg / t of diffusion deoxidizer is added for diffusion deoxidation, the furnace door is closed for 10-13 minutes, and when the molten steel temperature reaches 1630-1640°C, the chemical composition is sampled and analyzed for the second time, and the molten steel temperature is left when it reaches 1650-1660°C. The LF smelting cycle is 100-110 minutes; The RH refining is as follows: the inlet temperature is 1630-1640°C, the operation time is 35-45 minutes, the argon pressure is controlled at 0.1-0.3Mpa before the vacuum pump is started, the timing starts when the vacuum degree reaches 100-110Pa, the holding time is 10-15 minutes, and the argon pressure is adjusted to 0.3-0.5Mpa at the same time. After the static argon blowing is completed, a covering agent of 0.5-0.6kg / t steel is added, and the leaving temperature is 1585-1595°C; The continuous casting is as follows: the ladle arrival temperature is 1580-1590°C, the H in the tundish is controlled to be ≤2ppm, the casting time is 35min-45min, the superheat is 25-30°C, and the casting speed is 0.4-0.42m / min; The annealing process is as follows: annealing temperature is 580-620° C. and time is more than 32 hours.

3. The preparation method according to claim 2, characterized in that: In the ecological electric furnace smelting step, the amount of alloy added per ton of steel is: 16.5-17.5kg / t of high carbon ferromanganese, 1.9-2.1kg / t of ferroaluminum; the amount of auxiliary materials added per ton of steel is: 7.8-8.2kg / t of graphite pellets, 35-36kg / t of coke particles, 5.8-6.3kg / t of ladle ash, 40-41kg / t of active lime, and 29-31kg / t of dolomite; In the LF refining step, the amount of alloy added per ton of steel is: ferrosilicon 2.3-2.4kg / t, high carbon ferromanganese 3.5-3.6kg / t, alumina balls 1.4-1.5kg / t, aluminum wire 0.4-0.6kg / t; the amount of auxiliary materials added per ton of steel is: active lime 4-4.2Kg / t, silicon carbide 1.1-1.2kg / t, coke particles 0.5-0.6kg / t; In the continuous casting step, the casting is protected throughout the whole process, and the mold protection slag uses medium carbon steel protection slag.

4. The preparation method according to claim 2 or 3, characterized in that: The diameter of the aluminum iron is 40-70 mm, the diameter of the active lime is 10-70 mm, and the diameter of the dolomite is 20-70 mm; the diameter of the aluminum wire is 10-14 mm, and the diameter of the silicon carbide is 2-5 mm.

5. The preparation method according to claim 2, characterized in that: The scrap steel includes heavy scrap steel and steel offcuts, and by mass fraction, the heavy scrap steel comprises 80% to 90% and the steel offcuts comprise 10% to 20%; the diffusion deoxidizer is aluminum particles; and the covering agent is carbonized rice husk.

6. The preparation method according to claim 2, characterized in that: In the LF refining step, alloy, silicon carbide and coke particles are added to an argon gas stream.

7. The preparation method according to claim 2, characterized in that: The heating process is as follows: the temperature entering the heating furnace is 500°C~540°C, the temperature of the preheating section is required to be 650°C~680°C, and the time is 1.3~1.5h; the temperature of the heating section 2 is required to be 860°C~880°C, and the time is 1.3~1.5h; the temperature of the heating section 1 is required to be 1210°C~1220°C, and the time is 1.3~1.5h; the temperature of the soaking section is required to be 1200°C~1210°C, and the time is 1.3~1.5h; the steel tapping temperature is 1190°C~1198°C.

8. The preparation method according to claim 2, characterized in that: The rolling process is: (1) Initial rolling process: 9 passes; (2) Continuous rolling process: 11 rolling passes.

9. The preparation method according to claim 2, characterized in that: The insulation process is: steel insulation, lower insulation pit temperature ≥ 560°C, insulation 48 to 55 hours, pit exit temperature ≤ 120°C.

10. The preparation method according to claim 2, characterized in that: The steel after heat preservation is heat treated, and the heat treatment includes the following steps: 1) Quenching: 830-850℃, insulation 0.8-1.2h, oil cooling; 2) Tempering: 530-550℃, keep warm for 1.8-2.2h, water cooling.

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