Production and preparation method of steel bar for metro axle sealing element

Abstract

The invention discloses a production and preparation method of a steel bar for a metro axle sealing element, which comprises the following chemical components in percentage by mass: 0.13 to 0.17 percent of C, 0.17 to 0.40 percent of Si, 1.40 to 1.50 percent of Mn, less than or equal to 0.012 percent of P, less than or equal to 0.005 percent of S, 0.02 to 0.05 percent of V, 0.05 to 0.18 percent of Cr, less than or equal to 0.05 percent of Cu, less than or equal to 0.05 percent of Ni, 0.015 to 0.040 percent of Als, 0.40 to 0.45 percent of carbon equivalent and the balance of iron and inevitable impurities. According to the process route, a converter, LF refining, RH refining and continuous casting smelting process is adopted for smelting, so that the indexes such as impact performance, high hardness and high steel purity of a finished steel product of the steel for the metro axle sealing element are guaranteed, and the surface quality level of a steel bar for the metro axle sealing element is also guaranteed.

Description

Technical Field

[0001] The invention relates to the field of special steel, and in particular to a method for producing a steel bar for a subway axle seal. Background Art

[0002] The subway axle is the main part that transmits wheel force and carries the load of the carriage. The axle seal is an important component for sealing the axle. The steel used for the axle seal needs to maintain high strength, high corrosion resistance and other comprehensive performance requirements under high temperature conditions. The steel used for the subway axle seal is an important part of the boiler and is used to carry high pressure loads at high temperatures.

[0003] The quality of steel used in subway axle seals directly affects the service life and stability of the axle, and even affects the safety of the entire axle working process.

[0004] Therefore, it is necessary to develop steel bars for subway axle seals with excellent impact performance, high hardness and high steel purity to meet the requirements of high-end products. Summary of the invention

[0005] The purpose of the present invention is to provide a production and preparation method for steel bars for subway axle seals. The method adopts converter + LF + RH + continuous casting smelting process smelting and rolling process to produce steel bars for subway axle seals, which not only ensures the impact performance, high hardness and high steel purity of the finished steel for subway axle seals, but also ensures the surface quality level of the steel bars for subway axle seals, meets high-end use requirements, and achieves a breakthrough in the batch production of high-pressure boiler heat-resistant steel bars by the converter continuous casting process.

[0006] In order to achieve the above-mentioned invention object, the present invention provides a production and preparation method of steel bars for subway axle seals, including component design and process design, and specific steps: converter smelting → LF refining → RH vacuum degassing → continuous casting → heating → primary rolling mill rolling → continuous rolling mill group. The quality requirements of steel bars for subway axle seals are met, and the indicators such as impact performance, high hardness and high steel purity can also meet the standard requirements.

[0007] A steel bar for subway axle seals, the chemical composition of which, by mass percentage, is C: 0.13%-0.17%, Si: 0.17%-0.40%, Mn: 1.40%-1.50%, P: ≤0.012%, S: ≤0.005%, V: 0.02%-0.05%, Cr: 0.05%-0.18%, Cu: ≤0.05%, Ni: ≤0.05%, Als: 0.015%-0.040%, carbon equivalent (CEV): 0.40%-0.45%, and the balance is iron and unavoidable impurities.

[0008] The carbon equivalent calculation formula is: CEV (%) = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15

[0009] The production method of the steel bar for subway axle seals comprises the following process routes: converter smelting → refining outside the furnace (LF+RH) → continuous casting → heating in a heating furnace → rolling → insulation.

[0010] The converter smelting is as follows: using scrap steel and molten iron for smelting, with scrap steel accounting for 15-20% and molten iron accounting for 80-85% by mass fraction; oxygen oxidation, intense boiling, tapping temperature of 1630-1640°C, oxygen supply time of 13-14min, end point oxygen of 460-470ppm, operation time of 40-50min, C of 0.15-0.18% at tapping time, P≤0.010%, and adding auxiliary materials and alloys when 1 / 4-1 / 3 of the steel is tapped. The amount of alloy added per ton of steel: 7.2-7.6Kg / t of high carbon ferromanganese, 10.5-10.7Kg / t of silicon manganese, and 1.40-1.50Kg / t of aluminum particles. The amount of auxiliary materials added per ton of steel: 22.5-23Kg / t of dolomite, 18.5-19.5Kg / t of lime, and 20-21Kg / t of limestone.

[0011] The LF refining is as follows: a large current of 20000-22000A 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 5-10 minutes, the chemical composition is first sampled and analyzed; alloy is added according to the target value of the chemical composition, and carbon is increased by using a coke butadiene carburizer; the alloy and the coke butadiene carburizer should be added to the argon gas flow to promote rapid melting and homogenization of the alloy and the coke butadiene carburizer. The furnace body clearance is 550-620mm, the slag thickness is 45-55mm, argon blowing is 65-75min, the operation time is 110-120min, when the molten steel temperature reaches 1540-1550℃, add 1-3kg / t steel of diffusion deoxidizer for diffusion deoxidation, close the furnace door for 10-12min, when the molten steel temperature reaches 1650-1660℃, take a second sample to analyze the chemical composition to confirm the deviation of the content of each chemical element from the target value. After the second sample is taken, add 1-3kg / t steel of diffusion deoxidizer to continue slag adjustment. The amount of additional alloy added per ton of steel: high carbon ferromanganese 1.1~1.2kg / t, high carbon ferrochrome 0.40~0.42kg / t, medium carbon ferromanganese 0.95~1.0kg / t, aluminum particles 0.8~0.85kg / t, ferrosilicon 1.45~1.55kg / t, ferrovanadium 0.43~0.47kg / t. Keep the pH value of slag alkalinity at 2.5~3.5, slag viscosity 0.90~1.20Pa.s, and continue to smelt white slag for 20~30min. When the molten steel temperature reaches 1655~1665℃, start static argon blowing and keep it for 10~20min. The amount of additional auxiliary materials added per ton of steel: active lime 6.5~7.5kg / t, coke butane recarburizer 0.9~0.95Kg / t.

[0012] The RH refining is as follows: before the vacuum pump is started, the argon pressure is controlled at 0.1-0.3MPa, so that the slag surface moves slightly and the molten steel is not exposed, the timing starts when the vacuum degree reaches 100-110Pa, the holding time is 10-15min, the clearance is 530-570mm, the slag thickness is 65-75mm, the operation time is 25-30min, the temperature before treatment is 1645°C-1655°C, the temperature after treatment is 1600°C-1610°C, aluminum particles and high manganese are added according to the target composition of the molten steel, and the argon pressure is adjusted to 0.3-0.5MPa at the same time. After the static argon blowing is completed, 1.1-1.2 meters / t of silicon calcium wire (Φ10-12mm) is added.

[0013] Based on the above technical scheme, further, the continuous casting is: tundish temperature 1552℃~1559℃, pulling speed 0.40~0.44m / min, casting amount 155~160t / furnace, tundish H control ≤1.8ppm, crystallizer electromagnetic stirring current 400~450A, end electromagnetic stirring current 330~340A, frequency 8~8.2Hz; whole process protection casting, crystallizer protective slag uses medium carbon steel protective slag; light pressure is applied to put in the 2nd, 3rd and 4th rollers, and the pressure reduction is 3~3.1mm, 4~4.1mm and 4~4.1mm respectively; the billet cutting adopts a combination of automatic and manual methods, the billet insulation pit is insulated, red steel is used as the bottom, and the billets from two furnaces are pressed to ensure straightness, and the insulation time is 30~40h.

[0014] Based on the above technical scheme, further, the heating process is: the temperature entering the heating furnace is 380℃~420℃, the temperature of the preheating section is required to be 500℃~610℃, and the time is 1.4~1.5h; the temperature of the heating section 2 is required to be 850℃~870℃, and the time is 1.4~1.5h; the temperature of the heating section 1 is required to be 1190℃~1220℃, and the time is 1.4~1.5h; the temperature of the soaking section is required to be 1190℃~1220℃, and the time is 1.4~1.5h; the steel tapping temperature is 1190℃~1210℃.

[0015] Based on the above technical solution, further, the rolling process includes rolling by a primary rolling mill and rolling by a continuous rolling mill group, specifically:

[0016] (1) Initial rolling: The steel is rolled using a BD initial rolling mill and rolled in 7 passes. The rolling reduction is: steel turning → first pass reduction 70-70.2 mm → second pass reduction 80-80.2 mm → steel turning → third pass 74-74.2 mm → fourth pass 81-81.2 mm → steel turning → fifth pass 92-92.2 mm → sixth pass 30-30.2 mm → steel turning → seventh pass 38-38.2 mm. The steel is rolled through 3 850 mm rolling mills and 1 735 mm rolling mill, and then enters an 8-stand continuous rolling mill group for rolling.

[0017] (2) Medium rod rolling process:

[0018] The middle bar rolling process is as follows: the middle bar is rolled into an intermediate billet with a height of 268-268.2 mm and a width of 232-232.2 mm; the first pass is 229-229.2 mm high and 245-245.2 mm wide; the second pass is 192-192.2 mm high and 235-235.2 mm wide; the third pass is 200-200.2 mm high and 195-195.2 mm wide; the fourth pass is 160-160.2 mm high and 214.7-214.9 mm wide; the fifth pass is 164-164.2 mm high and 174.6-174.8 mm wide; the sixth pass is 192-192.2 mm high and 235-235.2 mm wide; the sixth pass is 192-192.2 mm high and 235-235.2 mm wide; the eighth ... high The pass height is 121~121.2mm and the width is 187.6~187.8mm; the 7th pass height is 139~139.2mm and the width is 138.5~138.7mm; the 8th pass height is 106~106.2mm and the width is 152~152.2mm; the 9th pass height is 118~118.2mm and the width is 121~121.2mm; the 10th pass height is 91~91.2mm and the width is 130.2~130.4mm; the 11th pass height is 101.4~101.6mm and the width is 101.4~101.6mm; the finished product is produced after the 11th pass.

[0019] Based on the above technical scheme, further, the insulation process is: steel insulation, pit entry temperature ≥ 550°C, pit exit temperature ≤ 150°C, insulation time ≥ 54h.

[0020] Based on the above technical solution, further, the process route includes finishing → inspection → packaging and storage → shipment after insulation.

[0021] Based on the above technical solution, further, the steel after heat preservation is subjected to heat treatment, and the heat treatment includes the following steps:

[0022] Normalizing: 900-920℃, keep warm for 1.8-2.2h, air cooling.

[0023] Beneficial effects of the present invention:

[0024] (1) The steel bars for subway axle seals are produced by converter + LF refining + RH refining + continuous casting smelting and rolling processes. The production specification is Φ100mm, 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, non-metallic inclusions and mechanical properties of the finished steel meet the requirements of high-end products. DETAILED DESCRIPTION

[0027] 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.

[0028] Example 1

[0029] 1Chemical composition

[0030] The chemical composition, by mass percentage, is C: 0.15%, Si: 0.25%, Mn: 1.45%, P: 0.010%, S: 0.004%, V: 0.03%, Cr: 0.10%, Cu: 0.02%, Ni: 0.03%, Als: 0.025%, and the balance is iron and inevitable impurities.

[0031] 2 Design of production process parameters for converter continuous casting of steel bars for subway axle seals

[0032] Process route: converter smelting → refining outside the furnace (LF+RH) → continuous casting → heating in the heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery. Among them:

[0033] (1) Converter smelting: Scrap steel and molten iron are used for smelting, with scrap steel accounting for 17% and molten iron accounting for 83% by mass; oxygen oxidation, intense boiling, tapping temperature 1635℃, oxygen supply time 13min, end point oxygen 464ppm, operation time 45min, C at tapping time 0.16%, P 0.009%, and auxiliary materials and alloys added when 1 / 4 of the steel is tapped. Alloy addition per ton of steel: 7.4Kg / t high carbon ferromanganese, 10.6Kg / t silicon manganese, 1.45Kg / t aluminum particles. Auxiliary materials addition per ton of steel: 22.7Kg / t dolomite, 19Kg / t lime, 20Kg / t limestone.

[0034] (2) LF furnace: Use a high current of 22,000 to heat and melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, add active lime. Take the first sample to analyze the chemical composition after 5 minutes. Add alloy according to the target value of the chemical composition, and use coke carburizer for carburization. The alloy and coke carburizer should be added to the argon gas flow to promote rapid melting and homogenization of the alloy and carbon powder. The furnace clearance is 580mm, the slag thickness is 50mm, the argon blowing is 70min, the operation time is 115min, when the temperature of the molten steel reaches 1545℃, 2kg / t of diffusion deoxidizer is added for diffusion deoxidation, the furnace door is closed for 10min, when the temperature of the molten steel reaches 1655℃, 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, 2kg / t of diffusion deoxidizer is added to continue slag adjustment, and the amount of alloy steel added is: high carbon ferromanganese 1.1kg / t, high carbon ferrochrome 0.41kg / t, medium carbon ferromanganese 0.97kg / t, aluminum particles 0.83kg / t, ferrosilicon 1.50kg / t, ferrovanadium 0.45kg / t. Keep the slag alkalinity pH value at 3.0, the slag viscosity at 0.98Pa.s, and continue to maintain white slag smelting for 25min, when the temperature of the molten steel reaches 1660℃, start static argon blowing, and keep it for 15min. The amount of supplementary auxiliary materials added per ton of steel: active lime 7kg / t, coke butane recarburizer 0.95Kg / t.

[0035] (3) RH refining: Before the vacuum pump is started, the argon pressure is controlled at 0.1 MPa, so that the slag surface moves slightly and the molten steel is not exposed. When the vacuum degree reaches 100 Pa, the timing starts, and the holding time is 12 min. The clearance is 550 mm, the slag thickness is 70 mm, and the operation time is 28 min. The temperature before treatment is 1650 °C, and the temperature after treatment is 1605 °C. Aluminum particles and high manganese are added according to the target composition of the molten steel. At the same time, the argon pressure is adjusted to 0.4 MPa. After the static argon blowing is completed, 1.1 m / t of silicon calcium wire (Φ10 mm) is added.

[0036] (4) Continuous casting: tundish temperature 1555℃, pulling speed 0.42m / min, casting volume 158t / furnace, tundish H control 1.2ppm, crystallizer electromagnetic stirring current 420A, end electromagnetic stirring current 335A, frequency 8Hz; whole process protective casting, crystallizer protective slag using medium carbon steel protective slag; light pressure is applied to the second, third and fourth rollers, with the pressure reduction being 3mm, 4mm and 4mm respectively; the ingot cutting is carried out by a combination of automatic and manual methods, the ingot is insulated in the insulated pit, red steel is used as the bottom, and the ingots from the two furnaces are pressed up to ensure straightness, and the insulation time is 35h.

[0037] (5) Heating process

[0038] Heating process: the temperature entering the heating furnace is 400℃, the temperature of the preheating section is required to be 560℃, and the time is 1.4h; the temperature of the heating section 2 is required to be 860℃, and the time is 1.5h; the temperature of the heating section 1 is required to be 1200℃, and the time is 1.5h; the temperature of the soaking section is required to be 1210℃, and the time is 1.5h; the steel tapping temperature is 1200℃.

[0039] (6) Initial rolling: The steel is rolled using a BD initial rolling mill and subjected to 7 rolling passes. The rolling reduction is as follows: steel turning → 70 mm reduction in the first pass → 80 mm reduction in the second pass → steel turning → 74 mm reduction in the third pass → 81 mm reduction in the fourth pass → steel turning → 92 mm reduction in the fifth pass → 30 mm reduction in the sixth pass → steel turning → 38 mm reduction in the seventh pass. The steel is then rolled through three 850 mm rolling mills and one 735 mm rolling mill, and then enters an eight-stand continuous rolling mill group for rolling.

[0040] (7) Rolling process:

[0041] The medium rod rolling process, the medium rod is rolled into an intermediate billet with a height of 268mm and a width of 232mm; 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 160mm high and 214.7mm wide; the fifth pass is 164mm high and 174.6mm wide; the sixth pass is 121mm high and 187.6mm wide; the seventh pass is 139mm high and 138.5mm wide; the eighth pass is 106mm high and 152mm wide; the ninth pass is 118mm high and 121mm wide; the tenth 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 the 11th pass.

[0042] (8) Insulation process

[0043] Insulation process: Steel insulation, pit entry temperature 580℃, pit exit temperature 130℃, insulation time 56h.

[0044] (9) Heat treatment process

[0045] The steel after heat preservation is heat treated, and the heat treatment includes the following steps:

[0046] Normalizing: 910℃, keep warm for 2h, air cooling.

[0047] Example 2

[0048] 1Chemical composition

[0049] The chemical composition, by mass percentage, is C: 0.15%, Si: 0.25%, Mn: 1.46%, P: 0.011%, S: 0.004%, V: 0.03%, Cr: 0.10%, Cu: 0.03%, Ni: 0.03%, Als: 0.024%, and the balance is iron and inevitable impurities.

[0050] 2 Design of production process parameters for converter continuous casting of high pressure boiler heat resistant steel bars

[0051] Process route: converter smelting → refining outside the furnace (LF+RH) → continuous casting → heating in the heating furnace → rolling → heat preservation → finishing → inspection → packaging and storage → delivery. Among them:

[0052] (1) Converter smelting: Scrap steel and molten iron are used for smelting, with scrap steel accounting for 18% and molten iron accounting for 82% by mass; oxygen oxidation, intense boiling, tapping temperature 1635℃, oxygen supply time 13min, end point oxygen 465ppm, operation time 45min, C at tapping time 0.16%, P≤0.010%, and auxiliary materials and alloys are added when 1 / 4 of the steel is tapped. Alloy addition per ton of steel: 7.3Kg / t high carbon ferromanganese, 10.6Kg / t silicon manganese, 1.45Kg / t aluminum particles. Auxiliary materials addition per ton of steel: 22.7Kg / t dolomite, 19.2Kg / t lime, 20Kg / t limestone.

[0053] (2) LF furnace: Use a high current of 22,000 to heat and melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, add active lime. Take the first sample to analyze the chemical composition after 5 minutes. Add alloy according to the target value of the chemical composition, and use coke carburizer for carburization. The alloy and coke carburizer should be added to the argon gas flow to promote rapid melting and homogenization of the alloy and carbon powder. The furnace clearance is 590mm, the slag thickness is 49mm, the argon blowing is 70min, the operation time is 114min, when the temperature of the molten steel reaches 1546℃, 1kg / t of diffusion deoxidizer is added for diffusion deoxidation, the furnace door is closed for 10min, when the temperature of the molten steel reaches 1655℃, 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, 2kg / t of diffusion deoxidizer is added to continue slag adjustment, and the amount of alloy steel added is: 1.1kg / t of high carbon ferromanganese, 0.40kg / t of high carbon ferrochrome, 0.97kg / t of medium carbon ferromanganese, 0.82kg / t of aluminum particles, 1.50kg / t of ferrosilicon, and 0.45kg / t of ferrovanadium. The pH value of the slag alkalinity is maintained at 3.0, the slag viscosity is 0.97Pa.s, and the white slag is continued to be smelted for 25min. When the temperature of the molten steel reaches 1660℃, static argon blowing is started, and the holding time is 15min. The amount of supplementary auxiliary materials added per ton of steel: active lime 7.0kg / t, coke butane recarburizer 0.95Kg / t.

[0054] (3) RH refining: Before the vacuum pump is started, the argon pressure is controlled at 0.1 MPa, so that the slag surface moves slightly and the molten steel is not exposed. When the vacuum degree reaches 100 Pa, the timing starts and the holding time is 10 min. The clearance is 550 mm, the slag thickness is 70 mm, the operation time is 27 min, the temperature before treatment is 1650 °C, and the temperature after treatment is 1605 °C. Aluminum particles and high manganese are added according to the target composition of the molten steel. At the same time, the argon pressure is adjusted to 0.4 MPa. After the static argon blowing is completed, 1.1 m / t of silicon calcium wire (Φ10 mm) is added.

[0055] (4) Continuous casting: tundish temperature 1556℃, pulling speed 0.42m / min, casting volume 158t / furnace, tundish H control 1.3ppm, crystallizer electromagnetic stirring current 420A, end electromagnetic stirring current 334A, frequency 8Hz; whole process protective casting, crystallizer protective slag using medium carbon steel protective slag; light pressure is applied to the second, third and fourth rollers, with the pressure reduction being 3mm, 4mm and 4mm respectively; the ingot cutting is carried out by a combination of automatic and manual methods, the ingot is insulated in the insulated pit, red steel is used as the bottom, and the ingots from the two furnaces are pressed to ensure straightness, and the insulation time is 35h.

[0056] (5) Heating process

[0057] Heating process: the temperature entering the heating furnace is 400℃, the temperature of the preheating section is required to be 560℃, and the time is 1.4h; the temperature of the heating section 2 is required to be 860℃, and the time is 1.4h; the temperature of the heating section 1 is required to be 1210℃, and the time is 1.4h; the temperature of the soaking section is required to be 1200℃, and the time is 1.4h; the steel tapping temperature is 1196℃.

[0058] (6) Initial rolling: The steel is rolled using a BD initial rolling mill and subjected to 7 rolling passes. The rolling reduction is as follows: steel turning → 70 mm reduction in the first pass → 80 mm reduction in the second pass → steel turning → 74 mm reduction in the third pass → 81 mm reduction in the fourth pass → steel turning → 92 mm reduction in the fifth pass → 30 mm reduction in the sixth pass → steel turning → 38 mm reduction in the seventh pass. The steel is then rolled through three 850 mm rolling mills and one 735 mm rolling mill, and then enters an eight-stand continuous rolling mill group for rolling.

[0059] (7) Rolling process:

[0060] The medium rod rolling process, the medium rod is rolled into an intermediate billet with a height of 268mm and a width of 232mm; 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 160mm high and 214.7mm wide; the fifth pass is 164mm high and 174.6mm wide; the sixth pass is 121mm high and 187.6mm wide; the seventh pass is 139mm high and 138.5mm wide; the eighth pass is 106mm high and 152mm wide; the ninth pass is 118mm high and 121mm wide; the tenth 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 the 11th pass.

[0061] (8) Insulation process

[0062] Insulation process: Steel insulation, pit entry temperature 570℃, pit exit temperature 140℃, insulation time 56h.

[0063] (9) Heat treatment process

[0064] The steel after heat preservation is heat treated, and the heat treatment includes the following steps:

[0065] Normalizing: 910℃, keep warm for 2.0h, air cooling.

[0066] Example 3

[0067] 1Chemical composition

[0068] The chemical composition, by mass percentage, is C: 0.15%, Si: 0.24%, Mn: 1.45%, P: 0.011%, S: 0.004%, V: 0.03%, Cr: 0.10%, Cu: 0.02%, Ni: 0.02%, Als: 0.025%, and the balance is iron and inevitable impurities.

[0069] 2 Design of production process parameters for converter continuous casting of high pressure boiler heat resistant steel bars

[0070] Process route: converter smelting → refining outside the furnace (LF+RH) → continuous casting → heating in the heating furnace → rolling → insulation → finishing → inspection → packaging and storage → delivery. Among them:

[0071] (1) Converter smelting: Scrap steel and molten iron are used for smelting, with scrap steel accounting for 18% and molten iron accounting for 82% by mass; oxygen oxidation, intense boiling, tapping temperature 1635℃, oxygen supply time 13min, end point oxygen 465ppm, operation time 44min, C at tapping time 0.16%, P 0.008%, and auxiliary materials and alloys added when 1 / 4 of the steel is tapped. Alloy addition per ton of steel: 7.4Kg / t high carbon ferromanganese, 10.6Kg / t silicon manganese, 1.45Kg / t aluminum particles. Auxiliary materials addition per ton of steel: 22.7Kg / t dolomite, 19Kg / t lime, 20Kg / t limestone.

[0072] (2) LF furnace: Use a high current of 23,000 to heat and melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, add active lime. Take the first sample to analyze the chemical composition after 5 minutes. Add alloy according to the target value of the chemical composition, and use coke carburizer for carburization. The alloy and coke carburizer should be added to the argon gas flow to promote rapid melting and homogenization of the alloy and carbon powder. The furnace clearance is 580mm, the slag thickness is 50mm, the argon blowing is 70min, the operation time is 115min, when the temperature of the molten steel reaches 1545℃, 1kg / t of diffusion deoxidizer is added for diffusion deoxidation, the furnace door is closed for 10min, when the temperature of the molten steel reaches 1645℃, 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, 2kg / t of diffusion deoxidizer is added to continue slag adjustment, and the amount of alloy steel added is: 1.1kg / t of high carbon ferromanganese, 0.41kg / t of high carbon ferrochrome, 0.97kg / t of medium carbon ferromanganese, 0.82kg / t of aluminum particles, 1.50kg / t of ferrosilicon, and 0.45kg / t of ferrovanadium. Keep the pH value of slag alkalinity at 2.8 and the viscosity of slag at 0.98Pa.s, and continue to keep the white slag smelting for 25min. When the temperature of the molten steel reaches 1660℃, start static argon blowing for 15min. The amount of supplementary auxiliary materials added per ton of steel: active lime 7.0kg / t, coke butane recarburizer 0.95Kg / t.

[0073] (3) RH refining: Before the vacuum pump is started, the argon pressure is controlled at 0.1 MPa, so that the slag surface moves slightly and the molten steel is not exposed. When the vacuum degree reaches 100 Pa, the timing starts, and the holding time is 12 min. The clearance is 550 mm, the slag thickness is 70 mm, and the operation time is 28 min. The temperature before treatment is 1650 °C, and the temperature after treatment is 1605 °C. Aluminum particles and high manganese are added according to the target composition of the molten steel. At the same time, the argon pressure is adjusted to 0.4 MPa. After the static argon blowing is completed, 1.1 m / t of silicon calcium wire (Φ10 mm) is added.

[0074] (4) Continuous casting: tundish temperature 1555℃, pulling speed 0.42m / min, casting volume 158t / furnace, tundish H control 1.3ppm, crystallizer electromagnetic stirring current 420A, end electromagnetic stirring current 335A, frequency 8Hz; whole process protective casting, crystallizer protective slag using medium carbon steel protective slag; light pressure is applied to the second, third and fourth rollers, with the pressure reduction being 3mm, 4mm and 4mm respectively; the ingot cutting is carried out by a combination of automatic and manual methods, the ingot is insulated in the insulated pit, red steel is used as the bottom, and the ingots from the two furnaces are pressed up to ensure straightness, and the insulation time is 34h.

[0075] (5) Heating process

[0076] Heating process: the temperature entering the heating furnace is 390℃, the temperature of the preheating section is required to be 560℃, and the time is 1.4h; the temperature of the heating section 2 is required to be 860℃, and the time is 1.5h; the temperature of the heating section 1 is required to be 1210℃, and the time is 1.5h; the temperature of the soaking section is required to be 1208℃, and the time is 1.4h; the steel tapping temperature is 1200℃.

[0077] (6) Initial rolling: The steel is rolled using a BD initial rolling mill and subjected to 7 rolling passes. The rolling reduction is as follows: steel turning → 70 mm reduction in the first pass → 80 mm reduction in the second pass → steel turning → 74 mm reduction in the third pass → 81 mm reduction in the fourth pass → steel turning → 92 mm reduction in the fifth pass → 30 mm reduction in the sixth pass → steel turning → 38 mm reduction in the seventh pass. The steel is then rolled through three 850 mm rolling mills and one 735 mm rolling mill, and then enters an eight-stand continuous rolling mill group for rolling.

[0078] (7) Rolling process:

[0079] The medium rod rolling process, the medium rod is rolled into an intermediate billet with a height of 268mm and a width of 232mm; 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 160mm high and 214.7mm wide; the fifth pass is 164mm high and 174.6mm wide; the sixth pass is 121mm high and 187.6mm wide; the seventh pass is 139mm high and 138.5mm wide; the eighth pass is 106mm high and 152mm wide; the ninth pass is 118mm high and 121mm wide; the tenth pass is 91mm high and 130.2mm wide; the 11th pass is 101.5mm high and 101.5mm wide; the finished product is produced after the 11th pass.

[0080] (8) Insulation process

[0081] Insulation process: Steel insulation, pit entry temperature 570℃, pit exit temperature 130℃, insulation time 56h.

[0082] (9) Heat treatment process

[0083] The steel after heat preservation is heat treated, and the heat treatment includes the following steps:

[0084] Normalizing: 910℃, keep warm for 2.0h, air cooling.

[0085] Test results of finished products of Examples 1 to 3:

[0086] (1) Φ100mm steel specification macrostructure (finished steel obtained by heat preservation process)

[0087]

[0088]

[0089] (2) Non-metallic inclusions in Φ100mm steel (finished steel obtained by thermal insulation process)

[0090]

[0091] (3) Impact performance of Φ100mm specification (finished steel obtained after heat treatment)

[0092] Serial number Normalizing / ℃ Sample size / mm <![CDATA[R m / MPa]]> <![CDATA[R el / MPa]]> A / ％ standard 910, air cooling Φ25 470～610 ≥255 ≥18 Example 1 910, air cooling Φ25 550 315 22 Example 1 910, air cooling Φ25 545 310 23 Example 2 910, air cooling Φ25 540 312 24 Example 2 910, air cooling Φ25 542 300 23 Example 3 910, air cooling Φ25 540 308 21 Example 3 910, air cooling Φ25 548 305 22

[0093] For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A steel bar for subway axle seal, characterized in that: In terms of mass percentage, C: 0.13% ~ 0.17%, Si: 0.17% ~ 0.40%, Mn: 1.40% ~ 1.50%, P: ≤0.012%, S: ≤0.005%, V: 0.02% ~ 0.05%, Cr: 0.05% ~ 0.18%, Cu: ≤0.05%, Ni: ≤0.05%, Als: 0.015% ~ 0.040%, carbon equivalent: 0.40% ~ 0.45%, and the balance is iron and unavoidable impurities.

2. The method for preparing the steel bar for subway axle seal according to claim 1, characterized in that: The method comprises: converter smelting→LF refining→RH refining→continuous casting→heating process→rolling process→insulation process; The converter smelting is as follows: using scrap steel and molten iron for smelting, wherein the scrap steel accounts for 15-20% by mass and the molten iron accounts for 80-85% by mass; oxygen oxidation, intense boiling, tapping temperature of 1630-1640°C, oxygen supply time of 13-14min, terminal oxygen of 460-470ppm, operation time of 40-50min, C of 0.15-0.18% at tapping time, P≤0.010%, and adding auxiliary materials and alloys when 1 / 4-1 / 3 of the steel is tapped; the amount of alloy added per ton of steel: 7.2-7.6Kg / t of high carbon ferromanganese, 10.5-10.7Kg / t of silicon manganese, and 1.40-1.50Kg / t of aluminum particles; the amount of auxiliary materials added per ton of steel: 22.5-23Kg / t of dolomite, 18.5-19.5Kg / t of lime, and 20-21Kg / t of limestone; The LF refining comprises: using a large current of 20000-22000A 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 sample for the first time after 5-10 minutes to analyze the chemical composition; adding alloy according to the target value of the chemical composition; and using coke carburizer for carburization; the furnace clearance is 550-620mm, the slag thickness is 45-55mm, argon is blown for 65-75min, the operation time is 110-120min, and when the molten steel temperature reaches 1540-1550°C, 1-3kg / t steel of diffusion deoxidizer is added for diffusion deoxidation. Oxygen, close the furnace door for 10-12 minutes, when the temperature of the molten steel reaches 1650-1660℃, take a second sample to analyze the chemical composition to confirm the deviation of the content of each chemical element from the target value. After the second sample is taken, add 1-3kg / t steel of diffusion deoxidizer to continue slag adjustment, keep the pH value of slag alkalinity at 2.5-3.5, and the viscosity of slag at 0.90-1.20Pa.s. At the same time, continue to maintain white slag smelting for 20-30 minutes. When the temperature of the molten steel reaches 1655-1665℃, start static argon blowing for 10-20 minutes; The RH refining is as follows: before the vacuum pump is started, the argon pressure is controlled at 0.1-0.3MPa, so that the slag surface is slightly moved and the molten steel is not exposed, when the vacuum degree reaches 100-110Pa, the timing starts, the holding time is 10-15min, the clearance is 530-570mm, the slag thickness is 65-75mm, the operation time is 25-30min, the temperature before treatment is 1645°C-1655°C, the temperature after treatment is 1600°C-1610°C, aluminum particles and high manganese are added according to the target composition of the molten steel, and the argon pressure is adjusted to 0.3-0.5MPa at the same time, after the static argon blowing is completed, 1.1-1.2m / t of silicon calcium wire is added; The continuous casting is as follows: tundish temperature is 1552°C to 1559°C, casting speed is 0.40 to 0.44 m / min, casting amount is 155 to 160 t / furnace, H in tundish is controlled to be ≤1.8ppm, crystallizer electromagnetic stirring current is 400 to 450A, terminal electromagnetic stirring current is 330 to 340A, and frequency is 8 to 8.2 Hz; The heating process is as follows: the preheating section temperature is required to be 500°C to 610°C, and the time is 1.4 to 1.5 hours; the heating section 2 temperature is required to be 850°C to 870°C, and the time is 1.4 to 1.5 hours; the heating section 1 temperature is required to be 1190°C to 1220°C, and the time is 1.4 to 1.5 hours; the soaking section temperature is required to be 1190°C to 1220°C, and the time is 1.4 to 1.5 hours; and the steel tapping temperature is 1190°C to 1210°C.

3. The preparation method according to claim 2, characterized in that: In LF refining, the amount of additional alloy added per ton of steel: high carbon ferromanganese 1.1-1.2kg / t, high carbon ferrochrome 0.40-0.42kg / t, medium carbon ferromanganese 0.95-1.0kg / t, aluminum particles 0.8-0.85kg / t, ferrosilicon 1.45-1.55kg / t, ferrovanadium 0.43-0.47kg / t; the amount of additional auxiliary materials added per ton of steel: active lime 6.5-7.5kg / t, coke butane recarburizer 0.9-0.95Kg / t.

4. The preparation method according to claim 2, characterized in that: During continuous casting, the casting is protected throughout the whole process, and medium carbon steel protective slag is used for the crystallizer protective slag; the 2nd, 3rd and 4th rollers are put into the casting with light pressure, and the pressure reduction amount is 3-3.1mm, 4-4.1mm and 4-4.1mm respectively; the ingot cutting adopts a combination of automatic and manual methods, the ingot is insulated in a heat-insulating pit, red steel is used as the bottom, and the ingots from two furnaces are pressed up to ensure straightness, and the insulation time is 30-40h.

5. The preparation method according to claim 2, characterized in that: During the heating process, the temperature entering the heating furnace is 380°C to 420°C.

6. The preparation method according to claim 2, characterized in that: The rolling process comprises the following steps: (1) Initial rolling: The steel is rolled using a BD initial rolling mill and rolled in 7 passes. The rolling reduction is: steel turning → first pass reduction 70-70.2 mm → second pass reduction 80-80.2 mm → steel turning → third pass 74-74.2 mm → fourth pass 81-81.2 mm → steel turning → fifth pass 92-92.2 mm → sixth pass 30-30.2 mm → steel turning → seventh pass 38-38.2 mm. The steel is rolled through 3 850 mm rolling mills and 1 735 mm rolling mill, and then enters an 8-stand continuous rolling mill group for rolling. (2) Medium bar rolling process: The medium bar is rolled into an intermediate billet with a height of 268-268.2 mm and a width of 232-232.2 mm; the first pass is 229-229.2 mm high and 245-245.2 mm wide; the second pass is 192-192.2 mm high and 235-235.2 mm wide; the third pass is 200-200.2 mm high and 195-195.2 mm wide; the fourth pass is 160-160.2 mm high and 214.7-214.9 mm wide; the fifth pass is 164-164.2 mm high and 174.6-174.8 mm wide; the The 6th pass is 121~121.2mm high and 187.6~187.8mm wide; the 7th pass is 139~139.2mm high and 138.5~138.7mm wide; the 8th pass is 106~106.2mm high and 152~152.2mm wide; the 9th pass is 118~118.2mm high and 121~121.2mm wide; the 10th pass is 91~91.2mm high and 130.2~130.4mm wide; the 11th pass is 101.4~101.6mm high and 101.4~101.6mm wide; the finished product is produced after the 11th pass.

7. The preparation method according to claim 2, characterized in that: The insulation process is: steel insulation, pit entry temperature ≥ 550°C, pit exit temperature ≤ 150°C, and insulation time ≥ 54h.

8. 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: Normalizing: 900-920℃, keep warm for 1.8-2.2h, air cooling.

9. The preparation method according to claim 2, characterized in that: In LF refining, the alloy and coke recarburizer are added to the argon stream.

10. The preparation method according to claim 2, characterized in that: The diameter of the calcium silicon wire is 10-12 mm.

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