Method for producing and preparing steel bar for metro axle sealing element

Abstract

Disclosed in the present invention is a method for producing and preparing a steel bar for a metro axle sealing element. The steel bar comprises the following chemical components, in percentages by mass: 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 being iron and inevitable impurities. The process route comprises: smelting by using a converter + LF refining + RH refining + continuous casting smelting process, which not only ensures the impact performance, high hardness, high steel purity and other properties of a finished steel product for a metro axle sealing element, but also ensures the surface quality level of the steel bar for the metro axle sealing element.

Description

Production and preparation method of subway axle sealing steel bar TECHNICAL FIELD

[0001] The present application relates to the field of special steel, in particular to a production and preparation method of subway axle sealing steel bar. BACKGROUND

[0002] The subway axle is the main part of transmitting the wheel force and bearing the load of the carriage, and the axle sealing part is an important component for sealing the axle. The axle sealing steel needs to maintain high strength, high corrosion resistance and other comprehensive performance requirements under high temperature environment conditions. The subway axle sealing steel is an important component of the boiler and is used to bear high pressure load at high temperature.

[0003] The quality of the subway axle sealing steel directly affects the service life and stability of the axle, and even relates to the safety of the entire axle working process.

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

[0005] SUMMARY

[0006] The purpose of the present application is to provide a production and preparation method of subway axle sealing steel bar, which adopts converter + LF + RH + continuous casting smelting process and rolling process to produce and manufacture subway axle sealing steel bar, which not only ensures the impact performance, high hardness and high steel purity of the finished subway axle sealing steel, but also ensures the surface quality level of the subway axle sealing steel bar, meets the high-end use requirements, and realizes the breakthrough of the converter continuous casting process for batch production of high-pressure boiler heat-resistant steel bar.

[0007] In order to achieve the above-mentioned purpose of the application, the present application provides a production and preparation method of subway axle sealing steel bar, including composition design and process design, and the specific steps are: converter smelting → LF refining → RH vacuum degassing → continuous casting → heating → roughing mill rolling → continuous rolling mill. The method meets the quality requirements of subway axle sealing steel bar, and the impact performance, high hardness and high steel purity can also meet the standard requirements.

[0008] A subway axle sealing steel bar, the chemical composition, by mass percent, 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%, the balance is iron and inevitable impurities.

[0009] The carbon equivalent calculation formula is: CEV(%)=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15

[0010] The subway axle sealing steel bar production method, the process route comprises: converter smelting→ secondary refining (LF+RH)→ continuous casting→ heating furnace heating→ rolling→ heat preservation.

[0011] The converter smelting is: using scrap and hot metal smelting, the mass fraction is 15~20% scrap and 80~85% hot metal; oxygen oxidation, violent boiling, tapping temperature 1630~1640℃, oxygen supply time 13~14min, end point oxygen 460~470ppm, operation time 40~50min, tapping C is 0.15~0.18%, P ≤0.010%, tapping 1 / 4~1 / 3 time adding auxiliary materials and alloy. Alloy ton steel addition amount: high-carbon ferromanganese 7.2~7.6Kg / t, silicon manganese 10.5~10.7Kg / t, aluminum particles 1.40~1.50Kg / t. Auxiliary material ton steel addition amount: dolomite 22.5~23Kg / t, lime 18.5~19.5Kg / t, limestone 20~21Kg / t.

[0012] The LF refining: using 20000-22000A large current to heat up the slag, when the slag surface fluctuates, the molten steel and the arc are not exposed, add active lime, 5-10 min later, take the first sample to analyze the chemical composition, add alloy according to the target value of the chemical composition, and use coke to increase carbon, the alloy and coke carbon additive should be added to the argon stream to promote the rapid melting and homogenization of the alloy and coke carbon additive. The net clearance of the furnace body is 550-620 mm, the slag thickness is 45-55 mm, the argon blowing time is 65-75 min, the operation time is 110-120 min, when the temperature of the molten steel reaches 1540-1550℃, add 1-3 kg / t of steel diffusion deoxidizer for diffusion deoxidation, close the furnace door for 10-12 min, when the temperature of the molten steel reaches 1650-1660℃, take the second sample to analyze the chemical composition to confirm the deviation of the chemical element content from the target value, after the second sample is taken away, add 1-3 kg / t of steel diffusion deoxidizer to continue to adjust the slag. The addition amount of the alloy per ton of steel: high-carbon ferromanganese 1.1-1.2 kg / t, high-carbon ferrochrome 0.40-0.42 kg / t, medium-carbon ferromanganese 0.95-1.0 kg / t, aluminum particles 0.8-0.85 kg / t, ferrosilicon 1.45-1.55 kg / t, vanadium iron 0.43-0.47 kg / t. Maintain the slag basicity pH value of 2.5-3.5 and the slag viscosity of 0.90-1.20 Pa.s, and continue to maintain white slag smelting for 20-30 min, when the temperature of the molten steel reaches 1655-1665℃, start to blow argon, and maintain for 10-20 min. The addition amount of the auxiliary material per ton of steel: active lime 6.5-7.5 kg / t, coke carbon additive 0.9-0.95 kg / t.

[0013] The RH refining: before the vacuum pump starts, the argon pressure is controlled at 0.1-0.3 MPa, the slag surface is slightly moved and the molten steel is not exposed, when the vacuum degree reaches 100-110 Pa, start timing, maintain for 10-15 min, the net clearance is 530-570 mm, the slag thickness is 65-75 mm, the operation time is 25-30 min, the temperature before treatment is 1645-1655℃, and the temperature after treatment is 1600-1610℃, according to the target composition, add aluminum particles and high-manganese, and adjust the argon pressure to 0.3-0.5 MPa, after the end of the static argon blowing, add 1.1-1.2 meters / t of steel silicon calcium wire (Φ10-12 mm).

[0014] Based on the above technical scheme, further, the continuous casting is: tundish temperature 1552-1559℃, casting 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 protection slag uses medium carbon steel protection slag; light press-down is put into the 2nd, 3rd and 4th rollers, and the press-down amount is 3-3.1mm, 4-4.1mm and 4-4.1mm respectively; the casting blank cutting adopts the automatic and manual combined mode, the casting blank is kept in the heat preservation pit, the red steel is used as the bottom pad, the upper pressure is used to ensure the flatness of two furnace casting blanks, and the heat preservation time is 30-40h.

[0015] Based on the above technical scheme, further, the heating process is: the temperature entering the heating furnace is 380-420℃, the preheating section temperature requirement is 500-610℃, the time is 1.4-1.5h; the heating 2 section temperature requirement is 850-870℃, the time is 1.4-1.5h; the heating 1 section temperature requirement is 1190-1220℃, the time is 1.4-1.5h; the soaking section temperature requirement is 1190-1220℃, the time is 1.4-1.5h; the steel tapping temperature is 1190-1210℃.

[0016] Based on the above technical scheme, further, the rolling process includes roughing mill rolling and continuous rolling mill group rolling, specifically:

[0017] (1) Roughing and blooming: BD roughing mill is adopted for blooming, 7 passes are rolled, and the rolling reduction is: turning over→1st pass reduction 70-70.2mm→2nd pass reduction 80-80.2mm→turning over→3rd pass 74-74.2mm→4th pass 81-81.2mm→turning over→5th pass 92-92.2mm→6th pass 30-30.2mm→turning over→7th pass 38-38.2mm, after passing through 3 sets of 850mm rolling mill and 1 set of 735mm rolling mill, then entering 8 sets of continuous rolling mill group rolling.

[0018] (2) Medium bar rolling process:

[0019] The middle bar rolling process is as follows: the middle bar is rolled into an intermediate blank with a height of 268-268.2 mm and a width of 232-232.2 mm; the first pass has a height of 229-229.2 mm and a width of 245-245.2 mm; the second pass has a height of 192-192.2 mm and a width of 235-235.2 mm; the third pass has a height of 200-200.2 mm and a width of 195-195.2 mm; the fourth pass has a height of 160-160.2 mm and a width of 214.7-214.9 mm; the fifth pass has a height of 164-164.2 mm and a width of 174.6-174.8 mm; the sixth pass has a height of 121-121.2 mm and a width of 187.6-187.8 mm; the seventh pass has a height of 139-139.2 mm and a width of 138.5-138.7 mm; the eighth pass has a height of 106-106.2 mm and a width of 152-152.2 mm; the ninth pass has a height of 118-118.2 mm and a width of 121-121.2 mm; the tenth pass has a height of 91-91.2 mm and a width of 130.2-130.4 mm; the eleventh pass has a height of 101.4-101.6 mm and a width of 101.4-101.6 mm; and the finished product is discharged after the eleventh pass.

[0020] Based on the above technical scheme, further, the heat preservation process is that: the steel material is heat preserved, the entering pit temperature is greater than or equal to 550 DEG C, the out pit temperature is less than or equal to 150 DEG C, and the heat preservation time is greater than or equal to 54 h.

[0021] Based on the above technical scheme, further, the heat preservation in the process route is followed by finishing, inspection, packaging and delivery to the warehouse.

[0022] Based on the above technical scheme, further, the steel material after heat preservation is heat treated, and the heat treatment comprises the following steps:

[0023] Normalizing: 900-920 DEG C, heat preservation for 1.8-2.2 h, air cooling.

[0024] The beneficial effects of the present application are as follows:

[0025] (1) The steel bar for subway axle sealing parts is produced by adopting the converter + LF refining + RH refining + continuous casting smelting process and rolling process, the production specification is Φ100 mm, the mechanical property requirements are met, and the steel purity is ensured.

[0026] (2) The reasonable component design and production process ensure the surface quality and mechanical property.

[0027] (3) The macrostructure, non-metallic inclusions and mechanical property of the finished steel material meet the requirements of high-end products. DETAILED DESCRIPTION

[0028] The following non-limiting examples can make those skilled in the art more fully understand the present application, but do not limit the present application in any way.

[0029] Example 1

[0030] 1 Chemical composition

[0031] Chemical composition, in mass percent, 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%, the balance being iron and unavoidable impurities.

[0032] 2 Design of each production process parameter of steel bar for subway axle sealing by converter continuous casting

[0033] Process route: converter smelting → secondary refining (LF + RH) → continuous casting → heating furnace heating → rolling → heat preservation → finishing → inspection → packaging and delivery to the warehouse → shipment. Among them:

[0034] (1) Converter smelting: smelting with scrap steel and hot metal, scrap steel accounts for 17% and hot metal accounts for 83% by mass fraction; oxygen oxidation, violent boiling, tapping temperature 1635℃, oxygen supply time 13min, end point oxygen 464ppm, operation time 45min, tapping C 0.16%, P 0.009%, auxiliary materials and alloys are added at 1 / 4 tapping time. Alloy addition per ton of steel: high-carbon ferromanganese 7.4Kg / t, silicon manganese 10.6Kg / t, aluminum particles 1.45Kg / t. Auxiliary material addition per ton of steel: dolomite 22.7Kg / t, lime 19Kg / t, limestone 20Kg / t.

[0035] (2) LF furnace: using 22000 large current heating slag, when the slag surface fluctuation, molten steel and arc not bare, add active lime, 5 min after the first sampling analysis chemical composition, according to the chemical composition target value of alloy, and using coke carbon additive carbon, alloy and coke carbon additive should be added to the argon stream, to promote alloy and carbon powder quickly melt and homogenization. The net clearance of the furnace body is 580 mm, the slag thickness is 50 mm, the argon blowing time is 70 min, the operation time is 115 min, when the molten steel temperature reaches 1545℃, add 2 kg / t of diffusion deoxidizer for diffusion deoxidation, close the furnace door for 10 min, when the molten steel temperature reaches 1655℃, the second sampling analysis chemical composition is carried out to confirm the deviation of each chemical element content from the target value, after the second sampling, add 2 kg / t of diffusion deoxidizer for slag adjustment, the alloy addition amount per ton of steel is: high carbon ferromanganese 1.1 kg / t, high carbon ferrochrome 0.41 kg / t, medium carbon ferromanganese 0.97 kg / t, aluminum grain 0.83 kg / t, ferrosilicon 1.50 kg / t, vanadium iron 0.45 kg / t. Maintain the slag basicity pH value of 3.0 and the slag viscosity of 0.98 Pa.s, and continue white slag smelting for 25 min, when the molten steel temperature reaches 1660℃, start argon blowing, and the holding time is 15 min. The auxiliary material addition amount per ton of steel is: active lime 7 kg / t, coke carbon additive 0.95 Kg / t.

[0036] (3) RH refining: before the vacuum pump starts, the argon pressure is controlled at 0.1 MPa, the slag surface is slightly moved and the molten steel is not bare, when the vacuum degree reaches 100 Pa, start timing, the holding time is 12 min, the net clearance is 550 mm, the slag thickness is 70 mm, the operation time is 28 min, the temperature before treatment is 1650℃, the temperature after treatment is 1605℃, according to the target composition, add aluminum grain and high manganese, at the same time, adjust the argon pressure to 0.4 MPa, after the end of argon blowing, add 1.1 meters / t of silicon calcium wire (Φ10 mm).

[0037] (4) Continuous casting: the tundish temperature is 1555℃, the casting speed is 0.42 m / min, the casting amount is 158 t / furnace, the tundish H control is 1.2 ppm, the crystallizer electromagnetic stirring current is 420 A, the end electromagnetic stirring current is 335 A, and the frequency is 8 Hz; the whole process is protected casting, and the crystallizer protective slag uses medium carbon steel protective slag; light pressing is put into the 2nd, 3rd and 4th rollers, and the pressing amount is 3 mm, 4 mm and 4 mm respectively; the casting blank cutting adopts the automatic and manual combined mode, the casting blank is kept in the heat preservation pit, the red steel is used as the bottom pad, the upper pressure is used to ensure the flatness of two furnace castings, and the heat preservation time is 35 h.

[0038] (5) Heating process

[0039] Heating process: the temperature of the steel entering the heating furnace is 400°C, the temperature of the preheating section is required to be 560°C, the time is 1.4h; the temperature of the heating 2 section is required to be 860°C, the time is 1.5h; the temperature of the heating 1 section is required to be 1200°C, the time is 1.5h; the temperature of the soaking section is required to be 1210°C, the time is 1.5h; the temperature of the steel leaving the furnace is 1200°C.

[0040] (6) blooming: BD blooming mill is used for blooming, 7 passes are rolled, the rolling reduction is: turning over the steel → the first pass reduction 70mm → the second pass reduction 80mm → turning over the steel → the third pass 74mm → the fourth pass 81mm → turning over the steel → the fifth pass 92mm → the sixth pass 30mm → turning over the steel → the seventh pass 38mm, after passing through 3 850mm rolling mills and 1 735mm rolling mill, the steel enters an 8-rolling mill train.

[0041] (7) rolling process:

[0042] The middle bar rolling process is used to roll the middle bar into an intermediate blank with a height of 268mm and a width of 232mm; the first pass has a height of 229mm and a width of 245mm; the second pass has a height of 192mm and a width of 235mm; the third pass has a height of 200mm and a width of 195mm; the fourth pass has a height of 160mm and a width of 214.7mm; the fifth pass has a height of 164mm and a width of 174.6mm; the sixth pass has a height of 121mm and a width of 187.6mm; the seventh pass has a height of 139mm and a width of 138.5mm; the eighth pass has a height of 106mm and a width of 152mm; the ninth pass has a height of 118mm and a width of 121mm; the tenth pass has a height of 91mm and a width of 130.2mm; the eleventh pass has a height of 101.4mm and a width of 101.4mm; the finished product is discharged after the eleventh pass.

[0043] (8) soaking process

[0044] Soaking process: the steel is soaked, the temperature of entering the pit is 580°C, the temperature of leaving the pit is 130°C, and the soaking time is 56h.

[0045] (9) heat treatment process

[0046] The steel after soaking is subjected to heat treatment, and the heat treatment comprises the following steps:

[0047] normalizing: 910°C, soaking for 2h, air cooling.

[0048] Example 2

[0049] 1 chemical composition

[0050] Chemical composition, by mass percent, 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%, balance iron and inevitable impurities.

[0051] 2 High-pressure boiler heat-resistant steel bar continuous casting process parameters design

[0052] Process route: converter smelting → secondary refining (LF + RH) → continuous casting → heating furnace heating → rolling → holding → finishing → inspection → packaging and delivery to the warehouse → delivery. Among them:

[0053] (1) Converter smelting: using scrap steel and molten iron smelting, scrap steel accounts for 18%, molten iron accounts for 82% by mass fraction; oxygen oxidation, vigorous boiling, tapping temperature 1635℃, oxygen supply time 13min, end point oxygen 465ppm, operation time 45min, tapping C 0.16%, P≤0.010%, auxiliary materials and alloys are added at 1 / 4 tapping time. Alloy addition per ton of steel: high-carbon ferromanganese 7.3Kg / t, silicon manganese 10.6Kg / t, aluminum particles 1.45Kg / t. Auxiliary material addition per ton of steel: dolomite 22.7Kg / t, lime 19.2Kg / t, limestone 20Kg / t.

[0054] (2) LF furnace: using 22000 large current to heat and slag, when the slag surface fluctuates, the steel and the electric arc are not exposed, active lime is added, the chemical composition is analyzed after 5min, the alloy is added according to the target value of the chemical composition, and the coke breeze carbonizer is used for carbonization, and the alloy and the coke breeze carbonizer should be added to the argon stream to promote the rapid melting and homogenization of the alloy and the carbon powder. The net clearance of the furnace body is 590mm, the slag thickness is 49mm, the argon blowing time is 70min, the operation time is 114min, the diffusion deoxidizer 1kg / t is added for diffusion deoxidization when the steel temperature reaches 1546℃, the furnace door is closed for 10min, the chemical composition is analyzed for the second time when the steel temperature reaches 1655℃, to confirm the deviation of each chemical element content from the target value. After the second sampling, 2kg / t of diffusion deoxidizer is added to continue slagging, alloy addition per ton of steel: high-carbon ferromanganese 1.1kg / t, high-carbon chromium iron 0.40kg / t, medium-carbon ferromanganese 0.97kg / t, aluminum particles 0.82kg / t, silicon iron 1.50kg / t, vanadium iron 0.45kg / t. Maintain the pH value of the molten slag basicity to 3.0 and the molten slag viscosity to 0.97Pa.s, and continue white slag smelting for 25min, start argon blowing when the steel temperature reaches 1660℃, and keep the time for 15min. Auxiliary material addition per ton of steel: active lime 7.0kg / t, coke breeze carbonizer 0.95Kg / t.

[0055] (3) RH refining: argon pressure is controlled at 0.1 MPa before vacuum pump is started, the slag surface is slightly moved without exposing the molten steel, the time is counted when the vacuum degree reaches 100 Pa, the holding time is 10 min, the net space is 550 mm, the slag thickness is 70 mm, the operation time is 27 min, the temperature before treatment is 1650℃, the temperature after treatment is 1605℃, the 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 end of the static argon blowing, the silicon calcium wire (Φ10 mm) 1.1 m / t is added.

[0056] (4) Continuous casting: the tundish temperature is 1556℃, the casting speed is 0.42 m / min, the casting amount is 158 t / furnace, the tundish H control is 1.3 ppm, the electromagnetic stirring current of the crystallizer is 420 A, the electromagnetic stirring current of the end is 334 A, the frequency is 8 Hz; the whole process is protected casting, the crystallizer protective slag uses medium carbon steel protective slag; the light press-down is put into the 2nd, 3rd and 4th rollers, and the press-down amounts are 3 mm, 4 mm and 4 mm respectively; the casting blank cutting adopts the automatic and manual combined mode, the casting blank is kept in the heat preservation pit, the red steel is used as the bottom pad, the upper pressure is used to ensure the flatness of two furnace casting blanks, and the heat preservation time is 35 h.

[0057] (5) Heating process

[0058] Heating process: the temperature entering the heating furnace is 400℃, the temperature required in the preheating section is 560℃, and the time is 1.4 h; the temperature required in the heating 2 section is 860℃, and the time is 1.4 h; the temperature required in the heating 1 section is 1210℃, and the time is 1.4 h; the temperature required in the soaking section is 1200℃, and the time is 1.4 h; the steel temperature is 1196℃.

[0059] (6) Initial rolling and cogging: BD cogging mill is used, 7 passes are rolled, the rolling reduction is: turning steel → 1st pass reduction 70 mm → 2nd pass reduction 80 mm → turning steel → 3rd pass 74 mm → 4th pass 81 mm → turning steel → 5th pass 92 mm → 6th pass 30 mm → turning steel → 7th pass 38 mm, after passing through 3 850 mm rolling mills and 1 735 mm rolling mill, it enters the 8-stand continuous rolling mill group.

[0060] (7) Rolling process:

[0061] The medium bar rolling process is to roll the medium bar into an intermediate blank with a height of 268 mm and a width of 232 mm; the first pass has a height of 229 mm and a width of 245 mm; the second pass has a height of 192 mm and a width of 235 mm; the third pass has a height of 200 mm and a width of 195 mm; the fourth pass has a height of 160 mm and a width of 214.7 mm; the fifth pass has a height of 164 mm and a width of 174.6 mm; the sixth pass has a height of 121 mm and a width of 187.6 mm; the seventh pass has a height of 139 mm and a width of 138.5 mm; the eighth pass has a height of 106 mm and a width of 152 mm; the ninth pass has a height of 118 mm and a width of 121 mm; the tenth pass has a height of 91 mm and a width of 130.2 mm; the eleventh pass has a height of 101.4 mm and a width of 101.4 mm; and the finished product is discharged after the eleventh pass.

[0062] (8) Holding process

[0063] The holding process is that the steel is held at a holding temperature of 570°C and a holding time of 56 h.

[0064] (9) Heat treatment process

[0065] The steel after holding is subjected to a heat treatment, and the heat treatment comprises the following steps:

[0066] Normalizing: 910°C, holding for 2.0 h, and air cooling.

[0067] Example 3

[0068] 1 Chemical composition

[0069] The chemical composition is as follows in terms of percentage by mass: 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.

[0070] 2 Design of various production process parameters of high-pressure boiler heat-resistant steel bar continuous casting by converter

[0071] The process route is: converter smelting→ secondary refining (LF+RH)→ continuous casting→ heating furnace heating→ rolling→ holding→ finishing→ inspection→ packaging and delivery to the warehouse→ shipment. Among them:

[0072] (1) Converter smelting: using scrap and hot metal smelting, scrap accounts for 18% and hot metal accounts for 82% by mass; oxygen oxidation, intense boiling, tapping temperature 1635 °C, oxygen supply time 13 min, end point oxygen 465 ppm, operation time 44 min, tapping C 0.16%, P 0.008%, and auxiliary materials and alloys are added at 1 / 4 tapping time. Alloy addition per ton of steel: high-carbon ferromanganese 7.4 Kg / t, silicon manganese 10.6 Kg / t, aluminum grain 1.45 Kg / t. Auxiliary material addition per ton of steel: dolomite 22.7 Kg / t, lime 19 Kg / t, limestone 20 Kg / t.

[0073] (2) LF furnace: using 23000 large current to heat and slag, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, active lime is supplemented, the chemical composition is analyzed after 5 min, the alloy is supplemented according to the target value of the chemical composition, and the coke breeze carbonizer is used for carbonization, and the alloy and the coke breeze carbonizer should be added to the argon stream to promote the rapid melting and homogenization of the alloy and the carbon powder. The net clearance of the furnace body is 580 mm, the slag thickness is 50 mm, the argon blowing time is 70 min, the operation time is 115 min, the diffusion deoxidizer 1 kg / t is added for diffusion deoxidation when the molten steel temperature reaches 1545 °C, the furnace door is closed for 10 min, and the chemical composition is analyzed for the second time when the molten steel temperature reaches 1645 °C to confirm the deviation of each chemical element content from the target value. After the second sample is taken away, the diffusion deoxidizer 2 kg / t is supplemented to continue slagging, and the alloy addition per ton of steel: high-carbon ferromanganese 1.1 kg / t, high-carbon chromium iron 0.41 kg / t, medium-carbon ferromanganese 0.97 kg / t, aluminum grain 0.82 kg / t, silicon iron 1.50 kg / t, vanadium iron 0.45 kg / t. Maintain the slag basicity pH value to 2.8 and the slag viscosity to 0.98 Pa.s, and continue white slag smelting for 25 min, and start static argon blowing when the molten steel temperature reaches 1660 °C, and maintain for 15 min. Auxiliary material addition per ton of steel: active lime 7.0 kg / t, coke breeze carbonizer 0.95 Kg / t.

[0074] (3) RH refining: the argon pressure is controlled to 0.1 MPa before the vacuum pump starts, the slag surface is slightly moved and the molten steel is not exposed, the vacuum degree reaches 100 Pa, the timing is started, the net clearance is 550 mm, the slag thickness is 70 mm, the operation time is 28 min, the temperature before treatment is 1650 °C, and the temperature after treatment is 1605 °C. Referring to the target composition, aluminum grain and high manganese are supplemented according to the composition of the molten steel, and the argon pressure is adjusted to 0.4 MPa. After static argon blowing is completed, 1.1 meters / t of silicon calcium wire (Φ10 mm) is added.

[0075] (4) Continuous casting: tundish temperature 1555°C, casting speed 0.42 m / min, casting amount 158 t / furnace, tundish H control 1.3 ppm, crystallizer electromagnetic stirring current 420 A, end electromagnetic stirring current 335 A, frequency 8 Hz; whole process protection casting, crystallizer protection slag using medium carbon steel protection slag; light press-down into the 2nd, 3rd and 4th rollers, press-down amount 3 mm, 4 mm and 4 mm respectively; casting blank cutting using automatic and manual combined mode, casting blank heat preservation pit, red steel pad bottom, upper pressure two furnace blanks to ensure flatness, heat preservation time 34 h.

[0076] (5) Heating process

[0077] Heating process: entering heating furnace temperature 390°C, preheating section temperature requirement 560°C, time 1.4 h; heating 2 section temperature requirement 860°C, time 1.5 h; heating 1 section temperature requirement 1210°C, time 1.5 h; soaking section temperature requirement 1208°C, time 1.4 h; tapping temperature 1200°C.

[0078] (6) Initial rolling and blooming: using BD initial rolling mill to bloom, rolling 7 passes, rolling reduction: turning steel → 1st pass reduction 70 mm → 2nd pass reduction 80 mm → turning steel → 3rd pass 74 mm → 4th pass 81 mm → turning steel → 5th pass 92 mm → 6th pass 30 mm → turning steel → 7th pass 38 mm, passing through 3 850 mm rolling mills, 1 735 mm rolling mill, and then entering 8 continuous rolling mill groups to roll.

[0079] (7) Rolling process:

[0080] Medium bar rolling process, medium bar rolling into intermediate blank high 268 mm, width 232 mm; 1st pass high 229 mm, width 245 mm; 2nd pass high 192 mm, width 235 mm; 3rd pass high 200 mm, width 195 mm; 4th pass high 160 mm, width 214.7 mm; 5th pass high 164 mm, width 174.6 mm; 6th pass high 121 mm, width 187.6 mm; 7th pass high 139 mm, width 138.5 mm; 8th pass high 106 mm, width 152 mm; 9th pass high 118 mm, width 121 mm; 10th pass high 91 mm, width 130.2 mm; 11th pass high 101.5 mm, width 101.5 mm; after 11th pass, finished product is discharged.

[0081] (8) Heat preservation process

[0082] Heat preservation process: steel heat preservation, into pit temperature 570°C, out of pit temperature 130°C, heat preservation time 56 h.

[0083] (9) Heat treatment process

[0084] The heat treated steel is subjected to a heat treatment comprising the following steps:

[0085] Normalizing: 910°C, holding for 2.0h, air cooling.

[0086] The results of the finished product inspection of Examples 1-3 are as follows:

[0087] (1) Macrostructure of Φ100mm steel (finished product steel obtained by the holding process)

[0088] (2) Non-metallic inclusions of Φ100mm steel (finished product steel obtained by the holding process)

[0089] (3) Impact property of Φ100mm steel (finished product steel obtained after heat treatment)

[0090] For any person skilled in the art, many possible variations and modifications, or equivalent embodiments of equivalent changes can be made to the technical solutions of the present application by using the technical contents disclosed above without departing from the scope of the technical solutions of the present application. Therefore, any simple modification, equivalent change and modification made to the above examples according to the technical essence of the present application, which does not depart from the content of the technical solutions of the present application, should still belong to the scope of protection of the technical solutions of the present application.

Claims

1. A steel bar for a subway axle seal characterized by, C: 0.13% to 0.17%, Si: 0.17% to 0.40%, Mn: 1.40% to 1.50%, P: ≤0.012%, S: ≤0.005%, V: 0.02% to 0.05%, Cr: 0.05% to 0.18%, Cu: ≤0.05%, Ni: ≤0.05%, Al: 0.015% to 0.040%, carbon equivalent: 0.40% to 0.45%, the balance being iron and inevitable impurities.

2. The method of producing a steel bar for a subway axle seal according to claim 1, characterized by, The method comprises: converter smelting → LF refining → RH refining → continuous casting → heating process → rolling process → heat preservation process; The converter smelting is: using scrap and hot metal smelting, the scrap accounts for 15-20% and the hot metal accounts for 80-85% by mass fraction; oxygen oxidation, vigorous boiling, tapping temperature 1630-1640℃, oxygen supply time 13-14min, end point oxygen 460-470ppm, operation time 40-50min, C 0.15-0.18% at tapping, P ≤0.010%, auxiliary materials and alloys are added at 1 / 4-1 / 3 of tapping time; alloy addition amount per ton of steel: high-carbon ferromanganese 7.2-7.6Kg / t, silicon manganese 10.5-10.7Kg / t, aluminum grain 1.40-1.50Kg / t; auxiliary material addition amount per ton of steel: dolomite 22.5-23Kg / t, lime 18.5-19.5Kg / t, limestone 20-21Kg / t; The LF refining is: using 20000-22000A large current to heat and slag, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, active lime is supplemented, the chemical composition is analyzed after 5-10min of the first sampling, the alloy is supplemented according to the target value of the chemical composition, and the coke butter carbonizer is used for carbonization; the furnace body clearance is 550-620mm, the slag thickness is 45-55mm, argon blowing is 65-75min, the operation time is 110-120min, diffusion deoxidizer 1-3kg / t steel is added for diffusion deoxidization when the molten steel temperature reaches 1540-1550℃, the furnace door is closed for 10-12min, the chemical composition is analyzed after the second sampling when the molten steel temperature reaches 1650-1660℃, to confirm the deviation value of each chemical element content from the target value, after the second sampling, diffusion deoxidizer 1-3kg / t steel is supplemented to continue slagging, the molten slag basicity pH value is maintained at 2.5-3.5, the molten slag viscosity is 0.90-1.20Pa.s, and the white slag smelting is continued for 20-30min at the same time, when the molten steel temperature reaches 1655-1665℃, the static argon blowing is started, and the holding time is 10-20min; The RH refining is: before vacuum pump starting, argon pressure is controlled at 0.1-0.3 MPa, the slag surface slightly moves the molten steel and is not exposed, when the vacuum degree reaches 100-110 Pa, timing is started, the holding time is 10-15 min, the net is 530-570 mm, the slag thickness is 65-75 mm, the operation time is 25-30 min, the temperature before treatment is 1645-1655 DEG C, the temperature after treatment is 1600-1610 DEG C, according to the target composition, aluminum particles, high manganese are added, at the same time, the argon pressure is adjusted to 0.3-0.5 MPa, after static argon blowing, 1.1-1.2 m / t steel of silicon calcium wire is added; The continuous casting is: the tundish temperature is 1552-1559 DEG C, the casting speed is 0.40-0.44 m / min, the casting amount is 155-160 t / furnace, the tundish H control is less than or equal to 1.8 ppm, the crystallizer electromagnetic stirring current is 400-450 A, the end electromagnetic stirring current is 330-340 A, the frequency is 8-8.2 Hz; The heating process is: the preheating section temperature requirement is 500-610 DEG C, the time is 1.4-1.5 h; the heating 2 section temperature requirement is 850-870 DEG C, the time is 1.4-1.5 h; the heating 1 section temperature requirement is 1190-1220 DEG C, the time is 1.4-1.5 h; the soaking section temperature requirement is 1190-1220 DEG C, the time is 1.4-1.5 h; the steel tapping temperature is 1190-1210 DEG C.

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

4. The preparation method according to claim 2, characterized in that, In the continuous casting, the whole process is protected casting, the crystallizer protective slag uses medium-carbon steel protective slag; the light press-down is put into the 2nd, 3rd and 4th rollers, and the press-down amounts are 3-3.1 mm, 4-4.1 mm and 4-4.1 mm respectively; the casting blank cutting adopts the automatic and manual combined mode, the casting blank is kept in the heat preservation pit, the red steel is used as the bottom pad, the upper pressure is used to ensure the flatness of two furnace casting blanks, and the heat preservation time is 30-40 h.

5. The preparation method according to claim 2, characterized in that, In the heating process, the temperature entering the heating furnace is 380-420 DEG C.

6. The preparation method according to claim 2, characterized in that, The rolling process comprises the following steps: (1) blooming: BD blooming mill is adopted, 7 passes are rolled, and the rolling reduction is: turning steel → the 1st pass reduction 70-70.2 mm → the 2nd pass reduction 80-80.2 mm → turning steel → the 3rd pass 74-74.2 mm → the 4th pass 81-81.2 mm → turning steel → the 5th pass 92-92.2 mm → the 6th pass 30-30.2 mm → turning steel → the 7th pass 38-38.2 mm, 3 sets of 850 mm rolling mills and 1 set of 735 mm rolling mill are passed, and then entering 8 sets of continuous rolling mill groups for rolling. (2) the middle bar rolling process: the middle bar is rolled into an intermediate blank with a height of 268-268.2 mm and a width of 232-232.2 mm; the first pass has a height of 229-229.2 mm and a width of 245-245.2 mm; the second pass has a height of 192-192.2 mm and a width of 235-235.2 mm; the third pass has a height of 200-200.2 mm and a width of 195-195.2 mm; the fourth pass has a height of 160-160.2 mm and a width of 214.7-214.9 mm; the fifth pass has a height of 164-164.2 mm and a width of 174.6-174.8 mm; the sixth pass has a height of 121-121.2 mm and a width of 187.6-187.8 mm; the seventh pass has a height of 139-139.2 mm and a width of 138.5-138.7 mm; the eighth pass has a height of 106-106.2 mm and a width of 152-152.2 mm; the ninth pass has a height of 118-118.2 mm and a width of 121-121.2 mm; the tenth pass has a height of 91-91.2 mm and a width of 130.2-130.4 mm; the eleventh pass has a height of 101.4-101.6 mm and a width of 101.4-101.6 mm; and the finished product is discharged after the eleventh pass.

7. The preparation method according to claim 2, characterized in that, The holding process is as follows: the steel material is held at a temperature of ≥550℃ and a temperature of ≤150℃, and the holding time is ≥54 h.

8. The method of claim 2, wherein the step of forming the first and second layers comprises the step of: The steel material after holding is subjected to heat treatment, and the heat treatment comprises the following steps: ​ normalizing: 900-920℃, holding for 1.8-2.2 h, and air cooling.

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

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

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