Ecological electric furnace steel bar for petroleum pipeline and production method thereof

Abstract

This invention discloses an eco-friendly electric furnace steel bar for oil pipelines and its production method, belonging to the field of steelmaking. The oil pipeline steel, by mass percentage, comprises: C: 0.36%–0.41%, Si: 1.00%–1.20%, Mn: 0.35%–0.50%, P: ≤0.016%, S: ≤0.010%, Cr: 1.35%–1.50%, Ni: ≤0.20%, Mo: ≤0.05%, Cu: ≤0.15%, with the balance being iron and unavoidable impurities. This method employs an eco-friendly electric furnace + LF + RH + continuous casting smelting process to produce oil pipeline steel bars, ensuring both the mechanical properties and high purity of the finished steel bars, as well as the surface quality level.

Description

Technical Field

[0001] This invention relates to a steel bar for an eco-friendly electric furnace oil pipeline and its production method, belonging to the field of steelmaking. Background Technology

[0002] An oil pipeline is a pipeline system used to transport oil and petroleum products. It typically consists of a series of interconnected pipes used to transport crude oil, natural gas, liquids, refined petroleum products, etc., from production sites to processing plants, storage facilities, or end users. The quality of the steel used in oil pipelines is crucial to the safety of oil transportation; therefore, the requirements for the steel used in oil pipelines are extremely high in terms of high-temperature resistance, wear resistance, mechanical properties, fatigue life, and steel purity to ensure the normal and safe operation of oil transportation processes.

[0003] This patent develops steel for oil pipelines with excellent mechanical properties and high steel purity, meeting the requirements of high-end products.

[0004] The production of steel bars for oil pipelines using an eco-friendly electric furnace + LF + RH + continuous casting smelting process and rolling process meets high-end application requirements and represents a breakthrough in the mass production of steel bars for oil pipelines using the eco-friendly electric furnace continuous casting process. Summary of the Invention

[0005] The purpose of this invention is to provide a manufacturing process for steel bars used in oil pipelines. This method employs an eco-friendly electric furnace + LF + RH + continuous casting smelting process to produce steel bars for oil pipelines. This process ensures both the mechanical properties and high purity of the finished steel bars for oil pipelines, as well as the surface quality of the steel bars.

[0006] To achieve the aforementioned objectives, this invention provides a compositional and process design for steel bars used in oil pipelines. The specific steps are: smelting in an eco-electric furnace + refining in an LF furnace + refining in an RH furnace + continuous casting billet → annealing, heating in a heating furnace → rolling → heat preservation. This method meets the quality requirements for steel bars used in oil pipelines, and also achieves the required standards for mechanical properties and high steel purity.

[0007] This invention provides a steel bar for an ecological electric furnace oil pipeline, comprising, by mass percentage: C: 0.36%–0.41%, Si: 1.00%–1.20%, Mn: 0.35%–0.50%, P: ≤0.016%, S: ≤0.010%, Cr: 1.35%–1.50%, Ni: ≤0.20%, Mo: ≤0.05%, Cu: ≤0.15%, with the balance being iron and unavoidable impurities.

[0008] This invention provides a method for producing the above-mentioned steel bars for ecological electric furnace oil pipelines, comprising the following steps:

[0009] The process route is: electric arc furnace smelting + LF furnace refining + RH refining + continuous casting → annealing + heating process → rolling → heat holding process. Further, after heat holding, the process proceeds to: finishing → inspection → packaging and warehousing → shipping.

[0010] The ecological electric furnace smelting process is as follows:

[0011] The steel is smelted using 100% scrap steel, with heavy scrap accounting for 85-95% and bale-shaped scrap accounting for 5-15%. The tapping temperature is 1610-1620℃, and the carbon content at tapping is 0.10-0.15wt%, and the phosphorus content is ≤0.010wt%. Auxiliary materials and alloys are added when 1 / 4 to 1 / 3 of the steel has been tapped. The smelting cycle is 45-55 minutes. The LF furnace refining process is as follows:

[0012] The LF furnace is fed into the furnace at a temperature of 1495–1505℃, and slag is formed by heating with a high current of 35000–36000A. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime and silicon carbide are added. After 5–6 minutes, the first sample is taken for chemical composition analysis. Alloy is added according to the target chemical composition value, and coke particles are added to increase carbon content, so as to promote rapid melting and homogenization of alloy and carbon powder. When the molten steel temperature reaches 1600–1610℃, 1.5–1.6 kg / t of diffusion deoxidizer alumina balls is added for diffusion deoxidation. The furnace door is closed for 10–13 minutes. When the molten steel temperature reaches 1580–1600℃, the second sample is taken for chemical composition analysis to confirm the deviation of the content of each chemical element from the target value. After the second sample is taken, the furnace is removed when the molten steel temperature reaches 1600–1610℃. The LF smelting cycle is 35–45 minutes.

[0013] The RH refining process is as follows:

[0014] The inlet temperature is 1580-1590℃, the operation time is 30-40 minutes, and the argon pressure is controlled at 0.1-0.3MPa before the vacuum pump is started, so that the molten steel is not exposed when the slag surface moves slightly. When the vacuum degree reaches 100-110Pa, the timing starts and is maintained for 10-15 minutes. At the same time, the argon pressure is adjusted to 0.3-0.5MPa. After the static argon blowing is completed, 0.6-0.7kg / t of carbonized rice husk is added as a covering agent. The outlet temperature is 1550-1560℃.

[0015] Furthermore, in the above technical solution, in the ecological electric furnace smelting, the alloy addition per ton of steel is as follows: ferrosilicon 12-12.2 kg / t, ferromanganese silicon 4.1-4.2 kg / t, high-carbon ferrochrome 25-25.5 kg / t, and aluminum wire segments (diameter 10-16 mm) 1.0-1.2 kg / t; the auxiliary material addition per ton of steel is as follows: active lime (particle size 10-70 mm) 40-41 kg / t, dolomite (particle size 20-70 mm) 20-21 kg / t, and ladle ash 6-6.2 kg / t.

[0016] Furthermore, in the above technical solution, during the LF furnace refining process, the amount of alloys added is: ferrosilicon 1.15-1.25 kg / t, high-carbon ferromanganese 0.6-0.7 kg / t, and high-carbon ferrochrome 0.5-0.6 kg / t; the amount of other auxiliary materials added is: diffusion deoxidizer alumina balls 1.4-1.6 kg / t, active lime (particle size 10-70 mm) 6-6.5 kg / t, silicon carbide (particle size less than or equal to 5 mm) 2.1-2.2 kg / t, and coke particles 0.7-0.9 kg / t.

[0017] Furthermore, in the above technical solution, the continuous casting is as follows: ladle arrival temperature 1545~1555℃, molten steel quantity 110~115t, tundish H control ≤2ppm, casting time 40min~45min, full-process protective casting, and medium carbon steel protective slag used in the crystallizer.

[0018] Furthermore, in the above technical solution, the heating process is as follows: The heating process in chronological order is as follows: Inlet temperature to the heating furnace: 480℃~550℃; Preheating section temperature: 680℃~700℃; Time: 1.3~1.5h; Heating section 2 temperature: 850℃~870℃; Time: 1.3~1.5h; Heating section 1 temperature: 1200℃~1220℃; Time: 1.3~1.5h; Soaking section temperature: 1190℃~1210℃; Time: 1.3~1.5h; Tap-out temperature: 1185℃~1195℃.

[0019] Furthermore, in the above technical solution, the rolling process includes a primary rolling process and a continuous rolling process for producing finished products;

[0020] The initial rolling process is as follows: 9 rolling passes, turning the steel over → Pass 1: Width 408-408.02mm, Height 421-421.02mm, Reduction 65-65.02mm → Pass 2: Width 426-426.02mm, Height 351-351.02mm, Reduction 70-70.02mm → Turning the steel over → Pass 3: Width 370-370.02mm, Height 362-362.02mm, Reduction 64-64.02mm → Pass 4: Width 397-397.02mm, Height 272-272.02mm, Reduction 90-90.02mm → Turning the steel over → Pass 5: Width 285-285.02mm, Height 355-355.02mm mm, reduction 42~42.02mm → 6th pass width 297~297.02mm, height 315~315.02mm, reduction 40~40.02mm → 7th pass width 307~307.02mm, height 280~280.02mm, reduction 35~35.02mm → 8th pass width 317~317.02mm, height 246~246.02mm, reduction 34~34.02mm → turn over → 9th pass width 271~271.02mm, height 235~235.02mm, reduction 82~82.02mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, then entering the continuous rolling mill group for rolling.

[0021] Furthermore, in the above technical solution, the continuous rolling process for the product is as follows: 11 passes; the first pass has a height of 229–229.02 mm and a width of 245–245.02 mm; the second pass has a height of 192–192.02 mm and a width of 235–235.02 mm; the third pass has a height of 200–200.02 mm and a width of 195–195.02 mm; the fourth pass has a height of 160–160.02 mm and a width of 214.7–214.72 mm; the fifth pass has a height of 165–165.02 mm and a width of 174.6–174.62 mm; the sixth pass has a height of 165–165.02 mm and a width of 174.6–174.62 mm; the seventh pass has a height of 165–165.02 mm and a width of 174.6–174.62 mm; the eleventh pass has a height of 160–160.02 mm and a width of 214.7–214.72 mm; the twelfth pass has a height of 165–165.02 mm and a width of 174.6–174.62 mm; the twelf ... The 6th pass has a height of 118–118.02 mm and a width of 187–187.02 mm; the 7th pass has a height of 135–135.02 mm and a width of 132–132.02 mm; the 8th pass has a height of 92–92.02 mm and a width of 148–148.02 mm; the 9th pass has a height of 110–110.02 mm and a width of 115–115.02 mm; the 10th pass has a height of 78–78.02 mm and a width of 118.7–118.72 mm; the 11th pass has a height of 91–91.02 mm and a width of 91–91.02 mm; the finished product is produced after the 11th pass.

[0022] Furthermore, in the above technical solution, the insulation process is as follows: steel insulation, the temperature of the lower insulation pit is ≥580℃, the insulation time is 52~55h, and the temperature of the material leaving the pit is ≤150℃.

[0023] Furthermore, in the above technical solution, a steel sample after the heat preservation process is subjected to heat treatment, which includes the following steps:

[0024] 1) Quenching: 880~920℃, hold for 0.8~1.2h, oil cooling;

[0025] 2) Tempering: 580~620℃, hold for 1.8~2.2h, then water-cooled.

[0026] Furthermore, in the above technical solution, the steel sample is a Φ25±0.1mm blank.

[0027] Beneficial effects of the invention

[0028] (1) The steel bars for oil pipelines are produced by using an ecological electric furnace + LF + RH + continuous casting smelting process and rolling process to meet the mechanical performance requirements and ensure the purity of the steel.

[0029] (2) Reasonable composition design and production process ensure surface quality and mechanical properties.

[0030] (3) The low magnification structure and non-metallic inclusions of the finished steel meet the requirements of high-end products. Detailed Implementation

[0031] Example 1:

[0032] 1. Chemical composition of steel bars for ecological electric furnace oil pipelines

[0033] The composition by mass percentage is: C: 0.39%, Si: 1.08%, Mn: 0.42%, P: 0.012%, S: 0.005%, Cr: 1.38%, Ni: 0.05%, Mo: 0.02%, Cu: 0.02%, with the balance being iron and unavoidable impurities.

[0034] 2. The production processes of electric arc furnace continuous casting of steel bars for oil pipelines include the following steps:

[0035] Process route: Eco-friendly electric furnace smelting + LF furnace refining + RH refining + continuous casting → annealing + heating process → rolling → heat preservation process → finishing → inspection → packaging and warehousing → shipment.

[0036] (1) Ecological electric furnace smelting

[0037] 100% scrap steel smelting, 90% heavy scrap steel and 10% bale-shaped scrap steel; tapping temperature 1615℃, C at tapping 0.12wt%, P at tapping 0.008wt%; auxiliary materials and alloys are added when 1 / 4 of the steel has been tapped; smelting cycle 49 minutes. Alloy addition per ton of steel: ferrosilicon 12Kg / t, ferromanganese silicon 4.1Kg / t, high-carbon ferrochrome 25.3Kg / t, aluminum wire segments (12mm diameter) 1.0Kg / t. Auxiliary material addition per ton of steel: active lime (35mm particle size) 40Kg / t, dolomite (40mm particle size) 20Kg / t, ladle ash 6Kg / t.

[0038] (2) LF furnace refining

[0039] The LF furnace is fed into the plant at a temperature of 1502℃. A high-current (35500A) is used for slag formation. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime and silicon carbide are added. After 5 minutes, a first sample is taken for chemical composition analysis. Alloys are added according to the target chemical composition values, and coke particles are added to increase carbon content, promoting rapid melting and homogenization of the alloys and carbon powder. When the molten steel temperature reaches 1604℃, 1.5 kg / t of diffusion deoxidizer alumina balls is added for diffusion deoxidation. The furnace door is closed for 10 minutes. When the molten steel temperature reaches 1590℃, a second sample is taken for chemical composition analysis to confirm the deviation of each chemical element content from the target value. After the second sample is taken, the furnace leaves the plant when the molten steel temperature reaches 1604℃. The LF smelting cycle is 40 minutes. Alloys are added: 1.12 kg / t ferrosilicon, 0.6 kg / t high-carbon ferromanganese, and 0.5 kg / t high-carbon ferrochrome. Additional auxiliary materials: 1.5 kg / t alumina balls, 6.2 kg / t quicklime (35 mm particle size), 2.1 kg / t silicon carbide (3 mm particle size), and 0.7 kg / t coke granules.

[0040] (3) RH refining

[0041] The inlet temperature is 1585℃, the operation time is 35min, the argon pressure is controlled at 0.1MPa before the vacuum pump is started, so that the molten steel is not exposed when the slag surface is slightly moved. When the vacuum degree reaches 104Pa, the timing starts and is maintained for 12min. At the same time, the argon pressure is adjusted to 0.3MPa. After the static argon blowing is completed, 0.6kg / t of carbonized rice husk is added as a covering agent. The outlet temperature is 1555℃.

[0042] (4) Continuous casting

[0043] The ladle temperature upon arrival was 1551℃, the molten steel volume was 112t, the tundish H was controlled at 1.4ppm, the casting time was 42min, the entire casting process was protected, and medium carbon steel protective slag was used for the crystallizer.

[0044] (5) Heating process

[0045] Heating process: Inlet temperature to the heating furnace is 520℃; preheating zone temperature is required to be 685℃ for 1.4 hours; heating zone 2 temperature is required to be 860℃ for 1.4 hours; heating zone 1 temperature is required to be 1208℃ for 1.3 hours; soaking zone temperature is required to be 1198℃ for 1.5 hours; tapping temperature is 1190℃.

[0046] (6) Rolling process

[0047] Initial rolling process: 9 rolling passes, turning over → Pass 1: Width 408mm, Height 421mm, Reduction 65mm → Pass 2: Width 426mm, Height 351mm, Reduction 70mm → Turning over → Pass 3: Width 370mm, Height 362mm, Reduction 64mm → Pass 4: Width 397mm, Height 272mm, Reduction 90mm → Turning over → Pass 5: Width 285mm, Height 355mm, Reduction 42mm → 6th pass, width 297mm, height 315mm, reduction 40mm → 7th pass, width 307mm, height 280mm, reduction 35mm → 8th pass, width 317mm, height 246mm, reduction 34mm → Turning steel → 9th pass, width 271mm, height 235mm, reduction 82mm. After passing through 3 850mm rolling mills and 1 735mm rolling mill, it enters the continuous rolling mill unit for rolling.

[0048] Continuous rolling process: 11 passes. Pass 1: 229mm high, 245mm wide; Pass 2: 192mm high, 235mm wide; Pass 3: 200mm high, 195mm wide; Pass 4: 160mm high, 214.7mm wide; Pass 5: 165mm high, 174.6mm wide; Pass 6: 118mm high, 187mm wide; Pass 7: 135mm high, 132mm wide; Pass 8: 92mm high, 148mm wide; Pass 9: 110mm high, 115mm wide; Pass 10: 78mm high, 118.7mm wide; Pass 11: 91mm high, 91mm wide; Finished product after 11 passes.

[0049] (7) Thermal Insulation Process

[0050] Insulation process: steel insulation, temperature of the lower insulation pit is 600℃, insulation time is 52 hours, and the temperature of the lower insulation pit is 120℃.

[0051] (8) Heat treatment process

[0052] A Φ25mm blank is subjected to heat treatment, which includes the following steps:

[0053] 1) Quenching: 900℃, hold for 1.0h, oil cooling;

[0054] 2) Tempering: 600℃, hold for 2.0h, then water-cooled.

[0055] Example 2:

[0056] 1. Chemical composition of steel bars for ecological electric furnace oil pipelines

[0057] The internal control chemical composition was determined to be: C: 0.39%, Si: 1.05%, Mn: 0.42%, P: 0.010%, S: 0.005%, Cr: 1.42%, Ni: 0.05%, Mo: 0.02%, Cu: 0.02%, with the balance being iron and unavoidable impurities.

[0058] 2. The production processes of electric arc furnace continuous casting of steel bars for oil pipelines include the following steps:

[0059] Process route: Eco-friendly electric furnace smelting + LF furnace refining + RH refining + continuous casting → annealing + heating process → rolling → heat preservation process → finishing → inspection → packaging and warehousing → shipment.

[0060] (1) Ecological electric furnace smelting

[0061] 100% scrap steel smelting, 90% heavy scrap steel and 10% bale-shaped scrap steel; tapping temperature 1616℃, C 0.11wt% and P 0.009wt% at tapping; auxiliary materials and alloys are added when 1 / 4 of the steel has been tapped; smelting cycle 48 minutes. Alloy addition per ton of steel: ferrosilicon 12Kg / t, ferromanganese silicon 4.1Kg / t, high-carbon ferrochrome 25Kg / t, aluminum wire segments (12mm diameter) 1.0Kg / t. Auxiliary material addition per ton of steel: active lime (35mm particle size) 40Kg / t, dolomite (40mm particle size) 20Kg / t, ladle ash 6Kg / t.

[0062] (2) LF furnace refining

[0063] The LF furnace is fed into the station at a temperature of 1499℃. A high current of 35600A is used for slag formation. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime and silicon carbide are added. After 5 minutes, the first sample is taken for chemical composition analysis. Alloys are added according to the target chemical composition values, and coke particles are added to increase carbon content, promoting rapid melting and homogenization of the alloys and carbon powder. When the molten steel temperature reaches 1606℃, 1.5 kg / t of diffusion deoxidizer alumina balls is added for diffusion deoxidation. The furnace door is closed for 10 minutes. When the molten steel temperature reaches 1592℃, a second sample is taken for chemical composition analysis to confirm the deviation of each chemical element content from the target value. After the second sample is taken, the molten steel leaves the station when the temperature reaches 1606℃. The LF smelting cycle is 40 minutes. Alloys are added: 1.19 kg / t ferrosilicon, 0.6 kg / t high-carbon ferromanganese, and 0.5 kg / t high-carbon ferrochrome. Additional auxiliary materials: 1.5 kg / t alumina balls, 6.2 kg / t quicklime (35 mm particle size), 2.1 kg / t silicon carbide (3 mm particle size), and 0.8 kg / t coke granules.

[0064] (3) RH refining

[0065] The inlet temperature is 1586℃, the operation time is 36min, the argon pressure is controlled at 0.1MPa before the vacuum pump is started, so that the molten steel is not exposed when the slag surface is slightly moved. When the vacuum degree reaches 104Pa, the timing starts and is maintained for 12min. At the same time, the argon pressure is adjusted to 0.3MPa. After the static argon blowing is completed, 0.6kg / t of carbonized rice husk is added as a covering agent. The outlet temperature is 1556℃.

[0066] (4) Continuous casting

[0067] The ladle temperature upon arrival was 1551℃, the molten steel volume was 112t, the tundish H was controlled at 1.7ppm, the casting time was 42min, the entire casting process was protected, and medium carbon steel protective slag was used for the crystallizer.

[0068] (5) Heating process

[0069] Heating process: Inlet temperature to the heating furnace is 510℃; preheating zone temperature is required to be 690℃ for 1.4 hours; heating zone 2 temperature is required to be 858℃ for 1.4 hours; heating zone 1 temperature is required to be 1210℃ for 1.4 hours; soaking zone temperature is required to be 1198℃ for 1.3 hours; tapping temperature is 1190℃.

[0070] (6) Rolling process

[0071] Initial rolling process: 9 rolling passes, turning over → Pass 1: Width 408mm, Height 421mm, Reduction 65mm → Pass 2: Width 426mm, Height 351mm, Reduction 70mm → Turning over → Pass 3: Width 370mm, Height 362mm, Reduction 64mm → Pass 4: Width 397mm, Height 272mm, Reduction 90mm → Turning over → Pass 5: Width 285mm, Height 355mm, Reduction 42mm → 6th pass, width 297mm, height 315mm, reduction 40mm → 7th pass, width 307mm, height 280mm, reduction 35mm → 8th pass, width 317mm, height 246mm, reduction 34mm → Turning steel → 9th pass, width 271mm, height 235mm, reduction 82mm. After passing through 3 850mm rolling mills and 1 735mm rolling mill, it enters the continuous rolling mill unit for rolling.

[0072] Continuous rolling process: 11 passes. Pass 1: 229mm high, 245mm wide; Pass 2: 192mm high, 235mm wide; Pass 3: 200mm high, 195mm wide; Pass 4: 160mm high, 214.7mm wide; Pass 5: 165mm high, 174.6mm wide; Pass 6: 118mm high, 187mm wide; Pass 7: 135mm high, 132mm wide; Pass 8: 92mm high, 148mm wide; Pass 9: 110mm high, 115mm wide; Pass 10: 78mm high, 118.7mm wide; Pass 11: 91mm high, 91mm wide; Finished product after 11 passes.

[0073] (7) Thermal Insulation Process

[0074] Insulation process: steel insulation, temperature in the lower insulation pit is 590℃, insulation time is 53 hours, and the temperature after exiting the pit is 130℃.

[0075] (8) Heat treatment process

[0076] A Φ25mm blank is subjected to heat treatment, which includes the following steps:

[0077] 1) Quenching: 900℃, hold for 1.0h, oil cooling;

[0078] 2) Tempering: 600℃, hold for 2.0h, then water-cooled.

[0079] Example 3:

[0080] 1. Chemical composition of steel bars for ecological electric furnace oil pipelines

[0081] The internal control chemical composition was determined to be: C: 0.39%, Si: 1.08%, Mn: 0.42%, P: 0.010%, S: 0.006%, Cr: 1.39%, Ni: 0.06%, Mo: 0.02%, Cu: 0.02%, with the balance being iron and unavoidable impurities.

[0082] 2. The production processes of electric arc furnace continuous casting of steel bars for oil pipelines include the following steps:

[0083] Process route: Eco-friendly electric furnace smelting + LF furnace refining + RH refining + continuous casting → annealing + heating process → rolling → heat preservation process → finishing → inspection → packaging and warehousing → shipment.

[0084] (1) Ecological electric furnace smelting

[0085] 100% scrap steel smelting, 90% heavy scrap steel and 10% bale-shaped scrap steel; tapping temperature 1615℃, C at tapping 0.12wt%, P at 0.008wt%; auxiliary materials and alloys are added when 1 / 4 of the steel has been tapped; smelting cycle 49 minutes. Alloy addition per ton of steel: ferrosilicon 12Kg / t, ferromanganese silicon 4.1Kg / t, high-carbon ferrochrome 25.2Kg / t, aluminum wire segments (12mm diameter) 1.0Kg / t. Auxiliary material addition per ton of steel: active lime (35mm particle size) 40Kg / t, dolomite (40mm particle size) 20Kg / t, ladle ash 6Kg / t.

[0086] (2) LF furnace refining

[0087] The LF furnace is fed into the station at a temperature of 501℃. A high current of 35600A is used for slag formation. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime and silicon carbide are added. After 5 minutes, the first sample is taken for chemical composition analysis. Alloys are added according to the target chemical composition values, and coke particles are added to increase carbon content, promoting rapid melting and homogenization of the alloys and carbon powder. When the molten steel temperature reaches 1602℃, 1.5 kg / t of diffusion deoxidizer alumina balls is added for diffusion deoxidation. The furnace door is closed for 11 minutes. When the molten steel temperature reaches 1590℃, a second sample is taken for chemical composition analysis to confirm the deviation of each chemical element content from the target value. After the second sample is taken, the molten steel leaves the station when the temperature reaches 1605℃. The LF smelting cycle is 42 minutes. Alloys added include: 1.19 kg / t ferrosilicon, 0.6 kg / t high-carbon ferromanganese, and 0.5 kg / t high-carbon ferrochrome. Additional auxiliary materials: 1.5 kg / t alumina balls, 6.2 g / t quicklime (35 mm particle size), 2.1 kg / t silicon carbide (3 mm particle size), and 0.8 kg / t coke granules.

[0088] (3) RH refining

[0089] The inlet temperature is 1585℃, the operation time is 35min, the argon pressure is controlled at 0.1MPa before the vacuum pump is started, so that the molten steel is not exposed when the slag surface is slightly moved. When the vacuum degree reaches 106Pa, the timing starts and is maintained for 12min. At the same time, the argon pressure is adjusted to 0.4MPa. After the static argon blowing is completed, 0.6kg / t of carbonized rice husk is added as a covering agent. The outlet temperature is 1557℃.

[0090] (4) Continuous casting

[0091] The ladle temperature upon arrival is 1550℃, the molten steel volume is 112t, the tundish H is controlled at 1.5ppm, the casting time is 42min, the entire casting process is protected, and medium carbon steel protective slag is used in the crystallizer.

[0092] (5) Heating process

[0093] Heating process: Inlet temperature of 520℃, preheating zone temperature requirement of 690℃, time 1.4h; heating zone 2 temperature requirement of 860℃, time 1.3h; heating zone 1 temperature requirement of 1210℃, time 1.3h; soaking zone temperature requirement of 1198℃, time 1.4h; tapping temperature of 1190℃.

[0094] (6) Rolling process

[0095] Initial rolling process: 9 rolling passes, turning over → Pass 1: Width 408mm, Height 421mm, Reduction 65mm → Pass 2: Width 426mm, Height 351mm, Reduction 70mm → Turning over → Pass 3: Width 370mm, Height 362mm, Reduction 64mm → Pass 4: Width 397mm, Height 272mm, Reduction 90mm → Turning over → Pass 5: Width 285mm, Height 355mm, Reduction 42mm → 6th pass, width 297mm, height 315mm, reduction 40mm → 7th pass, width 307mm, height 280mm, reduction 35mm → 8th pass, width 317mm, height 246mm, reduction 34mm → Turning steel → 9th pass, width 271mm, height 235mm, reduction 82mm. After passing through 3 850mm rolling mills and 1 735mm rolling mill, it enters the continuous rolling mill unit for rolling.

[0096] Continuous rolling process: 11 passes. Pass 1: 229mm high, 245mm wide; Pass 2: 192mm high, 235mm wide; Pass 3: 200mm high, 195mm wide; Pass 4: 160mm high, 214.7mm wide; Pass 5: 165mm high, 174.6mm wide; Pass 6: 118mm high, 187mm wide; Pass 7: 135mm high, 132mm wide; Pass 8: 92mm high, 148mm wide; Pass 9: 110mm high, 115mm wide; Pass 10: 78mm high, 118.7mm wide; Pass 11: 91mm high, 91mm wide; Finished product after 11 passes.

[0097] (7) Thermal Insulation Process

[0098] Insulation process: steel insulation, temperature in the lower insulation pit is 590℃, insulation time is 53 hours, and the temperature after exiting the pit is 140℃.

[0099] (8) Heat treatment process

[0100] A Φ25mm blank is subjected to heat treatment, which includes the following steps:

[0101] 1) Quenching: 900℃, hold for 1.0h, oil cooling;

[0102] 2) Tempering: 600℃, hold for 2.0h, then water-cooled.

[0103] Example 4:

[0104] 1. Chemical composition of steel bars for ecological electric furnace oil pipelines

[0105] The internal control chemical composition was determined to be: C: 0.38%, Si: 1.07%, Mn: 0.41%, P: 0.010%, S: 0.005%, Cr: 1.42%, Ni: 0.05%, Mo: 0.02%, Cu: 0.02%, with the balance being iron and unavoidable impurities.

[0106] 2. The production processes of electric arc furnace continuous casting of steel bars for oil pipelines include the following steps:

[0107] Process route: Eco-friendly electric furnace smelting + LF furnace refining + RH refining + continuous casting → annealing + heating process → rolling → heat preservation process → finishing → inspection → packaging and warehousing → shipment.

[0108] (1) Ecological electric furnace smelting

[0109] 100% scrap steel smelting, 90% heavy scrap steel and 10% bale-shaped scrap steel; tapping temperature 1615℃, C at tapping 0.12wt%, P at 0.008wt%; auxiliary materials and alloys are added when 1 / 4 of the steel has been tapped; smelting cycle 49 minutes. Alloy addition per ton of steel: ferrosilicon 12Kg / t, ferromanganese silicon 4.1Kg / t, high-carbon ferrochrome 25Kg / t, aluminum wire segments (12mm diameter) 1.0Kg / t. Auxiliary material addition per ton of steel: active lime (35mm particle size) 40Kg / t, dolomite (40mm particle size) 20Kg / t, ladle ash 6Kg / t.

[0110] (2) LF furnace refining

[0111] The LF furnace is fed into the station at a temperature of 1501℃. A high current of 35600A is used for slag formation. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime and silicon carbide are added. After 5 minutes, the first sample is taken for chemical composition analysis. Alloys are added according to the target chemical composition values, and coke particles are added to increase carbon content, promoting rapid melting and homogenization of the alloys and carbon powder. When the molten steel temperature reaches 1602℃, 1.5 kg / t of diffusion deoxidizer alumina balls is added for diffusion deoxidation. The furnace door is closed for 10 minutes. When the molten steel temperature reaches 1590℃, a second sample is taken for chemical composition analysis to confirm the deviation of each chemical element content from the target value. After the second sample is taken, the molten steel leaves the station when the temperature reaches 1604℃. The LF smelting cycle is 40 minutes. Alloys are added: 1.18 kg / t ferrosilicon, 0.6 kg / t high-carbon ferromanganese, and 0.5 kg / t high-carbon ferrochrome. Additional auxiliary materials: 1.4 kg / t alumina balls, 6.2 kg / t quicklime (35 mm particle size), 2.1 kg / t silicon carbide (3 mm particle size), and 0.7 kg / t coke granules.

[0112] (3) RH refining

[0113] The inlet temperature is 1585℃, the operation time is 35min, the argon pressure is controlled at 0.1MPa before the vacuum pump is started, so that the molten steel is not exposed when the slag surface is slightly moved. When the vacuum degree reaches 103Pa, the timing starts and is maintained for 11min. At the same time, the argon pressure is adjusted to 0.3MPa. After the static argon blowing is completed, 0.6kg / t of carbonized rice husk is added as a covering agent. The outlet temperature is 1555℃.

[0114] (4) Continuous casting

[0115] The ladle temperature upon arrival is 1550℃, the molten steel volume is 112t, the tundish H is controlled at 1.5ppm, the casting time is 42min, the entire casting process is protected, and medium carbon steel protective slag is used in the crystallizer.

[0116] (5) Heating process

[0117] Heating process: Inlet temperature of 520℃, preheating zone temperature requirement of 690℃, time 1.3h; heating zone 2 temperature requirement of 860℃, time 1.3h; heating zone 1 temperature requirement of 1210℃, time 1.3h; soaking zone temperature requirement of 1200℃, time 1.5h; tapping temperature of 1190℃.

[0118] (6) Rolling process

[0119] Initial rolling process: 9 rolling passes, turning over → Pass 1: Width 408mm, Height 421mm, Reduction 65mm → Pass 2: Width 426mm, Height 351mm, Reduction 70mm → Turning over → Pass 3: Width 370mm, Height 362mm, Reduction 64mm → Pass 4: Width 397mm, Height 272mm, Reduction 90mm → Turning over → Pass 5: Width 285mm, Height 355mm, Reduction 42mm → 6th pass, width 297mm, height 315mm, reduction 40mm → 7th pass, width 307mm, height 280mm, reduction 35mm → 8th pass, width 317mm, height 246mm, reduction 34mm → Turning steel → 9th pass, width 271mm, height 235mm, reduction 82mm. After passing through 3 850mm rolling mills and 1 735mm rolling mill, it enters the continuous rolling mill unit for rolling.

[0120] Continuous rolling process: 11 passes. Pass 1: 229mm high, 245mm wide; Pass 2: 192mm high, 235mm wide; Pass 3: 200mm high, 195mm wide; Pass 4: 160mm high, 214.7mm wide; Pass 5: 165mm high, 174.6mm wide; Pass 6: 118mm high, 187mm wide; Pass 7: 135mm high, 132mm wide; Pass 8: 92mm high, 148mm wide; Pass 9: 110mm high, 115mm wide; Pass 10: 78mm high, 118.7mm wide; Pass 11: 91mm high, 91mm wide; Finished product after 11 passes.

[0121] (7) Thermal Insulation Process

[0122] Insulation process: steel insulation, temperature of the lower insulation pit is 600℃, insulation time is 53 hours, and the temperature of the lower insulation pit is 140℃.

[0123] (8) Heat treatment process

[0124] A Φ25mm blank is subjected to heat treatment, which includes the following steps:

[0125] 1) Quenching: 900℃, hold for 1.0h, oil cooling;

[0126] 2) Tempering: 600℃, hold for 2.0h, then water-cooled.

[0127] Example 5:

[0128] 1. Chemical composition of steel bars for ecological electric furnace oil pipelines

[0129] The internal control chemical composition was determined to be C: 0.38%, Si: 1.09%, Mn: 0.41%, P: 0.010%, S: 0.005%, Cr: 1.42%, Ni: 0.05%, Mo: 0.02%, Cu: 0.02%, with the balance being iron and unavoidable impurities.

[0130] 2. The production processes of electric arc furnace continuous casting of steel bars for oil pipelines include the following steps:

[0131] Process route: Eco-friendly electric furnace smelting + LF furnace refining + RH refining + continuous casting → annealing + heating process → rolling → heat preservation process → finishing → inspection → packaging and warehousing → shipment.

[0132] (1) Ecological electric furnace smelting

[0133] 100% scrap steel smelting, 90% heavy scrap steel and 10% bale-shaped scrap steel; tapping temperature 1614℃, C 0.11wt%, P 0.008wt% at tapping; auxiliary materials and alloys added when 1 / 4 of the steel has been tapped; smelting cycle 50 minutes. Alloy addition per ton of steel: ferrosilicon 12Kg / t, ferromanganese silicon 4.1Kg / t, high-carbon ferrochrome 25Kg / t, aluminum wire segments (12mm diameter) 1.0Kg / t. Auxiliary material addition per ton of steel: active lime (35mm particle size) 40Kg / t, dolomite (40mm particle size) 20Kg / t, ladle ash 6Kg / t.

[0134] (2) LF furnace refining

[0135] The LF furnace is fed into the station at a temperature of 1501℃. A high current of 35600A is used for slag formation. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime and silicon carbide are added. After 5 minutes, the first sample is taken for chemical composition analysis. Alloys are added according to the target chemical composition values, and coke particles are added to increase carbon content, promoting rapid melting and homogenization of the alloys and carbon powder. When the molten steel temperature reaches 1604℃, 1.5 kg / t of diffusion deoxidizer alumina balls is added for diffusion deoxidation. The furnace door is closed for 10 minutes. When the molten steel temperature reaches 1585℃, a second sample is taken for chemical composition analysis to confirm the deviation of each chemical element content from the target value. After the second sample is taken, the furnace leaves the station when the molten steel temperature reaches 1604℃. The LF smelting cycle is 40 minutes. Alloys are added: 1.20 kg / t ferrosilicon, 0.6 kg / t high-carbon ferromanganese, and 0.5 kg / t high-carbon ferrochrome. Additional auxiliary materials: 1.5 kg / t alumina balls, 6.2 kg / t quicklime (35 mm particle size), 2.1 kg / t silicon carbide (3 mm particle size), and 0.8 kg / t coke granules.

[0136] (3) RH refining

[0137] The inlet temperature is 1585℃, the operation time is 35min, the argon pressure is controlled at 0.1MPa before the vacuum pump is started, so that the molten steel is not exposed when the slag surface is slightly moved. When the vacuum degree reaches 105Pa, the timing starts and is maintained for 12min. At the same time, the argon pressure is adjusted to 0.3MPa. After the static argon blowing is completed, 0.6kg / t of carbonized rice husk is added as a covering agent. The outlet temperature is 1555℃.

[0138] (4) Continuous casting

[0139] The ladle temperature upon arrival is 1550℃, the molten steel volume is 112t, the tundish H is controlled at 1.5ppm, the casting time is 42min, the entire casting process is protected, and medium carbon steel protective slag is used in the crystallizer.

[0140] (5) Heating process

[0141] Heating process: Inlet temperature of 510℃, preheating zone temperature requirement of 690℃, time 1.3h; heating zone 2 temperature requirement of 860℃, time 1.4h; heating zone 1 temperature requirement of 1210℃, time 1.4h; soaking zone temperature requirement of 1200℃, time 1.3h; tapping temperature of 1190℃.

[0142] (6) Rolling process

[0143] Initial rolling process: 9 rolling passes, turning over → Pass 1: Width 408mm, Height 421mm, Reduction 65mm → Pass 2: Width 426mm, Height 351mm, Reduction 70mm → Turning over → Pass 3: Width 370mm, Height 362mm, Reduction 64mm → Pass 4: Width 397mm, Height 272mm, Reduction 90mm → Turning over → Pass 5: Width 285mm, Height 355mm, Reduction 42mm → 6th pass, width 297mm, height 315mm, reduction 40mm → 7th pass, width 307mm, height 280mm, reduction 35mm → 8th pass, width 317mm, height 246mm, reduction 34mm → Turning steel → 9th pass, width 271mm, height 235mm, reduction 82mm. After passing through 3 850mm rolling mills and 1 735mm rolling mill, it enters the continuous rolling mill unit for rolling.

[0144] Continuous rolling process: 11 passes. Pass 1: 229mm high, 245mm wide; Pass 2: 192mm high, 235mm wide; Pass 3: 200mm high, 195mm wide; Pass 4: 160mm high, 214.7mm wide; Pass 5: 165mm high, 174.6mm wide; Pass 6: 118mm high, 187mm wide; Pass 7: 135mm high, 132mm wide; Pass 8: 92mm high, 148mm wide; Pass 9: 110mm high, 115mm wide; Pass 10: 78mm high, 118.7mm wide; Pass 11: 91mm high, 91mm wide; Finished product after 11 passes.

[0145] (7) Thermal Insulation Process

[0146] Insulation process: steel insulation, temperature in the lower insulation pit is 590℃, insulation time is 53 hours, and the temperature after exiting the pit is 130℃.

[0147] (8) Heat treatment process

[0148] A Φ25mm blank is subjected to heat treatment, which includes the following steps:

[0149] 1) Quenching: 900℃, hold for 1.0h, oil cooling;

[0150] 2) Tempering: 600℃, hold for 2.0h, then water-cooled.

[0151] 2. Inspection results of finished products in Examples 1-5: Two samples were inspected for each heat of steel.

[0152] (1) Φ90mm specification low magnification structure (finished steel obtained by heat preservation process)

[0153]

[0154] (2) Φ90mm non-metallic inclusions (finished steel obtained through insulation process)

[0155]

[0156]

[0157] (3) Mechanical properties of Φ90mm specimen (the test was conducted on a Φ25mm specimen obtained after heat treatment).

[0158] .

Claims

1. A method for the production of ecological electrically-arc-furnace steel rod for oil pipelines, characterized in that The steel bars used for the ecological electric furnace oil pipeline are, by mass percentage: C: 0.36%~0.41%, Si: 1.00%~1.20%, Mn: 0.35%~0.50%, P: ≤0.016%, S: ≤0.010%, Cr: 1.35%~1.50%, Ni: ≤0.20%, Mo: ≤0.05%, Cu: ≤0.15%, with the balance being iron and unavoidable impurities; The preparation method includes the following steps: The process route is: ecological electric furnace smelting + LF furnace refining + RH refining + continuous casting → annealing + heating process → rolling → heat preservation process; The ecological electric furnace smelting process is as follows: 100% scrap steel smelting, of which heavy scrap steel accounts for 85-95% and bale-shaped scrap steel accounts for 5-15%. The tapping temperature is 1610-1620℃. The carbon content at tapping is 0.10-0.15wt% and the phosphorus content is ≤0.010wt%. Auxiliary materials and alloys are added when 1 / 4 to 1 / 3 of the steel has been tapped. The smelting cycle is 45-55 minutes. The LF furnace refining process is as follows: The LF furnace is fed into the furnace at a temperature of 1495–1505℃. A high current of 35000–36000A is used for slag formation. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime and silicon carbide are added. After 5–6 minutes, the first sample is taken for chemical composition analysis. Alloy is added according to the target chemical composition value, and coke particles are added for carbonization. When the molten steel temperature reaches 1600–1610℃, 1.5–1.6 kg / t of diffusion deoxidizer alumina balls is added for diffusion deoxidation. The furnace door is closed for 10–13 minutes. When the molten steel temperature reaches 1580–1600℃, a second sample is taken for chemical composition analysis to confirm the deviation of each chemical element content from the target value. After the second sample is taken, the furnace is removed when the molten steel temperature reaches 1600–1610℃. The LF smelting cycle is 35–45 minutes. The RH refining process is as follows: The inlet temperature is 1580-1590℃, the operation time is 30-40 minutes, the argon pressure is controlled at 0.1-0.3MPa before the vacuum pump is started, so that the molten steel is not exposed when the slag surface moves slightly. When the vacuum degree reaches 100-110Pa, the timing starts and is maintained for 10-15 minutes. At the same time, the argon pressure is adjusted to 0.3-0.5MPa. After the static argon blowing is completed, 0.6-0.7kg / t of carbonized rice husk is added as a covering agent. The outlet temperature is 1550-1560℃. A steel sample after the heat preservation process is subjected to heat treatment, which includes the following steps: 1) Quenching: 880~920℃, hold for 0.8~1.2h, oil cooling; 2) Tempering: 580~620℃, hold for 1.8~2.2h, then water-cooled.

2. The method according to claim 1, characterized in that, In the aforementioned ecological electric furnace smelting, the alloy addition per ton of steel is as follows: ferrosilicon 12-12.2 kg / t, ferrosilicon 4.1-4.2 kg / t, high-carbon ferrochrome 25-25.5 kg / t, and aluminum wire segments 1.0-1.2 kg / t; the auxiliary material addition per ton of steel is as follows: active lime 40-41 kg / t, dolomite 20-21 kg / t, and ladle ash 6-6.2 kg / t.

3. The method according to claim 1, characterized in that, In the LF furnace refining process, the following alloy additions are made: ferrosilicon 1.15–1.25 kg / t, high-carbon ferromanganese 0.6–0.7 kg / t, and high-carbon ferrochrome 0.5–0.6 kg / t; the addition of diffusion deoxidizer alumina balls is 1.5–1.6 kg / t, active lime is 6–6.5 kg / t, silicon carbide is 2.1–2.2 kg / t, and coke particles are 0.7–0.9 kg / t.

4. The method according to claim 1, characterized in that, The continuous casting is: The ladle temperature upon arrival is 1545~1555℃, the molten steel volume is 110~115t, the H in the tundish is controlled to be ≤2ppm, the casting time is 40min~45min, the entire process is protected during casting, and medium carbon steel protective slag is used for the crystallizer.

5. The method according to claim 1, characterized in that, The heating process, in chronological order, is as follows: Inlet temperature to the heating furnace: 480℃~550℃; Preheating section temperature: 680℃~700℃; Time: 1.3~1.5h; Heating section 2 temperature: 850℃~870℃; Time: 1.3~1.5h; Heating section 1 temperature: 1200℃~1220℃; Time: 1.3~1.5h; Soaking section temperature: 1190℃~1210℃; Time: 1.3~1.5h; Tap-out temperature: 1185℃~1195℃.

6. The method according to claim 1, characterized in that, The rolling process includes primary rolling and continuous rolling processes; The initial rolling process is as follows: 9 rolling passes, turning the steel over → Pass 1: Width 408-408.02mm, Height 421-421.02mm, Reduction 65-65.02mm → Pass 2: Width 426-426.02mm, Height 351-351.02mm, Reduction 70-70.02mm → Turning the steel over → Pass 3: Width 370-370.02mm, Height 362-362.02mm, Reduction 64-64.02mm → Pass 4: Width 397-397.02mm, Height 272-272.02mm, Reduction 90-90.02mm → Turning the steel over → Pass 5: Width 285-285.02mm, Height 355-355.02mm mm, reduction 42~42.02mm → 6th pass width 297~297.02mm, height 315~315.02mm, reduction 40~40.02mm → 7th pass width 307~307.02mm, height 280~280.02mm, reduction 35~35.02mm → 8th pass width 317~317.02mm, height 246~246.02mm, reduction 34~34.02mm → turn over → 9th pass width 271~271.02mm, height 235~235.02mm, reduction 82~82.02mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, then entering the continuous rolling mill group for rolling.

7. The method according to claim 6, characterized in that, Continuous rolling process: 11 passes. Pass 1: Height 229–229.02 mm, width 245–245.02 mm; Pass 2: Height 192–192.02 mm, width 235–235.02 mm; Pass 3: Height 200–200.02 mm, width 195–195.02 mm; Pass 4: Height 160–160.02 mm, width 214.7–214.72 mm; Pass 5: Height 165–165.02 mm, width 174.6–174.62 mm; Pass 6: Height 118–… 118.02mm high, 187-187.02mm wide; 7th pass: 135-135.02mm high, 132-132.02mm wide; 8th pass: 92-92.02mm high, 148-148.02mm wide; 9th pass: 110-110.02mm high, 115-115.02mm wide; 10th pass: 78-78.02mm high, 118.7-118.72mm wide; 11th pass: 91-91.02mm high, 91-91.02mm wide; finished product after 11th pass.

8. The method according to claim 1, characterized in that, The insulation process is as follows: steel insulation, temperature of the lower insulation pit ≥580℃, insulation for 52~55h, and temperature of the lower pit ≤150℃.

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