Ecological electric furnace-produced steel bar for oil pipelines, and production method for steel bar

Abstract

The present invention relates to the field of steelmaking. Disclosed are an ecological electric furnace-produced steel bar for oil pipelines and a production method for the steel bar. The steel bar for oil pipelines comprises, in percentage by mass: 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%, and the balance being iron and inevitable impurities. The method employs an ecological electric furnace, LF, RH and continuous casting smelting process for smelting to produce the steel bar for oil pipelines, thereby ensuring that indicators such as mechanical properties and high steel purity of finished steel of the steel bar for oil pipelines meet standards, and also ensuring the surface quality level of the steel bar for oil pipelines.

Description

An ecological electric furnace petroleum pipeline steel bar and a production and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to an ecological electric furnace petroleum pipeline steel bar and a production and preparation method thereof, and belongs to the field of steelmaking. BACKGROUND

[0002] The petroleum pipeline is a pipeline system for transporting petroleum and petroleum products. It is usually composed of a series of interconnected pipelines for transporting crude oil, natural gas liquids, refined oil products, etc. from the production site to the processing plant, storage facility or end user. The quality of the petroleum pipeline steel is related to the safety of petroleum transportation, so the high-temperature resistance, wear resistance, mechanical properties, fatigue life and steel purity of the petroleum pipeline steel are required to be very high to ensure the normal and safe operation of the petroleum transportation process.

[0003] The present application develops a petroleum pipeline steel with excellent mechanical properties and high steel purity, which meets the requirements of high-end products. The present application uses an ecological electric furnace + LF + RH + continuous casting smelting process and rolling process to produce the petroleum pipeline steel bar, which meets the requirements of high-end use and realizes the breakthrough of batch production of the petroleum pipeline steel bar by the ecological electric furnace continuous casting process. SUMMARY

[0004] The present application aims to provide a production process and preparation method of a petroleum pipeline steel bar. The method uses an ecological electric furnace + LF + RH + continuous casting smelting process to smelt and produce the petroleum pipeline steel bar, which not only guarantees the mechanical properties and high steel purity of the finished steel bar of the petroleum pipeline steel bar, but also guarantees the surface quality level of the petroleum pipeline steel bar.

[0005] In order to achieve the above-mentioned application purposes, the present application provides a component design and process design of a petroleum pipeline steel bar, and the specific steps are as follows: ecological electric furnace smelting + LF furnace refining + RH refining + continuous casting blank → annealing, heating furnace heating → rolling → heat preservation. The quality requirements of the petroleum pipeline steel bar are met, and the mechanical properties and high steel purity indicators can also meet the standard requirements.

[0006] The present application provides an ecological electric furnace petroleum pipeline steel bar, which contains the following components in percentage by mass: C: 0.36% to 0.41%, Si: 1.00% to 1.20%, Mn: 0.35% to 0.50%, P: ≤0.016%, S: ≤0.010%, Cr: 1.35% to 1.50%, Ni: ≤0.20%, Mo: ≤0.05%, Cu: ≤0.15%, and the balance is iron and unavoidable impurities.

[0007] The present application provides a production and preparation method of the above-mentioned ecological electric furnace petroleum pipeline steel bar, which includes the following steps:

[0008] The process route is ecological electric furnace smelting + LF furnace refining + RH refining + continuous casting → annealing + heating process → rolling → heat preservation process. Further, after heat preservation, finishing → inspection → packaging and delivery to the warehouse → delivery process is carried out.

[0009] The ecological electric furnace smelting is:

[0010] 100% full scrap smelting, wherein the heavy scrap accounts for 85-95%, the bale type scrap accounts for 5-15%, the tapping temperature is 1610-1620℃, the C is 0.10-0.15wt% at tapping, the P≤0.010wt%, the auxiliary materials and alloys are added at 1 / 4-1 / 3 of tapping, and the smelting period is 45-55min;

[0011] The LF furnace refining is:

[0012] The LF inlet temperature is 1495-1505℃, the 35000-36000A large current is used to heat and slag, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, the active lime and silicon carbide are supplemented, the chemical composition is sampled and analyzed after 5-6min, the alloy is supplemented according to the chemical composition target value, and the coke particles are added for carbon addition, so as to promote the rapid melting and homogenization of the alloy and carbon powder. When the molten steel temperature reaches 1600-1610℃, the diffusion deoxidizer alumina ball 1.5-1.6kg / t is added for diffusion deoxidization, the furnace door is closed for 10-13min, when the molten steel temperature reaches 1580-1600℃, the chemical composition is sampled and analyzed for the second time to confirm the deviation of the chemical element content from the target value, after the second sampling, when the molten steel temperature reaches 1600-1610℃, the LF smelting period is 35min-45min;

[0013] The RH refining is:

[0014] The inlet temperature is 1580-1590℃, the operation time is 30min-40min, the argon pressure is controlled to 0.1-0.3MPa by static argon blowing before the vacuum pump is started, 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, at the same time, the argon pressure is adjusted to 0.3-0.5MPa, after the static argon blowing is finished, the covering agent carbonized rice husk 0.6-0.7kg / t is added, and the outlet temperature is 1550-1560℃.

[0015] Further, in the above technical solution, in the ecological electric furnace smelting, the alloy ton steel adding amount is: silicon iron 12-12.2 Kg / t, silicon manganese 4.1-4.2 Kg / t, high-carbon chromium iron 25-25.5 Kg / t, aluminum wire segment (diameter 10-16 mm) 1.0-1.2 Kg / t; the auxiliary ton steel adding amount is: active lime (particle size 10-70 mm) 40-41 Kg / t, dolomite (particle size 20-70 mm) 20-21 Kg / t, ladle ash 6-6.2 Kg / t.

[0016] Further, in the above technical solution, in the LF furnace refining, the alloy supplementing amount is: silicon iron 1.15-1.25 kg / t, high-carbon manganese iron 0.6-0.7 kg / t, high-carbon chromium iron 0.5-0.6 kg / t; the supplementing amount of other auxiliary materials is: diffusion deoxidizer alumina ball adding amount is 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, coke particles 0.7-0.9 kg / t.

[0017] Further, in the above technical solution, the continuous casting is: ladle to station temperature 1545-1555℃, molten steel amount 110-115 t, tundish H control≤2ppm, casting time 40min-45min, whole process protection casting, crystallizer protection slag uses medium carbon steel protection slag.

[0018] Further, in the above technical solution, the heating process is: the time sequence heating process is: heating process: entering the heating furnace temperature 480℃-550℃, preheating section temperature requirement 680℃-700℃, time 1.3-1.5h; heating 2 section temperature requirement 850℃-870℃, time 1.3-1.5h; heating 1 section temperature requirement 1200℃-1220℃, time 1.3-1.5h; soaking section temperature requirement 1190℃-1210℃, time 1.3-1.5h; steel temperature 1185℃-1195℃.

[0019] Further, in the above technical solution, the rolling includes rough rolling process and continuous rolling process;

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

[0021] Further, in the above technical solution, the continuous rolling production material rolling process is: rolling 11 passes, the 1st pass, height 229-229.02 mm, width 245-245.02 mm; the 2nd pass, height 192-192.02 mm, width 235-235.02 mm; the 3rd pass, height 200-200.02 mm, width 195-195.02 mm; the 4th pass, height 160-160.02 mm, width 214.7-214.72 mm; the 5th pass, height 165-165.02 mm, width 174.6-174.62 mm; the 6th pass, height 118-118.02 mm, width 187-187.02 mm; the 7th pass, height 135-135.02 mm, width 132-132.02 mm; the 8th pass, height 92-92.02 mm, width 148-148.02 mm; the 9th pass, height 110-110.02 mm, width 115-115.02 mm; the 10th pass, height 78-78.02 mm, width 118.7-118.72 mm; the 11th pass, height 91-91.02 mm, width 91-91.02 mm; after 11 passes, finished steel material is discharged.

[0022] Further, in the above technical solution, the heat preservation process is: steel material heat preservation, the temperature of the lower heat preservation pit is ≥580 ℃, heat preservation is 52-55 h, and the pit discharge temperature is ≤150 ℃.

[0023] Further, in the above technical solution, the steel sample after the heat preservation process is subjected to heat treatment, and the heat treatment comprises the following steps:

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

[0025] 2) Tempering: 580-620℃, holding for 1.8-2.2h, water cooling.

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

[0027] Advantages of the application

[0028] (1) The ecological electric furnace + LF + RH + continuous casting smelting process and rolling process are adopted to produce the steel bar for petroleum pipeline, which meets the mechanical property requirements and ensures the purity of the steel.

[0029] (2) The reasonable component design and production process ensure the surface quality and mechanical properties.

[0030] (3) The macrostructure and non-metallic inclusions of the finished steel meet the requirements of high-end products. DETAILED DESCRIPTION

[0031] Example 1:

[0032] 1. Chemical composition of the ecological electric furnace steel bar for petroleum pipeline

[0033] In terms of mass percentage: 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%, and the balance is iron and unavoidable impurities.

[0034] 2. Each production process of the ecological electric furnace steel bar for petroleum pipeline, including the following steps:

[0035] Process route: ecological electric furnace smelting + LF furnace refining + RH refining + continuous casting → annealing + heating process → rolling → heat preservation process → finishing → inspection → packaging and delivery to the warehouse → delivery.

[0036] (1) Ecological electric furnace smelting

[0037] 100% all scrap steel smelting, heavy scrap steel 90%, bale type scrap steel 10%; tapping temperature 1615°C, C 0.12wt% and P 0.008wt% at tapping time, auxiliary materials and alloys are added at 1 / 4 tapping time, smelting cycle 49 min. Alloy addition per ton of steel: ferrosilicon 12 Kg / t, silicon manganese 4.1 Kg / t, high-carbon ferrochrome 25.3 Kg / t, aluminum wire segment (diameter 12 mm) 1.0 Kg / t. Auxiliary material addition per ton of steel: active lime (particle size 35 mm) 40 Kg / t, dolomite (particle size 40 mm) 20 Kg / t, ladle powder 6 Kg / t.

[0038] (2) LF furnace refining

[0039] LF inlet temperature 1502°C, 35500A large current temperature rising slag, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, active lime and silicon carbide are supplemented, the first sampling analysis of chemical composition is taken after 5 min, the alloy is supplemented according to the target value of the chemical composition, and coke particles are added for carbon addition to promote the rapid melting and homogenization of the alloy and carbon powder. When the temperature of the molten steel reaches 1604°C, 1.5 kg / t of diffusion deoxidizer alumina balls are added for diffusion deoxidation, the furnace door is closed for 10 min, and when the temperature of the molten steel reaches 1590°C, the second sampling analysis of chemical composition is taken to confirm the deviation of the content of each chemical element from the target value. After the second sampling, when the temperature of the molten steel reaches 1604°C, the LF refining cycle is 40 min, and the supplementary alloy is: ferrosilicon 1.12 kg / t, high-carbon ferromanganese 0.6 kg / t, and high-carbon ferrochrome 0.5 kg / t. Supplementary auxiliary materials: alumina balls 1.5 kg / t, active lime (particle size 35 mm) 6.2 Kg / t, silicon carbide (particle size 3 mm) 2.1 kg / t, and coke particles 0.7 kg / t.

[0040] (3) RH refining

[0041] Inlet temperature 1585°C, operation time 35 min, argon is blown statically to control the argon pressure at 0.1 MPa before the vacuum pump is started, the slag surface is slightly moved and the molten steel is not exposed, the timing starts when the vacuum degree reaches 104 Pa, the holding time is 12 min, and at the same time, the argon pressure is adjusted to 0.3 MPa. After the static argon blowing is completed, 0.6 kg / t of covering agent carbonized rice husk is added, and the outlet temperature is 1555°C.

[0042] (4) Continuous casting

[0043] Ladle arrival temperature 1551°C, molten steel quantity 112 t, H control in the tundish 1.4 ppm, casting time 42 min, full-process protective casting, and crystallizer protective slag medium-carbon steel protective slag is used.

[0044] (5) Heating process

[0045] Heating process: the temperature of the inlet of the heating furnace is 520℃, the temperature of the preheating section is required to be 685℃, the time is 1.4h; the temperature of heating section 2 is required to be 860℃, the time is 1.4h; the temperature of heating section 1 is required to be 1208℃, the time is 1.3h; the temperature of the soaking section is required to be 1198℃, the time is 1.5h; the temperature of the outlet is 1190℃.

[0046] (6) Rolling process

[0047] Initial rolling process: 9 passes, turning over the steel → the first pass, width 408mm, height 421mm, reduction 65mm → the second pass, width 426mm, height 351mm, reduction 70mm → turning over the steel → the third pass, width 370mm, height 362mm, reduction 64mm → the fourth pass, width 397mm, height 272mm, reduction 90mm → turning over the steel → the fifth pass, width 285mm, height 355mm, reduction 42mm → the sixth pass, width 297mm, height 315mm, reduction 40mm → the seventh pass, width 307mm, height 280mm, reduction 35mm → the eighth pass, width 317mm, height 246mm, reduction 34mm → turning over the steel → the ninth pass, width 271mm, height 235mm, reduction 82mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, and then entering the continuous rolling mill group.

[0048] Continuous rolling process: 11 passes, the first pass, height 229mm, width 245mm; the second pass, height 192mm, width 235mm; the third pass, height 200mm, width 195mm; the fourth pass, height 160mm, width 214.7mm; the fifth pass, height 165mm, width 174.6mm; the sixth pass, height 118mm, width 187mm; the seventh pass, height 135mm, width 132mm; the eighth pass, height 92mm, width 148mm; the ninth pass, height 110mm, width 115mm; the tenth pass, height 78mm, width 118.7mm; the eleventh pass, height 91mm, width 91mm; after 11 passes, the finished steel material is discharged.

[0049] (7) Holding process

[0050] Holding process: the steel material is held, the temperature of the holding pit is 600℃, the holding time is 52h, and the temperature of the outlet is 120℃.

[0051] (8) Heat treatment process

[0052] A Φ25mm blank is taken for heat treatment, and the heat treatment comprises the following steps:

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

[0054] 2) Tempering: 600℃, holding for 2.0h, water cooling.

[0055] Example 2:

[0056] 1. Chemical composition of ecological electric furnace steel bar for petroleum pipeline

[0057] The internal control chemical composition is determined as follows: 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%, and the balance is iron and inevitable impurities.

[0058] 2. Each production process of electric furnace continuous casting of ecological electric furnace steel bar for petroleum pipeline, comprising the following steps:

[0059] Process route: ecological electric furnace smelting + LF furnace refining + RH refining + continuous casting → annealing + heating process → rolling → heat preservation process → finishing → inspection → packaging and delivery to the warehouse → delivery.

[0060] (1) Ecological electric furnace smelting

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

[0062] (2) LF furnace refining

[0063] LF inlet temperature 1499℃, 35600A large current to heat and slag, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, active lime and silicon carbide are supplemented, the first sampling analysis is taken after 5min, the alloy is supplemented according to the target value of the chemical composition, and the coke particles are added for carbon addition to promote the rapid melting and homogenization of the alloy and carbon powder. When the temperature of the molten steel reaches 1606℃, 1.5kg / t of aluminum oxide balls are added for diffusion deoxidation, the furnace door is closed for 10min, and the second sampling analysis is taken when the temperature of the molten steel reaches 1592℃ to confirm the deviation of the chemical element content from the target value. After the second sampling, the molten steel is taken away when the temperature reaches 1606℃, and the LF smelting cycle is 40min. Supplementary alloy: ferrosilicon 1.19kg / t, high-carbon ferromanganese 0.6kg / t, high-carbon chromium iron 0.5kg / t. Supplementary auxiliary materials: aluminum oxide balls 1.5kg / t, active lime (particle size 35mm) 6.2Kg / t, silicon carbide (particle size 3mm) 2.1kg / t, coke particles 0.8kg / t.

[0064] (3) RH refining

[0065] The inlet temperature was 1586℃, the operation time was 36min, the argon pressure was controlled to be 0.1MPa by static argon blowing before the vacuum pump was started, the argon pressure was adjusted to be 0.3MPa when the vacuum degree reached 104Pa, the slag surface was slightly moved and the molten steel was not exposed, 0.6kg / t of carbonized rice husk was added as a covering agent after the static argon blowing was finished, and the outlet temperature was 1556℃.

[0066] (4) Continuous casting

[0067] The ladle inlet temperature was 1551℃, the molten steel amount was 112t, the H content in the tundish was controlled to be 1.7ppm, the casting time was 42min, the whole process was protected casting, and the crystallizer protecting slag was a medium carbon steel protecting slag.

[0068] (5) Heating process

[0069] The heating process was as follows: the inlet temperature of the heating furnace was 510℃, the preheating section temperature was required to be 690℃, the time was 1.4h, the heating 2 section temperature was required to be 858℃, the time was 1.4h, the heating 1 section temperature was required to be 1210℃, the time was 1.4h, the soaking section temperature was required to be 1198℃, the time was 1.3h, and the outlet temperature was 1190℃.

[0070] (6) Rolling process

[0071] The rough rolling process was as follows: 9 passes were rolled, the steel was turned over, the width of the first pass was 408mm, the height was 421mm, the reduction was 65mm, the width of the second pass was 426mm, the height was 351mm, the reduction was 70mm, the steel was turned over, the width of the third pass was 370mm, the height was 362mm, the reduction was 64mm, the width of the fourth pass was 397mm, the height was 272mm, the reduction was 90mm, the steel was turned over, the width of the fifth pass was 285mm, the height was 355mm, the reduction was 42mm, the width of the sixth pass was 297mm, the height was 315mm, the reduction was 40mm, the width of the seventh pass was 307mm, the height was 280mm, the reduction was 35mm, the width of the eighth pass was 317mm, the height was 246mm, the reduction was 34mm, the steel was turned over, the width of the ninth pass was 271mm, the height was 235mm, the reduction was 82mm, 3 sets of 850mm rolling mills and 1 set of 735mm rolling mill were used, and then the steel was rolled into a continuous rolling mill group.

[0072] Continuous rolling process: 11 passes, 1st pass height 229 mm, width 245 mm; 2nd pass height 192 mm, width 235 mm; 3rd pass height 200 mm, width 195 mm; 4th pass height 160 mm, width 214.7 mm; 5th pass height 165 mm, width 174.6 mm; 6th pass height 118 mm, width 187 mm; 7th pass height 135 mm, width 132 mm; 8th pass height 92 mm, width 148 mm; 9th pass height 110 mm, width 115 mm; 10th pass height 78 mm, width 118.7 mm; 11th pass height 91 mm, width 91 mm; finished steel product after 11 passes.

[0073] (7) Holding process

[0074] Holding process: steel holding, holding pit temperature 590°C, holding for 53 h, pit exit temperature 130°C.

[0075] (8) Heat treatment process

[0076] Φ25 mm blank is taken for heat treatment, which comprises the following steps:

[0077] 1) Quenching: 900°C, holding for 1.0 h, oil cooling;

[0078] 2) Tempering: 600°C, holding for 2.0 h, water cooling.

[0079] Example 3:

[0080] 1. Chemical composition of ecological electric furnace steel bar for petroleum pipeline

[0081] The internal control chemical composition is determined as follows: 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%, and the balance is iron and inevitable impurities.

[0082] 2. Each production process of ecological electric furnace steel bar for petroleum pipeline by electric furnace continuous casting, comprising the following steps:

[0083] Process route: ecological electric furnace smelting + LF furnace refining + RH refining + continuous casting → annealing + heating process → rolling → holding process → finishing → inspection → packaging and delivery to warehouse → delivery.

[0084] (1) Ecological electric furnace smelting

[0085] 100% all scrap steel smelting, heavy scrap steel 90%, bale type scrap steel 10%; tapping temperature 1615°C, C 0.12wt% and P 0.008wt% at tapping time, auxiliary materials and alloys are added at 1 / 4 tapping time, smelting cycle 49 min. Alloy addition per ton of steel: ferrosilicon 12 Kg / t, silicon manganese 4.1 Kg / t, high-carbon ferrochrome 25.2 Kg / t, aluminum wire segment (diameter 12 mm) 1.0 Kg / t. Auxiliary material addition per ton of steel: active lime (particle size 35 mm) 40 Kg / t, dolomite (particle size 40 mm) 20 Kg / t, ladle powder 6 Kg / t.

[0086] (2) LF furnace refining

[0087] LF inlet temperature 501°C, 35600A large current temperature rising slag, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, active lime and silicon carbide are supplemented, the first sampling analysis of chemical composition is taken after 5 min, the alloy is supplemented according to the target value of the chemical composition, and coke particles are added for carbon addition to promote the rapid melting and homogenization of the alloy and carbon powder. When the temperature of the molten steel reaches 1602°C, 1.5 kg / t of diffusion deoxidizer alumina balls are added for diffusion deoxidation, the furnace door is closed for 11 min, and when the temperature of the molten steel reaches 1590°C, the second sampling analysis of chemical composition is taken to confirm the deviation of the content of each chemical element from the target value. After the second sampling, when the temperature of the molten steel reaches 1605°C, the LF refining cycle is 42 min, the supplementary alloy is 1.19 kg / t of ferrosilicon, 0.6 kg / t of high-carbon ferromanganese, and 0.5 kg / t of high-carbon ferrochrome. The supplementary auxiliary material is 1.5 kg / t of alumina balls, 6.2 g / t of active lime (particle size 35 mm), 2.1 kg / t of silicon carbide (particle size 3 mm), and 0.8 kg / t of coke particles.

[0088] (3) RH refining

[0089] Inlet temperature 1585°C, operation time 35 min, argon is blown statically to control the argon pressure at 0.1 MPa before the vacuum pump is started, the slag surface is slightly moved and the molten steel is not exposed, the timing starts when the vacuum degree reaches 106 Pa, the holding time is 12 min, and at the same time, the argon pressure is adjusted to 0.4 MPa. After the static argon blowing is completed, 0.6 kg / t of covering agent carbonized rice husk is added, and the outlet temperature is 1557°C.

[0090] (4) Continuous casting

[0091] Ladle arrival temperature 1550°C, molten steel quantity 112 t, H control in the tundish 1.5 ppm, casting time 42 min, full-process protective casting, mold powder of medium-carbon steel is used.

[0092] (5) Heating process

[0093] Heating process: the temperature of the inlet of the heating furnace is 520℃, the temperature of the preheating section is required to be 690℃, the time is 1.4h; the temperature of heating section 2 is required to be 860℃, the time is 1.3h; the temperature of heating section 1 is required to be 1210℃, the time is 1.3h; the temperature of the soaking section is required to be 1198℃, the time is 1.4h; the temperature of the outlet is 1190℃.

[0094] (6) Rolling process

[0095] Initial rolling process: rolling 9 passes, turning over the steel → the first pass, width 408mm, height 421mm, reduction 65mm → the second pass, width 426mm, height 351mm, reduction 70mm → turning over the steel → the third pass, width 370mm, height 362mm, reduction 64mm → the fourth pass, width 397mm, height 272mm, reduction 90mm → turning over the steel → the fifth pass, width 285mm, height 355mm, reduction 42mm → the sixth pass, width 297mm, height 315mm, reduction 40mm → the seventh pass, width 307mm, height 280mm, reduction 35mm → the eighth pass, width 317mm, height 246mm, reduction 34mm → turning over the steel → the ninth pass, width 271mm, height 235mm, reduction 82mm, passing through 3 rolling mills with a diameter of 850mm and 1 rolling mill with a diameter of 735mm, and then entering the continuous rolling mill group for rolling.

[0096] Continuous rolling process: rolling 11 passes, the first pass, height 229mm, width 245mm; the second pass, height 192mm, width 235mm; the third pass, height 200mm, width 195mm; the fourth pass, height 160mm, width 214.7mm; the fifth pass, height 165mm, width 174.6mm; the sixth pass, height 118mm, width 187mm; the seventh pass, height 135mm, width 132mm; the eighth pass, height 92mm, width 148mm; the ninth pass, height 110mm, width 115mm; the tenth pass, height 78mm, width 118.7mm; the eleventh pass, height 91mm, width 91mm; the finished steel material is discharged after 11 passes.

[0097] (7) Holding process

[0098] Holding process: the steel material is held, the temperature of the holding pit is 590℃, the holding time is 53h, and the temperature of the outlet is 140℃.

[0099] (8) Heat treatment process

[0100] The Φ25mm blank is subjected to heat treatment, and the heat treatment comprises the following steps:

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

[0102] 2) Tempering: 600℃, holding for 2.0h, water cooling.

[0103] Example 4:

[0104] 1. Chemical composition of ecological electric furnace steel bar for petroleum pipeline

[0105] The internal control chemical composition is determined as follows: 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%, and the balance is iron and inevitable impurities.

[0106] 2. Each production process of electric furnace continuous casting of ecological electric furnace steel bar for petroleum pipeline, comprising the following steps:

[0107] Process route: ecological electric furnace smelting + LF furnace refining + RH refining + continuous casting → annealing + heating process → rolling → heat preservation process → finishing → inspection → packaging and delivery to the warehouse → delivery.

[0108] (1) Ecological electric furnace smelting

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

[0110] (2) LF furnace refining

[0111] LF inlet temperature 1501℃, 35600A large current to heat and slag, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, active lime and silicon carbide are supplemented, the first sampling analysis is taken after 5min, the alloy is supplemented according to the target value of the chemical composition, and the coke particles are added for carbon addition to promote the rapid melting and homogenization of the alloy and carbon powder. When the temperature of the molten steel reaches 1602℃, 1.5kg / t of aluminum oxide balls are added for diffusion deoxidation, the furnace door is closed for 10min, and the second sampling analysis is taken when the temperature of the molten steel reaches 1590℃ to confirm the deviation of the chemical element content from the target value. After the second sampling, the molten steel is taken away when the temperature reaches 1604℃, and the LF smelting cycle is 40min. Supplementary alloy: ferrosilicon 1.18kg / t, high-carbon ferromanganese 0.6kg / t, high-carbon chromium iron 0.5kg / t. Supplementary auxiliary materials: aluminum oxide balls 1.4kg / t, active lime (particle size 35mm) 6.2Kg / t, silicon carbide (particle size 3mm) 2.1kg / t, coke particles 0.7kg / t.

[0112] (3) RH refining

[0113] The inlet temperature was 1585°C, the operation time was 35 min, argon was blown to control the argon pressure at 0.1 MPa before the vacuum pump was started, the argon pressure was adjusted to 0.3 MPa when the vacuum degree reached 103 Pa, and the holding time was 11 min. After the argon blowing was finished, 0.6 kg / t of carbonized rice husk was added as a covering agent, and the outlet temperature was 1555°C.

[0114] (4) Continuous casting

[0115] The ladle inlet temperature was 1550°C, the molten steel amount was 112 t, the H content in the tundish was controlled at 1.5 ppm, the casting time was 42 min, the whole process was protected casting, and a medium carbon steel powder was used as a mold powder.

[0116] (5) Heating process

[0117] The heating process was as follows: the inlet temperature of the heating furnace was 520°C, the preheating temperature was required to be 690°C, the time was 1.3 h, the temperature of the second heating stage was required to be 860°C, the time was 1.3 h, the temperature of the first heating stage was required to be 1210°C, the time was 1.3 h, the soaking temperature was required to be 1200°C, the time was 1.5 h, and the outlet temperature was 1190°C.

[0118] (6) Rolling process

[0119] The rough rolling process was as follows: 9 passes were rolled, the steel was turned over, the first pass was 408 mm wide and 421 mm high with a reduction of 65 mm, the second pass was 426 mm wide and 351 mm high with a reduction of 70 mm, the steel was turned over, the third pass was 370 mm wide and 362 mm high with a reduction of 64 mm, the fourth pass was 397 mm wide and 272 mm high with a reduction of 90 mm, the steel was turned over, the fifth pass was 285 mm wide and 355 mm high with a reduction of 42 mm, the sixth pass was 297 mm wide and 315 mm high with a reduction of 40 mm, the seventh pass was 307 mm wide and 280 mm high with a reduction of 35 mm, the eighth pass was 317 mm wide and 246 mm high with a reduction of 34 mm, the steel was turned over, the ninth pass was 271 mm wide and 235 mm high with a reduction of 82 mm, and the steel was rolled through 3 850 mm rolling mills, 1 735 mm rolling mill, and then entered a continuous rolling mill group.

[0120] Continuous rolling process: 11 passes, 1st pass height 229mm, width 245mm; 2nd pass height 192mm, width 235mm; 3rd pass height 200mm, width 195mm; 4th pass height 160mm, width 214.7mm; 5th pass height 165mm, width 174.6mm; 6th pass height 118mm, width 187mm; 7th pass height 135mm, width 132mm; 8th pass height 92m, width 148mm; 9th pass height 110mm, width 115mm; 10th pass height 78mm, width 118.7mm; 11th pass height 91mm, width 91mm; finished steel product after 11 passes.

[0121] (7) Holding process

[0122] Holding process: steel holding, holding pit temperature 600℃, holding 53h, pit temperature 140℃.

[0123] (8) Heat treatment process

[0124] Φ25mm blank is taken for heat treatment, which comprises the following steps:

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

[0126] 2) Tempering: 600℃, holding 2.0h, water cooling.

[0127] Example 5:

[0128] 1. Ecological electric furnace steel bar for petroleum pipeline

[0129] The internal control chemical composition is determined as follows: 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%, and the balance is iron and inevitable impurities.

[0130] 2. Each production process of ecological electric furnace steel bar for petroleum pipeline electric furnace continuous casting, comprising the following steps:

[0131] Process route: ecological electric furnace smelting + LF furnace refining + RH refining + continuous casting → annealing + heating process → rolling → holding process → finishing → inspection → packaging and delivery to the warehouse → delivery.

[0132] (1) Ecological electric furnace smelting

[0133] 100% all scrap smelting, heavy scrap 90%, bale type scrap 10%; tapping temperature 1614°C, C 0.11wt% and P 0.008wt% at tapping, auxiliary materials and alloys are added at 1 / 4 tapping, smelting cycle 50min. Alloy addition per ton of steel: ferrosilicon 12Kg / t, silicon manganese 4.1Kg / t, high carbon ferrochrome 25Kg / t, aluminum wire segment (diameter 12mm) 1.0Kg / t. Auxiliary material addition per ton of steel: active lime (particle size 35mm) 40Kg / t, dolomite (particle size 40mm) 20Kg / t, ladle powder 6Kg / t.

[0134] (2) LF furnace refining

[0135] LF inlet temperature 1501°C, 35600A large current temperature rising slag, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, active lime and silicon carbide are supplemented, the first sampling analysis of chemical composition is taken after 5min, the alloy is supplemented according to the target value of the chemical composition, and coke particles are added for recarburization, so as to promote the rapid melting and homogenization of the alloy and carbon powder. When the temperature of the molten steel reaches 1604°C, 1.5kg / t of diffusion deoxidizer alumina balls are added for diffusion deoxidation, the furnace door is closed for 10min, and when the temperature of the molten steel reaches 1585°C, the second sampling analysis of chemical composition is taken to confirm the deviation of the content of each chemical element composition from the target value. After the second sampling, when the temperature of the molten steel reaches 1604°C, the LF refining cycle is 40min, and the alloy is supplemented: ferrosilicon 1.20kg / t, high carbon ferromanganese 0.6kg / t, high carbon ferrochrome 0.5kg / t. The auxiliary materials are supplemented: alumina balls 1.5kg / t, active lime (particle size 35mm) 6.2Kg / t, silicon carbide (particle size 3mm) 2.1kg / t, coke particles 0.8kg / t.

[0136] (3) RH refining

[0137] Inlet temperature 1585°C, operation time 35min, argon is blown statically to control the argon pressure at 0.1MPa before the vacuum pump is started, the slag surface is slightly moved and the molten steel is not exposed, the timing is started when the vacuum degree reaches 105Pa, the holding time is 12min, and at the same time, the argon pressure is adjusted to 0.3MPa. After the static argon blowing is finished, 0.6kg / t of covering agent carbonized rice husk is added, and the outlet temperature is 1555°C.

[0138] (4) Continuous casting

[0139] Ladle arrival temperature 1550°C, molten steel quantity 112t, H control in tundish 1.5ppm, casting time 42min, full process protection casting, mold protection slag medium carbon steel protection slag is used.

[0140] (5) Heating process

[0141] Heating process: the temperature of the inlet of the heating furnace is 510℃, the temperature of the preheating section is required to be 690℃, the time is 1.3h; the temperature of heating section 2 is required to be 860℃, the time is 1.4h; the temperature of heating section 1 is required to be 1210℃, the time is 1.4h; the temperature of the soaking section is required to be 1200℃, the time is 1.3h; the temperature of the outlet is 1190℃.

[0142] (6) Rolling process

[0143] Primary rolling process: 9 passes, turn over the steel→the first pass, width 408mm, height 421mm, reduction 65mm→the second pass, width 426mm, height 351mm, reduction 70mm→turn over the steel→the third pass, width 370mm, height 362mm, reduction 64mm→the fourth pass, width 397mm, height 272mm, reduction 90mm→turn over the steel→the fifth pass, width 285mm, height 355mm, reduction 42mm→the sixth pass, width 297mm, height 315mm, reduction 40mm→the seventh pass, width 307mm, height 280mm, reduction 35mm→the eighth pass, width 317mm, height 246mm, reduction 34mm→turn over the steel→the ninth pass, width 271mm, height 235mm, reduction 82mm, pass through 3 850mm rolling mills, 1 735mm rolling mill, and then enter the continuous rolling mill group.

[0144] Continuous rolling process: 11 passes, the first pass, height 229mm, width 245mm; the second pass, height 192mm, width 235mm; the third pass, height 200mm, width 195mm; the fourth pass, height 160mm, width 214.7mm; the fifth pass, height 165mm, width 174.6mm; the sixth pass, height 118mm, width 187mm; the seventh pass, height 135mm, width 132mm; the eighth pass, height 92mm, width 148mm; the ninth pass, height 110mm, width 115mm; the tenth pass, height 78mm, width 118.7mm; the eleventh pass, height 91mm, width 91mm; after 11 passes, the finished steel is discharged.

[0145] (7) Holding process

[0146] Holding process: the steel is held, the temperature of the holding pit is 590℃, the holding time is 53h, and the temperature of the outlet is 130℃.

[0147] (8) Heat treatment process

[0148] A Φ25mm blank is taken for heat treatment, and the heat treatment comprises the following steps:

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

[0150] 2) Tempering: 600℃, holding for 2.0h, water cooling.

[0151] Results of finished product inspection of Examples 1 to 5, 2 samples per heat of steel were inspected

[0152] (1) Low magnification structure of Φ90 mm size (finished steel obtained by holding process)

[0153] (2) Non-metallic inclusions of Φ90 mm size (finished steel obtained by holding process)

[0154] (3) Mechanical properties of Φ90 mm size (Φ25 mm samples after heat treatment were tested)

Claims

1. An ecological electrically-arc-furnace steel rod for oil pipelines, characterized in that it comprises, in weight percent: : 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%, the balance is iron and inevitable impurities.

2. A method for producing the ecological electrically-arc-furnace steel bar for oil pipelines according to claim 1, characterized in that, It comprises 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 is: 100% full scrap smelting, wherein, heavy scrap accounts for 85~95%, bale scrap accounts for 5-15%, tapping temperature is 1610~1620℃, C is 0.10~0.15wt% at tapping, auxiliary materials and alloys are added when tapping 1 / 4~1 / 3, smelting period is 45~55min; The LF furnace refining is: The LF inlet temperature is 1495~1505℃, 35000~36000A large current is used to heat and slag, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, active lime and silicon carbide are supplemented, the first sampling analysis of chemical composition is carried out after 5~6min, the alloy is supplemented according to the target value of chemical composition, and coke particles are added for recarburization, so as to promote the rapid melting and homogenization of the alloy and carbon powder; when the molten steel temperature reaches 1600~1610℃, 1.5~1.6kg / t of diffusion deoxidizer alumina balls are added for diffusion deoxidization, the furnace door is closed for 10~13min, when the molten steel temperature reaches 1580~1600℃, the second sampling analysis of chemical composition is carried out to confirm the deviation of the content of each chemical element from the target value, after the second sampling, when the molten steel temperature reaches 1600~1610℃, the LF refining is finished, and the LF smelting period is 35min~45min; The RH refining is: The inlet temperature is 1580~1590℃, the operation time is 30min~40min, argon is blown statically to control the argon pressure to be 0.1~0.3MPa before the vacuum pump is started, the slag surface is slightly moved and the molten steel is not exposed, when the vacuum degree reaches 100~110Pa, the timing is started, the holding time is 10~15min, at the same time, the argon pressure is adjusted to be 0.3~0.5MPa, after the static argon blowing is finished, 0.6~0.7kg / t of covering agent carbonized rice husk is added, and the outlet temperature is 1550~1560℃.

3. The method of claim 2, wherein, In the ecological electric furnace smelting, the alloy addition amount per ton of steel is: ferrosilicon 12~12.2Kg / t, silicon manganese 4.1~4.2Kg / t, high-carbon chromium iron 25~25.5Kg / t, and aluminum wire segment 1.0~1.2Kg / t; the auxiliary material addition amount per ton of steel is: active lime 40~41Kg / t, dolomite 20~21Kg / t, and ladle ash 6~6.2Kg / t.

4. The method of claim 2, wherein, The LF furnace refining, the supplementary alloy amount is: silicon iron 1.15-1.25 kg / t, high-carbon ferromanganese 0.6-0.7 kg / t, high-carbon ferrochrome 0.5-0.6 kg / t; the diffusion deoxidizer alumina ball addition amount is 1.4-1.6 kg / t, active lime 6-6.5 Kg / t, silicon carbide 2.1-2.2 kg / t, coke particles 0.7-0.9 kg / t.

5. The method of claim 2, wherein, The continuous casting is: ladle to station temperature 1545-1555 DEG C, molten steel amount 110-115 t, tundish H control <= 2 ppm, casting time 40-45 min, whole process protective casting, crystallizer protective slag uses medium carbon steel protective slag.

6. The method of claim 2, wherein, The time sequence heating process is: entering heating furnace temperature 480-550 DEG C, preheating section temperature requirement 680-700 DEG C, time 1.3-1.5 h; heating 2 section temperature requirement 850-870 DEG C, time 1.3-1.5 h; heating 1 section temperature requirement 1200-1220 DEG C, time 1.3-1.5 h; soaking section temperature requirement 1190-1210 DEG C, time 1.3-1.5 h; steel tapping temperature 1185-1195 DEG C.

7. The method of claim 2, wherein, The rolling includes a rough rolling process and a continuous rolling process; The rough rolling process is: rolling 9 passes, turning over steel -> 1st pass wide 408-408.02 mm, high 421-421.02 mm, reduction 65-65.02 mm -> 2nd pass wide 426-426.02 mm, high 351-351.02 mm, reduction 70-70.02 mm -> turning over steel -> 3rd pass wide 370-370.02 mm, high 362-362.02 mm, reduction 64-64.02 mm -> 4th pass wide 397-397.02 mm, high 272-272.02 mm, reduction 90-90.02 mm -> turning over steel -> 5th pass wide 285-285.02 mm, high 355-355.02 mm, reduction 42-42.02 mm -> 6th pass wide 297-297.02 mm, high 315-315.02 mm, reduction 40-40.02 mm -> 7th pass wide 307-307.02 mm, high 280-280.02 mm, reduction 35-35.02 mm -> 8th pass wide 317-317.02 mm, high 246-246.02 mm, reduction 34-34.02 mm -> turning over steel -> 9th pass wide 271-271.02 mm, high 235-235.02 mm, reduction 82-82.02 mm, passing through 3 850 mm rolling mills, 1 735 mm rolling mill, and then entering a continuous rolling mill group for rolling.

8. The method of claim 7, wherein, The continuous rolling process is as follows: 11 passes, the first pass is 229-229.02 mm high and 245-245.02 mm wide; the second pass is 192-192.02 mm high and 235-235.02 mm wide; the third pass is 200-200.02 mm high and 195-195.02 mm wide; the fourth pass is 160-160.02 mm high and 214.7-214.72 mm wide; the fifth pass is 165-165.02 mm high and 174.6-174.62 mm wide; the sixth pass is 118-118.02 mm high and 187-187.02 mm wide; the seventh pass is 135-135.02 mm high and 132-132.02 mm wide; the eighth pass is 92-92.02 mm high and 148-148.02 mm wide; the ninth pass is 110-110.02 mm high and 115-115.02 mm wide; the tenth pass is 78-78.02 mm high and 118.7-118.72 mm wide; the eleventh pass is 91-91.02 mm high and 91-91.02 mm wide; and the finished steel is discharged after the 11 passes.

9. The method of claim 2, wherein, The heat preservation process is as follows: the steel is preserved at a temperature of 580 DEG C or above in a lower heat preservation pit for 52-55 hours, and the discharged temperature is 150 DEG C or below.

10. The method of claim 2, wherein, The steel sample after the heat preservation process is subjected to heat treatment, which comprises the following steps: 1) quenching at 880-920 DEG C for 0.8-1.2 hours and oil cooling; 2) tempering at 580-620 DEG C for 1.8-2.2 hours and water cooling.

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