Alloy structural steel bar production process adopting ecological electric furnace for smelting

Abstract

The invention relates to a production process of an alloy structural steel bar smelted by an ecological electric furnace. The alloy structural steel bar comprises the following chemical components: 0.39%-0.44% of C, 0.17%-0.37% of Si, 0.50%-0.80% of Mn, less than or equal to 0.020% of P, less than or equal to 0.020% of S, 0.90%-1.20% of Cr, less than or equal to 0.30% of Ni, 0.15%-0.25% of Mo, 0.02%-0.03% of Nb, 0.05%-0.10% of V, less than or equal to 0.20% of Cu and the balance of Fe and impurities. The production process route comprises ecological electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling, heat preservation and heat treatment. The smelting process flow of ecological electric furnace smelting, LF refining and RH refining is adopted, the high steel purity index is achieved, and the alloy structural steel bar has the excellent comprehensive mechanical property and meanwhile has the high surface quality level.

Description

Technical Field

[0001] This invention relates to the field of bar production technology, and in particular to a process for producing alloy structural steel bars using an eco-friendly electric furnace. Background Technology

[0002] Alloy structural steel bars are used to manufacture mechanical parts and various engineering components. Alloy structural steel is made by intentionally adding one or more alloying elements (such as silicon, manganese, chromium, nickel, molybdenum, vanadium, titanium, boron, etc.) to high-quality carbon structural steel, resulting in superior comprehensive mechanical properties such as strength, hardness, toughness, wear resistance, and hardenability. Through heat treatment processes such as quenching and tempering (tempering and quenching), its strength, hardness, and toughness can be precisely adjusted according to its final application.

[0003] Commonly used grades of alloy structural steel include 20CrMnTi, 40Cr, 42CrMo, 35CrMo, and 38CrMoAl. Conventional production processes include smelting and refining, casting, hot working (hot rolling or forging), and heat treatment. Smelting is usually carried out in an electric arc furnace or converter, and the chemical composition and purity are precisely controlled through ladle refining (such as LF furnace or VD furnace).

[0004] Eco-friendly electric arc furnace smelting is one of the core paths for the green transformation of the modern steel industry. It integrates the most advanced smelting technology, environmental protection technology, information technology and circular economy concept. It represents the transformation of the steel industry from the past linear model of "resource-product-waste" to the circular model of "resource-product-recycled resources". It achieves the ultimate reduction of energy consumption, emission reduction and efficiency improvement in the smelting process, while realizing harmonious coexistence with the environment and society.

[0005] This invention utilizes an eco-friendly electric furnace with a short process flow to produce alloy structural steel bars. It features low cost, excellent mechanical properties, and high steel purity, meeting the requirements of high-end products and achieving a breakthrough in the mass production of alloy structural steel bars using an eco-friendly electric furnace continuous casting process. Summary of the Invention

[0006] This invention provides a production process for alloy structural steel bars using an eco-friendly electric furnace. The smelting process, which combines eco-friendly electric furnace smelting with LF refining and RH refining, achieves high steel purity. The resulting alloy structural steel bars possess both excellent comprehensive mechanical properties and a high level of surface quality.

[0007] To achieve the above objectives, the present invention employs the following technical solution: A production process for alloy structural steel bars using an eco-friendly electric furnace smelting method is disclosed. The chemical composition of the alloy structural steel bars, by mass percentage, is: C: 0.39%–0.44%, Si: 0.17%–0.37%, Mn: 0.50%–0.80%, P≤0.020%, S≤0.020%, Cr: 0.90%–1.20%, Ni≤0.30%, Mo: 0.15%–0.25%, Nb: 0.02%–0.03%, V: 0.05%–0.10%, Cu≤0.20%, with the remainder being Fe and unavoidable impurities. The production process for the alloy structural steel bars includes eco-friendly electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling, heat preservation, and heat treatment.

[0008] A process for producing alloy structural steel bars using an eco-friendly electric furnace is described below: (1) Ecological electric furnace smelting: The process employs 100% scrap steel smelting, with a tapping temperature of 1615–1625℃, a smelting cycle of 70–80 minutes, and a furnace oxygen consumption of 27–28 m³ / min. 3 / t steel; Alloy addition: silicon-manganese alloy 7.4~7.5kg / t steel, high-carbon ferrochrome 13~14kg / t steel, aluminum ingot for remelting 0.9~1.1kg / t steel; Auxiliary material addition: steel ladle ash 5.8~6.0kg / t steel, quicklime 31~32kg / t steel, magnesite 5.8~6.0kg / t steel; (2) LF furnace refining: The LF inlet temperature is 1525-1535℃. The first sample is taken for chemical composition analysis 5-6 minutes after electrode heating. When the molten steel temperature reaches 1580-1600℃, a slag conditioner is added to adjust the slag basicity. A second sample is taken for chemical composition analysis when the molten steel temperature reaches 1610-1615℃. The molten steel leaves the station when the temperature reaches 1620-1630℃. The LF smelting cycle is 80-100 minutes, with a clearance of 380-400 mm. When the molten steel temperature reaches 1610-1615℃, alloys are added, including: ferrosilicon 0.25-0.3 kg / t steel, silicon-manganese alloy 0.5-0.6 kg / t steel, high-carbon ferrochrome 1.2-1.3 kg / t steel, ferromolybdenum 2-2.1 kg / t steel, ferroniobium 0.37-0.4 kg / t steel, and ferrovanadium 0.7-0.9 kg / t steel. (3) RH refining: The RH inlet temperature is 1620–1625℃, and the refining time is 45–50 min. Before starting the vacuum pump, the argon pressure is controlled at 0.1–0.3 MPa. When the vacuum degree reaches 100–110 Pa, the timing starts and is maintained for 30–35 min, while the argon pressure is adjusted to 0.3–0.5 MPa. The repressurization temperature is 1600–1605℃. After static argon blowing, add 0.75–0.8 kg / t steel of covering agent. The clearance is controlled at 390–400 mm. The outlet temperature is 1570–1580℃. After breaking the vacuum, add 0.8–0.81 kg / t steel of silicon-calcium alloy cored wire. (4) Continuous casting: The ladle temperature upon arrival is 1570–1580℃, the hydrogen content in the tundish is controlled to be ≤2ppm, the casting time is 45–50 min, the superheat is controlled to be 20–25℃, and the casting speed is 0.43–0.44 m / min; the entire process is protected during casting, and medium carbon steel protective slag is used in the crystallizer, with an addition amount of 2.2–2.3 kg / t steel; (5) Heating: The billet temperature entering the heating furnace is 620–650℃; the preheating zone temperature is 780–800℃, and the heating time is 1.4–1.6 hours; the second heating zone temperature is 850–870℃, and the heating time is 1.2–1.5 hours; the first heating zone temperature is 1210–1230℃, and the heating time is 1.4–1.6 hours; the soaking zone temperature is 1210–1220℃, and the heating time is 1.0–1.2 hours; the furnace exit temperature is 1180–1200℃. (6) Rolling: The initial rolling process involves at least 9 passes, followed by at least 6 passes on a continuous rolling mill. (7) Insulation: The temperature of rolled steel entering the insulation pit is ≥600℃, and it is kept in the insulation pit for 55~60h. The temperature of steel leaving the pit is ≤120℃. (8) Heat treatment: 1) Quenching temperature is 840~860℃, holding time is 0.5~0.8h, and oil cooling is performed to room temperature; 2) The tempering temperature is 550-570℃, the holding time is 1.5-1.8h, and then the water is cooled to room temperature.

[0009] In the process of ecological electric furnace smelting, the scrap steel includes 60% to 68% heavy scrap steel by weight, and the rest is light scrap steel.

[0010] In the ecological electric furnace smelting process, the grade of aluminum ingots used for remelting is Al99.00b, with an Al mass percentage content ≥99.00%; the particle size of the active lime is 10-70mm; and the particle size of the magnesite is 10-60mm.

[0011] During the LF furnace refining process, alumina balls are used as the slag conditioner, with an addition amount of 1.4 to 1.5 kg / t steel; the grade of ferrovanadium is FeV50-B.

[0012] During the RH refining process, the diameter of the silicon-calcium alloy cored wire is ø14~ø15mm.

[0013] The nominal dimension of the finished alloy structural steel bar is ø180mm. During the rolling process, the specific process parameters for the six consecutive rolling passes are as follows: For the first pass, the workpiece height is 229–229.01mm, the width is 245–245.01mm, and the rolling speed is 0.27–0.272m / s; for the second pass, the workpiece height is 192–192.01mm, the width is 235–235.01mm, and the rolling speed is 0.31–0.312m / s; for the third pass, the workpiece height is 200–200.01mm, the width is 195–195.01mm, and the rolling speed is 0.35–0.312m / s. The rolling speed is 0.352 m / s; during the 4th pass, the workpiece height is 173–173.01 mm, the width is 205–205.01 mm, and the rolling speed is 0.412–0.414 m / s; during the 5th pass, the workpiece height is 182.41–182.42 mm, the width is 182.41–182.42 mm, and the rolling speed is 0.530–0.532 m / s; during the 6th pass, the workpiece height is 182.41–182.42 mm, the width is 182.41–182.42 mm, and the rolling speed is 0.536–0.538 m / s; the 6th pass rolls the workpiece to the finished product specifications.

[0014] The finished properties of alloy structural steel bars are: tensile strength ≥1185MPa, yield strength ≥1010MPa, elongation ≥14%, reduction of area ≥45%, and impact energy KU2 ≥65J.

[0015] Compared with the prior art, the beneficial effects of the present invention are: (1) The smelting process of ecological electric furnace smelting + LF refining + RH refining was adopted to achieve the high steel purity index. (2) Through reasonable composition design and matching production process, the alloy structural steel bars produced are guaranteed to have both excellent comprehensive mechanical properties and high surface quality.

[0016] (3) The low magnification structure and non-metallic inclusions of the finished steel products meet the requirements of high-end products. Detailed Implementation

[0017] The present invention describes a production process for alloy structural steel bars smelted in an eco-friendly electric furnace. The chemical composition of the alloy structural steel bars, by mass percentage, is: C: 0.39%–0.44%, Si: 0.17%–0.37%, Mn: 0.50%–0.80%, P≤0.020%, S≤0.020%, Cr: 0.90%–1.20%, Ni≤0.30%, Mo: 0.15%–0.25%, Nb: 0.02%–0.03%, V: 0.05%–0.10%, Cu≤0.20%, with the remainder being Fe and unavoidable impurities. The production process of the alloy structural steel bars includes eco-friendly electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling, heat preservation, and heat treatment.

[0018] A process for producing alloy structural steel bars using an eco-friendly electric furnace is described below: (1) Ecological electric furnace smelting: The process employs 100% scrap steel smelting, with heavy scrap accounting for 60%–68% by weight, and the remainder being light scrap. The tapping temperature is 1615–1625℃, the smelting cycle is 70–80 minutes, and the furnace oxygen consumption is 27–28 m³ / min. 3 / t steel; Alloy addition: silicon-manganese alloy 7.4~7.5kg / t steel, high-carbon ferrochrome 13~14kg / t steel, aluminum ingot for remelting (preferred grade Al99.00b, Al mass percentage content ≥99.00%) 0.9~1.1kg / t steel; Auxiliary material addition: steel ladle ash 5.8~6.0kg / t steel, active lime (particle size 10~70mm) 31~32kg / t steel, magnesite (particle size 10~60mm) 5.8~6.0kg / t steel; (2) LF furnace refining: The LF inlet temperature is 1525–1535℃. The first sample is taken for chemical composition analysis 5–6 minutes after electrode heating. When the molten steel temperature reaches 1580–1600℃, a slag conditioner (preferably alumina balls, added at a rate of 1.4–1.5 kg / t steel) is added to adjust the slag basicity. The furnace door is closed for 10–11 minutes. When the molten steel temperature reaches 1610–1615℃, 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 removed, when the molten steel temperature reaches… When the temperature of the molten steel is 1620-1630℃, the LF smelting cycle is 80-100 minutes, and the clearance is 380-400 mm. When the temperature of the molten steel is 1610-1615℃, alloys are added, including: ferrosilicon 0.25-0.3 kg / t steel, silicon-manganese alloy 0.5-0.6 kg / t steel, high-carbon ferrochrome 1.2-1.3 kg / t steel, ferromolybdenum 2-2.1 kg / t steel, ferroniobium 0.37-0.4 kg / t steel, and ferrovanadium (preferred grade is FeV50-B) 0.7-0.9 kg / t steel. (3) RH refining: The RH inlet temperature is 1620–1625℃, and the refining time is 45–50 min. Before starting the vacuum pump, the argon pressure is controlled at 0.1–0.3 MPa to prevent the molten steel from being exposed due to slight movement of the slag surface. When the vacuum degree reaches 100–110 Pa, the timing begins and is maintained for 30–35 min, while the argon pressure is adjusted to 0.3–0.5 MPa. The repressurization temperature is 1600–1605℃. After the static argon blowing is completed, a covering agent of 0.75–0.8 kg / t steel is added. The net clearance is controlled at 390–400 mm. The outlet temperature is 1570–1580℃. After the vacuum is broken, a silicon-calcium alloy cored wire (preferably with a diameter of ø14–ø15 mm) of 0.8–0.81 kg / t steel is added. (4) Continuous casting: The ladle temperature upon arrival is 1570–1580℃, the hydrogen content in the tundish is controlled to be ≤2ppm, the casting time is 45–50 min, the superheat is controlled to be 20–25℃, and the casting speed is 0.43–0.44 m / min; the entire process is protected during casting, and medium carbon steel protective slag is used in the crystallizer, with an addition amount of 2.2–2.3 kg / t steel; (5) Heating: The billet temperature entering the heating furnace is 620–650℃; the preheating zone temperature is 780–800℃, and the heating time is 1.4–1.6 hours; the second heating zone temperature is 850–870℃, and the heating time is 1.2–1.5 hours; the first heating zone temperature is 1210–1230℃, and the heating time is 1.4–1.6 hours; the soaking zone temperature is 1210–1220℃, and the heating time is 1.0–1.2 hours; the furnace exit temperature is 1180–1200℃. (6) Rolling: The initial rolling process involves at least 9 passes, followed by at least 6 passes on a continuous rolling mill. Taking an alloy structural steel bar with a nominal finished size of ø180mm as an example, the specific process parameters for the six consecutive rolling passes are as follows: In the first pass, the workpiece height is 229–229.01mm, the width is 245–245.01mm, and the rolling speed is 0.27–0.272m / s; in the second pass, the workpiece height is 192–192.01mm, the width is 235–235.01mm, and the rolling speed is 0.31–0.312m / s; in the third pass, the workpiece height is 200–200.01mm, the width is 195–195.01mm, and the rolling speed is 0.35–… The rolling speed is 0.352 m / s; during the 4th pass, the workpiece height is 173–173.01 mm, the width is 205–205.01 mm, and the rolling speed is 0.412–0.414 m / s; during the 5th pass, the workpiece height is 182.41–182.42 mm, the width is 182.41–182.42 mm, and the rolling speed is 0.530–0.532 m / s; during the 6th pass, the workpiece height is 182.41–182.42 mm, the width is 182.41–182.42 mm, and the rolling speed is 0.536–0.538 m / s; the 6th pass rolls the workpiece to the finished product specifications.

[0019] (7) Insulation: The temperature of rolled steel entering the insulation pit is ≥600℃, and it is kept in the insulation pit for 55~60h. The temperature of steel leaving the pit is ≤120℃. (8) Heat treatment: 1) Quenching temperature is 840~860℃, holding time is 0.5~0.8h, and oil cooling is performed to room temperature; 2) The tempering temperature is 550-570℃, the holding time is 1.5-1.8h, and then the water is cooled to room temperature.

[0020] The finished properties of alloy structural steel bars are: tensile strength ≥1185MPa, yield strength ≥1010MPa, elongation ≥14%, reduction of area ≥45%, and impact energy KU2 ≥65J.

[0021] Microscopic inclusions in finished steel bars for metal structures shall be inspected according to GB / T10561 standard. Non-metallic inclusions shall meet the following requirements: Class A fine inclusions ≤ 2.0 grade, Class A coarse inclusions ≤ 2.0 grade; Class B fine inclusions ≤ 1.5 grade, Class B coarse inclusions ≤ 1.5 grade; Class C fine inclusions ≤ 1.5 grade, Class C coarse inclusions ≤ 1.5 grade; Class D fine inclusions ≤ 1.5 grade, Class D coarse inclusions ≤ 1.5 grade; Class DS ≤ 2.0 grade.

[0022] To more intuitively illustrate the present invention, the embodiments of the present invention will be further described in conjunction with the examples. The following examples are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention, including simple variations or equivalent substitutions, are all within the scope of protection of the present invention.

[0023]

Example 1

[0024] The production process of alloy structural steel bars includes ecological electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling, heat preservation and heat treatment. The specific process is as follows: (1) Ecological electric furnace smelting: The process employs 100% scrap steel smelting, with heavy scrap steel accounting for 63% by weight and the remainder being light scrap steel; the tapping temperature is 1619℃, the smelting cycle is 75 minutes, and the furnace oxygen consumption is 27m³. 3 / t steel. Alloy additions: 7.5kg / t steel for silicon-manganese alloy, 14kg / t steel for high-carbon ferrochrome, 0.95kg / t steel for remelting aluminum ingots (Al99.00b). Auxiliary material additions: 6.0kg / t steel for steel ladle ash, 32kg / t steel for active lime (35mm particle size), 6.0kg / t steel for magnesite (30mm particle size).

[0025] (2) LF furnace refining: The LF furnace temperature is 1529℃. The first sample is taken for chemical composition analysis 6 minutes after electrode heating. When the molten steel temperature reaches 1590℃, 1.5 kg / t of slag adjuster (alumina balls) is added to adjust the slag basicity. The furnace door is closed for 11 minutes. When the molten steel temperature reaches 1612℃, 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 1625℃. The LF smelting cycle is 90 minutes, with a clearance of 390 mm. At 1612℃, alloys are added, including: 0.28 kg / t ferrosilicon, 0.6 kg / t ferrosilicon-manganese alloy, 1.3 kg / t high-carbon ferrochrome, 2.1 kg / t ferromolybdenum, 0.38 kg / t ferroniobium, and 0.8 kg / t ferrovanadium (FeV50-B).

[0026] (3) RH refining: The inlet temperature was 1622℃, and the operation time was 47 minutes. Before starting the vacuum pump, the argon pressure was controlled at 0.1 MPa to prevent the molten steel from being exposed during slight slag movement. When the vacuum reached 105 Pa, the timer started and was maintained for 32 minutes. At the same time, the argon pressure was adjusted to 0.3 MPa, and the repressurization temperature was 1602℃. After the static argon blowing was completed, a covering agent of 0.77 kg / t steel was added, with a clearance of 395 mm. The outlet temperature was 1575℃. After breaking the vacuum, 0.8 kg / t steel of silicon-calcium alloy cored wire (diameter ø14 mm) was added.

[0027] (5) Continuous casting: The ladle temperature upon arrival is 1574℃, the H content in the tundish is controlled at 1.5ppm, the casting time is 48min, the superheat is 22℃, the casting speed is 0.43m / min, the entire casting process is protected, and medium carbon steel protective slag is used in the crystallizer, with an addition amount of 2.25kg / t steel.

[0028] (5) Heating: The billet enters the heating furnace at a temperature of 630℃, the preheating section at 785℃, and is heated for 1.5 hours; the second heating section at 862℃, is heated for 1.3 hours; the first heating section at 1223℃, is heated for 1.4 hours; the soaking section at 1215℃, is heated for 1.1 hours; and the tapping temperature is 1190℃.

[0029] (6) Rolling: In this embodiment, the nominal dimensions of the finished alloy structural steel bar are ø180mm. The initial rolling process involves 9 passes, followed by 6 passes on a continuous rolling mill. The first pass produces a piece with a height of 229mm and a width of 245.01mm at a rolling speed of 0.272m / s; the second pass produces a piece with a height of 192mm and a width of 235mm at a rolling speed of 0.31m / s; the third pass produces a piece with a height of 200.01mm and a width of 195.01mm at a rolling speed of 0.35m / s; the fourth pass produces a piece with a height of 173.01mm and a width of 205.01mm at a rolling speed of 0.414m / s; the fifth pass produces a piece with a height of 182.42mm and a width of 182.41mm at a rolling speed of 0.532m / s; and the sixth pass produces a piece with a height of 182.42mm and a width of 182.42mm at a rolling speed of 0.538m / s.

[0030] (7) Insulation: The temperature of the rolled steel entering the insulation pit is 610℃, and it is kept in the insulation pit for 57 hours. The temperature of the steel leaving the pit is 110℃.

[0031] (8) Heat treatment: 1) Quenching temperature 850℃, holding temperature for 0.6h, oil cooling to room temperature; 2) Tempering temperature 560℃, hold for 1.7h, then water cool to room temperature.

[0032] Two samples of alloy structural steel bars produced in this embodiment were tested. The results of the low-magnification microstructure test are shown in Table 1, the results of the non-metallic inclusion test are shown in Table 2, and the results of the mechanical property test are shown in Table 3.

[0033]

Example 2

[0034] The production process of alloy structural steel bars includes ecological electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling, heat preservation and heat treatment. The specific process is as follows: (1) Ecological electric furnace smelting: The process employs 100% scrap steel smelting, with heavy scrap steel comprising 65% by weight and the remainder being light scrap steel; the tapping temperature is 1618℃, the smelting cycle is 75 minutes, and the furnace oxygen consumption is 28m³. 3 / t steel. Alloy additions: 7.5kg / t steel for silicon-manganese alloy, 14kg / t steel for high-carbon ferrochrome, 0.96kg / t steel for remelting aluminum ingots (Al99.00b). Auxiliary material additions: 6.0kg / t steel for steel ladle ash, 31kg / t steel for active lime (35mm particle size), 6.0kg / t steel for magnesite (30mm particle size).

[0035] (2) LF furnace refining: The LF furnace temperature is 1528℃. The first sample is taken for chemical composition analysis 6 minutes after electrode heating. When the molten steel temperature reaches 1592℃, 1.5 kg / t of slag adjuster (alumina balls) is added to adjust the slag basicity. The furnace door is closed for 11 minutes. When the molten steel temperature reaches 1613℃, 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 1625℃. The LF smelting cycle is 90 minutes, with a clearance of 390 mm. At 1613℃, alloys are added, including: 0.28 kg / t ferrosilicon, 0.6 kg / t ferrosilicon-manganese alloy, 1.3 kg / t high-carbon ferrochrome, 2.1 kg / t ferromolybdenum, 0.38 kg / t ferroniobium, and 0.8 kg / t ferrovanadium (FeV50-B).

[0036] (3) RH refining: The inlet temperature was 1623℃, and the operation time was 48 minutes. Before starting the vacuum pump, the argon pressure was controlled at 0.3 MPa to prevent the molten steel from being exposed during slight slag movement. When the vacuum reached 104 Pa, the timer started and was maintained for 31 minutes. At the same time, the argon pressure was adjusted to 0.4 MPa, and the repressurization temperature was 1603℃. After the static argon blowing was completed, a covering agent of 0.78 kg / t steel was added, with a clearance of 395 mm. The outlet temperature was 1575℃. After breaking the vacuum, 0.8 kg / t steel of silicon-calcium alloy cored wire (diameter ø15 mm) was added.

[0037] (5) Continuous casting: The ladle temperature upon arrival is 1575℃, the H content in the tundish is controlled at 1.3ppm, the casting time is 48min, the superheat is 22℃, the casting speed is 0.43m / min, the entire casting process is protected, and medium carbon steel protective slag is used in the crystallizer, with an addition amount of 2.3kg / t steel.

[0038] (5) Heating: The billet enters the heating furnace at a temperature of 630℃, the preheating section at 785℃, and is heated for 1.6 hours; the second heating section at 857℃, is heated for 1.3 hours; the first heating section at 1227℃, is heated for 1.6 hours; the soaking section at 1217℃, is heated for 1.2 hours; and the tapping temperature is 1188℃.

[0039] (6) Rolling: In this embodiment, the nominal dimensions of the finished alloy structural steel bar are ø180mm. It undergoes 9 passes of initial rolling, followed by 6 passes on a continuous rolling mill. The first pass produces a piece with a height of 229mm and a width of 245mm at a rolling speed of 0.27m / s; the second pass produces a piece with a height of 192.01mm and a width of 235.01mm at a rolling speed of 0.312m / s; the third pass produces a piece with a height of 200.01mm and a width of 195.01mm at a rolling speed of 0.352m / s; the fourth pass produces a piece with a height of 173.01mm and a width of 205mm at a rolling speed of 0.414m / s; the fifth pass produces a piece with a height of 182.42mm and a width of 182.42mm at a rolling speed of 0.532m / s; and the sixth pass produces a piece with a height of 182.42mm and a width of 182.41mm at a rolling speed of 0.538m / s.

[0040] (7) Insulation: The temperature of the rolled steel entering the insulation pit is 610℃, and it is kept in the insulation pit for 57 hours. The temperature of the steel leaving the pit is 90℃.

[0041] (8) Heat treatment: 1) Quenching temperature 850℃, holding temperature 0.7h, oil cooling to room temperature; 2) Tempering temperature 560℃, hold for 1.6h, then water cool to room temperature.

[0042] Two samples of alloy structural steel bars produced in this embodiment were tested. The results of the low-magnification microstructure test are shown in Table 1, the results of the non-metallic inclusion test are shown in Table 2, and the results of the mechanical property test are shown in Table 3.

[0043]

Example 3

[0044] The production process of alloy structural steel bars includes ecological electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling, heat preservation and heat treatment. The specific process is as follows: (1) Ecological electric furnace smelting: The process employs 100% scrap steel smelting, with heavy scrap steel accounting for 64% by weight and the remainder being light scrap steel; the tapping temperature is 1618℃, the smelting cycle is 79 minutes, and the furnace oxygen consumption is 28m³. 3 / t steel. Alloy additions: 7.5kg / t steel for silicon-manganese alloy, 14kg / t steel for high-carbon ferrochrome, 0.96kg / t steel for remelting aluminum ingots (Al99.00b). Auxiliary material additions: 6.0kg / t steel for steel ladle ash, 32kg / t steel for active lime (35mm particle size), 5.9kg / t steel for magnesite (30mm particle size).

[0045] (2) LF furnace refining: The LF furnace temperature is 1530℃. A first sample is taken for chemical composition analysis 5 minutes after electrode heating. When the molten steel temperature reaches 1593℃, 1.5 kg / t of slag adjuster (alumina balls) is added to adjust the slag basicity. The furnace door is closed for 11 minutes. When the molten steel temperature reaches 1612℃, 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 1625℃. The LF smelting cycle is 90 minutes, with a clearance of 390 mm. At 1612℃, alloys are added, including: 0.26 kg / t ferrosilicon, 0.6 kg / t ferrosilicon-manganese alloy, 1.3 kg / t high-carbon ferrochrome, 2.1 kg / t ferromolybdenum, 0.38 kg / t ferroniobium, and 0.8 kg / t ferrovanadium (FeV50-B).

[0046] (3) RH refining: The inlet temperature was 1623℃, and the operation time was 47 minutes. Before starting the vacuum pump, the argon pressure was controlled at 0.2 MPa to prevent the molten steel from being exposed during slight slag movement. Timing began when the vacuum reached 106 Pa and was maintained for 32 minutes. Simultaneously, the argon pressure was adjusted to 0.4 MPa, and the re-pressure temperature was 1602℃. After static argon blowing, a covering agent of 0.77 kg / t steel was added, with a clearance of 395 mm. The outlet temperature was 1575℃. After breaking the vacuum, 0.8 kg / t steel of silicon-calcium alloy cored wire (diameter ø15 mm) was added.

[0047] (5) Continuous casting: The ladle temperature upon arrival is 1574℃, the H content in the tundish is controlled at 1.6ppm, the casting time is 47min, the superheat is 23℃, the casting speed is 0.43m / min, the entire casting process is protected, and medium carbon steel protective slag is used in the crystallizer, with an addition amount of 2.2kg / t steel.

[0048] (5) Heating: The billet enters the heating furnace at a temperature of 630℃, the preheating section at 790℃, and is heated for 1.5 hours; the second heating section at 860℃, is heated for 1.4 hours; the first heating section at 1220℃, is heated for 1.5 hours; the soaking section at 1215℃, is heated for 1.2 hours; and the tapping temperature is 1195℃.

[0049] (6) Rolling: In this embodiment, the nominal dimensions of the finished alloy structural steel bar are ø180mm. The initial rolling process involves 9 passes, followed by 6 passes on a continuous rolling mill. The first pass produces a piece with a height of 229.01mm and a width of 245.01mm at a rolling speed of 0.27m / s; the second pass produces a piece with a height of 192mm and a width of 235mm at a rolling speed of 0.312m / s; the third pass produces a piece with a height of 200.01mm and a width of 195mm at a rolling speed of 0.35m / s; the fourth pass produces a piece with a height of 173.01mm and a width of 205.01mm at a rolling speed of 0.414m / s; the fifth pass produces a piece with a height of 182.42mm and a width of 182.42mm at a rolling speed of 0.532m / s; and the sixth pass produces a piece with a height of 182.42mm and a width of 182.41mm at a rolling speed of 0.536m / s.

[0050] (7) Insulation: The temperature of the rolled steel entering the insulation pit is 615℃, and it is kept in the insulation pit for 57 hours. The temperature of the steel leaving the pit is 100℃.

[0051] (8) Heat treatment: 1) Quenching temperature 850℃, holding temperature 0.7h, oil cooling to room temperature; 2) Tempering temperature 560℃, hold for 1.6h, then water cool to room temperature.

[0052] Two samples of alloy structural steel bars produced in this embodiment were tested. The results of the low-magnification microstructure test are shown in Table 1, the results of the non-metallic inclusion test are shown in Table 2, and the results of the mechanical property test are shown in Table 3.

[0053] Table 1. Results of low-magnification tissue examination Table 2. Inspection Results of Non-metallic Inclusions Table 3 Results of Mechanical Property Tests The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A process for producing alloy structural steel bar by smelting in an ecological electric furnace, characterized in that, The chemical composition of the alloy structural steel bar is C: 0.39%~0.44%, Si: 0.17%~0.37%, Mn: 0.50%~0.80%, P≤0.020%, S≤0.020%, Cr: 0.90%~1.20%, Ni≤0.30%, Mo: 0.15%~0.25%, Nb: 0.02%~0.03%, V: 0.05%~0.10%, Cu≤0.20%, and the rest is Fe and inevitable impurities; the production process route of the alloy structural steel bar comprises ecological electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling, heat preservation and heat treatment.

2. The process for producing alloy structural steel bar by ecological electric furnace smelting according to claim 1, characterized in that, The specific process is as follows: (1) ecological electric furnace smelting: The smelting process is 100% scrap steel, tapping temperature is 1615-1625℃, smelting cycle is 70-80min, oxygen consumption is 27-28m 3 / t steel; alloy addition: silicon manganese alloy 7.4-7.5kg / t steel, high-carbon chromium iron 13-14kg / t steel, aluminum ingot for remelting 0.9-1.1kg / t steel; auxiliary material addition: ladle ash 5.8-6.0kg / t steel, active lime 31-32kg / t steel, magnesite 5.8-6.0kg / t steel; (2) LF furnace refining: The LF inlet temperature is 1525~1535℃, and the first sampling analysis of chemical composition is carried out after the electrode is heated for 5~6min; when the temperature of the molten steel reaches 1580~1600℃, the slag modifier is added to adjust the basicity of the slag; when the temperature of the molten steel reaches 1610~1615℃, the second sampling analysis of chemical composition is carried out; when the temperature of the molten steel reaches 1620~1630℃, the LF smelting cycle is 80~100min, and the clearance is 380~400mm; when the temperature of the molten steel is 1610~1615℃, the alloy is supplemented, including: ferrosilicon 0.25~0.3kg / t steel, silicon manganese alloy 0.5~0.6kg / t steel, high-carbon chromium iron 1.2~1.3kg / t steel, molybdenum iron 2~2.1kg / t steel, niobium iron 0.37~0.4kg / t steel, and vanadium iron 0.7~0.9kg / t steel; (3) RH refining: The RH inlet temperature is 1620~1625℃, and the refining time is 45~50min; before the vacuum pump is started, the argon pressure is controlled at 0.1~0.3MPa, when the vacuum degree reaches 100~110Pa, the timing is started, and is maintained for 30~35min, while the argon pressure is adjusted to 0.3~0.5MPa; the re-pressing temperature is 1600~1605℃, the covering agent 0.75~0.8kg / t steel is added after the static argon blowing is finished; the clearance is controlled at 390~400mm; the outlet temperature is 1570~1580℃; after the vacuum is broken, the silicon-calcium alloy cored wire 0.8~0.81kg / t steel is added; (4) continuous casting: The ladle inlet temperature is 1570~1580℃, the tundish controls the H mass content≤2ppm, the pouring time is 45~50min, the superheat degree is controlled at 20~25℃, and the drawing speed is 0.43~0.44m / min; the whole process is protected casting, and the crystallizer protection slag uses medium-carbon steel protection slag, and the adding amount is 2.2~2.3kg / t steel; (5) heating: The temperature of the casting blank entering the heating furnace is 620-650℃, the temperature of the preheating section is 780-800℃, and the heating time is 1.4-1.6h; the temperature of the second heating section is 850-870℃, and the heating time is 1.2-1.5h; the temperature of the first heating section is 1210-1230℃, and the heating time is 1.4-1.6h; the temperature of the soaking section is 1210-1220℃, and the heating time is 1.0-1.2h; and the temperature of the exit of the furnace is 1180-1200℃; (6) Rolling: The initial rolling is at least 9 passes, and then the rolling enters the continuous rolling unit for at least 6 passes; (7) Heat preservation: The temperature of the rolled steel entering the heat preservation pit is ≥600℃, the heat preservation time in the heat preservation pit is 55-60h, and the temperature of the exit of the pit is ≤120℃; (8) Heat treatment: 1) The quenching temperature is 840-860℃, the holding time is 0.5-0.8h, and the oil cooling is to room temperature; 2) The tempering temperature is 550-570℃, the holding time is 1.5-1.8h, and the water cooling is to room temperature.

3. The process for producing alloy structural steel bar by ecological electric furnace smelting according to claim 2, characterized in that, In the ecological electric furnace smelting process, the scrap steel includes 60%-68% of heavy scrap steel by weight, and the rest is light scrap steel.

4. The process for producing alloy structural steel bar by ecological electric furnace smelting according to claim 2, characterized in that, In the ecological electric furnace smelting process, the remelting aluminum ingot is Al99.00b, and the mass percentage content of Al is ≥99.00%; the particle size of the active lime is 10-70mm; and the particle size of the magnesite is 10-60mm.

5. The process for producing alloy structural steel bar by ecological electric furnace smelting according to claim 2, characterized in that, In the LF furnace refining process, the slag adjusting agent is alumina ball, and the addition amount is 1.4-1.5kg / t of steel; the vanadium iron is FeV50-B.

6. The process for producing alloy structural steel bar by ecological electric furnace smelting according to claim 2, characterized in that, In the RH refining process, the diameter of the silicon-calcium alloy cored wire is ø14-ø15mm.

7. The process for producing alloy structural steel bar by ecological electric furnace smelting according to claim 2, characterized by the fact that, The nominal size of the finished alloy structural steel bar is ø180mm; in the rolling process, the specific process parameters of the continuous rolling of 6 passes are as follows: in the first pass, the rolling piece height is 229-229.01mm, the width is 245-245.01mm, and the rolling speed is 0.27-0.272m / s; in the second pass, the rolling piece height is 192-192.01mm, the width is 235-235.01mm, and the rolling speed is 0.31-0.312m / s; in the third pass, the rolling piece height is 200-200.01mm, the width is 195-195.01mm, and the rolling speed is 0.35-0.352m / s; in the fourth pass, the rolling piece height is 173-173.01mm, the width is 205-205.01mm, and the rolling speed is 0.412-0.414m / s; in the fifth pass, the rolling piece height is 182.41-182.42mm, the width is 182.41-182.42mm, and the rolling speed is 0.530-0.532m / s; in the sixth pass, the rolling piece height is 182.41-182.42mm, the width is 182.41-182.42mm, and the rolling speed is 0.536-0.538m / s; and the sixth pass is rolled to the finished product specification.

8. The process for producing alloy structural steel bar by ecological electric furnace smelting according to claim 1 or 2, characterized in that, The performance of the finished alloy structural steel bar is as follows: the tensile strength is ≥1185MPa, the yield strength is ≥1010MPa, the elongation is ≥14%, the reduction of area is ≥45%, and the impact energy KU2 is ≥65J.

Images