Method for producing industrial pure iron bar through ecological electric furnace process

Abstract

The invention relates to the technical field of industrial pure iron production, in particular to a method for producing an industrial pure iron bar through an ecological electric furnace process. The production process comprises the steps of ecological electric furnace smelting, LF refining, RH refining, square billet continuous casting, heating, rolling and cooling. The produced industrial pure iron bar finished product comprises the following chemical components: less than or equal to 0.004% of C, less than or equal to 0.010% of Si, less than or equal to 0.050% of Mn, less than or equal to 0.004% of P, less than or equal to 0.005% of S, less than or equal to 0.005% of Co, less than or equal to 0.005% of Mo, less than or equal to 0.012% of Cu, 0.005-0.020% of Alt, less than or equal to 0.005% of Ti, less than or equal to 0.005% of Nb, less than or equal to 0.005% of Ni and the balance of Fe. The industrial pure iron bar is produced based on the ecological electric furnace process, it can be guaranteed that the chemical components and the steel purity of a finished product meet the requirements of high-quality industrial wire iron, the surface quality level of the finished product can be guaranteed, and a new way is provided for industrial production of the high-quality industrial pure iron.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial pure iron production, and particularly to a method for producing industrial pure iron bars by an ecological electric furnace process. Background Art

[0002] Industrial pure iron is a type of steel with a total impurity content of <0.2% and a carbon content of less than 0.04%. Since it is not actually pure iron (the purity of industrial pure iron is 99.5% - 99.9%), this kind of steel close to pure iron is called industrial pure iron. Industrial pure iron is extremely soft in texture, has great toughness, and excellent electromagnetic properties. It usually has two uses. One is as a deep-drawing material and can be stamped into extremely complex shapes. The other is as an electromagnetic material, which has high magnetic susceptibility and low diamagnetism. Industrial pure iron is also an important raw material for smelting precision alloys, superalloys, ultra-low carbon stainless steels, electrothermal alloys, etc.

[0003] As an important basic raw material for steel manufacturing, the purity of industrial pure iron directly determines the performance of metal products and the quality of steel, and even relates to the product use safety of downstream users of steel.

[0004] Currently, industrial pure iron is mainly produced by processes such as electric arc furnace, oxygen converter, electric arc furnace + vacuum degassing outside the furnace, oxygen converter + vacuum degassing outside the furnace, etc. Industrial pure iron produced by different processes has its own characteristics:

[0005] 1. Characteristics of industrial pure iron produced by the electric arc furnace process: As an early method for producing industrial pure iron, the lowest carbon content can reach 0.025%, but the nitrogen content of industrial pure iron is relatively high. In addition, affected by the carbon addition of graphite electrodes, industrial pure iron with a lower carbon content cannot be produced.

[0006] 2. Characteristics of industrial pure iron produced by the oxygen converter process: It can produce low-carbon industrial pure iron with a carbon content less than 0.01%. The nitrogen content of industrial pure iron is relatively low, but the oxygen content is high, and it can only be used for the production of industrial pure iron of general quality.

[0007] 3. Characteristics of industrial pure iron produced by the combined process of electric arc furnace process or oxygen converter and secondary refining outside the furnace: The carbon content of industrial pure iron is about 0.005%, and the contents of phosphorus, sulfur, oxygen, nitrogen, and non-metallic inclusions are low. It is currently the mainstream process method for producing high-quality industrial pure iron.

[0008] The present invention uses the process of "ecological electric furnace + LF refining + RH refining + bloom continuous casting + smelting + rolling" to produce industrial pure iron bars, realizing the batch production of industrial pure iron bars based on the "production electric furnace + continuous casting" process. The industrial pure iron product has high purity and can meet the requirements for the production of high-end steel products. Summary of the Invention

[0009] The present invention provides a method for producing industrial pure iron bars by an ecological electric furnace process, adopting a production process of "ecological electric furnace + LF refining + RH refining + billet continuous casting + smelting + rolling"; different from the production process based on the conventional smelting process, the present invention produces industrial pure iron bars based on the ecological electric furnace process, which can not only ensure that the chemical composition and steel purity of the finished product meet the requirements of high-quality industrial wire iron, but also ensure the surface quality level of the finished product (meeting the relevant quality requirements in the standard of "Hot-rolled round steel and square steel - Dimensions, shape, weight and tolerances" GB / T 702-2004), providing a new way for the industrial production of high-quality industrial pure iron.

[0010] In order to achieve the above object, the present invention is realized by adopting the following technical solutions:

[0011] A method for producing industrial pure iron bars by an ecological electric furnace process, the production process includes: ecological electric furnace smelting, LF refining, RH refining, billet continuous casting, heating, rolling and cooling; the specific process is as follows:

[0012] 1) Ecological electric furnace smelting:

[0013] Molten steel is smelted with hot metal and scrap steel; the requirements for the composition of the hot metal charged into the furnace are as follows by weight percentage: C ≤ 4%, Si ≤ 0.32%, Mn ≤ 0.15%, P ≤ 0.10%, S ≤ 0.001%; the temperature of the hot metal charged into the furnace is controlled at 1345 - 1350 °C; the temperature of the molten steel at the end of smelting is 1650 - 1655 °C; the oxygen content at the end ≥ 700 ppm, by weight percentage, [C] ≤ 0.04%, [Mn] ≤ 0.04%, [P] ≤ 0.005%, [S] ≤ 0.003% at the end;

[0014] 2) LF refining:

[0015] A large current of 35000 - 36000 A is used to raise the temperature and melt the slag. When the slag surface fluctuates and the molten steel and electric arc are not exposed, 7 - 8 kg / t of steel of active lime is added. The chemical composition is analyzed for the first time 5 - 8 minutes after refining, and lime is added according to the target value of the chemical composition; the temperature of the molten steel when it arrives at the station is 1565 - 1570 °C, the argon blowing time is 55 - 60 minutes, the power-on time is 40 - 45 minutes, the temperature of the molten steel when the argon blowing stops is 1658 - 1664 °C, and the total refining time is 50 - 60 minutes; the molten steel calming time is 10 - 15 minutes, the temperature of the molten steel when it leaves the station is 1650 - 1655 °C, and the bottom blowing argon flow rate is 16 - 17 m 3 / min;

[0016] 3) RH refining:

[0017] Start timing when the vacuum degree reaches 95 - 105 Pa and maintain for 10 - 15 min; the cycle time is 30 - 40 min, the refining treatment time is 60 - 65 min, the soft blowing argon time is 15 - 20 min, and the molten steel calming time is 40 - 45 min; the molten steel temperature before refining treatment is 1645 - 1650 °C, and the molten steel temperature after refining recompression is 1625 - 1630 °C; the oxygen content before refining treatment is 520 - 530 ppm, the top blowing oxygen time is 4 - 5 min, the lowest vacuum degree is 18 - 20 Pa, and the steam temperature at the lowest vacuum degree is 200 - 205 °C; the deoxidizing aluminum addition amount is 1.0 - 1.1 kg / t steel, and the heating aluminum addition amount is 0.6 - 0.65 kg / t steel; the oxygen content after decarburization is 415 - 420 ppm, and the deoxidizing time is 17 - 20 min; after the static blowing argon ends, add pure calcium wire with a diameter of 0.82 - 0.85 m / t steel;

[0018] 4) Continuous casting of square billets:

[0019] The molten steel temperature in the tundish is 1545 - 1555 °C, the casting speed is 0.43 - 0.44 m / min, the H content of the molten steel controlled in the tundish is ≤2 ppm, the consumption of the mold powder is 0.45 - 0.50 kg / t steel, and the consumption of the low-carbon tundish covering agent is 1.1 - 1.2 kg / t steel;

[0020] 5) Heating:

[0021] The temperature of the cast billet entering the heating furnace is 400 °C - 500 °C, the temperature of the preheating section is 550 °C - 600 °C, and the heating time is 1.0 - 1.3 h; the temperature of the second heating section is 850 °C - 860 °C, and the heating time is 1.0 - 1.3 h; the temperature of the first heating section is 1180 °C - 1210 °C, and the heating time is 1.0 - 1.3 h; the temperature of the soaking section is 1160 °C - 1180 °C, and the heating time is 1.0 - 1.5 h; the temperature of the cast billet leaving the furnace is 1000 °C - 1050 °C;

[0022] 6) Rolling:

[0023] Primary rolling process: The rolled piece enters the continuous rolling mill after being rolled through multiple stands of rolling mills in multiple passes;

[0024] Continuous rolling process: The rolled piece is rolled through multiple passes again to obtain industrial pure iron bars;

[0025] 7) Cooling: The rolled industrial pure iron bars are air-cooled to room temperature.

[0026] During the smelting process of the ecological electric furnace, 60% - 65% of hot metal and 35% - 40% of scrap steel are used for smelting by weight percentage.

[0027] During the smelting process of the ecological electric furnace, auxiliary materials are added, including: active lime with a particle size of 10 - 70 mm, with an addition amount of 28 - 29 kg / t of steel; lime with a particle size of 20 - 80 mm, with an addition amount of 3 - 3.1 kg / t of steel; limestone with a particle size of 25 - 40 mm, with an addition amount of 42 - 43 kg / t of steel; dolomite with a particle size of 20 - 70 mm, with an addition amount of 16 - 17 kg / t of steel; and 42 - 43 kg / t of sinter.

[0028] During the LF refining process, the ladle freeboard is controlled at 350 - 400 mm, and the slag thickness is 50 - 60 mm; 2.0 - 2.1 kg / t of steel of aluminum slag balls with a particle size of are added for top slag modification.

[0029] During the RH refining process, before the vacuum pump is started, the argon pressure is controlled at 0.1 - 0.3 MPa, at this time the slag surface moves slightly and the molten steel is not exposed; the ladle freeboard is controlled at 350 - 400 mm, and the slag thickness is 50 - 60 mm.

[0030] During the blooming process, the rolled piece is rolled 9 passes through 3 850 mm rolling mills. The specific process is as follows: after the first steel flipping, in the 1st pass, the rolled piece is rolled to a width of 408 - 408.01 mm and a height of 421 - 421.01 mm, with a reduction of 65 - 65.01 mm; in the 2nd pass, the rolled piece is rolled to a width of 426 - 426.01 mm and a height of 351 - 351.01 mm, with a reduction of 70 - 70.01 mm; after the second steel flipping, in the 3rd pass, the rolled piece is rolled to a width of 370 - 370.01 mm and a height of 362 - 362.01 mm, with a reduction of 64 - 64.01 mm; in the 4th pass, the rolled piece is rolled to a width of 397 - 397.01 mm and a height of 272 - 272.01 mm, with a reduction of 90 - 90.01 mm; after the third steel flipping, in the 5th pass, the rolled piece is rolled to a width of 285 - 285.01 mm and a height of 355 - 355.01 mm, with a reduction of 42 - 42.01 mm; in the 6th pass, the rolled piece is rolled to a width of 297 - 297.01 mm and a height of 315 - 315.01 mm, with a reduction of 40 - 40.01 mm; in the 7th pass, the rolled piece is rolled to a width of 307 - 307.01 mm and a height of 280 - 280.01 mm, with a reduction of 35 - 35.01 mm; in the 8th pass, the rolled piece is rolled to a width of 317 - 317.01 mm and a height of 246 - 246.01 mm, with a reduction of 34 - 34.01 mm; after the fourth steel flipping, in the 9th pass, the rolled piece is rolled to a width of 271 - 271.01 mm and a height of 235 - 235.01 mm, with a reduction of 82 - 82.01 mm.

[0031] In the continuous rolling process, the rolled piece is further rolled for 9 passes. The specific process is as follows: In the first pass, it is rolled to a height of 229 - 229.01 mm and a width of 245 - 245.01 mm; in the second pass, it is rolled to a height of 192 - 192.01 mm and a width of 235 - 235.01 mm; in the third pass, it is rolled to a height of 200 - 200.01 mm and a width of 195 - 195.01 mm; in the fourth pass, it is rolled to a height of 173 - 173.01 mm and a width of 210 - 210.01 mm; in the fifth pass, it is rolled to a height of 180 - 180.01 mm and a width of 178.2 - 178.21 mm; in the sixth pass, it is rolled to a height of 142 - 142.01 mm and a width of 190 - 190.01 mm; in the seventh pass, it is rolled to a height of 158 - 158.01 mm and a width of 154.8 - 154.81 mm; in the eighth pass, it is rolled to a height of 121 - 121.01 mm and a width of 162.8 - 162.81 mm; in the ninth pass, it is rolled to a height of 131.76 - 131.77 mm and a width of 131.76 - 131.77 mm.

[0032] The chemical composition of the produced finished industrial pure iron bars is, by weight percentage: C ≤ 0.004%, Si ≤ 0.010%, Mn ≤ 0.050%, P ≤ 0.004%, S ≤ 0.005%, Co ≤ 0.005%, Mo ≤ 0.005%, Cu ≤ 0.012%, Alt: 0.005% - 0.020%, Ti ≤ 0.005%, Nb ≤ 0.005%, Ni ≤ 0.005%, and the rest is Fe.

[0033] The specifications of the produced finished industrial pure iron bars are

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] (1) By adopting the production process of "eco - electric furnace + LF refining + RH refining + bloom continuous casting + smelting + rolling", the high - quality industrial pure iron bars produced can not only meet the chemical composition requirements of the standards but also ensure the steel purity.

[0036] (2) Through reasonable composition design and matching with optimized production processes, the surface quality and internal quality of the industrial pure iron bars are ensured.

[0037] (3) Different from the production processes based on conventional smelting processes, the present invention produces industrial pure iron bars based on the eco - electric furnace process, providing a new way for the industrial production of high - quality industrial pure iron. Detailed implementation manners

[0038] The method for producing industrial pure iron bars by an ecological electric furnace process according to the present invention has a production process including: ecological electric furnace smelting, LF refining, RH refining, billet continuous casting, heating, rolling and cooling; the specific process is as follows:

[0039] 1) Ecological electric furnace smelting:

[0040] Molten steel is smelted using hot metal and scrap steel; the requirements for the composition of the hot metal charged into the furnace are, by weight percentage: C≤4%, Si≤0.32%, Mn≤0.15%, P≤0.10%, S≤0.001%; the temperature of the hot metal charged into the furnace is controlled at 1345 - 1350°C; the temperature of the molten steel at the end of smelting is 1650 - 1655°C; the oxygen content at the end point is ≥700 ppm, and by weight percentage, [C]≤0.04%, [Mn]≤0.04%, [P]≤0.005%, [S]≤0.003% at the end point;

[0041] 2) LF refining:

[0042] Large current of 35000 - 36000 A is used to raise the temperature and melt the slag. When the slag surface fluctuates and the molten steel and electric arc are not exposed, 7 - 8 kg / t of steel of active lime is added. The chemical composition is analyzed for the first time 5 - 8 minutes after refining, and lime is added according to the target value of the chemical composition; the temperature of the molten steel when it arrives at the station is 1565 - 1570°C, the argon blowing time is 55 - 60 minutes, the power - on time is 40 - 45 minutes, the temperature of the molten steel when argon blowing stops is 1658 - 1664°C, and the total refining time is 50 - 60 minutes; the molten steel calming time is 10 - 15 minutes, the temperature of the molten steel when it leaves the station is 1650 - 1655°C, and the bottom - blown argon flow rate is 16 - 17 m 3 / min;

[0043] 3) RH refining:

[0044] Timing starts when the vacuum degree reaches 95 - 105 Pa and is maintained for 10 - 15 minutes; the circulation time is 30 - 40 minutes, the refining treatment time is 60 - 65 minutes, the soft argon blowing time is 15 - 20 minutes, and the molten steel calming time is 40 - 45 minutes; the temperature of the molten steel before refining treatment is 1645 - 1650°C, and the temperature of the molten steel after refining and recompression is 1625 - 1630°C; the oxygen content before refining treatment is 520 - 530 ppm, the top - blown oxygen time is 4 - 5 minutes, the lowest vacuum degree is 18 - 20 Pa, and the steam temperature at the lowest vacuum degree is 200 - 205°C; the addition amount of deoxidized aluminum is 1.0 - 1.1 kg / t of steel, and the addition amount of temperature - raising aluminum is 0.6 - 0.65 kg / t of steel; the oxygen content after decarburization is 415 - 420 ppm, and the deoxidation time is 17 - 20 minutes; after the static argon blowing ends, pure calcium wire with a diameter of 0.82 - 0.85 m / t of steel is added;

[0045] 4) Continuous casting of billets:

[0046] The molten steel temperature in the tundish is 1545 - 1555 °C, the casting speed is 0.43 - 0.44 m / min, the H content of the molten steel controlled in the tundish is ≤ 2 ppm, the consumption of mold powder is 0.45 - 0.50 kg / t of steel, and the consumption of low-carbon tundish covering agent is 1.1 - 1.2 kg / t of steel;

[0047] 5) Heating:

[0048] The temperature of the cast billet entering the heating furnace is 400 °C - 500 °C, the temperature of the preheating section is 550 °C - 600 °C, and the heating time is 1.0 - 1.3 h; the temperature of the second heating section is 850 °C - 860 °C, and the heating time is 1.0 - 1.3 h; the temperature of the first heating section is 1180 °C - 1210 °C, and the heating time is 1.0 - 1.3 h; the temperature of the soaking section is 1160 °C - 1180 °C, and the heating time is 1.0 - 1.5 h; the temperature of the cast billet leaving the furnace is 1000 °C - 1050 °C;

[0049] 6) Rolling:

[0050] Primary rolling process: The rolled piece enters the continuous rolling mill after being rolled through multiple stands of rolling mills for multiple passes;

[0051] Continuous rolling process: The rolled piece is further rolled through multiple passes to obtain industrial pure iron bars;

[0052] 7) Cooling: The rolled industrial pure iron bars are air-cooled to room temperature.

[0053] During the smelting process of the ecological electric furnace, 60% - 65% of hot metal and 35% - 40% of scrap steel are used for smelting by weight percentage.

[0054] Auxiliary materials are added during the smelting process of the ecological electric furnace, including: active lime with a particle size of 10 - 70 mm, and the addition amount is 28 - 29 kg / t of steel; lime with a particle size of 20 - 80 mm, and the addition amount is 3 - 3.1 kg / t of steel; limestone with a particle size of 25 - 40 mm, and the addition amount is 42 - 43 kg / t of steel; dolomite with a particle size of 20 - 70 mm, and the addition amount is 16 - 17 kg / t of steel; and 42 - 43 kg / t of sinter.

[0055] During the LF refining process, the net space in the ladle is controlled at 350 - 400 mm, and the slag thickness is 50 - 60 mm; 2.0 - 2.1 kg / t of steel of aluminum slag balls with a certain particle size are added for top slag modification.

[0056] During the RH refining process, the argon pressure is controlled at 0.1 - 0.3 MPa before the vacuum pump is started. At this time, the slag surface moves slightly and the molten steel is not exposed; the net space in the ladle is controlled at 350 - 400 mm, and the slag thickness is 50 - 60 mm.

[0057] In the blooming process, the rolled piece is rolled for 9 passes through 3 850 mm rolling mills. The specific process is as follows: After the first steel flipping, in the 1st pass, the rolled piece is rolled to a width of 408 - 408.01 mm and a height of 421 - 421.01 mm, with a reduction of 65 - 65.01 mm; in the 2nd pass, it is rolled to a width of 426 - 426.01 mm and a height of 351 - 351.01 mm, with a reduction of 70 - 70.01 mm; after the second steel flipping, in the 3rd pass, it is rolled to a width of 370 - 370.01 mm and a height of 362 - 362.01 mm, with a reduction of 64 - 64.01 mm; in the 4th pass, it is rolled to a width of 397 - 397.01 mm and a height of 272 - 272.01 mm, with a reduction of 90 - 90.01 mm; after the third steel flipping, in the 5th pass, it is rolled to a width of 285 - 285.01 mm and a height of 355 - 355.01 mm, with a reduction of 42 - 42.01 mm; in the 6th pass, it is rolled to a width of 297 - 297.01 mm and a height of 315 - 315.01 mm, with a reduction of 40 - 40.01 mm; in the 7th pass, it is rolled to a width of 307 - 307.01 mm and a height of 280 - 280.01 mm, with a reduction of 35 - 35.01 mm; in the 8th pass, it is rolled to a width of 317 - 317.01 mm and a height of 246 - 246.01 mm, with a reduction of 34 - 34.01 mm; after the fourth steel flipping, in the 9th pass, it is rolled to a width of 271 - 271.01 mm and a height of 235 - 235.01 mm, with a reduction of 82 - 82.01 mm.

[0058] In the continuous rolling process, the rolled piece is rolled for 9 passes. The specific process is as follows: In the 1st pass, the rolled piece is rolled to a height of 229 - 229.01 mm and a width of 245 - 245.01 mm; in the 2nd pass, it is rolled to a height of 192 - 192.01 mm and a width of 235 - 235.01 mm; in the 3rd pass, it is rolled to a height of 200 - 200.01 mm and a width of 195 - 195.01 mm; in the 4th pass, it is rolled to a height of 173 - 173.01 mm and a width of 210 - 210.01 mm; in the 5th pass, it is rolled to a height of 180 - 180.01 mm and a width of 178.2 - 178.21 mm; in the 6th pass, it is rolled to a height of 142 - 142.01 mm and a width of 190 - 190.01 mm; in the 7th pass, it is rolled to a height of 158 - 158.01 mm and a width of 154.8 - 154.81 mm; in the 8th pass, it is rolled to a height of 121 - 121.01 mm and a width of 162.8 - 162.81 mm; in the 9th pass, it is rolled to a height of 131.76 - 131.77 mm and a width of 131.76 - 131.77 mm.

[0059] The chemical composition of the produced finished industrial pure iron bars is, by weight percentage: C ≤ 0.004%, Si ≤ 0.010%, Mn ≤ 0.050%, P ≤ 0.004%, S ≤ 0.005%, Co ≤ 0.005%, Mo ≤ 0.005%, Cu ≤ 0.012%, Alt: 0.005% - 0.020%, Ti ≤ 0.005%, Nb ≤ 0.005%, Ni ≤ 0.005%, and the balance is Fe.

[0060] The specifications of the produced finished industrial pure iron bars are

[0061] Through the selective addition and content design of trace elements in the steel, combined with the setting of the production process and process parameters, the present invention ensures the surface quality and internal quality of the industrial pure iron bars.

[0062] All percentages not specified in the present invention are by weight percentage.

[0063] The following examples are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following examples. The methods used in the following examples are all conventional methods unless otherwise specified.

[0064]

Example 1

[0065] In this example, the process route for producing industrial pure iron bars using the ecological electric furnace process is: ecological electric furnace smelting → secondary refining (LF refining) → secondary vacuum refining (RH refining) → billet continuous casting → heating → rolling → cooling. The specific process is as follows:

[0066] 1. Ecological electric furnace smelting: Molten steel is smelted using 62% hot metal and 38% scrap steel (by weight percentage). The scrap steel is low-alloy scrap steel. The composition of the hot metal charged into the furnace is, by weight percentage: C: 3%, Si: 0.25%, Mn: 0.10%, P: 0.08%, S: 0.001%; the temperature of the hot metal charged into the furnace is 1347°C; the temperature of the molten steel at the end of smelting is 1652°C, the oxygen content at the end is 850 ppm, and by weight percentage, [C] at the end: 0.03%, [Mn]: 0.03%, [P]: 0.005%, [S]: 0.002%.

[0067] Auxiliary materials are added during the smelting process, and the addition amounts are: active lime (particle size 35 mm) 28 kg / t of steel, lime (particle size 40 mm) 3 kg / t of steel, limestone (particle size 40 mm) 42 kg / t of steel, dolomite (particle size 35 mm) 17 kg / t of steel, and sinter 42 kg / t of steel.

[0068] 2. LF Furnace Refining: A large current of 35600 A is used to raise the temperature and melt the slag. When the slag surface fluctuates and the molten steel and electric arc are not exposed, reactive lime is added, and the addition amount is 8 kg / t of steel. The chemical composition is analyzed for the first time after 7 minutes of refining, and lime is added according to the target value of the chemical composition. The temperature of the molten steel when it arrives at the station is 1568 °C, the argon blowing time is 57 minutes, the energizing time is 43 minutes, the temperature of the molten steel when argon blowing stops is 1660 °C, and the total refining time is 55 minutes; the clear height of the ladle is 380 mm, the slag thickness is 55 mm, and the aluminum slag balls (particle size ) with an addition amount of 2.0 kg / t of steel are used for top slag modification. The molten steel calming time is 13 minutes, the temperature of the molten steel when it leaves the station is 1653 °C, and the bottom argon blowing flow rate is 16.5 m 3 / min.

[0069] 3. RH Refining: Before starting the vacuum pump, the argon pressure is controlled at 0.1 MPa to make the slag surface slightly move and the molten steel not exposed; when the vacuum degree reaches 98 Pa, timing starts and is maintained for 11 minutes. The clear height of the ladle is 390 mm, the slag thickness is 56 mm, the circulation time is 35 minutes, the refining treatment time is 62 minutes, the soft argon blowing time is 17 minutes, the molten steel calming time is 42 minutes, the temperature of the molten steel before refining treatment is 1648 °C, and the temperature of the molten steel after refining and repressurization is 1626 °C; the oxygen content before refining treatment is 523 ppm, the top oxygen blowing time is 5 minutes, the lowest vacuum degree is 19 Pa, and the steam temperature at the lowest vacuum degree is 202 °C; the addition amount of deoxidizing aluminum is 1.0 kg / t of steel, the addition amount of heating aluminum is 0.61 kg / t of steel, the oxygen content after decarburization is 417 ppm, and the deoxidation time is 18 minutes; after the static argon blowing ends, pure calcium wire (diameter ) with an addition amount of 0.83 m / t of steel is added.

[0070] 4. Bloom Continuous Casting: The temperature of the molten steel in the tundish is 1551 °C, the casting speed is 0.43 m / min, the H content of the molten steel in the tundish is controlled at 1.6 ppm, the consumption of the mold powder is 0.47 kg / t of steel, and the consumption of the low-carbon tundish covering agent is 1.1 kg / t of steel.

[0071] 5. Heating: The temperature of the cast billet when it enters the heating furnace is 475 °C, the temperature of the preheating section is set at 570 °C, and the heating time is 1.2 h; the temperature of the second heating section is set at 855 °C, and the heating time is 1.2 h; the temperature of the first heating section is set at 1195 °C, and the heating time is 1.3 h; the temperature of the soaking section is set at 1168 °C, and the heating time is 1.3 h; the temperature of the cast billet when it leaves the furnace is 1020 °C.

[0072] 6. Rolling:

[0073] Blooming process: The rolled piece is rolled through 9 passes on 3 850mm rolling mills. The specific process is as follows: steel turning → rolled to a width of 408mm and a height of 421mm in the first pass, with a reduction of 65.01mm → rolled to a width of 426.01mm and a height of 351mm in the second pass, with a reduction of 70.01mm → steel turning → rolled to a width of 370mm and a height of 362.01mm in the third pass, with a reduction of 64mm → rolled to a width of 397.01mm and a height of 272mm in the fourth pass, with a reduction of 90.01mm → steel turning → rolled to a width of 285.01mm and a height of 355mm in the fifth pass, with a reduction of 42.01mm → rolled to a width of 297.01mm and a height of 315mm in the sixth pass, with a reduction of 40.01mm → rolled to a width of 307mm and a height of 280mm in the seventh pass, with a reduction of 35mm → rolled to a width of 317.01mm and a height of 246mm in the eighth pass, with a reduction of 34mm → steel turning → rolled to a width of 271.01mm and a height of 235mm in the ninth pass, with a reduction of 82mm; then the rolled piece enters the continuous rolling mill for rolling.

[0074] Continuous rolling process: The rolled piece is further rolled through 9 passes. The specific process is as follows: rolled to a height of 229.01mm and a width of 245mm in the first pass; rolled to a height of 192.01mm and a width of 235mm in the second pass; rolled to a height of 200.01mm and a width of 195mm in the third pass; rolled to a height of 173mm and a width of 210.01mm in the fourth pass; rolled to a height of 180mm and a width of 178.21mm in the fifth pass; rolled to a height of 142mm and a width of 190mm in the sixth pass; rolled to a height of 158.01mm and a width of 154.81mm in the seventh pass; rolled to a height of 121mm and a width of 162.81mm in the eighth pass; rolled to a height of 131.77mm and a width of 131.76mm in the ninth pass; After rolling, industrial pure iron bars are obtained.

[0075] 7. Cooling: The rolled industrial pure iron bars are air-cooled to room temperature.

[0076] The chemical composition (by weight percentage) of the industrial pure iron bars produced in this example is as follows:

[0077] C: 0.003%, Si: 0.005%, Mn: 0.025%, P: 0.003%, S: 0.001%, Co: 0.002%, Mo: 0.004%, Cu: 0.004%, Alt: 0.010%, Ti: 0.004%, Nb: 0.004%, Ni: 0.004%, the rest is Fe.

[0078]

Example 2

[0079] In this embodiment, the process route for producing industrial pure iron bars using the ecological electric furnace process is as follows: ecological electric furnace smelting → secondary refining (LF refining) → secondary vacuum refining (RH refining) → continuous casting of billets → heating → rolling → cooling. The specific process is as follows:

[0080] 1. Ecological electric furnace smelting: Molten steel is smelted using 63% hot metal and 37% scrap steel (by weight percentage). The scrap steel used is low-alloy scrap steel. The composition of the hot metal charged into the furnace is, by weight percentage, C: 3%, Si: 0.30%, Mn: 0.13%, P: 0.09%, S: 0.001%; the temperature of the hot metal charged into the furnace is 1348°C; the temperature of the molten steel at the end of smelting is 1652°C, the oxygen content at the end is 820 ppm, and by weight percentage, [C] at the end: 0.03%, [Mn]: 0.03%, [P]: 0.004%, [S]: 0.002%.

[0081] Auxiliary materials are added during the smelting process. The addition amounts are as follows: active lime (particle size 35 mm) 28.2 kg / t of steel, lime (particle size 40 mm) 3 kg / t of steel, limestone (particle size 40 mm) 42 kg / t of steel, dolomite (particle size 35 mm) 16 kg / t of steel, and sintered ore 43 kg / t of steel.

[0082] 2. LF furnace refining: A large current of 35500 A is used to raise the temperature and melt the slag. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime is added, and the addition amount is 8 kg / t of steel. The chemical composition is analyzed for the first time at 6 minutes of refining, and lime is added according to the target chemical composition values. The temperature of the molten steel when it arrives at the station is 1567°C, the argon blowing time is 58 minutes, the power-on time is 43 minutes, the temperature of the molten steel when argon blowing stops is 1660°C, and the total refining time is 57 minutes; the clear space in the ladle is 370 mm, the slag thickness is 54 mm, and the aluminum slag balls (particle size ) used for modifying the top slag are added in an amount of 2.1 kg / t of steel, the molten steel calming time is 12 minutes, the temperature of the molten steel when it leaves the station is 1653°C, and the bottom argon blowing flow rate is 16.7 m 3 / min.

[0083] 3. RH Refining: Before starting the vacuum pump, the argon pressure is controlled at 0.1 MPa to make the slag surface slightly move without exposing the molten steel; start timing when the vacuum degree reaches 97 Pa and maintain for 12 min; the ladle freeboard is 385 mm and the slag thickness is 52 mm; the circulation time is 37 min, the refining treatment time is 62 min, the soft blowing argon time is 18 min, and the molten steel calming time is 41 min; the molten steel temperature before refining treatment is 1646 °C, the molten steel temperature after refining and repressurization is 1626 °C, the oxygen content before refining treatment is 525 ppm, the top blowing oxygen time is 5 min, the lowest vacuum degree is 19 Pa, and the steam temperature at the lowest vacuum degree is 203 °C; the deoxidation aluminum addition amount is 1.1 kg / t of steel, and the heating aluminum addition amount is 0.61 kg / t of steel; the oxygen content after decarburization is 416 ppm, and the deoxidation time is 18 min; after the static blowing argon is completed, add pure calcium wire (diameter ) at 0.83 m / t of steel.

[0084] 4. Bloom Continuous Casting: The molten steel temperature in the tundish is 1551 °C, the casting speed is 0.44 m / min, the H content of the molten steel controlled in the tundish is 1.4 ppm, the consumption of mold powder is 0.47 kg / t of steel, and the consumption of low-carbon tundish covering agent is 1.2 kg / t of steel.

[0085] 5. Heating: The temperature of the cast slab entering the heating furnace is 460 °C, the temperature of the preheating section is set at 580 °C, and the heating time is 1.2 h; the temperature of the second heating section is set at 854 °C, and the heating time is 1.2 h; the temperature of the first heating section is set at 1198 °C, and the heating time is 1.2 h; the temperature of the soaking section is set at 1168 °C, and the heating time is 1.3 h; the temperature of the cast slab leaving the furnace is 1026 °C.

[0086] 6. Rolling:

[0087] Blooming Process: The rolled piece is rolled through 9 passes on 3 850-mm rolling mills. The specific process is as follows: steel turning → rolled to a width of 408.01 mm and a height of 421 mm in the first pass, with a reduction of 65.01 mm → rolled to a width of 426 mm and a height of 351 mm in the second pass, with a reduction of 70.01 mm → steel turning → rolled to a width of 370.01 mm and a height of 362.01 mm in the third pass, with a reduction of 64 mm → rolled to a width of 397.01 mm and a height of 272 mm in the fourth pass, with a reduction of 90.01 mm → steel turning → rolled to a width of 285.01 mm and a height of 355 mm in the fifth pass, with a reduction of 42.01 mm → rolled to a width of 297 mm and a height of 315.01 mm in the sixth pass, with a reduction of 40.01 mm → rolled to a width of 307.01 mm and a height of 280 mm in the seventh pass, with a reduction of 35 mm → rolled to a width of 317.01 mm and a height of 246 mm in the eighth pass, with a reduction of 34.01 mm → steel turning → rolled to a width of 271.01 mm and a height of 235 mm in the ninth pass, with a reduction of 82 mm; then the rolled piece enters the continuous rolling mill for rolling.

[0088] Continuous rolling process: The rolled piece is further rolled through 9 passes. The specific process is as follows: In the first pass, it is rolled to a height of 229.01 mm and a width of 245 mm; in the second pass, it is rolled to a height of 192.01 mm and a width of 235.01 mm; in the third pass, it is rolled to a height of 200.01 mm and a width of 195 mm; in the fourth pass, it is rolled to a height of 173.01 mm and a width of 210.01 mm; in the fifth pass, it is rolled to a height of 180 mm and a width of 178.21 mm; in the sixth pass, it is rolled to a height of 142 mm and a width of 190.01 mm; in the seventh pass, it is rolled to a height of 158.01 mm and a width of 154.81 mm; in the eighth pass, it is rolled to a height of 121 mm and a width of 162.8 mm; in the ninth pass, it is rolled to a height of 131.77 mm and a width of 131.77 mm. After the rolling is completed, an industrial pure iron bar is obtained.

[0089] 7. Cooling: The rolled industrial pure iron bar is air-cooled to room temperature.

[0090] The chemical composition (weight percentage) of the industrial pure iron bar produced in this embodiment is as follows:

[0091] C: 0.003%, Si: 0.005%, Mn: 0.028%, P: 0.003%, S: 0.001%, Co: 0.003%, Mo: 0.004%, Cu: 0.005%, Alt: 0.011%, Ti: 0.004%, Nb: 0.004%, Ni: 0.005%, and the rest is Fe.

[0092]

Example 3

[0093] In this embodiment, the process route for producing an industrial pure iron bar using an ecological electric furnace process is as follows: Ecological electric furnace smelting → Secondary refining (LF refining) → Vacuum secondary refining (RH refining) → Bloom continuous casting → Heating → Rolling → Cooling. The specific process is as follows:

[0094] 1. Ecological electric furnace smelting: Molten steel is smelted using 64% hot metal and 36% scrap steel (weight percentage). Low-alloy scrap steel is used for the scrap steel. The composition of the hot metal charged into the furnace is, by weight percentage, C: 3%, Si: 0.30%, Mn: 0.13%, P: 0.08%, S: 0.001%; the temperature of the hot metal charged into the furnace is 1348 °C; the temperature of the molten steel at the end of smelting is 1653 °C, the oxygen content at the end is 820 ppm, and by weight percentage, [C] at the end: 0.03%, [Mn]: 0.03%, [P]: 0.004%, [S]: 0.003%.

[0095] Auxiliary materials are added during the smelting process. The addition amounts are as follows: Active lime (particle size 35 mm) 28 kg / t of steel, lime (particle size 40 mm) 3.1 kg / t of steel, limestone (particle size 40 mm) 42 kg / t of steel, dolomite (particle size 35 mm) 17 kg / t of steel, and sintered ore 42 kg / t of steel.

[0096] 2. LF Furnace Refining: A large current of 35600 A is used to heat up and melt the slag. When the slag surface fluctuates and the molten steel and electric arc are not exposed, active lime is added, and the addition amount is 8 kg / t of steel. The chemical composition is analyzed by sampling for the first time at 5 min of refining, and lime is added according to the target value of the chemical composition. The temperature of the molten steel when it arrives at the station is 1567 °C, the argon blowing time is 57 min, the power-on time is 42 min, the temperature of the molten steel when argon blowing stops is 1660 °C, and the total refining time is 55 min; the net space of the ladle is 380 mm, the slag thickness is 54 mm, and aluminum slag balls (particle size is ) with an addition amount of 2.1 kg / t of steel are used for top slag modification. The molten steel is static for 12 min, the temperature of the molten steel when it leaves the station is 1652 °C, and the bottom argon blowing flow rate is 16.8 m 3 / min.

[0097] 3. RH Refining: Before starting the vacuum pump, the argon pressure is controlled at 0.1 MPa to make the slag surface slightly move and the molten steel not exposed; when the vacuum degree reaches 97 Pa, timing starts and is maintained for 11 min. The net space of the ladle is 385 mm, the slag thickness is 56 mm, the circulation time is 36 min, the refining treatment time is 62 min, the soft argon blowing time is 17 min, the static time is 42 min, the temperature of the molten steel before refining treatment is 1647 °C, and the temperature of the molten steel after refining and repressurization is 1628 °C; the oxygen content before refining treatment is 525 ppm, the top oxygen blowing time is 5 min, the lowest vacuum degree is 18 Pa, and the steam temperature at the lowest vacuum degree is 202 °C; the addition amount of deoxidizing aluminum is 1.1 kg / t of steel, the addition amount of heating aluminum is 0.62 kg / t of steel, the oxygen content after decarburization is 417 ppm, and the deoxidation time is 18 min; after the static argon blowing ends, pure calcium wire (diameter ) with an addition amount of 0.83 m / t of steel is added.

[0098] 4. Bloom Continuous Casting: The temperature of the molten steel in the tundish is 1549 °C, the casting speed is 0.44 m / min, the H content in the molten steel in the tundish is controlled at 1.5 ppm, the consumption of mold powder is 0.47 kg / t of steel, and the consumption of low-carbon tundish covering agent is 1.2 kg / t of steel.

[0099] 5. Heating: The temperature of the cast slab when it enters the heating furnace is 460 °C, the temperature of the preheating section is set at 580 °C, and the heating time is 1.2 h; the temperature of the second heating section is set at 854 °C, and the heating time is 1.2 h; the temperature of the first heating section is set at 1195 °C, and the heating time is 1.2 h; the temperature of the soaking section is set at 1174 °C, and the heating time is 1.0 - 1.5 h; the temperature of the cast slab when it leaves the furnace is 1010 °C.

[0100] 6. Rolling:

[0101] Blooming process: The rolled piece is rolled through 9 passes on 3 850mm rolling mills. The specific process is as follows: steel turning → rolled to a width of 408mm and a height of 421.01mm in the first pass, with a reduction of 65.01mm → rolled to a width of 426mm and a height of 351 - 351.01mm in the second pass, with a reduction of 70 - 70.01mm → steel turning → rolled to a width of 370.01mm and a height of 362.01mm in the third pass, with a reduction of 64.01mm → rolled to a width of 397mm and a height of 272mm in the fourth pass, with a reduction of 90mm → steel turning → rolled to a width of 285mm and a height of 355mm in the fifth pass, with a reduction of 42.01mm → rolled to a width of 297.01mm and a height of 315.01mm in the sixth pass, with a reduction of 40.01mm → rolled to a width of 307.01mm and a height of 280mm in the seventh pass, with a reduction of 35.01mm → rolled to a width of 317.01mm and a height of 246mm in the eighth pass, with a reduction of 34.01mm → steel turning → rolled to a width of 271.01mm and a height of 235mm in the ninth pass, with a reduction of 82mm, and then the rolled piece enters the continuous rolling mill for rolling.

[0102] Continuous rolling process: The rolled piece is further rolled through 9 passes. The specific process is as follows: rolled to a height of 229mm and a width of 245mm in the first pass; rolled to a height of 192.01mm and a width of 235mm in the second pass; rolled to a height of 200.01mm and a width of 195mm in the third pass; rolled to a height of 173.01mm and a width of 210mm in the fourth pass; rolled to a height of 180.01mm and a width of 178.2mm in the fifth pass; rolled to a height of 142.01mm and a width of 190mm in the sixth pass; rolled to a height of 158.01mm and a width of 154.81mm in the seventh pass; rolled to a height of 121.01mm and a width of 162.8mm in the eighth pass; rolled to a height of 131.77mm and a width of 131.77mm in the ninth pass; after rolling, an industrial pure iron rod is obtained.

[0103] 7. Cooling: The rolled industrial pure iron rod is air - cooled to room temperature.

[0104] The chemical composition (by weight percentage) of the industrial pure iron rod produced in this embodiment is as follows:

[0105] C: 0.003%, Si: 0.004%, Mn: 0.027%, P: 0.003%, S: 0.001%, Co: 0.004%, Mo: 0.005%, Cu: 0.005%, Alt: 0.010%, Ti: 0.005%, Nb: 0.004%, Ni: 0.005%, and the rest is Fe.

[0106] The results of finished product inspection are shown in Table 1:

[0107] Table 1 Results of macro - structure inspection of the finished industrial pure iron rod

[0108] Project General looseness / Grade Central looseness / Grade Ingot shape segregation / Grade General mottled segregation / Grade Edge mottled segregation / Grade Standard ≤1.5 ≤1.5 ≤1.5 ≤1.0 ≤1.0 Example 1-1 0.5 0.5 0.5 0 0 Example 1-2 0.5 0.5 0.5 0 0 Example 2-1 0.5 0.5 0.5 0 0 Example 2-2 0.5 0.5 0.5 0 0 Example 3-1 0.5 0.5 0.5 0 0 Example 3-2 0.5 0.5 0.5 0 0

[0109] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A method for producing industrial pure iron bars by an ecological electric furnace process, characterized in that: The production process includes: ecological electric furnace smelting, LF refining, RH refining, billet continuous casting, heating, rolling and cooling; the specific process is as follows: 1) Ecological electric furnace smelting: Molten steel is smelted using molten iron and scrap steel; the composition of the molten iron entering the furnace is required to be calculated by weight percentage: C≤4%, Si≤0.32%, Mn≤0.15%, P≤0.10%, S≤0.001%; ​​the temperature of the molten iron entering the furnace is controlled at 1345-1350°C; the temperature of the molten steel at the end of smelting is 1650-1655°C; the oxygen content at the end is ≥700ppm, and the end points [C]≤0.04%, [Mn]≤0.04%, [P]≤0.005%, [S]≤0.003% by weight; 2) LF refining: A large current of 35000-36000A is used to heat and melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, 7-8kg / t of active lime is added. After 5-8 minutes of refining, the chemical composition is analyzed for the first time, and lime is added according to the target value of the chemical composition. The temperature of the molten steel at the station is 1565-1570℃, the argon blowing time is 55-60min, the power-on time is 40-45min, the molten steel temperature is 1658-1664℃ when the argon blowing is stopped, and the total refining time is 50-60min; the molten steel calming time is 10-15min, the molten steel leaving the station temperature is 1650-1655℃, and the bottom argon blowing flow rate is 16-17m 3 / min; 3)RH refining: When the vacuum reaches 95-105Pa, start timing and keep it for 10-15min; the cycle time is 30-40min, the refining treatment time is 60-65min, the soft argon blowing time is 15-20min, and the molten steel calming time is 40-45min; the molten steel temperature before refining treatment is 1645-1650℃, and the molten steel temperature after refining and re-pressing is 1625-1630℃; the oxygen value before refining treatment is 520-530ppm, the top oxygen blowing time is 4-5min, the minimum vacuum degree is 18-20Pa, and the steam temperature at the minimum vacuum degree is 200-205℃; the amount of deoxidation aluminum added is 1.0-1.1kg / t steel, and the amount of heating aluminum added is 0.6-0.65kg / t steel; the oxygen content after decarburization is 415-420ppm, and the deoxidation time is 17-20min; after the static argon blowing is completed, add a diameter of Pure calcium wire 0.82~0.85m / t steel; 4) Billet continuous casting: The temperature of molten steel in the tundish is 1545-1555℃, the pulling speed is 0.43-0.44m / min, the H content of molten steel in the tundish is controlled to be ≤2ppm, the amount of mold protection slag is 0.45-0.50kg / t steel, and the amount of low-carbon tundish covering agent is 1.1-1.2kg / t steel; 5) Heating: The temperature of the billet entering the heating furnace is 400℃~500℃, the temperature of the preheating section is 550℃~600℃, and the heating time is 1.0~1.3h; the temperature of the second heating section is 850℃~860℃, and the heating time is 1.0~1.3h; the temperature of the first heating section is 1180℃~1210℃, and the heating time is 1.0~1.3h; the temperature of the soaking section is 1160℃~1180℃, and the heating time is 1.0~1.5h; the billet out of the furnace temperature is 1000℃~1050℃; 6) Rolling: Initial rolling process: the rolled piece enters the continuous rolling unit after being rolled in multiple passes on multiple rolling mills; Continuous rolling process: After the rolled piece is rolled for multiple times, industrial pure iron bars are obtained; 7) Cooling: The rolled industrial pure iron bars are air-cooled to room temperature.

2. The method for producing industrial pure iron bars by an ecological electric furnace process according to claim 1, characterized in that: In the ecological electric furnace smelting process, 60% to 65% by weight of molten iron and 35% to 40% by weight of scrap steel are used for smelting.

3. The method for producing industrial pure iron bars by an ecological electric furnace process according to claim 1, characterized in that: Auxiliary materials are added during the ecological electric furnace smelting process, including: active lime with a particle size of 10 to 70 mm, added in an amount of 28 to 29 kg / t steel; lime with a particle size of 20 to 80 mm, added in an amount of 3 to 3.1 kg / t steel; limestone with a particle size of 25 to 40 mm, added in an amount of 42 to 43 kg / t steel; dolomite with a particle size of 20 to 70 mm, added in an amount of 16 to 17 kg / t steel; and 42 to 43 kg / t steel of sintered ore.

4. The method for producing industrial pure iron bars by an ecological electric furnace process according to claim 1, characterized in that: During the LF refining process, the ladle clearance is controlled at 350-400 mm, the slag thickness is 50-60 mm; The aluminum slag balls of 2.0-2.1kg / t steel are used for top slag modification.

5. The method for producing industrial pure iron bars by an ecological electric furnace process according to claim 1, characterized in that: During the RH refining process, the argon pressure is controlled at 0.1-0.3 MPa before the vacuum pump is started, at which time the slag surface moves slightly and the molten steel is not exposed; the ladle clearance is controlled at 350-400 mm, and the slag thickness is 50-60 mm.

6. The method for producing industrial pure iron bars by an ecological electric furnace process according to claim 1, characterized in that: In the initial rolling process, the rolled piece is rolled 9 times by three 850mm rolling mills, and the specific process is as follows: after the first steel turning, the first pass is rolled to a rolled piece width of 408-408.01mm, a height of 421-421.01mm, and a reduction of 65-65.01mm; the second pass is rolled to a rolled piece width of 426-426.01mm, a height of 351-351.01mm, and a reduction of 70-70.01mm; after the second steel turning, the third pass is rolled to a rolled piece width of 370-370.01mm, a height of 362-362.01mm, and a reduction of 64-64.01mm; the fourth pass is rolled to a rolled piece width of 397-397.01mm, a height of 272-272.01mm, and a reduction of 90-90.01mm; after the third steel turning, the fifth pass is rolled to a rolled piece width of 397-397.01mm, a height of 272-272.01mm, and a reduction of 90-90.01mm; after the third steel turning, the fifth pass is rolled to a rolled piece width of 426-426.01mm, a height of 351-351.01mm, and a reduction of 70-70.01mm. The pass is rolled to a width of 285-285.01mm, a height of 355-355.01mm, and a reduction of 42-42.01mm; the 6th pass is rolled to a width of 297-297.01mm, a height of 315-315.01mm, and a reduction of 40-40.01mm; the 7th pass is rolled to a width of 307-307.01mm, a height of 280-280.01mm, and a reduction of 35-35.01mm; the 8th pass is rolled to a width of 317-317.01mm, a height of 246-246.01mm, and a reduction of 34-34.01mm; after the fourth steel turning, the 9th pass is rolled to a width of 271-271.01mm, a height of 235-235.01mm, and a reduction of 82-82.01mm.

7. The method for producing industrial pure iron bars by an ecological electric furnace process according to claim 1, characterized in that: In the continuous rolling process, the rolled piece is rolled through 9 passes, and the specific process is as follows: the first pass is rolled to a rolled piece height of 229-229.01 mm and a width of 245-245.01 mm; the second pass is rolled to a rolled piece height of 192-192.01 mm and a width of 235-235.01 mm; the third pass is rolled to a rolled piece height of 200-200.01 mm and a width of 195-195.01 mm; the fourth pass is rolled to a rolled piece height of 173-173.01 mm and a width of 210-210.01 mm; the fifth pass is rolled to a rolled piece height of 180 ~180.01mm, width 178.2~178.21mm; the 6th pass is rolled to the rolled piece height 142~142.01mm, width 190~190.01mm; the 7th pass is rolled to the rolled piece height 158~158.01mm, width 154.8~154.81mm; the 8th pass is rolled to the rolled piece height 121~121.01mm, width 162.8~162.81mm; the 9th pass is rolled to the rolled piece height 131.76~131.77mm, width 131.76~131.77mm.

8. The method for producing industrial pure iron bars by an ecological electric furnace process according to claim 1, characterized in that: The chemical composition of the finished industrial pure iron bar is C≤0.004%, Si≤0.010%, Mn≤0.050%, P≤0.004%, S≤0.005%, Co≤0.005%, Mo≤0.005%, Cu≤0.012%, Alt: 0.005%~0.020%, Ti≤0.005%, Nb≤0.005%, Ni≤0.005%, and the rest is Fe.

9. The method for producing industrial pure iron bars by an ecological electric furnace process according to claim 1, characterized in that: The specifications of the finished industrial pure iron bars are