A short process electric arc furnace smelting method of high-quality green steel with 80% high scrap steel ratio

Abstract

This invention relates to a short-process electric arc furnace (EAF) smelting method for high-quality green steel with a high scrap steel ratio of 80%. The method optimizes the steel feedstock and its distribution structure by adding biomass charcoal to the bottom of the feed basket, allowing the scrap steel to be added to the EAF in a single pass through the basket. The oxygen supply process of the EAF is optimized in stages: when the power supply to the EAF is ≤5000 kWh, the four furnace wall oxygen lances are activated to burner mode; when the power supply is between 5000 and 13000 kWh, the oxygen flow rate of the four furnace wall oxygen lances is controlled between 0.52 and 0.68 Nm³. 3 / (t·min); When the power supply is between 13000 and 18000 kWh, control the total oxygen supply flow rate between 1.14 and 1.35 Nm³. 3 Within the range of / (t·min); after the scrap steel is melted and cleaned, when the temperature is less than 1550℃, the oxygen supply intensity is controlled at 0.94~1.13Nm. 3 / (t·min), when the temperature is ≥1550℃, the oxygen supply intensity should be controlled between 0.52~0.68Nm. 3 / (t·min), carbon powder is continuously injected from the furnace wall carbon lance to reduce the decarburization rate of the molten pool; in the later stage of smelting, the furnace wall oxygen lance is used to supply weak oxygen + carbon powder injection mode to stabilize and control slag foam. The oxygen supply, powder injection and lime slag making are adjusted in real time according to the steel sample composition and P / C ratio to maintain full-process foam slag operation at a low decarburization rate and improve the final carbon content.

Description

Technical Field

[0001] This invention relates to a short-process electric arc furnace smelting method for producing high-quality green steel with a high scrap ratio of 80%, belonging to the technical field of steelmaking. Background Technology

[0002] Short-process electric arc furnace (EAF) smelting technology offers significant advantages in carbon emission reduction. The demand for high-scrap ratio smelting processes in electric arc furnaces is continuously increasing for key steel grades used in high-end equipment such as bearing steel, cord steel, and spring steel. High-quality steel grades have high requirements for properties such as elongation, fatigue, and impact resistance; therefore, it is necessary to strictly control the total oxygen and carbon content at the end of the EAF smelting process and improve the cleanliness of the molten steel to reduce the formation of deoxidation inclusions.

[0003] When smelting with an 80% high scrap ratio in an electric arc furnace (EAF), the total carbon content is only 0.5% to 1.0%. However, the EAF smelting process requires oxygen to heat, cut, and melt the scrap. After the scrap is melted, a certain oxygen supply is needed to homogenize the composition and temperature of the molten pool and remove harmful impurities. Simultaneously, to ensure smelting efficiency and effectiveness, the furnace wall oxygen lance and furnace door oxygen lance must provide sufficient oxygen during the smelting process. This results in a low carbon content at the end of the EAF process, mostly below 0.05%, leading to severe over-oxidation of the molten steel, with [O] reaching over 700 ppm. This increases deoxidation products during tapping, exacerbating quality problems in the finished steel. Furthermore, severe over-oxidation of the molten steel reduces alloy yield during refining, increases the amount of refining alloys used, and raises smelting costs.

[0004] Patent application CN114015831A discloses a smelting method for increasing the final carbon content of high-carbon steel in an electric arc furnace. By rationally planning and designing the charging system, power supply system, oxygen supply system, and slag formation system, the final carbon content of the electric arc furnace can be increased. However, this method requires a molten iron ratio of 35-40%, and the initial carbon content of the electric arc furnace is relatively high, ranging from 1.5-1.8%. Therefore, the final carbon control is relatively easy. At the same time, the molten iron ratio of 35-40% cannot meet the requirements of low carbon emissions for high-quality steel.

[0005] Patent application CN104328243A discloses an electric arc furnace steelmaking method that combines appropriate carbon addition, high electricity consumption, and controlled oxygen use. This method increases the final carbon content in all-scrap steel smelting in an electric arc furnace to over 0.07% through a combination of these measures. However, this method increases electricity consumption per ton of steel from 330 kWh to 420 kWh, resulting in a significant increase in energy consumption. Furthermore, the addition of carbon powder significantly increases carbon emissions.

[0006] Patent application CN111635978A discloses a method for reducing the carbon-oxygen product at the end of an electric arc furnace. This method increases the carbon content at the end of the electric arc furnace and reduces the oxygen content in the molten steel by continuously adding a large amount of carbon powder and ferrosilicon and adding a slag-forming agent during the electric arc furnace smelting process. However, this method requires the addition of a large amount of ferrosilicon, which leads to an increase in the amount of lime used. At the same time, the large amount of carbon powder and slag-forming agent added will also increase the smelting cost and carbon emissions of the electric arc furnace.

[0007] When smelting bearing steel, cord steel, and spring steel in an electric arc furnace, a high degree of cleanliness is required to ensure the quality of the finished steel. However, when using an electric arc furnace with an 80% high scrap ratio for smelting, the oxygen supply flow rates of the furnace wall oxygen lance and furnace door oxygen lance are increased to shorten the smelting cycle. This results in the carbon content at the final stage of the electric arc furnace being below 0.05%, severe over-oxidation of the molten steel, increased deoxidation products, and a decrease in the quality of the finished steel.

[0008] Currently, when electric arc furnaces (EAFs) smelt steel with a scrap ratio exceeding 80%, the total carbon content is 0.5%~1.0%, resulting in a low initial carbon content in the steel scrap. During EAF smelting, scrap is added to the furnace in two stages, increasing the average smelting time per furnace by 4~5 minutes and extending the smelting cycle. Furthermore, to ensure smelting efficiency and quality, the oxygen supply intensity and quantity of the furnace wall and door oxygen lances are increased, leading to a low final carbon content, mostly below 0.05%. This low final carbon content results in a high [O] content in the molten steel, exceeding 700 ppm, causing severe over-oxidation and increased deoxidation products during tapping, exacerbating quality issues in the finished steel. Reducing the oxygen supply intensity during smelting can increase the final carbon content and reduce the degree of over-oxidation in the molten steel, but it also leads to problems such as reduced scrap melting speed, weakened molten pool stirring intensity, and decreased electrode power supply efficiency. To address the aforementioned problems, this invention improves the carbon content at the end of the electric arc furnace by optimizing the scrap steel structure, pre-treating the peroxide residue, optimizing the oxygen supply process in stages, and stabilizing the foam slag, thereby solving the problem of severe peroxide oxidation of molten steel caused by the low carbon content at the end of the electric arc furnace. Summary of the Invention

[0009] To address the aforementioned problems, this invention discloses a short-process electric arc furnace smelting method for high-quality green steel with a high scrap steel ratio of 80%, the specific technical solution of which is as follows: A short-process electric arc furnace smelting method for producing high-quality green steel with a high scrap ratio of 80% specifically includes the following steps: Step 1: Steel charge is loaded. The steel charge includes scrap steel and molten iron. The amount of scrap steel in the furnace should be controlled to be more than 80% of the total steel charge. The composition of the steel charge and its proportion of the total mass of the steel charge are as follows: ordinary scrap steel 16%~20%, high carbon scrap steel 33%~40%, crushed material 8%~13%, heavy mechanical scrap 20%~22%, and molten iron 10%~20%. Scrap steel is added to the electric arc furnace in one go through a basket, and 300-500 kg of biomass char is added to the bottom of the basket. The initial char weight is 1.0%-1.3% of the steel scrap weight, and the scrap steel pile density is 0.8-1.2 t / m³. 3 ; Step 2: Open the furnace cover of the electric arc furnace. Scrap steel is loaded into the furnace from the top through the material basket. The scrap steel falls from the bottom of the material basket into the electric arc furnace. The material basket is reused. Close the furnace cover and lower the electrodes to start energizing. Step 3: The electric arc furnace is supplied with oxygen in stages, which are divided into four stages: (1) When the power supply of the electric arc furnace is ≤5000kWh, the four furnace wall oxygen lances of the electric arc furnace are turned on to burner mode to preheat the scrap steel; (2) When the power supply is greater than 5000kWh and less than or equal to 13000kWh, the oxygen supply flow rate of the four furnace wall oxygen lances is controlled at 0.52~0.68Nm. 3 / (t·min); (3) When the power supply is greater than 13000kWh, less than or equal to 18000kWh, or when the power supply is sufficient to basically melt and clear the electric arc furnace, control the total oxygen supply flow rate at 1.14~1.35Nm. 3 Within the range of / (t·min), the scrap steel is cut to accelerate its melting; (4) When the power supply is greater than 18000kWh or the scrap steel is basically melted, the total oxygen supply flow rate is controlled at 0.94-1.13Nm. 3 / (t·min); Step 4: After the scrap steel has melted and cleaned for 5 minutes, begin the first temperature measurement. Based on whether the first temperature measurement exceeds 1550℃, determine whether to adjust the oxygen supply intensity and whether steel sampling can begin. When the temperature is ≥1550℃, the oxygen supply intensity should be controlled between 0.52~0.68 Nm. 3 / (t·min), carbon powder is continuously sprayed from the carbon powder gun on the furnace wall to ensure slag foaming and reduce the decarburization rate of the molten pool; Step 5: In the later stage of smelting, the degree of slag foaming is stably controlled by using a weak oxygen supply mode of oxygen lance on the furnace wall and carbon powder injection. The oxygen supply, powder injection and lime slag making are adjusted in real time according to the steel sample composition and P / C ratio to maintain foam slag operation throughout the process and improve the final carbon content.

[0010] Furthermore, in step 1, when preparing the material basket, the scrap steel is loaded into the basket in a layered and cross-layered manner. From the bottom to the top of the basket, the components and their proportions to the total mass of the steel material are added in the following order: 5%~8% crushed material, biomass carbon, 10%~15% heavy mechanical scrap. The remaining ordinary scrap steel, high-carbon scrap steel and heavy mechanical scrap are added in a cyclical and cross-layered manner. Each time, the amount of ordinary scrap steel, high-carbon scrap steel and heavy mechanical scrap added is less than 3000 kg. Finally, 3~5% crushed material is loaded on the top layer of the basket.

[0011] Furthermore, step 3 specifically involves: Step 3.1: When the electrodes are energized, turn on the four oxygen lances on the furnace wall of the electric arc furnace to burner mode, and control the main oxygen flow rate of the oxygen lances at 0.05~0.08 Nm³. 3 / (t·min), supplementary oxygen flow rate controlled at 0.04~0.05Nm 3 / (t·min), natural gas flow rate controlled at 0.08~0.10Nm 3 / (t·min), preheat the scrap steel in the furnace; at the same time, add molten iron from the chute at the back of the electric arc furnace at a rate of 5~10t / min; Step 3.2: When the power supply for electric arc furnace smelting is greater than 5000 kWh and less than or equal to 13000 kWh, turn on the four furnace wall oxygen lances to blowing mode, and control the main oxygen flow rate of each furnace wall oxygen lance at 0.13~0.17 Nm³. 3 Between / (t·min), add a batch of lime and lightly calcined dolomite every 2~3 minutes. The amount of lime added in a batch is 3.5~4.5kg / t, and the amount of lightly calcined dolomite added in a batch is 4.5~5.0kg / t, until step 3.3 is reached; Step 3.3: When the power supply for electric arc furnace smelting is greater than 13000 kWh and less than or equal to 18000 kWh, or when the power supply reaches the point where the furnace is basically clean, open the oxygen lance at the furnace door, and control the main oxygen flow rate at 0.42~0.47 Nm³. 3 The oxygen flow rate is between 0.23 and 0.27 Nm³ / min; simultaneously, the main oxygen flow rate of the oxygen lances on furnace walls #1 and #3 is controlled between 0.23 and 0.27 Nm³ / min. 3 / (t·min), the main oxygen flow rate of the oxygen lances on the walls of furnaces #2 and #4 is controlled at 0.13~0.17 Nm³. 3 / (t·min), cut the scrap steel to accelerate its melting; add a batch of lime every 2~3 minutes, with a batch amount of lime being 2.5~3.5kg / t, until step 4 is reached.

[0012] Furthermore, step 4 specifically involves: Step 4.1: When the power supply for electric arc furnace smelting exceeds 18000 kWh or the scrap steel is basically melted, adjust the oxygen lance flow rate at the furnace door to 0.22~0.25 Nm. 3 / (t·min); at the same time, maintain the main oxygen flow rate of oxygen lances on furnace walls #1 and #3 at 0.23~0.27 Nm³. 3 / (t·min), the main oxygen flow rate of oxygen lances on furnace walls #2 and #4 is 0.13~0.17 Nm³. 3 / (t·min), open the furnace wall carbon powder gun to start spraying carbon powder, and control the carbon powder flow rate in the range of 0.1~0.3kg / (t·min); add a batch of lime every 3~4 minutes, with a batch addition amount of 1.5~2.0kg / t, until step 4.2 is entered; Step 4.2: After the scrap steel has melted for 5 minutes, begin temperature measurement, taking measurements every 2-3 minutes. If the temperature is between 1550-1570℃, close the furnace door oxygen lance, stop the power supply, and take the first steel sample. Control the main oxygen flow rate of all four furnace wall oxygen lances to 0.13-0.17 Nm³. 3 The carbon powder flow rate of the furnace wall carbon powder gun is adjusted to 0.3~0.5 kg / (t·min), and the decarbonization rate is controlled between 0.01%~0.03%C / min; a batch of lime is added every 3~4 minutes, with a batch addition amount of 1.5~2.0 kg / t, until step 5 is entered.

[0013] Furthermore, step 5 specifically involves: Step 5.1: Adjust the oxygen supply process of the electric arc furnace based on the steel sample composition results: When the carbon content in the steel sample is ≥0.6%, and the phosphorus content to carbon content ratio (P / C) is ≤0.07, the main oxygen flow rate of the oxygen lances in furnaces #1 and #3 should be controlled between 0.23 and 0.27 Nm³. 3 / (t·min), the main oxygen flow rate of the oxygen lances on the walls of furnaces #2 and #4 is controlled at 0.27~0.30 Nm³. 3 The carbon powder flow rate of the furnace wall carbon lance is controlled at 0.1~0.3 kg / (t·min), and the oxygen lance flow rate of the furnace door is controlled at 0.42~0.47 Nm³. 3 Add lime every 3-4 minutes, with a batch addition of 1.5-2.0 kg / t. If P / C > 0.07, control the main oxygen flow rate of the oxygen lances on furnace walls #1 and #3 at 0.23-0.27 Nm³. 3 / (t·min), the main oxygen flow rate of the oxygen lances on the walls of furnaces #2 and #4 is controlled at 0.13~0.17 Nm³. 3 The carbon powder flow rate of the furnace wall carbon lance is controlled at 0.3~0.5 kg / (t·min), and the oxygen lance flow rate of the furnace door is controlled at 0.42~0.47 Nm³. 3 / (t·min), add a batch of lime every 2~3 minutes, with a batch addition amount of 3.0~4.0 kg / t; When the carbon content in the steel sample is in the range of 0.4% to 0.6%, close the oxygen lance at the furnace door. If P / C ≤ 0.06, control the main oxygen flow rate of the oxygen lances on furnace walls #1 and #3 at 0.23 to 0.27 Nm³. 3 / (t·min), the main oxygen flow rate of the oxygen lances on the walls of furnaces #2 and #4 is controlled at 0.13~0.17 Nm³. 3 The carbon powder flow rate of the furnace wall carbon lance is controlled at 0.1~0.3 kg / (t·min), and a batch of lime is added every 3~4 minutes, with a batch addition amount of 1.5~2.0 kg / t; if P / C>0.06, the flow rate of the oxygen lance on furnace wall #1 is controlled at 0.23~0.27 Nm. 3 / (t·min), the main oxygen flow rate of the oxygen lances on the furnace walls of No. 2, No. 3 and No. 4 is controlled at 0.13~0.17Nm. 3 / (t·min), the carbon powder flow rate of the furnace wall carbon powder gun is controlled at 0.3~0.5kg / (t·min), and a batch of lime is added every 2~3 minutes, with a batch addition amount of 3.0~4.0kg / t; When the carbon content in the steel sample is less than 0.4%, close the oxygen lance at the furnace door. If P / C ≤ 0.05, control the flow rate of the oxygen lance on furnace wall #1 at 0.23~0.27 Nm. 3 / (t·min), the main oxygen flow rate of the oxygen lances on the furnace walls of No. 2, No. 3 and No. 4 is controlled at 0.13~0.17Nm. 3 The carbon powder flow rate of the furnace wall carbon lance is controlled at 0.3~0.5 kg / (t·min), and a batch of lime is added every 3~4 minutes, with a batch addition amount of 1.5~2.0 kg / t; if P / C>0.05, the main oxygen flow rate of all four furnace wall oxygen lances is controlled at 0.13~0.17 Nm³. 3 The carbon powder flow rate of the furnace wall carbon powder gun is controlled between 0.3 and 0.5 kg / (t·min), and a batch of lime is added every 2 to 3 minutes, with a batch addition amount of 3.0 to 4.0 kg / t. Step 5.2: Take a steel sample every 2-3 minutes. If the composition of the steel sample is not up to standard, repeat the operation in step 7. Step 5.3: After the steel sample composition is qualified, the temperature at the front of the electric arc furnace is measured. When the measured temperature at the front of the electric arc furnace is greater than or equal to 1600℃, the steel is tapped directly; when the measured temperature at the front of the electric arc furnace is less than 1600℃, the power supply is continued, the oxygen lance at the furnace door is closed, and the main oxygen flow rate of all four furnace wall oxygen lances is controlled at 0.13~0.17 Nm³. 3 The carbon powder flow rate of the furnace wall carbon powder gun is controlled between 0.3 and 0.5 kg / (t·min). Based on the molten pool temperature, the power supply time required to heat up to 1600℃ is calculated according to the heating rate of 20 to 30℃ per minute. After the power supply is completed, the steel is tapped.

[0014] Furthermore, the total amount of lime added during the electric arc furnace smelting process is controlled at 26 kg / t to 32 kg / t.

[0015] Furthermore, the carbon powder injected during the electric arc furnace smelting process has a C content ≥80%, an S content ≤0.2%, and a particle size ≤2mm.

[0016] Furthermore, the composition of biochar and its percentage by mass are as follows: C content ≥ 80%, S content ≤ 0.2%, ash content ≤ 15%, and other impurities.

[0017] The beneficial effects of this invention are: This invention addresses the problem of low carbon content and severe over-oxidation of molten steel at the end of high scrap ratio smelting in electric arc furnaces, caused by increased oxygen flow rates in the furnace wall and door oxygen lances. The solution involves optimizing the scrap structure to control the bulk density of the scrap basket at 0.8~1.2 t / m³. 3 To ensure that scrap steel can be added to the electric arc furnace in one go through the scrap steel basket, shortening the smelting time; 300-500 kg of biomass carbon is added to the bottom of the scrap steel basket to pretreat the peroxide slag, reducing (FeO) in the slag and lowering the oxygen content in the slag left in the electric arc furnace; the oxygen supply mode of each stage of electric arc furnace smelting is optimized: in the early stage of smelting, the preheating time of the burner mode for scrap steel is extended; during the scrap steel melting period, the oxygen lance on the furnace wall is turned on to a high oxygen supply mode, combined with the oxygen lance at the furnace door to cut the scrap steel and accelerate the melting of the scrap steel; after the scrap steel is melted and cleared, a control mode of weak oxygen supply + carbon powder injection is adopted to maintain the foam slag operation throughout the process while reducing the decarburization rate of the molten pool and increasing the final carbon content. Attached Figure Description

[0018] Figure 1 This is a diagram showing the distribution of electric arc furnace types according to the present invention. List of reference numerals in the attached diagram: 1—furnace door, 2—1# furnace wall oxygen lance, 3—electrode, 4—2# furnace wall oxygen lance, 5—tap hole, 6—molten iron chute, 7—3# furnace wall oxygen lance, 8—4# furnace wall oxygen lance. Detailed Implementation

[0019] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0020] The chemical composition and size requirements of the steel materials fed into the furnace in this invention are shown in Table 1 below. The crushed material includes scrap automotive steel sheets, color-coated steel, and scrap steel from the market that has been crushed, impurities removed, and screened by a crusher, with a bulk density of 1.0~2.0 t / m³. 3High-carbon scrap steel includes the cut ends of high-carbon steel rolling processes, the cut ends and scrap recycled from high-carbon wire rod processing plants; heavy mechanical scrap includes cast steel or cast iron scrap such as engines, counterweights, and mechanical castings; ordinary scrap steel includes social scrap steel, plate processing scraps, and non-cast medium and heavy scrap steel.

[0021] Table 1 Chemical composition and dimensional requirements of steel feedstock

[0022] The location distribution of the oxygen lances at the furnace door and furnace wall of the electric arc furnace of this invention is shown in the appendix. Figure 1 , attached Figure 1 This is a top cross-sectional view of the electric arc furnace of the present invention. Three electrodes 3 are arranged at the center of the furnace. Two furnace wall oxygen lances are arranged on each side of the furnace door 1. One side is numbered as furnace wall oxygen lance 1# (2) and furnace wall oxygen lance 2# (4), and the other side is numbered as furnace wall oxygen lance 3# (7) and furnace wall oxygen lance 4# (8). Furnace wall oxygen lance 1# (2) and furnace wall oxygen lance 4# (8) are located closest to the furnace door 1. A tapping hole 5 is provided opposite the furnace door 1, and a molten iron chute 6 is located next to the tapping hole 5. The layout and structure of this electric arc furnace are standard industry configurations, and the present invention does not improve the electric arc furnace. This description of the electric arc furnace is provided merely for the purpose of facilitating a quick understanding of the technical solution of the present invention.

[0023] Implementation Case 1: 1. Taking a 100-ton ultra-high power electric arc furnace as an example, the steel grade being smelted is 70 steel, with a target phosphorus content of ≤0.02%; during the smelting process, the amount of scrap steel charged is 89 tons and the amount of molten iron charged is 21 tons, with a scrap steel ratio of 80.9%.

[0024] Step 1: During the smelting process, the steel material is composed of 17.6t of ordinary scrap steel, 39.3t of high-carbon scrap steel, 8.9t of crushed material, 23.2t of heavy mechanical scrap, and 21t of molten iron. From the bottom to the top of the basket, add the following in sequence: 5.5t of crushed material, 380kg of biomass carbon, and 11.2t of heavy mechanical scrap. The remaining ordinary scrap steel, high-carbon scrap steel, and heavy mechanical scrap are added in a cyclical and alternating manner, with each addition being less than 3000kg. Finally, the remaining 3.4t of crushed material is placed on the top layer of the basket. Step 2: Open the electric arc furnace cover, add scrap steel, close the cover, lower the electrodes, and start energizing. Set the main oxygen flow rate of the four oxygen lances on the furnace wall to 300~480 Nm³. 3 / h, auxiliary oxygen flow rate set to 260~300 Nm 3 / h, gas flow rate set to 480~600 Nm 3 / h, preheat the scrap steel in the electric arc furnace; at the same time, add molten iron from the chute at the back of the electric arc furnace, and the molten iron is added over a period of 3.5 minutes. Step 3: When the total power consumption of the electric arc furnace smelting is 5460 kWh, turn on the four furnace wall oxygen lances to the blowing mode, and control the main oxygen flow rate at 900~1100 Nm³. 3 / h; Add a batch of lime and lightly calcined dolomite every 2~3 minutes. The amount of lime added in a batch is 400kg, and the amount of lightly calcined dolomite added in a batch is 500kg. Step 4: When the power supply for electric arc furnace smelting reaches 13240 kWh, open the oxygen lance at the furnace door and control the main oxygen flow rate at 2500~2800 Nm³. 3 The main oxygen flow rate of the oxygen lances on the walls of furnaces #1 and #3 is controlled between 1400 and 1600 Nm³ / h. 3 / h, the main oxygen flow rate of the bundled oxygen lances on the furnace walls of No. 2 and No. 4 is controlled at 900~1100 Nm³ / h. 3 / h, cut the scrap steel to accelerate its melting; add a batch of lime every 2-3 minutes, with each batch containing 350kg of lime; Step 5: When the power supply for electric arc furnace smelting is 18110 kWh, adjust the oxygen lance flow rate at the furnace door to 1300~1500 Nm. 3 The main oxygen flow rate of the No. 1 furnace wall cluster oxygen lance is controlled between 1400 and 1600 Nm³ / h. 3 Within the range of / h, the main oxygen flow rate of the bundled oxygen lances on the furnace walls of furnaces #2, #3, and #4 is controlled at 900~1100 Nm³. 3 / h; Open the furnace wall carbon powder gun to start spraying carbon powder, and control the carbon powder flow rate at 15~30kg / min; Add a batch of lime every 3~4 minutes, with a batch amount of lime being 200kg; Step 6: After the scrap steel has been melted and cleaned for 5 minutes, start temperature measurement. The first temperature measurement is 1563℃. Stop the power supply, close the furnace door oxygen lance, take the first steel sample, and control the main oxygen flow rate of all four furnace wall oxygen lances at 900~1100 Nm. 3 / h, adjust the carbon powder flow rate of the furnace wall carbon powder gun to 35~40kg / min, control the decarburization rate between 0.01%~0.03%C / min, add a batch of lime every 3~4min, and the amount of lime added in a batch is 200kg; Step 7: The first steel sample has a carbon content of 0.48%, a phosphorus content of 0.031%, and a P / C ratio of 0.065. The main oxygen flow rate of the No. 1 furnace wall cluster oxygen lance is controlled at 1400~1600 Nm³. 3 Within the range of / h, the main oxygen flow rate of the bundled oxygen lances on the furnace walls of furnaces #2, #3, and #4 is controlled at 900~1100 Nm³. 3 / h, the carbon powder flow rate of the furnace wall carbon powder gun is controlled between 40~50kg / min, and a batch of lime is added every 2~3min, with a batch of lime added at 380kg; The second steel sample contained 0.42% carbon and 0.023% phosphorus, with a P / C ratio of 0.055. The main oxygen flow rate of the oxygen lances in furnaces #1 and #3 was controlled at 1400-1600 Nm³. 3 / h, the main oxygen flow rate of the bundled oxygen lances on the furnace walls of No. 2 and No. 4 is controlled at 900~1100 Nm³ / h. 3 / h, the carbon powder flow rate of the furnace wall carbon powder gun is controlled at 20~30kg / min, and a batch of lime is added every 3~4min, with a batch of lime added at 220kg; The third steel sample contained 0.39% carbon and 0.017% phosphorus, which met the composition requirements. Table 2 below shows the test results of the steel samples taken in this case: Table 2. Results of Chemical Composition Analysis of Steel Sample in Case 1

[0025] In practical work, steel sample testing results are generally based on five components: C, Si, Mn, P, and S. The purpose of this patent is to increase the carbon content at the end of the electric furnace test to prevent over-oxidation of molten steel. Whether or not there is over-oxidation in the steel can generally be determined by the carbon content at the end. When the carbon content at the end of the molten steel is too low (e.g., 0.05%), it can indicate that over-oxidation has occurred. When the carbon content at the end of the electric furnace test reaches the range of this patent, over-oxidation is avoided.

[0026] Step 8: Measure the temperature at the front of the electric arc furnace; the temperature is 1582℃. Control the main oxygen flow rate of all four furnace wall oxygen lances to 900~1100 Nm³. 3 / h, with the oxygen lance at the furnace door closed, the electrodes were lowered and energized for another 1 minute. The temperature was measured again at the furnace, showing 1607℃, and steel tapping began. A total of 3100 kg of lime and 1500 kg of lightly calcined dolomite were added during the smelting process.

[0027] Implementation Case 2: 1. Taking a 100-ton ultra-high power electric arc furnace as an example, the steel grade being smelted is SWRH72B, with a target phosphorus content of ≤0.02%; the amount of scrap steel charged during the smelting process is 93 tons, and the amount of molten iron charged is 20 tons, with a scrap steel ratio of 82.3%. Step 1: During the smelting process, the steel material is composed of 18.6t of ordinary scrap steel, 40.7t of high-carbon scrap steel, 9.4t of crushed material, 24.3t of heavy mechanical scrap, and 20t of molten iron. From the bottom to the top of the basket, add the following in sequence: 5.8t of crushed material, 460kg of biomass carbon, and 13.6t of heavy mechanical scrap. The remaining ordinary scrap steel, high-carbon scrap steel, and heavy mechanical scrap are added in a cyclical and alternating manner, with each addition being less than 3000kg. Finally, the remaining 3.6t of crushed material is placed on the top layer of the basket. Step 2: Open the electric arc furnace cover, add scrap steel, close the cover, lower the electrodes, and start energizing. Set the main oxygen flow rate of the four oxygen lances on the furnace wall to 300~480 Nm³. 3 / h, auxiliary oxygen flow rate set to 260~300 Nm 3 / h, gas flow rate set to 480~600 Nm 3 / h, preheat the scrap steel in the electric arc furnace; at the same time, add molten iron from the chute at the back of the electric arc furnace, and the molten iron is added in 2.8min. Step 3: When the total power consumption of the electric arc furnace smelting is 5460 kWh, turn on the four furnace wall oxygen lances to the blowing mode, and control the main oxygen flow rate at 900~1100 Nm³. 3 / h; Add a batch of lime and lightly calcined dolomite every 2~3 minutes. The amount of lime added in a batch is 420kg and the amount of lightly calcined dolomite added in a batch is 480kg. Step 4: When the power supply for electric arc furnace smelting reaches 13240 kWh, open the oxygen lance at the furnace door and control the main oxygen flow rate at 2500~2800 Nm³. 3 The main oxygen flow rate of the oxygen lances on the walls of furnaces #1 and #3 is controlled between 1400 and 1600 Nm³ / h. 3 The main oxygen flow rate of the oxygen lances in furnaces #2 and #4 is controlled between 900 and 1100 Nm³ / h. 3 / h, cut the scrap steel to accelerate the melting of the scrap steel, and add a batch of lime every 2~3 minutes, with a batch of lime being 360kg; Step 5: When the power supply for electric arc furnace smelting is 18420 kWh, adjust the oxygen lance flow rate at the furnace door to 1300~1500 Nm. 3 / h; at the same time, the main oxygen flow rate of the No. 1 cluster oxygen gun is controlled at 1400~1600Nm 3 / h, the main oxygen flow rate of the bundled oxygen lances on the furnace walls of furnaces #2, #3, and #4 is controlled at 900~1100 Nm³ / h. 3 Between / h, open the furnace wall carbon powder gun to start spraying carbon powder, and control the carbon powder flow rate of the furnace wall carbon powder gun at 15~30kg / min; add a batch of lime every 3~4 minutes, with a batch of lime being 200kg; Step 6: After the scrap steel has been melted for 5 minutes, start temperature measurement. The first temperature measurement is 1557℃. Stop the power supply, close the oxygen lance at the furnace door, take the first steel sample, and control the main oxygen flow rate of all four furnace wall oxygen lances to 900~1100 Nm. 3 / h, adjust the carbon powder flow rate of the furnace wall carbon powder gun to 35~40kg / min, control the decarburization rate between 0.01%~0.03%C / min, add a batch of lime every 3~4min, and the amount of lime added in a batch is 200kg; Step 7: In the first steel sample, the carbon content is 0.51%, the phosphorus content is 0.027%, and the P / C ratio is 0.053. The main oxygen flow rate of the oxygen lances in furnaces #1 and #3 is controlled at 1400~1600 Nm³. 3 / h, the main oxygen flow rate of the bundled oxygen lances on the furnace walls of No. 2 and No. 4 is controlled at 900~1100 Nm³ / h. 3 Between / h, the carbon powder flow rate of the furnace wall carbon powder gun is controlled at 20~30kg / min, and a batch of lime is added every 3~4 minutes, with a batch of lime added at 200kg; The second steel sample contained 0.38% carbon and 0.015% phosphorus, which met the composition requirements. Table 3 below shows the test results of the steel samples taken in this case: Table 3. Results of Chemical Composition Analysis of Steel Samples in Case 2

[0028] Step 8: Measure the temperature at the front of the electric arc furnace; the temperature is 1572℃. Control the main oxygen flow rate of all four furnace wall oxygen lances to 900~1100 Nm³. 3 / h, with the oxygen lance at the furnace door closed, the electrodes were lowered and energized for another 1.5 minutes. The temperature was measured again at the furnace, reaching 1603℃, and steel tapping began. A total of 3180 kg of lime and 1440 kg of lightly calcined dolomite were added during the smelting process.

[0029] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0030] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A short-process electric arc furnace smelting method for high-quality green steel with a high scrap ratio of 80%, characterized in that, Specifically, it includes the following steps: Step 1: Steel charge is loaded. The steel charge includes scrap steel and molten iron. The amount of scrap steel in the furnace should be controlled to be more than 80% of the total steel charge. The composition of the steel charge and its proportion of the total mass of the steel charge are as follows: ordinary scrap steel 16%~20%, high carbon scrap steel 33%~40%, crushed material 8%~13%, heavy mechanical scrap 20%~22%, and molten iron 10%~20%. Scrap steel is added to the electric arc furnace in one go through a basket, and 300-500 kg of biomass char is added to the bottom of the basket. The initial char weight is 1.0%-1.3% of the steel scrap weight, and the scrap steel pile density is 0.8-1.2 t / m³. 3 ; Step 2: Open the furnace cover of the electric arc furnace. Scrap steel is loaded into the furnace from the top through the basket. The scrap steel falls into the furnace from the bottom of the basket. The basket is reused. Close the furnace cover and lower the electrodes to start energizing. Step 3: The electric arc furnace is supplied with oxygen in stages, which are divided into four stages: (1) When the power supply of the electric arc furnace is ≤5000kWh, the four furnace wall oxygen lances of the electric arc furnace are turned on to burner mode to preheat the scrap steel; (2) When the power supply is greater than 5000kWh and less than or equal to 13000kWh, the oxygen supply flow rate of the four furnace wall oxygen lances is controlled at 0.52~0.68Nm. 3 / (t·min); (3) When the power supply is greater than 13000kWh and less than or equal to 18000kWh, control the total oxygen supply flow rate at 1.14~1.35Nm. 3 Within the range of / (t·min), the scrap steel is cut to accelerate its melting; (4) When the power supply is greater than 18000kWh, the total oxygen supply flow rate is controlled between 0.94-1.13Nm. 3 / (t·min); Step 4: After the scrap steel has melted and cleaned for 5 minutes, begin the first temperature measurement. Based on whether the first temperature measurement is greater than or equal to 1550℃, determine whether to adjust the oxygen supply intensity and whether steel sampling can begin. When the temperature is ≥1550℃, the oxygen supply intensity should be controlled between 0.52 and 0.68 Nm. 3 / (t·min), carbon powder is continuously sprayed from the carbon powder gun on the furnace wall to ensure slag foaming and reduce the decarburization rate of the molten pool; Step 5: In the later stage of smelting, the degree of slag foaming is stably controlled by using a weak oxygen supply mode of oxygen lance on the furnace wall and carbon powder injection. The oxygen supply, powder injection and lime slag making are adjusted in real time according to the steel sample composition and P / C ratio to maintain foam slag operation throughout the process and improve the final carbon content.

2. The short-process electric arc furnace smelting method for high-quality green steel with a high scrap ratio of 80% according to claim 1, characterized in that, In step 1, when preparing the material basket, the scrap steel is loaded into the basket in a layered and cross-layered manner. The components and their proportions to the total mass of the steel material are added sequentially from the bottom to the top of the basket: 5%~8% crushed material, biomass carbon, 10%~15% heavy mechanical scrap, and the remaining ordinary scrap steel, high carbon scrap steel and heavy mechanical scrap are added in a cyclical and cross-layered manner. The amount of ordinary scrap steel, high carbon scrap steel and heavy mechanical scrap added each time is less than 3000 kg. Finally, 3~5% crushed material is loaded into the top layer of the basket.

3. The short-process electric arc furnace smelting method for high-quality green steel with an 80% high scrap ratio according to claim 1, characterized in that, Step 3 specifically involves: Step 3.1: When the electrodes are energized, turn on the four oxygen lances on the furnace wall of the electric arc furnace to burner mode, and control the main oxygen flow rate of the oxygen lances at 0.05~0.08 Nm³. 3 / (t·min), supplementary oxygen flow rate controlled at 0.04~0.05Nm 3 / (t·min), natural gas flow rate controlled at 0.08~0.10Nm 3 / (t·min), preheat the scrap steel in the furnace; at the same time, add molten iron from the chute at the back of the electric arc furnace at a rate of 5~10t / min; Step 3.2: When the power supply for electric arc furnace smelting is greater than 5000 kWh and less than or equal to 13000 kWh, turn on the four furnace wall oxygen lances to blowing mode, and control the main oxygen flow rate of each furnace wall oxygen lance at 0.13~0.17 Nm³. 3 Between / (t·min), add a batch of lime and lightly calcined dolomite every 2~3 minutes. The amount of lime added in a batch is 3.5~4.5kg / t, and the amount of lightly calcined dolomite added in a batch is 4.5~5.0kg / t, until step 3.3 is reached; Step 3.3: When the power supply for electric arc furnace smelting is greater than 13000 kWh and less than or equal to 18000 kWh, open the oxygen lance at the furnace door, and control the main oxygen flow rate at 0.42~0.47 Nm³. 3 The oxygen flow rate is between 0.23 and 0.27 Nm³ / min; simultaneously, the main oxygen flow rate of the oxygen lances on furnace walls #1 and #3 is controlled between 0.23 and 0.27 Nm³ / min. 3 / (t·min), the main oxygen flow rate of the oxygen lances on the walls of furnaces #2 and #4 is controlled at 0.13~0.17 Nm³. 3 / (t·min), cut the scrap steel to accelerate its melting; add a batch of lime every 2~3 minutes, with a batch amount of lime being 2.5~3.5kg / t, until step 3.4 is reached; Step 3.4: When the power supply for electric arc furnace smelting exceeds 18000 kWh, adjust the oxygen lance flow rate at the furnace door to 0.22~0.25 Nm. 3 / (t·min); at the same time, maintain the main oxygen flow rate of oxygen lances on furnace walls of No. 1 and No. 3 at 0.23~0.27 Nm³. 3 / (t·min), the main oxygen flow rate of the oxygen lances on the walls of furnaces #2 and #4 is 0.13~0.17 Nm³. 3 / (t·min), open the furnace wall carbon powder gun to start blowing carbon powder, and control the carbon powder flow rate in the range of 0.1~0.3kg / (t·min); add a batch of lime every 3~4 minutes, with a batch addition amount of 1.5~2.0kg / t, until step 4 is entered.

4. The short-process electric arc furnace smelting method for high-quality green steel with a high scrap ratio of 80% according to claim 3, characterized in that, Step 4 specifically involves: Temperature measurement begins 5 minutes after the scrap steel has melted and cleared, and is repeated every 2-3 minutes. If the temperature is between 1550-1570℃, the furnace door oxygen lance is closed, power is stopped, and the first steel sample is taken. The main oxygen flow rate of all four furnace wall oxygen lances is controlled at 0.13-0.17 Nm³. 3 The carbon powder flow rate of the furnace wall carbon powder gun is adjusted to 0.3~0.5 kg / (t·min), and the decarbonization rate is controlled between 0.01%~0.03% / min; a batch of lime is added every 3~4 min, with a batch addition amount of 1.5~2.0 kg / t, until step 5 is entered.

5. The short-process electric arc furnace smelting method for high-quality green steel with a high scrap ratio of 80% according to claim 4, characterized in that, Step 5 specifically involves: Step 5.1: Adjust the oxygen supply process of the electric arc furnace based on the steel sample composition results: When the carbon content in the steel sample is >0.6%, and the phosphorus content to carbon content ratio (P / C) is ≤0.07, the main oxygen flow rate of the oxygen lances in furnaces #1 and #3 should be controlled between 0.23 and 0.27 Nm³. 3 / (t·min), the main oxygen flow rate of the oxygen lances on the walls of furnaces #2 and #4 is controlled at 0.27~0.30 Nm³. 3 The carbon powder flow rate of the furnace wall carbon lance is controlled at 0.1~0.3 kg / (t·min), and the oxygen lance flow rate of the furnace door is controlled at 0.42~0.47 Nm³. 3 Add lime every 3-4 minutes, with a batch addition of 1.5-2.0 kg / t. If P / C > 0.07, control the main oxygen flow rate of the oxygen lances on furnace walls #1 and #3 at 0.23-0.27 Nm³. 3 / (t·min), the main oxygen flow rate of the oxygen lances on the walls of furnaces #2 and #4 is controlled at 0.13~0.17 Nm³. 3 The carbon powder flow rate of the furnace wall carbon lance is controlled at 0.3~0.5 kg / (t·min), and the oxygen lance flow rate of the furnace door is controlled at 0.42~0.47 Nm³. 3 / (t·min), add a batch of lime every 2~3 minutes, with a batch addition amount of 3.0~4.0 kg / t; When the carbon content in the steel sample is in the range of 0.4% to 0.6%, close the oxygen lance at the furnace door. If P / C ≤ 0.06, control the main oxygen flow rate of the oxygen lances on furnace walls #1 and #3 at 0.23 to 0.27 Nm³. 3 / (t·min), the main oxygen flow rate of the oxygen lances on the walls of furnaces #2 and #4 is controlled at 0.13~0.17 Nm³. 3 The carbon powder flow rate of the furnace wall carbon lance is controlled at 0.1~0.3 kg / (t·min), and a batch of lime is added every 3~4 minutes, with a batch addition amount of 1.5~2.0 kg / t; if P / C>0.06, the flow rate of the oxygen lance on furnace wall #1 is controlled at 0.23~0.27 Nm. 3 / (t·min), the main oxygen flow rate of the oxygen lances on the furnace walls of No. 2, No. 3 and No. 4 is controlled at 0.13~0.17Nm. 3 / (t·min), the carbon powder flow rate of the furnace wall carbon powder gun is controlled at 0.3~0.5kg / (t·min), and a batch of lime is added every 2~3 minutes, with a batch addition amount of 3.0~4.0kg / t; When the carbon content in the steel sample is less than 0.4%, close the oxygen lance at the furnace door. If P / C ≤ 0.05, control the flow rate of the oxygen lance on furnace wall #1 at 0.23~0.27 Nm. 3 / (t·min), the main oxygen flow rate of the oxygen lances on the furnace walls of No. 2, No. 3 and No. 4 is controlled at 0.13~0.17Nm. 3 The carbon powder flow rate of the furnace wall carbon lance is controlled at 0.3~0.5 kg / (t·min), and a batch of lime is added every 3~4 minutes, with a batch addition amount of 1.5~2.0 kg / t; if P / C>0.05, the main oxygen flow rate of all four furnace wall oxygen lances is controlled at 0.13~0.17 Nm³. 3 The carbon powder flow rate of the furnace wall carbon powder gun is controlled between 0.3 and 0.5 kg / (t·min), and a batch of lime is added every 2 to 3 minutes, with a batch addition amount of 3.0 to 4.0 kg / t. Step 5.2: Take a steel sample every 2-3 minutes. If the composition of the steel sample is not up to standard, repeat the operation of step 5.

1. Step 5.3: After the steel sample composition is qualified, the temperature at the front of the electric arc furnace is measured. When the measured temperature at the front of the electric arc furnace is greater than or equal to 1600℃, the steel is tapped directly; when the measured temperature at the front of the electric arc furnace is less than 1600℃, the power supply is continued, the oxygen lance at the furnace door is closed, and the main oxygen flow rate of all four furnace wall oxygen lances is controlled at 0.13~0.17 Nm³. 3 The carbon powder flow rate of the furnace wall carbon powder gun is controlled between 0.3 and 0.5 kg / (t·min). Based on the molten pool temperature, the power supply time required to heat up to 1600℃ is calculated according to the heating rate of 20 to 30℃ per minute. After the power supply is completed, the steel is tapped.

6. The short-process electric arc furnace smelting method for high-quality green steel with a high scrap ratio of 80% according to claim 5, characterized in that, The total amount of lime added during the electric arc furnace smelting process is controlled between 26 kg / t and 32 kg / t.

7. The short-process electric arc furnace smelting method for high-quality green steel with a high scrap ratio of 80% according to claim 5, characterized in that, The carbon powder injected during the electric arc furnace smelting process has a C content ≥ 80%, an S content ≤ 0.2%, and a particle size ≤ 2 mm.

8. The short-process electric arc furnace smelting method for high-quality green steel with a high scrap ratio of 80% according to claim 1, characterized in that, The composition of the biochar and its percentage by mass are as follows: C content ≥ 80%, S content ≤ 0.2%, ash content ≤ 15%, and other impurities.

Images