A steelmaking method for adding slag-forming materials outside the converter furnace

Abstract

This invention relates to a steelmaking method for adding slag-forming materials outside the converter furnace, belonging to the field of steelmaking technology in iron and steel metallurgy. It includes: 1) calculating the amount of various slag-forming materials to be added using a slag calculation model; 2) placing the scrap steel hopper on the scrap steel scale in advance, and using a loader to load various slag-forming materials into the bottom of the scrap steel hopper according to the calculation results; 3) after adding all the slag-forming materials to the bottom of the scrap steel hopper, using a crane to add various types of scrap steel into the scrap steel hopper; 4) after the converter tapping is completed, slag splashing and furnace protection operations are performed first, and after the slag is splashed dry, all the slag is poured into the slag basin; 5) the converter is then rocked to 45-50° to add scrap steel, and then the ferroalloy charging operation is performed; 6) after ferroalloy charging is completed, the converter is first rocked backward to about 28-32°, and then rocked back to the "zero position"; 7) the oxygen lance is lowered to the blowing lance position, nitrogen is first purged for about 25-35 seconds, the nitrogen is turned off, and oxygen is immediately switched to for ignition.

Description

Technical Field

[0001] This invention belongs to the field of steelmaking technology in iron and steel metallurgy, specifically relating to a steelmaking method for precisely adding slag-forming materials outside the converter ladle. Background Technology

[0002] Currently, the slag-forming materials used in converters (lime, dolomite, and ores, etc.) are transported from ground silos to corresponding high-level silos via belt conveyors and unloading trolleys. During converter smelting, various slag-forming materials are added through the high-level silos based on the molten iron conditions, scrap steel conditions, the steel grade being produced, and endpoint control conditions. In converter production, belt malfunctions, temporary maintenance, and high-level silo failures can prevent belt feeding or high-level silo unloading, disrupting normal production. Currently, to further reduce production costs, many large steel mills are building new large-scale steel enterprises using direct-feed blast furnaces without blast furnaces or torpedo ladles. If high-level silos cannot be fed or malfunction, converter shutdowns will occur, leading to blast furnace shutdowns or the production of cast iron blocks, significantly impacting normal stable production and production costs. Summary of the Invention

[0003] The purpose of this invention is to provide a steelmaking method for adding slag-forming materials outside the converter furnace. By adjusting the method of adding slag-forming materials (step 3), optimizing the slag retention process (step 4), pouring all the slag into the slag basin after slag splashing, adopting a no-slag-retention operation, and optimizing the blowing lance position (steps 6, 7, and 8), the slag-forming materials and scrap steel are added into the converter together through the scrap steel hopper, solving the problem of feeding and unloading due to belt conveyor and high-level hopper malfunctions. Optimizing the slag retention process, adopting a no-slag-retention operation, and optimizing the blowing and ignition method can solve the problem of poor blowing and ignition and failure to ignite when the slag-forming materials are added into the furnace through the scrap steel hopper at once, thus improving the success rate of blowing and ignition. Optimizing the blowing lance position in the process solves the problem of back-drying phenomenon during the blowing process when the slag-forming materials are added at once, improving the stability of the endpoint control.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] This invention provides a steelmaking method for precisely adding slag-forming materials outside the converter furnace, the method comprising the following steps:

[0006] 1) Based on the loading structure, the amount of various slag-forming materials to be added is calculated using the slag material calculation model;

[0007] 2) Place the scrap steel bucket on the scrap steel scale in advance, and use a loader to load various slag-forming materials into the bottom of the scrap steel bucket;

[0008] 3) After adding all the slag-forming materials to the bottom of the scrap steel, use a crane to load all types of scrap steel into the scrap steel hopper;

[0009] 4) After the converter tapping is completed, slag splashing and furnace protection operations are carried out first. After the slag is splashed dry, all the slag is poured into the slag basin.

[0010] 5) After slag removal, shake the converter to 45-50° to add scrap steel, and then proceed with the iron addition operation;

[0011] 6) After the iron is added, first rock the converter backward to about 28-32 degrees, then rock it back to the "zero position";

[0012] 7) Lower the oxygen lance to the purge position, purge with nitrogen for 25-35 seconds, turn off the nitrogen, immediately switch to oxygen, and start the purge and ignition. The oxygen pressure should be adjusted according to the purge curve.

[0013] 8) When starting to blow, the gun position should be 50-100mm lower than the normal gun position. After blowing for 2-3 minutes, raise the gun position to the normal gun position (1450mm). During the process, the gun position should be 50-100mm higher than the normal gun position to prevent back-drying. In the later stage, gradually lower the gun position to the normal gun position.

[0014] As an improvement to the method of the present invention, in step 1), the slag calculation model program includes: a secondary lance or a secondary flue gas analysis system, or a material and heat balance calculation model based on material and heat balance. If a secondary lance or a secondary flue gas analysis system is available, the amount of slag-forming material added can be calculated using the secondary lance or the secondary flue gas analysis system; if a secondary lance or a secondary flue gas analysis system is unavailable, a calculation program can be created based on material and heat balance. The secondary lance or secondary flue gas analysis system is a system known in the art.

[0015] As an improvement to the method of the present invention, in step 2), the various slag-forming materials include one or more of the following: lime, raw dolomite, and sludge balls (sintered ore). The scrap steel hopper is placed on the scrap steel scale in advance, and then the various slag-forming materials are accurately loaded according to the calculation results. The lime, raw dolomite, sludge balls (sintered ore), and other slag-forming materials should be evenly spread on the bottom of the scrap steel hopper.

[0016] The material and heat balance calculation model is as follows:

[0017] The formula for calculating the amount of sinter added is as follows:

[0018] Sinter addition amount = ((M) 铁 -120)*7.5+(20-M 废钢 )*10+(Si-0.3%)*10000*2.2+(0.30%-Si 铁水硅 )*100*80*0.67+(0.30%-Si 铁水硅 )*100*80*0.69+(T 铁水温度 -1350)*0.8*100 / 3+1000;

[0019] The formula for the amount of lime added is: Lime addition amount = 80 * Si 铁水硅 That is, the formula for adding lime is 80 * silicon number (for example, if the silicon content of molten iron is 0.30%, the amount of lime added is 80 * 30 = 2400 kg).

[0020] The amount of raw dolomite added is 50% of the amount of lime added; (theoretically, any excess should be ≤2000 kg):

[0021] Where: M 铁 For the amount of molten iron; M 废钢 For scrap steel quantity; Si 铁水硅 T represents the silicon content in molten iron. 铁水温度 The temperature of the molten iron.

[0022] The material and heat balance calculation model is based on the following data: 120 tons of molten iron, 0.30% silicon content, 1350℃ temperature, 20 tons of scrap steel, a final temperature of 1630℃, and a final carbon content of 0.10%. Specifically, in the material and heat balance calculation model, 120 represents the amount of molten iron (tons), 0.30 represents the silicon content (%), 1350 represents the temperature (℃), 20 represents the scrap steel (tons), 1630 represents the final temperature (℃), and 0.10 represents the final carbon content (%); 7.5 represents the temperature rise per ton of molten iron (℃), and the theoretical temperature rise per ton of molten iron is 8.1℃. The actual value is 7.5℃; 10 represents the temperature drop of 1 ton of scrap steel (℃), with a theoretical temperature drop of 11.88℃, but the actual value is 10℃; 2.2 represents the temperature rise of 0.01% silicon (℃), with a theoretical temperature rise of 2.78℃, but the actual value is 2.2℃; 3 represents the temperature drop of 100kg ore (℃), with a theoretical temperature drop of 4.32℃, but the actual value is 3℃; 0.69 represents the temperature drop of 100kg raw dolomite (℃); 0.67 represents the temperature drop of 100kg lime (℃); and 0.8 represents the influence of 1 degree of molten iron temperature on the final temperature (℃).

[0023] As an improvement to the method of the present invention, in step 3), the scrap steel includes: heavy scrap steel and / or steel cutting and crushing material briquettes.

[0024] Among them, the dimensions of heavy scrap steel are: length ≤ 1000mm, width ≤ 500mm, and height ≤ 300mm; the dimensions of steel cutting and crushing material briquettes are: length ≤ 400mm and width or diameter ≤ 350mm. The standard length, width, and height of scrap steel must not be less than 10cm. Scrap steel must not contain slag steel smaller than the standard produced by the crushing material to prevent affecting the start-up and ignition.

[0025] As an improvement to the method of the present invention, in step 4), in order to improve the effect of ignition, all the slag is poured into the slag basin after the slag splashing ends, and no slag is left.

[0026] As an improvement to the method of the present invention, in step 5), after the slag is discharged, the converter is shaken to 45-50° to add scrap steel. After the scrap steel and slag-forming material are added, the converter is shaken downward to 85-95°, and then the converter is shaken to the iron-adding position to add iron.

[0027] As an improvement to the method of the present invention, in step 7), the nitrogen regulating valve is opened to the maximum, the nitrogen main pipe pressure is not lower than 1.6 MPa, and before blowing, the oxygen gun is lowered to 3.0-3.5 m for 25-35 seconds, and then immediately converted into oxygen for blowing and ignition.

[0028] As an improvement to the method of the present invention, other parts without specified adjustment parameters are controlled according to the original control parameters.

[0029] The present invention has the following beneficial effects:

[0030] 1) This invention achieves a precise method for adding slag-forming materials outside the furnace by adjusting the method of adding slag-forming materials to the converter and optimizing the slag retention and ignition processes. This method can cope with situations such as the inability to feed materials into the high-level silo or malfunctions of the high-level silo, thus ensuring normal production organization of the converter.

[0031] 2) This invention can prevent heat loss and increased production costs caused by the inability to discharge materials from high-level silos, which would affect converter production and consequently blast furnace shutdown or cast iron blocks. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the slag placement according to the present invention;

[0033] Figure label:

[0034] 1. Scrap steel hopper; 2. Sintered ore; 3. Lime; 4. Burnt dolomite; 5. Steel cutting briquettes; 6. Rebar briquettes. Detailed Implementation

[0035] The present invention will be further described below with reference to embodiments and comparative examples. However, the scope of protection of the present invention is not limited thereto.

[0036] The insertion structure of the present invention, such as Figure 1 Specifically, the process involves: placing the scrap steel hopper 1 on the scrap steel scale in advance, and using a loader to load various slag-forming materials into the bottom of the scrap steel hopper 1; after all the slag-forming materials are added to the bottom of the scrap steel hopper, a crane is then used to add various types of scrap steel into the scrap steel hopper. The slag-forming materials include: sintered ore 2; lime 3; calcined dolomite 4; and the scrap steel includes steel cutting briquettes 5 and rebar briquettes 6.

[0037] Example 1: Slag-forming material is added from the scrap steel hopper to a 120-ton oxygen top and bottom blown converter.

[0038] This invention provides a steelmaking method for precisely adding slag-forming materials outside the converter furnace, the method comprising the following steps:

[0039] 1) The molten iron fed into the converter contains 0.38% silicon, 0.42% manganese, and has a temperature of 1387℃. The amount of molten iron is 122.5 tons, and the amount of scrap steel is 19.6 tons. The final target temperature is 1630℃ and the carbon content is 0.10%.

[0040] 2) Based on the above furnace conditions and target temperature, the amount of various slag-forming materials to be added is calculated through the secondary lance system (if there is no secondary lance system, a calculation program can be made based on heat balance and material balance). The amount of lime is 3230 kg, the amount of raw dolomite is 1615 kg, and the amount of sludge balls is 3042 kg.

[0041] 3) The actual amount of lime, raw dolomite, sludge balls, 19.6 tons of scrap steel, and 122.5 tons of molten iron added to the scrap steel hopper in this furnace batch was 3446 kg, 1512 kg, 2963 kg, 19.6 tons of scrap steel, and 122.5 tons of molten iron.

[0042] 4) After the slag splashing of the previous furnace is completed, pour all the slag into the slag basin, then shake the converter to 45-50° to add scrap steel. After adding the scrap steel, shake the converter downward to 85-95°, and then shake the converter to the iron charging position at 35-40°.

[0043] 5) After the iron is added, first shake the converter to the "zero position", then shake it back about 30 degrees, and then shake it back to the "zero position".

[0044] 6) Lower the oxygen lance from the waiting position to 3.0-3.5m, turn on nitrogen to purge the slag for 30 seconds, immediately switch to oxygen, and gradually lower the lance to 1.85m. The oxygen pressure should be adjusted according to the blowing curve, and the blowing and ignition should be monitored.

[0045] 7) The lance position during the blowing process is 1.40-1.45m, and no slag-forming material is added during the process. No back-drying or splashing occurs during the blowing process of this furnace.

[0046] 8) The blowing time of this furnace was 12 minutes and 36 seconds, with an end temperature of 1632℃, carbon content of 0.105%, and phosphorus content of 0.020%. The carbon was removed and the steel was discharged in one go.

[0047] Comparative Example 1: A 120-ton oxygen top and bottom blown converter with slag-forming material added from the scrap hopper.

[0048] 1) The molten iron fed into the converter contains 0.35% silicon and 0.39% manganese, with a temperature of 1369℃, a quantity of 121.6 tons of molten iron, 20.2 tons of scrap steel, and a final target temperature of 1630℃ and a carbon content of 0.10%.

[0049] 2) Based on the above furnace conditions and target temperature, the amount of various slag-forming materials to be added is calculated through the secondary lance system (if there is no secondary lance system, a calculation program can be made based on heat balance and material balance). The amount of lime is 3315 kg, the amount of raw dolomite is 1685 kg, and the amount of sludge balls is 2174 kg.

[0050] 3) The slag-forming material is loaded into the bottom of the scrap steel, and 3246 kg of lime, 1512 kg of raw dolomite, 2163 kg of sludge balls and 20.2 tons of scrap steel are actually added; then the scrap steel is loaded again.

[0051] 4) After the converter finishes tapping, move the converter to the furnace advance position, controlling the angle of the furnace to 110-115° to perform slag removal operation, and then move the converter back to the "zero position" to perform slag splashing and furnace protection.

[0052] 5) After the slag splashing protection is completed, the converter is tilted to 45-50° to add scrap steel. After adding scrap steel, the converter is tilted downwards to 85-95°, and then tilted to 35-40° to add iron. The amount of molten iron is 121.6 tons.

[0053] 6) After the iron charging operation is completed, the converter is rotated back to the "zero position" and the oxygen lance is lowered and the blowing is started directly. When the oxygen lance is lowered to 3.0-3.5m, the oxygen is turned on and the oxygen pressure is adjusted according to the blowing curve. If the flame does not rise after 40 seconds of blowing, the lance is raised and the oxygen is turned off. The flue is purged with nitrogen for 50 seconds. Then the furnace is first rotated backward and then forward, repeating this process twice each time. Then the furnace is rotated forward again to pour out some of the slag.

[0054] 7) After pouring out some slag, the converter was shaken back to the "zero position" and the blowing and ignition were performed normally again. The total time affected by this furnace run was 7 minutes and 20 seconds, and there was a risk of oxygen leaking from the oxygen lance.

[0055] 8) The blowing time of this furnace was 13 minutes and 56 seconds, the final temperature was 1603℃, the carbon content was 0.075%, the phosphorus content was 0.025%, and the carbon was removed and the steel was discharged in one go.

[0056] Comparative Example 2: A 120-ton oxygen top and bottom blown converter with slag-forming material added from the scrap steel hopper.

[0057] 1) The molten iron fed into the converter contains 0.33% silicon, 0.41% manganese, and has a temperature of 1372℃. The amount of molten iron is 121.1 tons, and the amount of scrap steel is 19.7 tons. The final target temperature is 1630℃ and the carbon content is 0.10%.

[0058] 2) Based on the above furnace conditions and target temperature, the amount of various slag-forming materials to be added is calculated through the secondary lance system (if there is no secondary lance system, a calculation program can be made based on heat balance and material balance): lime 2805kg, raw dolomite 1403kg, and sludge balls 2073kg.

[0059] 3) First, 19.7 tons of scrap steel were loaded into the scrap steel hopper; then various slag-forming materials were loaded on top of the scrap steel, including 2776 kg of lime, 1312 kg of raw dolomite, and 1952 kg of sludge balls.

[0060] 4) After the converter tapping is completed, slag splashing is performed to protect the furnace. After the slag splashing is completed, all the slag is poured into the slag basin.

[0061] 5) After the slag is poured into the slag basin, the converter is tilted to the scrap steel addition position at 45-50°, and scrap steel and all slag-forming materials are added; then the iron addition operation is carried out.

[0062] 6) After the iron charging is completed, the converter is returned to the "zero position" and then rocked backward 30°, then returned to the "zero position" again. The oxygen lance is lowered to 3.0-3.5m. Nitrogen is first purged for more than 30 seconds, then immediately switched to oxygen. The oxygen pressure is adjusted according to the blowing curve. In this heat, the furnace failed to ignite after 45 seconds of blowing. The lance was lifted and the oxygen was turned off. Nitrogen was first purged for more than 50 seconds, then the furnace was rocked backward, then forward, repeating this twice each time. The furnace was then rocked forward again to check the slag situation, and a large amount of lime and raw dolomite were found floating on top. After lifting the furnace, it was rocked forward and backward 4 times each at an angle of 45°. After the converter was returned to the "zero position", nitrogen was first purged for more than 50 seconds, then the furnace was ignited again. After 40 seconds of blowing, the flame was normal. In this heat, there was a large amount of slag overflow at 5 minutes and 23 seconds of blowing. This heat affected the process for a total of 12 minutes and 35 seconds, causing the continuous casting machine to need to replace the slide block and lower the liquid level, which had a negative impact on normal production organization and safe production.

[0063] 7) The blowing time for this furnace was 14 minutes and 29 seconds, with an end temperature of 1585℃, carbon content of 0.115%, and phosphorus content of 0.019%. The steel was discharged after 30 seconds of additional blowing.

[0064] As can be seen from the examples and Comparative Example 1, Comparative Example 1 performed slag retention operations according to normal furnace cycles. In addition, Comparative Example 1 added slag-forming material into the furnace through the scrap steel hopper at once, resulting in a high slag layer thickness in the furnace. Combined with the added slag-forming material, Comparative Example 1 experienced poor initial ignition. After lifting the lance, nitrogen was used to purge the flue, and the furnace was rocked back and forth twice each. Some slag was also poured out. The ignition was normal again afterward. The total time affected was 7 minutes and 20 seconds. Due to the poor initial ignition and the repeated rocking of the furnace, the temperature loss in this furnace cycle was significant, resulting in lower final carbon and temperature.

[0065] As can be seen from the examples and Comparative Example 2, in Comparative Example 2, scrap steel was first added to the bottom of the scrap steel hopper, and then various slag-forming materials were added. All the slag was poured into the slag basin without any slag retention operation. All other operations were the same as in the examples. The first ignition was poor. After lifting the lance, nitrogen was used to purge the flue, and the furnace was shaken back and forth twice. When the furnace was shaken forward again to check the slag situation in the furnace, a large amount of lime and dolomite were found floating on the molten iron and scrap steel. The oxygen flow was blocked from contacting the molten metal surface when the ignition was started, resulting in the poor first ignition of Comparative Example 2. During the initial furnace tilting, a large amount of lime and dolomite was found floating inside. The furnace was then rocked back and forth again to introduce the lime and dolomite into the molten metal surface or gaps in the scrap steel, partially exposing the molten metal. Upon restarting the blowdown process, the flame returned to normal after 40 seconds. However, the second blowdown lasted 40 seconds, resulting in an excess of iron oxide in the slag. In the two comparative heats, significant slag overflow occurred at 5 minutes and 23 seconds of blowing, and this heat was affected for a total of 12 minutes and 35 seconds, requiring the replacement of six slide blocks on the continuous casting machine and a lowering of the molten metal level, severely impacting normal production. It also resulted in a thinner slag layer in this heat. Due to the poor blowdown and subsequent rocking and nitrogen purging, the molten metal temperature dropped significantly, resulting in a final temperature 45°C lower than expected. Additional blowing was required, causing over-oxidation in this heat, affecting steel quality and increasing alloy costs.

[0066] All aspects not described in detail in this invention can be covered using conventional technical knowledge in the field.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A steelmaking method for adding slag-forming materials outside the converter furnace, the method comprising the following steps: 1) Calculate the amount of various slag-forming materials to be added using the slag calculation model; The slag calculation model includes: a secondary lance or flue gas analysis system, or a material and heat balance calculation model based on material and heat balance; the slag material includes: one or more of lime, raw dolomite, and sintered ore. The material and heat balance calculation model is as follows: The formula for calculating the amount of sinter added is as follows: Sinter addition amount = ((M) 铁 -120)*7.5+(20-M 废钢 )*10+(Si 铁水硅 -0.3%)*10000*2.2+(0.30%-Si 铁水硅 )*100*80*0.67+(0.30%-Si 铁水硅 )*100*80*0.69+(T 铁水温度 -1350)*0.8)*100 / 3+1000; The formula for the amount of lime added is: Lime addition amount = 80 * Si 铁水硅 , The amount of raw dolomite added is 50% of the amount of lime added; Where: M 铁 For the amount of molten iron; M 废钢 For scrap steel quantity; Si 铁水硅 T represents the silicon content in molten iron. 铁水温度 The temperature of the molten iron; 2) Place the scrap steel hopper on the scrap steel scale and load various slag-forming materials into the bottom of the scrap steel hopper; 3) After adding all the slag-forming materials to the bottom of the scrap steel hopper, load all types of scrap steel into the scrap steel hopper; 4) After the converter tapping is completed, slag splashing and furnace protection operations are carried out first. After the slag is splashed dry, all the slag is poured into the slag basin and no slag is left. 5) After the slag is removed, the converter is shaken to 45-50 degrees to add scrap steel, and then the iron is added. 6) After the iron is added, first rock the converter backward to 28-32 degrees, then rock it back to the "zero position"; 7) Lower the oxygen lance to the open lance position, first purge with nitrogen, then turn off the nitrogen to switch to oxygen and start ignition; 8) When starting the blowing process, the gun position should be 50-100mm lower than the normal gun position. After blowing, the gun position should be raised to the normal gun position. During the process, the gun position should be 50-100mm higher than the normal gun position, and then the gun position should be gradually lowered to the normal gun position.

2. The steelmaking method of adding slag-forming materials outside the converter furnace according to claim 1, characterized in that, In step 3), the scrap steel includes: heavy scrap steel and / or steel cutting and crushing briquettes. Among them, the dimensions of heavy scrap steel are: length ≤ 1000mm, width ≤ 500mm, and height ≤ 300mm; the dimensions of steel cutting and crushing material briquettes are: length ≤ 400mm, width or diameter ≤ 350mm, and the standard length, width and height of scrap steel are not less than 10cm.

3. The steelmaking method of adding slag-forming materials outside the converter furnace according to claim 1, characterized in that, In step 5), after the scrap steel and slag-forming material are added, the furnace is tilted downwards to 85-95°, and then the converter is tilted to the iron-collecting position of 35-40° to carry out the iron-collecting operation.

4. The steelmaking method of adding slag-forming materials outside the converter furnace according to claim 1, characterized in that, In step 7), the nitrogen regulating valve is opened to the maximum, the nitrogen main pipe pressure is not lower than 1.6 MPa, nitrogen is purged for 25 to 35 seconds, and then the nitrogen is turned off.

5. The steelmaking method of adding slag-forming materials outside the converter furnace according to claim 1, characterized in that, In step 7), before starting the blowing process, the oxygen lance is lowered to 3.0-3.5m and immediately converted into oxygen for starting the blowing and ignition. The oxygen pressure is adjusted according to the starting and ignition curve.

6. The steelmaking method of adding slag-forming materials outside the converter furnace according to claim 1, characterized in that, In step 8), the gun position is raised to the normal gun position after blowing for 2-3 minutes.

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