Novel method for producing aluminum-containing clean steel through slag washing calcium treatment and direct loading

Abstract

The invention belongs to the technical field of ferrous metallurgy, and provides a novel method for producing aluminum-containing clean steel through slag washing calcium treatment, which comprises the following steps: promoting a pre-deoxidation reaction by using coke breeze added in the initial stage of converter tapping to realize top slag foaming, and then adding an aluminum block to forcibly remove oxygen in steel; after the molten steel enters an argon station, a proper amount of composite deoxidation slag former and aluminum skimmings are added to the slag surface to remove oxygen in the slag, the effect that argon station refining white slag is preposed is achieved within 4 min after the molten steel enters the station, and the refining effects that the total oxygen content in the molten steel is smaller than or equal to 30 ppm, and the desulfurization rate is larger than 50% are achieved; and finally, a proper amount of calcium is fed in an argon station in reference to the condition of total oxygen content in the steel, solid AL2O3 inclusions in the molten steel are accurately denatured into low-melting-point liquid inclusions such as 12CaO. 7AL2O3, CaO. AL2O3 and 3CaO. AL2O3, and the castability of the molten steel is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and relates to the production of clean aluminum-containing steel. Specifically, the invention relates to a novel method for producing clean aluminum-containing steel by direct calcium treatment of slag washing. Background Art

[0002] Due to changes in supply and demand and the country's emphasis on environmental protection, steel companies are facing severe competition and survival pressure. As competition in the steel market becomes increasingly fierce, steel mills are forced to research new processes and technologies to develop high-quality, low-cost products to seize the market.

[0003] At present, in order to improve the purity of molten steel and ensure its castability, LF refining is required to produce white slag to improve the purity of molten steel. However, this method will increase production costs and is not conducive to the market share of mid- and low-end products. Summary of the invention

[0004] The purpose of the present invention is to provide a new slag calcium washing treatment direct aluminum-containing clean steel production process method, which improves the castability of molten steel and ensures continuous casting steady-state pouring while ensuring low cost, thereby improving the quality of the ingot.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: A novel slag-washing calcium treatment direct aluminum-containing clean steel production process method, comprising: S1, initial top slag reforming of converter steelmaking; S1.1 During the whole process of converter tapping, argon blowing operation with a large amount of argon gas of 400-800NL / min is carried out, and high-calcium lime and pre-melted slag are added to the ladle for washing simultaneously; S1.2 According to the final carbon content, add 0.25-0.50 kg / t of coke powder when 1 / 5 of the steel is tapped to perform diffusion pre-deoxidation and carbon-oxygen reaction to promote top slag foaming; S1.3 When 1 / 3 of the steel is discharged, add 0.8-1.2 kg / t of aluminum blocks for precipitation and strong deoxidation to ensure that the oxygen content entering the argon station is ≤15ppm and the acid-soluble aluminum content is ≥0.015% to meet the standards in one go.

[0006] S2, argon station top slag modification and calcium treatment; S2.1 After entering the argon station, adjust the ladle argon gas to 200-400NL / min for medium blowing operation, and then use the oxygen meter to determine the oxygen and measure the temperature, and then feed the aluminum wire for alloying and fine-tune the temperature; S2.2 Add composite deoxidizing slag-making agent and diffusion deoxidizer to the ladle slag surface in batches, keep blowing and stirring until the top slag is melted and completely diffused and deoxidized, and take the first molten steel sample after the top slag of the ladle turns yellow-white-gray, continue to keep blowing and dip the slag and make fine adjustments to the top slag, and make fine adjustments to the molten steel composition according to the test results of the first molten steel sample; S2.3 After the molten steel composition, temperature and ladle top slag retention state meet the requirements, refer to the argon station primary steel sample spectrum test composition [S], [Als] and [O] content, according to the formula: W t [Ca] = (0.34% to 0.81%)·W t [O], and calculate the amount of calcium feed line according to the 30% calcium recovery rate to ensure that the [Ca] at the station is controlled within the range of 0.0025-0.0035% to standardize the calcium feeding operation; S2.4 After feeding the calcium wire, continue the soft blowing operation for ≥5 minutes to ensure that the inclusions float fully and the composition and temperature are uniform.

[0007] Furthermore, the high-calcium lime described in S1.1 is active lime with a high effective calcium oxide content; the amount of high-calcium lime added is 4.0-5.0 Kg / t steel; the pre-melted slag washing material is fluxing lime with a certain size after high-temperature smelting, cooling, crushing and screening in an electric furnace, and an auxiliary slag-making material for adjusting the top slag composition; the amount of pre-melted slag washing material added is 1.0-1.5 Kg / t steel.

[0008] Furthermore, the steel tapping described in S1.2 adopts double slag blocking of slag blocking cone and slag blocking plug and the operation of lifting the furnace when the slag is seen, so as to minimize the amount of slag discharged; the coke dust is the screened material of coke.

[0009] Furthermore, in S1.3, the amount of aluminum blocks added must be adjusted according to the slag discharge conditions to ensure that the molten steel is completely precipitated and deoxidized in one step.

[0010] Furthermore, in S2.1, according to the oxygen and temperature conditions at the station, aluminum wire is used to adjust the acid-soluble aluminum in the molten steel, and scrap steel is used to adjust the temperature; the reference standard for the scrap steel temperature adjustment is: 100 kg of scrap steel, reducing the molten steel temperature by 4°C; the goals of the aluminum wire alloying and fine-tuning temperature operations are: molten steel temperature 1620±5°C, and acid-soluble aluminum content of the steel type 0.030~0.050%.

[0011] Further, the composite deoxidizing slag-forming agent in S2.2 is aluminum calcium balls, and the diffusion deoxidizing agent is aluminum chips; the aluminum calcium balls are composite slag-forming agents formed by mixing aluminum ash, aluminum foil, and calcite under pressure; Furthermore, in S2.2, the argon blowing process is performed for 1 to 3 times of slag dipping. If the slag sample does not turn yellow-white, continue to add aluminum powder to the slag surface in small amounts and batches for slag adjustment. After the top slag turns yellow-white and remains for ≥1 min, adjust the ladle argon gas to 50-100NL / min for soft blowing, and take a steel sample from the argon station once.

[0012] Furthermore, the calcium wire described in S2.3 is a splash-proof high-calcium calcium iron wire.

[0013] Beneficial effects of the present invention: Ensure that the aluminum block is fully precipitated and deoxidized during the first steelmaking process and that the aluminum wire is fully alloyed after the argon station oxygenation process, thereby reducing the number of secondary oxidation inclusions in the molten steel.

[0014] The argon station adds a light-density composite deoxidizing slag-making agent containing certain deoxidizing elements and having fluxing and foaming functions to achieve accurate removal of oxygen from the slag, and achieve the effect of pre-positioning the white slag from the argon station to enter the station within 4 minutes, so as to achieve the refining effect of controlling the total oxygen content in the molten steel to ≤30ppm and increasing the desulfurization rate to more than 50%, remove the harmful element sulfur in the steel, fully absorb inclusions, and improve the purity of the molten steel.

[0015] The argon station detects the total oxygen content in the steel with reference to the spectrum and feeds an appropriate amount of calcium to accurately transform the solid AL2O3 inclusions in the molten steel into low-melting-point liquid inclusions such as 12CaO·7AL2O3, CaO·AL2O3 and 3CaO·AL2O3, thereby improving the castability of the molten steel and increasing the service life of the continuous casting submerged nozzle and the tundish.

[0016] 4. This production process of completing refining and white slag making and precise calcium treatment operations in the argon station is of great significance to reducing refining costs and improving the purity of molten steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the data table of the standard requirements for physicochemical indicators of high calcium lime and pre-melted slag washing; Figure 2 It is a standard data table of aluminum wire adjustment amounts for different steel grades; Figure 3 It is a data sheet of physical and chemical index requirements for aluminum-calcium balls and aluminum chips; Figure 4 It is the physical and chemical index data table of splash-proof high calcium iron wire. DETAILED DESCRIPTION

[0018] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and understandable, the technical scheme of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0019] A novel slag-washing calcium treatment direct aluminum-containing clean steel production process method, comprising: S1, initial top slag reforming of converter steelmaking; During the whole process of steel tapping from the S1.1 converter, argon blowing operation with a large amount of argon at a rate of 400-800NL / min is carried out, and high-calcium lime and pre-melted slag washing material are added to the ladle simultaneously; high-calcium lime is active lime with a high effective calcium oxide content, and the addition amount is 4.0-5.0Kg / t steel, and the pre-melted slag washing material is fluxing lime with a certain size after high-temperature smelting, cooling, crushing and screening in an electric furnace, and auxiliary slag-making material for adjusting the top slag composition, and the addition amount is 1.0-1.5Kg / t steel.

[0020] The physicochemical index standard requirements for high calcium lime and pre-melted slag washing are as follows: Figure 1 As shown in the table.

[0021] Taking a 120-ton ladle as an example, the method of adding high-calcium lime is: The top ash system normally prepares 350kg of high calcium lime; 1) When the final carbon content is ≤0.04%, add 150-200kg of high-calcium lime, but do not add fluorite; 2) The final carbon content is 0.05% to 0.07%, and 100kg of high-calcium lime is added to the top slag without adding fluorite; 3) The final carbon is ≥0.08%, and the top slag is added normally at 350kg (no additional addition is required). 50kg fluorite is added when tapping. When the top slag sample is dipped at the argon station, if it is viscous and cannot be drawn, continue to add fluorite to adjust the slag until the top slag is completely engulfed by the slag rod for drawing.

[0022] S1.2 According to the final carbon content, add 0.25-0.50 kg / t of coke dust when 1 / 5 of the steel is tapped for diffusion pre-deoxidation and carbon-oxygen reaction to promote top slag foaming; the steel tapping must adopt double slag blocking with slag blocking cone and slag blocking plug and the operation of lifting the furnace when the slag is seen, so as to minimize the amount of slag; coke dust is the screened material of coke produced or purchased by the steel plant, and there is no special requirement for particle size and composition.

[0023] S1.3 When 1 / 3 of the steel is discharged, add 0.8-1.2 kg / t of aluminum blocks for precipitation and strong deoxidation to ensure that the oxygen content entering the argon station is ≤15ppm and the acid-soluble aluminum content is ≥0.015% to meet the standards in one go.

[0024] S2, argon station top slag reforming and calcium treatment; S2.1 After entering the argon station, adjust the ladle argon gas to 200-400NL / min for the middle blowing operation, and then use the oxygen meter to determine the oxygen and measure the temperature, and then feed the aluminum wire for alloying and fine-tuning the temperature; according to the oxygen and temperature conditions at the station, use aluminum wire to adjust the acid-soluble aluminum in the molten steel based on experience, and use scrap steel such as rebar shearing small materials to adjust the temperature. For 120 tons of molten steel, the standard of aluminum wire adjustment for different steel grades is as follows Figure 2 As shown in the table.

[0025] The reference standard for temperature adjustment of scrap steel such as 120-ton molten steel ladle, rebar shearing small pieces, etc. is: 100Kg scrap steel, reduce the molten steel temperature by 4℃.

[0026] The objectives of alloying the aluminum wire and fine-tuning the temperature are: molten steel temperature 1620±5℃, acid-soluble aluminum content of steel 0.030~0.050%.

[0027] S2.2 Add composite deoxidizing slag-making agent and diffusion deoxidizing agent to the slag surface of the ladle in batches, keep blowing and stirring until the top slag melts and is completely diffused and deoxidized, and dip the slag 1 to 3 times during the argon blowing process. If the slag sample does not turn yellow-white, continue to add aluminum powder to the slag surface in small amounts and batches for slag adjustment. After the top slag turns yellow-white and is maintained for ≥1min, adjust the argon gas in the ladle to 50-100NL / min for soft blowing, take a steel sample from the argon station, continue to keep blowing and dipping the slag and make fine adjustments to the top slag. During this period, fine-tune the composition of the molten steel according to the test results of the first molten steel sample; among them, the composite deoxidizing slag-making agent is aluminum calcium balls, and the diffusion deoxidizing agent is aluminum chips; the physical and chemical index requirements of aluminum calcium balls and aluminum chips are as follows Figure 3 As shown in the table.

[0028] Aluminum calcium balls are composite slag-making agents formed by mixing aluminum ash, aluminum foil, calcite and other materials under pressure. After being added to the surface of the ladle, they can quickly melt and promote the top slag to become foamy slag. The duration of the foamy slag must be maintained for 3 to 5 minutes. The rich aluminum foil and the function of promoting foamy slag and the added diffusion deoxidizer aluminum chips work synergistically to effectively promote the deoxidation efficiency of the top slag and make it quickly become reduced slag, i.e. "white slag". White slag with a content of (FeO) + (MnO) ≤ 1.0% can be quickly formed in the argon station for 3 to 5 minutes.

[0029] S2.3 After the molten steel composition, temperature and ladle top slag retention state meet the requirements, refer to the argon station primary steel sample spectrum to detect the content of [S], [Als] and [O] in the composition, according to the formula: W t [Ca] = (0.34% to 0.81%)·W t[O], and the amount of calcium wire fed is calculated according to the 30% calcium recovery rate to ensure that the [Ca] at the station is controlled within the range of 0.0025-0.0035% to standardize the calcium feeding operation; the calcium wire adopts splash-proof high-calcium iron wire, and the characteristics of splash-proof high-calcium iron wire are: 1) The iron sheet is made of DC04 raw material cold-rolled strip and is straightened and continuously annealed. The iron sheet has a high melting point, high toughness and strength. It can be effectively straightened and not easily broken before entering the wire feeding machine. It can effectively feed the molten steel into the target depth range of argon blowing downflow, thereby increasing the sustained release time of calcium; 2) calcium particles The iron powder is added according to the particle size and target ratio. The iron powder is filled evenly, and the calcium particles are not adhered or consolidated. After the calcium wire is fed into the molten steel, it can ensure that the iron powder is melted evenly to form a larger range of low-temperature fields and balanced reactions of calcium particles, reducing the kinetic energy of calcium gasification and reducing the splashing of molten steel. At the same time, it improves the effective reaction and recovery rate of calcium; 3) All calcium wires can be fed into the molten steel within 40 seconds, and the wire feeding speed is fast to save the processing time of the argon station; 4) The dispersed distribution and balanced reaction of calcium can ensure that the inclusions in the molten steel below 30ppm, mainly alumina inclusions, are effectively denatured, and the treatment effect is more stable. The physical and chemical indicators of splash-proof high-calcium iron wire are as follows: Figure 4 As shown in the table.

[0030] S2.4 After feeding the calcium wire, continue the soft blowing operation for ≥5 minutes to ensure that the inclusions float fully and the composition and temperature are uniform. Example

[0031] Take the production of SPHC steel as an example: 1. Steel production from converter 1) During the whole process of steel tapping, 800NL / min of large argon gas blowing operation is carried out, and 500Kg of high-calcium lime and 110Kg of pre-melted slag washing material are added to the ladle simultaneously; 2) Based on the end point [C]: 0.06%, [S]: 0.027%, add 50 kg of coke powder for diffusion pre-deoxidation when 1 / 5 of the steel is tapped; 3) Add 140Kg aluminum block when 1 / 3 of the steel is discharged; 4) The steel tapping adopts double slag blocking operation of slag blocking cone and slag blocking plug, and the slag blocking is successful without slag dropping; the end point P: 0.019%, the P of the first sample of the argon station: 0.020%.

[0032] 2. Argon station reforming treatment 1) After entering the station, adjust the ladle argon gas to 300NL / min for argon blowing operation, use an oxygen meter to determine the oxygen [O]: 10ppm, measure the temperature at 1641℃, feed 40m of aluminum wire, and add 700kg of temperature-adjusting small materials; 2) Add 70kg of aluminum calcium balls and 50kg of aluminum powder to the slag surface of the ladle, and stir for 4 minutes until the top slag is completely melted. After dipping the slag once during the argon blowing process, the slag sample is dark green, add 20kg of aluminum powder and 30kg of aluminum calcium balls to adjust the slag again, dip the slag twice to see if the slag sample turns yellow-white and maintains for ≥1min, adjust the ladle argon gas to 80NL / min for soft argon blowing operation, take a steel sample from the argon station, [ALs]: 0.0316%, and measure the temperature at 1617℃; 3) Referring to the spectrum test of the steel sample at the argon station, the contents of [S]: 0.024%, [Als]: 0.0316% and [O]: 0.0025, the calcium line was fed 150m, and the [Ca] from the station was in the range of 0.0025%; 4) After feeding the calcium wire, continue to maintain soft argon blowing operation for 6 minutes to ensure that the solid Al2O3 inclusions are transformed into liquid inclusions such as 12CaO·7AL2O3, CaO·AL2O3 and 3CaO·AL2O3, thereby improving the castability of the molten steel.

[0033] The argon station provides good protection for casting, the finished product [S]: 0.013%, the desulfurization rate reaches 51.85%, the castability of the molten steel is good, and no quality problems occur.

[0034] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A novel slag washing calcium treatment direct aluminum-containing clean steel production process, characterized by: include: S1, initial top slag reforming of converter steelmaking; S1.1 During the whole process of converter tapping, argon blowing operation with a large amount of argon gas of 400-800NL / min is carried out, and high-calcium lime and pre-melted slag are added to the ladle for washing simultaneously; S1.2 According to the final carbon content, add 0.25-0.50 kg / t of coke powder when 1 / 5 of the steel is tapped to perform diffusion pre-deoxidation and carbon-oxygen reaction to promote top slag foaming; S1.3 When 1 / 3 of the steel is tapped, add 0.8-1.2 kg / t aluminum blocks for precipitation and strong deoxidation to ensure that the oxygen content in the argon station is ≤15ppm and the acid-soluble aluminum content is ≥0.015% to meet the standards in one go; S2, argon station top slag reforming and calcium treatment; S2.1 After entering the argon station, adjust the ladle argon gas to 200-400NL / min for medium blowing operation, and then use the oxygen meter to determine the oxygen and measure the temperature, and then feed the aluminum wire for alloying and fine-tune the temperature; S2.2 Add composite deoxidizing slag-making agent and diffusion deoxidizer to the ladle slag surface in batches, keep blowing and stirring until the top slag is melted and completely diffused and deoxidized, and take the first molten steel sample after the top slag of the ladle turns yellow-white-gray, continue to keep blowing and dip the slag and make fine adjustments to the top slag, and make fine adjustments to the molten steel composition according to the test results of the first molten steel sample; S2.3 After the molten steel composition, temperature and ladle top slag retention state meet the requirements, refer to the argon station primary steel sample spectrum test composition [S], [Als] and [O] content, according to the formula: W t [Ca] = (0.34% to 0.81%)·W t [O], and calculate the amount of calcium feed line according to the 30% calcium recovery rate to ensure that the [Ca] at the station is controlled within the range of 0.0025-0.0035% to standardize the calcium feeding operation; S2.4 After feeding the calcium wire, continue the soft blowing operation for ≥5 minutes to ensure that the inclusions float fully and the composition and temperature are uniform.

2. The novel slag-washing calcium treatment direct aluminum-containing clean steel production process according to claim 1 is characterized by: The high calcium lime described in S1.1 is active lime with a high effective calcium oxide content; the amount of high calcium lime added is 4.0-5.0 kg / t steel; the pre-melted slag washing material is fluxing lime with a certain size after high-temperature smelting, cooling, crushing and screening in an electric furnace, and an auxiliary slag-making material for adjusting the top slag composition; the amount of pre-melted slag washing material added is 1.0-1.5 kg / t steel.

3. The novel slag-washing calcium treatment direct aluminum-containing clean steel production process according to claim 1 is characterized by: The coke dust described in S1.2 is the undersize of coke; the steel tapping process adopts double slag blocking of slag blocking cone and slag blocking plug and the operation of lifting the furnace when the slag is seen, so as to minimize the amount of slag.

4. The novel slag-washing calcium treatment direct aluminum-containing clean steel production process according to claim 1 is characterized by: In S1.3, the amount of aluminum blocks added must be adjusted according to the slag discharge conditions to ensure that the molten steel is completely precipitated and deoxidized in one step.

5. The novel slag-washing calcium treatment direct aluminum-containing clean steel production process according to claim 1 is characterized by: In S2.1, according to the oxygen and temperature conditions at the station, aluminum wire is used to adjust the acid-soluble aluminum in the molten steel, and scrap steel is used to adjust the temperature; the reference standard for scrap steel temperature adjustment is: 100 kg of scrap steel, reducing the molten steel temperature by 4°C; the goals of aluminum wire alloying and fine-tuning temperature operations are: molten steel temperature 1620±5°C, acid-soluble aluminum content of steel 0.030~0.050%.

6. The novel slag-washing calcium treatment direct aluminum-containing clean steel production process according to claim 1 is characterized by: The composite deoxidizing slag-forming agent described in S2.2 is aluminum-calcium balls, and the diffusion deoxidizing agent is aluminum chips; the aluminum-calcium balls are composite slag-forming agents formed by mixing aluminum ash, aluminum foil, and calcite under pressure.

7. The novel slag-washing calcium treatment direct aluminum-containing clean steel production process according to claim 1 is characterized by: In the argon blowing process in S2.2, the slag is dipped 1 to 3 times. If the slag sample does not turn yellow-white, aluminum powder is added to the slag surface in small amounts and batches for slag adjustment. After the top slag turns yellow-white and remains for ≥1 minute, the argon gas in the ladle is adjusted to 50-100NL / min for soft blowing, and a steel sample is taken from the argon station.

8. The novel slag-washing calcium treatment direct aluminum-containing clean steel production process according to claim 1 is characterized by: The calcium wire described in S2.3 is a splash-proof high-calcium iron wire.

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