A rapid deoxidation slag-making process

Abstract

The present invention discloses a rapid deoxidation slag making process, which belongs to the field of iron and steel metallurgy. It includes steps S1, making emulsified slag: adjusting the Al content, sprinkling 15-20kg calcium carbide on the slag surface, an argon flow rate of 450-600NL / min, and blowing argon for 3-5min; step S2, making emulsified slag: adding 1.0-3.0kg / t lime to the ladle after the foamed slag is formed, an argon flow rate of 300-400NL / min, and stirring for 3-5min; step S3, precipitation deoxidation: after the emulsified slag is formed for 2-4min, sprinkling 10-15kg aluminum cut shot on the slag surface, micro-argon soft blowing for 4-6min, and a bottom blowing argon flow rate of 50-100NL / min. The slag sample is fished out, and the slag color turns white, then continuing to soft blow to the exit. In the present invention, the molten steel does not need to be refined by the LF furnace, while meeting the product quality, effectively shortening the production cycle and reducing production costs.

Description

Technical Field

[0001] The present invention belongs to the field of iron and steel metallurgy, and more particularly, relates to a rapid deoxidation and slagging process. Background Art

[0002] With the rapid development of the steel industry, the requirements for product quality and molten steel cleanliness are becoming increasingly stringent. To minimize the content of impurities such as phosphorus, sulfur, oxygen, nitrogen, and hydrogen in steel, control the number, shape, and size of non-metallic inclusions, and improve the cleanliness of molten steel, molten steel is generally required to undergo LF furnace refining and RH refining. Through operations such as white slag formation, diffusion deoxidation, vacuum circulation, and soft blowing, the content of harmful elements such as oxygen, sulfur, hydrogen, and nitrogen in the steel is reduced, and the number, shape, and size of non-metallic inclusions are controlled.

[0003] Deoxidation and slag formation during steelmaking are key processes in producing high-quality steel. The deoxidation and slag formation process involves deoxidizing and alloying the molten steel during tapping, significantly reducing the oxygen content. The LF furnace uses aluminum pellets and other materials for precipitation deoxidation, while slag-forming materials such as calcium carbide and silicon carbide diffusely deoxidize the molten steel, reducing the oxidizing properties of the slag and achieving a "white slag" process. After adjusting the composition and temperature, the molten steel undergoes a soft blow process under the "white slag" to cause inclusions to collide, grow, and float upward until they are absorbed by the slag, thereby controlling the number, size, and morphology of inclusions. During RH refining, intense circulation and agitation of the molten steel reduces the hydrogen, nitrogen, and oxygen contents in the steel, while further colliding and growing inclusions until they are removed. Deoxidation and slag formation in the LF furnace significantly improves the cleanliness of the molten steel. However, this refining process increases production costs and lengthens the production cycle, impacting production schedules. At present, with the increasing competition pressure in the steel industry, the adoption of low-cost and high-efficiency production processes has become the main trend without affecting product quality. Therefore, it is imperative to propose a rapid deoxidation slag making process.

[0004] At present, the production process of rapid slagging and deoxidation is mainly concentrated in the process flow of converter → argon blowing station → LF furnace, and there has been no report on the rapid deoxidation and slagging process without LF furnace refining.

[0005] Patent CN103469050A discloses a smelting process for aluminum-containing cold heading steel, including blast furnace molten iron, converter, refining, and continuous casting; molten iron requirements: P ≤ 0.10%, 0.30% ≤ Si ≤ 0.50%, S ≤ 0.030%; converter refining requirements: lime: CaO ≥ 85%, activity ≥ 280; SiO2 in fluorite ≤ 6%; low-Si pre-melted slag or refining agent is used to replace part of the lime and fluorite during the converter tapping process to quickly form slag, and the refining furnace deoxidizer uses calcium carbide + aluminum particles after mixing to deoxidize the slag surface, and the use of Si-containing materials is prohibited; during continuous casting, pure Ca wire is used in the impact zone of the tundish and between each stream to allow Al2O3 generated by secondary oxidation in the tundish to react with Ca to form low-melting-point calcium aluminate, which can float up and be removed.

[0006] Patent CN115466906A discloses a low-slag bearing steel smelting process. The process specifically includes the following steps: 1) High-carbon smelting in an electric furnace, tapping from an eccentric bottom (EBT), adding 3.5 kg of lime per ton of steel and 1.0 kg of furnace protection agent per ton of steel during tapping, and bottom blowing of argon; 2) Refining to produce high-basicity slag, adding ≤1.0 kg of lime per ton of steel, and using small amounts of silicon carbide, calcium carbide, and carbon powder for mixed deoxidation; 3) Vacuum degassing using VD, maintaining a vacuum of ≤67 Pa for 10-15 minutes, a total vacuum treatment time of ≤20 minutes, and a soft blowing time of 30-50 minutes; and 4) Continuous casting. Both patents require refining treatment, resulting in a long process cycle. Summary of the Invention

[0007] 1. Problem to be solved

[0008] Aiming at the problem of long cycle in the existing deoxidation and slagging process, the present invention provides a rapid deoxidation and slagging process, which shortens the process cycle without undergoing LF furnace refining while ensuring the quality of molten steel.

[0009] 2. Technical solution

[0010] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

[0011] In the prior art, molten steel is refined during the LF process by adding deoxidizers and aluminum particles for deoxidation and slag formation. However, the LF refining process significantly prolongs the smelting cycle and increases production costs. Therefore, the present invention aims to shorten the smelting cycle by omitting the LF refining process. However, molten steel without LF refining suffers from poor quality and high inclusion content. Therefore, to ensure molten steel quality, the present invention utilizes the dynamics of the argon blowing station and the exothermic nature of the aluminum-oxygen reaction to achieve LF refining. By fully utilizing metallurgical thermodynamics, metallurgical kinetics, and metallurgical transport theory, the present invention combines precipitation deoxidation of the molten steel with diffusion deoxidation of the slag during the refining process to achieve "three-dimensional," all-round deoxidation of the molten steel and slag, thereby rapidly reducing the oxygen content in the molten steel and slag.

[0012] The present invention provides a rapid deoxidation slag making process, the main technical solutions of which are:

[0013] (1) Electric furnace or converter process: The smelting end point [C] is controlled between 0.10% and 0.30%, and the end point temperature is controlled above 1650℃; during the tapping process, ferrosilicon, ferromanganese alloy and recarburizer are added to adjust the content of elements such as [C], [Si] and [Mn] in the molten steel to near the lower limit of the required range of the tundish composition.

[0014] (2) Deoxidation and slagging:

[0015] Step S1, making foamed slag: After the molten steel enters the station, aluminum wire is fed into the molten steel, and the [Als] content is adjusted to "the outgoing target value + 0.030%". At the same time, 15-20 kg of calcium carbide is sprinkled on the slag surface, and the argon flow rate is controlled according to the target of 450-600 NL / min. The argon blowing time is controlled within 3-5 minutes. The carbon-oxygen reaction between the calcium carbide and the oxygen in the slag is used to promote the slag to become foamed slag; if the foamed slag is not formed, 15-20 kg of calcium carbide is sprinkled on the slag surface again, and the slag is vigorously stirred for 2-3 minutes to continue making foamed slag.

[0016] Step S2, making emulsified slag: After the foamed slag is formed, 1.0-3.0 kg / t of lime is added to the ladle in batches, and the argon flow rate is controlled according to the target of 300-400 NL / min. Stir for 3-5 minutes to turn the slag into emulsified slag. If the emulsified slag is not formed, add 15-20 kg of calcium carbide and 1.0-1.2 kg / t of lime to the ladle, stir for 2-3 minutes, and continue to make emulsified slag.

[0017] Step S3, Precipitation Deoxidation: After the emulsified slag has formed for 2-4 minutes, sprinkle 10-15 kg of aluminum shot on the slag surface. Maintain a gentle argon soft blow, with the bottom blow argon flow rate controlled to a target of 50-100 NL / min, for 4-6 minutes. Collect a slag sample. If the slag turns white, continue soft blowing until it exits the station. If the slag does not turn white, continue sprinkling 10-15 kg of aluminum shot on the slag surface until the slag turns white.

[0018] Step S4, continuous casting: the composition of the molten steel is adjusted according to the requirements of the steel grade and then cast on a continuous casting table.

[0019] Among them, the main component of calcium carbide is CaC2, which acts as a deoxidizer to react with oxygen in steel and slag. In the diffusion deoxidation process of steps S1 and S2, calcium carbide is mainly used to remove oxygen from the slag surface of the molten steel. In step S3, aluminum cut shot is used as a reducing agent for precipitation deoxidation, first removing oxygen from the slag and then removing oxygen from the molten steel. In steps S1 and S2, argon blowing is used to accelerate the circulation of slag and molten steel, thereby accelerating the mass transfer process of oxygen in the slag, achieving the effect of accelerating diffusion deoxidation, and the argon flow rate is controlled to be step S1>step S2>step S3.

[0020] The present invention first uses calcium carbide as a deoxidizer to react with oxygen in steel and slag. The main component of calcium carbide is CaC2, which reacts with oxygen in the slag to generate bubbles and foam slag for preliminary deoxidation. Since the carbon-oxygen reaction is violent, argon needs to be quickly introduced, and the argon flow rate is controlled to be 450-600NL / min so that the slag is quickly mixed and evenly mixed. After the foam slag is formed, lime is added for deep deoxidation to generate emulsified slag. Compared with step S1, the reaction in this process is milder. Therefore, although nitrogen bottom blowing and stirring are still required to disperse the bubbles and promote deoxidation, the argon flow rate is less than the argon flow rate in step S1. Therefore, the argon flow rate in step S2 is controlled to be 300-400NL / min. Finally, aluminum cut shots are added, and the aluminum and molten steel react directly to first remove oxygen in the steel slag and then remove oxygen in the molten steel. This step is precipitation deoxidation, and the argon flow rate can be kept at a lower rate of 50-100NL / min.

[0021] In addition, this reaction does not require heating during the deoxidation and slag-making process, and the process cycle is short. The molten iron releases heat through the aluminum-oxygen reaction during the precipitation deoxidation process, which can meet the temperature requirements of the molten steel and achieve the purpose of heating and raising the temperature of the molten steel without electrode heating.

[0022] The present invention provides a rapid deoxidation and slagging method, featuring a rationally designed deoxidation and slagging mechanism. During the electric furnace blowing process, this method improves the compatibility between deoxidation, slagging, and bottom blowing, establishes favorable thermodynamic and kinetic conditions, strengthens the deoxidation and slagging reactions in the early and middle stages, and establishes a rational process. Because the entire process involves no refining, the present invention significantly shortens the process cycle by adjusting the process in the argon blowing station while maintaining molten iron quality.

[0023] 3. Beneficial effects

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The molten steel in the present invention does not need to be refined in an LF furnace and can be directly transferred from the argon blowing station to the continuous casting table. While meeting product quality requirements, it effectively shortens the production cycle and reduces production costs.

[0026] (2) The present invention makes full use of metallurgical thermodynamics, metallurgical kinetics, and metallurgical transmission theory to combine the precipitation deoxidation of molten steel and the diffusion deoxidation of slag in the refining process to achieve "three-dimensional" all-round deoxidation of molten steel and slag, thereby rapidly reducing the oxygen content in molten steel and slag;

[0027] (3) The present invention fully utilizes the exothermic characteristic of the aluminum-oxygen reaction to achieve the purpose of heating and increasing the temperature of molten steel without using electrode heating. DETAILED DESCRIPTION

[0028] The following are exemplary embodiments of the present invention that can be implemented as examples. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, it should be understood that other embodiments can be implemented and various changes can be made to the present invention without departing from the spirit and scope of the present invention. The following more detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but is merely for the purpose of illustrating and not limiting the description of the features and characteristics of the present invention, in order to propose the best mode for carrying out the present invention and to enable those skilled in the art to implement the present invention. Therefore, the scope of the present invention is limited only by the appended claims.

[0029] The rapid deoxidation and slagging process provided by the present invention is used in a converter process with a nominal capacity of 120 tons in a certain factory, and the steel grade is bearing steel 50Mn.

[0030] Example 1

[0031] A rapid deoxidation and slagging process comprises the following steps:

[0032] (1) Converter smelting: The converter smelting endpoint requirements are: the converter smelting endpoint [C] content is 0.12%, the endpoint temperature is 1655℃, and 42kg / t recarburizer, 3.2kg / t ferrosilicon, and 12kg / t high carbon ferromanganese alloy are added to the ladle during the tapping process for deoxidation and alloying operations. After tapping, the molten steel is hoisted to the argon blowing station. At this time, the molten steel has a [C] content of 0.51%, a [Si] content of 0.30%, and a [Mn] content of 0.73%, all of which are close to the requirements of the tundish.

[0033] (2) Deoxidation and slagging:

[0034] Step S1, making foamed slag: after entering the argon blowing station, turn on the bottom argon blowing, adjust the argon flow rate to 500NL / min, feed 350 meters of aluminum wire into the molten steel, and after the wire feeding is completed, manually throw 20kg of calcium carbide onto the slag surface and vigorously stir for 5 minutes to form foamed slag.

[0035] Step S2, making emulsified slag: After the foamy slag is formed, the argon flow rate is adjusted to 350 NL / min, 300 kg of lime is added to the ladle, and stirred for 3 minutes to make the slag emulsified.

[0036] Step S3, precipitation deoxidation: After the emulsified slag is formed for 2 minutes, the argon flow rate is adjusted to 100NL / min, 15kg of aluminum cut shot is added to the slag surface, and after soft blowing for 5 minutes, the slag sample is collected and the slag color is observed to be white slag, and the molten steel is discharged.

[0037] Step S4, continuous casting: After the molten steel is poured in the continuous casting process, the molten steel is poured smoothly without nodules, and the stopper rod and the crystallizer liquid level curves are stable.

[0038] In the molten steel prepared in Example 1, [C]: 0.51 wt%, [Si]: 0.30 wt%, [Mn]: 0.73 wt%, and TO: 15 ppm.

[0039] The argon blowing station takes 20 minutes.

[0040] Example 2

[0041] A rapid deoxidation and slagging process comprises the following steps:

[0042] (1) The converter smelting process is the same as that in Example 1.

[0043] (2) Deoxidation and slagging:

[0044] Step S1, making foamed slag: After entering the argon blowing station, turn on the bottom argon blowing, adjust the argon flow rate to 450NL / min, feed 300 meters of aluminum wire into the molten steel, and after the wire feeding is completed, manually throw 15kg of calcium carbide onto the slag surface and vigorously stir for 3 minutes to form foamed slag.

[0045] Step S2, making emulsified slag: After the foamy slag is formed, the argon flow rate is adjusted to 300 NL / min, 150 kg of lime is added to the ladle, and stirred for 5 minutes to make the slag emulsified.

[0046] Step S3, precipitation deoxidation: After 3 minutes of emulsified slag formation, adjust the argon flow rate to 120NL / min, add 10kg of aluminum cut shot to the slag surface, and soft blow for 3 minutes, then take the slag sample and observe that the slag color is white slag, and the molten steel is discharged.

[0047] Step S4, continuous casting: After the molten steel is poured in the continuous casting process, the molten steel is poured smoothly without nodules, and the stopper rod and the crystallizer liquid level curves are stable.

[0048] In the molten steel obtained in Example 2: [C]: 0.50wt%, [Si]: 0.29wt%, [Mn]: 0.74wt%, TO: 13ppm.

[0049] The argon blowing station takes 18 minutes.

[0050] Example 3

[0051] A rapid deoxidation and slagging process comprises the following steps:

[0052] (1) The converter smelting process is the same as that in Example 1.

[0053] (2) Deoxidation and slagging:

[0054] Step S1, making foamed slag: After entering the argon blowing station, turn on the bottom argon blowing, adjust the argon flow rate to 600NL / min, feed 400 meters of aluminum wire into the molten steel, and after the wire feeding is completed, manually throw 20kg of calcium carbide onto the slag surface and vigorously stir for 4 minutes to form foamed slag.

[0055] Step S2, making emulsified slag: After the foamed slag is formed, the argon flow rate is adjusted to 400 NL / min, 200 kg of lime is added to the ladle, and stirred for 4 minutes to make the slag emulsified.

[0056] Step S3, precipitation deoxidation: After the emulsified slag is formed for 4 minutes, the argon flow rate is adjusted to 150NL / min, 15kg of aluminum cut shot is added to the slag surface, and after soft blowing for 4 minutes, the slag sample is collected and the slag color is observed to be white slag, and the molten steel is discharged.

[0057] Step S4, continuous casting: After the molten steel is poured in the continuous casting process, the molten steel is poured smoothly without nodules, and the stopper rod and the crystallizer liquid level curves are stable.

[0058] In the molten steel prepared in Example 3, [C]: 0.49wt%, [Si]: 0.31wt%, [Mn]: 0.75wt%, and TO: 12ppm.

[0059] The argon blowing station takes 21 minutes.

[0060] Comparative Example 1

[0061] Comparative Example 1 adopts LF refining process, and its specific steps include:

[0062] (1) The converter smelting process is the same as that in Example 1.

[0063] (2) Deoxidation and slagging:

[0064] Step S1: Bottom blowing argon and stirring for 3 minutes, then exiting the station and entering the LF furnace refining process;

[0065] Step S2, LF refining: In the LF furnace, 40 kg / t lime, 30 kg / t refined slag, and 50 kg aluminum particles are added to the molten steel to produce high-basicity, high-reducing slag. Simultaneously, electrode heating is performed for 31 minutes. 40 kg / t recarburizer, 3.0 kg / t ferrosilicon, and 10 kg / t high-carbon ferromanganese are added. The molten steel then leaves the station and enters the continuous casting process. The refining cycle is 50 minutes.

[0066] In the molten steel prepared in Comparative Example 1, [C]: 0.51 wt%, [Si]: 0.31 wt%, [Mn]: 0.73 wt%, and TO: 13 ppm.

[0067] The argon blowing station took 3 minutes, and LF refining took 50 minutes, for a total of 53 minutes.

[0068] Comparative Example 2

[0069] Comparative Example 2 adopts LF refining process, and its specific steps include:

[0070] (1) The converter smelting process is the same as that in Example 1.

[0071] (2) Deoxidation and slagging:

[0072] Step S1: Bottom blowing argon and stirring for 4 minutes, then exiting the station and entering the LF furnace refining process;

[0073] Step S2, LF refining: In the LF furnace, 42 kg / t of lime, 28 kg / t of refined slag, and 60 kg of aluminum particles are added to the molten steel to produce high-basicity, high-reducing slag. Simultaneously, electrode heating is performed for 36 minutes. After adding 43 kg / t of recarburizer, 3.2 kg / t of ferrosilicon, and 13 kg / t of high-carbon ferromanganese, the molten steel leaves the station and enters the continuous casting process. The refining cycle is 55 minutes.

[0074] In the molten steel prepared in Comparative Example 2, [C]: 0.50 wt%, [Si]: 0.30 wt%, [Mn]: 0.75 wt%, and TO: 12 ppm.

[0075] The argon blowing station took 4 minutes, and LF refining took 55 minutes, for a total of 59 minutes.

[0076] In summary, the above-mentioned Examples 1-3 adopt the rapid deoxidation slag-making process of the present invention, the molten iron obtained by the treatment meets the quality requirements, and the process cycle is controlled within 18 to 21 minutes, which is significantly shorter than the process cycle of the LF refining process adopted in Comparative Example 1 and Comparative Example 2, and the quality of the molten steel meets the process requirements.

Claims

1. A rapid deoxidation slag making process, characterized in that: The following steps are involved: Step S1, making foamed slag: After the molten steel enters the furnace, aluminum wire is fed into the molten steel, and the [Als] content is adjusted to "the exit target value + 0.030%". At the same time, 15-20 kg of calcium carbide is sprinkled on the slag surface, and the bottom blowing argon gas flow rate is 450-600 NL / min, and the blowing time is 3-5 minutes to make the slag foamed; Step S2, making emulsified slag: after the foamed slag is formed, 1.0-3.0 kg / t of lime is added to the ladle in batches, the bottom blowing argon flow rate is 300-400 NL / min, and stirring is carried out for 3-5 minutes to turn the slag into emulsified slag; Step S3, precipitation deoxidation: After the emulsified slag is formed for 2-4 minutes, sprinkle 10-15 kg of aluminum shot on the slag surface, maintain slight argon soft blowing, and the bottom blowing argon flow rate is 50-100 NL / min. Soft blowing for 4-6 minutes, collect the slag sample, and if the slag color turns white, continue soft blowing until it leaves the station.

2. The rapid deoxidation slag making process according to claim 1, characterized in that: In step S1, if the foamed slag is not formed, sprinkle 15-20 kg of calcium carbide on the slag surface again, stir vigorously for 2-3 minutes, and continue to make the foamed slag.

3. The rapid deoxidation slag making process according to claim 1, characterized in that: In step S2, if the emulsified slag is not formed, add 15-20 kg of calcium carbide and 1.0-1.2 kg / t of lime into the ladle, stir for 2-3 minutes, and continue to make the emulsified slag.

4. The rapid deoxidation slag making process according to claim 1, characterized in that: In step S3, if the slag does not turn white, continue to sprinkle 10-15 kg of aluminum cut shots on the slag surface until the slag turns white.

5. The rapid deoxidation slag making process according to claim 1, characterized in that: The molten steel is subjected to an electric furnace or converter process before entering the station: the smelting end point [C] is controlled between 0.10% and 0.30%, and the end point temperature is controlled above 1650°C.

6. The rapid deoxidation slag making process according to claim 5, characterized in that: During the converter smelting process, ferrosilicon, ferromanganese alloy and carburizer are added for deoxidation and alloying operations to adjust the element content in the molten steel. After tapping, the molten steel is hoisted to the argon blowing station.

7. The rapid deoxidation slag making process according to claim 6, characterized in that: The molten steel is continuously cast after deoxidation and slagging. The composition of the molten steel is adjusted according to the requirements of the steel grade and then poured on the continuous casting table.