Ultralow-sulfur steel smelting method

Abstract

The invention relates to the technical field of steel and iron smelting, and particularly discloses an ultra-low sulfur steel smelting method, which comprises the following steps of: washing a converter and washing a steel ladle before converter smelting; in the desulfurization process, high-temperature molten iron is used, deep desulfurization is conducted through a KR desulfurization method, and the sulfur content of the molten iron is smaller than or equal to 0.003%; converter working procedure: smelting by using a top-bottom combined blown converter, adopting a single-slag remaining method, adding self-produced first-class scrap steel, using low-sulfur lime, dolomite and iron-containing oxide, and controlling the end point of the converter: controlling the tapping carbon to be less than or equal to 0.04%, sulfur to be less than or equal to 0.005% and the temperature to be more than or equal to 1610 DEG C, adding lime for slag washing in the tapping process, adding part of lime for thick slag treatment after the tapping is finished, and then performing slagging-off operation; a refining process: adding lime and refining slag for slagging and desulphurizing, and finely adjusting components and raising the temperature; a continuous casting process: carrying out continuous casting; and finally, sulfur in a casting blank smelting finished product is less than or equal to 6ppm.

Description

Technical Field

[0001] The invention belongs to the technical field of steel smelting, and in particular relates to a method for smelting ultra-low sulfur steel. Background Art

[0002] As the market demand for high-quality steel grows, ultra-low sulfur steel, as an indispensable part of pure steel production, has received more and more attention. Using new technologies and processes to reduce the sulfur content in steel as much as possible has become the research direction of many steel companies.

[0003] Sulfur is a long-lived element in steel. Since it segregates at the grain boundaries of steel, it will affect the steel's resistance to sulfur stress cracking. Therefore, it is often regarded as a harmful element and needs to be removed during smelting. At present, some advanced steel companies at home and abroad usually use methods such as hot metal pre-desulfurization, converter "double method", LF desulfurization method, etc. to control sulfur in steel in the smelting of ultra-low sulfur steel. Using the above methods, the sulfur content of finished steel can generally be controlled within 6ppm. However, the above methods have many problems in desulfurization removal rate, ultra-low sulfur stability control and production cost. Summary of the invention

[0004] The purpose of the present invention is to provide an ultra-low sulfur steel smelting method to solve the problems of low desulfurization removal rate, unstable ultra-low sulfur control and high production cost in the existing steel smelting process.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for smelting ultra-low sulfur steel, the method comprising the following steps in sequence:

[0007] S1. The blast furnace molten iron is desulfurized by KR stirring method. The temperature of the molten iron entering the desulfurization station is ≥1300℃, the amount of desulfurizer is controlled to 7-10kg / t, the stirrer speed is controlled to 60-65rpm during feeding, the stirrer speed is controlled to 90-110rpm after feeding, the stirring time is controlled to 15-20min, and the sulfur content of the molten iron after desulfurization is ≤0.003%;

[0008] S2. Use top and bottom combined blowing converter for smelting, adopt single slag retention method, the weight percentage of raw material composition of metal main material is 80-88% of molten iron, the balance is self-produced Class I scrap steel, the phosphorus content of molten iron is ≤0.125%, the phosphorus content of self-produced Class I scrap steel is ≤0.015%, and the sulfur content is ≤0.010%; the oxygen ignition of the lower gun of the converter is normal, and low-phosphorus and low-sulfur slag-making auxiliary materials are added, and the slag-making auxiliary materials are lime, dolomite, and sintered ore, among which the sulfur content of lime is ≤0.030%, the sulfur content of dolomite is ≤0.030%, and the sulfur content of sintered ore is ≤0.02%;

[0009] S3, blowing adopts low-high-low oxygen supply operation mode, and the oxygen supply intensity is controlled at 1.7-3.7Nm 3 / (min·t), the bottom blowing argon flow rate is controlled at 0.05-0.10Nm 3 / (min·t), the ignition gun position is set to 1500mm, after normal ignition, when the blowing reaches 2% of the oxygen supply process, it is raised to the normal blowing gun position of 1400-1800mm, and the ignition flow rate is 15000Nm 3 / h, after 45 seconds, the oxygen supply will be automatically increased step by step to 30000-32000Nm 3 / h, before starting the gun at the end, the deep blowing gun position is lowered to 900mm, and the oxygen supply is increased to 32000Nm 3 / h, to carry out deep decarburization and make the molten steel composition and temperature uniform;

[0010] S4. When the blowing reaches 90% of the oxygen supply process, use the auxiliary gun TSC probe to determine carbon, measure temperature and take samples, then add part of the slag-making material for adjustment according to the carbon determination and the measured temperature, and track the smelting according to the auxiliary gun detection results until the smelting process requirements are met and the gun is started. At the end of blowing, use the auxiliary gun TSO probe to determine carbon, measure temperature, take samples and determine oxygen;

[0011] S5. Smelting endpoint control: steel tapping carbon ≤ 0.04%, sulfur ≤ 0.005% and temperature ≥ 1610℃, tapping is carried out when the control requirements are met, a certain amount of lime is added during the tapping process for slag washing, and some lime is added for thick slag treatment after tapping; after tapping, the converter is splashed to protect the furnace, and the intensity of the splashing nitrogen is controlled to 3.5-3.7Nm 3 / (min·t), the slag splashing gun position is controlled at 600-1500mm, and the slag splashing time is ≥2.5min; after the slag splashing is completed, the furnace is shaken to fill the large surface and then the residue is dumped;

[0012] S6. After steel tapping is completed, the ladle is hoisted to the slag removal station for slag removal, and alloying is performed after slag removal is completed;

[0013] S7. After entering the refining furnace, add more than 10kg / t of lime and 800kg / furnace of refined slag for slagging and desulfurization, and fine-tune the composition and increase the temperature. After adjusting the composition and reaching the required temperature of the molten steel, continuous pouring is carried out.

[0014] Preferably, step 1 further comprises the step of scraping off the high-sulfur slag on the surface of the molten iron by using argon blowing and slag removal method after desulfurization.

[0015] Preferably, in step 2, the amount of dolomite is 25-30 kg / t, the amount of lime is 45-50 kg / t, and the amount of sintered ore is 25-30 kg / t.

[0016] Preferably, in step 2, the first batch of lime can be added after ignition is normal, and the added amount is 1 / 3-1 / 2 of the total amount. If the flame is abnormal, stop adding in time, and add again in time after the flame is normal; the first batch of sintered ore is 1 / 3-1 / 2 of the total amount; the first batch of dolomite is 1 / 3-1 / 2 of the total amount; after the first batch of auxiliary materials are added, lime or sintered ore is continuously added, and the principle of adding materials is to add frequently and in small amounts, and the amount of each batch of auxiliary materials is 300-500kg; lime is added according to the basicity requirements before smelting for 10 minutes, and sintered ore is added according to the requirements according to the molten steel temperature before smelting for 12 minutes.

[0017] Preferably, the amount of lime added in step 5 is 4-6 kg / t.

[0018] Preferably, the weight percentages of the components of the desulfurizing agent in step 1 are: CaO≥78.0%, SiO2≤5.0%, CaF2≥7.0%, S≤0.040%; and the particle size of the desulfurizing agent is 0.3-1.6 mm.

[0019] Preferably, after slagging is completed, the argon gas in the ladle is opened, and 90-95% of the total amount of steel alloy is added for alloying, and the alloy is selected from the low-phosphorus and low-sulfur alloy in the alloy library.

[0020] Preferably, in step 5, after steel tapping is completed, the argon is adjusted to a soft blowing state with an argon pressure of 0.25±0.05Mpa, and then 1-2kg / t of lime is added to the surface of the molten steel to treat the thick slag.

[0021] Preferably, in step 7, the weight percentages of the components of the refined slag are: CaO 40-45%, Al2O3 40-45%, SiO2≤2.0%, MgO 5-10%, Fe2O3≤1.0%; and the particle size is 5-50 mm.

[0022] Compared with the prior art, the beneficial effects of the present invention are: the sulfur content of the finished steel is stably controlled within 6ppm, and lime is used for desulfurization during the steelmaking process, which not only reduces the difficulty of smelting low-sulfur steel but also reduces the blowing loss of the converter. The production process is simple and has a high degree of matching with the currently commonly used electrostatic precipitator process. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Embodiment 1:

[0025] This embodiment takes the smelting of 20CrMoVTiBNb steel as an example to explain in detail the smelting method of ultra-low sulfur steel.

[0026] The chemical composition of this steel grade is as follows:

[0027]

[0028] The ultra-low sulfur steel smelting method is used to smelt 20CrMoVTiBNb steel. The specific process steps are as follows:

[0029] S1. Wash the furnace and ladle before converter smelting;

[0030] S2. The blast furnace molten iron is desulfurized by KR stirring method. The temperature of the molten iron entering the desulfurization station is 1405°C. The amount of desulfurizer is controlled to be 9kg / t. The stirrer speed is controlled to be 65rpm during feeding. The stirrer speed is controlled to be 100rpm after feeding. The stirring time is controlled to be 18min. The sulfur content of the molten iron after desulfurization is 0.003%. After desulfurization, the high-sulfur slag on the surface of the molten iron is scraped off by argon blowing and slag removal method;

[0031] S3. Use top and bottom combined blowing converter for smelting, adopt single slag retention method, the weight percentage of raw material composition of metal main material is: molten iron accounts for 85%, the balance is self-produced Class I scrap steel, the phosphorus content of molten iron is 0.125%, the sulfur content of self-produced Class I scrap steel is 0.007%, and the phosphorus content is 0.013%; the oxygen ignition of the lower gun of the converter is normal, and low-phosphorus and low-sulfur slag-making auxiliary materials are added. The slag-making auxiliary materials are lime, dolomite, and sintered ore. Among them, the sulfur content of lime is 0.027%, the sulfur content of dolomite is 0.027%, and the sulfur content of sintered ore is 0.018%;

[0032] S4, blowing adopts low-high-low oxygen supply operation mode, and the oxygen supply intensity is controlled at 2.7Nm 3 / (min·t), bottom blowing argon gas flow rate is controlled to 0.08Nm 3 / (min·t), the ignition gun position is 1500mm, after normal ignition, when the blowing reaches 2% of the oxygen supply process, it is raised to the normal blowing gun position of 1600mm, and the ignition flow rate is 15000Nm 3 / h, and automatically increase the oxygen supply to 31000Nm in a step-by-step manner after 45 seconds 3 / h, before starting the gun at the end, the deep blowing gun position is lowered to 900mm, and the oxygen supply is increased to 32000Nm 3 / h, to carry out deep decarburization and make the molten steel composition and temperature uniform;

[0033] S5. When the blowing reaches 90% of the oxygen supply process, use the auxiliary gun TSC probe to determine carbon, measure temperature and take samples, then add part of the slag-making material for adjustment according to the carbon determination and the measured temperature, and track the smelting according to the auxiliary gun detection results until the smelting process requirements are met and the gun is started. At the end of blowing, use the auxiliary gun TSO probe to determine carbon, measure temperature, take samples and determine oxygen;

[0034] S6, smelting end point control: steel tapping carbon 0.037%, sulfur 0.005% and steel tapping temperature 1611 ℃, meet the control requirements for steel tapping, add 500 kg lime for slag washing during steel tapping, add 150 kg lime for thick slag treatment after steel tapping, sulfur sampling at the argon blowing station after the furnace: 0.0048%; after steel tapping, the converter is splashed to protect the furnace, and the intensity of the splashing nitrogen is controlled to 3.6 Nm 3 / (min·t), slag splashing gun position control: 1200mm, slag splashing time: 3.5min; after slag splashing, shake the furnace to fill the large surface and then pour out the residue;

[0035] S7, after steel tapping is completed, the ladle is hoisted to the slag removal station for slag removal, and after slag removal is completed, it is hoisted to the refining furnace;

[0036] S8. After entering the refining furnace, add 1300kg of lime and 800kg of refined slag for desulfurization, then fine-tune the composition and increase the temperature, add 93% of the total amount of steel alloy for alloying, and select low-phosphorus and low-sulfur alloys in the alloy library. After adjusting the composition and reaching the required temperature of the molten steel, continuous pouring is carried out.

[0037] Specifically, the temperature is raised, slag is melted, and deoxidation is performed (aluminum particles are used for full deoxidation) until sampling (steel sample and slag sample), and the composition is adjusted continuously. Soft blowing is performed for 20 minutes, and the smelting product sample is taken. The composition is as follows:

[0038]

[0039] As a preferred implementation of this embodiment, in step 3, the amount of dolomite used is 28 kg / t, the amount of lime used is 47 kg / t, and the amount of sintered ore used is 28 kg / t.

[0040] As a preferred implementation manner of this embodiment, in step 3, the first batch of lime can be added after the ignition is normal, and the added amount is 1 / 3-1 / 2 of the total amount. If the flame is abnormal, stop adding in time, and add it again in time after the flame is normal; the first batch of sintered ore is 1 / 3-1 / 2 of the total amount; the first batch of dolomite is 1 / 3-1 / 2 of the total amount; after the first batch of auxiliary materials are added, lime or sintered ore is continuously added, and the principle of adding materials is to add frequently and in small amounts, and the amount of auxiliary materials added for each batch is 300kg; lime is added according to the alkalinity requirements before smelting for 10 minutes, and sintered ore is added according to the requirements according to the molten steel temperature before smelting for 12 minutes.

[0041] As a preferred implementation of this embodiment, the weight percentages of the components of the desulfurizer in step 1 are: CaO: 85%, SiO2: 2.8%, CaF2: 8.1%, S: 0.029%; the particle size of the desulfurizer is 1.1 mm.

[0042] As a preferred implementation of this embodiment, in step 6, after steel tapping is completed, the argon gas is adjusted to a soft blowing state, and the argon gas pressure is 0.25 MPa.

[0043] As a preferred implementation of this embodiment, in step 8, the weight percentages of the components of the refined slag are: CaO 43%, Al2O3 42%, SiO2 1.5%, MgO 10%, Fe2O3 0.9%; and the particle size is 5 mm.

[0044] Embodiment 2:

[0045] This embodiment takes the smelting of 20CrMoVTiBNb steel as an example to explain in detail the smelting method of ultra-low sulfur steel.

[0046] The chemical composition of this steel grade is as follows:

[0047]

[0048] The ultra-low sulfur steel smelting method is used to smelt 20CrMoVTiBNb steel. The specific process steps are as follows:

[0049] S1. Wash the furnace and ladle before converter smelting;

[0050] S2. The blast furnace iron was desulfurized by KR stirring method. The temperature of the iron entering the desulfurization station was 1385°C. The amount of desulfurizer was controlled to 7kg / t. The stirrer speed was controlled to 63rpm during feeding. After feeding, the stirrer speed was controlled to 90rpm. The stirring time was controlled to 20min. The sulfur content of the iron after desulfurization was 0.0029%. After desulfurization, the high-sulfur slag on the surface of the iron was removed by argon blowing and slag removal method.

[0051] S3. Use top and bottom combined blowing converter for smelting, adopt single slag retention method, the weight percentage of raw material composition of metal main material input is: molten iron accounts for 88%, the balance is self-produced Class I scrap steel, the phosphorus content of molten iron is 0.124%, the sulfur content of self-produced Class I scrap steel is 0.008%, and the phosphorus content is ≤0.0145%; the oxygen ignition of the lower gun of the converter is normal, and low-phosphorus and low-sulfur slag-making auxiliary materials are added. The slag-making auxiliary materials are lime, dolomite, and sintered ore. Among them, the sulfur content of lime is 0.028%, the sulfur content of dolomite is 0.027%, and the sulfur content of sintered ore is 0.019%;

[0052] S4, blowing adopts low-high-low oxygen supply operation mode, and the oxygen supply intensity is controlled at 3.7Nm 3 / (min·t), bottom blowing argon gas flow rate is controlled at 0.10Nm 3 / (min·t), the ignition gun position is 1500mm, after normal ignition, when the blowing reaches 2% of the oxygen supply process, it is raised to the normal blowing gun position of 1800mm, and the ignition flow rate is 15000Nm 3 / h, and automatically increase the oxygen supply to 32000Nm in a step-by-step manner after 45 seconds 3 / h, before starting the gun at the end, the deep blowing gun position is lowered to 900mm, and the oxygen supply is increased to 32000Nm 3 / h, to carry out deep decarburization and make the molten steel composition and temperature uniform;

[0053] S5. When the blowing reaches 90% of the oxygen supply process, use the auxiliary gun TSC probe to determine carbon, measure temperature and take samples, then add part of the slag-making material for adjustment according to the carbon determination and the measured temperature, and track the smelting according to the auxiliary gun detection results until the smelting process requirements are met and the gun is started. At the end of blowing, use the auxiliary gun TSO probe to determine carbon, measure temperature, take samples and determine oxygen;

[0054] S6, smelting end point control: steel tapping carbon 0.038%, sulfur 0.0045% and steel tapping temperature 1615 ℃, meet the control requirements for steel tapping, add 600 kg lime for slag washing during steel tapping, add 100 kg lime for thick slag treatment after steel tapping, sulfur sampling at the argon blowing station after the furnace: 0.0047%; after steel tapping, the converter is splashed to protect the furnace, and the intensity of the splashing nitrogen is controlled to 3.7 Nm 3 / (min·t), slag splashing gun position control: 1500mm, slag splashing time: 3min; after slag splashing, shake the furnace to fill the large surface and then pour out the residue;

[0055] S7, after steel tapping is completed, the ladle is hoisted to the slag removal station for slag removal, and after slag removal is completed, it is hoisted to the refining furnace;

[0056] S8. After entering the refining furnace, add 1200kg of lime and 800kg of refined slag for desulfurization, then fine-tune the composition and increase the temperature, add 95% of the total amount of steel alloy for alloying, and select low-phosphorus and low-sulfur alloys in the alloy library. After adjusting the composition and reaching the required temperature of the molten steel, continuous pouring is carried out.

[0057] Specifically, the temperature is raised, slag is melted, and deoxidation is performed (aluminum particles are used for full deoxidation) until sampling (steel sample and slag sample), and the composition is adjusted continuously. Soft blowing is performed for 20 minutes, and the smelting product sample is taken. The composition is as follows:

[0058]

[0059] As a preferred implementation of this embodiment, in step 3, the amount of dolomite used is 30 kg / t, the amount of lime used is 50 kg / t, and the amount of sintered ore used is 30 kg / t.

[0060] As a preferred implementation mode of this embodiment, in step 3, the first batch of lime can be added after the ignition is normal, and the added amount is 1 / 3-1 / 2 of the total amount. If the flame is abnormal, stop adding in time, and add it again in time after the flame is normal; the first batch of sintered ore is 1 / 3-1 / 2 of the total amount; the first batch of dolomite is 1 / 3-1 / 2 of the total amount; after the first batch of auxiliary materials are added, lime or sintered ore is continuously added, and the principle of adding materials is to add frequently and in small amounts, and the amount of auxiliary materials added for each batch is 400kg; lime is added according to the alkalinity requirements before smelting for 10 minutes, and sintered ore is added according to the requirements according to the molten steel temperature before smelting for 12 minutes.

[0061] As a preferred implementation of this embodiment, the weight percentages of the components of the desulfurizer in step 2 are: CaO: 78%, SiO2: 3.8%, CaF2: 9%, S: 0.04%; the particle size of the desulfurizer is 1.6 mm.

[0062] As a preferred implementation of this embodiment, in step 6, after steel tapping is completed, the argon gas is adjusted to a soft blowing state, and the argon gas pressure is 0.20 MPa.

[0063] As a preferred implementation of this embodiment, in step 8, the weight percentages of the components of the refined slag are: CaO 45%, Al2O3 40%, SiO2 1.15%, MgO 8%, Fe2O3 0.009%; and the particle size is 35 mm.

[0064] Embodiment 3:

[0065] This embodiment takes the smelting of 20CrMoVTiBNb steel as an example to explain in detail the smelting method of ultra-low sulfur steel.

[0066] The chemical composition of this steel grade is as follows:

[0067]

[0068] The ultra-low sulfur steel smelting method is used to smelt 20CrMoVTiBNb steel. The specific process steps are as follows:

[0069] S1. Wash the furnace and ladle before converter smelting;

[0070] S2. The blast furnace molten iron is desulfurized by KR stirring method. The temperature of the molten iron entering the desulfurization station is 1400°C, the amount of desulfurizer is controlled to be 10kg / t, the stirrer speed is controlled to be 60rpm during feeding, the stirrer speed is controlled to be 110rpm after feeding, the stirring time is controlled to be 15min, the sulfur content of the molten iron after desulfurization is 0.0028%, and the high-sulfur slag on the surface of the molten iron is scraped off by argon blowing slag removal method after desulfurization;

[0071] S3. Use top and bottom combined blowing converter for smelting, adopt single slag retention method, the weight percentage of raw material composition of metal main material is: molten iron accounts for 80%, the balance is self-produced Class I scrap steel, the phosphorus content of molten iron is 0.1235%, the sulfur content of self-produced Class I scrap steel is 0.01%, and the phosphorus content is ≤0.015%; the oxygen ignition of the lower gun of the converter is normal, and low-phosphorus and low-sulfur slag-making auxiliary materials are added. The slag-making auxiliary materials are lime, dolomite, and sintered ore. Among them, the sulfur content of lime is 0.03%, the sulfur content of dolomite is 0.03%, and the sulfur content of sintered ore is 0.02%;

[0072] S4, blowing adopts low-high-low oxygen supply operation mode, and the oxygen supply intensity is controlled at 1.7Nm 3 / (min·t), bottom blowing argon gas flow rate is controlled to 0.05Nm 3 / (min·t), the ignition gun position is 1500mm, after normal ignition, when the blowing reaches 2% of the oxygen supply process, it is raised to the normal blowing gun position of 1400mm, and the ignition flow rate is 15000Nm 3 / h, and automatically increase the oxygen supply to 32000Nm in a step-by-step manner after 45 seconds 3 / h, before starting the gun at the end, the deep blowing gun position is lowered to 900mm, and the oxygen supply is increased to 30000Nm 3 / h, to carry out deep decarburization and make the molten steel composition and temperature uniform;

[0073] S5. When the blowing reaches 90% of the oxygen supply process, use the auxiliary gun TSC probe to determine carbon, measure temperature and take samples, then add part of the slag-making material for adjustment according to the carbon determination and the measured temperature, and track the smelting according to the auxiliary gun detection results until the smelting process requirements are met and the gun is started. At the end of blowing, use the auxiliary gun TSO probe to determine carbon, measure temperature, take samples and determine oxygen;

[0074] S6, smelting end point control: steel tapping carbon 0.04%, sulfur 0.005% and steel tapping temperature 1615 ℃, reach the control requirements for steel tapping, add 400 kg lime for slag washing during steel tapping, add 200 kg lime for thick slag treatment after steel tapping, sulfur sampling at the argon blowing station after the furnace: 0.0049%; after steel tapping, the converter is splashed to protect the furnace, and the intensity of the splashing nitrogen is controlled to 3.5 Nm 3 / (min·t), slag splashing gun position control: 600mm, slag splashing time: 2.5min; after slag splashing, shake the furnace to fill the large surface and then pour out the residue;

[0075] S7, after steel tapping is completed, the ladle is hoisted to the slag removal station for slag removal, and after slag removal is completed, it is hoisted to the refining furnace;

[0076] S8. After entering the refining furnace, add 1000kg lime and 800kg refined slag for desulfurization, then fine-tune the composition and increase the temperature, add 90% of the total amount of steel alloy for alloying, and select low-phosphorus and low-sulfur alloys in the alloy library. After adjusting the composition and reaching the required temperature of the molten steel, continuous pouring is carried out.

[0077] Specifically, the temperature is raised, slag is melted, and deoxidation is performed (aluminum particles are used for full deoxidation) until sampling (steel sample and slag sample), and the composition is adjusted continuously. Soft blowing is performed for 20 minutes, and the smelting product sample is taken. The composition is as follows:

[0078]

[0079]

[0080] As a preferred implementation of this embodiment, in step 3, the amount of dolomite used is 25 kg / t, the amount of lime used is 45 kg / t, and the amount of sintered ore used is 25 kg / t.

[0081] As a preferred implementation manner of this embodiment, in step 3, the first batch of lime can be added after normal ignition, and the amount added is 1 / 3-1 / 2 of the total amount. If the flame is abnormal, stop adding in time, and add again in time after the flame is normal; the first batch of sintered ore is 1 / 3-1 / 2 of the total amount; the first batch of dolomite is 1 / 3-1 / 2 of the total amount; after the first batch of auxiliary materials are added, lime or sintered ore is continuously added, and the principle of adding materials is to add frequently and in small amounts, and the amount of auxiliary materials added for each batch is 500kg; lime is added according to the alkalinity requirements before smelting for 10 minutes, and sintered ore is added according to the requirements according to the molten steel temperature before smelting for 12 minutes.

[0082] As a preferred implementation of this embodiment, the weight percentages of the components of the desulfurizer in step 2 are: CaO: 86%, SiO2: 5.0%, CaF2: 7.0%, S: 0.03%; the particle size of the desulfurizer is 0.3 mm.

[0083] As a preferred implementation of this embodiment, in step 6, after steel tapping is completed, the argon gas is adjusted to a soft blowing state, and the argon gas pressure is 0.30 MPa.

[0084] As a preferred implementation of this embodiment, in step 8, the weight percentages of the components of the refined slag are: CaO 40%, Al2O3 45%, SiO2 2.0%, MgO 5%, Fe2O3 1.0%; and the particle size is 50 mm.

[0085] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for smelting ultra-low sulfur steel, characterized in that: The method comprises the following steps in sequence: S1. The blast furnace molten iron is desulfurized by KR stirring method. The temperature of the molten iron entering the desulfurization station is ≥1300℃, the amount of desulfurizer is controlled to 7-10kg / t, the stirrer speed is controlled to 60-65rpm during feeding, the stirrer speed is controlled to 90-110rpm after feeding, the stirring time is controlled to 15-20min, and the sulfur content of the molten iron after desulfurization is ≤0.003%; S2. Use top and bottom combined blowing converter for smelting, adopt single slag retention method, the weight percentage of raw material composition of metal main material is 80-88% of molten iron, the balance is self-produced Class I scrap steel, the phosphorus content of molten iron is ≤0.125%, the phosphorus content of self-produced Class I scrap steel is ≤0.015%, and the sulfur content is ≤0.010%; the oxygen ignition of the lower gun of the converter is normal, and low-phosphorus and low-sulfur slag-making auxiliary materials are added, and the slag-making auxiliary materials are lime, dolomite, and sintered ore, among which the sulfur content of lime is ≤0.030%, the sulfur content of dolomite is ≤0.030%, and the sulfur content of sintered ore is ≤0.02%; S3, blowing adopts low-high-low oxygen supply operation mode, and the oxygen supply intensity is controlled at 1.7-3.7Nm 3 / (min·t), the bottom blowing argon flow rate is controlled at 0.05-0.10Nm 3 / (min·t), the ignition gun position is set to 1500mm, after normal ignition, when the blowing reaches 2% of the oxygen supply process, it is raised to the normal blowing gun position of 1400-1800mm, and the ignition flow rate is 15000Nm 3 / h, and after 45 seconds, the oxygen supply will be automatically increased step by step to 30000-32000Nm 3 / h, before starting the gun at the end, the deep blowing gun position is lowered to 900mm, and the oxygen supply is increased to 32000Nm 3 / h, to carry out deep decarburization and make the molten steel composition and temperature uniform; S4. When the blowing reaches 90% of the oxygen supply process, use the auxiliary gun TSC probe to determine carbon, measure temperature and take samples, then add part of the slag-making material for adjustment according to the carbon determination and the measured temperature, and track the smelting according to the auxiliary gun detection results until the smelting process requirements are met and the gun is started. At the end of blowing, use the auxiliary gun TSO probe to determine carbon, measure temperature, take samples and determine oxygen; S5. Smelting endpoint control: steel tapping carbon ≤ 0.04%, sulfur ≤ 0.005% and temperature ≥ 1610℃, steel tapping is carried out when the control requirements are met. A certain amount of lime is added during the steel tapping process for slag washing, and some lime is added for thick slag treatment after steel tapping. After steel tapping, the converter is splashed to protect the furnace, and the intensity of the splashing nitrogen is controlled to 3.5-3.7Nm 3 / (min·t), the slag splashing gun position is controlled at 600-1500mm, and the slag splashing time is ≥2.5min; after the slag splashing is completed, the furnace is shaken to fill the large surface and then the residue is dumped; S6. After steel tapping is completed, the ladle is hoisted to the slag removal station for slag removal, and alloying is performed after slag removal is completed; S7. After entering the refining furnace, add more than 10kg / t of lime and 800kg / furnace of refined slag for slagging and desulfurization, and fine-tune the composition and increase the temperature. After adjusting the composition and reaching the required temperature of the molten steel, continuous pouring is carried out.

2. The ultra-low sulfur steel smelting method according to claim 1, characterized in that: The step 1 also includes the step of scraping off the high-sulfur slag on the surface of the molten iron by using argon blowing and slag removal method after desulfurization.

3. The ultra-low sulfur steel smelting method according to claim 1, characterized in that: In the step 2, the amount of dolomite is 25-30 kg / t, the amount of lime is 45-50 kg / t, and the amount of sintered ore is 25-30 kg / t.

4. The ultra-low sulfur steel smelting method according to claim 3, characterized in that: In step 2, the first batch of lime can be added after the ignition is normal, and the added amount is 1 / 3-1 / 2 of the total amount. If the flame is abnormal, stop adding in time, and add it again in time after the flame is normal; the first batch of sintered ore is 1 / 3-1 / 2 of the total amount; the first batch of dolomite is 1 / 3-1 / 2 of the total amount; after the first batch of auxiliary materials are added, lime or sintered ore is continuously added, and the principle of adding materials is to add frequently and in small amounts, and the amount of each batch of auxiliary materials is 300-500kg; lime is added according to the basicity requirements before smelting for 10 minutes, and sintered ore is added according to the requirements according to the molten steel temperature before smelting for 12 minutes.

5. The ultra-low sulfur steel smelting method according to claim 1, characterized in that: The amount of lime added in step 5 is 4-6 kg / t.

6. The ultra-low sulfur steel smelting method according to claim 1, characterized in that: The weight percentages of the components of the desulfurizing agent in step 1 are: CaO≥78.0%, SiO2≤5.0%, CaF2≥7.0%, S≤0.040%; and the particle size of the desulfurizing agent is 0.3-1.6 mm.

7. The ultra-low sulfur steel smelting method according to claim 1, characterized in that: After the slag stripping is completed, the argon gas in the ladle is opened, and 90-95% of the total amount of steel alloy is added for alloying. The alloy is a low-phosphorus and low-sulfur alloy in the alloy library.

8. The ultra-low sulfur steel smelting method according to claim 1, characterized in that: In step 5, after steel tapping is completed, the argon gas is adjusted to a soft blowing state with an argon gas pressure of 0.25±0.05Mpa, and then 1-2kg / t of lime is added to the surface of the molten steel to treat the thick slag.

9. The ultra-low sulfur steel smelting method according to claim 1, characterized in that: In step 7, the weight percentage of each component of the refined slag is: CaO 40-45%, Al2O3 40-45%, SiO2≤2.0%, MgO 5-10%, Fe2O3≤1.0%; and the particle size is 5-50 mm.

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