Method for accurately controlling oxygen content at the end of RH decarburization of IF steel

Abstract

The application discloses a method for precisely controlling the oxygen content at the decarburization endpoint of RH of IF steel, which comprises a converter smelting and an RH refining step; the RH refining step comprises the following steps: measuring the oxygen content of molten steel at the RH inlet before vacuumizing the RH, and calculating the oxygen blowing amount by using the following formula (I): Q=(C 炉后 ×1.33‑O 进站 ‑(‑0.24×H 烘烤 2 +15.1×H 烘烤 )+O 目标 ) / (ρ O / m×η). The method can precisely control the oxygen content at the decarburization endpoint of RH by using an operation program, can consider the influence of the residual oxygen position of the RH baking vacuum tank and the oxygen gun position on the oxygen absorption rate, can avoid excessive aluminum in the RH deoxidation, can reduce Al2O3 generated by the deoxidation, can improve the purity of molten steel, and can reach more than 95% of the hit rate of the oxygen at the decarburization endpoint of RH, which is improved by more than 15% compared with conventional technologies; the method can ensure that the oxygen blowing hits the oxygen content at the decarburization endpoint, can shorten the decarburization cycle, can reduce the temperature loss in the decarburization process, and can further reduce the final temperature of the converter.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a method for precisely controlling the oxygen content at the endpoint of RH decarburization in IF steel. Background Technology

[0002] In the smelting process of IF steel, it is necessary to ensure a certain oxygen level at the decarburization endpoint to ensure that the carbon content of the molten steel meets the requirements. However, the higher the oxygen level at the decarburization endpoint, the more Al2O3 inclusions are generated after aluminum deoxidation, which not only increases the cost but also affects the quality of molten steel and casting stability. Therefore, accurately controlling the oxygen content at the RH decarburization endpoint of IF steel can not only reduce costs but also improve the quality of molten steel and enhance casting stability.

[0003] Patent application CN202110676225.9, entitled "A Two-Step Method and Model for Determining the Oxygen Blowing Amount in RH Refining Furnace for IF Steel Smelting," describes a method that measures temperature and oxygen content in the early stages of RH treatment, quantifies the influence of different states of the ladle and vacuum tank on the temperature and oxygen content of the molten steel, establishes a calculation method, and calculates the required oxygen blowing amount in two steps. After the first oxygen blowing, the temperature and oxygen content are measured again at a certain interval, and a second calculation and oxygen blowing are performed. This method can accurately determine the total oxygen blowing amount in RH, thereby improving the accuracy of RH cavitation temperature control and reducing RH treatment time. However, this method mainly controls the RH cavitation temperature by calculating the oxygen blowing amount and cannot accurately control the oxygen content at the RH decarburization endpoint. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for accurately controlling the oxygen content at the endpoint of RH decarburization in IF steel.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: including converter smelting and RH refining steps; the RH refining step: before RH vacuuming, the oxygen content of the molten steel entering the RH station is measured, and the oxygen blowing amount is calculated using the following formula (Ⅰ). During the RH refining process, oxygen is blown according to the calculated oxygen blowing amount. Q=(C 炉后 ×1.33-O 进站 -(-0.24×H 烘烤 2 +15.1×H 烘烤 )+O 目标 ) / (ρO / m×η) (Ⅰ) In the formula: Q: Oxygen blowing volume (Nm) in the RH refining process. 3 ; C 炉后 Carbon content of molten steel after converter furnace, in ppm; O 进站 RH oxygen content of molten steel entering the station, in ppm; H烘烤 RH vacuum oven baking time, min; O 进站 RH oxygen content of molten steel entering the station, in ppm; O 目标 : RH target decarbonization endpoint oxygen content, ppm; ρ O Oxygen density, g / L; m: RH steel inflow volume, kg; η: Oxygen absorption rate of molten steel in the RH refining process.

[0006] Furthermore, in the converter smelting step, the final carbon content ranges from 0.025 to 0.055 wt%, and the final oxygen level is required to be 300 to 600 ppm.

[0007] Furthermore, in the converter smelting step, the amount of modifier added is 1.9 to 2.1 kg / t.

[0008] Furthermore, in the RH refining step, the RH vacuum chamber baking time is ≤25 minutes, and the coke oven gas flow rate is 290~310Nm. 3 / h.

[0009] Furthermore, during the RH vacuum oven baking process, the gas volume / oxygen volume ratio is 0.78 to 0.82, and the top gun baking position is between 3950 and 4050 mm.

[0010] Furthermore, in the RH refining step, oxygen blowing is initiated 2-3 minutes after vacuuming.

[0011] Furthermore, in the RH refining process, the oxygen blowing flow rate is 2950–3050 Nm³. 3 / h, gun position 4950~5050mm.

[0012] The beneficial effects of adopting the above technical solution are as follows: This method calculates the oxygen blowing volume through a computational program, considering the residual oxygen level in the RH baking vacuum tank and the influence of the oxygen blowing lance position on the oxygen absorption rate. This allows for precise control of the oxygen content at the RH decarburization endpoint, avoiding excessive aluminum deoxidation, reducing Al2O3 production, and improving steel purity. The hit rate of ±50ppm oxygen at the RH decarburization endpoint reaches over 95%, an improvement of over 15% compared to conventional technologies. It ensures that the oxygen content at the decarburization endpoint is reached in a single oxygen blowing operation, shortening the decarburization cycle, reducing temperature loss during decarburization, and further lowering the converter endpoint temperature. This invention can control the oxygen content at the RH decarburization endpoint, improve steel purity, reduce the nozzle blockage index during continuous casting, and achieve stable casting of IF steel in 9 heats. It has significant application value for actual steel plant smelting production. Detailed Implementation

[0013] The present invention will now be described in further detail with reference to specific embodiments.

[0014] This method for precisely controlling the oxygen content at the endpoint of RH decarburization in IF steel includes converter smelting and RH refining steps, the processes of which are described below: (1) Converter smelting: The carbon content range at the end of the converter is 0.025 to 0.055 wt%, and the carbon content target is controlled at 0.040 wt%. After the blowing is completed, the oxygen level at the end is measured. The oxygen level at the end is required to be 300 to 600 ppm.

[0015] After tapping, a modifier is added. The amount of modifier added is determined based on the final oxygen level: for heats with a final oxygen level of 300-600 ppm, the amount of modifier added is 1.9-2.1 kg / t. After adding the modifier, the molten steel composition is sampled and analyzed after the converter.

[0016] (2) RH refining: Before RH vacuuming, measure the oxygen content of molten steel entering the RH station. Calculate the oxygen blowing amount based on the time of intermittent baking of the vacuum tank, the carbon content of the converter furnace sample, the oxygen content of RH entering the station, and the oxygen content at the RH target decarburization endpoint. The following formula (Ⅰ) is used for calculation. Q=(C 炉后 ×1.33-O 进站 -(-0.24×H 烘烤 2 +15.1×H 烘烤 )+O 目标 ) / (ρ O / m×η) (Ⅰ) In the formula: Q: Oxygen blowing volume (Nm) in the RH refining process. 3 ; C 炉后 Carbon content of molten steel after converter furnace, in ppm; O 进站 RH oxygen content of molten steel entering the station, in ppm; H 烘烤 RH vacuum oven baking time, min; O 进站 RH oxygen content of molten steel entering the station, in ppm; O 目标 : RH target decarbonization endpoint oxygen content, ppm; ρ O Oxygen density, g / L, is typically 1.43 g / L; m: RH steel inflow volume, kg; η: Oxygen absorption rate of molten steel in the RH refining process, %, typically 70%.

[0017] The baking time in the RH vacuum chamber should be controlled to be ≤25 minutes, and the coke oven gas flow rate should be 290~310Nm. 3 / h, gas volume / oxygen volume is 0.78~0.82, and the top gun baking gun position is between 3950~4050mm.

[0018] The minimum vacuum level during the decarburization period of the RH refining process is controlled at 1.2 mbar or below; oxygen blowing is carried out according to the oxygen blowing rate calculated above, and the RH oxygen blowing timing is to start oxygen blowing 2-3 minutes after vacuuming; the RH vacuum oxygen blowing flow rate is 2950-3050 Nm³. 3 / h, gun position 4950~5050mm.

[0019] Example 1: The method for precisely controlling the oxygen content at the RH decarburization endpoint of IF steel adopts the following specific process.

[0020] (1) Converter smelting: The ultra-low carbon steel produced is SPHETi-3. The steel composition requirements are shown in Table 1 below. The total amount of molten steel in this furnace is 252t. The final oxygen level is 428ppm and the final carbon content is 0.038wt%. After tapping, 504kg of modifier is added. The carbon content of the sample taken from the furnace is 0.030wt%.

[0021] Table 1: Composition requirements (wt%) for the SPHETi-3 steel grade

[0022] In Table 1, the balance of the components is Fe and unavoidable impurities.

[0023] (2) RH refining: The RH vacuum tank was not baked during the smelting interval. The ladle was lifted to the processing position by the jacking system, and the temperature and oxygen were measured. The temperature was 1636℃ and the oxygen level at the station was 435ppm. Processing began. Oxygen blowing started after 2.5 minutes of vacuuming. The target final deoxidation level was 150ppm. The oxygen blowing volume Q was calculated according to formula (Ⅰ) Q=(C 炉后 ×1.33-O 进站 -(-0.24×H 烘烤 2 +15.1×H 烘烤 )+O 目标 ) / (ρ O / m×1000×η)=(300×1.33-435-(-0.24×0 2 +15.1×0)+150) / (1.43 / 252×1000×0.7)=29Nm 3 The oxygen blowing flow rate is 3000 Nm³. 3 / h, gun position 5000mm, oxygen blowing 29Nm 3After 14 minutes of decarburization, the vacuum level reached 0.5 mbar. The oxygen level in the molten steel was measured, and the oxygen level at the end of decarburization was 153 ppm, which deviated from the target value by 3 ppm.

[0024] Example 2: The method for precisely controlling the oxygen content at the RH decarburization endpoint of IF steel adopts the following specific process.

[0025] (1) Converter smelting: The ultra-low carbon steel produced is SPHETi-3, and the steel composition requirements are shown in Table 1. The total amount of molten steel in this furnace is 256t. The final oxygen level is 306ppm and the final carbon content is 0.050wt%. After tapping, 501kg of modifier is added. After taking the furnace sample, the C content is 0.043wt%.

[0026] (2) RH refining: Bake the RH vacuum tank for 25 minutes during the smelting interval, with a coke oven gas flow rate of 302 Nm³. 3 / h, gas volume / oxygen volume is 0.78, and the top lance baking position is 4000mm. The ladle is lifted to the processing position using the jacking system. Temperature and oxygen levels are measured and determined; the temperature is 1615℃, and the inlet oxygen level is 277ppm. Processing begins; oxygen blowing starts after 2.5 minutes of vacuuming. The target final deoxygenation level is 250ppm. The oxygen blowing rate Q is calculated according to formula (Ⅰ) Q=(C 炉后 ×1.33-O 进站 -(-0.24×H 烘烤 2 +15.1×H 烘烤 )+O 目标 ) / (ρ O / m×1000×η)=(430×1.33-277-(-0.24×25 2 +15.1×25)+250) / (1.43 / 256×1000×0.7)=81Nm 3 The oxygen blowing flow rate is 3000 Nm³. 3 / h, gun position 5000mm, oxygen blowing 81Nm 3 After 15 minutes of decarburization, the vacuum level reached 0.6 mbar. The oxygen level in the molten steel was measured, and the oxygen level at the end of decarburization was 272 ppm, which deviated from the target value by 22 ppm.

[0027] Example 3: The method for precisely controlling the oxygen content at the endpoint of RH decarburization in IF steel adopts the following specific process.

[0028] (1) Converter smelting: The ultra-low carbon steel produced is SPHETi-3, and the steel composition requirements are shown in Table 1. The total amount of molten steel in this furnace is 259t. The final oxygen level is 579ppm and the final carbon content is 0.036wt%. After tapping, 573kg of modifier is added. After taking the furnace sample, the C content is 0.025wt%.

[0029] (2) RH refining: Bake the RH vacuum tank for 12 minutes during the smelting interval, with a coke oven gas flow rate of 291 Nm³. 3 / h, gas volume / oxygen volume is 0.82, and the top lance baking position is 4050mm. The ladle is lifted to the processing position using the jacking system. Temperature and oxygen levels are measured and determined; the temperature is 1610℃, and the inlet oxygen level is 393ppm. Processing begins; oxygen blowing starts after 2 minutes of vacuuming. The target final deoxygenation level is 280ppm. The oxygen blowing rate Q is calculated according to formula (Ⅰ) Q=(C 炉后 ×1.33-O 进站 -(-0.24×H 烘烤 2 +15.1×H 烘烤 )+O 目标 ) / (ρ O / m×1000×η)=(250×1.33-393-(-0.24×12 2 +15.1×12)+280) / (1.43 / 259×1000×0.7)=17Nm 3 The oxygen blowing flow rate is 2953 Nm³. 3 / h, gun position 4958mm, oxygen blowing 17Nm 3 After 15 minutes of decarburization, the vacuum level reached 0.6 mbar. The oxygen level in the molten steel was measured, and the oxygen level at the end of decarburization was 270 ppm, which deviated from the target value by 10 ppm.

[0030] Example 4: The method for precisely controlling the oxygen content at the endpoint of RH decarburization in IF steel adopts the following specific process.

[0031] (1) Converter smelting: The ultra-low carbon steel produced is SPHETi-5, and the steel composition requirements are shown in Table 2. The total amount of molten steel in this furnace is 262t. The final oxygen level is 430ppm and the final carbon content is 0.041wt%. After tapping, 506kg of modifier is added. After taking the furnace sample, the C content is 0.035wt%.

[0032] Table 2: Composition requirements (wt%) for the SPHETi-5 steel grade

[0033] (2) RH refining: Bake the RH vacuum tank for 20 minutes during the smelting interval, with a coke oven gas flow rate of 309 Nm. 3 / h, gas volume / oxygen volume is 0.80, and the top lance baking position is 3950mm. The ladle is lifted to the processing position using the jacking system. Temperature and oxygen levels are measured and determined; the temperature is 1615℃, and the inlet oxygen level is 361ppm. Processing begins; oxygen blowing starts after 3 minutes of vacuuming. The target final deoxygenation level is 220ppm. The oxygen blowing rate Q is calculated according to formula (Ⅰ) Q=(C 炉后 ×1.33-O 进站-(-0.24×H 烘烤 2 +15.1×H 烘烤 )+O 目标 ) / (ρ O / m×1000×η)=(350×1.33-361-(-0.24×20 2 +15.1×20)+220) / (1.43 / 262×1000×0.7)=31Nm 3 The oxygen blowing flow rate is 3045 Nm. 3 / h, gun position 5040mm, oxygen blowing 31Nm 3 After 14 minutes of decarburization, the vacuum level reached 0.6 mbar. The oxygen level in the molten steel was measured, and the oxygen level at the end of decarburization was 242 ppm, which deviated from the target value by 22 ppm.

[0034] Example 5: The method for precisely controlling the oxygen content at the endpoint of RH decarburization in IF steel adopts the following specific process.

[0035] (1) Converter smelting: The ultra-low carbon steel produced is SPHETi-36, and the steel composition requirements are shown in Table 3. The total amount of molten steel in this furnace is 259t. The final oxygen level is 412ppm and the final carbon content is 0.035%. After tapping, 501kg of modifier is added. The carbon content of the sample taken from the furnace is 0.033%.

[0036] Table 3: Composition requirements (wt%) for the SPHETi-36 steel grade

[0037] (2) RH refining: Bake the RH vacuum tank for 5 minutes during the smelting interval, with a coke oven gas flow rate of 302 Nm³. 3 / h, gas volume / oxygen volume is 0.79, and the top lance baking position is 3980mm. The ladle is lifted to the processing position using the jacking system. Temperature and oxygen levels are measured and determined; the temperature is 1621℃, and the inlet oxygen level is 383ppm. Processing begins; oxygen blowing starts after 2.5 minutes of vacuuming. The target final deoxygenation level is 150ppm. The oxygen blowing rate Q is calculated according to formula (Ⅰ) Q=(C 炉后 ×1.33-O 进站 -(-0.24×H 烘烤 2 +15.1×H 烘烤 )+O 目标 ) / (ρ O / m×1000×η)=(330×1.33-383-(-0.24×5 2 +15.1×5)+150) / (1.43 / 259×1000×0.7)=40Nm 3 The oxygen blowing flow rate is 3015 Nm.3 / h, gun position 5010mm, oxygen blowing 40Nm 3 After 14 minutes of decarburization, the vacuum level reached 0.5 mbar. The oxygen level in the molten steel was measured, and the oxygen level at the end of decarburization was 157 ppm, which deviated from the target value by 7 ppm.

Claims

1. A method for precisely controlling the oxygen content at the endpoint of RH decarburization in IF steel, characterized in that: It includes converter smelting and RH refining steps; the RH refining step: before RH vacuuming, the oxygen content of the molten steel entering the RH station is measured, and the oxygen blowing amount is calculated using the following formula (Ⅰ). During the RH refining process, oxygen is blown according to the calculated oxygen blowing amount; Q=(C 炉后 ×1.33-O 进站 -(-0.24×H 烘烤 2 +15.1×H 烘烤 )+O 目标 ) / (ρO / m×η) (Ⅰ) In the formula: Q: Oxygen blowing volume (Nm) in the RH refining process. 3 ; C 炉后 Carbon content of molten steel after converter furnace, in ppm; O 进站 RH oxygen content of molten steel entering the station, in ppm; H 烘烤 RH vacuum oven baking time, min; O 进站 RH oxygen content of molten steel entering the station, in ppm; O 目标 : RH target decarbonization endpoint oxygen content, ppm; ρ O Oxygen density, g / L; m: RH steel inflow volume, kg; η: Oxygen absorption rate of molten steel in the RH refining process.

2. The method for precisely controlling the oxygen content at the endpoint of RH decarburization in IF steel according to claim 1, characterized in that: The converter smelting step has an endpoint carbon content range of 0.025–0.055 wt% and an endpoint oxygen content requirement of 300–600 ppm.

3. The method for precisely controlling the oxygen content at the endpoint of RH decarburization in IF steel according to claim 2, characterized in that: In the converter smelting step, the amount of modifier added is 1.9 to 2.1 kg / t.

4. The method for precisely controlling the oxygen content at the endpoint of RH decarburization in IF steel according to claim 1, characterized in that: In the RH refining step, the RH vacuum chamber baking time is ≤25 minutes, and the coke oven gas flow rate is 290~310Nm³. 3 / h.

5. The method for precisely controlling the oxygen content at the endpoint of RH decarburization in IF steel according to claim 4, characterized in that: During the RH vacuum oven baking process, the gas volume / oxygen volume ratio is 0.78 to 0.82, and the top gun baking position is between 3950 and 4050 mm.

6. A method for precisely controlling the oxygen content at the endpoint of RH decarburization in IF steel according to any one of claims 1-5, characterized in that: In the RH refining step, oxygen blowing is initiated 2-3 minutes after vacuuming.

7. The method for precisely controlling the oxygen content at the endpoint of RH decarburization in IF steel according to claim 6, characterized in that: During the RH refining process, the oxygen blowing flow rate is 2950–3050 Nm³. 3 / h, gun position 4950~5050mm.

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