Smelting method of steel for RH light-treatment cold-rolled base stock

Abstract

The invention relates to a smelting method of steel for an RH light treatment cold-rolled base material. The smelting method comprises the following working procedures of converter steelmaking, RH refining furnace, LF refining furnace and continuous casting. Smelting chemical components and percentage contents are as follows: 0.0070-0.025% of C and less than or equal to 0.03% of Si; 0.15 to 0.25 percent of Mn; the steel comprises, by weight, 0.015% or less of P, 0.010% or less of S, 0.030%-0.055% of Als, 20 ppm or less of [O], 40 ppm or less of [N] and the balance Fe and inevitable impurities. According to the method, the smelting cost is reduced, the LF refining furnace fulfills the desulfurization task while meeting the metallurgical function, the desulfurization rate is improved, the consumption of granular magnesium and lime in a desulfurization station is reduced, the process target S content requirement is met, and the product quality is improved.

Description

Technical Field

[0001] The patented technology of the present invention relates to a steel smelting method, specifically to a smelting method for steel for RH light-treated cold-rolled base material. Background Art

[0002] At present, for Chenggang Iron and Steel, which uses vanadium-titanium magnetite as its main raw material, the phosphorus and sulfur content in the molten iron it produces is relatively high. Based on the characteristics of vanadium-titanium molten iron, the sulfur content in the vanadium-containing molten iron fluctuates greatly and is unstable, which makes it difficult to desulfurize the vanadium-containing molten iron. The single-spray granular magnesium molten iron pretreatment device is affected by the instability of the desulfurization product MgS after molten iron desulfurization and the thin molten iron desulfurization slag that is difficult to remove. The device adopts the early slag removal or multiple slag removal operations, which leads to increased iron loss, increased smelting costs, and serious resulfurization of the molten iron in the subsequent production process. Summary of the invention

[0003] Aiming at the characteristic of high residual elements in molten steel produced by existing blast furnace vanadium-titanium magnetite smelting, the present invention provides a smelting method for RH light-treated cold-rolled base steel, which improves the desulfurization rate, reduces the consumption of granular magnesium and lime in the desulfurization station, meets the process target S content requirement, and improves product quality.

[0004] The technical solution adopted to solve the above problems is:

[0005] A smelting method for RH light-treatment cold-rolled base steel, comprising the following steps: converter steelmaking - RH refining furnace - LF refining furnace - continuous casting;

[0006] The smelting chemical composition and percentage content are: C: 0.0070-0.025%, Si≤0.03%; Mn: 0.15-0.25%; P≤0.015%, S≤0.010%, ALs: 0.030-0.055%, [O]≤20ppm, [N]≤40ppm, and the balance is Fe and unavoidable impurities.

[0007] Preferably, in the converter steelmaking process, the mass percentage of S entering the furnace is ≤0.030%, and the smelting mode is selected according to the raw material conditions, steel type, and the principle of comprehensive consumption. In the early stage of smelting, in order to accelerate slag and early dephosphorization, the mass content of FeO in the slag should be maintained at 18-21%, the gun position adopts a high gun height of 1.7-1.8 meters, and the oxygen supply intensity adopts a medium oxygen supply of 32000-36000Nm 3 / h, bottom blowing adopts double annular seam air-permeable brick bottom blowing with large flow rate of 150-300Nm 3 / h, ensuring the bottom blowing flow rate strengthens the stirring intensity of the entire molten pool, effectively improves the uniformity of the composition and temperature in the molten pool, and further approaches the balance of the carbon-oxygen reaction, thus avoiding overoxidation of the molten steel, and having a positive effect on the smelting cycle, carbon-oxygen accumulation at the end of the converter, and dephosphorization effect of the converter.

[0008] Preferably, in the converter steelmaking process: in the middle carbon oxidation period of smelting, a low lance position of 1.4 to 1.5 meters and a maximum oxygen supply intensity of 36000 to 38000 Nm are used. 3 / h; during the blowing process, the slagging situation and blowing state are determined according to the flame state and the sound in the furnace, the gun position and the addition of cold materials are adjusted in time to smoothly control the blowing, and carbon is pulled once according to the trend of carbon-oxygen reaction to avoid strong oxidation of the terminal slag caused by post-terminal blowing. After smelting, 300-500kg / furnace of lime is added to the steel after steelmaking. The best control of the final mass percentage of converter steelmaking is C: 0.04%, P≤0.010%, S≤0.025%; the final temperature of the first converter furnace is 1670-1690℃, the continuous pulling temperature is 1640-1660℃, and the free oxygen in the steel is controlled at 200-400ppm.

[0009] Preferably, the RH refining process is naturally decarburized; avoid forced decarburization by the RH top gun, which makes the slag highly oxidizable, making it difficult to deoxidize in the LF furnace, and increasing the smelting cycle and smelting cost;

[0010] RH refining furnace process: steam pressure ≥1.3Mpa, steam temperature ≥190℃, good ventilation of the immersion pipe circulation pipe, ladle station opening to RH treatment position, ladle clearance 300~500mm, ladle top lift to immersion pipe inserted into molten steel 650~800mm, start vacuum pump for degassing operation, treatment at a relatively low vacuum degree of 6~26KPa. Main functions: float inclusions, adjust component temperature, reduce 〔O〕 in steel, natural decarburization, add aluminum and blow oxygen to increase temperature.

[0011] Preferably, RH refining furnace process: vacuum tank immersion tube circulation argon 70~90Nm 3 / h, the circulation of molten steel begins to be controlled. According to the chemical sample of the previous process, low-carbon ferromanganese is added to compensate for the mass percentage of Mn: 0.15-0.25%. According to the gradual carbon-oxygen reaction in the vacuum tank, the circulation gas is adjusted to 100-120Nm 3 / h, increase the decarburization speed, and circulate decarburization for 18 to 25 minutes.

[0012] Preferably, the RH refining furnace process: after decarburization, aluminum deoxidation and alloying are carried out, pure degassing is ≥5min, and after smelting, 60-100kg / furnace carbon-free covering agent is added, and the chemical composition and mass percentage of the molten steel are: C≤0.010%, Si≤0.01%, Mn: 0.15-0.20%, P≤0.011%, S≤0.025%, Als: 0.030-0.045%, [N]≤25ppm.

[0013] Preferably, the LF refining furnace process: entering the station for smelting treatment, setting the argon flow rate to 800-1500NL / min, adding 160-220kg / furnace of deoxidizer and 800-1200kg / furnace of lime after slag material, and the lime is added in batches; after the addition is completed, fully stir and melt, control the slag material addition time to 2-3min, and stir with argon for 2-3min to avoid incomplete melting of the material pile.

[0014] Preferably, the LF refining furnace process: perform heating treatment, reasonably select the sixth long arc heating gear, add 150-300 kg / furnace refining slag and make foam slag, ensure the submerged arc effect to improve the thermal efficiency of the electrode, ensure sufficient basicity of the slag, control the appropriate bottom blowing stirring intensity of 100-300 NL / min, uniform temperature to reduce the erosion of the ladle lining caused by local overheating of the slag, and the resulting carbon increase effectively controls the carbon content of the molten steel to meet the process target requirements.

[0015] Preferably, the LF refining furnace process: the electrode is heated once for ≤10min, and after the end, the argon is adjusted to 800-1500NL / min to perform deoxidation and desulfurization operations; the color and state of the sticky slag are observed and the deoxidizer and lime are added in time during the strong stirring of argon to form white slag through deep deoxidation, and the argon is adjusted to 200-300NL / min to stir to uniform the temperature and composition; temperature measurement and sampling, and the chemical components added according to the chemical sample meet the process requirements, and the argon is adjusted to 30-80NL / min, and the calcium line is fed at 150-300m / furnace without exposing the liquid surface, and the weak argon is blown for ≥12min to perform inclusion denaturation treatment and float the inclusions to the slag to purify the molten steel.

[0016] Preferably, in the LF refining furnace process, at the end of refining, [O]≤20ppm, [N]≤40ppm.

[0017] The beneficial effects of the present invention are:

[0018] The production process of converter steelmaking - RH refining furnace - LF refining furnace - continuous casting is adopted. The natural decarburization at a vacuum degree of 6 to 26 KPa through the RH light treatment process not only meets the process requirements for the C content of this steel grade, but also avoids the carbon content exceeding the upper limit due to electrode erosion and carbon increase in the LF furnace refining process, and the local overheating of the slag and the erosion of the lining and carbon increase, which will cause the steel to be scrapped or re-classified. This treatment also reduces the consumption of energy (steam, cooling water) and the smelting cost. In addition, while the LF refining furnace meets the metallurgical function, it also undertakes the desulfurization task, improves the desulfurization rate, reduces the consumption of granular magnesium and lime in the desulfurization station, meets the process target S content requirement, and improves the product quality.

[0019] The present invention implements a multi-stage combined comprehensive treatment method for vanadium-containing molten iron, realizes effective control of elements such as S, Ti, V, etc. in the smelting production process, completes the development and production of steel for cold-rolled base products with a yield strength Rel (Mpa) ≤ 300, a tensile strength Rm (Mpa) 270 ≤ Rm ≤ 390, and an elongation after fracture ≥ 40, thereby increasing the added value of the product. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described in detail below in conjunction with embodiments.

[0021] Examples 1-6

[0022] The present invention relates to a smelting method for RH light-treatment cold-rolled base steel, which is characterized by comprising the following steps: converter steelmaking - RH refining furnace - LF refining furnace - continuous casting; specifically as follows:

[0023] (1) Converter steelmaking process: The mass percentage of sulfur entering the furnace is ≤0.030%. The smelting mode is selected according to the raw material conditions, steel type, and the principle of comprehensive consumption. In the early stage of smelting, in order to accelerate slag formation and early dephosphorization, the mass content of FeO in the slag should be maintained at 18-21%. The gun position adopts a high gun height of 1.7-1.8 meters, and the oxygen supply intensity adopts a medium oxygen supply of 32000-36000Nm 3 / h, bottom blowing adopts double annular seam air-permeable brick bottom blowing with large flow rate of 150-300Nm 3 / h, ensuring the bottom blowing flow rate strengthens the stirring intensity of the entire molten pool, effectively improves the uniformity of the composition and temperature in the molten pool, and further approaches the balance of the carbon-oxygen reaction, thus avoiding overoxidation of the molten steel, and having a positive effect on the smelting cycle, carbon-oxygen accumulation at the end of the converter, and dephosphorization effect of the converter.

[0024] In the middle carbon oxidation period of smelting, a low lance position of 1.4 to 1.5 meters and a high oxygen supply intensity of 36,000 to 38,000 Nm are used. 3 / h; during the blowing process, the slagging situation and blowing state are determined according to the flame state and the sound in the furnace, the gun position and the cold material are adjusted in time to smoothly control the blowing, and the carbon is pulled once according to the trend of the carbon-oxygen reaction to avoid the strong oxidation of the terminal slag caused by the post-blowing at the end point. After the smelting is completed, 300-500kg / furnace of lime is added to the steel. The best control of the final mass percentage of converter steelmaking is C: 0.03-0.04%, P≤0.010%, S≤0.025%; the final temperature of the first converter furnace is 1670-1690℃, the continuous pulling temperature is 1640-1660℃, and the free oxygen in the steel is controlled at 200-400ppm.

[0025] Table 1 Converter process parameters of Examples 1-6

[0026]

[0027] (2) RH refining process: natural decarburization; avoid forced decarburization by RH top gun, which will make the slag highly oxidizable, making it difficult to deoxidize in the LF furnace, and increasing the smelting cycle and smelting cost;

[0028] RH refining furnace process: steam pressure ≥1.3Mpa, steam temperature ≥190℃, good ventilation of the immersion pipe circulation pipe, ladle station opening to the RH treatment position, ladle clearance 300~500mm, ladle top lift to the immersion pipe inserted into the molten steel 650~800mm, start the vacuum pump for degassing, and the treatment is carried out at a relatively low vacuum degree of 6~26KPa. Main functions: float inclusions, adjust component temperature, reduce [O] in steel, natural decarburization, add aluminum and blow oxygen to increase temperature. Vacuum tank immersion pipe circulation argon 70~90Nm 3 / h, the circulation of molten steel begins to be controlled. According to the chemical sample of the previous process, low-carbon ferromanganese is added to compensate for the mass percentage of Mn: 0.15-0.20%. According to the gradual carbon-oxygen reaction in the vacuum tank, the circulation gas is adjusted to 100-120Nm 3 / h, increase the decarburization speed, and circulate decarburization for 18 to 25 minutes. After decarburization, aluminum deoxidation and alloying are carried out, and pure degassing is ≥5 minutes. After smelting, 60 to 100 / kg / furnace of carbon-free covering agent is added. The chemical composition and mass percentage of the molten steel are: C≤0.010%, Si≤0.01%, Mn: 0.15 to 0.20%, P≤0.011%, S≤0.025%, Als: 0.030 to 0.045%, [N]≤25ppm.

[0029] Table 2 RH refining process parameters for Examples 1-6

[0030]

[0031] Table 3 Chemical composition and mass percentage of molten steel in Example 1-6RH

[0032] Example C Si Mn P S Als N / ppm 1 0.0045 0.01 0.15 0.010 0.025 0.030 25 2 0.0065 0.01 0.17 0.009 0.023 0.033 23 3 0.0081 0.01 0.18 0.008 0.022 0.036 23 4 0.0070 0.01 0.16 0.010 0.024 0.038 22 5 0.0089 0.01 0.19 0.008 0.023 0.040 25 6 0.0100 0.01 0.20 0.009 0.025 0.045 24

[0033] (3) LF refining furnace process: entering the station for smelting treatment, argon gas flow rate is set to 800-1500NL / min, deoxidizer 160-220kg / furnace and lime 800-1200kg / furnace is added after slag material is added, and lime is added in batches, each batch ≤800kg / furnace; after adding materials, stir and melt them fully, control the slag material addition time for 2-3min, stir with argon gas for 2-3min to avoid incomplete melting of the material pile, and heat treatment is carried out. Reasonably select the heating gear six-gear long arc, add 150-300kg / furnace of refined slag and make foam slag, ensure the submerged arc effect and improve the thermal efficiency of the electrode, ensure sufficient basicity of the slag, control the appropriate bottom blowing stirring intensity of 100-300NL / min, uniform temperature to reduce the erosion of the ladle lining caused by local overheating of the slag, and the resulting carbon increase effectively controls the carbon content of the molten steel to meet the process target requirements.

[0034] The electrode heating temperature rises for ≤10min at a time. After the end, adjust the argon to 800-1500NL / min for deoxidation and desulfurization operations. Observe the color and state of the sticky slag and add deoxidizer and lime in time. During the strong stirring of argon, deep deoxidation forms white slag. Adjust the argon to 200-300NL / min and stir to make the temperature and composition uniform. Measure the temperature and take samples. According to the chemical samples, add various chemical compositions that meet the process requirements. Adjust the argon to 30-80NL / min, feed the calcium line at 150-300m / furnace without exposing the liquid surface, and blow weak argon for ≥12min to denature the inclusions. Float the inclusions into the slag to purify the molten steel.

[0035] Table 4 LF refining process parameters of Examples 1-6

[0036]

[0037] Table 5 Chemical composition and mass percentage of molten steel in Examples 1-6 (%)

[0038] Example C Si Mn P S Als N / ppm 1 0.0070 0.02 0.15 0.010 0.010 0.030 40 2 0.017 0.02 0.17 0.009 0.006 0.039 33 3 0.020 0.03 0.18 0.008 0.003 0.036 38 4 0.015 0.02 0.22 0.010 0.005 0.038 36 5 0.018 0.02 0.25 0.008 0.002 0.045 37 6 0.025 0.03 0.20 0.009 0.004 0.055 35

[0039] In Table 5, the remainder is Fe and unavoidable impurities.

[0040] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments with equivalent changes without departing from the scope of the technical solution of the present invention.

Claims

1. A method for smelting steel for RH light treatment cold rolling base material, characterized in that: It includes the following processes: converter steelmaking - RH refining furnace - LF refining furnace - continuous casting; The smelting chemical composition and percentage content are: C: 0.0070~0.025%, Si≤0.03%; Mn: 0.15~0.25%; P≤0.015%, S≤0.010%, Als: 0.030~0.055%, [O]≤20 ppm, [N]≤40ppm, and the balance is Fe and unavoidable impurities.

2. The smelting method of a RH light-treatment cold-rolled base steel according to claim 1, characterized in that: Converter steelmaking process: the mass percentage of sulfur entering the furnace is ≤0.030%. In the early stage of smelting, the mass content of FeO in the slag is 18~21%. The gun position adopts a high gun height of 1.7~1.8 meters, and the oxygen supply intensity adopts a medium oxygen supply of 32000~36000 Nm 3 / h, bottom blowing adopts double annular seam air-permeable brick bottom blowing with large flow rate of 150-300Nm 3 / h.

3. The smelting method of a RH light-treatment cold-rolled base steel according to claim 1, characterized in that: Converter steelmaking process: In the middle carbon oxidation period of smelting, a low lance position of 1.4~1.5 meters and a maximum oxygen supply intensity of 36000~38000Nm are used. 3 / h; during the blowing process, the slagging situation and blowing state are determined according to the flame state and the sound in the furnace, the gun position and the addition of cold materials are adjusted in time to smoothly control the blowing, carbon is pulled once according to the trend of carbon-oxygen reaction, and 300-500 kg / furnace of lime is added when the steel is discharged after smelting. The optimal control of the final mass percentage of converter steelmaking is C: 0.04%, P≤0.010%, S≤0.025%; the final temperature of the first converter furnace is 1670-1690℃, the continuous pulling temperature is 1640-1660℃, and the free oxygen in the steel is controlled at 200-400ppm.

4. The smelting method of a RH light-treatment cold-rolled base steel according to claim 1, characterized in that: The RH refining process naturally decarbonizes; RH refining furnace process: steam pressure ≥1.3Mpa, steam temperature ≥190℃, ladle station opened to RH treatment position, ladle clearance 300~500 mm, ladle top raised to the immersion tube inserted into the molten steel 650~800mm, start the vacuum pump for degassing operation, and the treatment is carried out under a vacuum degree of 6~26 KPa.

5. The smelting method of a RH light-treatment cold-rolled base steel according to claim 1, characterized in that: RH refining furnace process: vacuum tank immersion tube circulation argon 70~90Nm 3 / h, the circulation of molten steel begins to be controlled. According to the chemical sample of the converter steelmaking process, low-carbon ferromanganese is added to compensate for the Mn mass percentage: 0.15~0.25%. According to the slow carbon-oxygen reaction in the vacuum tank, the circulation gas is adjusted to 100~120Nm 3 / h, cyclic decarburization for 18~25min.

6. The smelting method of a RH light-treatment cold-rolled base steel according to claim 5, characterized in that: RH refining furnace process: After decarburization, aluminum deoxidation and alloying are carried out, pure degassing ≥5 min, and 60~100 kg / furnace carbon-free covering agent is added after smelting. The chemical composition and mass percentage of the molten steel are: C≤0.010%, Si≤0.01%, Mn: 0.15~0.20%, P≤0.011%, S≤0.025%, Als: 0.030~0.045%, [N] ≤25ppm.

7. The smelting method of a RH light-treatment cold-rolled base steel according to claim 1, characterized in that: LF refining furnace process: entering the station for smelting treatment, set the argon flow rate to 800~1500NL / min, add 160~220 kg / furnace of deoxidizer and 800~1200 kg / furnace of lime after slag material, and add lime in batches; after adding, stir and melt thoroughly, control the slag material addition time to 2~3 min, and stir with argon for 2~3 min.

8. The smelting method of a RH light-treatment cold-rolled base steel according to claim 7, characterized in that: LF refining furnace process: carry out heating treatment, reasonably select the sixth long arc heating gear, add 150~300 kg / furnace refined slag and make foam slag, control the bottom blowing stirring intensity to 100~300NL / min.

9. The smelting method of a RH light-treatment cold-rolled base steel according to claim 8, characterized in that: LF refining furnace process: the electrode heating temperature rises once for ≤10min, after which the argon gas is adjusted to 800~1500 NL / min for deoxidation and desulfurization operations; Observe the color and state of the sticky slag, add deoxidizer and lime in time, deeply deoxidize to form white slag during the strong stirring process of argon, adjust the argon to 200~300 NL / min, stir to even out the temperature and composition; measure temperature and take samples, add various chemical compositions according to the chemical samples to meet the process requirements, adjust the argon to 30~80NL / min, feed the calcium line at 150~300m / furnace without exposing the liquid surface, weakly blow argon for ≥12min, perform inclusion modification treatment, float the inclusions into the slag to purify the molten steel.

10. The smelting method of RH light-treatment cold-rolled base steel according to claim 9, characterized in that: LF refining furnace process: after refining, [O]≤20ppm, [N]≤40ppm.

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