Method for producing square billet low-carbon low-silicon aluminum killed steel through top-blown converter

Abstract

The invention relates to the technical field of smelting, in particular to a method for producing square billet low-carbon low-silicon-aluminum killed steel through a top-blown converter, and aims to solve the production bottleneck that when square billet low-carbon low-silicon-aluminum killed steel is produced through an existing top-blown converter, slag adjusting and preparing difficulty is large when a high-alkalinity high-alumina slag system is refined through an LF furnace, and square billet low-carbon low-silicon-aluminum killed steel is difficult to pour. The method comprises the steps of molten iron pretreatment, converter smelting, converter tapping, argon blowing station treatment, refining treatment, square billet pouring and the like, the aluminum wire feeding amount of an argon blowing station and a refining inlet station is guided according to the oxygen value of the argon blowing station, yellow and white slag can be formed after primary temperature rise of refining, stable pouring of the square billet low-carbon low-silicon aluminum killed steel is effectively achieved, and the quality of the square billet low-carbon low-silicon aluminum killed steel is improved. And through controllable adding of converter refining alloy, lower limit control over silicon-manganese components of the low-carbon low-silicon-aluminum killed steel is achieved, the cold heading performance is improved, and the quality of a casting blank is improved through adjustment of the crystallizer and secondary cooling water amount and monitoring adjustment of the color of the casting blank.

Description

Technical Field

[0001] The invention relates to the technical field of smelting, and in particular to a method for producing square billet low-carbon, low-silicon aluminum killed steel in a top-blown converter. Background Art

[0002] When producing low-carbon, low-silicon aluminum-killed steel in the process of "converter → LF → billet", a high-basicity, high-alumina refining slag system is used to control the composition of the final refined slag within the low melting point area of ​​R=CaO / SiO2>6 and Al2O3=28% in the phase diagram, which can effectively solve the problem of water inlet for pouring aluminum-killed steel billet. However, with the increase of iron oxide content in the final slag of the converter, the viscosity of the slag decreases and the amount of slag discharged from the converter also increases accordingly. Under the conditions of high iron oxide content in the final slag of the converter and large amount of slag discharged per ton of steel in the converter, the difficulty of preparing the high basicity and high alumina refining slag system of the LF refining furnace is increased. That is, the oxidizing property of the final slag of the converter determines the difficulty of preparing the high basicity and high alumina refining slag system of the LF refining furnace, and ultimately determines whether the low carbon and low silicon aluminum killed steel can be cast smoothly. In order to reduce the difficulty of slag preparation and slag matching operation of the LF high basicity and high alumina slag system and thereby improve the castability of molten steel of square billet aluminum killed steel, most of the square billet low carbon and low silicon aluminum killed steel with difficult slag preparation in the industry is produced by top and bottom double blowing converters. When the "50T top-blown converter → LF → billet" is used to produce low-carbon, low-silicon, aluminum-killed steel ML08Al, the iron oxide content of the converter final slag is >22%, and the slag amount per ton of steel is still more than 10kg when the slag cone blocks the slag. Usually, when the free oxygen content of most molten steel arriving at the argon blowing station is ≥80PPm, it is difficult to prepare the high-basicity and high-alumina refined slag system, which seriously restricts the production of billet low-carbon, low-silicon, aluminum-killed steel ML08Al. In order to solve this smelting bottleneck, it is necessary to further optimize the production method of billet low-carbon, low-silicon, aluminum-killed steel. Summary of the invention

[0003] The present invention provides a method for producing low-carbon, low-silicon, aluminum-killed steel for square billets in a top-blown converter, so as to solve the problems existing in the above background that when producing low-carbon, low-silicon, aluminum-killed steel for square billets in a top-blown converter, slag adjustment and slag matching are difficult when refining high-basicity, high-alumina slag system in an LF furnace, and low-carbon, low-silicon, aluminum-killed steel for square billets is difficult to cast.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: A method for producing square billet low-carbon, low-silicon aluminum killed steel using a top-blown converter comprises the following steps: Step 1, molten iron pretreatment: After the blast furnace molten iron is desulfurized and mixed in the iron mixing furnace, the sulfur content of the molten iron entering the converter is S≤0.01%.

[0005] Step 2, converter smelting: single slag method is adopted for smelting, the top-blown converter blowing gun position height is 800mm-850mm, the working oxygen pressure is 0.85MPa-0.95MPa, the basicity is controlled to be 3-4, when the end carbon content reaches 0.03%-0.04%, the temperature is 1630℃-1650℃, the gun is raised for temperature measurement and sampling, and then supplementary blowing is carried out according to the carbon test results, the supplementary blowing time is 20s-40s, so that the end composition of the converter is C≤0.04%, P≤0.01%, S≤0.02%, and the tapping temperature is 1610℃-1640℃.

[0006] Step 3, tapping the converter: The converter is only equipped with aluminum-manganese-iron alloy. First, add the ladle synthetic slag for slag washing, and then add 5.6kg / t-6.4kg / t of aluminum-manganese-iron for deoxidation and alloying, so that the contents of various components in the molten steel are C: 0.03%-0.06%, Si≤0.01%, Mn: 0.20%-0.32%, P≤0.01%, and S≤0.01%.

[0007] Step 4, treatment at argon blowing station: After the molten steel arrives at the argon blowing station, add slag modifier into the ladle at a ratio of 1kg / t to adjust the slag. The components and contents of the slag modifier are MAl: 38%-44%, Al2O3: 22%-28%, CaO: 28%-34%. When the temperature reaches 1580℃-1600℃, start oxygen determination and feed aluminum wire, then blow argon for 1-2 minutes, and add low-carbon and low-silicon covering agent to exit the station.

[0008] Step 5, refining treatment: no silicon-containing alloy or alloy wire is added during refining. When the molten steel is in the refining position, the argon blowing flow rate is adjusted to 10m3 / h-20m3 / h, and 1.0kg / t-1.4kg / t of slag modifier and 10kg-20kg of aluminum particles are added to the slag surface of the ladle for slag surface deoxidation, and then the wire feeding speed is adjusted to 3.5m / s-4m / s, and the aluminum wire is fed into the refining station according to the oxygen value set by the argon blowing station.

[0009] Step 6, billet casting: the water flow rate of the crystallizer is 130-135t / h, the secondary cooling water volume is controlled at 1.2 m / kg-1.6m / kg, and the billet color is monitored and adjusted at the drawing and straightening machine, and argon blowing in the tundish is continued. The continuous casting temperature is controlled at 1540℃-1560℃, and the tundish drawing speed is controlled at 2.0m / min-2.4m / min. Finally, the billet is cast to form low-carbon, low-silicon aluminum killed steel.

[0010] The present invention has the following beneficial effects: The present invention guides the feeding amount of aluminum wire into the argon blowing station and the feeding amount of aluminum wire into the LF refining station according to the fixed oxygen value of 1580°C-1600°C when the temperature of molten steel entering the argon blowing station reaches, so that yellow-white slag can be formed after one refining temperature increase, solves the production bottleneck of producing square billet low-carbon, low-silicon aluminum killed steel with a 50T top-blown converter under the conditions of "slag amount per ton of steel>10kg, iron oxide content of final slag>22%", and realizes the stable casting of square billet low-carbon, low-silicon aluminum killed steel.

[0011] The present invention achieves the national standard lower limit control target of silicon and manganese elements in square billet low-carbon and low-silicon aluminum killed steel ML08Al by only adding aluminum-manganese-iron alloy in the converter and not adding silicon-containing alloy and alloy wire in refining, and effectively improves the cold heading performance of ML08Al.

[0012] The present invention increases the water volume of the crystallizer to 130 t / h-135 t / h, adjusts the secondary cooling water volume of the 150*150 square billet to 1.6 m / kg, implements color monitoring of the billet at the straightening machine position, controls the low-magnification defects of the ML08Al billet within level 1.0, and effectively improves the billet quality. DETAILED DESCRIPTION

[0013] The present invention will be further described below in conjunction with specific embodiments.

[0014] In the process of separating the different components of nickel anode mud, the following methods are used: Example 1 A method for producing square billet low-carbon, low-silicon aluminum killed steel using a top-blown converter comprises the following steps: Step 1: Pretreatment of molten iron: The molten iron in the blast furnace is desulfurized and then fed into the converter with a sulfur content of 0.01%.

[0015] Step 2, converter smelting: single slag method is adopted for smelting, the blowing gun height of 50T top-blown converter is 800mm, the working oxygen pressure is 0.85MPa, the basicity is 3, the end carbon content is 0.03%, the temperature is 1630℃, the re-blowing time is 20s, the converter steel composition is C: 0.03%, Mn: 0.10%, P: 0.005%, S: 0.012%, and the steel tapping temperature is 1610℃.

[0016] Step 3, tapping from the converter: During the tapping process, 200 kg / t of ladle synthetic slag is added for slag washing, and then 5.6 kg / t of aluminum-manganese-iron is added for deoxidation and alloying. The composition of the molten steel is as follows: C: 0.03%, Si: 0.006%, Mn: 0.2%, P: 0.006%, S: 0.011%.

[0017] Step 4, treatment at argon blowing station: When the molten steel arrives at the argon blowing station, 50kg of slag modifier is manually added into the ladle to adjust the slag. The temperature at the argon blowing station is 1580℃, the oxygen is set at 111PPm, and 101m of aluminum wire is fed. The aluminum wire feeding amount is shown in Table 1. Then, after blowing argon for 1 minute, low-carbon and low-silicon covering agent is added before leaving the station.

[0018] Step 5, refining treatment: ① When the molten steel reaches the refining position, the argon blowing flow rate is adjusted to 10 m³ / h, and 50 kg of slag modifier and 10 kg of aluminum particles are added to the slag surface of the ladle for deoxidation; ② The feeding wire speed is adjusted to 3.5 m / s, and 100 meters of aluminum wire is fed into the refining station according to the oxygen value of the argon blowing station; ③ First, 14600A power supply is used to increase the temperature for 1.8 minutes, and then 25400A power supply is used, and the argon blowing flow rate is adjusted to 28 m³ / h, lime was added in two batches during the process, 300kg lime was added in the first batch, and 150kg lime was added in the second batch to make slag, the primary temperature of the LF furnace was 1615℃, and the slag was yellow-white; ④ After the second heating, C: 0.065%, Si: 0.041%, Mn: 0.34%, P: 0.009%, S: 0.008%, Alt: 0.0376%; ⑤ The feeding speed was adjusted to 3.2m / s to feed 150m of metal calcium aluminum wire, and the calcium content of refined outlet was 0.003%; ⑥ The argon blowing flow rate was adjusted to 3.5 m³ / h, and after soft blowing for 9 minutes, the LF outlet temperature was 1613℃, and low-carbon and low-silicon covering agent was added to exit the station. The feeding amount of aluminum wire was shown in Table 2.

[0019] Step 6, billet casting: the water flow rate of the crystallizer is 130t / h, the secondary cooling water volume is 1.2m / kg. The tundish argon blowing is continued, the continuous casting temperature is controlled at 1540℃, the tundish drawing speed is controlled at 2.0m / min, and finally the billet is cast to form a low-carbon, low-silicon aluminum killed steel of qualified quality.

[0020] Example 2 A method for producing square billet low-carbon, low-silicon aluminum killed steel using a top-blown converter comprises the following steps: Step 1: Pretreatment of molten iron: The molten iron in the blast furnace is desulfurized and then fed into the converter with a sulfur content of 0.01%.

[0021] Step 2, converter smelting: single slag method is adopted for smelting, the blowing gun height of 50T top-blown converter is 820mm, the working oxygen pressure is 0.90MPa, the basicity is 3.5, the end carbon content is 0.035%, the temperature is 1640℃, the re-blowing time is 30s, the converter steel composition is C: 0.035%, Mn: 0.20%, P: 0.006%, S: 0.015%, and the steel tapping temperature is 1630℃.

[0022] Step 3, tapping from the converter: During the tapping process, 200 kg / t of ladle synthetic slag is added for slag washing, and then 6 kg / t of aluminum-manganese-iron is added for deoxidation and alloying. The composition of the molten steel is as follows: C: 0.04%, Si: 0.007%, Mn: 0.26%, P: 0.007%, S: 0.012%.

[0023] Step 4, treatment at argon blowing station: When the molten steel arrives at the argon blowing station, 50kg of slag modifier is manually added into the ladle to adjust the slag. The temperature at the argon blowing station is 1590℃, the oxygen is set at 111PPm, and 101m of aluminum wire is fed. The aluminum wire feeding amount is shown in Table 1. Then, after blowing argon for 1.5 minutes, low-carbon and low-silicon covering agent is added before leaving the station.

[0024] Step 5, refining treatment: ① When the molten steel reaches the refining position, the argon blowing flow rate is adjusted to 15 m³ / h, and 50 kg of slag modifier and 15 kg of aluminum particles are added to the slag surface of the ladle for deoxidation; ② The feeding wire speed is adjusted to 3.5 m / s, and 140 meters of aluminum wire is fed into the refining station according to the oxygen value of the argon blowing station; ③ First, 14900A power supply is used to increase the temperature for 1.8 minutes, and then 25700A power supply is used, and the argon blowing flow rate is adjusted to 28 m³ / h, lime was added in two batches during the process, 300kg lime was added in the first batch, and 200kg lime was added in the second batch to make slag, the primary temperature of the LF furnace was 1608℃, and the slag was yellow-white; ④ After the second heating, C: 0.049%, Si: 0.048%, Mn: 0.27%, P: 0.007%, S: 0.006%, Alt: 0.0499%; ⑤ The feeding speed was adjusted to 3.2m / s to feed 180m of metal calcium aluminum wire, and the calcium content of refined outlet was 0.0045%; ⑥ The argon blowing flow rate was adjusted to 3.5 m³ / h, and after soft blowing for 8min, the LF outlet temperature was 1609℃, and low-carbon and low-silicon covering agent was added to exit the station. The feeding amount of aluminum wire was shown in Table 2.

[0025] Step 6, billet casting: the water flow rate of the crystallizer is 133t / h, the secondary cooling water volume is 1.4m / kg. The tundish argon blowing is continued, the continuous casting temperature is controlled at 1550℃, the tundish drawing speed is controlled at 2.2m / min, and finally the billet is cast to form a low-carbon, low-silicon aluminum-killed steel of qualified quality.

[0026] Example 3 A method for producing square billet low-carbon, low-silicon aluminum killed steel using a top-blown converter comprises the following steps: Step 1: Pretreatment of molten iron: The molten iron in the blast furnace is desulfurized and then fed into the converter with a sulfur content of 0.01%.

[0027] Step 2, converter smelting: single slag method is adopted for smelting, the blowing gun height of 50T top-blown converter is 850mm, the working oxygen pressure is 0.95MPa, the basicity is 4, the end carbon content is 0.04%, the temperature is 1650℃, the re-blowing time is 40s, the converter steel composition is C: 0.04%, Mn: 0.30%, P: 0.007%, S: 0.017%, and the steel tapping temperature is 1640℃.

[0028] Step 3, tapping from the converter: During the tapping process, 200 kg / t of ladle synthetic slag is added for slag washing, and then 6.4 kg / t of aluminum-manganese-iron is added for deoxidation and alloying. The composition of the molten steel is as follows: C: 0.06%, Si: 0.005%, Mn: 0.32%, P: 0.004%, S: 0.015%.

[0029] Step 4, treatment at argon blowing station: When the molten steel arrives at the argon blowing station, 50kg of slag modifier is manually added into the ladle to adjust the slag. The temperature at the argon blowing station is 1600℃, the oxygen is set at 111PPm, and 101m of aluminum wire is fed. The aluminum wire feeding amount is shown in Table 1. Then, after blowing argon for 2 minutes, low-carbon and low-silicon covering agent is added before leaving the station.

[0030] Step 5, refining treatment: ① When the molten steel reaches the refining position, adjust the argon blowing flow rate to 20 m³ / h, and add 50kg of slag modifier and 20kg of aluminum particles to the slag surface of the ladle for deoxidation; ② Adjust the feeding wire speed to 4m / s, and guide the refining of 100 meters of aluminum feeding wire according to the oxygen value of the argon blowing station; ③ First use 15000A power supply to increase the temperature for 1.8min, and then use 26000A power supply, and adjust the argon blowing flow rate to 28 m³ / h, lime was added in two batches during the process, 300kg lime was added in the first batch, and 250kg lime was added in the second batch to make slag, the primary temperature of the LF furnace was 1600℃, and the slag was yellow-white; ④ After the second heating, C: 0.035%, Si: 0.0421%, Mn: 0.37%, P: 0.007%, S: 0.009%, Alt: 0.0276%; ⑤ The feeding speed was adjusted to 3.2m / s to feed 200m of metal calcium aluminum wire, and the calcium content of refined outlet was 0.0027%; ⑥ The argon blowing flow rate was adjusted to 3.5 m³ / h, and after soft blowing for 7min, the LF outlet temperature was 1600℃, and low-carbon and low-silicon covering agent was added to exit the station. The feeding amount of aluminum wire was shown in Table 2.

[0031] Step 6, billet casting: the water flow rate of the crystallizer is 135t / h, the secondary cooling water volume is 1.6m / kg. The tundish argon blowing is continued, the continuous casting temperature is controlled at 1560℃, the tundish drawing speed is controlled at 2.4m / min, and finally the billet is cast to form a low-carbon, low-silicon aluminum-killed steel of qualified quality.

Claims

1. A method for producing low-carbon, low-silicon aluminum killed steel in a square billet by a top-blown converter, characterized in that: The following steps are involved: Step 1, hot metal pretreatment: After the hot metal in the blast furnace is desulfurized and mixed in the iron mixing furnace, the sulfur content of the hot metal entering the converter is S≤0.01%; Step 2, converter smelting: single slag method is adopted for smelting, the top-blown converter blowing gun position height is 800mm-850mm, the working oxygen pressure is 0.85MPa-0.95MPa, the basicity is controlled to be 3-4, when the end point carbon content reaches 0.03%-0.04%, the temperature is 1630℃-1650℃, the gun is raised for temperature measurement and sampling, and then supplementary blowing is carried out according to the carbon test result, the supplementary blowing time is 20s-40s, so that the end point composition of the converter is C≤0.04%, P≤0.01%, S≤0.02%, and the tapping temperature is 1610℃-1640℃; Step 3, tapping the converter: the converter is only equipped with aluminum-manganese-iron alloy, firstly, the ladle synthetic slag is added for slag washing, and then 5.6kg / t-6.4kg / t of aluminum-manganese-iron is added for deoxidation and alloying, so that the content of each component of the molten steel is C: 0.03%-0.06%, Si≤0.01%, Mn: 0.20%-0.32%, P≤0.01%, S≤0.01%; Step 4, Argon blowing station treatment: After the molten steel arrives at the argon blowing station, add slag modifier into the ladle at a ratio of 1kg / t to adjust the slag. The components and contents of the slag modifier are MAl: 38%-44%, Al2O3: 22%-28%, CaO: 28%-34%. When the temperature reaches 1580℃-1600℃, start oxygen determination and feed aluminum wire, then blow argon for 1-2 minutes, add low-carbon and low-silicon covering agent and exit the station; Step 5, refining treatment: no silicon-containing alloy or alloy wire is added during refining. When the molten steel is in the refining position, the argon blowing flow rate is adjusted to 10m3 / h-20m3 / h, and 1.0kg / t-1.4kg / t of slag modifier and 10kg-20kg of aluminum particles are added to the slag surface of the ladle for deoxidation of the slag surface, and then the wire feeding speed is adjusted to 3.5m / s-4m / s, and the aluminum wire is fed into the refining station according to the oxygen value set at the argon blowing station; Step 6, billet casting: the water flow rate of the crystallizer is 130 t / h-135 t / h, the secondary cooling water volume is controlled at 1.2 m / kg-1.6 m / kg, and the billet color is monitored and adjusted at the straightening machine position, and argon blowing in the tundish is continued. The continuous casting temperature is controlled at 1540℃-1560℃, and the tundish drawing speed is controlled at 2.0m / min-2.4m / min. Finally, the billet is cast to form low-carbon, low-silicon aluminum killed steel.

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