CN118638981B - A method for controlling aluminum content in slag washed aluminum-killed steel - Google Patents

Abstract

The invention belongs to the field of ferrous metallurgy, and particularly relates to a method for controlling aluminum content in slag washing directly-feeding aluminum killed steel, which comprises the following steps: s1: and (3) controlling materials: checking scrap steel entering the furnace; s2: controlling the carbon temperature of the converter: controlling tapping temperatures of low carbon steel and medium carbon steel in the converter process to be 1650-1680 ℃; s3: controlling tapping and discharging slag; s4: and (3) tapping deoxidizing alloying: adding alloy, and adding lime, slag washing materials and aluminum blocks in batches to ensure that the inlet oxygen content of an argon station is between 15 and 50 PPM; s5: argon station slag washing is adjusted: the temperature is regulated to 1610+/-5 ℃, and aluminum wires are fed after middle blowing; adding aluminum-calcium balls, quickly adding aluminum powder after middle blowing slag foaming, adjusting the slag after middle blowing to be soft blowing, secondarily adjusting the acid-soluble aluminum content by using aluminum wires, and keeping a yellowish white slag sample for more than 2 minutes and adding calcium wires to ensure that the finished product Ca/Als:0.08-0.12; s6: and (5) continuous casting protection pouring. The method can accurately control the aluminum content, and has no flocculation flow stop casting accident.

Description

A method for controlling aluminum content in slag washed aluminum-killed steel

Technical Field

The invention belongs to the field of iron and steel metallurgy, and in particular relates to a method for controlling the aluminum content in slag-washed aluminum-killed steel.

Background Art

Aluminum is a strong deoxidizer, which can effectively reduce the oxygen content in steel and improve the cleanliness of molten steel. At the same time, aluminum is an important alloying element. A certain amount of aluminum in steel can refine the grains, improve the strength and toughness of steel, promote the nitriding layer, and improve the oxidation resistance. Under the premise of ensuring product quality, in order to reduce costs, the aluminum-containing steel is treated with argon station slag washing and desulfurization calcium treatment instead of refining process. However, during the implementation of the slag washing process, due to the strong deoxidation of aluminum, it is easy to combine with oxygen in molten steel to form alumina inclusions, and the yield is unstable. The actual control range of acid-soluble aluminum is 0.015%-0.060%, with a large fluctuation range. Acid-soluble aluminum can meet product requirements when it reaches 0.015%. Too high acid-soluble aluminum not only causes cost waste, but also to ensure the castability of molten steel and the calcium-aluminum ratio between 0.08-0.12, the amount of calcium wire added when the acid-soluble aluminum is high is significantly more than that when the acid-soluble aluminum is low, resulting in a smaller liquid window after calcium treatment, which is easy to produce floccules in continuous casting, which is not conducive to stable control of continuous casting.

Since aluminum is easily oxidized during the smelting process of molten steel, it is relatively difficult to stabilize the acid-soluble aluminum content in the steel within the optimal range of 0.015%-0.028%. Therefore, the precise control of the aluminum content in the production process of aluminum-killed steel is a major difficulty. The aluminum content in the steel is often too high or too low, and repeated aluminum adjustments can easily cause downgrades or surface quality problems. Chinese patent CN2023115223181 discloses a method for controlling the narrow component of acid-soluble aluminum in high-grade silicon steel, which accurately controls the acid-soluble aluminum content at 0.0285%-0.0315% during the refining process, thereby improving the performance and quality stability of silicon steel. Due to differences in production process technology, its control method is not suitable for the control of aluminum content in aluminum-killed steel directly from slag washing.

Summary of the invention

The purpose of the present invention is to provide a method for controlling the aluminum content in slag-washed aluminum-killed steel, so as to solve the problems in the slag-washing process such as the strong deoxidation of aluminum, unstable yield, large fluctuation range of acid-soluble aluminum, resulting in waste of resources, and a small liquid window after secondary calcium treatment of the acid-soluble aluminum blast furnace, which is easy to produce floccules during continuous casting and is not conducive to stable control of continuous casting.

In order to achieve the above object, the present invention adopts the following technical scheme:

A method for controlling the aluminum content in slag-washed aluminum-killed steel, the specific steps are as follows:

S1: Control materials: strictly check the scrap steel entering the furnace, and it is strictly forbidden to add refractory materials and large pieces of scrap steel into the furnace;

S2: Control the carbon temperature of the converter: Determine the temperature and composition in the furnace during the smelting process, intelligently batch the ingredients according to the composition and temperature of the molten iron, control the carbon of the low carbon steel at 0.04-0.07% and the carbon of the medium carbon steel at 0.07-0.12% in the converter smelting process, and control the tapping temperature at 1650-1680℃;

S3: Control slag during steel tapping: On the one hand, slag blocking is performed through slag blocking plugs, and the ground is marked according to the slag blocking position; on the other hand, the outside of the slag blocking cone is checked to ensure that there are no cracks, and then the slag blocking cone is added at 2/3 of the steel tapping. Under the action of double slag blocking, slag during steel tapping is eliminated;

S4: Deoxidation and alloying of steel: (1) Before steel is tapped, rotate the alloy chute to align it with the steel flow, add 30 kg of coke powder along with the steel flow for pre-deoxidation, and add it before 1/4 of the steel is tapped; (2) Start adding alloy from 1/4 of the steel is tapped, and add it before 1/3 of the steel is tapped; (3) Start adding lime, slag washing material and aluminum block in batches from 1/4 of the steel is tapped, and add it before 3/4 of the steel is tapped. Lime and slag washing material are used for top slag modification. The amount of lime and aluminum block added is adjusted according to the end carbon to ensure that the oxygen content entering the argon station is between 15-50PPM;

S5: Adjust argon station slag washing: Enter the argon station, measure the temperature and oxygen content of the molten steel, adjust the temperature to 1610±5℃, after medium blowing for 1 minute, according to the standard of 1.0~1.5ppm deoxidation per meter of φ11mm aluminum wire, feed aluminum wire into the ladle for deoxidation; add 70Kg/furnace of aluminum calcium balls, medium blowing for 1 minute to cause slag foaming, and then quickly add aluminum powder, adjust the argon medium blowing for 2 minutes, so that the aluminum powder can quickly remove oxygen from the slag during the top slag foaming period, adjust to soft blowing after slag melting, take a sample from the argon station, and use aluminum wire to adjust the acid-soluble aluminum content for the second time according to the test results. During this period, dip the slag sample, keep the yellow-white slag sample for more than 2 minutes, and then add calcium wire for treatment to ensure that the finished product Ca/Als: 0.08-0.12, the soft blowing time after the calcium wire is hit is ≥5min, leave the station and dip the slag sample, and leave the station to load steel;

S6: Continuous casting protective pouring: The ladle pouring adopts long nozzle argon seal protective pouring. When pouring the first furnace, the argon gas in the tundish is used to replace the air in the tundish in advance to reduce the continuous casting aluminum loss and the impact of unstable operation of pouring on the secondary oxidation of molten steel, ensuring the stable control of acid-soluble aluminum.

Preferably, the alloy in (2) in step S4 is any one of silicon-manganese alloy and high-carbon ferromanganese.

Preferably, in step S4 (3), the amount of lime added to the low carbon steel is 400-500 kg, the amount of slag washing material added is 400-500 kg, and the amount of aluminum block added is 100-150 kg; the amount of lime added to the medium carbon steel is 400 kg, the amount of slag washing material added is 400-500 kg, and the amount of aluminum block added is 50-80 kg.

Preferably, when measuring the temperature of the molten steel in step S5, when the temperature is greater than 1620°C, the temperature is adjusted according to the charging standard of reducing the temperature by 1°C for every 10kg of small material.

Preferably, in step S5, the amount of aluminum powder added to low carbon steel is 50-60 kg, and the amount of aluminum powder added to medium carbon steel is 40-45 kg.

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

(1) This method feeds aluminum wire into the ladle for deoxidation, quickly adds aluminum powder after slag foaming, and adjusts the acid-soluble aluminum content twice according to the test results after medium blowing, slag melting and soft blowing. After the argon station performs the slag washing process, the acid-soluble aluminum content of the aluminum wire can be accurately controlled to avoid the situation where the acid-soluble aluminum entering the station is too high due to one-time deoxidation and cannot be adjusted later. Compared with the original production steps, the alloy cost is reduced;

(2) This method uses aluminum blocks to remove oxygen from steel, aluminum powder to remove oxygen from slag, and aluminum-calcium balls to increase the foaming effect of the top slag, ensuring that the yellow-white slag is maintained for ≥2 minutes. The castability of the molten steel is ensured by observing the color change of the top slag sample after slag washing. The ladle casting adopts long-nozzle argon seal protection casting, and the argon gas in the tundish is used in advance to replace the air in the tundish when the first furnace is poured, thereby reducing continuous casting aluminum loss, ensuring continuous casting without floccules, ensuring stable control of continuous casting, improving the hot charging rate of the ingot, and reducing carbon emissions. While ensuring quality, no refining is required, which not only reduces costs but also shortens the production cycle.

DETAILED DESCRIPTION

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

The present invention optimizes the slag calcium washing treatment operation and accurately controls the acid-soluble aluminum content through the aluminum wire. The specific implementation process is as follows.

Example 1

S1: Control materials: strictly check the scrap steel entering the furnace, and it is strictly forbidden to add refractory materials and large pieces of scrap steel into the furnace;

S2: Control the carbon temperature of the converter: Determine the temperature and composition in the furnace during the smelting process, intelligently batch the ingredients according to the composition and temperature of the molten iron, control the carbon content of the steel at the converter smelting process to be 0.09%, the temperature to be 1650℃, and the oxygen content of the final molten steel to be 480PPm;

S3: Control slag during steel tapping: On the one hand, slag blocking is performed through slag blocking plugs, and the ground is marked according to the slag blocking position; on the other hand, the outside of the slag blocking cone is checked to ensure that there are no cracks, and then the slag blocking cone is added at 2/3 of the steel tapping. Under the action of double slag blocking, slag during steel tapping is eliminated;

S4: Deoxidation and alloying of steel: (1) Before steel is tapped, rotate the alloy chute to align it with the steel flow, add 30 kg of coke powder along with the steel flow for pre-deoxidation, and add it before 1/4 of the steel is tapped; (2) Add silicon-manganese alloy from 1/4 of the steel is tapped, and add it before 1/3 of the steel is tapped; (3) From 1/4 of the steel is tapped, add lime, slag washing material and aluminum blocks in batches, with the amount of lime added being 400 kg, the amount of slag washing material added being 450 kg, and the amount of aluminum blocks added being 60 kg, and add them before 3/4 of the steel is tapped. Lime and slag washing material are used for slag modification, and the amount of lime and aluminum blocks added is adjusted according to the end carbon to ensure that the oxygen content entering the argon station is 18.23 PPm;

S5: Adjust argon station slag washing: Enter the argon station, measure the temperature and oxygen content of the molten steel, the temperature is 1630℃, according to the charging standard of 10kg small material reducing 1℃, adjust the temperature to 1610℃, after 1 minute of medium blowing, according to the standard of 1.0～1.5ppm deoxidation per meter of φ11mm aluminum wire, feed aluminum wire into the ladle for deoxidation; add 70Kg/furnace of aluminum calcium balls with foaming function, and blow 1 minute. After the slag foams for 15 minutes, 40kg of aluminum powder is quickly added, and the argon gas is adjusted to blow for 2 minutes to quickly remove oxygen from the slag during the foaming of the top slag. After the slag is dissolved, it is adjusted to soft blowing. A sample is taken from the argon station, and the aluminum content is 0.0205%. According to the test results, 30 meters of φ11mm aluminum wire is added after the slag is washed to adjust the acid-soluble aluminum content for the second time. During this period, the slag sample is dipped. The yellow-white slag sample is kept for 3 minutes and then treated with calcium wire to ensure that the finished product Ca/Als: 0.08-0.12. After the calcium wire is applied, soft blowing is performed for 5 minutes, and the slag sample is dipped out of the station. The acid-soluble aluminum content out of the station is 0.023%;

S6: Continuous casting protective pouring: The ladle pouring adopts long nozzle argon seal protective pouring. When pouring the first furnace, the argon in the tundish is used to replace the air in the tundish in advance to reduce the impact of unstable operation during pouring on the secondary oxidation of molten steel and ensure that the Als content in the finished product is 0.020%.

Example 2

S1: Control materials: strictly check the scrap steel entering the furnace, and it is strictly forbidden to add refractory materials and large pieces of scrap steel into the furnace;

S2: Control the carbon temperature of the converter: Determine the temperature and composition in the furnace during the smelting process, intelligently batch the ingredients according to the composition and temperature of the molten iron, control the carbon content of the steel at the converter smelting process to 0.07%, the temperature to 1650℃, and the oxygen content of the final molten steel to 600PPm;

S3: Control slag during steel tapping: On the one hand, slag blocking is performed through slag blocking plugs, and the ground is marked according to the slag blocking position; on the other hand, the outside of the slag blocking cone is checked to ensure that there are no cracks, and then the slag blocking cone is added at 2/3 of the steel tapping. Under the action of double slag blocking, slag during steel tapping is eliminated;

S4: Deoxidation and alloying of steel: (1) Before steel is tapped, rotate the alloy chute to align it with the steel flow, add 30 kg of coke powder along with the steel flow for pre-deoxidation, and add it before 1/4 of the steel is tapped; (2) Add silicon-manganese alloy from 1/4 of the steel is tapped, and add it before 1/3 of the steel is tapped; (3) Add lime, slag washing material and aluminum blocks in batches from 1/4 of the steel is tapped, with the amount of lime added being 400 kg, the amount of slag washing material added being 450 kg, and the amount of aluminum blocks added being 80 kg, and add them before 3/4 of the steel is tapped. Lime and slag washing material are used for slag modification, and the amount of lime and aluminum blocks added is adjusted according to the end carbon to ensure that the oxygen content entering the argon station is 20 PPm;

S5: Adjust argon station slag washing: Enter the argon station, measure the temperature and oxygen content of the molten steel, the temperature is 1612℃, no adjustment is required, after 1 minute of medium blowing, according to the standard of 1.0-1.5ppm deoxidation per meter of φ11mm aluminum wire, feed aluminum wire into the ladle for deoxidation; add 70kg/furnace of aluminum calcium balls with foaming function, blow for 1 minute to produce slag foaming, and then quickly add 50kg of aluminum powder, adjust the argon medium blowing for 2 minutes, so that the aluminum powder can quickly remove oxygen from the slag during the foaming of the top slag, adjust to soft blowing after slag melting, take a sample from the argon station, the aluminum content is 0.0255%, according to the test results, no aluminum wire is needed, the yellow-white slag sample is kept for 3 minutes and then calcium wire is added for treatment to ensure that the finished product Ca/Als: 0.08-0.12, soft blow for 6 minutes after the calcium wire is hit, and take the slag sample out of the station, the acid-soluble aluminum content out of the station is 0.023%;

S6: Continuous casting protective pouring: The ladle pouring adopts long nozzle argon seal protective pouring. When pouring the first furnace, the argon in the tundish is used to replace the air in the tundish in advance to reduce the impact of unstable operation during pouring on the secondary oxidation of molten steel and ensure that the Als content in the finished product is 0.020%.

After the molten steel was treated with argon station slag calcium washing, there was no flocculation and casting suspension accident in continuous casting, the longitudinal cracking of the ingot and the production rate of hot-rolled coil secondary products dropped from 0.2% to 0.06%, the finished acid-soluble aluminum was stably controlled, the qualified rate of low-carbon steel acid-soluble aluminum (0.018-0.028%) increased from 24% to 85.25%, and the qualified rate of medium-carbon steel acid-soluble aluminum (0.015-0.025%) increased from 21% to 91.58%, saving 3.2 yuan/ton of steel in costs.

Comparative Example 1

S1: Control materials: strictly check the scrap steel entering the furnace, and it is strictly forbidden to add refractory materials and large pieces of scrap steel into the furnace;

S2: Control the carbon temperature of the converter: the carbon content of the steel produced in the converter smelting process is 0.07%, the temperature is 1650℃, and the oxygen content of the final molten steel is 600PPm;

S3: Control slag during steel tapping: On the one hand, slag blocking is performed through slag blocking plugs, and the ground is marked according to the slag blocking position; on the other hand, the outside of the slag blocking cone is checked to ensure that there are no cracks, and then the slag blocking cone is added at 2/3 of the steel tapping. Under the action of double slag blocking, slag during steel tapping is eliminated;

S4: 100kg of aluminum blocks are added during the steel-making process. The oxygen content of the incoming molten steel is 5PPm. 60kg of aluminum-calcium balls are added per furnace. After blowing for 1 minute to produce slag and foaming, aluminum powder is quickly added. The argon gas is adjusted to blow for 2 minutes. The aluminum content of the first sample is 0.040%. During this period, the slag sample is dipped. The yellow-white slag sample is kept for more than 2 minutes and then treated with calcium wire to ensure that the finished product Ca/Als is 0.08-0.12. The acid-soluble aluminum content at the outlet is 0.035%.

The acid-soluble aluminum content in Comparative Example 1 is 0.023%, which is higher than that in Example 1 and Example 2, resulting in cost waste and no room for adjustment in the later stage, which is not conducive to the precise control of acid-soluble aluminum.

Claims (5)

1. A method for controlling the aluminum content in slag washed aluminum killed steel, characterized in that the specific steps are as follows: S1: Control materials: strictly check the scrap steel entering the furnace, and it is strictly forbidden to add refractory materials and large pieces of scrap steel into the furnace; S2: Control the carbon temperature of the converter: Determine the temperature and composition in the furnace during the smelting process, intelligently batch the ingredients according to the composition and temperature of the molten iron, control the carbon of the low carbon steel at 0.04-0.07% and the carbon of the medium carbon steel at 0.07-0.12% in the converter smelting process, and control the tapping temperature at 1650-1680℃; S3: Control slag during steel tapping: On the one hand, slag blocking is performed through slag blocking plugs, and the ground is marked according to the slag blocking position; on the other hand, the outside of the slag blocking cone is checked to ensure that there are no cracks, and then the slag blocking cone is added at 2/3 of the steel tapping. Under the action of double slag blocking, slag during steel tapping is eliminated; S4: Deoxidation and alloying of steel: (1) Before steel is tapped, rotate the alloy chute to align it with the steel flow, add 30 kg of coke powder along with the steel flow for pre-deoxidation, and add it before 1/4 of the steel is tapped; (2) Start adding alloy from 1/4 of the steel is tapped, and add it before 1/3 of the steel is tapped; (3) Start adding lime, slag washing material and aluminum blocks in batches from 1/4 of the steel is tapped, and add it before 3/4 of the steel is tapped. The amount of lime and aluminum blocks added is adjusted according to the end point carbon to ensure that the oxygen content entering the argon station is between 15-50ppm; S5: Adjust argon station slag washing: Enter the argon station, measure the temperature and oxygen content of the molten steel, adjust the temperature to 1610±5℃, after medium blowing for 1min, according to the standard of 1.0~1.5ppm deoxidation per meter of φ11mm aluminum wire, feed aluminum wire into the ladle for deoxidation; add 70kg/furnace of aluminum calcium balls, blow for 1min to cause slag foaming, and then quickly add aluminum powder, adjust the argon medium blowing for 2min, so that the aluminum powder can quickly remove oxygen from the slag during the top slag foaming, adjust to soft blowing after slag melting, take a sample from the argon station, and use aluminum wire to adjust the acid-soluble aluminum content for the second time according to the test results. During this period, dip the slag sample, keep the yellow-white slag sample for more than 2min, and then add calcium wire for treatment to ensure that the finished product Ca/Als: 0.08-0.12, the soft blowing time after the calcium wire is hit is ≥5min, leave the station and dip the slag sample, and leave the station to load steel; S6: Continuous casting protective pouring: The ladle pouring adopts long nozzle argon seal protective pouring. When pouring the first furnace, the argon gas in the tundish is used to replace the air in the tundish in advance to reduce the continuous casting aluminum loss and the impact of unstable operation of pouring on the secondary oxidation of molten steel, ensuring the stable control of acid-soluble aluminum. 2. The method for controlling the aluminum content in slag washed aluminum killed steel according to claim 1, characterized in that the alloy in step S4 (2) is any one of silicon manganese alloy and high carbon ferromanganese. 3. The method for controlling the aluminum content in slag-washed aluminum-killed steel according to claim 2, characterized in that in step S4 (3), the amount of lime added to low carbon steel is 400-500kg, the amount of slag-washing material added is 400-500kg, and the amount of aluminum block added is 100-150kg; the amount of lime added to medium carbon steel is 400kg, the amount of slag-washing material added is 400-500kg, and the amount of aluminum block added is 50-80kg. 4. The method for controlling the aluminum content in slag washed aluminum killed steel according to claim 3 is characterized in that when measuring the molten steel temperature in step S5, when the temperature is greater than 1620°C, the temperature is adjusted according to the charging standard of reducing 1°C for every 10kg of small material. 5. The method for controlling the aluminum content in slag-washed aluminum-killed steel according to claim 4, characterized in that the amount of aluminum powder added to low carbon steel in step S5 is 50-60 kg, and the amount of aluminum powder added to medium carbon steel is 40-45 kg.