Production method of low-carbon low-silicon aluminum killed steel

Abstract

The invention belongs to the technical field of steelmaking continuous casting refining treatment, and particularly relates to a production method of low-carbon low-silicon aluminum killed steel, which comprises the following steps: 1) steelmaking: controlling the endpoint carbon content of a converter to be below 0.03%, carrying out zero-position bottom argon blowing on the converter for 1-2 minutes after blowing, and tapping; converter boiling tapping is carried out, and no deoxidizing agent is added in the tapping process; 2) refining: boiling molten steel reaches an LF furnace, and oxygen is determined after argon blowing; firstly adding slag charge, and then adding a carburant; heating the electrode and stirring; adding passivated aluminum powder to the surface of the molten steel under the condition of clean argon blowing; and adding a deoxidizing agent for final deoxidation and desulfurization. The method has the advantages that a steel production technology for producing the low-carbon low-silicon-aluminum killed steel through LF direct loading is adopted, molten steel is not subjected to a vacuum decarburization procedure, decarburization and component control are directly completed through the LF furnace, and the equipment investment and the process operation cost are greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of steelmaking continuous casting refining technology, and particularly relates to a method for producing low-carbon, low-silicon, aluminum-killed steel. Background Technology

[0002] In conventional steelmaking methods, especially for producing low-carbon, low-silicon killed steel with a maximum carbon content of 0.03%, there are two main processes: converter-vacuum-casting machine process and converter-vacuum-LF furnace-casting machine process. The decarburization process occurs under vacuum conditions, where excess carbon in the molten steel reacts with oxygen to form a carbon-oxygen reaction, causing the oxygen in the molten steel to be converted into CO and eliminated. In this vacuum state, carbon acts as a deoxidizer, and its deoxidizing capacity increases with the increase of vacuum level.

[0003] The converter-vacuum-casting machine process often results in nozzle turbulence, leading to generally lower steel quality. To meet continuous casting production requirements, fewer casting passes are needed, resulting in higher steel quality and production costs. For thin slab casting machines, to mitigate the impact of nozzle turbulence on production, the converter-vacuum-LF furnace-casting machine process is the only viable option. In this process, deoxidation of the LF furnace steel primarily relies on elements like silicon and aluminum, which have a higher affinity for oxygen than iron. While this process improves the steel's pourability, the additional LF process increases production costs. Existing technology, patent publication number CN110106316A, discloses a method for producing low-carbon aluminum-killed steel using a duplex process, reducing costs through carbon deoxidation. This process produces higher quality steel, but due to the use of a vacuum-LF duplex process, production costs remain high. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, the purpose of this invention is to provide a method for producing low-carbon, low-silicon, aluminum-killed steel. The molten steel does not undergo decarburization through a vacuum process. Instead, it uses a converter-LF-casting machine process to control the carbon content of the finished steel to below 0.03%, thereby significantly reducing production costs.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for producing low-carbon, low-silicon, aluminum-killed steel includes the following steps:

[0007] 1) Steelmaking process:

[0008] S1. The carbon content at the end of the converter is controlled below 0.030%. After the blowing is completed, the converter is blown with argon at the zero position for 1 to 2 minutes before tapping the steel.

[0009] S2, converter boiling tapping, no deoxidizer is added during the tapping process;

[0010] S3. The clear clearance of the molten steel ladle should be controlled between 400 and 600 mm.

[0011] 2) Refining process:

[0012] S1. Boiling molten steel arrives at the LF furnace, and after argon blowing, oxygen is determined.

[0013] S2. After the molten steel in boiling state enters the LF treatment station, it is stirred by high-flow-rate argon blowing, with an argon flow rate of 7L / min / ton of steel or more. The first batch of slag is added first. After the slag does not accumulate and is spread evenly on the surface of the molten steel, the argon blowing flow rate is adjusted to the net argon blowing flow rate, and then carbon deoxidizer is added. The first batch of slag and its addition amount are 5-8 kg / ton of quicklime and 1-2 kg / ton of slag-reducing agent; the amount of carbon deoxidizer added is 0.1-0.5 kg / ton of steel.

[0014] S3. After adding the carbon deoxidizer, immediately lower the electrode temperature and raise it for 9-10 minutes, then stir for 2-3 minutes after raising the temperature.

[0015] S4. Under the condition of purging argon, add 0.3-0.6 kg / ton of passivating aluminum powder to the surface of the molten steel; after 0.5-2 minutes, increase the argon flow rate to above 7 L / min / ton of steel, and add deoxidizer for final deoxidation and desulfurization.

[0016] In step S2 of the LF process, the carbon deoxidizer is added in the following manner:

[0017] For molten steel with an oxygen value ≥900ppm, add 0.03~0.05% carbon deoxidizer by weight of molten steel;

[0018] If the oxygen value of molten steel is greater than 900ppm and is greater than or equal to 800ppm, add 0.3kg / ton of carbon deoxidizer.

[0019] If the oxygen value of molten steel is greater than 800ppm and the oxygen value is greater than or equal to 700ppm, add 0.2kg / ton of carbon deoxidizer.

[0020] If the oxygen value of molten steel is ≥600ppm (700ppm > 600ppm), add 0.1kg / ton of carbon deoxidizer.

[0021] In step S3 of the refining process, the temperature of the molten steel after stirring is required to be 20-30°C higher than the temperature of the machine. If the temperature of the molten steel does not meet this requirement, the electrode continues to heat up for 1-10 minutes, and then stirs for 2-3 minutes until the temperature of the molten steel reaches the required level.

[0022] In step S3 of the refining process, two batches of slag are added during the heating process. The weight ratio of quicklime to slag-forming agent in the two batches of slag is 4:1 to 5:1. The amount of the two batches of slag added is controlled at 1 to 6 kg / ton of steel.

[0023] In step S4, after the top slag is modified, a process sample is taken, and the alloy composition is adjusted according to the process sample. After feeding the wire, argon is blown cleanly for more than 5 minutes before casting.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. This invention adopts the steel production technology of LF direct production of low carbon and low silicon aluminum killed steel. The molten steel does not go through the vacuum decarburization process, but directly uses the LF furnace to complete decarburization and composition control, which greatly reduces equipment investment and process operation costs.

[0026] 2. This invention utilizes the vacuum environment created by argon bubbles generated during the bottom blowing of argon in the LF heating process to promote the carbon-oxygen reaction between residual carbon and oxygen in the molten steel, generating CO and emitting it, thus successfully controlling the carbon content of the finished molten steel to below 0.03%, meeting the requirements of the steel grade.

[0027] 3. Compared with the converter-vacuum-casting machine process, the cleanliness of molten steel is significantly improved by the present invention.

[0028] 4. In the LF process, the present invention adds slag and carbon deoxidizer to the boiling molten steel, lowers the electrode temperature and raises the temperature. By taking advantage of the good conditions of the foam slag formed during the electrode heating process, heat loss is reduced, heating efficiency is improved and energy costs are reduced. Detailed Implementation

[0029] The present invention will now be described in detail, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0030] Example 1:

[0031] A method for producing low-carbon, low-silicon, aluminum-killed steel, wherein the carbon content of the finished product is capped at 0.030%, includes the following steps:

[0032] 1. Steelmaking process:

[0033] 1) The carbon content at the end of the converter is controlled below 0.030%. After the blowing is completed, the converter is blown with argon at the zero position for one minute before tapping the steel.

[0034] 2) Converter boiling tapping, no deoxidizer is added during the tapping process.

[0035] 3) The clear space of the molten steel ladle should be controlled between 400 and 600 mm.

[0036] 2. Refining process:

[0037] 1) When the boiling molten steel reaches the LF furnace, it is purged with argon and then oxygen is determined; the oxygen value is 650 ppm.

[0038] 2) After the molten steel in boiling state enters the LF treatment station, it is stirred by high-flow argon blowing with an argon flow rate greater than 7 L / min / ton of steel. The first batch of slag is added first. After the slag does not accumulate and is spread evenly on the surface of the molten steel, the argon blowing flow rate is adjusted to the net argon blowing flow rate, and then carbon deoxidizer is added. The first batch of slag and its addition amount are 6 kg of quicklime / ton of steel and 1.5 kg of slag-reducing agent / ton of steel; the amount of carbon deoxidizer added is 0.1 kg / ton of steel.

[0039] 3) Heat the electrodes for 10 minutes, using quicklime, carbon deoxidizer, and the high temperature of the electric arc to create a calcium carbide slag submerged arc. If additional slag is needed, add two batches of slag during the heating process. The weight ratio of quicklime to slag-forming agent in the two batches of slag should be controlled at 4.5:1; the amount of the two batches of slag should be controlled at 3 kg / ton of steel; after heating, stir for 3 minutes and measure the temperature to ensure that the molten steel temperature is 20-30°C higher than the machine temperature.

[0040] 4) After the molten steel temperature reaches the required temperature, add 0.5 kg / ton of passivating aluminum powder to the surface of the molten steel under clean argon blowing. After 40 seconds, the carbide slag on the surface of the molten steel is removed. Increase the argon flow rate, controlling it to above 7 L / min / ton of steel. Add deoxidizer for final deoxidation and desulfurization. After the top slag is modified, take a process sample. Adjust the alloy composition according to the process sample. After wire feeding, cleanly blow argon for 5 minutes before casting.

[0041] Example 2:

[0042] A method for producing low-carbon, low-silicon, aluminum-killed steel, wherein the carbon content of the finished product is capped at 0.03%, includes the following steps:

[0043] 1. Steelmaking process:

[0044] 1) The carbon content at the end of the converter is controlled below 0.030%. After the blowing is completed, the converter is blown with argon at the zero position for one minute before tapping the steel.

[0045] 2) Converter boiling tapping, no deoxidizer is added during the tapping process.

[0046] 3) The clear space of the molten steel ladle should be controlled between 400 and 600 mm.

[0047] 2. Refining process:

[0048] 1) When the boiling molten steel reaches the LF furnace, it is purged with argon and then oxygen is determined; the oxygen value is 730 ppm.

[0049] 2) After the molten steel in boiling state enters the LF treatment station, it is stirred by high-flow argon blowing. The argon flow rate is at least 7L / min / ton of steel. The first batch of slag is added first. After the slag does not accumulate and is spread evenly on the surface of the molten steel, the argon blowing flow rate is adjusted to the net argon blowing flow rate. Then, carbon deoxidizer is added. The first batch of slag and its addition amount are 7kg of quicklime / ton of steel and 1.8kg of slag-reducing agent / ton of steel; the amount of carbon deoxidizer added is 0.2kg / ton of steel.

[0050] 3) Heat the electrodes for 10 minutes, using quicklime, carbon deoxidizer, and the high temperature of the electric arc to create a calcium carbide slag submerged arc. If additional slag is needed, add two batches of slag during the heating process. The weight ratio of quicklime to slag-forming agent in the two batches of slag should be controlled at 4.2:1; the amount of the two batches of slag should be controlled at 3.5 kg / ton of steel; stir for 3 minutes after heating and measure the temperature. The molten steel temperature should be 25°C higher than the machine temperature. If the molten steel temperature does not reach this requirement, continue heating the electrodes to the required temperature.

[0051] 4) After the molten steel temperature reaches the required temperature, add 0.45 kg / ton of passivating aluminum powder to the surface of the molten steel under clean argon blowing. After the carbide slag on the surface of the molten steel is removed, increase the argon flow rate to above 7 L / min / ton of steel, and add deoxidizer for final deoxidation and desulfurization. After the top slag is modified, take a process sample, adjust the alloy composition according to the process sample, feed the wire, cleanly blow argon for 5 minutes, and then cast the steel.

[0052] Example 3:

[0053] A method for producing low-carbon, low-silicon, aluminum-killed steel, wherein the carbon content of the finished product is capped at 0.03%, includes the following steps:

[0054] 1. Steelmaking process:

[0055] 1) The carbon content at the end of the converter is controlled below 0.030%. After the blowing is completed, the converter is blown with argon at the zero position for one minute before tapping the steel.

[0056] 2) Converter boiling tapping, no deoxidizer is added during the tapping process.

[0057] 3) The clear space of the molten steel ladle should be controlled between 400 and 600 mm.

[0058] 2. Refining process:

[0059] 1) When the boiling molten steel reaches the LF furnace, it is purged with argon and then oxygen is determined; the oxygen value is 820 ppm.

[0060] 2) After the molten steel in boiling state enters the LF treatment station, it is stirred by high-flow-rate argon blowing, with an argon flow rate greater than 7 L / min / ton of steel. The first batch of slag is added first. After the slag does not accumulate and is spread evenly on the surface of the molten steel, the argon blowing flow rate is adjusted to the net argon blowing flow rate, and then carbon deoxidizer is added. The first batch of slag and its addition amount are 8 kg of quicklime / ton of steel and 2 kg of slag-reducing agent / ton of steel; the amount of carbon deoxidizer added is 0.15 kg / ton of steel.

[0061] 3) Heat the electrodes for 10 minutes, using quicklime, carbon deoxidizer, and the high temperature of the electric arc to create a calcium carbide slag submerged arc. Stir for 2 minutes after heating and measure the temperature. The molten steel temperature should be 24-30°C higher than the machine temperature. If the molten steel temperature does not reach this requirement, continue heating the electrodes until the molten steel temperature reaches the required temperature.

[0062] 4) After the molten steel temperature reaches the required temperature, add 0.4-0.5 kg / ton of passivating aluminum powder to the surface of the molten steel under clean argon blowing. After the carbide slag on the surface of the molten steel is removed, increase the argon flow rate to above 7 L / min / ton of steel, and add deoxidizer for final deoxidation and desulfurization. After the top slag is modified, take a process sample, adjust the alloy composition according to the process sample, feed the wire, cleanly blow argon for 5 minutes, and then cast the steel.

[0063] This invention employs an LF furnace to directly produce low-carbon, low-silicon, aluminum-killed steel. The molten steel does not undergo a vacuum decarburization process; instead, decarburization and composition control are directly achieved using the LF furnace, significantly reducing equipment investment and process operating costs.

Claims

1. A method for producing a low-carbon low-silicon killed aluminum steel, characterized by, The method comprises the following steps: 1) Steelmaking process: S1, the carbon content at the end point of the converter is controlled to be below 0.030%, and after the blowing is finished, the converter is argon-blown at zero position for 1-2 minutes before tapping; S2, the converter is tapped in a boiling state without adding a deoxidizer; S3, the clearance of the ladle is controlled to be 400-600 mm; 2) Refining process: S1, the boiling molten steel reaches the LF furnace, and oxygen is determined after argon blowing; S2, after the molten steel in a boiling state enters the LF treatment position, large-flow argon blowing stirring is performed, the argon flow is above 7 L / min / ton of steel, the first batch of slag is added, the slag is not stacked and is laid flat on the molten steel surface, then the argon flow is adjusted to the net argon flow, and then the carbon deoxidizer is added; the first batch of slag and the amount of addition are 5-8 kg / ton of steel of lime and 1-2 kg / ton of steel of slagging agent; the amount of addition of the carbon deoxidizer is 0.1-0.5 kg / ton of steel; S3, the electrode is immediately lowered to increase the temperature for 9-10 minutes after the carbon deoxidizer is added, and stirring is performed for 2-3 minutes after the temperature is increased; S4, the passivated aluminum powder is added to the molten steel surface under the condition of net argon blowing at 0.3-0.6 kg / ton of steel; 0.5-2 minutes later, the argon flow is adjusted to be above 7 L / min / ton of steel, the deoxidizer and the desulfurizer are added for final deoxidization and desulfurization.

2. The method of producing a low-carbon low-silicon killed aluminum steel according to claim 1, characterized by, In step S3 of the refining process, the temperature of the molten steel after stirring is required to be higher than the temperature of the upper machine by 20-30 DEG C; if the temperature of the molten steel cannot reach the requirement, the electrode is continuously heated for 1-10 minutes, and stirring is performed for 2-3 minutes again until the temperature of the molten steel reaches the requirement.

3. The method of producing a low-carbon low-silicon killed aluminum steel according to claim 1, characterized by, In step S3 of the refining process, the second batch of slag is added during the temperature increasing process, and the weight ratio of lime to slagging agent in the second batch of slag is 4:1-5:1; the amount of addition of the second batch of slag is controlled to be 1-6 kg / ton of steel.

4. The method of producing a low-carbon low-silicon killed aluminum steel according to claim 1, characterized by, In step S4, after the top slag is modified, the process sample is taken, the alloy composition is finally adjusted according to the process sample, the wire is fed, and the molten steel is cast after net argon blowing for more than 5 minutes.

5. The method of producing low carbon low silicon killed steel according to claim 1, wherein, In step S2 of the LF process, the carbon deoxidizer is added in the following manner: when the oxygen value of the molten steel is equal to or greater than 900 ppm, 0.03-0.05% of the carbon deoxidizer by weight of the molten steel is added; when 900 ppm>the oxygen value of the molten steel is equal to or greater than 800 ppm, 0.3 kg / ton of steel of the carbon deoxidizer is added; when 800 ppm>the oxygen value of the molten steel is equal to or greater than 700 ppm, 0.2 kg / ton of steel of the carbon deoxidizer is added; when 700 ppm>the oxygen value of the molten steel is equal to or greater than 600 ppm, 0.1 kg / ton of steel of the carbon deoxidizer is added.