A method for improving the castability of RH-treated high-silicon steel

Abstract

This invention provides a method for improving the castability of high-silicon steel treated with RH, comprising the following steps: Before RH production, based on the sampling of test steel used to rinse the vacuum chamber, it is pre-determined whether the circulation capacity of the vacuum chamber meets the requirements for producing the high-silicon steel; for vacuum chambers that meet the requirements for producing high-silicon steel, RH production of high-silicon steel is carried out, and after decarburization, batches of silicon alloy deoxidation treatment are performed. After the first batch of silicon alloy is added, a sample is taken, and the deviation between the actual value of Si content in the sample molten steel and the theoretical value of the Si content added to the molten steel by the first batch of silicon alloy is compared to determine whether the circulation capacity of the vacuum chamber in actual production meets the requirements for producing this high-silicon steel; if it meets the requirements, production continues; if it does not meet the requirements, argon blowing treatment is performed. This invention, by pre-determining the circulation capacity of the RH vacuum chamber, specifically determines whether it is necessary to increase the RH circulation flow rate by bottom blowing argon, ensuring that RH deoxidation products are completely removed, thereby improving the cleanliness and castability of the molten steel.

Description

Technical Field

[0001] This invention relates to the field of steelmaking process technology, and in particular to a method for improving the castability of RH-treated high-silicon steel. Background Technology

[0002] One of the basic requirements for continuous casting of molten steel is good castability, so as to enable continuous casting of multiple heats. Poor castability of molten steel will cause casting interruptions, which will have a significant impact on production organization.

[0003] For castability, the main influencing factors are the cleanliness of the molten steel, foreign matter in the molten steel channel, and the temperature of the molten steel. Foreign matter in the molten steel channel is a low-probability event and rarely occurs. The temperature of the molten steel is also relatively easy to control, and casting can be completed under appropriate superheat. The cleanliness of the molten steel is more difficult to control, and poor castability due to cleanliness issues often occurs, sometimes even leading to casting interruption.

[0004] RH-treated high-silicon steel typically refers to steel grades with a Si content greater than 1%. During the RH treatment process, if the alloy addition exceeds 15 kg / t, the deoxidation products in the steel cannot be completely removed, resulting in poor cleanliness of the molten steel and a high risk of casting interruption. Summary of the Invention

[0005] To address the aforementioned technical problems, a method for improving the castability of RH-treated high-silicon steel is provided. The technical means employed in this invention are as follows:

[0006] A method for improving the castability of RH-treated high-silicon steel includes the following steps:

[0007] Before RH production, based on the sampling of test steel used to clean the vacuum chamber, it is preliminarily determined whether the circulation capacity of the vacuum chamber meets the requirements of the high silicon steel to be produced.

[0008] For vacuum chambers that meet the requirements for producing high silicon steel, RH production of high silicon steel is carried out. After decarburization, silicon alloy deoxidation treatment is carried out in batches. After the first batch of silicon alloy is added, samples are taken. The deviation between the actual value of Si content in the sample molten steel and the theoretical value of the Si content added to the molten steel by the first batch of silicon alloy is compared to determine whether the circulation capacity of the vacuum chamber in actual production meets the requirements for producing this high silicon steel.

[0009] If the requirements are met, the remaining silicon alloy is replenished and production continues; if the requirements are not met, argon blowing is performed after the remaining silicon alloy is replenished.

[0010] Furthermore, prior to RH production, the following steps are specifically included:

[0011] The vacuum chamber is cleaned using steel with Si ≤ 0.03%;

[0012] The molten steel was boiled and tapped in a converter to produce test steel, which met the following conditions: oxygen mass fraction > 0.03%, carbon mass fraction < 0.07%, and tapping temperature > 1660℃.

[0013] For RH treatment of test steel that meets the conditions, the vacuum degree is maintained below 0.5 kPa, and the oxygen mass fraction of the molten steel is maintained at >0.02% for no less than 7 minutes. An initial sample is taken. If the carbon mass fraction of the initial sample is <0.005%, it is pre-judged that the circulation capacity of the vacuum chamber meets the requirements for producing high silicon steel; otherwise, this vacuum chamber is not used for production.

[0014] Further, high-silicon steel is produced by RH production. In the early stage of RH production, decarburization is carried out. After treatment for 20±5 minutes, the oxygen mass fraction of the molten steel is measured and deoxidation treatment is carried out.

[0015] Furthermore, in the silicon alloy deoxidation treatment, 8-10 kg / t of the first batch of silicon alloy to increase the Si content of the molten steel is added. After circulating for 3-5 minutes, a sample is taken. When the return sample shows that the actual value of Si in the molten steel and the theoretical value of the first batch of silicon alloy to increase the Si content of the molten steel are less than 0.03%, it is determined that the circulation capacity of the vacuum chamber meets the requirements for producing high silicon steel.

[0016] Furthermore, when the sample return shows a deviation of ≥0.03% between the actual Si content in the molten steel and the theoretical value for the increased Si content in the molten steel from the first batch of silicon alloy, bottom blowing of argon into the ladle is initiated, with an argon flow rate of 20-60 m³ / h. 3 / h, argon gas circulation time is 5-15min.

[0017] This invention pre-assesses the circulation capacity of the RH vacuum chamber, rinses the chamber with boiling steel, and reassesses the circulation capacity by taking samples during RH treatment of high-silicon steel. For vacuum chambers with poor circulation capacity in actual production, the RH circulation flow rate is increased by bottom-blowing argon. Through comprehensive assessment of multiple factors, this ensures that deoxidation products from the RH chamber fully float to the surface, are thoroughly removed, and the cleanliness of the molten steel is improved, significantly enhancing the castability of the steel. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention have been clearly and completely described. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] This invention relates to a method for improving the castability of high-silicon steel treated with RH. Specifically, the method involves pre-assessing the circulation capacity of the RH vacuum chamber, rinsing the chamber with rimmed steel, taking samples during RH treatment of the high-silicon steel to reassess the chamber's circulation capacity, and increasing the RH circulation flow rate by bottom-blowing argon. Through comprehensive assessment of multiple factors, this ensures that the deoxidation products from the RH process fully float to the surface, significantly improving the castability of the molten steel.

[0020] Once the production plan for steel with Si > 1% is issued, a vacuum chamber for rinsing steel with Si ≤ 0.03% is first arranged. The rinsing steel is then tapped in a converter at a boiling point, with an oxygen mass fraction > 0.03%, a carbon mass fraction < 0.07%, and a tapping temperature > 1660℃. The rinsing steel is then treated with RH, maintaining a vacuum level below 0.5 kPa and keeping the oxygen mass fraction > 0.02% for at least 7 minutes. An initial sample is taken. If the carbon mass fraction of the initial sample is < 0.005%, the vacuum chamber's circulation capacity is deemed sufficient for producing high-silicon steel; otherwise, this vacuum chamber is not used for production.

[0021] When producing steel with Si > 1%, decarburization is performed in the early stage of RH production. After approximately 20 minutes of treatment, the oxygen mass fraction of the molten steel is measured. Silicon alloy deoxidation is then used, with 8-10 kg / t of the first batch of silicon alloy added to increase the Si content of the molten steel. The mixture is circulated for 3-5 minutes, and samples are taken. The addition of silicon alloy to increase the Si content of the molten steel continues until the target steel grade is achieved. When the deviation between the actual Si value of the molten steel and the theoretical value of the Si content increased by the first batch of silicon alloy is less than 0.03%, the circulation capacity of the vacuum chamber is considered to meet the requirements for producing high-silicon steel. When the deviation between the actual Si value of the molten steel and the theoretical value of the Si content increased by the first batch of silicon alloy is ≥ 0.03%, bottom blowing argon is initiated in the ladle at a flow rate of 20-60 m³ / h and a circulation time of 5-15 minutes. After the required treatment time is reached, the steel is cast.

[0022] Example 1

[0023] Once the production target of 3.2% Si for steel grades was announced, a steel washing vacuum chamber with a Si mass fraction upper limit of 0.03% was first used. The washed steel was then tapped in a converter at a boiling point, with an oxygen mass fraction of 0.046% and a carbon mass fraction of 0.035%, at a tapping temperature of 1692℃, to determine the steel that met the requirements.

[0024] The test steel was subjected to RH treatment and rinsing, with the vacuum level maintained below 0.2 kPa for 8 minutes to maintain the oxygen mass fraction of the molten steel at 0.026%. An initial sample was taken. The carbon mass fraction of the initial sample was 0.0034%, indicating that the circulation capacity of the vacuum chamber met the requirements for producing high-silicon steel.

[0025] When producing steel with a target Si content of 3.2%, decarburization is performed in the early stage of RH production. After approximately 20 minutes of treatment, the oxygen mass fraction of the molten steel is measured. Silicon alloy deoxidation is then used, with the first batch of 8 kg / t silicon alloy added to increase the Si content of the molten steel. After 3 minutes of circulation, a sample is taken. The sample return shows that the actual Si content of the molten steel is 0.54%, while the first batch of silicon alloy increases the Si content by a theoretical 0.52%. This indicates that the circulation capacity of the vacuum chamber meets the requirements for producing high-silicon steel. Silicon alloy to increase the Si content of the molten steel is continued to be added, totaling 46 kg / t, until the target steel grade is achieved. After the required treatment time, the steel can be cast.

[0026] Example 2

[0027] After the production target of 2.1% Si for steel grades was issued, a steel rinsing vacuum chamber with a Si mass fraction upper limit of 0.03% was first set up. The rinsing steel was boiled and tapped in a converter, with an oxygen mass fraction of 0.053% and a carbon mass fraction of 0.032% at a tapping temperature of 1695℃. The rinsing steel was then treated with RH, maintaining a vacuum level below 0.3 kPa for 9 minutes to maintain an oxygen mass fraction of 0.027%, and an initial sample was taken. The initial sample had a carbon mass fraction of 0.0025%, indicating that the vacuum chamber's circulation capacity met the requirements for producing high-silicon steel.

[0028] When producing steel with a target Si content of 2.1%, decarburization was performed in the early stage of RH production. After approximately 20 minutes of treatment, the oxygen mass fraction of the molten steel was measured. Silicon alloy deoxidation was used, with the first batch of 9 kg / t silicon alloy added to increase the Si content of the molten steel. After 4 minutes of circulation, a sample was taken. The sample return showed an actual Si content of 0.53%, while the theoretical Si increase from the first batch of silicon alloy was 0.61%, indicating poor circulation capacity of the vacuum chamber. Further addition of silicon alloy to increase the Si content of the molten steel was made, totaling 36 kg / t, to achieve the target steel grade. Bottom blowing argon was then initiated in the ladle, with an argon flow rate of 30 m³ / t. 3 / h, argon gas circulation time is 10min. After the circulation ends, a sample is taken, and the sample shows that the actual value of Si is 2.13%. The addition of silicon alloy increases the theoretical value of Si content in the molten steel by 2.10%. The molten steel is uniform, the processing time is reached, and it is then cast on the machine.

[0029] In this embodiment, for steel grades with a silicon content greater than 1%, approximately 25% of the steel produced per casting run is turbulent. Each interrupted casting process recovers approximately 350 tons of molten steel. After application, the turbulence rate is zero, and the processing cost is 215 yuan / ton. With an annual production of 400 cans of high-silicon steel, the cost reduction is 400 / 6 * 0.25 * 350 * 215 = 1.254 million yuan.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the castability of RH-treated high-silicon steel, characterized in that, Includes the following steps: Before RH production, based on the sampling of test steel used to clean the vacuum chamber, it is preliminarily determined whether the circulation capacity of the vacuum chamber meets the requirements of the high silicon steel to be produced. Specifically, the steps include the following: The vacuum chamber is cleaned using steel with Si ≤ 0.03%; The molten steel was boiled and tapped in the converter to produce test steel, which met the following conditions: oxygen mass fraction > 0.03%, carbon mass fraction < 0.07%, and tapping temperature > 1660℃. For RH treatment of test steel that meets the conditions, the vacuum degree is maintained below 0.5 kPa, and the oxygen mass fraction of the molten steel is maintained at >0.02% for no less than 7 minutes. An initial sample is taken. If the carbon mass fraction of the initial sample is <0.005%, it is pre-judged that the circulation capacity of the vacuum chamber meets the requirements for producing high silicon steel. Otherwise, this vacuum chamber is not used for production. For vacuum chambers that meet the requirements for producing high silicon steel, RH production of high silicon steel is carried out. After decarburization, silicon alloy deoxidation treatment is carried out in batches. After the first batch of silicon alloy is added, samples are taken. The deviation between the actual value of Si content in the sample molten steel and the theoretical value of the Si content added to the molten steel by the first batch of silicon alloy is compared to determine whether the circulation capacity of the vacuum chamber in actual production meets the requirements for producing this high silicon steel. If the requirements are met, the remaining silicon alloy is replenished and production continues; if the requirements are not met, argon blowing is performed after the remaining silicon alloy is replenished.

2. The method for improving the castability of RH-treated high-silicon steel according to claim 1, characterized in that, In the RH production of high silicon steel, decarburization is carried out in the early stage of RH production. After treatment for 20±5 minutes, the oxygen mass fraction of the molten steel is measured and deoxidation treatment is carried out.

3. The method for improving the castability of RH-treated high-silicon steel according to claim 1, characterized in that, For silicon alloy deoxidation treatment, add 8-10 kg / t of the first batch of silicon alloy to increase the Si content of the molten steel. After circulating for 3-5 minutes, take a sample. If the deviation between the actual Si value of the molten steel and the theoretical value of the first batch of silicon alloy increasing the Si content of the molten steel is less than 0.03%, it is determined that the circulation capacity of the vacuum chamber meets the requirements for producing high silicon steel.

4. The method for improving the castability of RH-treated high-silicon steel according to claim 1, characterized in that, When the sample return shows a deviation of ≥0.03% between the actual Si content in the molten steel and the theoretical value for the increased Si content in the molten steel from the first batch of silicon alloy, bottom blowing of argon gas into the ladle is initiated, with an argon flow rate of 20-60 m³ / h. 3 / h, argon gas circulation time is 5-15min.