A method for controlling RH refining temperature of non-oriented silicon steel

Abstract

The present invention belongs to the technical field of non-oriented silicon steel metallurgy, and relates to a method for controlling the RH refining temperature of non-oriented silicon steel. The method adopts a process route of combined blowing converter → RH vacuum refining → continuous casting, and specifically comprises the following steps: step 1. charging molten iron and scrap steel into a converter for converter oxygen blowing smelting, and controlling the converter tapping temperature to be between 1670°C and 1690°C; step 2. performing RH vacuum refining on the molten steel after the converter tapping, controlling the RH arrival molten steel temperature to be between 1600°C and 1620°C, and performing the RH refining cycle for 3 minutes. The molten steel temperature is controlled at 1590°C to 1620°C; step 3. the molten steel temperature after the RH refining cycle for 15 minutes is controlled at 1585°C to 1600°C; step 4. after the RH refining cycle for 15 minutes, RH deoxidation and alloying are performed, and the temperature of the molten steel after the RH deoxidation and alloying is controlled at 1585°C to 1595°C; step 5. after the RH deoxidation and alloying is completed, the RH refining cycle is performed for another 5 to 10 minutes, and the RH outlet molten steel temperature is adjusted to 1580 to 1590°C, and then the molten steel is continuously cast.

Description

Technical Field

[0001] The invention belongs to the technical field of non-oriented silicon steel metallurgy, and relates to a method for controlling RH refining temperature of non-oriented silicon steel. Background Art

[0002] Silicon steel, also known as electromagnetic steel or electrical steel, refers to silicon alloy steel with a silicon content of 0.5% to 4.5% and a carbon content of less than 0.03% in the finished product. It is primarily used to manufacture cores for various generators and motors, transformers, relays, and various electrical instruments. It is an essential soft magnetic alloy for China's power, electronics, and military industries, and is also the most produced functional metal material. Silicon steel can be categorized by production process into hot-rolled and cold-rolled types. Cold-rolled electrical steel sheets are further categorized into non-oriented silicon steel and oriented silicon steel. Non-oriented silicon steel is primarily used as cores for rotating electrical machines such as motors and generators, while oriented silicon steel is primarily used in medium- and high-frequency motors, transformers, and pulse transformers.

[0003] A type of non-oriented silicon steel with a carbon content requirement of ≤0.005% is produced using a production process that includes molten iron desulfurization, top and bottom double-blowing in a converter, RH vacuum refining, continuous casting, and hot rolling. Temperature control is a major challenge during the RH refining process. High temperatures require the addition of scrap steel for temperature adjustment, which can cause carbon increase. Low temperatures, especially after deoxidation and alloying, can lead to unplanned interruptions in continuous casting and production interruptions without effective temperature compensation. How to accurately control the temperature during the RH refining process has become one of the focuses of attention in the production of non-oriented silicon steel. However, in the prior art, for example, a method for controlling deoxidation during RH refining of non-oriented silicon steel with publication number CN101768653A discloses a method for controlling deoxidation during the RH refining process of non-oriented silicon steel, which can reduce the number of inclusions in steel and change the morphology, thereby improving product performance. A method for reducing alloy costs by smelting non-oriented silicon steel in an RH refining furnace with publication number CN106755737A discloses that when the molten steel temperature is greater than 1615°C and the oxygen content is greater than 500ppm, high-carbon ferromanganese is added in the early stage of decarburization treatment, thereby reducing the smelting cost of non-oriented silicon steel. Although the above-mentioned prior art discloses the smelting process of non-oriented silicon steel, none of them describes the accurate temperature control during the RH refining process of non-oriented silicon steel, and therefore cannot solve the difficulty of temperature control during the RH refining process.

[0004] Therefore, there is an urgent need for a method for accurately controlling the temperature in the RH refining process of non-oriented silicon steel, which can accurately control the temperature in the RH refining process of non-oriented silicon steel, avoid high or low temperatures in the RH refining process of non-oriented silicon steel, and ensure the smooth production of non-oriented silicon steel. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a method for controlling the RH refining temperature of non-oriented silicon steel, by controlling the RH refining arrival temperature of non-oriented silicon steel, the decarburization end temperature control range, and the RH lifting gas flow rate, so as to accurately control the RH outlet temperature, avoid high or low temperature conditions in the production process of non-oriented silicon steel, and ensure the smooth production of non-oriented silicon steel.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for controlling the RH refining temperature of non-oriented silicon steel adopts a process route of combined blowing converter → RH vacuum refining → continuous casting, and specifically comprises the following steps:

[0008] Step 1. Loading molten iron and scrap steel into a converter for oxygen blowing smelting, and controlling the converter tapping temperature at 1670°C to 1690°C;

[0009] Step 2. The molten steel after tapping the converter is subjected to RH vacuum refining, and the temperature of the molten steel at the RH station is controlled at 1600℃~1620℃, and the temperature of the molten steel after the RH refining cycle for 3 minutes is controlled at 1590℃~1620℃;

[0010] Step 3. Control the temperature of the molten steel after 15 minutes of RH refining cycle to 1585°C to 1600°C;

[0011] Step 4. After RH refining cycle for 15 minutes, RH deoxidation and alloying are performed, and the temperature of the molten steel after RH deoxidation and alloying is controlled at 1585°C to 1595°C;

[0012] Step 5. After the RH deoxidation and alloying is completed, the RH refining cycle is continued for 5 to 10 minutes, and the RH outgoing molten steel temperature is adjusted to 1580 to 1590°C, and then the molten steel is continuously cast.

[0013] Furthermore, in step 1, the total loading amount of the molten iron and scrap steel is 235t, the iron-steel ratio is controlled at 850-930kg of scrap steel / furnace, the final oxygen content of the converter is controlled at 600-1000ppm, the final carbon content is controlled at 0.03-0.04%, and a turnover tank is used as a ladle for tapping.

[0014] Furthermore, in step 2, according to the real-time temperature of the molten steel arriving at the RH station, the vacuum degree of the RH vacuum furnace is controlled to be ≤273Pa, and the gas flow rate is increased by 90~120Nm3 / h to control the temperature of the molten steel after the RH refining cycle for 3 minutes to be between 1590℃ and 1620℃, and real-time temperature measurement is performed to adjust the gas flow rate accordingly during the subsequent RH refining process.

[0015] Furthermore, in step 3, after the RH refining cycle for 3 minutes, the vacuum degree of the RH vacuum furnace is controlled to be ≤273Pa, and the gas flow rate is increased to 120-150Nm3 / h, so as to control the temperature of the molten steel at 1585℃~1600℃ after the RH refining cycle for 15 minutes, and real-time temperature measurement is performed to adjust the gas flow rate accordingly during the subsequent RH refining process, and the oxygen content is controlled at 200-300ppm, and decarburization is reduced to below 30ppm.

[0016] Furthermore, in step 4, the lifting gas flow rate is controlled at 90-180 Nm3 / h to adjust the temperature of the molten steel after RH deoxidation and alloying to 1580-1590°C, and real-time temperature measurement is performed to correspondingly adjust the lifting gas flow rate in the subsequent RH refining process.

[0017] Furthermore, in step 5, the lifting gas flow rate is controlled at 90-180 Nm3 / h to adjust the RH outlet molten steel temperature to 1580-1590°C.

[0018] Furthermore, in step 1, in the slag washing process during the tapping of the molten steel, the amount of metallurgical lime added is controlled to be 400-800 kg / furnace.

[0019] Furthermore, in step 3, if the temperature of the molten steel after 15 minutes of RH refining cycle is lower than 1585°C, the molten steel is heated to 1585°C to 1600°C by blowing oxygen using an RH top lance.

[0020] The beneficial effects of the present invention are:

[0021] 1. The present invention provides a method for controlling the RH refining temperature of non-oriented silicon steel. The method achieves the purpose of accurately controlling the RH refining process temperature of non-oriented silicon steel by accurately controlling the converter tapping temperature, the RH arrival temperature, the 3-minute cycle temperature of the RH refining process, and the 15-minute cycle temperature of the RH refining process, and performing real-time temperature measurement. The method cooperates with RH oxygen blowing to increase the temperature and controls the temperature drop of the RH refining process by adjusting the RH circulation flow rate. The method can control the RH refining process temperature of non-oriented silicon steel with a carbon content of ≤0.005% within ±5°C of the design temperature value, avoids high or low temperatures during the RH refining process of non-oriented silicon steel, and ensures smooth production of non-oriented silicon steel.

[0022] 2. The present invention adopts the process of converter steelmaking, RH refining and continuous casting to obtain molten steel with qualified composition and temperature, shortening the production process, improving efficiency and reducing production costs.

[0023] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. DETAILED DESCRIPTION

[0024] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] A method for controlling the RH refining temperature of non-oriented silicon steel adopts a process route of 210t combined blowing converter → RH vacuum refining → continuous casting, and adopts the following smelting process, specifically:

[0026] a. Load molten iron and scrap into a converter for oxygen-blowing smelting to produce converter-smelted molten steel. The total charge is 235 tons, the iron-steel ratio is controlled at 850-930 kg of scrap steel per furnace, the converter endpoint oxygen content is controlled at 600-1000 ppm, the endpoint carbon content is controlled at 0.03-0.04%, and the tapping temperature is controlled at 1670°C-1690°C. A turnover tank is used as a ladle for tapping.

[0027] b. In the slag washing process during the steelmaking process, the amount of metallurgical lime added is controlled at 400-800 kg / furnace;

[0028] c. The molten steel after tapping the converter is subjected to RH vacuum refining in the RH vacuum furnace. The temperature of the molten steel arriving at the RH station is controlled at 1600℃~1620℃, the vacuum degree of the RH vacuum furnace is controlled to ≤273Pa, and the gas flow rate is increased by 90~120Nm 3 / h, so as to control the temperature of the molten steel at 1590℃~1620℃ after 3 minutes of RH refining cycle;

[0029] d. After 3 minutes of RH refining cycle, control the vacuum degree of the RH vacuum furnace to ≤273Pa and increase the gas flow rate to 120~150Nm 3 / h, so as to control the temperature of the molten steel at 1585℃~1600℃ after 15 minutes of RH refining cycle. If the molten steel is lower than 1585℃ at this time, RH top lance oxygen blowing is used to raise the temperature of the molten steel to 1585℃~1600℃, and the oxygen content is controlled at 200~300ppm, and decarburization is reduced to below 30ppm;

[0030] e. After 15 minutes of RH refining cycle, RH deoxidation and alloying are carried out. The vacuum degree of the RH vacuum furnace is controlled to be ≤273Pa, and the gas flow rate is increased to 120~180Nm 3 / h, so as to control the temperature of the molten steel after RH deoxidation and alloying at 1585℃~1595℃;

[0031] f. After RH deoxidation and alloying, RH refining cycle is continued for 5 to 10 minutes for degassing, and the lifting gas flow rate is controlled at 90 to 180 Nm 3 / h to adjust the molten steel temperature to 1580-1590°C, and then continuously cast the molten steel. The continuous casting cycle is controlled at 54 minutes.

[0032] Specifically, in the RH refining process, argon gas needs to be blown into the RH immersion tube under high vacuum conditions for the circulation of molten steel. This gas is called lifting gas, and the blowing flow rate is called lifting gas flow rate. The flow rate is adjustable. By adjusting the lifting gas flow rate, the temperature drop of the molten steel during the RH refining process can be controlled.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for controlling the RH refining temperature of non-oriented silicon steel, which adopts a process route of combined blowing converter → RH vacuum refining → continuous casting, characterized in that: The specific steps include: Step 1. Loading molten iron and scrap steel into a converter for converter oxygen blowing smelting, controlling the converter tapping temperature at 1670°C to 1690°C; the total loading amount of the molten iron and scrap steel is 235t, the iron-steel ratio is controlled at 850-930kg of scrap steel / furnace, the converter endpoint oxygen content is controlled at 600-1000ppm, the endpoint carbon content is controlled at 0.03-0.04%, and a turnover tank is used as a ladle for tapping; Step 2. The molten steel after tapping the converter is subjected to RH vacuum refining, and the temperature of the molten steel at the RH station is controlled at 1600℃~1620℃, and the temperature of the molten steel after the RH refining cycle for 3 minutes is controlled at 1590℃~1620℃; Step 3. Control the temperature of the molten steel after the RH refining cycle for 15 minutes to be between 1585°C and 1600°C; if the temperature of the molten steel after the RH refining cycle for 15 minutes is lower than 1585°C, use an RH top lance to blow oxygen to raise the temperature of the molten steel to 1585°C to 1600°C; Step 4. After RH refining cycle for 15 minutes, RH deoxidation and alloying are performed, and the temperature of the molten steel after RH deoxidation and alloying is controlled at 1585°C to 1595°C; Step 5. After the RH deoxidation and alloying is completed, the RH refining cycle is continued for 5 to 10 minutes, and the lifting gas flow rate is controlled at 90 to 180 Nm3 / h to adjust the RH outgoing molten steel temperature to 1580 to 1590°C, and then the molten steel is continuously cast.

2. The method for controlling RH refining temperature of non-oriented silicon steel according to claim 1, wherein: In step 2, according to the real-time temperature of the molten steel at the RH station, the vacuum degree of the RH vacuum furnace is controlled to ≤273Pa, and the gas flow rate is increased by 90~120Nm 3 / h to control the temperature of the molten steel at 1590℃~1620℃ after 3 minutes of RH refining cycle, and perform real-time temperature measurement to adjust the gas flow rate accordingly in the subsequent RH refining process.

3. The method for controlling RH refining temperature of non-oriented silicon steel according to claim 1, wherein: In step 3, after RH refining cycle for 3 minutes, control the vacuum degree of RH vacuum furnace to ≤273Pa, and increase the gas flow rate to 120~150Nm 3 / h to control the temperature of the molten steel at 1585℃~1600℃ after 15 minutes of RH refining cycle, and perform real-time temperature measurement to adjust the gas flow rate in the subsequent RH refining process accordingly, and control the oxygen content at 200~300ppm and decarburize to below 30ppm.

4. The method for controlling RH refining temperature of non-oriented silicon steel according to claim 1, wherein: In step 4, the lifting gas flow rate is controlled at 90-180 Nm 3 / h to adjust the temperature of the molten steel after RH deoxidation and alloying to 1580-1590°C, and perform real-time temperature measurement to adjust the gas flow rate in the subsequent RH refining process accordingly.

5. The method for controlling RH refining temperature of non-oriented silicon steel according to claim 1, wherein: In step 1, in the slag washing process during the tapping of molten steel, the amount of metallurgical lime added is controlled to be 400-800 kg / furnace.