A method for controlling hydrogen content in molten steel

Abstract

The present invention belongs to the technical field of steel production and relates to a method for controlling the hydrogen content of molten steel. The method adopts a process route of converter steelmaking, CAS refining, and continuous casting. By controlling the moisture content and storage of auxiliary materials, strictly controlling the converter slag making process, controlling the slag washing process during tapping, and controlling the use of scrap steel, the hydrogen content of the molten steel is stably controlled to ≤4.5ppm. The method is simple to operate and can be implemented with a smelting gun. It can effectively shorten the smelting process, improve production efficiency, and reduce production costs. It not only reduces the hydrogen content of the molten steel in the BC process path, but also reduces the hydrogen control pressure of the molten steel in the LF of the BLC process path, effectively reducing the hydrogen high off-line ratio of the steel billet, and ensuring production quality.

Description

Technical Field

[0001] The invention belongs to the technical field of steel production and relates to a method for controlling the hydrogen content of molten steel. Background Art

[0002] The hydrogen content of molten steel is a key factor affecting steel quality. High hydrogen content increases steel brittleness and reduces ductility, impacting the service life and safety of the steel. During the converter smelting process, moisture introduced from scrap steel, auxiliary materials, and slag wash materials added during the converter tapping process often decomposes into hydrogen at high temperatures and remains in the molten steel. To stabilize billet quality, it is crucial to reduce hydrogen content during converter smelting and minimize slag washing during tapping. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to solve the problem of controlling the hydrogen content of molten steel and provide a method for controlling the hydrogen content of molten steel.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A method for controlling the hydrogen content of molten steel, using a process route of converter steelmaking, CAS refining, and continuous casting to obtain molten steel with a hydrogen content of ≤4.5ppm. The slag forming requirements during the converter smelting process are:

[0006] A. When the iron-steel ratio is ≥910kg / t, all auxiliary materials required for smelting must be added within 7 minutes of oxygen addition; when the iron-steel ratio is <910kg / t, all auxiliary materials required for smelting must be added within 5 minutes of oxygen addition;

[0007] B. The smelting process is controlled by controlling the spraying through the gun position and oxygen flow rate. Within 7 minutes of oxygen supply, raw white, lime and limestone can be used for slag pressing. The total amount of auxiliary materials for slag pressing is ≤1t.

[0008] C. 7 minutes after the oxygen is turned on and after TSC measurement, the carbon temperature in the furnace is judged to be sufficient based on the furnace mouth flame and CO concentration. Dust removal ash balls can only be added for adjustment, and the addition must be completed before TSC measurement. The time interval between the addition of cold material and the TSC measurement must be ≥2 minutes. Among them, the amount of all dust removal ash balls added after 7 minutes is ≤1.5t / furnace, and the amount of dust removal ash balls added after TSC measurement is ≤1t / furnace. The dust removal ash balls added after TSC must be completed within 20s after the TSC measurement is completed.

[0009] Furthermore, the slag making requirements for the converter steel-making process are as follows: when the BC process route is adopted, the amount of metallurgical lime added to the ladle is controlled at 400±50kg / furnace; when the BLC process route is adopted, the amount of metallurgical lime added to the ladle during converter steel-making is controlled at 700±50kg / furnace.

[0010] Furthermore, the thickening agent during the converter tapping process is controlled at 100-150 kg / furnace; when the hydrogen content of the molten steel after the converter tapping is greater than 5 ppm, the addition of the thickening agent is cancelled.

[0011] Furthermore, the moisture control requirements for auxiliary materials in the converter smelting and steel-making process are: metallurgical lime ≤1.0%, raw dolomite ≤3.0%, magnesium balls ≤2.0%, limestone ≤3.0%, dust removal ash pellets ≤3.5%, and thickening agent ≤1%.

[0012] Furthermore, requirements for scrap steel used in converter smelting: it is strictly prohibited to use scrap steel containing water or oil.

[0013] Furthermore, the shelf life requirements for auxiliary materials are: metallurgical lime must be used up within 24 hours after entering the factory; metallurgical lime used for slag washing must be used up within 12 hours after entering the factory.

[0014] Furthermore, the molten steel is refined by CAS to uniformize the temperature and composition of the molten steel, and then continuous casting is carried out. The continuous casting speed is 0.80m / min to 0.95m / min. Protected casting is adopted throughout the continuous casting process to control the hydrogen content of the molten steel to ≤5ppm.

[0015] The beneficial effects of the present invention are:

[0016] 1. The method for controlling the hydrogen content of molten steel in the present invention adopts a process route of converter steelmaking, CAS refining, and continuous casting to obtain molten steel with a hydrogen content of ≤4.5ppm. It is simple to operate and has strong feasibility. It can effectively shorten the smelting process, improve production efficiency, and reduce production costs.

[0017] 2. The method for controlling the hydrogen content of molten steel in the present invention not only controls the moisture content and storage of auxiliary materials, strictly controls the converter slag-making process, controls the slag washing process for tapping, and controls the use of scrap steel, but also reduces the hydrogen content of molten steel in the BC process path, and reduces the hydrogen control pressure of molten steel in the BLC path in the LF, effectively reducing the hydrogen high-line ratio of steel billets, ensuring production quality, and saving production costs.

[0018] 3. Currently, the control of hydrogen in converters mainly relies on RH vacuum dehydrogenation, while the method of the present invention does not require vacuum refining.

[0019] 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

[0020] 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.

[0021] A method for controlling the hydrogen content of molten steel, using a process route of converter steelmaking, CAS refining, and continuous casting, wherein: A method for controlling the hydrogen content of molten steel, using a process route of converter steelmaking, CAS refining, and continuous casting, to obtain molten steel with a hydrogen content of ≤4.5ppm, the slag forming requirements of the converter smelting process are:

[0022] A. When the iron-steel ratio is ≥910kg / t, all auxiliary materials required for smelting must be added within 7 minutes of oxygen addition; when the iron-steel ratio is <910kg / t, all auxiliary materials required for smelting must be added within 5 minutes of oxygen addition;

[0023] B. The smelting process is controlled by controlling the spraying through the gun position and oxygen flow rate. Within 7 minutes of oxygen supply, raw white, lime and limestone can be used for slag pressing. The total amount of auxiliary materials for slag pressing is ≤1t.

[0024] C. 7 minutes after the oxygen is turned on and after TSC measurement, the carbon temperature in the furnace is judged to be sufficient based on the furnace mouth flame and CO concentration. Dust removal ash balls can only be added for adjustment, and the addition must be completed before TSC measurement. The time interval between the addition of cold material and the TSC measurement must be ≥2 minutes. Among them, the amount of all dust removal ash balls added after 7 minutes is ≤1.5t / furnace, and the amount of dust removal ash balls added after TSC measurement is ≤1t / furnace. The dust removal ash balls added after TSC must be completed within 20s after the TSC measurement is completed.

[0025] Slag making requirements during converter tapping process:

[0026] A. When the BC process route is adopted, the amount of metallurgical lime added to the ladle is controlled at 400±50kg / furnace; when the BLC process route is adopted, the amount of metallurgical lime added to the ladle during converter tapping is controlled at 700±50kg / furnace.

[0027] B. During the converter tapping process, the slag thickening agent is controlled at 100-150 kg / furnace; when the hydrogen content of the molten steel after converter tapping is greater than 5 ppm, the addition of the slag thickening agent is cancelled.

[0028] Moisture control requirements for auxiliary materials in converter smelting and steel-tapping processes: metallurgical lime ≤1.0%, raw dolomite ≤3.0%, magnesium balls ≤2.0%, limestone ≤3.0%, dust removal ash pellets ≤3.5%, and thickening agent ≤1%.

[0029] Requirements for scrap steel used in converter smelting: It is strictly prohibited to use scrap steel containing water or oil, such as iron filings and cakes.

[0030] Shelf life requirements for auxiliary materials: Metallurgical lime must be used up within 24 hours after entering the factory; metallurgical lime used for slag washing must be used up within 12 hours after entering the factory.

[0031] The molten steel is refined by CAS to uniform the temperature and composition of the molten steel, and then continuous casting is carried out. The continuous casting speed is 0.80m / min~0.95m / min. Protected casting is adopted throughout the continuous casting process to control the hydrogen content of the molten steel to ≤5ppm.

[0032] The present invention effectively controls the hydrogen content of molten steel to ≤4.5ppm, which not only reduces the hydrogen content of molten steel in the BC process path, but also alleviates the hydrogen control pressure of molten steel in the BLC path in the LF, effectively reduces the hydrogen high-line ratio of steel billets, ensures production quality, and saves production costs.

[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 hydrogen content of molten steel, which adopts a process route of converter steelmaking, CAS refining, and continuous casting to obtain molten steel with a hydrogen content of ≤4.5ppm, characterized in that: Slag making requirements in converter smelting process: A. When the iron-steel ratio is ≥910kg / t, all auxiliary materials required for smelting must be added within 7 minutes of oxygen opening; when the iron-steel ratio is <910kg / t, all auxiliary materials required for smelting must be added within 5 minutes of oxygen opening; B. During the smelting process, the spraying is controlled by the gun position and oxygen flow rate. Within 7 minutes of oxygen supply, raw white, lime and limestone are used to press the slag. The total amount of auxiliary materials for slag pressing is ≤1t; C. 7 minutes after oxygen is turned on and after TSC measurement, if the carbon temperature in the furnace is judged to be rich based on the furnace flame and CO concentration, only dust ash pellets can be added for adjustment, and the addition must be completed before TSC measurement. The time interval between the addition of cold material and the TSC measurement must be ≥ 2 minutes. Among them, the amount of all dust ash pellets added after 7 minutes is ≤ 1.5t / furnace, and the amount of dust ash pellets added after TSC measurement is ≤ 1t / furnace. The dust ash pellets added after TSC measurement must be completed within 20s after the completion of TSC measurement; Slag formation requirements during converter tapping: When the BC process is used, the amount of metallurgical lime added to the ladle is controlled at 400±50kg / furnace; when the BLC process is used, the amount of metallurgical lime added to the ladle is controlled at 700±50kg / furnace; the amount of thickening agent used during converter tapping is controlled at 100-150kg / furnace; when the hydrogen content of the molten steel is greater than 5ppm after converter tapping, the addition of thickening agent is canceled; Moisture control requirements for auxiliary materials in converter smelting and steel tapping processes: metallurgical lime ≤1.0%, raw dolomite ≤3.0%, magnesium balls ≤2.0%, limestone ≤3.0%, dust removal ash pellets ≤3.5%, thickening agent ≤1%; The molten steel is refined by CAS to uniform the temperature and composition of the molten steel, and then continuous casting is carried out. The continuous casting speed is 0.80m / min~0.95m / min. Protected casting is adopted throughout the continuous casting process to control the hydrogen content of the molten steel to ≤5ppm.

2. The method for controlling hydrogen content in molten steel according to claim 1, wherein: Requirements for scrap steel used in converter smelting: It is strictly prohibited to use scrap steel containing water or oil.

3. The method for controlling hydrogen content in molten steel according to claim 1, wherein: Shelf life requirements for auxiliary materials: Metallurgical lime must be used up within 24 hours after entering the factory; metallurgical lime used for slag washing must be used up within 12 hours after entering the factory.