Crystal permanent magnet stirring billet initial solidification shell preparation experimental device and method

Abstract

This invention discloses an experimental apparatus and method for preparing the initial solidified shell of a square billet using permanent magnet stirring in a crystallizer. The apparatus includes a control system, a crucible, a heating furnace for heating the crucible, a permanent magnet stirring module for permanently stirring the molten steel in the crucible, a crystallizer, and a casting module matched with the crystallizer. The crystallizer is equipped with a copper mold. The control system is electrically connected to the heating furnace, the permanent magnet stirring module, and the casting module. The apparatus and method of this application can simulate the preparation of the initial solidified shell of a square billet under different permanent magnet stirring conditions in a crystallizer. It has the advantages of simple structure, easy maintenance, low cost, and diversified magnetic field modes, improving the controllability and quality of the cast billet. It can be used to study the effect of permanent magnet stirring in the crystallizer on the initial solidified shell of the square billet, to explore the optimal permanent magnet stirring conditions for different steel grades, and to provide guidance for the industrial application of permanent magnet stirring in crystallizers.

Description

Technical Field

[0001] This invention belongs to the field of billet shell preparation technology, specifically relating to an experimental device and method for preparing the initial solidified billet shell of a crystallizer with permanent magnet stirring. Background Technology

[0002] Surface and internal defects in cast billets are closely related to the flow state of molten steel within the mold. Studies have shown that nearly 80% of surface defects in cast billets originate from the mold. Therefore, controlling and improving the flow of molten steel within the mold is crucial for improving billet quality, especially surface quality. Electromagnetic stirring in the mold can enhance the flow of molten steel during pouring and at the beginning of solidification, strengthen heat transfer within the mold, reduce superheat, and thus control the surface (shell) quality of the solidified billet, attracting widespread attention from metallurgists.

[0003] However, electromagnetic stirring requires high-power variable-frequency current to generate an alternating magnetic field, resulting in complex equipment, high energy consumption, and high maintenance costs. Furthermore, to prevent coil overheating, flowing water cooling is necessary. On the one hand, the cooling water carries away Joule heat from the coil, wasting electrical energy; on the other hand, even with high-quality cooling water, the coil's lifespan is still relatively short, not exceeding one year, requiring frequent replacement. With the continuous improvement of magnetic material performance, permanent magnet stirring has become an effective alternative to electromagnetic stirring. Studies have shown that the energy consumption of permanent magnet stirring is only one-tenth that of electromagnetic stirring. Therefore, developing permanent magnet stirring technology is of great significance for enterprises to reduce energy consumption and save production and operating costs.

[0004] Experimental results of permanent magnet stirring at the solidification end of small square billets for high-carbon cord steel show that permanent magnet stirring at the solidification end can reduce carbon segregation in small square billets, resulting in significant energy savings. Patent CN108580803A discloses a permanent magnet stirrer at the solidification end of a steelmaking continuous casting machine billet, which uses a hydraulic motor to drive the rotation of a permanent magnet to achieve the purpose of stirring the liquid core of the billet. However, the application of permanent magnet stirring technology in crystallizers is rarely reported. Utility model patent CN212419548U discloses a steelmaking continuous casting machine billet crystallizer, in which a permanent magnet stirrer is placed externally, and a hydraulic motor is used to drive the rotation of the permanent magnet to achieve stirring. The above patents have a single magnetic field motion mode, simply replacing permanent magnet stirring with electromagnetic stirring, and fail to address the needs of actual production problems.

[0005] To study the impact of permanent magnet stirring in the crystallizer on the initial solidified shell, the ideal method would be industrial field experiments or small-scale pilot continuous casting machine experiments. However, these methods face numerous problems, including high experimental risks, large raw material consumption, high energy consumption, disruption to normal production processes, and excessively high experimental costs. Furthermore, some researchers have established mathematical models to simulate the role of permanent magnet stirring in the initial solidification of the crystallizer. However, these methods are based on certain assumptions and require comprehensive and accurate boundary conditions and physical property parameters. These factors can affect the accuracy of the simulation results, and the simulation results often fail to fully and accurately explain the formation of the initial solidified shell in the crystallizer, which involves complex, multiphase, and transient "three-transmission-one-reaction" phenomena. Therefore, to effectively study the impact of permanent magnet stirring in the crystallizer on the initial solidification of molten steel and to realize the industrial application of permanent magnet stirring in the crystallizer, a new approach and method are urgently needed. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide an experimental apparatus and method for preparing the initial solidified shell of a billet under permanent magnet stirring in a crystallizer. This apparatus can simulate the preparation of the initial solidified shell of a billet under different permanent magnet stirring conditions in a crystallizer. It has the advantages of simple structure, easy maintenance, low cost, and diversified magnetic field modes, thereby improving the controllability of billet quality and enhancing billet quality. It can be used to study the influence of permanent magnet stirring in a crystallizer on the initial solidified shell of a billet, to explore the optimal permanent magnet stirring conditions for different steel grades, and to provide guidance for the industrial application of permanent magnet stirring in crystallizers.

[0007] The present invention solves the above problems through the following technical means:

[0008] In a first aspect, the present invention relates to an experimental apparatus for preparing the initial solidified billet shell of a square billet by permanent magnet stirring in a crystallizer, comprising a control system, a crucible for holding molten steel, a heating furnace for heating the crucible, a permanent magnet stirring module for permanently stirring the molten steel in the crucible, a crystallizer, and a billet pulling module matched with the crystallizer. The crystallizer is equipped with a crystallizer copper mold, and the control system is electrically connected to the heating furnace, the permanent magnet stirring module, and the billet pulling module respectively.

[0009] Furthermore, the heating furnace is equipped with a heating element and a thermocouple.

[0010] Furthermore, the crucible includes an outer pot body and an inner pot body that are fitted together, and the thermocouple is placed between the outer pot body and the inner pot body.

[0011] Furthermore, it also includes a crystallizer copper mold vibration motor that drives the crystallizer copper mold to vibrate, and the crystallizer copper mold vibration motor is electrically connected to the control system.

[0012] Secondly, the present invention relates to an experimental method for preparing an initial solidified shell of a square billet using the above-described apparatus, comprising the following steps:

[0013] 1) Place 20-25 kg of the required experimental steel in the crucible, place the crucible in the heating furnace, and adjust the height of the permanent magnet of the permanent magnet module according to the type of steel and experimental requirements to control the magnetic field strength at the crucible.

[0014] 2) Start the heating furnace to melt the experimental steel and maintain the temperature above the liquidus temperature of the steel grade at 30-70℃; start the permanent magnet stirrer and adjust the stirring speed to ensure that the composition and temperature of the molten steel are uniform; then add the mold protective slag that matches the steel grade to the molten steel, and after it is completely melted, a mold protective slag layer is formed, and the temperature of the mold protective slag layer is measured.

[0015] 3) Slowly insert the copper mold of the crystallizer into the molten pool, start the vibration motor of the copper mold of the crystallizer, and drive the copper mold of the crystallizer to vibrate at the set vibration frequency and vibration amplitude. The protective slag layer of the crystallizer cools rapidly on the copper mold of the crystallizer to form a protective slag film. As the copper mold of the crystallizer continues to be inserted, the molten steel solidifies rapidly on the copper mold of the crystallizer covered with the protective slag film.

[0016] 4) When the copper mold of the crystallizer descends to the set position, the copper mold of the crystallizer stops moving downward and stays for 1-10 seconds. The initial solidified billet shell formed by the solidification of molten steel on the surface of the crystallizer reaches a thickness of 1-6mm. The billet pulling module is started to drive the solidified billet shell downward. At the same time, new molten steel comes into contact with the copper mold of the crystallizer and pulls out a certain length of the initial solidified billet shell. During this process, the permanent magnet stirring module is kept running. During the process of pulling out the initial solidified billet shell, the vibration motor of the copper mold of the crystallizer is turned off.

[0017] 5) The copper mold of the crystallizer moves upward together with the initial solidified billet shell to get out of the molten pool in the crucible. After cutting, the initial solidified billet shell of the crystallizer permanent magnet stirred square billet is obtained; finally, the crystallizer permanent magnet stirring module is turned off.

[0018] Furthermore, the amplitude of the copper mold in the crystallizer is 1-6 mm, and the frequency is 50-350 times / minute.

[0019] Furthermore, the length of the initial solidified shell is 300-800 mm.

[0020] The beneficial effects of this invention are:

[0021] The apparatus and method of this application, by pre-adjusting the position of the permanent magnet and regulating the magnetic field strength and distribution at the crystallizer, allows for diversified control of the magnetic field at the crystallizer location by controlling the rotation speed and direction of the permanent magnet. Through realistic simulation of permanent magnet stirring in the crystallizer, it meets the research needs of initial solidified billet shells under different crystallizer permanent magnet stirring conditions for different steel grades. It can be used to explore the optimal crystallizer permanent magnet stirring conditions for different steel grades, providing a valuable reference for the industrial application of crystallizer permanent magnet stirring. Conventional permanent magnet stirring devices with fixed permanent magnet positions have limited controllable parameters, making it difficult to meet the stirring requirements of different melts and explore the optimal permanent magnet stirring conditions, thus hindering the provision of suitable and precise industrial application solutions. The apparatus and method of this patent application are convenient to operate, the simulation process is stable and reliable, and the experimental cost is low. It provides realistic simulation for industrial field experiments of crystallizer permanent magnet stirring, avoiding excessive energy waste and providing strong support for the industrial application of crystallizer permanent magnet stirring. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Figure 1 This is a schematic diagram of a preferred embodiment of an experimental apparatus for preparing the initial solidified shell of a square billet using a permanent magnet stirring crystallizer according to the present invention.

[0024] In the diagram: 1—Permanent magnet stirring module; 2—Adjustable height support; 3—Outer pot body; 4—Thermocouple; 5—Heating element; 6—Crystallizer protective slag layer; 7—Molten steel; 8—Inner pot body; 9—Ball pulling module; 10—Crystallizer; 11—Control system. Detailed Implementation

[0025] The present invention will be further described in detail below through embodiments. Through these descriptions, the features and advantages of the present invention will become clearer and more apparent. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0026] like Figure 1 As shown, the experimental apparatus for preparing the initial solidified billet shell of the crystallizer permanent magnet stirring billet in this embodiment includes a control system 11, a crucible for holding molten steel, a heating furnace for heating the crucible, a permanent magnet stirring module 1 for permanent magnet stirring of the molten steel in the crucible, a crystallizer 10, and a billet pulling module 9 matched with the crystallizer. The crystallizer is equipped with a crystallizer copper mold. The control system is electrically connected to the heating furnace, the permanent magnet stirring module, and the billet pulling module, respectively.

[0027] The permanent magnet stirring module includes a pair of permanent magnets, a permanent magnet rotary motor, and an up-and-down telescopic device. The permanent magnets are driven to rotate by the permanent magnet rotary motor. Both are mounted on the up-and-down telescopic device. The permanent magnet rotary motor can drive the permanent magnets to move at a set speed and in a set direction. At the same time, the up-and-down telescopic device can drive the permanent magnets to rise and fall. The control system is electrically connected to the permanent magnet rotary motor and the up-and-down telescopic device respectively.

[0028] The drawing module includes a drawing machine and a drawing machine moving device for driving the drawing machine to move. The drawing machine is matched with the crystallizer, and the drawing machine moving device is electrically connected to the control system.

[0029] The heating furnace is equipped with a heating element 5 and a thermocouple 4. In this embodiment, the heating furnace is an electric heating furnace, and the heating element is an electric heating element. The thermocouple is used to detect temperature. Preferably, the crucible includes an outer pot body 3 and an inner pot body 8 that are fitted together, and the thermocouple is placed between the outer pot body and the inner pot body so that the thermocouple is as close as possible to the molten liquid, thereby improving the accuracy of temperature detection.

[0030] It also includes a crystallizer copper mold vibration motor that drives the crystallizer copper mold to vibrate, the crystallizer copper mold vibration motor being electrically connected to the control system; the crystallizer copper mold vibration motor can drive the crystallizer copper mold to vibrate.

[0031] The method of using the above-mentioned device is described in detail below:

[0032] Example 1

[0033] An experimental method for preparing the initial solidified shell of a square billet using the above-mentioned apparatus includes the following steps:

[0034] 1) Place 20 kg of the required experimental steel in the crucible, place the crucible in the heating furnace, and adjust the height of the permanent magnet of the permanent magnet module according to the type of steel and experimental requirements to control the magnetic field strength at the crucible; the central magnetic field strength is controlled at 1400 Gs.

[0035] 2) Start the heating furnace to melt the experimental steel and maintain the temperature above 50°C above the liquidus temperature of the steel grade; start the permanent magnet stirrer and adjust the stirring speed to 180 rpm to ensure that the composition and temperature of the molten steel 6 are uniform; then add the mold protective slag that matches the steel grade to the molten steel, and after it is completely melted, a mold protective slag layer is formed, and the temperature of the mold protective slag layer is measured.

[0036] 3) Slowly insert the copper mold of the crystallizer into the molten pool, start the vibration motor of the copper mold of the crystallizer, and drive the copper mold of the crystallizer to vibrate at the set vibration frequency and vibration amplitude. The protective slag layer of the crystallizer cools rapidly on the copper mold of the crystallizer to form a protective slag film. As the copper mold of the crystallizer continues to be inserted, the molten steel solidifies rapidly on the copper mold of the crystallizer covered with the protective slag film. The amplitude of the copper mold of the crystallizer is 2mm and the vibration frequency is 200 times / minute.

[0037] 4) When the copper mold of the crystallizer descends to the set position, the copper mold of the crystallizer stops moving downward and stays for 5 seconds. The initial solidified billet shell formed by the solidification of molten steel on the surface of the crystallizer reaches a thickness of 1-6mm. The billet pulling module is started to drive the solidified billet shell downward. At the same time, new molten steel comes into contact with the copper mold of the crystallizer and pulls out a certain length of the initial solidified billet shell. During this process, the permanent magnet stirring module is kept running. During the process of pulling out the initial solidified billet shell, the vibration motor of the copper mold of the crystallizer is turned off.

[0038] 5) The copper mold of the crystallizer moves upward together with the initial solidified billet shell to detach from the molten pool in the crucible. After cutting, the initial solidified billet shell of the crystallizer permanent magnet stirring square billet is obtained. The length of the initial solidified billet shell is 500mm. Finally, the permanent magnet stirring module of the crystallizer is turned off.

[0039] Example 2

[0040] An experimental method for preparing the initial solidified shell of a square billet using the above-mentioned apparatus includes the following steps:

[0041] 1) Place 22 kg of the required experimental steel in the crucible, place the crucible in the heating furnace, and adjust the height of the permanent magnet of the permanent magnet module according to the type of steel and experimental requirements to control the magnetic field strength at the crucible; the central magnetic field strength is controlled at 1400 Gs.

[0042] 2) Start the heating furnace to melt the experimental steel and maintain the temperature above the liquidus temperature of the steel grade. Start the permanent magnet stirrer and adjust the stirring speed to 180 rpm to ensure uniform composition and temperature of the molten steel. Then add the mold protective slag that matches the steel grade to the molten steel. After it is completely melted, a mold protective slag layer is formed, and the temperature of the mold protective slag layer is measured.

[0043] 3) Slowly insert the copper mold of the crystallizer into the molten pool, start the vibration motor of the copper mold of the crystallizer, and drive the copper mold of the crystallizer to vibrate at the set vibration frequency and vibration amplitude. The protective slag layer of the crystallizer cools rapidly on the copper mold of the crystallizer to form a protective slag film. As the copper mold of the crystallizer continues to be inserted, the molten steel solidifies rapidly on the copper mold of the crystallizer covered with the protective slag film. The amplitude of the copper mold of the crystallizer is 1 mm and the vibration frequency is 50 times / minute.

[0044] 4) When the copper mold of the crystallizer descends to the set position, the copper mold of the crystallizer stops moving downward and pauses for 1 second. The initial solidified billet shell formed by the solidification of molten steel on the surface of the crystallizer reaches a thickness of 1-6mm. The billet pulling module is started to drive the solidified billet shell downward. At the same time, new molten steel comes into contact with the copper mold of the crystallizer and pulls out a certain length of the initial solidified billet shell. During this process, the permanent magnet stirring module is kept running. During the process of pulling out the initial solidified billet shell, the vibration motor of the copper mold of the crystallizer is turned off.

[0045] 5) The copper mold of the crystallizer moves upward together with the initial solidified billet shell to detach from the molten pool in the crucible. After cutting, the initial solidified billet shell of the crystallizer permanent magnet stirring square billet is obtained. The length of the initial solidified billet shell is 300mm. Finally, the permanent magnet stirring module of the crystallizer is turned off.

[0046] Example 3

[0047] An experimental method for preparing the initial solidified shell of a square billet using the above-mentioned apparatus includes the following steps:

[0048] 1) Place 25 kg of the required experimental steel in the crucible, place the crucible in the heating furnace, and adjust the height of the permanent magnet of the permanent magnet module according to the type of steel and experimental requirements to control the magnetic field strength at the crucible; the central magnetic field strength is controlled at 1400 Gs.

[0049] 2) Start the heating furnace to melt the experimental steel and maintain the temperature above 70°C above the liquidus temperature of the steel grade; start the permanent magnet stirrer and adjust the stirring speed to 180 rpm to ensure uniform composition and temperature of the molten steel; then add the mold protective slag that matches the steel grade to the molten steel, and after it is completely melted, a mold protective slag layer is formed, and the temperature of the mold protective slag layer is measured.

[0050] 3) Slowly insert the copper mold of the crystallizer into the molten pool, start the vibration motor of the copper mold of the crystallizer, and drive the copper mold of the crystallizer to vibrate at the set vibration frequency and vibration amplitude. The protective slag layer of the crystallizer cools rapidly on the copper mold of the crystallizer to form a protective slag film. As the copper mold of the crystallizer continues to be inserted, the molten steel solidifies rapidly on the copper mold of the crystallizer covered with the protective slag film. The amplitude of the copper mold of the crystallizer is 6 mm and the vibration frequency is 350 times / minute.

[0051] 4) When the copper mold of the crystallizer descends to the set position, the copper mold of the crystallizer stops moving downward and stays for 10 seconds. The initial solidified billet shell formed by the solidification of molten steel on the surface of the crystallizer reaches a thickness of 1-6mm. The billet pulling module is started to drive the solidified billet shell downward. At the same time, new molten steel comes into contact with the copper mold of the crystallizer and pulls out a certain length of the initial solidified billet shell. During this process, the permanent magnet stirring module is kept running. During the process of pulling out the initial solidified billet shell, the vibration motor of the copper mold of the crystallizer is turned off.

[0052] 5) The copper mold of the crystallizer moves upward together with the initial solidified billet shell to detach from the molten pool in the crucible. After cutting, the initial solidified billet shell of the crystallizer permanent magnet stirring square billet is obtained. The length of the initial solidified billet shell is 800mm. Finally, the permanent magnet stirring module of the crystallizer is turned off.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An experimental method for preparing the initial solidified shell of a square billet, characterized in that: The apparatus includes a control system, a crucible for holding molten steel, a heating furnace for heating the crucible, a permanent magnet stirring module for permanently stirring the molten steel in the crucible, a crystallizer, and a casting module matched with the crystallizer. The crystallizer is equipped with a copper mold. The control system is electrically connected to the heating furnace, the permanent magnet stirring module, and the casting module. The permanent magnet stirring module includes a pair of permanent magnets, a permanent magnet rotary motor, and an up-and-down telescopic device. The permanent magnets are driven to rotate by the permanent magnet rotary motor, and both are mounted on the up-and-down telescopic device. It also includes a crystallizer copper mold vibration motor for driving the copper mold to vibrate, and the crystallizer copper mold vibration motor is electrically connected to the control system. The apparatus includes the following steps: 1) Place 20-25 kg of the required experimental steel in the crucible, place the crucible in the heating furnace, and adjust the height of the permanent magnet of the permanent magnet module according to the type of steel and experimental requirements to control the magnetic field strength at the crucible. 2) Start the heating furnace to melt the experimental steel and maintain the temperature above the liquidus temperature of the steel grade at 30-70℃; start the permanent magnet stirrer and adjust the stirring speed to ensure that the composition and temperature of the molten steel are uniform; then add the mold protective slag that matches the steel grade to the molten steel, and after it is completely melted, a mold protective slag layer is formed, and the temperature of the mold protective slag layer is measured. 3) Slowly insert the copper mold of the crystallizer into the molten pool, start the vibration motor of the copper mold of the crystallizer, and drive the copper mold of the crystallizer to vibrate at the set vibration frequency and vibration amplitude. The protective slag layer of the crystallizer cools rapidly on the copper mold of the crystallizer to form a protective slag film. As the copper mold of the crystallizer continues to be inserted, the molten steel solidifies rapidly on the copper mold of the crystallizer covered with the protective slag film. 4) When the copper mold of the crystallizer descends to the set position, the copper mold of the crystallizer stops moving downward and stays for 1-10 seconds. The initial solidified billet shell formed by the solidification of molten steel on the surface of the crystallizer reaches a thickness of 1-6mm. The billet pulling module is started to drive the solidified billet shell downward. At the same time, new molten steel comes into contact with the copper mold of the crystallizer and pulls out a certain length of the initial solidified billet shell. During this process, the permanent magnet stirring module is kept running. During the process of pulling out the initial solidified billet shell, the vibration motor of the copper mold of the crystallizer is turned off. 5) The copper mold of the crystallizer moves upward together with the initial solidified billet shell to get out of the molten pool in the crucible. After cutting, the initial solidified billet shell of the crystallizer permanent magnet stirred square billet is obtained; finally, the crystallizer permanent magnet stirring module is turned off.

2. The experimental method according to claim 1, characterized in that: The heating furnace is equipped with a heating element and a thermocouple.

3. The experimental method according to claim 2, characterized in that: The crucible includes an outer pot body and an inner pot body that are fitted together, and the thermocouple is placed between the outer pot body and the inner pot body.

4. The experimental method according to claim 3, characterized in that: The amplitude of the copper mold in the crystallizer is 1-6mm, and the frequency is 50-350 times / minute.

5. The experimental method according to claim 4, characterized in that: The length of the initial solidified shell is 300-800 mm.

Images