Method for electrically baking submersed nozzle

Abstract

The invention relates to a method for electrically baking a submersed nozzle, and aims to solve the technical problems of non-uniform baking temperature rise, poor quality, short service life and the like of an electrically baked nozzle. The heating curves are reasonably arranged and comprise the rapid heating stage, the steady-state heating stage and the heat preservation stage, it is guaranteed that the upper portion and the lower portion of the water gap are evenly heated, and the baking efficiency and quality are improved. The electric baking oven is adopted, the control cabinet can accurately control the baking temperature, and energy waste caused by too high or too low temperature is avoided. In addition, an electric heating mode is adopted, no waste gas is discharged during baking, pollution to the environment is completely avoided, and the green and environment-friendly development concept is met. The temperature in the baking process is monitored and adjusted in real time through the intelligent temperature control system, it is ensured that the water gap is baked within the proper temperature range, the baking quality of the water gap is improved, and the service life of the water gap is prolonged. Compared with gas baking, the service life of the nozzle is not affected by 8-hour baking, the baked nozzle has a continuous standby circulating function, the use amount of standby nozzles is reduced, and therefore the production cost is reduced. The method is easy to operate, one-key operation is adopted, automatic control is easy to achieve, the production efficiency can be improved, and the production cost can be reduced.

Description

Technical Field

[0001] This invention relates to a method for baking an immersion nozzle, and more particularly to a method for baking an immersion nozzle of a slab continuous casting machine, belonging to the field of steel smelting and continuous casting technology. Background Technology

[0002] As one of the three major components of continuous casting, the preheating of the submersible nozzle is extremely critical. It needs to be heated to over 900℃, with a baking time ranging from 40 minutes to several hours. During the baking process, rapid and uniform heating is essential, and it is crucial to prevent oxidation of the nozzle during preheating; these are key to ensuring its service life. A search revealed no curves or methods for the electric baking of submersible nozzles.

[0003] Immersion inlets need to be preheated before use. Common preheating methods include gas preheating, induction heating preheating, and resistance wire heating preheating.

[0004] After preliminary searching, the relevant existing technologies are as follows:

[0005] Chinese patent application CN 113976874 A discloses an electric heating intermediate ladle immersion type sprue baker. The electric heating baker has an oven temperature control accuracy of ±5℃, uniform sprue heating, and good heat preservation effect. It saves more than 20% energy compared to gas baking.

[0006] Chinese patent application CN 105215345 A discloses an induction heating intermediate ladle immersion nozzle baking device and method. The device uses an induction coil to bake the immersion nozzle. The device can bake multiple nozzles at the same time. It takes 40-60 minutes for the nozzle temperature to rise from room temperature to 1000℃, which reduces baking costs and environmental pollution.

[0007] Chinese patent application CN 104785768 A discloses a high-efficiency baking device for immersion nozzles in continuous casting tundishes, which can bake several immersion nozzles at once, raising the nozzle temperature from room temperature to 1000℃ in only 60 minutes, effectively improving the baking efficiency of nozzles.

[0008] Existing technologies for electric baking of submersible nozzles in continuous casting machines focus solely on the baking device, neglecting the specific baking process of the nozzles, thus failing to guarantee the quality of the nozzle baking. Furthermore, existing technologies lack a baking method for submersible nozzles in slab continuous casting machines, failing to address the problems of uneven heating, poor quality, and short service life associated with electric baking of nozzles. This makes it difficult to fully utilize the nozzle's performance in actual production, impacting not only production efficiency but also potentially increasing production costs. Therefore, there is an urgent need for a scientifically sound and reasonable method for baking submersible nozzles in slab continuous casting machines to improve nozzle quality and service life, ensuring stable and efficient continuous casting production. Summary of the Invention

[0009] This invention addresses the technical problems existing in the prior art by providing a method for electrically baking submersible nozzles. The main objective of this solution is to overcome the technical difficulties of uneven heating, poor quality, and short service life in current electrically baked nozzles. This invention successfully solves the problem of poor nozzle quality and effectively extends the service life of submersible nozzles in slab continuous casting machines. This innovation not only improves nozzle performance but also reduces production costs, bringing higher efficiency to continuous casting production. It provides a reliable solution to the problems encountered in the electric baking process of submersible nozzles in continuous casting machines, promoting technological progress in the industry.

[0010] To achieve the above objectives, the technical solution of the present invention is as follows: a method for baking a submersible nozzle in a slab continuous casting machine, comprising the following steps:

[0011] Step 1: Configure the electric baking oven;

[0012] The electric baking oven consists of a cabinet and a control cabinet. The control cabinet is located on the right side of the cabinet. The exterior of the cabinet is sealed with steel plates, and the interior is filled with refractory high-temperature cotton. The inner wall of the cabinet is lined with heating elements (silicon carbide rods), control components, and a temperature controller. The interior includes a slab immersion-type sprue support rack with an insulated cover on top. The front of the cabinet has a double-leaf sealed door with a bracket in front of it. This configuration provides a heat source and insulation for rapid heating of the sprues, while the control cabinet enables precise temperature control during baking.

[0013] Step 2: Prepare auxiliary equipment; the auxiliary equipment includes guide rails, clamps, support frames, and brackets. The clamps hold the sprue on the bracket and guide it into the oven for baking, facilitating the baking and removal of the sprue's immersion sprue.

[0014] Step 3: The impact of low-temperature baking on immersion gates and the feasibility analysis of rapid heating to 1100℃;

[0015] First, consider the impact of low-temperature baking on the refractory properties of slabs with immersion gates:

[0016] Incomplete curing: When the baking temperature is too low, the glaze components cannot fully react and combine, affecting the density of the structure, leading to the appearance of pores and micro-defects, and reducing the resistance to corrosion of molten steel.

[0017] Insufficient thermal stability: Low-temperature baking may cause incomplete curing of the glaze layer on the nozzle. When exposed to high temperatures of molten steel, insufficient thermal stability may cause cracks or peeling, affecting the service life of the nozzle and the quality of the molten steel.

[0018] Decreased chemical stability: Low-temperature baking leads to incomplete transformation of chemical substances in the glaze, resulting in decreased chemical stability. When in contact with molten steel, the glaze easily reacts chemically with components in the steel, compromising its integrity and reducing its protective effect.

[0019] Reduced mechanical strength: When the glaze layer does not reach a sufficient temperature, crystal growth and bonding are incomplete, resulting in insufficient mechanical strength. Under the impact of molten steel and pressure, the glaze layer is easily worn and damaged, failing to effectively perform its isolation and protective functions.

[0020] Weakened bonding strength: Due to the different coefficients of thermal expansion, low-temperature baking may prevent the glaze and the body from deforming together when the temperature changes, resulting in stress concentration, weakening the bonding strength, and increasing the risk of glaze peeling off.

[0021] Secondly, a feasibility calculation for raising the temperature of the immersion inlet to 1100℃ in 40 minutes is performed:

[0022] When the electric oven starts operating, the heating element generates heat, which is transferred to the air inside the oven through radiation and convection. As the air temperature rises, heat is then transferred to the surface of the submersible gate through convection. The surface of the submersible gate absorbs heat, and its temperature gradually increases, while simultaneously transferring heat to the interior through conduction. Over time, the temperature of the submersible gate continuously rises until it reaches the set temperature of 1100℃.

[0023] Heat required for heating the submersible nozzle: Assuming the initial temperature of the submersible nozzle is room temperature (25℃) and its specific heat capacity is 1 KJ / (Kg·℃), and considering a total mass of 65 kg for heating two nozzles together, the heat required for heating is Q = 65 × 1 × (1100 - 25) = 69875 KJ.

[0024] The heating furnace provides the following heat: Heating time is 40 minutes, which translates to 40 ÷ 60 = 2 / 3 hours. The furnace power is 50 kilowatts, or 50,000 watts. According to the relationship between power and heat, Q = Pt, the furnace provides 50,000 × (2 / 3) × 3600 = 120,000,000 joules = 120,000 kJ. Comparing the required heat and the provided heat, the furnace provides significantly more heat than is needed to raise the temperature, making it theoretically feasible.

[0025] The electric baking equipment was set to a power of 50kW and a voltage of 380V, and the actual temperature rise of the sprue was measured. Practical data showed that setting the oven temperature to 1100℃ for baking met both the temperature requirements of the slab immersion sprue material and the requirements of on-site production organization.

[0026] Step 4: Establish baking temperature rise and hold curves and set up an automatic temperature control system:

[0027] The heating curve is divided into the following three stages:

[0028] The first stage is the rapid heating stage. When the immersion gate is placed inside the oven, the power of the electric baking equipment is increased to rapidly heat the immersion gate. The heating rate is set to 32℃ / min, the temperature range is from room temperature to 800℃, and the time is 25 minutes.

[0029] The rationale for determining this heating parameter is as follows:

[0030] 1. The foundation for building the model

[0031] Determining the heating rate requires comprehensive consideration of factors such as the material properties, dimensions, and heat transfer process of the submersible nozzle. For slab submersible nozzles, the material typically possesses a certain thermal conductivity and coefficient of thermal expansion, while the dimensions determine its heat capacity and the length of the heat transfer path. Heat transfer primarily occurs through radiation, convection, and conduction. Electric baking ovens generate heat through heating elements, transferring it to the air inside the oven via radiation and convection. The air then transfers the heat to the nozzle surface, and finally, conduction raises the internal temperature of the nozzle.

[0032] 2. Model Assumptions

[0033] Assume that the immersion nozzle is made of a homogeneous material and that all parts have the same thermal properties.

[0034] Ignore the thermal resistance between the sprue and the internal support structure of the oven.

[0035] It is assumed that the heat generated by the heating element is evenly distributed within the oven's interior space.

[0036] During heat transfer, the combined heat transfer coefficient of radiation and convection remains constant.

[0037] 3. Heat transfer equation

[0038] According to the principle of heat transfer, the heat absorbed by the sluice gate can be expressed by the following equation:

[0039]

[0040] Where Q is the heat, m is the mass of the nozzle, and c is the specific heat capacity of the nozzle. This is the rate of change of temperature over time, i.e., the heating rate.

[0041] 4. Parameter Determination

[0042] Sprue weight: It is known that the total weight of two sprues used for baking together is 65 kg.

[0043] Specific heat capacity: Assume the specific heat capacity of the immersion nozzle is 1 kJ / (kg·℃).

[0044] 5. Calculation process

[0045] ◆First, calculate the heat absorbed by the water outlet at different heating rates.

[0046] When the heating rate is 32℃ / min, the temperature rises by 32℃ in 1 minute, and the amount of heat absorbed is...

[0047] Assuming that at this heating rate, the outlet temperature rises from the initial temperature to the target temperature after a period of time.

[0048] According to the heat transfer equation That is, 2080 = 65 × 1 × 32, the equation holds true, indicating that at this heating rate, the heat absorption matches the temperature change.

[0049] ◆Analyze the internal thermal stress of the sprue.

[0050] Excessive heating rate can lead to significant thermal stress inside the nozzle, potentially causing cracks or damage. Finite element analysis and other methods can be used to calculate the thermal stress distribution inside the nozzle at different heating rates.

[0051] Simulation calculations revealed that when the heating rate is around 32℃ / min, the thermal stress inside the nozzle is within the tolerance range of the material. If the heating rate exceeds this value, the thermal stress will increase significantly, potentially exceeding the material's strength limit.

[0052] ◆Consider heat transfer efficiency.

[0053] The heating rate must not only ensure rapid heating of the nozzle but also guarantee high heat transfer efficiency. If the heating rate is too slow, although the thermal stress will be lower, it will prolong the baking time and reduce production efficiency.

[0054] Through analysis of the heat transfer process inside the oven and multiple experiments, it was found that when the heating rate is 32℃ / min, the radiative and convective heat transfer can better meet the heating requirements of the sprue, while conduction can also make the internal temperature of the sprue rise more evenly.

[0055] The second stage is the rapid heating stage followed by the steady-state heating stage. Once the immersion gate reaches 800℃, the heating rate is controlled at 20℃ / min. The temperature range is 800-1100℃, and the time is 15 minutes. Reducing the heating rate in this stage ensures a more uniform temperature inside the gate, preventing localized overheating. A heating rate of 20℃ / min allows for efficient achievement of the target temperature of 1100℃ while maintaining temperature uniformity.

[0056] The third stage is the rapid heating and holding stage. Once the immersion gate reaches the predetermined baking temperature, the temperature is maintained for a stable period. The holding temperature is generally 900℃-1100℃, and the time is 40-640 minutes. The gate can be used immediately after baking. The purpose of the holding stage is to homogenize the internal temperature of the gate, improving the baking quality. Determining the holding temperature range and time ensures that the gate is fully heated, eliminates internal stress, and improves its performance and service life. Practical experience has shown that within this temperature range and time, the gate achieves good baking results.

[0057] Compared with the prior art, the advantages of the present invention are as follows:

[0058] 1. Improved baking efficiency and rapid heating: Existing technologies may use traditional heating methods, resulting in relatively slow heating rates. This invention, however, by rationally setting the heating curve, can achieve a heating rate of 32℃ / min during the rapid heating phase, significantly shortening baking time and improving production efficiency.

[0059] Uniform heating: Existing technologies may suffer from uneven heating, leading to overheating or undercooling in certain areas of the sprue, affecting baking quality. The heating curve design of this invention includes a steady-state heating stage and a heat preservation stage, ensuring uniform heating of the upper and lower parts of the sprue, thus improving baking efficiency and quality.

[0060] 2. Reduced energy consumption and precise temperature control: This invention uses an electric baking oven, and the control cabinet enables precise temperature control during baking. Compared to existing technologies, this avoids energy waste caused by excessively high or low temperatures. Once the desired temperature is reached, the automatic temperature control system can maintain the temperature stably, further reducing energy consumption.

[0061] A reasonable heating curve was developed based on the material and size of the sprue. This minimized unnecessary energy consumption while ensuring baking quality. For example, different heating rates were used at different stages, satisfying the need for rapid heating while avoiding excessive energy consumption.

[0062] 3. Environmentally friendly and pollution-free, with zero emissions: In existing technologies, some heating methods may generate exhaust emissions, causing environmental pollution. This invention uses electric heating, which produces no exhaust emissions during baking, completely avoiding environmental pollution and truly achieving zero emissions, in line with the concept of green and environmentally friendly development.

[0063] Reduced generation of harmful gases: Since there are no exhaust emissions, the health hazards to on-site operators are greatly reduced, creating a safe and reliable working environment for staff.

[0064] 4. Improve the quality and service life of the nozzle and avoid the defects of low-temperature baking: In existing technologies, low-temperature baking may lead to problems such as incomplete curing, insufficient thermal stability, decreased chemical stability, reduced mechanical strength, and weakened bonding strength, affecting the service life of the nozzle and the quality of molten steel. This invention avoids these defects of low-temperature baking through a reasonable heating curve, improving the performance and quality of the nozzle. Precise temperature control: The intelligent temperature control system can monitor and adjust the temperature during the baking process in real time, ensuring that the nozzle is baked within a suitable temperature range. This results in uniform temperature inside the nozzle, improving the baking quality and service life of the nozzle. Compared with gas-fired baking, gas-fired baking for more than 4 hours affects the service life of the nozzle, while this invention bakes for 8 hours without affecting the service life of the nozzle.

[0065] 5. Easy to operate and achieve automated control, one-button operation: The method of this invention is simple to operate, requiring only one button. Compared with the complex operation process in existing technologies, it greatly reduces the workload of operators and improves work efficiency.

[0066] Automated control: Enables automated control, reducing the impact of human factors on the baking process. The automatic temperature control system can automatically raise and maintain the temperature throughout the entire process, ensuring the stability and reliability of the baking process. Attached Figure Description

[0067] Figure 1 A schematic diagram showing the temperature requirements of the material for the immersion gate of the slab.

[0068] Figure 2 This is a schematic diagram of the preheating curve for an immersion nozzle.

[0069] Figure 3 This is a schematic diagram of a slab being baked in an electric oven using an immersion gate. Detailed Implementation

[0070] To enhance understanding of the present invention, the embodiments will be described in detail below with reference to the accompanying drawings.

[0071] Example 1: A method for baking a submersible nozzle in a slab continuous casting machine, comprising the following steps:

[0072] Step 1: Configure the electric baking oven;

[0073] The electric baking oven consists of a cabinet and a control cabinet. The control cabinet is located on the right side of the cabinet. The exterior of the cabinet is sealed with steel plates, and the interior is filled with refractory high-temperature cotton. The inner wall of the cabinet is lined with heating elements (silicon carbide rods), control components, and a temperature controller. The interior includes a slab immersion-type sprue support rack with an insulated cover on top. The front of the cabinet has a double-leaf sealed door with a bracket in front of it. This configuration provides a heat source and insulation for rapid heating of the sprues, while the control cabinet enables precise temperature control during baking.

[0074] Step 2: Prepare auxiliary equipment; the auxiliary equipment includes guide rails, clamps, support frames, and brackets. The clamps hold the sprue on the bracket and guide it into the oven for baking, facilitating the baking and removal of the sprue's immersion sprue.

[0075] Step 3: The impact of low-temperature baking on immersion gates and the feasibility analysis of rapid heating to 1100℃;

[0076] First, consider the impact of low-temperature baking on the refractory properties of slabs with immersion gates:

[0077] Incomplete curing: When the baking temperature is too low, the glaze components cannot fully react and combine, affecting the density of the structure, leading to the appearance of pores and micro-defects, and reducing the resistance to corrosion of molten steel.

[0078] Insufficient thermal stability: Low-temperature baking may cause incomplete curing of the glaze layer on the nozzle. When exposed to high temperatures of molten steel, insufficient thermal stability may cause cracks or peeling, affecting the service life of the nozzle and the quality of the molten steel.

[0079] Decreased chemical stability: Low-temperature baking leads to incomplete transformation of chemical substances in the glaze, resulting in decreased chemical stability. When in contact with molten steel, the glaze easily reacts chemically with components in the steel, compromising its integrity and reducing its protective effect.

[0080] Reduced mechanical strength: When the glaze layer does not reach a sufficient temperature, crystal growth and bonding are incomplete, resulting in insufficient mechanical strength. Under the impact of molten steel and pressure, the glaze layer is easily worn and damaged, failing to effectively perform its isolation and protective functions.

[0081] Weakened bonding strength: Due to the different coefficients of thermal expansion, low-temperature baking may prevent the glaze and the body from deforming together when the temperature changes, resulting in stress concentration, weakening the bonding strength, and increasing the risk of glaze peeling off.

[0082] Secondly, a feasibility calculation for raising the temperature of the immersion inlet to 1100℃ in 40 minutes is performed:

[0083] When the electric oven starts operating, the heating element generates heat, which is transferred to the air inside the oven through radiation and convection. As the air temperature rises, heat is then transferred to the surface of the submersible gate through convection. The surface of the submersible gate absorbs heat, and its temperature gradually increases, while simultaneously transferring heat to the interior through conduction. Over time, the temperature of the submersible gate continuously rises until it reaches the set temperature of 1100℃.

[0084] Heat required for heating the submersible nozzle: Assuming the initial temperature of the submersible nozzle is room temperature (25℃) and its specific heat capacity is 1 KJ / (Kg·℃), and considering a total mass of 65 kg for heating two nozzles together, the heat required for heating is Q = 65 × 1 × (1100 - 25) = 69875 KJ.

[0085] The heating furnace provides the following heat: Heating time is 40 minutes, which translates to 40 ÷ 60 = 2 / 3 hours. The furnace power is 50 kilowatts, or 50,000 watts. According to the relationship between power and heat, Q = Pt, the furnace provides 50,000 × (2 / 3) × 3600 = 120,000,000 joules = 120,000 kJ. Comparing the required heat and the provided heat, the furnace provides significantly more heat than is needed to raise the temperature, making it theoretically feasible.

[0086] The electric baking equipment was set to a power of 50kW and a voltage of 380V, and the actual temperature rise of the sprue was measured. Practical data showed that setting the oven temperature to 1100℃ for baking met both the temperature requirements of the slab immersion sprue material and the requirements of on-site production organization.

[0087] Step 4: Establish baking temperature rise and hold curves and set up an automatic temperature control system:

[0088] The heating curve is divided into the following three stages:

[0089] The first stage is the rapid heating stage. When the immersion gate is placed inside the oven, the power of the electric baking equipment is increased to rapidly heat the immersion gate. The heating rate is set to 32℃ / min, the temperature range is from room temperature to 800℃, and the time is 25 minutes.

[0090] The rationale for determining this heating parameter is as follows:

[0091] 1. The foundation for building the model

[0092] Determining the heating rate requires comprehensive consideration of factors such as the material properties, dimensions, and heat transfer process of the submersible nozzle. For slab submersible nozzles, the material typically possesses a certain thermal conductivity and coefficient of thermal expansion, while the dimensions determine its heat capacity and the length of the heat transfer path. Heat transfer primarily occurs through radiation, convection, and conduction. Electric baking ovens generate heat through heating elements, transferring it to the air inside the oven via radiation and convection. The air then transfers the heat to the nozzle surface, and finally, conduction raises the internal temperature of the nozzle.

[0093] 2. Model Assumptions

[0094] Assume that the immersion nozzle is made of a homogeneous material and that all parts have the same thermal properties.

[0095] Ignore the thermal resistance between the sprue and the internal support structure of the oven.

[0096] It is assumed that the heat generated by the heating element is evenly distributed within the oven's interior space.

[0097] During heat transfer, the combined heat transfer coefficient of radiation and convection remains constant.

[0098] 3. Heat transfer equation

[0099] According to the principle of heat transfer, the heat absorbed by the sluice gate can be expressed by the following equation:

[0100]

[0101] Where Q is the heat, m is the mass of the nozzle, and c is the specific heat capacity of the nozzle. This is the rate of change of temperature over time, i.e., the heating rate.

[0102] 4. Parameter Determination

[0103] Sprue weight: It is known that the total weight of two sprues used for baking together is 65 kg.

[0104] Specific heat capacity: Assume the specific heat capacity of the immersion nozzle is 1 kJ / (kg·℃).

[0105] 5. Calculation process

[0106] ◆First, calculate the heat absorbed by the water outlet at different heating rates.

[0107] When the heating rate is 32℃ / min, the temperature rises by 32℃ in 1 minute, and the amount of heat absorbed is...

[0108] Assuming that at this heating rate, the outlet temperature rises from the initial temperature to the target temperature after a period of time.

[0109] According to the heat transfer equation That is, 2080 = 65 × 1 × 32, the equation holds true, indicating that at this heating rate, the heat absorption matches the temperature change.

[0110] ◆Analyze the internal thermal stress of the sprue.

[0111] Excessive heating rate can lead to significant thermal stress inside the nozzle, potentially causing cracks or damage. Finite element analysis and other methods can be used to calculate the thermal stress distribution inside the nozzle at different heating rates.

[0112] Simulation calculations revealed that when the heating rate is around 32℃ / min, the thermal stress inside the nozzle is within the tolerance range of the material. If the heating rate exceeds this value, the thermal stress will increase significantly, potentially exceeding the material's strength limit.

[0113] ◆Consider heat transfer efficiency.

[0114] The heating rate must not only ensure rapid heating of the nozzle but also guarantee high heat transfer efficiency. If the heating rate is too slow, although the thermal stress will be lower, it will prolong the baking time and reduce production efficiency.

[0115] Through analysis of the heat transfer process inside the oven and multiple experiments, it was found that when the heating rate is 32℃ / min, the radiative and convective heat transfer can better meet the heating requirements of the sprue, while conduction can also make the internal temperature of the sprue rise more evenly.

[0116] The second stage is the rapid heating stage followed by the steady-state heating stage. Once the immersion gate reaches 800℃, the heating rate is controlled at 20℃ / min. The temperature range is 800-1100℃, and the time is 15 minutes. Reducing the heating rate in this stage ensures a more uniform temperature inside the gate, preventing localized overheating. A heating rate of 20℃ / min allows for efficient achievement of the target temperature of 1100℃ while maintaining temperature uniformity.

[0117] The third stage is the rapid heating and holding stage. Once the immersion gate reaches the predetermined baking temperature, the temperature is maintained for a stable period. The holding temperature is generally 900℃-1100℃, and the time is 40-640 minutes. The gate can be used immediately after baking. The purpose of the holding stage is to homogenize the internal temperature of the gate, improving the baking quality. Determining the holding temperature range and time ensures that the gate is fully heated, eliminates internal stress, and improves its performance and service life. Practical experience has shown that within this temperature range and time, the gate achieves good baking results.

[0118] Example 2: A method for baking the submersible nozzle of a slab continuous casting machine.

[0119] 1. Temperature rise measurement at different temperatures:

[0120] The actual temperature rise of the sprue was measured using a handheld temperature gun at baking temperatures of 900 / 1000 / 1100 / 1200℃. The measurement data are summarized below:

[0121]

[0122] Based on the above practical data, setting the oven temperature to 1100℃ for baking satisfies both the temperature rise requirements of the slab material for immersion sprue and the requirements of on-site production organization. Therefore, 1100℃ was selected for baking and heat preservation on-site.

[0123] 2. Temperature tracking under automatic temperature control curve:

[0124]

[0125] Note: Time is in minutes; temperature is in degrees Celsius.

[0126] The entire process is automated, ensuring uniform preheating and a stable and reliable baking process.

[0127] 3. Tracking of sprue quality and service life:

[0128]

[0129] Note: Time unit is min; Sprue baking (use) is normal ★ Sprue oxidation - abnormalities such as cracking during sprue use ÷, sprues are baked according to this temperature rise curve, and the quality and service life are normal.

[0130] 4. First-time use of the electric oven, preparations before baking with a new sprue, handling of special situations such as baking with a new sprue, and safety precautions:

[0131] ◆First use of the electric oven:

[0132] When using the oven for the first time, it is necessary to preheat the oven to remove moisture from the lining and improve insulation performance. Baking time is 12 hours from room temperature to 200°C, and 8 hours from 200°C to 500°C. Afterward, bake at the normal gate baking temperature. This is because the new oven lining contains moisture. Without preheating, this moisture may rapidly vaporize during subsequent high-temperature baking, creating steam pressure that could damage the lining or affect baking results. Gradually increasing the oven temperature during preheating safely removes moisture and improves equipment reliability.

[0133] ◆Preparation before baking new sprue:

[0134] Before baking new sprues, ensure the electric baking oven is in heat preservation mode, with the set temperature between 1080-1120℃ and the actual temperature falling within this range. This ensures the oven is ready for use. This guarantees rapid heating after the sprues are placed in the oven, improving production efficiency. Maintaining a suitable temperature range also contributes to the baking quality of the sprues.

[0135] ◆ Baking of new sprues:

[0136] When the electric oven temperature is normal, new sprue nozzles should be preheated for 60-100 minutes before use. Place a new sprue nozzle on the front door support of the oven, clamp it with the holder, and open the oven door approximately 200-300mm from the neck. Push the track cart to place the nozzle on the oven storage rack. Preheating the new sprue nozzles ensures they have reached the appropriate temperature and baking quality before use, preventing production disruptions due to insufficient baking.

[0137] ◆Safety Precautions:

[0138] The water outlet electric heating device consists of refractory high-temperature cotton, high-temperature silicon carbide heating element, steel plate, control components, temperature controller, etc. During installation, leakage protection function must be provided to ensure leakage or electric shock protection.

[0139] During installation and use, ensure that the grounding device is reliably grounded to ensure the safety of operators. Operators are strictly prohibited from directly contacting the power supply and are only responsible for operating the control box. Report any malfunctions to professional repair personnel in a timely manner.

[0140] When using the baking oven for the first time, the oven lining should be dried to remove moisture and improve insulation performance. Bake at room temperature to 200°C for 12 hours, then at 200 to 500°C for 8 hours, and then bake at the normal gate baking temperature.

[0141] It is strictly forbidden to throw flammable and explosive materials such as gloves, or corrosive liquids, into the furnace. It is also forbidden to bake other tools and equipment that are not sprue types inside the furnace.

[0142] The electric oven heats the water inlet at 1080-1120℃ for an extended period. The surface temperature of the oven's steel plate, handles, and other metal surfaces is approximately 100℃. Do not open the door directly with your hands or touch the exterior of the oven to prevent burns.

[0143] To remove the drain spout, a clamp must be inserted into the oven to hold it in place. After removing the clamp, the tip of the clamp will be slightly hot. When lifting or handling the drain spout, protective gloves must be worn securely to prevent direct contact with human skin and to avoid burns.

[0144] Two people must work together to handle the placement and removal of the slab immersion gate. Pay attention to the surrounding environment of the electric baking oven, the rotation of the large ladle, and prevent collisions with the railcar under your feet.

[0145] When changing the water inlet, the oven door must be securely fixed after opening to prevent it from rotating automatically and causing burns. All personnel must wear appropriate protective equipment.

[0146] It should be noted that the above embodiments are not intended to limit the scope of protection of the present invention. Equivalent transformations or substitutions made based on the above technical solutions all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for electrically baking an immersion sprue, characterized in that, The method includes the following steps: Step 1: Configure the electric baking oven; the electric baking oven includes the oven body and the control cabinet; the oven can provide a heat source and insulation for rapid heating of the sprue, and the control cabinet enables precise temperature control of the baking process. Step 2: Prepare the necessary auxiliary equipment for the electric oven. Step 3: The impact of low-temperature baking on immersion gates and feasibility analysis of rapid heating to 1100℃. Step 4: Establish baking temperature rise and heat preservation curves and set up an automatic temperature control system.

2. The method for electrically baking immersion gates according to claim 1, characterized in that, Step 1: Configure the electric baking oven, as follows: The electric baking oven includes a cabinet and a control cabinet. The control cabinet is located on the right side of the cabinet. The exterior of the cabinet is sealed with steel plates, and the interior is filled with refractory high-temperature cotton. The inner wall of the cabinet is lined with heating elements, silicon carbide rods, control components, and a temperature controller. The interior is equipped with a slab immersion-type sprue support storage rack, and the top is equipped with an insulation cover. The front of the cabinet has a double-opening sealed door, and a bracket is located in front of the door. The control cabinet enables precise temperature control of the baking process.

3. The method for electrically baking immersion gates according to claim 1, characterized in that, Step 2: Prepare auxiliary equipment, which includes guide rails, clamps, support frames and brackets. The clamps are used to hold the sprue on the bracket and send it into the box for baking, so as to facilitate the baking and removal of the sprue immersion sprue.

4. The method for electrically baking immersion gates according to claim 2, characterized in that, Step 3: The impact of low-temperature baking on immersion gates and the feasibility analysis of rapid heating to 1100℃ are as follows: First, consider the impact of low-temperature baking on the refractory properties of slabs with immersion gates: Incomplete curing: When the baking temperature is too low, the glaze components cannot fully react and bond, affecting the density of the structure, leading to porosity and microscopic defects, and reducing the resistance to corrosion of molten steel. Insufficient thermal stability: Low-temperature baking may result in incomplete curing of the glaze layer on the nozzle. When exposed to the high temperature of molten steel, insufficient thermal stability can lead to cracks or peeling, affecting the service life of the nozzle and the quality of the molten steel. Decreased chemical stability: Low-temperature baking leads to incomplete transformation of chemical substances in the glaze, resulting in decreased chemical stability. When in contact with molten steel, the glaze easily reacts chemically with components in the steel, compromising its integrity and reducing its protective effect. Reduced mechanical strength: When the glaze layer does not reach a sufficient temperature, crystal growth and bonding are incomplete, resulting in insufficient mechanical strength. Under the scouring and pressure of molten steel, the glaze layer is easily worn and damaged, failing to effectively perform its isolation and protective functions. Weakened bonding strength: Due to the difference in thermal expansion coefficients, low-temperature baking may prevent the glaze layer and the substrate from deforming in tandem with temperature changes, resulting in stress concentration, weakening the bonding strength, and increasing the risk of glaze layer peeling off. Secondly, a feasibility calculation for raising the temperature of the immersion inlet to 1100℃ in 40 minutes is performed: When the electric baking oven starts working, the heating element generates heat, which is transferred to the air inside the oven through radiation and convection. After the air temperature rises, the heat is then transferred to the surface of the submersible gate through convection. The surface of the submersible gate absorbs heat and its temperature gradually rises. At the same time, heat is transferred to the interior through conduction. Over time, the temperature of the submersible gate continues to rise until it reaches the set temperature of 1100℃. Heat required to heat up the submersible nozzle: Assuming the initial temperature of the submersible nozzle is room temperature (25℃) and its specific heat capacity is 1 KJ / (Kg·℃), and using a total mass of 65 kg for heating two nozzles together, the heat required for heating is Q = 65 × 1 × (1100 - 25) = 69875 KJ. The heat provided by the heating furnace: The heating time of 40 minutes is converted to hours as 40 ÷ 60 = 2 / 3 hours. The power of the heating furnace is 50 kilowatts, or 50,000 watts. According to the relationship between power and heat, Q = Pt, the heat provided by the heating furnace is 50,000 × (2 / 3) × 3600 = 120,000,000 joules = 120,000 kJ.

5. The method for electrically baking immersion gates according to claim 4, characterized in that, Step 4: Establish baking temperature rise and hold curves and set up an automatic temperature control system, as detailed below. The heating curve is divided into the following three stages: The first stage, the rapid heating stage, involves placing the immersion gate into the oven and increasing the power of the electric baking equipment to rapidly heat the immersion gate. The heating rate is set to 32℃ / min, the temperature range is from room temperature to 800℃, and the time is 25 minutes. The rationale for determining this heating parameter is as follows: 1) The foundation for establishing the model, Determining the heating rate requires comprehensive consideration of factors such as the material properties, dimensions, and heat transfer process of the submersible nozzle. For slab submersible nozzles, the material typically has a certain thermal conductivity and coefficient of thermal expansion. The dimensions determine its heat capacity and the length of the heat transfer path. Heat transfer mainly occurs through radiation, convection, and conduction. Electric baking ovens generate heat through heating elements, which is then transferred to the air inside the oven via radiation and convection. The air then transfers the heat to the nozzle surface, and finally, conduction raises the internal temperature of the nozzle. 2) Model assumptions, Assuming the immersion gate is made of a homogeneous material and all parts have the same thermal properties, Ignoring the thermal resistance between the sprue and the internal support structure of the oven It is assumed that the heat generated by the heating element is evenly distributed within the oven's interior space. During heat transfer, the combined heat transfer coefficient of radiation and convection remains constant. 3) Heat transfer equation, According to the principle of heat transfer, the heat absorbed by the sluice gate can be expressed by the following equation: Where Q is the heat, m is the mass of the nozzle, and c is the specific heat capacity of the nozzle. This is the rate of change of temperature over time, i.e., the rate of temperature increase. 4) Parameter determination, Sprue weight: It is known that the total weight of two sprues used for baking together is 65 kg. Specific heat capacity: Assume the specific heat capacity of the immersion nozzle is 1 kJ / (kg·℃). 5) Calculation process, First, calculate the heat absorbed by the nozzle under different heating rates. When the heating rate is 32℃ / min, the temperature rises by 32℃ in 1 minute, then the amount of heat absorbed is... Assuming that at this heating rate, after a period of time, the nozzle temperature rises from the initial temperature to the target temperature, According to the heat transfer equation That is, 2080 = 65 × 1 × 32, the equation holds true, indicating that at this heating rate, the heat absorption matches the temperature change. The second stage, the rapid heating stage and the steady-state heating stage, involves raising the temperature of the immersion gate to 800℃, then controlling the heating rate at 20℃ / min, with a temperature range of 800-1100℃ and a time of 15 minutes. This reduced heating rate aims to ensure a more uniform temperature inside the gate and prevent localized overheating. A heating rate of 20℃ / min allows for efficient achievement of the target temperature of 1100℃ while maintaining temperature uniformity. The third stage is the rapid heating and heat preservation stage. After the immersion gate reaches the predetermined baking temperature, the temperature is kept stable for a period of time for heat preservation. The heat preservation temperature is 900℃-1100℃ and the time is 40-640 minutes. The gate can be used at any time after the baking is completed.

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