A device and method for synergistically regulating the thickness of the rotating liquid and the solidified shell in semi-continuous casting of magnesium alloy

Abstract

The application discloses a kind of magnesium alloy semi-continuous casting's liquid transfer and shell thickness coordination control device and method, the device mainly includes liquid transfer control system, condensed shell thickness partition control system and integrated controller.Liquid transfer control system is driven conical stopper by servo motor, cooperates temperature and flow sensor, realizes the accurate automatic control of metal melt flow;Condensed shell thickness partition control system is uniformly arranged multiple independent cooling units around crystallizer, and infrared thermometer is correspondingly arranged, and actual condensed shell thickness is calculated according to real-time temperature feedback by integrated controller, and the flow of cooling medium of each cooling unit is dynamically adjusted, and the partition closed-loop control of condensed shell thickness is formed.The application realizes the collaborative optimization of liquid transfer stability and circumferential condensed shell thickness uniformity, can control the difference of ingot circumferential condensed shell thickness within 0.4mm, significantly reduces surface drawing mark, crack and other casting defects, effectively improves ingot quality and production safety.

Description

Technical Field

[0001] This invention relates to the field of semi-continuous casting technology for magnesium alloys, specifically to a device and method for achieving automatic control of liquid transfer and precise regional control of ingot shell thickness during the semi-continuous casting process of magnesium alloys. It is particularly suitable for solving technical problems such as the large safety hazards of traditional manual liquid transfer and uneven circumferential thickness of the solidified shell. Background Technology

[0002] Semi-continuous casting is the core process for the large-scale production of magnesium alloy ingots, with the two key stages of liquid transfer and shell solidification control directly determining the ingot quality. During liquid transfer, the magnesium alloy melt has high chemical reactivity, and manual control of the stopper rod can easily lead to drastic fluctuations in the liquid level within the crystallizer and melt splashing due to operational errors, causing localized oxidation and inclusions in the ingot. During shell solidification, if the shell is too thick, the friction between the ingot and the crystallizer wall increases during casting, easily resulting in scratches on the surface; if the shell is too thin or uneven, it can easily lead to serious safety accidents such as cracking and leakage, and internal defects such as cracks and central segregation may also occur due to stress concentration within the ingot.

[0003] Currently, liquid transfer control largely relies on manual operation of stopper rods, resulting in unsatisfactory repeatability and response speed. Solidification shell thickness detection methods are mostly single-point, failing to reflect the circumferential thickness distribution of the ingot. Cooling systems lack zonal adjustment capabilities, making it difficult to promptly address solidification differences in different locations, thus hindering the maintenance of uniform circumferential solidification shell thickness. Furthermore, existing technologies cannot effectively combine liquid transfer flow control with solidification shell thickness regulation; these two aspects are disconnected, further restricting significant improvements in ingot quality. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a device and method for coordinated control of melt transfer and solidified shell thickness in semi-continuous casting of magnesium alloys. This solution combines automated melt transfer with closed-loop control of solidified shell thickness based on circumferential multi-point temperature monitoring, which can significantly reduce melt level fluctuations and ensure that the circumferential solidified shell thickness difference of the ingot is controlled within 0.4 mm, thereby systematically improving ingot quality and production safety.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A device for coordinated control of melt transfer and solidification shell thickness in semi-continuous casting of magnesium alloys includes a melt transfer control system, a solidification shell thickness zone control system, and an integrated controller. The melt transfer control system utilizes a servo motor to drive a stopper rod, combined with feedback from temperature and flow sensors, to achieve precise closed-loop control of the molten metal flow rate. The solidification shell thickness zone control system arranges multiple independent cooling units around the crystallizer, each equipped with a corresponding infrared thermometer. The integrated controller calculates the target solidification shell thickness and the actual thickness in real time, independently adjusting the cooling units; simultaneously, it integrates the melt transfer control and solidification shell control loops, stabilizing the melt level by fine-tuning the stopper rod opening, thus forming a coordinated melt transfer and solidification shell thickness control system.

[0006] A semi-continuous casting method for magnesium alloys using the above-mentioned apparatus includes the following steps.

[0007] Step 1: Based on the alloy's thermophysical parameters and cooling conditions, calculate the target thickness of the initial solidified shell using a mathematical model.

[0008] Step 2: Preheat the melting furnace, guide pipes, etc., to the specified temperature and maintain this temperature. Start casting; molten metal flows into the crystallizer through the guide pipes. In the initial stage, the integrated controller precisely controls the servo motor to drive the stopper rod based on temperature and flow signals, ensuring the melt smoothly covers the bottom of the crystallizer to prevent splashing and oxidation. Subsequently, the flow rate is appropriately increased. Throughout the filling and casting process, the integrated controller continuously adjusts the stopper rod opening to maintain a stable melt level.

[0009] Step 3: Once the initial solidified shell in the crystallizer reaches the target thickness, start the casting mechanism. The casting speed and shell thickness follow the square root law of solidification to ensure that the solidified shell does not break during the initial casting stage.

[0010] Step 4: During the casting process, multiple sets of infrared thermometers evenly distributed below the crystallizer collect the temperature field of the circumferential surface of the ingot in real time, and convert the temperature data into the actual solidified shell thickness in each direction through a heat transfer back-calculation model.

[0011] Step 5: The integrated controller compares the deviation between the actual thickness and the target thickness in real time at each location, and adjusts the flow rate of the corresponding independent cooling unit by 8% to 10% to keep the circumferential solidified shell thickness difference of the ingot within 0.4 mm. At the same time, the controller performs coordinated fine-tuning of the stopper rod based on flow and temperature signals to further reduce the interference of slight changes in liquid level on the uniformity of solidified shell growth.

[0012] The above mathematical model is: in, h The initial thickness of the condenser shell. Q The amount of cooling heat per unit time. p For metal density, c Specific heat capacity of the metal Tm The melting point of the metal, T 0 represents the cooling water temperature.

[0013] The formula for calculating the thickness of the solidified shell from temperature is as follows: in, d For the thickness of the condenser shell, T 1 represents the real-time surface temperature of the ingot. λ The thermal conductivity of the metal is... q The heat flux density of the crystallizer, t This refers to the time for throwing the pot.

[0014] Each independent cooling unit is equipped with a high-precision electromagnetic flow regulating valve, with an adjustment accuracy of up to 0.1 L / min, to ensure the sensitivity of fine-tuning the cooling.

[0015] The present invention has the following advantages compared with the prior art.

[0016] 1. Through the servo motor-driven conical stopper rod and flow-temperature dual feedback, the entire liquid transfer process is automatically controlled in a closed loop, completely replacing manual operation. This not only eliminates safety hazards such as high-temperature melt splashing, but also significantly suppresses liquid level fluctuations in the crystallizer, reduces secondary oxidation of magnesium alloy melt, and improves ingot purity.

[0017] 2. By employing circumferentially partitioned independent cooling units in conjunction with multi-point infrared temperature measurement, a real-time partitioned closed-loop control of the solidified shell thickness is established for the first time based on stable liquid transfer control. When the thickness deviates from the target at a certain point, the cooling intensity of the corresponding area can be adjusted within a few seconds, ensuring that the thickness difference across the entire circumference is less than 0.4 mm. This fundamentally solves a series of problems caused by uneven solidified shell thickness, such as thermal stress concentration, cracking, and surface scratches.

[0018] 3. The liquid transfer control loop and the solidified shell thickness control loop are integrated in the same controller to achieve data fusion and collaborative decision-making, so that the liquid flow state is highly matched with the solidification process in the crystallizer, further enhancing the process's resistance to disturbances and significantly improving the stability of ingot quality. Attached image description:

[0019] Figure 1 The schematic diagram of the magnesium alloy semi-continuous casting liquid transfer and solidified shell thickness coordinated control device of the present invention is as follows: 1-melting furnace, 2-temperature and flow sensor, 3-guide pipe, 4-integrated controller, 5-infrared thermometer, 6-crystallizer, 7-solidified metal, 8-ingot head, 9-independent cooling unit, 10-diverter plate, 11-conical stopper rod.

[0020] Figure 2 Here is a diagram of the crystallizer structure: 6-Crystallizer, 7-Solidified metal, 8-Initiator head, 9-Independent cooling unit.

[0021] Figure 3 Diagram of stopper rod control: 11-stopper rod, 12-slider, 13-slide rail, 14-servo motor, 15-lead screw. Detailed implementation method: Example 1

[0022] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0023] For magnesium alloy ingot production, the inner diameter of the crystallizer D =150mm, crystallizer length L =150mm. Alloy and cooling parameters are as follows: Magnesium alloy melting point... T m =923K, density of magnesium alloy p =1750Kg / m³, specific heat capacity of magnesium alloy c =1025 J / (kg·k), solidification coefficient of magnesium alloy K =1.4mm / s^0.5, thermal conductivity of magnesium alloy λ=156W / (m·K), cooling water temperature T 0 = 300K, cooling amount per unit time Q =100000W / m 2 .

[0024] First, preheat the melting furnace and guide pipes to 500 ℃ and keep them at that temperature for 1.5 h. The insulation layer should reduce the temperature of the magnesium alloy melt by ≤5 ℃ / h.

[0025] Step 1: Calculate the initial target thickness of the condensation shell based on the preset mathematical model: That is, the initial condenser shell thickness is 13.4 mm.

[0026] Step Two: When the magnesium alloy melt temperature reaches 700 ℃, the transfer process is initiated, and argon gas at a flow rate of 3 L / min is introduced for protection. The integrated controller controls the servo motor to drive the conical stopper rod, allowing the molten metal to flow smoothly into the distribution plate and crystallizer along the guide tube. During the initial pouring stage, the flow is slowed to avoid splashing, and the flow rate is appropriately increased after the initial pouring. Throughout the entire casting process, the integrated controller continuously fine-tunes the stopper rod based on temperature and flow rate signals to maintain a stable liquid level.

[0027] Step 3: Once the initial solidified shell thickness reaches 13.4 mm, begin the casting process. Adjust the casting speed accordingly. v With the thickness of the condenser shell δ The relationship between them is satisfied ， Set the initial casting speed (i.e., 98.4 mm / min) to ensure the stability of the condensation shell thickness during the casting process.

[0028] Step 4: Install three sets of infrared thermometers at 120° intervals around the crystallizer, 120mm below, to monitor the surface temperature of the ingot in real time. T 1. The temperature data is transmitted to the integrated controller, which then uses the formula... The actual thickness of the condenser shell at each location is calculated in real time.

[0029] The integrated controller compares the thickness in each direction with the target value of 13.4 mm. When the actual thickness in a certain area is lower than the target value, the flow rate of the corresponding independent cooling unit is increased by 8% to 10%; when it is higher than the target value, the flow rate is decreased by 8% to 10%, always maintaining the maximum thickness difference less than 0.4 mm. At the same time, the liquid level fluctuation on the thickness of the condensate is further reduced by fine-tuning the stopper rod in the liquid transfer circuit.

[0030] Example 2

[0031] Using a larger crystallizer length L =170mm, crystallizer inner diameter D =150mm, melting point of magnesium alloy T m =850K, density of magnesium alloy p =1780Kg / m³, specific heat capacity of magnesium alloy c =1075J / (kg·k), and other parameters and process steps are the same as in Example 1.

[0032] The initial target thickness of the condensation shell is calculated based on a pre-defined mathematical model: That is, the initial condenser shell thickness is 13.7 mm.

[0033] Set the initial casting speed (i.e., 106.8 mm / min).

[0034] The infrared thermometer was installed in the same location as in Example 1, and the circumferential thickness difference of the solidified shell was effectively controlled within 0.4 mm. The surface of the ingot was smooth, the internal structure was dense, and no cracks or obvious segregation were observed.

[0035] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for coordinated control of liquid transfer and solidified shell thickness in semi-continuous casting of magnesium alloys, characterized in that, include: The liquid transfer control system includes a smelting furnace, a guide pipe, a temperature sensor and a flow sensor installed on the guide pipe, and a conical stopper rod driven by a servo motor. The conical stopper rod is sealed to the inner wall of the guide pipe to control the flow rate of the molten metal. The condensation shell control system includes a crystallizer, multiple independent cooling units evenly arranged along the circumference of the crystallizer, and an infrared thermometer correspondingly installed below the crystallizer to monitor the circumferential surface temperature of the ingot. An integrated controller is connected to the temperature sensor, flow sensor, servo motor, each independent cooling unit, and infrared thermometer signals respectively; The integrated controller is configured as follows: a) Calculate the target condenser shell thickness based on the preset mathematical model; b) Based on the real-time surface temperature of the ingot collected by the infrared thermometer, the actual thickness of the condensation shell is calculated. c) By comparing the target thickness with the actual thickness, the cooling medium flow rate of the corresponding independent cooling unit is dynamically adjusted to achieve real-time closed-loop control of the condenser shell thickness. d) Based on the feedback signals from the temperature sensor and the flow sensor, adjust the opening of the stopper rod to stabilize the melt level in the crystallizer, forming a synergy with the closed-loop control of the condensation shell thickness.

2. The device for coordinated control of liquid transfer and solidified shell thickness in semi-continuous casting of magnesium alloys according to claim 1, characterized in that, The liquid transfer control system also includes: A smelting furnace with a 60-80mm thick composite insulation layer on its inner wall; A flow guide tube with a 0.8-1.0 mm thick high-temperature resistant ceramic coating on its inner wall connects the smelting furnace and the flow distribution plate. The temperature sensor is a type K thermocouple, and the flow sensor is an electromagnetic flow sensor; The conical stopper rod is sealed to the inner wall of the guide tube and is driven by a servo motor to control the flow rate of the molten metal.

3. The device for coordinated control of liquid transfer and solidified shell thickness in semi-continuous casting of magnesium alloys according to claim 1, characterized in that, Each independent cooling unit in the condenser shell control system includes an electromagnetic flow regulating valve with an adjustment accuracy of 0.1 L / min; the integrated controller is a Siemens PLC.

4. A semi-continuous casting method for magnesium alloys, employing the device for coordinated control of liquid transfer and solidified shell thickness in semi-continuous casting of magnesium alloys as described in any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Calculate the initial target thickness of the condensation shell using a mathematical model; Step 2: Preheat all equipment to the required casting temperature. After starting casting, the molten metal flows into the crystallizer through the guide pipe. The integrated controller controls the servo motor to drive the stopper rod according to the temperature and flow signals, so that the molten metal is smoothly spread to the bottom. After spreading to the bottom, the flow rate is appropriately increased, and the fluctuation of the melt level is kept to a minimum. Step 3: Once the initial condensation shell reaches the target thickness, casting begins. Step 4: During the casting process, an infrared thermometer is used to monitor the surface temperature of different positions around the ingot in real time, and the actual thickness of the condensation shell at each position is calculated based on the surface temperature feedback. Step 5: The integrated controller compares the actual thickness at each location with the target thickness and dynamically adjusts the cooling medium flow rate of the corresponding independent cooling unit to ensure that the thickness difference of the condensate shell in each area is less than 0.4 mm. At the same time, the integrated controller continuously receives temperature and flow signals and fine-tunes the stopper opening to stabilize the liquid level, thereby achieving coordinated control of liquid transfer and condensate shell thickness.

5. The semi-continuous casting method for magnesium alloys according to claim 4, characterized in that, The mathematical model described in step one is: in, h The initial thickness of the condenser shell. Q The amount of cooling heat per unit time. ρ For metal density, c Specific heat capacity of the metal T m The melting point of the metal, T 0 represents the cooling water temperature.

6. The semi-continuous casting method according to claim 4, characterized in that, Casting speed in step three v With the thickness of the condenser shell δ The relationship between them is satisfied: in, k The solidification coefficient of the metal melt. l These are the characteristic dimensions of the crystallizer.

7. The semi-continuous casting method for magnesium alloys according to claim 4, characterized in that, The formula for calculating the thickness of the condenser shell based on the real-time temperature in step four is as follows: in, d For the thickness of the condenser shell, λ The thermal conductivity of the metal is... T 0 represents the cooling water temperature. T 1 represents the real-time surface temperature of the ingot. q The heat flux density of the crystallizer, t This refers to the time for throwing the pot.

8. The semi-continuous casting method for magnesium alloys according to claim 4, characterized in that, The specific method for dynamically adjusting the cooling medium flow rate in step five is as follows: when the actual condenser shell thickness in a certain area is lower than the target value, increase the flow rate of the corresponding cooling unit by 8%-10%; when it is higher than the target value, decrease the flow rate by 8%-10%.

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