A method for measuring the depth of a liquid pool of an ingot in a semi-continuous casting process

Abstract

The application provides a kind of measurement method of ingot liquid cavity depth in semi-continuous casting process, comprising: step 1, obtaining the solid phase rate corresponding to each temperature value of the alloy to be measured;Step 2, assemble the measuring device;Step 3, mark the immersion position of each thermocouple;Step 4, obtain the liquid cavity depth;Step 5, draw the liquid cavity profile.The application upgrades the liquid cavity depth judgment basis from artificial tactile experience to temperature data, significantly improves the measurement accuracy and repeatability;The application can measure the liquid cavity depth of multiple positions synchronously through the measuring device, which synchronously obtains the liquid cavity depth information of multiple positions during the casting process, avoids the deviation caused by manual point-by-point operation, and improves the efficiency of liquid cavity profile drawing.

Description

Technical Field

[0001] This invention relates to a method for measuring the depth of the molten pool in a semi-continuous casting process, belonging to the field of aluminum alloy processing and casting technology. Background Technology

[0002] In semi-continuous casting (such as direct cooling casting of aluminum alloys), the depth of the liquid cavity and the profile of the solidus line inside the ingot are key process parameters that determine the internal quality of the billet, macroscopic segregation, hot cracks, shrinkage cavities, and other defects. Accurately determining the depth of the liquid cavity helps optimize process conditions such as casting speed, cooling intensity, and crystallizer design, thereby achieving refined control of the solidification structure. However, the liquid cavity is located inside the ingot, in a high-temperature, opaque, dynamic solidification environment, making it difficult to directly and online obtain its morphological information using traditional methods. In existing technologies, the commonly used method for measuring the morphology and depth of the liquid cavity is the wire insertion method (or probe method). Researchers have used a thin steel rod inserted vertically into the liquid cavity from the surface of the molten metal until it touches the solid phase of the ingot, then withdrawing it. The morphology of the liquid cavity is calculated by measuring the length of the inserted wire or probe at different positions. Because this method is relatively intuitive and simple, it has been applied to metal ingots and large ingots with relatively flat crystal surfaces.

[0003] However, the wire insertion method still has many shortcomings in practical applications. First, the insertion process relies entirely on the operator's tactile experience to determine the endpoint of "contacting the solid phase." The measurement accuracy is greatly affected by the operator's experience and the perpendicularity of the probe, resulting in significant errors and failing to accurately reflect changes in the morphology of the liquid cavity. If casting conditions or processes change, the error value will be even greater. Second, this method only provides a qualitative binary judgment of "whether the solid phase has been contacted," and cannot quantify the relationship between the gradually increasing mechanical resistance of the probe during insertion and the degree of alloy solidification. Therefore, it is impossible to obtain quantitative solid fraction information of the area contacted by the probe end. Third, this method is mostly manual, single-pronged, and sequential, making it difficult to achieve rapid, batch, multi-point simultaneous measurement in semi-continuous casting processes. This results in low efficiency and limited accuracy in depicting the complete two-dimensional or three-dimensional contour of the liquid cavity. Summary of the Invention

[0004] The purpose of this invention is to provide a method for measuring the depth of the molten ingot cavity during semi-continuous casting, so as to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides a method for measuring the depth of the ingot molten cavity during semi-continuous casting, including the use of a measuring device for measuring the depth of the ingot molten cavity during semi-continuous casting. The measuring device includes: a cross-shaped support frame and nine push rod stepper motors. One push rod stepper motor is arranged at the center of the support frame, and the other eight push rod stepper motors are evenly arranged on the four arms of the support frame. Each push rod stepper motor has a mechanical sensor connected to its push rod end. Each mechanical sensor is connected to a thermocouple through a fixing clamp. Each thermocouple is equipped with a thermocouple protection mechanism.

[0006] The testing method includes:

[0007] Step 1: Obtain the solid fraction corresponding to each temperature value of the alloy to be tested;

[0008] Step 2: Assemble the measuring device: At the start of casting, fix the testing device on the top of the casting device, with each thermocouple perpendicular to the horizontal plane, and the thermocouple at the center of the support frame coaxial with the center line of the alloy melt to be tested.

[0009] Step 3: Mark the immersion position of each thermocouple: When the casting process reaches a steady state, start each push rod stepper motor at the same time. Each push rod stepper motor drives the corresponding thermocouple to move vertically downward to enter the alloy melt to be tested. When the solid fraction corresponding to the temperature detected by a certain thermocouple in real time is the preset solid fraction, stop the corresponding push rod stepper motor and mark the immersion position of this thermocouple. Complete the marking of the immersion positions of all thermocouples according to the above method.

[0010] Step 4: Obtain the depth of the liquid cavity: Take out the test device and measure the longitudinal coordinate of the end of each thermocouple according to the immersion position of each thermocouple. The longitudinal coordinate of the end of each thermocouple is the depth of the liquid cavity at the corresponding position of the ingot.

[0011] Step 5: Draw the outline of the liquid cavity: Connect the positions of the ordinates of the ends of each thermocouple on the two opposite arms of the support frame and the end of the thermocouple at the center of the support frame to obtain the outline of the ingot liquid cavity.

[0012] In one specific implementation, each of the mechanical sensors is electrically connected to a PLC digital display panel, and each mechanical sensor transmits the mechanical resistance detected in real time to the PLC digital display panel in real time.

[0013] In one specific implementation, each of the thermocouples is electrically connected to a multi-channel paperless recorder, and each thermocouple transmits the temperature it detects in real time to the multi-channel paperless recorder in real time.

[0014] In one specific implementation, step 1 involves converting the temperature values ​​of the alloy under test into solid fractions using the Scheil solidification model in Thermo-Calc software.

[0015] In one specific implementation, in step 3, each thermocouple detects the temperature in real time and transmits the data to the multi-channel paperless recorder in real time, and each mechanical sensor detects the mechanical resistance in real time and transmits the data to the PLC digital display panel in real time.

[0016] In one specific implementation, the testing method further includes: combining the temperature readings of the multi-channel paperless recorder and the PLC digital display panel to obtain the temperature-mechanical resistance curve of the alloy under test; and then, based on the solid fraction corresponding to each temperature value of the alloy under test determined in step 1, the mechanical resistance corresponding to the preset solid fraction can be obtained.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. This invention measures the depth of a liquid cavity by determining whether the temperature detected by the thermocouple reaches the temperature corresponding to a preset solid fraction. This upgrades the basis for judging the depth of a liquid cavity from human tactile experience to temperature data, significantly improving the measurement accuracy and repeatability.

[0019] 2. The present invention can simultaneously measure the depth of liquid cavity at multiple locations through a measuring device. It can simultaneously acquire liquid cavity depth information at multiple locations during the casting process, avoiding the deviation caused by manual point-by-point operation and improving the efficiency of liquid cavity contour drawing.

[0020] 2. This invention uses mechanical resistance measured by a mechanical sensor to verify whether the thermocouple has reached the position corresponding to the preset solid fraction, thereby avoiding errors caused by relying solely on temperature measurement, preventing damage to the measuring device due to temperature errors, and effectively improving the robustness of the measuring device.

[0021] 4. This invention not only determines whether the solid phase is touched, but also establishes the relationship between mechanical resistance and temperature, and then obtains the relationship between mechanical resistance and solid phase ratio, providing reliable data support for solidification process analysis and simulation calibration. Attached Figure Description

[0022] Figure 1 This is a flowchart of the method for measuring the depth of the ingot cavitation during the semi-continuous casting process of the present invention.

[0023] Figure 2 This is a schematic diagram of the measuring device described in this invention.

[0024] Figure 3 This is a schematic diagram of an embodiment of the present invention where each thermocouple stops moving downwards.

[0025] Figure 4 This is a schematic diagram of the outline of the ingot molten cavity in an embodiment of the present invention.

[0026] Figure 5This is a temperature-mechanical resistance curve diagram of an embodiment of the present invention.

[0027] Figure 6 This is a comparison diagram of the contours of the liquid cavity in an embodiment of the present invention.

[0028] In the figure: 1. Support frame; 2. Push rod stepper motor; 3. Mechanical sensor; 4. Thermocouple; 5. Casting device; 6. Alloy melt to be tested. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the embodiments and accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0030] A method for measuring the depth of the ingot cavity during semi-continuous casting includes using a device for measuring the depth of the ingot cavity during semi-continuous casting, with reference to... Figure 2 The measuring device includes: a cross-shaped support frame 1 and nine push rod stepper motors 2. One push rod stepper motor 2 is arranged at the center of the support frame 1, and the other eight push rod stepper motors 2 are evenly arranged on the four arms of the support frame 1. Each push rod stepper motor has a mechanical sensor 3 connected to its push rod end. Each mechanical sensor 3 is connected to a thermocouple 4 through a fixing clip. Each thermocouple 4 is provided with a thermocouple 4 protection mechanism. Preferably, the thermocouple 4 protection mechanism is a boron nitride coating coated on the surface of the thermocouple 4.

[0031] Specifically, each of the thermocouples 4 is electrically connected to the multi-channel paperless recorder, and each thermocouple 4 transmits the real-time detected temperature to the multi-channel paperless recorder in real time.

[0032] Specifically, each of the mechanical sensors 3 is electrically connected to the PLC digital display panel, and each mechanical sensor 3 transmits the mechanical resistance experienced by the thermocouple 4 during the insertion of the thermocouple into the melt and solidified layer to the PLC digital display panel in real time.

[0033] The change curve of mechanical resistance value obtained by the mechanical sensor 3 can be used to verify whether the corresponding thermocouple 4 has reached the position corresponding to the preset solid fraction, thereby avoiding the error caused by relying solely on temperature measurement and avoiding damage to the device due to temperature error.

[0034] refer to Figure 1 The testing method includes: Step 1, obtaining the solid fraction corresponding to each temperature value of the alloy to be tested; in this embodiment, the alloy to be tested is AA2195 aluminum alloy; optionally, Step 1 specifically involves: converting each temperature value of the alloy to be tested into solid fraction using the Scheil solidification model in Thermo-Calc software.

[0035] Step 2: Assemble the measuring device: At the start of casting, fix the testing device on the top of the casting device 5. Each push rod stepper motor 2 is in a retracted state. Each thermocouple 4 is perpendicular to the horizontal plane. The thermocouple 4 at the center of the support frame 1 is coaxial with the center line of the alloy melt 6 to be tested. The movement of each push rod stepper motor 2 can drive the corresponding mechanical sensor 3 and thermocouple 4 to move up and down.

[0036] Step 3: Mark the immersion position of each thermocouple 4: When the surface of the alloy melt 6 is level and the heat input and heat dissipation in the casting system are relatively balanced, the casting process reaches a steady state. When the casting process reaches a steady state, refer to... Figure 3 Simultaneously, each push rod stepper motor 2 is started, and each push rod stepper motor 2 drives the corresponding thermocouple 4 to move vertically downward to enter the alloy melt 6 to be tested. Preferably, each thermocouple 4 detects the temperature in real time and transmits it to the multi-channel paperless recorder in real time. Each mechanical sensor 3 detects the mechanical resistance in real time and transmits it to the PLC digital display panel in real time. When the solid fraction corresponding to the temperature detected by a certain thermocouple 4 in real time is a preset solid fraction (in this embodiment, the preset solid fraction is 90%), the corresponding push rod stepper motor 2 is stopped, and the corresponding thermocouple 4 no longer moves vertically downward. The immersion position of this thermocouple 4 is marked. The immersion positions of all thermocouples 4 are marked according to the above method.

[0037] In step 3, each mechanical sensor 3 is positioned above the alloy melt 6 to be tested.

[0038] Step 4: Obtain the depth of the liquid cavity: Take out the test device and measure the longitudinal coordinate of the end of each thermocouple 4 according to the immersion position of each thermocouple 4. The longitudinal coordinate of the end of each thermocouple 4 is the depth of the liquid cavity at the corresponding position of the ingot.

[0039] Step 5: Draw the outline of the liquid cavity: Connect the ordinates of the four ends of each thermocouple sequentially to obtain the outline of the ingot liquid cavity. (Refer to...) Figure 4 .

[0040] Preferably, the testing method further includes: combining the temperature readings of the multi-channel paperless recorder and the PLC digital display panel to obtain the temperature-mechanical resistance curve of the alloy under test; and then, based on the solid fraction corresponding to each temperature value of the alloy under test determined in step 1, the mechanical resistance corresponding to the preset solid fraction can be obtained, which can provide quantitative evidence for subsequent calibration of solid fraction measurement. Figure 5 The temperature-mechanical resistance curve of the corresponding position of the alloy is obtained based on the temperature detected by a thermocouple 4 and the mechanical resistance detected by the corresponding mechanical sensor 3.

[0041] To verify the correctness of the measurement method of this invention, the measurement results of this invention are compared and verified with the simulation results. (Reference) Figure 6 , Figure 6 The solid fraction contour map is the result of simulation using Pro-Cast software. The liquid cavity contour map of this invention (…) Figure 4 Import them into the same coordinate system as the simulation. Figure 6 The white dots represent the positions where the thermocouple ends stop moving downwards. Adjacent white dots are connected by thin blue lines to fit the profile of the liquid cavity on the longitudinal section of the ingot. Figure 6 It can be seen that the liquid cavity contours of both the simulation results and the measurement results of the present invention are V-shaped, with the solidus line depth being the deepest at the center of the ingot and the shallowest at the edge.

[0042] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions and substitutions can be made without departing from the inventive concept, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for measuring the depth of the molten ingot cavity during a semi-continuous casting process, characterized in that, The invention includes a measuring device for measuring the depth of the ingot cavity during a semi-continuous casting process. The measuring device comprises: a cross-shaped support frame and nine push rod stepper motors. One push rod stepper motor is arranged at the center of the support frame, and the other eight push rod stepper motors are evenly arranged on the four arms of the support frame. Each push rod stepper motor has a mechanical sensor connected to its push rod end. Each mechanical sensor is connected to a thermocouple through a fixing clamp. Each thermocouple is equipped with a thermocouple protection mechanism. The measurement method includes: Step 1: Obtain the solid fraction corresponding to each temperature value of the alloy to be tested; Step 2: Assemble the measuring device: At the start of casting, fix the measuring device on the top of the casting device, with each thermocouple perpendicular to the horizontal plane, and the thermocouple at the center of the support frame coaxial with the center line of the alloy melt to be measured. Step 3: Mark the immersion position of each thermocouple: When the casting process reaches a steady state, start each push rod stepper motor at the same time. Each push rod stepper motor drives the corresponding thermocouple to move vertically downward to enter the alloy melt to be tested. When the solid fraction corresponding to the temperature detected by a certain thermocouple in real time is the preset solid fraction, stop the corresponding push rod stepper motor and mark the immersion position of this thermocouple. Complete the marking of the immersion positions of all thermocouples. In step 3, each thermocouple detects the temperature in real time and transmits the data to the multi-channel paperless recorder in real time, and each mechanical sensor detects the mechanical resistance in real time and transmits the data to the PLC digital display panel in real time. By combining the temperature readings of the multi-channel paperless recorder and the PLC digital display panel, the temperature-mechanical resistance curve of the alloy under test is obtained. Then, based on the solid fraction corresponding to each temperature value of the alloy under test determined in step 1, the mechanical resistance corresponding to the preset solid fraction is obtained. Step 4: Obtain the depth of the liquid cavity: Take out the measuring device and measure the ordinate of the end of each thermocouple according to the immersion position of each thermocouple. The ordinate of the end of each thermocouple is the depth of the liquid cavity at the corresponding position of the ingot. Step 5: Draw the outline of the liquid cavity: Connect the positions of the ordinates of the ends of each thermocouple on the two opposite arms of the support frame and the end of the thermocouple at the center of the support frame to obtain the outline of the ingot liquid cavity.

2. The method for measuring the depth of the ingot cavity during semi-continuous casting as described in claim 1, characterized in that, Each of the aforementioned mechanical sensors is electrically connected to the PLC digital display panel, and each mechanical sensor transmits the mechanical resistance detected in real time to the PLC digital display panel in real time.

3. The method for measuring the depth of the ingot cavity during semi-continuous casting as described in claim 2, characterized in that, Each thermocouple is electrically connected to a multi-channel paperless recorder, and each thermocouple transmits the temperature it detects in real time to the multi-channel paperless recorder in real time.

4. The method for measuring the depth of the ingot cavity during semi-continuous casting as described in claim 3, characterized in that, Step 1 specifically involves converting the temperature values ​​of the alloy under test into solid fractions using the Scheil solidification model in Thermo-Calc software.

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