Device and method for dynamically measuring liquid metal filling resistance

Abstract

The utility model relates to a kind of device for dynamically measuring liquid metal filling resistance, including quartz tube (1), gate (2), fixed base (3), DC stabilized power supply (4), protective resistance (5), ammeter (6), data real-time acquisition and processing module (7), computer (8), resistance wire (9), wire (10), data transmission line (11).The method for dynamically measuring liquid metal filling resistance using the device, the displacement change in the filling process of liquid metal is represented by the change of current in dynamic measurement circuit, the displacement is twice differentiated with respect to time, and the variation curve of filling resistance with time can be obtained.The device can provide reference for predicting the filling capacity of various liquid metals under certain filling conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to a device and method for dynamically measuring the filling resistance of liquid metal, belonging to the field of metallurgy. TECHNICAL BACKGROUND

[0002] As the first stage of forming a casting, the filling of the mold cavity by liquid metal directly affects the final quality of the casting. In the case of unfavorable filling, the casting is prone to defects such as underfilling, cold shut, entrapped porosity, and inclusions. The filling capacity of liquid metal is affected by the properties of the mold, the pouring conditions, and the structure of the casting. As the temperature of the liquid metal decreases, and the filling pressure head decreases during the upward filling of the metal liquid, the filling capacity of the liquid metal also decreases, and the filling resistance increases.

[0003] Under certain conditions of mold properties, pouring conditions, and casting structure, how to evaluate the filling capacity of liquid metal becomes an important reference. Under certain external conditions, the resistance experienced by liquid metal during the casting filling process is called filling resistance. Filling resistance hinders the filling of the mold cavity by liquid metal, and is not conducive to obtaining a complete shape and clear contour of the casting. Under the premise of constant mold conditions, casting structure, and pouring conditions, the filling resistance is only related to the properties of the liquid metal itself, such as chemical composition, crystallization characteristics, latent heat of crystallization, grain shape, and physical properties (thermal conductivity, specific heat capacity, density, surface tension, and viscosity). The greater the filling resistance of liquid metal during the filling process, the worse the filling capacity of liquid metal. In industrial production, when a workpiece with complex structure and complex wall thickness needs to be cast, the filling resistance can be investigated before the workpiece is officially cast, thereby evaluating the filling capacity of the liquid metal under the composition and casting process, and adjusting the composition and casting process parameters in a timely manner to avoid incomplete casting shape and reduce the possibility of casting failure, which is beneficial to controlling the cost of industrial production. The existing method for characterizing the filling capacity of liquid metal is to characterize the distance traveled by the liquid metal from pouring into the mold to stopping flowing, which often cannot dynamically reflect the changes in the filling capacity of liquid metal during the entire filling process, cannot reflect the relationship between the filling capacity and the temperature during the filling process, and cannot reflect the relationship between the filling capacity and the filling pressure head during the filling process, resulting in deviations in the prediction and evaluation of the filling capacity of liquid metal.

[0004] CN102974807A discloses a method and apparatus for improving the filling capacity of liquid metal. The mold / casting mold is designed as a conductive mold / casting mold, with the anode of a direct current source connected to the liquid metal end and the cathode connected to the conductive mold / casting end. During the liquid metal filling process, a direct current is applied to both the liquid metal end and the conductive mold / casting end. The apparatus includes a heated ladle, a plug remover, a tungsten electrode, a direct current power supply, a metal mold, and a mold cavity. This apparatus does not require altering the chemical composition of the metal and can improve the filling capacity of liquid conductive materials.

[0005] CN207372262U discloses a simple device for measuring the filling time in a vacuum casting process. This device utilizes the weight change of the liquid metal during the casting process, using a high-sensitivity electronic crane scale to display the net weight change in the casting chamber. A high-speed camera captures and records images of the net weight change displayed on the electronic crane scale. By analyzing these images to determine the start time of the initial filling weight and the end time of filling to a constant weight, the filling time of the entire casting can be obtained. This device has advantages in measuring filling time when the process cannot be directly observed.

[0006] Current liquid metal filling capabilities are all based on post-construction observation, making it impossible to predict and judge before filling. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides an apparatus and method for dynamically measuring the filling resistance of liquid metal. The apparatus represents the change in displacement during the liquid metal filling process by dynamically measuring the change in current in the circuit. By taking the second derivative of the displacement with respect to time, the curve of the filling resistance versus time can be obtained. The temperature change of the liquid metal during the filling process is measured by a thermocouple, thus revealing the relationship between the liquid metal filling resistance and the changes in time and temperature. Furthermore, the filling resistance of the liquid metal under three different filling head conditions can be compared.

[0008] When the properties of the mold, the pouring conditions, and the structure of the casting are fixed, the relationship between the filling resistance and the changes in time, temperature, and filling head during the filling process of liquid metal is measured, which provides data reference for predicting the filling capacity of a certain liquid metal under certain filling conditions.

[0009] One aspect of the present invention provides a device for dynamically measuring the filling resistance of liquid metal, comprising a quartz tube (1), a gate (2), a fixed base (3), a DC regulated power supply (4), a protective resistor (5), an ammeter (6), a real-time data acquisition and processing module (7), a computer (8), a resistance wire (9), a wire (10), and a data transmission line (11); wherein the quartz tube (1) is fixed in a groove of the fixed base (3), and there is an opening above the horizontal section of the quartz tube (1) to accommodate the resistance wire (9); the first and second ends of the resistance wire (9) are connected to a test circuit, wherein the DC regulated power supply (4) in the test circuit is connected to the resistance wire (9). The protective resistor (5) and ammeter (6) are connected in series. The DC regulated power supply (4) supplies power to the test circuit. The ammeter (6) measures the current value in the circuit. When the resistance wire is completely melted, the resistance value in the circuit is small. The protective resistor (5) can protect the circuit. The thermocouple (12) is inserted into the quartz tube for real-time measurement of the liquid metal temperature. The real-time data acquisition and processing module (7) is used to collect and process the current value and the thermocouple (12) at regular intervals. The computer (8) is used to display and record the curve of the filling resistance changing with time and the curve of the temperature of the measuring point changing with time in real time.

[0010] Preferably, the number of thermocouples (12) is 6-12, more preferably 8-10, and even more preferably 9.

[0011] Preferably, the quartz tube (1) includes a vertical section, N horizontal sections and (N-1) transition sections. The starting position of the quartz tube is a flared gate (2). The gate (2) is connected to the vertical section, and then sequentially connected to the first horizontal section, the first transition section, the second horizontal section, the second transition section, the third horizontal section, until the (N-1)th transition section and the Nth horizontal section. The horizontal position of each horizontal section increases sequentially, and the transition section is inclined and used to connect two adjacent horizontal sections.

[0012] Preferably, the quartz tube (1) includes a vertical section, three horizontal sections and two transition sections.

[0013] In another aspect, the present invention provides a method for measuring the filling resistance of liquid metal using the aforementioned device, comprising the following steps:

[0014] (1) Before pouring, fix the quartz tube on the fixed top base, install thermocouples at each temperature measuring point, insert the resistance wire into the quartz tube through the opening above the horizontal section of the quartz tube, and connect the test circuit, turn on the DC regulated power supply, the real-time data acquisition and processing module, and the computer; preferably, the number of temperature measuring points is 6-15, preferably 9-12.

[0015] (2) Input resistance wire cross-sectional area S R resistivity ρ RConstant voltage U, protective resistor R1, total length of resistance wire L, constant k;

[0016] (3) Begin casting;

[0017] (4) After the liquid metal flows into the mold cavity from the gate, it gradually fills the cavity. During the filling process, the thermocouples respond sequentially, measuring the temperature at their location in real time and transmitting the data to the acquisition module. The resistance wire is gradually melted by the liquid metal, whose resistance value is negligible, so that the resistance value R of the measuring resistance wire is measured. t and loop current I t Changes occur and are collected by the real-time data acquisition module;

[0018] (5) The current value I is monitored periodically by the real-time data acquisition and processing module. t By collecting and processing the data, the filling resistance F can be obtained. t The curves showing the changes in temperature over time, and the curves showing the changes in temperature over time, allow us to obtain the filling resistance F at different time points. t The curve showing the change with temperature is displayed and recorded on the computer.

[0019] (6) Record the filling resistance F through the real-time data acquisition and processing module. t The sudden increase occurred at times t1 and t2.

[0020] Liquid metal flows into the mold cavity from the gate, gradually filling the cavity. During the filling process, thermocouples respond sequentially and transmit the temperature at their measuring locations in real time. The filling resistance F is calculated by measuring and recording the current values ​​at different moments during the filling process. t .

[0021] The basic principle of this method is that a resistance wire placed at the bottom of the mold cavity is gradually melted by a molten metal with negligible resistance, causing the resistance wire to gradually shorten. According to the law of resistance, the shortening of the resistance wire will lead to a decrease in its resistance value R. t Gradually reduce the R value until the molten metal fills the cavity and the resistance wire is completely melted. t =0, and according to Ohm's law, the current value in the measuring circuit reaches its maximum at this point. The current value I at different times t during the entire filling process... t Each has a corresponding resistance wire length, and the liquid metal filling distance L c This is the difference between the total length of the resistance wire and the remaining length of the resistance wire. The current value I is adjusted periodically by the real-time data acquisition and processing module. t By collecting and processing data, the liquid metal filling distance L can be obtained. c The curve of L changing with time t c By performing a second integral with respect to time t, the acceleration 'a' during the liquid metal filling process can be obtained. c The curve showing how the filling resistance F changes with time t, and the filling resistance F.t1 , F t2 , F t3 , F c , F c , F t , F t , F R , F R , F t1 , F t2 , F t3 , F t , F t1 , F t2 , F t3 , F

[0022] For example, the quartz tube includes three horizontal sections, and the filling resistance calculation formula is as follows:

[0023]

[0024] Wherein: t is time; I t is current in the test circuit; U is constant voltage in the circuit; R1 is a protective resistor, p R is resistivity, S R is cross-sectional area of the resistor wire, L is total length of the resistor wire, S is liquid flow cross-sectional area, p is density of the liquid metal, g is acceleration of gravity, a1 is sprue height, a2 is height of the second section of the cavity from the sprue, and a3 is height of the third section of the cavity from the sprue.

[0025] When the metal liquid flows through the cavities with different heights in sequence, the filling pressure head gradually decreases, and the temperature of the metal liquid is further reduced, the filling resistance continuously increases, and the filling capacity is constantly changing. Similarly, under the conditions of three different filling pressure heads, the curves of F t1 , F t2 , F t3 varying with time t can be obtained, so that the filling resistance of the liquid metal under the conditions of three different filling pressure heads can be measured. t t1 , F t2 , F t3 varying with temperature T can be obtained.

[0026] The beneficial technical effects of the present application are as follows:

[0027] (1) The concept of filling resistance is proposed to more directly represent the filling capacity of the liquid metal; the filling capacity is related to the temperature and the filling pressure head, which is closer to the actual pouring process, and the obtained data is more widely applicable and more persuasive.

[0028] (2) The filling capacity of various metals can be evaluated.

[0029] (3) Real-time data collection and display on the computer are realized, which is more intuitive and accurate. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is the front view of the liquid metal filling resistance testing device; wherein the quartz tube (1), the sprue (2), the fixed base (3), the direct current stabilized power supply (4), the protection resistor (5), the ammeter (6), the data real-time acquisition and processing module (7), the computer (8), the resistance wire (9), the wire (10), the data transmission line (11), and the thermocouple (12) are shown in the figure.

[0031] Figure 2 is the top view of the liquid metal filling resistance testing device.

[0032] Figure 3 is the specific implementation flowchart.

[0033] Figure 4 is the filling resistance change trend graph with time obtained in Example 2.

[0034] Figure 5 is the filling resistance change trend graph with temperature obtained in Example 2.

[0035] Figure 6 is the filling resistance change trend graph with time obtained in Example 3.

[0036] Figure 7 is the filling resistance change trend graph with time obtained in Example 3. DETAILED DESCRIPTION

[0037] Example 1

[0038] A device for dynamically measuring the filling resistance of liquid metal, comprising a quartz tube (1), a sprue (2), a fixed base (3), a direct current stabilized power supply (4), a protection resistor (5), an ammeter (6), a data real-time acquisition and processing module (7), a computer (8), a resistance wire (9), a wire (10), a data transmission line (11), and a thermocouple (12); wherein the quartz tube (1) is fixed in the groove of the fixed base (3), and the horizontal section of the quartz tube (1) has an opening above it for placing the resistance wire (9); the first end and the last end of the resistance wire (9) are connected to the testing circuit, in which the direct current stabilized power supply (4), the protection resistor (5), and the ammeter (6) are connected in series, the direct current stabilized power supply (4) supplies power to the testing circuit, the ammeter (6) measures the current value in the circuit, when the resistance wire is completely melted, the resistance value in the circuit is small, and the protection resistor (5) can protect the circuit; the thermocouple (12) is inserted into the quartz tube for real-time measurement of the temperature of the liquid metal; the data real-time acquisition and processing module (7) acquires and processes the data of the current value and the thermocouple (12) at certain intervals; and the computer (8) is used for real-time display and recording of the curve of the filling resistance change with time and the curve of the temperature change of the temperature measurement point with time.

[0039] Example 2

[0040] The filling resistance of liquid metal is tested by using the device provided in Example 1, and the steps are as follows:

[0041] (1) Before starting pouring, the quartz tube is fixed on the fixed top and bottom base, the thermocouples are installed at 9 measuring points, the resistance wire is put into the quartz tube through the opening above the horizontal section of the quartz tube and connected to the test circuit, the direct current stabilized power supply, the data real-time acquisition and processing module and the computer are turned on;

[0042] (2) The cross-sectional area S of the resistance wire is input R = 0.196 mm 2 , the resistivity p R = 2.36 Ω / m, the constant voltage U = 20 V, the protective resistance R1 = 10 Ω, the total length L of the resistance wire = 1000 mm, the metal liquid density p = 7.3 g / cm 3 , the liquid flow cross-sectional area S = 314 mm 2 , the sprue height a1 = 200 mm, the height a2 of the second section of the cavity from the gate = 150 mm, and the height a3 of the third section of the cavity from the gate = 100 mm;

[0043] (3) The gray cast iron HT200 material (C: 3.0-3.6, Si: 1.4-2.2, Mn: 0.6-1.0, P ≤ 0.15, S ≤ 0.12) is smelted, and after inoculation is completed, pouring is started at 1356℃;

[0044] (4) After the liquid metal flows into the cavity from the gate, it gradually fills the cavity. During the metal liquid filling process, the 9 thermocouples obtain the corresponding temperatures in turn, so that the temperatures at the 9 measuring positions are collected and displayed in real time; the resistance wire is gradually melted by the metal liquid with negligible resistance value, causing the resistance R t of the measuring resistance wire and the loop current I t to change, which are collected by the data real-time acquisition module;

[0045] (5) The current value I t is collected and processed by the data real-time acquisition and processing module every certain period of time, and the curve of the filling resistance F t changing with time, the curve of the temperature changing with time, and the curve of the filling resistance F t changing with temperature at different time points can be obtained, which are displayed and recorded on the computer.

[0046] (6) The moments t1 and t2 of the sudden increase of the filling resistance F t are recorded by the data real-time acquisition and processing module.

[0047] The test procedure is as follows:

[0048] The liquid metal flows into the cavity from the sprue, and the liquid metal gradually fills the cavity. During the filling process of the metal liquid, the thermocouples respond in turn and upload the temperature of the measurement position in real time. The filling resistance F is calculated by measuring and recording the current value at different times during the filling process t . The test results are shown as follows, wherein T1 = 1343℃, T2 = 1322℃, T3 = 1301℃, T4 = 1270℃, T5 = 1254℃, T6 = 1240℃, T7 = 1193℃, T8 = 1180℃, and T9 = 1169℃.

[0049] The calculation formula is as follows:

[0050]

[0051] Wherein: t is time; I t is the current in the test circuit; U is the constant voltage in the circuit; R1 is the protection resistance, p R is the resistivity, S R is the cross-sectional area of the resistance wire, L is the total length of the resistance wire, S is the liquid flow cross-sectional area, p is the density of the liquid metal, g is the acceleration of gravity, a1 is the height of the sprue, a2 is the height of the second section of the cavity from the sprue, and a3 is the height of the third section of the cavity from the sprue.

[0052] Example 3

[0053] The filling resistance of the liquid metal is tested by using the device provided in Example 1, and the steps are as follows:

[0054] (1) Before starting pouring, fix the quartz tube on the fixed top and bottom seat, install the thermocouples at the 9 measurement points, put the resistance wire into the quartz tube through the opening above the horizontal section of the quartz tube, and connect the test circuit. Turn on the DC stabilized power supply, the data real-time acquisition and processing module, and the computer;

[0055] (2) Input the cross-sectional area of the resistance wire S R = 0.196mm 2 , the resistivity p R = 2.36Ω / m, the constant voltage U = 20V, the protection resistance R1 = 10Ω, the total length of the resistance wire L = 1000mm, the density of the metal liquid p = 7.8g / cm 3 , the liquid flow cross-sectional area S = 314mm 2 , the height of the sprue a1 = 200mm, the height of the second section of the cavity from the sprue a2 = 150mm, and the height of the third section of the cavity from the sprue a3 = 100mm;

[0056] (3) Adopt low-carbon cast steel material (C: 0.15-0.3, Si: 0.3-0.5, Mn: 0.4-0.8, P≤0.1, S≤0.1) for smelting, and pouring at 1485℃;

[0057] (4) After the liquid metal flows into the cavity from the sprue, it gradually fills the cavity. During the metal liquid filling process, the metal liquid can only fill the first two sections of the cavity, and the six thermocouples from left to right obtain the corresponding temperature in turn, so that the temperature of the six measuring positions is collected and displayed in real time; the resistance value of the resistance wire is gradually melted by the metal liquid with negligible resistance value, so that the resistance value R t of the measuring resistance wire and the circuit current I t change, and are collected by the data real-time collection module;

[0058] (5) The current value I t is collected and processed by the data real-time collection and processing module every certain period of time, and the curve of the filling resistance F t changing with time, the curve of the temperature changing with time can be obtained, and the curve of the filling resistance F t changing with temperature can be obtained at different time points, and is displayed on the computer and recorded.

[0059] (6) The moment t1 of the sudden increase of the filling resistance F t is recorded by the data real-time collection and processing module, and there is no t2 moment because the metal liquid can only fill the first two sections of the cavity.

[0060] The test procedure is as follows:

[0061] The liquid metal flows into the cavity from the sprue, and the liquid metal gradually fills the cavity. During the metal liquid filling process, the thermocouples respond in turn and the temperature of the measuring position is uploaded in real time. The filling resistance F t is calculated by measuring and recording the current value at different time points during the filling process. The test results are as follows, where T1=1463℃, T2=1451℃, T3=1440℃, T4=1429℃, T5=1420℃, and T6=1413℃.

[0062] Since the metal liquid can only fill the first two sections of the cavity, there is no value of F t3 , and the calculation formula is as follows:

[0063]

[0064] Where: t is time; I t is the current in the test circuit; U is the constant voltage in the circuit; R1 is the protection resistance, ρ R is the resistivity, and S RS is the cross-sectional area of the liquid flow, p is the density of the liquid metal, g is the acceleration of gravity, a1 is the height of the sprue, and a2 is the height of the second section of the cavity from the sprue.

[0065] The above merely illustrates the preferred embodiments of the present application, and is not intended to limit the present application. Various modifications or changes can be made by those skilled in the art without departing from the scope of the present application.

Claims

1. A device for dynamically measuring the filling resistance of liquid metal, characterized in that... The system includes a quartz tube (1), a gate (2), a fixed base (3), a DC regulated power supply (4), a protective resistor (5), an ammeter (6), a real-time data acquisition and processing module (7), a computer (8), a resistance wire (9), a wire (10), a data transmission line (11), and a thermocouple (12). The quartz tube (1) is fixed in the groove of the fixed base (3). The quartz tube (1) includes a vertical section, N horizontal sections, and (N-1) transition sections. The starting position of the quartz tube is a flared gate (2). The gate (2) connects to the vertical section, and then sequentially connects to the first horizontal section, the first transition section, the second horizontal section, the second transition section, the third horizontal section, until the (N-1)th transition section and the Nth horizontal section. The horizontal section of the quartz tube (1) has an opening above it to accommodate the resistor. The first and second ends of the resistance wire (9) are connected to the test circuit. In the test circuit, the DC regulated power supply (4), the protective resistor (5), and the ammeter (6) are connected in series with wires (10). The DC regulated power supply (4) supplies power to the test circuit, and the ammeter (6) measures the current value in the test circuit. When the resistance wire (9) is completely melted, the resistance value in the test circuit is small, and the protective resistor (5) plays a role in protecting the test circuit. The thermocouple (12) is inserted into the quartz tube (1) to measure the temperature of the liquid metal in real time. The real-time data acquisition and processing module (7) is used to acquire and process the current value and the thermocouple (12) at certain intervals. The computer (8) is used to display and record the curve of the filling resistance changing with time and the curve of the temperature of the measuring point changing with time in real time.

2. The apparatus according to claim 1, characterized in that... The number of thermocouples (12) is 6-12.

3. The apparatus according to claim 2, characterized in that... The number of thermocouples (12) is 8-10.

4. The apparatus according to claim 1, characterized in that... The horizontal position of each horizontal segment increases sequentially, and the transition segment is set at an angle to connect two adjacent horizontal segments.

5. The apparatus according to claim 1, characterized in that... The quartz tube (1) includes one vertical section, three horizontal sections and two transition sections.

6. A method for measuring the filling resistance of liquid metal using the apparatus as described in any one of claims 1-5, comprising the following steps: (1) Before starting the pouring, fix the quartz tube (1) on the fixed base (3), install the thermocouple (12) at each temperature measuring point, put the resistance wire (9) into the quartz tube (1) through the opening above the horizontal section of the quartz tube (1), connect the test circuit, and turn on the DC regulated power supply (4), the real-time data acquisition and processing module (7), and the computer (8). (2) Input resistance wire (9) cross-sectional area S R resistivity ρ R Constant voltage U, protective resistor R1, total length of resistance wire L, liquid metal density ρ, liquid flow cross-sectional area S, sprue height a1, height of the second horizontal section from the gate a2, height of the third horizontal section from the gate a3. (3) Begin casting; (4) After the liquid metal flows into the mold cavity from the gate, it gradually fills the mold cavity. During the process of filling the mold with liquid metal, the thermocouples respond in sequence, measure the temperature at their location in real time and transmit it to the real-time data acquisition and processing module (7); the resistance wire (9) is gradually melted by the liquid metal, and the resistance value of the liquid metal can be ignored, so that the resistance value R of the resistance wire can be measured. t and loop current I t Changes occur and are collected by the real-time data acquisition and processing module (7); (5) The current value I is monitored periodically by the real-time data acquisition and processing module (7). t By collecting and processing the data, the filling resistance F can be obtained. t The curves showing the changes in temperature over time, and the curves showing the changes in temperature over time, allow us to obtain the filling resistance F at different time points. t The curve of temperature change is displayed and recorded on the computer (8); (6) Record the moments t1 and t2 when the filling resistance Ft suddenly increases through the real-time data acquisition and processing module (7).

7. The method according to claim 6, characterized in that, When the quartz tube consists of three horizontal sections, the formula for calculating the filling resistance Ft is as follows: Where: t is time; I t The current in the test circuit is U; the constant voltage in the circuit is R1; and the protective resistor is ρ. R S is the resistivity. R ρ is the cross-sectional area of ​​the resistance wire, L is the total length of the resistance wire, S is the cross-sectional area of ​​the liquid flow, ρ is the density of the liquid metal, g is the acceleration due to gravity, a1 is the height of the sprue, a2 is the height of the second horizontal section from the gate, and a3 is the height of the third horizontal section from the gate.

8. The method according to claim 6, characterized in that, The number of temperature measurement points in step (1) is 6-15.

9. The method according to claim 8, characterized in that, The number of temperature measurement points in step (1) is 9-12.

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