A heating and temperature measuring electrode based on hot wire method

Abstract

The application relates to a heating and temperature measuring electrode based on a hot-wire method, which is characterized in that one end of two metal electrode rods is respectively connected with a platinum-rhodium wire for heating and is respectively connected with a positive electrode and a negative electrode of a power supply line, a heating loop is formed through the platinum-rhodium wire connection, the other end of the metal electrode rods is fixed to an electrode rod supporting member, one ceramic tube is arranged in the cavity of each metal electrode rod, a positive electrode and a negative electrode of a platinum-rhodium thermocouple are arranged in the ceramic tube as a temperature measuring cold end, one end of a screw micrometer is arranged on a screw micrometer supporting member, the screw micrometer supporting member is connected with the electrode rod supporting member through an intermediate connecting rod, the heating assembly is driven to move in the axial direction, and thus the electrode is adjusted in length. The electrode has the functions of heating and temperature measuring, the heating and temperature measuring signals do not interfere with each other, the temperature measurement is accurate, the electrode is driven to move through the adjustment knob of the screw micrometer to dynamically adjust the position, and the electrode can be stably used in a 1600 DEG C high-temperature environment for a long time.

Description

Technical Field

[0001] This invention relates to the field of electrodes used in hot-wire heating devices, and more particularly to a heating and temperature measuring electrode based on the hot-wire method, which has both heating and temperature measuring functions. Background Technology

[0002] In the 1950s, the hot-wire method was proposed in the literature "1. Techniques for growing and mounting small single crystals of refractory compounds (Fred Ordway, February 1952); 2. A simple microscope attachment for observing high-temperature phenomena (JH Welch, August 1954)". The hot-wire method refers to a thermocouple technique that involves welding platinum-rhodium wires of different compositions together to form a thermocouple. This thermocouple serves as both a heating element and a temperature measuring element during use. The thermocouple is formed into a "V" or "U" shape with the welding point of the positive and negative electrodes as the midpoint. The object to be measured is placed directly on the thermocouple, and the temperature is collected simultaneously by controlling the thermocouple to heat up, hold, and cool down according to predetermined conditions. Based on the fundamental principles of the hot-wire method, the literature "Development of double and single hot thermocouple technique for in situ observation and measurement of mold slag crystallization" (Y. Kashiwaya, CECicutti and AWCramb, April 1998) proposed the design concept and apparatus composition of the hot-wire method. The hot-wire method apparatus mainly consists of a control system, a heating furnace, a camera system, and a computer system. Using the hot-wire method, the melting and crystallization characteristics of substances such as slag, fly ash, minerals, and refractory materials in industries such as metallurgy, resources, mining, and ceramics can be studied. The image acquisition system enables in-situ observation of the sample's changes under high-temperature conditions.

[0003] The core technology of the hot-wire method is to simultaneously achieve heating and temperature measurement, which relies on the electrodes. The electrodes, as the core component of the hot-wire method, have three main functions: (1) Supporting the heating wire. The double platinum-rhodium heating wire is fixed to the electrode for sample testing. (2) Providing heating and temperature measurement. As an intermediate between heating and temperature measurement, the electrode connects the heating wire on one side and the control system on the other. The working process requires the electrode to simultaneously achieve thermocouple heating and temperature measurement, and the heating and temperature measurement signals must not interfere with each other, ensuring accurate temperature measurement. (3) Adjusting the width of the slag film in the heating zone. When using double thermocouples for experiments, a slag film is formed between the two pairs of thermocouples; therefore, the electrode must be able to move the position of the heating wire to adjust the width of the slag film.

[0004] Currently, the hot-wire method can be used for extended periods at high temperatures up to 1500℃, see the literature "High-temperature investigation of mold slag crystallization by single and double hotthermocouple techniques" (Nathalie). (Irmtraud Marschall and Harald Harmuth, April 2019). To achieve even higher operating temperatures, additional auxiliary heating methods are required. However, existing literature only describes the working principle and appearance of the electrodes, lacking detailed reports on their composition, connection methods, and materials. Given the expanding applications of hot-wire methods, such as in aerospace refractory materials, ceramic materials, and environmentally friendly materials, which require testing and research at 1600℃, more stringent requirements are placed on hot-wire electrodes. Therefore, there is an urgent need to develop a heating and temperature-measuring electrode for hot-wire methods, enabling long-term stable operation of the hot-wire device at ultra-high temperatures of 1600℃, while ensuring accurate temperature measurement, ease of use, and meeting the high-temperature experimental needs of a wider range of samples, including studies of melting characteristics, crystallization characteristics, solidification characteristics, dissolution kinetics, and contact angle measurement. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention provides a heating and temperature measuring electrode based on the hot wire method, which solves the following technical problems: first, simultaneously achieving thermocouple heating and temperature measurement; second, ensuring that the heating and temperature measurement signals do not interfere with each other and that temperature measurement is accurate; and third, enabling the electrode to operate stably at 1600℃ for extended periods.

[0006] To solve the aforementioned technical problem, the present invention adopts the following technical solution:

[0007] A heating and temperature measuring electrode based on the hot wire method includes two metal electrode rods as heating components. The characteristic is that one end of each metal electrode rod is connected to a platinum-rhodium wire for heating, and the other end of the metal electrode rod is fixed to an electrode rod support member. The two metal rods serve as heating electrodes, one connected to the positive terminal of a power supply line and the other connected to the negative terminal of a power supply line, and then connected through the platinum-rhodium wire to form a heating circuit.

[0008] Each metal electrode rod has a ceramic tube installed in its cavity. The positive and negative electrodes of the platinum-rhodium thermocouple assembly are respectively installed in the ceramic tube as the cold junction. One end of the positive electrode of the platinum-rhodium thermocouple is connected to the positive electrode of the temperature measuring lead, and the other end is connected to the positive electrode of the platinum-rhodium wire used for heating. One end of the negative electrode of the platinum-rhodium thermocouple is connected to the negative electrode of the temperature measuring lead, and the other end is connected to the negative electrode of the platinum-rhodium wire used for heating, so as to form a temperature measuring circuit.

[0009] One end of the micrometer is mounted on the micrometer support component, which is connected to the electrode rod support component via a central connecting rod. By rotating the adjustment knob of the micrometer, the heating component moves axially, thereby causing the metal electrode rod to extend and retract, thus achieving electrode extension and retraction adjustment.

[0010] Thus, the electrode of this invention has both heating and temperature measurement functions. The heating and temperature measurement signals do not interfere with each other due to the separation effect of the ceramic tube, and the temperature measurement is accurate. During the experiment, the electrode can be moved by rotating the adjustment knob of the micrometer screw, and the position can be dynamically adjusted. It can work stably in a high-temperature environment of 1600℃ for a long time and can reach 1700℃ for a short time.

[0011] A further feature is that the metal electrode rod is a hollow copper rod, using brass tubing as the main material and plated with a layer of nickel. Thus, by using a nickel-plated brass alloy tubing as the main heating and conductive element to transmit the heating signal, the electrode can heat up to 1600°C in as little as 10 seconds.

[0012] A further feature is that each metal electrode rod has a fixing screw hole and a limiting screw hole drilled at one end. The fixing screw hole is used to clamp and fix the platinum-rhodium wire for heating, and the limiting screw hole is used for limiting. This allows for accurate installation of the platinum-rhodium wire for heating.

[0013] A further feature is that the positive electrode of the platinum-rhodium thermocouple is a type B platinum-rhodium thermocouple with a diameter of 0.5 mm, and the negative electrode is a type B platinum-rhodium thermocouple with a diameter of 0.5 mm. Thus, PtRh30 is placed at the positive electrode and PtRh6 at the negative electrode, serving as an extension wire for heating the platinum-rhodium wire and a cold junction to transmit the temperature measurement signal.

[0014] A further feature is that the platinum-rhodium wire used for heating is made of the same material as the positive and negative electrodes of the thermocouple. This facilitates the connection between the platinum-rhodium wire used for heating and the positive and negative electrodes of the thermocouple, ensuring accurate temperature sampling signals and improving temperature measurement precision.

[0015] A further feature is that the electrode rod support component and the micrometer screw support component are made of nylon resin. Nylon resin is non-conductive, lightweight, high-strength, and heat-resistant, which can improve the overall performance of the electrode.

[0016] A further feature is that the intermediate connecting rod is made of steel, aluminum, or copper alloy.

[0017] A further feature is the inclusion of a stainless steel casing that encloses the intermediate connecting rod and some or all of the electrode rod support components. This provides excellent protection and forms a complete electrode.

[0018] A further feature is that a stainless steel back cover is provided on the outside of the micrometer support member, enclosing the micrometer support member; the stainless steel back cover is detachably connected to the rear end of the stainless steel outer shell. This provides excellent protection and forms a complete electrode.

[0019] A further feature is that a limiting groove is provided within the electrode rod support component. This limiting groove prevents the metal electrode rod from deflecting. Thus, the limiting groove ensures that the metal electrode rod only undergoes one-dimensional movement in the forward and backward direction, preventing deflection.

[0020] Compared with the prior art, the present invention provides a heating and temperature measuring electrode based on the hot filament method, which has the following technical features:

[0021] 1. In response to the usage requirements of hot wire method devices, this invention develops a heating and temperature measuring electrode that can realize simultaneous heating and temperature measurement of thermocouples.

[0022] 2. Rapid heating rate; electrodes can reach an average temperature of 200℃·s. -1 The heating rate is fast enough to reach the maximum test temperature within 10 seconds.

[0023] 3. The electrode can work stably for a long time at a high temperature of 1600℃, and can reach a short-term high temperature of 1700℃, which meets the requirements of certain experimental samples for high temperature testing conditions of 1600℃ and above.

[0024] 4. Heating and temperature measurement signals do not interfere with each other. The temperature measurement accuracy of the electrode is controlled within ±1℃. The high temperature measurement accuracy meets the various usage requirements of the hot wire method device and is easy to disassemble and maintain.

[0025] 5. The electrode adjustment and movement function of this invention can achieve precise control of the slag film width, with a control accuracy of up to 0.01 mm; the adjustment function can also be used to separate the slag film for studying the solid-liquid slag film width ratio, slag film drawing performance, etc.

[0026] 6. The present invention uses a spiral micrometer to make an adjustment and movement component, which can accurately control the position of the electrode movement with an accuracy of 0.01mm. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the electrode composition structure in an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram illustrating the working principle of the electrode of the present invention;

[0029] Figure 3 This is a schematic diagram of the dual-wire method testing process of the present invention;

[0030] Figure 4 Images of the electrodes in an embodiment of the present invention being kept at high temperatures of 1600°C and 1700°C;

[0031] Figure 5 Images showing the testing process of the dual-wire method in an embodiment of the present invention.

[0032] In the diagram, 1—fixed screw hole; 2—limiting screw hole; 3—metal electrode rod; 4—ceramic tube; 5—positive electrode of platinum-rhodium thermocouple; 6—negative electrode of platinum-rhodium thermocouple; 7—electrode rod support component; 8—stainless steel shell; 9—intermediate connecting rod; 10—stainless steel back cover; 11—micrometer support component; 12—insulating protective shell; 13—micrometer; 14—sealing groove; 15—limiting groove. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] Please refer to Figure 1This invention provides a heating and temperature measuring electrode based on a hot wire method, comprising two metal electrode rods 3 as heating components, a platinum-rhodium thermocouple positive electrode 5 and a platinum-rhodium thermocouple negative electrode 6 as temperature measuring components, a ceramic tube 4 for heat insulation and protection, and a micrometer screw 13. The metal electrode rods 3 are typically hollow copper rods, using brass tubing as the main material, such as brass or brass alloys, and are plated with a layer of nickel, exhibiting good wear resistance, strong oxidation resistance, and long service life. A platinum-rhodium wire for heating is connected to one end of each metal electrode rod 3. The figure shows two screw holes drilled at each end: a fixing screw hole 1 and a limiting screw hole 2. The fixing screw hole 1 is used to press and fix the platinum-rhodium wire for heating, and the limiting screw hole 2 is used to limit the platinum-rhodium wire, ensuring proper insertion of the heating wire. The other ends of the two metal electrode rods 3 are set (fixed) on the electrode rod support member 7; the two metal rods 3 serve as copper electrodes, one connected to the positive terminal of the power supply line and the other connected to the negative terminal of the power supply line, and then connected by a platinum-rhodium wire for heating to form a heating circuit.

[0035] Each metal electrode rod 3 has a ceramic tube 4 installed in its cavity. The platinum-rhodium thermocouple positive electrode 5 and platinum-rhodium thermocouple negative electrode 6, which serve as the temperature measuring thermocouple assembly, are respectively installed in a ceramic tube 4 as the temperature measuring cold junction. In a specific embodiment shown in the figure, the platinum-rhodium thermocouple positive electrode 5 is a 0.5mm diameter type B platinum-rhodium thermocouple positive wire (PtRh30), and the platinum-rhodium thermocouple negative electrode 6 is a 0.5mm diameter type B platinum-rhodium thermocouple negative wire (PtRh6). The temperature measuring platinum-rhodium thermocouple positive electrode 5 and platinum-rhodium thermocouple negative electrode 6 are each independent. One end of the platinum-rhodium thermocouple positive electrode 5 is connected to the positive electrode of the temperature measuring lead, and the other end is connected to the positive electrode of the platinum-rhodium wire used for heating on the metal electrode rod 3 where it is located. One end of the platinum-rhodium thermocouple negative electrode 6 is connected to the negative electrode of the temperature measuring lead, and the other end is connected to the negative electrode of the platinum-rhodium wire used for heating on the metal electrode rod 3 where it is located, thus forming a temperature measuring circuit. The platinum-rhodium wire used for heating and the positive and negative electrodes of the temperature-measuring thermocouple are made of the same material and composition, all being type B thermocouples with a diameter of 0.5 mm. The heating signal from the platinum-rhodium wire is transmitted through the copper electrode, while temperature measurement is performed through the type B platinum-rhodium thermocouple wire inside the metal electrode rod 3. The ceramic tube 4 acts as an insulator, preventing interference from heating on the temperature measurement signal and preventing the high temperature of the metal electrode rod 3 from being transmitted to the cold junctions of the platinum-rhodium thermocouple at the positive electrode 5 and the negative electrode 6, thus ensuring the accuracy of temperature measurement.

[0036] One end of the micrometer screw gauge 13 is mounted on the micrometer screw gauge support member 11 (the end away from the adjustment knob in the figure). The micrometer screw gauge support member 11 is connected to the electrode rod support member 7 via the intermediate connecting rod 9. The micrometer screw gauge 13 has a rotatable adjustment knob, which serves as an adjustment and movement component. The heating component (temperature measuring component) and the adjustment and movement component are connected via the intermediate connecting rod 9. By rotating the adjustment knob, the heating component is moved axially, thereby realizing the extension and retraction adjustment of the electrode. The micrometer screw gauge 13 is prior art and will not be further described here.

[0037] The electrode rod support component 7 and the micrometer support component 11 are made of nylon resin, which is non-conductive, lightweight, high-strength, and heat-resistant. The intermediate connecting rod 9 can be made of steel, aluminum, or copper alloy, providing high mechanical strength. The adjustment and movement assembly utilizes the existing micrometer measurement principle to achieve precise displacement control. The adjustment and measurement mechanism is constructed using the micrometer screw, scale (including fixed and movable scales), adjustment knob, and fine-tuning knob of the micrometer. The micrometer screw is connected to the intermediate connecting rod 9, which in turn is connected to the electrode rod support component 7. Rotating the adjustment knob moves the metal electrode rod 3. A limiting groove 15 is provided within the electrode rod support component 7. The limiting groove 15 ensures that the metal electrode rod 3 only undergoes one-dimensional movement in the forward and backward direction, preventing deflection.

[0038] A stainless steel outer shell 8 is provided to enclose the intermediate connecting rod 9 and part or all of the electrode rod support components 7, providing protection. The outer shell 8, made of 304 stainless steel, connects and assembles the various components of the metal electrode rod 3, encapsulating the intermediate connecting area of ​​the electrode within the outer shell 8 to form a complete electrode. A stainless steel rear cover 10 is provided on the outside of the micrometer support component 11, enclosing it for protection. The stainless steel rear cover 10 is detachably connected to the rear end of the stainless steel outer shell 8, such as via a threaded connection. A sealing groove 14 is provided at the junction of the electrode and the hot-wire method device, sealed with a rubber ring, allowing use in a ventilated environment. An insulating protective shell 12 made of resin is installed at the tail of the electrode to isolate the wires and provide safety protection.

[0039] Figure 2 This is a schematic diagram illustrating the working principle of the electrode of the present invention. A platinum-rhodium wire for heating is mounted and fixed onto the metal electrode rod 3 of the electrode, forming a circuit. The heating signal of the system is transmitted to the heating platinum-rhodium wire through the copper metal electrode rod 3, while temperature measurement is accomplished through a type B platinum-rhodium thermocouple wire inside the metal electrode rod 3, thus achieving simultaneous heating and temperature measurement. The heating and temperature measurement signals are transmitted through independent channels throughout the entire electrode usage process, without interference, and each heating and temperature measurement is completed alternately within a short time.

[0040] Figure 3 This diagram illustrates the dual-wire method experiment. Dual-wire experiments require two electrodes working in tandem, typically forming a slag film region between two heated platinum-rhodium wires. During testing, the width of the slag film region can be adjusted in real-time using the electrode adjustment mechanism, achieving precise control over the slag film width between the two wires. Furthermore, the electrode adjustment function allows for the application of external factors to create new experimental conditions.

[0041] The electrode of this invention is used in a hot-wire thermocouple device. It employs existing medium-frequency chopper technology to achieve both heating and temperature measurement of the thermocouple. Each unit of time includes one heating cycle and one temperature measurement cycle, thus simultaneously achieving temperature control and measurement functions for the thermocouple. Heating utilizes medium-frequency chopper technology, and the heating rate and temperature are controlled by adjusting the proportion of heating and temperature measurement within a unit of time. Therefore, the heating rate of the hot-wire thermocouple device is controlled by the heating duty cycle (given as a percentage). The heating rate and temperature of the electrode of this invention are achieved by controlling the power duty cycle of heating within a unit of time. This heating method offers fast response and high temperature control accuracy.

[0042] Example 1

[0043] The heating rate of the measuring electrode was determined by setting the heating duty cycle, as shown in Table 1.

[0044] Table 1 Heating rate test data

[0045]

[0046] Under a heating duty cycle of 200‰, the electrode can reach an average temperature of 160℃·s. -1 The heating rate; under a heating duty cycle of 300‰, the electrode can reach an average temperature of 200℃·s. -1 The heating rate is high. Therefore, using the electrode of this invention, the maximum test temperature can be reached within 10 seconds, resulting in high heating efficiency.

[0047] Example 2

[0048] Figure 4 Images show the electrode being kept at 1600℃ and 1700℃. Tests have shown that the hot wire method can operate stably at 1600℃ and reach 1700℃ for a short time using this electrode, meeting the requirements of certain experimental samples for high-temperature testing conditions of 1600℃ and above.

[0049] Example 3

[0050] After calibrating the thermocouple, the electrode was used to heat and melt potassium sulfate to determine the temperature measurement accuracy of the electrode. The test data are shown in Table 2.

[0051] Table 2 Temperature Measurement Accuracy Test Data

[0052]

[0053] The temperature measurement accuracy of the electrode was tested using potassium sulfate and calcium fluoride. The data shows that the temperature measurement accuracy of the electrode can be controlled to ±1℃, which is high.

[0054] Example 4

[0055] Figure 5 The image shows the process of adjusting the slag film width in the dual-wire method experiment. By adjusting the distance between the two electrodes (two metal electrode rods 3) using the adjustment and movement function of the electrodes of this invention, the width of the slag film can be precisely controlled, with a control accuracy of up to 0.01 mm. Simultaneously, the adjustment function can also be used to separate the slag film for studying the solid-liquid slag film width ratio, slag film drawing performance, etc.

[0056] The foregoing has provided a detailed description of a heating and temperature measuring electrode based on the hot filament method provided by embodiments of the present invention. This application has illustrated the principle, materials, assembly method, and implementation scheme of the invention with specific embodiments. The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit the technical solutions. Although the applicant has described the present invention in detail with reference to preferred embodiments, those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A heating and temperature measuring electrode based on the hot wire method, comprising two metal electrode rods (3) as heating components, characterized in that: One end of each metal electrode rod (3) is connected to a platinum-rhodium wire for heating, and the other end of the metal electrode rod (3) is set on the electrode rod support member (7); the two metal rods (3) serve as heating electrodes, one is connected to the positive terminal of the power line and the other is connected to the negative terminal of the power line, and then they are connected by platinum-rhodium wire to form a heating circuit; A ceramic tube (4) is installed in the cavity of each metal electrode rod (3). The positive electrode (5) and negative electrode (6) of the platinum-rhodium thermocouple assembly are respectively installed in a ceramic tube (4) as the cold junction of the temperature measuring thermocouple. One end of the positive electrode (5) of the platinum-rhodium thermocouple is connected to the positive electrode of the temperature measuring wire, and the other end is connected to the positive electrode of the platinum-rhodium wire for heating. One end of the negative electrode (6) of the platinum-rhodium thermocouple is connected to the negative electrode of the temperature measuring wire, and the other end is connected to the negative electrode of the platinum-rhodium wire for heating, so as to form a temperature measuring circuit. One end of the micrometer screw (13) is set on the micrometer screw support member (11), and the micrometer screw support member (11) is connected to the electrode rod support member (7) through the intermediate connecting rod (9); by rotating the adjustment knob of the micrometer screw (13), the heating component is driven to move axially, thereby driving the metal electrode rod (3) to move in extension and retraction; a limiting groove (15) is set in the electrode rod support member (7), and the limiting effect of the limiting groove (15) prevents the metal electrode rod (3) from deflecting.

2. The heating and temperature measuring electrode based on the hot filament method according to claim 1, characterized in that, The metal electrode rod (3) is a hollow copper rod, with brass tube as the main material and a layer of nickel plated on the surface.

3. The heating and temperature measuring electrode based on the hot filament method according to claim 1, characterized in that, Each metal electrode rod (3) has a fixing screw hole (1) and a limiting screw hole (2) drilled at one end. The fixing screw hole (1) is used to press and fix the platinum-rhodium wire for heating, and the limiting screw hole (2) is used for limiting.

4. A heating and temperature measuring electrode based on the hot filament method according to any one of claims 1-3, characterized in that, The positive electrode (5) of the platinum-rhodium thermocouple is a positive electrode wire of a type B platinum-rhodium thermocouple with a diameter of 0.5 mm, and the negative electrode (6) of the platinum-rhodium thermocouple is a negative electrode wire of a type B platinum-rhodium thermocouple with a diameter of 0.5 mm.

5. A heating and temperature measuring electrode based on the hot filament method according to claim 4, characterized in that, The platinum-rhodium wire used for heating is made of the same material as the positive and negative electrode wires of the thermocouple.

6. A heating and temperature measuring electrode based on the hot filament method according to any one of claims 1-3, characterized in that, The electrode rod support component (7) and the spiral micrometer support component (11) are made of nylon resin.

7. A heating and temperature measuring electrode based on the hot filament method according to any one of claims 1-3, characterized in that, The intermediate connecting rod (9) is made of steel, aluminum or copper alloy.

8. A heating and temperature measuring electrode based on the hot filament method according to any one of claims 1-3, characterized in that, A stainless steel housing (8) is provided to enclose the intermediate connecting rod (9) and part or all of the electrode rod support members (7).

9. A heating and temperature measuring electrode based on the hot filament method according to claim 8, characterized in that, A stainless steel back cover (10) is provided on the outside of the micrometer support member (11) to surround the micrometer support member (11); the stainless steel back cover (10) is detachably connected to the rear end of the stainless steel shell (8).

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