Super thermocouple and method of making same

Abstract

The application relates to the field of thermocouple production and processing methods, in particular to a super thermocouple and a preparation method thereof. The super thermocouple comprises a positive electrode thermocouple wire and a negative electrode thermocouple wire. The positive electrode thermocouple wire comprises an alloy material with a set molar percentage of raw materials, and the negative electrode thermocouple wire comprises an alloy material with a preset molar percentage of raw materials. The method comprises vacuum induction melting, swaging, intermediate annealing, drawing and reducing, heat treatment and spot welding. When the same temperature is measured, a higher potential difference can be obtained between the positive electrode and the negative electrode, so that the slight change of the temperature can be captured by the super thermocouple, and the sensitivity and accuracy of room temperature temperature measurement are improved.

Description

Technical Field

[0001] The present invention relates to the field of thermocouple production and processing methods, and in particular to a super thermocouple and a preparation method thereof. Background Art

[0002] Mercury thermometers, platinum-rhodium-platinum thermocouples, and nickel-chromium-nickel-silicon thermocouples are common temperature measurement devices for room temperature. While widely used, these existing temperature measurement devices suffer from the following issues: Mercury thermometers are not sensitive enough, requiring high-quality equipment to store the temperature they measure. If they break, mercury can evaporate into the air or come into contact with the human body, posing a health hazard. Platinum-rhodium-platinum thermocouples lack high room temperature measurement accuracy, resulting in large errors and high cost. Nickel-chromium-nickel-silicon thermocouples offer low temperature measurement accuracy, limited to ±1.6°C, failing to meet the requirements for high-precision temperature measurement. Summary of the Invention

[0003] One of the purposes of the present invention is to provide a super thermocouple to solve the problems of low safety, low precision and high cost of existing room temperature measurement equipment.

[0004] The super thermocouple in this solution includes a positive electrode thermocouple wire and a negative electrode thermocouple wire;

[0005] The positive electrode galvanic wire comprises an alloy material of the following raw materials in molar percentage:

[0006] Iron: 15% to 35%; Cobalt: 15% to 35%; Nickel: 15% to 35%; Vanadium: 15% to 35%;

[0007] The negative electrode galvanic wire comprises an alloy material of the following raw materials in molar percentage:

[0008] Iron: 20%~40%; Cobalt: 20%~40%; Nickel: 20%~40%.

[0009] Preferably, the positive electrode galvanic wire comprises the following alloy materials in molar percentages:

[0010] Iron: 20% to 30%; Cobalt: 20% to 30%; Nickel: 20% to 30%; Vanadium: 20% to 30%;

[0011] The negative electrode galvanic wire comprises the following alloy materials in molar percentages:

[0012] Iron: 30%~36%; Cobalt: 30%~36%; Nickel: 30%~36%.

[0013] A second object of the present invention is to provide a method for preparing a super thermocouple to obtain a thermocouple with low cost and accurate room temperature measurement results.

[0014] The preparation method of the super thermocouple comprises the following steps:

[0015] Step 1: vacuum induction melting, according to the molar percentage ratio of raw materials of the super thermocouple, under preset melting operating conditions, respectively, to obtain ingots of positive and negative electrodes;

[0016] Step 2: rotary forging, heating and keeping the ingot in turn, and then processing it to a set diameter to obtain alloy materials for the positive and negative electrodes;

[0017] Step 3, intermediate annealing, subjecting the alloy materials of step 2 to hydrogen protection annealing heat treatment within a set temperature range;

[0018] Step 4: Drawing and reducing the diameter of the positive electrode and negative electrode alloy materials after annealing heat treatment, respectively, to obtain positive electrode material and negative electrode material wires with diameters of φ0.03 to φ8 mm, respectively;

[0019] Step 5, heat treatment, placing the positive electrode material and negative electrode material wires in step 4 in a hydrogen protection furnace or a vacuum furnace, and performing heat treatment under different insulation conditions;

[0020] Step 6: spot welding, connecting one end of the positive electrode material wire with one end of the negative electrode material wire to obtain a super thermocouple.

[0021] Preferably, in step 1, the preset smelting operating conditions are: first, the raw materials are proportioned and then the melting power is 20-40 kW, and the power is gradually increased from low power until the raw materials are fully melted; then, under a vacuum degree of ≤2.5×10 -3 Under Pa conditions, vacuum refining is carried out at a power of 15 to 30 kW for 10 to 30 minutes; stirring and adjusting the temperature to 1600-1800°C for pouring.

[0022] More preferably, in order to ensure that the alloy liquid has a certain fluidity, the pouring temperature of the alloy material of the negative electrode is 1600°C, and the pouring temperature of the alloy material of the positive electrode is 1800°C.

[0023] Preferably, in step 2, the heating temperature is 1300-1500° C., the heat preservation time is 1-3 hours, and the set diameter is φ2.5-φ15 mm.

[0024] More preferably, in order to soften the alloy material so as to be easier to process to a set diameter, the heating temperature of the alloy material of the negative electrode is 1300°C, and the heating temperature of the alloy material of the positive electrode is 1500°C.

[0025] Preferably, in step 3, the temperature is set in the range of 1200 to 1400°C.

[0026] More preferably, in order to eliminate the stress generated in the spinning step, the alloy material annealing temperature of the negative electrode is 1200℃, and the alloy material annealing temperature of the positive electrode is 1400℃.

[0027] Preferably, in step 5, the heat preservation condition of the wire of the positive electrode is 1300-1400℃±5℃ for 1-3h, and the heat preservation condition of the wire of the negative electrode is 1000-1250℃±5℃ for 1-3h.

[0028] Compared with the prior art, the beneficial effects of the present application are:

[0029] By setting different alloy material components of the positive electrode and the negative electrode, a larger Seebeck coefficient difference is obtained. Compared with the existing nickel-chromium-nickel-silicon thermocouple, a higher potential difference between the positive electrode and the negative electrode can be obtained when measuring the same temperature, and the thermoelectric power factor is extremely high, representing that more electricity can be generated per unit temperature difference. Therefore, the super thermocouple can capture the slight change of temperature, and the sensitivity and accuracy of room temperature measurement are improved. The alloy material component setting of the positive electrode and the negative electrode has good mechanical properties, is not easy to damage, has high safety, high oxidation resistance and corrosion resistance, is easy to process and store, and has low cost. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The flowchart of the preparation method embodiment of the super thermocouple of the present application is shown in the figure.

[0031] Figure 2 The Seebeck coefficient diagram of the positive electrode thermocouple wire and the negative electrode thermocouple wire of the super thermocouple of the present application is shown in the figure.

[0032] Figure 3 The thermoelectric power factor diagram of the positive electrode thermocouple wire and the negative electrode thermocouple wire of the super thermocouple of the present application is shown in the figure.

[0033] Figure 4 The potential comparison diagram of the super thermocouple of the present application and the existing nickel-chromium alloy-nickel-silicon alloy is shown in the figure. DETAILED DESCRIPTION

[0034] The following will be further described in detail through specific embodiments.

[0035] Embodiment 1

[0036] The super thermocouple comprises a positive electrode thermocouple wire and a negative electrode thermocouple wire, and the obtained thermocouple is used for temperature measurement in the range of 0℃-300℃.

[0037] The positive electrode thermocouple wire comprises an alloy material of the following raw materials in mole percentage:

[0038] Iron: 25%; cobalt: 25%; nickel: 25%; vanadium: 25%;

[0039] The negative electrode galvanic wire comprises an alloy material with the following molar percentages:

[0040] Iron: 34%; Cobalt: 33%; Nickel: 33%.

[0041] The thermocouple of this embodiment 1 is as follows Figure 2 As shown in the figure, the negative electrode material FeCoNi alloy has a high negative Seebeeck coefficient of -40 to -50 μV / K, and the positive electrode material FeCoNiV alloy has a positive Seebeeck coefficient of 10 to 20 μV / K. The difference in Seebeeck coefficient between the positive and negative electrode materials is 50 to 70 μV / K, which is the largest among alloy thermocouples. Figure 4 As shown, compared with the existing nickel-chromium-nickel-silicon thermocouple, the Seebeeck coefficients of nickel-chromium alloy and nickel-silicon alloy are both negative, and the thermoelectromotive force rate (i.e., Seebeeck coefficient) of the nickel-chromium-nickel-silicon thermocouple in its entire temperature measurement range is less than 43μV / K. When measuring the same temperature, the thermocouple of this embodiment 1 can obtain a higher potential difference between the positive and negative alloys, and has high measurement accuracy. Figure 3 As shown, the negative electrode alloy material FeCoNi alloy of this embodiment 1 has an extremely high thermoelectric power factor, which is about 10000~12000μW / mK^2. The extremely high thermoelectric power factor means that more electricity can be generated per unit temperature difference, so that even slight changes in temperature can be captured by the super thermocouple of the present invention, and the temperature measurement sensitivity is high.

[0042] Preparation method of super thermocouple, such as Figure 1 As shown, the following steps are included:

[0043] Step 1, vacuum induction melting: melt the raw materials prepared from the positive and negative galvanic wires according to the above ratios respectively, with a melting power of 20-40kW, and gradually increase the power from low to high until the materials are fully melted. -3 Pa, vacuum refining for 20 minutes; mechanically adding electromagnetic stirring and adjusting the temperature to 1600-1800°C for pouring, the pouring temperature of the negative electrode alloy material is 1600°C, and the pouring temperature of the positive electrode alloy material is 1800°C.

[0044] Step 2: Rotary forging. Heat the ingot to 1300-1500℃, keep it warm for 1-3 hours, and process it to the set diameter. The heating temperature of the alloy material of the negative electrode is 1300°C, and the heating temperature of the alloy material of the positive electrode is 1500°C.

[0045] Step 3: intermediate annealing, subjecting the swaged positive electrode alloy material and the negative electrode alloy material to hydrogen protection annealing heat treatment at 1400° C. and 1200° C., respectively.

[0046] Step 4: Drawing and reducing the diameter: the annealed positive electrode and negative electrode alloy materials are respectively drawn and reduced to obtain wires with a diameter of φ0.03 to φ8 mm.

[0047] Step 5: Heat treatment. The drawn and reduced positive and negative electrode wires are placed in a hydrogen-protected furnace or vacuum furnace and heat treated under different holding conditions. The positive electrode wire is held at 1300-1400°C ± 5°C for 3 hours, and the negative electrode wire is held at 1000-1250°C ± 5°C for 2 hours. This results in the positive and negative electrode materials for the super thermocouple.

[0048] Step 6: spot welding, connecting one end of the positive electrode material wire with one end of the negative electrode material wire to form a super thermocouple.

[0049] The super thermocouple obtained by the above preparation method with the first material ratio of this embodiment 1 is used for measuring temperatures of 50°C, 100°C, 150°C, 200°C, 250°C, and 300°C for convenience of measurement. Other temperatures within the range of 0 to 300°C are also applicable to the thermocouple of this embodiment for measurement, and the thermocouple potential table shown in Table 1 can also be obtained.

[0050] Table 1 Thermocouple potential of the first material ratio

[0051]

[0052] As can be seen from Table 1, the thermocouple with the first material ratio in Example 1 has a temperature measurement accuracy of ±0.01°C, which is higher than the maximum temperature measurement accuracy of ±1.6°C of the existing nickel-chromium-nickel-silicon thermocouple and can accurately measure temperature in the range of 20°C to 300°C, with high temperature measurement accuracy.

[0053] The super thermocouple prepared by the above method with the first material ratio of Example 1 was kept at 150° C. for 720 h, and the change in its thermoelectric potential was measured to obtain a long-term test comparison table as shown in Table 2.

[0054] Table 2 Comparison of long-term thermocouple test of the first material ratio

[0055]

[0056] As can be seen from Table 2, the super thermocouple with the first material ratio in Example 1 can achieve a thermoelectric potential change of less than ±0.02°C at 150°C after 720 hours, and has good long-term high-temperature stability.

[0057] Example 2

[0058] The difference from Example 1 is that the positive electrode wire of the super thermocouple includes an alloy material with the following molar percentages:

[0059] Iron: 15%; Cobalt: 15%; Nickel: 35%; Vanadium: 35%;

[0060] The negative electrode galvanic wire comprises an alloy material with the following molar percentages:

[0061] Iron: 34%; Cobalt: 33%; Nickel: 33%.

[0062] The preparation method of the super thermocouple is carried out using the method steps in Example 1.

[0063] The super thermocouple obtained by the above preparation method with the second material ratio of this embodiment 2 is used for measuring temperatures of 50°C, 100°C, 150°C, 200°C, 250°C, and 300°C for convenience of measurement. Other temperatures within the range of 0 to 300°C are also applicable to the thermocouple of this embodiment for measurement, and the thermocouple potential table shown in Table 3 can also be obtained.

[0064] Table 3 Thermocouple potential of the second material ratio

[0065]

[0066] As can be seen from Table 3, the thermocouple with the second material ratio in Example 2 has a temperature measurement accuracy of ±0.02°C, which is higher than the maximum temperature measurement accuracy of ±1.6°C of the existing nickel-chromium-nickel-silicon thermocouple. It can accurately measure temperature in the range of 20°C to 300°C and has high temperature measurement accuracy.

[0067] The super thermocouple prepared by the above preparation method with the second material ratio of Example 2 was kept at 150° C. for 720 h, and the change in its thermoelectric potential was measured to obtain a long-term test comparison table as shown in Table 4.

[0068] Table 4 Comparison of long-term thermocouple test results for the second material ratio

[0069]

[0070] As shown in Table 4, the super thermocouple with the second material ratio in Example 2 can maintain a thermoelectric potential change of less than ±0.02°C at 150°C for 720 hours, and has good long-term high-temperature stability.

[0071] Example 3

[0072] The difference from Example 1 is that the positive electrode wire of the super thermocouple includes an alloy material with the following molar percentages:

[0073] Iron: 25%; Cobalt: 25%; Nickel: 25%; Vanadium: 25%;

[0074] The negative electrode filament comprises an alloy material with the following raw materials in mole percentage:

[0075] Iron: 20%; Cobalt: 40%; Nickel: 40%.

[0076] The preparation method of the super thermocouple adopts the method steps in Embodiment 1.

[0077] The super thermocouple obtained by the preparation method and the third material ratio in Embodiment 3 is measured at 50℃, 100℃, 150℃, 200℃, 250℃ and 300℃ for the convenience of measurement, and other temperatures in the range of 0-300℃ are also applicable to the thermocouple in this embodiment for measurement, and the thermocouple potential table shown in Table 5 can also be obtained.

[0078] Table 5: Thermocouple potential table of the third material ratio

[0079]

[0080] As can be seen from Table 5, the thermocouple with the third material ratio in Embodiment 3 has a temperature measurement accuracy of ±0.02℃, which is higher than the highest accuracy of ±1.6℃ of the existing nickel-chromium-nickel silicon thermocouple, and can accurately measure the temperature in the range of 20℃ to 300℃.

[0081] The super thermocouple obtained by the preparation method and the third material ratio in Embodiment 2 is used to maintain 720h at 150℃, and the change of thermoelectric potential is measured, and the long-term test comparison table shown in Table 6 is obtained.

[0082] Table 6: Long-term test comparison table of the third material ratio thermocouple

[0083]

[0084] As can be seen from Table 4, the super thermocouple with the third material ratio in Embodiment 2 has a thermoelectric potential change of less than ±0.02℃ after 720 hours at 150℃, and has good long-term high-temperature stability.

[0085] In summary, the super thermocouple has the advantages of high temperature measurement accuracy, high sensitivity, good long-term stability and low cost, and can be widely used in most room temperature measurement scenes. Based on the preparation method of the material ratio of the super thermocouple, the positive and negative electrode filaments have good mechanical properties, oxidation resistance and corrosion resistance, and are easy to process and store.

[0086] The above is only an embodiment of the present invention, and the common knowledge such as the specific structure and characteristics of the scheme is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A super thermocouple comprising a positive electrode wire and a negative electrode wire; characterized in that: The positive electrode galvanic wire is made of the following alloy materials in molar percentage: composition: Iron: 15%~35%; Cobalt: 15%~35%; Nickel: 15%~35%; Vanadium: 15%~35%; The negative electrode galvanic wire is made of the following alloy materials in molar percentage: composition: Iron: 20%~40%; Cobalt: 20%~40%; Nickel: 20%~40%.

2. The super thermocouple according to claim 1, characterized in that: The positive electrode galvanic wire is composed of the following alloy materials in molar percentage: composition: Iron: 20%~30%; Cobalt: 20%~30%; Nickel: 20%~30%; Vanadium: 20%~30%; The negative electrode galvanic wire is composed of the following alloy materials in molar percentage: composition: Iron: 30%~36%; Cobalt: 30%~36%; Nickel: 30%~36%.

3. A method for preparing a super thermocouple according to claim 1 or 2, characterized in that: The following steps are involved: Step 1: vacuum induction melting, according to the molar percentage ratio of raw materials of the super thermocouple, under preset melting operating conditions, respectively, to obtain ingots of positive and negative electrodes; The preset smelting operation conditions are as follows: first, the raw materials are proportioned and then the melting power is 20-40 kW, and the power is gradually increased from low power until the raw materials are fully melted; then, under vacuum degree ≤ Under Pa conditions, vacuum refining is performed at a power of 15 to 30 kW for 10 to 30 minutes; stirring and adjusting the temperature to 1600-1800 °C for pouring; Step 2: rotary forging, heating and keeping the ingot in sequence, and then processing it to a set diameter to obtain alloy materials for the positive and negative electrodes. The heating temperature is 1300-1500° C. and the temperature is kept for 1-3 hours. The set diameter is φ2.5-φ15 mm. Step 3, intermediate annealing, subjecting the alloy materials of step 2 to hydrogen protection annealing heat treatment within a set temperature range; Step 4: Drawing and reducing the diameter of the positive electrode and negative electrode alloy materials after annealing heat treatment, respectively, to obtain positive electrode material and negative electrode material wires with diameters of ϕ0.03 to ϕ8 mm, respectively; Step 5, heat treatment, placing the positive electrode material and negative electrode material wires in step 4 in a hydrogen protection furnace or a vacuum furnace, and performing heat treatment under different insulation conditions; Step 6: spot welding, connecting one end of the positive electrode material wire with one end of the negative electrode material wire to obtain a super thermocouple.

4. The preparation method according to claim 3, wherein: The casting temperature of the alloy material of the negative electrode is 1600°C, and the casting temperature of the alloy material of the positive electrode is 1800°C.

5. The preparation method according to claim 3, wherein: The heating temperature of the alloy material of the negative electrode is 1300°C, and the heating temperature of the alloy material of the positive electrode is 1500°C.

6. The preparation method according to claim 3, wherein: In step 3, the temperature is set in the range of 1200-1400°C.

7. The preparation method according to claim 6, characterized in that: The annealing temperature of the alloy material of the negative electrode is 1200°C, and the annealing temperature of the alloy material of the positive electrode is 1400°C.

8. The preparation method according to claim 6, wherein: In step 5, the positive electrode wire is kept at 1300-1400°C ±5°C for 1-3 hours, and the negative electrode wire is kept at 1000-1250°C ±5°C for 1-3 hours.

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