CN110763370A - Calibration method of W-Re galvanic couple for temperature measurement of metal melt - Google Patents
Calibration method of W-Re galvanic couple for temperature measurement of metal melt Download PDFInfo
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- CN110763370A CN110763370A CN201810832390.7A CN201810832390A CN110763370A CN 110763370 A CN110763370 A CN 110763370A CN 201810832390 A CN201810832390 A CN 201810832390A CN 110763370 A CN110763370 A CN 110763370A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K15/00—Testing or calibrating of thermometers
- G01K15/005—Calibration
Abstract
The invention relates to the field of precision casting and material preparation, in particular to a method for calibrating a W-Re galvanic couple for measuring the temperature of a metal melt. Firstly, preparing a ceramic crucible with high stability, then fixing the crucible on a workbench of a small vacuum induction furnace, and loading a metal simple substance ingot. And finally, transmitting electricity to heat the furnace charge, inserting the W-Re couple into the melt when the metal begins to melt, and reading after standing for a certain time. After the metallization is cleared, the power is reduced to a certain value below 10kw and is kept unchanged, when the metal begins to solidify, a W-Re galvanic couple is inserted into the melt, and the reading is carried out after the standing for a certain time. The invention solves the problems that the temperature of the metal melt can not be accurately measured, the thermocouple for high temperature can not be calibrated and the like, can be directly applied to actual production, has great practicability and controllability, and is beneficial to improving the quality and the performance of parts.
Description
The technical field is as follows:
the invention relates to the field of precision casting and material preparation, in particular to a method for calibrating a W-Re galvanic couple for measuring the temperature of a metal melt.
Background art:
the thermocouple is a sensor for measuring temperature based on thermoelectric effect, and is a commonly used temperature measuring element in a temperature measuring instrument. It is formed by welding two different metal elements together, and when current passes through the metal elements, the voltage difference is generated, and the temperature is displayed by the voltage difference. The common galvanic couple materials comprise nickel chromium, platinum rhodium, tungsten rhenium and the like, the galvanic couple measurement temperature of the materials of nickel chromium, platinum rhodium and the like is high and can reach 1400 ℃, the measurement environment is in air or vacuum in a hearth, and the measurement environment can also be verified through a standard couple, so that a unified calibration procedure and standard are formed.
However, the W-Re thermocouples used to measure superalloy liquids, molten steel and ultra-high melt temperatures do not currently form a uniform calibration protocol and standard. The main reasons are: (1) the galvanic couple needs to be inserted into the high-temperature melt, and a metering department cannot be equipped with corresponding smelting equipment, qualified equipment operators and maintenance personnel; (2) the temperature of molten metal is greatly influenced by the conditions of equipment of different manufacturers and the high-temperature melting environment of materials, such as: the measurement error is large and can not be unified due to factors such as the air leakage rate of the vacuum furnace, the stability of crucible materials and the like; (3) the measurement temperature is too high, and a standard substance is not easy to select; (4) the calibration work is complicated in operation and wastes cost and time. Therefore, the W-Re thermocouple has not actually been verified more accurately.
As industry develops and progresses, higher demands are made on the quality and performance of some parts, and temperature is a key parameter in the part casting process and needs to be accurately controlled. The calibration of the thermocouple to ensure its reliability and accuracy is one of the main ways to precisely control the temperature.
Disclosure of Invention
The invention aims to provide a method for calibrating a W-Re thermocouple for measuring the temperature of a metal melt, which is suitable for calibrating all material temperature measuring couples with melting characteristics, in particular for calibrating the temperature measuring couples of the metal melt.
The technical scheme of the invention is as follows:
a calibration method of a W-Re galvanic couple for measuring the temperature of a metal melt comprises the following steps:
(1) a 1kg capacity small vacuum induction furnace is used, and a hearth is cylindrical, has the height of 100-600 mm, the outer diameter of 80-300 mm and the inner diameter of 60-240 mm;
(2) preparing a crucible wax pattern: processing the crucible wax pattern by using low-temperature paraffin at room temperature;
(3) coating ceramic on the crucible wax mold at the room temperature of 18-24 ℃ and the humidity of 40-60%;
(4) after dewaxing the ceramic crucible, roasting for more than 2 hours at 900-1200 ℃;
(5) placing a ceramic crucible into a hearth of a vacuum induction furnace;
(6) 0.5-1.0 kg of metal is put into the crucible;
(7) transmitting power for heating;
(8) when the metal begins to melt, a W-Re couple is used for measuring the temperature.
The calibration method of the W-Re galvanic couple for measuring the temperature of the metal melt comprises the following steps: the height is 50-200 mm, the outer diameter is 60-150 mm, the inner diameter is 50-100 mm, and the bottom thickness is 10-30 mm.
According to the method for calibrating the W-Re couple for measuring the temperature of the metal melt, the thickness of the coated ceramic layer is more than or equal to 10mm, and the viscosity of the coated ceramic layer is 12-28 s by using a No. 5 flow cup.
According to the calibration method of the W-Re couple for measuring the temperature of the metal melt, the compressive strength of the ceramic crucible is more than or equal to 40 MPa.
According to the method for calibrating the W-Re couple for measuring the temperature of the metal melt, the metal is all metal simple substances or alloys with the melting point of more than 200 ℃.
The calibration method of the W-Re galvanic couple for measuring the temperature of the metal melt comprises the following steps of: in the 1 st minute, the power range is 5-20 kw; starting at minute 2 until melting begins, the power range is above 20 kw.
According to the method for calibrating the W-Re galvanic couple for measuring the temperature of the metal melt, when the metal begins to melt, the W-Re galvanic couple enters the melt, and the depth of the W-Re galvanic couple entering the melt is more than or equal to 10 mm.
According to the method for calibrating the W-Re galvanic couple for measuring the temperature of the metal melt, the W-Re galvanic couple enters the melt, standing is carried out for 5-10 s, then reading is carried out, and the numerical value is the temperature at which the metal starts to melt, namely the melting point.
According to the calibration method of the W-Re galvanic couple for measuring the temperature of the metal melt, after metallization is cleared, the power is reduced to a value below 10kw and is kept unchanged; when the metal begins to solidify, inserting a W-Re galvanic couple, standing for 5-10 s, and reading, wherein the numerical value is the temperature when the metal begins to solidify, namely the solidification point; the theoretical freezing point is equal to the melting point, and then the thermocouple is considered to be satisfactory if the error is within ± 10 ℃ compared to the melting point of the metal.
The method is suitable for calibrating all material temperature measuring couples with melting characteristics, and is particularly suitable for calibrating the temperature measuring couples of the metal melt.
The design idea of the invention is as follows:
the present invention is designed based on the problems occurring in actual production work and with reference to calibration standards of thermocouples such as nickel chromium, platinum rhodium, etc. The traditional method is compensated and contrasted by electromotive force difference, and a standard couple is easy to determine. The W-Re thermocouple was immersed inside the metal melt and could not be compensated and compared by electromotive force difference, nor was a reference identified. However, the metals themselves can be selected as targets, and the W-Re thermocouples can be calibrated by comparing the melting points of different metals.
The invention has the advantages and beneficial effects that:
1. the invention relates to a calibration method of a W-Re thermocouple for measuring the temperature of a metal melt, which solves the problems that the temperature of the metal melt cannot be accurately measured, the thermocouple for high temperature cannot be calibrated and the like.
2. The invention can be directly applied to actual production, has great practicability and controllability, and is beneficial to improving the quality and performance of parts.
Description of the drawings:
FIG. 1 is a view of a ceramic crucible fixed to a table.
FIG. 2 is a diagram of elemental metal ingot morphology.
FIG. 3 is a topographical map of the beginning of metal solidification.
FIG. 4 is a profile diagram of thermocouple during temperature measurement.
The specific implementation mode is as follows:
in the specific implementation process, the method for calibrating the W-Re couple for measuring the temperature of the metal melt comprises the steps of firstly preparing a high-stability ceramic crucible, then fixing the crucible on a workbench of a small vacuum induction furnace, and filling a metal simple substance ingot. And finally, feeding electricity to heat the furnace charge, inserting a W-Re galvanic couple into the melt when the metal begins to melt, and standing for 5-10 s for reading. After metallization is cleared, reducing the power to a certain value below 10kw and keeping the value unchanged, inserting a W-Re galvanic couple into the melt when the metal begins to solidify, and reading after standing for 5-10 s.
The present invention will be explained in further detail below by way of examples and figures.
Example 1
In this example, the W — Re thermocouple was calibrated according to the method described in the technical solution of the present invention. A small vacuum induction furnace with the capacity of 1kg is subjected to the front inspection, and a hearth is cylindrical and has the height of 100mm, the outer diameter of 120mm and the inner diameter of 100 mm. Processing the crucible wax pattern by using low-temperature paraffin at room temperature, wherein the dimensions are as follows: height 50mm, external diameter 60mm, internal diameter 50mm, bottom thickness 10 mm. Coating ceramic on the crucible wax mold at the room temperature of 18-20 ℃ and the humidity of 40-50%, wherein the coating thickness is 20mm, and the viscosity of a coating layer is 28 s. After coating and hanging ceramic, removing wax material, and roasting for 2 hours at 900 ℃. A ceramic crucible was placed in the hearth of a vacuum induction furnace (FIG. 1), and 0.5kg of metallic Ni elemental ingot was placed in the crucible (FIG. 2). Finally, power is transmitted to heat, and the power is 5kw within 1 minute; starting at 2 nd minute until melting began, the power was 20 kw. When the metal began to melt, a W-Re couple was inserted to a depth of 10mm, and after standing for 5s, the reading was 1457 ℃. After clearing, the power is reduced to 6kw and kept unchanged, when the metal begins to solidify (FIG. 3), a W-Re couple (FIG. 4) is inserted with an insertion depth of 10mm, and the reading is 1463 ℃ after standing for 5 s. The melting point of the Ni simple substance is 1453 ℃, the errors are 4 ℃ and 10 ℃, and the thermocouple can meet the engineering use requirements.
Example 2
In this example, the W — Re thermocouple was calibrated according to the method described in the technical solution of the present invention. A small vacuum induction furnace with the capacity of 1kg is subjected to the front inspection, and a hearth is cylindrical and has the height of 200mm, the outer diameter of 200mm and the inner diameter of 150 mm. Processing the crucible wax pattern by using low-temperature paraffin at room temperature, wherein the dimensions are as follows: the height is 100mm, the outer diameter is 120mm, the inner diameter is 90mm, and the bottom thickness is 25 mm. The crucible wax mold is coated with ceramics at the room temperature of 22 ℃ and the humidity of 56 percent, the coating thickness is 18mm, and the viscosity of the coating layer is 36 s. Removing wax material after coating ceramic, and roasting for 3.5 hours at 1200 ℃. The ceramic crucible was placed in the hearth of a vacuum induction furnace (fig. 1), and 0.9kg of metallic elemental Co ingot was placed in the crucible (fig. 2). Finally, power is transmitted to heat, and the power is 15kw within 1 minute; starting at 2 nd minute until melting began, the power was 35 kw. When the metal begins to melt, a W-Re couple is inserted to a depth of 13mm, and the reading is 1487 ℃ after standing for 9 s. After clearing, the power is reduced to 8kw and kept unchanged, when the metal begins to solidify (figure 3), a W-Re couple (figure 4) is inserted with an insertion depth of 15mm, and after standing for 6s, the reading is 1483 ℃. The melting point of the Co simple substance is 1485 ℃, the errors are 2 ℃ and-2 ℃, and the thermocouple can meet the engineering use requirements.
Example 3
In this example, the W — Re thermocouple was calibrated according to the method described in the technical solution of the present invention. A small vacuum induction furnace with the capacity of 1kg is inspected in front of the furnace, and the hearth is cylindrical and has the height of 120mm, the outer diameter of 240mm and the inner diameter of 180 mm. Processing the crucible wax pattern by using low-temperature paraffin at room temperature, wherein the dimensions are as follows: the height is 70mm, the outer diameter is 150mm, the inner diameter is 100mm, and the bottom thickness is 30 mm. The crucible wax mold is coated with ceramics at the room temperature of 24 ℃ and the humidity of 49 percent, the coating thickness is 17mm, and the viscosity of the coating layer is 31 s. After coating and hanging ceramic, removing wax material, and roasting for 4 hours at 1080 ℃. A ceramic crucible was placed in the hearth of a vacuum induction furnace (FIG. 1), and 0.6kg of metallic Fe elemental ingot was placed in the crucible (FIG. 2). Finally, power is transmitted to heat, and the power is 20kw within 1 minute; starting at 2 nd minute until melting began, the power was 50 kw. When the metal begins to melt, a W-Re couple is inserted with a depth of 15mm, and the reading is 1547 ℃ after standing for 10 s. After clearing, the power was reduced to 10kw and held constant, and when the metal started to solidify (FIG. 3), a W-Re couple (FIG. 4) was inserted to a depth of 20mm, and the reading was 1543 ℃ after standing for 10 s. The melting point of the Fe simple substance is 1538 ℃, the errors are respectively 9 ℃ and 5 ℃, and the thermocouple can meet the engineering use requirements.
The embodiment result shows that the invention solves the problems that the temperature of the metal melt can not be accurately measured, the thermocouple for high temperature can not be calibrated and the like, can be directly applied to actual production, has great practicability and controllability, and is beneficial to improving the quality and performance of parts.
Claims (10)
1. A calibration method of a W-Re galvanic couple for measuring the temperature of a metal melt is characterized by comprising the following steps:
(1) a 1kg capacity small vacuum induction furnace is used, and a hearth is cylindrical, has the height of 100-600 mm, the outer diameter of 80-300 mm and the inner diameter of 60-240 mm;
(2) preparing a crucible wax pattern: processing the crucible wax pattern by using low-temperature paraffin at room temperature;
(3) coating ceramic on the crucible wax mold at the room temperature of 18-24 ℃ and the humidity of 40-60%;
(4) after dewaxing the ceramic crucible, roasting for more than 2 hours at 900-1200 ℃;
(5) placing a ceramic crucible into a hearth of a vacuum induction furnace;
(6) 0.5-1.0 kg of metal is put into the crucible;
(7) transmitting power for heating;
(8) when the metal begins to melt, a W-Re couple is used for measuring the temperature.
2. The method of calibrating a W-Re couple for use in the thermometry of molten metal of claim 1, wherein the dimensions of the crucible wax pattern: the height is 50-200 mm, the outer diameter is 60-150 mm, the inner diameter is 50-100 mm, and the bottom thickness is 10-30 mm.
3. The method for calibrating a W-Re galvanic couple for measuring the temperature of molten metal according to claim 1, wherein the thickness of the coated ceramic layer is more than or equal to 10mm, a No. 5 flow cup is used, and the viscosity of the coated ceramic layer is 12-28 s.
4. The method for calibrating a W-Re couple for measuring the temperature of molten metal according to claim 1, wherein the compressive strength of the ceramic crucible is not less than 40 MPa.
5. The method of claim 1, wherein the metal is any metal element or alloy having a melting point greater than 200 ℃.
6. The method for calibrating a W-Re couple for measuring the temperature of molten metal according to claim 1, wherein the transmitted electric power is: in the 1 st minute, the power range is 5-20 kw; starting at minute 2 until melting begins, the power range is above 20 kw.
7. The method of claim 1, wherein the W-Re couple enters the melt at the beginning of melting of the metal to a depth of 10mm or more.
8. The method for calibrating a W-Re couple for measuring the temperature of a metal melt according to claim 7, wherein the W-Re couple enters the melt and is read after standing for 5 to 10 seconds, and the value is the temperature at which the metal starts to melt, namely the melting point.
9. The method of claim 8, wherein the power reduction to a value below 10kw is maintained after the metallization is cleared; when the metal begins to solidify, inserting a W-Re galvanic couple, standing for 5-10 s, and reading, wherein the numerical value is the temperature when the metal begins to solidify, namely the solidification point; the theoretical freezing point is equal to the melting point, and then the thermocouple is considered to be satisfactory if the error is within ± 10 ℃ compared to the melting point of the metal.
10. Method for calibrating a W-Re couple for the thermometry of a metal melt according to one of claims 1 to 9, characterized in that it is suitable for the calibration of all thermometric couples of materials with melting characteristics, in particular for the calibration of thermometric couples of metal melts.
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| CN201810832390.7A CN110763370A (en) | 2018-07-26 | 2018-07-26 | Calibration method of W-Re galvanic couple for temperature measurement of metal melt |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111912542A (en) * | 2020-07-02 | 2020-11-10 | 核工业西南物理研究院 | Temperature measuring method based on antimony-containing alloy |
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| DE69936758T2 (en) * | 1998-12-11 | 2008-06-05 | The Agency Of Industrial Science And Technology | Fixed point crucible and device for generating a fixed point temperature, and temperature calibration method with this crucible |
| CN201852440U (en) * | 2010-11-18 | 2011-06-01 | 沈阳维用精密机械有限公司 | Aluminum alloy melting furnace |
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2018
- 2018-07-26 CN CN201810832390.7A patent/CN110763370A/en active Pending
Patent Citations (5)
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| DE69936758T2 (en) * | 1998-12-11 | 2008-06-05 | The Agency Of Industrial Science And Technology | Fixed point crucible and device for generating a fixed point temperature, and temperature calibration method with this crucible |
| CN1390963A (en) * | 2002-07-25 | 2003-01-15 | 上海交通大学 | Mg alloy smelting furnace |
| CN1820190A (en) * | 2003-07-09 | 2006-08-16 | 贺利氏电子耐特国际股份公司 | Method and apparatus for calibration and measurement of temperatures in melts by optical fibers |
| CN2901209Y (en) * | 2006-06-08 | 2007-05-16 | 刘仁超 | Crucible with thermocouple plug hole |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111912542A (en) * | 2020-07-02 | 2020-11-10 | 核工业西南物理研究院 | Temperature measuring method based on antimony-containing alloy |
| CN111912542B (en) * | 2020-07-02 | 2022-04-19 | 核工业西南物理研究院 | Temperature measuring method based on antimony-containing alloy |
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