阅读说明：本技术 一种冷坩埚定向凝固过程中温度测量装置及测量方法 (Temperature measuring device and measuring method in directional solidification process of cold crucible ) 是由 陈瑞润 方虹泽 王琪 杨劼人 王亮 丁宏升 苏彦庆 郭景杰 于 2021-06-28 设计创作，主要内容包括：一种冷坩埚定向凝固过程中温度测量装置及测量方法,它涉及一种温度测量装置及方法。本发明为了解决现有定向凝固过程的测温装置存在无法测量物料的瞬时温度变化以及易与物料发生反应,从而影响物料的熔体质量的问题。本发明的B型热电偶的一端插入到陶瓷管内,B型热电偶的另一端与外部数据处理组件连接,上升降系统安装在测温系统本体内与B型热电偶连接,K型热电偶的一端与位于铜坩埚内的物料连接,K型热电偶的另一端穿过测温系统本体并与外部数据处理组件连接。物料熔铸,熔化后,对熔体测温,并上下移动,以避免热电偶在钛铝熔体中因长时间停留而与熔体反应熔化。本发明用于冷坩埚定向凝固过程中温度测量。(A temperature measuring device and a temperature measuring method in the directional solidification process of a cold crucible relate to a temperature measuring device and a temperature measuring method. The invention aims to solve the problems that the existing temperature measuring device for the directional solidification process cannot measure the instantaneous temperature change of materials and is easy to react with the materials, so that the melt quality of the materials is influenced. One end of a B-type thermocouple is inserted into a ceramic tube, the other end of the B-type thermocouple is connected with an external data processing assembly, an ascending and descending system is arranged in a temperature measuring system body and connected with the B-type thermocouple, one end of a K-type thermocouple is connected with a material in a copper crucible, and the other end of the K-type thermocouple penetrates through the temperature measuring system body and is connected with the external data processing assembly. And (3) casting the materials, measuring the temperature of the melt after the materials are melted, and moving up and down to prevent the thermocouple from reacting with the melt and melting due to long-time residence in the titanium-aluminum melt. The invention is used for measuring the temperature in the directional solidification process of the cold crucible.)

1. A temperature measuring device in the directional solidification process of a cold crucible comprises a temperature measuring system body; the method is characterized in that: it also comprises a ceramic tube (3), a B-type thermocouple (4), an ascending and descending system (16), a K-type thermocouple (10) and an external data processing component,

the ceramic tube (3) is vertically inserted into the upper part of the copper crucible (5) of the temperature measuring system body, one end of the B-type thermocouple (4) is inserted into the ceramic tube (3), the other end of the B-type thermocouple (4) penetrates through the temperature measuring system body and is connected with an external data processing assembly, the ascending and descending system (16) is installed in the temperature measuring system body and is connected with the B-type thermocouple (4), the ascending and descending system (16) drives the B-type thermocouple (4) to move up and down in the ceramic tube (3), one end of the K-type thermocouple (10) is connected with a material (6) located in the copper crucible (5), and the other end of the K-type thermocouple (10) penetrates through the temperature measuring system body and is connected with the external data processing assembly.

2. The device for measuring the temperature in the directional solidification process of the cold crucible as claimed in claim 1, wherein: the lifting system (16) comprises a fixed frame (20), a motor (19), a rack (18), a gear (50), a bracket (17) and a thermocouple clamp (21),

the fixing frame (20) is arranged at the upper part in the temperature measuring system body, the support (17) is vertically arranged on the fixing frame (20), the rack (18) is slidably arranged on the support (17), the motor (19) is arranged on the fixing frame (20), the output shaft of the motor (19) is connected with the gear (50), the gear (50) is meshed with the rack (18), and the rack (18) is connected with the B-type thermocouple (4) through the thermocouple clamp (21).

3. The device for measuring the temperature in the directional solidification process of the cold crucible as claimed in claim 2, wherein: the bracket (17) is provided with scale marks.

4. The device for measuring the temperature in the directional solidification process of the cold crucible as claimed in claim 1 or 2, wherein: the temperature measuring system body comprises a tank body (1), a copper crucible (5), a coil (15) and a lower lifting system (12), wherein the lower lifting system (12) is installed at the lower end of the tank body (1), the copper crucible (5) is installed right above the lower lifting system (12), a material (6) extends into the copper crucible (5) and moves up and down under the driving of the lower lifting system (12), and the coil (15) is sleeved on the outer side of the copper crucible (5).

5. The device for measuring the temperature in the directional solidification process of the cold crucible as claimed in claim 4, wherein: the external data processing assembly comprises a compensation wire (8), a temperature patrol instrument (9) and a host (7), the B-type thermocouple (4) and the K-type thermocouple (10) are intersected and then extend out of the tank body (1) to be connected with the temperature patrol instrument (9) through the compensation wire (8), the temperature patrol instrument (9) is connected with the host (7), and data analysis is carried out on information collected by the B-type thermocouple (4) and the K-type thermocouple (10) through the host (7).

6. The device for measuring the temperature in the directional solidification process of the cold crucible as claimed in claim 5, wherein: the material (6) is a columnar material and is made of Ti-46Al-6 Nb.

7. The device for measuring the temperature in the directional solidification process of the cold crucible as claimed in claim 6, wherein: a plurality of temperature measuring grooves are horizontally arranged on the material (6) from top to bottom at equal intervals.

8. The device for measuring the temperature in the directional solidification process of the cold crucible as claimed in claim 7, wherein: the distance between two adjacent temperature measuring grooves is 6mm-9 mm.

9. The device for measuring the temperature in the directional solidification process of the cold crucible as claimed in claim 8, wherein: the temperature measuring device is characterized by further comprising a plurality of metal shielding wires (22), wherein one metal shielding wire (22) is installed in each temperature measuring groove, a ceramic tube (3) is inserted into each metal shielding wire (22), and a K-type thermocouple (10) is arranged in each ceramic tube (3).

10. A measuring method using the temperature measuring device in the directional solidification process of the cold crucible as claimed in any one of claims 1 to 9, characterized in that: it comprises the following steps:

the method comprises the following steps of firstly, slotting in the axial direction of a material (6), drilling holes at different heights to the center, wherein the distance between every two adjacent drilled holes is 6-9mm, and the size of the slotting is enough to accommodate a K-type thermocouple (10) for temperature measurement;

step two, using high-purity Al₂O₃Ceramic tubes (3) and Y₂O₃The coating protects the K-type thermocouple (10), so that the K-type thermocouple (10) can stay in the titanium-aluminum melt for a long time to measure the temperature;

thirdly, winding a metal shielding wire for preventing electromagnetic field interference on the K-type thermocouple (10), and then placing the K-type thermocouple (10) in the axial groove of the material (6) so as to measure the temperature of the solid phase of the material, wherein the temperature measuring range of the K-type thermocouple (10) is 0-800 ℃;

fourthly, placing the material (6) in a copper crucible (5) for fusion casting, measuring the temperature of the melt after the top end of the material (6) is melted, on one hand, carrying out infrared temperature measurement on the surface of a molten pool at a window at the top of a hearth, on the other hand, controlling a B-type thermocouple (4) to be inserted into the molten pool for temperature measurement, wherein the temperature measurement range of the B-type thermocouple (4) is 500-1800 ℃, the B-type thermocouple (4) inserted into the molten pool is controlled to move up and down through an ascending and descending system (16) and a descending and ascending system (21), and in the material heating process, the temperature change of the material (6) is recorded through a K-type thermocouple (10);

step five, after the temperature of the molten pool is stable, controlling the B-type thermocouple (4) to be slowly inserted from the central position of the molten pool, recording the temperature of the molten pool, and then lifting the B-type thermocouple (4) out of the molten pool;

step six, changing process parameters, and moving the B-type thermocouple (4) downwards to measure the temperature when measuring the temperature again, so that the B-type thermocouple (4) is repeatedly used;

and seventhly, numerical calculation of the electromagnetic field in the cold crucible, the temperature field during loading and the flow field is carried out by adopting finite element software until the temperature measurement of directional solidification of the cold crucible is completed.

Technical Field

The invention relates to a temperature measuring device and a temperature measuring method, in particular to a temperature measuring device and a temperature measuring method in a cold crucible directional solidification process, and belongs to the field of temperature measurement.

Background

When the heat balance steady state period is reached in the directional solidification process, the temperature distribution condition in the molten pool, especially the temperature distribution of the material in the directional solidification of the cold crucible, has important significance for understanding the heat transfer of the material and controlling the shape of an interface. However, due to the high chemical activity of the TiAl alloy melt, an electromagnetic field exists in the cold crucible, so that the temperature measurement of the material is very difficult.

At present, the existing temperature measuring device and method in the directional solidification process, such as the patent continuous temperature measuring device and method in the directional solidification process (application number: 201210251785.0), solve the engineering problems that the temperature in the directional solidification furnace is difficult to continuously measure, the temperature gradient is difficult to accurately calculate, and the like. However, the patent does not take into account the instantaneous temperature changes at different locations and the important influence of the temperature distribution of the material on the directional solidification. In addition, the thermocouple needs to measure in the molten pool for a long time, and is easily reacted with the material under the influence of a high-temperature environment, so that the quality of the melt of the material is influenced.

In conclusion, the existing temperature measuring device for the directional solidification process has the problems that the instantaneous temperature change of the material cannot be measured, and the material is easy to react with the material, so that the melt quality of the material is influenced.

Disclosure of Invention

The invention aims to solve the problems that the existing temperature measuring device for the directional solidification process cannot measure the instantaneous temperature change of materials and is easy to react with the materials, so that the melt quality of the materials is influenced. Further provides a temperature measuring device and a temperature measuring method in the directional solidification process of the cold crucible.

The technical scheme of the invention is as follows: a temperature measuring device in the directional solidification process of a cold crucible comprises a temperature measuring system body; the ceramic tube is vertically inserted into the upper part of the copper crucible of the temperature measuring system body, one end of the B-type thermocouple is inserted into the ceramic tube, the other end of the B-type thermocouple penetrates through the temperature measuring system body and is connected with the external data processing assembly, the ascending and descending system is installed in the temperature measuring system body and is connected with the B-type thermocouple, the ascending and descending system drives the B-type thermocouple to move up and down in the ceramic tube, one end of the K-type thermocouple is connected with a material in the copper crucible, and the other end of the K-type thermocouple penetrates through the temperature measuring system body and is connected with the external data processing assembly.

Furthermore, the ascending and descending system comprises a fixing frame, a motor, a rack, a gear, a support and a thermocouple clamp, wherein the fixing frame is installed on the upper portion in the temperature measuring system body, the support is vertically installed on the fixing frame, the rack is slidably installed on the support, the motor is installed on the fixing frame, an output shaft of the motor is connected with the gear, the gear is meshed with the rack, and the rack is connected with the B-type thermocouple through the thermocouple clamp.

Furthermore, the bracket is provided with scale marks.

Further, the temperature measurement system body includes jar body, copper crucible, coil and lower operating system, and lower operating system installs the lower extreme in the jar body, and the copper crucible is installed under operating system directly over, and the material stretches in the copper crucible and reciprocates under operating system's drive down, and the coil suit is in the outside of copper crucible.

Further, the external data processing assembly comprises a compensation wire, a temperature patrol instrument and a host, the B-type thermocouple and the K-type thermocouple stretch out of the tank body after intersection and are connected with the temperature patrol instrument through the compensation wire, the temperature patrol instrument is connected with the host, and information collected by the B-type thermocouple and the K-type thermocouple is subjected to data analysis through the host.

Furthermore, the material is columnar material and is Ti-46Al-6 Nb.

Furthermore, a plurality of temperature measuring grooves are horizontally arranged on the material from top to bottom at equal intervals.

Furthermore, the distance between two adjacent temperature measuring grooves is 6mm-9 mm.

Furthermore, the temperature measuring device also comprises a plurality of metal shielding wires, wherein one metal shielding wire is arranged in each temperature measuring groove, a ceramic tube is inserted in each metal shielding wire, and a K-type thermocouple is arranged in each ceramic tube.

The invention also provides a method for measuring the temperature in the directional solidification process of the cold crucible, which comprises the following steps:

the method comprises the following steps of firstly, slotting in the axial direction of a material, drilling holes at different heights to the center, wherein the distance between every two adjacent drilled holes is 6-9mm, and the size of the slotting is enough to accommodate a K-type thermocouple for temperature measurement;

step two, using high-purity Al₂O₃Ceramic tube and Y₂O₃The coating protects the K-type thermocouple, so that the K-type thermocouple can stay in the titanium-aluminum melt for a long time to measure the temperature;

step three, winding a metal shielding wire for preventing electromagnetic field interference on the K-type thermocouple, and then placing the K-type thermocouple in the axial groove of the material to measure the temperature of the solid phase of the material, wherein the temperature measuring range of the K-type thermocouple is 0-800 ℃;

fourthly, placing the materials in a copper crucible for fusion casting, measuring the temperature of the melt after the top of the materials is melted, on one hand, carrying out infrared temperature measurement on the surface of a molten pool on a window at the top of a hearth, on the other hand, controlling a B-type thermocouple to be inserted into the molten pool for temperature measurement, wherein the temperature measurement range of the B-type thermocouple is 500-1800 ℃, the B-type thermocouple inserted into the molten pool is controlled to move up and down through an upper lifting system and a lower lifting system, and the temperature change of the materials is recorded through a K-type thermocouple in the material heating process;

step five, after the temperature of the molten pool is stable, controlling a B-type thermocouple to slowly insert the B-type thermocouple from the central position of the molten pool, recording the temperature of the molten pool, and then lifting the B-type thermocouple out of the molten pool;

step six, changing process parameters, and moving the B-type thermocouple downwards to measure temperature when measuring the temperature again, so that the B-type thermocouple is repeatedly used;

and seventhly, numerical calculation of the electromagnetic field in the cold crucible, the temperature field during loading and the flow field is carried out by adopting finite element software until the temperature measurement of directional solidification of the cold crucible is completed.

Compared with the prior art, the invention has the following effects:

1. the invention adopts the ascending and descending system to move the B-type thermocouple in the ceramic tube up and down, thereby effectively avoiding the problem that the B-type thermocouple is easy to melt or react with materials if the B-type thermocouple is positioned in the copper crucible for a long time when the temperature of the titanium-aluminum alloy melt is measured. The height of the B-type thermocouple in the copper crucible can be adjusted at any time according to the temperature environment in the tank body. Provides a solution to the problem that the thermocouple cannot be placed in the melt for a long time. Meanwhile, the thermocouple can not work normally in the magnetic field environment.

2. The invention avoids the thermocouple from reacting with the material when the growing period is in a high-temperature environment, thereby realizing the repeated use of the thermocouple and improving the experimental efficiency and the economical efficiency. The service life of the thermocouple is prolonged by nearly 2 times.

3. The ascending and descending system can control the insertion depth of the thermocouple, thereby ensuring that the thermocouple is inserted into the molten pool at the same depth every time and ensuring the reliability of data.

4. The measuring method solves the problem that the temperature of the material is difficult to measure due to the high chemical activity of the titanium-aluminum alloy and the existence of a magnetic field in the cold crucible.

5. The method can realize the repeated use of the thermocouple and improve the experimental efficiency and the economical efficiency.

6. The method can ensure that the downward moving depth of the thermocouple inserted into the molten pool every time is the same, and ensure the reliability of data.

7. The invention calculates the change of the temperature field through model establishment and compares the change with the data measured by experiments to ensure the reliability of the test data.

Drawings

FIG. 1 is a schematic view of a temperature measuring system, FIG. 2 is a partial enlarged view of A in FIG. 1, FIG. 3 is a partial enlarged view of B in FIG. 1, and FIG. 4 is a temperature change during heating of a material; FIG. 5 is an enlarged view of a portion of the material;

FIG. 6(a) is a finite element induction heating model 1; FIG. 6(b) is a finite element induction heating model 2;

FIG. 7 is a schematic view of material position selection;

FIG. 8 is a graph of the effect of heating power on the Ti-46Al-6Nb alloy temperature field and solidification interface;

FIG. 9 is a graph of the effect of heating frequency on the temperature field and solidification interface of a Ti-46Al-6Nb alloy;

FIG. 10 is a graph of the effect of lateral heat transfer coefficient on the Ti-46Al-6Nb alloy temperature field and solidification interface;

FIG. 11 is a graph of the effect of material height on the Ti-46Al-6Nb alloy temperature field and solidification interface;

FIG. 12 is a comparison of steady state temperature calculations and measurements made by varying the distance of the material level from the bottom of the crucible;

FIG. 13 is a comparison of steady state temperature calculations and measurements made by varying the distance of the heating power from the bottom of the crucible;

FIG. 14 is a surface feature of a cold electromagnetic crucible heating Ti-46Al-6Nb alloy melting start process, wherein (a), (b) are before melting; (c) the edge part begins to melt; (d) forming a molten pool;

FIG. 15 shows the results of Ti-46Al-6Nb bath temperature measurements at different heating powers, in this case surface temperatures measured by infrared.

FIG. 16 shows the results of Ti-46Al-6Nb bath measurements at different heating powers, in this case thermocouple vs. bath measurements.

Detailed Description

The first embodiment is as follows: the present embodiment is described with reference to fig. 1 to 3 and 5, and the temperature measuring device and the measuring method in the directional solidification process of the cold crucible of the present embodiment includes a temperature measuring system body; the ceramic tube type temperature measuring device further comprises a ceramic tube 3, a B-type thermocouple 4, an ascending and descending system 16, a K-type thermocouple 10 and an external data processing assembly, wherein the ceramic tube 3 is vertically inserted into the upper portion of the copper crucible 5 of the temperature measuring system body, one end of the B-type thermocouple 4 is inserted into the ceramic tube 3, the other end of the B-type thermocouple 4 penetrates through the temperature measuring system body and is connected with the external data processing assembly, the ascending and descending system 16 is installed in the temperature measuring system body and is connected with the B-type thermocouple 4, the ascending and descending system 16 drives the B-type thermocouple 4 to move up and down in the ceramic tube 3, one end of the K-type thermocouple 10 is connected with a material 6 located in the copper crucible 5, and the other end of the K-type thermocouple 10 penetrates through the temperature measuring system body and is connected with the external data processing assembly.

In the embodiment, the type of the thermocouple for temperature measurement is selected according to the material state. When the solid phase of the material is measured, a K-type thermocouple is selected for measuring the temperature, and the use temperature range of the thermocouple is required to be 0-800 ℃; when the temperature of the material melt is measured, a B-type thermocouple is selected for measurement, and the use temperature measurement range of the thermocouple is required to be 500-1800 ℃.

According to the specific working conditions of the thermocouple, when the K-type thermocouple is used for measuring the temperature of a solid phase of a material in a magnetic field environment, a metal shielding wire is wound outside the K-type thermocouple to avoid magnetic field interference.

The second embodiment is as follows: referring to fig. 2, the ascending and descending system 16 of the present embodiment includes a fixed frame 20, a motor 19, a rack 18, a gear 50, a bracket 17, and a thermocouple clamp 21, wherein the fixed frame 20 is installed at an upper portion in the temperature measuring system body, the bracket 17 is vertically installed on the fixed frame 20, the rack 18 is slidably installed on the bracket 17, the motor 19 is installed on the fixed frame 20, an output shaft of the motor 19 is connected to the gear 50, the gear 50 is engaged with the rack 18, and the rack 18 is connected to the B-type thermocouple 4 through the thermocouple clamp 21. So set up, simple structure, control is convenient, and the transmission form that adopts rack and pinion moreover is more stable, and the height that the motor is convenient for control goes up and down, and transmission precision is high. Other components and connections are the same as in the first embodiment.

The thermocouple holder 21 of the present embodiment is mainly a fixing bracket 17 and a B-type thermocouple 4. By the arrangement, the B-type thermocouple 4 can stably work in the process that the motor 19 drives the rack 18 to work up and down.

The third concrete implementation mode: in the present embodiment, scale marks are provided on the side wall of the holder 17 in the present embodiment, which is described with reference to fig. 2. So set up, be convenient for measure the lifting accuracy of thermocouple. Other compositions and connections are the same as in the first or second embodiments.

The fourth concrete implementation mode: the embodiment is described with reference to fig. 1, the temperature measuring system body of the embodiment includes a tank body 1, a copper crucible 5, a coil 15 and a lower lifting system 12, the lower lifting system 12 is installed at the lower end in the tank body 1, the copper crucible 5 is installed right above the lower lifting system 12, a material 6 extends into the copper crucible 5 and moves up and down under the driving of the lower lifting system 12, and the coil 15 is sleeved outside the copper crucible 5. So set up, according to the difference of temperature measurement position in the required fuse-element, drive the rack through the motor, the reciprocating of thermocouple is realized to power control motor speed and direction. Other compositions and connection relationships are the same as in the first, second or third embodiment.

An infrared temperature measuring window 2 is arranged on the tank body 1.

The fifth concrete implementation mode: referring to FIG. 1, the temperature measuring system of the present embodiment further includes a Ga-In container 11, the Ga-In container 11 is mounted at the lower end of the tank 1, and the Ga-In container 11 is mounted on a lower elevating system 12. So set up, can guarantee that material 6 has from the top down temperature gradient, guarantee that host computer 7 can record the not temperature variation value of co-altitude. Other compositions and connection relationships are the same as those in the first, second, third or fourth embodiment.

The sixth specific implementation mode: the embodiment is described with reference to fig. 1, the external data processing component of the embodiment includes a compensation lead 8, a temperature polling instrument 9 and a host 7, the B-type thermocouple 4 and the K-type thermocouple 10 extend out of the tank 1 after meeting and are connected with the temperature polling instrument 9 through the compensation lead 8, the temperature polling instrument 9 is connected with the host 7, and the information collected by the B-type thermocouple 4 and the K-type thermocouple 10 is subjected to data analysis through the host 7. The arrangement is realized, and the temperature change of different positions in the material 6 can be accurately monitored in real time due to the compensation lead 8. Other compositions and connection relationships are the same as in the first, second, third, fourth or fifth embodiment.

The model of the polling instrument for processing thermoelectric signals and recording temperature values in the embodiment is a 16-channel XJY-160 model. The usb interface of the inspection tester is used to export the experimental data of the five channels 1-5 to the host 7, origin software is used to draw a temperature-induction heating time curve, and the measured temperature curves at different positions are shown in fig. 4, fig. 12 and fig. 13. The model of the infrared gun is PT300B, the infrared gun is used for measuring the surface temperature of the melt, experimental data are exported to the host 7, origin software is used for drawing a temperature-induction heating time curve, and the surface temperature is compared with the temperature of the channel 1 of the inspection tour instrument, as shown in FIG. 15.

The seventh embodiment: referring to FIG. 1, the material 6 of the present embodiment is a columnar material made of Ti-46Al-6 Nb. So set up, can carry out the measurement of temperature parameter and the measurement of heat transfer parameter to a specific alloy composition to the material 6 of column not only is close actual shape, can make things convenient for putting of K type thermocouple 10 moreover. Other compositions and connection relationships are the same as in the first, second, third, fourth, fifth or sixth embodiment.

The specific implementation mode is eight: referring to fig. 1 and 5, the embodiment is described, in which a plurality of temperature measuring grooves are horizontally arranged on a material 6 at equal intervals from top to bottom. The temperature measuring groove is axially opened, and the sleeve belt Y with the width of the groove capable of placing the lower outer layer wrapped with the metal shielding wire₂O₃Coated Al₂O₃The thermocouple of the ceramic tube can be ensured to move in the groove. Other compositions and connection relationships are the same as in the first, second, third, fourth, fifth or sixth embodiment.

The specific implementation method nine: the present embodiment is described with reference to fig. 5, and the pitch between two adjacent temperature measurement grooves of the present embodiment is 6mm to 9 mm. According to the arrangement, the materials are drilled according to the height of the required temperature measuring position, the distance between drilled holes is 6-9mm, the number of the drilled holes is determined according to the height of the materials, the height of a hearth and other related data, and the drilling depth is up to the center of the materials. Other compositions and connection relationships are the same as in the first, second, third, fourth, fifth or sixth embodiment.

The detailed implementation mode is ten: the present embodiment is described with reference to fig. 5, and further includes a plurality of metal shielding wires 22, one metal shielding wire 22 is installed in each temperature measuring tank, a ceramic tube 3 is inserted into each metal shielding wire 22, and a K-type thermocouple 10 is installed in each ceramic tube 3. By the arrangement, the K-type thermocouple 10 with the metal shielding wire 22 can accurately measure the temperature value change of different positions of the material 6 without being influenced by an electromagnetic field. Other compositions and connection relationships are the same as in the first, second, third, fourth, fifth or sixth embodiment.

Example (b):

according to the schematic diagram of the temperature measuring system in fig. 1, at the beginning of the experiment, the computer 7, the temperature polling instrument 9 and the internal cooling system are turned on to ensure the normal operation of the equipment. The material 6 in the copper crucible 5 is heated by induction, and along with the gradual increase of the temperature of the material 6, the temperature change at different positions measured by the K-type thermocouple 10 is transmitted to the computer host 7 through the temperature polling instrument 9 and is recorded, and the recording result is shown in fig. 4. According to the change rule of the curve of fig. 4, it can be seen that the closer to the center of the copper crucible 5, the higher the temperature, the closer to the Ga-In container 11, the lower the temperature, and the temperature change rule measured by the method conforms to the theoretical change rule, so that a temperature gradient during solidification is ensured during the directional solidification of the electromagnetic cold crucible, and the stable growth of the columnar crystal is further ensured.

The concrete implementation mode eleven: the present embodiment is described with reference to fig. 5, and the present embodiment is a method for measuring temperature in a cold crucible directional solidification process, which includes the following steps:

firstly, grooving in the axial direction of the material, and drilling holes to the center at different heights so as to place thermocouples. The distance between two adjacent holes of the drilled holes is 6-9 mm. The size of the notch can be just enough to accommodate a thermocouple for temperature measurement, and the distance from the top end of the material to the bottom end of the crucible is 58-49 mm;

step two, using high-purity Al₂O₃Ceramic tube and Y₂O₃The coating protects the thermocouple, so that the thermocouple can stay for a long time in the titanium-aluminum melt for temperature measurement;

step three, winding a metal shielding wire for preventing electromagnetic field interference on the K-type thermocouple, and then placing the K-type thermocouple in the axial groove of the material to measure the temperature of the solid phase of the material, wherein the temperature measuring range of the K-type thermocouple is 0-800 ℃;

and fourthly, placing the materials in an electromagnetic cold crucible for fusion casting, wherein the heating power is 30KW-50KW, and the power frequency is 15KHz-115 KHz. And after the top end of the material is melted, measuring the temperature of the melt, namely performing infrared temperature measurement on the surface of a molten pool on a window at the top of the hearth on the one hand, and controlling a B-type thermocouple to be inserted into the molten pool on the other hand, wherein the temperature measurement range of the B-type thermocouple is 500-1800 ℃. The thermocouple inserted into the molten pool can be controlled by the thermocouple motion device which is designed by self-processing to move up and down, so that the thermocouple is prevented from reacting and melting with the melt due to long-time stay in the titanium aluminum melt. In the material heating process, recording the temperature change of the material by a K-type thermocouple;

after the temperature of the molten pool is stable, controlling a thermocouple to slowly insert the thermocouple from the central position of the molten pool, recording the temperature of the molten pool, and then quickly lifting the thermocouple out of the molten pool;

step six, changing process parameters, and moving the thermocouple downwards to measure temperature when measuring temperature again, so that the thermocouple can be used repeatedly;

and seventhly, adopting commercial finite element software ANSYS 11.0 (authorized by Harbin university of industry) to carry out numerical calculation of the electromagnetic field, the temperature field when in loading and the flow field in the cold crucible. The 3-D modeling adopts a quarter symmetrical structure for 36mm multiplied by 36mm square crucibles, and the limited unit number is about 30-40 ten thousand by calculating the electromagnetic field and the flow field. For the induction heating calculation, the thermophysical parameters of the material are continuously updated along with the change of the temperature, the repeated coupling of an electromagnetic field and a temperature field is required, so that the calculated amount of a 3-D model is huge, a reasonably simplified 2-D axisymmetric model is adopted, the number of finite elements is about 3-5 ten thousand, and the finite element model and the mesh subdivision are shown in a figure 6(a) and a figure 6 (b). Wherein the slotted region is treated as a material with resistivity, the crucible wall in the equivalent 3-D structure has the shielding effect on an electromagnetic field, and the lateral heat exchange coefficient is 800W/m²·K-1000W/m²·K。

The variation range of the power supply power in the fourth step is 30-50 KW, and the simulation calculation result is shown in FIG. 8.

The variation range of the power supply frequency in the fourth step is 15KHz to 115KHz, and the simulation calculation result is shown in fig. 9.

The lateral heat exchange coefficient in the seventh step is 800W/m²·K-1000W/m²K, the simulation calculation results are shown in fig. 10.

The distance between the top end of the material and the bottom end of the crucible is 58-49mm, and the simulation calculation result is shown in FIG. 11.

Experimental measurements and simulation calculations were compared and the comparison is shown in fig. 12.

Example (b):

the implementation mode is realized by the following steps:

firstly, grooving in the axial direction of the material, and drilling holes to the center at different heights so as to place thermocouples. The distance between two adjacent holes of the drilled holes is 6-9 mm. The size of the notch can be just enough to accommodate a thermocouple for temperature measurement, and the distance from the top end of the material to the bottom end of the crucible is 58-49 mm;

step two, using high-purity Al₂O₃Ceramic tube and Y₂O₃The coating protects the thermocouple, so that the thermocouple can stay for a long time in the titanium-aluminum melt for temperature measurement;

step three, winding a metal shielding wire for preventing electromagnetic field interference on the K-type thermocouple, and then placing the K-type thermocouple in the axial groove of the material to measure the temperature of the solid phase of the material, wherein the temperature measuring range of the K-type thermocouple is 0-800 ℃;

and fourthly, placing the materials in an electromagnetic cold crucible for fusion casting, wherein the heating power is 30KW-50KW, and the power frequency is 15KHz-115 KHz. And after the top end of the material is melted, measuring the temperature of the melt, namely performing infrared temperature measurement on the surface of a molten pool on a window at the top of the hearth on the one hand, and controlling a B-type thermocouple to be inserted into the molten pool on the other hand, wherein the temperature measurement range of the B-type thermocouple is 500-1800 ℃. The thermocouple inserted into the molten pool can be controlled by the thermocouple motion device which is designed by self-processing to move up and down, so that the thermocouple is prevented from reacting and melting with the melt due to long-time stay in the titanium aluminum melt. In the material heating process, recording the temperature change of the material by a K-type thermocouple;

after the temperature of the molten pool is stable, controlling a thermocouple to slowly insert the thermocouple from the central position of the molten pool, recording the temperature of the molten pool, and then quickly lifting the thermocouple out of the molten pool;

step six, changing process parameters, and moving the thermocouple downwards to measure temperature when measuring temperature again, so that the thermocouple can be used repeatedly;

and seventhly, adopting commercial finite element software ANSYS 11.0 (authorized by Harbin university of industry) to carry out numerical calculation of the electromagnetic field, the temperature field when in loading and the flow field in the cold crucible. The 3-D modeling adopts a quarter symmetrical structure for 36mm multiplied by 36mm square crucibles, and the limited unit number is about 30-40 ten thousand by calculating the electromagnetic field and the flow field. For the induction heating calculation, the thermophysical parameters of the material are continuously updated along with the change of the temperature, the repeated coupling of an electromagnetic field and a temperature field is needed, so that the calculated amount of a 3-D model is huge, a reasonably simplified 2-D axisymmetric model is adopted, the number of finite elements is about 3-5 ten thousand, and a finite element model and a mesh subdivision are shown in figures 6(a) and (b). Wherein the slotted region is treated as a material with resistivity, the crucible wall in the equivalent 3-D structure has the shielding effect on an electromagnetic field, and the lateral heat exchange coefficient is 800W/m²·K -1000W/m²·K。

And step four, adjusting the heating power to obtain a molten pool. In the research, two schemes of an infrared thermometer and a thermocouple are adopted to measure the temperature of the molten pool, and the height of the material is 50 mm. When the infrared temperature measurement is performed, the power is maintained at about 16kW, and the material head is gradually melted to form a molten pool, and the front and rear states are shown in FIG. 14. Fig. 14 (a) and (b) show the state before melting, and it is seen from the color that the edge of the stub bar is higher in temperature and brighter than the center because of the skin effect and the heat flow is transmitted from the surface to the inside of the sample, and as the heating time is prolonged, the edge of the stub bar in fig. 14 (c) has already melted and the stub bar in fig. 14 (d) has substantially completely melted to form a molten pool.

Through the fourth step in the embodiment, the temperature of the top end of the material is measured through infrared temperature measurement, and a relation function between the infrared temperature measurement and the power supply heating power is calculated through fitting. After the molten pool is formed, infrared temperature measurement is started, and the detection position of the surface of the melt is required to be the same every time, and the detection position is selected to be in the central area of the molten pool, as shown in (a) in fig. 14. FIG. 15 shows the infrared temperature measurement result of the surface of the molten pool, and the relationship between the infrared temperature Tin and the heating power P can be obtained by fitting the measurement data:

T_in＝1603+3.1P (1)

measuring the temperature of the molten pool by a thermocouple to obtain the temperature T of the thermocouple_thRelation to heating power P:

T_th＝1427+4.6P (2)

further, T can be established by the formulae (5-1) and (5-2)_thAnd T_inThe relationship between, is noted as:

T_th＝1.48T_in-952 (3)

the direction of heat flow in the mushy zone is closely connected with the macroscopic morphology of the solidification interface, and the former determines the latter to a certain extent. The final purpose of controlling the heat flow direction of the mushy zone and the macroscopic morphology of the solidification interface is the continuous parallel growth of columnar crystals. When the crucible and the alloy are constant, the current parameters and the drawing speed are the main control means. The research considers that the control of the initial height and the triple point position of the material is the key of the solidification interface straightening. In the practical process, the two points are realized by adjusting the power and the drawing speed.

According to the third step, the fourth step, the fifth step and the sixth step in the embodiment, the temperature changes under different power supply powers are repeatedly measured, and corresponding change rules are obtained. From the analysis of fig. 8, it can be seen that increasing the power within a certain range causes the solidification boundary to transition from convex to concave, and the concave boundary becomes more obvious as the power is higher. But factors influencing the appearance of the solidification interface are complexly coupled with each other. The soft contact degree of the materials is changed while the power is increased, and the lateral heat dissipation degree is further influenced. Fig. 10 shows that the solidification interface transitions from concave to convex as the lateral heat exchange area increases. More materials can be melted after the power is increased, when the electromagnetic force cannot completely balance the radial pressure generated by a melt with a certain height, more materials can be contacted with the crucible wall to form a solidified shell, and the heat exchange between the solidified shell and the crucible wall can greatly influence the unevenness of an interface. Therefore, the shape of the solidification interface is controlled by power, the coupling influence caused by lateral heat exchange must be comprehensively considered, and under the condition of ensuring the superheat degree, proper power is obtained by optimizing process parameters in combination with an experimental result. On the other hand, through the seventh step in the embodiment, the accuracy of the actual measurement result is judged according to the comparison of the numerical simulation result and the actual measurement result, and the feasibility of the method is ensured. Both theoretical analysis and numerical calculations indicate that increasing the frequency within a certain range has a positive effect on improving the straightness of the solidification interface.