KR100862223B1 - Apparatus and method for testing thermal fatigue properties - Google Patents

Abstract

The present invention relates to a thermal fatigue test apparatus.

The thermal fatigue test apparatus of the present invention is a heating unit for heating the test piece to a high temperature, a cooling unit for mounting the test piece and cooling the heated test piece by the heating unit, the cooling unit equipped with the test piece to carry in or take out the heating unit It includes a transfer device, wherein the heating unit is provided with at least one heating element, a heating furnace in which the heating element is installed along the inner circumferential surface, ASP (Asphalt Protected Metal) tube tube is installed in the heating furnace.

As a heat source, the upper part of the test piece is heated to a high temperature environment formed by a heating furnace in which the heating element of the thermal fatigue test device configured as described above is heated, and the lower part of the test piece is cooled through the air circulation of the cooling part to generate a temperature gradient over the thickness of the test piece. Since no flame and laser are used, manufacturing cost can be greatly reduced, and the time required for testing can be greatly reduced, and temperature control and control are easy.

Thermal fatigue test device, heating furnace, test piece, temperature gradient, heating element

Description

Thermal fatigue test apparatus and method {APPARATUS AND METHOD FOR TESTING THERMAL FATIGUE PROPERTIES}

1 is a view schematically showing a conventional thermal fatigue test apparatus.

Figure 2 is a side view showing a thermal fatigue test apparatus according to the present invention.

Figure 3 is a side view showing a state of use of the thermal fatigue test apparatus according to the present invention.

Figure 4 is a bottom perspective view showing a thermal conductor according to the present invention.

5 is a perspective view showing another embodiment of the thermal conductor according to the present invention.

6 is a flow chart showing a thermal fatigue test method according to the present invention.

<Explanation of symbols for the main parts of the drawings>

100: heating unit 110: heating element

120: heating furnace 130: APM tube tube

140: upper insulation plug 150: lower insulation plug

160: case 170: thermocouple

200: cooling unit 210: thermal conductor

230: test piece holder 240: first finishing piece

250: second finishing piece

300: feeder 310: drive motor

320: gear unit

400: compressed air jet device

The present invention relates to a thermal fatigue test apparatus and method, and more particularly to a thermal fatigue test apparatus and method for testing the thermal fatigue properties for a test piece that repeatedly experiences heating and cooling.

Generally, high temperature parts of gas turbine power generation operated at 1,100 ° C or higher are exposed to high temperature and high pressure combustion gases, and are used in an environment that is subjected to mechanical stress by 3,600 revolutions per minute.

In particular, since gas turbine power generation is operated by repeating start and stop every day, high-temperature parts are repeatedly heated and cooled, and the original material properties are degraded more quickly.

As such, better materials and surface treatments have been developed and applied to prevent high-temperature components from deteriorating quickly. These materials or surface-treated components have been tested in advance before being applied to actual gas turbine power generation to prove their safety. Should be.

One of the many tests necessary for this is the thermal cycle test.

That is, the thermal cycle test has been repeatedly performed by using a thermal fatigue tester or a thermal tensile tester in a laboratory, or by directly inserting a specimen into a furnace kept at a high temperature, and then removing it and cooling it again after a certain time.

However, these thermal fatigue and tensile tests are difficult to test at the actual gas turbine operating temperature, and it is not only impossible to test several specimens under the same conditions, but also has a disadvantage in that rapid cooling is difficult.

Moreover, there was a hassle for equipment operators to check the test progress from time to time.

In order to solve the above problems, the "thermal fatigue test apparatus" of the Republic of Korea Utility Model Registration No. 20-0406102 has been disclosed.

The conventional thermal fatigue test apparatus, as shown in Figure 1, by measuring the thermal fatigue strength for the specimen of the high-temperature components used in the gas turbine power generation, the tube furnace (1) for heating the specimen (not shown) to a high temperature And a cooling unit for quenching the heated specimen to room temperature, and a specimen transfer means for mounting the specimen to the tube furnace 1 or the cooling unit, and controlling the temperature, time, and number of repetitions of the tube furnace 1 and the cooling unit. It includes a control unit.

In addition, the specimen conveying means includes a specimen mounting portion 7 for mounting the specimen and transporting it to the tube furnace 1 or the cooling portion, and an air cylinder 5 for driving the specimen mounting portion 7.

The cooling unit also includes an air compressor 3 and a compressed air injection nozzle 4.

That is, in the conventional thermal fatigue test apparatus, the six specimens are simultaneously mounted in the mounting holes of the specimen mounting portion 7, and then the air cylinder 5 is driven by operating the forward switch of the control panel 8, and the specimen mounting portion 7 ) Is introduced into the quartz tube 2.

In this state, the specimen is kept at a high temperature for a set temperature and time as needed, and after the set time has elapsed, the specimen mounting portion 7 is again taken out and transferred to the lower portion of the compressed air injection nozzle 4 connected to the air compressor 3. do.

In this state, compressed air is injected and rapidly cooled to room temperature. Thus, the test can be repeated for as many cycles as necessary with one cycle of heating and cooling.

Through the above test, the thermal fatigue strength of the specimen of the high temperature component can be automatically tested, and the temperature, time, and number of repetitions of the thermal fatigue test can be freely set, thereby increasing the reliability of the test.

However, since the conventional thermal fatigue test apparatus is heated at the same temperature across the thickness of the test piece, the time required until the fracture of the thermal fatigue becomes long, and thus the efficiency of the test is greatly reduced.

Furthermore, in the conventional thermal fatigue test apparatus, during the thermal fatigue test, the coating layer is directly heated using a laser or a flame as a heat source, and the opposite side of the specimen is cooled by spraying compressed air or by contacting a block in which cooling water circulates to cool. Although it is possible to apply, there are disadvantages in that it is difficult to control and adjust the temperature and position of the flame, and the cost of manufacturing and testing the device is expensive.

An object of the present invention is to solve the above problems, the temperature control by heating the coating layer of the test piece through a high-temperature environment using a heating furnace is installed without a flame and a laser as a heat source when the thermal fatigue test It is to provide a thermal fatigue test apparatus that can be easily adjusted and can greatly reduce the manufacturing cost of the apparatus.

The thermal fatigue test apparatus of the present invention for achieving the above object is a heating unit for heating the test piece to a high temperature, a cooling unit for mounting the test piece and cooling the test piece heated by the heating unit, the cooling unit is mounted Transfer device to be carried in or withdrawn in the heating unit, the heating unit is provided with at least one heating element, a heating furnace in which the heating element is installed along the inner circumferential surface, APM (Asphalt Protected Metal) tube tube is installed in the heating furnace, The cooling unit is provided with a heat conductor for cooling the lower portion of the test piece heated by the heating unit and a cooling member for cooling the heat conductor through air circulated.

The heating unit is coupled to the upper and lower surfaces of the APM tube tube to prevent heat loss, the upper and lower insulation plugs, the transfer hole is formed on the upper surface of the lower insulation plug to carry in or withdraw the cooling unit, surrounding the main surface of the heating furnace It is characterized in that it is further provided with a case which is installed in the form to fix the APM tube tube.

In addition, the heating unit is characterized in that it further comprises a thermocouple (R type thermocouple) which is installed inside the furnace to sense the internal temperature of the furnace heated by the heating element.

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The cooling member includes an air tube having an air supply pipe and a recovery pipe for cooling the heat conductor through air circulated, an air controller for supplying or recovering air to the air supply pipe and the recovery pipe of the air tube, and the air tube and the heat conductor. Characterized in that it is provided with a socket for connecting.

In addition, the cooling member further includes a heat-resistant tube coupled to the outside of the air tube to surround the outer circumferential surface of the air tube, the heat-resistant tube and the socket is characterized in that it is made of Inconel.

The thermal conductor is characterized in that it is provided with a mounting portion for mounting the test piece on the upper surface, the coupling portion is formed on the bottom surface of the mounting portion is coupled to the socket, the heat dissipation portion formed on the bottom surface of the coupling portion.

The heat dissipation portion is characterized in that it is provided with a plurality of heat dissipation fins protruding from the blocking groove formed on the bottom of the coupling portion, the blocking groove.

The cooling unit is characterized in that it further comprises a test piece holder coupled to the upper surface of the thermal conductor to fix the movement of the test piece.

The test piece holder is characterized in that the thermal conductor is coupled in a form surrounding the upper surface and the outer peripheral surface so as not to be exposed in the heating furnace.

At least one fixing groove is provided on a main surface of the test piece holder to fix the plurality of test pieces in a state of being in close contact with the thermal conductor.

The test piece holder is characterized in that it is made of a ceramic as a heat insulating material.

The cooling member may further include an air controller installed on an air supply line to which the air controller and the air tube are connected.

The cooling unit is formed on an upper surface of the test piece holder, the first finishing piece to close the transfer hole when the heat conductor is drawn out in the heating furnace, the transfer hole when formed in one side of the heat-resistant tube and the heat conductor is brought into the heating furnace It characterized in that it further comprises a second finishing piece to finish the.

The transfer device is characterized in that it comprises a drive motor and a gear unit for raising or lowering the cooling unit by the power transmission of the drive motor.

The heating unit is characterized in that it further comprises a compressed air spraying device which is installed outside the heating furnace to quench the heated test piece when the cooling unit is drawn out from the inside of the heating furnace.

Referring to the method of measuring the characteristics of the specimen through the thermal fatigue test device configured as described above are as follows.

The test piece is placed on the heat conductor, fixed to the test piece holder so as not to move, and then the test piece mounting step of bringing the heat conductor fixed with the test piece into the heating furnace through the transfer means. A test piece test step of generating a temperature gradient by cooling the lower part of the test piece disposed on the upper surface of the thermal conductor with air circulating through the cooling unit at the same time as heating the upper part of the test piece. The test piece withdrawal step of drawing the heat conductor in the heating furnace is performed, and the test piece evaluation step of evaluating the thermal fatigue characteristics of the test piece is performed after the extracted test piece is rapidly cooled through the compressed air spraying device.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 2 to 5.

The thermal fatigue test apparatus of the present invention is to evaluate the thermal fatigue characteristics by repeatedly providing a high-temperature environment to the test piece 10, as shown in Figure 2 and 3, the heating to heat the test piece 10 to a high temperature The cooling part 200 equipped with the part 100, the test piece 10 mounted on one surface, and cooling the test piece 10 heated by the heating part 100, and the cooling part 200 to which the test piece 10 is mounted. It includes a conveying apparatus 300 for carrying in or withdrawing into the heating unit 100.

The heating unit 100 is for heating the test piece 10 in a high temperature environment of 1100 ° C. or higher, a heating element 110 for heating the test piece 10, a heating furnace 120 in which the heating element is installed, and a heating furnace 120. APM tube tube 130 is installed in the), and the upper and lower insulation plugs 140, 150 to close the upper and lower APM tube tube 130 and the case 160 for fixing the APM tube tube 130 It includes.

The heating element 110 generates heat when an external power is applied, and at least one or more heat generators 110 are installed at equal intervals along the main surface of the heating furnace 120.

The heating furnace 120 is to create a high temperature environment by preventing the diffusion of heat generated by the heating element 110, and has a tube shape.

APM (Asphalt Protected Metal) tube tube 130 is for preventing the heating furnace 120 from being damaged by the heated test piece 10 and downward from the center of the upper surface of the heating furnace 120. Installed through.

That is, the APM tube tube 130 blocks the inside of the heating furnace 120 from being damaged by the reaction gas generated when the test piece 10 is heated by the heating element 110 and the oxidation reaction of the test piece 10. do.

The upper and lower insulation plugs 140 and 150 are fitted in close contact with the inner circumferential surfaces of the upper and lower portions of the APM tube tube 130, thereby closing the inside of the APM tube tube 130 to seal the heat loss. Remarkably reduced, the upper surface of the lower insulating plug 150 is formed with a transfer hole 151 which is a passage through which the cooling unit 200 lifted by the transfer apparatus 300 to be described later is carried in or taken out.

The case 160 has a shape of a thermal fatigue tester in the form of surrounding the main surface of the heating furnace 120, the top and bottom of the upper and lower insulation plugs 140, 150 coupled to the APM tube tube 130 is firmly A fixing piece 161 is formed to secure the upper surface, and a plurality of supports 162 are formed on the bottom edge to separate the case 160 from the bottom surface to a predetermined height.

Here, the thermocouple (R type thermocouple; 170) for detecting the internal temperature is installed in the heating furnace 120, the temperature detected by the thermocouple 170 is a control unit (not shown) installed in the thermal fatigue test apparatus in real time Is delivered).

The cooling unit 200 is for cooling the lower portion of the test piece 10 to a specific temperature (for example, 850 degrees) above room temperature or above room temperature, and the heat conductor 210 on which the test piece 10 is mounted on one surface and air circulated. It consists of a cooling member for cooling the thermal conductor 210 through.

That is, the thermal conductor 210 is cooled through the cooling member, and the lower portion of the test piece 10 is cooled through the cooled thermal conductor 210.

The thermal conductor 210 is for cooling the lower portion of the test piece 10 to room temperature, and is formed on a mounting portion 211 on which the test specimen 10 is mounted and a lower surface of the mounting portion 211 and smaller than the mounting portion 211. It has a coupling portion 212 is coupled to the cooling member on the outer peripheral surface.

Here, the heat dissipation portion 213 is formed on the bottom of the coupling portion 212 to improve cooling efficiency, and the heat dissipation portion 213 is a blocking groove formed on the bottom surface of the coupling portion 212 as shown in FIG. 4. (Not shown) and a plurality of heat dissipation fins 214 protruding from the blocking groove.

In addition, the specimen holder 230 for fixing the movement of the specimen 10 is coupled to the upper surface of the thermal conductor 210.

The test piece holder 230 is made of ceramic, which is a heat insulating material, and is bonded in a form surrounding the upper and outer circumferential surfaces of the heat conductor 210 so that the heat conductor 210 is not exposed in the heating furnace 120. The fixing hole 231 for inserting and fixing is formed.

The cooling member includes an air supply tube 221 and an air supply tube of the air tube 221 formed through the air supply pipe 221a and the recovery pipe 221b for cooling the heat conductor 210 through the circulated air. An air controller 222 connected to an end of the air inlet 221a and the recovery pipe 221b, and connects an upper surface of the air tube 221 and an upper surface of the coupling portion 212 of the thermal conductor 210. Consisting of a socket 223.

In addition, an accommodating space is formed between the heat conductor 210 and the socket 223 to accommodate a predetermined amount of air, and the air supplied through the air supply pipe 221a is accommodated in the accommodating space for a predetermined time. It is recovered through the recovery pipe 221b to improve the cooling efficiency of the thermal conductor 210.

In addition, the outer side of the air tube 221, the heat-resistant tube 224 is coupled in a form surrounding the outer circumferential surface, and protects the air tube 221 from the high temperature through the heat-resistant tube 224.

In addition, on the air supply line to which the air controller 222 and the air tube 221 are connected, a regulator (not shown) for adjusting the amount of air is selectively installed.

Here, the socket 223 and the heat resistant pipe 224 are preferably manufactured using a high temperature material such as Inconel.

The upper surface of the test piece holder 230 is provided with a first finishing piece 240 for closing the transfer hole 151 formed in the lower insulating plug 150, the first finishing piece 240 is the transfer device 300 When the heat conductor 210 mounted with the test piece 10 in the heating furnace 120 is drawn out, it is positioned in the transfer hole 151.

And, one side of the heat-resistant tube 224 is provided with a second finishing piece 250 for closing the transfer hole 151 when the heat conductor 210 mounted with the test piece 10 is loaded into the heating furnace.

That is, when the heat conductor 210 having the test piece 10 mounted in the heating furnace 120 is brought in or taken out, the first and second finishing pieces 240 and 250 are positioned on the inner circumferential surface of the transfer hole 151. This greatly reduces the heat loss.

Here, the first and second finishing pieces 240 and 250 are preferably manufactured using a high temperature material such as Inconel.

The transfer apparatus 300 is for selectively carrying in or drawing out the cooling unit 200 into the heating furnace 120, and includes a driving motor 310 mounted at the center of the bottom surface of the case 160, and a driving motor 310. The gear unit 320 is configured to raise or lower the cooling unit 200 by power transmission.

The gear unit 320 is composed of a worm 321 and a worm wheel 322, the worm 321 is connected to the drive motor 310 so as to transmit power, the main surface of the worm wheel 322 and the worm 321 The upper surface is fixed to the lower surface of the heat-resistant tube 224 of the cooling unit 200.

That is, the worm 321 of the gear unit 320 is rotated by the power transmission of the drive motor 310, the worm wheel 322 is rotated by the rotation of the worm 321 and ascends in the vertical direction, thereby The cooling unit 200 fixed to the worm wheel 322 is lifted to work in conjunction.

Then, as shown in FIG. 3, a compressed air injection device 400 for quenching the drawn test piece 10 is installed outside the heating furnace 120.

The compressed air injection device 400 is fixed to the bottom of the heating furnace 120 in a state in which the injection direction is directed toward the test piece 10 mounted on the thermal conductor, and is operated by a controller (not shown) provided in the thermal fatigue test apparatus. Done.

The method of testing the thermal fatigue characteristics of the test piece through the thermal fatigue test apparatus of the present invention configured as described above will be described with reference to FIG. 6.

First, the test piece 10 is disposed on the upper surface of the thermal conductor 210 of the cooling unit 200, the test piece holder 230 is coupled to the upper surface of the thermal conductor 210, and the test piece 10 is fixed so as not to move. When the fixing of the 10 is completed, the heat conductor 210 passes through the transfer hole 151 of the lower insulation plug 150 through the transfer device 300, and then is carried into the heating furnace 120 (S10).

At this time, when the heat conductor 210 is carried in the heating furnace 120, the transfer hole 151 is closed by the second finishing piece 250.

As such, when the mounting of the test piece 10 in the heating furnace 120 is completed, the heating element 110 is heated by a control unit installed in the thermal fatigue test apparatus to heat the inside of the heating furnace 120 by 1100 ° C. or more, and the heated high temperature environment. The upper part of the test piece 10 is heated through.

Then, the heat conductor 210 is cooled by air circulated through the cooling unit 200, and the lower portion of the test piece 10 is cooled by the cooled heat conductor 210, and a temperature gradient according to the thickness of the test piece 10 is provided. To generate (S20).

At this time, the oxidation reaction and the reaction gas of the heated test piece 10 is blocked through the APM tube tube 130 having a space enclosed by the upper and lower insulating plugs 140 and 150 inside the heating furnace 120 Can be prevented from being damaged.

After heating and cooling the test piece 10 for a predetermined time, the heat conductor 210 is drawn out in the heating furnace 120 through the transfer device 300 (S30).

In this case, the opening transfer hole 151 is closed by the second finishing piece 250 provided on the upper surface of the test piece holder 230 to prevent the high temperature inside the heating furnace 120 from being lost to the outside.

The extracted test piece 10 is selectively quenched through the compressed air spraying device 400, and the thermal fatigue test of the test piece is completed when the thermal fatigue property is evaluated through the test piece 10 cooled to room temperature (S40).

By repeating such a method, it is possible to evaluate the thermal cycle fatigue characteristics of the test specimen more accurately.

Hereinafter, in describing another embodiment of the thermal fatigue test apparatus according to the present invention, the same reference numerals are used for components having the same configuration and function as the present invention, and detailed description thereof will be omitted.

FIG. 5 shows another embodiment of the above-described thermal conductor and a specimen holder coupled to the thermal conductor, for example, for testing the thermal cycle fatigue characteristics of a plurality of, for example, four specimens 10 simultaneously under the same conditions.

FIG. 5A is a front perspective view according to the present embodiment, and FIG. 5B is a bottom perspective view according to the present embodiment.

Referring to the drawings, the thermal conductor 210 'is formed of a mounting portion 211' made of a trapezoidal cube and a coupling portion 212 'coupled to the air tube 221 on the bottom of the mounting portion 211'. do.

The test piece holder 230 ′ is closely coupled to the upper surface and the outer circumferential surface of the test piece holder 230 ′ except for the bottom surface of the thermal conductor 210 ′, and at least one or more test pieces 10 may be inserted into and fixed to the vertical surface of the test piece holder 230 ′. The fixing hole 231 'is formed.

Therefore, after the test pieces 10 are mounted in the plurality of fixing holes 231 ′, thermal cycle fatigue characteristics of the plurality of test pieces 10 may be tested in the same manner as in the above-described embodiment.

As a heat source, the upper part of the test piece is heated to a high temperature environment formed by a heating furnace in which the heating element of the thermal fatigue test device configured as described above is heated, and the lower part of the test piece is cooled through the air circulation of the cooling part to generate a temperature gradient over the thickness of the test piece. Since no flame and laser are used, manufacturing cost can be greatly reduced, and the time required for testing can be greatly reduced, and temperature control and control are easy.

Claims (18)

A heating unit for heating the test piece to a high temperature, A cooling unit for mounting the test piece and cooling the test piece heated by the heating unit, Transfer device for carrying in or taking out the cooling unit equipped with a test piece into the heating unit, The heating unit includes at least one heating element, a heating furnace in which the heating element is installed along an inner circumferential surface thereof, and an asphalt protected metal (APM) tube tube installed in the heating furnace, The cooling unit is a thermal fatigue test apparatus, characterized in that the heat conductor for cooling the lower portion of the test piece heated by the heating unit and a cooling member for cooling the heat conductor through the air circulated. The method of claim 1, The heating unit includes upper and lower insulation plugs coupled to the upper and lower surfaces of the APM tube tube to prevent heat loss, transfer holes formed on the upper surface of the lower insulation plug to carry in or withdraw the cooling unit, and main surfaces of the heating furnace. Heat fatigue test apparatus, characterized in that the case is further provided with a case for fixing the APM tube tube fixed. The method of claim 2, The heating unit is a thermal fatigue test apparatus, characterized in that further provided with a thermocouple (R type thermocouple) installed in the heating furnace to sense the internal temperature of the heating furnace heated by the heating element. delete The method of claim 1, The cooling member includes an air tube having an air supply pipe and a recovery pipe for cooling the heat conductor through air circulated, an air controller for supplying or recovering air to the air supply pipe and the recovery pipe of the air tube, and the air tube and the heat conductor. Thermal fatigue test apparatus, characterized in that the socket is further provided for connecting. The method of claim 5, wherein The cooling member is a thermal fatigue test apparatus further comprises a heat-resistant tube coupled to the outside of the air tube to surround the outer peripheral surface of the air tube. The method of claim 6, The heat-resistant tube and the socket is thermal fatigue test apparatus, characterized in that made of Inconel (Inconel). The method of claim 5, wherein The thermal conductor is a thermal fatigue test apparatus, characterized in that the mounting portion is mounted to the test piece on the upper surface, the coupling portion is formed on the bottom surface of the mounting portion is coupled to the socket, the heat dissipation portion is formed on the bottom surface of the coupling portion. The method of claim 8, The heat dissipation unit is a thermal fatigue test apparatus, characterized in that provided with a plurality of heat dissipation fins protruding in the blocking groove, the blocking groove formed on the bottom of the coupling portion. The method of claim 1, The cooling unit is a thermal fatigue test apparatus further comprises a test piece holder coupled to the upper surface of the heat conductor to fix the movement of the test piece. The method of claim 10, The test piece holder is thermal fatigue test apparatus, characterized in that coupled to the form surrounding the outer surface and the outer surface so that the heat conductor is not exposed in the heating furnace. The method of claim 11, At least one fixing groove is provided on the main surface of the test piece holder is provided with at least one fixing groove for fixing a plurality of test pieces in a state in close contact with the thermal conductor. The method of claim 12, The test piece holder is a thermal fatigue test apparatus, characterized in that made of ceramic as a heat insulating material. The method of claim 5, wherein The cooling member is thermal fatigue test apparatus, characterized in that the air controller is installed on the air supply line is connected to the air controller and the air tube is further provided to control the air volume. The method of claim 10, The cooling unit is formed on an upper surface of the test piece holder, the first finishing piece for closing the transfer hole when the heat conductor is drawn out in the heating furnace, formed on one side of the heat-resistant tube and transferred when the heat conductor is brought into the heating furnace. Thermal fatigue test apparatus, characterized in that further provided with a second finishing piece for closing the hole. The method of claim 1, The transfer device is a thermal fatigue test apparatus, characterized in that consisting of a drive motor and a gear unit for raising or lowering the cooling unit by the power transmission of the drive motor. The method according to any one of claims 1 to 3, 5 to 16, The heating unit is provided with a thermal fatigue test apparatus further comprises a compressed air injection device which is installed outside the heating furnace to quench the heated test piece when the cooling unit is drawn out from the inside of the heating furnace. In the thermal fatigue test method, The test piece mounting step of placing the test piece on the heat conductor and fixing it with the test piece holder so as not to move, and then carrying the heat conductor with the test piece fixed in the heating furnace through a transfer means, Test piece test step of generating a temperature gradient by heating the upper part of the test piece by heating the internal temperature of the furnace over 1100 ° C. through the heating element and cooling the lower part of the test piece arranged in the heat conductor with air circulated through the cooling unit, After the specimen is heated and cooled for a predetermined time, the specimen withdrawal step of withdrawing the thermal conductor in the heating furnace through the transfer device, And a test piece evaluating step of evaluating the thermal fatigue characteristics of the test piece after quenching the drawn test piece through the compressed air spraying device.

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