JP7836040B2 - Apparatus for measuring the physical properties of a test specimen under high temperature and method for measuring the physical properties of a test specimen using the same. - Google Patents

Description

Applicable under Article 30, Paragraph 2 of the Patent Law March 1, 2021 "Refractories (Summary of Lectures at the 33rd Annual Academic Conference of the Refractories Technology Association)" [Publications, etc.] October 1, 2021 "Ceramics Okayama" [Publications, etc.] December 10, 2021 "Notice of Equipment Demonstration" [Publications, etc.] December 22, 2021 "Report of the 9th Refractories Research Meeting for Steel" [Publications, etc.] December 23, 2021 "The 9th Refractories Research Meeting for Steel" hosted by the Refractories Technology Association

This invention relates to an apparatus for measuring the physical properties of a test specimen under high temperature conditions and a method for measuring the physical properties of a test specimen using the apparatus.

Refractories used in various furnaces and other equipment in steel mills operate at temperatures exceeding 1500°C. Under such conditions, contact between the refractories and pig iron, steel, slag, etc., can lead to erosion and penetration, resulting in delamination, cracking, and fracture, potentially causing serious accidents. Therefore, the technology for evaluating material properties at high temperatures is particularly important.

Conventionally, when measuring the physical properties of ceramics, metals, etc., at high temperatures of 1000°C or higher, electric furnaces (Patent Document 1) were used. However, heating the test specimen took several hours, and cooling the apparatus took several more hours, resulting in a long measurement time for each test. Furthermore, the position and size of the observation window were often limited, making it difficult to observe the test specimen inside from outside the enclosure as desired.

On the other hand, Patent Document 2 describes a high-speed heating device using infrared radiation. According to this device, synthetic quartz powder can be heated to 1700°C to 1800°C at a heating rate of 10 to 30°C/sec under atmospheric or reduced pressure. However, the method of high-speed heating of a test specimen using infrared radiation is a concentrated heating method, and it has the problem of being difficult to heat the entire test specimen uniformly and at high speed.

Japanese Patent Publication No. 2000-266471 Japanese Patent Publication No. 2010-101814

This invention was made to solve the above problems, and aims to provide a device for measuring the physical properties of a test specimen at high temperatures, which allows for rapid heating and cooling of the specimen, enables repeated measurements at short intervals, and facilitates observation of the specimen from the outside.

The above problem is solved by providing an apparatus for measuring the physical properties of a test specimen at high temperatures, wherein carbon heaters are arranged on the underside of the test specimen, or on both the underside and the upper side, the carbon heaters are housed in a stainless steel casing, observation windows are provided on at least the side and top surfaces of the casing, and a measuring instrument for measuring the physical properties of the test specimen is installed on the outside of the casing through the observation windows.

In this case, it is preferable that the measuring instrument is a camera or a thermometer. It is preferable that the device is a state observation device, and more preferably that the state observation device is a contact angle measuring device.

A preferred embodiment of the present invention is a method for measuring a test specimen using the apparatus, comprising the steps of heating the test specimen with the carbon heater and measuring the test specimen using the measuring instrument. A more preferred embodiment of the present invention is a method for measuring the contact angle of a test specimen using the contact angle measuring device, comprising the steps of heating and melting the test specimen with the carbon heater and measuring the contact angle of the molten test specimen using the camera.

According to the apparatus of the present invention, it is possible to measure the physical properties of a test specimen at high temperatures, to rapidly heat and cool the test specimen, to repeat measurements at short intervals, and to easily measure the test specimen from the outside.

This is a schematic diagram of an example of the apparatus 1 of the present invention. This is an example of a top view photograph of a carbon heater on which a test specimen is placed. This is an example of a photograph showing the external appearance of a measuring instrument installed on the outside of the enclosure. This is an example of a measuring instrument configuration for measuring contact angle and thermal conductivity. This figure plots the voltage applied to the carbon heater against time in Example 1. This shows the temperature distribution of the test specimen and carbon heater measured from above in Example 1. This is a photograph of the carbon heater 3 and test specimen 4 taken with a front-side camera in Example 2.

This invention relates to an apparatus for measuring the physical properties of a test specimen at high temperatures. The apparatus comprises carbon heaters positioned on the underside of the test specimen, or on both the underside and the upper side. The carbon heaters are housed within a stainless steel casing, with observation windows installed on at least the side and top surfaces of the casing. A measuring instrument for measuring the physical properties of the test specimen is mounted on the outside of the casing via the observation windows. In this apparatus, the test specimen is efficiently heated by the carbon heaters positioned on the underside, or on both the underside and the upper side, allowing it to reach extremely high temperatures in a short time. Furthermore, the radiant heat from the carbon heaters and the test specimen has minimal impact on the casing and other components. Additionally, the small heat capacity of the carbon heaters and casing allows for rapid cooling of the test specimen. Therefore, even when the test specimen is heated to extremely high temperatures, measurements can be repeated at short intervals. Moreover, because the radiant heat from the carbon heaters and the test specimen has minimal impact, there is no need to install insulating material inside the casing, and there are fewer restrictions on the position, size, and number of observation windows. Consequently, various physical properties of the test specimen at high temperatures can be easily measured using the measuring instrument located outside the casing.

The following explanation will be illustrated with drawings. Figure 1 is a schematic diagram of an example of the apparatus 1 of the present invention. In Figure 1, the right side and top surface of the housing 2 are not shown in order to show the inside of the housing 2. A carbon heater 3 is housed inside the housing 2. The carbon heater 3 is positioned on the underside of the test specimen 4, or on both the underside and the top. Whether to position the carbon heater 3 only on the underside of the test specimen 4, or on both the underside and the top, can be appropriately selected depending on the physical properties to be measured and the type of test specimen.

In this invention, a plate-shaped carbon heater 3 is preferably used, and typically, the test specimen 4 is placed on the heating element 5 of the lower carbon heater 3. Figure 2 is an example of a top view photograph of the carbon heater 3 with the test specimen 4 placed on it. Both ends of the carbon heater 3 are fixed with clamps to a fixing part 6 installed on the bottom surface of the housing 2, and are also connected to terminals 7 for power supply connection. By applying voltage to both ends of the carbon heater 3, the test specimen 4 placed on the heating element 5 is heated. To prevent damage to the terminals, etc., it is preferable to install a cooling pipe inside the fixing part 6. The resistance value of the carbon heater 3 is typically 0.002 to 0.1 Ω.

The area of the heating element 5 of the carbon heater 3 is typically 0.2 to 40 ^cm² . If this area exceeds 40 ^cm² , the cooling time of the device 1 may become too long, or the radiant heat from the carbon heater 3 and the test specimen 4 may damage the observation window 8 and the sealing member for sealing the inside of the housing 2. The area is preferably 25 ^cm² or less, more preferably 10 ^cm² or less, and even more preferably 1 ^cm² or less, in order to heat the test specimen to an extremely high temperature. On the other hand, the area is preferably 0.8 ^cm² or more, and more preferably 1 ^cm² or more. If a carbon heater 3 is also installed on the upper side of the test specimen 4, the same type as the one installed on the lower side is used, and it is installed so that the heating element 5 faces downwards.

In the apparatus 1 of the present invention, a stainless steel housing 2 is used, and the inside of the housing 2 is sealed. The shape of the housing 2 is not particularly limited, but a box shape is an example. In the case of a box shape, the thickness of the housing 2 is usually 3 to 50 mm, preferably 10 to 20 mm. In the apparatus 1 shown in Figure 1, the top surface of the housing 2 is attached to the side surface by a hinge so that it can be opened and closed, and the test specimen 4 is placed in a predetermined position from the top of the housing 2. Furthermore, to seal the inside of the housing 2, a sealing material is usually interposed between the top surface and the side surface. Fluororubber, silicone rubber, etc., are used as the sealing material.

While insulating material may be placed on the inner or outer surface of the stainless steel housing 2 of the apparatus 1 of the present invention, as long as it does not hinder the effects of the present invention, it is preferable that insulating material is not placed on the inner and outer surfaces of the housing 2. Conventionally, in electric furnaces and the like used for evaluating material properties at high temperatures, the entire furnace interior heats up, requiring the placement of highly heat-capacity insulating material on the inside of the housing. Therefore, once the temperature rises, cooling the apparatus takes several hours, limiting the number of measurements that can be taken per day. In contrast, in the apparatus 1 of the present invention, only the heating element 5 of the carbon heater 3 generates heat, efficiently heating the test specimen 4. Therefore, the radiant heat from the carbon heater 3 and the test specimen 4 has little impact on the housing. As a result, there is no need to install insulating material, and by not installing insulating material, the overall heat capacity of the apparatus 1 can be reduced. This further shortens the cooling time of the apparatus 1, allowing measurements to be repeated at shorter intervals.

In the apparatus 1 of the present invention, observation windows 8 must be installed on at least the side and top surfaces of the housing 2. A measuring instrument installed on the outside of the housing 2 measures the physical properties of the test specimen 4 inside the housing 2 through the observation windows 8. The apparatus 1 shown in Figure 1 has a total of four observation windows 8 installed on the housing 2: one on the front side, one on the rear side, one on the top, and one on the bottom. It is preferable that observation windows 8 are installed on at least three of the side, top, and bottom surfaces of the housing 2, and more preferably on four or more surfaces. While the position of the observation windows 8 is not particularly limited as long as the test specimen 4 inside can be measured through the observation windows 8 using a measuring instrument placed on the outside of the housing 2, it is preferable that the observation windows 8 be installed in a position where the carbon heater 3 or the test specimen 4 can be viewed through the observation windows 8 from a direction perpendicular to the outer surface of the housing 2.

The size and shape of the observation window 8 are not particularly limited and can be adjusted as appropriate depending on the size of the test specimen 4 and the type of physical properties to be measured. Examples of observation window 8 shapes include rectangles, circles, and ovals, with a circular shape being preferred. If the observation window 8 is circular, its effective diameter is preferably 30 to 300 mm. A diameter of 30 mm or more makes it easier to measure the test specimen 4 using a measuring instrument installed on the outside of the housing 2. A diameter of 60 mm or more is more preferable, 70 mm or more is even more preferable, and 90 mm or more is particularly preferable. On the other hand, from the viewpoint of maintenance and durability, a diameter of 200 mm or less is more preferable, 150 mm or less is even more preferable, and 120 mm or less is particularly preferable. From the viewpoint of availability and heat resistance, the material of the observation window 8 is preferably borosilicate glass or quartz glass, with borosilicate glass being more preferable. The thickness of the observation window 8 is usually 3 to 40 mm, preferably 6 to 20 mm. In the apparatus 1 shown in Figure 1, observation windows 8 are installed on each outer surface of the housing 2 via tubular connecting parts 9. However, the observation windows 8 may also be installed directly on the housing 2. Although not shown in Figure 1, a sealing member is usually interposed between the observation window 8 and the connecting part 9. Fluororubber, silicone rubber, etc., are used as this sealing member. Although not shown in Figure 1, it is preferable that a cooling jacket be installed around the periphery of the observation window 8 to prevent damage to the sealing member and the observation window 8 from radiant heat from the carbon heater 3 and the test specimen 4.

The distance between the observation window 8 and the test specimen 4 is preferably 50 to 500 mm. A distance of 50 mm or more prevents damage to the sealing member and the observation window 8 from radiant heat from the carbon heater 3 and the test specimen 4. A distance of 60 mm or more is more preferable, 80 mm or more is even more preferable, 100 mm or more is particularly preferable, and 120 mm or more is most preferable. On the other hand, a distance of 500 mm or less further improves measurement accuracy. A distance of 400 mm or less is more preferable, 300 mm or less is even more preferable, 200 mm or less is particularly preferable, and 180 mm or less is most preferable.

Furthermore, from the viewpoint of preventing damage to the sealing member and observation window 8 due to radiant heat from the carbon heater 3 and test specimen 4, and from the viewpoint that narrowing the observation range may be effective depending on the observation purpose, it is also preferable to install a reflector between the observation window 8 and the carbon heater 3. For example, a circular opening type or a slit opening type reflector can be used. The material of the reflector is not particularly limited, but stainless steel, titanium, etc. are preferred.

Although not shown in Figure 1, measuring instruments for measuring the physical properties of the test specimen 4 are installed on the outside of the housing 2 of the apparatus 1 of the present invention. The measuring instruments are positioned so that the physical properties of the test specimen 4 can be measured through the observation windows 8. The number of measuring instruments can be appropriately determined depending on the physical properties to be measured and the type of test specimen 4, but it is preferable to have at least two, with one near the side observation window 8 and one near the top observation window 8. Multiple measuring instruments may be installed near one observation window 8. Figure 3 is an example of a photograph of the external appearance of measuring instruments installed on the outside of the housing 2. In the apparatus 1 shown in Figure 3, a camera is installed as a measuring instrument in a position opposite to the observation window 8 installed on the front side of the housing 2, and two-color radiation thermometers are installed as measuring instruments near the observation windows 8 installed on the front side and bottom of the housing 2, respectively. The physical properties of the test specimen 4 are measured through the observation windows 8 using these measuring instruments. The type of measuring instrument can be selected according to the physical properties being measured and the type of test specimen 4, and is not particularly limited, but examples include cameras, thermometers, and dimensional measuring instruments, with cameras or thermometers being preferred. As for the camera, in the visible region, CCD cameras, CMOS cameras, FOVEON X3, organic thin-film image sensors, etc., are used, while in the infrared region, HgCdTe, InSb, PtSi, QWIP, InGaAs, InAsSb, T2SL, microbolometers, etc., are used. The thermometer may be capable of measuring temperature distribution. Examples of thermometers include two-color radiation thermometers and thermal imaging thermometers. Furthermore, if necessary, other measuring instruments besides those used to measure the physical properties of the test specimen through the observation window 8 described above may be installed inside or outside the housing 2. Examples of such other measuring instruments include voltmeters, gas monitors, and stress meters.

Although not shown in Figures 1 and 4, the enclosure 2 typically also includes gas inlet, gas outlet, degassing port, internal cooling water inlet, signal input/output ports, etc.

According to the apparatus 1 of the present invention, the test specimen 4 is heated to an extremely high temperature in a short time, and both the test specimen 4 and the apparatus 1 are cooled in a short time, allowing measurements to be repeated at short intervals. Furthermore, since the housing 2 does not reach such high temperatures, there are fewer restrictions on the position, size, and number of observation windows 8. For these reasons, various physical properties of the test specimen 4 can be easily measured over a wide temperature range using measuring instruments on the outside of the housing 2. Among these, the apparatus 1 of the present invention is particularly suitable for use as a state observation device. Examples of such state observation devices include contact angle measuring devices, thermal conductivity measuring devices, specific heat measuring devices, thermal diffusivity measuring devices, spalling measuring devices, and expansion/contraction measuring devices. Among these, contact angle measuring devices and thermal conductivity measuring devices are preferred, and contact angle measuring devices are more preferred.

A preferred embodiment of the present invention is a method for measuring a test specimen 4 using the apparatus 1, comprising the steps of heating the test specimen 4 with the carbon heater 3 and measuring the test specimen 4 using the measuring instrument.

The measurement method will be described below. In this invention, the type of test specimen 4 is not particularly limited and includes metals, ceramics, refractories, and heat-resistant materials. In this invention, the size of the test specimen 4 is not particularly limited, but typically the distance between the two furthest points of the test specimen 4 is 1 to 100 mm. This distance is preferably 70 mm or less, and more preferably 60 mm or less.

Typically, the test specimen 4 is placed on the lower carbon heater 3. The number of test specimens 4 measured at one time may be one or two or more. For example, when measuring the contact angle, a plate-shaped test specimen 4 made of ceramics or the like is placed on the lower carbon heater 3. A test specimen 4 that melts when heated, such as a metal, is then placed on top of the plate-shaped test specimen 4. After heating these specimens, the contact angle of the molten test specimen 4 with respect to the plate-shaped test specimen 4 can be measured. From the viewpoint of heating the test specimen 4 more efficiently, it is preferable to place the test specimen 4 directly on the lower carbon heater 3.

The test specimen 4 is measured using the measuring instrument located on the outside of the housing 2. Figure 4 shows an example of the configuration of the measuring instrument when performing contact angle measurement and thermal conductivity measurement. As shown, the main camera is installed near the observation window 8 on the front side of the housing 2, and thermometers (two-color radiation thermometers, two-color thermal imaging measurement systems) are installed near the observation windows 8 on the rear side, top, and bottom. When performing contact angle measurement, the temperatures of the upper and lower carbon heaters 3 are measured using the thermometers on the top and bottom sides, and the temperature of the test specimen 4 is measured using the thermometer on the rear side. Then, the contact angle of the molten test specimen 4 is measured by the main camera on the front side. The thermal conductivity of the test specimen 4 is determined by measuring the temperature gradient from the bottom to the top of the test specimen 4 using the thermometers on the top, rear, and bottom sides. Furthermore, it is possible to record video of the test specimen 4 during heating and cooling using the camera, and to measure the temperature distribution of the test specimen 4 using the thermometers, allowing for the measurement of various physical properties of different test specimens 4 using the measuring instrument located on the outside of the housing 2.

It is preferable to heat the test specimen 4 under a non-oxidizing atmosphere such as an inert atmosphere (e.g., an argon atmosphere, a nitrogen atmosphere), a vacuum, or a reducing atmosphere.

The test specimen 4 may be heated using only the lower carbon heater 3, or a carbon heater 3 may be placed above the test specimen 4, and heating may be performed using both the lower and upper carbon heaters 3. When performing contact angle measurement, it is preferable to heat the test specimen 4 using both the lower and upper carbon heaters 3. When performing thermal conductivity measurement, it is preferable to heat the test specimen 4 using only the lower carbon heater 3.

The voltage applied to the carbon heater 3 when heating the test specimen 4 is not particularly limited, but is usually 1 to 20V. The current can be either AC or DC. The heating rate when heating the test specimen 4 with the carbon heater 3 can be set appropriately according to the physical properties being measured, and is not particularly limited, but 50 to 20,000°C/min is preferred. From the perspective of utilizing the features of the apparatus 1 of the present invention, a heating rate of 100°C/min or higher is more preferable, 1,000°C/min or higher is even more preferable, 2,000°C/min or higher is particularly preferable, and 4,000°C/min or higher is most preferable.

The maximum temperature of the test specimen 4 during heating is not particularly limited, but 500 to 3000°C is preferred. According to the apparatus 1 of the present invention, the test specimen 4 is heated to an extremely high temperature in a short time, and cooling is also possible in a short time. Furthermore, the measurement interval is short. To better utilize these features, the maximum temperature is more preferably 1000°C or higher, and even more preferably 1500°C or higher. The heating time is not particularly limited, but is usually 5 seconds to 60 minutes.

Preferably, the measurement method further includes a step of cooling the test specimen 4. The cooling rate of the test specimen 4 can be appropriately set according to the physical properties being measured and is not particularly limited, but 50 to 20,000°C/min is preferred. From the perspective of making better use of the features of the apparatus 1 of the present invention, a cooling rate of 100°C/min or higher is more preferable, 1,000°C/min or higher is even more preferable, 2,000°C/min or higher is particularly preferable, and 4,000°C/min or higher is most preferable. When using apparatus 1, the test specimen 4 can be cooled at such high speed simply by stopping the application of voltage to the carbon heater 3.

According to the above measurement method, the test specimen 4 is heated to an extremely high temperature in a short time, and cooling is also possible in a short time. Furthermore, the measurement interval is short. Therefore, this measurement method can be used to measure various physical properties of various test specimens 4. For example, it is suitably used for measuring the contact angle of molten materials; the thermal conductivity, specific heat, thermal diffusivity, expansion coefficient, contraction coefficient, and thermal shock characteristics of various materials; and spalling of refractories. Among these, a more preferred embodiment of the present invention is a method for measuring the contact angle of a test specimen 4 using the apparatus 1, which includes the steps of heating and melting the test specimen 4 with the carbon heater 3 and measuring the contact angle of the molten test specimen 4 using the camera.

The present invention will be described in more detail below using examples.

Example 1
A heating test of the test specimen 4 was performed using the apparatus 1 shown in Figures 1 and 4. As the test specimen 4, a square alumina ceramic "SSA-S" manufactured by Nikkatoh Co., Ltd., with sides of 10 mm and a thickness of 2 mm, was used. The test specimen 4 was placed on the upper surface of the heating section 5 of the carbon heater 3 (resistance value 0.002 to 0.02 Ω), which is a square with sides of 30 mm. Figure 4 shows the configuration of the measuring instrument. As shown in Figure 4, a camera for recording video of the test specimen 4 was installed near the observation window 8 on the front side of the housing 2. Two-color radiation thermometers ("IR-CZH8N3" manufactured by Chino Corporation) for measuring the test specimen 4 and the carbon heater 3 were installed near the observation windows 8 on the rear side and bottom of the housing 2, respectively. A two-color thermal imaging measurement system ("Thermera SeenU" manufactured by Novitec Co., Ltd.) for measuring the test specimen 4 and the carbon heater 3 was installed near the observation window 8 on the top of the housing 2.

After degassing the inside of the enclosure 2, a voltage was applied to the carbon heater 3 on the underside of the test specimen 4 under conditions of an argon gas flow rate of 1 l/min, and the temperature change was measured using a two-color radiation thermometer and a two-color thermal imaging system. Figure 5 is a graph plotting the voltage applied to the carbon heater 3 against time. During measurement, water was flowed through the cooling jacket installed around the observation window 8 and the cooling pipes in the fixing part 6 to cool the sealing member, observation window 8, and fixing part 6. Figure 6 shows the temperature distribution measured by the two-color thermal imaging system on the top side 20 seconds after the start of voltage application. At this time, the temperature of the heating part 5 was approximately 1900°C, and the temperature of the test specimen 4 was approximately 1660°C. The heating rate of the test specimen 4 measured by the two-color thermal imaging system on the top side was 5400°C/min. Furthermore, when the voltage application to the carbon heater 3 was stopped, the test specimen 4 cooled at a rate of more than 2000°C/min. Measurement results from the two-color thermal imaging system on the top surface and the two-color radiation thermometers on the rear side and bottom surface confirmed a thermal gradient from the bottom to the top surface of test specimen 4, reflecting the heat transfer characteristics of the alumina ceramics, demonstrating that the thermal conductivity of test specimen 4 can be measured.

Example 2
The contact angle of molten steel to refractory brick was measured using the apparatus 1 shown in Figures 1 and 4. A square _Al₂O₃ - _SiO₂ refractory brick SK34 with sides of 10 mm and a thickness of ₂ mm was placed on the upper surface of the heating section 5 (a square with sides of 30 mm) of the carbon heater 3, and a cubic steel material SS400 with sides of 2.5 mm was placed on top of the refractory brick. In addition, although not shown in Figures 1 and 4, a carbon heater 3 similar to the above was placed above the test specimen 4 with the heating section 5 on the lower side.

After degassing the inside of the enclosure 2, voltage was applied to the upper and lower carbon heaters 3 under an argon gas flow rate of 1 l/min, as shown in Figure 5, and the temperature change was measured using a two-color radiation thermometer. Figure 7 shows images of the carbon heaters 3 and test specimen 4 taken with the front-side camera 45, 50, 60, and 63 seconds after the start of voltage application. Temperature 1, indicated in the lower right of each image, is the temperature of the SS400 steel measured by the side-side two-color radiation thermometer, and Temperature 2 is the temperature of the carbon heater 3 measured by the bottom-side two-color radiation thermometer.

As shown in Figure 7, the temperature of the test specimen 4 (SS400 steel) followed the temperature of the carbon heater 3 well. After 60 seconds from the start of heating, the temperatures of the carbon heater 3 and the test specimen 4 (SS400 steel) were almost identical, indicating uniform heating. The contact angle of the molten steel with respect to the refractory brick, measured 63 seconds from the start of heating, was 105.9° using the 2θ method and 104.5° using the tangential method. The heating and cooling rates of the SS400 steel, measured with a two-color radiation thermometer on the side, were both over 2000°C/min.

1. Apparatus 2. Housing 3. Carbon heater 4. Test specimen 5. Heating section 6. Fixing section 7. Terminals 8. Observation window 9. Connection section

Claims (6)

A device for measuring the physical properties of a test specimen under high temperature conditions,
Plate-shaped carbon heaters are arranged on the lower side of the test specimen, or on both the lower and upper sides.
The test specimen is placed on the lower carbon heater,
The carbon heater is housed in a stainless steel casing.
Observation windows are provided on at least the side and top surfaces of the housing.
A measuring instrument for measuring the physical properties of the test specimen is installed on the outside of the housing through the observation window.
A device in which no insulating material is placed inside or on the outside of the aforementioned enclosure. The apparatus according to claim 1, wherein the measuring instrument is a camera or a thermometer. The apparatus according to claim 1 or 2, which is a state observation device. The apparatus according to claim 3, wherein the state observation device is a contact angle measuring device. A method for measuring a test specimen using the apparatus according to any one of claims 1 to 4, comprising the steps of heating the test specimen with the carbon heater and measuring the test specimen using the measuring instrument. A method for measuring the contact angle of a test specimen using the apparatus according to claim 4, comprising the steps of heating and melting the test specimen with the carbon heater, and measuring the contact angle of the molten test specimen using a camera as a measuring instrument.