JPH03186747A - Melting point measuring method - Google Patents

Abstract

PURPOSE:To exactly and easily derive a melting point of a high vapor pressure/ high melting point substance by covering the upper part of a containing recessed part of a sample containing and heating container in which a substance to be measured is contained, with a cover material, heating and melting it in a closed state, and measuring its melting point by a radiation thermometer. CONSTITUTION:The upper part of a containing recessed part 20 of a sample containing and heating container 2 in which a substance 1 to be measured is contained is covered with a cover material 3, the containing recessed part 20 is set to a closed state, and thereafter, the substance 1 to be measured is heated and melted, and a melting point of the substance 1 to be measured is measured by a radiation thermometer 4. Also, this heating container 2 is usually installed in a chamber. The heating container 2 is formed from a high melting point metal and its alloy, for instance, tungsten, molybdenum, tantalum, etc., and their alloy. Also, as for a forming material of the cover material 3, any of those which can be used for the forming material of the heating container 2 can be used, and tungsten, molybdenum and tantalum are especially desirable.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for measuring the melting point, and more specifically, the present invention relates to a method for measuring the melting point of a substance with a high melting point and high vapor pressure. The present invention relates to a method for measuring melting point that can be accurately and easily determined while preventing.

[Prior Art and Problems to be Solved by the Invention] For example, in various nuclear reactor plants, high melting point substances are often used as forming materials for various structural materials such as fuel cladding tubes, piping, heat exchangers, and turbine parts. ing.

In order to ensure the safety of nuclear reactor plants, it is necessary to accurately know the melting point of each high melting point substance used in various structural materials.

By the way, when measuring the melting point of a substance that has a melting point in the high temperature range of around 3000°C, if the substance to be measured or its constituent components have a high vapor pressure, the substance to be measured or its constituent components may have a high vapor pressure during the measurement. Since a part of the fraction evaporates and disappears, for example, the material to be measured is heated to a high melting point metal (e.g. W, Mo, Ta, etc.) using electron beam welding.
A method of measuring the melting point of the substance to be measured using a radiation thermometer by enclosing it in a manufactured capsule and heating the substance to be measured in this state,
Alternatively, as shown in FIG. 2, for example, the analyte A is placed on an oven-shaped boat B, ignoring the evaporation of the analyte or its constituent components, and the analyte A is placed in this state. A method is used in which the melting point of the substance to be measured A is measured by heating it and using a radiation thermometer C.

However, in the former method, W.

Problems include that it is difficult to process capsules made of high-melting point metals such as Mo and Ta, and that the electron beam welding equipment used is expensive.

On the other hand, in the latter method, the generated steam interferes with temperature measurement using a radiation thermometer, and if some of the constituents of the substance to be measured evaporate, the substance is no longer the same as the substance to be measured. The melting point of the substance of the composition is to be measured, and in any case there is a problem in that the melting point of the substance to be measured cannot be accurately measured.

The present invention has been made based on the above circumstances.

The purpose of the present invention is to reduce the melting point of a substance with high vapor pressure and high melting point by preventing evaporation of the substance to be measured, changes in its components, or reactions with atmospheric gas, etc. It is an object of the present invention to provide a melting point measuring method that can accurately and easily determine the melting point of.

[Means for Solving the Problems] The structure of the invention according to claim 1 which is distantly related to the above-mentioned object is to cover the storage recess of the sample storage heating container containing the substance to be measured with a lid material, and to A melting point measuring method is characterized in that the substance to be measured is brought into a sealed state, the substance to be measured is heated and melted, and the melting point of the substance to be measured is measured using a radiation thermometer. 2. The melting point measuring method according to claim 1, wherein the lid material is made of tungsten, molybdenum, or tantalum.

In the method of the present invention, for example, as shown in FIG. 1, after the storage recess 20 of the sample storage heating container 2 containing the substance to be measured 1 is covered with a lid material 3 and the storage recess 20 is sealed. , the substance 1 to be measured is heated and melted, and the melting point of the substance 1 to be measured is measured by the radiation thermometer 4. And this sample storage heating container 2.

Usually, it is installed in a chamber (not shown).

The sample storage heating container used is provided with a storage recess for storing the substance to be measured, and can be suitably made of, for example, a high melting point metal or an alloy thereof. Specific examples of such high melting point metals and alloys thereof include tungsten, molybdenum, tantalum, chromium, vanadium, niobium, and alloys thereof. Among these, tungsten, molybdenum, and tantalum are preferred.

In the method of the present invention, a substance to be measured is stored in a storage recess formed in a sample storage heating container, and the storage recess is covered with a lid material to seal or semi-seal the storage recess. It is necessary to.

That is, in the method of the present invention, the inside of the storage recess containing the substance to be measured is sealed or semi-sealed, and the substance to be measured in the storage recess is directly heated and melted in the sample storage heating container, and then the radiation thermometer is heated. Since the melting point is measured by the method, it is possible to prevent evaporation of the sample, change in composition, reaction with atmospheric gas, etc., from occurring during the measurement.

As the material for forming the lid material that covers the storage recess and makes the inside of the storage recess into a sealed or semi-sealed state, any material that can be suitably used as the material for forming the sample storage heating container is suitable. Particularly preferred are tungsten, molybdenum, and tantalum.

The shape of the lid material is usually a plate shape, and preferably a foil shape or a sheet shape. Furthermore, if the lid material is in the form of a foil or sheet, its thickness must be as follows.

Usually 0.003 to 0.5 mm, preferably 0.003 to 0.5 mm.
020-0.1 Sonoho.

In the method of the present invention, in order to cover the storage recess containing the substance to be measured with the lid material to bring the inside of the storage recess into a sealed or semi-sealed state, for example, the storage recess is completely covered. Til the lid material onto the storage recess.
t. A portion (indicated by 30 in FIG. 1) where the upper surface of the sample storage/heating container (peripheral surface of the storage recess) and the lid material come into contact is filled with an arbitrary gas such as Ar/H2 gas. In the atmosphere.

Normally, a welding process such as seam welding or spot welding may be performed. Note that the semi-sealed state refers to a state in which the storage recess ZO is not completely sealed.

In the method of the present invention, the storage recess in which the substance to be measured is stored as described above is covered with the lid material, the inside of the storage recess is sealed or semi-sealed, and then the sample storage heating container is closed. Connected and fixed to a designated electrode in the melting point measurement chamber, and any temperature increase that does not reach the melting point of the substance to be measured.
According to a holding-cooling program, the storage recess and the substance to be measured are heated, held for a certain period of time, and then cooled.

At this time, since the contact portion between the upper surface of the sample storage heating container (peripheral surface of the storage recess) and the lid material is in close contact with each other due to mutual diffusion between metals, the sample to be measured stored in the storage recess is is completely sealed (hereinafter, this process is referred to as heat-sealing process). Therefore, in the method of the present invention, the inside of the storage recess is not necessarily in a sealed state before the heat-sealing process is performed. It may be in a semi-sealed state as described above.

Furthermore, if the thickness of the lid material and the method of placing it on the storage recess are appropriately selected, the above-mentioned contact area between the top surface of the sample storage heating container (peripheral surface of the storage recess) and the lid material can be adjusted. The welding process can be omitted. That is, in that case, by performing the heat sealing treatment with the lid material placed on the storage recess, the substance to be measured stored in the storage recess will be completely sealed. The thickness of the lid material that allows the welding process to be omitted is as follows:
Usually 0.003-0.5mm, preferably 0.0
It is desirable that the thickness of the lid material be within the range of 0.003 to 0.11. If it exceeds .5++n, it may become difficult to make close contact between the lid material and the sample storage/heating container, making it impossible to seal them.

In the method of the present invention, after the heat-sealing process is performed, the substance to be measured stored in the storage recess is heated, held, and cooled according to an arbitrary melting point program, and the thermal arrest (heating The temperature of the substance to be measured does not rise or fall, respectively, until a certain amount determined according to the balance between energy and energy lost due to radiation, conduction, etc. is completely melted or solidified. Determine the melting point of the substance to be measured.

Note that a series of temperature changes can be measured using a radiation thermometer.

Further, in the method of the present invention, it is preferable that the inside of the chamber be made into a mixed gas atmosphere of an inert gas and a reducing gas or an inert gas atmosphere during the measurement.

The method of the present invention applies the melting point of high melting point and high vapor pressure substances used for forming materials such as fuel cladding tubes, plasma vessel walls, heat exchangers, turbine parts, etc. of various nuclear reactors, high temperature gas reactors, nuclear fusion reactors, etc. It can be suitably used for the measurement of.

[Function] In the method of the present invention, when the substance to be measured stored in the sealed storage recess of the sample storage/heating container is heated by the sample storage/heating container, the substance to be measured reaches its melting point and starts melting. The temperature of the substance to be measured is maintained without rising until a certain amount, determined according to the balance between heating energy and energy lost due to radiation, conduction, etc., is completely melted, exhibiting so-called thermal arrest.

If heating is continued further, the temperature of the substance to be measured starts rising again. In the method of the present invention, heating by the sample storage heating container is stopped at this point.

The substance to be measured, which has started to cool down due to the lack of heating energy, reaches its melting point and begins to solidify, exhibiting thermal arrest again.

If the temperature change in the substance to be measured is measured using a radiation thermometer over the entire process of heating → melting → cooling → solidification, the melting point of the substance to be measured can be determined by the evaporation of the substance or its components. Therefore, it is possible to easily measure the temperature with high precision while preventing interference with temperature measurement due to evaporated steam or fume and errors due to compositional fluctuations of the substance to be measured.

[Example] Next, Examples and Comparative Examples of the present invention will be shown to further specifically explain the present invention.

(Example 1) Thickness 0.2 mm x Width 15 s
0.13g of UO and a powder sample were stored in the hemispherical recess (0.05m5 + tx 14mm).
A tungsten foil of φ×24×1φ was placed.

Next, after evacuating this tungsten boat in a chamber, 10% Ar/Ht gas was introduced, a 2-inch width of the tungsten foil was seam welded onto the tungsten boat, and the C in the melting point measuring device was heated.
It was connected and fixed to the u electrode.

After that, the inside of the chamber was heated to 10% Ar/Ht.
After replacing with gas, the temperature was raised to 2000°C at a rate of 20°C per second, held at that temperature for 10 minutes, and cooled again.

After performing the heat sealing treatment as described above, the temperature reached 2950 °C at the same heating rate, held for 10 seconds, and then cooled at the same cooling rate.The melting point of the sample was measured using a radiation thermometer according to a normal melting point measurement program. When determined from the appearance of thermal arrest, a value of 2855°C was obtained.

This value was in good agreement with the literature value of 2845°C±25°C.

In addition, since the sample storage area was completely sealed with a tungsten foil welded at four seams during the II4 test, no generation of steam, fumes, etc. to the outside was detected.

(Comparative Example 1) In a boat/heater having the same shape as in Example 1, 0.1% of UO2/1.3 mol%-Nb, 05 powder sample was placed.
After the gas was replaced in the same manner as in Example 1, heating was started according to the same melting point measurement program as in Example 1. However, as the sample began to melt, steam and fumes were generated on the boat. This caused the temperature measurement by the radiation thermometer to be interfered with, resulting in a severe temperature drift from around 2300°C.

Analyzing the sample after the measurement was completed.

The Nb2O content was 0.7 mol%. The reason for this is presumed to be that the composition changed due to evaporation and disappearance during heating and melting.

[Effects of the Invention] According to the present invention, the storage recess containing the substance to be measured is sealed, the substance to be measured is heated and melted, and the melting point of the substance to be measured is measured using a radiation thermometer. (1) Measurement. It is possible to prevent the substance to be measured or its constituent components from evaporating and disappearing during the process, thus eliminating interference with temperature measurement due to evaporated steam or fumes and errors caused by compositional fluctuations of the substance to be measured. It is possible to provide an industrially useful melting point measuring method which has the following advantages: (2) it is easy to operate; and (2) it is easy to operate.

[Brief explanation of drawings]

FIG. 1(a) is a cross-sectional explanatory diagram showing an example of the configuration of the measurement system in the method of the present invention, FIG. 1(b) is an explanatory plan view thereof, and FIG. A cross-sectional explanatory diagram showing an example, and FIG.
...Lid material, 20...Storage recess Fig. 1 (A) (B) Fig. 2 (A) (B)

Claims (2)

[Claims] (1) After covering the storage recess of the sample storage heating container containing the substance to be measured with a lid material and making the storage recess into a sealed or semi-sealed state, the substance to be measured is heated and melted, and the radiation thermometer is A method for measuring a melting point, comprising: measuring the melting point of the substance to be measured. (2) The melting point measuring method according to claim 1, wherein the lid material is made of any one of tungsten, molybdenum, and tantalum.