JP2006349475A - Fixed point crucible for thermometer calibration - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixed point crucible for calibrating a thermometer for measuring temperature in a high temperature region, which prevents breakage of a well section into which a thermometer to be calibrated is inserted. <P>SOLUTION: The fixed point crucible 1 for thermometer calibration separately comprises: a crucible body 2 made of graphite of high purity; a fixed point material 3 formed of an eutectic structure of metal and carbon; and the well section 4 that has the same material as that of the crucible body 2 and is inserted into the crucible body 4 for holding the thermometer to be calibrated. The contact surface contacting when the well section 4 is stored in the crucible body 2 is formed so as to be sandwiched gradually in a tapered shape in the inserting direction of the well section. Thus, the tensile stress and compressive stress produced by contraction of the fixed point material adhering with the crucible body 2 and well section 4, are dispersed and relaxed in calibrating the thermometer, thereby preventing the breakage of the well section 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixed point crucible for calibration of a thermometer that measures temperature in, for example, a high temperature range (for example, around 1100 to 2300 ° C.), and relates to a fixed point crucible for thermometer calibration that prevents damage to a well portion into which a thermometer to be calibrated is inserted. It is about.

  Conventionally, when a thermometer is calibrated, the solidification point or melting point of a metal is adopted as a temperature-defined fixed point above the room temperature range, and a temperature fixed point crucible is used as a method for realizing it. A temperature fixed point crucible usually comprises a crucible body made of high-purity graphite (generally having a purity of 99.99% or more) and a well portion (hereinafter referred to as a well portion) which is a thermometer insertion portion.

  And, as a thermometer calibration device using this type of temperature fixed point crucible, for example, a crucible body containing pure metal cast as a fixed point material is stored, a well portion is attached, and a heat insulating material is packed, A fixed-point cell with a lid having an inert gas inlet for preventing oxidation is known. This fixed-point cell is heated in an electric furnace and the temperature inside is measured with a thermometer, and the temperature change of the crucible is observed when the temperature of the environment is raised and lowered by placing the temperature fixed-point crucible inside a temperature-variable furnace. , The thermometer is calibrated by taking advantage of the fact that the temperature change disappears in the state where the liquid phase and solid phase of the fixed point substance coexist. "See Chapter 7, Nippon Kogyo Publishing (1997)).

  However, in a temperature fixed point crucible in which pure metal is cast using such graphite, when a metal having a higher melting point is dissolved in the graphite crucible, the graphite is eluted into the metal, the metal purity is lowered, and the freezing point drop is reduced. Therefore, the copper temperature of 1085 ° C. is the highest temperature. Moreover, although it has been reported that a fixed point is realized by using a metal-metal eutectic structure as a fixed point material, since a metal is also used as a fixed point material, the maximum temperature is 1085 ° C. of the copper point.

Therefore, in recent years, in order to realize a fixed point in a temperature range of 1100 ° C. or higher, research on a fixed point crucible for thermometer calibration as disclosed in Patent Document 1 below has been advanced. This thermometer calibration fixed point crucible uses a fixed point material that forms a eutectic structure of a metal and a carbon having a higher melting point than copper as the fixed point material. As a result, it has become possible to achieve high accuracy of calibration of radiation thermometers, thermocouples, and other thermometers used in high temperature ranges.
Japanese Patent No. 2998759 Edited by the Japan Electric Measuring Instruments Manufacturers Association, “How to Use a New Thermometer”, Chapter 7, Nippon Kogyo Publishing Co., Ltd. (1997), pages 254-290

  By the way, when using a fixed point material composed of a eutectic structure consisting of metal and carbon for the fixed point crucible for thermometer calibration as described above, the fixed point material is stuck to the crucible part or the well part when the temperature is lowered. When the fixed point material contracts during the transition (melting or solidification), compressive stress is applied to the crucible portion and tensile stress is applied to the well portion. For this reason, if the crucible part and the well part are used in a structure in which the crucible part and the well part are integrated or fixed, the stress applied by the contraction of the fixed point substance cannot be relieved, resulting in a problem that the well part is damaged. .

  Accordingly, the present invention has been made in view of the above problems, and a fixed point crucible for thermometer calibration that prevents breakage of a well portion even when a fixed point material composed of a eutectic structure composed of metal-carbon is used. It is intended to provide.

In order to achieve the above-mentioned object, a fixed point crucible for thermometer calibration according to claim 1 is a crucible main body that contains a fixed point material, and a temperature fixed point that is housed in the crucible main body and is in a phase equilibrium state of the fixed point material. In a fixed point crucible for thermometer calibration composed of a well part for inserting a thermometer to be calibrated by
The crucible body and the well part are mainly composed of carbon,
The contact surface when the well portion is housed in the crucible body is formed to be gradually tapered in the insertion direction of the well portion.

  The fixed point crucible for thermometer calibration according to claim 2 is the fixed point crucible for thermometer calibration according to claim 1, wherein the thermometer to be calibrated is a thermocouple, a resistance thermometer, or an optical fiber radiation thermometer. And

  The fixed point crucible for thermometer calibration according to claim 3 is the fixed point crucible for thermometer calibration according to claim 1 or 2, wherein the fixed point substance is a eutectic structure of metal and carbon.

  According to the fixed point crucible for thermometer calibration of the present invention, the crucible main body and the well portion are configured separately, and the contact surface that comes into contact when the well portion is accommodated in the crucible main body gradually moves toward the well portion insertion direction. In order to reduce the tensile and compressive stress caused by the shrinkage of the fixed point material that sticks to the crucible body and well during temperature calibration, the well can be prevented from being damaged. it can.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a full sectional view showing each configuration of a thermometer calibration fixed point crucible according to the present invention, and FIG. 2 is a detailed sectional view of a portion S in FIG.

  The fixed point crucible for thermometer calibration in this example is a temperature fixed point crucible containing a fixed point material placed inside a temperature variable furnace, and the temperature change of the crucible when the ambient temperature is raised or lowered is observed. Various thermometers that measure the temperature in a high temperature range (for example, around 1100 to 2300 ° C.) are calibrated by utilizing the fact that the temperature change disappears in the state where the phase and the solid phase coexist.

  In this example, the well portion and the crucible body constituting the thermometer calibration fixed point crucible are configured separately, and the contact surface of the well portion and the crucible body is gradually inclined from the thermometer insertion port toward the insertion direction by a predetermined angle. Thus, when the temperature is raised or lowered, the well portion slightly moves with respect to the crucible body to prevent breakage of the well portion.

  First, the configuration of the thermometer calibration fixed point crucible of this example will be described with reference to the attached drawings. As shown in FIG. 1, a thermometer calibration fixed point crucible 1 includes a crucible body 2 made of high-purity graphite, a fixed point material 3 made of a eutectic structure of metal and carbon, and the same material as the crucible body 2. The well portion 4 inserted into the crucible body 2 to hold the thermometer to be calibrated is configured separately.

  As the fixed-point substance 3, a material that forms a eutectic structure with carbon is used, and the following materials are used as materials for the eutectic crystal. As the metal material, a material that forms a carbon eutectic having a melting point higher than the copper point is used. Specific examples include iron, cobalt, nickel, palladium, rhodium, platinum, ruthenium, iridium, rhenium, and osmium.

  The thermometer to be calibrated is not particularly limited as long as it is a thermometer that can be inserted into the well portion 4 of the thermometer calibration fixed point crucible 1. For example, a thermocouple, a resistance thermometer, an optical fiber radiation thermometer (Rod type, consumable type, black body type) etc. are used.

  Next, detailed shapes of the crucible body 2 and the well portion 4 in the thermometer calibration fixed point crucible 1 having the above-described configuration will be described with reference to FIGS. 1 and 2. The center of each diameter in the shape described below is based on the center line L in the figure.

  As shown in FIG. 1, the crucible main body 2 has a bottomed cylindrical shape, and has a well storage portion 2A and a well contact portion 2B integrally. The well storage portion 2A has an outer diameter a1, an inner diameter a2, and a thickness X, and the inner portion of the crucible closing portion on the bottom side is formed in a mortar shape in cross section. The well contact portion 2B is a portion that comes into contact with the well portion 4 when the well portion 4 is accommodated in the crucible body 2, and the contact surface has an inner diameter from a2 toward the well portion insertion port from the upper end of the well storage portion 2A. a3, a predetermined distance is formed so that the thickness gradually increases at an angle α so that the thickness is from X to Z.

The well portion 4 has a bottomed cylindrical shape, and integrally includes a crucible insertion portion 4A, a crucible contact portion 4B, and a flange portion 4C. The crucible insertion portion 4A has an outer diameter b1, an inner diameter b2, and a thickness Y, and the shape of the well closing portion on the bottom side is formed in a mortar shape on both the outer side and the inner side, and further toward the thermometer insertion port direction from a predetermined position. A predetermined distance is formed so that the outer diameter gradually increases at an angle β so that the outer diameter is from b1 to a2. The crucible contact portion 4B is a portion that comes into contact with the crucible body 2 when the well portion 4 is accommodated in the crucible body 2, and the contact surface is well contact portion 2B from the upper end of the crucible insertion portion 4A toward the thermometer insertion port. A predetermined distance is formed so as to be in surface contact with each other. The flange portion 4C has an outer diameter a1 and a length of the flange substantially the same as the upper end of the well contact portion 2B. When the well portion 4 is mounted on the crucible body 2, the well portion 4 and the crucible body 2 They are integrally formed so that there is a predetermined distance between them.
Further, the well portion 4 is formed at a predetermined distance so as to gradually expand at an angle γ from the predetermined position inside the crucible contact portion 4B toward the thermometer insertion port so that the inner diameter is b2 to b3.

  In addition, since the flange part 4C is a part having the effect of facilitating the attachment / detachment of the well part 4 from the crucible body 2, it is not particularly necessary to form the flange part unless it is particularly difficult to attach / detach, and the flange part is formed. Therefore, it is necessary to provide a space E with a predetermined interval between the crucible body 2 and the well portion 4 so that the flange portion 4C and the crucible body 2 do not contact each other even when the environmental temperature is raised or lowered. Further, the inclination angle α of the contact surfaces of the well contact portion 2B and the crucible contact portion 4B may be an acute angle, but in order to facilitate the movement of the well portion 4 with respect to the crucible body 2, the angle is set to an acute angle of more than 30 °. Is more preferred.

  In the thermometer calibration fixed point crucible 1 formed as described above, first, a predetermined amount of the fixed point material 3 made of a eutectic structure of metal and carbon is placed in the crucible body 2. And the well part 4 is inserted in the crucible main body 2, and the fixed point crucible 1 for thermometer calibration is comprised. Insert the thermometer to be calibrated into the well 4 and place it inside the temperature-variable furnace, observe the temperature change of the crucible when the environmental temperature is raised or lowered, and the liquid phase and solid phase of the fixed point substance 3 coexist The thermometer is calibrated by taking advantage of the fact that there is no temperature change in the state of

  At this time, when the fixed point substance 3 sticks to the crucible body 2 or the well part 4 and a phase transition occurs due to temperature drop or melting or solidification in this state, the well contact part 2B and the crucible contact part 4B Tensile stress or compressive stress is applied to the contact surface. However, since the well contact portion 2B of the crucible body 2 and the crucible contact portion 4B of the well portion 4 are formed in a tapered shape so that the respective contact surfaces coincide with each other, the well portion 4 slightly differs from the crucible body 2. Moving. Accordingly, the tensile stress and compressive stress applied to the well portion 4 can be dispersed and relaxed.

  By the way, although the shape of the thermometer calibration fixed point crucible 1 according to the present invention has been described with reference to FIGS. 1 and 2, it is not limited to this, and the contact surface between the crucible body 2 and the well portion 4 is the well portion. The shape of the crucible body 2 and other portions of the well portion 4 is not limited to that shown in FIG.

As described above, the above-described thermometer calibration fixed point crucible 1 is composed of the crucible body 2 and the well part 4 separately, and the fixed point substance 3 sticks to the crucible body 2 and the well part 4 at the time of thermometer calibration. When a phase transition due to melting or solidification occurs, the well portion 4 slightly moves in the axial direction due to tensile stress or compressive stress applied to the contact surface between the well contact portion 2B and the crucible contact portion 4B due to contraction of the fixed point material 3 As a result, the tensile stress and the compressive stress applied to the well portion 4 are dispersed and relaxed.
Thereby, even if it is a case where the fixed point substance comprised by the eutectic structure which consists of a metal and carbon is used, there exists an effect which prevents the damage of a well part.

  As mentioned above, although the best form was demonstrated using this invention, this invention is not limited with the description and drawing by this form. That is, it is a matter of course that all other forms, examples, operation techniques, and the like made by those skilled in the art based on this form are included in the scope of the present invention.

It is the whole sectional view showing each composition of a fixed point crucible for thermometer calibration concerning the present invention. FIG. 2 is a detailed cross-sectional view of a portion S in FIG.

Explanation of symbols

1 Fixed point crucible for thermometer calibration 2 Crucible body 3 Fixed point material 4 Well part

Claims (3)

For thermometer calibration consisting of a crucible body that contains a fixed-point substance and a well portion that is inserted into the crucible body and into which a thermometer to be calibrated is calibrated by a temperature fixed point that is in a phase equilibrium state of the fixed-point substance. In the fixed point crucible,
The crucible body and the well part are mainly composed of carbon,
A fixed point crucible for thermometer calibration, characterized in that a contact surface when the well portion is housed in the crucible body is gradually narrowed in a taper shape in the insertion direction of the well portion. The fixed point crucible for thermometer calibration according to claim 1, wherein the thermometer to be calibrated is a thermocouple, a resistance thermometer, or an optical fiber radiation thermometer. The fixed point crucible for thermometer calibration according to claim 1 or 2, wherein the fixed point substance is a eutectic structure of metal and carbon.

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