JPH11326250A - Test method for thermal conductivity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a test method in which a precise temperature change can be measured by a thermocouple by a method wherein a test piece, a hot wire and the thermocouple are insulated completely, precise electric power is applied to the hot wire and heat is transmitted to the test piece from the hot wire without any loss. SOLUTION: In a test method, a hot wire 5 and a thermocouple 6 are buried, at a prescribed interval, in a test piece 1 and a test piece 2 which are placed in a prescribed high-temperature nonoxidizing atmosphere, and a temperature change is measured by the thermocouple 6 when the test pieces 1, 2 are heated locally by the hot wire 5. In this case, insulating materials 8, 8 which are heat- resistant and whose thermal conductivity is high are executed around the hot wire 5 and the thermocouple 6 which are buried in the test pieces 1, 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for testing the thermal conductivity of a conductive refractory using a hot wire and a thermocouple.

[0002]

2. Description of the Related Art The thermal conductivity of refractories is important data for selecting furnace materials in furnace design or for evaluating thermal spalling properties in research and development. However, conductive refractories mainly composed of carbon (MgO-C material,
Al ₂ O ₃ -C quality, SiC quality, etc.), or high temperature despite ZrO ₂ quality refractory conductive arises such production volume is increased with a suitable thermal conductivity testing method has not been established.

As a method for testing the thermal conductivity of refractories, there are a heat flow method, a hot wire method, a laser flash method, and the like, and among these test methods, the hot wire method is generally used. As a suitable test standard by this hot wire method, Japanese Industrial Standard JIS
R2618 (a test method for the thermal conductivity of a refractory insulating brick by the hot wire method), and International Standard ISO 8894-1-2 (a test method for the thermal conductivity of refractory). However, these preferred hot wire test standards apply to refractories having insulating properties.

Therefore, as a method for testing the thermal conductivity of a refractory having conductivity, the thermal conductivity test method by the above-mentioned hot wire method has been tentatively attempted, and a method in which a hot wire and a thermocouple are insulated by a mica plate. Alternatively, a thermocouple for temperature measurement is buried in a groove as disclosed in JP-A-64-66553, and a method of using a ceramic base material for coating an insulating layer having good electrical insulation, and other methods, A method of heating a carbon-containing refractory in air and thinly decarburizing only the surface has been performed. However, these test methods were not sufficient test methods, such as having a problem in test accuracy as described later.

FIG. 6 (perspective view) shows an example of a conventional method for testing the thermal conductivity of a conductive refractory according to International Standard I.
A description will be given of a thermal conductivity test method for SO8894-2 refractories and a test method to which a hot wire method (parallel arrangement method) is applied (a mica plate is used for insulating a hot wire and a thermocouple). This test method is 8
Applies to materials with a thermal conductivity of 25 W / (m · K) or less at temperatures up to 00 ° C. FIG. 6 shows an arrangement state of the heating wire and the thermocouple set on the test piece (an exploded view showing the setting state). As shown in FIG.
A plurality of mica plates 3 and 4 are arranged, and a thermocouple 6 is arranged at a predetermined distance from a heating wire 5 linearly arranged between the mica plates 3 and 4. The heating wire 5 and the thermocouple 6 are arranged so as to be in close contact with the test pieces 1 and 2 via the mica plates 3 and 4. In the case of dense materials or refractories having a thermal conductivity of 5 W / m · K or more, a groove 7 for embedding the heating wire 5 and the thermocouple 6 in the test piece.
Is provided.

Next, the test piece on which the heating wire 5 and the thermocouple 6 are arranged is heated to a predetermined test temperature in a non-oxidizing atmosphere and is kept at that temperature. After the specimen temperature stabilizes at a constant temperature, the specimen is further locally heated by passing a current of known power that is constant over the length of the specimen for a predetermined time through the heating wire 5. The temperature change of the test piece is measured from the time when a heating current is applied to the hot wire 5 by the thermocouples 6 arranged at predetermined intervals in parallel with the hot wire. The power applied to the heating wire 5 is obtained from the applied voltage (V) and the current (A).

The thermal conductivity λ (W / m · K) of the test piece is calculated by the following equation. V: applied voltage (V) I: heating current (A) 1: length of heating wire (m) r: distance between the hot wire and the measuring thermocouple (m) a: thermal diffusion coefficient (m ² / s) t: opening and closing time of the heating circuit (s) Δθ (t): temperature change of the thermocouple at time t (K)

[0008]

As is apparent from the above formula, in order to carry out a high-precision thermal conductivity test, accurate power applied to a hot wire and its measurement, and a test piece with little loss from the hot wire are used. The important factors are the heat transfer of the sample and the accurate measurement of the temperature change by the thermocouple of the test piece. However, in a conventional test method for a refractory having conductivity, when a mica plate is used for insulation between a test piece, a heating wire, and a thermocouple, there are the following problems. (1) The heat-resistant temperature of the mica plate is limited to 800 ° C. If the temperature exceeds the limit, the mica plate is deteriorated, and the insulation between the heating wire and the thermocouple and the test piece is reduced, so that accurate measurement cannot be performed. (2) 0.7 W / m · K due to low thermal conductivity of mica plate
(400 ° C.) measurement error occurs. (3) Since the mica plate is not flexible, the following problem arises when the test piece is provided with a groove even when used at a temperature of 800 ° C. or less. In some cases, cracks occur in the mica plate and the insulation between the test piece and the heating wire or thermocouple decreases, and a stable test cannot be performed. Poor adhesion between the hot wire and the mica plate, and between the mica plate and the test piece, resulting in insufficient heat transfer from the hot wire to the test piece, causing measurement errors. Poor adhesion between the thermocouple and the mica, and between the mica plate and the test piece, making accurate temperature measurement impossible, resulting in measurement errors. (4) Because of the CO gas present around the hot wire and the thermocouple, the hot wire and the thermocouple are carburized and deteriorate the characteristics. Further, in the method of heating in air and thinly decarburizing only the surface, it is difficult to oxidize the surface to such an extent that the insulating property is secured and the thermal conductivity is not affected, and the measured values vary. Japanese Unexamined Patent Publication (Kokai) No. 64-66553 discloses a thermocouple for temperature measurement embedded in a groove, and a ceramic base material is used as a filler for an insulating layer having good electrical insulation. However, according to this method, the refractory material to be symmetrical in the present application has many types and the test frequency is high, so that such a manufacturing means is complicated, and it is difficult to obtain a predetermined test accuracy. Insulation is not interposed between the measurement object and the thermocouple, insulation is only between the thermocouple and the heater, and detailed description of the insulation coating material is also provided. No, test temperature is 800 ~ 1
In the present application, it is possible to measure up to 1500 ° C. against 000 ° C., which is not a sufficient means.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. In a thermal conductivity test of a refractory having conductivity, insulation between a test piece, a heating wire and a thermocouple is completed so that accurate power is applied to the heating wire. In addition, heat is transferred from the hot wire to the test piece without any loss, and accurate measurement of temperature change by the thermocouple is enabled, thereby enabling a highly accurate and stable thermal conductivity test.

[0010]

According to a first aspect of the present invention, a test wire placed in a predetermined high-temperature, non-oxidizing atmosphere is provided with a hot wire and a thermocouple embedded at a predetermined interval, and the test bar is inserted. In a thermal conductivity test method in which a temperature change when locally heated by a hot wire is measured by a thermocouple, an insulating material having heat resistance and high thermal conductivity is provided around the hot wire embedded in the test piece and the thermocouple. It is characterized by having done. The invention according to claim 2 is characterized in that the insulating material is made of a coating material having viscosity, adhesion and high airtightness after curing which can be applied with a brush, and the aggregate of the coating material is made of alumina or mullite or magnesia or titania and a binder. It is characterized by comprising a complex alkoxide partial hydrolyzate. The invention according to claim 3 is characterized in that the insulating material is formed of a hollow fired material having high airtightness, and the hollow fired material is mainly composed of alumina, mullite, magnesia, or titania. According to a fourth aspect of the present invention, the test piece is divided into two parts and a groove is excavated from one or both surfaces thereof, and the aggregate is made of alumina or mullite or magnesia or titania and a binder and a composite alkoxide partial hydrolyzate. A coating material having viscosity, adhesion, and high airtightness after coating is applied to the hot wire and the thermocouple, cured, and then disposed in the groove. The invention according to claim 5 is that the test piece is divided into two and a groove is excavated from the surface on one side, and the aggregate is composed of alumina or mullite or magnesia or titania and a binder and a composite alkoxide partial hydrolyzate. After applying a coating material having possible viscosity, adhesion and high airtightness after curing to the groove and curing the same, the hot wire and the thermocouple are arranged in the groove, and further the gap between the hot wire and the thermocouple and the groove. Characterized by being filled with the coating material. According to a sixth aspect of the present invention, the test wire is divided into two parts, and the hot wire and the thermocouple disposed on a groove excavated from the surface on one or both sides thereof are made of an insulating material mainly composed of alumina, mullite, magnesia, or titania. It is characterized by being inserted into a hollow fired product having high airtightness formed from a material. The invention according to claim 7 is characterized in that, in the gap between the hollow fired product, the heat wire and the thermocouple, the aggregate is composed of alumina or mullite or magnesia or titania and a binder and a composite alkoxide partial hydrolyzate, It is characterized by being filled with a coating material having adhesiveness and high airtightness after curing. The invention according to claim 8 is that the aggregate is made of alumina or mullite or magnesia or titania and a binder and a partially hydrolyzed composite alkoxide in a gap between the hollow fired product and the test piece, and is a viscous and adhesive material that can be brush-coated. And a filling material having high airtightness after curing is filled.

[0011]

Embodiments of the present invention will be described below. FIG. 1 is a diagram for explaining the basic configuration of the thermal conductivity test method of the present invention. In FIG. 1, test pieces 1, 2
Is a test piece made of a conductive refractory, which is divided into two parts. A groove 7 having a predetermined depth is excavated from the surface of each of the divided surfaces, and a heating wire 5 and a thermocouple 6 are embedded in the grooves. The test pieces 1 and 2 and the hot wire 5 are applied from a low temperature to a high temperature of 1500 ° C. by applying an insulating material 8 having heat resistance and high thermal conductivity around the hot wire 5 and the thermocouple 6. And complete insulation of the thermocouple 6 so that accurate power is applied to the hot wire and the test piece 1,
The heat transfer to the thermocouple 2 is performed without loss, and the temperature change can be accurately measured by the thermocouple 6, thereby enabling a highly accurate and stable thermal conductivity test.

[First Embodiment] FIG. 2 is a view for explaining a first embodiment. A test piece 230 mm × 115 mm × 65 mm cut from a conductive refractory was divided into two parts as shown in FIG. 2 (a), and the upper surface of the test piece 1 and the lower surface of the test piece 2 were smoothed beforehand. A groove 7 having a width Y (= 1 mm) and a depth Z (= 1 mm) is dug in the center of the upper surface at an interval X (= 15 mm) in parallel from the side, and a PR 13% having a wire diameter of 0.5 mm is previously formed in the groove 7. Hot wire (rhodium 13%
And a R thermocouple with a wire diameter of 0.5 mm (platinum on the-leg, rhodium 1 on the + leg)
A coating material 9 is applied to the outer periphery of a platinum-rhodium alloy (containing 3%) 6 having a thickness of 150 μm, and then heated and cured at 200 ° C. is provided. Further, a coating material 9 is filled in the groove 7 of the test piece 1 and the gap between the test piece 2 and the groove 7. Next, the test pieces 1 and 2 on which such a heating wire 5 and a thermocouple 6 are set are placed in an electric furnace in a non-oxidizing atmosphere, and the temperature is increased to 1200 ° C .; Perform the measurement. Note that FIG.
As shown in (b), the groove 7 is formed on the upper surface of the test piece 1 and on the
Excavation may be performed over the lower surface, and a heating wire and a thermocouple may be disposed in the same manner as in the case of FIG. The coating material 9 is made of an aggregate having a suitable viscosity and adhesion that can be applied with a brush and having high airtightness, heat resistance, insulation and high thermal conductivity after curing, and 100% by weight of ultra-fine fused alumina.
And a binder in which 70% by weight of a composite alkoxide partial hydrolyzate is added externally and mixed.

Second Embodiment FIG. 3 is a diagram for explaining a second embodiment. A test piece 230 mm × 115 mm × 65 mm cut out of a conductive refractory is divided into two as shown in FIG. 3, and the upper surface of the test piece 1 and the lower surface of the test piece 2 are smoothed in advance, and then the test piece as shown in the drawing. 1 Width and depth 1 mm parallel to the side at a distance of 15 mm at the center of the upper surface
The coating material 9 of Example 1 is applied to the groove 7 so as to have a cured thickness of 150 μm to form a coating layer 10, and then heated and cured at 200 ° C. Next, the coating layer 10
The PR 13% hot wire 5 having a wire diameter of 0.5 mm and the R thermocouple 6 having a wire diameter of 0.5 mm are fitted into the respective grooves.
The coating material 9 is applied to the gap between the groove 7 and the surface of the test piece 2 so as to be flush with the lower surface of the test piece 2, and then heated and cured at 200 ° C. next,
The test pieces 1 and 2 on which the above-mentioned heating wire 5 and the thermocouple 6 are set are placed in an electric furnace in a non-oxidizing atmosphere, heated to a temperature of 1200 ° C., and then the thermal conductivity is measured by an ordinary method.

Third Embodiment FIG. 4 is a view for explaining a third embodiment. A test piece 230 mm × 115 mm × 65 mm cut from a conductive refractory was divided into two parts, and the upper surface of the test piece 1 and the lower surface of the test piece 2 were smoothed in advance, and then, as shown in FIG. A groove 7 having a width and a depth of 1.5 mm is excavated in the center of the upper surface at a distance of 15 mm in parallel from the side. Next, a hot wire 5 made of a nichrome wire having a wire diameter of 0.5 mm and a thermocouple 6 having a wire diameter of 0.5 mm and an outer diameter of 1 mm and an inner diameter of 0.7 m having high airtightness, heat resistance and insulation properties are provided.
m, an alumina-based hollow fired product (insulating sleeve) 11 having a thickness of 150 μm is inserted. Next, the heat wire 5 and the R thermocouple 6 inserted into the sleeve are fitted into the grooves 7 on the upper surface of the test piece 1 respectively, and the insulation and heat conduction between the test pieces 1 and 2 and the heat wire 5 and the R thermocouple 6 are further improved. To increase the height, 60% by weight of ultra-fine powder of electrofused magnesia as a coating material 9 and 60% by weight of a composite alkoxide partial hydrolyzate are added to the binder in the gap between the groove 7 and the alumina-based hollow fired product 11, The mixture is applied so as to be flush with the lower surface of the test piece 2, and then cured by heating at 200 ° C. FIG.
As shown in (b), the groove 9 is formed on the upper surface of the test piece 1 and on the
The excavation may be performed over the lower surface, and the heating wire and the thermocouple may be embedded in a similar manner.

Next, the heat wire 5 and the R thermocouple 6 inserted into the sleeve are respectively fitted into the grooves 7 on the upper surface of the test piece 1 and covered with the test piece 2, and then the test pieces 1 and 2 are placed in a non-oxidizing atmosphere. After placing in an electric furnace and raising the temperature to 1000 ° C,
The thermal conductivity is measured by an ordinary method.

Fourth Embodiment FIG. 5 is a view for explaining a fourth embodiment. In Example 3, in order to further improve the test accuracy, as shown in FIG. 5, the alumina-based hollow fired product (insulating sleeve) 11 was applied to the gap 12 between the hot wire 5 and the R thermocouple 6 inserted therein. As a material, a mixture of 100% by weight of electro-fused magnesia ultrafine powder and 65% by weight of a composite alkoxide partially hydrolyzed product in a binder is filled, and the mixture is heated and cured at 200 ° C. In addition, FIG.
As shown in (1), the groove 7 may be excavated over the upper surface of the test piece 1 and the lower surface of the test piece 2 so as to embed a hot wire and a thermocouple in a similar manner.

The preferred heating wires, thermocouples, grooves, insulating materials, and insulating sleeves in the above embodiments are as follows. (1) It is preferable that the hot wire and the thermocouple for temperature measurement have a wire diameter of 0.5 mm or less, and the contacts of the thermocouple (platinum / platinum rhodium) have the same wire diameter and have no tip. (2) The grooves for burying hot wires and thermocouples are excavated on one or both sides of the test piece. The groove depth is 0.6mm
~ 2 mm is preferred. (3) The insulating material for burying a hot wire and a thermocouple has a coating property, a filling property, a heat resistance property, an insulating property, and a high thermal conductivity. For example, the inorganic material heat-resistant composition proposed by the present applicant ( JP-A-1-297471) is preferred. An inorganic material heat-resistant composition comprising 100 parts by weight of refractory aggregate and 10 to 200 parts by weight of a composite alkoxide partially hydrolyzed sol comprising at least one selected from Si alkoxide, Ti alkoxide, Al alkoxide and Zr alkoxide is preferred. As the refractory aggregate, a powder of alumina, mullite, magnesia, and titania having a size of 0.5 to 50 μm is used. The complex alkoxide partially hydrolyzed sol is composed of metal alkoxides of Ti, Al, Zr 7 to 2 with respect to Si alkoxides.
A composite ratio of 5 parts by weight is used. In addition, 30 to 9 of the OR group
5 mol% remained. The coating and filling properties can be obtained by adding the composite alkoxide partially hydrolyzed sol to the refractory aggregate in an amount of 40 to 100 parts by weight (28 to 50 parts by weight) on the outside. The insulating material can be applied to the heating wire and the groove or the like by 50 to 300 μm or more.

(4) Insulation Sleeve There is a known insulation sleeve made of alumina, mullite, and magnesia having heat resistance, high airtightness, insulation, and high thermal conductivity. Further, the outer diameter is preferably 0.8 to 2 mm and the inner diameter is 0.6 to 1 mm.

[0019]

As described above, according to the present invention, the insulation between the test piece, the heating wire and the thermocouple from the low temperature to the high temperature is completely completed, accurate power is applied to the heating wire, and heat is transferred from the heating wire to the test piece without any loss. As a result, accurate measurement of temperature change by a thermocouple became possible, and as a result, a thermal conductivity test of a highly accurate and stable conductive refractory was made possible.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a basic configuration of a thermal conductivity test method of the present invention.

FIG. 2 is a diagram illustrating a first embodiment.

FIG. 3 is a diagram illustrating a second embodiment.

FIG. 4 is a diagram illustrating a third embodiment.

FIG. 5 is a diagram illustrating a fourth embodiment.

FIG. 6 is a diagram illustrating an example of a conventional method for testing the thermal conductivity of a refractory having conductivity.

[Explanation of symbols]

1, 2, ... test piece, 5 ... hot wire, 6 ... thermocouple, 7 ... groove, 8 ...
Insulating material, 9: coating material, 11: hollow fired product, 12: gap.

Claims (8)

[Claims] 1. A hot wire and a thermocouple are buried at a predetermined interval in a test piece placed in a predetermined high-temperature non-oxidizing atmosphere, and a temperature change when the test piece is locally heated by the hot wire is measured by the thermocouple. A heat conductivity test method, characterized in that a heat-resistant insulating material having high heat conductivity is provided around a heat wire and a thermocouple embedded in the test piece. 2. The insulating material comprises a coating material having viscosity, adhesion, and high airtightness after curing, which can be applied with a brush. The coating material is composed of alumina, mullite, magnesia, or titania as an aggregate, and a binder as a composite. 2. The method for testing thermal conductivity according to claim 1, wherein an alkoxide partial hydrolyzate is used. 3. The insulating material is made of a hollow fired material having high airtightness, and the hollow fired material is mainly made of alumina, mullite, magnesia, or titania. The described thermal conductivity test method. 4. A test piece is divided into two parts and a groove is cut out from one or both sides of the test piece, and alumina, mullite or magnesia or titania is used as an aggregate, and a composite alkoxide partial hydrolyzate is used as a binder. 2. A thermal conductivity test according to claim 1, wherein a coating material having high viscosity, adhesion and high airtightness after curing is applied to said hot wire and thermocouple and cured, and then disposed in said groove. Method. 5. The test piece is divided into two parts, a groove is excavated from the surface on one side, and alumina, mullite or magnesia or titania is used as an aggregate, and a composite alkoxide partial hydrolyzate is used as a binder. After applying and curing the coating material having viscosity, adhesiveness and high airtightness after curing in the groove, the hot wire and the thermocouple are arranged in the groove, and furthermore, in the gap between the hot wire and the thermocouple and the groove. The thermal conductivity test method according to claim 1, wherein the coating material is filled. 6. The hot wire and the thermocouple provided in a groove excavated from the surface on one or both sides of the test piece divided into two parts, wherein the main component is made of an insulating material mainly composed of alumina, mullite, magnesia or titania. 2. The thermal conductivity test method according to claim 1, wherein the thermal conductivity test method is inserted into the formed fired material having high airtightness. 7. A viscous material which can be brush-coated by using alumina or mullite or magnesia or titania as an aggregate and a composite alkoxide partial hydrolyzate as a binder in a gap between the hollow fired product and a heat wire or a thermocouple. 7. The method for testing thermal conductivity according to claim 6, wherein the coating material is filled with an application material having high airtightness after curing. 8. A gap between the hollow fired product and the test piece,
An alumina or mullite or magnesia or titania as an aggregate and a composite alkoxide partial hydrolyzate as a binder, which is filled with a coating material which can be brushed and has high viscosity, adhesion and high airtightness after curing. Item 6. The thermal conductivity test method according to Item 6.