JPH0359374B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an acoustic vibration method elastic modulus measuring device for determining hot elasticity values of refractories, ceramics, graphite, metals, etc. used in furnaces and other structures. Hot elastic modulus measuring device (hereinafter referred to as measuring device) When stress is applied within the elastic limit of fire-resistant materials and heat-resistant materials (hereinafter referred to as materials) used in high-temperature ranges, deformation (strain) occurs, but when the stress is removed, Return to the original state again. The elastic modulus, which is the ratio of this stress to strain, is quantitatively determined.

The elastic modulus is closely related to the material's structure and spalling resistance, and is extremely important for estimating the stability of kilns and structures and determining the suitability of materials before use. .

BACKGROUND ART Conventionally, as a method for measuring the elastic modulus of a material in hot conditions, bending vibration of the sonic vibration method is used. Alternatively, various measuring devices that use longitudinal vibration have been used, but the measurement results vary depending on the measuring device and it is common that accurate data cannot be obtained.
This was largely due to structural defects in the measuring device.

Measurement of elastic modulus using longitudinal vibration utilizes the natural longitudinal vibration of the material, and there is the following relationship between the natural frequency of the object and the elastic system number.

f=1/2l・√E/ρ E=4ρl ² f ² ∴E ₁ =4ρl ² f ² /g×100 l...Sample length (cm) ρ...Specific gravity f...Natural frequency (Hz) ) E...Modulus of elasticity (dyne/ ^cm2 ) _E1 ...Modulus of elasticity (Kg/ ^mm2 ) G...Gravity conversion coefficient (980665dyn/ ^cm2 ) Therefore, by measuring the natural frequency f, the modulus of elasticity can be determined. is required.

As a measuring device using longitudinal vibration, for example, Asahi Glass Research Report 4.30-41 (1954), as shown in Figure 1,
The vibration electrode 3 installed at the outside lower part of the electric furnace 6 transmits vibration to the sample 1 via the vibration transmission rod 2, and the vibration is transmitted to the outside upper part of the electric furnace 6 by the vibration detection rod 4, and is transmitted to the detector 5. In this case, the vibration transmission rod 2 and the sample 1 are connected through alumina powder, but it is not easy to set up, and the vibration attenuation at the contact surface is large, making it difficult for the sample 1 to be connected. There is a problem that vibrations are not transmitted sufficiently.

With this method, when the vibration transmission rod 2, sample 1, and vibration detection rod 4 are combined to produce coupled vibration, the resonant frequencies of the individual materials appear, making it difficult to determine the true resonant frequency of the sample 1. .

Furthermore, by increasing the temperature, the resonance frequencies of the vibration transmission rod 2 and the vibration detection rod 4 also change, resulting in a lack of stability, and only an approximate value of the resonance frequency of the sample 1 can be obtained. Since the elastic modulus of the vibration transmission rod 2 must be equal to or higher than the elastic modulus of the sample 1, there is a problem in that it is impossible to measure a material exhibiting a high elastic modulus.

For example, J.Am.Cer.SoC.37.445-457 (1954) has the second
As shown in the figure, a vibration electrode 3 installed at the outside lower part of the electric furnace 6 transmits vibration to the sample 1 via the vibration transmission rod 2, and a vibration detection rod 4 transmits the vibration to the outside upper part of the electric furnace 6. It is transmitted to the detector 5 and converted into an electrical signal, but in this case, the elastic modulus of the vibration transmission rod 2 and the vibration detection rod 4 changes depending on the temperature inside the furnace, and the melting point (1455°C) of the material is the nickel rod. Considering this, there is a drawback that continuous measurement at high temperatures cannot be performed.

The present inventors have succeeded in developing a hot elastic modulus measuring device that completely eliminates such defects. In this configuration, a cooling cylinder is installed inside the furnace from the upper part outside the furnace, and a detector with a heat-resistant metal needle connected to the lower end of the cooling cylinder is installed.

The main object of this invention is to provide a measuring device that can easily measure materials with low to high elastic modulus from room temperature to high temperature.

Another object of the present invention is to provide a measuring device in which a heat-resistant vibrating electrode is disposed within an electric furnace.

Still another object of the present invention is to provide a measuring device in which the distance between a measuring sample and a detector for detecting vibrations is reduced.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be further described below with reference to the accompanying drawings showing specific examples thereof.

FIG. 3 schematically shows an embodiment of the present invention, in which a heat-resistant vibrating electrode 10 and a sample 1 are set on a ceramic block 7 in an electric furnace 6, and a detector 5 11 is connected to a heat-resistant metal needle 12. It is a cooling cylinder that protects the cooling cylinder 11 from the heat inside the furnace, and a through hole (not shown) for a heat-resistant metal needle is bored at the lower end of the inside of the cooling cylinder 11.

FIG. 4 shows a detailed schematic diagram of the heat-resistant vibrating electrode 10, which has a structure in which a ceramic insulating plate 9 is inserted between the heat-resistant metal electrodes 8 to provide electrical insulation. As the heat-resistant metal electrode 8 of the heat-resistant vibrating electrode 10, metals that are difficult to oxidize or melt at high temperatures, such as platinum, rhodium, molybdenum, or alloys thereof, can be used.

The thickness of the heat-resistant metal electrode 8 is set to 0.01 to 1 in order to obtain enough force to drive the sample 1 and in consideration of economic efficiency.
Preferably, it is about mm. When it is less than 0.01 mm, the elasticity is small and it adheres closely to the ceramic insulating plate 9, resulting in small suction and repulsion forces. Moreover, if it exceeds 1 mm, it is not preferable because it becomes economically expensive and at the same time increases the rigidity, makes it difficult to vibrate, and makes it impossible to obtain sufficient driving force.

The ceramic insulating plate 9 of the heat-resistant vibrating electrode 10 provides insulation between the heat-resistant metal electrodes at room temperature and in hot conditions.The thickness of the ceramic insulating plate 9 is preferably thin in terms of driving force, but withstand voltage When I think about it
Approximately 0.1 to 2 mm can be used. If it is less than 0.1 mm, the withstand voltage will be low and at the same time the mechanical strength will be weak and it will not be able to withstand vibrations, which is not preferable.

The ceramic insulating plate 9 is preferably made of a material that has a high electrical resistance at high temperatures, and preferably has a specific resistance of 10 ³ Ωcm or more at 1400° C. If it is less than 10 ³ Ωcm, insulation will be poor and the drive voltage will drop. Ceramic insulating plates made of materials with a dielectric constant of 5 or more at 1400°C, such as Al ₂ O ₃ , MgO, BeO,
Preferably, a dense material with a porosity of 3% or less is sintered or electrocontacted with ThO ₂ , BN, SiO ₂ or the like alone or in a mixture.

The ceramic block 7 is a pedestal for the heat-resistant vibrating electrode 10 and the sample 1, and preferably has a large electrical resistance, and by making it larger than the sample 1, the vibrating force of the heat-resistant vibrating electrode 10 is restrained on one side. This provides sufficient driving force to sample 1.
It is also possible to make the upper surface of the ceramic block 7 concave and insert a heat-resistant vibrating electrode therein to prevent the heat-resistant vibrating electrode 10 and the sample 1 from moving due to vibration.

As the detector 5 connected to the heat-resistant metal needle 12, any of the known ceramic type, moving magnet type, and moving coil type, which have a high output voltage and flat frequency characteristics, can be used by changing the amplification degree of the amplifier. can. The heat-resistant metal needle 12 is heat-resistant;
For example, a rhodium or rhodium-platinum alloy rod, which has little deflection, is connected to the detector by an appropriate means and passed through a hole at the lower end of the cooling cylinder 11 for vibration detection. When using the heat-resistant metal needle 12 in this manner, it is desirable to shorten the length to be heated. In other words, the elastic modulus of the heat-resistant metal needle 12 changes depending on the temperature inside the electric furnace, and the effect increases in proportion to the heated length, so the length of the heat-resistant metal needle is 30 mm.
The following are preferred.

The cooling cylinder 11 has a structure that prevents the detector 5 from overheating and reduces the distance between the detector 5 and the sample 1. The material of the cooling cylinder 11 that protects the detector 5 can be copper, brass, stainless steel, etc., which have good thermal conductivity, and cooling can be done by cooling, air cooling, etc. as appropriate.

In addition, when a water-cooling system is adopted, by covering the inner part of the furnace with a fire-resistant heat insulating material, it is possible to suppress vibrations caused by bumping of cooling water in the water-cooled pipes at high temperatures. As a result of the experiment, cooling cylinder 1 using water cooling
Even when 1 is charged into an electric furnace at 1500℃, the cooling cylinder 1
The temperature inside 1 was kept below 30°C, and the detector was completely protected from heat.

Next, to explain the principle of operation, when the temperature is raised to a constant temperature by an electric furnace, the heat-resistant vibrating electrode 10 is formed by three electrically insulated heat-resistant metal electrodes 8.
When an alternating current voltage is applied from a low frequency oscillator → amplifier (not shown) using the center one as a pole and the heat-resistant metal electrodes 8 at both ends as poles, attraction and repulsion forces are generated between the heat-resistant metal electrodes 8. work and generate vibrations. In this case, it is also possible to apply a DC voltage in advance in order to strengthen the attraction and repulsion forces, and then apply an AC voltage over it.

The vibration of the heat-resistant vibrating electrode 10 directly drives the sample 1 to cause resonance in the sample 1, and the vibration is converted into an electrical signal by the detector 5 via the heat-resistant metal needle 12 on the top of the sample, and the natural vibration of the resonance point is detected. It measures numbers.

By reducing the distance between the heat-resistant vibrating electrode and the sample and the detector for detecting vibrations of the present invention, the sample is directly driven by the heat-resistant vibrating electrode, so there is no connection problem between them. Therefore, the measurement positions of the present invention where hot measurements can be performed using the same standards as measurements at room temperature are: (1) The true resonant frequency can be easily determined.

(2) Since the sample is directly driven, it is possible to easily measure samples that have defects inside the sample and have large attenuation of sound vibration waves.

(3) Can measure from room temperature to high temperature of 1500℃.

(4) Since continuous measurement is possible, sudden changes in elastic modulus can be measured without missing them.

There are other effects.

Although the present invention has been explained using a sound vibration method using longitudinal vibration, it goes without saying that it can also be applied to bending vibration.

Next, an example will be given and explained.

As shown in Figures 3 and 4, a sample (silica brick) is measured using a heat-resistant vibrating electrode consisting of a 0.05 mm heat-resistant metal electrode of an 80% platinum-20% rhodium alloy and a 0.5 mm alumina ceramic insulating plate. directly driven.

A well-known ceramic type detector is used, and a platinum/rhodium 0.5φ20mm detection needle is glued to a rubber damper inside the detector.The detector is placed inside a water-cooled cooling cylinder to prevent heat transfer from inside the electric furnace. Prevented.

The results of measuring the elastic modulus of refractory bricks at temperatures from room temperature to 1400°C using the measuring device of the present invention as described above are in good agreement with the measurement point 14 at room temperature using the flexural vibration acoustic vibration method, as shown in Figure 5.13. I was able to find the curve.

[Brief explanation of drawings]

1 and 2 are sectional views of a conventional hot elastic modulus measuring device, and FIG. 3 is a sectional view showing an embodiment of the device of the present invention. FIG. 4 is an enlarged view of an example of the heat-resistant vibrating electrode of the present invention. Figure 5 shows an example of the results obtained by measuring with the measuring device of the present invention. In the figure: 1 is the sample, 2 is the vibration transmission rod, 3 is the vibration electrode, 4 is the vibration detection rod, and 5 is the Detector, 6 is electric furnace,
7 is a ceramic block, 8 is a heat-resistant metal electrode, 9
is a ceramic insulating plate, 10 is a heat-resistant vibrating electrode, 1
1 is a cooling cylinder, and 12 is a heat-resistant metal needle.

Claims (1)

[Claims] 1. A heat-resistant vibrating electrode consisting of a heat-resistant metal electrode and a ceramic insulating plate is installed in an electric furnace, and a cooling cylinder with a detector connected to a heat-resistant metal needle inside the bottom end of the cooling cylinder is placed inside the furnace from the outside of the furnace. A hot elastic modulus measuring device characterized by: