JPS63162585A - Ceramic joining method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for joining ceramics.

[Conventional technology]

Ceramics are generally bonded by applying a bonding agent that melts at high temperatures, bringing the bonded surfaces together, and heating the bonded portion. Electric furnaces and gas burners are commonly used heating means.

Since heating in the electric furnace 1 is performed while the entire ceramic is housed in the electric furnace, not only the joint portion but also the entire ceramic is exposed to high temperature.

Heating with a gas burner involves blowing gas burners (generally a plurality of gas burners) onto the joint and igniting the joint with a gas flame. In the heating method using a gas burner, temperature unevenness tends to occur at the joint, so in order to suppress this,
It is necessary to periodically change the position where the gas flame hits, and a moving (or rotating) device is provided on the ceramic side or the gas burner side.

[Problem that the invention seeks to solve]

Heating with the electric furnace described above exposes the entire ceramic to high temperatures, resulting in large thermal contractions and thermal distortions, leading to problems such as thermal deterioration of the base material. In addition, the energy cost required for the bonding work is high, and when bonding long ceramics, a large electric furnace is required, resulting in high equipment costs.

When heating with a gas burner, it is difficult to control the temperature of the joint, and the positional temperature difference or temporal temperature change at the joint may become excessive, which can result in considerable thermal stress being applied to the joint. be. A large thermal stress can lead to cracking, a decrease in bonding strength, etc., but even if it does not reach that point, there are problems in terms of quality control, such as a tendency for large variations in bonding strength.

SUMMARY OF THE INVENTION An object of the present invention is to provide a ceramic bonding device that has low thermal shrinkage, thermal distortion, thermal stress, etc., and can easily bond even long objects using a relatively small heating device.

[Means for solving problems]

A bonding agent that is conductive at high temperatures is applied and the ceramics to be bonded are butted together, and at this bonding point and in the vicinity, a cylindrical heat-resistant conductive material surrounding the outer periphery of the ceramics with a slight space is removed. Place a heating element. The outside of the heating element is covered with a layered wall made of a heat-resistant heat insulating material, and a coil is further wound around the outside of the layered wall. Since Joule heat is generated in the coil, air cooling is sufficient for relatively small currents, but water cooling is used for large currents. An alternating current is applied to the coil to inductively heat the heating element.

The heating element becomes high in temperature due to induction heating, and the heat of this heating element is transferred to the ceramic joint and its vicinity, which are arranged inside the heating element with some space between them. Due to this heat transfer, the high-temperature bonding agent becomes electrically conductive and generates induced heat generation by itself, further increasing the temperature.

By the method described above, the ceramic bonding area and its vicinity are heated to a high temperature, the applied bonding agent is melted, and the ceramics are bonded.

[Effect]

A conductor placed under an alternating magnetic field will generate an induced current according to Lenz's law, or as a result, the conductor will generate heat and its temperature will rise. The loss generated per unit volume of the conductor is W (w
), it is given by W=K(FB)2/ρ. Here, F, B, and ρ are the frequencies (H
z), magnetic flux density (T), volume-specific resistance (Ωm), and K
is a constant determined by the shape of the conductor. If a lenoid coil (in the following [Operations] section, the coil refers to a lenoid coil) is used as a magnetic flux generating means, the strength H (AT/m) of the magnetic field generated within the coil will be maximum at the center in the axial direction of the coil. In other words, if this is Ha, it is given as Ho = N I /. However, it is assumed that the winding density (number of turns per unit length: N/L) is uniform along the coil axis direction, and N
, I, and L are the total number of turns of the coil, current (A), and length (m), respectively. Further, the strength of the magnetic field at the end of the coil is 1/2 of Ho.

The above behavior of the magnetic field in the coil holds true when the length of the coil is sufficiently larger than the diameter of the coil. As the length of the coil becomes smaller, the strength of the magnetic field at the center in the axial direction of the coil and the strength of the magnetic field at the ends become smaller than above, but the ratio of the strength of the end magnetic field to the center magnetic field is
It is theoretically known that the difference in magnetic field strength distribution will be larger than the above (that is, the difference in the distribution of magnetic field strength will be smaller). However, by changing the winding density in the axial direction, it is possible to change the ratio of the strength of the magnetic field at the ends of the coil and at the center of the coil. For example, by increasing the winding density at the center of the coil compared to the ends of the coil, the ratio of the strength of the coil end magnetic field to the center field can be made smaller than when the winding density is equal (i.e., the magnetic field (can increase the difference in strength distribution).

Also, if the permittivity of the space under the magnetic field is μ, then B = μH There is a relationship.

From the above, if a conductor is placed inside a coil and an alternating current is passed through the coil, the conductor will generate heat, but the larger the current, frequency, winding density, and magnetic permittivity, the smaller the volume resistivity. It can be seen that the heat generated by the conductor increases. It can also be seen that if the winding density at the center of the coil is increased, the amount of heat generated at the center of the conductor coil increases.

However, since ceramics generally have extremely high volume resistivity, simply placing them inside a coil and passing an alternating current through them will not raise the temperature to a point where the ceramics can be bonded. Therefore, a cylindrical conductive heating element (hereinafter referred to as the heating element) with high conductivity and heat resistance is placed inside the coil, and a bonding agent that is conductive at high temperatures is coated on the inside of the heating element. Ceramics are stored with their joint surfaces butted together. In addition, in order to insulate between the heating element and the coil,
Install heat-resistant insulation material between the two.

In the above arrangement, the ceramics, heating element, heat insulating material, and coil are arranged outward from the center in the radial direction, and AC current is applied to the coil.

This generates an induced current in the heating element, and the heated heating element heats the ceramic inside by heat transfer (radiation, convection, conduction).

In the case of ceramic joints, when this part reaches a height of 1, the adhesive or conductivity begins to accumulate.

Furthermore, since the demagnetizing effect of the heating element is not strong, magnetic flux due to the coil also exists in the ceramic portion.

The bonding agent, which has become more conductive, generates an electric current within itself, leading to self-heating.

The heat generated by the bonding agent itself overlaps with the heat transfer from the heating element, and the bonding agent and its vicinity become even hotter, causing the bonding agent to melt and join the ceramics.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of a joining apparatus according to the present invention, showing a case where cylindrical ceramics are butt joined.

Ceramics Ia and lb are butt-supported at high FA via a conductive bonding agent 2.

As a bonding agent that has conductivity at high temperatures, the main component is a glass component such as kaolin, Al2O3, 5i02, etc.
Oxides, sulfides, chlorides, etc. of copper, nickel, manganese, indium, molybdenum, zinc, etc.; oxides of textile-class elements such as lanthanum, indium, vanadium, holmium, aluminum, molybdenum, manganese, Some of them contain metals such as tungsten, iron, copper, silver, nickel, tin, and zinc, and fluorides such as calcium fluoride and sodium fluoride.

The heating device 3 is arranged so as to cover the bonding surface of the ceramics and the outer periphery thereof with a slight space, and the center of the heating device 3 is located at the bonding portion of the ceramics. The heating device 3 includes a heating element 4, a heat insulator 45, and a coil 6. The heating element 4 is a cylindrical heat-resistant conductor (graphite, molybdenum, etc.) wound around the coil 6. The coil 6 is a cylindrical conductor (copper pipe, etc.) wound around the coil. Cooling.

The cylindrical conductor is a suitable shape not only from the above-mentioned standpoint of cooling, but also from the viewpoint of dealing with the skin effect when AC current is applied. The winding density of the coil is adjusted so that the winding density is greatest at the center in the axial direction of the coil and is smaller at the ends.

The above winding density can be adjusted by winding the center densely in the center and sparsely at the ends if the coil is single-layer winding, or by winding the winding density in one turn in the center if the coil is multi-layer winding. This can be done by increasing the number of points at the ends. Figure 2 shows an example of the winding density distribution. By adjusting the winding density, the temperature at the center of the heating element 4 can be made higher than that at the ends, and the height can also be changed.

Since the ceramic joint is located at the center of the heating element 4, the ceramic joint can be heated intensively by adjusting the winding density as described above.

The coil 6 is connected to a power source 7 by a connecting wire. It is desirable that the power source 7 can be variably adjusted in both current and frequency.

Also, although not shown, there is a matching impedance on the load side of the power supply (such as connecting a capacitor load in parallel to coil 6).
can be added to reduce the power supply capacity.

Cooling water supplied from the cooling water source 8 enters the coil conductor from the lower side of the coil 6 and is discharged from the upper coil 8B side.

The outline of the ceramic bonding procedure is as follows. Apply an adhesive 2 that is conductive at high temperatures to the bonding surfaces of ceramics la and lb, pass it through the heating device 3, and place it away from the heating device 3, that is, in a place where the bonded part can be seen directly without being hidden behind the heating device 3. The ceramics la and lb are matched and the la and lb are aligned with each other.

Next, either the ceramics la, lb or the heating device 3 is moved to align the joint of the ceramics with the axial center of the heating device, and the ceramics Ia is moved.

After adjusting the positions so that the heating device 1b and the heating device 3 are arranged concentrically, the ceramic la
, lb and the heating device 3 are fixed.

After this, electricity is applied while passing cooling water. The heating element becomes high in temperature due to induction heating, and the heat of this heating element is transferred to the ceramic joint and its vicinity, which are arranged inside the heating element with some space between them. Due to this heat transfer,
The high-temperature bonding agent becomes conductive and generates induction heat by itself, further increasing the temperature.

Figure 3 shows the temperature distribution of ceramics during bonding. Eventually, the applied bonding agent melts and the ceramics bond together. Appropriate values for the energization conditions (current, frequency, time) are determined by the material and shape of the ceramics to be bonded and the type of bonding agent, and these are determined in advance through experiments. After the bonding agent is melted, it is slowly cooled and the bonded ceramics are removed from the heating device 3.

11. In the device according to the present invention, an excessive temperature change is not exerted on the ceramics both when the current is applied and when the current is cut off. The goal can be easily achieved by gradually decreasing the current.

Other Embodiments In the embodiments described above, the distribution of the magnetic flux density in the axial direction of the heating device was adjusted by adjusting the winding density of the coil. This can also be done by dividing the coil in the axial direction and changing the current value of the divided coils.

In Figure 4, the coil is divided into 3 parts in the axial direction, 6 parts from the top.
a, 6b, 6c). In FIG. 4, by making the current in the central coil 6b larger than the current in the end coils 6a r 6c, it is possible to intensively heat the ceramic joint. Alternatively, by using an intermittent energization method and setting the energization time in the intermittent cycle to be longer for 6b and shorter for 6a and 6c, it is possible to intensively heat the bonded portion of the ceramic.

In addition, ceramics may not have a simple cylindrical shape, but may have a complex shape such as varying diameters, or the two objects to be joined (la
, lb) are made of different materials, it may be difficult to heat the joint appropriately by changing the conditions only on the coil side. In such a case, it is possible to deal with the above-mentioned case by changing the thickness of the heating element 4 in the axial direction or configuring the heating element 4 by combining conductors with different volume resistivities. can.

Further, in order to prevent oxidative deterioration of the ceramics and the heating element 4, an inert gas (for example, argon) may be fed into the space between the ceramics and the heating device from the lower part of the heating device 3 during bonding.

In your example, the coil was cooled by water cooling, but
If bonding can be performed with a small current, an air cooling method can be used instead of a water cooling method.

〔Effect of the invention〕

According to the present invention, since it is possible to intensively heat the bonded portion of ceramics and the vicinity thereof, it is possible to reduce thermal shrinkage and thermal deformation during bonding, and it is also possible to reduce energy costs. Furthermore, since the heating and cooling temperatures can be easily controlled, the generation of thermal stress can be suppressed. For this reason,
It is possible to prevent cracks and cracks during bonding, improve bonding strength, and reduce variations in bonding strength.

Furthermore, since it is not necessary to put the entire part to be welded into a heating device, there is an advantage that a small device is required even when joining long objects.

Furthermore, since the device according to the present invention is a stationary device that does not require a feeding mechanism, a rotation mechanism, etc., the joining operation is also simple.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of an embodiment of the present invention;
Figure 3 is a diagram showing the distribution of the winding density of the coil in Figure 2, Figure 3 is a diagram showing the temperature distribution during ceramic bonding in the coil winding density distribution of Figure 2, Figure 4 is another example according to the present invention. FIG.

Claims (1)

[Claims] Ceramics to be bonded are butted together by applying a bonding agent that is conductive at high temperatures, and a heat-resistant cylindrical shape is formed that surrounds the outer periphery of the ceramics with a slight space at the bonded portion of the ceramics and in the vicinity thereof. A heating element made of a conductive material is arranged, the outside of the heating element is covered with a heat-resistant heat insulating material, a coil is wound around the outside of the heat-resistant heat insulating material, and an alternating current is applied to the coil to turn off the heat generating element. Induction heating is performed, and heat transfer from the heating element heats the bonded portion of the ceramics and its vicinity, and the heat generated by the induction heating also occurs in the bonding agent itself, which has become high temperature and has become conductive. A ceramic joining method characterized by heating and melting a ceramic agent.