JPH0424311B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of bonding ceramics using electrical energy.

Conventional techniques and their problems Traditionally, ceramics have been bonded by interposing an adhesive between the objects to be bonded, or without intervening an adhesive.
This was done by heat treatment using an electric furnace or the like. However, in such a method,
A heating furnace with a large capacity is required to bond large products, odd-shaped products, long products, etc., and the disadvantage is that there is a large loss of heating energy.

Therefore, in order to bond large items, etc., a local heating method is used in which only the bonded portion is heated.

Known local heating methods include laser, high-frequency heating, electron beam heating, and electrical discharge heating in oil, but these methods require large chambers for sample preheating and atmosphere adjustment. Alternatively, there is a problem that it is uneconomical in terms of equipment, such as requiring a high-output beam power source and a converging device for them.

Furthermore, Japanese Patent Publication No. 40-26908 discloses a method of welding fused refractories using arc heat, but in this method, a continuous arc discharge is passed between the two materials to be welded. , since the arc heat melts and joins the parts to be welded,
A gap is required to allow the arc discharge to penetrate. Therefore, especially when the material to be welded is a porous material containing large pores, molten material due to arc heat is buried in the pores in the porous material, resulting in pores being generated at the joint surface. The joint strength or airtightness required for ceramic joints used as mechanical structures cannot be obtained sufficiently. Furthermore, due to the penetration of the arc discharge, the entire bonding surface is exposed to the high-temperature arc, which causes unevenness due to decomposition of the bonding surface material and cracks due to thermal shock, which improves the bonding strength. It becomes extremely difficult to do so.

Means for Solving the Problems In view of the problems of the prior art as described above, the inventors of the present invention have conducted intensive research to find an easy and economically advantageous local heating method for bonding ceramics together, and have found that high temperature In this process, an adhesive having higher conductivity than the ceramics to be adhered is interposed on the bonding surface of the ceramics, and an arc discharge is generated without penetrating the gap between the two ceramics to be adhered, and the electric current applied to the adhesive is used to reduce the Joule heat. We have discovered that it is possible to bond ceramics by heating the bonding surface using a method of heating, and we have also discovered that it is possible to improve the bonding strength and to bond complexly shaped bonding surfaces.

That is, the present invention provides the following method for bonding ceramics;
Layer the ceramic objects to be bonded, () install at least one pair of blowpipe on both sides of the bonding surface so that the combustible gas ejection holes face the edge of the bonding surface, and () blow the gas flame from the blowpipe to the edge of the bonding surface. At the same time, a DC or AC voltage of 1,000 to 10,000 V is applied between the blowpipe to start arc discharge, and an arc discharge is generated between the blowpipe and the end of the adhesive or the end of the adhesive surface of the ceramic to be bonded. A conductive path is formed and the adhesive is energized, and both the adhesive and the area near the bonding surface of the ceramic to be bonded are heated by Joule heat, which is determined by the resistance value of the adhesive and the current value passed through the adhesive. A method for bonding ceramics, characterized by:

Hereinafter, a method for implementing the present invention will be explained in detail.

First, adhesives that have higher conductivity than the ceramics to which they are bonded at high temperatures are adhesives that are normally used for bonding ceramics. In some cases, a current of approximately 10 mA or more flows through the adhesive through an arc. Specifically, such adhesives mainly contain glass components such as kaolin, alumina, and silicic acid.
Oxides, sulfides, and chlorides of copper, nickel, manganese, indium, molybdenum, and zinc, lanthanum, indium, vanadium, holmium,
Known adhesives containing appropriate combinations of rare earth element oxides such as yttrium, metals such as molybdenum, manganese, tungsten, iron, copper, silver, nickel, tin, and zinc, and fluorides such as calcium fluoride and sodium fluoride. However, the present invention is not limited to these as long as it satisfies the above-mentioned conductivity conditions. In addition, when using a non-conductive material as the main component of the adhesive, conductive components such as carbon, fluoride,
Glass, metal oxides, rare earth elements, etc. may be blended to impart higher conductivity than the adherend ceramics.

Both ceramics that are electrically conductive at high temperatures and ceramics that are not electrically conductive can be used as the ceramic to be adhered. Examples of ceramics having conductivity include lantachromite, tin oxide, alumina, zirconia, and cordierite, and examples of ceramics having no conductivity include non-oxide ceramics such as silicon nitride and sialon. be able to.

Next, as for the bonding method, as shown in FIG.
After the blowpipe 3, 4 is placed on both sides of the ceramic to be bonded, facing the end of the bonding surface. At this time, the ceramics to be bonded together are processed so that the surface roughness (Rmax) and the bonding surface are undulated to an accuracy that does not cause arc discharge during bonding between the ceramics and the adhesive. Accuracy is determined by its relationship to the flexibility of the adhesive.

The blowpipe may be of any type as long as it is conductive and heat resistant, such as brass, copper,
Materials such as tungsten, carbon, and molybdenum can be used.

Next, the bonding surface is heated with gas flames 7 and 8 from blowing tubes installed on both sides of the ceramic, and a DC or AC voltage of 1,000 to 10,000 V is applied between both blowing tubes. The power supply device 5 of the electrical connection device used here may be one having a no-load voltage of about 1000 to 10000V. Although the output current is not constant depending on the area of the adhesive surface, etc., it is sufficient to supply a small current of about several amperes or less.

Next, the conductivity of the adhesive improves at the adhesive part heated to a high temperature by a gas flame, and the conductivity of the adhesive increases to 1000 ~
Start arc discharge with a voltage of about 10,000V.
In this case, the arc discharge is generated only between the blowpipe and the end of the adhesive or the end of the bonding surface of the ceramics to be bonded, without penetrating between the two ceramics to be bonded. In this way, a current-carrying path is formed by arc discharge between the blowpipe and the ceramics to be adhered, so that the current flows concentrated in the adhesive, which has higher conductivity than the ceramics to be adhered.
The adhesive is heated to a high temperature by Joule heat,
It melts in a short time and firmly bonds ceramics.

At this time, when the adhesive is melted by heating with electricity, its composition changes due to reactions among the adhesive components, reactions with the components of the objects to be bonded, reactions with the atmosphere, etc., and the adhesive moves through the current-carrying area while gradually increasing its resistance. Complete the entire surface bonding. Therefore, the composition of the joint is different from that of the initial joint.

Note that the adhesive is rapidly heated by the generated Joule heat, its electrical resistance is significantly reduced, and its conductivity is rapidly increased. For this reason, the electrical connection device used in the present invention incorporates an output current control circuit 6 to maintain the current at an appropriate value. Since the appropriate current value varies depending on the type of adhesive and ceramics used, it may be determined as appropriate depending on these types.

Further, instead of the power supply device and the output current control circuit, a generator having an output current control function may be used.

Further, in the bonding method of the present invention, bonding may be performed while moving the ceramics or blowpipe,
By providing multiple pairs of blowpipe, it is also possible to bond a wide area at the same time.

Effects of the Invention The method for adhering ceramics according to the present invention can provide the following excellent effects.

(1) Since ceramics can be bonded with very simple operations, the time required for bonding can be shortened, and effects such as improved safety due to low voltage, cost reduction, and energy saving can also be obtained.

(2) Substantially all ceramics can be bonded, and the types of ceramics to be bonded may be the same or different. In particular, the method of the present invention can also be applied to non-melting non-oxide ceramics.

(3) Regardless of the shape of the bonding surface of ceramics, it is possible to bond ceramics with any bonding surface shape, such as plate or round shape.

(4) When bonding, it is necessary to apply electricity only to the bonded part, and no special equipment is required, so it is very economically advantageous. Further, since the current flows through the entire bonded portion, the bonded portion is heated uniformly, so that a strong bond is formed as a whole.

(5) Since local adhesion can be easily performed, on-site construction at chemical plants, etc. is possible.

(6) Since we use an adhesive that has higher conductivity than the ceramics to be adhered at high temperatures, current flows in a concentrated manner through the adhesive, and the resulting joule heat can efficiently heat the adhesive surface to high temperatures in a short period of time. can.

(7) Since the entire surface of the bonded surface is not brought into contact with the high-temperature arc, the bonding strength can be increased by preventing the occurrence of unevenness due to decomposition of the bonded surface and the occurrence of cracks due to thermal shock.

(8) Since the gap during bonding is extremely small,
The bonding strength can be increased by preventing the formation of pores on the bonded surfaces.

(9) Since it uses Joule heat, it is easier to control the heat input such as the current value of the current and the waveform of the current over time compared to arc discharge. Can be combined.

Examples Examples are shown below to make the characteristics of the present invention even clearer.

Example 1 As an electrical connection device for ceramics, a copper metal welding nozzle was used as a blowpipe, and a commercial AC power supply was used.
An inductive voltage regulator, a variable inductance reactor, and a 200V/6600V step-up transformer's primary winding are connected in series to 200V, and the secondary winding is connected to the metal welding nozzle.
Ceramics were bonded by the following method. The output current control circuit in the electrical connection device is a variable inductance reactor connected in series with a 200V commercial power source.

The object to be adhered to is a silicon nitride plate (thickness 10 mm,
Using two flat plates (10 cm long and 5 cm wide),
Two flat plates were stacked on a 10 mm x 10 cm surface with 3 g of an adhesive consisting of 70% by weight of calcium fluoride and 30% by weight of kaolin interposed therebetween. Next, two blowpipe tubes were installed toward the long sides of the adhesive surface so that the combustible gas ejection holes faced each other on both sides of the adhesive surface.

The distance between the blowpipe and the end of the adhesive surface was 3 cm.

City gas is discharged from each blowpipe and ignited,
After adjusting the length of the gas flame to 3cm, place it between both blowpipes.
An AC voltage of 5000V was applied. After 10 seconds the current is
0.5A, and after that, 0.5A with the current control circuit.
The current was maintained. Next, electricity was continued while moving the ceramic in the length direction at a speed of 5 cm per minute to bond the entire adhesive surface.

The adhesive strength of the bonded body at this time was 40 Kg/mm ² in terms of three-point bending strength.

In the above example, the temperature at which the adhesive and ceramics were preheated by a gas flame was 800° C. immediately before voltage was applied to the blowpipe. Also, the electrical conductivity of silicon nitride ceramics at that time was approximately 10 ^-8 (Ω cm) ^-1
The conductivity of the adhesive with 70 wt% CaF ₂ and 30 wt% kaolin was approximately 10 ^-4 (Ω cm) ^-1 . This shows that in the method of the present invention, the current flowed in a concentrated manner through the adhesive.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a bonding device for ceramics according to the present invention. 1 and 2 are ceramics to be adhered, 3 and 4 are blowpipe, 5 is a power source (device), 6 is a current control circuit, and 7 and 8 are gas flames.

Claims (1)

[Claims] 1 () By interposing an adhesive having higher conductivity than the ceramics to be adhered at high temperatures,
Layer the ceramics to be bonded, () At least one pair of blowpipe on both sides of the bonding surface,
Install the combustible gas outlet so that it faces the edge of the bonding surface, and () heat the edge of the bonding surface with the gas flame from the blowpipe, and apply a DC or AC voltage of 1,000 to 10,000 V between the blowpipe. The arc discharge is started, and a current-carrying path is formed between the blowpipe and the end of the adhesive or the end of the adhesive surface of the ceramics to be adhered, and the adhesive is energized, and the resistance value of the adhesive and the adhesive A method for bonding ceramics, characterized in that both an adhesive and the vicinity of the bonding surface of the ceramic to be bonded are heated by Joule heat determined by the value of the current applied.