JPS60226465A - Axial joint of ceramic to metal - 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 [Field of Application of the Invention] The present invention relates to a shaft fastening method between ceramics and metal, and particularly to a shaft fastening method suitable for obtaining high strength at high temperatures.

[Background of the invention]

Conventionally, the ceramic shaft and the metal shaft are connected as shown in Fig. 1 by bringing the ceramic shaft 1, the metal shaft 2, and the end surfaces together via a bonding material 3, and using methods such as solid state welding and soldering. was. Bonding is performed at a temperature higher than the product's usage temperature, and for ceramic products aiming for high-temperature strength,
High-temperature bonding reaching 00°C is required. After joining, the parts are cooled from such a high temperature range to room temperature, but during this time thermal stress is generated due to the difference in thermal deformation, resulting in residual stress in the joined part. In other words, the coefficient of linear expansion of the structural ceramics with excellent heat resistance (S iCp Si! I Na, etc.) used for the ceramic shaft 1 is several times smaller than that of the low thermal expansion metal material such as Kovar used for the metal shaft 2. This is a one-fold lower value. Therefore, in the cooling process after joining, the metal shaft exhibits larger shrinkage deformation, and a force based on thermal deformation as shown in FIG. 2 is applied to the joined portion of the ceramic shaft, generating thermal stress. When this thermal stress exceeds the fracture strength of ceramics,
A crack 6 as shown in FIG. 2 occurs, and in the worst case, even if the zero crack does not occur, a high residual stress remains, so that the loading force of the shaft fastening portion becomes extremely low.

As described above, the conventional fastening method has a problem in that as the heat resistance is increased and high-temperature bonding is performed, the residual stress increases and the loading force of the shaft fastening portion decreases.

[Purpose of the invention]

An object of the present invention is to provide a method for fastening ceramics and metal shafts, in which bonding treatment is performed at high temperatures, which has a high loading force.

[Summary of the invention]

In order to improve the loading force of the shaft fastening method by joining ceramics and metal, it is effective to reduce the residual stress generated during joining. The above object is achieved by focusing on the high ductility of metals, reducing the rigidity of the outer periphery of the joint of the metal shaft to facilitate deformation, and absorbing the difference in thermal deformation between the ceramic shaft and the metal shaft.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIG. When the ceramic shaft 1 and the metal shaft 2 are fastened together via the bonding material 3, an overhang is provided outside the joint of the metal shaft 2, and the overhang has a thinner end. In addition, if pressurization is required during the bonding process, pressurizing force is applied to the overhang using the pressurizing rod 4. When this method is used, the difference in shrinkage deformation between the metal shaft and the ceramic shaft due to cooling after completion of bonding is absorbed by the deformation of the metal shaft overhang, which has low rigidity.
The residual stress generated in the ceramic shaft can be reduced, and by changing the thickness of the overhanging part, it is possible to smoothly transmit the external load stress applied to the shaft fastening part from the ceramic shaft to the metal shaft.

Another embodiment will be explained with reference to FIG. Ceramic shaft 1
When a cylindrical ring 5 made of metal is fastened via the bonding material 3, an overhang is provided inside the joint of the ring 5, and shafts are provided at several locations on the circumference of the ring as shown in FIG. Provide a groove in the direction.

If pressurization is required during the bonding process, a pressurizing rod 4 is used to apply pressurizing force to the overhanging portion. Further, the metal shaft and the ring 5 can be joined by friction welding or other ordinary joining methods. Since the ring manufactured using this method has low rigidity against radial deformation, it is possible to reduce the residual stress generated in the ceramic shaft as in the previous example.

Another embodiment will be explained with reference to FIG. This is an example in which a metal fastening body 7 is used instead of the ring 5 in the same fastening as described above, and an overhang is provided on the outside of the joint, the thickness of the outer periphery of the joint is made thin, and a protrusion is provided on the outside. , the protrusion engages with the outer periphery of the ceramic shaft. The protrusion may have a thin wall.

As shown in FIG. 7, a structure with low rigidity is achieved by providing grooves on the outer periphery at several locations on the circumference. FIG. 6 shows an example in which the mating portion is machined into a tapered shape, and in consideration of thermal expansion at the high temperature at which the joining is performed, processing is performed in a manner that allows a gap greater than the thickness of the joining material to be obtained during the joining process. At the time of joining, pressure is applied using a pressure rod 4 to forcibly deform the fastening body 7 until the joined portion is brought into close contact. At a high temperature of about 800°C, the plastic deformability of metal is high, and stress relaxation ends quickly, so the above operation does not cause damage to the fastened body.By cooling after the joining process, the fastened body 7 becomes a ceramic shaft. Although a shrinkage deformation larger than 1 is attempted, this deformation is prevented by the fitting portion. At this time, since the rigidity of the protruding portion of the fastening body 7 is low, it is easily deformed, and the thin portion corresponding to the outer periphery of the joint portion is also deformed. That is, the difference in thermal deformation with the ceramic shaft is absorbed and reduced by plastic deformation, and the residual stress generated in the ceramic shaft can be reduced. Note that although the mating portion in this embodiment was machined into a tapered shape, the same effect can be obtained by controlling the dimensions even if it is machined into a cylindrical shape. Further, the metal shaft and the fastening body 7 can be easily joined by a usual method for joining metals together.

Furthermore, when the outer peripheral part of the fastening body 7 is unnecessary, it can be removed by machining after the joining is completed.

〔Effect of the invention〕

As explained above, according to the present invention, the residual stress generated in the ceramic shaft when joining the ceramic shaft and the metal shaft can be reduced, so the ceramic-metal shaft fastening structure has a high loading force and can be used at high temperatures. For this reason, ceramics can be used only in the parts that require high-temperature strength, which is advantageous in terms of price.The simple shape reduces manufacturing defects and improves product reliability. It has the effect of improving sex.

[Brief explanation of drawings]

Fig. 1 is an external view of a conventional shaft fastening structure by joining ceramics and metal, Fig. 2 is an explanatory diagram of residual stress and cracks applied to the ceramic shaft during joining, and Fig. 3. 4 and 6 are explanatory diagrams of the joining method according to the present invention, and FIG.
The figure is an external view of a ring used in the present invention, and FIG. 7 is a front and side view of a fastening body according to the present invention. ■... Ceramic shaft, 2... Metal shaft, 3... Bonding material. 4...Pressure rod, 5...Ring, 6...Ceramics first opening

Claims (1)

[Claims] In a method of integrally fastening a ceramic shaft and a metal shaft by butting each other, an overhang is provided on the outside or inside of the joint of the metal shaft, and the overhang has a thinner end, or a thin wall on the circumference of the overhang. The thickness of the outer periphery is made thinner by providing grooves in the axial direction at several locations on the shaft or protruding parts on the outside, and protrusions are provided on the outside of the axial grooves so that the protrusions engage with the outer periphery of the ceramic shaft. Features a shaft fastening method between ceramic and metal.