JPS6411878B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to connections between ceramic tubes and metal tubes used in industrial fields that handle pressure fluids, particularly energy-related and heat engine-related fields that handle high-temperature pressure fluids. It is related to.

[Prior art] In the temperature range around room temperature, if attention is paid to the brittleness of ceramics, a connection method similar to the connection between metal tubes using O-rings or packing can be used for connecting ceramic tubes and metal tubes. Adoptable. In addition, if the connecting parts are to be used at room temperature, it is possible to connect the pipes airtightly by metallizing the surface of the ceramic and brazing it with metal, or by adhering with frits. Due to the difference in coefficient of thermal expansion between ceramics and metal materials, there is currently no satisfactory pipe joint for connecting pressure fluid piping when subject to significant heating or cooling. .

For example, in the case of the joint shown in "Pipe joint for equipment structures" disclosed in Japanese Patent Application Laid-Open No. 57-54792, the metal flange and the ceramic flange can be pressed against each other without loosening. For example, the intended airtight joint can be achieved, but no explanation is given on how to press them together.

[Problems to be solved by the invention] In recent years, great progress has been made in the development of ceramics for strong structural materials. Much effort has been devoted to the development of ceramics that utilize the characteristics of ceramics that are not required of metal materials, such as elasticity, wear resistance, and insulation, and overcome the disadvantages of being brittle, difficult to process, and difficult to use. There is.

One of the problems in the development of applications is the connection problem. In other words, while ceramics have valuable characteristics, using ceramics for structural materials is currently expensive, so ceramics are used only in areas where the characteristics of ceramics can be demonstrated, and metal materials are connected in other areas. However, ceramics usually have a lower coefficient of thermal expansion than metal materials, so if a joint that is connected at room temperature is used in a high or low temperature atmosphere, it will cause thermal stress due to the difference in thermal expansion. This will cause cracks and loose connections.

Examples of linear expansion coefficients of ceramics and metal materials are shown below.

Alumina 0.8～0.9×10 ^-5 /℃ Silicon nitride 0.33～0.35×10 ^-5 /℃ Silicon carbide 0.42～0.49×10 ^-5 /℃ Austenitic stainless steel
1.6 to 1.7×10 ^-5 /℃ Ferritic stainless steel 1.1 to 1.3×10 ^-5 /℃ Carbon steel 1.1 to 1.4×10 ^-5 /℃ For slight rises and falls in temperature, check the metal parts used in combination and O The seal can be maintained to a limited extent depending on the elasticity of the ring, packing, etc. Furthermore, in the invention disclosed in Japanese Patent Application Laid-Open No. 57-54792,
The purpose of connection can be achieved if there is an appropriate method of pressing the ceramic flange and metal flange together, but when tightening with bolts and nuts or cap nuts, take measures to prevent the temperature of the connection part from fluctuating much above room temperature. Alternatively, although it is not possible to make the connection part compact, it is necessary to use a method such as placing an elastic body such as a spring in a place where the temperature does not rise and pressing it. When connected using the conventional union joint shown in Fig. 1 and tightening the cap nut, the elasticity of the elastic metal member tightens the connection.
Since the thermal expansion in the tube axis direction of the metal cap nut that locks the flange 1A is greater than the thermal expansion in the tube axis direction of the flange 1A, the pipe joint may loosen at high temperatures, and the cap nut may loosen at high temperatures. If tightened further, the ceramic tube 1 or the metal tube 2 will break during cooling. In the case of cooling, the relationship is the opposite. In Figure 1, 2A is a metal flange, 2B, 3B
are the male thread of the metal flange 2A and the female thread of the cap nut 3 which are screwed together, and 3A is the bag portion of the cap nut 3.

In addition, since the inner peripheral part S of the flange end face is not directly tightened, the internal pressure of the pipe seeps into the end face of the ceramic flange 1A, and when the internal pressure is large, a large tightening force is required. As shown in Figure 2,
A problem arises in that a large bending stress is generated in the ceramic flange 1A, making the ceramic tube 1 easy to break.

[Means for Solving the Problems] In the first aspect of the present invention, a connecting portion between a ceramic pipe and a metal pipe is used to configure a pipe joint that avoids the occurrence of cracks and loosening caused by the difference in thermal expansion between ceramics and metal. two flange portions,
By absorbing the difference in thermal expansion between the pressed or tightened part when the temperature rises and cools by the distance piece, which is a third metal member with a large coefficient of thermal expansion that is sandwiched between the two flanges, the pressure welding of the flanges is improved. In addition, in the second aspect of the invention, the position and direction of the pressure contact surface of the flange part is configured so as not to generate bending stress in the flange part, and the metal bag nut is used for tightening.

In the pipe joint of the first invention according to the present invention, a tubular distance piece made of a material with a coefficient of linear expansion larger than that of the cap nut described later is sandwiched between both flanges, and a thread is threaded on the outer peripheral surface of the metal flange. The pipe joint is characterized in that the bag portion of a union nut-shaped cap nut is locked to a ceramic flange, the female thread is screwed to the male thread of the metal flange, and both flanges are pressed together.

A second pipe joint according to the present invention is provided with a conical shoulder on the outer part of the ceramic flange, and a conical pressure contact part on the inner peripheral part of the end face,
A tubular distance piece, which has a conical pressure contact portion that engages with the pressure contact portion of the ceramic flange, and is made of a material with a linear expansion coefficient larger than that of the cap nut described later, is sandwiched between both flanges, and the outer surface of the metal flange is A thread is carved on the side surface, an engaging part is provided in the bag part of the union nut-shaped metal bag nut to engage with the shoulder part of the ceramic flange, and the engaging part is engaged with the shoulder part, Screw the female thread onto the male thread of the metal flange,
This is a pipe joint characterized by having both flanges pressed together.

Next, preferred embodiments of the second invention according to the present invention will be listed in individual articles.

The radial width of the pressure welding portion of the ceramic flange is smaller than the radial width of the flange, the radial width of the distance piece is approximately equal to the width of the pressure welding portion, and a distance piece is provided on the end face of the metal flange. There is an annular recess into which the material is inserted.

The taper of the pressure contact portion is larger than the taper of the shoulder portion, and more preferably, the angles formed by the pressure contact portion and the shoulder portion with a plane perpendicular to the tube axis are respectively
Within the range of 5° to 60°, 50° to 80°.

One or more divided annular spacers are interposed between the shoulder portion of the ceramic flange and the engaging portion of the bag portion of the cap nut. More preferably, the annular spacer is tapered outward to reduce its width. In another more preferred embodiment, the inner diameter of the bag portion of the cap nut is larger than the outer diameter of the ceramic flange.

A plurality of slits are provided on the bag side of the cap nut in a plane direction including the shaft. This increases the elastic strain on the cap nut side against the pressing force that locks the ceramic flange of the cap nut, making it possible to widen the tightening range by the cap nut.

A locking nut for the male threaded cap nut of the metal flange is tightened on the remaining metal tube side into which the male threaded cap nut is screwed.

The metal flange of the distance piece and the pressure contact portion form a conical surface whose inner diameter side protrudes, and the end surface of the metal flange that engages with the conical surface is formed with a concave conical surface.

A packing is interposed between the pressure contact surfaces of the distance piece and the ceramic flange and the metal flange.

The distance piece and the spacer are made of a metal material having a coefficient of linear expansion of 1.6×10 ⁻⁵ /° C. or more.

EMBODIMENT OF THE INVENTION Hereinafter, the pipe joint of this invention is demonstrated based on the drawing of an Example. FIG. 3 is a longitudinal sectional view of an embodiment of the pipe joint according to the first aspect of the present invention.

This pipe joint, similar to the pipe joints shown in FIGS. 4 and below, is a pipe joint in which the ceramic pipe 10 and the metal pipe 20, respectively, and integral flanges 11 and 21 are brought into pressure contact with each other to connect the pipes.

A tubular distance piece 30 is sandwiched between the flanges 11 and 21. metal flange 21
A male thread 22 is threaded on the outer circumferential surface. A metal bag nut 40 is used in this pipe joint. The bag nut 40 has the shape of a union nut, and a bag portion 41 is open so that the ceramic tube 10 can be inserted therethrough. Furthermore, a female thread 42 is threaded on the inside of the cap nut 40. Insert the cap nut 40 from the other end of the ceramic tube 10 as shown in FIG.
The female thread 42 of the cap nut 40 is screwed into the male thread 22 of the metal flange 21, thereby pressing the flanges 11, 21 together. The distance piece 30 is made of a material having a larger coefficient of linear expansion than the cap nut 40.

Although a more detailed explanation of the pipe joint of the first invention of the present invention will be omitted, in the detailed description of the pipe joint of the second invention described below, the pressing surface and the pressure contact surface in the second invention will be explained below. The explanations other than the description regarding the configuration as a conical surface can be applied to the pipe joint of the first invention.

FIG. 4 is a longitudinal cross-sectional view of an embodiment of a pipe joint according to the second aspect of the present invention. A conical shoulder 12 is formed on the outer side of the flange 11 of the ceramic tube 10 in this pipe joint. In addition, the flange 11
A pressure contact portion 13 having a conical surface is formed on the inner peripheral portion of the end surface. Ceramic flange 11 and metal tube 20
Attach the tubular distance piece 3 to the flange 21 of the tube.
0 is interposed. Naturally, the pressure contact portion of the distance piece 30 with the ceramic flange 11 is formed with a protruding conical surface that engages with the pressure contact portion 13 of the flange 11.

In the embodiment shown in FIG. 4, the radial width of the pressure contact portion 13 of the ceramic flange 11 is made smaller than the radial width of the flange 11, that is, the fourth
The diameter df of the pressure welding part 13 in the figure is the diameter of the flange 11.
It is said to be smaller than ds. This is to increase the contact pressure. Further, the width of the distance piece 30 in the radial direction is made approximately equal to the width of the pressure contact portion 13, that is, the diameter of the distance piece 30 is made almost equal to df. Further, an annular recess 23 is provided on the end face of the metal flange 21, and the distance piece 30 is fitted into the recess 23. Furthermore, a male thread 22 is threaded on the outer peripheral surface of the metal flange 21.

A union nut-shaped metal bag nut 40 is also used for this pipe joint, and a female thread is threaded on the inside. The bag portion 41 of the cap nut 40 is provided with an engaging portion 43 having a conical surface that engages with the shoulder portion 12 of the ceramic flange 11.

To form this pipe joint, flanges 11 and 2
1, insert the distance piece 30 between them, fit the cap nut 40, engage the engaging portion 43 of the cap nut 40 with the shoulder portion 12 of the flange 11, and tighten the female thread 4.
2 is screwed onto the male thread 22 of the metal flange 21, and both flanges 11 and 21 are pressed together. In the embodiment shown in FIG. 4, an annular spacer 50 is interposed between the shoulder portion 12 and the engaging portion 43. The annular spacer 50 may be integrated or divided into a plurality of pieces. In addition, the inner diameter of the bag portion 41 of the bag nut 40
dc is larger than the diameter ds of the flange 11. In this case, the cap nut 40 can be inserted into the ceramic tube 10 from the flange 11 side first, and after inserting the cap nut 40, the flange 11
sandwich the distance piece 30 and press the flange 21 of the metal tube 20, place the spacer 50 on the shoulder 12 (in this case, it is necessary to divide the spacer 50 into multiple pieces), and place the bag on the spacer 50. Contact the engaging portion 43 of the nut 40 and tighten the cap nut 40.
This pipe joint is formed by threading the female thread 42 onto the male thread 22. That is, by setting dc>ds, the pipe joint according to the present invention can be formed at both ends of the ceramic pipe. The other end of the ceramic tube is a straight tube or has a small flange, and the inner diameter of the bag portion 41 of the bag nut 40 is dc.
If it is possible to insert the bag 41 even if it is made smaller, the inner diameter dc of the bag portion 41 may be made smaller than the outer diameter ds of the flange, and the spacer 50 may not be used. However, in this case, it goes without saying that the minimum diameter of the female thread 42 must be larger than ds.

In this pipe joint, a material with a larger coefficient of linear expansion than the cap nut 40 is used for the distance piece.

One of the important features of the pipe joint of the present invention is that the distance piece pressure contact part that receives the ceramic flange has a substantially vertical conical surface or a slight conical surface that receives the ceramic flange in the direction of the resultant force acting on the ceramic flange from the shoulder part. The large taper of the conical surface prevents excessive bending stress from acting on the ceramic tube, regardless of whether it is cold or hot. Another important feature is that by appropriately selecting the materials of the distance piece and the cap nut, and by appropriately selecting the taper of the press contact between the ceramic flange and the distance piece, it is possible to eliminate loosening of the joint at high temperatures. or can be made extremely small.

Next, regarding the important features of the pipe joint of the present invention,
The explanation will be based on the drawings. FIG. 5 shows the state of force generation in the tightened state of the embodiment of the pipe joint of the present invention. By tightening the cap nut, a direct external force Pn acts on the shoulder 12 surface. Further, a force Pt=μPn (μ is the maximum coefficient of static friction) is generated in parallel to the surface of the shoulder portion 12, and a resultant force P of both is generated in the direction shown in the figure. Therefore, if the pressure joint 13 is provided in the direction of the resultant force P and at right angles thereto, the reaction force N generated when the pressure contact surface 13 is brought into pressure contact with the pressure contact surface 31 will be canceled out by P. Only a very small bending moment remains inside the flange due to the force F caused by the fluid pressure.

In this case, strictly speaking, it is preferable that the straight line in the direction of the resultant force P intersects with the end of the pressure contact portion 13 closer to the inner diameter. This is because a moment acts to rotate the flange 11 inward due to the internal pressure of the pipe, so if the straight line intersects with an end closer to the outer diameter than the pressure welding part 13, it will hit the inner diameter side of the pressure welding part 13. This is because there is a possibility that the pressure becomes weaker and the fluid pressure acts to force the pressure contact parts 13 and 31 apart.

Another way to reduce this possibility is to
The tapers 3 and 31 may be slightly larger than the taper of the conical surface perpendicular to the straight line in the direction.

The angle between the shoulder 12 of the flange 11 and the plane perpendicular to the tube axis is preferably as large as possible from the viewpoint of compactness of the flange, but from the design consideration of the stress acting on the ceramic flange, it is 50° to 80°. is desirable. Further, the direction of the resultant force P is inclined in a direction parallel to the tube axis by approximately 20° to 40° from the direction of the force Pn due to the maximum coefficient of static friction between the spacer 50 and the shoulder portion 12.
As an example, if the angle between the shoulder 12 of the flange 11 and the plane perpendicular to the tube axis is 60 degrees, that is, the taper of the shoulder 12 is 2/√3, The angle formed with the surface is between the spacer and the shoulder 12
flange 11 due to the maximum static friction coefficient and internal pressure.
The angle is selected in the range of 5° to 40° depending on consideration of rotation.

The angle between the pressure contact portions 13 and 31 with the plane orthogonal to the tube axis is generally selected in the range of 5° to 60°, but the angle between the shoulder portion 11 and the plane orthogonal to the tube axis is 20° to 60°.
Must be 40° smaller.

Another important feature of the pipe joint of the present invention is that it eliminates or minimizes the loosening of the joint at high temperatures. First, regarding the effect of using a material with a larger coefficient of linear expansion than the cap nut for the distance piece, we will discuss the effect of using a material with a larger coefficient of linear expansion than the cap nut when using it at high temperatures based on FIG. 6 of an embodiment of the pipe joint of the first invention, which is similar to FIG. 3. I will explain about it.

Since the cap nut 40 is screwed together with the metal flange 21, a cap nut made of the same material as the metal flange 21 or a material having almost the same coefficient of linear expansion is used.
When the temperature of this joint increases, the axial length h ₃ and elongation of the cap nut 40 and the thickness h ₁ of the flange 11 increase.
If the sum of the elongations of the distance piece and the length _h2 of the distance piece are equal, the joint will not become loose or overtightened.

As mentioned above, the linear expansion coefficient of ceramics is, for example, 0.33 to 0.35×10 ^-5 / for typical silicon nitride.
℃, and for silicon carbide it is 0.42 to 0.49×10 ^-5 /℃. In order to minimize the difference between the linear expansion coefficient of the metal tube and the cap nut type and that of ceramics, it is desirable to use a material with a small coefficient of linear expansion. Examples include ferritic stainless steel SUS430 (linear expansion coefficient 1.2×10 ^-5 /°C) and martensitic stainless steel SUS410 (linear expansion coefficient 1.2×10 ^-5 /°C). The material for the distance piece and spacer must have a coefficient of linear expansion greater than that of the metal tube and cap nut, such as austenitic stainless steel or nickel-chromium iron alloy with a coefficient of linear expansion of 1.6×10 ^-5 /℃ or higher. etc. is desirable.

Here, the ceramic flange 11, distance piece 30 and cap nut 40 in FIG.
Assuming that the linear expansion coefficients of are 0.4, 2.0, and 1.2×10 ^-5 /℃, respectively, the elongation due to temperature rise (△t) on the h ₁ × h ₂ side and h ₃ side is (0.4 h ₁ + 2. 0h ₂ )△t×
10 ^-5 and 1.2h ₃ △t×10 ^-5 . Since h ₁ + h ₂ = h ₃ , if h ₁ = h ₂ , then (0.4h ₁ + 2.0h ₂ )△t×1.2h ₃ △t, and if materials with linear thermal expansion are properly combined, Even if the temperature rises, the joints will not loosen or overtighten.

The above is an explanation of the ideal pipe joint of the first invention. Of course, in the pipe joint of the first invention, the materials of the cap nut and distance piece, the thickness of the ceramic flange, and the distance piece Loosening of the joint at high temperatures can be avoided by selecting the length appropriately. Second
In the joint of the invention, the ceramic tube is pushed upwards by the axial and radial expansion of the distance piece, which further effectively eliminates loosening of the joint at high temperatures. be able to. The outline will be explained based on FIG.

In FIG. 7, the elongation of the length h ₄ of the distance piece 30 due to temperature is shown broken down into axial expansion a and radial expansion b. When the inclination angle of the pressure contact portion 31 is θ, the inner diameter (radius) of the distance piece 30 is γ, and the coefficient of linear expansion of the distance piece 30 is αd, the elongations a and b due to temperature rise of Δt are as follows.

a=αd△th ₄ , b=αd△tγtanθ However, for simplicity, the thermal expansion of the ceramic flange is ignored. Therefore, if γ=h ₄ and θ is 45°, the ceramic tube will move upwards by twice the axial extension of the distance piece. In this way, by appropriately selecting the material and length of the distance piece, it is possible to avoid the influence of the difference in thermal expansion between the ceramic material and the cap nut material.

Furthermore, if the coefficient of linear expansion of the cap nut is set smaller than that of the distance piece, the difference in radial displacement between the cap nut and the ceramic flange is absorbed by upward movement of the spacer with respect to the locking surface of the cap nut. In this case, in order to facilitate the upward movement of the spacer, a spacer 50 is attached as shown in FIG. It is better to add a taper instead of a straight line.

As shown in FIG. 9, the bag portion 41 of the bag nut 40
By inserting a plurality of slits 44 in the axial direction on the side, sufficient elasticity can be ensured in the cap nut 40.

As shown in Figure 10, distance piece 3
When the pressure contact part 32 with the metal flange 21 of 0 is made into a conical surface whose inner diameter side protrudes, and a concave conical surface is formed on the end face of the metal flange 21 that engages with this, the upper part of the ceramic tube 10 at high temperature. The movement can be further increased.

Furthermore, as shown in FIG.
It is desirable to tighten the locking nut 60 of the cap nut 40 on the remaining metal tube 20 side into which the cap nut 40 (female thread 42) of the male thread 22 is screwed.

In the illustrated embodiment, the distance piece 30 is brought into direct pressure contact with the ceramic flange 11 and the metal flange 21, but if necessary, a packing may be interposed between these pressure contact surfaces.

[Effects of the Invention] In the pipe joint between a ceramic pipe and a metal pipe according to the first invention of the present invention, even if the temperature is raised and lowered after tightening at room temperature, the problem due to the difference in thermal expansion between the ceramic and the metal can be solved by the distance piece of the present invention. This problem can be solved by using the joint, and damage caused by loosening or over-tightening of the joint due to temperature changes does not occur, and it is possible to maintain a state in which a sufficient surface pressure is applied to the press-contact surfaces. Furthermore, the pipe joint of the present invention can be constructed compactly and can be used without cooling in an atmosphere within the heat-resistant temperature range of metal flanges, cap nuts, etc.

Furthermore, according to the second aspect of the invention, the ceramic flange can be constructed so that almost no bending stress is generated, and the possibility of damaging the ceramic tube is reduced.

Applications of the pipe joint of the present invention include, for example, when connecting a ceramic pipe to a metal pipe outside a heat exchange room, which performs heat exchange by passing a pressurized fluid on the low temperature side inside the pipe and bringing the outside of the pipe into contact with a high temperature fluid. Pipe joints, pipe joints used to flow high temperature pressurized fluid inside the pipe and cool or insulate the outside of the pipe, and pipe joints used to connect ceramic pipes in the middle when electrically insulating between two metal pipes. It can be used as

The present invention is particularly useful in constructing high-temperature systems related to energy and heat engines, and has many industrial advantages.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view of an example of an assumed pipe joint;
FIG. 2 is an explanatory diagram of the phenomenon when the pipe joint shown in FIG. A top view, FIG. 5 is an explanatory diagram showing the state of force generation in the tightened state of the embodiment of the pipe joint of the present invention, and FIGS. 6 and 7 are diagrams showing members due to temperature changes in the embodiment of the pipe joint of the present invention. A diagram to explain the relationship between thermal expansion of
FIG. 8 is a partial longitudinal sectional view of only the spacer portion of one embodiment, FIG. 9 is a partially cutaway side view of the cap nut, and FIG.
The figure is a partial side view of another embodiment of the pipe joint of the present invention. 10... Ceramics tube, 11... Ceramics flange, 12... Shoulder, 13... Pressure welding part, 2
0...Metal tube, 21...Metal flange, 22...
Male thread, 23... Annular recess, 24... Pressure contact, 3
0... Distance piece, 31, 32... Pressure contact part, 40... Cap nut, 41... Bag part, 42...
Female thread, 43... Engaging portion, 44... Slit, 5
0...Spacer, 60...Loosening nut.

Claims (1)

[Scope of Claims] 1. In a pipe joint that connects a ceramic pipe and a metal pipe by pressing integral flanges against each other, a tubular diameter made of a material with a coefficient of linear expansion larger than that of a cap nut described later is provided between both flanges. Hold the stance piece in place, thread a thread on the outer circumferential surface of the metal flange, lock the bag part of the union nut-shaped metal bag nut to the ceramic flange, and screw the female thread onto the male thread of the metal flange. A pipe joint characterized by having both flanges pressed together. 2. In a pipe joint that connects a ceramic pipe and a metal pipe by pressing integral flanges against each other, a conical shoulder is provided on the outer periphery of the ceramic flange, and a conical pressure contact part is provided on the inner periphery of the end face. A tubular distance piece, which has a pressure contact part of a conical surface that engages with the pressure contact part of the ceramic flange and is made of a material with a coefficient of linear expansion larger than that of the cap nut described later, is sandwiched between both flanges, and the metal A screw is threaded on the outer circumferential surface of the flange, and an engaging portion that engages with the shoulder portion of the ceramic flange is provided in the bag portion of the union nut-shaped metal bag nut, and the engaging portion is engaged with the shoulder portion. A pipe joint characterized in that the female thread is screwed into the male thread of a metal flange, and both flanges are pressed together. 3. The radial width of the pressure welding portion of the ceramic flange is smaller than the radial width of the flange;
3. The pipe joint according to claim 2, wherein the radial width of the distance piece is approximately equal to the width of the pressure contact portion, and an annular recess is provided in which the distance piece is fitted into the end face of the metal flange. 4. The pipe joint according to claim 2 or 3, wherein the taper of the pressure contact portion of the ceramic flange is larger than the taper of the shoulder portion. 5. The angle between the shoulder of the ceramic flange and the surface of the joint surface perpendicular to the tube axis is 50° to 80°, respectively.
The pipe joint according to claim 2, wherein the angle is 5° to 60°. 6. Claims 2 and 3, wherein an annular spacer divided into one or more pieces is interposed between the shoulder part of the ceramic flange and the engaging part of the bag part of the cap nut. , the pipe joint according to any one of paragraphs 4 and 5. 7. The pipe joint according to claim 6, wherein the annular spacer is tapered outward to reduce its width. 8. According to any one of claims 2, 3, 4, and 6, a plurality of slits are provided on the bag side of the cap nut in the direction of a plane including the tube axis. pipe fittings. 9. Claims 2 or 3, wherein the pressure contact portion of the distance piece with the metal flange has a conical surface whose inner diameter side protrudes, and the end surface of the metal flange that engages with the conical surface is formed with a conical surface. Pipe fittings listed. 10 Claim 6, wherein the inner diameter of the bag portion of the cap nut is larger than the outer diameter of the ceramic flange.
Section pipe fittings. 11. The pipe joint according to claim 1 or 3, wherein a locking nut of the male threaded cap nut of the metal flange is tightened on the remaining metal pipe side into which the male threaded cap nut is screwed. 12. The pipe joint according to claim 2 or 3, wherein a packing is interposed between the distance piece and the pressure contact surfaces of the ceramic flange and the metal flange. 13 The distance piece and spacer are
The pipe joint according to any one of claims 2, 3, and 6, which is a metal material having a coefficient of linear expansion of 1.6×10 ^-5 /°C or more.