JP2006088190A - Joined body and joining method of minute ball having conductivity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joined body and the joining method that enable a minute member to be freely shaped without using an adhesive and an outer mold in contact with the member. <P>SOLUTION: This is a fusion welding (discharge welding) method by applying an electric voltage to members to be joined and using a discharge generated between the members, wherein at least one of the members has a minute spherical surface with a diameter of ≤5 mm. The invention also refers to a joined body joined by this method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for joining microspheres having microspherical surfaces and the joined body, and more particularly, at least one of the members to be joined has a voltage applied to a member having a microspherical surface having a diameter of 5 mm or less. The present invention relates to a method of applying and joining these microspheres using a discharge generated between members, and a joined body joined by the method. Examples of the member having a microspherical surface according to the present invention include, for example, a sphere or a lot obtained by processing the tip, and the present invention enables precision processing of these members, as well as the production and microfabrication of a porous material. It provides new microsphere joining technology that can be expected to develop into technology.

  Conventionally, as a method for joining members having spherical surfaces, for example, fusion welding methods such as arc welding, laser welding, and electron beam welding, pressure welding methods such as resistance welding (spot welding) and stud welding, diffusion joining, and TLP are used. A solid-phase bonding method or an adhesion method using a low melting point material such as solder is used. An adhesion method using a resin such as a photo-curable resin as a paste is also used.

  However, fusion welding methods such as arc welding have problems such as difficulty in positioning in narrow areas such as spherical contact, and pressure welding methods such as resistance welding cause deformation of members due to large pressure. Often it becomes a problem. In addition, solid-phase bonding methods such as diffusion bonding require a long time to obtain sufficient bonding strength, and soldering methods such as solder have different wettability to the spherical surface depending on the material. Further, it is necessary to select a solder material for each material, and there is a problem that the bonding strength is lowered. Furthermore, in the bonding method using resin, the heat resistance is often inferior to the bonding member, and it has been difficult to apply to a member that generates heat.

  In addition, the conventional bonding technique has problems such as a method for fixing a member, a method for controlling heat and force on a bonded portion, and a method for controlling the amount of adhesive material applied to a member such as a minute sphere. These members are not necessarily suitable for joining (Patent Document 1, Non-Patent Document 1).

JP-A-5-179374 Ryo Kawasaki et al. “Regular Sintering of Monodispersed Thermoelectric Microparticles and Their Thermoelectric Properties” Material Integration, Vol. 14, No. 8 (2001) p51

  As a result of diligent research to solve the above problems, the present inventors applied a voltage to a member having a minute spherical surface, and used the charge generated on the surface of the member or inside the member to discharge between the members. As a result, it was found that the members can be joined by melting a part of the members, and the present invention has been completed. The present invention was made to produce a member having a minute spherical surface in a free shape without using an adhesive material and an outer mold that contacts the member, and a joined body of the member having the minute spherical surface, An object of the present invention is to provide a joining method.

  The present invention for solving the above-described problems is a joined body characterized in that conductive microspheres and the microspheres or other members are melt-bonded at their contact portions. In this joined body, at least one of the joined microspheres has a microsphere having a diameter of 5 mm or less, the area of the joined portion is smaller than the cross-sectional area passing through the center of the microsphere, Is hollow or solid, the material of the microspheres is a metal, carbonized ceramics, boride ceramics, oxide ceramics, or graphite, and the conductive microspheres are non-conductive. It is characterized in that a conductive substance is mixed into the material to make it conductive, and that the conductive microspheres are formed by forming a conductive substance on the surface. Further, the present invention relates to a method for joining microspheres and microspheres or other members, wherein at least one of the conductive members to be joined has a microsphere having a diameter of 5 mm or less, the inside of the member or the surface. The method for joining microspheres is characterized in that the joining is performed by discharging using the electric charges generated in the microspheres. In this method, melt bonding is performed by discharging using the charge generated in or on the member, and the oxide layer on the surface of the conductive material or the air layer between the bonding members is generated using the charge generated in or on the member. Do not use an outer mold that contacts the member when melting and softening between the members by discharge generated during dielectric breakdown, or when melting and joining by discharging using the charge generated in or inside the member The obtained joined body is further heat-treated.

Next, the present invention will be described in more detail.
The member used in the present invention preferably has, for example, at least one member having a spherical surface with a diameter of 5 mm or less. In the present invention, this is necessary because the electric charges are concentrated and discharged because the bonding is performed using the discharge. In addition, it is possible to bond a large spherical surface with a diameter exceeding 5 mm by the conventional technique, and it is difficult to control the heat, time, position, etc. generated at the time of bonding to a small spherical surface. A joining method as in the invention is required.

  The material of the member used in the present invention is not particularly specified. However, in the present invention, since it is necessary to use the electric charge generated on the surface or inside of the member to be joined, a conductive material such as metal or carbide-based ceramics, Boride-based ceramics, oxide-based ceramics, graphite, and the like are preferable. Examples thereof include, for example, all metals such as aluminum, titanium, magnesium, iron, gold, platinum, and alloys thereof, titanium carbide, zirconium carbide, titanium boride, zirconium boride, and ITO (indium tin oxide). Is done. In addition, in a resin or an oxide ceramic that is a non-conductive material, a member that is made conductive by mixing a conductive substance is also an object of the present invention. Examples thereof include, for example, conductive polymer and titanium powder mixed zirconia. Further, a non-conductive material whose surface is coated with a conductive substance is also an object of the present invention. Examples of these include, for example, a zirconium oxide surface coated with a bismuth-tellurium alloy. However, the present invention is not limited to these materials.

  The discharge in the present invention is generated as a result of the electric charge generated on the surface or inside of the members to be joined breaking the insulation between the joining members. For this reason, both the breakdown of the air gap in the gap between the members to be joined and the breakdown of the oxide layer formed on the surface of the joining member can be considered as the discharge path. Contains. Due to the electric discharge generated as a result of these dielectric breakdowns, a large amount of heat is generated in a minute part of the member, and a part of the member is instantaneously melted to cause fusion bonding (discharge bonding). As a feature of the discharge bonding of the present invention, since the amount of heat generated is small compared to the size of the entire member, it does not occur that the member melts and changes its shape.

  The electric charge used for the discharge may be supplied from the outside, or the member charged before joining may be used. However, in order to perform bonding, it is necessary to partially dissolve the contact portion, and since it is easier to dissolve when the current flows continuously, it is often preferable to supply from the outside rather than charging. Usually, this can be achieved by applying a voltage between the electrodes. As the timing of applying the voltage, there are a case where the members are brought close to each other while applying the voltage before the contact, and a case where the voltage is applied after bringing the members into contact with each other, both of which are objects of the present invention.

  When the members are brought into contact with each other before the voltage is applied, the contact pressure needs to be lowered. When the pressure is increased, the material is deformed, the contact area is increased, and a temperature rise sufficient for joining is not observed, or even when joined, there is a phenomenon that the member is deformed. Although this pressure varies depending on the material, for example, if the member to be used is a 0.5 mm titanium sphere and a titanium plate, a load of 2 kgf or less is desirable.

  The surface roughness of the members to be joined is preferably smooth in order to discharge at a target position. However, in the case of performing strong bonding, it is preferable to preferentially dissolve and join the fine protrusions generated on the surface, and it is better to use the surface roughness as required.

  At least one of the members to be joined preferably needs to be a spherical surface having a diameter of 5 mm or less, for example. If the spherical surface has a diameter larger than 5 mm, the electric charge required for bonding becomes large, and efficient bonding is difficult in the present invention. In particular, in a joining member having a spherical surface with a diameter larger than 5 mm, heat generated by electric discharge diffuses into the member and does not lead to partial melting, so that joining is difficult. In addition, when the spherical surface has a diameter larger than 5 mm, it is impossible to control where the discharge is generated as in the case of joining between flat plate-like members.

  For example, the member having a diameter of 5 mm or less has no problem whether it is a hollow member or a solid member. Some conventional joining techniques are effective for joining hollow members, but the present invention can deal with solid members by supplying electric charge from the outside. Further, even if the members to be joined are made of different materials, they can be joined if they have conductivity. In the joining method of the present invention, as a discharge condition, it is necessary to flow an electric charge, that is, an electric current. Therefore, a member to be joined needs to be connected to a power source by an electrode or an electric wire. Joining conditions vary depending on the material. For example, in the case of joining a titanium sphere having a diameter of 0.5 mm and a titanium plate, the power supply is set so that a current of about 200 A flows for 0.5 to 1 ms at a voltage of about 25 V. good. The setting method differs depending on the power source used. Since the current value also depends on the voltage, it is necessary to change each according to the material. For example, a member having high resistance needs to have a high voltage. A material having a low resistance and a high melting point (platinum or tungsten) needs to have a large current for melting. When the voltage is too low, it is usually 20 V or less (in the air, which varies depending on the atmosphere), and the discharge itself is difficult to occur. Although it is possible to join without generating electric discharge, if the time during which the current flows becomes long, portions other than the joined portion are heated, which is not appropriate. In this invention, these discharge conditions can be arbitrarily set according to the member to be used.

The atmosphere at the time of joining is not particularly specified, but an inert atmosphere or a vacuum is used as necessary for a member that easily forms an oxide film such as metal. In addition, for a member such as a nitride-based ceramic, it is possible to prevent a nitrogen defect from occurring at the joint by using a nitrogen atmosphere or the like. However, the use of flammable gas is not preferable because discharge occurs. Advantages of the present invention include the following points.
-No external heat source such as a heater or laser is required for bonding.
・ Energy efficiency is good.
-Equipment required for joining can be simplified.
-It can be easily automated (no need to align an external heat source such as a laser).
・ Porous bodies with complex shapes can be made by automation.
-It can be made into the space rate below the space rate (about 26%) of the porous body at the time of carrying out the close packing of the sphere of the same system. According to this method, since the grains can be joined one by one, the arrangement can be arbitrarily changed (for example, body-centered legislative structure).
-Porous materials with partially different porosity can be made.
-Since only the vicinity of the joint is heated, the other parts of the member are hardly affected by heat.
-There is no influence of heat, that is, softening due to coarsening of crystal grains, embrittlement due to changes in crystal phase and appearance of precipitates.
-Even dissimilar materials with large differences in melting points can be joined.
-A porous structure composed of a joined body obtained by joining microspheres can be produced and provided.

  According to the present invention, 1) a joined body of members having a minute spherical surface can be provided, and 2) a joined body is produced, and the method for joining members having a minute spherical surface of the present invention is used to form a spherical member or a minute member having a spherical surface. 3) It is possible to produce and provide a joined body without using an adhesive or the like for the joining of 3). 3) The joining of members having a minute spherical surface so far is the control of the amount of heat applied and the control of the joining position. In the present invention, a part of the member is melted by utilizing the discharge phenomenon, taking into account the problem that the strength and heat resistance of the bonding material are reduced. 4) In the present invention, the member to be joined is required to have a conductive property. However, a non-conductive member such as a resin also has a conductive material. Can be handled by combining 5) A porous structure composed of a joined body of microspheres can be produced and provided. 6) The present invention can be suitably used as a joining technique for microspheres having a diameter of 5 mm or less, for example. By adding a sphere to increase the surface area, it is possible to use as a manufacturing technique for a porous filter or catalyst having improved characteristics.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited at all by the following examples.

  Experiments were performed using an apparatus as shown in FIG. Spherical particles 2 of pure titanium having a diameter of 0.5 mm were picked up by the suction electrode 1, brought into contact with the pure titanium plate 3, and a voltage was applied. Since discharge did not occur at less than 20V, the voltage was set at 20V or more. As a result of the discharge, a melted portion was observed between the particles and the plate and bonded (discharge bonding). The higher the voltage and the larger the current, the wider the junction.

  Using the same apparatus as in Example 1, spherical particles of pure titanium having a diameter of 0.5 mm were picked up by a suction electrode and brought close to a pure titanium plate in a state where a voltage of 23 V was applied in advance. As a result, discharge occurred and bonding was performed. When the voltage was increased, intense flashing was observed along with intense flashing, spherical particles were completely evaporated, and depressions were also formed on the pure titanium plate. This is because the discharge energy was too high.

  In the same manner as in Example 1, spherical particles of pure titanium having a diameter of 0.5 mm were brought into contact with each other, and a voltage of 20 V or more was applied. As a result, the spherical particles were joined together. A melted mark was observed at the joint. Similar to Example 1, the size of the junction changed depending on the voltage and current.

  When the same experiment as in Example 1 was performed with a load at the time of contact of 1.5 kgf, deformation of spherical particles was observed when the voltage and current increased.

  In the same manner as in Example 1, 0.5 mm titanium particles were bonded to a titanium plate, and then titanium particles were bonded to the bonded titanium particles in the same manner as in Example 3. The result is shown in FIG. By continuing this, a continuous body could be produced.

  In the same manner as in Example 1, 0.7 mm titanium particles could be bonded to the stainless steel plate. The voltage could be over 20V. The joint part had a rapidly solidified phase.

  In the same manner as in Example 1, a stainless steel ball having a diameter of 3 mm was brought into contact with the titanium plate, and a voltage was applied. By setting the voltage to 60 V, a melted part was formed and joined although it was minute.

  Using a device similar to that of Example 1, a direct 0.5 mm titanium sphere was picked up by a suction electrode and brought close to the zirconium carbide plate while applying a voltage of 24V. As a result, discharge occurred and the titanium sphere and the zirconium carbide plate were joined.

  In advance, a carbon-containing zirconium oxide plate prepared by sintering a powder obtained by mixing 4% by mass of carbon powder and zirconium oxide powder was prepared. This member has conductivity. Using a device similar to that of Example 1, a titanium sphere having a diameter of 0.5 mm was picked up by a suction electrode and brought close to a carbon-containing zirconium oxide plate while applying a voltage of 60 V. As a result, discharge occurred, and the titanium sphere and the carbon-containing zirconium oxide plate were joined.

  In advance, a member in which a bismuth-tellurium alloy film having a thickness of 2 to 3 μm was coated on a zirconium oxide sphere having a diameter of 3 mm was prepared. Using the same apparatus as in Example 1, the coating sphere was brought close to the titanium plate while a voltage of 400 V was applied. As a result, electric discharge occurred and the coating sphere was bonded to the titanium plate. The coating film at the joint portion was evaporated, but the joining was achieved by melting titanium.

  As described in detail above, the present invention relates to a conductive microsphere assembly and a bonding method, and the present invention provides a conductive microsphere assembly and a bonding method thereof. Can do. The technique of the present invention can be automated, for example, using a system similar to CAD-CAM to stack spheres at any location. From this, it is possible to create a free-form porous body, a product that requires a partially porous state, or a product with a partially different degree of voids by using the joined body of the present invention. it can. According to the present invention, for example, by applying to the inner wall of a pipe for a heat exchanger, the surface area that comes into contact with the fluid is widened, a member that improves thermal efficiency, a high-performance filter with a different degree of space depending on the place with one filter, etc. It becomes possible to provide.

The outline | summary of the apparatus used in the Example is shown. The photograph of an example of the joined body produced in the Example is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrode with a suction function 2 Spherical member 3 Plate-like member 4 Power supply 5 Vacuum pump 6 Vacuum hose 7 Electric wire

Claims (12)

  A joined body comprising conductive microspheres and the microspheres or other members being melt-bonded at their contact portions.   The joined body according to claim 1, wherein at least one of the joined microspheres has a microsphere having a diameter of 5 mm or less.   The joined body according to claim 1, wherein an area of the joined portion is smaller than a cross-sectional area passing through the center of the microsphere.   The joined body according to claim 1, wherein the microsphere is hollow or solid.   The joined body according to claim 1, wherein the material of the microsphere is a metal, a carbonized ceramic, a boride ceramic, an oxide ceramic, or graphite.   The joined body according to claim 1, wherein the conductive microspheres are obtained by mixing a non-conductive material with a conductive substance to provide conductivity.   The joined body according to claim 1, wherein the conductive microspheres are formed by forming a conductive material on the surface.   In a method of joining microspheres and microspheres or other members, at least one of the conductive members to be joined uses a member having a microspherical surface with a diameter of 5 mm or less, using charges generated inside or on the surface. A method for joining microspheres, characterized in that joining is performed by discharging them.   The bonding method according to claim 8, wherein the fusion bonding is performed by discharging using charges generated inside or on the surface of the member.   9. The members are melted or softened and joined by electric discharge generated when the oxide layer on the surface of the conductive material or the air layer between the joining members is subjected to dielectric breakdown using charges generated in or on the members. Joining method.   The bonding method according to claim 8, wherein an outer mold that contacts the member is not used when melt-bonding is performed by discharging using an electric charge generated inside or on the member. The joining method according to claim 8, wherein the obtained joined body is further heat-treated.