JP2015066558A - Joint method for metallic component, and joint metal product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metallic component jointing method for diffusion-jointing metallic components, while heating the metal members in abutment against each other, to provide jointed parts excellent in mechanical strengths, and a jointed metal product using that method.SOLUTION: Abutment interfaces are made to abut against each other, after a residual compression strain was applied under a pressure of 50% or less to at least one of butting interfaces in the vicinity of the interface, and are heated at or higher than a re-crystallization temperature.

Description

  The present invention relates to a method for joining metal members that are heated and diffused while abutting metal members together, and a joined metal product using this method.

  When metal members are brought into contact with each other and atoms on the surface thereof are brought closer to each other by a certain distance or more, the metal members can be joined to each other in an attempt to bond the atoms to each other by metal bonding. Actually, on a smooth surface obtained by machining, etc., there are irregularities with a size that far exceeds the distance that allows atoms to be metal-bonded, and all atoms on the surface of the metal member are more than a certain distance apart. It is difficult to bring them close to each other. Therefore, bonding is performed while the atoms are diffused by heating above the recrystallization temperature. In such a “diffusion bonding method”, for example, if there is an oxide film or the like that inhibits the diffusion of atoms at the butt interface, the atoms cannot be bonded without progressing. In general, diffusion bonding is performed while pressing metal members together by mechanically removing the oxide film formed on the surface of the metal members by pressurization and obtaining a new surface as a bonding surface. This is for spreading. Further, the reason why the metal members are brought into contact with each other immediately after the bonding surfaces are cleaned with the cleaning liquid is also the same.

  For example, Patent Document 1 discloses a method of performing diffusion bonding while mechanically obtaining such a new surface. Specifically, the second metal plate material is overlaid on the first metal plate material, and the first and second metal plate materials are simultaneously punched. The second metal plate is fitted into the first metal plate while a new surface is generated by the punching process. Furthermore, when the second metal plate is heated while being fitted in the first metal plate, a compressive force is generated on the new surface due to the difference in the coefficient of thermal expansion between the first and second metal plates. It is said that a new surface can be formed and diffusion bonding of both metal plate materials can be made more reliable.

  Further, Patent Document 2 discloses a method of obtaining a new surface of a bonding surface with a cleaning liquid in diffusion bonding in order to perform flip chip bonding at a temperature lower than that of soldering. Specifically, the surfaces of metal members containing at least one of tin are boiled in a formic acid or citric acid solution, or exposed to formic acid vapor or citric acid vapor, and then the surfaces of the metal members are butted against each other and heated. And pressurization. Here, the oxide on the surface of the metal member is removed and the metal surface from which the oxide has been removed is not oxidized again by being replaced by a formic acid compound in which the metal and formic acid have reacted or a citric acid compound in which the metal and citric acid have reacted. I am going to do so.

  By the way, a method for improving the bonding property in diffusion bonding other than the formation of a new surface has also been proposed.

  For example, Patent Document 3 discloses that diffusion bonding of a flat foil and a corrugated foil of a metal carrier can be stably performed by using a stainless foil having a high rolling reduction. The grain boundary has a larger diffusion coefficient than the grain interior, so the smaller the grain size, the higher the grain boundary density and the more the diffusion is promoted. It states that stainless steel foil is superior in diffusion bonding.

  Further, in Patent Document 4, after strain is introduced in advance on the surface to be joined of the metal member, the metal members are superposed on each other and heated while applying a pressure higher than the yield point, while causing dynamic recrystallization at the joint interface. A diffusion bonding method for diffusion bonding is disclosed. The conventional diffusion bonding method presupposes bonding under conditions that do not cause plastic deformation, but here, when the joint is plastically deformed, dynamic recrystallization proceeds and the bonding strength is improved. It is said.

JP 2009-248125 A JP 2011-200930 A JP-A-9-279310 JP 2002-103055 A

  Like the method disclosed in Patent Document 3 or 4, it is possible to bond at a lower temperature by increasing the bonding property by diffusion bonding, and the metal member is not softened. Therefore, a bonded part having excellent mechanical strength can be manufactured. On the other hand, in order to create a new surface at the interface in the butt-matching of the metal members, a butting force to the extent that the interface is plastically deformed is required, and due to the plastic deformation, there is a problem of a change in the outer shape of the metal member and a deterioration of the mechanical strength. It has become.

  The present invention has been made in view of the situation as described above, and the object of the present invention is to join a metal member having a high mechanical strength in a joining method in which metal members are heated and diffused together while abutting each other. The present invention provides a method for obtaining a component while maintaining a sound appearance and a bonded metal product using the method.

  The method according to the present invention is a method in which metal members are heated while being butted together and diffusion-bonded to each other, and at least one of the butted interfaces is applied with a residual compressive strain in the vicinity of the interface exceeding 50% reduction. And heating above the recrystallization temperature.

  According to this invention, it is possible to obtain a bonded component having excellent mechanical strength while maintaining a sound appearance. Furthermore, by adjusting the internal energy given in advance, that is, the residual compressive strain by the heating temperature and time, and adjusting the internal microstructure near the joint interface, the material production and parts assembly can be performed in a series of steps. Further, since the joining can be performed without greatly depending on the adsorption of oxygen at the joining interface, the metal member can be easily handled.

  In the above-mentioned invention, it is good also as giving a load below the yield point of the said metal member, and matching. According to this invention, it is possible to obtain a joined component having excellent mechanical strength while maintaining a particularly healthy appearance.

  In the above-described invention, the insert material given the residual compressive strain may be heated after being sandwiched between the metal members. According to this invention, it is possible to obtain a joined part having excellent mechanical strength with a simple operation while maintaining a sound appearance.

  The bonded metal product according to the present invention is obtained by the above-described method. According to this invention, it is excellent in mechanical strength while maintaining a sound appearance.

It is sectional drawing which shows the joining method by this invention. It is process drawing which shows the joining method by this invention. It is an optical microscope photograph of the cross section of the copper-type material joined by the joining method by this invention. It is a graph which shows the hardness after annealing 90% rolled pure titanium at various temperatures. It is a graph which shows the hardness after annealing the pure nickel which rolled 90% at various temperature.

  The inventor of the present application paid attention to the “recrystallization phenomenon” in the heat treatment for adjusting the structure of the metal material. In such a phenomenon, newly generated crystal grains (recrystallized grains) inside the metal material grow while taking atoms into the surface from the surroundings. The driving force for this growth depends on the internal energy difference between the recrystallized grains having a low internal energy and being stable in an equilibrium state and the unrecrystallized grains having a high internal energy and an unstable strain.

  By the way, with reference to FIG. 1, the case where the principle of the “recrystallization phenomenon” is applied to diffusion bonding with the bonding interface 12 sandwiched therebetween will be considered. If the internal energy of one or both of the metal members 10 and 11 to be joined (here, one of the metal members 11) is increased to be unstable, the vicinity of the surface of the metal member 11 is increased. It is more stable for the atoms to move beyond the bonding interface 12 to the surface of the recrystallized grains appearing on the surface of the metal member 10 on the bonding partner side. Further, when the bonding interface 12 disappears, the energy can be made lower and stable. That is, when a driving force for atomic movement by heating is applied, the recrystallized grains on the other side of the metal member 11 grow beyond the bonding interface 12 to form a strong bond in which the metal members 10 and 11 are integrated (see FIG. 1 (c)). At this time, if the internal energy difference between the two sandwiching the bonding interface 12 is sufficiently large, the growth of crystal grains can proceed without being hindered by some contamination of the bonding interface 12.

  Specifically, an example in which the above-described principle is applied to a joining method in which metal members are heated while being brought into contact with each other and diffusion-bonded to each other will be described with reference to FIG.

  First, prior to heating (S4) for performing diffusion bonding, at least one of the butted interfaces of the metal members 10 and 11 (here, the metal member 11) is reduced, and preferably 50% or more in the vicinity of the interface. A large reduction is applied to accumulate a large residual compressive strain inside the metal member 11, particularly in the vicinity of the interface (S1).

  Next, the surface of the metal member 11 to which the residual compressive strain is given is appropriately processed so as to have a smoothness that does not hinder the butt (S2). It goes without saying that such surface processing should not remove or release residual compressive strain.

  Next, the metal members 10 and 11 are brought into contact with each other (S3), and heated to a recrystallization start temperature or higher which is a temperature at which the recrystallization starts (S4). As a result, recrystallized grains are generated inside the metal member 11, grows to the metal member 10 side beyond the bonding interface 12, and tries to disappear the bonding interface 12. Therefore, it is possible to obtain a strong joint excellent in mechanical strength while maintaining a sound appearance.

  As described above, since this method is excellent in diffusion bonding property, it can be firmly bonded even if it is a butt load below the yield point of the metal members 10 and 11 only by heating to a relatively low temperature, and the bonding interface. It is possible to maintain higher soundness around 12 (joint portions). Moreover, even if there exists adsorption | suction of oxygen in the joining interface 12, it can join and the handling of the metal members 10 and 11 in joining is easy.

  In addition, in the step (S1) of accumulating the residual compressive strain at the butt interface between the metal members 10 and 11, an insert material to which the residual compressive strain is applied may be sandwiched between the metal members 10 and 11.

  Next, a joining experiment using several kinds of metal members will be described.

[Diffusion bonding of copper-based metal members]
90% rolling was applied to pure copper which was annealed at 550 ° C. for 1 hour to remove internal strain. The 1 mm thick plate was cut into small pieces of 12 mm width × 20 mm length, and one side was polished with emery paper and buffing in the atmosphere and mirror finished. The polished surfaces were opposed to each other in a cross shape and placed in a vacuum chamber. The overlapping area at this time is 12 mm × 12 mm. After evacuation, while applying a load of 5 kN so that the plates are in close contact with each other, it is heated to 350 ° C., which is higher than the recrystallization temperature of pure copper by high-frequency heating, held for 30 minutes, and then the load is removed. I took it out.

  In FIG. 3, the optical micrograph of the joining interface in an overlapping surface was shown. It can be seen that crystal grains grow across the bonding interface indicated by the arrow. Usually, it is pure copper that can perform diffusion bonding at about 600 ° C., but it can be firmly bonded at a lower temperature by bonding by this method. Moreover, the crystal | crystallization grain was refined | miniaturized and the metal member after joining was harder than the annealed board so that it may mention later.

  Further, from the annealed pure copper, two small pieces cut into a thickness of 1 mm × 12 mm width × 20 mm length were cut out. This one side was polished with emery paper and buffing in the atmosphere and mirror finished. The polished surfaces face each other in a cross shape and are placed in a vacuum chamber. At this time, the overlapping area is 12 mm × 12 mm.

  In order to confirm the joining state, one of the metal members joined in a cross shape was fixed with a vise, and the other was struck with a hammer in a direction to peel off the other. Then, the metal members fixed with a vise were bent without peeling off the metal members. In other words, it was harder than the annealed plate. On the other hand, for comparison, a 1 mm thick pure copper plate subjected to annealing at 550 ° C. for 1 hour to remove internal strain, that is, a pure copper plate not imparting residual compressive strain, was subjected to a joining experiment under the same temperature and pressure conditions. When I went there, it came off easily by hand.

[Diffusion bonding of titanium metal members]
An arc-melted button-like sample was formed into a plate-like body having a thickness of 10 mm by cold end rolling, and 90% rolling was applied to pure titanium from which internal strain was removed by annealing at 700 ° C. for 4 hours. Two small pieces obtained by cutting a plate having a thickness of 1 mm into a width of 12 mm and a length of 20 mm were each mirror polished by emery paper and buffing on one side. The polished surfaces face each other in a cross shape and are placed in a vacuum chamber. The overlapping area at this time is 12 mm × 12 mm. After vacuuming, while applying a load of 5 kN so that the plates are in close contact, it is heated to 530 ° C., which is higher than the recrystallization temperature of pure titanium by high frequency heating (see FIG. 4. Hardness after annealing for 1 hour at each temperature ) After holding for 1 hour, the load was removed, and after cooling, it was removed from the vacuum chamber.

  In order to confirm the joining state, one of the metal members joined in a cross shape was fixed with a vise, and the other was struck with a hammer in a direction to peel off the other. Then, the metal members fixed with a vise were bent without peeling off the metal members. On the other hand, for comparison, bonding was performed under the same temperature and pressure conditions using a pure titanium plate having a thickness of 1 mm that had been subjected to annealing at 700 ° C. for 4 hours to remove internal strain, that is, a pure titanium plate that did not impart residual compressive strain. When the experiment was conducted, it was easily peeled off with a slight hammer hit.

[Diffusion bonding of nickel-based metal members]
90% rolling was applied to pure nickel that had been annealed at 800 ° C. for 1 hour to remove internal strain. Two small pieces obtained by cutting a plate having a thickness of 1 mm into a width of 12 mm and a length of 20 mm were each mirror polished by emery paper and buffing on one side. The polished surfaces face each other in a cross shape and are placed in a vacuum chamber. The overlapping area at this time is 12 mm × 12 mm. After vacuuming, while applying a load of 5 kN so that the plates are in close contact, it is heated to 550 ° C., which is higher than the recrystallization temperature of pure nickel by high-frequency heating (see FIG. 5. Hardness after annealing for 1 hour at each temperature ) After holding for 1 hour, the load was removed, and after cooling, it was removed from the vacuum chamber.

  In order to confirm the joining state, one of the metal members joined in a cross shape was fixed with a vise, and the other was struck with a hammer in a direction to peel off the other. Then, the metal members fixed with a vise were bent without peeling off the metal members. On the other hand, for comparison, bonding is performed under the same temperature and pressure conditions using a pure nickel plate having a thickness of 1 mm that has been subjected to annealing at 800 ° C. for 1 hour to remove internal strain, that is, a pure nickel plate that does not impart residual compressive strain. When the experiment was conducted, it was easily peeled off to the extent that it was lightly hammered.

  As described above, the method of the present invention can be applied regardless of the material type of the metal member to be joined based on the principle described above. Further, it can be widely applied to general assembly of metal members. For example, the metal member is a thin metal plate or foil, and the present invention can also be applied to a manufacturing method in which only a plurality of metal members are stacked and joined together.

  So far, representative examples and modified examples based on the examples have been described, but the present invention is not necessarily limited thereto. Those skilled in the art will recognize a variety of alternative embodiments without departing from the scope of the appended claims.

10,11 Metal member 12 Bonding interface

Claims (4)

It is a method in which the metal members are heated while abutting each other to diffusely bond them,
A method for joining metal members, characterized in that at least one of the butt interfaces is subjected to a residual compressive strain exceeding 50% in the vicinity of the interface and then butted and heated to a recrystallization temperature or higher. The metal member joining method according to claim 1, wherein the metal members are matched by applying a load equal to or lower than a yield point of the metal members.   The method for joining metal members according to claim 1 or 2, wherein the insert member given the residual compressive strain is heated after being sandwiched between the metal members. A bonded metal product obtained by the method according to claim 1.

Images