JP2010094683A - Diffusion bonding method of aluminum alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such the problem that diffusion bonding of an aluminum alloy is carried out by using a vacuum furnace, and the cost is increased since a man-hour is required for the bonding. <P>SOLUTION: By heating and pressurizing an aluminum alloy in an atmosphere of nitrogen substitution and the residual amount of oxygen of ≤70 ppm, the oxide film of a bonding surface is broken since a reduction rate by magnesium contained in the aluminum alloy is higher than the oxidation rate of the bonding surface with residual oxygen, and the diffusion bonding is carried out at a low cost. Further, since the diffusion bonding can be carried out at a pressure higher than the normal pressure, the content such as magnesium is hardly evaporated, and the physical properties of a joined article can be stabilized. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for diffusion bonding of aluminum alloys by heating and pressing.

Conventional diffusion bonding of aluminum alloy has a strong oxide film on its surface. Therefore, using an alloy containing magnesium, the oxide film on the surface is reduced by magnesium contained in the alloy in a vacuum atmosphere, and the oxide film is destroyed. As a result, diffusion bonding is performed by bringing aluminum alloys into direct contact with each other (see, for example, Patent Document 1). At this time, heating and pressurization were performed at the diffusion temperature of magnesium.
Japanese Patent Publication No. 5-62034

  However, the conventional method has a problem that since the joining is performed in a vacuum heating furnace in order to create a vacuum atmosphere, the joining process becomes a batch process, and the number of man-hours for joining increases the cost.

  Further, since diffusion bonding is performed in a vacuum, inclusions such as magnesium evaporate, and the physical properties of the bonded material are not stable.

  Furthermore, since diffusion bonding is performed in a vacuum, inclusions such as magnesium evaporate, and the oxide film on the surface becomes difficult to be reduced, resulting in a problem that bonding strength is reduced.

  Furthermore, since the heating and pressurization is performed at the diffusion temperature of the inclusion such as magnesium, there is a problem that the diffusion of the aluminum alloy of the base material hardly proceeds and the bonding strength is weak.

  An object of the present invention is to solve the above-described conventional problems, and to provide a diffusion bonding method of an aluminum alloy that can be continuously and inexpensively bonded, stabilizes the physical properties of a bonded product, and has high bonding strength. To do.

  In order to solve the above-described conventional problems, the aluminum alloy diffusion bonding method of the present invention heats and pressurizes in a nitrogen atmosphere.

  This makes it possible to join in a continuous furnace because it is cheap and easy to manage, and can be joined in a continuous furnace, so that diffusion joining can be done at low cost and diffusion joining can be performed at atmospheric pressure or higher. And the physical properties of the bonded product can be stabilized.

  Since the diffusion bonding method of the aluminum alloy of the present invention can be diffusion bonded in an atmosphere not in a vacuum, it can provide inexpensive bonding, stabilize the physical properties of the bonded material, and strengthen the bonding strength. .

  The invention according to claim 1 heats and pressurizes in a nitrogen atmosphere when aluminum alloy is diffusion-bonded, and can be bonded in a continuous furnace because it is bonded in a nitrogen-substituted atmosphere that is inexpensive and easy to manage. Thus, diffusion bonding can be performed at low cost, and diffusion bonding can be performed at a pressure higher than normal pressure, so that contents such as magnesium are less likely to evaporate, the physical properties of the bonded product can be stabilized, and the bonding strength can be increased.

  Invention of Claim 2 uses the alloy containing 2 weight% or more of magnesium as an insert material in the invention of Claim 1, or uses the alloy containing 2 weight% or more of magnesium, It is difficult to evaporate, the oxide film on the surface is easily reduced, and the bonding strength is increased.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the remaining amount of oxygen is heated and pressurized in an atmosphere of 70 ppm or less. The rate of reduction with magnesium contained in the steel is faster, so the oxide film on the bonding surface is broken and the bonding strength can be increased. The residual oxygen amount can be 70 ppm or less, and the residual oxygen can be easily managed. Diffusion bonding can be performed.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the heating temperature is between a temperature lower than the solidus temperature of the aluminum alloy by 45 ° C. and a solidus temperature. In some cases, the diffusion of aluminum in the base material is more likely to proceed, and the bonding can be performed firmly in a short time, so that diffusion bonding can be performed at a lower cost.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the applied pressure is 3 MPa or more and 5 MPa, so that the pressure increases while suppressing deformation due to pressurization. Adhesion is improved, diffusion is more likely to proceed, and since bonding can be performed firmly in a short time, diffusion bonding can be performed at a lower cost.

  Hereinafter, experimental results that led to the present invention will be shown and described in detail.

(Embodiment 1)
A5052 was used as a bonding material, and diffusion bonding was performed. A5052 is a magnesium-based aluminum alloy, the magnesium content is 2.2 to 2.8% by weight, and the solidus temperature is about 607 ° C.

  The materials used in the experiment were a commercially available aluminum alloy plate (block material) having a thickness of 18 mm and an aluminum alloy plate (plate material) having a thickness of 3 mm. The sample size is 20 mm wide × 40 mm long for the block material and 25 mm wide × 50 mm long for the plate material.

  In the experimental method, after the bonding material is washed with an organic solvent, the block material, the plate material, and the block material are superposed in this order. This is put into a furnace, the inside of the furnace is evacuated so that the amount of residual oxygen becomes 70 ppm, then filled with nitrogen and heated. There are two heating conditions: 562 ° C., which is 45 ° C. lower than the solidus temperature, and 577 ° C., which is 30 ° C. lower than the solidus temperature. After heating to a predetermined temperature, it was left for about 5 to 10 minutes, and pressurization was started. The applied pressure is two conditions of 3 MPa and 4 MPa. After pressurizing for 60 to 90 minutes, the pressure was gradually increased, and the sample was taken out from the furnace after the temperature became near room temperature by furnace cooling.

  The joined sample was cut with an electric discharge machine into a shape that allows the block material to be attached to the chuck of the tensile tester, the block material at both ends was pulled at a tensile rate of 0.5 mm / min, and the stress until breakage was measured.

  As a result, the tensile strength of the joint surface was 94 MPa at a heating temperature of 562 ° C. and a pressure of 4 MPa. Thus, since it is joining in nitrogen substitution atmosphere, joining becomes possible in a continuous furnace. Nitrogen is an inexpensive and easy-to-manage gas. As a result, diffusion bonding can be performed at low cost, and diffusion bonding can be performed at normal pressure or higher, so that contents such as magnesium are less likely to evaporate, and the physical properties of the bonded article are stabilized. In addition, since magnesium does not easily evaporate, even if the residual oxygen amount is 70 ppm, the rate of oxide film reduction with magnesium is faster than the rate of oxidation with residual oxygen, and strong diffusion bonding is possible. Further, as a preferable heating temperature, by bonding at a temperature lower by 45 ° C. than the solidus temperature on the basis of the solidus temperature, diffusion of aluminum itself is promoted and stronger bonding can be obtained.

  However, since the aluminum alloy becomes softer as it approaches the solidus temperature, if the heating temperature is increased too much, the bonding strength increases, but the deformation of the shape increases. When the heating temperature is 562 ° C., which is 45 ° C. lower than the solidus temperature, the deformation rate (height difference between the block and the plate before and after joining / height before joining) is about 15%, and the heating temperature is fixed. At 577 ° C., which is 30 ° C. lower than the phase line temperature, increases to about 40%, and beyond this, the amount of deformation greatly increases. Therefore, a more preferable heating temperature is 45 ° C. to 30 ° C. lower than the solidus temperature. It is good to do diffusion bonding with. That is, when the heating temperature is lower by 30 ° C. to 45 ° C. than the solidus temperature of the aluminum alloy, the strength of diffusion bonding can be increased and deformation due to heating and pressing can be suppressed.

  In addition, similar diffusion bonding was attempted in the atmosphere, but bonding was not possible.

  In addition, the same experiment was performed using A6061 (magnesium content is 0.8 to 1.2% by weight) and A1050 (magnesium content 0.05% by weight or less) with a low magnesium content. In all cases, the bonding strength was extremely low.

  Further, the bonding was attempted at 547 ° C., which is 60 ° C. lower than the solidus temperature, but the bonding could not be performed.

  Thus, since it can join in a nitrogen-substituted atmosphere that is inexpensive and easy to manage, it is possible to use a continuous furnace, and it is possible to join at a low cost. Furthermore, since the residual oxygen amount is 70 ppm or less, the reduction action by magnesium can be faster than the oxidation rate of the aluminum surface by residual oxygen, so that strong diffusion bonding can be performed and the residual oxygen amount can be easily managed, so that bonding can be performed at low cost. It has high industrial versatility and is suitable for continuous production.

  In addition, since bonding is performed in a nitrogen-substituted atmosphere, bonding is performed under normal pressure rather than under a negative pressure as in vacuum, so that scattering of easily diffusing contents such as magnesium can be suppressed and bonding with stable physical properties is possible. In addition to obtaining a product, since magnesium has a function as a reducing agent for aluminum oxide, diffusion can easily proceed and strong diffusion bonding can be achieved in a short time.

  The heating temperature is not controlled by the diffusion temperature of inclusions such as magnesium as in the prior art, but is controlled by the solidus temperature of the aluminum alloy. Specifically, the heating temperature is 45 to 45 from the solidus temperature of the aluminum alloy. Unlike conventional bonding at the diffusion temperature of magnesium, diffusion bonding between the low temperature and the solidus temperature can facilitate the diffusion of the aluminum alloy of the base material, resulting in a stronger bond. It becomes possible. In particular, when diffusion bonding is performed at a temperature 30 ° C. to 45 ° C. lower than the solidus temperature, deformation due to heat and pressure can be suppressed to a small level.

  Note that in the present embodiment, the aluminum alloys are shown to be overlapped with each other, but an alloy containing 2% by weight or more of magnesium as an insert material may be sandwiched and joined between the aluminum alloys.

  In the present embodiment, an aluminum alloy is used as the metal material, but the same effect can be obtained even if pure aluminum is used.

  As a thing manufactured using the diffusion joining of the aluminum alloy shown in this Embodiment, a laminated type heat exchanger is mention | raise | lifted. Since the laminated type heat exchanger has a fine flow path through which the refrigerant flows, brazing material may flow out and block the flow path in brazing, so it is desirable to manufacture by diffusion bonding. Moreover, since it is a heat exchanger, it is better that the material has a high thermal conductivity, and aluminum and aluminum alloys that are inexpensive and have a high thermal conductivity are optimal materials.

  As described above, the diffusion bonding method of the aluminum alloy according to the present invention can perform diffusion bonding in an atmosphere not in a vacuum, so that it can provide inexpensive bonding, stabilize the physical properties of the bonded material, and increase the bonding strength. Because it can be solidified, it is used for refrigerator / refrigerator equipment such as refrigerators and vending machines, room air conditioners, packaged air conditioners, air conditioners for automobiles, water heaters, radiators for automobiles, electronic devices, etc. It can be applied to applications such as heat exchangers and waste heat recovery equipment.

Claims (5)

  A diffusion bonding method of aluminum alloy in which aluminum alloy is heated and pressurized in a nitrogen atmosphere when diffusion bonding is performed.   2. The aluminum alloy diffusion bonding method according to claim 1, wherein an alloy containing 2% by weight or more of magnesium is used as an insert material, or an aluminum alloy containing 2% by weight or more of magnesium is used.   The aluminum alloy diffusion bonding method according to claim 1 or 2, wherein the oxygen remaining amount is heated and pressurized in an atmosphere of 70 ppm or less.   4. The aluminum alloy diffusion bonding method according to claim 1, wherein the heating temperature is between a temperature lower than the solidus temperature of the aluminum alloy by 45 ° C. and a solidus temperature. 5.   The aluminum alloy diffusion bonding method according to any one of claims 1 to 4, wherein the applied pressure is 3 MPa or more and 5 MPa.