WO2014030416A1

WO2014030416A1 - Method for plane brazing of aluminum alloy members

Info

Publication number: WO2014030416A1
Application number: PCT/JP2013/066840
Authority: WO
Inventors: 貴訓小久保; 堀　久司; 亮介富樫
Original assignee: 日本軽金属株式会社
Priority date: 2012-08-22
Filing date: 2013-06-19
Publication date: 2014-02-27
Also published as: JP2014039947A; TWI562849B; KR101570949B1; KR20140114858A; CN104114311A; CN104114311B; JP5906994B2; TW201408415A

Abstract

The purpose of the present invention is to form a sound fillet on the periphery of surfaces to be brazed, when two aluminum alloy members are brazed to each other by plane brazing using a single-layer brazing sheet. When aluminum alloy members having a solidus temperature of 610ºC or higher are brazed to each other by plane brazing using a single-layer brazing sheet constituted of an Al-Si-Mg alloy brazing material, a flux is applied not to the surfaces of the aluminum alloy members which are to be brazed with the single-layer brazing sheet but to an area which lies in the surface of the aluminum alloy member that is the larger in terms of plan-view area and which is separated from the periphery of the surface to be brazed. The single-layer brazing sheet is sandwiched between the aluminum alloy members. The aluminum alloy members are brazed to each other in an inert-gas atmosphere while keeping the brazing sheet in areal contact with the aluminum alloy members and while keeping the stack at a given brazing temperature and applying an areal pressure thereto.

Description

Surface brazing method for aluminum alloy members

The present invention relates to a surface brazing method for aluminum alloy members capable of forming a sound fillet when the aluminum alloy members are brazed to each other in an inert gas atmosphere using a single layer brazing sheet. It is.

For example, as seen in the brazing of fins and tubes of aluminum heat exchangers, the conventional brazing techniques have been based on line contact so that a fillet shape is obtained. In such a brazing method, for example, when the lower plate is a brazing sheet and a plate-like fin is joined vertically thereto, the molten brazing material flows on the brazing sheet to form a fillet. .
In such a brazing technique based on line contact, brazing is generally performed using a flux in the air or in an inert gas atmosphere in order to suppress oxidation during brazing heating. ing.

For example, in Patent Document 1, a member that is brazed using a non-corrosive flux and metal powder, Fe: 0.7-2.5 wt%, Mn: 0.5-2.0 wt%, 2 types are included, Mg: 0.2 wt% or less, and the number of second phase particles having a maximum diameter exceeding 5 μm at a depth of 20 μm from the surface to which the non-corrosive flux and the metal powder are applied is 200 particles / mm. A brazing aluminum material characterized by being ² or less has been proposed.
According to this, according to the brazing method that does not use a clad material, it is possible to form an excellent fillet with good brazing fluidity, and to provide an aluminum material for brazing that is excellent in strength.

By the way, in recent years, a demand for a heat exchange system that cools heat generated by an in-vehicle IGBT or the like by surface contact is increasing, and a technique for brazing the surfaces of aluminum members with a brazing material is required.
For example, Patent Document 2 discloses a powdered aluminum alloy braze containing Cu: 23 to 37% by mass, Si: 4 to 10% by mass, the balance being Al and inevitable impurities, and an average particle size of 10 to 100 μm. An aluminum alloy brazing material slurry in which a material and a fluoride-based flux containing 11% by mass or more of CsF as a solid content are suspended in a dispersion medium is brazed into an aluminum alloy casting to be brazed or the other brazed member A method of brazing an aluminum alloy casting characterized in that after being applied to the surface of the brazed part, the other brazed member is assembled to the brazed part to which the aluminum alloy brazing material slurry has been applied and the assembly is heated. ing.
According to this method, a low-temperature brazing method for an aluminum alloy casting is provided in which a brazing material having high wettability and corrosion resistance is used, and a sound joint can be obtained even by brazing in a furnace.

In this surface brazing technique, after a mixed slurry containing a powdered brazing material and a flux is applied to the surface of the brazed portion of the brazed member, the brazed members are assembled together and the assembly is heated. . For this reason, a void defect or the like is likely to occur at the joint, and the flux is easily contained. Therefore, the technique of brazing the surfaces of the aluminum alloy members with a brazing material is a very difficult technique compared to the brazing technique based on the fillet formation.

On the other hand, in recent years, a method has been developed in which a brazing sheet in which an Al—Si alloy brazing material is clad with a core material is brazed in an inert gas without flux.
For example, in cited document 3, an aluminum clad material containing an Al—Si based brazing material containing 0.1 to 5.0% Mg and 3 to 13% Si in mass% is used to reduce the pressure. There has been proposed a method in which the Al—Si brazing material and the brazing target member are brought into contact and in close contact with each other in a non-oxidizing atmosphere without heating, and the core material and the brazing target member are joined.
According to this method, fluxless brazing at atmospheric pressure is possible without the need for flux or vacuum equipment, and even when Mg is added to brazed components other than brazing material, It must not be.

However, in the brazing method described in Patent Document 3, a clad material having two or more layers composed of a core material and a brazing material is used. In order to apply this clad material to a brazing sheet as a brazing sheet, it is necessary to make the clad material into a three-layer structure in which a braze material is disposed on both sides of a core material. Becomes complicated and increases costs.
In view of this, the inventors of the present invention, in the process of earnestly studying a surface brazing method that is low in cost and stable in quality as compared with the prior art, use a single-layer brazing sheet as shown in Patent Document 4 to connect two aluminum alloy members. A technology for surface brazing without flux in an inert gas atmosphere was proposed.

The method proposed in Patent Document 4 includes Si: 3 to 12% by mass, Mg: 0.1 to 5.0% by mass between aluminum alloy members having a solidus temperature of 570 ° C. or higher, A brazing temperature of 570 in an inert gas atmosphere with a single-layer brazing sheet made of a brazing material having a thickness of 15 to 200 μm sandwiched between and having a component composition consisting of Al and inevitable impurities as the balance. It is intended to braze aluminum alloy members without flux while applying a surface pressure of 0.6 gf / mm ² or more while maintaining the temperature at or above.

Japanese Patent Laid-Open No. 09-194976 JP 2007-83271 A Japanese Patent No. 4547032 JP 2012-71335 A

However, according to this technique, it is necessary to perform brazing heating while applying a pressure equal to or higher than a predetermined pressure between two aluminum alloy members sandwiching a single layer brazing sheet. For this reason, the brazing material melted at the time of brazing heating flows out from between the aluminum alloy members, and hits a wall where a healthy fillet is not formed at the periphery of the brazed surface.

On the other hand, as described above, there is an increasing demand for a heat exchange system that cools heat generated by an in-vehicle IGBT or the like by surface contact, and when the surfaces of aluminum members used in such a heat exchange system are brazed to each other It is necessary to form a healthy fillet at the periphery of the brazing surface. If a healthy fillet is not formed at the periphery of the brazing surface, repeated stress is applied to the joint interface due to the thermal cycle when the heat exchange system is used, and cracks occur in the brazing material present at the joint interface due to cycle fatigue. The possibility of entering is increased.
The present invention has been devised to solve such a problem, and two aluminum alloy members are brazed to each other with a single layer brazing sheet, and a healthy fillet is further formed on the periphery of the brazed surface. The object is to provide a surface brazing method that can be formed.

In order to achieve the object, the surface brazing method for an aluminum alloy member of the present invention has a solidus temperature of 610 ° C. or higher using a single layer brazing sheet made of a brazing material of an Al—Si—Mg alloy. When the surface brazing between aluminum alloy members, without applying flux to the brazing surface of the single-layer brazing sheet and the aluminum alloy member, on the surface of the aluminum alloy member having the larger area in plan view Then, a flux is applied to a region separated from the peripheral edge of the brazing surface, and the single-layer brazing sheet is sandwiched between aluminum alloy members and brought into contact with the surface, and a predetermined brazing is performed in an inert gas atmosphere. The aluminum alloy members are brazed together while applying a surface pressure while maintaining the brazing temperature.

An alloy containing Si: 3.0 to 12% by mass, Mg: 0.1 to 0.35% by mass as a brazing material for an Al—Si—Mg based alloy, with the balance being composed of Al and inevitable impurities Is preferably used.
Further, it is preferable to apply a flux to a region separated from the periphery of the brazing surface within a range of 0.5 to 35 mm.
Further, the amount of the flux applied is preferably 2 to 40 g / m ² .

According to the surface brazing method of an aluminum alloy member provided by the present invention, two aluminum alloy members are subjected to surface brazing by applying a surface pressure between the two aluminum alloy members using a single layer brazing sheet, and the brazing surface A healthy fillet can be formed on the periphery of the.
Since a single layer brazing sheet is used instead of a brazing sheet made of a clad material of two layers or three or more layers, the cost can be reduced as a whole. Also, since the brazing surface between the single-layer brazing sheet and the aluminum alloy member is brazed by applying a surface pressure between the two aluminum alloy members without applying flux, it occurs between the two aluminum alloy members. As a result, surface brazing with stable quality can be performed. Furthermore, since the flux is applied to the surface of one aluminum alloy member having a large area in plan view and separated from the periphery of the brazing surface, a healthy fillet is formed on the periphery of the brazing surface. Can do.

Diagram explaining the shape and arrangement of the test piece Conceptual diagram explaining assembly of test specimen Diagram explaining the cutting position and observation position of the test piece Illustration explaining the throat thickness of the fillet Cross-sectional metallographic structure of a fillet with a throat thickness of 150 μm or more Cross-sectional metallographic structure of a fillet with a throat thickness of less than 150 μm Diagram showing the effect of Mg content in brazing filler metal Diagram showing the effect of flux application position Diagram showing the effect of flux application amount

Usually, when brazing, the flux is applied to the surface of the brazing material and the brazing surface of the aluminum alloy member, and the brazing material is inserted between the surfaces of the aluminum alloy member to be joined for brazing heating. As a result, void defects or the like are likely to occur at the joint, and the flux can be easily contained. For this reason, the quality of brazed products tends to vary.
Further, in the conventional flux-free surface brazing method, since a clad material of two layers or three or more layers is used as a brazing sheet, the cost is high. Furthermore, in the conventional flux-free surface brazing method, since there is no flux, the molten brazing material flows out between the aluminum alloy members, and it is difficult to form a healthy fillet at the periphery of the brazed surface. there were.

As described above, there is an increasing demand for heat exchange systems that cool heat generated by in-vehicle IGBTs by surface contact. When brazing the surfaces of aluminum members used in such a heat exchange system, brazing is performed. It is necessary to form a healthy fillet at the periphery of the surface. If a healthy fillet is not formed at the periphery of the brazing surface, repeated stress is applied to the joint interface due to the thermal cycle when the heat exchange system is used, and cracks occur in the brazing material present at the joint interface due to cycle fatigue. The possibility of entering is increased.
Accordingly, the present inventors have achieved a stable fillet at the periphery of the brazing surface, without the need to apply flux to the surface of the brazing material and the brazing surface of the aluminum alloy member, at a lower cost than in the prior art. The present invention has been reached in the process of earnestly studying the surface brazing method capable of forming the film.
Details will be described below.

First, in the present invention, a single-layer brazing sheet is sufficiently formed in a state in which a single-layer brazing sheet made of a brazing material is sandwiched between two aluminum alloy members and the surface is in contact with each other without applying flux on the brazing surface. It melt | dissolves and wets the interface between aluminum alloy members with a brazing material, and is going to carry out surface brazing.
Of the two aluminum alloy members, one aluminum alloy member may be an aluminum alloy plate, or both may be aluminum alloy plates. For example, an engaging portion may be provided so that parts made of aluminum alloy can be connected to each other, and a portion where the single-layer brazing sheet is sandwiched may be provided in the engaging portion. In short, in the present invention, the material to be joined is not limited to the aluminum alloy plate, and any material may be used as long as it is made of an aluminum alloy having a smooth surface that can be brazed at least partially.

When brazing using an Al—Si—Mg brazing material, it is necessary to braze at a temperature of 580 ° C. or higher in order to sufficiently dissolve the brazing material. For this reason, as an aluminum alloy member which is a to-be-joined material, what consists of an aluminum alloy whose solidus temperature is 610 degreeC or more is preferable. Specifically, AA1000 type is preferable.
When the solidus temperature of the aluminum alloy member to be joined is less than 610 ° C., a part of the aluminum alloy member is melted during brazing heating, and the applied aluminum alloy The member itself may be deformed.
A more preferable solidus temperature of the aluminum alloy member is 615 ° C. or higher. A more preferable solidus temperature of the aluminum alloy member is 620 ° C. or higher.

The first feature of the present invention is that a brazing sheet comprising a single layer of brazing material having a predetermined composition and thickness is used to reduce costs.
Therefore, first, a brazing material and a brazing sheet using the same as a thin plate will be described.
As the brazing material, an alloy containing Si: 3.0 to 12% by mass, Mg: 0.1 to 0.35% by mass, and the balance being composed of Al and inevitable impurities is used.

Si: 3.0 to 12% by mass
Si is an element for lowering the liquidus temperature of the single-layer brazing sheet depending on its content and improving wettability during surface brazing. If the amount of Si contained in the brazing material is less than 3.0% by mass, the temperature of the liquidus of the single-layer brazing sheet becomes too high, and even if a predetermined brazing temperature is reached, the single-layer brazing sheet There is a possibility that dissolution is insufficient and sufficient brazing strength cannot be obtained. When the amount of Si contained in the brazing material exceeds 12% by mass, there is a high possibility that primary Si precipitates (crystallizes) in the center of the ingot during casting, and a healthy hot-rolled sheet was obtained. However, it becomes difficult to obtain a single layer brazing sheet having a microscopically homogeneous structure.
Therefore, the Si content of the brazing filler metal is in the range of 3.0 to 12% by mass. A more preferable Si content is in the range of 4.0 to 12% by mass. A more preferable Si content is in the range of 5.0 to 12% by mass.

Mg: 0.1 to 0.35% by mass
Since Mg acts as a reducing agent when oxidized itself, Mg suppresses the oxidation of aluminum at the interface between the aluminum alloy plate and the brazing material of the single-layer brazing sheet by brazing heating, and wets during surface brazing. It is considered to be an element for improving the properties.
If the amount of Mg contained in the brazing material is less than 0.1% by mass, although depending on the brazing temperature and the like, the effect is insufficient and sufficient brazing strength may not be obtained. When the amount of Mg contained in the brazing material exceeds 0.35% by mass, the molten flux diffused to the periphery of the brazing surface contacts the molten brazing material during the brazing heating and reacts with Mg contained in the brazing material. By doing so, the function of a flux is impaired and a healthy fillet is not formed.
Therefore, the Mg content of the brazing filler metal is in the range of 0.1 to 0.35% by mass. A more preferable Mg content is in the range of 0.1 to 0.32% by mass. A more preferable Mg content is in the range of 0.1 to 0.3% by mass.

Inevitable impurities include Fe, Cu, Mn, Zn, and the like. For these elements, Fe: less than 1.0% by mass, Cu: less than 1.0% by mass, Mn: less than 1.0% by mass, If it is the range of less than Zn: 1.0 mass%, the effect of this invention will not be prevented. Therefore, the content of the components as inevitable impurities is preferably less than 1.0% by mass.

Other impurity elements include Cr, Ni, Zr, Ti, V, B, Sr, Sb, Ca, Na, etc., but Cr: less than 0.5 mass%, Ni: less than 0.5 mass% , Zr: less than 0.2% by mass, Ti: less than 0.2% by mass, V: less than 0.1% by mass, B: less than 0.05% by mass, Sr: less than 0.05% by mass, Sb: 0.0% by mass. If it is in the range of less than 05% by mass, Ca: less than 0.05% by mass, and Na: less than 0.01% by mass, the performance characteristics of the single-layer brazing sheet according to the present invention will not be significantly hindered. It may be contained as an impurity. About Pb, Bi, Sn, and In, each is less than 0.02 mass%, and each other is less than 0.02 mass%. Even if it contains an element outside the control in this range, the effect of the present invention is not hindered. .

Single-layer brazing sheet made of brazing material In the present invention, the brazing material is made into a thin plate and used as a single-layer brazing sheet. The thickness should just be the thickness which can achieve sound surface brazing. If the thickness is less than 15 μm, sufficient brazing strength may not be obtained. When the thickness exceeds 200 μm, the amount of the brazing material that oozes out from the joint surface becomes too large, resulting in an increase in cost.
Therefore, the thickness range of the single-layer brazing sheet made of the brazing material is 15 to 200 μm. A more preferable thickness range is 15 to 150 μm. A more preferable thickness range is 20 to 100 μm.

Manufacturing method of single layer brazing sheet made of brazing material For example, a single layer brazing sheet made of brazing material having a thickness of 100 μm is manufactured as follows.
Ingots, scraps, and the like as raw materials are blended and put into a melting furnace to melt a molten aluminum having a predetermined brazing material composition. The melting furnace is generally a burner furnace in which the raw material is heated and melted directly by a burner flame. After the molten aluminum reaches a predetermined temperature, for example, 800 ° C., an appropriate amount of the flux for removing the debris is added, and the molten metal is stirred with a stirring rod to dissolve all raw materials. After that, an additional raw material, such as Mg, is added for component adjustment, and after calming for about 30 to 60 minutes, the metal soot floating on the surface is removed. After the molten aluminum is cooled to a predetermined temperature, for example, 740 ° C., the molten aluminum is poured out from the hot water outlet into a bowl, and if necessary, casting is started through an inline rotary degasser, a CFF filter, and the like. In the case where a melting furnace and a holding furnace are provided side by side, after the molten metal melted in the melting furnace is transferred to the holding furnace, casting is started after further sedation or the like in the holding furnace.

The jacket of the DC casting machine may be a single pour, but may be a multi-pour that places importance on production efficiency. For example, while pouring through a dip tube and a float into a water-cooled mold having a size of 700 mm × 450 mm, the lower mold is lowered at a casting speed of 60 mm / min, and direct water cooling (Direct Chill), the molten metal in the sump is solidified and cooled to obtain a slab having a predetermined size, for example, 700 mm × 450 mm × 4500 mm. After the end of casting, the front and rear ends of the slab were cut and double-sided with 25 mm on one side. The 400 mm thick slab was inserted into a soaking furnace and homogenized at 450 to 540 ° C. for 1 to 12 hours ( HO treatment). After the homogenization treatment, the slab is taken out of the soaking furnace and subjected to several passes of hot rolling with a hot rolling mill to obtain, for example, a 6 mm thick hot rolled plate coil (Reroll).

The 6 mm thick hot rolled plate coil is subjected to several passes of cold rolling to obtain a single layer brazing sheet made of a brazing material having a predetermined thickness, for example, 100 μm. In the cold rolling process, if the work hardening of the cold rolled sheet is significant, a coil is inserted into the annealer as necessary, and an intermediate annealing process at a holding temperature of 300 to 450 ° C. is performed to perform cold rolling. It is desirable to soften the plate.

The second feature of the present invention is the surface of one of the aluminum alloy members having a large area in plan view without applying a flux to the brazing surface of the single-layer brazing sheet and the aluminum alloy member, It is in the point which applies a flux to the area | region spaced apart from the periphery of the attaching surface.
Then, the application | coating form of a flux is demonstrated next.
In addition, the brazing surface in this specification is the surface which is in contact with the other aluminum alloy member among the surfaces of the single-layer brazing sheet in an assembled state before brazing heating, or one aluminum alloy member. Means the surface overlapping with the other aluminum alloy member in plan view.

In general, when flux is applied to the brazing surface of a single-layer brazing sheet and an aluminum alloy member, void defects are likely to occur on the brazing surface as described above, and the flux may be contained. There is. Specifically, when the flux is directly applied to the contact surface between the other aluminum alloy member and the brazing material, or the surface of one aluminum alloy member that overlaps the other aluminum alloy member in plan view. The flux melted during the brazing heating is taken into the brazing surface, and the possibility that defects due to the flux occur on the brazing surface increases.

Therefore, in the present invention, the flux is not applied to the brazing surface, but the flux is applied to the surface of one of the aluminum alloy members having a large area in a plan view and separated from the periphery of the brazing surface. Decided to do.
A surface of one aluminum alloy member having a large area in plan view, and applying a flux to a region separated from the periphery of the brazing surface,
If flux is applied to such a region, the applied flux melts during brazing heating, diffuses the surface of one aluminum alloy member having a large area in plan view, and the other aluminum alloy member To the periphery (the periphery of the brazing surface). In this way, the molten flux that has reached the periphery of the brazing surface stays at the periphery as it is, and improves the wettability between the molten brazing material and the aluminum alloy member without penetrating the brazing surface. A healthy fillet is formed on the periphery of the affixing surface.

Of course, the flux may be applied as long as it is a surface not in contact with the single-layer brazing sheet among the surfaces of one of the aluminum alloy members having a large area in plan view in the assembled state before brazing heating. Moreover, even if it is a surface which is in contact with the single-layer brazing sheet among the surfaces of one aluminum alloy member having a large area in plan view, it is a surface that does not overlap with other aluminum alloy members in plan view. The flux may be applied because it deviates from the definition of the brazing surface. Even in such a case, since the predetermined surface pressure is applied to the brazed surface after assembly, the flux does not penetrate into the brazed surfaces of the single-layer brazing sheet and the aluminum alloy member. There is a low possibility that the flux will be contained inside the brazing surface during brazing heating.

For example, when a single layer brazing sheet is sandwiched between two aluminum alloy members of different sizes before brazing heating, the surface of the single layer brazing sheet is from the edge of the aluminum alloy member with the smaller area in plan view. There is a case where it is set so as to protrude by a predetermined width. In such a case, the surface of the single-layer brazing sheet protruding from the edge of the aluminum alloy member having the smaller area is not a brazed surface, and therefore flux may be applied on this surface. Even in such a case, after assembling, a predetermined surface pressure is applied to the brazing surface, so that the flux does not penetrate into the brazing surfaces of the aluminum alloy members, and brazing. It is unlikely that the flux will be contained inside the brazing surface during heating. Further, the melted flux tends to stay at the edge of the brazing surface, and improves the wettability of the molten brazing material with the aluminum alloy member without degrading the quality of the brazing surface, thereby forming a healthy fillet.

The brazing surface is preferably a flat surface, but is not necessarily a flat surface. For example, a cylindrical concave surface is formed on one aluminum alloy member having a large area in plan view, and a cylindrical convex surface is formed on the other aluminum alloy member having a small area in plan view. The convex surface can be fitted together, and surface brazing may be performed by sandwiching a single-layer brazing sheet that has been bent into the fitting surface.

In addition, the area | region which applies a flux needs to be slightly spaced apart from the edge of one brazing surface, and is the surface of one aluminum alloy member with a large area by planar view. When the flux application position (the shortest distance from the periphery of the brazing surface to the flux application area) exceeds 35 mm, the molten flux is not sufficiently supplied to the periphery of the brazing surface, depending on the brazing conditions and the amount of flux applied. There is a high probability that a healthy fillet will not be formed.
Considering the flux application accuracy and the like, the preferred flux application position is in the range of 0.5 to 35 mm. A more preferable flux application position is in the range of 0.5 to 30 mm. A more preferable flux application position is in the range of 1.0 to 30 mm.

A preferable flux application amount is in the range of 2 to 40 g / m ² . If the amount of flux applied is less than 2 g / m ² , depending on the flux application position, the supply of flux to the peripheral edge of the brazing surface is insufficient, so that a healthy fillet cannot be formed. Even if the amount of flux applied exceeds 40 g / m ² , the effect of forming a healthy fillet cannot be expected to increase any more, but rather the amount of flux used increases and the production cost increases. A more preferable flux application amount is in the range of 2 to 35 g / m ² .

The application of the flux may be performed by roll-printing a slurry mixed with a solvent, a flux, a binder, and the like from the surface of one aluminum alloy member that has been sealed only in a predetermined region in advance. You may carry out by air-spraying the liquid mixture diluted with the solvent. Alternatively, an appropriate amount of slurry mixed with a solvent, flux, binder, or the like may be applied around the other aluminum alloy member without applying a seal to the aluminum alloy member in advance. Examples of the flux include fluoride-based non-corrosive flux, and typical compound forms include KAlF ₄ , K ₂ AlF ₅ , K ₃ AlF ₆ , AlF ₃ , KF, and CsF. It is more preferable to use these fluxes in combination than to use them alone because they approach the eutectic composition and lower the melting point. As described above, the preferable flux application amount is in the range of 2 to 40 g / m ² .

In order to sufficiently braze the single-layer brazing sheet made of the brazing material of the Al—Si—Mg alloy as described above in an inert gas atmosphere and wet the interface between the aluminum alloy members, It is necessary to hold at a holding temperature of 580 ° C. or higher for a predetermined time.
For this reason, even during brazing heating, it is necessary to perform surface brazing in an inert gas atmosphere in order to suppress oxidation of the brazing surface of the aluminum alloy member or the brazing material surface of the single-layer brazing sheet. There is.

As the inert gas, nitrogen gas, argon gas, helium gas, or the like can be used. The oxygen concentration in the inert gas is preferably 500 ppm or less. If the oxygen concentration in the inert gas exceeds 500 ppm, the joint strength (shear stress) after surface brazing decreases. A more preferable oxygen concentration in the inert gas is 100 ppm. A more preferable oxygen concentration in the inert gas is 10 ppm or less. Specifically, for the industrial nitrogen gas, since the standard is defined as an oxygen concentration of 10 ppm or less, it is most preferable to use the industrial nitrogen gas from the viewpoint of cost.
Of course, it is preferable to fill the inside of the heating apparatus with an inert gas atmosphere during brazing heating, brazing temperature holding and cooling. However, in the case of rapid heating such as electromagnetic induction heating, the inert gas may be injected to replace the atmosphere in the heating device with the inert gas before reaching a predetermined holding temperature.

In the surface brazing method according to the present invention while applying a surface pressure, a single layer brazing sheet made of a brazing material of an Al—Si—Mg based alloy having a predetermined composition is melted to bring the brazing material and the aluminum alloy member into a surface. Brazing heating is performed in the state of contact, and at this time, it is necessary to maintain a predetermined brazing temperature while applying a surface pressure of 1.0 gf / mm ² or more (0.01 MPa or more) to the joint surface. There is. Of course, it is possible to perform surface brazing by applying a surface pressure of 1.0 gf / mm ² or more to the joint surface after reaching a predetermined holding temperature without applying surface pressure during brazing heating. Good.
When the surface pressure is less than 1.0 gf / mm ² , sufficient brazing strength cannot be obtained. Of course, in order to sufficiently secure the brazing strength after the surface brazing, it is preferable that the surface pressure applied to the joint surface is high. Therefore, a more preferable surface pressure is 5.0 gf / mm ² or more (0.05 MPa or more). A more preferable surface pressure is 10 gf / mm ² or more (0.1 MPa or more).

In the surface brazing method according to the present invention while maintaining a predetermined brazing temperature, a single-layer brazing sheet (brazing material) having a predetermined composition is dissolved to wet the interface between the aluminum alloy members, thereby reliably brazing. In order to perform brazing and secure sufficient brazing strength, it is necessary that the brazing temperature is at least 580 ° C. or higher.
When the brazing temperature is less than 580 ° C., the brazing material is not sufficiently dissolved, and sufficient brazing strength cannot be obtained. Of course, higher brazing strength can be obtained when the holding temperature is higher. Therefore, a more preferable holding temperature is 585 ° C. or higher. A more preferable holding temperature is 590 ° C. or higher.
The holding time at the brazing temperature is preferably 2 minutes or more. Although depending on the brazing temperature, if the holding time is less than 2 minutes, sufficient brazing strength cannot be obtained due to uneven temperature at the joint surface. A more preferable holding time is 5 minutes or more.

Preparation of Single-layer Brazing Sheet Various predetermined ingots were weighed and blended, and 9 kg (total 5 samples) of raw materials were charged into a # 30 crucible coated with a release material. These crucibles were inserted into an electric furnace and melted at 760 ° C. to remove the soot, and then the molten metal temperature was kept at 740 ° C. Next, degassing treatment was performed by blowing nitrogen gas into the molten metal at a flow rate of 1 Nl / min for 10 minutes with a small rotary degassing apparatus. Thereafter, the sedation was performed for 30 minutes, and the cocoon floating on the surface of the molten metal was removed with a stirring rod, and a disk sample was collected with a spoon as a mold for component analysis.
Next, the crucible was sequentially taken out from the electric furnace using a jig, and molten aluminum was cast into five molds (70 mm × 70 mm × 15 mm) preheated to 200 ° C. The disk sample of each brazing material sample was subjected to composition analysis by emission spectroscopic analysis. The results are shown in Table 1.

The ingot was chamfered by 3 mm after cutting the hot water to a thickness of 9 mm. The ingot is charged into an electric heating furnace, heated to 480 ° C. at a heating rate of 100 ° C./hr, homogenized at 480 ° C. for 1 hour, and then 3 mm thick by a hot rolling mill. Hot rolling was applied.
Thereafter, the hot-rolled plate was cold-rolled to obtain a cold-rolled plate having a thickness of 1.2 mm, and subjected to a primary intermediate annealing at 390 ° C. × 2 hours for softening. Further, it was cold-rolled to obtain a cold-rolled sheet having a thickness of 0.3 mm, and subjected to secondary intermediate annealing at 390 ° C. × 2 hours for softening. Further, cold rolling was performed to obtain a final cold rolled plate having a thickness of 0.06 mm (60 μm). This final cold-rolled sheet was cut into a predetermined size (26 mm × 26 mm) to obtain a plurality of single-layer brazing sheets.

Production of Test Piece As shown in FIG. 1, a seal (27 mm × 27 mm) was attached to the center of a 40 mm × 40 mm surface of a block A (40 mm × 40 mm × 4 mm) made of AA1050 alloy, and the mass was measured. Furthermore, a predetermined amount was applied onto a 40 mm × 40 mm surface by spraying a mixed solution of fluoride flux and water, and the mass was measured after drying at 200 ° C. The mass difference after fluxing before / coating is divided by application area ^{^{(1.6 × 10 3 mm 2)}} , it was calculated flux application amount (g / ^{m 2).} Further, the seal is peeled off, and a single-layer brazing sheet (25 mm × 25 mm × 60 μm) is placed on the center of the surface where the flux is not applied (27 mm × 27 mm), and further the single-layer brazing sheet (25 mm × 25 mm). A surface of 25 mm × 25 mm in AA1050 alloy block B (25 mm × 25 mm × 3 mm) was overlapped on the center of the surface.

As shown in FIG. 2, using a jig, a disc spring was set on the upper surface of the block B, a pressure of 1.5 MPa was applied, and the assembled block or the like was inserted into the test furnace. While measuring the actual temperature with a thermocouple attached to block A, heating to 600 ° C. at a rate of 50 ° C./min by PID control, holding at a brazing temperature of 600 ° C. for 5 minutes, and then outputting to the resistance wire The assembled block and the like were furnace-cooled with OFF. After the thermocouple attached to the block A showed 500 ° C. or lower, the assembled block and the like were taken out of the furnace and cooled to room temperature. The atmosphere during heating was adjusted using industrial nitrogen gas (nitrogen having an oxygen concentration of 10 ppm or less).

3. Measurement of fillet formation rate As shown in FIG. 3, in the block AB after brazing, the cross-sectional microstructure was observed at 6 points marked with ◯, and the fillet formation rate was measured. The fillet formation rate here is a value obtained by dividing the number of locations where healthy fillets are formed in the block AB after brazing by 6 of all the observed locations. Whether or not a healthy fillet was formed was determined by measuring the “throat thickness” of the fillet portion as shown in FIG. Where a fillet with a throat thickness of 150 μm or more was observed, it was determined that a healthy fillet was formed. A place where a fillet with a throat thickness of less than 150 μm was observed, or a place where no fillet was observed at all was determined as a healthy fillet was not formed. FIGS. 5 and 6 show examples of a cross-sectional metallographic structure of a fillet having a “throat thickness” of 150 μm or more, and a cross-sectional metallographic structure of a fillet having a “throat thickness” of less than 150 μm, respectively.

As described above, on the fillet formation rate, (1) the influence of the amount of Mg added in the brazing material, (2) the influence of the flux application position (the shortest distance from the periphery of the block B to the flux application area), (3 ) The effect of flux application amount was investigated. However, (2) When investigating the influence of the flux application position, the size of the block A is changed (48 mm × 48 mm × 4 mm, 68 mm × 68 mm × 4 mm, 98 mm × 98 mm × 4 mm, 118 mm × 118 mm × 4 mm) Also, the flux application position was adjusted by using seals of various sizes (35 × 35 mm, 55 × 55 mm, 85 × 85 mm, 105 × 105 mm).

The results are shown in Tables 2 to 4 and FIGS. In addition, in the charts of the examples shown below, for those where there is no indication of detailed conditions, a C alloy brazing material (Mg addition amount: 0.19 mass%) is used, and the flux application position is set to 1 mm. Then, the amount of flux applied was set to 10 g / m ² , and brazing was performed under the above brazing conditions to produce the joining block AB.

As shown in Table 2 and FIG. 7, regarding the influence of the amount of Mg added in the brazing filler metal on the fillet formation rate, if the amount of Mg contained in the brazing filler metal is 0.29% by mass or less, the fillet formation rate is 6/6 (100%). When the amount of Mg contained in the brazing material was 0.51% by mass, the fillet formation rate was 2/6 (33%). Considering that there is a possibility that sufficient brazing strength may not be obtained when the amount of Mg contained in the brazing material is less than 0.1% by mass, the preferable Mg content of the brazing material is 0.1 to 0. The range is .35% by mass.

As shown in Table 3 and FIG. 8, regarding the influence of the flux application position (the shortest distance from the periphery of the block B to the flux application area) on the fillet formation rate, fillet formation is achieved if the flux application position is 30 mm or less. The rate was 6/6 (100%). Further, when the flux application position was 40 mm, the fillet formation rate was 0/6 (0%). Considering the flux application accuracy and the like, the preferred flux application position is in the range of 0.5 to 35 mm.

As shown in Table 4 and FIG. 9, regarding the influence of the flux application amount on the fillet formation rate, if the flux application amount is 3 g / m ² or more, the fillet formation rate is 6/6 (100%). It was. Further, even when the flux application amount is 1 g / m ² , the fillet formation rate is 5/6 (83%), and the fillet formation rate when the flux is not applied is 1/6 (17%). It is clear that it contributed to the improvement of fillet formation rate. Even if the application amount of the flux exceeds 40 g / m ² , the effect of forming a healthy fillet cannot be expected to increase any more. Considering that the amount of use of the flux increases and the production cost increases, A preferable flux application amount is in the range of 2 to 40 g / m ² .

As described above, according to the present invention, it is possible to provide a surface brazing method capable of brazing two aluminum alloy members to each other with a single layer brazing sheet and further forming a healthy fillet at the periphery of the brazed surface. .

Claims

When performing a surface brazing of aluminum alloy members having a solidus temperature of 610 ° C. or more using a single layer brazing sheet made of a brazing material of an Al—Si—Mg alloy, the single layer brazing sheet and the aluminum The flux is not applied to the brazing surface with the alloy member, but the flux is applied to the surface of the aluminum alloy member having a larger area in plan view and spaced from the periphery of the brazing surface. In a state where the layer brazing sheet is sandwiched between the aluminum alloy members and brought into contact with each other, the aluminum alloy members are brazed while applying a surface pressure while maintaining a predetermined brazing temperature in an inert gas atmosphere. A surface brazing method for an aluminum alloy member.
The brazing material of the Al—Si—Mg alloy includes Si: 3.0 to 12% by mass, Mg: 0.1 to 0.35% by mass, and the balance is composed of Al and inevitable impurities. The method for brazing aluminum alloy members according to claim 1, wherein an alloy is used.
The method for brazing an aluminum alloy member according to claim 1 or 2, wherein the distance from the periphery of the brazing surface is in the range of 0.5 to 35 mm.
The method for brazing an aluminum alloy member according to any one of claims 1 to 3, wherein a coating amount of the flux is 2 to 40 g / m 2 .