JP2006326621A - Solder material wire for soldering aluminum alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solder material wire at low cost, which solder material wire is excellent in machinability, and can solder an aluminum alloy casting product at a soldering temperature of 530 to 560°C. <P>SOLUTION: A hollow sheath 1 made of an Al-Si alloy is filled with a Cu wire material 2 together with fluoride-based non-corrosive flux powder 3 containing cesium fluoride. When the sheath is made of an Al-Si alloy plate containing 5 to 15 mass% of Si, and the Cu wire material supplied in the sheath has become an Al-Cu-Si ternary alloy by being alloyed with the sheath material, it is preferable that the Cu wire material has a diameter corresponding to that containing 22 to 37 mass% of Cu in the ternary alloy. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a brazing wire used for brazing an aluminum alloy, and relates to a brazing material wire for brazing an aluminum alloy in which a flux is filled in an aluminum alloy sheath.

Generally, an aluminum-silicon alloy (Al-Si alloy) is used for cast products. This Al-Si alloy has a lower melting point than that of pure aluminum, and can be manufactured in a complicated shape with a mold, so that it is used for applications such as pistons and cylinder heads. In addition, it is used for applications such as building panels by utilizing the gray color.
Even when used in these applications, a plurality of casting parts are combined and used. There are various means as a method for joining aluminum alloy cast parts. However, when the joining surface is complicated or airtightness is required, the brazing method is heavily used.

As a brazing method for an aluminum material, a method using a potassium fluoride-based non-corrosive flux (commonly called “Nocolok” (registered trademark)) and an Al—Si based brazing material is widely known.
However, this “Nocolok” brazing method uses a flux having a eutectic composition of KF and AlF ₃ . Since the melting point of the eutectic point of KF and AlF ₃ is 560 to 570 ° C., and the melting point of JIS A4045 and A4047 Al—Si alloys used as the brazing material is 577 ° C. It is heated to about 600 ° C., which is about 30 ° C. higher than the melting point of the material.
By this heating, the oxide film on the surface of the aluminum material is dissolved and removed by the molten potassium fluoride-based flux, the wettability with the brazing material is extremely improved, and the flow diffusion of the molten brazing material is promoted. The brazing material that has flowed to the part where the joints are in contact with each other forms a fillet to join the members to be brazed.

  However, in the case of an aluminum alloy cast part, the member to be joined is an Al—Si alloy of the same system as the brazing material. For this reason, at the brazing temperature of 600 ° C. when the potassium fluoride-based flux is used, there arises a problem that the parts to be joined themselves melt and the product shape cannot be maintained. Since this brazing temperature problem can be solved by lowering the brazing temperature below the melting point of the aluminum alloy, conventionally, countermeasures for lowering the melting point of the brazing material and lowering the melting point of the flux have been taken.

Regarding the flux, a cesium fluoride-based non-corrosive flux having a melting point lower than that of the potassium fluoride-based flux has been developed.
On the other hand, as a low melting point brazing material, a Zn—Al alloy having a melting point of around 480 ° C. has been known for a long time. However, in recent years, development of an Al—Cu alloy brazing material having a melting point of 520 ° C. to 550 ° C. has been reported because the flowability of the solder is poorer than the Al—Si alloy and the corrosion resistance of the fillet is inferior.
Further, as a method of supplying flux and brazing material to the brazed joint, a brazing material wire containing or containing flux has been proposed in order to improve work efficiency.

For example, Non-Patent Document 1 proposes a cored wire in which a brazing aluminum alloy material (JIS A4047) is used as a sheath and the core is filled with a “Nokorok” flux or a cesium fluoride non-corrosive flux.
In Patent Document 1, an aluminum material or an alloy thereof (JIS A1000 series) is used as a sheath, and a metal powder such as copper, silicon, or zinc is mixed at a predetermined ratio with a “Nokorok” flux or a cesium fluoride noncorrosive flux. A brazing wire filled in the sheath core has been proposed.
Furthermore, in Patent Document 2, each metal powder for obtaining an Al—Cu—Si ternary alloy composition and a cesium fluoride-containing fluoride-based non-corrosive flux powder are enclosed in an aluminum can and 400 ° C. under vacuum. The production of a flux-containing aluminum alloy brazing material obtained by extruding a solid material heated and pressed into a wire is described.
“Industrial Materials”, published by Nikkan Kogyo Shimbun, June 2003 (Vol.51, No.6) p.90-91 US Pat. No. 5,418,072 JP-A-8-164492

However, the brazing wire proposed in Non-Patent Document 1 also has a brazing temperature of about 600 ° C. because an A4047 alloy having a melting point of 577 ° C. is used as the brazing material. For this reason, it cannot be used for brazing of an aluminum alloy casting having a melting point lower than 600 ° C.
Further, in the brazing wire proposed in Patent Document 1, if copper is selected as the metal powder to be filled in the sheath, the melting point becomes an alloy composition of around 550 ° C., and brazing at a temperature of about 570 ° C. is possible. Cannot be used for brazing castings having a temperature lower than 570 ° C. In order to apply to a wider range of casting alloys, it is necessary to fill a mixed powder of a plurality of metals such as copper and silicon to obtain a brazing material having a lower melting point. However, when mixing and filling a plurality of metal powders, filling in a uniform mixed state is very difficult due to the difference in particle size distribution and specific gravity. Further, since the metal powder to be filled is fine and the total surface area is very large, it is accompanied by a very large amount of oxides that inhibit brazing. For this reason, in order to obtain good brazing properties, it is necessary to use a large amount of flux, which causes an increase in manufacturing cost.

  Furthermore, the wire-forming flux-containing aluminum alloy brazing material proposed in Patent Document 2 can be brazed at a temperature of about 550 ° C. because the melting point of the brazing material is as low as about 530 ° C. However, there is a difficulty in the manufacturing process, and the powder forming wire containing the flux has poor formability, and the bending process into the shape along the joint part of the casting, such as a ring shape, is also possible from the examples described in the same document. As can be seen, it must be carried out at a high temperature of 400 ° C., leading to an increase in manufacturing cost.

As described above, in the conventional brazing material, when Al—Si alloy castings are brazed and joined, as a result, an element composition that forms an Al—Cu—Si ternary alloy with a low melting point of the brazing material Even if the composition is achieved, the productivity cannot be improved, the manufacturing cost is high, and the processability is low, so that the usability is not good.
The present invention has been devised to solve such problems, and has a low brazing wire that is excellent in workability and enables brazing of an aluminum alloy casting at a brazing temperature of 530 to 560 ° C. The purpose is to provide at a cost.

In order to achieve the object, a brazing filler metal wire for an aluminum alloy brazing of the present invention includes a hollow sheath constructed from an Al-Si based alloy material, and a fluoride system including cesium fluoride filled in the sheath. It consists of a non-corrosive flux powder and Cu wire.
The sheath is constructed from an Al—Si based alloy plate containing 5 to 15% by mass of Si, and a Cu wire filled in the sheath is alloyed with the sheath material to form an Al—Cu—Si ternary alloy. When it becomes, it is preferable to have a diameter corresponding to 22 to 37 mass% Cu in the ternary alloy. In addition, the number of Cu wires filled in the sheath may be one or more, and the total cross-sectional area of the Cu wires is a diameter corresponding to 22 to 37 mass% Cu in the ternary alloy. What is necessary is just to have.

In the present invention, the brazing filler metal component is divided into a sheath portion made of an Al—Si based alloy material and a Cu wire filled in the sheath. For this reason, the alloy composition which has a melting point of about 525-530 degreeC can be produced easily by adjusting mass ratio of both materials.
As a result of reducing the melting point of the brazing material, it becomes possible to braze at about 550 ° C. in combination with the use of a low melting point flux, and aluminum alloy castings, especially Al-Si alloy castings, can be easily brazed at a low brazing temperature. Can be brazed. Further, since the brazing material is divided into the Al—Si alloy material and the Cu wire material, the brazing material can be processed in a soft state, and a brazing material having a desired shape along the joining portion is provided at low cost.
In summary, by providing the brazing wire according to the present invention, the brazing operation of the aluminum alloy member can be performed with high productivity and low cost.

The inventors of the present invention have studied measures for improving the brazing material wire in consideration of lowering the melting point and improving workability.
As a result, a technique using a fluoride non-corrosive flux containing cesium fluoride is adopted for lowering the melting point of the flux. This will be described in detail later.
For lowering the melting point of the brazing material, it is effective to make the best use of the fact that the ternary eutectic composition of Al—Cu—Si has a melting point of 525 ° C. However, the Al—Cu—Si ternary eutectic alloy has extremely poor plastic workability. Therefore, not only is it difficult to form the sheath of the brazing wire, but even if the wire can be constructed, it is difficult to bend it into a shape along the joint part.

Therefore, in the present invention, the three components are separately supplied as an Al—Si alloy material and a Cu material so as to produce an Al—Cu—Si ternary eutectic alloy when heated by brazing. . And as a means, as shown in FIG. 1, the aspect supplied with the form of the sheath material 1 which consists of an Al-Si type-alloy material, and the Cu wire 2 with which it was filled was employ | adopted. Reference numeral 3 denotes a fluoride-based non-corrosive flux powder filled in the sheath together with the Cu wire.
By using a sheath material made of an Al—Si alloy material and a Cu wire filled therein, Al—Si alloy and Cu react (eutectic) during brazing heating, and an Al—Cu melting point of 525 ° C. -Si ternary eutectic solder can be produced. As a result, brazing can be easily performed in a low temperature range of 530 to 560 ° C.

Moreover, by filling the sheath with Cu wire in advance, the amount of the oxide film that is normally formed on the surface and inhibits brazing can be reduced, and the amount of flux to be filled can also be reduced.
Furthermore, both the Al—Si based alloy material and the Cu wire constituting the brazing material have good plastic workability. Even after the Cu wire is filled in the sheath material made of an Al-Si alloy material, good plastic workability is maintained. In addition to easy flux filling, bending according to the joint shape of the brazed body can be easily performed. And even when using an automatic torch brazing apparatus, continuous supply can be performed without problems.

  In order to facilitate the formation of eutectic brazing when the sheath is filled with a wire as described above, the Al—Si based alloy plate constituting the sheath has a Si content of 5 to 15% by mass. Thus, the ratio of the Al—Si based alloy plate to the Cu wire is preferably adjusted so that the mass of Cu with respect to the Al—Cu—Si ternary alloy used as the brazing material corresponds to 22 to 37% by mass. If the amount of Si and / or Cu is out of these numerical ranges, the resulting braze composition and the Al—Cu—Si ternary eutectic composition (Cu; 26.7 mass%, Si; 5.3 mass%) ) Becomes too large, and brazing in the temperature range of 530 to 560 ° C. becomes difficult.

JIS A4343, A4045, A4047, 4N43, 4N45 etc. can be used as an Al-Si system alloy material with Si content of 5-15 mass%.
Since the specific gravity of Cu is 8.9 and the specific gravity of Al-Si alloy is 2.7, the mass of Cu wire is 22-37% by mass with respect to the Al-Cu-Si ternary alloy used as the brazing filler metal. When the cross-sectional area is 100, it can be satisfied by setting the cross-sectional area of the Cu wire to 8.6 to 17.8.

Filling the inside of the sheath with a flux is also performed by a normal method.
As the filling flux, a flux having a low melting point and excellent non-corrosiveness is used. In order to omit the flux residue removal step after brazing, it is necessary to use fluoride-based non-corrosive flux powder. Further, in order to lower the melting point of the flux to the melting point of 525 ° C. or lower of the Al—Cu—Si ternary eutectic brazing alloy, it is essential to contain cesium fluoride (CsF).

The compound form of the fluoride-based non-corrosive flux includes KAlF ₄ , K ₂ AlF ₅ , K ₃ AlF ₆ , AlF ₃ , KF, CsF, etc., but a mixture thereof is used as in the conventional case.
The proportion of cesium fluoride (CsF) in the fluoride-based non-corrosive flux is more advantageous in terms of cost, but if it is less than 10 mol%, the effect of lowering the melting point of the flux is not sufficient. Brazing at 530 to 560 ° C becomes difficult. Therefore, the proportion of cesium fluoride (CsF) in the fluoride-based non-corrosive flux is preferably 10 mol% or more.

Since the brazing filler metal wire for brazing aluminum alloy of the present invention uses a brazing filler metal having a small oxide film, brazing is possible even with a small amount of filled flux.
The mass of the flux relative to the mass of the brazing wire, so-called filling rate, does not need to be specified in particular, and it is sufficient if it is 20 to 40%, which is the same as the filling rate of the conventional cored wire.

  As described above, a brazing material for brazing aluminum alloy in which an Al-Si alloy material is used as a sheath and a cesium fluoride is contained therein and the melting point is lowered to fill the fluoride non-corrosive flux and Cu wire. When the wire is heated, first, the fluoride non-corrosive flux having a low melting point is melted at a temperature of 440 to 510 ° C., and the oxide film on the sheath, the Cu wire, and the brazed body joint is removed. When further heated to exceed the Al-Cu-Si ternary eutectic temperature of 525 ° C, the sheath Al-Si alloy and Cu react (eutectic) and Al-Cu-Si ternary eutectic An alloy braze is formed, and the molten braze flows into the brazed joint at a brazing temperature of 530 to 560 ° C., and good brazing is achieved.

Next, an example is shown in which a brazing wire in which the cross-sectional area ratio of the Al—Si alloy material as the sheath and the Cu wire filled therein is variously changed is actually manufactured and a brazing test is performed.
Preparation of Al-Si alloy plate for sheath material, Cu wire rod and flux JIS A4045 plate with a thickness of 10 mm, hot rolling, intermediate annealing, cold rolling, final annealing, and a thickness of 0.3 mm An Al—Si based alloy plate for a sheath material was produced.
Separately from the alloy plate for the sheath, Cu wires having various diameters were prepared.
Furthermore, as a flux to be filled in the sheath, a K—Cs—Al—F fluoride non-corrosive flux containing 48 mol% of cesium fluoride (Daiichi Rare Element Industries Co., Ltd .; trade name “CF-2” ") A powder was prepared.

Production of brazing material wire The above Al-Si alloy plate for sheath material is cut into a width of 5.3 mm and a length of 200 mm, a Cu wire material of a length of 200 mm is disposed on the upper surface thereof, and passed through a forming roll stand for the sheath material. Fluoride-based non-corrosive flux powder is supplied onto the curved plate material from above while curving with the upper surface of the Al-Si-based alloy plate facing inward, and finally passed through a forming roll stand, and finally fluoride-based non-corrosive flux powder. A brazing wire having a diameter of 2.0 mm filled with Cu wire was prepared. In addition, the filling rate of the flux was 20-30 mass%.
As a reference example, a brazing wire not filled with a Cu wire was also produced.

Brazing test thickness 1 mm, width 25mm, and the JIS-A3003 aluminum alloy plate length 55mm and the lower plate, thickness 1 mm, width 25mm, inverted T-where the JIS-A3003 aluminum alloy sheet of length 25mm and vertical plates A mold brazing test piece was assembled, and the brazing wire was cut into a length of 20 mm on one side of the line of intersection between the lower plate and the vertical plate. This assembly was heated in a nitrogen gas atmosphere furnace to 550 ° C. at a heating rate of 50 ° C./min, held at 550 ° C. for 3 minutes, and then cooled to room temperature at about 100 ° C./min.

Brazing property evaluation The brazing property was determined by observing the appearance of the inverted T-shaped test piece with the naked eye and a stereomicroscope and observing the erosion state of the base by observing the cross section at the center of the joint with an optical microscope.
Appearance evaluation of the joint was made with a fillet with a sufficiently large size on both the brazing wire set side and the opposite side, and a part of the sheath material remaining on the brazing wire set side or the fillet on the opposite side △ is a small one, and × is a case where no wax is generated.
Further, the erosion state of the substrate is measured by measuring the maximum depth of erosion (that is, melting of the substrate) due to the molten wax, and the maximum depth is 0.1 mm or less, and the maximum depth is 0.1 to 0. A sample having a maximum depth of 0.3 to 0.5 mm is indicated by ◯, and a sample having a maximum depth of 0.5 mm or more is indicated by ×.
The evaluation results are shown in Table 2.

As can be seen from the results in Table 2, the present invention is No. In the case of brazing using 2 to 5 brazing material wires, the brazing material is brazed well, and both the brazing material wire set side and the opposite side are well brazed. The erosion of the base generated on the brazing wire set side was also 0.3 mm or less.
On the other hand, No. 1 which is a comparative example and has a small Cu ratio. In the case of brazing using one brazing wire, a large amount of the sheath material remained on the brazing wire set side, and few brazes flowed on the opposite side. In addition, No. with a large Cu ratio. In the case of brazing using the brazing material wire No. 6, the base on the brazing wire set side was severely eroded. This is because if the ratio of Cu to the sheath material becomes too large, Cu of the brazing wire becomes excessive and reacts (eutectic) with the underlying aluminum alloy to be bonded to form an Al—Cu—Si ternary eutectic. As a result, it is presumed that severe erosion (erosion = melting) occurred in the substrate as a result.

In addition, No. which is a conventional product not containing Cu. In the case of brazing using the brazing material wire No. 7, although the oozing of the melted flux was seen, the brazing material wire remained in its original shape and no brazing was formed.
As described above, it can be understood that good brazing can be performed at a low temperature by appropriately adjusting the ratio of the mass of the Cu wire filled in the sheath made of the Al—Si alloy to the sheath.

The figure explaining the cross-sectional shape of the brazing filler metal wire with which Cu wire and the flux were filled in the Al-Si type alloy sheath material

Claims (2)

  For aluminum alloy brazing comprising a hollow sheath constructed from an Al-Si alloy material, a fluoride non-corrosive flux powder containing cesium fluoride filled in the sheath, and a Cu wire. Brazing wire.   The sheath is constructed from an Al—Si based alloy plate containing 5 to 15% by mass of Si, and the Cu wire filled in the sheath is alloyed with the sheath material to form an Al—Cu—Si ternary alloy The brazing filler metal wire for brazing an aluminum alloy according to claim 1, wherein the wire has a diameter corresponding to 22 to 37 mass% Cu in the ternary alloy.

Images