JPH07284982A - Aluminum brazing filler metal - Google Patents

Abstract

PURPOSE:To prevent a molten brazing filler metal from flowing and spreading to parts exclusive of a desired part at the time of brazing by incorporating a specific ratio of a high melting material and flux into an aluminum alloy. CONSTITUTION:The high melting material having the m. p. higher than the m. p. of the aluminum alloy at 0.5 to 80 pts. and the flux at 0 to 15 pts. per 100 pts. aluminum alloy are incorporated into the aluminum alloy. Powder which is the nitride and oxide of aluminum and has an average particle diameter about 10 to 500mum is used as the high melting material. The aluminum alloy having the m. IP. lower than the brazing temp. and the high melting material described above are interposed in the joint parts of aluminum structural members in the presence of the flux as desired and are heated to the specific brazing temp. at the time of brazing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum brazing material and a brazing method used for joining structural members made of aluminum or various aluminum alloys (hereinafter simply referred to as aluminum structural members or structural materials).

[0002]

2. Description of the Related Art In-furnace brazing has been remarkably developed in recent years as a brazing method for aluminum structural members. The reason is that it is suitable for manufacturing heat exchangers made of aluminum structural materials for automobiles, and it is possible to braze hundreds of brazing points in one product in one step. As an example of conventional brazing material of aluminum, a brazing sheet is used for brazing the body of the heat exchanger, a brazing sheet is used for brazing pipes, and the brazing sheet of the heat exchanger is used as the other. Powdered brazing paste is used as an auxiliary material for brazing and as an alternative to the brazing filler metal for brazing pipes. In any form of the aluminum brazing material, an aluminum-silicon alloy brazing material is used as the brazing material composition. This is because the melting point is low and silicon easily diffuses into aluminum, so that the aluminum brazing filler metal spreads and flows, so that brazing can be performed without brazing even when the brazing portion is long. Various patents have been issued up to the present material regarding the composition of the brazing material, and all of them were aimed at improving the brazing property, that is, those which were spread and flowed.

[0003]

These methods are effective when the brazing material portion of the aluminum structural member has no gap, but when there is a gap, for example, in the case of an automobile heat exchanger, a tube is used. When brazing between the header pipe and the header pipe, or between the partition plate inside the header pipe and the header pipe, the gap may be large depending on the machining accuracy. However, since it spreads and flows, the gap cannot be completely filled, resulting in defective brazing, that is, defective products. Also, when brazing a limited part of the aluminum structural members that are in contact, that is,
The same applies to the case of spot brazing, and since the brazing material spreads and flows, one or more limited portions are brazed, so that the conventional aluminum brazing material cannot be used. Flux brazing can be dealt with to some extent by reducing the amount of flux, but in order not to spread the spreading aluminum brazing material, the amount of flux must be the minimum amount at which the aluminum brazing material melts. That is, since the amount of flux becomes the minimum required amount for brazing, brazing may not be possible due to a slight difference in brazing atmosphere, so the control range of the brazing atmosphere becomes extremely narrow.
Since the control becomes difficult, the failure rate naturally increases. Therefore, it is very difficult to carry out industrially.

[0004]

The invention comprises 100 parts by weight of an aluminum braze alloy, a melting point above the melting point of the aluminum brazing alloy, preferably at least 30 ° C. above the melting point of the aluminum brazing alloy, and at least above the brazing temperature. An aluminum brazing material characterized by containing 0.5 to 80 parts by weight of a high melting point substance having a melting point of 20 ° C. or higher, and 0 to 25 parts by weight of a flux, and a melting point higher than that of the aluminum brazing alloy, preferably A high-melting substance having a melting point higher than that of the aluminum brazing alloy by at least 30 ° C. and higher than the brazing temperature by at least 20 ° C. is interposed in the joining portion of the aluminum structural members to be joined in the presence of a flux, if desired. Brazing of aluminum member characterized by heating to brazing temperature Regarding attachment method.

In the present invention, the aluminum brazing alloy melts at the brazing temperature, but the high melting point substance that does not melt at that temperature raises the viscosity of the molten brazing material and makes it difficult to spread.
Particularly when the high-melting point substance is aluminum or its alloy, a solid-liquid coexisting phase is formed on the surface of aluminum, and the surface tension pulls the solid-liquid coexisting phase on the surface of aluminum, so that it does not spread further. This effect is particularly remarkable when the aluminum brazing alloy and the high melting point substance are used in the form of powder particles.

The composition of the aluminum brazing alloy used in the present invention may be any aluminum alloy having a melting point lower than that of the aluminum structural members to be joined and a melting point lower than the brazing temperature. Among them, aluminum-silicon alloy system is preferable, aluminum-silicon (7 to 15%) system, aluminum-silicon (7 to 15%)-X system (X includes at least one of copper, magnesium and zinc). Further, those containing bismuth, tin, barium or the like as the third additional element can be exemplified. When the refractory substance is aluminum, the aluminum-silicon alloy easily diffuses to the surface of the aluminum because silicon easily diffuses to the surface of the non-melting refractory substance, aluminum, which is used at the same time, easily integrates, and flows unnecessarily. It is preferable because the desired part can be brazed without fail. It is particularly preferable that the melting point of these aluminum alloy brazing filler metals is 500 ° C to 590 ° C.

Aluminum braze alloys include plates, foils, rods, grains,
It can be used in various forms such as powder, but as will be described later,
It is typically in powder form. The refractory material used in the present invention has a melting point higher than that of the aluminum brazing alloy, preferably at least 3 above the melting point of the aluminum brazing alloy.
It is a substance having a melting point higher than 0 ° C. and higher than the brazing temperature by at least 20 ° C. or higher. The melting point of the high melting point substance is 620 ° C. or higher (normal brazing of aluminum structural members is performed at 580 to 600 ° C.), preferably 6
It is 30 ° C or higher, more preferably 640 ° C or higher. Since the melting point of the high-melting-point substance mentioned here refers to the liquidus temperature, even when the solidus temperature is lower than the brazing temperature, the liquidus temperature is lower than the brazing temperature.
If it is higher than ℃, it does not become a complete liquid, so there is no problem in use. The high melting point substance is 0.5 to 80 parts by weight, and if it is less than 0.5 parts by weight, there is no effect for preventing the flow from spreading, and if it exceeds 80 parts by weight, the proportion of the high melting point substance increases, This is because it is not possible to completely cover the surface of the high-melting-point substance mixed with the aluminum brazing alloy, so that an unmelted portion, that is, a portion that cannot be brazed is formed.

When the high melting point substance is aluminum or its alloy, aluminum or its alloy having a purity of 95% by weight or more of aluminum and 1% or less of each of silicon and copper is preferable. As a result, during brazing, the aluminum brazing alloy melts, and the molten aluminum brazing alloy first spreads to the surroundings because it flows due to surface tension so as to envelop the unmelted high melting point substance aluminum or its alloy. There is no.

As described above, when the brazing temperature is between the solidus temperature and the liquidus temperature of the high melting point aluminum or its alloy, the high melting point aluminum or its alloy is also in the solid-liquid coexisting phase. However, it is sufficient and effective in increasing the viscosity of the molten wax and inhibiting the fluidity, that is, spreading and flowing. When the high-melting point substance is aluminum having an aluminum purity of 95% or more and silicon and copper are each 1% or less, the compounding amount is 5 to 80 parts by weight, preferably 10 to 60 parts by weight, and more preferably 10 parts by weight. ˜50 parts by weight. The aluminum material added to the present invention has a purity of 95% or more and silicon and copper each have a purity of 1% or less. This is less than this purity, and the melting point is the brazing temperature when the content of silicon and copper is 1% or more. This is because the following may occur.

Aluminum nitride and / or oxide can be used as the high melting point material. These are first
Since it is dispersed in the molten wax, thicken the molten wax,
Make it difficult to spread and flow. After that, since these things are ceramics, they do not get wet with metallic aluminum,
Since it is discharged to the surface of the molten brazing material and does not remain in the brazing material, it does not affect the brazing structure. However, since these are ceramics as described above, a large amount of the compound may impair the brazing property, so the compounding amount is 0.
5 to 10 parts by weight, preferably 0.5 to 8 parts by weight, more preferably 0.5 to 6 parts by weight.

Other than the above, there is no particular limitation, but in the case of brazing with a non-corrosive flux, that is, an aluminum potassium fluoride flux, as an unavoidable impurity to aluminum when the brazing material is aluminum and the high melting point substance is aluminum. It is preferable not to include magnesium other than the magnesium contained. Since the above flux reacts with magnesium due to the presence of magnesium, the performance of the flux deteriorates, and the flux action is impaired as the amount of magnesium increases.
Further, the composition of the aluminum material may be restricted by various brazing methods. Therefore, aluminum having a purity of 99.0% or more is preferable as the high melting point substance. This is because the composition is restricted by various brazing methods as described above, and if the purity is 99.0% or more,
This is because all the restricted elements enter only as unavoidable impurities and are below the upper limit value of the restriction, so that they can be used in any brazing method without any problems. Also, regardless of the shape of aluminum, it is easy to obtain and there is no quantitative restriction,
It is also cheap. A powder is particularly suitable for the shape of the high melting point substance. This is because the powder can be applied to any brazing shape, and in the case of flux brazing, the same application as the flux is possible, so that the number of steps is not increased and it is industrial. Other shapes of high melting point materials may be used depending on the brazing method.

As the flux that can be used in the present invention, aluminum fluoride series is preferable. The aluminum fluoride type referred to here is a flux containing fluorine and aluminum, and is a potassium aluminum fluoride type flux, that is, AlF ₃ -KF, KAlF ₄ -K ₃ Al.
F _6, K ₃ has _{AlF 6, KAlF 4, KF-} AlF 3 -Al 2 O 3 or the like, other can also be exemplified in CsxAlyF ₂ or the like. Aluminum potassium fluoride based flux is particularly preferable.

The blending amount of the above-mentioned flux is 0 to 25 parts by weight. From 0 parts by weight, no flux is required for brazing such as vacuum brazing that does not use flux, so 0 parts by weight is sufficient, and flux brazing depends on the range to be brazed, that is, the range of flow. It can be dealt with by adjusting the amount of flux and the high melting point substance to be added. In this case, the cause of making the spreading flow difficult is the high melting point substance.Therefore, unmelted residue of aluminum braze alloy caused by lack of flux amount does not occur. Absent. Also, it is the oxygen content of the aluminum brazing alloy that affects the amount of flux to be blended, but since the oxygen content varies depending on the shape of the aluminum brazing alloy, timely,
By considering and blending, it is possible to sufficiently cope with the present invention without any problem. If the amount is more than 25 parts by weight, it will spread easily and flow, and a large amount of white residue or black spots will be generated on the surface of the fillet, leading to poor appearance of the product.

Various uses of the aluminum brazing material of the present invention can be considered depending on the combination of the shape of the aluminum brazing alloy and the shape of the refractory material. For example, as a method of filling the gap, an aluminum braze alloy having a rod shape or a shape matched with the gap, in the case of flux brazing, flux is applied, then wrapped with a foil-like high melting point substance and placed at a brazing point, Brazing or placing an aluminum brazing alloy at the brazing location, applying no flux in advance, but applying a mixture of powder high melting point substance and flux, and brazing. Alternatively, an aluminum brazing alloy is also made into a powder, is in the form of paste as described above, and is applied to the brazed portion by overlaying and brazing. Alternatively, a high melting point substance is placed, and a paste of aluminum brazing alloy and flux is applied around the substance. In any case, brazing can be performed to fill the gap by placing it at the brazing point. The same applies to a limited part of brazing, that is, spot brazing. As described above, when both the aluminum brazing alloy and the high melting point substance are powders, the work is completed because the work is completed by one coating step, which is preferable. By using the aluminum brazing material of the present invention as described above, it is very useful as a brazing method such as gap filling brazing and spot brazing of aluminum structural members.

In a typical example of the present invention, both the aluminum brazing alloy and the high melting point substance are made into powder, and this is made into a paste by using a flux and, if necessary, an appropriate organic solvent or organic binder. It is a material. By making it into a paste, handling becomes easy, powder is prevented from scattering, build-up can be performed on the brazing point, and workability is improved. Also, when it is used for filling gaps, it does not fall from the gap because it is pasty. Especially in the brazing material of this form, since the high melting point substance does not melt rapidly at the brazing temperature,
This is a particularly suitable form in that the aluminum braze alloy does not flow out due to a rapid decrease in viscosity even when melted, maintains a build-up state at a desired portion, or does not cause sagging. Further, since the brazing material contains powder, it is possible to impart suitable thixotropy and sagability to the brazing material. As a result, the brazing material can be accurately applied to the desired part, and the other parts can be used without being contaminated.

As the organic binder used for such purpose, those which do not inhibit the brazing of aluminum and do not remain are suitable. In particular, liquid polyisobutylene having a molecular weight of 300 to 2000 and / or its hydrogenated product, and an average molecular weight of 1 containing polyalkylene oxide as a main constituent component
It is suitable to exemplify a liquid of 0,000 to 5,000,000 organic polymers in an organic solvent.

When the high melting point substance is used as a powder, the average particle size is preferably 10 to 500 μm, more preferably 40 to 1 μm.
It is 50 μm, and if it is less than 10 μm, the specific surface area of the powder becomes excessively large, and the oxide film on the surface cannot be completely removed due to the large amount of oxide contained, so the molten aluminum braze alloy melts on the surface of the high melting point substance. It becomes difficult to wear and integrate. On the other hand, if it exceeds 500 μm, the number of powders in the added weight becomes small and the powders are scattered on or in the aluminum brazing alloy, which makes it difficult to spread the aluminum brazing material and make it difficult to flow. . The shape of the powder does not matter.

The same applies to the case where the aluminum brazing alloy is powder, and the average particle diameter is 10 to 500 μm, preferably 4
The specific surface area of the powder becomes excessively large when it is less than 10 μm, and the content of oxides becomes large, so that it becomes difficult to sufficiently fuse and integrate the powders. Again 5
If it exceeds 00 μm, the number of powders per weight of the aluminum brazing alloy decreases, and the gaps between the powders become too large, making it difficult to perform precise brazing. The shape of the powder does not matter. In the case of flux brazing as described above,
Since it can be applied without increasing the number of steps, it is suitable for flux brazing, and is particularly effective for non-corrosive flux brazing because the subsequent cleaning step can be omitted.

The present invention will be described below with reference to examples.

Examples and Comparative Examples Tables 1 and 2 show the structures of the aluminum brazing materials used in the examples and comparative examples. Examples 1 to 4, 6 and 7 and Comparative Examples 1 to 4 are powdered aluminum braze alloy powder, powdered high melting point substance and flux of hydrogenated liquid polyisobutylene having a molecular weight of 500. It is made into a paste using 50 parts by weight per part.

In Example 5, a rod-shaped aluminum brazing alloy (φ1 mm × 10 mm) coated with flux was wrapped with A1570 aluminum having a thickness of 15 μm which is a high melting point substance.

In the formulation 8 of the example and the formulation 5 of the comparative example, 50 parts by weight of a powder of a high melting point substance and a flux of hydrogenated liquid polyisobutylene having a molecular weight of 500 are added around 100 parts by weight of all powders around a rod-shaped aluminum brazing alloy. The paste is used to apply a predetermined amount.
Comparative example formulation 6 used a rod-shaped aluminum brazing alloy.

Evaluation test Aluminum structural member (1) (A3003: 2 mm × 25 mm
Another aluminum structural member (2) (A3
003: 2.5 mm × 11 mm × 50 mm) was temporarily fixed as shown in FIG. The structural members (1) and (2) are arranged at right angles to each other along the longitudinal direction, and (2) has a notch with a length of 40 mm and a depth of 1 mm on one side, and has a U-shape. There is. Both ends (3) of the U-shape and the member (1) are temporarily fixed, and a width of 1 is provided between (1) and (2).
A slit (4) of mm is formed. This slit (4)
Aluminum brazing filler metal (5) at one end in the longitudinal direction
The aluminum structural member was tilted 10 ° in the longitudinal direction with the brazing filler metal on the upper side. In the flux brazing, brazing in a furnace in an argon stream (purity 99.999%) (holding for 5 minutes after melting at 600 ° C.) was performed, and in Example 8 and Comparative Example 6, a vacuum brazing material without using flux. (Melting at 600 ° C., holding for 5 minutes, vacuum degree: 5 × 10 ⁻⁵ torr) was performed, and each evaluation was performed using the test piece.

Evaluation Criteria Wax Flowability (Aluminium remaining in the position where it was placed
Amount of um brazing material) A: The total amount of aluminum brazing material placed is brazed without spreading. B: 80% of the placed aluminum brazing material remains and is brazed. C: 30% of the aluminum brazing material that was placed is left and brazed. D: Almost everything is flowing. E: Not evaluated (aluminum brazing material is not melted)

Fillet shape and appearance A: The surface is smooth and fillets are continuously formed to fill the thickness of the test piece. B: The surface is smooth, and there is one wax break, but the thickness of the test piece is filled. C: The surface is a little rough, and there are several cracks in the wax, but the thickness of the test piece is filled. D: Does not form a fillet. E: Not evaluated (aluminum brazing material is not melted)

Observation of brazing cross section A: It has a beautiful brazing structure. B: There are some pores, but it has a beautiful brazing structure. C: Some pores were observed and some unmelted aluminum brazing material was observed on the surface. D: Pore is seen and unmelted aluminum brazing material is seen inside. E: Not evaluated (aluminum brazing material is not melted)

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

EFFECTS OF THE INVENTION By using the aluminum brazing material of the present invention, it is easy to braze without filling a large gap, which has been difficult with the conventional aluminum brazing material, and the brazing material does not flow from a limited part. And it can be cheap.

[Brief description of drawings]

FIG. 1 is a diagram showing a joining mode of aluminum structural members used for a brazing evaluation standard of an example.

[Explanation of symbols]

 (1), (2): Aluminum structural member (3): U-shaped portion of (2) (4): Slit (5): Aluminum brazing material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiaki Ogura 3-8-10 Mitsuyanaka, Yodogawa-ku, Osaka-shi, Nihongenma Co., Ltd. (72) Inventor Tadashi Takemoto 5-11-28 Kasuga, Toyonaka-shi, Osaka −506

Claims (5)

[Claims] 1. 100 parts by weight of an aluminum brazing alloy, 0.5 to 80 parts by weight of a refractory substance having a melting point higher than that of the aluminum brazing alloy, and 0 to 25 parts of flux.
An aluminum brazing material characterized by containing parts by weight. 2. The aluminum brazing material according to claim 1, wherein the high melting point substance is powder of aluminum or an alloy thereof, and the content thereof is 5 to 80 parts by weight. 3. The high melting point substance is aluminum nitride and / or oxide powder, and the content thereof is 0.5 to 0.5.
The aluminum brazing material according to claim 1, which is 10 parts by weight. 4. The aluminum brazing material according to claim 1, wherein the aluminum brazing alloy and the high melting point substance are powders having an average particle diameter of 10 μm to 500 μm. 5. An aluminum braze alloy having a melting point lower than the brazing temperature and a high melting point substance having a melting point higher than that of the aluminum braze alloy are optionally present in the presence of a flux at the joining site of the aluminum structural member to be joined, A brazing method for an aluminum structural member, which comprises heating to a predetermined brazing temperature.