JPS59144592A - Flux for brazing aluminum material - Google Patents

Abstract

PURPOSE:To provide a flux for brazing an aluminum material which is decreased in the m. p. without spoiling the advantage intrinsic to a fluoride flux by incorporating transition alumina and Al(OH)3 in potassium fluoroaluminate or a mixture composed thereof and AlF3. CONSTITUTION:A flux for brazing an Al material is incorporated with 100pts.wt. potassium fluoroaluminate having the structure of 60:40-50:50 in the ratio of AlF3/KF or a mixture composed dereof and AlF3 and 1-8pts.wt., more preferably 3-7pts.wt. transition alumina such as rho alumina and Al(OH)3 in terms of an alumina-component. Such flux is mixed with water to prepare a slurry which is then coated on the joint surfaces to be brazed of the Al material. A brazing material is disposed on the coated surface and the joint surfaces are joined by brazing under heating. The brazing from the neighborhood of about 56 deg.C lower by 30-40 deg.C than with the conventional fluoride flux is made possible by using such flux.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applied to the joint portions of aluminum and aluminum alloy materials (hereinafter referred to as "aluminum materials") and aluminum materials, or when joining aluminum materials and dissimilar metal materials by brazing. This article relates to a reactive flux for brazing elbows used to improve the brazing properties of parts.

When joining aluminum materials by brazing, a brazing metal is installed between the materials to be joined, or one or both of the materials to be joined are clad with brazing material in advance, and the materials to be joined are placed together and the brazing material is placed between the materials to be joined. The soldering material existing between the parts to be joined is melted by heating to a melting temperature of .

Therefore, as a brazing material, the melting point is 30 to 40
°C, and the brazing temperature, i.e., in the molten state, is required to have excellent fluidity so that the brazing material spreads between the parts to be joined in +1 minute, and from these points of view, silicon-containing aluminum is generally used. Alloy (melting start temperature 520~5
)7°C) is used.

Although the brazing temperature varies depending on the materials to be joined and the type of brazing alloy used, brazing is generally performed at a temperature of 560 to 60°C.

However, since the surface of aluminum materials is usually covered with an oxide film, this reduces the bondability of the materials to be joined during brazing. Apply reactive fusix to the joint surface, destroy and remove the oxide film that has formed on the contact surface during brazing temperature,
By exposing the metal surface, the brazing material is used to strengthen and facilitate bonding.

This reactive slack 4 has a temperature higher than the melting point of the brazing material.
It is required to melt at a low temperature and to have properties that improve wetting and spreading properties of the brazing material on the joint surface.

Traditionally? - As a flux that has both of these properties, chloride-based slack is often used, as it has a melting point of 450 to 540"C and also has an excellent effect of promoting wetting and spreading properties of the brazing material. However, this type of flux is water-soluble. Because of its strong and air-absorbing properties, it had the disadvantage that if the solder flux or reaction residue remained in the joint, it would corrode the aluminum material in this area.

For this reason, when chloride flux is used, it is necessary to wash off the residue after the brazing process, and even if a washing process is performed, it is often the case that the product has a narrow solder area. The presence of removed flux could cause corrosion.

US Pat. No. 4951.3 is a reactive slack that can avoid the corrosion problem caused by cyclide fluxes.
Fu disclosed in No. 28.

Chemical fluxes are attracting attention.

The flux of Patent No. 6.951.32s has an aluminum fluoride/aluminum fluoride ratio of 60:
40 to 50: 50 is a close mixture of potassium fluoroaluminate and aluminum fluoride.It is water-insoluble and has no hygroscopicity, so residual flux in the brazed area will cause damage to the materials to be joined. Will not cause corrosion! Although it can satisfy both the effect of removing oxides from the surface to be joined and the effect of promoting wetting and spreading of the brazing material,
This is natural since its melting temperature or melting start temperature is theoretically close to the eutectic point of aluminum fluoride and potassium fluoride, 560°C, and is higher than that of the 7 lux of batides. However, since the brazing temperature is approximately 600℃ or higher, the types of brazing filler metals and materials to be joined that can be used are limited in practice, and in particular, brazing filler metals with relatively low temperatures such as aluminum alloy castings must be used. It was difficult to use it for brazing aluminum materials.

The present invention improves the problems with the above-mentioned fluoride-based flux without impairing the 10 points of this system, and lowers the melting point, and the weight ratio of aluminum fluoride flux is expressed as a single compound. Ni/potassium heptadide ratio is 60:40 to 50
: Preferably 100 parts by weight of potassium fluoroaluminate or a mixed composition of potassium fluoroaluminate and aluminum heptafluoride having a composition equivalent to 50% and transition alumina and/or aluminum hydroxide as the alumina content of 1 to 8 parts. is an aluminum solder elbow flux containing 3 to 71 parts.

In the present invention, "potassium fluoroaluminate" and ti
KAI3F K hAF5-H2O Oyobini 3A
! It refers to a complex compound represented by F64' 2, etc., and includes both a single substance and a mixture thereof. Also, "transition alumina" refers to a complex compound represented by F64' 2 etc.
Various alumina intermediates obtained between 50 and 900'C 1 For example, ρ alumina, χ alumina, η alumina, γ alumina and alumina, ? Refers to activated alumina groups such as alumina and θ-alumina, and refers to those containing one or more of these.

Depending on the starting material, there may be some alumina fired within the above temperature range that can be measured as alpha alumina, but if the alumina is completely converted into alpha alumina, its contribution to the lowering of the melting point of slack will be small. There is no force, and most of it remains as a residue in the soldered joint during brazing, damaging the appearance of the product! It is undesirable to mix in a large amount of it, since it will impede the tarosing properties.

Further, corundumized alumina-based materials are also not preferred because they have similar problems.

(2) Potassium fluoroaluminate or a mixed composition of potassium fluoroaluminate and aluminum fluoride, which is the main component of Fusix of the present invention, contains alumina derived from the raw material aluminum heptadide as an impurity during its production. However, the alumina content in the above impurities is not necessarily contained as transition alumina or aluminum hydroxide, and most of it is alpha alpena or aluminum oxyfluoride combined with fluorine (for example, Alp2). Since it is contained in the form of (oH)),
It is not preferable because it has little effect on lowering the melting point of 7-ralekunu during brazing and may even impair brazability and product appearance.

Potassium fluoroaluminate or a mixture thereof with aluminum fluoride having a weight ratio of aluminum fluoride/potassium fluoride ranging from bo:4o to so:so, which constitutes the main constituent PJm of the 7 lacs of the present invention. The composition should satisfy the basic characteristics required as a flux, such as the ability to destroy and remove the oxide film on the surface of the aluminum material to be joined, and the property of promoting wetting and spreading of the brazing filler metal.
When the composition is out of the above range, the melting point becomes extremely high despite the inclusion of transition alumina and aluminum hydroxide, and a white insoluble residue is generated during brazing, causing the wax to become cloudy and spread. This is not preferable because the effect of promoting silica is reduced.

Transition alumina and aluminum hydroxide, which are other constituents of the 7 lacs of the present invention, can be used as either one or both in a mixed state in 100 parts by weight of potassium fluoroaluminate or a mixed composition of potassium fluoroaluminate and aluminum fluoride. By containing 1 to 8 parts by weight of alumina, preferably 7 parts by weight, the wA
, a can be lowered by 30 to 40°C compared to the conventional potassium fluoroaluminate 7six.

That is, when the content of transition alumina and/or aluminum hydroxide is less than 1 part by weight in terms of alumina, the effect is insufficient and a product with a low melting point cannot be stably obtained. When the weight part is exceeded, a white stain may be generated during brazing.
This is undesirable as it will generate G-decomposable residue and deteriorate the fusics properties, especially if the
5Ke), the melting point decreases and the stability of the 7 lux properties is remarkable.

The flux of the present invention can be manufactured by several methods.

To give a standard example, for example, commercially available particle size 70 μm
KhpF below or X, five! F4 alone or mixed with Fi, and aluminum fluoride powder added as desired,
Further, a method of blending N & transition alumina or aluminum hydroxide with a particle size of 50 μm or less in the t7Ig combination of the present invention, and a method of blending and mixing aluminum heptadide and potassium fluoride in a content ratio according to the present invention. The mixture is melted to form a mixed composition of fluoroaluminic acid, fluoroaluminic acid, and aluminum fluoride, which is pulverized.
Examples include a method of blending a predetermined 9-phase transitional alumina or aluminum hydroxide.

Regarding the impurities that are unavoidably contained in the flux of the present invention, 1. For example, sodium fluoride and calcium fluoride are each 2% by weight or less, and iron oxide and silicon oxide are each 0% by weight.
．． It is desirable that the total weight of impurities is 7-3 or less.
It is desirable that the total amount of lux be less than 4% by weight.

Also, when using similar production methods, the presence of unreacted, ie, free, potassium heptafluoride in the flux must be avoided as much as possible.

For handling purposes, it is desirable that the particle size of 76x is 80 m or less, and in particular, for transition alumina and alumina hydroxide, it is desirable to have a particle size of 204 m or less from the viewpoint of solubility in potassium fluoroaluminate. - The brazing operation of aluminum materials using the flux of the present invention is performed in the same procedure as conventionally followed in brazing properties using fluoride-based fluxes.

That is, a method in which the powder is placed on the soldering surface.

Alternatively, there is a method of mixing it with a medium that does not produce a residue during brazing, such as water or alcohol, and applying it in the form of a paste or slurry to the brazed surface by spraying or brushing. The procedure for brazing work when used as an aqueous slurry will be described.

The 7lux of the present invention has a fusix concentration of 2 to 60% by weight.
, preferably 5 to 25% by weight, is mixed with water to form an aqueous slurry, which is then subjected to appropriate pretreatment such as degreasing and roughening treatment, and the materials to be joined, that is, aluminum materials, aluminum materials, and aluminum materials. It is applied to the joining surface of different metal materials. As a coating means, known methods such as a brush method, a spray method, and a dipping method are used.

The amount of flux applied to the joint surface varies depending on the slope and shape of the materials to be joined, but it is generally 2 to 50 g/v?
, 5 to ROji/d (in terms of dry matter) is suitable.

After drying, the brazing filler metal is placed on the surface to which the flux has been applied, but when using powdered brazing filler metal, it can be mixed with flux and applied to the surface to be joined in the same way as slurry application, and then dried. good.

Furthermore, it goes without saying that a brazing filler metal may be applied to one or both surfaces of the materials to be joined.

After placing the flux and brazing material on the joining surfaces, the soldering material is heated to a temperature at which the soldering material melts using a fitting jig so that the materials to be joined are formed into a predetermined shape. It will be done.

As mentioned above, the flux of the present invention has an F point 30 to 40°C lower than that of conventional fluoride-based fusix, and is 53.0°C.
Since it melts in the range of ~560°C, the brazing material can be selected from around 540°C or higher, so the range of aluminum alloys that can be joined is correspondingly wider. It is also possible to braze aluminum alloys for castings, which have been difficult to braze.

The brazing alloy corresponding to the flux of the present invention is 9
For example, aluminum-silicon alloy brazing materials (Mu404 Otsu Alloy, AAO45
In addition to the A4145 alloy and the A4047 alloy, aluminum-silicon-copper alloys and aluminum-silicon-copper-zinc alloys can be used.

Brazing can be carried out in a normal atmosphere, but it is desirable to carry out the brazing in an atmosphere of an inert gas such as nitrogen gas or argon gas, and more preferably under conditions where the moisture content in the atmosphere is 20°0PP111 or less.

In addition, brazing can be performed at a temperature of 560°C, which is 30 to 40°C lower than when using conventional fluoride-based fluxes, and the oxidation film rupture ability of the surface to be joined and wetting spread to the brazing material are reduced. The ability to promote sex is almost unchanged, and the franks for deaf elbows have satisfactory performance.

Examples and usage examples will be described below to clarify various aspects of the flux of the present invention.

Example 1 Aluminum fluoride 521yt subjected to Xi A by melting method
% and 7) Potassium chloride 47.9 w1% average particle size 2
For 100 parts by weight of 0 μm aluminum ξ aluminate, Bayer process aluminum hydroxide was calcined under 600″C4α3
Transition alumina (mixture of χ alumina and ρ aluminum ξ, purity 99.5% (based on line standard)) with an average particle size of 1 μm was produced by flash firing for 2 seconds, and a specified amount was added thereto. An evaluation test was conducted after preparing 7 lux and making it into an aqueous slurry with 1αQ vl of 1%.

The result is the following passage.

As is clear from these results, the content of transition alumina is 1.
It can be seen that when the amount is between 0 and 0 parts by weight, the overall properties as a flux are excellent.

In addition, in the case of only fluoroaluminate without transition alumina, its melting point usually varies in the range of 560 to 585 °C between lots even if the composition is the same, but when transition alumina is added, In the case of the flux of the present invention, by adjusting the content of alumina to compensate for such dispersion in melting point, a flux with a nearly constant melting point can be obtained, which also contributes to stabilizing the melting point of the flux. I understand.

Example 2 Commercially available potash cryolite (manufacturer indicated purity 98% average particle size z
8 μm) and aluminum fluoride (industrial grade 3F3 with a purity of 96% and an average particle size of 52 μm) are expressed as simple compounds with aluminum fluoride 552 wt% and potassium fluoride 4 &
A predetermined amount of aluminum hydroxide (industrial A stone (OH) 3 with a purity of 99.7% and an average particle size of 50 μm) was added to the mixture so that the flux was 8 wt%, and the flux was adjusted to 8 wt%. % aqueous slurry, an evaluation test was conducted and the results are as follows.

From this result, even when aluminum hydroxide is added, 1. It can be seen that excellent properties as a flux can be expected when the amount is o-as parts by weight. Moreover, it can be seen that some transitional aluminas have a somewhat superior melting point lowering effect.

Example 6 Aluminum hydroxide and potassium hydroxide were mixed and reacted in a 7-hydrofluoric acid solution, dried at 150°C, and further heated to 400°C.
AJF3513”%r KF 45.8 wt% as a single compound with an average particle size of 5μm after firing for 1 hour at °C
, a complex compound containing 0.9 wt% of impurities was obtained.

This complex compound was added to aluminum hydroxide (
Made by crushing Bayer process aluminum hydroxide, purity 9.
When B was added in an amount of 0 parts by weight (5.2 parts by weight in terms of alumina), a flux with a melting point of 536°C was obtained.

This flux was mixed with water to make an aqueous slurry with a flux of 150 wt%, and an A40
A car cooler capacitor product, which was assembled with a corrugated fin member formed from a collected material made of 45 alloy material clad on both sides, was spray-coated to a coating amount of 6 y/d (dry coating).

Next, after drying at 200°C for 3 minutes, it was placed in a brazing furnace in a nitrogen gas atmosphere for 5°C. The brazing operation was completed by holding at O''C for 3 minutes.

In the quality evaluation test of the manufactured capacitor, the bonding rate between the corrugated pipe and the flat tube was over 99%, forming a good fillet, and no insoluble residue was observed in the brazed part, indicating a good bond. It was confirmed that this was done.

In addition, when we conducted a corrosion acceleration test using salt water spray K, we found that
Even after 00 hours had passed, no aromatic pitting corrosion was observed, and no effect of the invention flux on the corrosion resistance of the product was observed, and all the required properties of 7lux were satisfied.

Patent applicant: Nippon Light Metal Co., Ltd.

Claims (1)

[Claims] (1) Fluoalumin #, ;lium or potassium fluoroaluminate and aluminum fluoride having a structure in which the weight ratio of aluminum 7 fluoride/potassium fluoride is 60:40 to 50:50 when expressed as a single compound. An aluminum wax elbow flux comprising 400 parts by weight of a mixed composition of: (1) and 1 to 8 parts by weight of alumina and/or aluminum hydroxide.