JPH055600B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a flux composition used for brazing Al materials made of aluminum (Al) or its alloys, and in particular has a low melting start temperature, so that it can be used even at low temperatures of about 450°C. , relates to a flux composition that enables brazing. (Background Art) When brazing Al materials, an oxide film formed on the surface of the material obstructs the wetting and flow of the solder, so in order to remove this oxide film, NaCl −KCl−
A chloride-based flux whose main component is LiCl-based alkali metal chloride is used. However, when using this chloride-based flux, the flux remaining after brazing is
Since the flux is highly corrosive to Al materials, the flux residue must be removed after brazing, which is troublesome. For this reason, various brazing _methods for Al materials using non-corrosive fluoride fluxes have _been investigated.
A flux composition consisting of a mixture of AlF ₆ has been proposed, but since the melting point of such flux is quite high at around 560°C, the brazing temperature will inevitably be high, and this will result in a high brazing temperature. Therefore, there were inherent problems such as restrictions on the Al material (base material) that could be brazed. That is, in terms of materials, there were limitations, especially from the melting point of the Al material (base material), and there were also limitations in terms of dimensions, such as the inability to make the walls thinner. In addition, due to the high brazing temperature, there are inherent disadvantages such as expensive brazing equipment and high energy consumption during brazing. (Problem to be solved) Under such circumstances, the problem to be solved by the present invention is to reduce the melting start temperature to 450°C.
The object of the present invention is to provide a novel flux composition that enables brazing of Al materials at temperatures as low as 0.degree. (Solution Means) In order to solve this problem, the present inventors have selected among various compositions proposed as flux compositions that have low corrosiveness to Al materials and start melting at a relatively low temperature. So, JP-A-61-
AlF ₃ −CsF disclosed in Publication No. 162295 etc.
As a result of further investigation into the composition of the AlF 3 -CsF system, it was discovered that the melting temperature of the AlF ₃ -CsF system composition could be further lowered by adding a certain amount of LiF as a third component to the system. They also discovered that when these components are prepared as a molten composition, they are highly effective as a flux, and based on these findings, they have completed the present invention. That is, in the flux composition for brazing Al materials according to the present invention, LiF, AlF ₃ and
A composition whose main component is a melted and solidified powder mixture consisting of CsF, and the composition of these three components is
In the triangular coordinates indicating (LiFmo1%, AlF ₃ mo1%, CsFmo1%), (2,0,98) and (2,98,0)
Straight line A connecting (0, 22, 78) and (78, 22, 0)
Straight line B connecting (30,0,70) and (30,70,0)
straight line C connecting them, and (60, 40, 0) and (0, 70,
30) is adjusted so that it falls within the range surrounded by four straight lines consisting of straight line D connecting. (Specific composition) By the way, in the flux composition according to the present invention, the melted and solidified powder mixture consisting of LiF, AlF ₃ and CsF, which are the main components, is prepared by preparing these three components in the above-mentioned specific composition. By doing so, the melting start temperature can be controlled between 435°C and 460°C. In other words, such melted and solidified material is
It can be melted at a lower temperature than a composition consisting of a mixture of KAlF ₄ and K ₃ AlF ₆ , as well as a binary composition of AlF ₃ -CsF. The main component is the melted and solidified material
The flux composition according to the present invention enables the brazing temperature to be as low as about 450°C, which eliminates the limitation imposed by the melting point of the brazing base material (Al material) and enables brazing of all Al materials. becomes possible. In contrast, the flux composition
If the proportions of LiF, AlF ₃ and CsF are outside the above range, the melting temperature will become high, making it impossible to fully achieve the object of the present invention. The composition ranges of LiF, AlF ₃ and CsF in the present invention are actually expressed in triangular coordinates as shown in Fig. 1, where the range of the present invention is defined by straight lines A, B, C, D. This is the shaded area surrounded by . By the way, in the present invention, LiF, AlF ₃ and
Since the three components of CsF are provided as a compound that has been melted and solidified as one, the melting progresses uniformly and integrally during brazing heating.
It has the advantage that it works well as a three-component flux, and unlike powder mixtures,
Since there is no chance of any of the components remaining, it is possible to avoid CsF, which has hygroscopic properties, from remaining alone, and to prevent corrosion of the material.
It is even more advantageous. Note that the flux composition according to the present invention is
Although it may be composed only of LiF, AlF ₃ and CsF, it is also possible to add other components as necessary. For example, in addition to these three components, it is well known that Zn, ZnF ₂ , etc. can be added in order to perform the function of a sacrificial anode, and thereby the Al material (base material) It is possible to effectively prevent pitting corrosion at brazed parts. Specifically, those Zn powders and ZnF ₂
The powder is preferably used in a particle size of 200 mesh or less, and in particular in the present invention, the LiF,
When melting a powder mixture consisting of AlF ₃ and CsF,
It is preferable to mix them in a predetermined ratio and simultaneously melt and solidify them to form an integrated compound. In addition, the amount used is preferably 4/6 to 9/1 by weight in the case of Zn powder, and the molar ratio in the case of ZnF ₂ powder to the powder mixture of LiF, AlF ₃ and CsF. It is preferable to use a ratio of 85/15 to 94/6. The flux composition according to the present invention is made by pulverizing the above-mentioned melted and solidified material again to form a powder, and when using such a flux composition, it is diluted with water etc. as in the past. , it is applied to an Al material made of Al or its alloy to be made into a paste and to be brazed. Then, heat brazing is performed in the same manner as in the past, and at that time, the flux composition according to the present invention is
Since its melting temperature is as low as 435-460°C, the brazing temperature can be lowered to as low as 450°C, thereby eliminating the limitations imposed by the melting point of the Al material to be brazed. ,
This makes it possible to braze all Al materials. In addition, by making such low-temperature brazing operations possible, it becomes possible to braze Al materials made of high-strength Al alloys, making it possible to effectively reduce the thickness and weight of constituent materials. Moreover, since the brazing temperature is low, it can exhibit characteristics such as less decrease in strength of the Al material (base material) due to brazing heating. (Examples) Below, some examples of the present invention will be shown to clarify the present invention more specifically. Needless to say, it is not subject to any restrictions. In addition to the following examples and the above-mentioned specific description, the present invention includes various changes, modifications, and changes based on the knowledge of those skilled in the art, as long as they do not depart from the spirit of the present invention. It should be understood that improvements and the like may be made. First, with various compositions shown in Table 1 below,
Various flux compositions were prepared by mixing powders of LiF, AlF ₃ and CsF, melting and solidifying the resulting compositions, and pulverizing them into powders. Next, using each flux composition, an Al plate made of JIS-A-3003 alloy (thickness: 1
A board with a length of 30 mm and a height of 20 mm cut from a similar Al plate was assembled into an inverted T-shaped joint structure on a board with a width of 30 mm and a length of 50 mm made from I did the attaching. Each flux was diluted at a ratio of water:flux = 9:1 (weight ratio), and the diluted product was applied to the brazed portion of each Al plate. In addition, at the joint,
As a brazing material, 1mm ^t × 15mm × 7 of Zn-Al solder
mm is placed, and heating temperature: 500℃
Brazing was carried out at. Table 1 below shows the ratios of flux components and brazing results, and it is clear that when using a flux having the composition according to the present invention, good brazed joints can be obtained even at temperatures as low as 500°C. However, when using a flux with a ratio outside the range of the present invention shown as a comparative example, the flux does not melt and the fluidity of the solder cannot be obtained, making it difficult to perform effective brazing. I couldn't do it.

[Table] (Effects of the Invention) As is clear from the above explanation, if the flux composition according to the present invention is used, based on its low melting temperature (435 to 460°C), it can be heated to as low as 450°C. The brazing temperature can be lowered, which eliminates the limitations imposed by the melting point of Al materials, making it possible to braze all Al materials.
It is also possible to braze high-strength Al alloys, making it possible to make the constituent materials thinner and lighter. Furthermore, since the brazing temperature is low, there is also the effect that there is little decrease in the strength of the Al material due to brazing heating. Furthermore, the use of the flux composition according to the invention reduces the brazing temperature;
In addition to making various equipment such as a brazing heating furnace cheaper, the amount of energy consumed during brazing heating can also be reduced, thereby contributing to a reduction in brazing costs.

[Brief explanation of the drawing]

FIG. 1 is a triangular coordinate showing the composition ranges of LiF, AlF ₃ and CsF employed in the flux composition according to the present invention.

Claims (1)

[Claims] 1 A composition whose main component is a melted and solidified powder mixture consisting of LiF, AlF ₃ and CsF, and the composition of these three components is (LiFmo 1%, AlF ₃ mo 1%,
In the triangular coordinates indicating (CsFmo1%), (2,0,
Straight line A connecting (98) and (2,98,0), (0,22,
Line B connecting 78) and (78, 22, 0), (30, 0,
70) and (30, 70, 0), and (60,
A flux composition for brazing Al materials prepared so as to fall within a range surrounded by four straight lines D connecting (0,70,30) and (0,70,30).