JPS6240998A - Flux for brazing and its production - Google Patents

Abstract

PURPOSE:To produce a fluoride flux having a stable compsn. by a simple method by mixing gammaAlF3 and KF controlled in grain size to a specific ratio and calcining the mixture composed thereof to annihilate KF. CONSTITUTION:50-60wt% gammaAlF3 having <=74mum grain size and 40-50% KF having <=74mum grain size are mixed. The mixture is calcined under conditions of about >=200 deg.C and about >=0.5hr to annihilate KF. The fluoride flux in the powder state which can be used as it is for brazing is obtd. by such treatment. The brazability is improved if a small amt. of >=1 kinds among LiF, CaF and NaF are added to the flux curing or after the production thereof. Energy is economized as there is no need for a melting or pulverizing stage in this method.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a novel brazing flux and a method for producing the same, and in particular, to materials for plates, pipes and other structures made of aluminum or aluminum alloy. This invention relates to a brazing flux useful for joining.

[Prior Art] When joining aluminum plates, pipes, and other structural materials manufactured from aluminum or aluminum alloys, the oxide film on each joint surface is destroyed by n times m degrees, and each Flux for brazing 11 is used so that the aluminum materials are brought into metal contact with each other and the molten brazing material exhibits good wetting and diffusivity on the joint surfaces.

At first, chloride-based flux was used as the flux used for this purpose, but this chloride-based flux is water-soluble and hygroscopic, and the flux itself and brazing deteriorate over time. If reaction residue adheres to and remains on the joint part, corrosion will occur in this part, and after brazing, the flux residue and reaction residue must be thoroughly cleaned and removed. When this occurs, the cleaning and removal process becomes extremely troublesome, and there is a problem in that cleaning and removal is often insufficient, resulting in corrosion.

Fluoride flux has been proposed as a solution to the problem of chloride flux, and its production method involves melting AlF3 and KF together in an appropriate ratio, and producing the molten product. KAlF4 is obtained by cooling and then pulverizing it to a predetermined particle size (Japanese Patent Publication No. 58-27.037), or by reacting caustic potash with IA I F4 obtained by reacting hydrogen fluoride with aluminum hydroxide. Alternatively, a method for producing an aqueous solution thereof has been proposed (Japanese Patent Application Laid-open No. 5
8-202.996) etc. have been proposed.

[Problems to be solved by the invention] However, in the former method, the manufacturing method is a batch type, which has poor production efficiency, requires a melting process and a pulverization process, resulting in high costs, and the use of starting materials Strictness is required in the formulation of K A in the generated flux.
It is difficult to keep the component ratio of IF6 and KA it F4 constant at all times, and if this component ratio changes, it will affect the brazing property and the wetting and diffusivity of the brazing material during brazing, resulting in a decrease in brazing strength. There is a problem that becomes inconsistent.

In addition, the latter method, which uses chemical reactions, is batch-type and has poor production efficiency, and requires processes such as heating, stirring, drying, and separation that are unique to chemical reactions, requiring complicated manufacturing equipment and rod management. There is a problem in that it becomes necessary and costs increase.

[Means for Solving the Problems] The present invention was devised in view of this point of view, and provides a fluoride-based flux having a stable composition, and at the same time, allows the fluoride-based flux to be produced using an extremely simple method. The present invention provides a method for manufacturing.

That is, the present invention provides γ-AjF with a particle size of 74 μm or less.
KF40~ with a particle size of 350~60% by weight and 74μm or less
The powdered braze obtained by firing a mixed system with 50% by weight provides a flux for use.
Melting process and pulverization in which 350 to 60% by weight of γ-AlF with a particle size of 74 μm or less and 40 to 50% by weight of KF with a particle size of 74 μm or less are mixed and the resulting mixture is fired under conditions where the above KF disappears. Brazing, which eliminates the process, provides a method for producing flux.

In the present invention, the aluminum fluoride (AlF3) used as a raw material for producing flux is preferably γ monolithic, and those with other crystal structures such as α monolithic are difficult to complete the reaction in a short time, making it difficult to It is disadvantageous.

When using this γ-AlF3, it is best to grind the particle size as finely as possible, usually 74 μm.
m or less, preferably around 44 It m. When the particle size of this γ-AlF3 becomes larger than 74 μm, there arises a problem that the contact between the KF powder particles decreases and the reaction progresses slowly.

In addition, potassium fluoride (
Similarly to γ-AlF3, KF) is preferably ground as finely as possible and used in powder form, preferably with its particle size adjusted to 74 μm or less, preferably around 44 μm. If the particle size of this KF is larger than 74 μm, there will be a problem that the contact with the γ-AIJF3 particles will be reduced and the progress of the reaction will be impaired.

In the present invention, when producing flux by firing γ-AlF3 and KF, the mixing ratio of both is usually 350 to 60% by weight of γ-AjF and 40 to 50% by weight of KF.
% by weight, preferably 353.2-59.2% by weight of γ-AlF and 46.8-40.8% by weight of KF. γ-Aj
In the blending ratio of F3 and KF, if the amount of γ-AlF3 used exceeds the above range, a problem arises in that dissolution residue will remain on the product and the surface smoothness will be lost.
Also, if the amount of KF used exceeds the above range, excessive K
A problem arises in that F remains on the joint surface, resulting in incomplete brazing Gj.

Furthermore, the firing regulations for producing flux by firing γ-ΔlF3 and KF are, in principle, such that the raw materials disappear, and depending on the degree of pulverization of each raw material γ-AlF3 and KF, Although it varies, usually the firing temperature is 200°C or higher and the firing time is 0.5 hours or longer.
-, preferably for more than 1 hour, and 8 rays and 1 γ-AI
When IF3 and KF are ground more finely, the firing temperature can be lowered and the firing time can be further shortened.

Regarding the flux for brazing of the present invention, a small amount of one or more additives selected from 1.1F1CaF and NaF is added as a brazing improver during or after its production. However, brazing can also improve properties.

The flux for brazing produced in this way is 1 q in powder form, so it can be used as is for brazing, but if necessary, it may be further pulverized to make the particle size finer before use.

[Function] In the present invention, the manufacturing source of fluoride flux
By using γ-AlF3 as aluminum fluoride, it is possible to create a powder with a stable composition that can be used for brazing as is by mixing it with potassium fluoride (KF) and a simple firing process. Fluoride-based flux can be produced.

[Example 1] Hereinafter, the present invention will be specifically explained based on Examples and Comparative Examples.

Examples 1 to 8 The raw materials γ-AIIF3 and KF were ground to the particle size shown in Table 1, mixed at a ratio of 1=1, and fired under the conditions shown in Table 1 to produce a powdered flux. was manufactured. The component composition of each of the 7 luxes obtained was investigated using an X-ray microanolizer. The results are shown in Table 1.

Comparative Examples 1 to 3 Using α-AlF3 as aluminum fluoride, it was ground to the particle size shown in Table 1 in the same manner as in the Example above, and α-AlF3 was used as aluminum fluoride.
-AlF3 and KF were mixed at a ratio of 1:1 and fired under the conditions shown in Table 1 to produce a powdered flux. For each flux obtained, X-ray microanolite 1
The component composition was investigated using f-. The results are shown in Table 1.

In addition, in the column of particle size in Table 1, the - mark means under (below), and in the soil means upper (above), and in the column of the composition of the generated flux, the ◎ mark means contained. A mark of 0 means that the content is normal, a mark of Δ means that the content is small, and a mark of X means that the amount is not detected.

-〇 - Examples 9 to 16 and Comparative Examples 5 to 12 In the examples, γ-Al crushed to a particle size of -74 to +44 μm
F3 and KF were mixed at a ratio of 1:1 and fired under the conditions shown in Table 2, and in the comparative example, the particle size was -74 to +44 μm.
U-AlF2 and KF, which were ground into powders, were mixed at a ratio of 1:1 and fired under the conditions shown in Table 2 to produce 7 lux powders.

7 lux 0°029 of each example and each comparative example obtained
was placed on the center part of an aluminum plate (A105(')) having a size of 50MRX 50#l#IX1 tntrr, and heated at a heating rate of 50℃/1n in a nitrogen gas atmosphere, and a holding temperature and time of 600℃ x 21 inches. Heat according to the conditions, each 7
We investigated the spreadability of Lux. The results are shown in Table 2.

In addition, 7 luxes 5 to 1 of each of these Examples and Comparative Examples
0g/Td 50m1RX 50aaX 1, 2m+
After applying the coating uniformly to the lower plate (A4045/A3003 plating sheet) of size and drying for 1011 inches at 120°C, 10 shoes were folded into 7 strips in the center.
50m5 (25as+X 25#l1lI) X 1
, 0 IuR size upper -10 = A plate (A1050) was placed upright in a dogleg shape, and in a nitrogen gas atmosphere, the dew point was -40°C, and the temperature increase rate was 5.
0°C/1n, and holding temperature/time 600°C x 2 mt
Brazing was performed under the conditions of n, and the brazing properties were examined from the fillet formation at the upper plate/lower plate joint.

The results are shown in Table 2.

In addition, in this Table 2, the spreadability evaluation (EX property evaluation) is as follows: ◎: eroded, O: good, Δ:
A 4-level evaluation was adopted: poor and ×: not recognized, and the evaluation of brazing properties (Br property evaluation) was ◎:
A four-level evaluation was adopted: excellent fillet formation, O: good fillet formation, Δ: no fillet formation, and ×: no fillet formation.

Table 2 = 13- [Effects of the invention] The flux for brazing of the present invention has a stable component composition of A, and can be used as a flux with stable properties for brazing. Since it is obtained by simply mixing it with KF and performing an in-cylinder firing process, there is no need for a melting process or crushing process as in the past, and it is possible to save a considerable amount of T energy. Not only can it be manufactured at a low cost, it can also be hung on the ceiling.

Patent applicant Nippon Light Metal Co., Ltd. Representative Patent attorney Tomohiro Nakamura (2 others)

Claims (5)

[Claims] (1) γ-AlF_350-60 with a particle size of 74 μm or less
1. A powdery brazing flux characterized by being obtained by firing a mixed system of 40 to 50% by weight of KF having a particle size of 74 μm or less. (2) LIF, CaF and N as brazing property improvers
The brazing flux according to claim 1, which contains a small amount of one or more additives selected from aF. (3) γ-AlF_350-60 with a particle size of 74 μm or less
% by weight and 40 to 50% by weight of KF having a particle size of 74 μm or less, and the resulting mixture is fired under conditions in which the KF disappears, which eliminates the melting and pulverizing steps. Manufacturing method of flux for use. (4) LiF, CaF and N as brazing property improvers
The method for producing a brazing flux according to claim 3, which contains a small amount of one or more additives selected from aF. (5) The method for producing a brazing flux according to claim 3 or 4, wherein the firing conditions are a firing temperature of 200°C or more and a firing time of 0.5 hours or more.