JPS6068188A - Brazing material for al and brazing method - Google Patents

Abstract

PURPOSE:To obtain a brazed part having high joining strength in a nonoxidative atmosphere by adding a prescribed amt. of P to an Al-Si system. CONSTITUTION:A brazing material for Al contg., by weight, 5-13% Si and 0.004-<0.08 P and consisting of the balance Al is used. Al is brazed by using such brazing material for Al without flux in a nonoxidative atmosphere having <=-20 deg.C dew point or in the atmosphere into which the nonoxidative atmosphere gas having <=-20 deg.C dew point is fed under the reduced pressure. Since the soldering material has good wettability with Al or Al alloy, the brazed part having high joint strength is obtd. in the nonoxidative atmosphere having <=-20 deg.C dew point.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a brazing material for At and a brazing method, and particularly to a brazing material for At,
The present invention relates to a brazing material for At and a brazing method suitable for brazing alloys in a non-oxidizing atmosphere without flux.

[Background of the invention]

Conventionally, At or At alloys have been brazed using an At-8i brazing filler metal containing 5 to 12% Si by weight, and using a halide as a flux. However, in this brazing method, the flux is extremely corrosive, so
There was a drawback that it took time to remove the flux after brazing. Another drawback was that 7 lux of steam was generated in the brazing filler metal, making work difficult.

In order to eliminate these drawbacks, we have added Mg to the kt-Si system or Bi, sr, sb to the At-5i system.
Attempts have been made to braze in a vacuum or inert gas without using flux, using a brazing filler metal containing a small amount of .

However, these methods require strict control of the pretreatment during brazing, and even if the pretreatment is strictly performed in this way, there is a problem with poor brazing properties, so brazing without flux is necessary. In this case, there is a problem that the brazing property does not improve even if the dew point is sufficiently lower.

Furthermore, a method of brazing at a dew point of about -201Z using an ht-sr brazing filler metal to which Ll, BeXLa, 00, etc. are added has also been proposed (Japanese Patent Laid-Open No. 101651/1983). However, even with this method, there is a problem in that brazing properties are insufficient even if pretreatment is performed strictly.

[Purpose of the invention]

The purpose of the present invention is to solve the problems of the prior art described above,
A brazing filler metal for At that has good brazing properties without requiring strict pretreatment requirements for the KT or A7 alloys that are the parts to be joined, and a brazing filler metal for At that can be brazed without flux using this At brazing filler metal. The purpose is to provide a method.

[Summary of the invention]

The present inventors have conducted various studies on brazing filler metals that can remove the oxide film of A I-20g formed on the surfaces of kt and A7 alloys of the materials to be joined and have good wettability for kt or At alloys. It was discovered that a brazing material capable of achieving the above objectives could be obtained by adding a predetermined amount of P to the -8i system, and when brazing such a brazing material without 7 lux, the It has been found that a non-oxidizing atmosphere, or a non-oxidizing atmosphere at a dew point below -20C with reduced pressure, provides excellent joints.

The present invention was made based on such knowledge, and the weight ratio is 81:5 to 13%, P: 0, 004 to 0.0
A brazing filler metal for At that is characterized by containing less than This is a 4S brazing method that involves brazing without flux in an oxidizing atmosphere.

The present invention will be explained in more detail below.

In the present invention, the brazing filler metal for At has a si of 5 to 13
%, P 0.004 to less than 0.08. Such brazing materials for At include (1) Si: 5 to 13%, P: less than 0.004 to 0.08% by weight;
and the balance is unavoidable impurities and A, /- brazing filler metal for At, (2) weight ratio of Si: 5 to 13%, P: 0
．． Brazing material for At, (3
) Weight ratio -csi: 5-13%, P: 0.0
04 to 0.1%, at least one selected from Ca, I, i, Mg and Na: 0.004 to 1.0%, and the remainder consisting of inevitable impurities and At, (4
) Weight ratio: 5 to 13%, P: O, 0,04
~Less than 0.08%, cu:o, i~5%, Caz L
At least one building selected from i, Mg, and Na: 0
．． For example, a brazing filler metal for At may be used, in which the brazing filler metal is made up of 0.004% to 1.0% and the balance being unavoidable impurities and At.

The various At brazing materials mentioned above have a brazing temperature of 560 to 6.
3071:' and is also a range in which brazing properties, particularly wettability, are improved.

That is, when 81 contained in At is 5 to 13%, it becomes suitable for the above-mentioned brazing temperature. P's fixed force is O, O
If the amount of P added is less than 4%, the wettability will be reduced and the brazing property will be insufficient.On the other hand, if the amount of P added is greater than 8%, the melting point of the brazing material will increase and the appropriate brazing temperature will be maintained. There is a risk of melting the base material. The amount of Cu added is 0.
If the amount of Cu added is less than 1%, the wettability will decrease and the brazing property will be insufficient.On the other hand, if the amount of Cu added is more than 5%, the melting point of the brazing metal will rise and there is a risk of melting the base material during brazing. .

Further, the same effect can be obtained by adding j9n in the same composition instead of CuO. If the addition amount of at least one selected from ca, L 15Mg, and Na is less than 0.004%, the wettability will decrease and the brazing property will be insufficient; If it exceeds 0%, the melting point of the brazing filler metal will rise and there is a risk that the base metal will melt during brazing.

In addition, when these brazing materials are melted and produced, a master alloy such as ht-P% Si-P% cup is used for P, and when other additive compositions are used in addition to P,
Using master alloys of P and other compositions, these master alloys are
- A of a predetermined composition by blending and dissolving in si etc.
A brazing filler metal for t can be obtained.

When brazing using such a brazing material for At, -20
t: Brazed in a non-oxidizing atmosphere with a dew point below 7 lux. If the connection point is 120C or less, the brazing bondability will be sufficiently high.

That is, although the dew point of 12 CI is not an atmosphere that can reduce the oxide film of the At material, pX'p+cu exists in the brazing material.

P+Cu+MgX: When additive elements such as r, i, ca, and Na are included, sufficient brazing is possible in an atmosphere with a dew point of -20C due to the effects of these additive elements. When brazing at a low dew point, a device is required to control the dew point in the brazing atmosphere, but when the dew point is around 1201Z', it is advantageous in terms of equipment because it can be used as is in a gas cylinder such as N2. . Ar is used as a non-oxidizing atmosphere.
N2,)(e.

It can be a N2 and vacuum atmosphere.

[Embodiments of the invention]

The purity of the metal used as the raw material for the brazing material is A7 of 99% or more, Si of 99.99% or more, Cu75f of 99% or more,
Mg is 99.5% or more, B1 is 99.5% or more, PIL
The metals of 1 and Na were of available high purity.

Using these ingots, solders having the compositions of the present invention listed in Table 1 and comparative conventional waxes were melted and produced.

A master alloy prepared by melting in advance was used because if waxes of various compositions were melted using only a single base metal, the melting temperature would be extremely high and it would be difficult to achieve a predetermined composition. The master alloy is A7-20%si, htp <ht-
5a% P), Cu s P (Cu-15% P), etc., and were blended using these to obtain the compositions shown in Table 1. The melting was performed in a graphite crucible using a high-frequency electric furnace, and after sufficient stirring, the graphite mold 3
Cast in 1501. The melting was performed in an atmosphere containing Ar gas. The wax produced as described above was processed to have a width of 2 mm x thickness of 2 fi x length of 15 m.

On the other hand, the At plate of the member to be joined was ultrasonically cleaned with trichlorethylene, then ultrasonically cleaned with acetone, and then with N
It was washed with an aOH aqueous solution and then with water.

This At board (A1050: 50■×50-1 thickness 1mm
) 2 sheets arranged at right angles, so-called inverted T-shaped binding (gap between A7 sheets is 0.1 mm), fillet)
Brazing properties were tested based on the formation status of

In addition, the tensile test was conducted using a flat tube (width 5 mm) as shown in Figure 1.
The above-mentioned brazing was used to braze the joints of a heat exchanger combining fins (width: 50 mm, wall thickness: 0.17+m++) 2 without flux.

Both of the above-mentioned brazeability and tensile test pieces were heated at 620 tr for 1 minute in an N2 inflow aeration furnace. In this case, the dew point of the N2 gas was controlled in three stages: -10C1-2 (l) and -50C, and test pieces were prepared.
As shown in the figure, the flat tube 1 and fins 2 are connected to the brazing material 3 (
The brazed fins 2 were held together with a chuck 4 and measured using a spring meter 95. The results are shown in Table 2.

Regarding the evaluation of the fracture location by a tensile test, if the fillet (braze sealing part) is well formed, the fillet has a higher tensile strength than the fins, so it is possible to evaluate the state of fillet formation.

As is clear from Table 2, the dew point of N2 gas and brazing property (
Regarding the fillet formation condition), no fillet was formed in the conventional brazing material (Comparative Example 6) even in -500, which is a good brazing atmosphere. In Comparative Example 7 and Comparative Example 8, only a few fillets were formed at a dew point of -50C, and conventional brazing cannot be adequately brazed without flux. On the other hand, the solder of the present invention does not exhibit sufficient brazing properties at a dew point of -10C, but forms a good fillet at a dew point of -20C or lower. In this way, in the solder of the present invention, there is also a correlation between the dew point of the gas in the brazing material and the brazability; the lower the dew point of the gas, the better the fillet formation. It can be seen that the temperature should be kept below -20C.

The results are summarized in Table 2 regarding the brazing properties of each type of solder, but when observed microscopically, Sample A
2 is slightly superior, and the effect of the added element is also seen in A3°4 and A5.

Regarding the tensile test, Comparative Example 6 showed a tensile strength of O at a dew point of -500, and Comparative Example 7 showed a tensile strength of O from a dew point of -5°C.
Furthermore, in Comparative Example 8, the tensile strength started to increase from -20C. The lower the dew point, the more difficult it is to create that atmosphere and the more expensive the equipment costs.

On the other hand, in the case of the solder according to the present invention, some test pieces broke from the fins even at a dew point of -10C, and all samples broke from the fins at a dew point of -200C or lower. That is, the brazing material of the present invention exhibits extremely good bonding strength at a dew point of -20C or less. Such an effect is caused by P% P+Cu, P+C
This seems to be because Atzoa formed on the materials to be joined is removed due to each element such as u+Li or their synergistic effect, and the surface tension of the brazing material itself is further lowered. Note that in the examples, N2 gas was used as the brazing atmosphere, but Ar
, HeXH2, and a vacuum atmosphere, and it was confirmed that similar results were obtained when the dew point was changed. Good brazing properties can also be obtained by mixing these gases and vacuum, for example, by using N2 gas and vacuum at the same time, that is, by introducing N2 gas into the atmosphere before evacuation.

The brazing material of the present invention can also be applied to joining At or At alloys with other metals or alloys, such as Cu-based alloys, Fe-based alloys, etc. Since it is more difficult to remove the oxide film with A, 4, or At alloys than with Cu-based alloys and Fe-based alloys, the brazing material of the present invention that is effective for At or At alloys is A7 or At alloys and Cu-based alloys. , there is no problem in joining with Fe-based alloys.

Furthermore, in the present invention, a so-called plating sheet is prepared in which the brazing material of the present invention is applied to the fins, and when brazing this sheet to a flat tube, the brazing is performed in a non-oxidizing atmosphere having a dew point of -20C or less. can improve workability.

〔Effect of the invention〕

As described above, according to the present invention, since it has good wettability with Kt or At alloy, it is possible to obtain a braze part with high bonding strength in a non-oxidizing atmosphere having a dew point of -20C or less.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a heat exchanger brazed using the brazing material of the present invention, and FIG. 2 is a sectional view showing a tensile test method for the brazed heat exchanger. 1... Flat tube, 2... Fin, 3... Wax (Fi No. IF $211￥] Kei = 2 5 1) Do2]

Claims (1)

[Scope of Claims] A brazing filler metal for At, characterized in that it contains Si: 5 to 13%, P: 0.004% or more and less than 0.013%, and the balance consists of At at a weight ratio of 11. 2. M amount ratio: Si: 5-13%, P: 0.004-0.
A brazing filler metal for At, characterized in that it contains less than 0.08% and Cu: 1 to 5%, and the balance consists of A and t. 3. Weight ratio: Si: 5-13%, P: 0.004-0
．． 1%, Ca s L 1% M g and at least one selected from Na 0. A brazing filler metal for A7, characterized in that it contains 4 to 1.0% OO, with the remainder being At. 4. Si: 5-13%, P: 0.004-0.
Less than 08%, CLI: 0.1-5%, Ca, T,'sM
At least one selected from g and Na = 0.00
A brazing filler metal for A7, characterized in that it contains 4 to 1.0%, and the remainder consists of A7. 5. Weight ratio: Si: 5-13%, P: 0.004-00
Using a brazing material containing less than 8% and the remainder being A7,
A method for brazing A7 members, characterized by brazing without flux in a non-oxidizing atmosphere having a dew point of 0C or less, or in a depressurized or depressurized non-oxidizing atmosphere having a dew point of 20C or less.