JPH0985433A - Fluxless non-oxidizing atmosphere brazing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent reduction of brazability, contamination of furnace, external appearance defect, etc., by covering an object to be brazed with a cover, suppressing flow of atmosphere gas inside a cover and providing Mg supply source inside the cover. SOLUTION: An object to be brazed 2 of aluminum is placed in a brazing furnace 3 and covered with a cover 1, flow of atmosphere gas is suppressed inside the cover 1 and Mg supply source is placed inside the cover 1, fluxless nonoxidixing atmosphere brazing is executed with arranging a hole 4 to the cover 1 for replaceing inside atmosphere with outside atmosphere. A flow speed of the atmosphere gas inside cover 1 of 6m/min, an oxygen concentration in nonoxidizing atmosphere outside the cover 1 of 20-1000ppm and a dew point of -60 to 120 deg.C are used for the process, further, an aluminum alloy containing 5-20wt.% Si, 0.02-6.0wt.% Mg is used for a brazing filler metal Mg as Mg supply source. By this method, an aluminum alloy containing Mg is used for structural member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brazing method for a product manufactured by brazing aluminum (including an aluminum alloy; the same applies hereinafter) to heat exchangers for automobiles and the like.

[0002]

2. Description of the Related Art When manufacturing an aluminum product as described above by brazing, a method of brazing and joining structural members using a non-corrosive fluoride type flux is often used. Conventionally, when performing such non-corrosive fluoride-based flux brazing, the aluminum material is first press-molded or cut as needed to temporarily assemble it into a product shape, and then the aqueous suspension solution of the flux is applied to the surface of the aluminum material. After that, it was pre-dried and then brazed by heating to the brazing temperature in a non-oxidizing atmosphere. At this time, recently, a continuous furnace in which a flux pre-drying furnace and a brazing furnace are connected has become the mainstream.

Since a flux film of a normal non-corrosive fluoride flux brazing is formed by immersing it in a suspension, it is likely to have an extreme unevenness in the thickness, and the thickness is 100 at a thick portion.
Since it is about μm and is brittle, it is partially peeled off by pressing or other handling after coating and drying, and it becomes impossible to braze the part. Therefore, usually, as described above, the product is assembled into a complicated product shape, and the work of applying and drying the suspension is performed immediately before brazing. However, in such a method, the work efficiency is not good because the work of applying and drying the suspension is required after assembling into a complicated product shape. In addition, since there is a drying process immediately before the brazing process, unless sufficient time is taken for this process, the generated water may be brought into the brazing furnace and the brazing property may be deteriorated. If too much, there was a dilemma that it would be a rate-determining process for the entire line.

Further, since the coating is performed in a complicated product shape, the coating amount tends to be non-uniform and the coating amount has to be increased for safety, and the amount of flux deposited on the aluminum member tends to increase in general. As a result, the brazing furnace is easily contaminated, and the molten flux in the furnace drops and accumulates in the furnace, corroding the metal furnace wall. There was also the problem of being forced to do so.

Furthermore, since the commonly used non-corrosive fluoride-based flux component becomes a liquid phase at the brazing temperature, excess flux flows and the excess residual locally remained on the surface of the aluminum product after brazing. There is also a problem that the flux causes gray or white stains to cause color tone unevenness and impair the appearance, and also hinders the subsequent surface treatment. Further, excessive flux application has been a problem in terms of cost. Further, in brazing using a non-corrosive fluoride-based flux, when an aluminum material containing Mg is used, F in the flux and Mg in the aluminum material react rapidly to form MgF ₂ having poor wettability.
A material containing more than 2% of Mg could not be used, and the user's needs of improving strength and reducing thickness and weight were encountered.

On the other hand, vacuum brazing without using flux is also widely used. When aluminum is brazed in a vacuum, Mg is added to the brazing filler metal to destroy the oxide film formed on the surface due to the evaporation of Mg during brazing to improve the brazing flow. . But,
If Mg is added to the brazing filler metal, the inside of the vacuum furnace is contaminated because Mg evaporates, and there is a drawback that cleaning or the like takes time.

Therefore, there is also a demand for a method capable of vacuum brazing without using a Mg getter material. However, ordinary non-corrosive fluoride-based flux cannot be used for vacuum brazing because it becomes liquid phase or vapor phase at brazing temperature and causes corrosion and contamination of the brazing furnace, as well as contamination of the entire vacuum system. It was Further, even if an attempt is made to use a material containing Mg as a structural material of the object to be brazed in order to improve the strength of the brazed product, the material is almost evaporated during the vacuum brazing and the purpose cannot be achieved.

There is an improved technique that attempts to solve the problems of these conventional techniques. (1) One uses an Al-Si-Mg-Bi brazing material,
In order to release O ₂ and H ₂ O adsorbed on the surface of the brazing material by heat, preheat in a vacuum furnace at a temperature of about 500 ° C., then exhaust and once high vacuum of 10 ⁻⁵ to 10 ⁻⁶ Torr. Then, nitrogen is sealed and high-speed circulation is performed, and the O ₂ concentration in the brazing atmosphere is set to 10 p.
This is a method that enables brazing by restricting the amount of H ₂ O to 10 ppm (about −61 ° C. in dew point) or less very strictly. (U.S. Pat. No. 4,240,574) (2) Further, there is a method in which an Al-Si-Bi brazing material is used and an oxide film is removed by etching with an acid or an alkali, followed by brazing in a non-oxidizing atmosphere. In this method, the gas is evacuated and evacuated, then nitrogen is filled and the pressure is set to 800 Torr.
The O ₂ concentration is 5 ppm or less and the dew point is about −73 ° C. or less, and the brazing atmosphere is further strictly regulated. Further, it is said that when only nitrogen substitution is carried out under the condition of 1 atm, the O ₂ concentration is 2 ppm or less and the dew point is about −65 ° C. or less and the brazing condition is not controlled more strictly, so that the brazing cannot be performed properly. (Sumitomo Light Metal Technical Report, Vol.21, No.1 (1980)
76) The above-mentioned improved technique requires strict control of the brazing atmosphere, and the additive element Bi in the brazing material is expensive.

[0009]

Therefore, the inventors of the present invention avoid the above problems of the non-corrosive fluoride flux brazing and the vacuum brazing of the prior art and, at the same time, have the problem of the above-mentioned improved technology. Intensive research has been conducted in search of a brazing method that does not require strict requirements regarding the active atmosphere.

[0010]

As a result, the present inventors have proposed a fluxless braze by providing a cover for suppressing the flow of atmospheric gas and a Mg source in the cover in a non-oxidizing atmosphere. The inventors have found that this can be done and have reached the present invention. That is,

In the brazing of aluminum according to claim 1, the braze object is covered, the flow of atmospheric gas inside the cover is suppressed, and a Mg supply source is provided inside the cover. Oxidizing atmosphere brazing method.

The brazing method according to claim 1, wherein the cover is provided with a hole or a gap to the extent that the atmosphere is replaced with the outside.

The flow of the atmospheric gas inside the cover according to claim 3 is suppressed to less than 6 m / min.
Brazing method.

The oxygen concentration in the non-oxidizing atmosphere outside the cover according to claim 4 is 20 to 1000 ppm, and the dew point is -60 to-.
20 degreeC, The brazing method of Claims 1-3 characterized by the above-mentioned.

The brazing method according to any one of claims 1 to 4, wherein the ratio of the inner volume X of the cover to the outer volume Y of the object to be brazed is 1 <X / Y ≤ 50.

As the Mg supply source of claim 6, 5 to 20% by weight of Si and 0.02 of Mg are contained in the brazing material of the object to be brazed.
The brazing method according to any one of claims 1 to 5, wherein an aluminum alloy containing ~ 6.0% by weight is used.

Further, in the seventh aspect, Bi is 0.02 to 1.2.
The brazing method according to claim 6, wherein a brazing filler metal containing wt% is used.

As the Mg source of claim 8, an aluminum alloy containing 0.05 to 1.3% by weight of Mg is used as a structural material of the object to be brazed. How to attach.

The brazing method according to any one of claims 1 to 8, wherein pure Mg or a Mg alloy is placed in the cover as the Mg supply source and brazing is performed.

A brazing method according to any one of claims 1 to 9, wherein an aluminum alloy containing 0.05 to 8% by weight of Mg is used for at least an inner material of the cover as the Mg supply source. . It is.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, fluxless brazing is enabled by providing a Mg supply source and a cover for suppressing the flow of atmospheric gas under a non-oxidizing atmosphere.

Here, the non-oxidizing atmosphere is an atmosphere of nitrogen gas, argon gas, or the like, which is the same as in ordinary non-corrosive flux brazing. In the case of the present invention, the oxygen concentration in the non-oxidizing atmosphere outside the cover is 20 to 1000 ppm, and the dew point is −.
Brazing is possible at a temperature of 60 to -20 [deg.] C., which is considerably looser than that of normal non-oxidizing atmosphere brazing. The lower the oxygen concentration and the dew point, the better, but it is 20 for each in consideration of cost.
The lower limit was ppm and -60 ° C. Oxygen concentration is 1000p
When the pm and the dew point exceed -20 ° C, the oxidation is so severe that brazing cannot be performed by the method of the present invention.

The cover is for shutting off the gas flow due to the fan in the furnace and the blowing of the atmospheric gas, and for minimizing the gas flow near the surface of the object to be brazed. As the material of the cover, any material can be used as long as it can withstand heating at 600 ° C. or higher and does not generate a gas that adversely affects brazing, but a metal material such as stainless steel, mild steel or aluminum alloy is usually used. If the cover is completely sealed, O ₂ , H ₂ O, etc. released from the brazed object will stay in the vicinity as the temperature rises, obstruct brazing, and there is no point in regulating the atmosphere outside the cover. Therefore, a slight gap needs to be opened so that replacement of O ₂ , H ₂ O, etc. occurs inside and outside the cover. A gap may be formed at the time of manufacturing the cover, but if a cover having a high sealing property is used, it is preferable to provide a hole that allows the atmosphere to be replaced with the outside. However, if the flow of the atmospheric gas in the cover is fast, it is difficult for Mg to leave the vicinity of the surface of the object to be brazed and contribute to brazing, so it is inconvenient to provide too large a hole or a large number of holes. The flow rate of the atmospheric gas in the cover is preferably less than 6 m / min in terms of flow rate.

Inner volume X of the cover and outer volume Y of the object to be brazed
The ratio is 1 <X / Y ≦ 50. Since it is necessary for the braze to enter at least in the cover, it must be greater than 1, and if it exceeds 50, convection of atmospheric gas occurs inside the cover.

As the Mg supply source, in addition to the brazing material of the object to be brazed and the structural material of the object to be brazed, pure Mg or Mg alloy is placed inside the cover, or Mg is contained as a material at least inside the cover. It is conceivable to use an aluminum alloy.

When a brazing material to be brazed is used as a Mg supply source, Si is 5 to 20% by weight and Mg is 0.02.
The aluminum alloy contains ˜6.0 wt%. Si in this composition range is necessary for the fluidity of the wax and is Al-S.
It is a normal content in the i-based brazing material. Mg is 0.0
If it is less than 2% by weight, the effect of Mg is not sufficient and 6.0
Even if it is contained in excess of weight%, the effect is saturated and the cost is high. The Mg added to the brazing material also has the effect of diffusing to the core material side by the heat during brazing and contributing to the strength improvement. If the Al-Si-Mg brazing material further contains 0.02 to 1.2% by weight of Bi, it will be costly, but the fluidity of the brazing material will be further improved. If it is less than 0.02% by weight, it has no effect, and if it is contained in an amount of more than 1.2% by weight, the effect is saturated and only cost is required.

When the structural material of the object to be brazed is used as the Mg supply source, an aluminum alloy containing 0.05 to 1.3% by weight of Mg is used. If it is less than 0.05% by weight, there is no effect, and if it exceeds 1.3% by weight, it cannot withstand the high temperature during brazing and buckles, which is costly. In addition to Mg, for example, Mn, Cu, Fe, Zn, Si, Ti, V, Zr, and
It does not matter at all if it appropriately contains Cr and the like. The term "structural material of the object to be brazed" means that it does not melt and flow like brazing material during brazing and acts as a member that forms the structure even after brazing, for example, a brazing sheet core material or a bare header. It is something like a plate.

Pure Mg or Mg in the cover is used as a Mg supply source.
The alloy can also be placed and brazed. This is the same as the "placement Mg" method that was performed by vacuum brazing. It is important to place it in a place where the temperature tends to be high so that Mg can evaporate as easily as possible, and to place the vaporized Mg so as to act on all brazing parts.

As the Mg supply source, an aluminum alloy containing Mg as a material for the cover may be used. In this case, an aluminum alloy containing 0.05 to 8% by weight of Mg is used at least inside the cover. "At least the inside" is mainly because the action of Mg is necessary inside the cover, and when using a cover made of a normal aluminum alloy that is not a clad, the outside may be made of the same material. If it is less than 0.05% by weight, it has no effect, and if it exceeds 8% by weight, it cannot withstand the high temperature at the time of brazing and buckles. The inconvenience of being contaminated by The upper limit of the Mg content of the material of the cover is higher than the upper limit of the Mg content of the structural material of the object to be brazed because the plate thickness is large.

The Mg supply source may be a single source,
You may combine two or more. When combined, it is natural that the amount of each Mg may be small. However, the method of using the brazing material of the material to be brazed and the structural material of the material to be brazed as the Mg supply source is effective for the internal brazing property described later, so either one of them is used as the Mg supply source (when using the other. It is also preferable to use it together.

The brazing mechanism in the present invention has not been clarified yet, but is presumed below.

The Mg of the Mg source evaporates as the temperature approaches the brazing temperature. However, because of the pressure of the atmosphere in the inert atmosphere brazing, M in the vacuum brazing
It is a small amount rather than a large amount like evaporation of g.

Since the flow of the atmospheric gas in the vicinity of the surface of the object to be brazed is very weak, the evaporated Mg does not diffuse to the surroundings and stays in the vicinity of the surface to be brazed. It will be shielded with. The evaporated Mg in the shielded state reacts with oxygen and moisture inside the cover to become magnesium oxide, which prevents oxidation of the surface of the object to be brazed. If oxidation is prevented, the oxide film will not grow, and it will be destroyed by the evaporated Mg to form a new surface, improving the wettability and improving the brazing property. Such covering weakens the flow of the atmospheric gas near the surface of the object to be brazed, so that the shielding effect of Mg is not disturbed and the reaction of Mg with oxygen and moisture is made efficient. For the above reasons, it is considered that good brazeability can be maintained even if the oxygen concentration and dew point in the furnace are higher than when there is no cover. Since the requirement for the atmosphere is loose, the need for adjusting the atmosphere by flowing a large amount of atmosphere gas is reduced, so that the running cost is reduced and the brazing operation is very easy and efficient.

On the other hand, in the non-oxidizing atmosphere brazing without covering, there is a strong atmospheric gas flow near the surface of the object to be brazed, and evaporated Mg diffuses to the surroundings. Further, even if oxygen and water in the vicinity are reduced by reacting with Mg, oxygen and water from other parts are newly supplied to the vicinity of the brazing surface. Therefore, the oxide film becomes thick and the oxide film is less likely to be destroyed by Mg that evaporates thereafter, which makes brazing difficult. For this reason, in order to improve the brazing property, it is necessary to strictly control the oxygen concentration and dew point to an extremely low level, and it is necessary to evacuate and evacuate once, or preheat the vacuum to expel oxygen and moisture. It is thought that was necessary.

[0035]

The present invention will be described in detail below based on examples. Press oil is applied to various brazing sheets with a plate thickness of 0.6 mm, pressed, then washed and dried with an organic solvent, and in one step, length 115 mm x width 135 mm x height 14 m.
m drone cup type heat exchanger models were stacked in two stages and temporarily assembled. In Comparative Examples 1 to 4, instead of washing with an organic solvent, 10% H ₂ SO ₄ was used for pickling, followed by thorough washing with water.

The temporarily assembled heat exchanger model was placed in a brazing furnace, except for Comparative Examples 1 to 4, directly without evacuation.
The atmosphere was replaced with nitrogen gas and kept at 1 atm, 610 ° C x 10
Brazed in minutes. As shown in FIG. 1, the brazing was performed by covering a drone cup type heat exchanger model with a box-shaped cover having a hole in the center of the upper surface. The influence of each was investigated by changing the inner volume of the cover, the material of the cover, the placement Mg in the cover, the oxygen concentration / dew point of the non-oxidizing atmosphere, and the flow rate of the atmospheric gas in the cover. The flow velocity of the atmospheric gas in the cover was changed by adjusting the size and number of the holes with respect to the size of the cover and by disposing a baffle plate at the gas outlet into the furnace. Place Mg is pure M
The g ribbon was placed around the braze along the inside of the cover. Tables 1 and 2 show details of brazing conditions.

[0037]

[Table 1]

[0038]

[Table 2]

In the table, "core material" means the material of the brazing sheet core as "structural material of the object to be brazed". “3003” in this column refers to JIS A 3003, which is 1.2% Mn, 0.1% Cu, 0.3% Fe, 0.
A chemical composition of 2% Si was used. In addition, "3003
A "system" is the above component with the addition of the amount of Mg in parentheses at the end. Furthermore, "6010 series" is 1.0% Si,
0.3% Fe, 0.4% Mn, 0.2% Cu with the amount of Mg added in the parentheses at the back. (The amount of Mg is the total amount.) The brazing properties of the above invention examples 1 to 21 and comparative examples 1 to 8 were visually evaluated, and the results are shown in Table 1 and Table 2.

In the table, "external brazing property" means the brazing property of the fillet portion seen from the outside of the heat exchanger model, and "internal brazing property" means the brazing property of the fillet portion inside the heat exchanger model. (The sample is cut and observed).

The evaluation criteria of brazing property are as follows. ◎ No wax breakage, 100% wax flow (wax runs over the entire length of the fillet). ○ There is no wax breakage, and the flow of wax is 100%, which is acceptable as a product, but the fillet is slightly small. × There is wax breakage, and wax flow is less than 80% (less than 80% of fillet length is flowing).

The following can be seen from Tables 1 and 2. Inventive Examples 1 to 21 all have a "cover" that is an essential component of the present invention and a "Mg supply source" inside the cover. In the invention example 1, since the Mg supply source is only in the structural member (core material) of the object to be brazed, the internal brazing property is good because the flow of the atmospheric gas is smaller than that in the outside, but the external brazing property is a little. Inferior. . In Invention Example 2, since the Mg supply source is only Mg placed inside the cover, the external brazing property and the internal brazing property are slightly inferior. In Invention Example 3, since the Mg supply source is only Mg in the material of the cover, the external brazing property and the internal brazing property are slightly inferior.
In the invention example 4, since the Mg supply source is only Mg in the brazing material, the internal brazing property is good because the flow of the atmospheric gas is smaller than that in the outside, but the external brazing property is slightly inferior. Invention Example 5
Since the brazing material contains Bi in addition to Mg in the brazing material, the external brazing property is improved as compared with Inventive Example 4 without Bi. Inventive Example 6 has two brazing materials and a covering material as the Mg supply source, but since the amount of Mg in the brazing material is as small as 0.02%, the external brazing property is somewhat inferior. Inventive Example 7 has a high content of Mg in the brazing material of 0.1%, which is higher than that of Inventive Example 6. Inventive Example 8 is within the scope of the invention, but X / Y
Is as large as 30 and the gas flow in the cover is as fast as 5.9 m / min, so external brazing property is somewhat inferior.
Inventive Example 9 has a high oxygen concentration of 800 ppm in a nitrogen atmosphere, but a large amount of Mg in the brazing material is 5.0%, and the covering material is M.
Since g is also included, both internal brazing and external brazing properties are good. Inventive Example 10 has a large X / Y of 30 and accordingly the gas flow in the cover is as fast as 5.9, but since there are three brazing filler metals, cover materials, and Mg and Mg supply sources in the cover, the internal braze Good in both brazing and external brazing. Inventive Example 11 is brazing material, Mg placed in the cover and Mg
Since there are three supply sources, both internal and external brazing properties are good. Inventive Example 12 has three brazing materials, Mg placed inside the cover, structural members to be brazed, and Mg supply sources, so that both internal brazing properties and external brazing properties are good.
Inventive Example 13 has two brazing materials, structural members to be brazed and Mg sources, but since the brazing material has a small amount of Mg of 0.02%, the external brazing property is somewhat inferior. . Inventive Example 14 has two brazing materials, structural members to be brazed, and a Mg supply source, and the amount of Mg in the brazing material is as high as 1.0%, so that the internal brazing property and the external brazing property are good. Inventive Example 15 is a brazing material,
Since there are three covering materials, structural members to be brazed and Mg sources, both internal brazing and external brazing properties are good. Inventive Example 16 is almost the same as Inventive Example 15 with respect to the Mg supply source, and since the oxygen concentration in the nitrogen atmosphere is as high as 800 ppm, the external brazing property is slightly inferior. Invention Example 17 is
The Mg source is almost the same as in Invention Examples 15 and 16,
The oxygen concentration in the nitrogen atmosphere was 800 p, as in Invention Example 16.
Although it is as high as pm, since the brazing material contains Bi, the external brazing property was also improved. Inventive Example 18 has two materials for the covering material, Mg placed inside the covering, and a Mg supply source, but since the brazing material does not contain Mg, the internal brazing property and the external brazing property are slightly inferior. Inventive Example 19 is good in both internal brazing property and external brazing property because it has three covering materials, Mg placed inside the covering, structural member to be brazed and Mg supply source. Invention Example 20
Is a cover material, brazed structure member and Mg source 2
Since each has a large amount of Mg, the brazing material does not contain Mg, but the internal brazing property and the external brazing property are good.
Inventive Example 21 has two places of Mg inside the cover, the brazed object structural member and the Mg supply source, and the amount of Mg is not so large,
Since the brazing material does not contain Mg, the external brazing property is slightly inferior. It goes without saying that the strength of the brazed object structural member using the Mg-containing material was higher than that of the member not using the Mg-containing material after brazing.

Since Comparative Examples 1 to 4 all lack the cover, which is an essential component of the present invention, the X / Y ratio (calculated with X as the inner volume of the furnace instead of the inner volume of the cover) is as large as 100. Accordingly, the flow velocity of the gas in the cover becomes 10.0 m / min. Therefore, Comparative Examples 1 and 3 having no Mg supply source are poor in both internal brazing property and external brazing property. Mg as a brazing material
Even in Comparative Example 2 including the above, only the inside is good and the external brazing property is poor. The same was true in Comparative Example 4 in which the brazing material further contained Bi. In Comparative Examples 1 to 4, as described above, all of the brazed members were pretreated by using pickling, evacuated and then filled with nitrogen.

In Comparative Example 5, there is a cover, but there is no Mg supply source, so both internal brazing and external brazing are poor.

In Comparative Examples 6 to 8, both the cover and the Mg supply source are provided, but the oxygen concentration in the atmospheric gas and the dew point are outside the range of the present application. With one Mg source (Comparative Example 6), both internal brazing and external brazing were poor. When the number of Mg sources is two or more (Comparative Examples 7 and 8), the internal brazing property becomes a pass level, but the external brazing property remains poor.

[0046]

[Effect] As can be seen from the above detailed description, the present invention has many effects as listed below.

That is, in the non-corrosive fluoride-based flux brazing performed in A nitrogen atmosphere: Eliminate the productivity hindrance factors that result from flux application and drying after assembling into a complicated product shape. 2. When a continuous furnace is used, the brazing property is prevented from deteriorating due to water being brought into the brazing furnace from the drying furnace. Due to the tendency to apply a large amount of flux,
3. Avoid all the disadvantages of brazing furnace contamination, cleaning of the brazing furnace for this purpose, increased frequency of overhaul and increased costs. Furthermore, it eliminates the poor appearance of the product surface after brazing and the adverse effects on the subsequent surface treatment due to the flux becoming a liquid phase at the brazing temperature. 5. No need for large-scale equipment for processing, Allows the use of Mg-containing aluminum alloys for structural members.

Further, in the B vacuum brazing, 1. 1. Prevent the brazing furnace from being contaminated by using a large amount of Mg getter material in vacuum, 2. Even if an Mg-containing aluminum alloy is used for the structural member, most of it remains in the structural member because it is not in a vacuum, so strength improvement and thinning can be achieved. Furthermore, a vacuum pump for creating a vacuum and a highly confidential facility for maintaining a vacuum are not required.

Further, in the conventional improved technology: 1. Since the strict regulation of oxygen concentration and water content of non-oxidizing atmosphere (nitrogen) is loosened, a) large consumption of atmospheric gas becomes unnecessary and running cost is reduced. Since it is not necessary to replace with atmospheric gas after evacuating, the merit described in 3 of vacuum brazing also occurs, 2. The expensive additional element Bi becomes unnecessary, and the material cost can be reduced. 3. Acid or alkali Since etching is not necessary, the equipment and the time and labor required for careful washing and drying after etching are unnecessary.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the concept of brazing of the present invention. The cover covers the braze in the furnace body.

FIG. 2 is a perspective view of an example of a cover used in the present invention. There is a hole in the center of the top surface.

[Explanation of symbols]

 1 cover 2 braze object 3 brazing furnace 4 hole on top of cover

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location B23K 35/28 310 B23K 35/28 310A C22C 21/00 C22C 21/00 D (72) Inventor Masada Hiromi 4-3 Nihombashi Muromachi, Chuo-ku, Tokyo Sky Aluminum Co., Ltd.

Claims (10)

[Claims] 1. In brazing aluminum, the braze object is covered to suppress the flow of atmospheric gas inside the braze,
Also, a fluxless non-oxidizing atmosphere brazing method, characterized in that a Mg supply source is provided inside the cover. 2. The brazing method according to claim 1, wherein the cover is provided with a hole or a gap to the extent that the atmosphere is replaced with the outside. 3. The brazing method according to claim 1, wherein the flow of the atmospheric gas inside the cover is suppressed to less than 6 m / min. 4. The brazing method according to claim 1, wherein the oxygen concentration in the non-oxidizing atmosphere outside the cover is 20 to 1000 ppm and the dew point is -60 to -20 ° C. 5. An inner volume X of the cover and an outer volume Y of the object to be brazed.
The ratio of 1 <X / Y <50 is a brazing method of Claims 1-4 characterized by the above-mentioned. 6. An aluminum alloy containing 5 to 20% by weight of Si and 0.02 to 6.0% by weight of Mg is used as a source of Mg for a brazing material to be brazed. Brazing method according to items 1 to 5. 7. The brazing method according to claim 6, further comprising using a brazing material containing 0.02 to 1.2% by weight of Bi. 8. A brazing method according to claim 1, wherein an aluminum alloy containing 0.05 to 1.3% by weight of Mg is used as a structural material of a material to be brazed as a Mg supply source. . 9. The brazing method according to any one of claims 1 to 8, wherein pure Mg or a Mg alloy is placed in a cover and brazed as a Mg supply source. 10. The brazing method according to claim 1, wherein an aluminum alloy containing 0.05 to 8% by weight of Mg is used as a Mg supply source in at least an inner material of the cover.