JPH03264189A - Aluminum brazing sheet for vacuum brazing - Google Patents

Abstract

PURPOSE:To prevent the interruption of brazing by adjusting the thickness of the surface film of a brazing material consisting of an Al-Si-Mg alloy contg. specific wt.% of Si, Mg and Fe to a specific thickness at a specific heating temp. CONSTITUTION:The brazing sheet formed by cladding an Al alloy brazing material to both or one surface of a core material consisting of Al or Al alloy is subjected to vacuum brazing. The brazing material of of the Al-Si-Mg alloy contg., by weight %, >=6% to <=20% Si, >=0.05% to <0.6% Mg and <=0.3% Fe and consisting of the balance Al and unavoidable impurities is thereupon used. The thickness of the surface film of the brazing material is adjusted to <=750A at 530 deg.C during the course of vacuum brazing. The brazing sheet having excellent brazeability is provided in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an aluminum alloy brazing sheet used for vacuum brazing, and more specifically to a brazing sheet that has excellent vacuum brazing properties and does not cause brazing breakage. It provides sheets.

[Conventional technology and its problems]

Normally, when brazing aluminum or aluminum alloys, the aluminum or aluminum alloy members to be joined are fixed to the aluminum or aluminum alloy members through a brazing material whose melting point is lower than that of aluminum, etc., to form an assembly. This is done by heating the aluminum or aluminum alloy member to a temperature lower than its melting point. And the brazing filler metal alone is generally AA.
'-8i alloy is used, and its shape can be plate-shaped, wire-shaped, or powdered brazing material, or a laminated material (hereinafter referred to as brazing sheet) in which a core material made of aluminum or aluminum alloy is coated with this brazing material. ) is used in the form.

Brazing methods include flux brazing, which uses flux to remove the oxide film on the surface of the parts to be brazed, brazing in a non-oxidizing atmosphere using non-corrosive flux, and brazing without flux. A vacuum brazing method is commonly used in which an assembly to be joined is placed in a vacuum and then brazed and heated.

Figure 1 shows a laminated type evaporator manufactured by vacuum brazing.
) and (2') are alternately laminated and joined by vacuum brazing. Here, the fin material has a thickness of 0. Around Imm is used, and the passage construction sheet has a thickness of 0.6m.
A brazing sheet of around m is used. In such an evaporator, the fin material includes Al-Mn
In order to impart a sacrificial effect to the system alloy, Zn, In.

An alloy to which Sn or the like is added is used. Brazing sheets are generally made of JI33003 alloy as a core material, and the surface thereof is clad with an Al-3i-Mg brazing alloy.

Figure 2 shows a serpentine type evaporator.
A fin (1
) on both sides of the extruded multi-hole tube (4).
5) and (5') were attached and joined by vacuum brazing. The fin material used has a thickness of about 0.15 mm, and the extruded multi-hole tube has a thickness of about 5 mm, a width of 22-1, and a wall thickness of about 1.0 mm. In such an evaporator, a brazing sheet with the AA'-Mn alloy as the core material and AlAl-8j-based brazing alloy cladding is used as the fin material, and the extruded multi-hole tube is made of It33003 alloy, Al- Cu-based alloy, AlCu-
Mn alloy is used.

What these brazing sheets have in common is that the brazing material contains Mg, which evaporates during brazing heating and enables vacuum brazing due to getter action.

By the way, when a brazing furnace is used for a long period of time, the degree of vacuum decreases due to contamination of the furnace, etc. In such a case, the wettability of the solder decreases and a fillet of the solder does not form, making it impossible to perform brazing. A wax breakage phenomenon occurs. Also, the first
When brazing the inside of a sealed structure like the evaporator shown in the figure, there was a problem because the brazability often differed between the inside and outside.

[Means to solve the problem]

In view of this, the present invention has developed a brazing sheet suitable for vacuum brazing.

That is, the brazing sheet of the present invention is made by cladding Al alloy brazing material on both or one side of an Al or Al alloy core material, and in the brazing sheet to be subjected to vacuum brazing, S i of 6 wt% or more and 20 w1% or less, 0 .05
Mg and Q of w1% or more and less than 0.6wt%, 3wt%
An AZ-3i-Mg alloy brazing filler metal containing the following Fe and the balance being Al and unavoidable impurities was used, and the surface film thickness of the brazing filler metal was 7.5℃ at 530℃ during vacuum brazing heating.
It is characterized by being 50A or less.

Another brazing sheet of the present invention is a brazing sheet that is made by cladding Al alloy brazing material on both or one side of an Al or Al alloy core material, and is 6wt% or more and 20w1% or less, and is used for vacuum brazing. S i ,
0.05w1% or more Q, 1) Using an Al-Si-Mg alloy brazing filler metal containing less than wt% Mg and QJw1% or less Fe, the balance being Al and unavoidable impurities, and existing inside the brazing filler metal. 100 Mg2Si particles with a size of 2 μm or more were collected at 540°C during vacuum brazing heating.
mm 2 or more, and the surface film thickness of the brazing material is 750 A or less at 530° C. during vacuum brazing heating.

[For production]

First, the structure of the brazing sheet of the present invention will be explained.

The alloy tempering of the core material of the brazing sheet is not particularly specified. Depending on the material used, for example, It33003 alloy, Mg, Cu, and Zn.

An alloy to which Sn, In, etc. are added or a pure aluminum alloy with consideration given to thermal conductivity may be used as appropriate.

The brazing filler metal contains sx of 6% or more and 20% or less, Mg of os% or more and less than 0.6%, and Fe of 0.3v+% or less.
An Al-3i-Mg alloy containing the following is used.

Si in the brazing filler metal is an additive element that lowers the melting point of the alloy and enables brazing. and the content is less than 6% or 2
If it exceeds 0%, the melting point of the solder increases and brazing properties decrease.

Furthermore, Mg in the brazing material evaporates during brazing and has the effect of improving the degree of vacuum through getter action and the effect of destroying the oxide film through evaporation.

It was previously thought that if the content was less than 0.6%, the above effects would not be sufficiently produced and the brazing properties would deteriorate.

However, due to the effect of Fe and the effect of film thickness, which will be described later, brazing can be performed with Mg of 0.05% or more and less than 0.6% according to the present invention. When the amount of Mg is reduced in this way, it has the effect of preventing contamination of the furnace and has the advantage of facilitating maintenance of the furnace.

Further, in the present invention, the amount of Fe plays an important role. In other words, an oxide film grows on the surface of the brazing material before Mg starts to evaporate during brazing heating, and Fe is an element that promotes the growth of the film, and Fe exceeds 0.3%. Since the amount of growth of the film increases, the film is not sufficiently destroyed during Mg evaporation, and the wettability between wax and wax decreases, resulting in solder breakage.

The above is the composition of the brazing filler metal alloy of the present invention.
It is possible to add 0.01% or more and 0.2% or less. In this case, Bi improves the flowability of the solder and
It has the function of promoting the evaporation of Mg and making the film more likely to be destroyed. If the amount of Bi added is less than 0.01%, the above effect is not sufficient, and if it is more than 0.2%, the rollability of the brazing material decreases, making it difficult to manufacture a brazing sheet.

The alloy of the present invention contains 0.2% or less of C as an unavoidable impurity.
u, added for the purpose of improving corrosion resistance (1.3% or less Zn, T added as a grain refining agent during casting)
j, B, added for the purpose of improving brazing properties, etc.
Mn, In.

Sn, Cr, Zr, Ca, V, Pb, Ag.

It may contain less than 0.05% of elements such as Be.

One or both sides are clad with such an alloy brazing material, but the coverage rate is not particularly determined. It is sufficient to coat each member in the required amount.

The alloy composition of the brazing sheet has been described above, but in the present invention, the thickness of the brazing metal surface film of the brazing sheet is set to be 750 A or less at 530° C. during vacuum brazing heating. The surface film referred to here mainly refers to an oxide film, and its thickness can be measured by heating the brazing sheet to 530°C at a temperature increase rate of 30°C/min in a vacuum level of 10-5 Torr. After quenching with nitrogen gas, we measured an area of approximately 4 square diameters using glow discharge spectroscopy.
It is converted by measuring the step difference after measurement.

This surface film is deeply related to the solder breakage phenomenon mentioned above.
If the film thickness is 750A or less, Mg is added during brazing heating.
Evaporation of Mg occurs from around 530°C, and this evaporation of Mg occurs from the entire surface of the film to make it porous. When the wax melts, Mg evaporates rapidly and breaks this film into smaller pieces, improving brazing properties. . However, if the film thickness at 530℃ exceeds 75OA, Mg
Evaporation occurs intensively from weak areas of the film, and conversely, the film grows thick and strong in other parts. Mg rapidly evaporates when the wax melts, but this evaporation occurs mainly in the same places as during heating, so the film on the wax surface is not sufficiently destroyed and the wettability between the wax and wax decreases. , wax breaks occur.

The thickness of such a surface film is approximately 100 OA in the conventional brazing sheet manufacturing process.

Therefore, in order to obtain the film thickness of the present invention, it is necessary to perform sufficient washing with alkali during the manufacturing process.

In addition to the above, Mg2S in the brazing sheet brazing metal
When the i-particles are determined as described above, brazing properties are further improved.

This is because Mg exists in the form of solid solution Mg5Al-Mg intermetallic compounds or Mg2Si particles in the brazing filler metal.
This is because the inventors have discovered that among these particles, Mg2Si particles have a large effect on brazing performance.

In other words, Mg, which exists in solid solution Mg and Al-Mg intermetallic compounds in the brazing filler metal, evaporates from a relatively early stage of vacuum brazing and improves the degree of vacuum due to the getter action. Because it exists in the wax, it evaporates explosively when the wax melts and does not have the power to destroy the coating.

On the other hand, if Mg2Si particles remain until the wax melts, they cause explosive evaporation of Mg during melting and destroy the surface film. Therefore, at 540° C. during vacuum brazing heating, the number of Mg2Si particles of 2 μm or more existing inside the brazing material is limited to 100 particles/mA or more.

Here, the reason why the particles are determined at 540° C. during vacuum brazing heating is that the amount of particles immediately before the wax melts is a problem. The particle size is set to 2 .mu.m or more because particles smaller than 2 .mu.m at 540.degree. C. do not have sufficient explosive force to destroy the surface film when melting the wax. Further, even if the number is less than 100 pieces/#l1li, the destructive power is insufficient.

The particles were prepared by heating a brazing sheet to 540°C at a temperature increase rate of 30°C/rain under a vacuum level of 10-5 Torr, quenching it with nitrogen gas, and then polishing its cross section.
Observed using a backscattered electron image using a scanning electron microscope.
Particles that appear darker than the matrix in the backscattered electron image are Mg.
The particle was determined to be a 2Si particle, and its equivalent circular diameter was determined by image analysis.

Incidentally, a brazing material having such a particle distribution can be obtained by controlling the homogenization treatment conditions, rolling rate, etc. of the manufacturing process.

In the present invention, the above-mentioned Mg2Si particles of 2 μm or more are present inside the brazing filler metal at a rate of 100 particles/mir or more at 540°C during vacuum brazing heating, and the surface film thickness of the brazing filler metal is reduced during vacuum brazing heating. A brazing sheet with even better brazing properties can be obtained by having both of the following characteristics: 750A or less at 530°C.

〔Example〕

The present invention will be specifically explained below using Examples.

Brazing sheets having the compositions shown in Table 2 (thickness 0.6 mm: cladding on both sides with a cladding ratio of 15%) were produced using aluminum alloy core materials and brazing fillers having the compositions shown in Table 1. In addition, the tempering of the brazing sheet was made using O material (
annealed material).

The Mg2Si particles and surface film in the table were measured using the method described above. The Mg2Si particles here were adjusted by casting conditions and homogenization treatment conditions, and the surface coating was variously adjusted by performing alkaline cleaning with NaOH solution before and after final annealing.

Using each of these brazing sheets, individual cup-shaped products (6) as shown in FIG.
) were laminated together as shown in FIG. 3, and then a brazing test was conducted on 100 pieces of each. The heating conditions for the brazing test were a heating rate of 30°C/min, and 10ml/min after reaching 600°C.
, held. The ultimate vacuum level is approximately 5 x 10-'Tour
It is. 500 to these laminated cups in the same furnace at the same time.
A brazing test was performed by covering the material with a ml beaker and assuming a case where the degree of vacuum was reduced. Table 3 shows the number and appearance of the cups in which the wax broke after heating.

As is clear from Table 2, Table 3, and Table 3, the brazing sheet of the present invention exhibits excellent properties with no occurrence of solder breakage and a silvery white surface. On the other hand, in the brazing sheet of the comparative material, the properties deteriorate significantly when heated in a beaker, especially when the degree of vacuum is assumed to be reduced.

〔Effect of the invention〕

As described above, the brazing sheet of the present invention has excellent brazing properties, and in particular, even when the degree of vacuum in the brazing furnace fluctuates, the brazing sheet does not break out of the solder, and has a remarkable industrial effect.

[Brief explanation of drawings]

Figure 1 is a partially cutaway perspective view of an example of a laminated type evaporator, Figure 2 is a side view of a part of an example of a serpentine type evaporator, and Figure 3 is an example of a laminated cup used in a cup brazing test. FIG. 3 is a side view showing a partial cross section. 1. Fin 2.2', Passage construction sheet Figure 1 Figure 2. 3.3'. 4゜5.5゜6゜ Refrigerant passage extruded multi-hole tube connector cup shape product Figure 3 Procedural amendment (voluntary) May 10, 1990 1. Case indication 1990 Patent application No. 59326 2. Invention Name: Aluminum brazing sheet used for vacuum brazing 3, Relationship to the amended case Patent applicant address: 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Name: Furukawa Aluminum Industry Co., Ltd. 4, Agent address: Chiyoda, Tokyo 3rd Floor 5, Ei Building, 16 Kanda-kita Jorimono-cho, 101 Ward, Contents of Amendment 1 in Table 2, Scope of Claims and Detailed Explanation of the Invention in the Specification Subject to Amendment Correct as expected. 2. The following matters will be corrected in the Detailed Description of the Invention column. (1) Specification page 6, line 11, page 7, line 3, page 10, line 1, page 10, line 10, page 10, line 16, and
On page 3, line 13, replace r 750Aj with “75
θA (Angstrom)”. (2) On page 11, line 5 of the specification, "rloooAJ" is corrected to "rloooA (angstrom)." Claims (1) A brazing sheet made by cladding an Al alloy brazing material on both or one side of an Al or Al alloy core material and subjected to vacuum brazing, S i of 6 wt % or more and 20 w 1 % or less, 0 Contains .05wt% or more and less than 0.6w% of Mg and Q, 3wt% or less of Fe, and the balance is Al.
Using an Al-Si-Mg alloy brazing filler metal consisting of unavoidable impurities, the surface film thickness of the brazing filler metal was 750A (angstrom) at 530℃ during vacuum brazing heating.
An aluminum brazing sheet used for vacuum brazing, characterized by the following: (2) In a brazing sheet made by cladding Al alloy brazing filler metal on both or one side of an Al or Al alloy core material and subjected to vacuum brazing, Si is 6 wt% or more and 20 wt% or less, and 0.05 wt% or more. Contains less than 0.6 wt% Mg and 0.3 wt% Fe, with the balance being Al.
Using an AlSl-Mg alloy brazing filler metal consisting of unavoidable impurities, the Mg with a size of 2 μm or more existing inside the brazing filler metal
2Si particles are 100 particles/mm2 or more at 540°C during vacuum brazing heating, and the surface film thickness of the brazing material is 750A (at 530°C during vacuum brazing heating).
An aluminum brazing sheet used for vacuum brazing, which is characterized by having a thickness of less than (Angstrom) or less.

Claims (2)

[Claims] (1) In a brazing sheet made by cladding Al alloy brazing material on both or one side of an Al or Al alloy core material and subjected to vacuum brazing, Si of 6 wt% or more and 20 wt% or less and 0.05 wt% or more of 0 Less than .6wt% Mg
An Al-Si-Mg alloy brazing filler metal containing 0.3 wt% or less of Fe with the remainder being Al and unavoidable impurities is used, and the surface film thickness of the brazing filler metal is 5% during vacuum brazing heating.
An aluminum brazing sheet used for vacuum brazing, characterized by having a resistance of 750A or less at 30°C. (2) In a brazing sheet made by cladding Al alloy brazing filler metal on both or one side of an Al or Al alloy core material and subjected to vacuum brazing, Si of 6 wt% or more and 20 wt% or less and 0.05 wt% or more of 0 Less than .6wt% Mg
Using an Al-Si-Mg alloy brazing filler metal containing 0.3 wt% or less of Fe and the remainder being Al and unavoidable impurities, Mg_2 with a size of 2 μm or more existing inside the brazing filler metal
1 at 540°C during vacuum brazing heating.
An aluminum brazing sheet used for vacuum brazing, characterized in that the brazing filler metal has a surface film thickness of 750 A or less at 530° C. during vacuum brazing heating.