JPH09176767A - Al brazing sheet for vacuum brazing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Al brazing sheet for vacuum brazing, capable of producing sufficient corrosion protective effect even after vacuum brazing. SOLUTION: A sacrificial corrosion layer 13 composed of an Al-Zn alloy containing, at least, >2-5wt.% Zn is formed between a core material 11, having a composition consisting of, by weight, 0.3-1.5% Mn, 0.1-0.8% Cu, 0.01-0.2% Ti, and the balance Al with inevitable impurities, and a brazing filler metal layer 12a having a composition consisting of, by weight, 5-15% Si, 0.3-2.5% Mg, and the balance Al with inevitable impurities.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an Al brazing sheet used for vacuum brazing.

[0002]

2. Description of the Related Art Conventionally, as a material for various Al brazing products, an Al brazing sheet in which a brazing material is clad on one side or both sides of a core material has been widely used because the brazing work is easy, and various materials are used depending on the application. Various anticorrosion measures have been adopted. For example, in a heat exchanger in which a tube element through which a heat exchange medium flows and fins are alternately laminated and brazed, an element having a sacrificial corrosion effect is added to a part of the constituent material of the brazing sheet. ing. Specifically, 0.3 to 2.0 wt% Z is present between the brazing material and the core material of the brazing sheet that constitutes the tube element.
A tube element having an anticorrosion effect by interposing a sacrificial anode material containing n (Japanese Patent Publication No. 63-149).
No.).

[0003]

However, in the brazing sheet in which the sacrificial anode material containing Zn is interposed, the brazing sheet brazed in the atmosphere can obtain the anticorrosion effect due to Zn, but if it is vacuum brazed, However, there was a problem that the anticorrosion effect was drastically reduced due to the scattering.

The present invention has been made in view of the above technical background, and an object thereof is to provide an Al brazing sheet for vacuum brazing which can exhibit a sufficient anticorrosion effect even by vacuum brazing.

[0005]

Means for Solving the Problems The inventors have conducted repeated experiments on the amount of Zn lost by vacuum heating, and have determined the amount of Zn that can reliably obtain an anticorrosive effect even after vacuum heating, and completed the present invention. That is, A for vacuum brazing according to the present invention
l brazing sheet, Mn: 0.3 ~ 1.5wt%,
Cu: 0.1-0.8 wt% and Ti: 0.01-0.
A core material (11) containing 2 wt% and the balance being Al and inevitable impurities, Si: 5 to 15 wt% and Mg: 0.3
At least Zn: 2 between the brazing filler metal layer (12a) containing Al and unavoidable impurities in an amount of up to 2.5 wt%.
It is characterized in that the sacrificial corrosion layer (13) made of an Al-Zn alloy containing more than 5 wt% and less than 5 wt% is formed.

In the Al brazing sheet for vacuum brazing of the present invention, Mn and C which are effective as an aluminum alloy forming the core material (11) to make the pitting corrosion potential of the core material (11) noble.
An alloy containing u and Ti is used. This is because the content of Zn makes the pitting corrosion potential of the sacrificial corrosion layer (13) base, while making the pitting potential of the core material (11) noble expands the potential difference between the two and ensures the anticorrosion effect. This is because The content of these elements is such that Mn is less than 3 wt% and Cu
Is less than 0.1 wt% and Ti is less than 0.01 wt%, the above effect is poor. On the other hand, when the Mn content exceeds 1.5 wt%, the intermetallic compound becomes large and the work hardening becomes large so that the formability deteriorates. Also, the Cu content is 0.8
After brazing, it diffuses to the surface after passing through the brazing material grain boundary, and the corrosion resistance deteriorates. Also, the Ti content is 0.2 wt.
If it exceeds%, the melting point of the alloy becomes high and the difficulty of casting increases. Therefore, the Mn content needs to be in the range of 0.3 to 1.5 wt%, and the preferable lower limit is 0.6 wt% and the upper limit is 1.3 wt%. Also, the Cu content is
It should be in the range of 0.1 to 0.8 wt%, the preferred lower limit is 0.3 wt%, and the upper limit is 0.6 wt%. Further, the Ti content needs to be in the range of 0.01 to 0.2 wt%, and the preferable lower limit value is 0.1 wt% and the upper limit value is 0.15 wt%.

In the aluminum alloy forming the brazing filler metal layer (12a), the significance of addition of Si and Mg and the reasons for limiting the contents are as follows.

Si is added in order to lower the melting point of the alloy to obtain good brazing property, and the liquidus temperature becomes high when the content thereof is less than 5 wt% or more than 15 wt%, so that 5-1 is used.
It must be in the range of 5 wt%. Particularly preferred lower limit is 6 wt% and upper limit is 13 wt%. In addition, Mg
Is added in order to activate the joint surface and obtain good brazing property in vacuum brazing without supplying flux. M
If the g content is less than 0.3 wt%, the above effect is poor, while if it exceeds 2.5 wt%, corrosion resistance decreases and contamination of the brazing furnace is promoted. And need to. Particularly preferred lower limit is 0.6 wt%
And the upper limit value is 1.8 wt%.

The sacrificial corrosion layer (13) interposed between the core material (11) and the brazing material layer (12a) makes the pitting corrosion potential of the sacrificial corrosion layer (13) base so that the core material (11) and Due to the sacrificial corrosion action due to the potential difference, an anticorrosion effect is exerted on the core material (11). The sacrificial corrosion layer (13) is composed of the core material (11) and the brazing material layer (1).
2a) and Zn during vacuum brazing
The amount of Zn can be minimized, and a sufficient amount of Zn can be ensured to exhibit the anticorrosion effect even after being scattered by brazing due to the high content.

Al-Zn constituting the sacrificial corrosion layer (13)
In the system alloy, the content of elements other than Zn is not particularly limited, but it is preferable to use pure Al or an Al—Mn system alloy similar to the core material (11). If the Zn content in the alloy is 2 wt% or less, the amount of Zn remaining after vacuum brazing becomes too small, making it difficult to improve the corrosion resistance of the brazed product, while if it exceeds 5 wt%, the effect is increased. Not only that, but it also has the disadvantage of promoting contamination of the brazing furnace. Therefore, the Zn content in the alloy forming the sacrificial corrosion layer (13) must be more than 2 wt% and 5 wt% or less, and the preferable lower limit is 3 wt% and the preferable upper limit is 4 wt%.
It is.

The vacuum brazing Al brazing sheet (A) of the present invention has three typical modes shown in FIGS. 1 (a), 1 (b) and 1 (c). (A) is a three-layer structure in which a brazing material layer (12a) and a sacrificial corrosion layer (13) are formed on only one surface of the core material (11), and (b) is a brazing material layer (12a) on both surfaces of the core material (11). (12b)
Is formed and the sacrificial corrosion layer (13) is formed on only one side, (c) is a brazing filler metal layer (12a) (12) on both sides of the core material (11).
It is a five-layer structure in which a) and the sacrificial corrosion layer (13) (13) are formed. This is because the corrosive environments on both sides of the brazing sheet of the brazed product are not necessarily the same, and the required anticorrosion performance may differ. Further, for the same reason, even when the sacrificial corrosion layers (13) are formed on both surfaces (b) and (c), the Zn contents can be different as long as they are within the above ranges.

Further, such an Al brazing sheet for vacuum brazing is generally manufactured by clad rolling an alloy constituting the core material (11), the brazing material layer (12) and the sacrificial corrosion layer (13). The clad ratio at that time is 45 to 70 for the core material (11).
%, The brazing filler metal layers (12a) and (12b) are preferably 10 to 15% on one side, and the sacrificial corrosion layer (13) is preferably 15 to 25% on one side. The strength of the brazing sheet is reduced when the core material (11) is thinner than the above range, the brazing property is reduced when the brazing material layer (12) is thinner than the above range, and the sacrificial corrosion layer (13) is less than the above range. This is because as the thickness decreases, the anticorrosion effect becomes poor.

Since the Al brazing sheet for vacuum brazing according to the present invention contains a high concentration of Zn in the sacrificial corrosion layer interposed between the core material and the brazing material layer, the anticorrosion effect is obtained even after vacuum brazing. The amount of Zn required for the expression of is obtained, and an excellent anticorrosion effect on the core material is obtained.

[0014]

EXAMPLES Next, concrete examples of the Al brazing sheet for vacuum brazing of the present invention will be described.

First, aluminum ingots of various compositions shown in Table 1 were subjected to homogenizing treatment, chamfering, and hot rolling, and 14 kinds of combinations shown in Table 2 were used to form a sacrificial corrosion layer and a brazing material layer on one side of the core material. Was clad-welded to the brazing material layer on the other surface side.
Then, after undergoing clad rolling, intermediate annealing, cold rolling, final annealing, and cold rolling, the four-layer structure Al brazing sheet for vacuum brazing (A having a thickness of 0.5 mm shown in FIG. 1B) is finally obtained. ) Was produced. This brazing sheet is
56% of core material (11) and brazing material (12a) (12a)
b) is 12% and sacrificial corrosion layer (13) is 20%.

[0016]

[Table 1]

[0017]

[Table 2]

Next, using the above-mentioned vacuum brazing Al brazing sheet (A), a drone cup type heat exchanger shown in FIGS. 2 and 3 was produced and a corrosion test was conducted.

In the overall view of the heat exchanger shown in FIG.
(1) is a plurality of flat tube elements that are vertically stacked in the left-right direction, (2) is between the adjacent tube elements (1) and (1) and the outermost tube element
It is a corrugated fin located outside (1) and integrated with brazing. Each tube element (1)
Has a bulging tank portion (3a) (3b) at both ends in the length direction, and a flat refrigerant passage that connects both tank portions (3a) (3b) to the middle portion in the length direction. It has a plate part (5) that operates. Then, as shown in the enlarged view of the main part of FIG.
Each tube element (1) is brazed so that adjacent ones are in contact with each other in the tank portions (3a) (3b), and the refrigerant circulation holes (6) provided in each tank portion (3a) (3b). The adjacent tank portions are in communication with each other via (6).

Each of the tube elements (1) is formed by superposing two dish-shaped core plates (7) so as to face each other and integrally brazing them. The core plate
(7) is formed by pressing each of the Al brazing sheets (A) for vacuum brazing, and the core plates (7) are joined to each other without interposing the sacrificial corrosion layer of the core plates (7). This is done through the material layer (12b). The corrugated fin (2) has JIS A3203Al.
A sheet made of alloy with a thickness of 0.12 mm is bent into a corrugated shape, and the tube element (1) and the corrugated fin (2) are joined by vacuum brazing Al that constitutes the core plate (7). It is performed through the brazing material layer (12a) with the sacrificial corrosion layer (13) of the brazing sheet (A) interposed.
Further, the adjacent tube elements (1) and (1) are joined to each other through the brazing material layer (12a) with the sacrificial corrosion layer (13) of the vacuum brazing Al brazing sheet (A) interposed. Thus, the heat exchanger has a tube element (1).
The sacrificial corrosion layer (13) is preferentially corroded by using the core plate (7) that composes the core plate (7) with the sacrificial corrosion layer (13) existing on the outer side of the core material (11), that is, on the fin side. In other words, the structure is such that the core material (11) of the tube element (1) is protected against corrosion, and the occurrence of pitting corrosion of the tube element (1) can be suppressed.

The brazing conditions are such that a plurality of the above-mentioned chive elements (1) are arranged with corrugated fins (2) interposed therebetween, and the adjacent ones are connected to the tank parts (3a) (3b). ) In the abutting state, and the assembly is
It was decided to heat at 600 ° C. for 3 minutes in a vacuum of × 10 ^-5 Torr.

The obtained heat exchangers were all brazed well. Then, these heat exchangers were subjected to a corrosion test by the following two types of methods.

[SWATT] 49 at pH 2.8-3.0
Sprayed with artificial artificial seawater at 30 ℃ for 30 minutes, then 98% at 49 ℃
One cycle (2 hours) was allowed to stand for 90 minutes in a humid atmosphere of RH, and 325 cycles (650 hours) were repeated.

[Salt water intermittent test] 60% immersion in 5% salt water for 30 minutes and natural drying for 90 minutes was set to 60.
Repeated for days.

After these corrosion tests, the tube element
(1) Tank part brazed to other tube elements
Corrosion resistance was evaluated by the corrosion states of (3a) and (3b) and the plate portion (5) brazed to the corrugated fins (2). These results are also shown in Table 2.

From the results shown in Table 2, in the brazing sheet of the present invention, the sacrificial corrosion layer containing a high concentration of Zn is interposed between the core material and the brazing material layer to prevent corrosion of the core material even after vacuum brazing. It was confirmed that the effect was obtained.

[0027]

As described above, the Al brazing sheet for vacuum brazing according to the present invention has an Mn of 0.3 to 1.
5 wt%, Cu: 0.1-0.8 wt% and Ti: 0.0
A core material containing 1 to 0.2 wt% and the balance Al and inevitable impurities; Si: 5 to 15 wt% and Mg:
At least Zn: 2 between the brazing filler metal layer containing 0.3 to 2.5 wt% and the balance Al and unavoidable impurities.
Since the sacrificial corrosion layer made of an Al-Zn alloy containing more than 5 wt% and less than 5 wt% is formed, the amount of Zn required for exhibiting the anticorrosion effect is secured even by vacuum heating. An excellent anticorrosion effect on the heartwood can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a brazing sheet for vacuum brazing of the present invention, where (a) is a three-layer structure in which a brazing material layer and a sacrificial corrosion layer are formed on only one side of the core material, and (b) is both sides of the core material. A four-layer structure in which a brazing filler metal layer is formed on and a sacrificial corrosion layer is formed only on one surface, and (c) is a five-layer structure in which a brazing filler metal layer and a sacrificial corrosion layer are formed on both surfaces of the core material.

FIG. 2 is an overall view of a drone cup heat exchanger manufactured using the brazing sheet of the present invention.

FIG. 3 is an enlarged sectional view of a main part of FIG. 2;

[Explanation of symbols]

 A ... Al brazing sheet for vacuum brazing 11 ... Core materials 12a, 12b ... Brazing material layer 13 ... Sacrificial corrosion layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshitomo Kato 6224, Kaiyamacho, Sakai City Showa Aluminum Co., Ltd.

Claims (1)

[Claims] 1. Mn: 0.3 to 1.5 wt%, Cu: 0.
A core material containing 1 to 0.8 wt% and Ti: 0.01 to 0.2 wt% with the balance being Al and inevitable impurities (11)
And Si: 5 to 15 wt% and Mg: 0.3 to 2.5 wt
%, And the balance between the brazing filler metal layer (12a) consisting of Al and the unavoidable impurities, the sacrificial corrosion layer (13) consisting of an Al-Zn alloy containing at least Zn: more than 2 wt% and not more than 5 wt%. An Al brazing sheet for vacuum brazing, characterized in that