JPH07303985A - Aluminum brazing sheet - Google Patents

Abstract

PURPOSE:To provide an aluminum brazing sheet in which flowability of a brazing filler metal itself is improved so as to execute high quality brazing even in the case a coating quantity of flux is not sufficient. CONSTITUTION:One surface at least of an aluminum or aluminum alloy core material 2, a skin material 3, which has a composition consisting of, by weight, 5-15% Si, 0.1-2.0% Bi, or further 0.4-5% Zn and the balance Al with inevitable impurities, is formed as covered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum brazing sheet used as a constituent member of a heat exchanger manufactured according to brazing specifications.

[0002]

2. Description of the Related Art Al-Si alloys have been generally used in the past as a brazing material as a skin material formed on at least one side of a core material of an aluminum brazing sheet.

However, in a brazing sheet using an Al-Si alloy as a brazing material, it has been found that the brazing fluidity may deteriorate depending on the brazing part, resulting in defective joining.

The heat exchanger manufactured by the brazing specification, for example, the multi-flow type aluminum condenser shown in FIGS. 3 and 4 will be described below.

That is, in FIGS. 3 and 4, (13) and (14)
Is a pair of headers arranged in parallel at a distance from each other, (11) is a large number of heat exchange tubes arranged in parallel by connecting both ends to the headers, (12)
Is a fin arranged in the air flow gap between adjacent tubes. Further, as the headers (13) and (14), an aluminum tube in which at least the inner surface of the core material is coated with a brazing material is used, and also as the fins (12), an aluminum brazing sheet is used.

The manufacture of the heat exchanger shown in FIGS. 3 and 4 is carried out from the slit-shaped tube insertion hole (15) formed in the circumferential direction of each header (13) (14) to both ends of the tube (11). After inserting the part so as to project into the header, the fins (12) are arranged between the adjacent tubes to make a temporary assembled state. Next, the flux suspension is applied to the joint, or the flux is directly applied to the joint by an electrostatic powder coating method or the like, and then heated in an inert gas atmosphere to melt the brazing filler metal, and the header (13 ) (14) and the tube (11) and the fins (12) and the tube (11).

[0007]

However, in the above heat exchanger, the tube due to the brazing flow of the brazing material on the inner surface of the header at the time of brazing, particularly with respect to the connection part between the header (13) (14) and the tube (11). Insufficient wraparound to the peripheral surface causes brazing failure between the header and tube,
Therefore, it has been found that the refrigerant may leak.

When the cause of this was investigated, the following was found. That is, in the flux application process performed after the temporary assembly of the heat exchanger and before brazing, the headers (13) (14)
It is practically difficult to apply sufficient flux deep inside, so that the flux action cannot be fully exerted at the connection part between the header (13) (14) and the tube (11). As a result, it was found that the wettability and spreadability of the brazing material deteriorated.

Of course, it is possible to improve the wettability and spreadability of the brazing material to some extent by increasing the amount of flux supplied into the headers (13) and (14). But in this case,
Since the flux application work is usually performed collectively in the heat exchanger temporary assembly state, increasing the amount of flux supplied to the inside of the header causes the outer surfaces of the headers (13) and (14), tubes (11) and fins (12) to be increased. The amount of flux applied to the surface of) also increases, and this causes a new problem that the residual flux after brazing causes deterioration of appearance quality and the like.

In addition, a single header (13) (1) before temporary assembly
It may be possible to apply flux to the 4) and the tube (11), but there was a problem that productivity was reduced and cost was increased due to complicated processes and increased man-hours.

The problem of brazing failure is not limited to the heat exchanger described above, but similarly occurs in brazed products that require brazing inside the tubular body.

The present invention has been made in view of the above technical background, and the brazing filler metal itself is provided so that good brazing can be performed even if the amount of flux applied is insufficient. An object of the present invention is to provide an aluminum brazing sheet having improved wax flowability.

[0013]

In order to achieve the above object, the present invention provides Si: 5 to 15 wt% and Bi: on at least one surface of an aluminum or aluminum alloy core material.
0.1 to 2.0 wt%, or further Zn:
The gist of an aluminum brazing sheet is characterized in that a skin material containing 0.4 to 5 wt% and the balance aluminum and inevitable impurities is formed by coating.

In the above-mentioned aluminum brazing sheet, the composition of the core material is not particularly limited, and various kinds of aluminum or aluminum alloy can be used. However, when the aluminum brazing sheet needs to be formed into a predetermined shape, it has excellent formability. Al such as JIS3003
It is desirable to use a —Mn alloy.

In the composition of the skin material, Si lowers the melting point and causes the skin material to function as a brazing material. However, if the content is less than 5 wt%, it may not function as a brazing material and brazing may be difficult, and conversely if it exceeds 15 wt%, rolling during sheet production may become difficult. Therefore, the amount of Si in the skin material must be specified to be 5 to 15 wt%. The preferred lower limit of Si content is 7 wt%
And the preferable upper limit is 10 wt%.

Bi has a role of improving the flowability of the skin material (brazing material). However, if less than 0.1 wt%, the effect is poor. On the other hand, even if it exceeds 2.0 wt%, the effect of improving the flowability is saturated, and not only a remarkable increase in the effect cannot be expected, but also economical waste is generated. Therefore, the Bi content in the skin material must be regulated to 0.1 to 2.0 wt%. The lower limit of the Bi content is preferably 0.6 wt%, and more preferably 1.0 wt%. On the other hand, the preferable upper limit of Bi content is 2.0 wt%, and more preferably 1.
It is 8 wt%.

Zn, which is optionally added to the skin material, imparts sacrificial anode characteristics to the skin material, but if it is less than 0.4 wt%, its effect is poor. On the other hand, if it exceeds 5% by weight, the disadvantage that the initial corrosion becomes severe is derived. Therefore, Zn
If added, its amount must be specified to 0.4-5 wt%. The preferable lower limit of the amount of Zn is 0.6
wt%, and more preferably 0.9 wt%. On the other hand, the preferable upper limit of the amount of Zn is 2.0 wt%, more preferably 1.4 wt%.

The above skin material may be coated on only one surface of the core material, or may be coated on both surfaces of the core material. Further, the manufacturing conditions of the aluminum brazing sheet are not specified at all, and the conventional conventional method may be used.

[0019]

By adding and adding a predetermined amount of Bi, the fluidity of the skin material as a brazing material during brazing is improved. Therefore,
Even if the flux cannot be applied sufficiently because brazing must be done inside the aluminum pipe material, for example, when joining the header and tube in a multi-flow type condenser, the brazing material should be applied around the joint. It can be sufficiently wet and spread.

[0020]

【Example】

(Example 1) A Bi additive amount of 0 to 3. was added to both surfaces of a core material of a JIS3003 aluminum alloy having a Mn content of 1.0 wt%.
An aluminum brazing sheet was manufactured by coating a skin material having a composition as shown in Table 1 which was changed in the range of 0 wt%.
The core material has a thickness of 1.1 mm and the skin material has a thickness of 80 μm.
It was m. The production was carried out by sequentially performing hot rolling, intermediate annealing, and cold rolling according to a conventional method. Also, Si
Regarding, the content was changed to two kinds of 8.5 wt% and 9.0 wt%.

Then, as shown in FIG. 1 (a), the brazing sheet (1) is abutted against the surface of a bare material (2) of JIS3003 aluminum alloy having an Mn content of 1.0 wt% in an inverted T shape to form a joint. Was formed. Next, the joint is dipped in a 25 wt% suspension of a fluoride-based flux in water to apply the flux to the abutting portion of the joint and dry it, and then in an inert gas (nitrogen gas) atmosphere. Brazing was performed by heating the joint at 620 ° C. for 5 minutes.

After brazing, as shown in FIG. 1 (b), the core material (1a) and the skin materials (1b) on both surfaces of the brazing sheet (1) wet and spread on the surface of the bare material (2) to form the bare material (1). The fillet (3) was formed in the abutting part of 2) and the brazing sheet (1). Then, the length L from the surface of the core material (1a) to the tip of the fillet (3) was measured, and the change of the fillet length L with respect to the Bi content was examined. The results are shown numerically in Table 1 and also shown in FIG.
Is shown in the graph. The results were not different due to the difference in the amount of Si.

[0023]

[Table 1] As can be seen from the results in Table 1 and FIG.
By adding 1 to 2.0 wt%, fillet length L
It turns out that is longer. This is because the addition of Bi improves the fluidity of the brazing material. Also, Bi is 2.
Even if the content exceeds 0 wt%, the fillet length L is B
It can be seen that the effect of improving the fluidity is saturated, which is no different from the case of i2 wt%.

Further, a test was conducted under the same conditions as above except that Zn was not added to the skin material (1b), and the fillet length L was measured. As shown in Table 1 and FIG. Almost the same results were obtained.

Example 2 A brazing test was conducted on a multi-flow type aluminum condenser as shown in FIGS.

First, the condenser shown in FIGS. 3 to 6 will be described. This condenser is interposed between a large number of tubes (11) arranged in parallel in the horizontal direction and adjacent tubes (11) (11). Left and right corrugated fins (12) placed in parallel with each other at both ends of the tube group.
And a pair of headers (13) (14).

The tube (11) is made of a flat extruded shape made of aluminum material, and has a reinforcing wall (11a) extending in the widthwise middle between the upper and lower walls, as shown in FIG. Have The tube (11) may be of a porous type so-called harmonica tube. Also, using electric resistance welded pipes regardless of the extruded shape,
A reinforcing member corresponding to the reinforcing wall (11a) may be inserted and joined inside. The corrugated fin (12) has almost the same width as the tube (11) and is joined to the tube by brazing. The corrugated fin (12) is also made of aluminum, and it is preferable to use a louver cut and raised.

The headers (13) and (14) are made of aluminum pipe material having a circular cross section. Slit tube insertion holes (15) in the circumferential direction are formed in each header at intervals along the length direction of the header, and both ends of each tube (11) are inserted into the holes, and It is firmly joined and connected by brazing. Further, the refrigerant inlet pipe (16) and the refrigerant outlet pipe (17) are connected to the upper and lower peripheral side portions of the left header (13), while the left and right headers (13) (14) are connected.
Closing lid pieces (18) and (19) are attached to the upper and lower ends of the. Note that (20) and (21) shown in FIG. 3 are upper and lower side plates arranged outside the outermost corrugated fins (12) and (12).

Further, in the headers (13) (14) on both sides, a plurality of partition plates (22) partitioning the refrigerant circuit into meandering circuits.
Is provided to partition the inside of each header (13) (14) in the lengthwise direction so that the refrigerant flows in a meandering manner.

By the way, the tube (11) and the headers (13) and (14) are joined by brazing at least a brazing material layer coated in advance on the inner surface of the header. That is, as shown in FIG. 4, an aluminum brazing sheet (1) in which at least one surface of a core material (1a) is coated with a skin material (1b) as a brazing material layer is used as a member for forming a header. (1) is formed into a pipe by abutting both ends of the sheet so that the skin material (1b) is arranged at least on the inner surface. After forming the pipe, the abutting portions may be closed by electric resistance welding, or may be joined at the same time as brazing the headers (13) and (14) and the tube (11).

In the condenser having the above structure, the header (1
3) As the aluminum brazing (1) for the constitution (14), one side of the core material (1a) of JIS3003 aluminum alloy having a Mn content of 1.0 wt% was coated with a skin material (1b) having the composition shown in Table 2. I used one. The core material (1a) had a thickness of 1.1 mm, and the skin material (1b) had a thickness of 80 μm. The brazing sheet (1) was manufactured by sequentially performing hot rolling, intermediate annealing, and cold rolling according to a conventional method.

Then, each brazing sheet (1) is
A pipe having a circular cross section was formed so that the skin material (1b) was on the inner surface side to form headers (13) and (14), and tube insertion holes (15) were formed. The left and right headers (13)
For (14), a brazing sheet having the same composition was used.

Using the various headers thus manufactured,
A plurality of condenser cores were temporarily assembled. The temporary assembly is shown in FIGS.
As shown in, insert both ends (11b) (11b) of the tube (11) into the tube insertion holes (15) of the headers (13) and (14) until they project into the headers (13) and (14). The corrugated fins (12) are interposed between the adjacent tubes (11) (11), and the side plates (20) (21) are arranged on the outermost side.
By arranging. As the tube (11), a porous flat extruded profile made of JIS1070 aluminum alloy was used. As the corrugated fin (12), a molded aluminum brazing sheet having the same composition as No. 4 in Table 2 was used.

Next, a fluoride-based flux was adhered to the surface of each condenser core assembly by an electrostatic powder coating method, but the amount of flux adhered to the inner surface of the header was small.

Next, after setting the lids (18) (19), the refrigerant inlet / outlet pipes (16) (17) and the like at predetermined positions, each condenser assembly is placed in an inert gas (nitrogen gas) atmosphere. Then, it was brazed by heating at 620 ° C. for 5 minutes.

Then, the brazing state of the headers (13) (14) and the tube (11) inside the header after brazing was examined. As a result, in the condenser using the No. 2 to No. 8 aluminum brazing sheets in which the Bi content is in the range of 0.1 to 2 wt%, as shown in FIG. 5 and FIG. , Header (13) (1
A good fillet (30) was formed over the entire circumference of the tube that protruded inward in 4), and the brazing filler metal sufficiently circulated to the tip of the protruding part of the tube.

On the other hand, No containing no Bi
In the condenser using the brazing sheet of No. 1, the brazing material did not flow easily into the lower surface of the tube (11), and breakage of the brazing material was observed at this portion.

[0038]

[Table 2]

[0039]

As described above, according to the present invention, at least one surface of the aluminum or aluminum alloy core material is coated with S.
i: 5 to 15 wt%, Bi: 0.1 to 2.0 wt%, or Zn: 0.4 to 5 wt%, with the balance being aluminum and inevitable impurities. Therefore, the fluidity of the skin material as a brazing material at the time of brazing can be improved by adding and containing Bi. Therefore, even when the flux cannot be sufficiently applied because brazing must be performed inside the aluminum pipe material, for example, in the case where the header and the tube are joined in a multi-flow type condenser, the brazing material is joined at the joint part. It is possible to sufficiently wet and spread the material around the periphery, and it is possible to prevent inconvenience such as liquid leakage due to defective bonding due to wax breakage.

[Brief description of drawings]

1A is a perspective view of a test piece in a brazing test of Example 1, and FIG. 1B is a sectional view taken along line I-I of FIG.

2 is a graph showing the results of a brazing test in Example 1. FIG.

FIG. 3 is a front view of a multi-flow type condenser used in a brazing test of Example 2.

FIG. 4 is a perspective view showing a header, tubes and fins of a multi-flow type condenser used in a brazing test of Example 2 in a separated manner.

FIG. 5 is the III-FIG. 3 of FIG.
It is a sectional view taken along line III.

6 is a sectional view taken along line VI-VI of FIG.

[Explanation of symbols]

 1 ... Blazing sheet 2 ... Heart material 3 ... Leather material

Claims (1)

[Claims] 1. Si: 5 to 15 wt% and Bi: on at least one surface of an aluminum or aluminum alloy core material.
0.1 to 2.0 wt%, or further Zn:
An aluminum brazing sheet, characterized by comprising 0.4-5 wt% of aluminum and a balance of aluminum and unavoidable impurities.