JPH08291353A - Aluminum alloy brazing sheet strip with excellent electric resistance workability - Google Patents

Abstract

(57) [Summary] [Constitution] Si: more than 0.2 wt% and 2.5 wt% or less, Cu:
Over 0.7 wt% and under 2.5 wt%, Fe: over 0.05 wt%
An Al alloy containing 2.0 wt% or less and Mn: more than 0.05 wt% and 2.0 wt% or less is used as a core material, and Mg: 0.05 wt% is provided on one side thereof.
Over 2.5 wt%, Zn: over 0.5 wt% over 6.0 wt%, In: over 0.002 wt% over 0.3 wt%, Sn: 0.0
Over 02 wt% and under 0.3 wt%, Mn: over 0.05 wt% 1.6
Brazing for obtaining a tube for heat exchanger by electric sewing with a three-layer structure in which an Al alloy containing one or more of wt% or less is clad as a sacrificial material and an Al alloy brazing material is clad on the other side. An aluminum alloy brazing sheet strip having an average crystal grain size of 30 μm or less in a cross section of the sheet strip perpendicular to the longitudinal direction of the core material and using the strip as a hard material and having excellent electric resistance workability. [Effect] The aluminum alloy material of the present invention does not cause cracks during electric resistance sewing, has high strength, and can reduce the size and weight of a heat exchanger.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy brazing sheet strip for a heat exchanger used as a tube material for a heat exchanger of an automobile or the like, and more specifically, an aluminum alloy brazing sheet strip used as a tube material by electric resistance sewing. The brazing sheet strip according to the present invention can be electro-sewn, and the obtained tube material has high strength after brazing.

[0002]

2. Description of the Related Art A heat exchanger such as a radiator has a plurality of flat tubes (1) integrally formed with corrugated thin fins (2) as shown in FIG. Both ends of the flat tube (1) are opened in the space formed by the header (3) and the tank (4), and the flat tube (1) is passed through from the space on the side of one tank to a high temperature. The refrigerant is sent to the space on the other side of the tank (4), and heat exchanged between the tubes (1) and the fins (2) causes the refrigerant having a low temperature to be circulated again.

The tube material of such a heat exchanger uses, for example, JIS3003 alloy as a core material, and JIS70 is used as a lining material on the inside of the core material, that is, on the side which is constantly in contact with the refrigerant.
72 alloy, and the outside of the core is usually JIS 4
A brazing sheet in which a brazing material such as 045 is clad is used as a tube material by electric resistance welding, and is integrally assembled by brazing with other members such as corrugated fins. As the brazing method, a flux brazing method, a Nocolock brazing method using a non-corrosive flux, etc. are performed.
It is brazed by heating it to a temperature around 600 ° C.

By the way, in recent years, heat exchangers have been in the direction of weight reduction and downsizing, and therefore, thinning of materials has been desired. In order to reduce the thickness of the tube material, first, it is necessary to improve the strength by the reduction of the material thickness and ensure the corrosion resistance. On the other hand, some high-strength alloys have been proposed, and a method of improving the strength by adding a large amount of Si or Cu to the core material alloy or a method of improving the strength by adding Mg to the sacrificial material is considered to be a promising method. Has been done. However, in recent years, due to the increase in strength as described above, problems that have not heretofore arisen have occurred as the wall thickness has been reduced. That is,
This is a problem that the tube cracks during ERW processing. If the tube breaks, it may leak or corrode, and cannot be used as a product.

[0005]

As a result of intensive studies in view of such circumstances, the present invention has developed an aluminum alloy brazing sheet strip for a heat exchanger, which has excellent strength after brazing and does not cause cracks due to electric resistance welding. It is a thing.

That is, one of the brazing sheet strips of the present invention is: Si: more than 0.2 wt% and 2.5 wt% or less;
Over 0.7 wt% and under 2.5 wt%, Fe: over 0.05 wt% 2.
An aluminum alloy containing 0 wt% or less, Mn: more than 0.05 wt% and 2.0 wt% or less, the balance aluminum and unavoidable impurities is used as a core material, and Mg: 0.05 wt% or more and 2.5 wt% or less on one side thereof. Zn: over 0.5 wt% and 6.0 wt% or less, In: over 0.002 wt% and 0.3 wt% or less, Sn: 0.0
Over 02wt% and under 0.3wt%, Mn: over 0.05wt% and 1.6
A three-layer structure in which one or more of wt% or less is clad as a sacrificial aluminum alloy consisting of the balance aluminum and unavoidable impurities, and a brazing material consisting of an aluminum alloy is clad on the other side, Of brazing sheet strip to obtain a tube for heat exchanger by electric resistance sewing,
The average crystal grain size in a cross section perpendicular to the longitudinal direction of the core material
It is characterized in that it is 30 μm or less and that the brazing sheet strip is made of a hard material.

Another one of the brazing sheet strips of the present invention is Si: more than 0.2 wt% and 2.5 wt% or less, Cu: 0.7
over wt% and under 2.5 wt%, Fe: over 0.05 wt% and 2.0 wt%
%, Mn: more than 0.05 wt% and 2.0 wt% or less,
Further, Mg: more than 0.05 wt% and 0.5 wt% or less, Cr: 0.03
Wt% over 0.3 wt%, Zr: 0.03 wt% over 0.3 wt
%, Ti: more than 0.03 wt% and 0.3 wt% or less, one or more kinds are contained, and an aluminum alloy composed of the balance aluminum and unavoidable impurities is used as a core material, and Mg: 0.05 wt% on one side thereof. Over 2.5wt%, Zn: 0.5wt%
Over 6.0 wt%, In: over 0.002 wt% 0.3 wt%
Below, Sn: more than 0.002 wt% and 0.3 wt% or less, Mn: 0.
An aluminum alloy containing more than 05 wt% and less than 1.6 wt% of 1 or 2 or more and the balance aluminum and unavoidable impurities was clad as a sacrificial material, and a brazing material made of an aluminum alloy was clad on the other surface. The brazing sheet strip having a three-layer structure for obtaining a heat exchanger tube by electric resistance sewing has an average crystal grain size of 30 μm or less in a cross section perpendicular to the longitudinal direction of the core material, and the brazing sheet strip is made of a hard material. It is characterized by that.

Yet another one of the brazing sheet strips of the present invention is, among the brazing sheet strips described above, a brazing sheet using an aluminum alloy as a sacrificial material, which essentially contains at least Mg: 0.05 wt% and 2.5 wt% or less. 5 from the interface between the sacrificial material and the core material of the strip into both materials
Mg ₂ S with a grain size of 0.2 μm or more existing within the depth of μm
The feature is that the area ratio of i particles is 0.5% or less.

Further, in these brazing sheet strips, the brazing filler metal is Si: more than 7.0 wt% and not more than 12.0 wt%, C:
u: Contains more than 0.1 wt% and less than 8.0 wt% and further Z
n: more than 0.5 wt% and 6.0 wt% or less, In: more than 0.002 wt% and 0.3 wt% or less, Sn: more than 0.002 wt% and 0.3 wt% or less, and contains one or more types, and balance aluminum It is characterized by being an aluminum alloy composed of unavoidable impurities.

[0010]

First, the alloy composition of the brazing sheet strip produced by the present invention will be described. The core alloy used in the present invention is a high-strength alloy, and is characterized by a high addition amount of Cu. That is, the core material is Si: 0.2 wt% over 2.5 wt
% Or less, Cu: over 0.7 wt% and 2.5 wt% or less, Fe: 0.
More than 05wt% and less than 2.0wt%, Mn: 0.05wt% and more than 2.0
An aluminum alloy containing wt% or less and consisting of balance aluminum and unavoidable impurities, or M
g: over 0.05 wt% and under 0.5 wt%, Cr: over 0.03 wt% and under 0.3 wt%, Zr: over 0.03 wt% and under 0.3 wt%,
Ti: An aluminum alloy added with one or more than 0.03 wt% and 0.3 wt% or less. In this
Especially alloys with Si addition exceeding 1.2 wt% and 1.2 wt%
The alloy containing Cu in excess of 5% has a melting point lowered, and is an alloy that has not been conventionally used for brazing.

The role of each additional element of the core alloy will be described below. Si contributes to the strength improvement. When Si is 0.2 wt% or less, the strength improving effect is not sufficient, and when it exceeds 2.5 wt%, the melting point is lowered and even the brazing alloy of the present invention is melted during brazing. Therefore, although Si is more than 0.2 wt% and 2.5 wt% or less, particularly stable ERW characteristics are exhibited at 0.8 wt% or less, and excellent strength and brazing properties are around 1.2%. Therefore, 0.4wt% ~ 1.2wt
A range of% is especially recommended.

Cu exists in the alloy in a solid solution state after brazing and improves the strength. When the Cu content is 0.7 wt% or less, the strength improving effect is small, but the Cu content exceeding 1.2 wt% lowers the melting point, so that the composition has not been used conventionally.
Here, when the amount of Cu exceeds 2.5 wt%, the melting point is lowered and even the brazing alloy of the present invention is melted during brazing. Therefore, Cu is set to more than 0.7 wt% and 2.5 wt% or less, and particularly 1.2 wt% or less is excellent in the balance of electric resistance working characteristics, strength, brazing property and corrosion resistance.

Fe distributes a coarse intermetallic compound in the alloy to make the crystal grains of the brazing sheet strip of the present invention finer and prevent cracking during electric resistance sewing. If the amount is 0.05 wt% or less, it is not sufficient, and if added in excess of 2.0 wt%, the formability decreases and the brazing sheet cracks during electric resistance sewing.

Mn is an essential element for distributing a fine intermetallic compound in the alloy and improving the strength without lowering the corrosion resistance. If the amount is 0.05 wt% or less, it is not sufficient, and if added in excess of 2.0 wt%, the formability decreases and the brazing sheet cracks during electric resistance sewing.

Mg exists in the alloy as a solid solution and as a fine precipitation phase of Mg ₂ Si, and improves the strength. If the amount is less than 0.05 wt%, there is no effect, and if added over 0.5 wt%, when brazing using a non-corrosive flux, the flux reacts with Mg and brazing cannot be performed.

Cr, Zr, and Ti all have the function of forming a fine intermetallic compound and improving the strength of the alloy.
However, if the content is 0.03 wt% or less, there is no effect, and if it is added in excess of 0.3 wt%, the formability deteriorates and the brazing sheet cracks during processing such as assembly.

The above are the components of the core alloy of the present invention.
Elements other than the above, such as B added for refining the structure of the ingot, may be contained if the content is 0.05 wt% or less.

Next, the sacrificial material of the brazing sheet strip of the present invention will be described. The sacrificial alloy of the present invention is Mg: 0.
Over 05wt% and under 2.5wt%, Zn: over 0.5wt% and 6.0
wt% or less, In: more than 0.002 wt% and 0.3 wt% or less, S
An aluminum alloy containing one or more of n: more than 0.002 wt% and less than 0.3 wt% and Mn: more than 0.05 wt% and less than 1.6 wt% and the balance aluminum and unavoidable impurities.

The addition of Mg has a sacrificial effect and enhances the strength of the sacrificial alloy, improving the strength of the entire material. If the amount is less than 0.05 wt%, there is no effect, and if it exceeds 2.5 wt%, the melting point lowers and the alloy melts during brazing.

The addition of Zn gives the alloy a sacrificial effect. If the amount is 0.5 wt% or less, the effect is not sufficient and the amount is
If it exceeds 6.0 wt%, the melting point will be lowered, and even if the brazing alloy of the present invention is used, it will melt during brazing. In the case of the brazing sheet strip of the present invention, since the core material contains a relatively large amount of Cu, Zn of 3.0 wt% to 5 wt% is the most suitable amount.

The addition of In and Sn also gives a sacrificial effect to the alloy. If the amount is 0.002 wt% or less, the effect is not sufficient, and if the amount exceeds 0.3 wt%, the rolling workability of the alloy decreases.
It becomes unsuitable as a sacrificial material used for a brazing sheet of three-layer material.

The addition of Mn increases the strength of the sacrificial alloy and improves the strength of the entire material. If the amount is less than 0.05 wt%, there is no effect, and if it exceeds 1.6 wt%, the rolling workability of the alloy deteriorates.
It becomes unsuitable as a sacrificial material used for a brazing sheet of three-layer material.

The sacrificial alloy according to the present invention contains one or more of these elements, and is 3.0 wt% to 5 wt.
% Zn as an essential element and one or more other elements are the best from the viewpoint of corrosion resistance, 3.0 wt% to 5 wt% Zn and 0.5 wt% to 2 wt% Those containing Mg as an essential element and containing one or more other elements are most recommended in terms of strength and corrosion resistance.

Although the sacrificial alloy elements of the present invention are as described above, Si also serves as an unavoidable impurity to improve the strength. From the viewpoint of corrosion resistance, it can be contained if it is 0.5 wt% or less, but 0.1 wt% or less is desirable. Fe
Can be contained if it is 0.8 wt% or less, and 0.1 wt% or less is desirable. Elements other than the above, such as Cr, Zr, and Ti for improving strength, may be contained as impurity elements as long as the content is 0.05 wt% or less.

Next, the brazing alloy of the present invention will be described. In the present invention, 1.2 wt% of the alloy composition of the core material
In the composition range of less than Si and less than 1.2 wt% of Cu, an Al-Si alloy such as JIS 4343 alloy or JIS 4045 alloy which has been conventionally used as a brazing material, or a brazing material specified in the present invention may be used. It is possible. However, in the present invention, a high-strength core material alloy (Si containing 1.2 wt% or more
Alternatively, when a core alloy containing 1.2 wt% or more of Cu is used, a braze having the composition specified in the present invention is used.

This is because there is a problem that the external corrosion resistance is reduced and that the core material alloy has a low melting point and thus melts during brazing. The brazing alloy of the present invention solves this problem and exhibits an effect when combined with the core alloy of the present invention. That is, various studies have been conducted on the external corrosion resistance of the heat exchanger, and when the conventionally used brazing alloy and the high strength core alloy of the present invention are combined, Cu added to the core alloy is brazed. It has been found that, at times, it diffuses into the brazing material and a low Cu area is generated near the boundary between the brazing material and the core, which is preferentially corroded, resulting in severe corrosion accompanied by blistering.

In the present invention, by adding Cu to the brazing alloy, the diffusion of Cu from the core material to the brazing material is prevented, and the low Cu region is not generated near the boundary between the brazing material and the core, thereby improving the corrosion resistance. Let If brazing at a temperature of 585 ° C or less was used instead of brazing at a temperature of around 600 ° C in the past, melting of the core alloy will disappear, and the brazing temperature will be lower than that of conventional brazing alloys. Developed alloy.

The role of each element of the braze alloy and the reason for limitation thereof will be described below. Here, the alloy composition of the brazing filler metal of the present invention contains Si: more than 7.0 wt% and not more than 12.0 wt%, Cu: more than 0.1 wt% and more than 8.0 wt%, and Zn: more than 0.5 wt% and 6.0 wt%. The following is an aluminum alloy containing one or more of In: more than 0.002 wt% and less than 0.3 wt% and Sn: more than 0.002 wt% and less than 0.3 wt% with the balance aluminum and inevitable impurities. .

Addition of Si lowers the melting point of the alloy, but if the amount is 7.0 wt% or less, the melting point is not sufficiently lowered and the core material melts at the brazing temperature. Furthermore, the amount is 12.0 wt%
On the other hand, if it exceeds, the melting point rises, so that the core material is melted.

The addition of Cu lowers the melting point of the alloy and improves the wax flowability. Further, for the above reason, it has a function of enhancing the external corrosion resistance of the heat exchanger when the alloy containing Cu is used for the refrigerant passage constituting member. However, if the amount of Cu is 0.1wt
% Or less, the above effect is not sufficient and the amount is 8.0 wt%
Beyond this, the brazing potential becomes too noble, and the core material corrodes preferentially, which reduces corrosion resistance and also reduces the rolling workability of the alloy, making it a brazing sheet for heat exchangers. Disappear. Therefore, Cu is 0.1 wt%
Over 8.0wt% but especially 0.5wt% ~ 3.5wt%
Shows stable characteristics.

The addition of Zn lowers the melting point of the alloy. Further, although the occurrence of blistering due to external corrosion is suppressed in the brazing alloy to which Cu is added as in the present invention, the electric potential of the brazing becomes nobler than that of the core, and the external corrosion progresses in a pit-like shape and its speed is high. There's a problem. The addition of Zn lowers the brazing potential, brings the brazing potential closer to that of the core alloy, and improves the corrosion resistance. However, if the amount exceeds 6.0 wt%, the self-corrosion resistance of the braze is lowered and the rolling workability of the alloy is lowered, which makes it unsuitable as a brazing filler metal for brazing sheets for heat exchangers.

In and Sn make the brazing potential base and improve the corrosion resistance of the refrigerant passage constituting member. The amount of each
Below 0.002wt%, the effect is not sufficient, and each is 0.
If it exceeds 3 wt%, the rolling workability of the alloy will be deteriorated.

The alloying elements of the brazing material of the present invention are as described above, but Fe can be contained as an unavoidable impurity as long as it is 1.0 wt% or less. However, Fe forms an intermetallic compound when the brazing solidifies, which is the starting point of corrosion.
Therefore, the Fe content is preferably 0.5 wt% or less. As an unavoidable impurity other than Fe, each of other elements is also 0.05 wt%
You may contain if it is the following.

Here, when the brazing material of the present invention is used, it is desirable to perform brazing at a brazing temperature higher than 570 ° C and lower than 585 ° C. This is because when the brazing temperature is 570 ° C. or lower, it may not be melted depending on the composition of the brazing material of the present invention, so brazing cannot be performed. Also, 585
This is because if the temperature exceeds ° C, the core material may melt depending on the composition of the core material. Brazing using the brazing material of the present invention also has the effect of improving the high temperature buckling resistance and thermal conductivity of the fan. It should be noted that lowering the brazing temperature in this way also has the effect of extending the life of the brazing furnace.

The alloy composition of the brazing sheet used in the manufacturing method of the present invention has been described above, and its constitution will be described below. The aluminum alloy brazing sheet strip for a heat exchanger manufactured by the present invention has a three-layer structure as shown in FIG. That is, a high-strength aluminum alloy is used as a core material (5), and a brazing material (6) is provided on one side of the core material and a sacrificial material (7) is provided on the other side. Then, it is a strip for forming a tube in which the brazing material is on the outside and the sacrificial material is on the refrigerant passage forming side by electric resistance welding. The brazing sheet strip has a thickness of 0.4 mm or less, the sacrificial layer has a clad ratio of 5 to 30%, and the brazing material has a clad ratio of 5 to 30%.

Further, in the present invention, the average crystal grain size in a cross section perpendicular to the longitudinal direction of the core material is 30 μm or less,
Moreover, the brazing sheet strip is made of a hard material. Further, in the present invention, the depth 5 from the interface between the sacrificial material and the core material into both materials is 5
The area ratio of Mg ₂ Si particles having a particle size of 0.2 μm or more and existing in the range of μm or less is 0.5% or less.

In explaining the reason for this limitation,
The cracks that occur during electric resistance sewing, which is solved by the present invention, will be described. There are two types of cracks of this type, one of which is a whisker-like crack (9) near the weld (8) as shown in FIG.
Then, as shown in FIG. 4, there is a crack (10) generated at the interface between the sacrificial material (7) and the core material (5). The crack (9) in FIG. 3 is
It occurs in those using a high strength core alloy as in the present invention,
The crack (10) in FIG. 4 occurred only in the high-strength alloy in which Mg was added to the sacrificial material.

When the cracked portion in FIG. 3 was examined in detail, it was found that recrystallization did not occur in the welded portion although the aluminum alloy strip was a hard material and was at a high temperature during welding. Normally, when an aluminum alloy (hard material) in which strain is accumulated is heated, recrystallization occurs, but it is considered that recrystallization does not occur because the temperature rises very quickly in the case of electric resistance welding. It was found that the cracks were cracks that occurred along the grain boundaries of the strip.
In the present invention, when the study was conducted based on the above findings, the deformation stress at the time of electric resistance welding concentrates at the grain boundaries and cracks occur at the grain boundaries, but the average crystal grain size in the cross section perpendicular to the longitudinal direction of the core material. It was found that when the value is 30 μm or less, the amount of grain boundaries increases, so that stress is dispersed and cracking does not occur. The lower limit is about 3 μm.

The crack in FIG. 4 was generated at the interface between the sacrificial material and the core material. Therefore, conventionally, a brazing sheet is usually pressure-bonded by hot rolling to have a three-layer structure. However, it is considered that an alloy containing Mg is likely to form an oxide film on the surface, so that the interface is difficult to bond, or the core alloy Since the deformation resistance of the sacrificial material alloy and the sacrificial material alloy are very different, it is considered that they are not crimped, and various measures were taken based on these. However, such measures did not solve it at all.

Therefore, the inventors of the present invention diligently examined the structure in the vicinity of the interface in detail, and found that when Mg ₂ Si particles were present in the vicinity of the interface, as schematically shown in FIG. It was found that cracks occur during sewing. Then, it was found that if the amount of the Mg ₂ Si particles is not more than a certain value, cracking does not occur during electric resistance sewing. Further, the reason for the generation of the Mg ₂ Si particles is that Mg ₂ Si particles are diffused from the sacrificial material to the core material during the production of the brazing sheet and react with Si contained in the core material, and It was found that Si diffuses and reacts with Mg contained in the sacrificial material. That is, it was clarified that this is a phenomenon peculiar to the brazing sheet in which the amount of Si added to the core material is increased to increase the strength and Mg is added to the sacrificial material.

Therefore, in the present invention, an aluminum alloy containing Si is used as the core material, and Mg as the sacrificial material exceeds 0.05 wt%.
A clad strip material for high strength electric resistance sewing using an aluminum alloy containing 2.5 wt% or less, and a grain size of 0.2 μm or more existing within 5 μm on both material sides from the interface between the sacrificial material and the core material. Area size of Mg ₂ Si particles of
It was set to 0.5% or less.

Now, the Mg ₂ Si particles existing within 5 μm on both sides from the interface between the sacrificial material and the core material are defined here as the range in which Mg ₂ Si particles are easily generated by diffusion. This is because it is a range. That is, Mg ₂ Si particles are most likely to be generated at the interface, and the diffusion amount decreases as the distance from the interface increases, so if the depth is within 5 μm from the interface (5 μm on the sacrificial layer side, 5 μm on the core side, 10 μm portion). It's good.

The problem with the Mg ₂ Si particles having a particle size of 0.2 μm or more is that if the particle size is smaller than this, solid solution occurs at the time of heating during electric resistance working, and swelling is not affected.

Here, in order to measure the area ratio, the cross section in the thickness direction may be polished and observed by reducing the accelerating voltage in the backscattered electron image of the scanning electron microscope. The particle size is the maximum size. M
If the area ratio of the g ₂ Si particles exceeds 0.5%, that portion is easily melted during electric resistance sewing and cracks occur. Therefore,
According to the present invention, the Mg ₂ Si particles having a particle size of 0.2 μm or more and existing within a depth range of 5 μm from the interface between the sacrificial layer and the core material have an area ratio of 0.5% or less.

Although the crystal grain size and the distribution state of Mg ₂ Si are controlled in this way, the most typical method is the solution heat treatment by rapid temperature rising. That is, since Mg ₂ Si particles are mainly generated during hot rolling and annealing, the coil after annealing may be heated to a temperature higher than the solutionizing temperature and rapidly cooled at a rate at which Mg ₂ Si does not occur during cooling. . Since this solution heat treatment / quenching is usually higher than the recrystallization temperature, the grain size within the range specified in the present invention can be obtained by performing the annealing also as the annealing.

The brazing sheet strip of the present invention is made of a hard material. The hard material referred to here is, of the heat treatments specified in JIS H 0001, H1X material (work-hardened only) and H2X material (work-hardening is followed by appropriate heat treatment to obtain a predetermined strength). No.), H3X material (which obtains strength and elongation by stabilization treatment after work hardening), etc., and has increased strength by work hardening regardless of the presence or absence of heat treatment in the subsequent process. .

In the case of the O material, the hard material is not recrystallized during the brazing heat, so that the crystal grains do not become coarse during brazing and the brazing is performed with the crystal grain size of the present invention. Therefore, the wax diffusion becomes very large.
By using a hard material, the recrystallized grains generated during brazing become coarser than before heating, and the brazing diffusion does not occur. Specifically, it is desirable that the final cold rolling rate be about 10 to 80%.

In the present invention, the process after electric resistance sewing is not particularly limited. The heat exchanger may be manufactured by brazing as is conventionally done.

[0049]

EXAMPLES The present invention will be specifically described below with reference to examples. A three-layer brazing sheet strip having a plate thickness of 0.25 mm for the aluminum alloy tube material having the composition shown in Table 1 was manufactured.
The core alloys shown in Table 1 were DC cast to a thickness of 400 mm and then
After homogenizing in the temperature range of 600 ° C., after chamfering, it was combined with the brazing alloy plate and the sacrificial alloy plate that had been prepared in advance, and hot rolling was performed after heating to obtain a hot rolling coil with a plate thickness of 3.5 mm.
Clad rate of brazing material is 13%, clad rate of sacrificial material is 14%
Is. In the sacrificial material, Fe, as an impurity element,
Si is contained in the range of 0.01 wt% to 0.2 wt%, respectively. The hot rolled coil was cold rolled to 0.4 mm and annealed under various annealing conditions. Further, cold rolling was performed to 0.25 mm, and after the cold rolling, partial annealing was performed if necessary.

The coiled plate material thus obtained was slitted into a strip material having a width of 35.0 mm in accordance with the size of the electric resistance welded pipe. A sample is taken from the obtained bar material, the structure of the cross section is observed, the average crystal grain size in the cross section perpendicular to the longitudinal direction of the core material is obtained by the cutting method, and the average grain size is determined from the interface between the core material and the sacrificial material on both sides. The area ratios of Mg ₂ Si particles having a size of 0.2 μm or less existing within the depth of 5 μm were measured, and the results are shown in Tables 2 and 3.

Further, the obtained strip material is subjected to electric resistance sewing,
The obtained tube was pressurized to a pressure of up to 5 MPa, and a pressure test and cross-section observation were conducted to check the occurrence of leakage. Further, the obtained strip material was heated in N ₂ gas to perform a tensile test. The results are shown in Tables 2 and 3. The brazing heat is alloy number B, F, H, I, J
At 580 ° C for 5 minutes and other alloys at 600 ° C for 5 minutes.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

[Table 3]

From Tables 2 and 3, Comparative Examples 14 to 24 have the composition of the present invention, but the conventional process (intermediate annealing is performed at 320 ° C to 420 ° C).
In a batch furnace for 0.5 to 4 hours), the crystal grain size of the core material and the amount of Mg ₂ Si deviate from the conditions of the present invention, so cracking occurs in the electric resistance sewing process and the pressure resistance value is low. I understand. Further, Comparative Examples 25 and 26 are out of the range of the amount of Cu of the core material of the present invention, and cracks do not occur in the electric resistance welding process, but the strength after brazing is low, and Conventional Example 27 also shows cracks in the electric resistance processing. Although it does not occur, it can be seen that the strength after brazing is low. On the other hand, in the examples of the present invention, despite the high strength after brazing, no cracks were formed by electric resistance sewing.

[0056]

Industrial Applicability As described above, the aluminum alloy material of the present invention does not cause cracks during electric resistance sewing, has high strength, and when a heat exchanger is manufactured, it can be reduced in size and weight and is industrially used. It has a remarkable effect.

[Brief description of drawings]

FIG. 1 is a perspective view, partly in section, showing a radiator.

FIG. 2 is a cross-sectional view showing the structure of the brazing sheet of the present invention.

FIG. 3 is a cross-sectional view of an electric resistance welded pipe showing a state of occurrence of cracks during electric resistance welding.

FIG. 4 is a cross-sectional view of an electric resistance welded tube showing a state of occurrence of another crack during electric resistance welding.

FIG. 5 is a schematic diagram showing a state at an interface between a core material and a sacrificial material of a brazing sheet.

[Explanation of symbols]

 1 Flat Tube 2 Fins 3 Header 4 Tank 5 Core Material 6 Brazing Material 7 Sacrificial Material 8 ERW Welding Section 9 Crack 10 Crack 11 Interface between Core Material and Sacrificial Material

Claims (4)

[Claims] 1. Si: more than 0.2 wt% and 2.5 wt% or less, C
Aluminum alloy containing u: more than 0.7 wt% and less than 2.5 wt%, Fe: more than 0.05 wt% and less than 2.0 wt%, Mn: more than 0.05 wt% and less than 2.0 wt% with the balance aluminum and inevitable impurities. Is used as the core material, and Mg: 0.05wt on one side
% Over 2.5 wt%, Zn: over 0.5 wt% 6.0 wt%
Below, In: more than 0.002 wt% and 0.3 wt% or less, Sn:
Over 0.002wt% and under 0.3wt%, Mn: over 0.05wt%
A three-layer structure in which one or more of 1.6 wt% or less is clad as a sacrificial aluminum alloy consisting of the balance aluminum and unavoidable impurities, and a brazing filler material consisting of an aluminum alloy is clad on the other side. A brazing sheet strip for obtaining a heat exchanger tube by electric resistance sewing has an average crystal grain size of 30 μm or less in a cross section perpendicular to the longitudinal direction of the core material, and the brazing sheet strip is made of a hard material. Aluminum alloy brazing sheet strip with excellent electric resistance workability. 2. Si: more than 0.2 wt% and 2.5 wt% or less, C
u: 0.7 wt% to 2.5 wt%, Fe: 0.05 wt% to 2.0 wt%, Mn: 0.05 wt% to 2.0 wt%, Mg: 0.05 wt% to 0.5 wt% Below, C
r: 0.03 wt% or more and 0.3 wt% or less, Zr: 0.03 wt% or more and 0.3 wt% or less, Ti: 0.03 wt% or more and 0.3 wt% or less, and one or more types are contained, and the balance is aluminum. With an aluminum alloy consisting of inevitable impurities as the core material,
On one side, Mg: more than 0.05 wt% and 2.5 wt% or less, Zn:
Over 0.5wt% and under 6.0wt%, In: over 0.002wt%
0.3 wt% or less, Sn: more than 0.002 wt% and 0.3 wt% or less,
Mn: A brazing filler metal clad as a sacrificial material with an aluminum alloy containing more than 0.05 wt% and less than 1.6 wt% and containing one or more types of aluminum and the balance aluminum and unavoidable impurities, and the aluminum alloy on one side. The brazing sheet strip having a three-layer structure in which a tube for heat exchanger is obtained by electric resistance sewing has an average crystal grain size of 30 μm or less in a cross section perpendicular to the longitudinal direction of the core material, and the brazing sheet strip is hard. Aluminum alloy brazing sheet strip with excellent electric resistance workability, characterized by being used as a material. 3. The brazing sheet strip according to claim 1 or 2, wherein Mg: 0.05 wt% or more and 2.5 wt% or more.
% Of the aluminum alloy as a sacrificial material, the grain size existing within a depth of 5 μm from the interface between the sacrificial material and the core material to the both materials.
An aluminum alloy brazing sheet strip excellent in electric resistance workability, characterized in that an area ratio of Mg ₂ Si particles of 0.2 μm or more is 0.5% or less. 4. The brazing material for brazing sheet according to claim 1, 2 or 3, wherein Si: more than 7.0 wt% and 12.0 wt%.
Below, Cu: more than 0.1 wt% and less than 8.0 wt% is contained, and further Zn: more than 0.5 wt% and less than 6.0 wt%, In: 0.002
over 0.3% by weight, Sn: over 0.002% by weight 0.3
An aluminum alloy brazing sheet strip excellent in electric resistance workability, which is an aluminum alloy containing one or more of wt% or less and the balance aluminum and inevitable impurities.