JPH1053827A - Brazing sheet made of aluminum alloy for heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the brazability and formability of a brazing sheet bar made of aluminum for resistance welding, used for a tube material for heat exchanger for automobile, etc., after being subjected to resistance welding. SOLUTION: An aluminum alloy, having a composition consisting of, by weight, 0.05-0.8% Si, 0.05-0.6% Fe, 0.3-1.1% Cu, 0.6-1.6% Mn, further <=0.3% each of one or >=2 elements among Cr, Zr, and Ti, and the balance Al with inevitable impurities, is used as a core material, and one side or both sides of this core material are clad with Al-Si alloy as brazing filler metal. In the resultant brazing sheet made of aluminum alloy constituted as mentioned above, the ratio between the rolling-directional average length (a) of the crystalline grains, before brazing heating, of the core material and the sheet-thickness- directional average length (b), a/b, is regulated to 7.5-3.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in brazing properties and formability of an aluminum brazing sheet for electric resistance welding which is subjected to electric resistance processing and used as a tube material for a heat exchanger of an automobile or the like. is there.

[0002]

2. Description of the Related Art A heat exchanger such as a radiator is shown in FIG.
As shown in the figure, a thin fin 7 processed into a corrugated shape between flat tubes 6 each composed of a plurality of brazing sheets.
The ends of the flat tube are opened in the space defined by the header 8 and the tank 9.

[0003] The tube material of such a heat exchanger is JI
An Al-Mn-based alloy such as S3003 is used as a core material, and an Al-Zn-based alloy such as JIS7072 is used as a sacrificial anode material on the inner surface of the core material, that is, on the side that is constantly in contact with the refrigerant, and on the outer surface of the core material. Is usually formed by an electric resistance welding process using an aluminum brazing sheet clad with an Al-Si alloy such as JIS 4045 as a brazing material, and is integrally assembled by brazing with other members such as fins subjected to corrugation. I have. As a brazing method, a flux brazing method, a Nocolok brazing method using a non-corrosive flux, and the like are performed.
It is brazed by heating to a high temperature around 00 ° C.

[0004]

In recent years, the weight of automobiles has been reduced in terms of energy saving and pollution control, and materials for heat exchangers have been reduced in thickness. With the reduction in thickness, the amount of erosion of the brazing material into the core material during brazing cannot be ignored, and there is a shortage of brazing material contributing to joining, resulting in a problem of deterioration in brazing properties, and a core material portion contributing to strength. The thickness of the heat exchanger decreases, the strength of the heat exchanger decreases,
In addition, there is a problem of forming accuracy and micro-cracking during tube forming and welding. Addressing these issues,
Japanese Patent Application Laid-Open No. 63-1577791 discloses that an aluminum brazing sheet used in a drone cup type heat exchanger with a press forming step has a cold working ratio after final annealing of 3 to 10% in order to improve brazing properties. A method has been proposed in which the grain size of the core material is regulated to 66 μm or less. This is to cause recrystallization when vacuum brazing heating is performed and to increase the recrystallized grain size to prevent the brazing material from eroding into the core material.

In Japanese Patent Application Laid-Open No. 63-197895, an aluminum brazing sheet assembled into an evaporator by press molding and vacuum brazing is subjected to an annealing treatment before brazing and heating, and the crystal grain size is defined within a certain range. Techniques for preventing the erosion of the brazing material into the core material have been proposed. The above two examples are assembled by press forming and vacuum brazing, and do not involve electric sewing.

On the other hand, in Japanese Patent Publication No. 4-71638, the relationship between the average length a in the rolling direction and the average length b in the thickness direction of the core material crystal grains at the end of the final annealing of the brazing sheet having the core material thickness t is a / B ≧ 5 and t / b ≧ 5,
A method for producing a brazing sheet which is then cold-rolled at a cold rolling reduction of 20 to 50% is disclosed. In this method, since the ratio of the grain size at the end of the final annealing is set to a / b ≧ 5, after cold working, the width expansion during rolling is ignored.
a / b ≧ 7.8. However, when the a / b is increased in this manner and the tube is formed by ERW processing, slip at the grain boundaries occurs unevenly when heat is input during ERW, and local stress concentrates, causing micro-cracking and A step occurs at the time of abutment. On the other hand, when the a / b value is extremely large, since the cold working ratio is high, the crystal grains after recrystallization accompanying brazing heating become finer, and the brazing material diffuses into the core material through the crystal grain boundaries. Therefore, there is a problem that the brazing property is deteriorated. Also, if the a / b value is too small, there is a large number of crystal grain boundaries in the direction penetrating the core material, which causes a problem that the erosion of the brazing material into the core material is accelerated.

[0007]

In view of the above, the present inventor has ascertained from the above-mentioned viewpoints that a heat exchanger which ensures brazing properties and brazing strength and is excellent in tube formability (electric resistance workability). As a result of research to develop a thin brazing sheet for tubes, by optimizing the crystal grain shape of the core material before brazing for aluminum heat exchanger,
We have invented an aluminum alloy brazing sheet that improves brazing properties and prevents uneven sliding of grain boundaries during ERW.

That is, the first invention is characterized in that Si 0.05 to 0.8
wt%, Fe 0.05-0.6 wt%, Cu 0.3-1.1
An aluminum alloy containing wt% and Mn of 0.6 to 1.6 wt%, with the balance being Al and unavoidable impurities is used as a core material, and one or both surfaces of the core material is clad with an Al-Si alloy as a brazing material. Wherein the ratio a / b of the average length a in the rolling direction and the average length b in the thickness direction of the crystal grains before brazing and heating of the core material is 7.5 to 3.0. This is a brazing sheet made of an aluminum alloy, which is a feature.

The second invention is characterized in that Si 0.05 to 0.8
wt%, Fe 0.05-0.6 wt%, Cu 0.3-1.1
wt.%, Mn 0.6 to 1.6 wt.
One or two or more of Zr and Ti are each contained in an amount of 0.3 wt% or less, and the remainder is made of an aluminum alloy containing Al and unavoidable impurities as a core material.
-A brazing sheet clad with a Si-based alloy as a brazing material, wherein the ratio a / b of the average length a in the rolling direction and the average length b in the thickness direction of the crystal grains of the core material before brazing and heating is 7. It is an aluminum alloy brazing sheet characterized by being 5 to 3.0.

[0010] The third invention is characterized in that Si 0.05-0.8.
wt%, Fe 0.05-0.6 wt%, Cu 0.3-1.1
wt. and an alloy containing 0.6 to 1.6 wt.% of Mn, with the balance being Al and an unavoidable impurity as a core material, and an Al-Si alloy brazing material on the outer surface (atmosphere side) of the core material. And 0.3 to 5.0 wt% of Zn as a sacrificial anode material, 0.05 to 4.0 Mg on the inner surface (refrigerant passage side).
a brazing sheet clad with an aluminum alloy containing at most 0.5% by weight of Si and at most 0.5% by weight of Si, with the balance being Al and unavoidable impurities, wherein the average length a of the core material in the rolling direction of the crystal grains before brazing and heating is a. A ratio of a / b to the average length b in the thickness direction of the brazing sheet is 7.5 to 3.0.

The fourth invention is characterized in that Si 0.05 to 0.8
wt%, Fe 0.05-0.6 wt%, Cu 0.3-1.1
wt.%, Mn 0.6 to 1.6 wt.
One or more of Zr and Ti are each contained in an amount of 0.3 wt% or less, and the remainder is made of an aluminum alloy containing Al and unavoidable impurities as a core material, and A is provided on the outer surface (atmosphere side) of the core material.
l-Si alloy braze, 0.3 to 5.0 wt% Zn, 0.05 to 4.0 Mg as sacrificial anode material on inner surface (coolant passage side)
a brazing sheet clad with an aluminum alloy containing at most 0.5% by weight of Si and at most 0.5% by weight of Si, with the balance being Al and unavoidable impurities, wherein the average length a of the core material in the rolling direction of the crystal grains before brazing and heating is a. A ratio of a / b to the average length b in the thickness direction of the brazing sheet is 7.5 to 3.0.

First, the effects of the elements added to the aluminum alloy brazing sheet of the present invention will be described. S
i promotes precipitation of Mn, increases intermetallic compounds, and improves strength. Therefore, when the content of Si is less than 0.05 wt%, the above effect is not sufficient, and when the content is more than 0.8 wt%, the diffusion of the brazing material at the time of heating by brazing increases, and the brazing property is reduced. Further, the corrosion resistance of the tube is reduced. Therefore, the Si content is set to 0.05 wt% or more and 0.8 wt% or less.
In particular, it shows stable characteristics at 0.3 to 0.7 wt%.

[0013] Fe forms an intermetallic compound with Mn to improve the strength. If the added amount is less than 0.05 wt%, the effect cannot be sufficiently obtained. If the added amount exceeds 0.6 wt%, coarse crystals are formed during casting, and the recrystallized grain size of the core material during heating by brazing becomes small. In addition, the diffusion of the brazing material is increased, and the brazing property is reduced. Therefore, the Fe content is 0.05 wt.
% Or more and 0.6 wt% or less. Cu exists in the alloy in a solid solution state and improves the strength. Further, the potential of the alloy (core material) is made noble to improve the corrosion resistance. If the content is less than 0.3 wt%, the effect cannot be sufficiently obtained, and if the content exceeds 1.1 wt%, the melting point of the alloy decreases, and microcracks occur during electric resistance welding. Furthermore, during cooling after brazing heating, a Cu-based precipitation phase is formed at the grain boundary, and grain boundary corrosion is likely to occur. Therefore, the Cu content is set to 0.3 wt% or more and 1.1 wt% or less.

Mn is an essential element for distributing the intermetallic compound in the alloy. If the amount is less than 0.6% by weight, it is not sufficient. Cracks. Therefore, the Mn content is 0.6 wt%
At least 1.6 wt%. Further, in the present invention, one or two or more of Cr, Zn, and Ti are each used as a core material.
3 wt% or less may be added. These elements form fine intermetallic compounds and improve the strength of the alloy. However, if it is added in excess of 0.3 wt%, the moldability deteriorates and cracks occur during processing, which is not preferable. In addition, 0.01 wt% or less of the crystal grain refinement element B is added, or JIS
The inclusion of Zn, Mg, etc., which are inevitable impurities of aluminum specified by 3004, 1050, etc., to the extent permitted by JIS does not affect the properties of the present alloy.

The brazing material used in the brazing sheet of the present invention may be JIS4004 alloy, JIS4045 alloy or the like. Further, as shown in, for example, JP-A-7-88634 or the like, elements such as Cu and Zn may be added to the brazing material.

An example of the sacrificial anode material is an Al—Zn—Mg-based alloy. However, when pitting occurs in the lining material under the use environment of the heat exchanger, it is necessary to prevent the lining from spreading to the core material. It has the effect of preventing. Zn is an essential element for making the potential of the sacrificial anode material lower than that of the core material, and gives an anticorrosion effect. If the amount of Zn added is less than 0.3 wt%, there is no effect, and if it exceeds 5.0 wt%, the effect is saturated.
Mg is in a solid solution state in the alloy, MgZn2 and Mg2Si
Exists as a finely precipitated phase, and improves the strength. If the amount is less than 0.05 wt%, the effect is not sufficient, and
If the content exceeds wt%, problems occur in clad production and rollability. Further, the melting point of the alloy is lowered, and there is a possibility that the alloy is melted during brazing. Si exists as a fine precipitation phase of Mg2Si and improves the strength. If the amount exceeds 0.5% by weight, the corrosion resistance of the tube decreases. The amount of unavoidable impurities in Al is each 0.05 wt% or less, and the total is 0.1 wt% or less.

The ratio of the average grain length a in the rolling direction and the average length b in the sheet thickness direction of the crystal grain size of the core material before brazing is a / b = 7.5 to 7.5.
The reason for setting the value to 3.0 is as follows. Normally, at the time of brazing heating, Si in the brazing material diffuses along the crystal grain boundaries of the core material during the temperature rise, and the melting point of the grain boundaries decreases. Thereafter, the brazing material diffuses preferentially along the molten grain boundaries and erosion occurs, so that erosion due to brazing diffusion is largely governed by the crystal grain shape of the core material before brazing and heating. In other words, if the value of a / b of the crystal grains of the core material before melting the brazing material is large, the diffusion of Si in the brazing material will be more diffused in the rolling direction than in the center direction of the core material, and will be inward toward the core material. The erosion of the brazing material can be suppressed. However, when the cold working rate is high and the a / b value is extremely large, recrystallization occurs rapidly during brazing and fine crystals are formed, and erosion of the brazing material occurs. Further, by controlling the a / b value, it is possible to suppress local stress concentration due to uneven slip of grain boundaries during heat input during electric resistance welding, and to prevent occurrence of micro-cracks and steps at the time of butting. This can be prevented. A that satisfies such conditions
The value of / b is 7.5 or less. On the other hand, when the a / b value is too small, there are many crystal grain boundaries in the direction penetrating the core material, and the diffusion of Si in the brazing material toward the inside of the core material becomes large. The erosion of the brazing material becomes severe. In order to suppress the erosion of the brazing material, the a / b value needs to be 3.0 or more.

The crystal grain size of the core material and the value of a / b are as follows:
This is performed by controlling the intermediate annealing conditions and the cold working ratio of the clad material.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. (Example 1) A tube material in which a brazing material was clad on one side of a core material and a sacrificial anode material was clad on the other side was produced by the following method.
The ingot of the core material, the brazing material, and the lining material are subjected to a predetermined homogenization treatment, and thereafter, the core material is 50 mm, the brazing material is 8 mm, and the lining material as the sacrificial anode material is 10 mm by facing and hot rolling. These sheet materials were superposed on both sides of a core material to form a three-layer structure material, which was hot-rolled and pressed to form a clad material having a sheet thickness of 5 mm. This clad material was subjected to cold rolling and intermediate annealing to produce a brazing sheet having a thickness of 0.25 mm. The value of a / b was controlled by changing the sheet thickness during intermediate annealing. FIG. 1 shows a cross section of the produced brazing sheet.
In the figure, reference numeral 1 denotes a brazing material provided on one surface of the core material 2 and 3 denotes a sacrificial anode material provided on the other surface of the core material 2. A 10 × 60 mm test piece for a hanging test was cut out from the brazing sheet thus prepared, and the protruding length was set to 50 mm, and brazing heating was performed at 600 ° C. for 3.5 minutes in a nitrogen gas atmosphere. The amount of free end droop was measured. Also 0.2
5 mm thick brazing sheet and 1 mm thick 300
As shown in FIG. 2, the three alloys were combined and heated by brazing at 600 ° C. for 3.5 minutes in a nitrogen gas atmosphere to examine the state of fillet formation. In FIG. 2, 5 is a brazing sheet, and 4 is a 3003 alloy. The case where the brazing material is sufficiently filled in the fillet portion is indicated by ○, the case where fillet formation is observed but not good is indicated by Δ, and the case where almost no fillet is formed is indicated by ×. Further, the state of diffusion of the brazing material into the core material at this time was examined. The case where the brazing material is hardly eroded is indicated by “○”, the case where the brazing material is slightly eroded is indicated by “△”, and the case where the brazing material is deeply eroded is indicated by “×”. Further, the cross section of the welded portion when the electric resistance welding was performed was observed, and the case where welding was performed normally was evaluated as ○, and the case where microcracks or steps were generated and welding defects were generated was evaluated as x. The components of the brazing sheet subjected to these tests are shown in Table 1. Table 2 shows the average length b in the thickness direction, the ratio of a / b, and the test results.
Shown in

[0020]

[Table 1]

[0021]

[Table 2]

The products 1 to 7 of the present invention shown in Tables 1 and 2 are two-layer materials composed of a core material and a brazing material.
33 are three-layer materials of a sacrificial anode material, a core material, and a brazing material. The products 1 to 7 of the present invention have different addition components Cr, Zr and Ti of the core material, but the aspect ratio a / b value of the crystal grains of the core material is within the scope of the claims, and there is a problem in the characteristics of the brazing sheet. Did not occur. The products 8 to 33 of the present invention are different from each other in the components of the sacrificial anode material and the core material, the amount of addition, and the plate thickness during the intermediate annealing, but all fall within the scope of the claims, and the aspect ratio of the crystal grains is also within the scope of the claims. No problem occurred in the characteristics of the brazing sheet.

On the other hand, in Comparative Example A shown in Tables 1 and 2, the clad material could not be produced because the sacrificial anode material as the lining material had a large amount of Mg. In Comparative Examples B and C, since the amounts of Si and Cu in the core material were large, microcracks occurred during welding and welding defects occurred. Further, the wax diffusion was large and the fillet formation was insufficient. Comparative Example D shows Fe in the core material.
The amount was large, the erosion of the brazing material was large, and the formation of fillets was insufficient. In Comparative Example E, the cold work ratio was high and the aspect ratio a / b of the crystal grains was extremely large, so that fine recrystallization occurred during brazing heating, and the erosion of the brazing material was large.
Fillet formation was also inadequate. Further, slippage of the grain boundaries was uneven during the tube forming and welding, and a step was generated. In Comparative Example F, the a / b value was large, the fillet was not good, and a step at the time of tube forming welding was observed. In Comparative Example G, the a / b value was small, the erosion of the brazing material into the core material progressed, and the fillet formation was not good. From the above results, in the product of the present invention, there is no diffusion of the brazing material into the core material after the heating by brazing, the dripping resistance is excellent, and the fillet formation is good. In addition, good results were obtained for the weldability. On the other hand, in the comparative example, erosion of the brazing material into the core material was observed, and the formation of fillets was not sufficient. Some microcracks were generated during welding. In order to obtain good corrosion resistance, a sacrificial anode material is clad on the refrigerant passage side of the tube material, but even if there is no sacrificial anode material as in claims 1 and 2, or a brazing material is clad on both surfaces of the core material. Even in this case, no problem occurred by using the coolant as the refrigerant.

[0024]

From the above results, the average length a in the rolling direction and the average length b in the thickness direction of the crystal grain size before heating the core material by brazing.
The brazing sheet prepared with the ratio a / b of 7.5 to 3.0 has little erosion of the brazing material during brazing heating, has excellent droop resistance, and has good fillet formation and weldability.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a brazing sheet-like structure of the present invention.

FIG. 2 is an explanatory view showing a test core for evaluating fillet forming ability.

FIG. 3 is a perspective view of a partial cross section showing a heat exchanger.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Brazing material 2 Core material 3 Sacrificial anode material 4 3003 alloy 5 Brazing sheet 6 Flat tube 7 Thin fin 8 Header 9 Tank

Claims (4)

[Claims] (1) Si 0.05 to 0.8 wt%, Fe 0.05
~ 0.6wt%, Cu0.3 ~ 1.1wt%, Mn0.6 ~
A brazing sheet comprising an aluminum alloy containing 1.6 wt%, the balance being Al and unavoidable impurities as a core material, and cladding an Al-Si alloy on one or both sides of the core material with a brazing material, An aluminum alloy brazing, wherein the ratio a / b of the average length a in the rolling direction and the average length b in the thickness direction of the crystal grains of the core material before brazing and heating is 7.5 to 3.0. Sheet. (2) 0.05 to 0.8 wt% of Si, 0.05% of Fe
~ 0.6wt%, Cu0.3 ~ 1.1wt%, Mn0.6 ~
1.6% by weight, and one of Cr, Zr and Ti
0.3% by weight or less of each type
a brazing sheet in which an aluminum alloy consisting of 1 and unavoidable impurities is used as a core material, and one or both surfaces of the core material are clad with an Al-Si alloy as a brazing material, and the crystal grains of the core material before brazing are heated. Wherein the ratio a / b of the average length a in the rolling direction to the average length b in the thickness direction is 7.5 to 3.0. 3. 0.05 to 0.8 wt% of Si, 0.05% of Fe
~ 0.6wt%, Cu0.3 ~ 1.1wt%, Mn0.6 ~
An aluminum alloy containing 1.6 wt% and the balance being Al and unavoidable impurities is used as a core material, and A is coated on one surface of the core material.
An l-Si based alloy is clad as a brazing material, and on the other surface, as a sacrificial anode material, Zn 0.3 to 5.0 wt%, Mg 0.05 to
4.0 wt%, Si 0.5 wt% or less, the balance being Al
A brazing sheet clad with an aluminum alloy comprising: and an unavoidable impurity, wherein the ratio a / b of the average length a in the rolling direction and the average length b in the thickness direction of the crystal grains of the core material before brazing and heating is increased. An aluminum alloy brazing sheet having a particle size of 7.5 to 3.0. 4. 0.05 to 0.8 wt% of Si, 0.05% of Fe
~ 0.6wt%, Cu0.3 ~ 1.1wt%, Mn0.6 ~
1.6% by weight, and one of Cr, Zr and Ti
0.3% by weight or less of each type
and an unavoidable impurity as a core material, an Al—Si alloy brazing material on one surface of the core material, and a sacrificial anode material of 0.3 to 5.0 wt% Zn, Mg 0.05 on the other surface.
~ 4.0 wt%, 0.5 wt% or less of Si, the balance being A
a brazing sheet clad with an aluminum alloy comprising 1 and unavoidable impurities, wherein the ratio a / b of the average length a in the rolling direction and the average length b in the thickness direction of the crystal grains of the core material before brazing and heating. Is an aluminum alloy brazing sheet, wherein is 7.5 to 3.0.