JP4705452B2 - High strength aluminum alloy, high strength aluminum alloy sheet, and heat exchanger excellent in brazing - Google Patents

Description

  The present invention relates to a high-strength aluminum alloy having excellent brazing properties, and further relates to a sheet using this high-strength aluminum alloy and a heat exchanger made from this sheet.

In recent years, in applications of heat exchangers such as automotive radiators, there is an increasing demand for thinning of tube materials and header plate materials, which are main components, for the purpose of weight reduction and price reduction. As a result, development of an aluminum alloy material having high strength and excellent brazing properties has been urgently required.
In general, a radiator for an automobile is assembled by joining the main constituent members produced by processing a brazing sheet composed of three layers of a brazing material, a core material, and a sacrificial anode material by a norocock brazing method.

  By the way, increasing the strength of the brazing sheet is achieved by adding Mg to the core material made of an aluminum alloy. However, when Mg is contained in the core material in this way, the wettability of the molten brazing material is lowered, so that there is a problem that the reliability of the brazed joint portion is lowered. The reason for this is that the flux applied to the surface of the member for the purpose of improving the bondability by brazing is eroded by chemically reacting with Mg in the core material, and the applied flux achieves the above purpose. It is because it becomes impossible.

Therefore, in order to avoid such a problem, in the prior art, in the brazing sheet, not the core material but Mg is contained in the sacrificial anode material to obtain high strength. That is, this brazing sheet achieves high strength by Mg in the sacrificial anode material diffusing to the core material side by brazing heat and combining with Si contained in the core material to produce MgSi. However, since Mg does not diffuse into the flux, the applied flux is not eroded. For this reason, since the wettability of the molten brazing material is not impaired, the reliability of the brazed joint is not reduced (for example, Patent Document 1).
Japanese Patent Laid-Open No. 2-175093 (second page, lower right column, lines 12 to 18)

However, the above-described prior art has a problem that the surface on which the core material can be brazed is restricted to one side opposite to the layer containing Mg (sacrificial anode material). For this reason, when a brazing material is arrange | positioned on both surfaces of a core material, the above-mentioned prior art cannot be applied.
On the other hand, it is possible to increase the strength of the aluminum core material by increasing the content of other metal elements (for example, Cu, Si) instead of Mg, but the melting point of the aluminum alloy also greatly decreases at the same time. Therefore, when brazing, a part of the core material is melted to increase erosion, and there is a problem in that the reliability of the joint portion cannot be reduced.

  An object of the present invention is to solve such problems, and by optimizing the content of a plurality of trace elements contained in aluminum, the wettability, high melting point and high strength of the brazing material are well balanced. In addition, the present invention provides a high-strength aluminum alloy and a high-strength aluminum alloy sheet that are excellent in brazeability, and further provides a heat exchanger that is reduced in weight and price.

In order to solve the problems described above, the invention according to claim 1 is a high-strength aluminum alloy having excellent brazing properties, in which Si is 0.30 mass%, Fe is 0.20 mass%, and Mn is 0.75 % by mass, Cu 0.6 % by mass, Mg 0.35-0.50 % by mass, Ni 0.30% by mass, Ti 0.05% by mass, Ag 0 .. 30 mass%, inevitable impurities, and the balance Al.
The invention according to claim 2 is a high-strength aluminum alloy having excellent brazeability, in which Si is 0.30% by mass, Fe is 0.50% by mass, Mn is 1.25% by mass, Cu 0.25 mass%, Mg 0.50 mass%, Ti 0.05 mass%, Ag 0.15 to 0.30 mass%, unavoidable impurities, and the balance Al, It is the structure which carries out.
The invention according to claim 3 is a high-strength aluminum alloy excellent in brazeability, in which Si is 0.30% by mass, Fe is 0.20% by mass, Mn is 0.75% by mass, Cu 0.25% by mass, Mg 0.20-0.50% by mass, Ni 0.26-0.27% by mass, Ti 0.03% by mass, and Ag 0.30% by mass. And unavoidable impurities and the remaining Al.

Since the invention according to any one of claims 1 to 3 has such a configuration, the Mg content is reduced to 0.2 to 0.5 mass%, so that Mg is aluminum during the brazing operation. Even when the alloy material diffuses to the surface, the amount of the flux applied to the surface is eroded by a chemical reaction can be reduced.
Further, the strength of the aluminum alloy can be increased by supplementing the above-mentioned reduced amount of Mg by increasing the Cu content. Further, Cu that contributes to the improvement of the strength of the aluminum alloy at the same time contributes to the lowering of the melting point, but the contribution rate of the latter to the lowering of the melting point of the latter is small.

The invention according to claim 4 is a high-strength aluminum alloy sheet in which the high-strength aluminum alloy having excellent brazing properties according to any one of claims 1 to 3 is formed into a sheet. The brazing material is arranged on at least one surface of the core material.

By having the invention according to this structure to claim 4, high-strength aluminum arrangement surface of the brazing material alloy sheet workpieces contact, both, the melting point of the melting point or less and the brazing material of the core member If heat treatment is performed at a temperature set as described above, the two are joined by brazing. This makes it possible to assemble products with brazing work that are suitable for mass production.

The invention according to claim 5 is a high-strength aluminum alloy sheet, wherein the high-strength aluminum alloy having excellent brazing properties according to any one of claims 1 to 3 is formed into a sheet. The sacrificial material is arranged on at least one surface of the core material.

When the invention according to claim 5 has such a configuration, pitting corrosion and crevice corrosion of the core material can be prevented by the sacrificial anodic action of the sacrificial material.

The invention described in claim 6 is characterized in that, in the high-strength aluminum alloy sheet, a sacrificial material is disposed on at least one surface of the high-strength aluminum alloy sheet according to claim 4 . Further the invention described in claim 7 is the high-strength aluminum alloy sheet, characterized in that a brazing material to the high strength of at least one surface of the aluminum alloy sheet according to claim 5.

When the inventions according to claims 6 and 7 have such a configuration, a high-strength aluminum alloy sheet having excellent corrosion resistance and excellent brazing productivity can be obtained.

According to an eighth aspect of the present invention, in the heat exchanger, the high strength aluminum alloy sheet according to any one of the fourth to seventh aspects is joined by brazing.

When the invention according to claim 8 has such a configuration, it is possible to reduce the thickness of the tube material and the header plate material, which are essential components of the heat exchanger.

  According to the present invention, the content of Mg for increasing the strength of aluminum is reduced and replaced with other metal elements, so that the wettability, high melting point and high strength of the brazing material are well balanced, Provided are a high-strength aluminum alloy and a high-strength aluminum alloy sheet that are excellent in adhesion, and a heat exchanger that is further reduced in weight and price.

The high-strength aluminum alloy and the high-strength aluminum alloy sheet of the present invention will be described with reference to the drawings.
FIG. 1 is a table showing measured values related to physical properties such as alloy composition, tensile strength at normal temperature and high temperature (250 ° C.), melting point, brazing property, and the like of a high-strength aluminum alloy.
And the alloy composition shown to the sample numbers 1-6 of FIG. 1 is an Example which shows the high intensity | strength aluminum alloy which concerns on embodiment of this invention, The alloy composition shown to the same and sample numbers 7-9 is well-known high It is a comparative example shown about a strength aluminum alloy.
Here, Comparative Example 7 corresponds to JIS name A3003, Comparative Example 8 corresponds to A3004, and Comparative Example 9 corresponds to A2014 equivalent.

  Moreover, the value of the tensile strength at room temperature and 250 ° C. shown in FIG. 1 is measured by a test piece produced as follows. That is, a shape conforming to a 14A test piece defined in JIS Z 2201 from a plate material obtained by hot rolling a high-strength aluminum alloy having a corresponding alloy composition and then cold-rolling to a plate thickness of 3 mm. Pull out the test piece. Furthermore, in order to add a thermal history corresponding to brazing to the test piece, a heat treatment was performed in the air at 570 ° C. for 30 minutes and then air cooling. And the test of tensile strength was done on the conditions of the tensile speed of 3 mm / min based on the metal tensile test method JISZ2241.

In addition, the preferable range of the trace element contained in the high-strength aluminum alloy in this invention and its content is as follows, Examples 1-6 of FIG. 1 are typical examples which have such an alloy composition. .
Si (silicon) coexists with Mg and improves the strength of the high-strength aluminum alloy. The content of Si in the high-strength aluminum alloy is preferably in the range of 0.05 to 1.0% by mass.
When the content of Si is less than 0.05% by mass, the effect of improving the strength of the high-strength aluminum alloy becomes insufficient. And when content of Si exceeds 1.0 mass%, while corrosion resistance of a high intensity | strength aluminum alloy will fall, melting | fusing point will also fall and brazing property will fall.

Mn (manganese) improves the strength without reducing the corrosion resistance of the high-strength aluminum alloy. The content of Mn in the high-strength aluminum alloy is preferably in the range of 0.5 to 1.5% by mass.
If the Mn content is less than 0.5% by mass, the effect of improving the strength of the high-strength aluminum alloy becomes insufficient. And when content of Mn exceeds 1.5 mass%, work moldability will fall.

Cu (copper) improves the self-corrosion resistance due to the sacrificial anticorrosive effect described later by improving the strength of the high-strength aluminum alloy and making the potential noble. The content of Cu in the high-strength aluminum alloy is preferably in the range of 0.2 to 0.8% by mass.
If the Cu content is less than 0.2% by mass, the effect of improving the strength of the high-strength aluminum alloy becomes insufficient. And when content of Cu exceeds 0.8 mass%, while self-corrosion resistance will fall, melting | fusing point will also fall and brazing property will fall.

Mg (magnesium) coexists with Ag and Si and improves the strength of the high-strength aluminum alloy. The Mg content in the high-strength aluminum alloy is preferably in the range of 0.2 to 0.5 mass%.
If the Mg content is less than 0.2% by mass, the effect of improving the strength of the high-strength aluminum alloy becomes insufficient. If the Mg content exceeds 0.5% by mass, it diffuses to the surface during the brazing operation, reacts with the flux, and lowers the brazing property. That is, the wettability of the molten brazing material is reduced by the corrosion of the flux.

Ag (silver) coexists with Mg and improves the strength of the high-strength aluminum alloy. The content of Ag in the high-strength aluminum alloy is preferably in the range of 0.15 to 0.5% by mass.
When the content of Ag is less than 0.15% by mass, the effect of improving the strength of the high-strength aluminum alloy becomes insufficient. When the content of Ag exceeds 0.5% by mass, the melting point of the high-strength aluminum alloy is lowered and the brazing property is lowered.

Ni (nickel) improves the strength by dispersing and precipitating intermetallic compounds in a high-strength aluminum alloy. The Ni content in the high-strength aluminum alloy is preferably in the range of 0.15 to 0.5 mass%.
When the content of Ni is less than 0.15% by mass, the effect of improving the strength of the high-strength aluminum alloy becomes insufficient. If the Ni content exceeds 0.5% by mass, the processability is deteriorated.

  FIG. 2 shows the relationship between the Cu, Mg, Ni, and Ag contents, the 250 ° C. tensile strength, and the melting point in the high-strength aluminum alloys of sample numbers 1 to 9 based on the various data shown in FIG. It is the graph which visualized and showed.

FIG. 3 is a view showing an evaluation sample for evaluating the brazing property of the high-strength aluminum alloy described in the rightmost column of FIG. 1, wherein (a) shows a good state (◯), (b) Indicates a bonding failure state (x) due to a decrease in the wettability of the brazing material, and (c) indicates a bonding failure state (x) in which erosion has occurred due to a decrease in the melting point of the high-strength aluminum alloy.
In FIG. 3, the evaluation sample 1 (1 a, 1 b, 1 c) is composed of a test piece 2 and a counterpart material 3. This test piece 2 is produced with the alloy composition in any one of Examples 1-6 of FIG. 1 or Comparative Examples 7-9. The mating material 2 is obtained by clad the A4343 brazing material 12 on one side using JIS designation A3003 as the core material 11 as shown in FIG. 5 (a) or (b) described later.
And the brazing operation | work of the evaluation sample 1 contact | abuts the test piece 2 which apply | coated the flux to the clad surface of the brazing | wax material of the other party material 3 by predetermined stress, and hold | maintains for 350 second in a 600 degreeC temperature atmosphere, Cooled at room temperature.

  Here, the brazing material has a lower melting point than the members to be joined (here, the core material of the test piece 2 and the counterpart material 3 (FIG. 5)), and therefore melts itself to join these members to be joined. To do. Here, as a brazing material generally used, an Al—Si alloy is used, and its melting point is 570 ° C. to 590 ° C.

  The flux has an action of removing the oxide film of the brazing material melted with the member to be joined, preventing oxidation again during heating, and cleaning the surfaces thereof. As a result, the flux improves the wettability of the molten brazing material with respect to the member to be joined and promotes its flow.

Next, the results of FIG. 2 and FIG. 3 will be compared and examined.
The brazeability of the test piece 1 made of a high-strength aluminum alloy composed of the alloy compositions of Examples 1 to 6 and Comparative Example 7 is good when the fillet 4a is formed as shown in FIG. )Met.
However, in the alloy composition of Comparative Example 7, since the tensile strength at 250 ° C. is as small as 56 MPa, although not particularly illustrated, a case in which the specimen 1 is buckled and deformed in the brazing operation of the evaluation sample 1a was recognized. On the other hand, in Examples 1-6, the buckling deformation | transformation in such brazing operation | work is not recognized, but it can be said that the favorable brazing result was obtained also from the form observation of the whole evaluation sample 1a.

And the brazing property of the test piece 1 which consists of a high-strength aluminum alloy comprised by the alloy composition of the comparative example 8 has bad wettability with respect to the test piece 2 of the molten brazing material as shown in FIG.3 (b). The formation state of the fillet 4b was poor (x).
This is because the alloy composition of Comparative Example 8 is sufficiently higher than the brazing material in terms of the melting point (628 ° C.), but there is no problem, but since the Mg content is as high as 1.0%, the brazing operation is in progress. Furthermore, it can be said that this Mg diffuses on the surface of the core material and reacts with the flux to erode it.

Further, the brazing property of the test piece 1 made of a high-strength aluminum alloy composed of the alloy composition of Comparative Example 9 is such that a part of the test piece 2 melts and erosion occurs as shown in FIG. The fillet 4c was formed poorly (x).
This is presumably because the alloy composition of Comparative Example 9 is lower than the melting point (510 ° C.) and the melting point of the brazing material and melts under the set heat treatment conditions.

FIG. 4 is a graph for examining the fluctuation amount of the 250 ° C. proof stress and the melting point with respect to the contents of Cu and Mg in the high-strength aluminum alloy.
The graph of FIG. 4 starts from the composition (1) (Cu: 0.25 mass%, Mg: 1.05 mass%) corresponding to Comparative Example 8 in which the Cu and Mg contents are The composition (Cu: 0.25% by mass, Mg: 0.5% by mass), the composition of (3) corresponding to Example 6 (Cu: 0.6% by mass, Mg: 0.5% by mass) FIG. 4 is a plot of changes in 250 ° C. proof stress and melting point when the Mg content is changed.

In general, when the content of Cu and Mg as trace elements is increased with respect to the aluminum parent phase, the melting point is lowered and the 250 ° C. proof stress is improved. However, within the content range shown in the graph of FIG. 4, the rate at which the 250 ° C. proof stress per unit increased amount of the trace elements contained and the rate at which the melting point does not decrease are higher for Cu than for Mg. It can be said that it is winning.
From this result, in order to obtain a high-strength aluminum alloy with excellent brazeability, the content of Mg, which greatly contributes to the increase in strength but deteriorates the wettability of the brazing material, is reduced. It is derived that it is better to increase the content of Cu that contributes to high strength without adversely affecting the strength.
Then, in order to obtain a high-strength aluminum alloy having excellent brazing properties, the optimum range of the amount of trace elements to be contained was experimentally clarified, and the above-described preferable content range was obtained.

  Furthermore, referring to FIG. 2, when Example 2 and Example 4 are compared, it can be said that the latter has improved tensile strength due to the Ni content. Thus, it is clear that Ni as a trace element contained in the aluminum alloy contributes to increasing its strength. Moreover, in contrast with Example 1 and Example 2, it can be said that the value of tensile strength is improving by increasing the Ag content in the latter. As a result, it is apparent that Ag as a trace element contained in the aluminum alloy contributes to increasing its strength.

5A to 5F are cross-sectional views showing the configuration of the high-strength aluminum sheet 10 (10a, 10b, 10c, 10d, 10e, 10f) according to the embodiment of the present invention.
The high-strength aluminum sheet 10 includes at least a core material 11 obtained by molding the high-strength aluminum alloy having the alloy composition exemplified in Examples 1 to 6 into a sheet shape (not shown, but the core material 11 is a single layer). Including some cases). Then, as shown in FIGS. 5A, 5 </ b> B, and 5 </ b> E, the brazing material 12 may be disposed on at least one surface of the core material 11. Furthermore, as shown in FIGS. 5C, 5D, 5E, and 5F, the sacrificial material 13 may be disposed on at least one surface of the core material 11.

Thus, as the high-strength aluminum sheet 10 according to the present embodiment, a brazing sheet obtained by clad the brazing material 12 and / or the sacrificial material 13 with respect to the core material 11 in a single layer, two layers, three layers, or more. Can be mentioned.
As described above, when the high-strength aluminum alloy sheet 10 in which the brazing material 12 is disposed on the core material 11 is used, the bonded member is brought into contact with the arrangement surface of the brazing material 12 so that both of them are below the melting point of the core material and are brazed. If heat treatment is performed at a temperature set higher than the melting point of the material, both are joined by brazing. Thereby, if parts are constituted by such a high-strength aluminum alloy sheet 10, it is easy to braze and assemble these parts, which is suitable for mass production.
Even in the case of the high-strength aluminum alloy sheet 10 in which the brazing material 12 is not disposed, the brazing material can be separately applied to be brazed with excellent bondability.

  Here, the sacrificial material 13 is an aluminum alloy having a lower potential than the core material 11, and the sacrificial material 13 itself is preferentially corroded by the sacrificial anodic action, thereby causing pitting corrosion and crevice corrosion of the core material 11. Is to prevent.

The heat exchanger in the present invention is not particularly illustrated, but includes an automobile radiator, an oil cooler, an intercooler, and the like, which are manufactured by brazing the above-described high-strength aluminum sheet 10 having excellent brazing properties. .
Here, taking a radiator for an automobile as an example, the manufacturing process will be described. First, the high-strength aluminum sheet 10 described above is manufactured by manufacturing fins, tubes, head plates and side plates, which are constituent parts of the radiator. Next, these components are assembled, degreased and washed with an organic solvent vapor, and then flux is applied.

Then, when this assembly is placed in a furnace adjusted to a predetermined temperature and heat-treated, the brazing material is melted at the portions where the components abut each other, and these components are integrated. At this time, the core material does not melt, and Mg in the core material does not diffuse into the flux in a large amount and does not erode it. A good brazing joint is achieved.
Thus, if a high-strength aluminum alloy having excellent brazing properties is used, the aluminum alloy sheet can be used in a thin state, and the heat exchanger configured thereby can be reduced in weight and price. .

Measured values related to physical properties such as alloy composition, tensile strength at normal temperature and high temperature (250 ° C.), melting point, brazing property, and the like of a high strength aluminum alloy according to an embodiment of the present invention and a high strength aluminum alloy as a comparative example. It is a table | surface which shows. Based on the various data in FIG. 1, in the high-strength aluminum alloys of sample numbers 1 to 9, the relationship between the contents of each Cu, Mg, Ni, and Ag, the 250 ° C. tensile strength and the melting point was visualized. It is the graph shown. It is a figure which shows the evaluation sample which evaluates the brazing property of the high intensity | strength aluminum alloy described in the rightmost column of FIG. 1, Comprising: (a) shows a good state ((circle)) and (b) is brazing material. A defective state (x) due to a decrease in wettability is shown, and (c) shows a defective state (x) where erosion has occurred due to a drop in the melting point of the high-strength aluminum alloy. It is a graph for examining the fluctuation amount of 250 degreeC yield strength and melting | fusing point with respect to content of Cu and Mg in a high strength aluminum alloy. (A)-(f) is sectional drawing which shows the structure of the high intensity | strength aluminum sheet which concerns on embodiment of this invention.

Explanation of symbols

1 (1a, 1b, 1c) Evaluation sample 2 Test piece 3 Mating material 4 (4a, 4b, 4c) Fillet 10 (10a, 10b, 10c, 10d, 10e, 10f) High strength aluminum alloy sheet 11 Core material 12 Brazing material 13 Sacrificial materials

Claims (8)

0.30 % by mass of Si, 0.20% by mass of Fe, 0.75 % by mass of Mn, 0.6 % by mass of Cu, 0.35 to 0.50 % by mass of Mg, Ni 0.30% by mass, Ti 0.05% by mass, Ag 0.30 % by mass, unavoidable impurities and the balance Al, and a high-strength aluminum alloy having excellent brazing properties . 0.30 % by mass of Si, 0.50% by mass of Fe, 1.25 % by mass of Mn, 0.25 % by mass of Cu, 0.50 % by mass of Mg, and 0.05 % of Ti A high-strength aluminum alloy having excellent brazing characteristics, comprising: mass%; Ag: 0.15 to 0.30 mass%; inevitable impurities; and the balance: Al. 0.30 % by mass of Si, 0.20% by mass of Fe, 0.75 % by mass of Mn, 0.25 % by mass of Cu , 0.20 to 0.50 % by mass of Mg, Ni 0.26 to 0.27% by mass, Ti 0.03% by mass, Ag 0.30 % by mass, unavoidable impurities, and the balance Al. High strength aluminum alloy. A high-strength aluminum alloy excellent in brazeability according to any one of claims 1 to 3 is used as a core material, and a brazing material is disposed on at least one surface of the core material. High strength aluminum alloy sheet. A high-strength aluminum alloy excellent in brazeability according to any one of claims 1 to 3 in a sheet form is used as a core material, and a sacrificial material is disposed on at least one surface of the core material. High strength aluminum alloy sheet. A high-strength aluminum alloy excellent in brazeability according to any one of claims 1 to 3 is formed into a sheet, and a brazing material is disposed on one surface of the core material, and the remaining surface is disposed. A high-strength aluminum alloy sheet characterized in that a sacrificial material is disposed. A high-strength aluminum alloy sheet, wherein a brazing material is disposed on at least one surface of the high-strength aluminum alloy sheet according to claim 5 . A heat exchanger produced by joining the high-strength aluminum alloy sheet according to any one of claims 4 to 7 by brazing.

Images