JP2009228010A - Brazing sheet made from aluminum alloy and method for manufacturing heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brazing sheet made from an aluminum alloy which has high formability before being brazed and has both of superior corrosion resistance and high mechanical properties after having been brazed. <P>SOLUTION: The brazing sheet 10 comprises: a core material 11 comprising, by mass%, 0.5 to 1.1% Si, 0.6 to 2.0% Mn, 0.5 to 1.1% Cu, 0.05 to 0.25% Ti and the balance Al; a skin material 12 which is provided on one side of the core material 11, comprises, by mass%, more than 0.5 to 1.1% Si, 0.01 to 1.7% Mn, 3.0 to 6.0% Zn and the balance Al, and has a thickness of 25 to 50 μm; and a soldering material 13 which is provided on the other side of the core material 11, comprises 7.0 to 12 mass% Si and the balance Al, and has a thickness of 25 to 55 μm. The brazing sheet 10 has a yield strength of 110 to 210 MPa. The core material 11 shows an average crystal grain size of 50 μm or larger but smaller than 300 μm in a rolling direction after the brazing sheet has been heat-treated at 580 to 610°C for 3 to 10 minutes. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an aluminum alloy brazing sheet used for a heat exchanger or the like and a method for producing the heat exchanger.

  For example, a heat exchanger such as a radiator mounted on an automobile is manufactured by assembling and brazing a tube material and a fin material each formed of a brazing sheet made of an aluminum alloy into a predetermined shape. Here, as the brazing sheet, a three-layer structure in which a skin material (sacrificial anode material) is provided on one main surface of the core material and a brazing material is provided on the other main surface is widely used. .

  In recent years, with the reduction in weight of automobiles, heat exchangers are also required to be lighter, smaller and have higher performance. For this purpose, it is necessary to reduce the thickness of the material constituting the brazing sheet. However, in order to realize a reduction in the thickness of each constituent material, the mechanical characteristics and corrosion resistance of each constituent material must be improved.

Therefore, as a method for improving the mechanical strength of the brazing sheet, a method of adding Cu to the core material is known, and for example, it is proposed to use a core material made of an Al-Mn-Cu alloy (for example, a patent Reference 1). In addition, as a technique for improving the corrosion resistance of the brazing sheet, a method of reducing the average grain size of the core material after brazing to 300 μm or more and reducing the crystal grain boundary of the core material that is likely to be a brazing intrusion route (for example, Patent Document 2). The technique disclosed in Patent Document 2 is to improve erosion resistance, which is one of the important elements of corrosion resistance. When brazing a brazing sheet, the brazing material erodes the core material (erosion). By suppressing this, a local decrease in the thickness of the core material is prevented.
JP-A-9-95749 (paragraphs [0011] to [0018] etc.) JP 2004-17116 (paragraphs [0007], [0008], etc.)

  However, since the brazing sheet disclosed in Patent Document 1 does not sufficiently add Si to the skin material, the Al—Mn intermetallic compound is likely to precipitate at the grain boundaries, which may reduce the corrosion resistance. Moreover, since the strength of the skin material is insufficient, the mechanical strength of the brazing sheet may be insufficient. In the brazing sheet disclosed in Patent Document 1, Cu is added to the core material to improve the mechanical strength of the brazing sheet, but this is not always sufficient. On the other hand, if the mechanical properties of the brazing sheet before brazing are too high, the moldability of the brazing sheet is lowered. Therefore, it is necessary to optimize the mechanical characteristics of the brazing sheet before brazing, particularly the proof stress of the brazing sheet.

  Further, the technique disclosed in Patent Document 2 has a problem that the mechanical strength after brazing is lowered because the average crystal grain size after brazing of the core material is too large. In addition, since the core material is not homogenized in order to increase the average crystal grain size of the core material after brazing, rolling cladding is performed in a state where the additive elements contained in the core material are segregated. Therefore, local melting may occur due to segregation during brazing.

  The present invention has been made in view of such circumstances, has high formability before brazing, exhibits good brazing properties during brazing, and has excellent corrosion resistance and high mechanical properties after brazing. An object of the present invention is to provide an aluminum alloy brazing sheet having both characteristics. Moreover, an object of this invention is to provide the manufacturing method of the heat exchanger using such an aluminum alloy brazing sheet.

  The brazing sheet made of an aluminum alloy according to the present invention has Si: 0.5 to 1.1 mass%, Mn: 0.6 to 2.0 mass%, Cu: 0.5 to 1.1 mass%, Ti: 0 0.05 to 0.25% by mass, and the balance is provided on one side of the core with Al and inevitable impurities, Si: more than 0.5% by mass and 1.1% by mass or less, Mn: 0.01 to 1.7% by mass, Zn: 3.0 to 6.0% by mass, with the balance being 25-50 μm thick consisting of Al and inevitable impurities, and the other side of the core And having a brazing material having a thickness of 25 to 55 μm containing Si: 7.0 to 12% by mass and the balance being Al and inevitable impurities, and the core material, the skin material, and the brazing material are It is clad by rolling, and the proof stress of the aluminum alloy brazing sheet is 110 The average crystal grain size of the core material after the aluminum alloy brazing sheet is heat-treated at 580 to 610 ° C. for 3 to 10 minutes is 50 μm or more and less than 300 μm in the rolling direction.

  In this way, by controlling the composition of the core material and the average crystal grain size after the heat treatment, mechanical strength suitable for molding can be obtained before brazing, and high brazing properties can be obtained during brazing. In addition, melting of the core material can be prevented, and high corrosion resistance and high mechanical strength can be obtained after brazing. In addition, by controlling the composition and thickness of the skin material, melting of the skin material can be prevented during brazing, and high mechanical strength and high corrosion resistance (sacrificial anti-corrosion action) can be obtained after brazing. It is done. Furthermore, by controlling the composition and thickness of the brazing material, it is possible to prevent erosion of the core material during brazing and to obtain excellent brazing properties.

  In this aluminum alloy brazing sheet, the core material preferably further contains Mg. In this case, the Mg content is 0.05% by mass or more and less than 0.45% by mass.

  Thus, the mechanical strength of the brazing sheet after brazing can be further improved by adding a predetermined amount of Mg.

  The method for producing a heat exchanger according to the present invention is characterized in that the aluminum alloy brazing sheet is formed into a predetermined shape and brazed by a brazing process. The brazing step preferably includes a step of heating the aluminum alloy brazing sheet at 580 to 610 ° C. for 3 to 10 minutes. Moreover, it is preferable that the average crystal grain size of the core material in the portion that was the brazing sheet made of the aluminum alloy is 50 μm or more and less than 300 μm in the rolling direction by the brazing step.

  According to such a heat exchanger manufacturing method, since an aluminum alloy brazing sheet having high mechanical strength and excellent corrosion resistance is used as described above, a heat exchanger having excellent durability is obtained. be able to.

  Since the brazing sheet made of aluminum alloy according to the present invention has high formability before brazing, the clearance at the brazed portion can be reduced, so that the bondability at the time of brazing is improved. Can do. In addition, good brazing properties are obtained during brazing, and an excellent effect of having both excellent corrosion resistance and high mechanical properties after brazing is achieved. Therefore, the heat exchanger using the aluminum alloy brazing sheet according to the present invention is easy to manufacture and exhibits excellent durability.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing a schematic structure of an aluminum alloy brazing sheet (hereinafter referred to as “brazing sheet”) according to the present invention. The brazing sheet 10 has a structure in which a skin material 12 is clad on one surface of a core material 11 made of an aluminum alloy and a brazing material 13 is clad on the other surface. The brazing sheet 10 is formed into a tube having a skin 12 on the inner surface side, and this tube is used for assembling a heat exchanger such as a radiator of an automobile as a heat transfer tube through which a refrigerant flows. It is done.

  The core material 11 includes 0.5 to 1.1% by mass of Si, 0.6 to 2.0% by mass of Mn, 0.5 to 1.1% by mass of Cu, and 0.05 to 0.25. It contains Ti by mass and the balance consists of Al and inevitable impurities. The skin material 12 contains more than 0.5 mass% and 1.1 mass% or less of Si, 0.01-1.7 mass% of Mn, and 3.0-6.0 mass% of Zn. The balance consists of Al and inevitable impurities. The brazing material 13 contains 7.0 to 12% by mass of Si, and the balance is made of Al and inevitable impurities. The thickness of the skin material 12 is 25 to 50 μm, and the thickness of the brazing material 13 is 25 to 55 μm. The proof stress (0.2% proof stress) of the brazing sheet 10 is 110 to 210 MPa, and the average crystal grain size of the core material 11 after the brazing sheet 10 is heat-treated at 580 to 610 ° C. for 3 to 10 minutes is 50 μm in the rolling direction. This is less than 300 μm. Hereinafter, each element constituting the brazing sheet 10 will be described in detail.

<< Heartwood 11 >>
[Si content of core material 11: 0.5 to 1.1% by mass]
When Si coexists with Mn, it forms an Al—Mn—Si-based intermetallic compound and is finely distributed within the grains, thereby contributing to the improvement of the mechanical strength of the core material 11. Si, when coexisting with Mg, forms Mg ₂ Si and improves the mechanical strength after brazing. When the Si content is less than 0.5% by mass, these effects are small, and the Al—Mn intermetallic compound is likely to precipitate at the grain boundaries, so that the corrosion resistance is lowered. On the other hand, if the Si content exceeds 1.1% by mass, the solidus temperature of the core material 11 decreases, and therefore the core material 11 melts during brazing. Therefore, Si content in the core material 11 shall be 0.5-1.1 mass%.

[Mn content of core material 11: 0.6 to 2.0 mass%]
As described above, Mn reacts with Al and Si to form an Al—Mn—Si intermetallic compound, and improves the mechanical strength after brazing. When the Mn content is less than 0.6% by mass, the amount of Al—Mn—Si intermetallic compound decreases, the amount of Si solid solution increases, the solidus temperature of the core material 11 decreases, and brazing At this time, the core material 11 melts. On the other hand, when the Mn content exceeds 2.0% by mass, an Al—Mn—Si giant intermetallic compound is formed, and the corrosion resistance and formability are lowered. Therefore, the Mn content in the core material 11 is set to 0.6 to 2.0 mass%.

[Cu content of core material 11: 0.5 to 1.1% by mass]
Since Cu has the property of making the potential noble, it improves the corrosion resistance. When the Cu content is less than 0.5% by mass, the potential difference from the skin material 12 becomes insufficient, and the corrosion resistance decreases. On the other hand, if the Cu content exceeds 1.1% by mass, the solidus temperature of the core material 11 decreases, so that the core material 11 melts during brazing. Therefore, Cu content in the core material 11 shall be 0.5-1.1 mass%.

[Ti content of core material 11: 0.05 to 0.25% by mass]
Ti forms an Al—Ti intermetallic compound in an Al alloy and disperses in layers. Since the Al—Ti intermetallic compound has a noble potential, the corrosion form is layered, and there is an effect that it is difficult to progress to corrosion (pitting corrosion) in the thickness direction. When the Ti content is less than 0.05% by mass, the layering effect of the corrosion form is small. When the Ti content exceeds 0.25% by mass, an Al—Ti giant intermetallic compound is formed, resulting in a decrease in formability and corrosion resistance. To do. Therefore, the Ti content in the core material 11 is set to 0.05 to 0.25% by mass.

[Mg content of core material 11: 0.05 mass% or more and less than 0.45 mass%]
Mg is added to the core material 11 as necessary in an amount of 0.05% by mass or more and less than 0.45% by mass. As described above, Mg forms Si and Mg ₂ Si and is aged to improve the mechanical strength after brazing. This effect is small when the Mg content is less than 0.05% by mass. On the other hand, since Mg has an effect of reducing the flux brazing property, when the Mg content is 0.45% by mass or more, Mg diffuses into the brazing material 13 during brazing and the brazing property is lowered. . Therefore, Mg in the core material 11 is an optional component and does not necessarily have to be added. However, when Mg is added from the viewpoint of improving the mechanical strength of the core material 11, the Mg content is 0.05 mass. % Or more and less than 0.45 mass%.

[Contents of inevitable impurities in the core material 11]
In addition to Si, Mn, Cu, Ti, and Mg, addition of 0.2% by mass or less of Fe, Cr, or Zr does not impair the effects of the present invention. In addition, as an unavoidable impurity, Zn may be contained in an amount of 1.5% by mass or less, and In and Sn may be contained in an amount of 0.03% by mass or less, respectively.

[Average crystal grain size after heat treatment of core material 11: 50 μm or more and less than 300 μm]
When the average grain size in the rolling direction of the core material 11 (hereinafter referred to as “average grain size after heating”) after the brazing sheet 10 is heat-treated for 3 to 10 minutes at 580 to 610 ° C. is less than 50 μm In the brazing sheet 10, the crystal grain boundaries of the core material 11 are eroded by brazing (liquid phase generated by melting of the brazing material 13 during brazing), so-called erosion of the core material 11. Is likely to occur. On the other hand, when the average crystal grain size after heating is 300 μm or more, the mechanical strength after brazing decreases. Therefore, the core material 11 having an average crystal grain size after heating of 50 μm or more and less than 300 μm is used.

  The above-described heat treatment conditions for the brazing sheet 10 at 580 to 610 ° C. for 3 to 10 minutes correspond to preferable brazing conditions for assembling a product such as a heat exchanger using the brazing sheet 10. Therefore, the average crystal grain size after heating being 50 μm or more and less than 300 μm means that the brazing sheet 10 after brazing has good erosion resistance and high mechanical strength. In addition, when it deviates from above-mentioned heat processing conditions, brazing using the brazing sheet 10 cannot be performed at all, and the product cannot be assembled.

  The component composition of the core material 11 is defined as described above, and, as will be described later, the conditions for the homogenization heat treatment of the core material 11 (core material ingot) and the finish processing rate in the final cold rolling (finish cold work) The average crystal grain size after heating of the core material 10 by the heat treatment at 580 to 610 ° C. for 3 to 10 minutes can be controlled within the range of 50 μm or more and less than 300 μm. Homogenization heat treatment and finish cold working rate will be described later.

  The “rolling direction of the core material 11” means that the soaked core material ingot is sandwiched between the skin material rolled plate and the brazing material rolled plate and clad by hot rolling, as will be described later. It refers to the rolling direction in hot rolling and cold rolling when producing a brazing sheet 10 by performing predetermined cold rolling or the like as a plate material, for example, hot rolling and cold rolling are performed by a rolling roll. In the case, it refers to one direction in which the plate material is extruded by a rolling roll.

<Skin 12>
[Si content of skin 12: more than 0.5% by mass and 1.1% by mass or less]
When Si coexists with Mn, it forms an Al—Mn—Si intermetallic compound and is finely distributed within the grains, thereby contributing to dispersion strengthening. Further, Si contributes to improvement of mechanical strength after brazing by solid solution strengthening. When the Si content is 0.5% by mass or less, these effects are small, and the Al—Mn-based intermetallic compound easily precipitates at the grain boundaries, and the corrosion resistance decreases. On the other hand, if the Si content exceeds 1.1% by mass, the solidus temperature of the skin material 12 decreases, so that the skin material 12 melts during brazing. Therefore, the Si content in the skin material 12 is more than 0.5 mass% and 1.1 mass% or less.

[Mn content of skin 12: 0.01 to 1.7% by mass]
As described above, Mn forms Al, Si and an Al—Mn—Si-based intermetallic compound to improve mechanical strength after brazing and suppress precipitation of Si alone at grain boundaries. When the Mn content is less than 0.01% by mass, the number of Al—Mn—Si intermetallic compounds decreases, so that Si alone precipitates at the grain boundaries, and the corrosion resistance decreases. On the other hand, if the Mn content exceeds 1.7% by mass, an Al—Mn-based giant intermetallic compound is formed, and the corrosion resistance decreases. Therefore, the Mn content in the skin material 12 is set to 0.01 to 1.7% by mass.

[Zn content of skin 12: 3.0 to 6.0 mass%]
Since Zn has a property of lowering the potential, the skin material 12 can act as a sacrificial anode material. When the Zn content is less than 3.0% by mass, the potential difference from the core material 11 becomes insufficient, and the corrosion resistance decreases. On the other hand, if the Zn content exceeds 6.0% by mass, the solidus temperature of the skin material 12 is lowered, so that the skin material 12 melts during brazing. Therefore, Zn content in the skin material 12 shall be 3.0-6.0 mass%.

[Contents of inevitable impurities, etc. in the skin material 12]
In addition to Si, Mn, and Zn described above, addition of 0.2% by mass or less of Fe, Cr, or Zr does not impair the effects of the present invention. Further, as an unavoidable impurity, Cu may be contained in an amount of 0.2% by mass or less, and In and Sn may be contained in an amount of 0.03% by mass or less.

[Thickness of skin 12: 25-50 μm]
For example, when the brazing sheet 10 is used as a tube material of a heat exchanger such as a radiator, the skin material 12 is indispensable for ensuring corrosion resistance of the inner surface as a sacrificial anode material. If the thickness of the skin material 12 is less than 25 μm, the absolute Zn content of the skin material 12 decreases even with the above-described Zn content, so that the potential is not sufficiently low with respect to the core material 11 and the corrosion resistance is reduced. To do. Further, when the brazing sheet 10 is formed into a tube material, the skin 12 side surface and the brazing material 13 side surface of the inner surface of the tube may be joined. Here, if the thickness of the skin material 12 is insufficient when the core material 11 contains Mg, the Mg diffused from the core material 11 reacts with the flux applied to the surface of the skin material 12 to oxidize the flux. The destructive action of the film is reduced, and this lowers the brazeability of the joint. On the other hand, if the thickness of the skin material 12 exceeds 50 μm, the amount of Zn diffused into the core material 11 increases, the potential of the core material 11 becomes low, the potential difference becomes insufficient, and the potential of the entire brazing sheet 10 becomes low. As a result, the corrosion rate increases and the corrosion resistance decreases. Further, if the skin material 12 is made thicker, the absolute thickness of the core material 11 must be reduced, and the mechanical strength after brazing is lowered. Therefore, the thickness of the skin material 12 shall be 25-50 micrometers.

<< Brazing material 13 >>
[Si content of brazing filler metal 13: 7.0 to 12% by mass]
The Al—Si alloy begins to melt at about 577 ° C., and the liquid phase flows and flows. When the Si content is less than 7.0% by mass, the amount of brazing is insufficient and the brazing property is lowered. On the other hand, when the Si content exceeds 12 mass%, the flow amount of the wax increases, a part of the wax diffuses into the core material 11 and erodes the core material 11, and erosion of the core material 11 occurs. Therefore, the Si content in the brazing material 13 is 7.0 to 12% by mass.

[Content of inevitable impurities and the like in the brazing material 13]
In addition to the Si described above, even if Fe is added in an amount of 0.3% by mass or less and Ti is added in an amount of 0.05% by mass or less, the effects of the present invention are not impaired. As unavoidable impurities, Zn and Cu may be contained in an amount of 2.0% by mass or less, and In and Sn may be contained in an amount of 0.03% by mass or less.

[Thickness of brazing material 13: 25 to 55 μm]
Since the brazing material 13 is an Al—Si alloy, it begins to melt at about 777 ° C., and the liquid phase flows as a brazing fluid and fills the joint. If the thickness is less than 25 μm, when the core material 11 contains Mg, Mg diffused from the core material 11 reacts with the flux applied to the surface of the brazing material 13 to reduce the destruction action of the oxide film of the flux. For this reason, the brazability is reduced. On the other hand, when the thickness exceeds 55 μm, the flow amount of the wax increases and a part of the wax diffuses into the core material 11, causing erosion of the core material 11. Therefore, the thickness of the brazing material 13 is set to 25 to 55 μm.

[Strength of brazing sheet 10; 110 to 210 MPa]
If the proof stress of the brazing sheet 10 is less than 110 MPa, it will buckle during molding due to excessive softening and a good shape cannot be obtained. On the other hand, if the proof stress of the brazing sheet 10 exceeds 210 MPa, the moldability deteriorates due to excessive curing, and a stable fillet is not formed during brazing. Therefore, the proof stress of the brazing sheet 10 is 110 to 210 MPa.

  The yield strength of the brazing sheet 10 can be controlled within a range of 110 to 210 MPa by adjusting the finish cold working rate as will be described later and further adjusting the finish annealing as necessary. The finish cold working rate and finish annealing will be described later.

<< Manufacturing Method of Brazing Sheet 10 >>
Next, an example of the manufacturing method of the brazing sheet 10 will be described. The aluminum alloy for the skin material and the aluminum alloy for the brazing material are respectively cast, chamfered, and homogenized heat-treated (hereinafter referred to as “soaking”) by a known method to obtain the ingot for the skin material and the ingot for the brazing material. Make it. The ingot for skin material and the ingot for brazing material are each made to have a predetermined thickness by hot rolling to produce a rolled sheet for skin material and a rolled sheet for brazing material. On the other hand, the aluminum alloy for core material is cast and chamfered by a known method, and is soaked at 440 to 570 ° C. for 2 hours or more. By soaking the aluminum alloy for the core material under predetermined conditions, the average crystal grain size of the core material 11 after the brazing heat treatment can be controlled to 50 μm or more and less than 300 μm. Moreover, segregation of the additive element contained in the aluminum alloy for core material can be suppressed, and local melting of the core material 11 during brazing can be prevented.

  Next, the soaked core material ingot is sandwiched between the skin material rolling plate and the brazing material rolling plate, and heat treated (reheated) at a temperature of 440 ° C. or higher and lower than the core material homogenizing heat treatment temperature. A sheet is formed by pressure bonding by rolling. Thereafter, cold rolling and intermediate annealing are carried out to a predetermined thickness, and the final cold rolling is finished and cold worked in order to control the average crystal grain size of the core material 11 after brazing heat treatment to 50 μm or more and less than 300 μm. It implements so that a rate may be 20 to 85%, and it is finished to predetermined plate | board thickness, and is set as the brazing sheet 10. FIG. The intermediate annealing is preferably performed at 350 to 400 ° C. for 2 to 4 hours. Moreover, in order to control the yield strength of the brazing sheet 10 to 110-210 MPa after final cold rolling, finish annealing is performed at 150-320 degreeC for 5 hours or less as needed. When performing final annealing, intermediate annealing can be omitted.

<< Production Method of Heat Exchanger >>
The brazing sheet 10 according to the embodiment described above can be used for manufacturing a heat exchanger made of aluminum alloy. The manufacturing method of the heat exchanger using the brazing sheet 10 can include the following steps. First, the brazing sheet 10 is formed into a shape as a part of a heat exchanger. The brazing sheet 10 can be formed into the shape of a part constituting a tube or a tank as a flow path through which the heat exchange medium of the heat exchanger flows. The brazing sheet 10 can also be formed as a fin for promoting heat exchange.

  Next, the pre-molded parts are assembled into a predetermined shape as a heat exchanger. A plurality of brazing sheets 10 can be combined in a predetermined shape. Moreover, a predetermined shape can also be made by combining the brazing sheet 10 and an aluminum plate made of a different material composition. The assembly including the brazing sheet 10 is positioned in a brazing furnace and brazed (a brazing process). The assembly is heated to the melting temperature of the brazing material, for example in a nitrogen environment. The assembly is heated, for example, at 580-610 ° C. for 3-10 minutes and then cooled. For example, the brazing process can be performed at a temperature of about 590 ° C. for about 7 minutes. As a result, the brazing material is solidified again after being melted, and the brazing sheet 10 is joined via the brazing material.

  According to this manufacturing method, the portion of the brazing sheet 10 prior to brazing becomes an average crystal grain size of the core material of 50 μm or more and less than 300 μm in the rolling direction by the brazing process. Thus, as described above, the portion that was the brazing sheet 10 before brazing has high corrosion resistance and mechanical strength. Thus, the heat exchanger excellent in durability is manufactured using the brazing sheet 10.

  Next, the present invention will be described in more detail with examples belonging to the present invention as examples and those not belonging to the present invention as comparative examples. However, the present invention is not limited to the following examples.

[Production of test materials]
An aluminum alloy for core material having the composition shown in Table 1 was cast and face cut. Further, a rolled plate made of an aluminum alloy for skin material having the composition shown in Table 2 (hereinafter referred to as “rolled plate for skin material”), and a brazing material added with (containing) the amount of Si shown in Tables 3 and 4 Rolled sheets made of an aluminum alloy (hereinafter referred to as “rolled sheet for brazing material”) were produced. The prepared aluminum alloy for core material was soaked under the conditions shown in Tables 3 and 4, and the soaked core alloy for core material was sandwiched between the combinations shown in Tables 3 and 4 between the rolled sheet for skin material and the rolled sheet for brazing material. Overlap, clad by hot rolling, followed by cold rolling, intermediate annealing is performed under the conditions shown in Table 3 and Table 4, and then the final cold is applied at the processing rates shown in Table 3 and Table 4. Rolling was performed to prepare a brazing sheet having a three-layer structure, and used as test materials for various tests described later. Note that some samples were subjected to finish annealing under the conditions shown in Table 3 and Table 4, and some samples were omitted from the intermediate annealing when finishing annealing was performed.

[Evaluation of test material strength]
A JIS No. 5 test material was cut out from the prepared test material, a tensile test was performed, and the yield strength was measured. The measurement results are also shown in Tables 3 and 4. As described above, the acceptance criterion for the proof stress was 110 MPa or more and 210 MPa or less.

[Evaluation of Springback]
FIG. 2 shows a processed shape of the test piece for evaluating the spring back property. Evaluation of the springback property is performed by testing the skin material side surface 16 of the test piece 15 cut out from the test material so that the surface dimension is 15 mm × 10 mm upward, and a 2 mmR, 90 ° punch from the skin material side surface 16. The test piece 15 was formed by bending it 90 ° parallel to the rolling direction of the test piece 15 and measuring the spring back angle θ after this forming. The results are shown in Tables 3 and 4 (abbreviated as “SB angle θ”). The acceptance criterion was a springback angle θ of 94 ° or less.

[Test material heat treatment]
A sheet having a predetermined shape was cut out from the test material for heat treatment, a hole was formed in the upper portion of the sheet, and the sheet was hung on a jig, followed by heat treatment at 595 ° C. for 3 minutes in a nitrogen atmosphere. This heat treatment is a heat treatment that simulates brazing of the test material in order to investigate various characteristics of the test material, that is, the brazing sheet, after brazing, and is performed within a range of suitable brazing conditions of the test material. Is called. The sample prepared by this heat treatment is hereinafter referred to as “sample after heating”. Including the heat treatment for 3 minutes, the time during which the heat treatment was performed at a high temperature of 380 ° C. or higher was set to 20 minutes.

[Measurement of tensile strength of specimen after heating]
A JIS No. 5 test material was cut out from the test material after heating (after one week of room temperature aging from the heat treatment described above), and the tensile strength was measured. The measured tensile strength can be considered as the tensile strength after the test material, i.e., the brazing sheet, is actually brazed for assembly of a predetermined product, and the acceptance criterion is that this tensile strength is 160 MPa or more. did. The measurement results are shown in Tables 3 and 4 (abbreviated as “tensile strength after heating”).

[Measurement of average crystal grain size of core material in specimen after heating]
After heating, the specimen is cut into a predetermined size (size suitable for the subsequent polishing, etching, and particle size measurement operations), and polishing is started from one surface, and the center of the core material in the thickness direction is almost centered. Then, the polished surface was etched with an electrolytic solution, and the etched surface was photographed 100 times. The average grain size in the rolling direction of the core material constituting the test material after heating is determined by obtaining the average of the five measured values by the intercept method based on this photograph, and as described above, the acceptance criteria are determined. The range was 50 μm or more and less than 300 μm. The measurement results are shown in Tables 3 and 4 (abbreviated as “average grain size after heating”).

[Evaluation of brazeability]
FIG. 3 schematically shows the configuration of a test piece for evaluating brazeability. Two test pieces 20 having a surface dimension of 25 mm × 20 mm are cut out from the test material, and the two test pieces 20 are projected at the center in the longitudinal direction as shown in FIG. It shape | molded so that 21 might become a protrusion side. A non-corrosive flux is applied at 5 (± 0.2) g / m ² to the top sides of the two test specimens 20 (the projecting side surface of the projecting portion at the center in the longitudinal direction). 3 were superposed as shown in FIG. 3 and brazed under the above-mentioned heat treatment conditions (under nitrogen atmosphere at 595 ° C. for 3 minutes). The test piece 20 after brazing was cut and embedded in resin, the cut surface of the test piece 20 was polished, and the length of the fillet 22 on the polished surface was measured. When the length of the fillet 22 was 4 mm or more, it was judged that the brazing property was good. The evaluation results are shown in Tables 3 and 4. In Tables 3 and 4, the judgment that the brazing property is good is “◯”, the judgment that the brazing property is bad is “x”, and the evaluation that cannot be evaluated is “−”. Respectively.

[Evaluation of erosion resistance]
Samples that were cold-rolled at a processing rate of 10% and 20% were prepared, and these were heat-treated under the same conditions as the heat-treatment that simulated the brazing described above. The two kinds of new post-heat specimens thus obtained and the post-heat specimens not subjected to cold rolling were cut and embedded in resin, the cut surfaces were polished, and the polished surfaces were examined with a microscope. The erosion resistance was evaluated based on whether or not erosion of the core material occurred. The evaluation results are shown in Tables 3 and 4. In Tables 3 and 4, the case where it is determined that the erosion of the core material is not substantially generated is indicated by “◯”, and the case where the erosion of the core material is confirmed is indicated by “X”. In addition, it was assumed that the erosion of the core material did not occur in all of the three types of post-heating specimens with different cold rolling conditions belonged to the examples.

[Evaluation of corrosion resistance]
After heating, a test piece having a surface dimension of 60 mm × 50 mm is cut out from the test material, and the entire surface of the brazing material side, the entire end surface and the outer edge of the skin material side surface are 5 mm wide so that the skin material side surface becomes the test surface. Coated with a quick-drying adhesive. An aqueous solution containing 118 ppm Na ⁺ , 58 ppm Cl ⁻ , 60 ppm SO ₄ ²⁻ , 1 ppm Cu ²⁺ and 30 ppm Fe ³⁺ was prepared as a corrosion test solution, and an adhesive-coated test piece was prepared. The sample was immersed in a corrosion test solution, and the corrosion test solution was allowed to stand at 88 ° C. for 8 hours and then allowed to stand at room temperature for 16 hours. Tables 3 and 4 show the results of observing the presence or absence of penetration corrosion in the test piece after completion of this test. In Tables 3 and 4, the case where penetration corrosion was not observed is indicated by “◯”, and the case where occurrence of penetration corrosion was confirmed is indicated by “x”. This corrosion resistance evaluation is performed only when good results are obtained in both brazing evaluation and erosion resistance evaluation. Corrosion resistance evaluation is performed in Tables 3 and 4. For those that do not, the evaluation results are indicated by “−”.

[Test results]
The specimens according to Examples 31 to 46, i.e., the brazing sheets, have an appropriate yield strength of 110 to 210 MPa before the heat treatment, and therefore have good springback properties and excellent moldability. Was confirmed. By using a brazing sheet having such a high formability, the clearance at the brazed portion can be reduced during actual brazing, thus improving the bondability during brazing and good bonding. The state can be obtained.

  Moreover, since the average crystal grain size in the rolling direction of the core material of the specimens after heating according to Examples 31 to 46 is 50 μm or more and less than 300 μm, it has high tensile strength even after the heat treatment. Moreover, it was confirmed that the erosion resistance was also good. Further, in Examples 31 to 46, since the core material, the skin material, and the brazing material have appropriate compositions, and the thicknesses of the brazing material and the skin material are also appropriate, brazing property, erosion resistance, and Good results were obtained in all of the corrosion resistance.

  On the other hand, in Comparative Example 51, since the Si content in the core material is insufficient, the Al—Mn-based intermetallic compound is precipitated at the grain boundary, and the Cu content in the core material is insufficient, Thus, the potential difference was insufficient, and the corrosion resistance decreased. In Comparative Example 52, since the Mn content in the core material is insufficient, the Al—Mn—Si intermetallic compound in the core material is decreased and the amount of solute Si is increased, thereby causing erosion of the core material. In Comparative Example 53, the amount of Mg exceeding the allowable amount that can be contained in the core material is included in the core material, so that the brazing property is lowered. In Comparative Example 54, since the Ti content in the core material was excessive, an Al—Ti giant intermetallic compound was formed, and the corrosion resistance was lowered.

  In Comparative Example 55, since the Si content in the skin material was insufficient, Al—Mn intermetallic compounds were precipitated at the grain boundaries, and the corrosion resistance was reduced. In Comparative Example 56, since the Mn content in the skin material was excessive, an Al—Mn-based giant intermetallic compound was formed, and the corrosion resistance was lowered. In Comparative Example 57, since the Zn content in the skin material was excessive, the skin material melted during the heat treatment simulating brazing, and a test material after heating could not be obtained.

  In Comparative Example 58, since the Si content in the brazing material was insufficient, the flow amount of the brazing was insufficient, and the brazing property was lowered. In Comparative Example 59, since the Si content in the brazing material was excessive, the flow amount of the brazing was excessive, and erosion of the core material occurred. In Comparative Example 60, since the brazing material was too thick, the amount of brazing flow became excessive, and erosion of the core material occurred. In Comparative Example 61, since the brazing material was too thin, the amount of brazing was insufficient, and the brazing property was lowered.

  In Comparative Example 62, since the thickness of the skin material was too thin, the brazing property was lowered by Mg diffusing from the core material.

  In Comparative Example 63, the crystal of the core material was coarsened by the heat treatment, so that the tensile strength after the heat treatment was insufficient. In Comparative Example 64, erosion of the core material occurred because the average crystal grain size in the rolling direction of the core material after the heat treatment was small.

  In Comparative Example 65, since the yield strength was high, the springback angle θ was large. Therefore, when molding a test piece (see FIG. 3) for evaluation of brazeability, sufficient moldability was not obtained, and a stable fillet was not formed. In Comparative Example 66, since the yield strength was excessively small, buckling occurred when a test piece for brazing evaluation was formed.

It is sectional drawing which shows schematic structure of a brazing sheet. It is a figure which shows the processing shape of the test piece for the measurement of springback property. It is a figure which shows typically the structure of the test piece for evaluation of brazing property.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Brazing sheet 11 Core material 12 Skin material 13 Brazing material 15 Test piece 16 Skin material side surface 20 Test piece 21 Brazing material side surface 22 Fillet

Claims (5)

Si: 0.5-1.1% by mass, Mn: 0.6-2.0% by mass, Cu: 0.5-1.1% by mass, Ti: 0.05-0.25% by mass , And the balance material consisting of Al and inevitable impurities as the balance,
Provided on one surface of the core material, Si: more than 0.5% by mass and 1.1% by mass or less, Mn: 0.01-1.7% by mass, Zn: 3.0-6.0% by mass Containing, with a balance of Al and inevitable impurities and a thickness of 25-50 μm,
Provided on the other surface of the core material, containing Si: 7.0 to 12% by mass, the balance having a brazing material with a thickness of 25 to 55 μm made of Al and inevitable impurities,
An aluminum alloy brazing sheet in which the core material, the skin material, and the brazing material are clad by rolling,
The proof stress of the aluminum alloy brazing sheet is 110 to 210 MPa,
The aluminum alloy brazing sheet, wherein an average crystal grain size of the core material after heat treatment of the aluminum alloy brazing sheet at 580 to 610 ° C for 3 to 10 minutes is 50 µm or more and less than 300 µm in the rolling direction.   The aluminum alloy brazing sheet according to claim 1, wherein the core material further contains Mg: 0.05 mass% or more and less than 0.45 mass%.   A method for producing a heat exchanger, wherein the aluminum alloy brazing sheet according to claim 1 or 2 is formed into a predetermined shape and brazed by a brazing process.   The said brazing process includes the process of heating the said brazing sheet made from an aluminum alloy at 580-610 degreeC for 3 to 10 minutes, The manufacturing method of the heat exchanger of Claim 3 characterized by the above-mentioned.   The heat exchanger production according to claim 4, wherein the brazing step sets the average crystal grain size of the core material in the portion that was the brazing sheet made of aluminum alloy to 50 µm or more and less than 300 µm in the rolling direction. Method.

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