JP2015206063A - Aluminum alloy fin material for heat exchanger excellent in room temperature strength, high temperature strength, and corrosion resistance after brazing and heating and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy fin material for a heat exchanger excellent in room temperature strength, high temperature strength, and corrosion resistance after brazing and heating.SOLUTION: There are provided an aluminum alloy fin material for a heat exchanger excellent in room temperature strength, high temperature strength, and corrosion resistance after brazing and heating, containing Si:0.7 to 1.5%, Fe:0.4 to 1.2%, Mn:0.5 to 1.8%, Zn:0.5 to 3.0%, having an intermetallic compound density of an equivalent circle diameter of 0.01 μm or more and less than 0.15 μm (d1) of 5.0×10/mmand an intermetallic compound density of an equivalent circle diameter of 0.15 μm to 5.00 μm (d2) of 5.0×10to 3.0×10/mmwith d1/d2 of 0.30 or more before brazing and heating and an intermetallic compound density of an equivalent circle diameter of 0.01 μm to 5.00 μm (d3) of 5.0×10/mmor more and Si solid solution amount of 0.30 to 0.80 mass% after brazing and heating and a manufacturing method therefor.

Description

  In particular, the present invention is suitably used as a heat exchanger fin material for radiators, heater cores, condensers, intercoolers, etc., and has excellent room temperature strength, high temperature strength and corrosion resistance after brazing heat addition, and aluminum alloy fin material for heat exchanger and its It relates to a manufacturing method.

  Aluminum alloys are suitable for heat exchanger materials such as radiators, heater cores, condensers, and intercoolers because they are lightweight and have excellent strength and thermal conductivity.

  Conventionally, such a heat exchanger is assembled by brazing and joining aluminum alloy fins, which are formed into a corrugated shape by, for example, corrugation, to other members. As the aluminum alloy fin material, a pure aluminum alloy such as JIS1050 alloy having excellent thermal conductivity and an Al-Mn alloy such as JIS3003 alloy having excellent strength and buckling resistance have been generally used. In addition, a technique for preventing corrosion of a tube of a heat exchanger by preferentially corroding the fin material by the sacrificial anode effect by making the fin material electrochemically base potential is also generally used.

  By the way, in recent years, demands for weight reduction, size reduction, and high performance have been increasing for heat exchangers. Accordingly, the aluminum alloy fin material is also required to be thin. In order to realize such thinning, it is strongly desired to improve characteristics such as room temperature strength, heat conductivity and corrosion resistance after brazing heat.

  In recent years, heat exchangers have been increasingly used in a high-temperature and high-pressure environment. For example, the case of a radiator that cools the engine is taken as an example. When trying to obtain a high engine output, the amount of heat generated from the engine increases. In order to cool this, a refrigerant for cooling the engine is circulated at a high pressure. If it does so, high temperature and a high pressure refrigerant will flow into a radiator, the load concerning a radiator will become large, and the case which will cause a failure of a radiator increases. For this reason, it is desired to improve the durability of the heat exchanger not only by increasing the strength of the tube material but also by increasing the strength of the fin material. In this case, in addition to general characteristics such as thermal conductivity, it is necessary to ensure high temperature strength and corrosion resistance.

  Aluminum alloy fins are generally manufactured by a semi-continuous casting (DC) method, and standard alloys such as JIS1100 and JIS3003 are inferior in room temperature strength after brazing heat, so heat exchangers have sufficient durability. Can not.

  Patent Document 1 proposes an aluminum alloy fin material for a heat exchanger that is cast by a semi-continuous casting method and has excellent strength and corrosion resistance after brazing addition heat by adding Ni to the alloy component. However, a compound containing Ni has a large potential difference from the matrix and is likely to be a base point for corrosion. Thus, Ni-containing alloys have low self-corrosion resistance and are insufficient in practice. In addition, the semi-continuous casting method is inferior in self-corrosion resistance because the size of the compound produced during casting is larger than that in the continuous casting rolling method, and many compounds are the starting point of corrosion and the corrosion is likely to proceed.

  In order to improve the room temperature strength after brazing heat, an aluminum alloy fin material may be manufactured by a continuous casting method (CC method). Patent Document 2 discloses a high strength for heat exchangers excellent in erosion resistance of 0.1 mm or less in final plate thickness, which is cast by a continuous casting and rolling method, and the first annealing is performed at a temperature of 450 to 600 ° C. for 1 to 10 hours. A method for producing an aluminum alloy material has been proposed. However, since the intermediate annealing is performed at a high temperature, the compound becomes coarse during annealing and its distribution becomes sparse, so that the room temperature strength after the brazing addition heat is lowered. In addition, the crystal grain size after brazing heating is expected to be fine, and there is a possibility that brazing properties cannot be ensured. There is a need for aluminum alloys having more optimized manufacturing conditions and microstructures.

  Patent Document 3 discloses an aluminum alloy fin material excellent in room temperature strength after brazing heat, in which the size of 90% or more of the intermetallic compound deposited on the fin material is controlled to a metal structure having a maximum value of 5 μm or less. Has been proposed. However, as will be described later, the dispersion strengthening by the intermetallic compound contributes less to the improvement of the high-temperature strength after the brazing heat addition than the solid solution strengthening. Therefore, the fin material of this patent document has sufficient brazing heat addition. It cannot be said that it has post-high temperature strength, and is inferior to the high temperature durability of the heat exchanger.

  Patent Document 4 discloses that an aluminum alloy fin material having improved droop resistance by adding Mn and Zr to improve high-temperature strength after brazing addition heat and making the metal structure after brazing addition heat coarse grains. Has been proposed. However, in Patent Document 4, Si addition effective for improving the high-temperature strength in the vicinity of 100 ° C. has not been studied, and the high-temperature strength of the fin material in the actual vehicle environment is insufficient. Moreover, since Zr is added, the electrical conductivity after brazing addition heat is low. If the electrical conductivity is low, the thermal conductivity is lowered, so that the heat exchange rate is lowered and sufficient heat exchange performance cannot be exhibited.

  Patent Document 5 proposes to obtain an aluminum alloy fin material for a heat exchanger having excellent corrosion resistance by regulating the amount of Si solid solution in the central portion of the plate thickness after brazing heat to 0.7% or less. Yes. However, since solid solution Si improves the high temperature strength as will be described later, a sufficient high temperature strength cannot be obtained if the Si solid solution amount is regulated to 0.7% or less. Moreover, since the density of the dispersed particles before the heat of brazing is not specified, it is impossible to achieve both excellent room temperature strength, high temperature strength and corrosion resistance after heat of brazing.

JP 2003-147466 A JP 2008-307661 A JP 2001-226730 A JP 61-217547 A Japanese Patent No. 4166613

  Thus, in recent years, aluminum alloy fin materials produced by various alloy components and production processes have been proposed. In addition to general characteristics such as thermal conductivity, aluminum alloys that can ensure high-temperature strength and corrosion resistance. The present condition is that the fin material is not obtained.

  As described above, in the conventional technology, an aluminum alloy fin material having sufficient performance as a fin material for a heat exchanger has not been obtained, and in particular, strength performance has not been improved in a high temperature environment such as around 100 ° C. . The present invention has been made in view of such a technical background, and an object thereof is to provide an aluminum alloy fin material for a heat exchanger excellent in room temperature strength, high temperature strength and corrosion resistance after brazing addition heat, and a method for producing the same. To do.

  The present inventor conducted intensive research to solve these problems, and optimized metal conditions by applying optimized annealing conditions and rolling conditions using aluminum alloy materials having specific components. An aluminum alloy fin material for heat exchangers having an intermetallic compound distribution and an element solid solution amount and capable of solving the above problems has been obtained.

Specifically, the present invention provides the method according to claim 1, wherein Si: 0.7 to 1.5 mass%, Fe: 0.4 to 1.2 mass%, Mn: 0.5 to 1.8 mass%, Zn: 0.00. The intermetallic compound density (d1) having a circle equivalent diameter of 0.01 μm or more and less than 0.15 μm is 5.0 when it contains 5-3.0 mass%, consists of the balance Al and inevitable impurities, and before brazing addition heat. in × 10 is ^four or / mm ² or more, an intermetallic compound having a circle equivalent diameter of 0.15~5.00μm density (d2) is 5.0 × ¹⁰ 4 to 3.0 × 10 ⁷ cells / mm ² Yes, d1 / d2 is 0.30 or more, and the density of the intermetallic compound (d3) having an equivalent circle diameter of 0.01 to 5.00 μm after the brazing heat is 5.0 × 10 ⁴ pieces / mm ² That is the above, and the Si solid solution amount is 0.30 to 0.80 mass%. Room temperature strength after heating brazing to symptoms, and the heat exchanger use aluminum alloy fin material excellent in high temperature strength and corrosion resistance

  Further, in the present invention, the present invention is characterized in that the tensile strength at room temperature is 130 MPa or more, the tensile strength at 120 ° C. is 90 MPa or more, and the tensile strength after SWAAT for 480 hours is obtained. TS1 (MPa) was assumed, and TS1 / TS0 was 0.40 or more when the tensile strength before SWAAT was TS0 (MPa).

  The present invention is the method for producing an aluminum alloy fin material for a heat exchanger having excellent room temperature strength, high temperature strength and corrosion resistance after brazing addition heat according to claim 1, wherein Si: 0.7 to Aluminum containing 1.5 mass%, Fe: 0.4 to 1.2 mass%, Mn: 0.5 to 1.8 mass%, Zn: 0.5 to 3.0 mass%, the balance being Al and inevitable impurities A casting process for casting the molten alloy, an annealing process for annealing the ingot, and a cold rolling process including a final cold rolling stage, wherein the casting process is a continuous casting rolling process for continuously casting and rolling the molten aluminum alloy. The annealing step includes a high-temperature annealing stage in which the rolled plate is heat-treated at 450 to 560 ° C. for 1 to 10 hours, and a rolled plate is heat-treated at 200 to 450 ° C. for 1 to 10 hours, immediately before the final cold rolling step. Including one or more low-temperature annealing steps, and the cold rolling step further includes one or more cold rolling steps in a step preceding the final cold rolling step, and the rolling rate in the final cold rolling step is 10 It was set as -50%, It was set as the manufacturing method of the aluminum alloy fin material for heat exchangers which is excellent in the room temperature strength after brazing addition heat, high temperature strength, and corrosion resistance.

  Further, the present invention according to claim 4 is the method according to claim 3, wherein the continuous casting and rolling step, the high-temperature annealing step of high-temperature annealing the rolled ingot, and the cold rolling step as a pre-process of the final cold rolling step are provided. The cold rolling stage for cold rolling the high temperature annealed ingot, the low temperature annealing stage for low temperature annealing of the cold rolled sheet, and the final cold rolling stage for cold rolling the low temperature annealed rolled sheet Included.

  The aluminum alloy fin material for a heat exchanger according to the present invention is excellent in room temperature strength, high temperature strength and corrosion resistance after brazing heat in addition to general characteristics such as thermal conductivity.

It is sectional drawing of the minicore which shows the assembly | attachment state of a corrugated fin and a tube. It is sectional drawing which shows the structure of a heat exchanger core. It is a perspective view which shows the structure of a heat exchanger core. It is a microscope picture which shows the specific example of the pass and failure in wax diffusion evaluation.

  Hereinafter, embodiments for carrying out the present invention will be described in detail.

(1) Reason for limitation of alloy composition Si: 0.7 to 1.5 mass%
Si is an essential element for securing room temperature strength and high temperature strength after brazing heat. Si, together with Fe and Mn added at the same time, forms an Al—Fe (—Si) -based intermetallic compound and an Al—Mn—Si (—Fe) -based intermetallic compound, contributing to dispersion strengthening, Room temperature strength after brazing heat). Part of Si is dissolved in the material by brazing heat, and the strength at room temperature and high temperature after brazing heat is improved by solid solution strengthening. The Al—Mn—Si (—Fe) -based compound formed by the addition of Si precipitates at the grain boundaries after the heat of brazing, and causes a grain boundary corrosion if the amount of precipitation is large. If the Si content is less than 0.7 mass% (hereinafter simply referred to as “%”), the above effect cannot be obtained sufficiently, and sufficient room temperature strength and high temperature strength after brazing heat can be obtained. Absent. On the other hand, if the Si content exceeds 1.5%, the solidus temperature of the material is greatly reduced, so that the material melts during brazing addition heat and brazing failure is likely to occur. Furthermore, precipitation of Al—Mn—Si (—Fe) -based compounds at grain boundaries increases, and intergranular corrosion is particularly likely to occur.

Fe: 0.4-1.2%
Fe is an essential element for securing room temperature strength and high temperature strength after brazing heat. Fe forms an Al—Fe (—Si, Mn) -based intermetallic compound together with Mn added at the same time during casting, thereby contributing to dispersion strengthening, and in particular, improving room temperature strength after heat applied by brazing. If the Fe content is less than 0.4%, the above effects cannot be obtained sufficiently, and sufficient room temperature strength and high temperature strength after sufficient brazing heat cannot be obtained. On the other hand, if the Fe content exceeds 1.2%, an Al-Fe coarse crystallized product is generated during casting, and the plastic deformability is lowered, so that the rollability is lowered. In addition, the Al—Fe compound acts as a cathodic site for corrosion, and pitting corrosion is likely to occur, resulting in poor corrosion resistance.

Mn: 0.5 to 1.8%
Mn is an essential element for securing room temperature strength and high temperature strength after brazing heat. Mn forms an Al—Mn—Si intermetallic compound together with Si added at the same time, contributing to dispersion strengthening and improving material strength (particularly room temperature strength after brazing addition heat). If the Mn content is less than 0.5%, the above effects cannot be obtained sufficiently. On the other hand, when the Mn content exceeds 1.8%, Al-Mn coarse crystals are generated during casting, and the plastic deformability is lowered, so that the rollability is lowered. In addition, precipitation of Al—Mn—Si (—Fe) -based compounds at grain boundaries increases, and intergranular corrosion is likely to occur. Furthermore, when there is too much content, since the Mn solid solution amount after brazing addition heat will increase, electrical conductivity will fall.

Zn: 0.5-3.0%
Zn lowers the natural potential of the material and contributes to the improvement of the sacrificial anticorrosive effect. If the Zn content is less than 0.5%, the above effects cannot be obtained sufficiently. On the other hand, if the Zn content exceeds 3.0%, the self-corrosion rate increases and the self-corrosion resistance decreases.

  Further, for the purpose of refining crystal grains and Al-Si based crystals, Ti: 0.001 to 0.300%, Sr: 0.0001 to 0.0100%, Na: 0.0001 to 0.0100 %, Ca: 0.0001 to 0.0100% may be added. Further, Zr: 0.01 to 0.300% may be added for the purpose of coarsening the crystal grain size. Inevitable impurities other than Si, Fe, Mn, Zn, Ti, Sr, Na, Ca, and Zr are each preferably 0.05% or less and 0.15% or less in total.

(2) Intermetallic compound density of aluminum alloy fin material Before brazing heat, the intermetallic compound density (d1) having an equivalent circle diameter of 0.01 μm or more and less than 0.15 μm is 5 × 10 ⁴ pieces / mm ² or more. And the density of the intermetallic compound (d2) having an equivalent circle diameter of 0.15 to 5.00 μm is 5 × 10 ^{4 to} 3.0 × 10 ⁷ pieces / mm ² , and d1 / d2 is 0.30. As described above, the density of the intermetallic compound (d3) having an equivalent circle diameter of 0.01 to 5.00 μm after the brazing heat is 5 × 10 ⁴ pieces / mm ² or more. In order to secure room temperature strength, high temperature strength and corrosion resistance after brazing heat, it is defined by the size of the intermetallic compound before brazing heat (in the present invention, the equivalent circle diameter, specifically the projected area equivalent circle diameter (Heywood diameter)). ) And the density of existence needs to be adjusted optimally.

  Here, in the present invention, “before brazing addition heat” and “after brazing addition heat” are “brazing addition heat” using any brazing material at a temperature of 580 to 610 ° C. and a holding time of 0.5 to 10 ° C. An actual brazing addition heat treatment or a heat treatment with a holding time of 0.5 to 10 minutes at a temperature of 580 to 610 ° C. corresponding to actual brazing addition heat without using a brazing material. Note that, whether or not brazing material is used, the heat treatment condition is preferably a temperature of 600 ° C. and a holding time of 3 minutes. Moreover, in the case of brazing addition heat treatment using a brazing material, both the case where a flux is used and the case where it is not used are included.

  An intermetallic compound means an Al—Fe (—Mn) -based compound and an Al—Mn—Si (—Fe) -based compound. The Al—Fe (—Mn) -based compound is mainly formed during casting and exists as a crystallized product, and the equivalent circle diameter is often about 0.15 μm or more. On the other hand, the Al—Mn—Si (—Fe) -based compound is also formed in the cooling process after casting, annealing, and brazing heat treatment, and the equivalent circle diameter is 5.00 μm or less, less than about 0.15 μm. In many cases.

(2) -1 Before brazing heat addition, the density of the intermetallic compound (d1) having an equivalent circle diameter of 0.01 μm or more and less than 0.15 μm is regulated to 5.0 × 10 ⁴ pieces / mm ² or more. Improvement of high-temperature strength after heating largely depends on solid solution strengthening, and it is necessary to ensure a certain amount of element solid solution after brazing heat. Intermetallic compounds having an equivalent circle diameter of less than 0.15 μm before brazing heat (especially Al—Mn—Si (—Fe) -based compounds) easily dissolve in the material during brazing heat and improve high-temperature strength. Contribute to. When the density of the intermetallic compound having a circle-equivalent diameter of 0.01 μm or more and less than 0.15 μm is less than 5.0 × 10 ⁴ pieces / mm ² , the present inventors have insufficient brazing and brazing. It was found that sufficient high-temperature strength after heating could not be ensured.

  The above-mentioned intermetallic compound having an equivalent circle diameter of 0.15 μm or more has a small effect. Further, since the above-mentioned intermetallic compound having an equivalent circle diameter of less than 0.01 μm is extremely fine and density measurement is difficult, those having an equivalent circle diameter of less than 0.01 μm were excluded. Here, the higher the intermetallic compound density, the more the amount of solid solution after the brazing addition heat tends to increase, and the high temperature TS tends to improve. Therefore, the upper limit of the intermetallic compound density is not particularly limited.

(2) -2 Intermetallic compound density (d2) having an equivalent circle diameter of 0.15 to 5.00 μm to 5.0 × 10 ^{4 to} 3.0 × 10 ⁷ pieces / mm ² before brazing addition heat Since the intermetallic compound having an equivalent circle diameter of 0.15 to 5.00 μm (particularly an Al—Fe (—Mn) -based compound) contributes to dispersion strengthening due to its small amount of solid solution during brazing addition heat, The higher the dispersion density, the higher the room temperature strength after brazing addition heat. On the other hand, the intermetallic compound of the size takes in a solid solution element during cooling after the brazing heat and lowers the amount of solid solution in the material. It is necessary to control the intermetallic compound density. When the present inventors have less than 5.0 × 10 ⁴ pieces / mm ² , the density of the intermetallic compound is small, so the dispersion strengthening is reduced and the room temperature strength after the brazing addition heat is lowered. It has been found that if it exceeds 3.0 × 10 ⁷ pieces / mm ² , the incorporation of solid solution elements by the intermetallic compound increases, and the high-temperature strength after brazing addition heat decreases.

  In addition, when it has an equivalent circle diameter exceeding 5.00 μm, substantially most of the crystallized material is coarse, the intermetallic compound density is lowered, and sufficient dispersion strengthening cannot be obtained, and the room temperature strength is lowered. .

(2) -3 After brazing addition heat, specify the density of intermetallic compound (d3) having an equivalent circle diameter of 0.01 to 5.00 μm to 5.0 × 10 ⁴ pieces / mm ² or more. Brazing addition heat The density of the intermetallic compound (especially Al—Fe (—Mn) -based compound) having an equivalent circle diameter of 0.01 to 5.00 μm later needs to be 5.0 × 10 ⁴ pieces / mm ² or more. . When this intermetallic compound density is less than 5.0 × 10 ⁴ pieces / mm ² , the room temperature strength after brazing addition heat cannot be sufficiently ensured. Here, when the equivalent-circle diameter exceeding 5.00 μm is obtained, the density of the intermetallic compound is less than 5.0 × 10 ⁴ pieces / mm ² because most of the crystallized material is substantially coarse. The room temperature strength cannot be secured sufficiently. Further, since the above-mentioned intermetallic compound having an equivalent circle diameter of less than 0.01 μm is extremely fine and density measurement is difficult, those having an equivalent circle diameter of less than 0.01 μm were excluded. In addition, reinforcement | strengthening by the dispersion | strengthening strengthening after brazing addition heat | fever increases so that the said intermetallic compound density is high, and room temperature TS tends to improve. Therefore, the upper limit of the intermetallic compound density is not particularly limited.

(2) -4 d1 (intermetallic compound density having an equivalent circle diameter of 0.01 μm or more and less than 0.15 μm) / d2 (intermetallic compound density having an equivalent circle diameter of 0.15 to 5.00 μm) If d1 / d2 is less than 0.30, the amount of intermetallic compound that takes in a solid solution element is too much to reduce the amount of solid solution element when d1 / d2 is less than 0.30. Therefore, sufficient high-temperature strength after brazing addition heat cannot be ensured. The upper limit of d1 / d2 is not particularly limited.

(3) Specifying the amount of Si solid solution after heat of brazing addition to 0.30 to 0.80% Solid solution strengthening is effective for improving the high temperature strength. It is considered that the contribution of the dispersion strengthening by the compound to the strength improvement is small. This is presumably because dislocations move easily in a high temperature environment, and dispersed particles are unlikely to hinder dislocation movement. Therefore, in order to strengthen the solid solution, it is necessary to ensure a solid solution amount above a certain level. The Si diffusion rate and the dislocation movement rate in the vicinity of 100 ° C. are approximately the same, and since the Si diffusion easily inhibits the dislocation movement, it is effective in improving the high-temperature strength. If the Si solid solution amount is 0.30% or more, high-temperature TS can be sufficiently secured. On the other hand, if it is less than 0.30%, sufficient high-temperature tensile strength (TS) cannot be secured. When the amount of Si solid solution exceeds 0.80%, precipitation of Al—Mn—Si (—Fe) -based compounds at the grain boundaries increases, and intergranular corrosion is likely to occur.

(4) Tensile strength In the present invention, the tensile strength (TS) of the aluminum alloy fin material under various conditions is defined as follows.

(4) -1 Defining TS at room temperature after brazing addition heat to 130 MPa or more In order to ensure the durability of the heat exchanger at room temperature, it is desirable that the room temperature TS after brazing addition heat is high. For that purpose, it is preferable to set TS at room temperature after brazing addition heat to 130 MPa or more. If it is less than 130 MPa, the durability of the heat exchanger is lowered, and practically sufficient durability cannot be obtained. In the present invention, 25 ° C. is the room temperature. Note that the higher the TS at room temperature after the brazing heat, the easier it is to improve the core durability at room temperature. Therefore, the upper limit of the room temperature TS is not particularly limited.

(4) -2 Specifying TS at 120 ° C. after brazing addition heat to 90 MPa or more As described above, cases where heat exchangers are used in a high temperature environment are increasing. The high temperature environment is about 100 ° C., which is higher than the conventional temperature. Therefore, if the TS at 120 ° C., which is higher than 100 ° C., is 90 MPa or more, sufficient high-temperature durability of the heat exchanger can be obtained. If the TS at 120 ° C. is less than 90 MPa, sufficient high temperature durability cannot be obtained. The higher the TS at 120 ° C. after the brazing heat, the easier the core durability at 120 ° C. improves. Therefore, the upper limit of 120 ° C. TS is not particularly limited.

(4) -3 After brazing addition heat, TS after 480 hours SWAAT (TS1 <MPa>) / (TSA before SWAAT (TS0 <MPa>) should be specified as 0.40 or more. When the fins are used in an environment and the corrosion of the fins progresses, the durability of the heat exchanger core decreases.It is desirable that the fins have excellent corrosion resistance, so that TS1 (MPa) / TS0 (MPa) is set to 0. By setting the ratio to 40 or more, the fins have practically sufficient corrosion resistance, and can sufficiently ensure the durability of heat exchange even in a corrosive environment, where TS1 (MPa) / TS0 (MPa) is high. Since it is so excellent in corrosion resistance, the upper limit of TS1 (MPa) / TS0 (MPa) is not particularly limited.

(5) Manufacturing method Below, the manufacturing method of the aluminum alloy fin material for heat exchangers which concerns on this invention is demonstrated. In addition, this manufacturing method shows one embodiment, and does not limit the manufacturing method of the aluminum alloy fin material of the present invention.

  First, an overall process flow of the manufacturing method will be described. First, the Al metal and the Al mother alloy are melted in a melting furnace to adjust the components. Thereafter, casting is performed by a continuous casting and rolling method. As the continuous casting and rolling method, a twin roll method, a belt method, or the like is used. Next, the obtained ingot is annealed and cold-rolled twice or more to obtain a plate-like fin material as a final product.

(5) -1 Casting Process The alloy of the present invention is characterized by being cast by a continuous casting and rolling method (CC method). When casting by CC method, the cooling rate (about 100-1000 degreeC / sec) at the time of casting is very large. Therefore, compared to a general semi-continuous casting method (DC method) (cooling rate of about 10 to 100 ° C./second), an Al—Fe (—Mn) system formed by added Si, Fe, and Mn and Al -Mn-Si (-Fe) intermetallic compounds are finely and densely dispersed. As a result, the dispersion strengthening is large and greatly contributes to the improvement of the room temperature strength after the brazing addition heat. In addition, since the intermetallic compound is finely and densely dispersed, Si, Fe, and Mn that are dissolved during casting are easily taken into the intermetallic compound. For this reason, the electrical conductivity is improved. Therefore, an aluminum alloy cast by the CC method is superior in strength and thermal conductivity than that cast by the DC method. In addition, since the intermetallic compound is finely dispersed in the CC method, there is little mold wear when corrugating the fin material, and there is an advantage that it is economical. In the present invention, the cooling rate during casting in the CC method is preferably 15 to 1000 ° C./second.

  In general, it is preferable to maintain the molten metal temperature at 680 to 800 ° C. in the casting of the CC method. The molten metal temperature is the temperature of the head box immediately before the hot water supply nozzle. If the molten metal temperature is less than 680 ° C., coarse crystals are easily formed during casting, and the plastic deformability of the material may be lowered. As a result, the plate may break during the subsequent cold rolling process. On the other hand, if the molten metal temperature exceeds 800 ° C., the molten metal does not solidify during casting, and a plate-shaped ingot may not be obtained.

(5) -2 Annealing process (high temperature annealing stage)
Next, the cast ingot is subjected to an annealing process. The annealing process includes a high temperature annealing stage and a low temperature annealing stage. The conditions for the high-temperature annealing stage are 450 to 560 ° C. and 1 to 10 hours. This high-temperature annealing process is performed in the pre-process of the below-mentioned low-temperature annealing stage. By this high temperature annealing process, the size and density of the intermetallic compound in the material and the solid solution amount of the additive element can be optimally adjusted.

  When the high-temperature annealing temperature is less than 450 ° C., the intermetallic compound dispersed in the material is finely and densely precipitated, so that the dispersion strengthening is increased. This is advantageous for increasing the room temperature strength after brazing heat, but strengthening with dispersed particles does not make a significant contribution in high-temperature environments, and solid solution in the material during brazing heat. To reduce the amount, it is disadvantageous to obtain high temperature strength. On the other hand, when the high-temperature annealing temperature exceeds 560 ° C., the intermetallic compound precipitates loosely. The high-temperature strength after brazing addition heat can be maintained high because it is difficult to incorporate solid solution elements and the amount of solid solution in the material is difficult to decrease, but the room temperature strength after brazing addition heat is lowered because dispersion strengthening is reduced. Therefore, high temperature annealing at 450 to 560 ° C. makes it possible to achieve both room temperature strength and high temperature strength after brazing addition heat. Moreover, the above effects are not sufficient when annealing is performed for less than 1 hour, and even if annealing is performed for more than 10 hours, the above effects are saturated and further improvement cannot be obtained, which is economically disadvantageous.

(5) -3 Annealing process (low temperature annealing stage)
One or more low-temperature annealing steps are provided immediately before the final cold rolling step described later. This low temperature annealing step is performed to soften the material and obtain the desired material strength in the final cold rolling step. The conditions for this low-temperature annealing are 200 to 450 ° C. and 1 to 10 hours. When the annealing temperature is less than 250 ° C., the material is not sufficiently softened, and it is difficult to adjust the strength in the final cold rolling. On the other hand, when annealing is performed at a temperature exceeding 450 ° C., the amount of heat input to the material during the manufacturing process is excessively increased, so that the intermetallic compound is coarsely and sparsely distributed and dispersion strengthening is reduced. As a result, the room temperature strength after brazing heat is reduced. Further, the above effect is not sufficient at an annealing temperature of less than 1 hour, and the above effect is saturated and further improvement cannot be obtained at an annealing time of more than 10 hours, which is economically disadvantageous.

(5) -4 Cold rolling step After the casting step, two or more cold rolling steps are provided. The cold rolling performed at the end of the manufacturing process is the final cold rolling stage, and one or more cold rolling stages are provided by then. The cold rolling step before the final cold rolling step is performed in order to obtain a desired final thickness in the final cold rolling step, and cold rolling may be performed according to a conventional method.

  The final cold rolling step is performed to obtain the desired strength before brazing heat. The rolling rate (final rolling rate) in the final cold rolling stage is 10 to 50%. When the rolling rate is less than 10%, the brazing material invades from the sub-crystal that has not been sufficiently recrystallized during the brazing addition heat, and erosion is strongly generated. Due to the occurrence of erosion, the strength of the fin material is reduced, so that the durability of the heat exchanger is lowered. On the other hand, when the final rolling ratio exceeds 50%, recrystallization occurs easily during brazing addition heat, and the recrystallized grains become very fine. When the recrystallized grains become finer, the wax enters from the grain boundaries. As a result, erosion is strongly generated in the fin. Due to the occurrence of this erosion, the core size of the heat exchanger changes, so that the durability decreases. In the present invention, generation of fin erosion due to incomplete recrystallization and generation of fin erosion due to fine recrystallization are collectively referred to as wax diffusion. The degree of wax diffusion is called wax diffusion.

(5) -5 Order of annealing step and cold rolling step In the method for producing an aluminum alloy fin material for a heat exchanger according to the present invention, annealing and cold rolling are each performed twice or more after the casting step. For example, (i) high temperature annealing stage → first cold rolling stage → low temperature annealing stage → final cold rolling stage may be used. Alternatively, (ii) first cold rolling stage → high temperature annealing stage → low temperature annealing. It is good also as a step-> last cold rolling process. Moreover, in said (i) and (ii), you may perform a low-temperature annealing step continuously twice or more. Furthermore, in the above (ii), the first cold rolling step may be provided again after the high temperature annealing step.

  Hereinafter, the present invention will be described in detail based on examples. A plate-shaped ingot having a thickness of 6 mm was obtained by a twin-roll continuous casting and rolling method using a molten metal having a temperature of 720 ° C. with the alloy composition shown in Table 1. The cooling rate in casting was 500 ° C./second. Next, the obtained ingot was subjected to a high temperature annealing process. Further, it was subjected to an initial cold rolling process with a plate thickness of 0.056 to 0.1 mm. Next, the cold-rolled sheet was subjected to a low-temperature annealing process and then subjected to a final cold-rolling process. Table 2 shows the conditions of the high temperature annealing step, the low temperature annealing step, and the final cold rolling step.

  The plate thickness of the final fin material sample thus obtained was all 0.05 mm. The present invention is not limited to the cast plate thickness and the final plate thickness of this embodiment. The cast plate thickness is generally about 2 to 10 mm, and the final plate thickness is generally about 0.03 to 0.20 mm in many cases.

  Further, in the evaluation of core durability described later, a material configuration in which a tube, a side support, a header, and a tank are assembled to a fin material is adopted, and as a material other than these fin materials, the core material of JIS3003 has a total thickness of 5 The clad material which clad JIS4045 brazing material in the ratio of% is used. The present invention is not limited to these material configurations and cladding materials. As an embodiment of the aluminum alloy fin material according to the present invention, a combination with all members used as a heat exchanger material is possible.

  With respect to the fin material obtained as described above, the following (a) and (b) were measured as characteristics before the heat of brazing. Moreover, the following (c)-(f) was measured as a fin characteristic after brazing addition heat (it does not use a brazing material). Furthermore, a mini-core or a heat exchanger core was produced as a characteristic after brazing addition heat (using brazing material), and brazing evaluation (g) to (j) was performed. The brazing heat application condition was set at 600 ° C. for 3 minutes, whether or not brazing material was used. The results are shown in Tables 3-5.

(A) Solidus temperature The solidus temperature is a standard for determining the superiority or inferiority of the brazing property of the fin material. If the solidus temperature is too low, fin melting and fin buckling occur during brazing heat. If it is 610 degreeC or more, it has sufficient solidus temperature.

(B) Measurement of density of intermetallic compound before heat of brazing addition The compound on the surface of the fin material sample is observed using a FE-SEM (Field Emission-Scanning Electron Microscopy), and a predetermined equivalent circle diameter is determined by image analysis. The density of the intermetallic compound having was measured. Specifically, 20 visual fields were observed at a magnification of 20000, and binarization was performed to calculate the density. As described above, an intermetallic compound having an equivalent circle diameter of less than 0.01 μm is too fine to be distinguished from noise, and was not counted when binarized. The ratios of d1 / d2 are also shown in Tables 3 to 5.

(C) Room temperature TS after brazing heat
The fin material sample after the brazing heat was formed into a JIS No. 13 B tensile test piece, and the TS at room temperature was measured with an AG-20kN tester manufactured by Shimadzu. The test was performed using three test pieces prepared from the same sample, and the arithmetic average value was defined as TS at room temperature. As described above, in order to ensure the durability of the heat exchanger, a higher room temperature TS is desirable. If it is 130 MPa or more, the durability of the heat exchanger can be sufficiently secured, so that it was accepted, and less than that was rejected.

(D) High temperature TS after brazing heat
Similarly to room temperature TS, a test piece was prepared and TS at 120 ° C. was measured. Further, similarly, an arithmetic average value was defined as TS at a high temperature (120 ° C.). As described above, in order to ensure the durability of the heat exchanger, a higher high temperature TS is desirable. If this is 90 MPa or more, the durability of the heat exchanger can be sufficiently secured, so that it was accepted, and less than that was rejected.

(E) Measurement of intermetallic compound density after brazing heat The d3 was measured in the same manner as the intermetallic compound density before brazing heat, and the density was calculated by binarization.

(F) Si solid solution amount after brazing addition heat The Si solid solution amount of the fin material after brazing addition heat was calculated. Specifically, ICP (Induced Coupled Plasma) was used to determine the Si content of the aluminum alloy, and then the total Si amount of the Si-based intermetallic compound was determined by a phenol dissolution method. And the amount of Si solid solution was computed by subtracting the latter from the former.

(G) Brazing diffusivity When the amount of brazing erosion to the fins is large, the fins buckle, and therefore the dimensions of the heat exchanger after brazing heat treatment are not as set and the durability is lowered. Therefore, wax diffusivity was evaluated as follows as an index of wax erosion to fins. As shown in FIG. 1, the fin material 2 produced as described above was corrugated into a width of 16 mm, a peak height of 5 mm, and a peak interval of 3 mm, and the core material of JIS3003 was coated with JIS4045 brazing material at a cladding ratio of 5%. The mini-core 1 was produced by assembling and brazing the tube material 3 made of a clad brazing sheet having a thickness of 0.5 mm. The produced mini-core 1 was brazed at 600 ° C. for 3 minutes using a non-corrosive flux amount of 5 g / m ² . The cross-section of the brazed mini-core was micro-observed with an optical microscope to observe the presence or absence of brazing erosion. Wax diffusivity was evaluated as “good” when wax erosion did not occur, and “X” when wax erosion occurred when wax erosion occurred. A specific example in the case of acceptance is shown in FIG. 4A, and a specific example in the case of failure is shown in FIG. 4B. In the figure, 2 and 3 are the same as in FIG. 1, and 10 indicates an erosion wax.

(H) Natural potential If the natural potential of the fin is noble, the sacrificial anode effect is small, and the corrosion resistance of the heat exchanger cannot be ensured. If the natural potential of the brazed fin material shown in FIG. 1 is −720 mV or less, the fin material has a sufficient sacrificial anode effect. In Table 3, the case where the natural potential was −720 mV or less was determined to be acceptable (◯), and the case where the natural potential was higher than −720 mV was determined to be unacceptable (×). The natural potential was measured by using Ag / AgCl (s) as a reference electrode and immersing only the fin portion brazed to the minicore in a 5% NaCl aqueous solution at 25 ° C. in the measurement solution.

(I) Fin residual strength after SWAAT In FIG. 1, a mini-core 1 was produced in which only the width of the fin material sample was changed to 20 mm. The produced mini-core 1 was brazed at 600 ° C. for 3 minutes using a non-corrosive flux amount of 5 g / m ² . The mini-core 1 brazed in this manner was subjected to 480 h SWAAT (artificial seawater spray test in accordance with ASTM G85-A). First, with respect to the mini-core 1 after SWAAT, a tensile test is performed in a state where the tube 3 is fixed and a tensile load is applied only to the fin 2, so that the tensile strength of the fin (tensile strength TS1 <MPa after 480 hours SWAAT) >) Was measured. On the other hand, for the mini-core 1 before SWAAT, the fin tensile strength (tensile strength TS0 <MPa> before SWAAT) was similarly measured. Then, TS1 / TS0 is assumed to be the fin residual strength after SWAAT, and if it is 0.40 or more, it is accepted as a fin having sufficient corrosion resistance, and if less than 0.40, it is assumed that the corrosion resistance is insufficient. It was rejected.

(J) Room temperature core durability and high temperature core durability As shown in FIGS. 2 and 3, corrugated fin material 2 was produced by corrugating a fin material sample into a width of 20 mm, a peak height of 5 mm, and a peak interval of 3 mm. Next, for the production of the tube material 3, header material 5, tank material 6 and side support material 7 as other members, a clad material obtained by clad JIS4045 brazing material with a clad rate of 5% on the core material of JIS3003 was used. The plate thickness of the tube material 3 was 0.2 mm, and the thickness of the header material 5, the tank material 6 and the side support material 7 was 1.0 mm. Each molded member is assembled as shown in FIGS. 2 and 3 and brazed at 600 ° C. for 3 minutes using a non-corrosive flux amount of 5 g / m ^{2 to} obtain a heat exchanger core 4 for durability evaluation. . 2 indicates a refrigerant supply port, and 9 indicates a refrigerant discharge port.

The evaluation of the core durability was performed by a repeated pressure durability test in which the inside of the tube was filled with water and the pressurized state where the maximum water pressure applied to the tube at a frequency of 1 Hz was 100 kPa and the non-pressurized state were repeated. The core durability at room temperature was 25 ° C in the test atmosphere, and the core durability at high temperature was 120 ° C in the test atmosphere. If neither the buckling of the fin nor the breaking of the fin occurs after repeating the pressurized state and the non-pressurized state 10 ⁵ times each, it is judged that the core has sufficient practical durability. (○), and the others were rejected (×).

  In Examples 1 to 43 of the present invention in Tables 3 and 4, the solidus temperature before brazing heat is sufficiently high so that the brazing property is good and the room temperature strength after brazing heat is sufficiently high. The room temperature core durability was sufficiently ensured, and the high temperature core durability was sufficiently ensured because the high temperature strength after brazing heat was sufficiently high. In addition, the density of the intermetallic compound after the brazing heat is within an appropriate range, the final rolling rate is set appropriately, the brazing diffusivity is passed, and the natural potential is set appropriately, which is sacrificed. Excellent anodic effect and excellent corrosion resistance due to high residual fin strength after SWAAT.

  On the other hand, as shown in Table 5, in Comparative Example 44, since the high temperature annealing temperature was too low, the density of the intermetallic compound having an equivalent circle diameter of 0.15 to 5.00 μm before brazing heating was high. As a result, too much solid solution element was taken in, so the amount of solid solution Si decreased, and the high temperature TS decreased after heat of brazing. Moreover, the core durability at high temperature after the brazing heat was also rejected.

  In Comparative Example 45, since the high-temperature annealing temperature was too high, the density of the intermetallic compound having a circle-equivalent diameter of 0.01 to 5.00 μm after the brazing addition heat was lowered and the dispersion strengthening was lowered. Room temperature TS decreased. Moreover, the core durability at room temperature after the brazing heat was also rejected.

  In Comparative Example 46, the high-temperature annealing time was too short, and the density of the intermetallic compound having an equivalent circle diameter of 0.15 to 5.00 μm before brazing heating was too high. As a result, since a large amount of solid solution element was taken in, the amount of solid solution Si decreased, and the high temperature TS decreased after the additional heat. Moreover, the core durability at high temperature after brazing addition heat was disqualified.

  In Comparative Example 47, there was a portion where the low-temperature annealing temperature was too low and the material was not sufficiently softened. Since the gap between the fins after the corrugation molding became uneven and the load from the core was too large at the part where the gap was long, the core durability at room temperature and high temperature after the brazing heat was rejected.

  In Comparative Example 48, the low-temperature annealing temperature was too high, and the heat input to the material was too much. Since the density of the intermetallic compound having an equivalent circle diameter of 0.01 to 5.00 μm after the brazing heat was reduced and the dispersion strengthening was lowered, the room temperature TS was lowered after the brazing heat. Moreover, the core durability at room temperature after brazing addition heat was unacceptable.

  In Comparative Example 49, there was a portion where the low-temperature annealing time was too short and the material was not sufficiently softened. The fins after corrugated molding had uneven crest intervals, and the load from the core was too large at the crest portions, so that the core durability at room temperature and high temperature after brazing addition heat was rejected.

  In Comparative Example 50, the final rolling rate was too low, and erosion due to non-recrystallization occurred during brazing addition heat, so that the resistance to brazing diffusion was poor. Moreover, since the core dimensions were not accurately maintained due to erosion, the core durability at room temperature and high temperature after brazing addition heat was rejected.

  In Comparative Example 51, since the final rolling rate was too high, erosion caused by fine recrystallized grains occurred during brazing addition heat, and the brazing resistance to brazing was insufficient. Further, due to erosion, the core durability at room temperature and high temperature after brazing addition heat was rejected.

  In Comparative Example 52, the Si content of the fin material was small, and the intermetallic compound density of d1 and d3 was reduced. Moreover, d1 / d2 decreased due to the decrease in d1, and the amount of Si solid solution after the brazing addition heat also decreased. As a result, room temperature TS and high temperature TS after brazing addition heat decreased. Moreover, the core durability at room temperature and high temperature after brazing addition heat was unacceptable.

  In Comparative Example 53, since the Si content was too high, the solidus temperature was greatly reduced, and fin melting occurred during brazing addition heat. Moreover, since the core dimensions were not accurately maintained, the core durability at room temperature and high temperature after brazing heat was insufficient.

  In Comparative Example 54, since the Fe content was too small, the density of the intermetallic compound having an equivalent circle diameter of 0.01 to 5.00 μm after the brazing addition heat was lowered, and the room temperature TS was lowered after the brazing heat. Moreover, the core durability at room temperature was insufficient.

  In Comparative Example 55, since the Fe content was too large, a coarse crystallized product was generated at the time of casting, and a plate breakage occurred in the subsequent rolling process, and evaluation could not be performed.

  In Comparative Example 56, since the Mn content was too small, the density of the intermetallic compound having an equivalent circle diameter of 0.01 to 5.00 μm after the brazing addition heat was lowered, and the room temperature TS was lowered after the brazing addition heat. Moreover, the core durability at room temperature was insufficient.

  In Comparative Example 57, since the Mn content was too large, a coarse crystallized product was generated at the time of casting, and a plate breakage occurred in the subsequent rolling process, and evaluation could not be performed.

  In Comparative Example 58, since the Zn content was too small, the natural potential became noble, and a sufficient potential difference from the tube material could not be secured. The sacrificial anticorrosion does not work sufficiently, the amount of corrosion of the tube increases, and the core does not have sufficient corrosion resistance.

  In Comparative Example 59, since the Zn content was too high, the corrosion rate increased and the corrosion weight loss was large, so that the self-corrosion resistance was inferior. Therefore, TS1 / TS0 after SWAAT could not satisfy 0.40 or more.

  In addition, Table 6 shows which comparative examples 44 to 59 correspond to which comparative example.

  The aluminum alloy fin material for a heat exchanger according to the present invention has excellent characteristics such as room temperature strength, high temperature strength and corrosion resistance after brazing heat in addition to general characteristics such as thermal conductivity.

DESCRIPTION OF SYMBOLS 1 ... Minicore 2 ... Fin material, Fin 3 ... Tube material, tube 4 ... Heat exchanger core 5 ... Header material, header 6 ... Tank material, tank 7 ... Side support Material, side support 8 ... Refrigerant supply port 9 ... Refrigerant discharge port 10 ... Erosion wax

Claims (4)

Si: 0.7 to 1.5 mass%, Fe: 0.4 to 1.2 mass%, Mn: 0.5 to 1.8 mass%, Zn: 0.5 to 3.0 mass%, the balance Al and The density of the intermetallic compound (d1) having an equivalent circle diameter of 0.01 μm or more and less than 0.15 μm, which is unavoidable, is 5.0 × 10 ⁴ pieces / mm ² or more before brazing heat, The intermetallic compound density (d2) having an equivalent circle diameter of 15 to 5.00 μm is 5.0 × 10 ^{4 to} 3.0 × 10 ⁷ pieces / mm ² , and d1 / d2 is 0.30 or more, After brazing heat, the intermetallic compound density (d3) having an equivalent circle diameter of 0.01 to 5.00 μm is 5.0 × 10 ⁴ pieces / mm ² or more, and the Si solid solution amount is 0.30. Room temperature strength after brazing heat, high temperature, characterized by 0.80 mass% Heat exchanger use aluminum alloy fin material excellent in degrees and corrosion resistance.   After brazing heat, the tensile strength at room temperature is 130 MPa or more, the tensile strength at 120 ° C. is 90 MPa or more, the tensile strength after SWAAT for 480 hours is TS1 (MPa), and the tensile strength before SWAAT is TS0 ( The aluminum alloy fin material for heat exchangers having excellent room temperature strength, high temperature strength and corrosion resistance after brazing addition heat according to claim 1, wherein TS1 / TS0 is 0.40 or more.   It is a manufacturing method of the aluminum alloy fin material for heat exchangers which is excellent in the room temperature strength after a brazing addition heat of Claim 1 or 2, high temperature strength, and corrosion resistance, Comprising: Si: 0.7-1.5mass%, Fe: 0 A casting process for casting a molten aluminum alloy containing 4 to 1.2 mass%, Mn: 0.5 to 1.8 mass%, Zn: 0.5 to 3.0 mass%, and the balance Al and inevitable impurities; An annealing process for annealing the ingot, and a cold rolling process including a final cold rolling stage, the casting process is a continuous casting and rolling process for continuously casting and rolling a molten aluminum alloy, and the annealing process includes: A high-temperature annealing stage in which the rolled sheet is heat-treated at 450 to 560 ° C. for 1 to 10 hours, and the rolled sheet is heat-treated at 200 to 450 ° C. for 1 to 10 hours, and one or more low-temperature annealing stages immediately before the final cold rolling stage. When The cold rolling step further includes at least one cold rolling step in the previous step of the final cold rolling step, and the rolling rate in the final cold rolling step is 10 to 50%. The manufacturing method of the aluminum alloy fin material for heat exchangers which is excellent in room temperature strength, high temperature strength, and corrosion resistance after heat addition.   Cold rolling of the continuous ingot rolling process, the high temperature annealing stage for high temperature annealing of the rolled ingot, and the cold rolling stage as a pre-process of the final cold rolling stage, and cold rolling the high temperature annealed ingot. The brazing additional heat according to claim 3, comprising the cold rolling step, the low temperature annealing step for low-temperature annealing the cold rolled plate, and the final cold rolling step for cold rolling the low-temperature annealed rolled plate. The manufacturing method of the aluminum alloy fin material for heat exchangers which is excellent in later room temperature strength, high temperature strength, and corrosion resistance.

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