JP2019131858A - Aluminum alloy fin material for heat exchanger excellent in strength, conductivity, corrosion resistance, and brazability, and heat exchanger - Google Patents

Abstract

To provide an aluminum alloy fin material for heat exchanger excellent in strength, conductivity, corrosion resistance, and brazability without brazing defect due to fin deformation during brazing, and a heat exchanger.SOLUTION: An aluminum alloy fin material for heat exchanger consists of an aluminum alloy having a composition containing Mn:1.2 to 2.0%, Si:0.5 to 1.3%, Cu:0.001 to less than 0.05%, Fe:0.1 to 0.5%, Zn:0.5 to 2.5% and the balance Al with inevitable impurities, and having tensile strength of 140 MPa or more, 0.2% bearing force of 50 MPa or more, conductivity of 42%IACS or more, electrical potential of -800 mV to -710 mV, and corrosion weight loss after 16 weeks in a neutral saline spraying test of 120 mg/dmor less at an ordinary temperature after brazing heating.SELECTED DRAWING: None

Description

  The present invention relates to an aluminum alloy fin material for a heat exchanger and a heat exchanger that are excellent in strength, conductivity, corrosion resistance, and brazing properties.

  Aluminum alloy fin materials for automotive heat exchangers are required to have high thermal conductivity and corrosion resistance in addition to the strength to withstand repeated vibrations when mounted on a vehicle. Furthermore, there is a demand for brazing that does not cause poor bonding due to the buckling of the fin material during brazing. Therefore, research on fin materials for heat exchangers that are excellent in strength, electrical conductivity, corrosion resistance, and brazing is underway.

  For example, in Patent Document 1, even in a composition having an Fe content of 0.5% or more, Si: 0.005% by mass is intended to realize low brazing and sag resistance at low cost. 6 to 1.6%, Fe: 0.5 to 1.2%, Mn: 1.2 to 2.6%, Zn: 0.4 to 3.0%, Cu: less than 0.2%, The balance is inevitable impurities and Al, Mg as impurities is limited to less than 0.05%, the tensile strength before brazing heating is 160 to 260 MPa, the tensile strength before brazing heating and 0.2% proof stress A fin material characterized by a difference of 10 to 50 MPa has been proposed.

  In Patent Document 2, Si: 0.5 to 1.5 mass%, Fe: more than 1.0 mass percent to 2.0 mass% or less, Mn: 0.4 to 1.0 mass%, Zn: 0.4 -1.0% by mass, the balance being Al and inevitable impurities, defining the size and distribution density of the second layer particles as a metal structure before brazing addition heat, and the tensile strength before brazing addition heat There has been proposed an aluminum alloy fin material for a heat exchanger that has excellent tensile strength after heat addition, corrugated formability that defines the plate thickness of the fin material, and strength after heat addition to brazing.

  Patent Document 3 includes Si: 0.7 to 1.4 wt%, Fe: 0.5 to 1.4 wt%, Mn: 0.7 to 1.4 wt%, Zn: 0.5 to 2.5 wt% Further, Mg as an impurity is limited to 0.05 wt% or less, and the balance is inevitable impurities and Al, and the tensile strength and proof strength after brazing, the recrystallized grain size after brazing, and after brazing An aluminum alloy fin material for heat exchangers having high electrical conductivity, excellent heat transfer characteristics, erosion resistance, sag resistance, sacrificial anode effect and self-corrosion resistance has been proposed.

  In Patent Document 4, as an aluminum alloy fin material for a heat exchanger that is excellent in strength, conductivity, and brazing, it is expressed by mass%, Mn: 1.2 to 2.0%, Cu: 0.05 to 0.20%, From an aluminum alloy containing Si: 0.5 to 1.30%, Fe: 0.05 to 0.5%, Zn: 1.0 to 3.0%, and the balance of Al and inevitable impurities A fin material having a tensile strength of 140 MPa or more, a proof stress of 50 MPa or more, an electrical conductivity of 42% IACS or more, an average crystal grain size of 150 μm or more and less than 700 μm, and a potential of −800 mV or more and −720 mV or less after brazing heat. Is described.

Japanese Patent Laying-Open No. 2015-218343 Japanese Patent Laying-Open No. 2015-14034 JP 2012-212393 A Japanese Patent Laying-Open No. 2006-121393

  However, if the brazing time is further shortened in order to improve productivity, the shape of Al-Si brazing is difficult to reach the entire heat exchanger and the fins undergo deformation due to thermal expansion from other members. The ratio of poor bonding between the fin and each member increases due to the fact that it cannot be maintained. In addition, in order to obtain the required rigidity even when the heat exchanger is reduced in weight, the strength of the fin material after brazing is necessary. Self-corrosion resistance is also required so that there is no gap or dropout.

  The present invention has been made against the background of the above problems, and an object thereof is to provide an aluminum alloy fin material for a heat exchanger and a heat exchanger that are excellent in strength, conductivity, corrosion resistance, and brazing.

In the present invention, by paying attention to the alloy composition and the temperature and strength in the softening process during brazing, it is possible to obtain a fin with less brazing and higher brazing properties than in the past.
That is, among the aluminum alloy fin materials for heat exchangers excellent in strength, conductivity, corrosion resistance, and brazing properties of the present invention, the first form is mass%, Mn: 1.2 to 2.0%, Si : 0.5 to 1.3%, Cu: 0.001 to less than 0.05%, Fe: 0.1 to 0.5%, Zn: 0.5 to 2.5%, the balance being Al And an aluminum alloy having a composition consisting of inevitable impurities,
After brazing heat, at normal temperature, tensile strength is 140 MPa or more, 0.2% proof stress is 50 MPa or more, conductivity is 42% IACS or more, potential is −800 mV or more and −710 mV or less, neutral salt spray test for 16 weeks The subsequent weight loss by corrosion is 120 mg / dm ² or less.

  The invention of the aluminum alloy fin material for heat exchangers having excellent strength, electrical conductivity, corrosion resistance, and brazing properties in another form is the above-described form. In the above form, the aluminum alloy further contains, in mass%, Ti: 0.01-0. 20%, Cr: 0.01 to 0.20%, Mg: 0.01 to 0.20%, Zr: 0.01 to 0.20%, containing one or more. Features.

  In another aspect of the invention of the aluminum alloy fin material for heat exchangers excellent in strength, conductivity, corrosion resistance, and brazing property, the aluminum alloy has a relational expression (i) ... 2.1 ≦ [Mn content Amount (mass%)] + [Si content (mass%)] + 7.5 * [Cu content (mass%)] ≦ 3.4 and relational expression (ii) ... [Zn content (mass%) )]-18.8 * [Cu content (% by mass)] ≧ 0.2.

  The invention of the aluminum alloy fin material for heat exchangers having excellent strength, conductivity, corrosion resistance, and brazing properties in another form is that the average crystal grain size after brazing addition heat is 100 μm or more and 2000 μm or less in the above form. Features.

  The invention of the aluminum alloy fin material for heat exchangers excellent in the strength, conductivity, corrosion resistance, and brazing properties of other forms is the above-mentioned form, in which the 0.2% proof stress is 15 to 15 at each temperature in the range of 400 to 550 ° C. It is within the range of 40 MPa.

The invention of the aluminum alloy fin material for heat exchangers having excellent strength, conductivity, corrosion resistance, and brazing properties in other forms is the above-described form. The number density of Al—Mn, Al—Mn—Si, and Al—Fe—Si second phase particles is 1.0 × 10 ⁵ particles / mm ² or more, and the crystal structure is a fibrous metal structure It is characterized by being.

The invention of the aluminum alloy fin material for heat exchangers having excellent strength, conductivity, corrosion resistance, and brazing properties in another form is the Al-Fe having an equivalent circle diameter of 1.0 μm or more after the brazing addition heat in the above form. Al-Mn-based, Al-Mn-Si-based, and Al-Fe- having a number density of the crystallization system of 1.0 × 10 ⁴ pieces / mm ² or less and an equivalent circle diameter of 0.01 to 0.10 μm. Si-type second phase particles are 1.0 × 10 ⁴ particles / mm ² or more, and Al—Cu-based second phase particles having an equivalent circle diameter of 0.05 μm or more are 1.0 × 10 ³ particles / mm ² or less. It exists in.

  Another aspect of the invention of the aluminum alloy fin material for heat exchangers excellent in strength, conductivity, corrosion resistance, and brazing property is characterized in that the plate thickness is 100 μm or less.

The invention of the aluminum alloy fin material for heat exchangers having excellent strength, conductivity, corrosion resistance, and brazing properties in another form is characterized in that, in the form, the corrosion current density is 0.05 mA / cm ² or less. .

  The invention of the aluminum alloy fin material for heat exchangers having excellent strength, electrical conductivity, corrosion resistance, and brazing properties in another form is the above-described form, in which the tensile strength at room temperature is 250 MPa or less and 0 .2% proof stress is 230 MPa or less.

  The invention of the aluminum alloy fin material for heat exchangers having excellent strength, conductivity, corrosion resistance, and brazing properties in another form is characterized in that, in the above form, the recrystallization completion temperature is 450 ° C. or less before brazing. And

  Among the heat exchangers of the present invention, the first mode is characterized by including the aluminum alloy fin material for heat exchangers of the present invention.

  Hereinafter, the reasons for limitation of the chemical composition and mechanical properties in the present invention will be described. In addition, all chemical composition is the mass%.

・ Mn: 1.2-2.0%
Mn is added to precipitate Al—Mn—Si intermetallic compounds and obtain strength after brazing by dispersion strengthening. If Mn is less than 1.2%, the effect of dispersion strengthening by the Al—Mn—Si compound is small, and the desired strength after brazing cannot be obtained. Moreover, when Mn is added exceeding 2.0%, there is a concern that an Al—Mn-based giant intermetallic compound is crystallized at the time of casting the ingot and breaks during rolling. Further, the solid solubility in the matrix increases, the solidus temperature (melting point) decreases, and the fins may melt during brazing, which is not preferable. For this reason, content of Mn is made into the said range.
For the same reason, it is preferable that the lower limit of the Mn content is 1.4% and the upper limit is 1.8%.

・ Si: 0.5 to 1.3%
Si is added to precipitate an Al—Mn—Si intermetallic compound and obtain strength after brazing by dispersion strengthening. If Si addition is less than 0.5%, the effect of dispersion strengthening by the Al—Mn—Si compound is small, and the desired strength after brazing cannot be obtained. If Si is added in excess of 1.3%, the solid solubility in the matrix increases, the solidus temperature (melting point) decreases, and the fins may melt during brazing, which is not preferable. . For this reason, content of Si is made into the said range.
For the same reason, it is desirable that the lower limit of Si content is 0.7% and the upper limit is 1.2%.

Cu: 0.001 to less than 0.05% Cu is present as a solid solution in an Al matrix or by generating an Al-Cu compound. If Cu is less than 0.001%, the contribution to the strength after brazing by solid solution strengthening is small. On the other hand, if Cu is 0.05% or more, a θ-CuAl ₂ stable phase or θ′-CuAl ₂ metastable phase having a higher potential than the matrix is present as a compound, which becomes a starting point of corrosion and lowers corrosion resistance. . For this reason, content of Cu is made into the said range.
For the same reason, it is desirable that the lower limit of the Cu content is 0.003% and the upper limit is 0.045%.

・ Fe: 0.1-0.5%
Fe is added to obtain Al-Fe-based and Al-Fe-Si-based intermetallic compounds for crystallization and precipitation, and to obtain strength after brazing by dispersion strengthening. If Fe is less than 0.1%, the effect is small, and the desired strength after brazing cannot be obtained. Moreover, since it is limited to the use of high-purity bullion, it is not preferable because it increases costs. On the other hand, if the Fe content exceeds 0.5%, an Al—Fe-based or Al—Fe—Si-based compound acts as a starting point of corrosion and corrosion resistance is lowered, which is not preferable. For this reason, content of Fe is made into the said range.
For the same reason, it is desirable that the lower limit of the Fe content is 0.15% and the upper limit is 0.4%.

Zn: 0.5-2.5%
Zn has the effect of dissolving in the Al matrix and lowering the potential, and is added to obtain the sacrificial anode effect of the fins. However, if it is less than 0.5%, the action of lowering the potential is small, the desired sacrificial anode effect cannot be obtained, and the erosion depth of the combined tube becomes large. On the other hand, if it exceeds 2.5%, the potential becomes excessively low and the self-corrosion resistance of the fin is lowered, which is not preferable. For this reason, content of Zn is made into the said range.
For the same reason, it is desirable that the lower limit of Zn content is 0.7% and the upper limit is 2.2%.

-Ti: 0.01-0.20%, Cr: 0.01-0.20%, Mg: 0.01-0.20%, Zr: One of 0.01-0.20% or Two or more types Ti, Cr, Mg, Zr forms an intermetallic compound with aluminum, and improves the strength by dispersion strengthening and solid solution strengthening. However, when each content is less than the lower limit, the influence on dispersion strengthening and solid solution strengthening is small, and the effect of improving the strength is small. If Ti, Cr, and Zr exceed their respective upper limits, a huge intermetallic compound may crystallize during casting of the ingot, and there is a concern that fracture may occur during rolling. On the other hand, when Mg exceeds the upper limit, the brazing property is lowered. Therefore, it is desirable that the content of each element is in the above range.
For the same reason, Ti, Cr, Mg, and Zr are more preferably set to a lower limit of 0.03% and an upper limit of 0.15%.

-Tensile strength at normal temperature after brazing heat: 140 MPa or more In accordance with the demand for weight reduction of heat exchangers, thin and high strength materials are also required for fin materials. If the strength of the fin after brazing is low, repeated vibrations applied to the heat exchanger when mounted on the vehicle and expansion and compression of the cooling water cannot be suppressed, and the tube expands like a drum and breaks early. It leads to leakage of internal cooling water. For this reason, when the thickness of the fin is 100 μm or less, it is desirable to have a tensile strength of 140 MPa or more.

-Normal temperature 0.2% proof stress after brazing heat: 50 MPa or more 0.2% proof stress indicates the elastic limit of the fin, and if the proof strength after brazing is low, the fin may break due to repeated vibration when mounted on the car. Even if not reached, plastic deformation occurs and the original shape cannot be retained, and the heat exchanger core is deformed. Even if the plate thickness of the fin is 100 μm or less, if the yield strength after brazing is 50 MPa or more, the above deformation can be prevented. Therefore, the 0.2% yield strength after brazing addition heat is desirably 50 MPa or more. .

-Conductivity after brazing heat addition: 42% IACS or more In order to ensure thermal conductivity when used as a heat exchanger, it is desirable that the conductivity after brazing is 42% IACS or more.

-Potential after brazing heat: -800 mV to -710 mV (vs Ag / AgCl)
When the potential of the fin is less than −800 mV, the potential of the fin is excessively low (low) with respect to the other members to be joined. Therefore, corrosion of the fin is accelerated by galvanic corrosion. When the potential of the fin exceeds -710 mV, a sufficient potential difference cannot be obtained for other members to be joined, and the sacrificial anode effect cannot be obtained. In this case, for example, corrosion of the tube is accelerated. More preferably, it is −720 mV or less.
For this reason, it is desirable that the potential of the fin material is within the above range.

・ Corrosion weight loss after 16 weeks in neutral salt spray test after brazing heat: 120 mg / dm ² or less It is desirable that the measured weight loss after 16 weeks of the fin material is 120 mg / dm ² or less. If the corrosion weight loss after 16 weeks is 120 mg / dm ² or less, performance deterioration and partial dropout due to corrosion of the fin itself can be suppressed even in the actual use environment, so the characteristics as a heat exchanger are maintained. be able to.

-Relational expression (i)
2.1 ≦ [Mn content (mass%)] + [Si content (mass%)] + 7.5 * [Cu content (mass%)] ≦ 3.4
-Relational expression (ii)
[Zn content (mass%)]-18.8 * [Cu content (mass%)] ≧ 0.2
By satisfying the above relational expressions (i) and (ii), an aluminum alloy fin material for a heat exchanger that is excellent in strength, conductivity, and corrosion resistance can be obtained.
Relational expression (i) represents the material strength of the fin material in relation to the amount of Mn and Si relative to the amount of Cu. When the result of the relational expression (i) is less than 2.1, the 0.2% yield strength at a high temperature during brazing, the tensile strength at room temperature and the 0.2% yield strength are low, and the fin joint ratio tends to decrease. It was in. If the result of the relational expression (i) exceeds 3.4, the tensile strength before brazing and the 0.2% proof stress are high, and it is difficult to form the fin, the solidus temperature is low, and the corrosion There were many fins with many weight loss.
The relational expression (ii) is an expression representing a potential in relation to the amount of Zn with respect to the amount of Cu. Cu is an element that makes the electric potential of aluminum noble, and Zn is an element that makes the electric potential base, and each contributes greatly to the electric potential. By controlling the ratio, the potential can be adjusted to the target range, but it has been found that the relationship is not linear but needs to satisfy the above relational expression.
When the result of the relational expression (ii) is 0.2 or more, it has a necessary and sufficient potential difference with respect to the tube, and a desired sacrificial anode effect can be obtained.

-Average crystal grain size after brazing heat: 100 μm or more and less than 2000 μm If the average crystal grain size after brazing is as fine as less than 100 μm, braze erosion (erosion) is likely to occur along the crystal grain boundary, resulting in buckling of the fins. It tends to occur. On the other hand, when the grain size after brazing is coarse and is 2000 μm or more, the strength of the fin is lowered as represented by the Hall-Petch rule (relational expression that the crystal grain size affects the proof stress value). In particular, in the case of thin fins, it is necessary to control the crystal grain size in consideration of brazability and high strength.
For this reason, it is desirable that the crystal grain size after brazing heat is in the above range.

-0.2% yield strength at 400-550 ° C: 15-40 MPa
When the 0.2% proof stress value at a high temperature of 400 to 550 ° C. during brazing addition heat is 15 MPa or more, the fin has a shape after molding even with respect to stress generated due to thermal expansion of other members during brazing. Since it can maintain, the deformation | transformation of the fin material during brazing can be prevented. On the other hand, when it has a 0.2% proof stress exceeding 40 MPa in the range of 400 to 550 ° C., the strength is greatly reduced in the process of recovery and recrystallization during brazing and tempering of the O material. As a result of the verification, it was found that the amount of deformation with respect to the above was large, and a gap was formed between the tube and the fin, which was likely to lead to poor bonding. For this reason, it is desirable that the 0.2% proof stress at 400 to 550 ° C. be within the above range.

・ Before heat addition
-Number density of Al-Mn-based, Al-Mn-Si-based, Al-Fe-Si-based second phase particles having an equivalent circle diameter of 0.01 to 0.10 μm: 1.0 × 10 ⁵ particles / mm ² -Metal structure: Fibrous crystal grain structure The dispersion state and metal structure of the intermetallic compound before brazing have a major effect on the recrystallization behavior during brazing. The fine second-phase particles of 0.01 to 0.10 μm prevent the formation of dislocation cells accompanying recovery at the initial stage of brazing, and the recrystallization temperature is relatively low due to the effect of preventing the movement of subgrain boundaries. Therefore, it has an effect of contributing to the coarsening of the crystal grain size. Further, the rolling ratio before brazing is high and plastic strain is accumulated, and the metal structure is a fibrous crystal structure (in the present invention, the average aspect ratio of crystal grains within the observation field of view is 7.0 or more. Recrystallized at a low temperature during brazing. In the present invention, the balance between the effect of lowering the recrystallization temperature with a fibrous crystal grain structure and the distribution state of the second phase particles of 0.01 to 0.10 μm allows the recrystallization temperature and material during brazing heat to be added. Strength is controlled.

・ After brazing heat addition, 1.0 × 10 ⁴ Al-Mn, Al—Mn—Si, and Al—Fe—Si second phase particles having an equivalent circle diameter of 0.01 to 0.10 μm / mm ² or more The state of the intermetallic compound after the brazing addition heat affects the material strength of the fin contributing as dispersion strengthening. In a structure in which Al-Mn, Al-Mn-Si, and Al-Fe-Si second phase particles are present at 1.0 × 10 ⁴ particles / mm ² or more, high material strength is obtained after brazing. Can do.

-After brazing, the number density of Al-Fe-based crystallized crystals having an equivalent circle diameter of 1.0 μm or more is 1.0 × 10 ⁴ pieces / mm ² or less, and the Al—Cu-based crystal is 0.05 μm or more. The second phase particles are 1.0 × 10 ³ particles / mm ² or less. The Al—Fe-based crystallized substance and the Al—Cu-based second phase particles have a higher potential than the matrix and act as a starting point for corrosion. , Causing the self-corrosion resistance of the fins to decrease. For this reason, the content of Al-Fe-based crystallized substances of 1.0 μm or more is 1.0 × 10 ⁴ particles / mm ² or less, and the content of Al—Cu-based second phase particles of 0.05 μm or more is 1.0 × It is desirable to control to 10 ³ pieces / mm ² or less.

Plate thickness: 100 μm or less In order to achieve a reduction in the weight of the heat exchanger core, the plate thickness of the fins is desirably 100 μm or less, and the effect of improving the strength becomes remarkable. The lower limit is preferably 30 μm.

- Corrosion current density: 0.05 mA / cm ² or less corrosion current density, larger the corrosion rate exceeds 0.05 mA / cm ^2, the corrosion current density is 0.05 mA / cm ² or less, the corrosion rate of the fin Is small and has excellent self-corrosion resistance. For this reason, it is desirable that the corrosion current density is 0.05 mA / cm ² or less.

・ Before brazing heat, normal temperature tensile strength: 250 MPa or less, normal temperature 0.2% proof stress: 230 MPa or less Fins are coiled or molded into multiple shapes, for example, corrugated The The formed fin material is brazed in combination with other members for the heat exchanger. At this time, if the tensile strength at room temperature is 250 MPa or more and the 0.2% proof stress is 230 MPa or more before the brazing heat, bending deformation is not easy and it is difficult to obtain a fin having a correct shape.

-The higher the solidus temperature of the fin material, the easier it is to braze. In the case of a normal brazing method, if the temperature is 615 ° C. or higher, brazing can be performed without melting the fins.

・ Recrystallization is completed at 450 ° C or less during brazing addition heat Defines the distribution of intermetallic compounds before brazing and makes the metal structure a fibrous crystalline structure, so that the fin during brazing addition heat is 450 ° C or less Can be softened. Under the condition that the fin is recrystallized at 450 ° C. or lower, the 0.2% proof stress can be in the range of 15 to 40 MPa at each temperature of 400 to 550 ° C., so that the bonding failure at the time of brazing can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the aluminum alloy fin material for heat exchangers and heat exchangers which have few joining defects compared with the past, and have high brazing property.

It is a perspective view which shows a part of heat exchanger in one Embodiment of this invention. Example No. 22, 33 and Comparative Example No. 19 is a drawing-substituting photograph showing micrographs in FIGS. It is a graph which shows the component distribution relevant to the relational expression (i) in an Example and a comparative example. It is a graph which shows the component distribution relevant to relational expression (ii) in an Example and a comparative example.

Hereinafter, an embodiment of the present invention will be described.
First, the manufacturing method of an aluminum alloy fin material is demonstrated.
The aluminum alloy fin material may be manufactured, for example, by semi-continuous casting (DC method) of molten metal and homogenizing, hot rolling, or cold rolling of the ingot, or continuous casting rolling of a twin roll casting machine or the like. It can also be manufactured by casting using (CC method) and homogenizing and cold rolling the cast plate.
In mass%, Mn: 1.2 to 2.0%, Si: 0.5 to 1.3%, Cu: 0.001 to less than 0.05%, Fe: 0.1 to 0.5%, Zn : 0.5 to 2.5%, if desired, further, by mass, Ti: 0.01 to 0.20%, Cr: 0.01 to 0.20%, Mg: 0.01 to A molten aluminum alloy containing one or more of 0.20% and Zr: 0.01 to 0.20% is manufactured, and a DC (Direct Hill Casting) method and a CC (Continuous Casting) method. An aluminum alloy ingot or cast plate is obtained by a conventional method such as the above.
In addition, in the component composition, regarding the contents of Cu, Mn, Si, Zn,
Relational expression (i): 2.1 ≦ [Mn content (mass%)] + [Si content (mass%)] + 7.5 * [Cu content (mass%)] ≦ 3.4 and relation It is desirable that the formula (ii) ... [Zn content (% by mass)]-18.8 * [Cu content (% by mass)] ≧ 0.2.

  It is necessary to homogenize the obtained aluminum alloy ingot or cast plate under appropriate conditions. The homogenization treatment is performed, for example, under heat treatment conditions of a temperature rising rate of 25 to 75 ° C./hour, a holding temperature of 350 to 480 ° C., a holding time of 1 to 10 hours, and a cooling rate of 20 to 50 ° C./hour. By setting the composition range of Mn, Si, and Cu shown in the relational expression (i) and performing the homogenization treatment within this range, both dispersion strengthening and solid solution strengthening are balanced, and before brazing, during brazing, and The desired fin strength can be obtained after brazing.

Thereafter, the obtained aluminum alloy is subjected to hot rolling and cold rolling in the DC method, and cold rolling in the CC method. When performing hot rolling by the DC method, it is necessary to carry out at a temperature equal to or lower than the temperature of the homogenization treatment to maintain a balance between dispersion strengthening and solid solution strengthening. In the middle of cold rolling, intermediate annealing is performed after the rolling rate reaches 60% or more. Intermediate annealing is performed at a temperature of 200 to 300 ° C. and a holding time of 6 hours, and after intermediate annealing, cold rolling is performed at a rolling rate of 10 to 25%, so that the fiber has a crystalline structure before brazing addition heat. Then, an aluminum alloy fin material having a desired thickness is obtained. In addition, as for plate | board thickness, it is desirable to set it as 30-100 micrometers.
The fin material for heat exchangers can be obtained by the above process.

The obtained fin material is excellent in strength, conductivity, corrosion resistance, and brazing property, and is suitable as a fin material for heat exchangers.
In particular, the fin material has a 0.2% proof stress within the range of 15 to 40 MPa at each temperature of 400 to 550 ° C. during the softening process during brazing. Since the fin material can maintain the shape after the molding against the stress generated with the expansion, the deformation during brazing can be prevented.
Further, when subjected to brazing heat, the fin material after brazing heat has a tensile strength of 140 MPa or more, a 0.2% proof stress of 50 MPa or more, a conductivity of 42% IACS or more, and a potential of − 800 mV to −710 mV, corrosion weight loss after 16 weeks in neutral salt spray test is 120 mg / dm ² or less, corrosion current density is 0.05 mA / cm ² or less, average grain size after brazing heat is 100 μm to 2000 μm The strength, conductivity, and corrosion resistance are excellent.

In addition, a heat exchanger can be manufactured by corrugating the obtained fin material into fins and performing brazing joining in combination with a heat exchanger member such as a header, a tube, or a side plate. In the present invention, brazing heat treatment conditions and method (brazing temperature, atmosphere, presence / absence of flux, type of brazing material, etc.) are not particularly limited, and brazing can be performed by a desired method.
Since the obtained heat exchanger is provided with the fin material of this embodiment, the brazing joint is good and the strength, conductivity, and corrosion resistance are excellent.
FIG. 1 shows a heat exchanger 1 manufactured by assembling a tube 3, a header 2, and a side plate 5 to the fin 4 of this embodiment and brazing.

  According to this embodiment, it is possible to obtain an aluminum alloy fin material for a heat exchanger and a heat exchanger that are excellent in strength, conductivity, corrosion resistance, and brazing.

Examples of the present invention will be described below.
An aluminum alloy ingot or cast plate was produced from the molten metal adjusted to have the components shown in Table 1 (the balance Al and inevitable impurities). As shown in Table 2, with respect to the obtained ingot or cast plate, the heating rate was 25 to 75 ° C./hour, the holding temperature was 350 to 480 ° C., the holding time was 1 to 10 hours, and the cooling rate was 20 Homogenization was performed at ˜50 ° C./hour, and then, in the DC method, hot rolling and cold rolling were performed in this order, and in the CC method, cold rolling was performed.
In the middle of cold rolling, intermediate annealing was performed after the rolling rate reached 60% or more. About intermediate annealing and subsequent cold rolling, in Examples 1-45 and Comparative Examples 1-17, 20, 22, 24-37, in order to obtain a fibrous crystal structure, it hold | maintains at 200-300 degreeC for 6 hours. Annealing was performed, and then cold rolling was performed at a rolling rate shown in Table 2 (10 to 25%). In Comparative Examples 18, 19, 21, and 23, in order to obtain a recrystallized structure, after intermediate annealing held at 350 ° C. for 6 hours, cold rolling was performed at a rolling rate shown in Table 2 (25 to 40%). It was. Thus, H14 tempered fin material having a thickness shown in Table 3 was produced.
The following measurements were performed on the obtained fin material. The results are shown in Tables 3 and 4. Moreover, in some sample materials, the micrograph was shown in FIG.

1. Before heat addition to brazing The test piece of fin material obtained was subjected to solidus temperature, tensile strength at room temperature, 0.2% proof stress at room temperature, and an equivalent circle diameter of 0.01 to 0.10 μm. The number density and crystal structure of the two-phase particles were measured. The measuring method is as follows. The measurement results are shown in Table 3.

(Solidus temperature)
The solidus temperature of the fin material was measured using a differential thermal analyzer (DTA).

(Normal temperature strength before brazing)
A sample was cut out parallel to the rolling direction to prepare a JIS13B-shaped test piece, and a tensile test was performed at room temperature under a condition of a tensile speed of 5 mm / min, and the tensile strength and 0.2% proof stress of the test piece were measured. .

(Distribution of intermetallic compounds)
With respect to the test material of the fin material, the number density (number / mm ² ) of the second phase particles (equivalent circle diameter of 0.01 to 0.10 μm) was measured by a transmission electron microscope (TEM). Before brazing, the material is subjected to salt bath annealing at 400 ° C. for 15 seconds to remove the deformation strain to make the compound easy to observe, and then mechanical polishing and electrolytic polishing are performed by ordinary methods to form a thin film. And a photograph was taken at 50000 times using a transmission electron microscope. Photographing was performed for each of five visual fields, and the size and number density of the second phase particles were measured by image analysis of the photograph.

2. During brazing addition heat Assuming the strength of the fin material during brazing addition heat, 0.2% yield strength at 400 to 550 ° C. was measured. The recrystallization temperature of the fin material was also measured. The measuring method is as follows. The measurement results are shown in Table 3.

(0.2% proof stress during brazing heat)
A sample was cut out from the fin material before brazing in parallel with the rolling direction, and machined into a JIS No. 5 shape to prepare a test piece. After the test piece was put into a preheated thermostat, the test piece was 400 ° C. , 450 ° C., and 550 ° C. immediately after reaching each temperature, a high temperature tensile test was performed. The tensile rate of the high temperature tensile test was 1 mm / min, and 0.2% yield strength at high temperature was measured.

(Recrystallization temperature)
Assuming brazing heat, the temperature was raised from room temperature to 600 ° C. at a constant rate (100 ° C./min), and after reaching each predetermined temperature, it was cooled to room temperature. The sample surface was observed after cooling, and the temperature at which 80% or more of the fin material surface with a surface area of 300 mm ² was recrystallized was defined as the recrystallization temperature.

3. After brazing The fin material is subjected to a heat treatment equivalent to brazing, and the heated fin material is subjected to tensile strength, 0.2% proof stress, conductivity, average crystal grain size, potential, corrosion weight loss, corrosion at room temperature. Current density, number density of Al-Fe-based crystals having an equivalent circle diameter of 1.0 μm or more, number density of second phase particles having an equivalent circle diameter of 0.01 to 0.10 μm, equivalent circle diameter of 0.05 μm The number density of the above Al—Cu second phase particles was calculated.
Furthermore, in order to evaluate brazeability, the fin material was corrugated and subjected to brazing heat treatment in combination with other members, and the joint locations were observed to calculate the fin joint rate. The brazing heat treatment conditions and the measurement / evaluation methods for each item are as follows. The measurement results are shown in Table 4.

(Brazing heat treatment conditions)
The temperature was increased from room temperature to 600 ° C. at an average temperature increase rate of 50 ° C./minute, held at 600 ° C. for 3 minutes, and then subjected to brazing equivalent heat treatment under the conditions of heat treatment to cool at a temperature decrease rate of 100 ° C./minute. .

(Tensile strength after brazing, 0.2% yield strength)
A sample was cut out in parallel with the rolling direction from a sample subjected to heat treatment equivalent to brazing, and a JIS 13B-shaped test piece was produced. A tensile test was performed on the test piece at room temperature, and tensile strength and 0.2% yield strength were measured. The tensile speed was 5 mm / min.

(conductivity)
The conductivity was measured with a double bridge conductivity meter by the conductivity measuring method described in JIS H0505.

(Average crystal grain size)
Etching the sample surface with a mixed solution of hydrochloric acid, hydrofluoric acid, and nitric acid, and taking a photograph of the surface of the test material that has undergone heat treatment equivalent to brazing. The average crystal grain size was measured by a linear cutting method using a structure photograph.

(Potential)
A sample for potential measurement was cut out from the fin material subjected to the brazing equivalent heat treatment, and the sample was immersed in a 5% NaOH solution heated to 50 ° C. for 30 seconds, and then immersed in a 30% HNO ₃ solution for 60 seconds. Further, the sample was washed with tap water and ion-exchanged water, and the potential after being immersed in a 5% NaCl solution (adjusted to pH 3 with acetic acid) at 25 ° C. for 60 minutes without being dried was measured. A silver-silver chloride electrode (Ag / AgCl) was used as the reference electrode.

(Corrosion weight loss)
A neutral salt spray test (NNS) was performed by a method according to JIS Z2371. A 120 mm × 40 mm sample was cut out from the fin material, and three samples per condition were put into a corrosive environment, and the corrosion weight loss was determined from the weight difference before and after the test. The test solution was 5% NaCl, the pH of the test solution was in the range of 6.5-7.2, and the test bath temperature was 35 ± 2 ° C.

(Corrosion current density)
A test piece of 15 mm × 60 mm was prepared for the test material subjected to brazing equivalent heat treatment. About the prepared test piece, 1 cm ² of the measurement area was exposed, and the others were protected by masking, and pretreated in the same manner as the potential measurement (immersion in a 5% NaOH solution heated to 50 ° C. for 30 seconds, and then 30% After immersing in HNO3 solution for 60 seconds and further washing with tap water and ion-exchanged water), polarization measurement was performed. Polarization measurement was performed by immersing the test piece in a 5% NaCl solution (adjusted to pH 3 with acetic acid) at 25 ° C. for 5 minutes to stabilize the natural potential, and then increasing the potential at a sweep rate of 0.5 mV / s to anodic polarization. Measurement was carried out to obtain an anodic polarization curve.
Further, cathodic polarization measurement was carried out by decreasing the potential from the natural potential at the same sweep rate to obtain a cathodic polarization curve. The current density at the intersection of the anodic polarization curve and the cathodic polarization curve was taken as the corrosion current density.

(Distribution of intermetallic compounds)
For specimens subjected to brazing equivalent heat treatment, Al-Fe-based crystallized material (equivalent circle diameter is 1.0 μm or more), Al-Cu second phase particles (equivalent circle diameter is 0.05 μm or more) ), The number density (number / mm ² ) of Al—Mn, Al—Mn—Si, and Al—Fe—Si based second phase particles (equivalent circle diameter of 0.01 to 0.10 μm) is transmitted. It was measured by an electron microscope (TEM). The measurement method is mechanical polishing and electropolishing by ordinary methods to produce a thin film, and using a transmission electron microscope, the Al-Fe-based crystallized product is 3000 times, Al-Cu-based, Al-Mn As for the second phase particles of the system, Al—Mn—Si system and Al—Fe—Si system, photographs were taken at 50000 times. Photographing was performed for each of five visual fields, and the size and number density of intermetallic compounds were measured by image analysis of the photographs.

(Fin bonding rate)
The produced fin material was corrugated, combined with other members (header plate, tube, side plate) and assembled, and then flux was applied and brazed to produce a heat exchanger measuring 50 cm in length and 50 cm in width. Then, the joint location of the fin and tube of a heat exchanger is observed, the number of defective joint locations is calculated | required, and it is (1- (defective joint location / all joint locations)) x100 (% ) Was calculated. A bonding rate of 95% or more was evaluated as ○ (good bonding state), 90 to 95% as Δ (necessary and sufficient bonding state), and 90% or less as × (bonding failure).

  As shown in Tables 1 to 4, all of Examples 1 to 45 having the component composition and characteristics defined in the present invention were excellent in strength, conductivity, corrosion resistance, and brazing (fin bonding rate). On the other hand, in Comparative Examples 1 to 37 that did not satisfy any one or more of the provisions of the present invention, good results were not obtained in any one or more of strength, conductivity, corrosion resistance, brazing property, and the like.

With respect to the above examples and comparative examples, the distribution according to each component for relational expression (i) is shown in FIG. 3, and the distribution according to each component for relational expression (ii) is shown in FIG.
Regarding relational expression (i), Examples 6, 17, 24, 27, 29, 30, 35, and 36 and some of the comparative examples have calculated values less than 2.1, as shown in Tables 3 and 4 The 0.2% yield strength at a high temperature during brazing, the tensile strength at normal temperature and the 0.2% yield strength were low, and the fin joint ratio tended to decrease. Further, in Examples 3, 15, 18, 21, and 31 and some of the comparative examples, the calculated value of the relational expression (i) exceeds 3.4, and the tensile strength before brazing is 0.2. It was a fin material with high% yield strength, which makes fin formation difficult, or has a low solidus temperature and a large amount of corrosion weight loss.
Regarding relational expression (ii), Examples 3, 4, 17, 18, 20, 33, 42, and 45 and some of the comparative examples have calculated values less than 0.2, as shown in Tables 3 and 4 Further, the potential of the fin material was not in a more preferable range.

1 Heat exchanger 2 Header 3 Tube 4 Fin 5 Side plate

Claims (12)

In mass%, Mn: 1.2 to 2.0%, Si: 0.5 to 1.3%, Cu: 0.001 to less than 0.05%, Fe: 0.1 to 0.5%, Zn : 0.5 to 2.5%, the balance is made of an aluminum alloy having a composition consisting of Al and inevitable impurities,
After brazing heat, at normal temperature, tensile strength is 140 MPa or more, 0.2% proof stress is 50 MPa or more, conductivity is 42% IACS or more, potential is −800 mV or more and −710 mV or less, neutral salt spray test for 16 weeks An aluminum alloy fin material for heat exchangers having excellent strength, conductivity, corrosion resistance, and brazing characteristics, characterized in that the subsequent weight loss by corrosion is 120 mg / dm ² or less.   The aluminum alloy is further, in mass%, Ti: 0.01 to 0.20%, Cr: 0.01 to 0.20%, Mg: 0.01 to 0.20%, Zr: 0.01 to The aluminum alloy fin material for heat exchangers having excellent strength, electrical conductivity, corrosion resistance, and brazing characteristics according to claim 1, comprising one or more of 0.20%.   The aluminum alloy has a relational expression (i): 2.1 ≦ [Mn content (mass%)] + [Si content (mass%)] + 7.5 * [Cu content (mass%)] ≦ 3. 4 and a relational expression (ii) ... [Zn content (% by mass)]-18.8 * [Cu content (% by mass)] ≧ 0.2 Or the aluminum alloy fin material for heat exchangers which is excellent in strength, electrical conductivity, corrosion resistance, and brazing characteristics described in 2.   The average crystal grain size after brazing addition heat is 100 µm or more and less than 2000 µm, for a heat exchanger excellent in strength, conductivity, corrosion resistance, and brazing characteristics according to any one of claims 1 to 3 Aluminum alloy fin material.   The strength, conductivity, corrosion resistance, and the resistance according to any one of claims 1 to 4, wherein 0.2% proof stress is within a range of 15 to 40 MPa at each temperature in a range of 400 to 550 ° C. Aluminum alloy fin material for heat exchangers with excellent brazing characteristics. Prior to brazing heat, the number density of Al-Mn, Al-Mn-Si, and Al-Fe-Si second phase particles having an equivalent circle diameter of 0.01 to 0.10 μm is 1.0 × 10 and ^five or / mm ² or more, the strength of any one of claims 1 to 5, wherein the metal structure is crystalline grain structure of the fibrous, conductive, corrosion resistance, and brazing properties Excellent aluminum alloy fin material for heat exchanger. After brazing heat addition, 1.0 × 10 ⁴ second phase particles of Al—Mn, Al—Mn—Si, and Al—Fe—Si based on an equivalent circle diameter of 0.01 to 0.10 μm / mm ² or more, an equivalent circle diameter of second phase particles of 0.05μm or more Al-Cu system in a Al-Fe-based crystallized matter and the circle equivalent diameter of more than 1.0μm is 1.0 × 10 ³ cells / mm ² The aluminum alloy fin material for heat exchangers according to any one of claims 1 to 6, which is excellent in strength, conductivity, corrosion resistance, and brazing characteristics.   The aluminum alloy fin material for a heat exchanger having excellent strength, conductivity, corrosion resistance, and brazing characteristics according to any one of claims 1 to 7, wherein the plate thickness is 100 µm or less. The aluminum alloy fin for heat exchangers having excellent strength, conductivity, corrosion resistance and brazing characteristics according to any one of claims 1 to 8, wherein the corrosion current density is 0.05 mA / cm ² or less. Wood.   Before brazing addition heat, normal temperature tensile strength is 250 MPa or less, 0.2% proof stress at normal temperature is 230 MPa or less, strength, conductivity according to any one of claims 1 to 9, Aluminum alloy fin material for heat exchangers with excellent corrosion resistance and brazing characteristics.   11. The heat exchanger excellent in strength, conductivity, corrosion resistance, and brazing characteristics according to any one of claims 1 to 10, wherein the recrystallization completion temperature is 450 ° C. or lower before brazing addition heat. Aluminum alloy fin material.   A heat exchanger comprising the aluminum alloy fin material for a heat exchanger according to any one of claims 1 to 11.