JP2013057132A - Method for producing high strength aluminum alloy fin material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high strength aluminum alloy fin material for a heat exchanger, which has high strength and thermal conductivity after brazing and is excellent in sag resistance, erosion resistance, self-corrosion resistance and sacrificial anode effect, and to provide a method for producing the fin material.SOLUTION: In the method for producing a high strength aluminum alloy fin material for a heat exchanger, a molten metal having a chemical composition containing, by weight, 0.8 to 1.4% of Si, 0.15 to 0.7% of Fe, 1.5 to 3.0% of Mn and 0.5 to 2.5% of Zn, wherein the content of Mg as an impurity is limited to <0.05%, and the remainder comprising Al and ordinary impurities is poured, then a thin slab with a thickness of 5 to 10 mm is continuously cast by a twin belt type caster and coiled around a roll, is thereafter cold-rolled to have a sheet thickness of 1.0 to 6.0 mm, is subjected to a primary intermediate annealing at 200 to 350°C, is further cold-rolled to have a sheet thickness of 0.05 to 0.4 mm, is subjected to a secondary intermediate annealing at 360 to 450°C, and is subjected to cold rolling at a final cold rolling ratio of ≥10 and <50% to have a final sheet thickness of 40 to 200 μm.

Description

  TECHNICAL FIELD The present invention relates to an aluminum alloy fin material for a heat exchanger excellent in brazing and a method for manufacturing the same, and more specifically, a fin and a working fluid passage component material are joined by brazing, such as a radiator, a car heater, and a car air conditioner. Aluminum alloy fin material used in heat exchangers that have a moderate strength before brazing, so fin forming is easy, that is, the strength before brazing is too high and fin forming is not difficult. In addition, the present invention relates to an aluminum alloy fin material for a heat exchanger that has high strength after brazing and is excellent in heat transfer characteristics, erosion resistance, sag resistance, sacrificial anode effect, and self-corrosion resistance, and a method for producing the same.

  Heat exchangers for automobile radiators, air conditioners, intercoolers, oil coolers, etc. are composed of working fluid passage materials composed of Al-Cu alloys, Al-Mn alloys, Al-Mn-Cu alloys, and Al-Mn alloys. It is assembled by brazing a fin made of an alloy or the like. The fin material is required to have a sacrificial anode effect in order to prevent the working fluid passage constituent material from being corroded, and has excellent sag resistance and resistance to prevent deformation due to high temperature heating during brazing and penetration of the braze. Erosion is required.

  The reason why Al-Mn aluminum alloys such as JIS 3003 and JIS 3203 are used as the fin material is that Mn acts effectively to prevent deformation during brazing and erosion of the brazing. In order to impart the sacrificial anode effect to the Al—Mn alloy fin material, a method of adding Zn, Sn, In, or the like to this alloy to make it electrochemically base (Patent Document 1 (Japanese Patent Laid-Open No. 62-120455)). In order to further improve the high temperature buckling resistance (sag resistance), a method in which an Al—Mn based alloy contains Cr, Ti, Zr, etc. No. 50-118919))).

  Recently, however, there is an increasing demand for weight reduction and cost reduction of heat exchangers, and it is necessary to further reduce the thickness of heat exchanger constituent materials such as working fluid passage constituent materials and fin materials. However, for example, if the fins are made thinner, the heat transfer cross-sectional area becomes smaller and the heat exchange performance deteriorates, causing problems with the strength and durability of the heat exchanger as a product. The strength, sag resistance, erosion resistance and self-corrosion resistance after application are desired.

  A conventional Al-Mn alloy has a problem that thermal conductivity is lowered because Mn is dissolved by heating during brazing. As a fin material that solves this problem, an aluminum alloy that limits the Mn content to 0.8 wt% or less and contains Zr: 0.02 to 0.2 wt% and Si: 0.1 to 0.8 wt% has been proposed. (Patent Document 3 (Japanese Patent Publication No. 63-23260)). This alloy has improved thermal conductivity, but because Mn is low, the strength after brazing is insufficient, fins are liable to collapse and deform during use as a heat exchanger, and the potential is not sufficiently low. However, the sacrificial anode effect is small.

  On the other hand, by increasing the cooling rate when casting the slab by pouring molten aluminum alloy, the crystallization of the slab crystallizes even if the Si, Mn content, etc. is 0.05-1.5 mass%. It has become possible to reduce the size of the intermetallic compound to a maximum value of 5 μm or less, and a proposal has been made to improve the fatigue characteristics of the fin material by performing a rolling process from such a slab (Patent Document 4 (Japanese Patent Laid-Open No. 2003-32083). 2001-226730 gazette)). However, the present invention is intended to improve the fatigue life, and although there is a description of thinning the casting slab as a means for increasing the cooling rate when casting the slab, it is a twin belt casting on an actual operation scale. There is no specific disclosure of thin slab continuous casting by machine.

Japanese Patent Laid-Open No. Sho 62-120455 JP 50-118919 A Japanese Patent Publication No. 63-23260 JP 2001-226730 A

  The object of the present invention is to have a moderate strength before brazing that allows easy fin molding, and a high strength after brazing, and is excellent in sag resistance, erosion resistance, self-corrosion resistance, and sacrificial anode effect. It is providing the manufacturing method of the aluminum alloy fin material for heat exchangers.

  In order to achieve the above object, the high-strength aluminum alloy fin material for a heat exchanger of the present invention has Si: 0.8 to 1.4 wt%, Fe: 0.15 to 0.7 wt%, Mn: 1.5 -3.0wt%, Zn: 0.5-2.5wt%, Mg as impurities is limited to 0.05wt% or less, and the balance has a chemical composition consisting of ordinary impurities and Al. The metal structure before brazing is a fiber crystal grain structure, the tensile strength before brazing is 240 MPa or less, the tensile strength after brazing is 150 MPa or more, and the recrystallized grain size after brazing is 500 μm or more. Features.

  The first method for producing the high-strength aluminum alloy fin material for a heat exchanger according to the present invention is to pour a molten metal having the chemical composition of the fin material, and to form a thin film having a thickness of 5 to 10 mm by a twin belt casting machine. After the slab is continuously cast and wound on a roll, it is cold-rolled to a thickness of 1.0 to 6.0 mm, subjected to a first intermediate annealing at 200 to 350 ° C., and further cold-rolled. The steel sheet is cold-rolled to a thickness of 0.05 to 0.4 mm, subjected to secondary intermediate annealing at 360 to 450 ° C., and subjected to cold rolling with a final cold rolling rate of less than 10 to 50% to obtain a final thickness of 40 It is set to -200 micrometers.

  The second method for producing the high-strength aluminum alloy fin material for a heat exchanger according to the present invention is to pour a molten metal having the chemical composition of the fin material, and to form a thin film having a thickness of 5 to 10 mm by a twin belt casting machine. After the slab is continuously cast and wound on a roll, it is cold-rolled to a thickness of 1.0 to 6.0 mm, subjected to first intermediate annealing at 200 to 450 ° C., and further cold-rolled. The steel sheet is cold-rolled to a thickness of 0.08 to 2.0 mm, subjected to secondary intermediate annealing at 360 to 450 ° C., and cold-rolled at a cold rolling rate of 50 to 96% to obtain a final thickness of 40 to 200 μm. The final annealing is performed at 200 to 400 ° C.

  In the first and second methods, it is preferable that the first intermediate annealing is performed in a continuous annealing furnace at a temperature rising rate of 100 ° C./min or more and a holding temperature of 400 to 500 ° C. within a holding time of 5 minutes.

  In the first and second methods, the metal structure is a fiber crystal grain structure at any stage after the first intermediate annealing, after the second intermediate annealing, and after the final annealing (before brazing). It is desirable.

According to the present invention, by limiting the chemical composition, the crystal grain structure before and after brazing, and the tensile strength as described above, high strength and heat transfer characteristics, erosion resistance, sag resistance, sacrificial anode effect, and self A high-strength aluminum alloy fin material for heat exchangers excellent in corrosion resistance can be obtained.
This aluminum alloy fin material can be manufactured by the first and second methods.

  In order to develop an aluminum alloy fin material that satisfies the requirements for thinning the heat exchanger fin material, the present inventor is concerned with strength characteristics, heat transfer performance, sag resistance, erosion resistance, self-corrosion resistance, and sacrificial anode effect. As a result of performing various studies on the relationship between the composition, intermediate annealing conditions, rolling reduction, and final annealing, while comparing the rolling material from the conventional DC slab casting and the rolling material from the twin belt type continuous casting, The present invention has been completed.

  The significance and reasons for limitation of the alloy components in the aluminum alloy fin material for heat exchangers of the present invention will be described below.

[Si: 0.8 to 1.4 wt%]
Si coexists with Fe and Mn to form submicron-level Al- (Fe · Mn) -Si compounds during brazing, improving strength, and simultaneously reducing the amount of Mn solid solution to conduct heat. Improve the rate. If the Si content is less than 0.8 wt%, the effect is not sufficient. If it exceeds 1.4 wt%, the fin material may be melted during brazing. Therefore, a preferable content range is 0.8 to 1.4 wt%. A more preferable content of Si is in the range of 0.9 to 1.4 wt%.

[Fe: 0.15 to 0.7 wt%]
Fe coexists with Mn and Si to produce submicron-level Al- (Fe · Mn) -Si compounds during brazing, improving strength and reducing Mn solid solution to conduct heat. Improve the rate. If the Fe content is less than 0.15 wt%, a high-purity metal is required, which is not preferable because the production cost increases. If it exceeds 0.7 wt%, coarse Al- (Fe.Mn) -Si-based crystallized products are produced during casting of the alloy, making it difficult to produce a plate material. Therefore, a preferable content range is 0.15-0.7 wt%. A more preferable content of Fe is in the range of 0.17 to 0.6 wt%.

[Mn: 1.5 to 3.0 wt%]
By coexisting with Fe and Si, Mn precipitates at a high density as a sub-micron level Al— (Fe · Mn) —Si compound at the time of brazing, and improves the strength of the alloy material after brazing. Further, since the submicron level Al- (Fe.Mn) -Si-based precipitate has a strong recrystallization inhibiting action, the recrystallized grains become coarser to 500 μm or more, and the sag resistance and erosion resistance are improved. If Mn is less than 1.5 wt%, the effect is not sufficient, and if it exceeds 3.0 wt%, coarse Al- (Fe · Mn) -Si-based crystallized products are produced during casting of the alloy, making it difficult to produce a plate material. At the same time, the solid solution amount of Mn increases and the thermal conductivity decreases. Therefore, a preferable content range is 1.5 to 3.0 wt%. A more preferable content of Mn is 1.6 to 2.8 wt%.

[Zn: 0.5 to 2.5 wt%]
Zn lowers the potential of the fin material and provides a sacrificial anode effect. If the content is less than 0.5 wt%, the effect is not sufficient, and if it exceeds 2.5 wt%, the self-corrosion resistance of the material is deteriorated, and the thermal conductivity is lowered by solid solution of Zn. Therefore, a preferable content range is 0.5 to 2.5 wt%. A more preferable content of Zn is in the range of 1.0 to 2.0 wt%.

[Mg: 0.05 wt% or less]
Mg affects the brazing property, and if the content exceeds 0.05 wt%, the brazing property may be impaired. Particularly in the case of fluoride-based flux brazing, fluorine (F), which is a component of the flux, easily reacts with Mg in the alloy, and works effectively during brazing due to the formation of compounds such as MgF _2. The absolute amount of flux to be used is insufficient, and brazing defects are likely to occur. Therefore, the content of Mg as an impurity is limited to 0.05 wt% or less.

  For impurity components other than Mg, Cu is preferably limited to 0.2 wt% or less in order to make the potential of the material noble, and Cr, Zr, Ti, and V significantly reduce the thermal conductivity of the material even in a small amount. Therefore, the total content of these elements is preferably limited to 0.20 wt% or less.

  Next, the significance of the casting conditions, the intermediate annealing conditions, the final cold rolling rate, and the final annealing conditions of the thin slab in the present invention and the reasons for limitation will be described below.

[Thin slab casting conditions]
In the double belt casting method, molten metal is poured between rotating belts facing each other up and down, and the molten metal is solidified by cooling from the belt surface to form a slab. It is a continuous casting method that is drawn out and wound into a coil.
In the present invention, the thickness of the cast slab is preferably 5 to 10 mm. With this thickness, the solidification rate in the central part of the plate thickness is fast, and with a uniform structure and with a composition within the range of the present invention, there are few coarse compounds and excellent properties with a large crystal grain size after brazing. It can be a fin material.

  When the thickness of the thin slab by the twin belt type casting machine is less than 5 mm, the amount of aluminum passing through the casting machine per unit time becomes too small and casting becomes difficult. On the other hand, if the thickness exceeds 10 mm, winding with a roll cannot be performed, so the slab thickness range is preferably 5 to 10 mm.

  In addition, it is preferable that the casting speed at the time of solidification of a molten metal is 5-15 m / min, and it is desirable that solidification is completed within a belt. A casting speed of less than 5 m / min is not preferable because it takes too much time for casting and decreases productivity. When the casting speed exceeds 15 m / min, the supply of the molten aluminum cannot catch up, and it becomes difficult to obtain a thin slab having a predetermined shape.

[First intermediate annealing condition]
In the case where the final cold rolling rate is lowered to less than 10-50% in order to keep the strength of the product low (second embodiment), the holding temperature of the first intermediate annealing is preferably 200 to 350 ° C. When the holding temperature of the first intermediate annealing is less than 200 ° C., a sufficient softened state cannot be obtained. When the holding temperature of the first intermediate annealing exceeds 350 ° C., the solid solution Mn in the matrix is precipitated as an Al— (Fe · Mn) —Si compound during the intermediate annealing at a high temperature. Recrystallization occurs during annealing, and the subsequent cold rolling rate of less than 10-50% remains in an unrecrystallized state during brazing, and sag resistance and erosion resistance during brazing descend.

  When the final cold rolling rate is as high as 50 to 96%, it is important to keep the strength of the product low by performing final annealing. In this case (third embodiment), the holding temperature of the first intermediate annealing is preferably 200 to 450 ° C. When the holding temperature of the first intermediate annealing is less than 200 ° C., a sufficient softened state cannot be obtained. When the holding temperature of the first intermediate annealing exceeds 350 ° C., the solid solution Mn in the matrix is precipitated as an Al— (Fe · Mn) —Si based compound at the time of intermediate annealing at a high temperature. The high rate means that the dislocation density is low because the cold rolling rate before the second intermediate annealing treatment is low, and recrystallization does not occur during the second intermediate annealing. However, when the holding temperature of the first intermediate annealing exceeds 450 ° C., the solid solution Mn in the matrix is precipitated in a large amount and coarsely as an Al— (Fe · Mn) —Si based compound at the intermediate annealing at a high temperature. Therefore, not only recrystallization occurs at the time of the second intermediate annealing, but the recrystallization inhibiting action at the time of brazing is weakened, and the recrystallized grain size becomes less than 500 μm, and the sag resistance and erosion resistance at the time of brazing are lowered. .

  The holding time of the first intermediate annealing is not particularly limited, but is preferably in the range of 1 to 5 hours. If the holding time of the first intermediate annealing is less than 1 hour, the temperature of the entire coil remains non-uniform, and a uniform recrystallized structure in the plate may not be obtained. If the holding time of the first intermediate annealing exceeds 5 hours, the precipitation of the solid solution Mn proceeds, which is not only disadvantageous in securing a recrystallized grain size of 500 μm or more after brazing, but also processing. This is not preferable because it takes too much time to reduce productivity.

  The temperature increase rate and the cooling rate during the first intermediate annealing treatment are not particularly limited, but are preferably 30 ° C./hour or more. When the heating rate and cooling rate during the first intermediate annealing treatment are less than 30 ° C./hour, precipitation of solute Mn proceeds to stably secure a recrystallized grain size of 500 μm or more after brazing. Not only is it disadvantageous, but it takes too much time for processing, and productivity is lowered, which is not preferable.

  The temperature of the first intermediate annealing in the continuous annealing furnace is preferably 400 to 500 ° C. When the temperature is lower than 400 ° C., a sufficient softened state cannot be obtained. However, when the holding temperature exceeds 500 ° C., the solid solution Mn in the matrix is coarsely precipitated as an Al— (Fe · Mn) —Si-based compound during intermediate annealing at a high temperature. Or the recrystallization inhibitory action at the time of brazing becomes weak, the recrystallized grain size becomes less than 500 μm, and the sag resistance and erosion resistance at the time of brazing deteriorate.

  The holding time for continuous annealing is preferably within 5 minutes. When the holding time of continuous annealing exceeds 5 minutes, not only is the solid solution Mn precipitating progressing, but it is disadvantageous in securing a recrystallized grain size of 500 μm or more after brazing, and it takes time for processing. This is not preferable because the productivity is lowered due to excessive application.

  The heating rate and the cooling rate during the continuous annealing treatment are preferably 100 ° C./min or more for the heating rate. When the rate of temperature increase during the continuous annealing process is less than 100 ° C./min, the process takes too much time and productivity is lowered, which is not preferable.

[Secondary intermediate annealing conditions]
The holding temperature of the second intermediate annealing is preferably 360 to 450 ° C. When the holding temperature of the second intermediate annealing is less than 360 ° C., a sufficient softened state cannot be obtained. However, when the holding temperature of the second intermediate annealing exceeds 450 ° C., the solid solution Mn in the matrix is coarsely precipitated as an Al— (Fe · Mn) —Si based compound at the intermediate annealing at a high temperature. And since it becomes a recrystallized structure, the recrystallization inhibiting action at the time of brazing is weakened, the recrystallized grain size becomes less than 500 μm, and the sag resistance and erosion resistance at the time of brazing are lowered.

  The holding time of the second intermediate annealing is not particularly limited, but is preferably in the range of 1 to 5 hours. If the holding time of the second intermediate annealing is less than 1 hour, the temperature of the entire coil remains non-uniform, and a uniform recrystallized structure in the plate may not be obtained. If the holding time of the second intermediate annealing exceeds 5 hours, the precipitation of the solid solution Mn progresses, which is not only disadvantageous in securing a recrystallized grain size of 500 μm or more after brazing but also processing. This is not preferable because it takes too much time to reduce productivity.

  The temperature increase rate and the cooling rate during the second intermediate annealing treatment are not particularly limited, but are preferably 30 ° C./hour or more. When the heating rate and cooling rate during the second intermediate annealing treatment are less than 30 ° C./hour, precipitation of solute Mn proceeds to stably secure a recrystallized grain size of 500 μm or more after brazing. Not only is it disadvantageous, but it takes too much time for processing, and productivity is lowered, which is not preferable.

[Fiber crystal grain structure]
The metal structure is a fiber crystal grain structure at any stage after the first intermediate annealing, after the second intermediate annealing, and after the final annealing (before brazing). It means that the structure is a fiber crystal grain structure not including a crystal grain structure of 200 μm or more.

[Final cold rolling rate]
The final cold rolling rate is preferably 10 to 96%. When the final cold rolling rate is less than 10%, the strain energy accumulated by cold rolling is small, and recrystallization is not completed in the temperature rising process during brazing, so the sag resistance and erosion resistance are lowered. When the final cold rolling rate exceeds 96%, the ear cracks at the time of rolling become remarkable and the yield decreases. When final annealing is not performed, if the final cold rolling rate exceeds 50%, the product strength becomes too high, and it becomes difficult to obtain a predetermined fin shape in fin material molding. On the other hand, when the final cold rolling rate is 50% or more, depending on the composition, the product strength becomes too high, and it becomes difficult to obtain a predetermined fin shape in the fin forming. Even if final annealing (softening treatment) is performed at 200 to 400 ° C. for about 1 to 3 hours, various characteristics are not impaired. In particular, after performing the first intermediate annealing by a continuous annealing furnace, the fin material that has been subjected to final annealing (softening treatment) for about 1 to 3 hours at a holding temperature of 200 to 400 ° C. Excellent fin moldability, high strength after brazing, and excellent sag resistance.

  The fin material of the present invention is subjected to corrugation after slitting to a predetermined width, and alternately laminated with flat tubes made of a clad plate made of a working fluid passage material, for example, a 3003 alloy coated with a brazing material. A heat exchanger unit is obtained by jointing.

  According to the method of the present invention, at the time of thin slab casting by a twin belt type casting machine, Al- (Fe · Mn) -Si compound is crystallized uniformly and finely in the slab and supersaturated in the matrix Al. The solid solution Mn and Si are deposited at a high density as a sub-micron level Al- (Fe.Mn) -Si phase by high-temperature heating during brazing. As a result, the amount of solid solution Mn in the matrix that greatly lowers the thermal conductivity is reduced, so that the electrical conductivity after brazing is increased and excellent thermal conductivity is exhibited. For the same reason, the Al- (Fe · Mn) -Si compound finely crystallized and the submicron-level Al- (Fe · Mn) -Si phase precipitated at high density are dislocations during plastic deformation. The tensile strength of the final plate after brazing shows a high value. In addition, the sub-micron-level Al- (Fe.Mn) -Si phase that precipitates during brazing has a strong recrystallization-inhibiting action, so that the recrystallized grain size after brazing is 500 μm or more, thus providing good sag resistance. Thus, for the same reason, it exhibits excellent erosion resistance even after brazing. In the present invention, since the Mn content is limited to 1.5 wt% or more, the tensile strength does not decrease even if the average grain size of the recrystallized grains after brazing exceeds 3000 μm.

  Further, the twin-belt casting machine has a high solidification rate of the molten metal, and the Al— (Fe · Mn) —Si compound crystallized in the thin slab becomes uniform and fine. Therefore, in the final fin material, second phase particles having a circle-equivalent diameter of 5 μm or more due to coarse crystals are not present, and excellent self-corrosion resistance is exhibited.

  Thus, by casting the thin slab by the twin belt type continuous casting method, the Al— (Fe · Mn) —Si compound in the slab ingot is made uniform and fine, and the submicron level Al— (Fe・ Mn) -Si phase precipitates are densified and the grain size after brazing is coarsened to 500 μm or more, so that strength after brazing, thermal conductivity, sag resistance, erosion resistance, self By increasing the corrosivity and simultaneously containing Zn, the potential of the material can be reduced, the sacrificial anode effect can be improved, and the aluminum alloy fin material for a heat exchanger having excellent durability can be obtained.

Examples of the present invention will be described below in comparison with comparative examples.
As an example of the present invention and a comparative example, a molten alloy having the composition of alloy numbers 1 to 12 shown in Table 1 was melted, passed through a ceramic filter, poured into a twin belt casting mold, and cast at a casting speed of 8 m / min. A 7 mm thick slab was continuously cast. The cooling rate during solidification of the molten metal was 50 ° C./sec. The thin slab was cold-rolled to a plate thickness (I / A1 plate thickness) shown in Tables 2-4. Thereafter, the sample is inserted into an annealer, heated at a heating rate of 50 ° C./hr and held at each temperature shown in Tables 2 to 2 for 2 hours, and then cooled to 100 ° C. at a cooling rate of 50 ° C./hr, Alternatively, the sample was kept in a salt bath at 450 ° C. for 15 seconds, and then subjected to a first intermediate annealing treatment in which water quenching was performed. Next, the sample was cold-rolled to the plate thickness shown in Tables 2 to 4 (I / A2 plate thickness), then inserted into an annealer, heated at a heating rate of 50 ° C./hr, and each shown in Tables 2 to 4 After maintaining at the temperature for 2 hr, a second intermediate annealing treatment was performed in which the temperature was cooled to 100 ° C. at a cooling rate of 50 ° C./hr. Subsequently, it cold-rolled with the final cold rolling rate shown in Tables 2-4, and set it as the fin material of thickness 60 micrometers. For some of these samples, the sample was further inserted into an annealer, heated at a heating rate of 50 ° C./hr, held at each temperature shown in Table 4 for 2 hr, and then cooled at a cooling rate of 50 ° C./hr to 100 The final annealing process which cools to degreeC was given.

As comparative examples, molten alloys having the compositions of Alloy Nos. 13 and 14 shown in Table 1 were melted and subjected to conventional DC casting (thickness 500 mm, cooling rate at solidification of about 1 ° C./sec), face grinding, soaking treatment. A fin material having a thickness of 60 μm was manufactured by hot rolling, cold rolling (thickness 100 μm), intermediate annealing (400 ° C. × 2 hr), and cold rolling.
The following measurements (1) to (3) were performed on the fin materials of the present invention examples and comparative examples.

(1) Tensile strength of the obtained fin material (MPa)
(2) Heating was performed at 600 to 605 ° C. for 3.5 minutes assuming a brazing temperature, and the following items were measured after cooling.
[1] Tensile strength (MPa)
[2] After the surface is electropolished and the grain structure is revealed by the Barker method, the grain size parallel to the rolling direction by the cutting method (μm)
[3] Natural potential (mV) after 60 min immersion in 5% saline using silver-silver chloride electrode as reference electrode
[4] Corrosion current density (μA / cm ² ) obtained from cathodic polarization using a silver-silver chloride electrode as a reference electrode in 5% saline at a potential sweep rate of 20 mV / min
[5] Conductivity [% IACS] according to the conductivity test method described in JIS-H0505

(3) Sag amount (mm) with a protruding length of 50 mm by the sag test method described in LWS T 8801
(4) Place the fin material processed into corrugated on the brazing material surface of brazing sheet (brazing material 4045 alloy clad rate 8%) with non-corrosive fluoride flux applied (load load) 324 g), and heated to 605 ° C. at a heating rate of 50 ° C./min and held for 5 min. After cooling, the brazed cross section was observed, and a slight erosion of the fin material crystal grain boundary was judged as good (◯ mark), and a erosion was severe and the fin material melted markedly as poor (x mark). The corrugated shape was as follows.
Corrugated shape: height 2.3 mm × width 21 mm × pitch 3.4 mm, 10 peaks The results are shown in Tables 5-7.

From the results of Table 5, it can be seen that the fin materials (fin material numbers 1 to 5) according to the present invention have good tensile strength, erosion resistance, sag resistance, sacrificial anode effect and self-corrosion resistance after brazing. . Fin material number 6 of the comparative example has a low Mn content and a low tensile strength after brazing.
The fin material No. 7 of the comparative example had a large Mn content, a large crystallized product was generated during casting, cracking occurred during cold rolling, and a fin material was not obtained. Fin material number 8 of the comparative example has a low Si content and a low tensile strength after brazing. Fin material number 9 of the comparative example had a large Si content and was inferior in erosion resistance. The fin material No. 10 of the comparative example had a large Fe content, a large crystallized product was generated during casting, cracks occurred during cold rolling, and a fin material was not obtained.

  Fin material number 11 of the comparative example had a low Zn content, a natural potential was noble, and the sacrificial anode effect was inferior. Fin material number 12 of the comparative example had a large Zn content, inferior self-corrosion resistance, and inferior in erosion resistance. Conventional DC casting (thickness 500 mm, solidification cooling rate about 1 ° C./sec), chamfering, soaking, hot rolling, cold rolling (thickness 100 μm), intermediate annealing (400 ° C. × 2 hr), cooling The fin material number 13 of the comparative example with low Mn content obtained by hot rolling and the fin material number 14 of the comparative example with low Si and Mn content have low tensile strength after brazing, and the crystal grain size after brazing The sag resistance and erosion resistance were inferior.

  From the results shown in Table 6, the fin materials according to the present invention (fin material numbers 1, 15, and 16) have a tensile strength before brazing of 240 MPa or less and excellent moldability, and have a tensile strength, erosion resistance, and sag resistance after brazing. It turns out that all of sex is favorable. The fin material number 17 of the comparative example had a final cold rolling rate of 60%, and therefore had high tensile strength before brazing and poor moldability. Since the fin material numbers 18 and 19 of the comparative examples had a high temperature in the first intermediate annealing treatment, the structure after brazing was not recrystallized, and the sag resistance and the erosion resistance were inferior. The fin material number 20 of the comparative example has a final cold rolling rate of 60%, and thus has a high tensile strength before brazing heating and is inferior in erosion resistance. The fin material numbers 21 and 22 of the comparative examples had a high tensile strength before brazing heating and a poor moldability because the temperature of the second intermediate annealing treatment was low. The fin material numbers 23 and 25 of the comparative examples had a low tensile strength before brazing heating because the temperature of the secondary annealing treatment was low, and the moldability was poor. Since the fin material number 24 of the comparative example had a high temperature for the second intermediate annealing treatment, recrystallization occurred and the erosion resistance was inferior.

  From the results of Table 7, the fin material according to the present invention (fin material numbers 26 to 29) has a tensile strength before brazing of 240 MPa or less and excellent moldability, and has a high tensile strength, erosion resistance and sag resistance after brazing. It turns out that all are good. The fin material No. 30 of the comparative example was inferior in erosion resistance because recrystallization occurred because the temperature of the final annealing treatment was high. The fin material No. 31 of the comparative example has a low tensile strength before brazing heating because the temperature of the final annealing treatment is low, and the moldability is poor.

  According to the present invention, it has an appropriate tensile strength before brazing that facilitates fin molding and high strength after brazing, and is excellent in heat transfer characteristics, sag resistance, erosion resistance, self-corrosion resistance, and sacrificial anode effect. An aluminum alloy fin material for a heat exchanger is provided.

Claims (6)

  Si: 0.8-1.4 wt%, Fe: 0.15-0.7 wt%, Mn: 1.5-3.0 wt%, Zn: 0.5-2.5 wt%, and further as impurities A molten slab with a thickness of 5 to 10 mm is continuously cast by a twin-belt casting machine by pouring a molten metal having a chemical composition consisting of ordinary impurities and Al, with Mg limited to 0.05 wt% or less. After being wound on a roll, it is cold-rolled to a plate thickness of 1.0 to 6.0 mm, subjected to first intermediate annealing at 200 to 350 ° C., and further cold-rolled to obtain a plate thickness of 0.05 Cold rolling to ˜0.4 mm, subjecting to secondary intermediate annealing at 360 to 450 ° C., and performing cold rolling with a final cold rolling rate of less than 10 to 50% to obtain a final thickness of 40 to 200 μm. A method for producing a high-strength aluminum alloy fin material for a heat exchanger.   Si: 0.8-1.4 wt%, Fe: 0.15-0.7 wt%, Mn: 1.5-3.0 wt%, Zn: 0.5-2.5 wt%, and further as impurities A molten slab with a thickness of 5 to 10 mm is continuously cast by a twin-belt casting machine by pouring a molten metal having a chemical composition consisting of ordinary impurities and Al, with Mg limited to 0.05 wt% or less. After being wound on a roll, it is cold-rolled to a thickness of 1.0 to 6.0 mm, subjected to a first intermediate annealing at 200 to 450 ° C., and further cold-rolled to obtain a thickness of 0.08. Cold rolling to ˜2.0 mm, second intermediate annealing at 360 to 450 ° C., and cold rolling with a cold rolling rate of 50 to 96% to obtain a final thickness of 40 to 200 μm at 200 to 400 ° C. A method for producing a high-strength aluminum alloy fin material for a heat exchanger, characterized by performing final annealing.   2. The method according to claim 1, wherein the first intermediate annealing is performed by a continuous annealing furnace at a temperature rising rate of 100 ° C./min or more and a holding temperature of 400 to 500 ° C. within a holding time of 5 minutes.   The method according to claim 2, wherein the first intermediate annealing is performed by a continuous annealing furnace at a temperature rising rate of 100 ° C./min or more and a holding temperature of 400 to 500 ° C. within a holding time of 5 minutes.   4. The method according to claim 1, wherein the metal structure is an unrecrystallized structure or a partially recrystallized structure at any stage after the first intermediate annealing and after the second intermediate annealing.   5. The method according to claim 2, wherein the metal structure is an unrecrystallized structure at any stage after the first intermediate annealing, after the second intermediate annealing, and after the final annealing.