Aluminum alloy brazing sheet

Abstract

An aluminum alloy brazing sheet may include a sacrificial material having a function of a brazing material on at least one surface of a core material, wherein the sacrificial material has a composition containing: in a mass %, 2% to 5% of Si; 3% to 5% of Zn; and an Al balance with inevitable impurities the core material is made of an Al—Mn-based alloy, an in the core material before brazing, Al—Mn based secondary particles having an equivalent circle diameter of 100 to 400 nm are distributed with a number density of 0.3 to 5 particles/μm.sup.2.

Claims

1. An aluminum alloy brazing sheet, comprising: a sacrificial material having a function of a brazing material on at least one surface of a core material, wherein the sacrificial material has a composition comprising, in mass %: 2.0% to 5.0% of Si; 3.0% to 5.0% of Zn; and Al, wherein the core material comprises an Al—Mn-based alloy, and in the core material before brazing, Al—Mn-based secondary particles having an equivalent circle diameter of 150 to 400 nm are distributed with a number density of 0.3 to 5 particles/μm.sup.2.

2. The sheet of claim 1, wherein when the sheet is subjected to a heat treatment equivalent to brazing in which a temperature is raised from 590° C. to 615° C., a Mn/Si ratio is 0.5 to 5.0 in a region of 50 μm from the sacrificial material/core material interface.

3. The sheet of claim 1, wherein the core material comprises, in mass %: 0.3% to 2.0% of Mn; 0.05% to 1.0% of Si; 0.01% to 1.0% of Cu; and 0.1% to 0.7% of Fe.

4. The sheet of claim 1, wherein the sacrificial material further comprises, in mass %: 0.1% to 1.0% of Mn; and/or 0.1% to 0.7% of Fe.

5. The sheet of claim 1, wherein when the sheet is subjected to a heat treatment equivalent to brazing in which a temperature is raised from 590° C. to 615° C., an eutectic filler and a primary filler are formed in the sacrificial material, wherein after the heat treatment, a pitting potential is less noble in an order of the eutectic filler, the primary filler, and the sacrificial material/core material interface, and wherein after the heat treatment, a potential difference between a most noble layer in the sacrificial material and a least noble layer in the core material is 50 to 200 mV.

6. The sheet of claim 2, wherein the core material comprises, in mass %: 0.3% to 2.0% of Mn; 0.05% to 1.0% of Si; 0.01% to 1.0% of Cu; and 0.1% to 0.7% of Fe.

7. The sheet of claim 2, wherein the sacrificial material further comprises, in mass %: 0.1% to 1.0% of Mn; and/or 0.1% to 0.7% of Fe.

8. The sheet of claim 3, wherein the sacrificial material further comprises, in mass %: 0.1% to 1.0% of Mn; and/or 0.1% to 0.7% of Fe.

9. The sheet of claim 6, wherein the sacrificial material further comprises, in mass %: 0.1% to 1.0% of Mn; and/or 0.1% to 0.7% of Fe.

10. The sheet of claim 2, wherein when the sheet is subjected to a heat treatment equivalent to brazing in which a temperature is raised from 590° C. to 615° C., an eutectic filler and a primary filler are formed in the sacrificial material, wherein after the heat treatment, a pitting potential is less noble in an order of the eutectic filler, the primary filler, and the sacrificial material/core material interface, and wherein after the heat treatment, a potential difference between a most noble layer in the sacrificial material and a least noble layer in the core material is 50 to 200 mV.

11. The sheet of claim 3, wherein when the sheet is subjected to a heat treatment equivalent to brazing in which a temperature is raised from 590° C. to 615° C., an eutectic filler and a primary filler are formed in the sacrificial material, wherein after the heat treatment, a pitting potential is less noble in an order of the eutectic filler, the primary filler, and the sacrificial material/core material interface, and wherein after the heat treatment, a potential difference between a most noble layer in the sacrificial material and a least noble layer in the core material is 50 to 200 mV.

12. The sheet of claim 4, wherein when the sheet is subjected to a heat treatment equivalent to brazing in which a temperature is raised from 590° C. to 615° C., an eutectic filler and a primary filler are formed in the sacrificial material, wherein after the heat treatment, a pitting potential is less noble in an order of the eutectic filler, the primary filler, and the sacrificial material/core material interface, and wherein after the heat treatment, a potential difference between a most noble layer in the sacrificial material and a least noble layer in the core material is 50 to 200 mV.

13. The sheet of claim 6, wherein when the sheet is subjected to a heat treatment equivalent to brazing in which a temperature is raised from 590° C. to 615° C., an eutectic filler and a primary filler are formed in the sacrificial material, wherein after the heat treatment, a pitting potential is less noble in an order of the eutectic filler, the primary filler, and the sacrificial material/core material interface, and wherein after the heat treatment, a potential difference between a most noble layer in the sacrificial material and a least noble layer in the core material is 50 to 200 mV.

14. The sheet of claim 7, wherein when the sheet is subjected to a heat treatment equivalent to brazing in which a temperature is raised from 590° C. to 615° C., an eutectic filler and a primary filler are formed in the sacrificial material, wherein after the heat treatment, a pitting potential is less noble in an order of the eutectic filler, the primary filler, and the sacrificial material/core material interface, and wherein after the heat treatment, a potential difference between a most noble layer in the sacrificial material and a least noble layer in the core material is 50 to 200 mV.

15. The sheet of claim 8, wherein when the sheet is subjected to a heat treatment equivalent to brazing in which a temperature is raised from 590° C. to 615° C., an eutectic filler and a primary filler are formed in the sacrificial material, wherein after the heat treatment, a pitting potential is less noble in an order of the eutectic filler, the primary filler, and the sacrificial material/core material interface, and wherein after the heat treatment, a potential difference between a most noble layer in the sacrificial material and a least noble layer in the core material is 50 to 200 mV.

16. The sheet of claim 9, wherein when the sheet is subjected to a heat treatment equivalent to brazing in which a temperature is raised from 590° C. to 615° C., an eutectic filler and a primary filler are formed in the sacrificial material, wherein after the heat treatment, a pitting potential is less noble in an order of the eutectic filler, the primary filler, and the sacrificial material/core material interface, and wherein after the heat treatment, a potential difference between a most noble layer in the sacrificial material and a least noble layer in the core material is 50 to 200 mV.

17. The sheet of claim 1, wherein the sacrificial material comprises 2.5 mass % to 5.0 mass % of Si.

18. The sheet of claim 1, wherein the sacrificial material comprises the Al, the Si, and the Zn, inevitable impurities, and optionally Mn in a range of from 0.1 to 1.0 mass % and/or Fe in a range of from 0.1 to 0.7 mass %.

19. The sheet of claim 1, wherein the sacrificial material comprises 2.0 mass % to 4.0 mass % of Si.

20. The sheet of claim 1, wherein when an inverted T-shaped test is performed using the sheet having an upper surface as the sacrificial material for a horizontal material and using an A3003 alloy for a vertical material, unjoined parts are not formed and erosion of 150 μm or more from the sacrificial material/core material interface in the core material direction does not occur.

Description

DESCRIPTION OF EMBODIMENTS

(1) Hereinafter, embodiments of the present invention will be described.

(2) An aluminum alloy for a core material and an aluminum alloy for a sacrificial material having a composition of the present invention are prepared. These alloys can be produced by a conventional method, and the production method is not particularly limited. For example, it can be manufactured by semi-continuous casting.

(3) An Al—Mn-based alloy is used as the aluminum alloy for the core material, and an Al—Zn—Si-based alloy is used as the aluminum alloy for the sacrificial material.

(4) For the Al—Mn-based alloy for the core material, an alloy containing a composition of Mn: 0.3% to 2%, Si: 0.05% to 1%, Cu: 0.01% to 1.0%, Fe: 0.1% to 0.7% in terms of mass % and a balance of Al and inevitable impurity can be suitably used. However, in the present invention, the composition of the Al—Mn-based alloy is not limited to the above.

(5) For the aluminum alloy for the sacrificial material, an alloy preferably containing Si: 2.0% to 5.0% and Zn: 3.0% to 5.0%, and if desired, in terms of mass %, one kind or two or more kinds of Mn: 0.1% to 1.0% and Fe: 0.1% to 0.7% can be used.

(6) The aluminum alloy for the core material or the aluminum alloy for the sacrificial material can be subjected to the homogenization treatment, if desired, after being melted. The conditions of the homogenization treatment are not particularly limited, and for example, the core material can be subjected to the homogenization treatment at 400° C. to 600° C. for 4 to 16 hours, and the sacrificial material can be subjected to the homogenization treatment at 400° C. to 500° C. for 4 to 16 hours.

(7) The aluminum alloy for the core material and the aluminum alloy for the sacrificial material is obtained as plate materials through the hot rolling. In addition, these may be obtained as plate materials through continuous casting and rolling.

(8) These plate materials are clad with an appropriate clad ratio in a state where the sacrificial material is disposed on one surface or both surfaces of the core material and to be overlapped. In a case of disposing the sacrificial material on one surface of the core material, a sacrificial material having other compositions may be overlapped on another surface thereof.

(9) The cladding is generally performed by hot rolling. Then, cold rolling is further performed to obtain an aluminum alloy brazing sheet having a desired thickness.

(10) In the present invention, a clad ratio of a clad material is not particularly limited, and for example, 5% to 25% of a sacrificial material thickness, 75% to 95% of a core material thickness, or the like is used.

(11) The clad material is cold-rolled to a thickness of 0.15 to 0.80 mm. In the middle of cold rolling, process annealing may be performed. The conditions for process annealing can be selected from a range of 200° C. to 380° C. and 1 to 6 hours.

(12) After the cold rolling, final annealing can be performed. The final annealing is performed under the conditions at 400° C. for 4 hours, for example.

(13) The obtained clad material can be used, for example, as a tube material for a heat exchanger.

(14) The tube material for the heat exchanger is brazed and joined to an appropriate brazing member such as an inner fin.

(15) A material, a shape, and the like of the brazing member are not particularly limited in this invention, and aluminum material can be suitably used.

(16) As a result of the brazing, a heat exchanger tube is obtained.

(17) The heat treatment conditions at the time of brazing are not particularly limited, except that the temperature is raised to 590° C. to 615° C. For example, the heat treatment can be performed under the conditions in which the heating is performed at a temperature increase rate such that the time to reach a target temperature from 550° C. is 1 to 10 minutes, the temperature is maintained at the target temperature of 590° C. to 615° C. for 1 minute to 20 minutes, then, cooling is performed to 300° C. at 50 to 100° C./min, and then air cooling is performed to room temperature.

Example 1

(18) Aluminum alloys for the sacrificial material and the core material were cast by semi-continuous casting. The alloys shown in examples (balance of Al and inevitable impurity) were used as the aluminum alloys for the sacrificial material and the core material. Each alloy was subjected to the homogenization treatment for 10 hours under temperature conditions shown in the examples.

(19) Next, the hot rolling was performed under predetermined conditions, and cold rolling was further performed to obtain a plate thickness of 0.5 mm. After that, the annealing was carried out for 3 hours under the temperature conditions described in the examples to prepare a plate material having temper O.

(20) Manufacturing Process

(21) Homogenization Treatment

(22) After slab casting, the homogenization treatment is performed for the purpose of removing inhomogeneous structures such as segregation.

(23) Due to the high-temperature homogenization treatment, an additive element supersaturated and solid-solved in a matrix is precipitated as an intermetallic compound during casting. Since a size or a distribution amount of the precipitated intermetallic compound is affected by the temperature and time of the homogenization treatment, it is necessary to select the heat treatment conditions according to the type of the additive element.

(24) Hot Rolling Finishing Temperature

(25) Normally, the hot rolling is loaded at a high temperature of approximately 500° C., but after the rolling is completed, it is coiled and cooled to room temperature. In this case, a holding time at a high temperature changes depending on the finishing temperature of hot rolling, and accordingly, it affects the precipitation behavior of the intermetallic compound.

(26) Brazing Process

(27) The heat treatment equivalent to brazing was performed by a method for increasing the temperature from room temperature to 590° C. to 615° C. in approximately 20 minutes, holding the temperature at 590° C. to 615° C. for 3 to 20 minutes, and then controlling the cooling from 590° C. to 615° C. to 300° C. at a cooling rate of 100° C./min

(28) Evaluation Method

(29) Distribution State of Dispersoids

(30) The equivalent circle diameter and the number density (particles/μm.sup.2) of the dispersoids were measured by a scanning electron microscope (FE-SEM).

(31) In the measurement method, a cross section of the plate material (parallel cross section in a rolling direction) was exposed to a sample material before brazing heat treatment by mechanical polishing and cross section polisher (CP) processing to manufacture a sample, and images were captured with FE-SEM at 10,000 to 50,000 times. The images were captured at 10 fields of view, and the equivalent circle diameter and the number density of the dispersoids were measured by image analysis.

(32) Pitting Potential Measurement

(33) The pitting potential was measured by anodic polarization measurement. A saturated calomel electrode (SCE) was used as a reference electrode, and an electrolyte was measured under the conditions of a 2.67% AlCl.sub.3 solution at 40° C., which was sufficiently degassed by blowing high-purity N.sub.2 gas, and a sweep rate was 0.5 mV/s.

(34) The potential measurement of the eutectic filler of sacrificial material, the sacrificial material/core material interface layer, and the core material was performed after etching and removing a sample after a brazing heat treatment from an outermost surface of the sacrificial material with 5% NaOH (caustic soda) to obtain a predetermined plate thickness. The potential measurement of the primary filler of sacrificial material was performed after the eutectic filler of sacrificial material having the lowest potential was completely eliminated by anodic dissolution.

(35) Element Diffusion State and Mn/Si Ratio after Brazing

(36) The Zn, Cu, Fe, and Si concentrations in a plate thickness direction of the sample after brazing were measured by EPMA ray analysis. The Mn concentration was measured for each layer by EPMA semi-quantitative analysis. Since Mn has an extremely slow diffusion rate with respect to an Al matrix and shows a substantially constant concentration in each layer regardless of the plate thickness direction, it was measured at an arbitrary position in the plate thickness direction. In the line analysis, only the count number was analyzed, but it was determined whether the diffusion state in each layer was uniform. As a result, the Mn/Si ratio in region of 50 μm from sacrificial material/core material interface in core material depth direction was calculated. The concentration ratio is calculated in terms of % by weight.

(37) The Mn/Si ratio after brazing greatly depends on, not only the alloy component, but also the heat treatment conditions. Generally, when heat treatment is performed at a high temperature, the precipitation and growth of dispersoids are promoted, and the solid solubility of Mn and Si decreases. It is necessary to control the Mn/Si ratio by appropriately combining the homogenization treatment, the hot rolling, and the annealing temperature conditions.

(38) OY Water Immersion Corrosion Test

(39) An immersion test with OY water (Cl—: 195 ppm, SO4.sup.2−: 60 ppm, Cu.sup.2+: 1 ppm, Fe.sup.3+: 30 ppm, and balance of pure water) was carried out. In test conditions, room temperature×16 h+88° C.×8 h (without stirring) was defined as a daily cycle, and evaluation was performed up to 12 weeks. A corrosion depth was measured and the presence or absence of intergranular corrosion was confirmed. The evaluation results are shown by A, B, C, and D in the corrosion resistance evaluation in Table 1.

(40) [Evaluation Criteria] D: Significant intergranular corrosion occurred, C: Both intergranular corrosion and transgranular corrosion occur, B: Intergranular corrosion (minor) and transgranular corrosion occurs, A: Only transgranular corrosion Regarding the corrosion resistance, although the intergranular corrosion does not occur, if through holes are generated in the OY water immersion corrosion test for 12 weeks, it is evaluated as D.

(41) Inverted T-Shaped Fluidity Test

(42) In order to evaluate the brazability, an inverted T-shaped test was performed using a sample material having an upper surface as the sacrificial material for a horizontal material and using an A3003 alloy for a vertical material. The evaluation results are indicated by A and B based on the brazability evaluation in Table 1.

(43) [Evaluation Criteria] A: No unjoined parts, B: There are unjoined parts. In addition, a material in which the erosion of 150 μm or more from the sacrificial material/core material interface in the core material direction was also evaluated as B.

(44) TABLE-US-00001 TABLE 1 Alloy composition Alloy composition Condition for Finishing of sacrificial material of core material core material temperature Final Sample material (mass %) (mass %) homogenization of hot annealing No. Si Zn Mn Fe Mn Si Cu Fe treatment rolling temperature Example 1 2.02 4.02 0.01 0.02 1.12 0.01 0.49 0.38 450° C., 10 h 433° C. 360° C. 2 4.88 4.02 0.02 0.03 1.13 0.51 0.50 0.40 450° C., 10 h 430° C. 362° C. 3 3.52 3.11 0.01 0.02 1.15 0.50 0.01 0.40 450° C., 10 h 440° C. 362° C. 4 3.52 4.90 0.01 0.01 1.15 0.50 0.50 0.37 450° C., 10 h 428° C. 365° C. 5 3.55 4.02 0.14 0.01 1.12 0.48 0.51 0.40 580° C., 10 h 440° C. 440° C. 6 3.54 3.99 0.95 0.30 1.15 0.50 0.50 0.33 450° C., 10 h 450° C. 436° C. 7 3.50 3.58 0.52 0.15 1.16 0.50 0.51 0.40 400° C., 10 h 351° C. 402° C. 8 3.54 3.44 0.52 0.66 1.15 0.47 0.50 0.41 450° C., 10 h 429° C. 500° C. 9 3.51 3.40 0.51 0.44 0.35 0.50 0.52 0.03 450° C., 10 h 430° C. 430° C. 10 3.50 3.62 0.52 0.40 1.90 0.50 0.50 0.40 450° C., 10 h 420° C. 420° C. 11 3.49 3.49 0.51 0.41 1.15 0.10 0.51 0.41 500° C., 10 h 440° C. 415° C. 12 4.02 3.98 0.50 0.43 1.17 0.95 0.50 0.43 450° C., 10 h 408° C. 408° C. 13 4.02 4.00 0.53 0.44 1.15 0.50 0.10 0.39 450° C., 10 h 430° C. 430° C. 14 4.11 3.99 0.48 0.42 1.18 0.48 0.95 0.40 450° C., 10 h 380° C. 360° C. 15 4.10 4.02 0.53 0.44 0.25 0.50 0.50 0.13 450° C., 10 h 422° C. 422° C. 16 3.98 3.97 0.50 0.41 1.14 0.47 0.51 0.68 450° C., 10 h 408° C. 408° C. 17 3.50 3.21 0.01 0.01 1.15 0.11 1.05 0.42 450° C., 10 h 425° C. 362° C. 18 3.51 3.82 0.01 0.02 1.80 0.80 0.55 0.81 450° C., 10 h 428° C. 358° C. 19 3.55 3.85 0.02 0.01 1.15 1.12 0.47 0.39 450° C., 10 h 420° C. 361° C. 20 3.40 3.88 0.01 0.01 0.20 0.40 0.50 0.40 450° C., 10 h 428° C. 361° C. 21 4.52 3.12 1.10 0.01 1.12 0.51 0.52 0.41 580° C., 10 h 433° C. 365° C. 22 3.55 3.85 0.02 0.01 0.33 0.48 0.50 0.39 380° C., 20 h 430° C. 358° C. 23 2.12 3.90 0.01 0.02 1.20 0.15 0.47 0.41 620° C., 8 h  431° C. 360° C. Comparative 24 1.89 4.02 0.01 0.01 1.15 0.50 0.50 0.40 450° C., 10 h 422° C. 362° C. example 25 5.22 4.02 0.02 0.02 1.15 0.48 0.50 0.35 450° C., 10 h 425° C. 364° C. 26 3.52 2.85 0.03 0.03 1.15 0.50 0.49 0.38 450° C., 10 h 415° C. 362° C. 27 3.52 5.12 0.01 0.02 0.50 0.10 0.10 0.40 450° C., 10 h 430° C. 360° C. 28 3.20 3.95 0.01 0.02 1.15 0.50 0.50 0.41 580° C., 10 h 438° C. 480° C. 29 3.52 3.90 0.51 0.81 1.15 0.49 0.48 0.40 580° C., 10 h 450° C. 451° C. 30 3.50 3.70 0.44 0.17 1.14 0.48 0.49 0.38 400° C., 10 h 352° C. 300° C. Potential difference Number density of most noble layer of Al—Mn in sacrificial based secondary Mn/Si ratio in material and least particles in region immediately noble layer in core material below sacrificial core material Evaluation of Sample material before brazing material/interface after brazing Evaluation of corrosion No. (particles/μm.sup.2) after brazing (mV) brazability resistance Example 1 1.4 4.6 180 A B 2 1.4 1.2 60 A B 3 1.5 1.8 100 A B 4 1.5 1.9 190 A B 5 0.3 1.9 155 A B 6 1.0 1.8 100 A A 7 3.5 1.9 110 A A 8 0.7 1.9 110 A A 9 0.6 0.6 40 A B 10 4.8 3.3 120 A A 11 0.9 3.0 130 A A 12 1.6 0.7 100 A A 13 1.5 1.8 160 A A 14 4.0 1.6 185 A B 15 0.3 0.5 70 A B 16 1.5 1.8 120 A A 17 1.4 1.6 150 A C 18 2.0 1.3 110 A C 19 2.2 1.0 80 A C 20 0.3 0.3 110 A C 21 1.0 1.3 45 A C 22 0.8 0.4 70 A C 23 1.0 5.1 210 A C Comparative 24 1.4 4.6 160 B B example 25 1.4 1.2 40 B D 26 1.5 1.9 45 A D 27 1.4 1.0 210 A D 28 0.2 1.9 160 A D 29 0.2 1.8 130 A D 30 5.2 1.8 110 B B