ALUMINUM ALLOY HEAT EXCHANGER FOR EXHAUST GAS RECIRCULATION SYSTEM

Abstract

An aluminum alloy heat exchanger for an exhaust gas recirculation system, the heat exchanger obtained by brazing: a tube material comprising a core material comprising 0.05 mass % to 1.50 mass % of Si, 0.05 mass % to 3.00 mass % of Cu, and 0.40 mass % to 2.00 mass % of Mn, and a sacrificial anticorrosion material comprising 2.00 mass % to 6.00 mass % of Zn, clad on an inner side surface of the core material; and a fin material comprising a core material comprising 0.05 mass to 1.50 mass % of Si, and 0.40 mass % to 2.00 mass % of Mn, and a brazing material comprising 3.00 mass % to 13.00 mass % of Si, clad on both surfaces of the core material; the heat exchanger having a ratio of a surface area S.sub.b (mm.sup.2) of the fin material to a surface area S.sub.a (mm.sup.2) of the sacrificial anticorrosion material of less than 200%.

Claims

1-6. (canceled)

7. An aluminum alloy heat exchanger for an exhaust gas recirculation system, which is a heat exchanger installed in an exhaust gas recirculation system of an internal combustion engine, with an ammonium ion concentration of 100 ppm or more in condensed water of an exhaust gas, to cool the exhaust gas, the heat exchanger obtained by brazing: a tube material comprising at least a core material made of aluminum alloy comprising 0.05 mass % or more and 1.50 mass % or less of Si, 0.05 mass % or more and 3.00 mass % or less of Cu, and 0.40 mass % or more and 2.00 mass % or less of Mn, and optionally one or more selected from the group consisting of 0.05 mass % or more and 0.50 mass % or less of Mg, 0.10 mass % or more and 1.00 mass % or less of Fe, 0.05 mass % or more and 1.00 mass % or less of Ni, 0.05 mass % or more and 0.30 mass % or less of Cr, 0.05 mass % or more and 0.30 mass % or less of Zr, 0.05 mass % or more and 0.30 mass % or less of Ti, and 0.05 mass % or more and 0.30 mass % or less of V, with the balance being Al and unavoidable impurities, and a sacrificial anticorrosion material made of aluminum alloy comprising 2.00 mass % or more and 6.00 mass % or less of Zn, and optionally one or more selected from the group consisting of 0.05 mass % or more and 2.00 mass % or less of Mn, 0.05 mass % or more and 0.50 mass % or less of Mg, 0.10 mass % or more and 1.00 mass % or less of Fe, 0.05 mass % or more and 1.00 mass % or less of Ni, 0.05 mass % or more and 0.50 mass % or less of Si, 0.05 mass % or more and 0.30 mass % or less of In, 0.05 mass % or more and 0.30 mass % or less of Sn, 0.05 mass % or more and 0.30 mass % or less of Ti, 0.05 mass % or more and 0.30 mass % or less of V, 0.05 mass % or more and 0.30 mass % or less of Cr, and 0.05 mass % or more and 0.30 mass % or less of Zr, with the balance being Al and unavoidable impurities, clad on an inner side surface of the core material; and a fin material comprising a core material made of aluminum alloy comprising 0.05 mass % or more and 1.50 mass % or less of Si, and 0.40 mass % or more and 2.00 mass % or less of Mn, and optionally one or more selected from the group consisting of 0.05 mass % or more and 0.50 mass % or less of Mg and 0.10 mass % or more and 1.00 mass % or less of Fe, with the balance being Al and unavoidable impurities, and a first brazing material clad on one surface of the core material and a second brazing material clad on another surface of the core material, wherein the first brazing material made of aluminum alloy comprising 3.00 mass % or more and 13.00 mass % or less of Si, with the balance being Al and unavoidable impurities, the second brazing material made of aluminum alloy comprising 3.00 mass % or more and 13.00 mass % or less of Si, with the balance being Al and unavoidable impurities; the heat exchanger having a ratio of a surface area Sb (mm.sup.2) of the brazing material of the fin material on an inner side of the tube (a total surface area of the first brazing material and the second brazing material) to a surface area Sa (mm.sup.2) of the sacrificial anticorrosion material of the tube material constituting the inner side of the tube, i.e., ((Sb/Sa)x100), of less than 200%.

8. The aluminum alloy heat exchanger for an exhaust gas recirculation system according to claim 7, wherein the tube material comprises a brazing material comprising 3.00 mass % or more and 13.00 mass % or less of Si, with the balance being Al and unavoidable impurities, clad on a surface opposite to the surface clad with the sacrificial anticorrosion material of the tube material.

9. The aluminum alloy heat exchanger for an exhaust gas recirculation system according to claim 8, wherein the brazing material of the tube material further comprises 1.00 mass % or more and 3.00 mass % or less of Zn.

Description

EXAMPLES

Examples, Comparative Examples and Reference Examples

<Preparation of Tube Material>

[0069] Each of aluminum alloy ingots for the core material, the sacrificial anticorrosion material and the brazing material of the tube material having a composition shown in Tables 1 to 3 was cast by semi-continuous casting, which was machine-finished to be plane and subject to homogenization treatment at 520 C. for 6 hours.

[0070] Subsequently, based on the combination shown in Table 5, the ingot for the sacrificial anticorrosion material was overlapped on one surface of the ingot for the core material. When a brazing material is clad, an ingot for the brazing material is overlapped on the opposite surface. Thereby overlapped ingots were prepared. The thickness of the sacrificial anticorrosion material and thickness of the brazing material were adjusted such that each had a clad ratio of 10%.

[0071] Subsequently, the overlapped ingots were heat treated up to 520 C. before the step of hot rolling, and immediately hot rolled to make a two-layer or three-layer clad plate having a thickness of 3.5 mm. Subsequently, the clad plate obtained was cold rolled to a thickness of 0.30 mm, and then annealed at 500 C. for 2 hours. Through the steps described above, a two-layer or three-layer tube material having a whole thickness of 0.30 mm and a clad ratio of the sacrificial anticorrosion material layer of 10% was prepared.

<Preparation of Fin Material>

[0072] Each of aluminum alloy ingots for the brazing material and the core material for a fin material shown in Table 3 and Table 4 was cast by semi-continuous casting, which was machine-finished and subject to homogenization treatment at 520 C. for 6 hours.

[0073] Subsequently, based on the combination shown in Table 5, an ingot for the brazing material was overlapped on both surfaces of an ingot for the core material to prepare an ingot. The thickness of the brazing material was adjusted such that each had a clad ratio of 10%.

[0074] Subsequently, the overlapped ingots were heat treated up to 520 C. before the step of hot rolling, and immediately hot rolled to make a three-layer clad plate having a thickness of 3.5 mm. Further, cold rolling and final annealing at 390 to 450 C. for 4 hours were performed to prepare a three-layer fin material having a thickness of about 0.1 mm.

<Preparation of Test Sampler for Evaluation>

[0075] The fin material obtained above was slit into a width of 16 mm, corrugated, and formed into a fin shape for a heat exchanger.

[0076] Subsequently, the tube material was cut into a width of 16 mm and a length of 70 mm to prepare a test piece of tube material, and a KF-AlF-based flux (KAlF.sub.4 or the like) powder was applied to the surface of the sacrificial anticorrosion material of the test piece of tube material.

[0077] Subsequently, the corrugated fin material was sandwiched between two test pieces of the tube material, such that the surface of the sacrificial anticorrosion was on the fin side, and brazing heating was performed at 600 C. for 3 minutes in a nitrogen atmosphere. On this occasion, the fin pitch of the fins formed by corrugation was adjusted to change the surface area of the fin material of a test sample for evaluation, so that the ratio of the surface area S.sub.b (mm.sup.2) of the fin material to the surface area S.sub.a (mm.sup.2) of the sacrificial anticorrosion material of the tube material was adjusted. After brazing heating, a test sample for evaluation was prepared with temperature decreased to room temperature.

(Measurement of Pitting Potential)

[0078] A tube and a fin were cut out from the test sample for evaluation, and portions other than the measurement surface were masked with epoxy resin. These were used as test materials, and as a pretreatment, the surfaces of the test materials were cleaned by immersing in a 5% NaOH aqueous solution at 60 C. for 30 seconds and in a 30% HNO.sub.3 aqueous solution for 60 seconds. Subsequently, acetic acid was added to a 5% NaCl aqueous solution to adjust to pH 3, which was subjected to deaeration with nitrogen for 30 minutes to prepare a measurement solution. The tube or the fin was immersed in the measurement solution at 25 C., and an anodic polarization curve was measured using a potentiostat. In the polarization curve, the potential at which the current suddenly increased was defined as the pitting potential. The results are shown in Table 5.

(Corrosion Resistance)

[0079] A test sample for evaluation was subjected to a cycle corrosion test including spraying for 2 hours (spray amount: 1 to 2 ml/80 cm.sup.2/h) using, as a spray liquid, an aqueous solution at pH 4.8 containing 500 ppm of ammonium, 6 ppm of hydrochloric acid, 10 ppm of sulfuric acid, 10 ppm of nitric acid, 1000 ppm of acetic acid and 1000 ppm of formic acid, drying (relative humidity: 20 to 30%) for 2 hours, and humidifying (relative humidity: 95% or more) for 2 hours. The temperature in the test chamber was set at 50 C., and the test time was set to 3000 hours. After completion of the test, the corrosion products were removed with concentrated nitric acid. The depth of the corroded pores generated on the surface of the sacrificial anticorrosion material was then measured by the focal depth method to determine a maximum one as the corrosion depth. A sample having a maximum corrosion depth of less than 100 m was considered to be good, and a sample having a maximum corrosion depth of 100 m or more was considered to be poor. The results are shown in Table 5.

TABLE-US-00001 TABLE 1 Si Cu Mn Fe Mg Ni Ti V Cr Zr Al A1 0.50 0.50 1.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 bal. A2 0.05 0.50 1.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 bal. A3 1.50 0.50 1.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 bal. A4 0.50 0.05 1.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 bal. A5 0.50 3.00 1.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 bal. A6 0.50 0.50 0.40 0.10 0.00 0.00 0.00 0.00 0.00 0.00 bal. A7 0.50 0.50 2.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 bal. A8 0.50 0.50 1.00 0.10 0.50 0.00 0.00 0.00 0.00 0.00 bal. A9 0.50 0.50 1.00 1.00 0.00 0.00 0.00 0.00 0.00 0.00 bal. A10 0.50 0.50 1.00 0.10 0.00 1.00 0.00 0.00 0.00 0.00 bal. A11 0.50 0.50 1.00 0.10 0.00 0.00 0.20 0.00 0.00 0.00 bal. A12 0.50 0.50 1.00 0.10 0.00 0.00 0.00 0.20 0.00 0.00 bal. A13 0.50 0.50 1.00 0.10 0.00 0.00 0.00 0.00 0.20 0.00 bal. A14 0.50 0.50 1.00 0.10 0.00 0.00 0.00 0.00 0.00 0.20 bal. A15 0.01 0.50 1.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 bal. A16 2.00 0.50 1.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 bal. A17 0.50 0.01 1.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 bal. A18 0.50 5.00 1.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 bal. A19 0.50 0.50 0.30 0.10 0.00 0.00 0.00 0.00 0.00 0.00 bal. A20 0.50 0.50 2.50 0.10 0.00 0.00 0.00 0.00 0.00 0.00 bal.

TABLE-US-00002 TABLE 2 Si Zn Mn Fe Mg Ni In Sn Ti V Cr Zr Al B1 0.05 3.00 0.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bal. B2 0.05 2.00 0.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bal. B3 0.05 6.00 0.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bal. B4 0.50 3.00 0.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bal. B5 0.05 3.00 2.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bal. B6 0.05 3.00 0.00 0.10 0.50 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bal. B7 0.05 3.00 0.00 1.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bal. B8 0.05 3.00 0.00 0.10 0.00 1.00 0.00 0.00 0.00 0.00 0.00 0.00 bal. B9 0.05 3.00 0.00 0.10 0.00 0.00 0.10 0.00 0.00 0.00 0.00 0.00 bal. B10 0.05 3.00 0.00 0.10 0.00 0.00 0.00 0.10 0.00 0.00 0.00 0.00 bal. B11 0.05 3.00 0.00 0.10 0.00 0.00 0.00 0.00 0.20 0.00 0.00 0.00 bal. B12 0.05 3.00 0.00 0.10 0.00 0.00 0.00 0.00 0.00 0.20 0.00 0.00 bal. B13 0.05 3.00 0.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.00 bal. B14 0.05 3.00 0.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 bal. B15 0.05 0.50 0.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bal. B16 0.60 3.00 0.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bal. B17 0.05 8.00 0.00 0.10 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bal.

TABLE-US-00003 TABLE 3 Si Zn Al D1 7.00 0.00 bal. D2 3.00 0.00 bal. D3 13.00 0.00 bal. D4 7.00 1.00 bal. D5 7.00 3.00 bal.

TABLE-US-00004 TABLE 4 Si Mn Fe Mg Al C1 0.50 1.00 0.10 0.00 bal. C2 0.05 1.00 0.10 0.00 bal. C3 1.50 1.00 0.10 0.00 bal. C4 0.50 0.40 0.10 0.00 bal. C5 0.50 2.00 0.10 0.00 bal. C6 0.50 1.00 0.10 0.05 bal. C7 0.50 1.00 0.10 0.50 bal. C8 0.50 1.00 0.20 0.00 bal. C9 0.50 1.00 1.00 0.00 bal. C10 0.01 1.00 0.10 0.00 bal. C11 2.00 1.00 0.10 0.00 bal. C12 0.50 0.20 0.10 0.00 bal. C13 0.50 2.50 0.10 0.00 bal.

TABLE-US-00005 TABLE 5 Tube/Core Tube/Sacrificial Tube/Brazing Fin/Core Fin/Brazing Surface area ratio Corrosion test material material material material material (Sb/Sa) 100 (%) .sup.1) result (m) Example 1 A1 B1 C1 D1 142 56 Example 2 A2 B1 C1 D1 140 56 Example 3 A3 B1 C1 D1 152 61 Example 4 A4 B1 C1 D1 140 62 Example 5 A5 B1 C1 D1 150 58 Example 6 A6 B1 C1 D1 158 55 Example 7 A7 B1 C1 D1 142 54 Example 8 A8 B1 C1 D1 156 64 Example 9 A9 B1 C1 D1 158 52 Example 10 A10 B1 C1 D1 150 54 Example 11 A11 B1 C1 D1 154 60 Example 12 A12 B1 C1 D1 140 62 Example 13 A13 B1 C1 D1 152 56 Example 14 A14 B1 C1 D1 154 68 Example 15 A1 B2 C1 D1 140 51 Example 16 A1 B3 C1 D1 156 55 Example 17 A1 B4 C1 D1 158 80 Example 18 A1 B5 C1 D1 150 62 Example 19 A1 B6 C1 D1 150 58 Example 20 A1 B7 C1 D1 148 58 Example 21 A1 B8 C1 D1 144 66 Example 22 A1 B9 C1 D1 144 58 Example 23 A1 B10 C1 D1 150 54 Example 24 A1 B11 C1 D1 154 52 Example 25 A1 B12 C1 D1 142 66 Example 26 A1 B13 C1 D1 146 52 Example 27 A1 B14 C1 D1 142 58 Example 28 A1 B1 C2 D1 150 68 Example 29 A1 B1 C3 D1 156 63 Example 30 A1 B1 C4 D1 150 70 Example 31 A1 B1 C5 D1 148 54 Example 32 A1 B1 C6 D1 150 60 Example 33 A1 B1 C7 D1 142 54 Example 34 A1 B1 C8 D1 144 60 Example 35 A1 B1 C9 D1 154 56 Example 36 A1 B1 C1 D2 152 60 Example 37 A1 B1 D1 C1 D3 150 51 Example 38 A1 B1 D2 C1 D1 146 56 Example 39 A1 B1 D3 C1 D1 142 58 Example 40 A1 B1 D4 C1 D1 148 62 Example 41 A1 B1 D5 C1 D1 150 50 Comparative Example 1 A1 B1 C1 D1 320 259 Comparative Example 2 A15 B1 C1 D1 144 202 Comparative Example 3 A16 B1 C1 D1 146 Comparative Example 4 A17 B1 C1 D1 150 191 Comparative Example 5 A18 B1 C1 D1 142 Comparative Example 6 A19 B1 C1 D1 144 194 Comparative Example 7 A20 B1 C1 D1 Comparative Example 8 A1 B15 C1 D1 158 205 Comparative Example 9 A1 B16 C1 D1 146 220 Comparative Example 10 A1 B17 C1 D1 148 211 Comparative Example 11 A1 B1 C10 D1 156 194 Comparative Example 12 A1 B1 C11 D1 152 Comparative Example 13 A1 B1 C12 D1 142 201 Comparative Example 14 A1 B1 C13 D1
1) Surface area ratio (Sb/Sa)100 (%): ratio of the surface area S.sub.b (mm.sup.2) of the fin material (the total surface area of the brazing material on both surfaces) to the surface area S.sub.a (mm.sup.2) of the sacrificial anticorrosion material of the tube material, i.e., ((S.sub.b/S.sub.a)100) (%).

[0080] In all Examples, there existed no problem with manufacturability of the tube material or the fin material, the brazing property was good, and the corrosion resistance after the cycle corrosion test was excellent.

[0081] In Comparative Examples 7 and 14, melting or cracking occurred during manufacturing of the tube material or the fin material, so that the subsequent evaluations were unable to be performed.

[0082] In Comparative Examples 3, 5 and 12, the tube or the fin was melted during brazing, so that the subsequent evaluations were suspended.

[0083] In Comparative Examples 1, 2, 4, 6, 8 to 11 and 13, the corrosion resistance was poor.