Flux-free brazing aluminum alloy brazing sheet

Abstract

A flux-free brazing aluminum alloy brazing sheet includes: a core material formed of aluminum alloy comprising Si of 0.50 to 0.90 mass %, Cu of 0.30 to 2.50 mass %, and Mn of 1.40 to 1.80 mass %, with a Mg content limited to 0.05 mass % or less, and with the balance being Al and inevitable impurities; an intermediate material being formed of aluminum alloy comprising Mg of 0.40 to 1.00 mass %, and Zn of 2.00 to 6.00 mass %, with the balance being Al and inevitable impurities; and a brazing material being formed of aluminum alloy comprising Si of 6.00 to 13.00 mass %, Mg of 0.05 to 0.40 mass %, and Bi of 0.010 to 0.050 mass %, with the balance being Al and inevitable impurities.

Claims

1. An aluminum alloy brazing sheet used for brazing in an inert gas atmosphere without using a flux, the aluminum alloy brazing sheet comprising: a core material; an intermediate material cladded onto one side surface of the core material; and a brazing material cladded onto a side surface of the intermediate material opposite to a side surface on which the core material exists, wherein the core material is formed of aluminum alloy consisting of Si of 0.50 to 0.90 mass %, Cu of 0.30 to 2.50 mass %, and Mn of 1.40 to 1.80 mass %, with a Mg content limited to 0.05 mass % or less, and with the balance being Al and inevitable impurities, the intermediate material is formed of aluminum alloy consisting of Mg of 0.40 to 1.00 mass %, and Zn of 2.00 to 6.00 mass %, optionally Mn, with the balance being Al and inevitable impurities, and the brazing material is formed of aluminum alloy consisting of Si of 6.00 to 13.00 mass %, Mg of 0.05 to 0.40 mass %, and Bi of 0.010 to 0.050 mass %, optionally Sr, optionally Cu, with the balance being Al and inevitable impurities.

2. The aluminum alloy brazing sheet according to claim 1, wherein the brazing material further comprises Sr of 0.001 to 0.05 mass %.

3. The aluminum alloy brazing sheet according to claim 1, wherein the brazing material further comprises Cu of 0.02 to 1.20 mass %.

4. The aluminum alloy brazing sheet according to claim 1, wherein the intermediate material further comprises Mn of 0.05 to 0.50 mass %.

Description

EXAMPLES

Examples and Comparative Examples

(1) The core material, the intermediate material, and the brazing material were manufactured using alloys having compositions listed in Table 1. In the alloy compositions listed in Table 1, the symbol “-” indicates that the value is equal to the detection limit or less, and the term “balance” comprises inevitable impurities.

(2) First, the aluminum alloy used for the core material listed in Table 1, the aluminum alloy used for the intermediate material listed in Table 1, and the aluminum alloy used for the brazing material listed in Table 1 were casted by DC casting, and were subjected to facing. The core material and the intermediate material were heated at 600° C., and thereafter the brazing material and the intermediate material were subjected to hot rolling to predetermined thicknesses at 480° C. The hot-rolled intermediate material aluminum alloy and the brazing material aluminum alloy were combined onto one side surface of the core material ingot in order of the core material, the intermediate material, and the brazing material, to obtain a combined material (clad material) having a 10% clad ratio of the intermediate material and a 10% clad ratio of the brazing material. The combined material was heated at 480° C., and thereafter rolled to 2.6 mm by hot clad rolling. Thereafter, the obtained rolled material was subjected to cold rolling to 0.5 mm, and subjected to final annealing to acquire a sample material. In the manufacturing process described above, the case where the test piece could be normally manufactured is denoted by the symbol “0”, the case where the material could be manufactured, but longer manufacturing time than the normal case was required and productivity was deteriorated is denoted by the symbol “A”, and the case where manufacturing was impossible is denoted by the symbol “x”. Table 2 lists the results thereof.

(3) The sample materials prepared as described above were subjected to heating corresponding to brazing at 600° C. for three minutes, and cooled at the speed of 50° C./min. Thereafter, the properties “tensile strength”, “brazability”, “presence/absence of occurrence of erosion”, “corrosion resistance of internal surface general portion”, and “corrosion resistance of internal surface joining portion” of each of the sample materials were evaluated by the following methods. Table 2 lists results of the evaluation.

(4) <Tensile Strength>

(5) A JIS No. 5 test piece was cut out of each of the sample materials. The test pieces were subjected to the heating corresponding to brazing described above, left at room temperature for one week, and thereafter subjected to tensile test compliant with JIS Z 2241:2011. The test pieces having the tensile strength of 150 MPa or more were evaluated as “passed” (O), and the test pieces having the tensile strength less than 150 MPa were evaluated as “failed” (x).

(6) <Brazability>

(7) To evaluate the brazability of the brazing material and the core material, clearance filling test was performed. A horizontal sheet having a width of 25 mm and a length of 60 mm was sampled from each of the sample materials. A perpendicular sheet having the same material as that of the horizontal sheet was used, and the brazing material layer and the intermediate layer thereof were removed by polishing to obtain a core material single layer. The sample was subjected to clearance filling test under the condition of the heating corresponding to brazing described above. Thereafter, the filling length was measured, the samples having the filling length of 30 mm or more were evaluated as “00”, the samples having the filling length of 25 mm or more and less than 30 mm were evaluated as “0”, and the samples having the filling length less than 25 mm were evaluated as “x”. The samples evaluated as “00” and “0” are samples that passed the test, and the samples evaluated as “x” are samples that failed the test with respect to brazability.

(8) <Presence/Absence of Occurrence of Erosion and Material Melting>

(9) The section of a portion of the horizontal sheet of each of the clearance filling test samples prepared as described above in which no fillet was formed was subjected to micro-observation to check presence/absence of occurrence of erosion (brazing filler metal diffusion) and material melting in the core material and/or the sacrificial anode material. The cases where neither erosion nor material melting occurred were evaluated as “passed” (O), and the cases where at least one of erosion and material melting occurred were evaluated as “failed” (x).

(10) <Corrosion Resistance of Internal Surface General Portion>

(11) The brazing material surface of each of the sample materials subjected to heating corresponding to brazing was subjected to immersion test simulating the environment with a water-based coolant.

(12) The samples were subjected to CASS test for 1,000 hours on the basis of JIS H 8502. As a result, the samples in which no corrosion penetration occurred in the clad material for 1,000 hours were evaluated as “passed” (0) CASS with respect to corrosion resistance, and the samples in which corrosion penetration occurred in the clad material for 1,000 hours were evaluated as “failed” (x) CASS with respect to corrosion resistance.

(13) <Corrosion Resistance of Internal Surface Joining Portion>

(14) A portion of each of the clearance filling test samples in which a fillet was formed was cut out, and subjected to CASS test for 1,000 hours on the basis of JIS H 8502. The samples having a corrosion decrement (volume ratio) less than 10% in the joining portion for 1,000 hours were evaluated as “OO”, the samples having a corrosion decrement of 10% or more and less than 30% were evaluated as “O”, and the samples having a corrosion decrement of 30% or more were evaluated as “x” with respect to corrosion resistance in CASS.

(15) TABLE-US-00001 TABLE 1 Alloy Alloy Composition (mass %) Member No. Si Cu Mn Mg Bi Sr Zn Balance Examples Core A1 0.70 1.00 1.60 — — — — Al Material A2 0.50 1.00 1.60 — — — — Al A3 0.90 1.00 1.60 — — — — Al A4 0.70 0.30 1.60 — — — — Al A5 0.70 2.50 1.60 — — — — Al A6 0.70 1.00 1.40 — — — — Al A7 0.70 1.00 1.80 — — — — Al Brazing B1 10.00 — — 0.20 0.020 — — Al Material B2 6.00 — — 0.20 0.020 — — Al B3 13.00 — — 0.20 0.020 — — Al B4 10.00 — — 0.05 0.020 — — Al B5 10.00 — — 0.40 0.020 — — Al B6 10.00 — — 0.20 0.010 — — Al B7 10.00 — — 0.20 0.050 — — Al B8 10.00 0.02 — 0.20 0.020 — — Al B9 10.00 1.20 — 0.20 0.020 — — Al B10 10.00 — — 0.20 0.020 0.001 — Al B11 10.00 — — 0.20 0.020 0.05 — Al Intermediate C1 — — — 0.60 — — 4.00 Al Material C2 — — — 0.60 — — 2.00 Al C3 — — — 0.60 — — 6.00 Al C4 — — — 0.40 — — 4.00 Al C5 — — — 1.00 — — 4.00 Al C6 — — 0.05 0.60 — — 4.00 Al C7 — — 0.50 0.60 — — 4.00 Al Comparative Core A8 0.20 1.00 1.60 — — — — — Examples Material A9 1.20 1.00 1.60 — — — — — A10 0.70 0.10 1.60 — — — — — A11 0.70 2.80 1.60 — — — — — A12 0.70 1.00 0.90 — — — — — A13 0.70 1.00 2.00 — — — — — A14 0.70 1.00 1.60 0.30 — — — — Brazing B12 4.00 — — 0.20 0.020 — — — Material B13 15.00 — — 0.20 0.020 — — — B14 10.00 1.50 — 0.20 0.020 — — — B15 10.00 — — 0.03 0.020 — — — B16 10.00 — — 0.60 0.020 — — — B17 10.00 — — 0.20 0.002 — — — B18 10.00 — — 0.20 0.500 — — — B19 10.00 — — 0.20 0.020 0.10 — — Intermediate C8 — — 0.02 0.60 — — 4.00 — Material C9 — — 1.30 0.60 — — 4.00 — C10 — — — 0.60 — — 0.50 — C11 — — — 0.60 — — 7.00 — C12 — — — 0.10 — — 4.00 — C13 — — — 1.50 — — 4.00 —

(16) TABLE-US-00002 TABLE 2 Tensile Strength Core Brazing After Brazing (MPa) Erosion Internal Surface Material Material Intermediate Tensile and Corrosion Resistance Possibility of Alloy Alloy Material Strength Material General Joining Manufacturing No. No. No. Alloy No. (MPa) Evaluation Melting Brazability Portion Portion of Test Piece Examples 1 A1 B1 C1 160 ∘ ∘ ∘ ∘ ∘ ∘ 2 A2 B1 C1 157 ∘ ∘ ∘ ∘ ∘ ∘ 3 A3 B1 C1 163 ∘ ∘ ∘ ∘ ∘ ∘ 4 A4 B1 C1 152 ∘ ∘ ∘ ∘ ∘ ∘ 5 A5 B1 C1 185 ∘ ∘ ∘ ∘ ∘ ∘ 6 A6 B1 C1 157 ∘ ∘ ∘ ∘ ∘ ∘ 7 A7 B1 C1 164 ∘ ∘ ∘ ∘ ∘ ∘ 8 A1 B1 C1 158 ∘ ∘ ∘ ∘ ∘ ∘ 9 A1 B2 C1 170 ∘ ∘ ∘ ∘ ∘ ∘ 10 A1 B3 C1 158 ∘ ∘ ∘ ∘ ∘ ∘ 11 A1 B4 C1 169 ∘ ∘ ∘ ∘ ∘ ∘ 12 A1 B5 C1 161 ∘ ∘ ∘ ∘ ∘ ∘ 13 A1 B6 C1 158 ∘ ∘ ∘ ∘ ∘ ∘ 14 A1 B7 C1 163 ∘ ∘ ∘ ∘ ∘ ∘ 15 A1 B8 C1 169 ∘ ∘ ∘ ∘ ∘∘ ∘ 16 A1 B9 C1 155 ∘ ∘ ∘ ∘ ∘∘ ∘ 17 A1 B10 C1 159 ∘ ∘ ∘∘ ∘ ∘ ∘ 18 A1 B11 C1 157 ∘ ∘ ∘∘ ∘ ∘ ∘ 19 A1 B1 C1 169 ∘ ∘ ∘ ∘ ∘ ∘ 20 A1 B1 C2 156 ∘ ∘ ∘ ∘ ∘ ∘ 21 A1 B1 C3 155 ∘ ∘ ∘ ∘ ∘ ∘ 22 A1 B1 C4 159 ∘ ∘ ∘ ∘ ∘ ∘ 23 A1 B1 C5 164 ∘ ∘ ∘ ∘ ∘ ∘ 24 A1 B1 C6 168 ∘ ∘ ∘ ∘ ∘ ∘ 25 A1 B1 C7 170 ∘ ∘ ∘ ∘ ∘ ∘ Comparative 26 A8 B1 C1 135 x ∘ ∘ ∘ ∘ ∘ Examples 27 A9 B1 C1 172 ∘ x ∘ ∘ ∘ ∘ 28 A10 B1 C1 130 x ∘ ∘ x ∘ ∘ 29 A11 B1 C1 223 ∘ x ∘ ∘ ∘ ∘ 30 A12 B1 C1 140 ∘ ∘ ∘ x ∘ ∘ 31 A13 B1 C1 — — — — — — x 32 A14 B1 C1 195 ∘ ∘ x ∘ ∘ ∘ 33 A1 B12 C1 156 ∘ ∘ x ∘ ∘ ∘ 34 A1 B13 C1 165 ∘ x ∘ ∘ ∘ ∘ 35 A1 B14 C1 — — — — — — x 36 A1 B15 C1 156 ∘ ∘ x ∘ ∘ ∘ 37 A1 B16 C1 163 ∘ ∘ x ∘ ∘ ∘ 38 A1 B17 C1 166 ∘ ∘ x ∘ ∘ ∘ 39 A1 B18 C1 — — — — — — x 40 A1 B19 C1 155 ∘ ∘ x ∘ ∘ ∘ 41 A1 B1 C8 157 ∘ ∘ ∘ ∘ ∘ Δ 42 A1 B1 C9 — — — — — — x 43 A1 B1 C10 156 ∘ ∘ ∘ x ∘ ∘ 44 A1 B1 C11 160 ∘ x ∘ ∘ ∘ ∘ 45 A1 B1 C12 159 ∘ ∘ x ∘ ∘ ∘ 46 A1 B1 C13 161 ∘ x ∘ ∘ ∘ ∘

(17) Table 2 lists evaluation results. In Examples 1 to 25, the samples passed in evaluation of tensile strength after brazing, erosion, brazability, and internal surface corrosion resistance in the general portion and the joining portion, and the test pieces could be normally manufactured.

(18) By contrast, Comparative Example 26 failed in evaluation, because the Si concentration of the core material was low and the tensile strength after brazing was low. Comparative Example 27 failed in evaluation, because the Si concentration of the core material was high, the melting point of the core material was low, and melting of the core material occurred. Comparative Example 28 failed in evaluation, because the Cu concentration of the core material was low and the tensile strength after brazing was low. Comparative Example 29 failed in evaluation, because the Cu concentration of the core material was high, the melting point of the core material was low, and melting of the core material occurred. Comparative Example 30 failed in evaluation, because the Mn concentration of the core material was low and the tensile strength after brazing was low. In addition, Comparative Example 30 also failed in evaluation of corrosion resistance of the general portion, because the potential of the core material was low and a difference in potential thereof from the intermediate layer was small. In Comparative Example 31, manufacturing of the test piece was impossible, because the Mn concentration of the core material was high, a coarse compound was generated in casting, and rollability was deteriorated. Comparative Example 32 failed in evaluation, because the Mg concentration of the core material was high, oxidization progressed during heating in the brazability test, and the clearance filling length was shortened. Comparative Example 33 failed in evaluation, because the Si concentration of the brazing material was low, the flowability of the brazing filler metal was low, and the clearance filling length was shortened. Comparative Example 34 failed in evaluation, because the Si concentration of the brazing material was high, the Si concentration diffused into the core material increased, the melting point of the core material was lowered, and melting of the core material occurred. In Comparative Example 35, manufacturing of the test piece was impossible, because the Cu concentration of the brazing material was high, the strength of the brazing material increased, and the brazing material was not joined to the intermediate material in clad rolling. Comparative Example 36 failed in evaluation, because the Mg concentration of the brazing material was low and the clearance filling length was shortened. Comparative Example 37 failed in evaluation, because the Mg concentration in the brazing material was high, oxidization progressed during heating in the brazability test, and the clearance filling length was shortened. Comparative Example 38 failed in evaluation, because the Bi concentration of the brazing material was low and the clearance filling length was shortened. In Comparative Example 39, manufacturing of the test piece was impossible, because the Bi concentration of the brazing material was high, a coarse Mg—Bi-based compound was generated in casting, and rollability was deteriorated. Comparative Example 40 failed in evaluation, because the Sr concentration in the brazing material was high, oxidization of the surface of the brazing material progressed during heating in the brazability test, and the clearance filling length was shortened. In Comparative Example 41, the test piece could be manufactured, although the Mn concentration of the intermediate material was low, the joining property in clad rolling was poor, time twice as long as time in the normal case was required for manufacturing, and productivity was deteriorated. In Comparative Example 42, manufacturing of the test piece was impossible, because the Mn concentration of the intermediate material was high, the strength of the intermediate material increased, and the joining property in clad rolling was deteriorated.

(19) Comparative Example 43 failed in evaluation of corrosion resistance of the general portion, because the Zn concentration of the intermediate material was low, the potential became positive, and the difference in potential thereof from the core material was small. Comparative Example 44 failed in evaluation, because the Zn concentration of the intermediate material was high, the melting point of the intermediate material was lowered, and melting of the intermediate material occurred. Comparative Example 44 also failed in evaluation of corrosion resistance of the general portion, because the corrosion speed was high. Comparative Example 45 failed in evaluation, because the Mg concentration of the intermediate material was low, the effect of weakening the oxide film was small, and the clearance filling length was shortened. Comparative Example 46 failed in evaluation, because the Mg concentration of the intermediate material was high, the melting point of the intermediate material was low, and melting of the intermediate material occurred.