JP2003082427A - Aluminum alloy brazing sheet having excellent vibration fatigue resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy brazing sheet which has excellent vibration fatigue resistance in a weld zone, and is useful for various structural members such as a tube for a heat exchanger. SOLUTION: The aluminum alloy brazing sheet having excellent corrosion resistance in a weld zone 5 is obtained by coating one side or both sides of a core material 1 containing, by mass, >0.5 to 1.0% Cu, 0.05 to 0.3% Ti and 0.3 to 1.5% Mn, <=0.2 Si, Fe and Mg, and the balance Al with inevitable impurities with an aluminum alloy brazing filler metal 2 in a cladding ratio of 10 to 20% per one side. The crystal grain diameter L in a rolling direction in the longitudinal direction of the core material 1 is 150 to 200 μm.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy brazing sheet useful for various structural members such as tubes for heat exchangers, and particularly excellent in vibration fatigue resistance of a welded portion. . [0002] Automotive heat exchangers (radiators, etc.)
As shown in FIG. 3, a core 9 in which a header 7 for connecting the tube 6 and a radiation fin 8 are brazed to the tube 6.
The main part is configured. In FIG. 3, reference numeral 10 denotes a skin material. For example, as shown in FIG. 4, the tube 6 is made of a brazing material 3 coated with a brazing material 2 on one side of a core material 1 and a skin material 10 on another side, and a brazing material 2.
Is roll-formed into a cylindrical shape with the outside facing, induction heating by a high-frequency coil 11, and welding by pressing the molten end face by a pressure roll 12 to produce a weld. When the tube 6 is used in a radiator of an automobile or the like, the tube 6 is placed under vibration for a long time, so that cracks due to vibration fatigue tend to occur. . When this crack penetrates, it causes liquid leakage, and therefore, improvement of the vibration fatigue resistance of the welded portion is regarded as an important issue. In addition, pitting corrosion also causes liquid leakage, and a method for preventing the pitting corrosion has been studied. For example, Ti is added to a core material, and this Ti is distributed in a layered manner in the length direction (rolling direction) of the core material. A method has been proposed to prevent pitting corrosion by forming a local cell between light and shade layers to promote corrosion in the surface direction (Japanese Unexamined Patent Publication No. Hei 8-
No. 283891). [0004] However, no effective improvement measures have been found for the vibration fatigue resistance of the welded portion, and the method of preventing pitting corrosion by adding Ti has a problem in the case where Ti is welded. In addition, there is a problem that the pits diffuse along the crystal grain boundaries to form a concentrated layer of Ti at the bonding interface, and pitting proceeds along the concentrated layer of Ti. Therefore, the present inventors have studied measures for improving the vibration fatigue resistance and corrosion resistance of the welded portion of the aluminum alloy brazing sheet, and have found that the vibration fatigue resistance can be improved by adding an appropriate amount of Cu. The corrosion resistance is Ti
Was found to be able to be improved by adding a crystal grain and defining the crystal grain size of the core material. The present inventors completed further studies and completed the present invention. An object of the present invention is to provide an aluminum alloy brazing sheet that is particularly excellent in vibration fatigue resistance of a weld. Means for Solving the Problems The invention according to claim 1 is:
Cu is more than 0.5 mass% and 1.0 mass% or less, and Ti is 0.1 mass% or less.
One or both sides of a core material containing 0.5 to 0.3 mass%, Mn of 0.3 to 1.5 mass%, and each of Si, Fe, and Mg being regulated to 0.2 mass% or less, with the balance being Al and unavoidable impurities. Aluminum alloy brazing material on one side
A brazing sheet coated with a cladding ratio of 20%, wherein the core material has a crystal grain size in a rolling direction in a longitudinal section of 150 to 200 μm, and is an aluminum alloy brazing sheet excellent in vibration fatigue resistance. is there. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aluminum alloy core material 1 as shown in FIG.
A brazing sheet 3 coated with a cladding ratio of
The core material 1 contains appropriate amounts of Cu, Mn, and Ti, and Si, F
e, the amount of Mg is regulated, and the size of the crystal grain size is appropriately defined. As shown in FIG. 2, Cu contained in the core material is solid-dissolved or finely precipitated in the Al matrix by heating during welding at the welded portion 5, and Cu is welded to the welded portion 5 of the core material 1. To increase the strength and vibration fatigue resistance. In FIG. 2, reference numeral 4 denotes a welding interface. If the Cu content is 0.5 mass% or less, the above effect cannot be sufficiently obtained. If the Cu content exceeds 1.0 mass%, the Al-Cu intermetallic compound precipitates at the crystal grain boundaries to increase the susceptibility to intergranular corrosion and increase corrosion resistance. Decreases. Therefore, the content of Cu is specified to be more than 0.5 mass% and 1.0 mass% or less. In particular, it is desirable to be more than 0.5 mass% and 0.7 mass% or less. In the present invention, Ti contained in the core material precipitates in a layer parallel to the surface of the core material to suppress pitting corrosion, and also increases the corrosion resistance of the core material by shifting the potential of the core material to noble. T
When the content of i is less than 0.05 mass%, the above effect cannot be sufficiently obtained. When the content exceeds 0.3 mass%, the above effect is saturated, and a coarse compound is formed to deteriorate processability. For this reason, Ti is defined as 0.05 to 0.3 mass%. In particular, 0.05 to 0.2 mass% is desirable. In the present invention, as shown in FIG. 1, the reason why the grain size L in the rolling direction in the longitudinal section (section in the rolling direction) of the core material 1 is defined as 150 to 200 μm is that the grain size L is less than 150 μm. In the case, Ti becomes easy to diffuse, and Ti concentrates at the joint interface of the welded portion, and pitting corrosion occurs there.
On the other hand, if the crystal grain size L exceeds 200 μm, micro-cracks tend to occur in the welded portion during welding. The crystal grain size L can be controlled by selecting a cold working rate, an intermediate annealing condition, and the like of the aluminum alloy brazing sheet. An appropriate annealing temperature is around 360 ° C. In addition, in this invention, the welding part 5 means the area | region containing the part fuse | melted by the welding heat at the time of performing the electric resistance welding of a tube, for example. Mn enhances the corrosion resistance, weldability and strength of the core material. If the content of Mn is less than 0.3 mass%, the above effect cannot be sufficiently obtained, and if it exceeds 1.5 mass%, a coarse intermetallic compound is formed and the workability is reduced. For this reason, the content of Mn is specified to be 0.3 to 1.5 mass%. Especially 0.
3 to 1.2 mass% is desirable. [0012] Si forms an intermetallic compound with Fe to increase the strength of the core material, but if the amount is large, a noble compound is formed and the corrosion resistance of the matrix is reduced. Therefore, Si is 0.2
Restrict to mass% or less. Especially 0.02 to 0.2 mass%
Is desirable. [0013] As described above, Fe forms an intermetallic compound with Si to increase the strength of the core material and to reduce the crystal grain size L to 2%.
It is refined to not more than 00 μm and further enhances the weldability of the core material. However, when the amount is large, the corrosion resistance of the core material is reduced.
For this reason, Fe is restricted to 0.2 mass% or less. In particular, 0.02 to 0.2 mass% is desirable. [0014] Mg increases the strength of the core material, but if the amount is large, the brazing property is reduced in a Nocolok brazing method using a fluoride-based flux. For this reason, the content of Mg is 0.1.
Restrict to 2 mass% or less. In particular, 0.1 mass% or less is desirable. In the present invention, the cladding ratio of the brazing material is set to 1
The reason for defining the range from 0 to 20% is that if it is less than 10%, the brazing properties with the fins decrease, and if it exceeds 20%, the residual thickness of the core material becomes thin when the brazing material soaks into the core material. This is because a heat exchanger having a skeleton may cause fatigue fracture due to external force. Although any aluminum alloy brazing material can be used as the brazing material, an Al-Si alloy brazing material is desirable because good brazing properties are stably obtained. The brazing sheet of the present invention includes a core material having both surfaces coated with a brazing material, a core material having one surface coated with a brazing material, another surface coated with a brazing material, and a core material having one surface coated with a brazing material. What was just done. The present invention will be described below in more detail with reference to examples. (Example 1) A 4045 alloy brazing material (Si10.
5 mass%, Fe 0.05 mass%, Cu 0.05 mass%,
(Ti 0.01 mass%, Al remainder)
The sheet is hot-rolled to 5 mm, and then cold-rolled, intermediately annealed, and cold-rolled in this order to obtain a sheet having a thickness of 3.5 mm. This sheet is repeatedly subjected to cold-rolling and intermediate annealing to obtain a sheet having a thickness of 0.1 mm. A 4 mm H14 aluminum alloy brazing sheet was produced. The cladding ratio of the brazing material was variously changed within the range of 10 to 20%. The crystal grain size of the core material was adjusted within the range of 150 to 200 μm by controlling the cold rolling ratio, the conditions of the intermediate annealing, and the like. Comparative Example 1 An aluminum alloy brazing sheet was manufactured in the same manner as in Example 1 except that an aluminum alloy having a composition outside the range specified in the present invention shown in Table 2 was used as a core material. (Comparative Example 2) An aluminum alloy brazing sheet was manufactured in the same manner as in Example 1 except that the clad ratio of the brazing material was outside the range specified in the present invention. A test piece was cut out from each of the brazing sheets produced in Example 1 and Comparative Examples 1 and 2, and (1)
Brazing properties, (2) tensile strength, (3) fatigue strength, (4)
Various characteristics of corrosion resistance (pitting depth) were examined and evaluated by the following methods. The results are shown in Tables 1 and 2. (1) Brazing properties A drop test was carried out by a conventional method to determine a flow coefficient. A flow coefficient of 60% or more was judged to be acceptable. (2) Brazing conditions (600 ° C) for tensile strength test piece (JIS No. 5 test piece)
× 3.5 minutes) and leave it at room temperature for one week.
A tensile test was performed according to H.241. Tensile strength 160N / m
m ² or more was judged to be acceptable. (3) Conditions for brazing a fatigue strength test piece (width 10 mm) (600 ° C. × 3.
5 minutes) and leave it at room temperature for 1 week, then JISZ2273
In accordance with to determine the fatigue strength at 10 ⁷ times by adding a repeated bending stress. The bending was a double swing at a frequency of 15 Hz, and the applied stress was changed according to the length of the test piece. The amplitude was constant. A fatigue strength of 45 MPa or more was determined to be acceptable. (4) After heating a corrosion resistance test piece (width 30 mm, length 120 mm) under brazing conditions (600 ° C. × 3.5 minutes), the end portion was masked with an insulating tape, and a CASS test was performed for 750 hours according to JIS H8601. After the test, corrosion products were removed, and the pit depth was measured by a depth of focus method using an optical microscope.
A pit depth of 160 μm or less was determined to be acceptable. [Table 1] [Table 2] As apparent from Tables 1 and 2, Example 1
No. (Example of the present invention). All of Nos. 1 to 18 were excellent in the above various properties. On the other hand, in Comparative Example No. Nos. 19 and 20 each have a large amount of core material Si and Fe. Nos. 24 and 26 were inferior in corrosion resistance because each of the core materials had little Mn and Ti. No. In No. 21, the fatigue strength was reduced due to the small amount of Cu. No. In No. 22, the corrosion resistance was reduced due to the large amount of Cu. No. No. 23 has a large amount of Mg in the core material. No. 28 had low brazing properties because of low cladding ratio. No. No. 25 has a large amount of Mn in the core material. In the case of No. 27, since the core material had a large amount of Ti, cracks occurred during rolling and rolling could not be performed. No. In No. 29, the fatigue strength decreased due to a large cladding ratio. In addition, the brazing sheet of the present invention was confirmed to be able to be favorably brazed by other atmosphere brazing, flux brazing, vacuum brazing, etc., through a test conducted separately. (Example 2) No. 2 manufactured in Example 1
Each of the brazing sheets 1, 3, and 5 was processed into a 10 mmφ tube by an electric resistance welding method using a high-frequency welding method. Comparative Example 3 The crystal grain size of the core material was controlled to 50 μm or 250 μm by controlling the cold rolling reduction and the intermediate annealing conditions.
An aluminum alloy brazing sheet was manufactured in the same manner as in Example 1 except that the value was adjusted to m. (Comparative Example 4) 2
Each of the brazing sheets 1 and 22 was processed into a 10 mmφ tube by an electric resistance welding method using a high-frequency welding method. Each of the tubes produced in Example 2 and Comparative Example 4 was examined for vibration fatigue resistance and corrosion resistance. Vibration fatigue resistance is measured by a length of 2
A 00 mm sample was cut out, and the test piece was heated under brazing conditions (600 ° C. × 3.5 minutes), allowed to stand at room temperature for one week, and then repeatedly subjected to a bending stress of 10 ⁷ times in accordance with JISZ2273 at a frequency of 15 Hz. After addition, the presence or absence of cracks was observed. The bending stress was set to 60% of the tensile strength. Those without cracks were judged to have good vibration fatigue resistance (O), and those with cracks were judged as poor (X). The corrosion resistance was examined by the same method as in Example 1, and when the pit depth was 150 μm or less, the corrosion resistance was good (良好), and when the pit depth exceeded 150 μm, it was judged as poor (×).
Table 3 shows the results. [Table 3] As is apparent from Table 3, No. 2 of Example 2 (Example of the present invention). Each of Nos. 30 to 32 was excellent in vibration fatigue resistance and corrosion resistance. Microcracks did not occur in the welds, and the pit depth was shallow. On the other hand, N
o. In No. 33, since the crystal grain size of the core material was small, Ti diffused into the welding interface, and deep pitting occurred at the interface. No. Three
No. 4 had a large crystal grain size, and microcracks occurred in the welded portion during the electric resistance welding. No. In No. 35, a crack was generated in the welded portion in the vibration fatigue test due to a low Cu content. No. 36 is C
The corrosion resistance was poor due to the high content of u. Separately, other brazing sheets (No. 2,
4, 6 to 18), the vibration fatigue resistance and corrosion resistance were examined in the same manner as described above. 1,
Excellent characteristics were exhibited as in the cases of Nos. 3 and 5. As described above, the present invention relates to Cu,
Contains an appropriate amount of Ti and Mn, regulates a small amount of Si, Fe, and Mg.
The core material is coated with a cladding ratio of 0 to 20%, and has a grain size of 150 to 200 μm in a rolling direction in a longitudinal section of the core material.
The brazing sheet is characterized by having various properties such as brazing properties, tensile strength, fatigue strength, and corrosion resistance, and is particularly excellent in vibration fatigue resistance and corrosion resistance of a welded portion when it is welded to a tube or the like. Therefore, a remarkable industrial effect is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of a crystal grain size in a core material of a brazing sheet of the present invention. FIG. 2 is an explanatory diagram of a welded portion of the brazing sheet of the present invention. FIG. 3 is a partial explanatory view of a radiator core. FIG. 4 is an explanatory diagram of an electric resistance sewing method. [Description of Signs] 1 core material 2 brazing material 3 brazing sheet 4 welding interface 5 welded portion 6 tube 7 header 8 radiating fin 9 core 10 skin material 11 high frequency coil 12 pressure roll

Claims (1)

Claims: 1. More than 0.5 mass% of Cu and 1.0 mass% or less, 0.05 to 0.3 mass% of Ti, and 0.3 to 0.3 mass% of Mn.
1.5 mass%, and each of Si, Fe, and Mg is 0.1%.
A brazing sheet in which the aluminum alloy brazing material is coated on one or both sides of a core material comprising Al and unavoidable impurities at a cladding rate of 10 to 20% per one side, with the balance being restricted to 2 mass% or less. An aluminum alloy brazing sheet having excellent vibration fatigue resistance, wherein a crystal grain size in a rolling direction in a longitudinal section is 150 to 200 μm.