JPH0575491B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is directed to Al-0.2~1.0wt%Cu alloy or Al-0.2
This invention relates to a method for manufacturing an aluminum extruded flat multi-hole tube for a heat exchanger, in which both flat surfaces of the flat multi-hole extruded tube of ~1.0 wt% Cu-0.05~1.0 wt% Mn alloy are coated with Zn. [Prior Art] In general, since the natural oxide film on the surface of aluminum is strong and dense as a passive state, corrosion grows in the form of pitting corrosion. Therefore, coating aluminum members with Zn is extremely effective in providing cathodic protection to the members. When aluminum is used as a heat exchanger for an automobile, salt (Cl ^- ) may be present depending on the environment in which it is used, and this may trigger pitting corrosion, leading to accidents that lead to penetration. As a way to prevent this pitting corrosion, Zn, which has a low potential, is applied to the surface of aluminum parts.
It is known to coat these layers with sacrificial anodes for corrosion protection. When the aluminum member is a plate or a mandrel-type extruded material, methods of producing the clad material by clad rolling or clad extrusion are known.
In addition, extruded materials such as porthole-type multi-hole flat tubes can be coated by immersing them in molten Zn, or by applying Zn to the tube immediately after extrusion as shown in JP-A-58-204169. A method of melting and a method of pressing Zn or the like onto a tube immediately after extrusion as shown in Japanese Patent Laid-Open No. 58-157522 are known. Especially on the tube surface immediately after extrusion.
The method of thermal spraying Zn has low equipment costs and good workability, and its practical application is being considered as the easiest method. [Problems to be solved by the invention] However, in the case of multi-hole flat tubes made of pure aluminum, such as A1050, used in car air conditioner condensers, Zn must be sprayed on the entire surface.
Therefore, as shown in Japanese Patent Application Laid-Open No. 58-204169, it is necessary to arrange four thermal spray guns on the top, bottom, left and right sides of the tube. In order to perform thermal spraying under these conditions, the tube can be extruded through one hole, and only one tube can be extruded through a die from a so-called extruder. Therefore, productivity is extremely low and costs are high. That is, generally, this type of flat multi-hole tube is produced by punching two or four holes in a die and producing two or four tubes at the same time in one extrusion. However, in the case of thermal spraying, it is necessary to deposit Zn on the entire surface, so extrusion must be performed with one piece. As a result, productivity is reduced to 1/2 or 1/4, making it impossible to avoid high costs. [Means for solving the problems] In view of this, as a result of various studies, the present invention is based on two conventional methods.
Combining thermal spraying equipment with the main or four extrusion process,
Furthermore, the extruded material is Al-0.2~1.0wt%Cu alloy or Al-
By limiting the alloy to 0.2 to 1.0 wt% Cu and 0.05 to 1.0 wt% Mn, we have developed a method for manufacturing extruded aluminum flat multi-hole tubes for heat exchangers that have good corrosion resistance and are low in cost. That is, in the method of the present invention, in hot extrusion of flat multi-hole tubes made of Al-0.2-1.0wt% Cu alloy or Al-0.2-1.0wt%Cu-0.05-1.0wt%Mn alloy, a plurality of tubes are The tubes are extruded side by side in the long diameter direction with a gap of ~40 mm, and Zn is thermally sprayed from the short diameter direction on both flat surfaces of these tubes near the extrusion exit of the tube to coat both flat surfaces at 3 to 30 g/m ^{2 .}
It is characterized by being coated with Zn.
At this time, 0.5 to 5
Zn is thermally sprayed onto the flat surface of the tube at a position of m, preferably 1 to 3 m. Zn is sent in powder or wire form to a thermal spray gun, where it is melted and sprayed. Generally, pure metal is used for Zn, but trace amounts of elements such as Al, Cr, Ti, Mg, etc.
Even if 5wt%) is added, the effect does not change at all. [Function] The present invention uses Al-0.2 to 1.0wt% Cu alloy or Al-0.2
A plurality of tubes, for example, four flat multi-hole tubes 1 made of ~1.0wt%Cu-0.05~1.0wt%Mn alloy, as shown in Fig. 1, are placed horizontally with a distance of 3~40 mm from each other in the major axis direction. The flat multi-hole tube 1 is formed as shown in FIG.
3 to 30 g/m ² of Zn3 is deposited on the flat surface 1b of the tube 1, and even if Zn is not deposited on the R portion 1a of the tube 1, that portion can be sufficiently protected from corrosion. i.e. conventional pure aluminum, e.g. A1050,
For A1070, for example, the potential in a 3.5% NaCl solution is -732 mV and -735 mV, respectively, and the potential difference with the Zn layer is small, and with these pure Al, there is a sufficient gap between the Zn layer around the R part of the tube and the Zn layer. Since no corrosion protection current flows, the R section is not protected against corrosion, but the above
Al-0.2~1.0wt% Cu alloy or Al-0.2~1.0wt%
In the present invention using a Cu-0.05 to 1.0 wt% Mn alloy, the potential becomes noble, and a sufficient anti-corrosion current flows between the R part and the Zn layer surrounding it, resulting in corrosion protection. If this is an alloy having the composition according to the present invention,
The potential in 5% NaCl solution is -710mV or more,
The potential difference between the Zn layer potential and -780 mV or less is sufficient.
Corrosion protection is achieved even if there is no Zn layer in the R portion. However, if the content of Cu or Mn in the above alloy is less than the lower limit, the potential will not become noble, and a sufficient potential difference with the Zn diffusion layer will not be maintained, resulting in a decrease in pitting corrosion resistance. On the other hand, if the content exceeds the upper limit, extrudability deteriorates and it becomes impossible to obtain an appropriate shape as a multi-hole tube. Note that Fe, Si
Impurities contained in ordinary Al ingots, such as, do not affect the effects of the present invention in any way. In the present invention, the amount of Zn deposited on both flat surfaces of the tube is 3 to 30 g/m ² , preferably 6 to 20 g/m 2 .
The reason why it is set to g/m ² is to further improve the pitting corrosion resistance of the R portion. However, the amount of Zn attached was 3 to 30
g/m ² is because if the Zn coating amount is less than 3 g/m ² , Zn will not diffuse to the R part during brazing, and ^no improvement in pitting corrosion resistance can be expected. If it exceeds this value, not only will the pitting corrosion resistance become constant and saturated, but also the amount of Zn deposited will increase, making corrosion corrosion (meltdown) more likely to occur during brazing, which is not only undesirable, but also increases the amount of raw materials used. This is negative in terms of cost. In addition, the distance between the extruded tubes arranged in the longitudinal direction is set to 3 to 40 mm, preferably 10 to 30 mm, because a suitable amount of Zn adheres to the R part during Zn thermal spraying.
This is because pitting corrosion resistance can be further improved. However, the reason why the distance between the tubes was limited to 3 to 40 mm is because if the distance between the tubes is less than 3 mm, the Zn adhesion near the R part of the tube will be uneven, and there will be no adhesion at all or an abnormally large amount of Zn adhesion. Phenomena such as this occur. As a result, there are many problems such as not being able to improve the pitting corrosion resistance, or conversely, the amount of Zn deposited is too large and corrosion corrosion occurs during brazing. If the distance exceeds 40mm,
During this process, Zn is wasted and the Zn adhesion efficiency decreases. Furthermore, by setting the spraying position of Zn at a distance of 0.5 to 5 m, preferably 1 to 3 m from the exit surface of the tube extrusion, the distance between the tubes can be stabilized and an appropriate amount of Zn deposited can be obtained. However, the distance from the tube extrusion exit to the Zn spraying position was limited to 0.5 to 5m.If it was less than 0.5m, it would be too close to the extrusion exit and it would be difficult to spray, and the distance between the extruded tubes would not be stable, making it suitable for Zn spraying. The amount of Zn deposited cannot be obtained.
On the other hand, if the length exceeds 5 m, the temperature of the tube will drop below 300°C, and the adhesion of Zn will be poor.
This is because the Zn layer peels off due to bending or the like. If there is one thermal spray gun at the top and one at the bottom as shown in FIG. 1, the total extrusion width (l) must be 300 mm or less. However, if two thermal spray guns are placed one above the other, the total extrusion width can be increased to a maximum of 600 mm. As described above, the present invention is an improvement of the invention disclosed in JP-A-58-204169, and in particular, the composition of the flat multi-hole tube to be extruded is changed from Al-0.2 to Al-0.2, which has a high potential.
1.0wt%Cu alloy or Al-0.2~1.0wt%Cu-0.05~
1.0wt%Mn alloy, preferably two or more
～R section of flat multi-hole tube by simultaneous extrusion of 4 tubes
Even if Zn is not sufficiently adhered, the Zn layer around the R section provides sufficient corrosion protection, improving productivity and providing an extruded aluminum flat multi-hole tube for heat exchangers that is advantageous in terms of cost. can. [Examples] The present invention will be described below with reference to Examples. Example 1 Width 22 mm, height 5 mm, 5 channels, pipe thickness 0.7 mm, as shown in Fig. 2, consisting of 0.4% Cu, 0.1% Mn, and the remainder of Al.
Four extruded aluminum flat tubes for condensers with a partition wall thickness of 0.5 mm are arranged horizontally in the major axis direction with a gap of 20 mm as shown in Figure 1, and the total extruded width is 250 mm.
The tube was extruded so that the tube was extruded, and one thermal spray gun was placed at the top and bottom of the flat tube at a position 3 m from the extrusion exit. In this way, use a puller (a jig that grabs the end of the tube and pulls it) to pull it out horizontally.
The puller was run in synchronization with the extrusion speed, and when the speed reached a steady state (approximately 50 m/min), the thermal spray guns placed above and below the flat tube were activated, and metallic Zn was continuously sprayed from the top and bottom of the flat tube. . After heating the flat tube coated with 5 to 30 g/m ² of Zn at 600°C for about 5 minutes,
I took the CASS exam for one month. The results are shown in Table 1 in comparison with the case of a conventional flat tube using A1050 as the aluminum material.

[Table] As is clear from Table 1, the flat parts of all tubes No. 1 to 7 obtained by the method of the present invention were completely corroded, and deep pitting corrosion did not occur especially in the R part.
Good results were obtained. On the other hand, in Comparative Methods No. 8 to 10 using A1050 as the aluminum material, the flat surface suffers full-scale corrosion, but fairly deep pitting corrosion occurs on the R part, and if the amount of Zn coating is small, through-pitting corrosion occurs. (0.7mm) occurred. Example 2 Example 1 consisting of Cu0.35%, Mn0.2%, balance Al
Zn-coated flat multi-hole tubes shown in Table 2 were obtained by extruding and thermal spraying flat multi-hole tubes having the same shape as shown in Table 2 under the same conditions. Using this, the tube 1 was bent into a serpentine shape as shown in Figure 3, and a 0.16 mm thick corrugated fin 4 made of BA12PC (placing sheet) was assembled between the two and fixed with a stainless steel jig. After that, the flux was applied by immersing it in a 10% aqueous solution of fluoride-based flux (KAlF ₄・K ₂ AlF ₅・H ₂ O), and after thoroughly drying at 120℃, it was heated to 600℃ in a N ₂ gas atmosphere for 5 minutes. Brazing was performed by holding for a minute. In addition to investigating corrosion during brazing, these were also tested in a one-month CASS test.
The corrosion status of the parts (including parts) was investigated. The second result is
Also listed in the table.

[Table] As is clear from Table 2, tubes Nos. 11 to 13 obtained by the method of the present invention did not suffer from any corrosion, the flat portions were completely corroded, and even the rounded portions had deep pitting corrosion. No problems occurred, and good results were obtained. On the other hand, pitting corrosion occurred in comparative tube No. 14, which had a small amount of Zn adhesion at 2 g/m ² , and the pitting corrosion penetrated through the R section in particular, and comparative tube No. 14, which had a large amount of Zn adhesion at 35 g/m ² .15 indicates full corrosion, but it can be seen that corrosion occurs during brazing. Example 3 A flat multi-hole tube made of 0.5% Cu and the remainder of Al and having the same shape as in Example 1 was extruded by changing the distance between the extruded tubes, and the tube surface was formed in the same manner as in Example 1.
Zn was sprayed to provide a coating of 15 g/m ² of Zn. In addition to investigating the Zn adhesion efficiency of this flat tube, after heating the flat tube at 600℃ for about 5 minutes, CASS
The test was conducted for one month. The results are shown in Table 3.

[Table] As is clear from Table 3, the present invention method Nos. 16 to 18
The Zn adhesion efficiency was over 45%, and the flat and rounded areas were completely corroded. On the other hand, in comparison method No. 19, where the distance between the tubes is narrow, large corrosion occurs during brazing, and as a result, deep pitting corrosion occurs in the R part in the CASS test, and the distance between the tubes is wide. Law No.20
In this case, both the flat part and the R part were completely corroded, but Zn
It can be seen that the adhesion efficiency is as low as 30%, and Zn is wasted throughout the process. Example 4 In Example 1, the installation position of the thermal spray gun provided near the extrusion outlet was changed, and metal Zn was continuously sprayed from above and below the flat tube to coat the tube surface with 15 g/m ² of Zn. . The uniformity of Zn adhesion and the adhesion of Zn against bending were investigated for the tube coated with Zn in this way. The results are shown in Table 4.

[Table] As is clear from Table 4, the present invention method No. 21~
24, the uniformity of Zn adhesion and Zn
Although the adhesion was good, Comparative Method No. 25, where the thermal spraying position was too close to the extrusion outlet, did not provide an appropriate amount of Zn coating, and Comparative Method No. 26, which was too far away from the extrusion outlet, resulted in the tube temperature being below 300°C. As a result, the adhesion of the adhered Zn is poor, and the Zn layer peels off during bending. [Effects of the Invention] As described above, according to the present invention, Al-0.2~1.0wt% Cu alloy or Al-0.2~1.0wt%
By using Cu-0.05~1.0wt%Mn alloy,
Even if Zn is not attached to the R part of the tube, that part is sufficiently protected from corrosion, so it is possible to simultaneously extrude multiple tubes and coat them with Zn by thermal spraying.
This has significant industrial effects, such as being able to provide a thermal spray tube with high productivity and advantageous in terms of cost.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention, and FIG.
The figure is a sectional side view showing an example of a sprayed tube obtained by the present invention, and FIG. 3 is a perspective view showing an example of a capacitor. 1...Tube, 2...Thermal spray gun, 3...Zn
Layer, 4...Fin.

Claims (1)

[Claims] 1 Al-0.2~1.0wt% Cu alloy or Al-0.2~1.0wt
In hot extrusion of flat multi-hole tubes made of %Cu-0.05~1.0wt%Mn alloy, multiple tubes are extruded side by side in the long diameter direction with a distance of 3~40mm from each other, and these tubes are separated near the extrusion exit of the tube. A method for manufacturing an extruded aluminum flat multi-hole tube for a heat exchanger, characterized in that Zn is thermally sprayed from the minor axis direction of the tube onto both flat surfaces to coat both flat surfaces with 3 to 30 g/ ^m2 of Zn. . 2. The method for manufacturing an extruded aluminum flat multi-hole tube for a heat exchanger according to claim 1, wherein Zn is thermally sprayed on both flat surfaces of the tube at a position 0.5 to 5 m from the extrusion exit surface of the tube.