JPH02138455A - Production of extruded flat perforated aluminum tube for heat exchanger - Google Patents

Abstract

PURPOSE:To impart corrosion resistance to a tube with good productivity by horizontally arranging plural Al-Cu-based flat perforated tubes in the major axis direction, extruding the tubes simultaneously, and spraying molten Zn on the upper and lower flat surfaces of the tube in the vicinity of the extrusion outlet. CONSTITUTION:In the hot extrusion of a Al-Cu-based or Al-Cu-Mn-based flat perforated tube, plural flat perforated tubes 1 are horizontally arranged in the major axis direction and simultaneously extruded. A thermally spraying gun 2 is provided above and below the tube 1 in the vicinity of the extrusion outlet of the tube 1. Molten Zn is sprayed on the flat surface 1b of the tube 1 to form a Zn layer 3. In this case, the amt. of Zn to be deposited is controlled to 3-30g/m<2>, the gap between the tubes 1 to 3-40mm, and the distance between the Zn spraying position and the tube extrusion outlet surface to 0.5-5m. By this method, even if Zn is not deposited on the R part 1a of the tube 1, the corrosion of the part is sufficiently prevented, and the extruded flat perforated tube is produced with good productivity.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is an aluminum heat exchanger tube made of an A1-Cu type or A12-Cu-Mn type alloy and coated with Zn on both flat surfaces of a flat multi-hole extruded tube. The present invention relates to a method for manufacturing an extruded flat multi-hole tube.

[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 an aluminum member with Zn is extremely effective in providing cathodic protection to the member. When aluminum is used as a heat exchanger for an automobile, salt (Cj!-) is present depending on the usage environment, and this can trigger pitting corrosion, leading to accidents that lead to penetration. As a method for preventing pitting corrosion, it is known to coat the surface of an aluminum member with Zn, which has a low potential, and use this layer as a sacrificial anode to prevent corrosion.

When the aluminum member is a plate or a mandrel-type extruded material, methods of making 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 using Japanese Patent Application Laid-Open No. 58-204169.
As shown in the publication, Zn was added to the tube immediately after extrusion.
A method of thermally spraying Zn or a method of pressing Zn or the like onto a tube immediately after extrusion as shown in Japanese Patent Laid-Open No. 58-157522 is known. In particular, the method of thermally spraying Zn on the tube surface immediately after extrusion has low equipment costs and good workability.
Practical application is being considered as the simplest 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 thermally sprayed on the entire surface. As shown, four thermal spray guns need to be placed on the upper and lower left stones of the tube.

In order to perform thermal spraying under these conditions, only one tube can be extruded through a single-hole extruder die. Therefore, productivity is extremely low and costs are high. That is, generally, this type of flat multi-hole tube is manufactured by punching two or four holes in a die and extruding it once to produce two or four tubes at the same time.

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, and high costs cannot be avoided.

(Means for solving the problem) In view of this, the present invention has been developed as a result of various studies.
Melt into the extrusion process! i! Combine one equipment and one extruded material! By limiting the method to -CLI-based or A1-Cu-Mn-based alloys, 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, the method of the present invention allows A, f! -CLI system or /1-Cu
- In hot extrusion of Mn-based flat multi-hole tubes, a plurality of tubes are extruded side by side in the longitudinal direction, Zn is thermally sprayed on both flat surfaces of the tube near the extrusion exit of the tube, and Zn is applied to both flat surfaces of the extruded tube. 3 to 309/T on both sides of the tube.
tt, preferably 6 to 209/rd of Zn, and the gap between each tube extruded in the longitudinal direction is 3 to 3.
40. , desirably 10-30#, Zn is thermally sprayed,
Further, Zn@ is thermally sprayed onto the flat surface of the tube at a position of 0.5 to 5 m, preferably 1 to 3 m from the extrusion exit surface of the tube. Note that Zn is sent into a thermal spray gun in the form of a powder or a wire, and is molten and sprayed. Generally, a pure metal is used as Zn, but even if a small amount (0 to 5 wt%) of an element such as Al-, Cr, Ti, Mg, etc. is added, the effect does not change at all.

[For production]

The present invention involves simultaneously extruding a plurality of flat multi-hole tubes (1) made of Al--Cu alloy or /l-CIJ-Mn alloy, for example, four flat multi-hole tubes (1) as shown in Fig. 1, arranged horizontally in the longitudinal direction. , near the extrusion exit of tube (1)
Above and below 1)? A H'l gun (2) was installed, and 7-n was sprayed onto the flat surface of the tube (1).
(3) and attach it to the R part (1a) of the tube (1).
Even if Zn is not attached to the surface, the area is sufficiently protected from corrosion. That is, conventional pure aluminum, such as A1050, A
1070 has a low potential, and with this method, a sufficient corrosion protection current does not flow between the R part and the Zn layer, so it is not corrosion protected, but l! In the present invention using a -Cu-based alloy or an A1-CLI-Mn-based alloy, the potential becomes a member, and a sufficient anticorrosion current flows between the R portion and the Zn layer surrounding the R portion, thereby preventing corrosion.

As an Al-Cu alloy, Cu0.2 to 1.0 wt% (
(hereinafter wt% is abbreviated as %), compositions consisting of Al-balance and unavoidable impurities are preferable, and A1-Cu-Mn
As a system alloy, CuO, 2~i, o%, Mn0.0
It is preferable to have a composition of 5 to 1.0%, the remainder of Al, and unavoidable impurities. With this composition, 5% NaC
The potential in one solution is -710 mV or more, and the potential difference with the potential of the Zn layer -780 mV or less is sufficient, and Z
Corrosion protection is achieved even without the n-layer.

In the present invention, 3 to 30 (j/
The pitting corrosion resistance of the R portion can be further improved by applying 49 layers of 7-n with a desirable Kuha of 6 to 20 g/T/i. However, the reason why the Zn adhesion amount was limited to 3 to 309/m is that if the 7-n adhesion amount is less than 39/Trt, Zn will not diffuse to the R part at any time in the solder, and no improvement in pitting corrosion resistance can be expected. Zn adhesion amount is 30! ? /m, the pitting corrosion resistance becomes constant and saturated, and the amount of Zn adhesion increases, making corrosion corrosion (null 1 to down) more likely to occur during soldering, which is not only undesirable, but also reduces the use of raw materials. There will be more trust, which will be negative in terms of cost.

Also, the gap between each tube extruded in the longitudinal direction is 3
~40. If Zn is thermally sprayed to a thickness of preferably 10 to 30 m, an appropriate amount of 7n will be deposited up to the R part, and the edibility of the layer can be improved. However, the gap between the tubes is 3
The reason why we limited it to ~40M is that if the gap is less than 3m, the Zn adhesion near the R part of the tube will be uneven, and no adhesion will occur.
Sometimes it doesn't stick, or it sticks in an abnormally large amount. As a result, there are many problems such as not being able to improve the pitting corrosion resistance, or conversely, too much Zn-coated Ml causes corrosion to occur during soldering. If the gap exceeds 40m, Zn will pass through the gap.
is wasted, reducing the adhesion efficiency of 7n.

Furthermore, the Zn spraying position was changed from the tube extrusion exit [■1 side to 0
．． By setting it at a position of 5 to 5 m, preferably 1 to 3 Tn, the gap between the tubes can be stabilized and an appropriate amount of Zn deposited can be obtained. However, the distance from the tube extrusion outlet to the Zn spraying position was limited to 0.5 to 5 m because the distance was 0.5 m to 5 m.
If it is within 5 m, it is too close to the extrusion exit), and it is not only difficult to inject, but also the gap between the extruded tubes is unstable, making it difficult to maintain proper Zn.
Unable to obtain adhesion amount. On the other hand, if the length exceeds 5 m, the temperature of the tube will drop to 300'C or less, which will result in poor adhesion of the adhered Zn, and the Zn layer will peel off during bending or the like.

As shown in Figure 1, if there is one solvent gun on the top and one on the top, the total extrusion width (1>) must be less than 300, w.However, if two solvent guns are placed on the top and bottom, the maximum extrusion width is 60
The total extrusion width can be increased to 0 trm.

As described above, the present invention relates to an improvement of the invention disclosed in JP-A No. 58-204169, and in particular, the composition of the flat multi-hole tube to be extruded is changed to a high potential A1-CU alloy or Al.
--Cu-Mn based alloy, preferably two or more
Even if Zn is not sufficiently attached to the R part of the flat multi-hole tube due to four-hour extrusion, the Zn layer around the R part provides sufficient corrosion protection, improving productivity and cost-effective aluminum extrusion for heat exchangers. It is possible to provide flat multi-hole tubes.

(Example〕 The present invention will be described below with reference to Examples.

Example (1) 2nd layer consisting of CLJo, 4%, MnO, 1%, remainder Af
As shown in the figure, the width is 22m, the height is 5cm, there are 5 channels, and the pipe thickness is 0.
7m, partition wall thickness 0.5. As shown in Figure 1, 4 extruded aluminum flat tubes for condensers are arranged horizontally in the long diameter direction with 8 gaps on 20 sides, and the extruded total width is 250 mm.
One solvent gun was placed above and below the flat tube at a position 3 m from the extrusion outlet. In this way, the puller (a jig that grasps and pulls the end of the tube)
Pull it out horizontally, run the blur in synchronization with the extrusion speed, and when it reaches a steady speed (approximately 50 m/min),
Thermal spray guns placed above and below the flat tube were operated to continuously spray metal Zn from the upper and lower sides of the flat tube.

After heating the flat tube coated with Zn of 5 to 309/m at 600° C. for about 5 minutes, a CASS test was conducted for one month. Transfer the results to the aluminum material A
Table 1 shows a comparison with a conventional flat tube using 1050.

Table 1 As is clear from Table 1, all tubes Nos. 1 to 7 obtained by the method of the present invention showed good results, with the flat portions being completely corroded, and deep pitting corrosion not occurring particularly in the R portions. Obtained. On the other hand, in comparison methods Nα8 to Nα10 using A1050 as the aluminum material, the flat surface is completely corroded, but the R part has quite deep pitting corrosion, and when the amount of Zn coating is small, through pitting corrosion ( 0.7 m> occurred.

Example (2) A flat multi-hole tube having the same shape as Example (1) consisting of 35% CuO, 2% MnO, and the remainder of Al was extruded and sprayed under the same conditions to obtain the Zn coating shown in Table 2. A flat multi-hole tube was obtained. Using this, bend the tube (1) into a meandering shape as shown in Figure 3, and while doing so, 8A1
Consisting of 2PC (Plazing Sheet), thickness 0.16m
After combining the corrugated fins (4) and fixing them with a stainless steel jig, apply fluoride flux (KAl-P4).
2A1F5 .H2O) to apply flux, and after thoroughly drying at 120°C, brazing was performed by holding at 600°C for 5 minutes in an N gas atmosphere.

These were examined for corrosion during brazing, and a one-month CASS test was conducted to examine the corrosion status of the tube surface (including the R section). The results are also listed in Table 2.

Table 2 As is clear from Table 2, tubes Nos. 11 to 13 obtained by the method of the present invention did not cause any corrosion, the flat portions were completely corroded, and deep pitting corrosion did not occur even in the R portions. , good results were obtained. On the other hand, pitting corrosion occurred in comparison tube No. 14, which had a small Zn adhesion amount of 29/TIt, and the pitting corrosion penetrated particularly in the R portion, and the Zn adhesion amount was 35! ? Comparison tube No. 15, which has a large number of tubes with a large number of /m, has corrosion on the entire surface, but it can be seen that corrosion occurs during brazing.

Example (3) A flat multi-hole tube with the same shape as Example (1) consisting of 5% CuO and the balance of A1 was extruded by changing the gap between the extruded tubes, and the tube surface was coated in the same manner as Example (1). Zn was sprayed and coated with 15 g/m l r+. In addition to examining the Zn adhesion efficiency of this flat tube, the flat tube was heated at 600° C. for about 5 minutes, and then a CASS test was conducted for one month.

The results are shown in Table 3.

As is clear from Table 3, the Zn adhesion efficiency of methods Nos. 016 to 18 of the present invention was 45% or more, and the flat portions and R portions were completely corroded. On the other hand, in comparison method No. 19, where the gap between tubes 1 is narrow, large corrosion occurred during the soldering process, and as a result, deep pitting corrosion occurred in the R part in the CASS test, and the gap between tubes was wide. In comparative method No. 20, both the flat portion and the R portion were completely corroded, but the Zn attachment efficiency was as low as 30%, indicating that Zn was wasted through the gaps.

Example (4) In Example (1), the installation position of the thermal spray gun installed near the extrusion outlet was changed, and metallic Zn was continuously sprayed from above and below the flat tube, resulting in a Z of 159/m on the tube surface.
n was coated.

Regarding the tube coated with Zn in this way, the uniformity of Zn adhesion and the adhesion of Zn against bending were investigated. The results are shown in Table 4.

Table 4 As is clear from Table 4, the method of the present invention Nα21-24
Although the uniformity of Zn adhesion and Zn adhesion are good in both cases, the comparative method Nα25, in which the thermal spraying position is too close to the extrusion outlet, cannot obtain an appropriate 7n adhesion, and the spraying position is too close to the extrusion outlet. In the comparison method Nα26, the temperature of the tube is 3
Since the temperature decreases below 00'C, the adhesion of the adhered Zn is poor and the Zn pattern peels off during bending.

(Effects of the Invention) According to the present invention, Af-
By using C1J alloy or Al--Cu-Mn alloy, even if the R part of the tube is not coated with Zn, that part is sufficiently protected from corrosion, so it is possible to extrude multiple tubes at the same time. It has industrially significant effects, such as being able to provide a thermally sprayed coating with Zn, high productivity, and being advantageous in terms of cost.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing one embodiment of the present invention, Fig. 2 is a side sectional view showing an example of a displacement tube according to the present invention, and Fig. 3 is a perspective view showing an example of a condenser. Ru. (1) Tube (2) Molten copper can (3) Zn layer (4) Fin Figure 1 Figure 2

Claims (4)

[Claims] (1) In hot extrusion of Al-Cu or Al-Cu-Mn flat multi-hole tubes, multiple tubes are extruded side by side in the longitudinal direction, and Zn is thermally sprayed on both flat surfaces of the tube near the extrusion exit. A method for manufacturing an extruded aluminum flat multi-hole tube for a heat exchanger, characterized in that both flat surfaces of the extruded tube are coated with Zn. (2) 3 to 30 g/m^2 of Zn on both flat surfaces of the tube
A method for manufacturing an extruded aluminum flat multi-hole tube for a heat exchanger according to claim 1, wherein the extruded aluminum flat multi-hole tube is coated with a heat exchanger. (3) Claim 1, in which Zn is thermally sprayed with a gap of 3 to 40 mm between the tubes extruded in the longitudinal direction.
A method for manufacturing an extruded aluminum flat multi-hole tube for a heat exchanger according to item 1 or 2. (4) An extruded aluminum flat for a heat exchanger according to claim 1, 2, or 3, in which 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. A method for manufacturing a multi-hole tube.