JP2862949B2 - Manufacturing method of aluminum plate for fin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing an aluminum plate for fins which is used after being subjected to overhanging, ironing and drawing, and which has excellent formability.

[Conventional technology]

Conventionally, Al and Al alloys have been widely used as excellent molding materials, and fin materials as molding materials are required to have excellent fin moldability. Conventionally known factors affecting the formability include the alloy component of the material, physical or mechanical property values that depend on the metal structure, etc., and the components of the lubricant (lubricating oil), additives, and viscosity used during molding. Have been. Further, the shape of the material surface at the microscopic level is related to the lubricant retention during molding (the permeability of the lubricant to the material surface), and is therefore positioned as a factor affecting the moldability.

On the other hand, since the surface shape of the roll used for rolling is transferred to the surface of the forming plate material, it is considered that control of the microscopic shape of the roll surface is important in producing a material having excellent formability. The surface shape of the roll is usually finished by finishing the surface of the rolling roll with a grindstone, and the finished state varies depending on the polishing conditions such as the roughness of the grindstone surface, the feed speed of the grindstone, and the rotation speed of the roll. Conventional molding plate surface is JIS
Ra 0.2-0.4μm when expressed in terms of surface roughness specified in
have. There is a view that it is better to increase Ra to some extent for the retention of lubricant, but there is no established theory.
Therefore, at present, the improvement of the formability of the fin material to be formed into a fin is mainly achieved by controlling the metallographic structure.

[Problems to be solved by the invention]

Therefore, at present, conventional aluminum plates for fins use the same alloy material, depending on the shape and use of the fin, with delicate control of the metallographic structure and composition, and there are few materials applicable to a wide range of uses. However, with the progress of processing technology, the quality level required for the material has been increasing year by year, and at present, there is a strong demand for improvement in formability. However, a dramatic improvement cannot be expected only with the conventional technology. For example, drawless type fins are shown in Figs.
As shown in (d), a collar portion (2) for inserting a heat exchange tube into a fin (1) is formed, and punching, hole expansion (a), burring (b), ironing (c), and flaring ( D) The ironing process is the center of the process, and the molding defects that occur during the forming process include ironing cracks occurring in the ironing process and flower cracks occurring in the refraining process. Since the adhesiveness between the collar portion and the heat exchange tube is impaired, the heat exchange characteristics are reduced, and the appearance of the formed fin is impaired, the value as a product may be reduced. These molding failures are affected by the material and mechanical strength of the material, but may occur even if the mechanical strength is appropriate, and the occurrence is not limited to the entire material and is often localized. It is concentrated and scattered, and stabilization of quality is desired.

[Means for solving the problem]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, an object of the present invention is to form an aluminum fin that has been subjected to ironing and stretch flange processing so as to eliminate cracks generated during forming and to stabilize quality. A method for producing an aluminum plate for fins having excellent workability has been developed.

That is, as a result of various studies, the present inventors have determined that, in a plate rolled with rolls finished by conventional grinding stone polishing, the rolls are transferred along the rolling direction, so that the rolling direction and the direction perpendicular to the rolling direction. The appearance of the microscopic shape of the surface is different,
For example, since the peaks or valleys appear periodically along the rolling direction, the surface has a directional surface shape, and it has been found that the lubricity during fin processing varies slightly depending on the part. Based on this knowledge, the surface of the aluminum plate before forming was etched with an alkaline solution to produce an alloy plate with reduced directional properties and pits (dents) of a specific size on the surface of the rolled plate. As a result, it has been found that a dent on the surface of the rolled plate acts as a lubricating oil reservoir and that the surface shape is less directional, so that a material having significantly better formability than the conventional material can be obtained. The present invention has been developed based on these findings.

That is, the present invention, in the manufacturing process of the aluminum plate for fins, by washing one or both sides of the Al or Al alloy rolled plate after the final cold rolling with an alkaline solution having a pH of 10 or more for 1 to 900 seconds, before forming processing A depression having a diameter of 0.1 to 200 [mu] m and a depth of 0.1 to 5 [mu] m at an average center interval of 1 to 1000 [mu] m.

(Operation) In the present invention, the diameter of the depressions arranged on the surface is 0.1 to 200 μm.
When the diameter is less than 0.1 μm, the lubricating oil does not have an oil collecting effect and does not contribute to the improvement of moldability.
If the thickness exceeds 0 μm, the lubricating oil is difficult to be retained on the plate surface, and the lubricating effect is reduced, and the moldability is rather deteriorated.

When the depth of the depression is 0.1 to 5 μm, the depth is 0.1 μm.
If the depth is less than 5 μm, the lubricating oil has no retaining effect and does not contribute to the improvement of the formability. If the depth exceeds 5 μm, it becomes a source of stress concentration during the fin forming process and forms cracks.

The reason that the average center distance between adjacent dents is 1 to 1000 μm is that when these center distances are less than 1 μm, the effect of improving the formability is not seen, and when the center distance exceeds 1000 μm, the lubricant holding effect is reduced, and This is because the effect of improving the properties is not seen.

In the present invention, the term “cleaning” refers to etching-type cleaning that generates pits (dents) on the aluminum surface, and has a sufficient effect even in an acid system or an alkali system.
Washing with 10 or more alkaline solutions is highly effective. If the washing time is 1 second or more, the above-mentioned dent shape and distribution can be obtained. However, if washing is performed for 10 seconds or more, a dent of a predetermined size can be obtained stably, and the effect is further enhanced. Here, if the pH is less than 10 or the washing time is less than 1 second, a depression of a predetermined size cannot be obtained, and a sufficient effect of improving moldability cannot be obtained. In addition, the cleaning time exceeding 900 seconds is not only undesirable from the viewpoint of productivity, and the generation of coarse pits starting from an intermetallic compound such as an Al-Fe-based or Al-Mn-based surface due to excessive cleaning, Alternatively, it is not preferable because the moldability is deteriorated as a result of dropout of the intermetallic compound.

After the above-described washing is performed during the cold rolling to generate the pits, the pits can be formed on the surface of the final cold-rolled sheet by further performing the cold rolling, but the final cold rolling is preferably performed. If cleaning is performed later, a depression having a predetermined shape and distribution can be obtained, so that the effect is higher.

〔Example〕

 Next, the present invention will be described in more detail based on examples.

In the process of manufacturing a drawless fin thin plate using a JISA1050 aluminum alloy, the surface of the Al alloy plate was washed with an alkaline cleaning solution after the completion of cold rolling to produce the materials shown in Table 1. Next, these thin plates were subjected to finish annealing, and then fins were formed using an actual drawless fin machine to examine the occurrence of cracks. A sample with severe occurrence of ironing cracks was judged as x, a sample with mild cracking was evaluated as Δ, and a sample with no occurrence was evaluated as ○. Table 2 shows the results.

As is clear from Tables 1 and 2, for fins having a diameter of 0.1 to 200 [mu] m and a depth of 0.1 to 5 [mu] m formed on the surface of the Al alloy plate by alkali etching and having an average center interval of 1 to 1000 [mu] m. The aluminum alloy plate is less likely to cause ironing cracks than the material used in the conventional process. Further, when the cleaning is not sufficient and the predetermined dent shape and distribution are not obtained, the effect of improving the formability is not sufficient. In addition, it can be seen that the mold which has been excessively washed is liable to form cracks.

〔The invention's effect〕

As described above, according to the present invention, remarkable stabilization of the surface properties of the aluminum plate for fins can be achieved, so that there is a remarkable effect that the fin formability is improved and the defective rate can be significantly reduced.

[Brief description of the drawings]

FIGS. 1 (a) to 1 (d) are explanatory views showing a draw-less type processing step, and FIG. 1 (a) shows punching, hole expansion, (b) burring, (c) ironing, and (d) refrea.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C23G 1/22 C23F 1/36 C22F 1/04 F28F 1/32

Claims (1)

(57) [Claims] In a manufacturing process of an aluminum plate for a fin, one or both sides of a rolled Al or Al alloy plate are washed with an alkaline solution having a pH of 10 or more for 1 to 900 seconds after final cold rolling, so that the aluminum plate is formed before forming. The diameter of the surface of the aluminum plate
A method for producing an aluminum plate for fins, wherein a depression having a depth of 0.1 to 200 μm and a depth of 0.1 to 5 μm is formed with an average center interval of 1 to 1000 μm.