JPS6353477B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a cross fin material for a heat exchanger. Specifically, the present invention relates to a method of manufacturing a cross fin material for a heat exchanger with improved strength and fin workability using an aluminum alloy containing 0.1 to 2% by weight of manganese. Traditionally, room coolers, refrigerators, etc.
A heat exchanger is used in which a hole with a diameter of 5 to 15 mm with a collar-like rise is bored in a thin plate of 0.15 to 0.3 mm (fin processing), and a tube for passing the cooling medium is inserted into this hole. It is being The thin plate used in this heat exchanger and subjected to the above-mentioned fin processing is generally called a cross fin. The heat of the cooling medium is conducted to the cross fins through the tubes and collar-like rises, and is effectively dissipated to the outside through the large surface area of the cross fins. The material for this cross fin (hereinafter referred to as cross fin material) is one that is easy to process.
Pure aluminum such as JIS 1050, JIS 1100, and JIS 1200 or aluminum-manganese alloy such as JIS 3003 is used. Cross fin materials are generally made by casting the above-mentioned molten aluminum or aluminum-manganese alloy into a slab using a semi-continuous casting method, hot rolling it to obtain a strip plate with a thickness of 3 to 10 mm, and then casting it into a slab. After further cold rolling this into a thin plate, it is manufactured by subjecting it to annealing treatment. In recent years, there has been a desire to make cross fins thinner in order to reduce costs, but thinner cross fins also reduce the strength of the fins, so it is important to make sure that the collar-shaped rising part of the fins is in close contact with the pipe. This results in insufficient heat transfer efficiency between the cooling medium in the tube and the fins. Therefore, the present inventors found that fin processing is easy and
In order to obtain a cross fin material with high strength, we conducted a direct continuous casting and rolling method, in which molten aluminum-manganese alloy was introduced into a mold consisting of a pair of rotating rolls, and the mold was The present inventors have discovered that if the strip plate is produced directly from the molten alloy by cooling and rolling, the resulting cross-fin material has excellent fin workability and high strength, and has thus arrived at the present invention. That is, an object of the present invention is to produce a cross fin material having excellent fin processability and high strength, and this purpose is to
A molten aluminum alloy containing manganese is continuously cast and rolled directly into a strip of 3 to 10 mm, and then this strip is cold rolled to a thickness of 0.05 to 10 mm.
This is achieved by making a 0.15 mm thin plate and then annealing it. Next, the present invention will be explained in detail. In the method of the present invention, the cross fin material is 0.1
Manufactured using an aluminum alloy containing ~2% by weight manganese. Manganese is contained in aluminum within the above range, without impairing the corrosion resistance and workability of the fin.
Improve strength. Manganese content 2.5% by weight
If it exceeds this, the corrosion resistance of the fin material will decrease. Also,
During casting, manganese-containing intermetallic compounds crystallize coarsely, which reduces workability, so when fin processing is applied to fin material, some cracks occur in the collar-shaped rising portions of the fins. In addition, the manganese content
If it is less than 0.1% by weight, the strength of the fin cannot be improved, so the manganese content should be 0.1% by weight.
-2.5% by weight, preferably 0.3-2% by weight. When the manganese content is less than 0.3% by weight,
If necessary to improve the strength of the fin material
The alloy can also contain 0.05-0.2% by weight of zirconium. Aluminum alloys contain impurities such as iron, copper, magnesium, and silicon, but in the fin material of the present invention, iron promotes the crystallization of intermetallic compounds including manganese during casting, and improves fin workability. Copper reduces corrosion resistance. Silicon also reduces fin processability and strength. Therefore, iron is 0.5% by weight or less, especially 0.3% by weight or less, and copper is 0.2% by weight or less, especially 0.1% by weight.
The content of silicon is preferably 0.4% by weight or less, particularly 0.2% by weight or less. Magnesium becomes difficult to process if it exceeds 0.5% by weight, so it should be less than 0.5% by weight, preferably 0.3%.
% by weight or less. In the method of the present invention, a molten aluminum alloy containing 0.1 to 2% by weight of manganese is continuously cast and rolled to directly obtain a strip plate with a thickness of 3 to 10 mm, which is then cold rolled to a thickness of 0.05 to 10 mm. A thin plate of 0.15mm. The plate thickness of the strip plate obtained by the above continuous casting and rolling process is 3 to 10 mm, which means that the component elements of the alloy such as manganese, iron, and silicon are sufficiently forced to form a solid solution in the aluminum. This is the thickness that allows the effects of casting and rolling to be fully utilized, that is, the thickness that allows casting and rolling to be achieved in which the molten metal is uniformly and rapidly cooled. It is technically difficult to directly obtain a strip plate with an extremely thin plate thickness of less than 3 mm from the molten metal by continuous casting and rolling.On the other hand, with a thick plate of more than 10 mm, it is difficult to cool the molten metal uniformly and rapidly. There are particular technical difficulties. In addition, the thickness of the thin plate obtained by the above-mentioned cold rolling is 0.05 to 0.15 mm because it provides sufficient properties such as fin workability and mechanical strength required as a cross fin material for heat exchangers. The plate thickness is .
If the plate is cold rolled to a thickness that is too thin (less than 0.05 mm), it will be difficult to obtain sufficient mechanical strength as cross fin material for heat exchangers;
If the plate thickness is greater than 100 mm, it is disadvantageous in terms of cost and the efficiency of heat exchange deteriorates. To continuously cast and roll a molten alloy, the molten alloy is introduced between the molds through a nozzle placed between the molds, which are composed of two rotating casting rolls or a running casting belt. Then, it may be rolled at the same time while being cooled in a mold. The above method is known as the direct continuous casting and rolling method. If a strip plate with a thickness of 3 to 10 mm is manufactured using this method, the amount of forced solid solution of manganese will increase during casting, so if the content of elements such as manganese, iron, and silicon is low, it may contain manganese. Almost no intermetallic compounds crystallize, and conversely, even if the content of these elements is high, the amount of crystallized substances is small and their size is small, so the fin processability of the resulting fin material is impaired. Never get caught. In the direct continuous casting and rolling method, the casting speed (progress speed of the strip plate) is 0.8 to 1.4 m/min, and the molten metal temperature is 680 to 680 m/min.
A range of 710°C is appropriate. The strip plate thus obtained is cold rolled into a thin plate, and then annealed. The higher the working degree in cold rolling, the more uniform and fine the structure of the thin plate after annealing treatment can be made, so the working degree is preferably 95% or more. The annealing conditions vary depending on the amount of manganese in the alloy, etc., but the annealing temperature is appropriately selected from the range of 200 to 350°C and the annealing time of 1 to 2 hours. The cross fin material obtained by the method of the present invention has excellent fin processability, and the cross fin obtained by fin processing has excellent corrosion resistance and high tensile strength. Fin processing of the cross fin material can be carried out according to a conventional method. That is, a hole is punched in the fin material, and then a cylindrical punch is inserted to form a collar-shaped rise around the hole, or the fin material is stretched to form a cup-shaped protrusion. This is then done by punching out the bottom. As explained above in detail, according to the method of the present invention, it is possible to produce a cross fin material with excellent fin processability, corrosion resistance, and tensile strength, and the fin material obtained by the method of the present invention can be used. This allows the cross fin to be made thinner. Next, the present invention will be specifically explained with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Examples 1 to 4 and Comparative Examples 1 to 4 Aluminum alloys having various compositions shown in Table 1 below were melted in a gas furnace, and the molten metal temperature after melting was set to 750°C.
℃, and a well-dried mixed gas of chlorine and nitrogen was blown thereto for degassing. After that, an aluminum-titanium-boron mother alloy (titanium content: 5% by weight, boron content: 1% by weight) was added to these molten metals so that the titanium content was 0.02% by weight, and then directly cast and rolled using the continuous casting and rolling method. Alternatively, a strip plate with a thickness of 5 mm was produced by vertical semi-continuous casting and hot rolling, respectively. In the direct continuous casting rolling method, the radius is used as the driving mold.
Two 30cm rolls were used, and the casting speed was
It was 130cm/min. On the other hand, in the vertical semi-continuous casting method, the casting speed is 4 cm/
A slab with a cross section of 9 cm x 20 cm was cast in minutes, and this
A strip plate was formed by hot rolling at 400 to 500°C. Next, the obtained strip plate was cold-rolled into a thin plate with a final thickness of 0.1 mm (cold working degree 98%), and after annealing for 2 hours at the temperature shown in Table 1 below, the fin It was subjected to a processability test, a tensile strength test and a corrosion resistance test. The fin workability test was performed by punching a hole with a diameter of 12 mm in a thin plate using a punching die, then inserting a cylindrical punch with a diameter of 16.5 mm into the hole to form a collar-like rise, and repeating this 5 times. I did it.
As a result, no cracks were observed in the collar-shaped rising portions formed on any of the fin materials, and the fin processability was good. The tensile strength test was conducted using a test piece with a parallel length of 60 mm and a width of 10 mm at a tensile speed of 10 mm/min. Corrosion resistance test was conducted in accordance with JIS Z 2371 method.
A salt spray test was conducted for a week, and the corrosion loss of the thin plate (before and after the test)
The weight difference due to corrosion per 1 dm ² (mg/dm ² ) is expressed. These results are shown in Table 1.

【table】

[Table] Comparative Examples 5 to 8 In Comparative Examples 1 to 4, each annealing temperature was set to correspond to Examples 1 to 4 as shown in Table 2, and then a fin workability test and a tensile strength test were conducted. Ta. As a result, the occurrence of 1 to 10 cracks per collar-like rising portion of the fin material was observed in all cases. The tensile strength test results are shown in Table 2 together with those of Examples 1 to 4.

[Table] Comparative Examples 9 to 12 In Comparative Examples 1 to 4, the annealing temperature conditions were determined so that the tensile strength was almost the same as that of Examples 1 to 4 having the same alloy composition, and the annealing temperature conditions were determined. A fin processability test and a tensile test were conducted on the product. As a result, cracks were found in the collar-shaped rising portions of the fin materials in all cases. The results of the tensile test are shown in Table 3 together with those of Examples 1 to 4.

【table】

Claims (1)

[Claims] 1 A molten aluminum alloy containing 0.1 to 2% by weight of manganese is continuously cast and rolled to a thickness of 3
A strip of ~10 mm is then cold rolled into a thin sheet of 0.05 to 0.15 mm thick, and then
A method for producing a cross fin material for a heat exchanger, which comprises subjecting the material to an annealing treatment.