JPS5982115A - Production of aluminum finned iron pipe - Google Patents

Abstract

PURPOSE:To join securely an aluminum fin to an iron pipe and to produce inexpensively the finned pipe by forming a spiral hollow groove on the surface of the iron pipe, winding the fin thereon so as to fit the same into the hollow groove and brazing both in a furnace. CONSTITUTION:A steel pipe or an iron alloy pipe is used as an iron pipe 1 and is pretreated by a chemical treatment or mechanical treatment. A hollow groove 2 is formed by using a universal tool. A brazing sheet consisting of a brazing material layer clad on at least one surface of a thin aluminum sheet is used as an aluminum fin material 3. An aluminum-silicon or aluminum-silicon-magnesium material is used for the brazing material layer. A wire-like brazing material is wound between the pipe 1 and the spiral fin 3 in the case of using a single material such as pure aluminum or aluminum-manganese alloy as the aluminum fin material. A mixture composed of a flux for an aluminum alloy as well as zinc chloride, tin chloride and water is used as the flux and the brazing in furnace is accomplished in accordance with a conventional method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing aluminum finned iron pipes used for heat pipes, heat exchanger elements, and the like.

Conventional aluminum finned iron pipes are made by spirally forming strip-shaped fin material formed from a brazing core consisting of a thin aluminum plate and a brazing material layer clad on the brazing core on an iron pipe whose outer peripheral surface has been aluminized. Wrap it around the
It was manufactured by a method in which the fin material was bonded to the pipe by vacuum brazing (see Japanese Patent Application Laid-Open No. 132449/1982). However, in this method, it was necessary to aluminize at least the outer circular surface of the iron pipe. However, in order to treat only the outer circumferential surface, it was necessary to weld a closing plate to one end of the pipe and immerse the pipe diagonally in the treatment liquid, which inevitably increased costs. In the brazed bone method, the length of the brazed product is limited by the furnace length, so in order to obtain a long finned pipe, it is necessary to connect the brazed products, which further increases costs. Furthermore, in the vacuum fistula method,
If a material containing an element with high vapor pressure, such as zinc, is used as the material for aluminum fins, the zinc in the material will gradually evaporate and its content will decrease, and the evaporated zinc will adhere to the furnace wall. This made maintaining the furnace difficult.

Another method for manufacturing aluminum finned iron pipes is to form spiral grooves on the surface of the iron pipe, apply a strip of aluminum fin-in material, and mechanically bond the fin material to the pipe. There was a way to get what's called an embedded pipe. However, in this case, the equipment cost required for the caulking process increases the cost of the product, and it is difficult to make the connection between the fin and the pipe strong.
In particular, at high temperatures (200 to 300° C. or higher), there was a risk that the fins would come off the pipe due to the difference in thermal expansion coefficients between iron and aluminum.

This invention solves all the problems mentioned above,
An object of the present invention is to provide a method for manufacturing an aluminum finned iron pipe that can inexpensively manufacture a finned pipe with a strong connection between the fin and the pipe.

The method of manufacturing an aluminum finned iron pipe according to the present invention involves forming a spiral groove on the surface of the iron pipe, and attaching a strip of aluminum fin material to the iron pipe so that the inner part of the aluminum fin material fits into the groove. Wrapping and furnace brazing are characterized by joining the fin material to the pipe by a method.

As the iron pipe, a steel pipe, an iron-based alloy pipe, etc. are used. Iron pipes are pretreated by chemical treatments such as mixed acid cleaning and mechanical treatments such as wire brushing.

The formation of grooves on the surface of iron pipes is carried out using a general-purpose tool such as a tool. The pitch of the grooves is preferably in the range of 1 to 5. The depth of the groove is preferably 0.2~
It is 0.5 pharynx. The shape of the groove is preferably V-shaped in cross section, but is not limited thereto.

Following the formation of the groove, a strip of aluminum fin material is wound around the steel 7N6 pipe using a processing machine, and the inner part of the fin material is tightly fitted into the groove.

As the aluminum fin material, one made of a brazing sheet consisting of a thin aluminum plate and a brazing metal layer clad on at least one side thereof is often used.

The thickness of the brazing sheet is preferably 0.3mm or more, and the thickness of the brazing material layer is preferably 801mm or more. The brazing sheet may also be a thin aluminum plate clad with a brazing metal layer on only one side.

The material of the aluminum thin plate is A3003, Al10.
0, A6951, etc. are used. Aluminum-silicon and aluminum-silicon-magnesium materials are often used for the brazing filler metal layer.

In addition to the above-mentioned materials, a single material such as pure aluminum, aluminum-manganese alloy, aluminum-magnesium alloy, aluminum-indium alloy, aluminum-zinc alloy, etc. may be used as the aluminum fin material. . Since a material made of an aluminum-zinc alloy acts as a cathodic protector, its use can improve the corrosion resistance, particularly the pitting corrosion resistance, of the resulting product.

When using a single material as described above as the fin material, a wire-shaped brazing material is wrapped around the iron pipe between spiral fin materials. The wire-shaped brazing material preferably has a diameter of 0.5 to 1.5 tan.

As the brazing filler metal, aluminum-silicon type and aluminum-zinc type are often used. In the latter case, the preferred composition is 5-60% by weight aluminum, 40-95% zinc.
Weight%. When aluminum-zinc brazing filler metal is used, even if the formation of the aluminum coating layer described later is insufficient, the coating layer made of the brazing filler metal will cover the iron pipe, and the sacrificial corrosion of this coating will cause damage to the iron pipe. Provides sufficient corrosion protection. After the fin material and brazing material are wrapped, the processing oil used for grooving and wrapping is removed by washing.

As a flux for brazing, a mixture of a commercially available aluminum alloy flux, zinc chloride, tin chloride, and water is often used. The flux is applied by dipping, spraying, or the like.

Furnace brazing is done according to conventional methods. Preferred brazing conditions are pressure - atmospheric pressure, heating temperature -570 to 650.
℃, and heating time was 4 to 13 minutes. Examples of heating means include gas furnaces, electric furnaces, and high-frequency induction heating furnaces. By brazing, the fins are joined to the pipe and an aluminum coating layer is formed on the outer peripheral surface of the pipe.

After brazing, the flux is removed by washing with hot water and mixed acid.

Since the method for manufacturing an aluminum finned iron pipe according to the present invention is configured as described above, the fin pitch can be defined by forming the grooves, so there is a risk that the fin pitch will be disordered during brazing. There is no problem at all, and the quality of the product can be improved. Furthermore, in the method of the present invention, there is no need to aluminize the outer surface of the iron pipe as in the conventional method, and the cost can be reduced by omitting the number of steps. Further, by furnace brazing, an aluminum coating layer can be formed on the surface of the pipe at the same time as the fins and the pipe are joined, and as a result, a product with excellent corrosion resistance of iron pipes, especially oxidation resistance at high temperatures can be obtained. In addition, since this invention uses a method for brazing in a furnace, brazing can be performed continuously, and unlike the method for vacuum brazing, brazing by a furnace length does not limit the length of the product. It is possible to manufacture long products without any damage.

Furthermore, since the inner part of the fin material is fitted into the groove and brazed, the connection between the fin and the pipe can be made strong. Therefore, according to the method of the present invention, it is possible to obtain a finned pipe that can be used at higher temperatures than the embedded finned pipe described at the beginning.

Furthermore, since the present invention does not require the caulking process mentioned at the beginning, cost reduction can also be achieved in this respect.

In the example construction drawing, a steel pipe with an outer diameter of 25.4 mm and a thickness of 1.6 mm is immersed in a mixed acid for 10 minutes to pre-treat the surface. Next, use a cutting tool to cut a groove (2
) with a pitch of 2.54M. Separately, a 0-thick aluminum (A3003) thin plate and a pair of brazing filler metal (aluminum 90% by weight, silicon 8% by weight, magnesium 2% by weight) layers are clad on both sides.
．． A band-shaped fin material (3) with a width of 12.6 mm is formed from the five-piece brazing sheet. Then, the band-shaped fin (3) is wound around the steel pipe (1) using a processing machine so that the inner side of the band-shaped fin (3) fits tightly into the groove (2). After removing the processing oil used for grooving and winding by washing, the pipe is immersed in a flux bath to apply flux for winding the fin material. As the flux, a mixture of commercially available aluminum alloy agent Franks, zinc chloride, tin chloride, and water in a volume ratio of 100:5:2.5:40 is used. Next, to wrap the fin material, the steel pipe is placed in a high frequency induction heating furnace and heated at 610° C. for 7 minutes under atmospheric pressure. In this way, the fin material is joined to the pipe by brazing in the furnace. Finally, the wax antique is immersed in a mixed acid for about 10 minutes to remove the flux and obtain a finned pipe product.

Example 2 A concave groove was formed in the iron pipe by the same operation as in Example 1,
A band-shaped aluminum fin material made of an aluminum-zinc alloy is then wrapped around this steel pipe so that its inner side fits into the groove. Next, between the spiral fin materials, a steel pipe with a diameter of 1. Own wire-shaped aluminum-zinc (30 near 0 by weight)
Wrap with brazing filler metal. The following operations are performed in the same manner as in Example 1 to obtain a finned pipe product.

[Brief explanation of drawings]

The drawing is a longitudinal sectional view of a finned pipe showing an embodiment of the invention. (1)...Steel pipe, (2)...9 grooves, (3)...
・Aluminum fin material. that's all

Claims (3)

[Claims] (1) A spiral groove is formed on the surface of the iron pipe, and a strip of aluminum fin material is wrapped around the iron pipe so that the inside part fits into the groove. A method for manufacturing aluminum finned iron pipes, which is characterized by joining materials to the pipe. (2) Claim 1 in which the fin material is made of a brazing sheet made of a thin aluminum plate and a brazing metal layer clad on at least one side of the fin material.
The method described in section. (3) The method according to claim 1, wherein a wire-shaped brazing material is wound around an iron pipe between spiral fin materials.