JPS59190365A - Formation of aluminum film on outside of iron pipe - Google Patents

Abstract

PURPOSE:To form easily an Al film on the outside of an iron pipe by spirally winding wiry Al around the pipe and by heating the pipe to melt the wiry Al. CONSTITUTION:An iron pipe 1 is pretreated by chemical treatment such as cleaning with a mixed acid or by mechanical processing such as wire brushing. Wiry Al 2 of 0.5-1.5mm. diameter is spirally wound around the pipe 1 at 3-10 turns per 1 inch winding pitch. An Al-Si alloy or an Al-Zn alloy may be used in place of Al. The pipe 1 is then heated at 570-700 deg.C for 10-60min. The wiry Al 2 is melted by the heating to form an Al film 3 on the outside of the pipe 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming an aluminum coating on the outer peripheral surface of an iron pipe.

For example, a heat pipe for a device used in high humidity, such as a heat pipe type waste heat recovery device, must be made of iron pipe that can withstand high humidity. Preferably, the outer surface of such a heat pipe is brazed with aluminum fins to improve thermal efficiency. In order to braze aluminum fins to the outer surface of an iron pipe, it is necessary to form an aluminum coating only on the outer peripheral surface of the iron pipe in advance. The reason why an aluminum coating is formed only on the outer circumferential surface is that if an aluminum coating is formed on the inner circumferential surface of an iron pipe, hydrogen gas may be generated due to a reaction between the working fluid sealed inside the iron pipe and the aluminum. This is because there is a risk of explosion. Conventionally, the method of forming an aluminum coating only on the outer peripheral surface of an iron pipe was to weld a lid to one end of the iron pipe to close it, and then melt the iron pipe so that the other end would not be exposed to the molten aluminum. There is a method of immersing it in aluminum. In this method, it is necessary to cut out the portion of the iron pipe that is not immersed in the molten aluminum, resulting in a problem of poor material yield. In addition, it is necessary to weld a lid to one end of the iron pipe, which increases the cost and makes the work troublesome. Furthermore, there are ion blasting methods and vacuum evaporation methods for forming aluminum coatings only on the outer circumferential surface of iron pipes, but in order to thicken the aluminum coatings, it is necessary to increase the processing time, resulting in high costs. The problem is that it gets expensive. Additionally, if the iron pipe is long, there is a problem in that a special vacuum device is required. Furthermore, there is a problem that it is difficult to form an aluminum film containing an element that easily vaporizes in a vacuum.

An object of the present invention is to provide a method for forming an aluminum coating on the outer circumferential surface of an iron pipe, which solves the above-mentioned problems all at once.

In this specification, the term "iron pipe" includes iron alloy pipes and steel pipes. Furthermore, the term "aluminum" includes not only pure aluminum but also aluminum alloys.

The method of forming an aluminum coating on the outer circumferential surface of an iron pipe according to the present invention is to spirally wrap aluminum wire around the outer circumferential surface of the iron pipe, and then heat the iron pipe to melt the wire aluminum. It is characterized by forming a film.

Iron pipes are pretreated by chemical treatments such as mixed acid cleaning and mechanical treatments such as wire brushing.

Examples of wire-shaped aluminum include pure aluminum, Al-8i alloy, p, 7? -Zn-based alloys are used. Both the AJ-3i series alloy and the A,1-Zn series alloy are used as waxes. Furthermore, since the Al-Zn alloy has a cathodic protection effect, it has the effect of preventing corrosion of iron pipes. The preferred diameter of the wire aluminum is 05 to 1.5 nvn. In addition, the winding pitch of wire-shaped aluminum is 3~]
It is preferable to set it to 0 rows/inch. The thickness of the formed aluminum film can be changed by changing the diameter of the aluminum wire and the O winding pitch. After wrapping the aluminum wire, the oil used for wrapping is removed by washing.

It is preferable to wrap the aluminum wire around the outer peripheral surface of the iron pipe and then apply flux. Flux has the effect of removing the oxide film on wire-shaped aluminum when heating the iron pipe in the atmosphere in a subsequent process, and also improving the BEE brittleness of molten aluminum. As for the flux, you can use commercially available aluminum solder flux or ZnCl! 2.5nCz
It is better to use one to which 2-nato is added.

These are applied by dissolving them in water or organic solvents. The flux is applied by a dipping method, a spray method, or the like.

A steel pipe wrapped with aluminum wire is heated in a furnace. Preferred heating conditions are pressure car pressure, heating temperature -570 to 700' C1 heating time -10 to 60
It is a minute. Examples of heating means include gas furnaces, electric furnaces, and high-frequency induction heating furnaces. When heated, the wire-shaped aluminum melts, the molten aluminum flows and covers the surface of the iron pipe, and is cooled to form an aluminum coating. Thereafter, hot water washing, acid washing or mixed acid washing, and water washing are performed in the above order to remove the flux.

The method of forming an aluminum coating on the outer circumferential surface of an iron pipe according to the present invention is configured like a double series.
It is possible to form an aluminum coating only on the outer peripheral surface without welding a lid to the opening of the iron pipe as in the conventional dipping method. Therefore, the trouble of welding the lid is eliminated and the cost is also reduced. Further, unlike the conventional dipping method, there is no need to cut out the portion where the aluminum coating is not formed, so the material yield is improved. On the other hand, unlike the conventional ion blating method and vacuum evaporation method, special vacuum equipment is not required, so the cost is reduced. Furthermore, since the thickness of the aluminum coating can be controlled by changing the diameter of the wire-shaped aluminum and the winding pitch, a thick coating can be obtained without taking the time required by conventional ion blasting methods. Furthermore, an aluminum film containing elements that easily vaporize in vacuum can also be formed.

Embodiments of the present invention will be described below with reference to the drawings.

Iron pipe (1) with an outer diameter of 27.2 mm and a length of 200 mm.
Cleaned with mixed acid, then applied AI! to the iron pipe (1). -8i
Wire-shaped aluminum (2) made of an alloy and having a diameter of 0.8 rttm was wound spirally at a pitch of 5 mm (first
(see Figure 1). After removing the oil used for winding by washing, flux was applied. As the flux, commercially available aluminum flux and 7.
n'C7!2 and 5nCI! 2 and water 100:5:2.
A mixture at a weight ratio of 5:40 was used.

After that, the iron pipe (1) wrapped with wire-shaped aluminum (2) is placed in a furnace and heated to 610-600 m
Heated at 30°C for 5-6 minutes. Finally, the furanx was removed by washing with a mixed acid at 70'C for 5 minutes. As a result, as shown in Figure 2, there are 5
An aluminum coating (3) with a thickness of 0 to several liters Q Q Pm was formed.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a partially cutaway side view showing a state in which wire-shaped aluminum is wrapped around an iron pipe, and FIG. It is a partially cutaway side view showing N+ Eve. (1) - Iron pipe, (2)... wire-shaped aluminum, (3)... e-aluminum coating. The above four people.

Claims (1)

[Claims] An aluminum coating is formed on the outer circumferential surface of an iron pipe, characterized in that aluminum wire is spirally wound around the outer circumferential surface of the iron pipe, and then the iron pipe is heated to melt the aluminum wire and form an aluminum coating. How to form.