JPS59185778A - Method for removing sprayed aluminum film - Google Patents

Abstract

PURPOSE:To remove a sprayed Al film covering the surface of a steel material without damaging the surface of the steel material by jetting water on the Al film under superhigh pressure. CONSTITUTION:A jet gun 3 having one or more nozzles 4 is placed at a position 10-100mm. away from the surface of a steel material 5 having a sprayed Al film in a direction perpendicularly to the surface of the material 5. A jet pump 1 is worked to jet water on the surface of the material 5 under 400-500kg/cm<2> superhigh pressure from the gun 3 through a superhigh pressure hose 2. At the same time, the gun 3 is moved with a moving device 6 to remove the sprayed Al film from the whole surface of the material 5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing an aluminum spray coating, and particularly to a method for removing an aluminum spray coating formed on the surface of oil tanks and steel materials for rust prevention and corrosion prevention.

In general, structural steel materials are easily corroded, so rust prevention and corrosion prevention have become a major problem in structures constructed under harsh conditions such as marine environments. As a means to solve this problem, in recent years it has been proposed to utilize the rust prevention effect of aluminum spray coating, and steel sheets coated with aluminum spray coating,
Steel pipes became commercially available and were used in buildings, chemical equipment, and other structures. This thermally sprayed aluminum is usually constructed by welding, but if welded over the aluminum thermally sprayed coating, the aluminum will penetrate into the weld, causing deterioration of the toughness of the joint and defective bead shape. Therefore, either remove the aluminum spray coating by the necessary width and weld, or weld using a frame-shaped steel plate that has been sprayed in advance to prevent the aluminum spray coating from forming on the part corresponding to the welding area. There is a need. In addition, after construction, in order to prevent rust and corrosion at welded parts that do not have an aluminum sprayed coating, aluminum is sprayed on the welded parts to form a protective coating, but this is done on a regular basis, such as when oil tanks are opened. In the case of structures that require inspection, it is difficult to perform non-destructive testing such as magnetic particle inspection of welds or ultrasonic thickness measurement of steel materials over the aluminum spray coating, so the aluminum spray coating is removed. This is necessary.

Conventionally, methods for removing aluminum spray coatings include:
Sandpaper, sandblasting, etc. were used, but they not only scraped off the coating but also the base steel, and had the disadvantages of generating dust and poor work efficiency.

An object of the present invention is to provide a method that can remove an aluminum sprayed coating without damaging the steel material that is the base material, eliminate the generation of dust, and efficiently remove the aluminum sprayed coating. shall be.

The gist of the present invention resides in a method for removing an aluminum sprayed coating, which comprises injecting ultra-high pressure water onto the aluminum sprayed coating covering the surface of a steel material.

That is, the present invention utilizes the difference in strength and hardness between the aluminum spray coating and the base steel material to remove only the aluminum coating by spraying an ultra-high pressure water jet onto the aluminum spray coating. The adhesion of the aluminum thermal spray coating is easily affected by preheating and surface treatment during thermal spraying, thermal spraying conditions, and atmosphere during thermal spraying, so it is recommended that the water pressure of the spray jet be set according to the adhesion of the coating. preferable. When removing an aluminum thermal spray coating formed by normal gas wire thermal spraying using oxygen or propane as a heat source, depending on the thickness of the coating,
Usually 9/d or more in 400, preferably 9/d in 800'
This is done by injecting a jet with a water pressure of cJ or more. In addition, under special thermal spraying conditions, high adhesion (usually 400 to 500
9/cJ) when removing an aluminum spray coating,
It is preferable to use a jet with a water pressure of 1000 to 100 d/d or more.

FIG. 1 shows an example of an apparatus used to carry out the present invention, and shows 1
2 is a jet pump, 2 is an ultra-high pressure hose, 3 is a jet gun, and 4 is a nozzle head which has one or more nozzles and is rotatable.

When using the above device to peel off and remove an aluminum sprayed coating, a jet gun is placed at an appropriate distance from the coating surface, for example, 10 to 100 rmr, in a direction perpendicular to the surface, and a water jet at a predetermined pressure is applied. What is necessary is to move it at a low speed by the moving device 6 while injecting it.

Example: A jet with a water pressure of 800~/d and a flow rate of 3.517 minutes.
．． When two nozzles of 3 W mΦ were sprayed in the pattern shown in Figure 2 onto a steel material 5 with an aluminum spray coating located 30 rrrIn apart and moved at a speed of 05 m/min, the aluminum spray coating was removed. The aluminum coating was completely removed from the base steel material. Furthermore, no peeled aluminum coating was scattered into the air, and no damage was observed on the surface of the base steel material. Note that the jet water spray pattern may be as shown in FIGS. 3 to 5.

As explained above, according to the present invention, the aluminum thermal spray coating can be easily removed by a simple operation of jetting ultra-high pressure water without damaging the base steel material, and the aluminum thermal spray coating can be peeled off and removed. The coating does not turn into dust and pollute the atmosphere, and work efficiency can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an apparatus used to carry out the method of the present invention, FIG. 2 is a diagram showing an example of the injection pattern, and FIGS. 3 to 5 are diagrams showing other examples of the injection pattern. 1...Jet pump, 2...Ultra high pressure hose, 3.
... Jet gun, 4... Nozzle head, M material, 6
...Movement device.

Claims (1)

[Claims] (1) A method for removing an aluminum sprayed coating, which comprises spraying ultra-high pressure water onto the aluminum sprayed coating covering the surface of the material.