JPS6126763A - Formation of thermal sprayed film having high adhesion - Google Patents

Abstract

PURPOSE:To form a thermal sprayed film having superior adhesion by heating the surface of a steel material to form an oxide film of a specified thickness and by thermal sparying Al or Zn on the oxide film. CONSTITUTION:An iron or steel material is heat treated in the air or an oxidizing atmosphere to form an iron oxide film of 50-1,000Angstrom thickness on the surface of the material. An Al, Zn, or Al-Zn alloy film of about 50-500mum thickness is then formed on the iron oxide film by thermal spraying with a gas flame, arc, plasma or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for forming a highly adhesive thermal spray coating.

(Prior art and problems) In recent years, iron: - In order to protect the material from corrosion, its surface has been given excellent corrosion resistance. Thermal spray coating with AR or Zn or their alloys is widely used.

That is, Al, Zn, or their alloys are more excellent in protecting iron and steel materials from corrosion than other metals, and are therefore widely used in the atmospheric environment, marine environment, and other fields. Incidentally, such a thermal spray coating layer is generally formed on a roughened surface of the steel material by blasting the surface of the steel material with a shot material or a grid material as a pretreatment.

However, the thermal spray coating layer formed in this manner is generally maintained bonded to the base due to the anchor effect. In addition, the activity of iron and steel surfaces that have been roughened due to pretreatment decreases over time, so the time from roughening to thermal spraying must be short, and Even 4
It is a well-known fact that it is necessary to thermally spray to a specified thickness within a certain amount of time, and this is a major time constraint in thermal spraying work.

In general, as described, for example, in Thermal Spraying Handbook, published by Nikkan Kogyo Shimbun in 1960, page 507, and in "Thermal Spraying Engineering" by Hasui, published by Yokendo in 1962, page 89.

Mo has good adhesion to the base steel material to increase adhesion.

Alternatively, Ni-Ag alloy or the like can be thermally sprayed as a bonding coat, and then Al or Zn or their alloys can be thermally sprayed on top of that, or iron or steel materials can be thermally sprayed as described in page 499 of the same thermal spraying handbook. The method of preheating the surface and thermal spraying has been used. However, these known methods for improving the adhesion of thermal sprayed coatings still cannot be said to provide sufficient adhesion, and furthermore, the time constraints for thermal spraying after the surface of the iron/steel material has been roughened have not been alleviated in any way. However, this only makes the process within the time limit more complicated, and on the contrary, makes it more difficult.

Here, AQ or i>zn or their alloys include pure Zn, pure AE, or their alloys, as well as one or both of these metals and a small amount of MOlCr.

It means an alloy containing one or more of Ni 1Mn, MP, etc.

(Structure of the invention) In view of the above situation, the present inventors attempted various improvements, and as a result, they achieved the five present inventions. That is, the present invention heat-treats the iron/steel material to be thermally sprayed in air or in an oxidizing atmosphere to form an iron oxide film on the surface of the steel material in advance to a film thickness of 50 mm and 11,000 mm. This is a method for forming a highly adhesive thermal sprayed coating, which is characterized in that A8 or Zn or an alloy thereof is thermally sprayed thereon. The present invention will be explained in detail below.

First, in the present invention, steel materials refer to steel plates, steel pipes, shaped steel, steel bars, etc. defined by JIS or standards similar to JIS, or structures using them. Next, the reason why an iron oxide film is formed on the surface of these steel materials is as follows.

In other words, during thermal spraying, sprayed particles of AQ or Zn or their alloys adhere to the steel surface due to the wetting phenomenon that is forced to expand on the surface of the steel material by a jet of compressed air, combustible gas, or plasma flame. Although the surface of the oxide film does not have the same degree of activity as the surface of steel materials roughened for thermal spraying, it has very good wettability with sprayed particles of AA or Zn or their alloys. The adhesion of the sprayed ruptured film is significantly improved. In addition, unlike roughened steel materials, there is no need to worry about a decrease in activity, so there is an advantage that there is no time restriction from roughening to thermal spraying. Therefore, the iron and steel materials to be thermally sprayed are heat-treated in air or in an oxidizing atmosphere using a heating furnace or the like.

Forms an iron oxide film on the surface of these iron and steel materials.

In this case, if the thickness of the iron oxide film is less than 50X, wettability cannot be improved satisfactorily, and the effect is extremely poor. Also, if the thickness of the iron oxide film exceeds 1oooX, AQ
Alternatively, even though the adhesion between the Zn or alloy-based sprayed coating and the iron oxide film is strong, the adhesion between the iron base and the iron oxide film decreases, so that the effect cannot be expected. After forming an iron oxide film on the surface of the iron/ζ-material in this way, an AA or Zn, or alloy-based film thereof is further formed thereon by thermal spraying means such as gas flame, arc, or plasma. . The thickness of the thermally sprayed coating varies depending on its intended use, and a thickness of approximately 50 μm to 500 μm can be practically used.

In the present invention, the adhesion strength is measured using ASTM D1.
062 standard, and in the present invention, high adhesion is defined as 300KP/C according to the measurement method based on the above standard.
A thermally sprayed coating that can achieve coating adhesion of a to h is called high adhesion.

Finally, the effects of the present invention will be explained in more detail with reference to Examples.

(Example) Plate thickness 12. After cleaning organic substances such as oil and fat. aX length 30 (
1m, aX width 300, J+ 8841 steel plate surface.

Steel grids with an average grain size of 1 were roughened by a blast treatment, and then each first
Heat treatment was carried out under the conditions shown in the table. 1 Invention Examples 1 to 6
For Examples 1 to 4 of the present invention, an iron oxide film of various thicknesses was formed on top of the iron oxide film using a gas wire spraying machine.
Aε thermal sprayed coating with a thickness of 200μ was formed by thermal spraying, and a thermal sprayed coating with a thickness of 200μ of each of Zn and 15 AP and -Zn alloy was sprayed for Invention Example 5 and -Zn alloy, respectively. formed. At this time, the time from roughening of the steel plate to thermal spraying is classified into four types shown in Table 1. At the same time, a thermal spray plate film of Comparative Example 1.2 was also formed. Next, the adhesion strength of the various sprayed coatings obtained as a result was measured.

The adhesion strength was measured by fixing the above-mentioned thermal sprayed steel plate, adhering a mild steel holder for tensile testing to the surface of the thermal sprayed coating using epoxy adhesive, and then peeling it off perpendicular to the adhesion surface of the thermal sprayed coating. The results are shown in Table 1.

From the results shown in Table 1, the thermal spray coating formed by the thermal spray coating formation method of the present invention has excellent adhesion, and even after the surface roughening of the steel material and the thermal spraying process take a long time, the adhesion remains strong. It is clear that this is an excellent thermally sprayed coating that does not cause any deterioration in its properties.

(Effects of the Invention) As described above, according to the method of the present invention, a thermal spray coating with excellent adhesion can be formed.

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Claims (1)

[Claims] By heat-treating the iron or steel material to be thermally sprayed in air or in an oxidizing atmosphere, an iron oxide film with a thickness of 50 Å to 1000 Å is formed on the surface of the iron or steel material, and then Al or A method for forming a highly adhesive thermal spray coating, which comprises thermal spraying Zn or an alloy thereof.