JP6718644B2 - Method for forming self-fluxing alloy coating layer - Google Patents

Description

The present invention relates to a method for forming a self-fluxing alloy coating layer on the surface of a base material such as steel.

It is generally practiced to coat the surface of a base material such as steel used in a harsh environment with a self-fluxing alloy to impart good heat resistance, corrosion resistance and wear resistance.

As a method of forming a self-fluxing alloy coating layer on the surface of a base material such as steel material, the following Patent Document 1 discloses that a self-fluxing alloy powder having wear resistance is placed on the surface of a blasted base material. A method is described in which the powder layer is adjusted to a predetermined thickness and then carried into a heating furnace and heated to sinter the powder layer and weld it to the surface of the base material.

Therefore, when forming the self-fluxing alloy coating layer on the surface of the base material, heat treatment of the powder layer to be sintered to form the self-fluxing alloy coating layer is performed in order to improve productivity. It is desirable to carry out by a process of short time and rapid heating, rather than by carrying out in a heating furnace as described in.

Here, high-frequency induction heating is known as a short-time rapid heating process. For example, in Patent Document 2 below, after remelting treatment by high-frequency induction heating after spraying a self-fluxing alloy on the surface of a base material. Has been introduced.

JP-A-6-240307 JP, 7-188892, A

However, since the powder layer in a state where the powders are not bonded to each other has poor thermal conductivity and the powder surface is easily oxidized during melting, the heat treatment of the powder layer formed on the surface of the base material is short by induction heating. When the process of time/rapid heating is performed, the self-fluxing alloy powder in the powder layer is not melted uniformly, the unmelted portion is formed in the formed self-fluxing alloy coating layer, and the substrate surface is exposed. However, there is a problem in that a uniform self-fluxing alloy coating layer cannot be formed.

The present invention has been made based on the above circumstances.
The object of the present invention is to provide a uniform and dense self-fluxing alloy coating even if the heat treatment of the powder layer containing the self-fluxing alloy powder formed on the surface of the substrate is carried out by a short-time rapid heating process by induction heating. It is to provide a method for forming a self-fluxing alloy coating layer capable of forming a layer on the surface of a base material.

The method for forming the self-fluxing alloy coating layer of the present invention is defined in JIS H8260, and the particle size measured by the sieving method is 100 to 100 parts by mass of the self-fluxing alloy powder having a particle size of 45 to 125 μm, and the particle size measured by the sieving method. Of 0.05 to 1.0 part by mass of borax powder having a particle size of 125 μm or less (hereinafter, also referred to as “powder mixing step”);
A step of supplying the mixed powder to the surface of the base material to form a powder layer (hereinafter, also referred to as "powder layer forming step"),
Sintering by sintering the powder layer by induction heating under conditions of a temperature of 1000 to 1200° C. and a moving speed of an induction heating unit of 0.5 to 5 mm/s to sinter the self-fluxing alloy powder in the powder layer. And a step of forming a self-fluxing alloy coating layer composed of a body and having a porosity of 10% or less on the surface of the base material (hereinafter, also referred to as "sintering step").

According to such a forming method, since the borax powder is mixed, the melting property of the powder layer (mixed powder) is remarkably improved, and the heat treatment of the powder layer is performed by induction heating for a short time/rapid heating. Even if it is carried out by the above process, a uniform and dense self-fluxing alloy coating layer can be formed on the substrate surface.

In the powder mixing step, the self-fluxing alloy powder and the borax powder may be mixed with ceramic particles to prepare the mixed powder.

According to the method for forming the self-fluxing alloy coating layer of the present invention, the heat treatment of the powder layer containing the self-fluxing alloy powder is carried out by the process of short-time and rapid heating by induction heating, but the uniform and dense self-heating is performed. The molten alloy coating layer can be formed on the surface of the base material.
Then, by performing the heat treatment of the powder layer by the process of short-time and rapid heating by induction heating, the productivity can be improved as compared with the conventional forming method in which the powder layer is heat-treated in the heating furnace. You can

3 is a photograph showing the surface condition of the self-fluxing alloy coating layer formed on the substrate surface in Example 1. 5 is a photograph showing the surface state of the self-fluxing alloy coating layer formed on the substrate surface in Example 2. 5 is a photograph showing the surface state of the self-fluxing alloy coating layer formed on the substrate surface in Comparative Example 1. 7 is a photograph showing the surface state of the self-fluxing alloy coating layer formed on the substrate surface in Comparative Example 2.

Hereinafter, the present invention will be described in detail.
The method for forming a self-fluxing alloy coating layer of the present invention includes a powder mixing step, a powder layer forming step, and a powder sintering step.

<Powder mixing process>
The powder mixing step of the forming method of the present invention is a step of mixing the self-fluxing alloy powder and the borax powder to prepare a mixed powder.

Examples of the self-fluxing alloy powder used in the forming method of the present invention include those specified in JIS H8260 (powder material for thermal spraying).
Regarding the particle size of the self-fluxing alloy powder, the particle size measured by a sieving method is preferably 250 μm or less, and more preferably 45 to 125 μm.

The borax powder used in the forming method of the present invention consists of a hydrate or anhydrate of sodium tetraborate.
As the particle size of the borax powder, the particle size measured by a sieving method is preferably 125 μm or less. Borax powder with an excessively large particle size cannot penetrate between the self-fluxing alloy powders and therefore cannot sufficiently contribute to the improvement of the meltability, and the surface of the obtained self-fluxing alloy coating layer has a glass-based composition. The compound of (3) may be scattered, resulting in poor appearance.

The meltability of the mixed powder (powder layer) formed by mixing the self-fluxing alloy powder and the borax powder is far superior to that of the self-fluxing alloy powder alone.
Although the reason is not clear, the borax powder having a relatively low melting point is melted before the melting of the self-fluxing alloy powder to improve the thermal conductivity of the powder layer, and is contained in the borax. It is presumed that this is because boron binds with oxygen in the powder layer and oxygen on the surface of the base material to suppress the oxidation of the powder surface and the like.

By directly mixing the borax powder with the self-fluxing alloy powder, the meltability of the powder layer (mixed powder) can be significantly improved. The whole is melted uniformly, and as a result, a uniform and dense self-fluxing alloy coating layer can be formed.

Even if borax is added to the self-fluxing alloy powder in a mode other than directly mixing with the self-fluxing alloy powder (for example, a liquid composition containing borax is applied to a powder layer made of the self-fluxing alloy powder). However, the meltability of the powder cannot be improved (see Comparative Example 2 described later).

The content ratio of borax in the mixed powder is preferably 0.05 to 1.0 parts by mass (parts by mass of decahydrate of sodium tetraborate) per 100 parts by mass of the self-fluxing alloy powder, which is preferable. If one example is shown, it will be 0.2 mass part.

When the content ratio of borax is too small, the meltability of the mixed powder cannot be sufficiently improved, and it becomes difficult to form a uniform and dense self-fluxing alloy coating layer.
On the other hand, when the content ratio of borax is excessive, a glass-based compound may be scattered on the surface of the self-fluxing alloy coating layer to be obtained, resulting in poor appearance.

In this powder mixing step, the mixed powder may be prepared by mixing the ceramic particles together with the self-fluxing alloy powder and the borax powder. Thereby, the wear resistance can be further improved.

<Powder layer forming step>
The powder layer forming step of the forming method of the present invention is a step of forming the powder layer by supplying the mixed powder prepared in the powder mixing step to the surface of the base material.
Specifically, the powder layer is formed by placing the mixed powder on the surface of the base material and adjusting it to a predetermined thickness.

Here, the base material (object to be processed) on which the powder layer is formed is usually made of a metal such as steel (mild steel/SUS). The shape of the base material is not particularly limited, but a plate shape is preferable.
The surface of the base material forming the powder layer is preferably roughened by blasting.

The method of supplying the mixed powder to the surface of the base material is not particularly limited, and examples thereof include a method of providing an outer frame on the surface of the base material and causing the mixed powder to flow into the frame.

The thickness of the powder layer is preferably about 1.4 to 2.0 times the thickness of the self-fluxing alloy coating layer to be formed in consideration of the thickness change (loss) due to sintering.
As a method for adjusting the thickness of the powder layer, for example, after inflowing an excessive amount of the mixed powder into the outer frame provided on the surface of the base material, the excess mixed powder is adjusted to an appropriate thickness regulating member (for example, a blade). ).

In the forming method of the present invention, the mixed powder containing the self-fluxing alloy powder and the borax powder is formed on the surface of the base material as a powder layer maintaining the powder state.
As a result, it is possible to improve productivity and reduce production cost, and it is possible to avoid thermal strain of the base material which may be caused by the shape of the base material. Further, it becomes possible to mix the ceramic particles in the mixed powder.
When a thermal spray coating is formed by a thermal spraying method instead of the powder layer, the heat treatment is performed twice, resulting in a decrease in productivity and an increase in production cost, depending on the shape of the base material (for example, in the case of a thin plate shape). In addition, it may cause thermal strain.

<Sintering process>
In the sintering step of the forming method of the present invention, the powder layer formed on the surface of the base material is heated to 1000 to 1200° C. by an induction heating means, and the self-fluxing alloy powder in the powder layer is sintered to burn it. It is a step of forming a self-fluxing alloy coating layer made of a bonded body.

This sintering step is characterized in that the heat treatment of the powder layer is carried out by a short-time rapid heating process by induction heating (movement heating).
By performing the heat treatment of the powder layer by the process of short-time and rapid heating by induction heating, the productivity can be improved as compared with the conventional forming method in which the powder layer is heat-treated in the heating furnace.

The heating temperature of the powder layer is 1000 to 1200°C, preferably 1050 to 1150°C.
If the heating temperature is lower than 1000° C., the powder is not sufficiently melted, so that a dense film (self-fluxing alloy coating layer) cannot be formed. On the other hand, if the heating temperature exceeds 1200° C., it may be excessively melted and the shape of the coating layer may not be maintained, or the hardness of the coating layer may decrease due to overheating.

The moving speed of the induction heating means with respect to the powder layer is 0.5 to 5 mm/s, preferably 1 to 3 mm/s.

Through this sintering process, the powder layer formed on the surface of the base material (mixed powder in which borax powder is directly mixed with self-fluxing alloy powder) is uniformly melted as a whole, resulting in uniform and dense sintering. A body (self-fluxing alloy coating layer) can be formed on the surface of the base material.
The thickness of the self-fluxing alloy coating layer formed by the method of the present invention is, for example, 0.5 to 5 mm, preferably 1.0 to 2.0 mm, and 2.0 mm if a suitable example is shown. ..

The composite member in which the self-fluxing alloy coating layer is formed on the surface of the base material by the forming method of the present invention is provided with good heat resistance, corrosion resistance and wear resistance, and in particular, a cyclone, a stirrer, which is a wear resistant member, It is applied to ducts, screws, various rails, etc., and also to furnace wall materials, which are heat and corrosion resistant members, and various high temperature pipes.

Examples of the present invention will be described below, but the present invention is not limited thereto.
The particle diameters of the powders used in the following examples and comparative examples are the values measured by the sieving method.

<Example 1>
(1) Powder mixing step:
100 parts by mass of Ni-based self-fluxing alloy powder “13017” (manufactured by Eutectic Canada Inc.) having a particle diameter of 45 to 125 μm, which corresponds to JIS H 8303 2.14A, and borax powder having a particle diameter of 125 μm or less “sodium tetraborate” Decahydrate" (manufactured by Kanto Chemical Co., Inc.) 0.2 part by mass was uniformly mixed to prepare a mixed powder.

(2) Powder layer forming step:
The mixed powder obtained in (1) above is supplied to the surface of a substrate (width 150 mm × length 800 mm × thickness 4.5 mm) made of blasted general structural rolled steel material SS400, and the substrate surface concerned The thickness was adjusted to 3.5 mm to form a powder layer.

(3) Sintering process:
By moving the high frequency induction heating device in the length direction of the substrate to perform induction heating on the powder layer formed on the substrate surface by the above (2), and sintering the self-fluxing alloy powder in the powder layer. A self-fluxing alloy coating layer made of a sintered body was formed on the surface of the substrate. Here, the moving speed (feeding amount) of the induction heating device was set to 1 mm/s.

<Example 2>
In the powder mixing step, 100 parts by mass of a mixture “23005” (manufactured by Eutectic Canada Inc.) of Ni-based self-fluxing alloy powder having a particle size of 45 to 125 μm and WC powder, which corresponds to JIS H 8303 2.29B, and a particle size. In the same manner as in Example 1 except that 0.2 parts by mass of borax powder "sodium tetraborate decahydrate" (manufactured by Kanto Kagaku Co., Ltd.) having a particle size of 125 μm or less was uniformly mixed to prepare a mixed powder. Then, a self-fluxing alloy coating layer made of a sintered body was formed on the surface of the substrate.

<Comparative Example 1>
In the powder layer forming step without performing the powder mixing step of Example 1, self-fluxing alloy powder having a particle diameter of 45 to 125 μm, which corresponds to JIS H 8303 2.14A, is supplied to the substrate surface to give a thickness of 3 A self-fluxing alloy coating layer made of a sintered body was formed on the surface of the substrate in the same manner as in Example 1 except that the powder layer (powder layer consisting only of self-fluxing alloy powder) was formed to have a thickness of 0.5 mm.
The obtained self-fluxing alloy coating layer was non-uniform and part of the substrate surface was exposed.

<Comparative example 2>
After completion of the powder layer forming step of Comparative Example 1, borax powder alcohol containing 5 parts by mass of borax powder “sodium tetraborate decahydrate” (manufactured by Kanto Chemical Co., Inc.) and 95 parts by mass of ethanol (solvent). About 80 g of the solution was applied to the powder layer formed on the surface of the substrate by spraying, and after drying, a sintering process was performed in the same manner as in Comparative Example 1 to form a self-fluxing alloy coating layer made of a sintered body on the substrate surface. Formed.

<Evaluation of coating layer>
The following items (1) to (4) were evaluated for each of the self-fluxing alloy coating layers formed in Examples 1 and 2 and Comparative Examples 1 and 2. The evaluation method (evaluation criteria) is as follows. The results are shown in FIG. 1 and Table 1 below.

(1) Visual inspection:
The surface state of the self-fluxing alloy coating layer was visually observed and evaluated according to the following criteria.
“◯”: A uniform and dense surface state in which the entire surface is melted uniformly and there are no wrinkles on the surface.
“Δ”: Wrinkles due to uneven melting are observed on the surface.
“X”: There is a portion where the substrate surface is exposed due to large cracks or wrinkles.

(2) Measurement of film thickness:
The film thickness of the formed self-fluxing alloy coating layer was measured with a micrometer [reference (coating layer+substrate)-substrate=coating layer].

(3) Hardness:
The formed self-fluxing alloy coating layer was cut together with the substrate, and the Vickers hardness of the coating layer cross section was measured according to JIS Z 2244 (Vickers hardness test-test method).

(4) Method of measuring porosity (evaluation of denseness):
The cross section of the formed self-fluxing alloy coating layer was observed with an optical microscope, and the porosity was measured by image analysis. Here, in order for the compactness to be good, the porosity must be 10% or less.

Claims (2)

According to JIS H8260, 100 parts by mass of self-fluxing alloy powder having a particle size of 45 to 125 μm measured by a sieving method, and borax powder of 0.05 to 1 having a particle size of 125 μm or less measured by a sieving method. 0.0 parts by mass to prepare a mixed powder,
Supplying the mixed powder to the substrate surface to form a powder layer,
Sintering by sintering the powder layer by induction heating under conditions of a temperature of 1000 to 1200° C. and a moving speed of an induction heating unit of 0.5 to 5 mm/s to sinter the self-fluxing alloy powder in the powder layer. Forming a self-fluxing alloy coating layer having a porosity of 10% or less on the surface of the base material. The method for manufacturing a composite member according to claim 1, comprising a step of preparing ceramic particles together with self-fluxing alloy powder and borax powder to prepare the mixed powder.