JP2017110254A - Method for forming self-fluxing alloy coating layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a self-fluxing alloy coating layer capable of forming the uniform and close self-fluxing alloy coating layer on a substrate surface even when a heating treatment of a powder layer containing the self-fluxing alloy coating layer formed on the substrate surface is conducted by a process of short time quick heating by induction heating.SOLUTION: A method includes a powder mixing process for preparing a mixed powder by mixing a self-fluxing alloy powder and a borax powder, a powder layer forming process for forming a powder layer by supplying the resulting mixed powder to a substrate surface, a sintering process for forming a self-fluxing alloy coating layer consisting of a sintered body on the substrate surface by sintering the self-fluxing alloy powder in the powder layer by heating the formed powder layer to 1000 to 1200°C with induction heating means.SELECTED DRAWING: Figure 1

Description

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

  Generally, it is common practice to provide a good heat resistance, corrosion resistance and wear resistance by coating the surface of a base material such as steel used in a harsh environment with a self-fluxing alloy.

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

  Thus, when the self-fluxing alloy coating layer is formed on the surface of the base material, the heat treatment of the powder layer that is sintered to form the self-fluxing alloy coating layer is performed from the viewpoint of improving productivity. It is desirable to carry out by a short time and rapid heating process rather than in a heating furnace as described in the above.

  Here, high-frequency induction heating is known as a short-time and rapid heating process. For example, in Patent Document 2 below, a self-fluxing alloy is sprayed on the surface of a base material and then re-melted by high-frequency induction heating. It has been introduced.

JP-A-6-240307 Japanese Patent Laid-Open No. 7-188882

  However, a powder layer in a state where the powders are not bonded is inferior in thermal conductivity, and oxidation of the powder surface easily occurs at the time of melting. Therefore, the heat treatment of the powder layer formed on the substrate surface is short by induction heating. When implemented by the time and rapid heating process, the self-fluxing alloy powder in the powder layer is not uniformly melted, resulting in unmelted portions in the formed self-fluxing alloy coating layer, and the substrate surface being exposed. There is a problem that a uniform self-fluxing alloy coating layer cannot be formed.

The present invention has been made based on the above situation.
The object of the present invention is to provide a uniform and dense self-fluxing alloy coating even when the heat treatment of the powder layer containing the self-fluxing alloy powder formed on the substrate surface is carried out by a short time and rapid heating process by induction heating. It is providing the formation method of the self-fluxing alloy coating layer which can form a layer in the base-material surface.

The method for forming a self-fluxing alloy coating layer of the present invention includes a step of mixing a self-fluxing alloy powder and a borax powder to prepare a mixed powder (hereinafter also referred to as “powder mixing step”),
Supplying the mixed powder to the substrate surface to form a powder layer (hereinafter also referred to as “powder layer forming step”);
A self-fluxing alloy coating layer made of a sintered body is formed on the surface of the base material by heating the powder layer to 1000 to 1200 ° C. by induction heating means to sinter the self-fluxing alloy powder in the powder layer. And a step (hereinafter also referred to as “sintering step”).

  According to such a forming method, the meltability of the powder layer (mixed powder) is remarkably improved by mixing the borax powder, and the heat treatment of the powder layer is performed in a short time and rapidly by induction heating. Even with this process, a uniform and dense self-fluxing alloy coating layer can be formed on the substrate surface.

  In the powder layer forming step, it is preferable that 0.05 to 1.0 parts by mass of borax powder is mixed with 100 parts by mass of self-fluxing alloy powder to prepare the mixed powder.

  In the powder mixing step, the mixed powder may be prepared by mixing ceramic particles together with self-fluxing alloy powder and borax powder.

According to the method for forming a self-fluxing alloy coating layer of the present invention, the heat treatment of the powder layer containing the self-fluxing alloy powder is performed by a short-time and rapid heating process by induction heating, and the uniform and dense self-heating is performed. A molten alloy coating layer can be formed on the substrate surface.
And, by carrying out the heat treatment of the powder layer by a short-time and rapid heating process by induction heating, the productivity can be improved compared with the conventional forming method in which the powder layer is heat-treated in a heating furnace. Can do.

2 is a photograph showing a surface state of a self-fluxing alloy coating layer formed on a substrate surface in Example 1. FIG. 4 is a photograph showing a surface state of a self-fluxing alloy coating layer formed on a substrate surface in Example 2. FIG. 4 is a photograph showing a surface state of a self-fluxing alloy coating layer formed on a substrate surface in Comparative Example 1. 6 is a photograph showing a surface state of a self-fluxing alloy coating layer formed on a 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 preparing a mixed powder by mixing self-fluxing alloy powder and borax powder.

Examples of the self-fluxing alloy powder used in the forming method of the present invention include those specified in JIS H 8260 (powder material for thermal spraying).
The particle size of the self-fluxing alloy powder is preferably 250 μm or less, more preferably 45 to 125 μm, as measured by a sieving method.

The borax powder used in the forming method of the present invention comprises a hydrate or an anhydride of sodium tetraborate.
As the particle diameter of the borax powder, the particle diameter 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 thus cannot sufficiently contribute to the improvement of the meltability, and the surface of the resulting self-fluxing alloy coating layer is made of glass. In some cases, these compounds are 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 remarkably superior to that of the self-fluxing alloy powder alone.
Although it is not clear as such a reason, the borax powder having a relatively low melting point is melted before melting the self-fluxing alloy powder to improve the thermal conductivity of the powder layer and is contained in the borax. This is presumed to be because boron combines with oxygen in the powder layer and oxygen on the surface of the substrate to suppress 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. Therefore, in the sintering step (heat treatment by induction heating) described later, the powder layer The whole is uniformly melted, 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 part by mass (parts by mass in sodium tetraborate decahydrate) per 100 parts by mass of the self-fluxing alloy powder. If an 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, an appearance defect may be caused due to, for example, glass-based compounds scattered on the surface of the obtained self-fluxing alloy coating layer.

  In this powder mixing step, mixed powder may be prepared by mixing ceramic particles together with self-fluxing alloy powder and borax powder. Thereby, the further improvement of abrasion resistance can be aimed at.

<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 substrate surface.
Specifically, the powder mixture is formed by placing the mixed powder on the surface of the substrate and adjusting it to a predetermined thickness.

Here, the base material (processed object) on which the powder layer is formed is usually made of a metal such as a steel material (soft steel / SUS). Although it does not specifically limit as a shape of a base material, It is preferable that it is plate shape.
In addition, it is preferable that the base material surface which forms a powder layer is roughened by the blast process.

  The method for supplying the mixed powder to the surface of the substrate is not particularly limited, and examples thereof include a method of providing an outer frame on the surface of the substrate and allowing 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 thickness change (loss) due to sintering.
As a method for adjusting the thickness of the powder layer, for example, an excessive amount of mixed powder is allowed to flow into the outer frame provided on the surface of the base material, and then the excess mixed powder is added to an appropriate thickness regulating member (for example, a blade). ) To scrape off.

In the forming method of the present invention, a mixed powder containing self-fluxing alloy powder and borax powder is formed on the surface of the substrate as a powder layer that maintains the powder state.
As a result, productivity can be improved and production cost can be reduced, and thermal strain of the base material, which may be caused by the shape of the base material, can be avoided. Further, it is possible to mix ceramic particles in the mixed powder.
When a thermal spray coating is formed by a thermal spraying method instead of a powder layer, a decrease in productivity and an increase in production cost are caused by performing heat treatment twice, depending on the shape of the substrate (for example, in the case of a thin plate) B) may cause thermal distortion.

<Sintering process>
In the sintering process of the forming method of the present invention, the powder layer formed on the surface of the substrate is heated to 1000 to 1200 ° C. by induction heating means, and the self-fluxing alloy powder in the powder layer is sintered. This is a step of forming a self-fluxing alloy coating layer comprising a ligation.

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

The heating temperature of a powder layer shall be 1000-1200 degreeC, Preferably you may be 1050-1150 degreeC.
When the heating temperature is less 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, when the heating temperature exceeds 1200 ° C., it is excessively melted and the shape of the coating layer cannot be maintained, or the hardness of the coating layer is reduced by overheating.

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

By this sintering process, the powder layer formed on the substrate surface (mixed powder obtained by directly mixing borax powder 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 substrate surface.
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 substrate by the forming method of the present invention is imparted with good heat resistance, corrosion resistance and wear resistance. It is applied to applications such as ducts, screws, and various rails, and is also applied to applications such as furnace wall materials and various high-temperature pipes that are heat and corrosion resistant members.

Examples of the present invention will be described below, but the present invention is not limited thereto.
In addition, the particle size of the powder used in the following Examples and Comparative Examples is a value measured by a sieving method.

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

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

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

<Example 2>
In the powder mixing step, 100 parts by mass of a mixture “23005” (manufactured by Electronic Canada Inc.) of a Ni-based self-fluxing alloy powder having a particle size of 45 to 125 μm and WC powder corresponding to JIS H 8303 2.29B; Except that a mixed powder was prepared by uniformly mixing 0.2 parts by mass of borax powder “sodium tetraborate decahydrate” (manufactured by Kanto Chemical Co., Inc.) with a particle size of 125 μm or less. Then, a self-fluxing alloy coating layer made of a sintered body was formed on the substrate surface.

<Comparative Example 1>
Without carrying out the powder mixing step of Example 1, in the powder layer forming step, self-fluxing alloy powder having a particle size of 45 to 125 μm corresponding to JIS H 8303 2.14A was supplied to the substrate surface to obtain a thickness of 3 A self-fluxing alloy coating layer made of a sintered body was formed on the substrate surface in the same manner as in Example 1 except that the powder layer (powder layer consisting only of self-fluxing alloy powder) was formed by adjusting to 0.5 mm.
The obtained self-fluxing alloy coating layer was non-uniform and the substrate surface was partially 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., Ltd.) and 95 parts by mass of ethanol (solvent) About 80 g of the solution is applied to the powder layer formed on the substrate surface by spraying, and after drying, a sintering process is 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 1-2 and Comparative Examples 1-2. The evaluation method (evaluation criteria) is as follows. The results are shown in FIG. 1 and Table 1 below.

(1) Appearance inspection:
The surface state of the self-fluxing alloy coating layer was visually observed and evaluated according to the following criteria.
“◯”: The surface is melted uniformly over the entire surface, the surface is free of wrinkles, and the surface is uniform and dense.
“Δ”: Wrinkles due to uneven melting are observed on the surface.
“X”: There is a site where a large crack or wrinkle is generated and the substrate surface is exposed.

(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 in accordance with JIS Z 2244 (Vickers hardness test-test method).

(4) Porosity measurement (dense evaluation) method:
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 to say that the denseness is good, the porosity needs to be 10% or less.

Claims (3)

A step of preparing a mixed powder by mixing self-fluxing alloy powder and borax powder;
Supplying the mixed powder to a substrate surface to form a powder layer;
A self-fluxing alloy coating layer made of a sintered body is formed on the surface of the base material by heating the powder layer to 1000 to 1200 ° C. by induction heating means to sinter the self-fluxing alloy powder in the powder layer. Forming a self-fluxing alloy coating layer.   The method for forming a self-fluxing alloy coating layer according to claim 1, comprising a step of mixing 0.05 to 1.0 parts by mass of borax powder with respect to 100 parts by mass of self-fluxing alloy powder to prepare the mixed powder.   The manufacturing method of the composite member of Claim 1 or Claim 2 including the process of mixing a ceramic particle with self-fluxing alloy powder and borax powder, and preparing the said mixed powder.