JP2006102672A - Production method of atomized powder for flame spraying - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method of atomized powder for flame spraying where spray properties are excellent and the properties of obtained spray deposit are excellent. <P>SOLUTION: Powder produced by an atomization method is accumulated to a prescribed thickness, and vibration is applied to the accumulated powder to remove deformed particles and hollow particles coming to the surface layer part of a layer comprising the accumulated powder. It is preferable that the vibration applied to the powder is horizontal rotating vibration, and the revolution number per min is 20-50 rpm and the rotating radius is 5-100 mm. The horizontal rotating vibration can be carried out by a circular vibrator. A container 3 is put in the circular vibrator, and it is preferable that the powder to which the vibration is applied is fed into the container so that the depth of the powder is ≥1 cm and ≤5 cm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing atomized powder for thermal spraying.

  The thermal spraying method is a surface treatment method in which a thermal spray material is put into a combustion flame or a plasma heat source, and the thermal spray material is melted or semi-molten particles and sprayed onto the surface of a substrate to be coated to form a coating. As one of the most powerful means to improve wear resistance, corrosion resistance, heat resistance, heat insulation, etc., since it can be carried out with simple work, excellent workability and easy formation of hard coating, Today it is used in various industrial fields.

  Thermal spray materials include metals, ceramics, cermets, etc., and are used in the form of powder, wire, rod, etc., depending on the specifications of the thermal spray gun.

  Among these, for the production of thermal spraying powder, which is a powdered thermal spraying material, for example, an atomizing method using an apparatus described in Patent Documents 1 and 2 is often used. The atomizing method is a kind of molten metal spraying method. The raw material is melted in a melting furnace, and the flow rate and flow rate adjusted by a tundish are pulverized with a cooling medium such as high-pressure water or an inert gas, and then in a cooling tank. This is a method of obtaining an alloy powder by cooling and solidifying in the process of falling. Due to the surface tension of the molten metal, the molten metal solidifies into a spherical shape.

  The powder obtained by the atomization method has high fluidity because the particle surface is smooth and the shape is spherical. Moreover, since it is alloyed, each grain has a uniform composition. For this reason, compared with the case where thermal spraying is performed using powders such as mixed powders and granulated sintered powders obtained by other manufacturing methods, the coating obtained by thermal spraying is excellent in homogeneity.

  One of the important characteristics in the evaluation of thermal spraying powder is apparent density. The apparent density is the mass of the powder filled per unit volume and represents the amount of the powder filled. The smaller the particle size, the smaller the number of irregularly shaped particles deviating from the spherical shape, and the higher the value, the more voids are present inside the particles. In particular, the presence of irregularly shaped particles whose shape deviates from a spherical shape makes it difficult to supply particles for thermal spraying at a constant rate, and causes a decrease in thermal spraying properties such as difficulty in obtaining a uniform thermal sprayed film. . In addition, a thermal spray coating obtained by using a powder containing a large amount of particles having hollow particles (hollow particles) as the thermal spray powder has a problem in that there are many voids and the properties of the coating deteriorate.

  On the other hand, as for the particle size of the thermal spraying powder, according to the material of the particle itself and the specifications of the thermal spray gun, classification and adjustment to a desired particle size range are also made in the conventional method for producing atomized powder for thermal spraying. However, it was difficult to remove the irregularly shaped particles and the hollow particles.

  For this reason, when spraying using the atomized powder manufactured with the conventional manufacturing method of the atomizing powder for thermal spraying, there existed a problem that the characteristic of a desired thermal spraying property and a thermal spray coating was not acquired.

JP-A-5-179315

Japanese Patent Laid-Open No. 9-20901

  This invention is made | formed in view of this problem, Comprising: It aims at providing the manufacturing method of the atomized powder for thermal spraying with the favorable thermal spraying property and the characteristic of the thermal spray coating obtained.

  The method for producing atomized powder for thermal spraying according to the present invention comprises depositing a powder produced by the atomizing method to a predetermined thickness, applying vibration to the deposited powder, and a surface layer portion of the layer comprising the deposited powder. It is characterized by removing irregularly shaped particles and hollow particles floating on the surface.

  It is preferable that the vibration applied to the powder is horizontal swirling vibration, and has a rotation speed of 20 to 50 rpm per minute and a swirling radius of 5 to 100 mm.

  The horizontal turning vibration is performed by, for example, a circular vibrator.

  Moreover, it is preferable that a container is placed in the circular vibrator, and the powder to which the vibration is applied is put into the container so that the depth is 1 cm or more and 5 cm or less.

  According to the present invention, an atomized powder for thermal spraying from which irregularly shaped particles and hollow particles are effectively removed can be produced. As a result, it is possible to obtain an atomized powder for thermal spraying that has good thermal spraying properties and good thermal spray coating characteristics.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has made the layer with the powder after atomization slowly and horizontally oscillated in a horizontal direction by a circular vibrator, so that the irregularly shaped particles can It was found that the hollow particles can be separated by the apparent specific gravity difference due to the difference in sedimentation from the spherical particles.

  That is, irregularly shaped particles have lower fluidity than other spherical particles, and therefore do not easily settle in the layer on which the powder is deposited. Although the hollow particles have the same fluidity as the other particles, since the particles have voids, the specific gravity of the particles is small and it is difficult to settle in the deposition layer. Therefore, normal particles preferentially settle in the deposition layer by vibrating the atomized powder for thermal spraying. As a result, the irregularly shaped particles and the hollow particles are relatively lifted on the surface layer of the deposited layer.

  In addition, irregularly shaped particles and hollow particles have a color tone different from that of normal particles.

  Therefore, after the atomized powder for thermal spraying is vibrated, only the irregularly shaped particles and the hollow particles can be removed.

  Further, the method of the present invention is characterized in that the vibration method is horizontal turning vibration in the horizontal direction, and since this vibration method is used, a high separation effect can be obtained. In vertical movement and horizontal reciprocating movement, irregularly shaped particles and hollow particles floating on the surface of the sedimentary layer settle down again, or particles that bounce off the side of the container cover the surface of the sedimentary layer. Shaped particles and hollow particles remain other than the surface layer part, or a certain amount of normal particles remain in the surface layer part. On the other hand, in the method of the present invention, since the vibration method is horizontal swirling vibration in the horizontal direction, the irregularly shaped particles and the hollow particles that have emerged are unlikely to settle again. In addition, the particles are unlikely to rebound on the side of the container.

  In addition, since the horizontal swirling vibration in the present invention is required to give moderate vibration to the powder and the powder does not jump up, the rotation speed of the horizontal swirling vibration is 20 to 50 rpm. It is necessary to be. When the rotational speed of the horizontal swirling vibration is less than 20 rpm, the vibration amount of the powder is small, and the irregularly shaped particles and the hollow particles are not lifted up. On the other hand, when the rotational speed of the horizontal swirling vibration exceeds 50 rpm, the jumped powder is covered with the surface layer. Moreover, as a turning radius of a horizontal turning vibration, it is required to be 5-100 mm. When the turning radius of the horizontal turning vibration is less than 5 mm, the amount of vibration of the powder is small, and lifting of irregularly shaped particles and hollow particles does not occur. On the other hand, when the turning radius of the horizontal turning vibration exceeds 100 mm, the jumped powder covers the surface layer.

  In addition, in order to obtain a higher effect in the method according to the present invention, it is desirable that the amount of powder introduced into the container placed in the circular vibrator does not exceed a depth of 5 cm. This is to promote the lifting of irregularly shaped particles and hollow particles by shortening the necessary settling distance of normal particles and the necessary lifting distance of irregularly shaped particles and hollow particles, and the depth of the powder in the container is 5 cm. This is because the irregularly shaped particles and the hollow particles in the vicinity of the bottom of the container are not sufficiently lifted and cannot be removed. On the other hand, when the depth is less than 1 cm, the particles cannot settle and lift, and therefore cannot be separated.

  FIG. 1 is a schematic diagram of a circular vibrator that can be used in the practice of the present invention. The vibration device 1 rotates the shaft 2 at a predetermined rotation speed, the container 3 rotates at the turning radius r, and a horizontal swirling vibration is applied to the powder layer 4.

  Hereinafter, the method according to the present invention will be described specifically by way of examples.

Example 1
Raw materials blended such that C: 0.9%, Si: 4.3%, Cr: 17.0%, B: 3.5%, Fe: 4.0%, balance: Ni in mass ratio Was melted in a vacuum using a high-frequency induction vacuum melting furnace, and the resulting molten metal at about 1650 ° C. was made into an alloy powder by a water atomization method. This alloy powder was dried with hot air and then classified into 45 to 125 μm with a vibration classifier (manufactured by Tokuju Kogakusho Co., Ltd.). The obtained powder was put into a substantially cylindrical stainless steel container and placed in a circular vibrator (manufactured by Tokuju Kogakusho Co., Ltd.), and vibration was applied for 10 minutes at a rotation speed of 30 rpm. The powder for thermal spraying of Example 1 was produced by removing particles with different color tones that floated on the surface with a brush. Table 1 shows the fluidity and apparent density of the thermal spraying powder.

  The fluidity of the powder was measured according to the method for measuring the fluidity of metal powder described in JIS Z 2502, and the apparent density was measured according to the method for measuring the apparent density of metal powder described in JIS Z 2504.

  Next, this alloy powder was sprayed to a thickness of 3 mm on a SS400 mild steel substrate with a powder flame spray gun, and then heated to 1000 ° C. or more with a combustion flame torch (oxygen-acetylene burner). A melt treatment was applied to form a self-fluxing alloy spray coating. Further, the surface of this film was cut and polished to prepare a test piece. With this test piece, the porosity and hardness (surface, cross section) of the obtained thermal spray coating were measured. The measurement results are shown in Table 1.

  The porosity of the film is measured by X-ray reflectivity measurement, the surface hardness is measured by a Rockwell hardness meter (C scale), and the cross-sectional hardness is measured by a Vickers hardness meter (load: 9.807 N (1.0 kgf)). did.

(Example 2)
A thermal spraying powder of Example 2 was produced in the same manner as in Example 1 except that the classified particle size range was 20 to 53 μm. Table 1 shows the fluidity and apparent density of the thermal spraying powder.

  Next, using this alloy powder, a spray coating layer having a thickness of 1 mm is formed on a SS400 mild steel substrate by a high-speed gas flame spraying method (fuel: kerosene-oxygen), and then a combustion flame torch (oxygen-acetylene burner). ) Was heated to 1000 ° C. or higher and subjected to remelting treatment to produce a test piece. With this test piece, the porosity and hardness (cross section) of the obtained thermal spray coating were measured. The measurement results are shown in Table 1.

(Comparative Example 1)
In Example 1, after classifying the alloy powder produced by the water atomization method to 45 to 125 μm, horizontal swirling vibration is applied by a circular vibrator, and particles having different color tones floating on the surface are removed with a brush to obtain a thermal spraying powder. However, in Comparative Example 1, the operation with the circular vibrator was not performed, and the alloy powder produced by the water atomizing method was only classified into 45 to 125 μm as the thermal spraying powder.

  For the thermal spraying powder obtained as a sample of Comparative Example 1, the fluidity and apparent density of the thermal spraying powder, and the porosity and hardness (surface, cross section) of the thermal spray coating obtained in the same manner as in Example 1. It was measured. The measurement results are shown in Table 1.

(Comparative Example 2)
In Example 2, after classifying the alloy powder produced by the water atomization method to 20 to 53 μm, horizontal swirling vibration is applied by a circular vibrator, and particles having different color tones that have floated on the surface are removed with a brush to obtain a thermal spraying powder. However, in Comparative Example 2, the operation with the circular vibrator was not performed, and the alloy powder produced by the water atomizing method was only classified into 20 to 53 μm as the thermal spraying powder.

  About the thermal spraying powder obtained as a sample of Comparative Example 2, the fluidity and apparent density of the thermal spraying powder and the porosity and hardness (cross section) of the obtained thermal spray coating were measured in the same manner as in Example 2. . The measurement results are shown in Table 1.

  As can be seen from the results shown in Table 1, the atomized powder for thermal spray produced by the method of the present invention (Examples 1 and 2) is higher than the atomized powder for thermal spray produced by a known production method (Comparative Examples 1 and 2). Has fluidity and apparent density. For this reason, it is considered that the thermal spray coating obtained by thermal spraying is better when the atomized powder for thermal spraying of Examples 1 and 2 is used than when the atomized powder for thermal spraying of Comparative Examples 1 and 2 is used. .

  When the porosity and hardness of the actually obtained thermal spray coating were measured, as shown in Table 1, the thermal spray coatings using the atomized powders for thermal spraying of Examples 1 and 2 were those of Comparative Examples 1 and 2. The porosity was smaller than that of the thermal spray coating using the atomized powder for thermal spraying, and the hardness was high.

It is a schematic diagram of the circular vibrator which can be used for implementation of this invention.

Explanation of symbols

1 Exciter 2 Shaft 3 Container 4 Powder layer r Turning radius

Claims (4)

The powder produced by the atomization method is deposited to a predetermined thickness, and the deposited powder is vibrated to remove irregularly shaped particles and hollow particles floating on the surface layer portion of the deposited powder layer. A method for producing atomized powder for thermal spraying. The atomized powder for thermal spraying according to claim 1, wherein the vibration applied to the powder is horizontal swirling vibration, and has a rotation speed of 20 to 50 rpm per minute and a swirling radius of 5 to 100 mm. Production method. The method for producing atomized powder for thermal spraying according to claim 2, wherein the horizontal swirling vibration is performed by a circular vibrator. The atomized powder for thermal spraying according to claim 3, wherein a container is placed in the circular vibrator, and the powder to which the vibration is applied is put into the container so as to have a depth of 1 cm or more and 5 cm or less. Manufacturing method.

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