KR101088005B1 - Method of thermal spraying - Google Patents

Abstract

In performing plasma spraying on the metal body, it is possible to improve the workability of the roughening process and to reduce the spraying cost while maintaining the anticorrosive effect. Roughening treatment is performed using a grinding tool so that the average roughness Ra of the surface of the target object is in the range of 2 to 10 µm, and 1 of the molten particles when the molten particles of the thermal spray material adhere to the surface of the target object By spraying on the condition that the average area per particle becomes 10000-100000 micrometer <^2> , even if it is roughening by a simple tool, the adhesive force of the sprayed coating of the same grade as the case where the conventional blasting process and gas flame spraying are combined can be obtained. Roughening by grinding tools does not require large devices such as blasting, and portable small tools can be used for high-level work at local maintenance. little.

Grinding, Coating, Spraying, Spraying, Surface Roughness, Particle Diameter, Plasma, Blast

Description

Champion Method {METHOD OF THERMAL SPRAYING}

TECHNICAL FIELD The present invention relates to a thermal spraying method for forming an anticorrosive metal thermal spray coating on a surface of a metal body, in particular, a thermal spraying method suitable for on-site repair of a steel structure or the like.

BACKGROUND ART As a countermeasure against steel structures such as steel towers, bridges, expensive facilities, tanks, and the like, coating methods are generally used. However, such a coating method has a problem that the painting cost is expensive and the number of years of durability is limited, and also the maintenance cost is expensive because regular renovation is required. Therefore, as a countermeasure against the coating method, a method of forming a thermal sprayed coating on the surface of steel materials has been proposed. For example, Patent Document 1 describes a corrosion protection structure of a steel structure in which thermal spraying is performed on a poor environment portion of a steel structure and weather resistant steel is used in a portion other than the poor environment portion. According to such a structure, the corrosion resistance of the whole steel structure can be improved and construction cost and repair cost can be reduced.

In addition, a method of forming a resin lining film is conventionally used in a marine structure exposed to a severe corrosive environment for a long time, and a spraying method has been proposed as a method of repairing a damaged part of the lining film locally. For example, after the base treatment such as roughening the defect portion generated in the lining film, the preheating of the defect portion to the required temperature, and then spraying the powder of the polymer compound into the defect portion to form a repair film The repair method of is described in patent document 2. According to such a repair method, it is possible to perform repairs in the local area which have a long life and high reliability as compared with the conventional method of repairing a paint of a room temperature curing type.

The thermal spray coating has excellent properties such as corrosion resistance, heat resistance, abrasion resistance, and the like. The thermal spraying coating is not limited to steel, which is a member of a steel structure, and is used in a wide range of fields as a technology for surface modification of various materials and products. The thermal spraying sprays the thermal spraying material heated in a molten or semi-melt state onto the target to form a thermal spray coating. The main thermal spraying methods include a gas flame spraying method and a plasma spraying method.

The gas flame spraying method is a thermal spraying method which uses a combustion flame of oxygen and a combustible gas to heat a spraying material of linear, rod or powder form, and sprays the sprayed material to a molten or close state to form a film. The gas flame spraying method is most widely used because of its simple operation, low equipment cost, and low operating cost.

Plasma spraying is a spraying method in which a spraying material is heated and accelerated by using a plasma jet, melted or brought into close contact with a sprayed object to form a coating film. The plasma spraying method can be used as a thermal spraying material from a high melting point ceramic to a metal and a plastic, and can be sprayed in an air atmosphere, an inert atmosphere or a reduced pressure atmosphere. Although the thermal spraying material of a plasma spraying material is mainly powder type, the plasma arc torch using the linear or rod-shaped spraying material was proposed in patent documents 3-5 recently.

Patent Document 1: Japanese Patent Application Laid-Open No. 2001-89880

Patent Document 2: Japanese Patent Application Laid-Open No. 2002-69604

Patent Document 3: Japanese Patent Application Laid-Open No. 5-80273

Patent Document 4: Japanese Patent Application Laid-Open No. 6-39682

Patent Document 5: Japanese Patent No. 3215518

However, in performing the thermal spraying, as a pretreatment for the target, a process of removing the paint, the plating film, the oxide, etc. on the surface of the target to be sprayed and roughening the surface is required. By roughening the surface of the workpiece, a so-called anchor effect is generated in which the thermal spray particles are mechanically engaged with the roughness of the roughened surface to improve the adhesion between the thermal spray coating and the target. This roughening is generally carried out by a method called blasting. There are several methods for blasting, which are generally performed by using compressed air to project natural minerals, artificial minerals, metal grit, non-metal grit, cutting wire, etc. onto the subject to expose the material to the surface, It is a method of forming irregular micro irregularities on the surface.

The blasting process requires a large apparatus such as a hopper for blast material, a tank, an air compressor, a compressed air pipe, a blast material supply pipe, a torch, a blast material recovery device, and a dust collector. In the case of a construction process in which these devices are installed in a material processing plant, such as a steel structure, blasting is performed in the material processing step, and the blasted material is transported to the construction site to assemble the steel structure, etc. There is no such problem in the implementation of the processing. However, in the case of on-site maintenance, the problem is large in terms of cost, work and environment, and it is very difficult to implement. It is difficult to equip all of the above devices at the repair site to perform blast treatment at the repair site. In addition, in the case of on-site repair of a large structure is often a high-level work, it is difficult to install the necessary equipment in a high place. In addition, there is a problem that the recovery of the blast material during the treatment and the collection of the generated dust are difficult, and the working environment is deteriorated due to scattering blast material or dust and contaminates the environment.

Therefore, when the thermal spraying is carried out at local maintenance, the blasting process cannot be performed in practice, so it is necessary to devise a roughening method that replaces the blasting process. In addition, the deterioration of the working environment is inevitable even when the blast treatment is performed in the material processing plant, and if a roughening method that replaces the blast treatment can be applied, it is very good.

The problem to be solved by the present invention is to form a thermal spray coating by spraying a metal spray material on a metal body to form roughening conditions and thermal spray conditions of the target to obtain sufficient adhesion between the thermal spray coating and the target. It is not only to maintain the anticorrosive effect, but also to improve the workability of the roughening process and reduce the spraying cost.

The present inventors earnestly examine the roughening conditions and the effect of the thermal spraying conditions on the adhesion between the thermal spray coating and the thermal spraying target as a pretreatment of the thermal sprayed spray. By realizing that adhesive force of the thermal spray coating sufficient in practical use can be obtained, the present invention was completed.

In other words, the thermal spraying method according to the present invention is a thermal spraying method for spraying a metal thermal spraying material on a metal body by a thermal spraying method, in particular, a plasma thermal spraying method, to form a thermal spray coating for corrosion protection. The process of roughening so that Ra) may be in the range of 2-10 micrometers, and when the molten particle of a thermal spray material adheres to the surface of a to-be-sprayed body, the average area per particle | grains of the said molten particle will be 10000-100000 micrometers ² Characterized in that it comprises a step of performing a spraying under the conditions.

Here, it is preferable to use the thermal spraying apparatus which uses a linear or rod-shaped metal thermal spraying material, and it is preferable to use an aluminum alloy, more preferably an aluminum-magnesium alloy as said metallic thermal spraying material. Moreover, you may include the process of performing a sealing process to the film after spraying.

It is a figure which shows typically the lamination | stacking state of the sprayed coating in the case of spraying with a plasma spraying apparatus.

It is a figure which shows typically the lamination | stacking state of the sprayed coating in the case of spraying with a gas flame spraying apparatus.

FIG. 1C is a diagram showing the lamination state of the thermal sprayed coating in the case of spraying with a gas flame spraying device and having a large surface roughness.

2 is a perspective view showing an example of the grinding tool used in the embodiment.

3 is a view showing the structure of the main portion of the plasma spraying apparatus used in the embodiment under a spraying state.

&Lt; Description of reference numerals &

1: grinding tool 2: roller

3: sand paper 4: steel

5: sprayed coating 6: plasma spraying device

7: plasma torch 8: electrode

9: nozzle 10: rear wall

11 circumferential wall 12 tapered cylindrical portion

13 inlet port 14 wire

15 supply device 16 guide member

17: extrusion roller 18: DC power supply

19: outer nozzle 20: outlet

21: molten particles

In the present invention, the object of thermal spraying is a metal body. The thermal spraying itself is also applied to non-metallic materials, but in the present invention, the thermal spraying is assumed, and the thermal spraying forming a metal thermal spray coating on the metal structure or its members for the purpose of enhancing the anticorrosive function of the metal structure and reducing the repair cost. Adopt the method.

In the present invention, the roughening treatment as the pretreatment of thermal spraying is performed using a grinding tool. The grinding tool herein refers to a power tool in which abrasive particles are fixed to a disk or belt type substrate, and a power tool in which flaps or wires are planted on an outer circumferential surface of a wheel. It can be used suitably at the time of repair. Grinding the surface of a subject using such a grinding tool produces a large number of parallel linear marks on the surface. When the grinding tool is moved in a certain direction, the linear marks are in a certain direction, and when the movement directions are crossed, the linear marks also cross. In order to form a large number of unevenness as in the case of blast treatment, it is preferable to cross the moving direction of the grinding tool, and the roughening treatment of the present invention can obtain sufficient adhesion even in a linear mark in a certain direction. On the other hand, the crossing angle in the case of crossing the linear mark may be several degrees, but the crossing angle is preferably 60 to 90 degrees.

As for the surface roughness obtained by such roughening process, the average roughness Ra is 2-10 micrometers, More preferably, the range of 5-8 micrometers is the most preferable. Moreover, it is preferable that the maximum roughness Rz is 20-100 micrometers, and the peak count value RPc of roughness is 30-100. When the surface roughness is in the above-described range, when the molten particles collide with the rough surface at the time of thermal spraying, the anchor effect that is tightly spread on the surface and meshes with the rough surface is enhanced.

If the average roughness Ra of the surface roughness is less than 2 µm, a sufficient anchor effect is not obtained, and the adhesion of the thermal sprayed coating is lowered. If the average roughness (Ra) is larger than 10 μm, it is rather preferable in terms of the adhesion of the thermal spray coating, but in order to generate such rough surface, it is necessary to increase the particle diameter of the abrasive grain used in the grinding tool, and the grinding resistance This increase is not practical because the burden on the operator to operate the grinding tool increases. In addition, when the surface roughness becomes extremely large, the molten metal does not fully spread the rough surface sufficiently flatly, and a gap is generated between the surface and the molten particles, and consequently, the adhesion of the thermal spray coating is lowered.

If the maximum roughness Rz is less than 20 µm, it is necessary to set it to a homogeneous surface roughness to obtain an appropriate average roughness, and the roughening treatment using the above-described grinding tool becomes difficult. When the maximum roughness Rz is larger than 100 µm, a grinding tool having a large grinding particle diameter is required, and since the large grinding particles are consumed quickly, it is difficult to perform a homogeneous construction and workability is lowered. If the peak count value RPc of the roughness is less than 30, the number of unevennesses is small, and many small smooth portions exist, and the adhesion of the molten particles is lowered. On the contrary, when the peak count value RPc is larger than 100, the gap between the irregularities is too small, and the molten particles are not sufficiently fused to the surface without any gaps, resulting in gaps, thereby lowering the adhesion of the molten particles.

In the present invention, a thermal spraying apparatus is used as the thermal spraying apparatus, preferably a thermal spraying apparatus using a linear or rod-shaped metal thermal spraying material. Such a thermal spraying apparatus itself is well-known as described in patent documents 3-5, and a well-known thermal spraying apparatus can also be used also in this invention. In the present invention, the spraying is carried out using the plasma spraying device so that the average area per molten particles of the molten particles of the thermal sprayed material is 10000 to 100,000 m ² when the molten particles of the thermal spraying material adhere to the surface of the target body.

When spraying with a plasma spraying apparatus using a linear or rod-shaped metal spraying material, as shown in FIG. 1A, molten particles collide with the surface of the sprayed object S and are stacked flatly. The adhesion of the thermal sprayed coatings m is increased, and the adhesion of the overall thermal sprayed coating M is also increased. In addition, by spraying the molten particles of the thermal sprayed material to have an average area per particle of the molten particles when the molten particles adhere to the surface of the target to be 10000 to 100000 µm ² , the temperature of the surface of the target is raised to increase the volume of the volume of the target surface. Wetting is improved.

On the other hand, when spraying with a gas flame spraying device, as shown in Fig. 1B, the initial molten particles fill up the concave portion of the surface of the sprayed object S, and the individual sprayed coating m has a thin scale piece. Therefore, there is a problem that the coating surface becomes smooth, and the adhesion force with the coating film laminated thereon is lowered and the adhesion force of the thermal spray coating M is lowered as a whole. Therefore, when spraying with the gas flame spraying apparatus, the surface roughness of roughness similar to the case of roughening by a blasting process is needed. When the surface roughness is large, as shown in Fig. 1C, the thermal spray coating m of each thin scale piece is formed along the uneven surface of the surface of the workpiece S, and the thermal spray coating m sequentially stacked. Since the fall of the adhesive force of is suppressed, the adhesive force of the whole sprayed coating M becomes enough.

In the present invention, plasma spraying is performed on a surface of a workpiece having an average roughness Ra of 2 to 10 μm by pretreatment, wherein molten particles of 1 particle when the molten particles of the thermal spraying material adhere to the surface of the target By spraying on a condition that the average area per sugar is 10000 to 100,000 µm ² , lamination of individual thermal spray coatings as shown in FIG. 1A is obtained, and a high adhesion of the thermal spray coating is obtained as a whole. Even if the average area per particle of the molten particles is too small or larger than the above range, a gap is formed between the individual sprayed coatings, so that the temperature of the surface of the sprayed object cannot be sufficiently raised, and sufficient adhesion of the sprayed coating is not obtained. In the case of gas flame spraying, the average area per particle of molten particles is several hundred to several thousand μm ² , and in the arc spray coating, the average area per particle of the molten particles is several hundred to several thousand μm ^2, which is slightly lower than that of gas flame spraying. Although large molten particles are contained, when the average roughness Ra on the surface of the workpiece is about 2 to 10 µm, sufficient adhesion of the thermal sprayed coating cannot be obtained.

There is no requirement in particular except the above-mentioned roughening process, surface roughness, and thermal spraying conditions. The thickness of the thermal spray coating may be selected in the range of 50 ~ 200μm depending on the anticorrosive performance required. As a metal as a thermal spraying material, various metals, such as aluminum, zinc, copper, cobalt, titanium, these alloys, etc. which are conventionally well-known, can be used. Among them, aluminum alloys such as aluminum or aluminum-magnesium alloys and zinc aluminum alloys are particularly suitable in that the sacrificial anode action is sufficiently exhibited. In addition, you may perform a sealing process after forming a sprayed coating. In particular, in the case of local repairs, sealing should be done as soon as possible after spraying. Conventionally well-known resins and organic chemicals can be used as a sealing material.

Hereinafter, an embodiment in which the thermal spraying method of the present invention is applied to on-site repair of steel structures will be described in order of major processes. Here, the steel structure already installed is a structure in which the coating is applied on the galvanized steel, and the case where the coating is locally peeled off and the galvanization is corroded will be described as an example.

[Roughening process]

2 is a perspective view showing an example of the grinding tool used in the present embodiment.

This grinding tool 1 is an electric grinding tool called a grinding roller type sander, and attaches the sand paper 3 to the roller 2, and performs surface grinding of the damaged part of steel by the rotation. In the sand paper 3, abrasive grains such as silicon carbide and alumina having particle size numbers # 20 to # 40 (average particle diameters of 1000 to 425 µm) are fixed by a resin binder. By grinding the steel surface by this grinding tool 1, damaged portions of the coating and plating are ground, and the steel surface is a rough surface having an average roughness Ra of about 5 to 8 µm. In addition, as a grinding tool, a belt sander, a disk sander, a flap wheel, a rotary brush, etc. can be used suitably besides a grinding roller type sander.

[Spray device]

Fig. 3 is a diagram showing the structure of the main portion of the plasma spraying apparatus used in this embodiment under a spraying state.

The electrode 8 of the plasma torch (the internal structure of the body part is omitted) 7 of the plasma spraying device 6 protrudes toward the end from the rear wall portion 10 having the insulating property of the nozzle 9. The nozzle 9 is provided in the cylindrical circumferential wall 11 connected to the rear wall portion 10 and at the end of the circumferential wall 11, and the conical tapered cylindrical portion 12 whose cross-sectional shape is rapidly reduced toward the end. Has) The circumferential wall 11 is formed with a plurality of inlets 13 for injecting plasma gas into the nozzle 9 along the circumferential direction. The plasma gas may be used alone or in combination of an inert gas such as nitrogen, argon and helium.

At the outer circumferential portion of the tapered cylindrical portion 12 of the nozzle 9, an outer circumferential nozzle 19 is provided along the outer circumferential surface to eject the gas toward the end of the center line of the nozzle 9. As the gas, air, nitrogen, argon, helium and the like are used. Moreover, the supply apparatus 15 which delivers the Al-Mg alloy wire 14 as a thermal spraying material in the base side rather than the gas blowing part as the end of the center line of the nozzle 9 is provided in the outer side of the outer nozzle 19. The supply device 15 is provided with a guide member 16 and an extrusion roller 17.

The electrode 8 is connected to the negative pole of the DC power supply 18, and the wire 14 is connected to the plus pole of the DC power supply 18. The DC power supply 18 may supply a DC voltage of about 30 to 200V and a DC current of about 50 to 500A. In addition, the DC power supply 18 can apply a high voltage of about 3000V in a short time.

[Spray process]

Plasma spraying apparatus 6 is arrange | positioned so that the center line of the nozzle 9 of the plasma spraying apparatus 6 may become perpendicular | vertical with respect to the surface of the steel material 4 which is a to-be-injected body.

When the plasma gas is introduced from the inlet 13 of the plasma spraying device 6, the plasma gas generates a swirl flow along the circumferential wall 11. When 3000 V voltage is applied by the DC power supply 18 in this state, spark discharge will generate between the electrode 8 and the wire 14. The plasma gas turns and the pressure in the center portion is lowered, and the plasma gas in the center portion is preferentially discharged by spark discharge. When the spark discharge occurs, the plasma gas between the electrode 8 and the wire 14 is ionized to create an electric dissociation state, so that a direct current flows. As a direct current flows through the plasma gas, the plasma is further gasified and plasma arcs are formed. The plasma arc flows along the center portion of the plasma gas which is depressurized by the swirl flow, and the plasma gas is heated by the plasma arc and is ejected vigorously as a plasma flame from the outlet 20 of the nozzle 9.

The end of the wire 14 is rapidly heated by the plasma arcs and melted. The molten wire 14 becomes the molten particle 21 and blows to the steel material 4 side by a plasma flame. Since the plasma gas uses an inert gas, the amount of oxygen that reaches the molten particles 21 decreases, and oxidation of the sprayed coating 5 formed is prevented. In addition, the end of the wire 14 is melted away is moved toward the end by the extrusion roller 17 so that the end coincides with the center line of the nozzle (9). The outer circumferential nozzle 19 flows the compressed gas from the rear, and ejects it conically from the front. By injecting gas into the molten particles 21 from the outer circumferential side, the molten particles 21 are miniaturized to have a size most suitable for forming the thermal sprayed coating 5. The refined molten particles 21 collide with the surface of the steel material 4 and are flattened. A large number of the molten particles 21 are laminated, bonded, and cooled to form a thermal sprayed coating 5.

[Adherence force measurement result]

In order to confirm the effect by the thermal spraying method of the present invention, a known gas flame spraying apparatus and a plasma spraying apparatus shown in FIG. 3 are used for the roughening of the surface of a target by blasting and the grinding. The surface roughness and the adhesive force of the thermal sprayed coating after the roughening process at the time of thermal spraying were measured, respectively. The measurement results are shown in Table 1. On the other hand, in the commentary of ISO (lnternational organization for standardization) 2063, the practically sufficient adhesion is said to be 4.5 N / mm ² or more. In the present Example, this value was adopted and it was set as the required value of adhesive force.

Note) The adhesion was measured using an elmeter in accordance with JIS H8661.

As can be seen from Table 1, in the case of gas flame spraying, if the surface roughness (Ra) is about 20 μm by performing blasting as a roughening treatment, the adhesion of the thermal spray coating is 6 to 7 N / mm ^2. When sufficient adhesion is obtained, and only a roughness having a surface roughness (Ra) of less than 15 μm is obtained by the grinding treatment, the adhesion of the thermal sprayed coating is 4 N / mm ^2. It becomes below and cannot obtain practical adhesive force. In general, the surface roughness Ra in the case of blasting is about 15 to 40 µm, and the adhesion of about 6 to 7 N / mm ² is obtained in the gas flame spraying. On the other hand, in the case of plasma spraying, even if the surface roughness Ra by a grinding process is 2-10 micrometers, the adhesive force of a thermal sprayed coating will be 6-7 N / mm <^2> , and sufficient adhesive force will be obtained. However, when surface roughness Ra is less than 2 micrometers, since adhesive force becomes low, it is not practically preferable.

Although the thermal spraying method of the present invention has been described using a steel structure as an example, the thermal spraying method of the present invention can be applied to various metal structures including steel structures and methods of members thereof. In addition, by appropriately selecting the material and the spraying conditions of the metal spray material, it is possible to apply to structures and members other than the metal body.

Plasma spraying is carried out under conditions in which the average area per particle when the molten particles adhere to the surface of the subject becomes a predetermined range, thereby increasing the temperature of the surface of the subject and improving the wettability of the volume on the surface of the subject. Thereby, even if it is roughening by the grinding tool which becomes lower in the roughening degree than in the blasting process, the adhesive force of the sprayed coating of the same grade as the case where the blasting process and the gas flame spraying are combined can be obtained. In the roughening by the grinding tool, as in the case of the blasting process, a large tool is not required, and a portable, small tool can be used for work at high places in the local maintenance. Is less. In addition, if the thermal spraying can be performed using the arc spraying method instead of the plasma spraying under the condition that the average area per particle of the molten particles becomes 10000 to 100000 µm ² , the same effects and effects as described above can be obtained.

Claims (12)

A thermal spraying method for forming a thermal spray coating by spraying a metal thermal spraying material on a metal body, Grinding the surface of the subject using a grinding tool to generate linear marks, and performing a roughening treatment so that the average roughness Ra of the surface of the subject is in the range of 2 to 10 μm; Average area per particle of the molten particles when the molten particles of the thermal spraying material adhered to the surface of the thermal spray by using a plasma spraying apparatus using a linear or rod-shaped metal thermal spraying material on the surface of the target after the roughening treatment; A spraying method comprising the step of performing a plasma spray so that the 10000 ~ 100,000 μm ² . delete delete The spraying method according to claim 1, wherein aluminum, aluminum-magnesium alloy, or zinc aluminum alloy is used as the metal spraying material. delete delete The spraying method according to claim 1, further comprising a step of performing a sealing operation after forming the sprayed coating. delete delete The spraying method according to claim 4, further comprising a step of performing a sealing operation after forming the sprayed coating. delete delete

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