JP6411814B2 - Arc spraying method and arc spray gun used therefor - Google Patents

Description

  The present invention relates to an arc spraying method in which a linear thermal spray material is melted and sprayed by arc discharge, and an arc spray gun used therefor.

  Arc spraying is normally performed by direct current arc discharge between the tips of two sprayed materials (metal wire and wire) fed continuously, as shown in the schematic diagram of the spray gun used in FIG. Electric sparks are generated, and metal droplets melted (dissolved) by this discharge energy are sprayed toward the subject (base material) while atomizing with an air stream (atomizing jet) using compressed air, etc. This is a surface treatment method in which a metal coating (spray coating) is continuously formed (film formation) on the surface of the subject.

  In addition to the characteristics that arc spraying has relatively high strength and adhesion strength of the resulting thermal spray coating, and the amount of thermal spraying per hour (material discharge rate) is larger than other thermal spraying methods such as flame spraying, there are two types of arc spraying. If two different metals are used as the thermal spraying material (metal wire), it is possible to form a pseudo-alloy coating (corrosion-resistant coating), so it is possible to form a corrosion-resistant coating on large-scale structures such as bridges. Is often used.

  By the way, in the normal arc spraying method, since the temperature of the molten metal generated by the arc is higher than that of the flame spraying method or the like, the composition of the material changes before and after the spraying, and the metal ( It is known that oxides or nitrides of the thermal spray material may be mixed. When such oxides or nitrides are generated due to a high melting temperature, or dust (fumes) derived from mineral vapor is generated, the performance of the thermal spray coating itself deteriorates. Of course, there may be a case where the performance as a “film” (coating film) is impaired, such as the generation of pores (pinholes) due to the oxides or the like or the formation of a porous structure. When a metal containing carbon such as steel is used, the carbon content is reduced by oxidation, and as a result, the hardness of the sprayed coating may be lowered.

  Therefore, as an "improved" spraying method that reduces the arc temperature (spark temperature) in arc spraying and suppresses the formation of the above oxides, etc., an "in-vacuum arc spraying method in which the pressure around the generated arc is negative (under a reduced pressure atmosphere) Is implemented (see Patent Document 1). As shown in FIG. 5, a partial cross-sectional view of the spray gun used in the reduced-pressure arc spray is formed around the arc from the outer periphery of a cone provided as the inner cylinder of the spray gun (spray nozzle). A high-pressure, high-speed air stream (atomizing jet) is injected so that it jumps over and crosses forward (converges), and the ejecting action (mist spraying phenomenon) of this atomizing jet intersects two wires for spraying (wire) The arc point (arc) and its surroundings are decompressed.

  Also, the droplets of the wire melted at the arc point are sucked out by the reduced pressure (negative pressure) to the front side of the gun (nozzle) (right side in the figure) and are refined by the air current, Injected toward the work. An opening communicating with the outside is provided on the rear side (the left side in the figure) of the arc spray gun, and external air for relieving negative pressure generated at the arc point (arc) from the rear opening. (Atmosphere) flows in (illustration is omitted for a feed roller, a wire feed mechanism, a drive device, and the like located further on the rear side).

  According to the above-described reduced pressure arc spraying method, the metal (wire for spraying) melts at a “low temperature” within the range of about twice its melting point, so that the generation of metal vapor is small, and the oxide as described above. A good thermal spray coating can be formed by avoiding the problem of occurrence of the above. Moreover, since the high-pressure and high-speed gas (atomizing air) used for injection does not directly touch the arc, the temperature does not rise, and the metal droplet melted at the arc point can be rapidly cooled. Therefore, in the atomizing jet, a “supercooling phenomenon” is maintained in which the liquid phase is temporarily maintained even when the metal particles are rapidly cooled, and these supercooled liquid metal particles are efficiently irradiated. It can be solidified (solidified) on the surface of the body (base material).

JP-A-62-183869

  However, according to the verification by the present inventors, it is still unavoidable that a certain amount of metal oxide or the like is inevitably mixed in the sprayed coating (the coating after spraying) even by the above-described reduced pressure arc spraying method. I understand. There is room for improvement here.

  The present invention has been made in view of such circumstances, an arc spraying method capable of forming a dense thermal spray coating having a high density and excellent adhesion, with little mixing of oxides and the like that obstruct film formation, and the like. The purpose is to provide an arc spray gun to be used.

In order to achieve the above object, the present invention provides two thermal spray wires from the rear side of a thermal spray nozzle comprising a cylindrical outer end and a tapered outer cylinder and a conical inner cylinder on the front end side. Feeding toward the front end, applying a high-frequency current between these two wires, crossing at the front end position of the inner cylinder to generate an arc between the ends of both wires, and melting these wires While generating droplets, the compressed atomizing gas is ejected forward from the gap between the outer cylinder and the inner cylinder of the spray nozzle, and a negative pressure is generated at the arc generation position. the droplet of sucking the above wire, the atomizing while finer ride the airflow Ising gas, a arc spraying method of spraying toward the front of the morphism body of the spray nozzle, the upper Symbol spray nozzle , For feeding each of the above two wires Way from providing two wires supply pipe which is formed in an arc shape to bend gently inward along the reduced diameter of the inner cylinder, reaches the outside of the front end of the inner cylinder through the wire inside these wire feed pipe It is, in each of the wire feed pipe, by placing the air injector pipe, with flow toward the supply source direction of the introduced wire part of the gas above atomizing the wire feed pipe, the generation position of the arc In order to relieve the negative pressure generated in the arc portion, a gas supply means for arc portion purge is provided which communicates from the rear side of the inner tube to the front end small diameter portion of the inner tube through the inside of the inner tube . An arc spraying method for supplying an inert gas having a concentration of 90% or more for purging an arc portion from a gas supply means is a first gist.

Further, the present invention provides a double-structure nozzle portion comprising an outer cylinder having a cylindrical rear end side and a tapered front end side and a conical inner cylinder, a gun body and a gun grip for supporting the nozzle part, the positive and negative to the applied thermal spray wire respectively, and two wires supply pipe for supplying to the intersection that is located in front end side of the nozzle portion through the inside of the inner cylinder of the nozzle portion from the gun body, the the nozzle portion before the end surface of the periphery of the cross section, and an annular slit provided between the outer tube and the inner tube, placed on a stream of atomizing gas emitted forward from the annular slit, top droplet of wire was melted by an arc generated by the intersection, a arc spray gun to blow toward the front of the morphism of the nozzle portion, the upper Symbol two wires supply pipe, respectively, from the middle diameter of the serial inner tube Is formed in an arc shape to bend gently inward along these wires by passing the inside wire of the supply pipe being configured wire to the outside of the front end of the inner cylinder reaches, the wire feed pipe in, together with air injector pipe for flowing a part of the atomizing gas toward the supply source direction of the introduced wire to the wire feed pipe is arranged, the inner side or et inner tube after the nozzle portion An arc portion purge gas supply means is provided that communicates with the front end small diameter portion of the inner cylinder, and corresponds to the negative pressure generated at the intersection by the emission of the atomizing gas forward. An arc spray gun in which an inert gas having a concentration of 90% or more for arc part purge is supplied from the arc part purge supply means is a second gist.

That is, the inventors of the present invention have repeated trial and error in order to solve the above-mentioned problem, and as a result, in the arc spraying method under reduced pressure, the “negative pressure” usually generated around the arc by the atomizing jet is alleviated. Therefore, the “negative pressure relaxation” external air (purge gas) introduced from the rear side of the spray nozzle and introduced to the arc point is replaced with “inert gas” that does not increase the oxidation of the metal. with the outlet of the arrangement of the upper Symbol inert gas, by limiting the construction of the two wires supply pipe, adhesion and densification of the sprayed coating adhered and solidified to be painful (object) The present inventors have found that the physical properties such as can be further improved and have reached the present invention.

  The “inert gas” defined in the present invention includes “rare gas group element” gases in a narrow sense such as helium (He) and argon (Ar), and is represented by nitrogen and the like. In other words, it also includes “low chemical reactivity” gases in a broad sense.

In the arc spraying method of the present invention, in order to relieve the negative pressure generated around the arc generated at the crossing position (intersection) of the two spraying wires, the arc is passed through the inside of the inner cylinder of the spray nozzle. as sites generating gas for negative pressure moderately sum supplied to (the arc points) (purging gas), the use concentration of 90% or more of an inert gas, and the arrangement of the outlet of the upper Symbol inert gas, two The structure in the wire supply pipe is limited. According to this configuration, generation of oxides at the arc generation site is suppressed, and physical properties such as adhesion of the metal spray coating adhered to the object to be irradiated (processing object) can be drastically improved.

  Further, the arc spraying method suppresses evaporation (transpiration) of the sprayed metal accompanying the oxidation and the like, and reduces the amount of sprayed metal that is scattered (wasteful) without being fixed on the surface of the subject. . As a result, the cost of the sprayed metal film can be reduced. Furthermore, since the arc spraying method has a high spraying metal fixing rate as described above, it is possible to form a spray coating that is sufficiently thicker than before without having to repeatedly reciprocate the spray gun (spray nozzle). be able to. Therefore, the arc spraying method of the present invention, in combination with improvement in workability and workability, makes it possible to efficiently form a sprayed metal film having a required thickness at low cost.

  Further, in the arc spraying method of the present invention, the inert gas having a concentration of 90% or more is also supplied between the outer cylinder and the inner cylinder of the spray nozzle so that the atomizing gas is also used. If this is the case, there is little need to prepare “preparation” of “inert gas for relaxation of negative pressure” to be supplied to the arc point. It is possible to efficiently produce a strong thermal spray coating excellent in cost at low cost.

  Furthermore, in the arc spraying method of the present invention, in particular, when nitrogen gas having a concentration of 95% or more is used as the inert gas having a concentration of 90% or more, generation of oxide at the arc point is further suppressed. Physical properties such as adhesion of the metal spray coating adhering to the object to be irradiated (processed object) are greatly improved.

Next, arc spray gun of the present invention are those used in the arc spraying method of the first aspect, up to the front end small diameter portion of the inner cylinder through the inner side or et inner tube after the nozzle portion An arc purge gas supply means for supplying an inert gas having a concentration of 90% or more is provided in a specific arrangement in communication . With this structure, the spray gun can fill the periphery of the intersection (arc point) where “negative pressure” is generated by the emission of the atomizing gas forward with the inert gas having a concentration of 90% or more. it can. Therefore, in the arc spray gun, the generation of oxide at the intersection (arc point) is suppressed, and the physical properties such as the adhesion of the metal spray coating to the object to be irradiated (processing object) are compared with the conventional method. Improve dramatically.

Further, among the arc spray guns of the present invention, the rear end side of the conical inner cylinder of the nozzle part is formed in a sealed shape, and the outer surface of the cylindrical outer cylinder of the nozzle part serves as the arc part purge gas supply means. communicating to the front small-diameter portion of the inner cylinder through the inside of the upper Symbol inner cylinder from the gas inlet port provided in, the arc portion purge gas supply pipe toward the front side of the intersection blowing arc portion purge gas What is provided can stably and efficiently supply the above-mentioned inert gas with a concentration of 90% or more for purging the arc portion to a required portion without being influenced by other processing conditions. It has become.

  Furthermore, in the arc spray gun of the present invention, an inert gas having a concentration of 90% or more is supplied as the atomizing gas emitted toward the front of the nozzle portion, as in the arc portion purge. It has a dense and tight adhesion without the need to separately prepare (prepare) the “inert gas for reducing negative pressure” supplied to the arc point, and with little inclusion of oxides or the like that interfere with film formation. An excellent strong thermal spray coating can be produced efficiently and at low cost.

  Further, among the arc spray guns of the present invention, in particular, when the inert gas having a concentration of 90% or more for reducing the negative pressure is a nitrogen gas having a concentration of 95% or more, the formation of oxide at the arc point is performed. Is further suppressed, and physical properties such as adhesion of the metal sprayed coating adhering to the object to be irradiated (processed object) are significantly improved.

Incidentally, arc spray gun of the present invention, since the two wire feed pipe is formed in each of an arcuate bend gently inward along the reduced diameter of the upper Symbol inner cylinder from the middle of the wire There is little flow resistance in a supply pipe, and it becomes possible to insert the wire for thermal spraying of a large diameter smoothly compared with the past. Therefore, the arc spray gun of the present invention can be achieved by the use of the thermal spraying wire above KiFutoshi diameter, the improvement of the thermal spray rate and spray efficiency.

(A) is explanatory drawing of the whole structure of the arc spraying apparatus used by embodiment of this invention, (b) is a side view of the arc spray gun used for the arc spraying method of embodiment of this invention. It is a cross-sectional view illustrating the internal structure of the arc spray gun. (A)-(c) is a figure explaining the method of the bending test in the Example of this invention. It is a figure explaining the structure and arc spraying method of a general arc spray gun. It is a figure explaining the structure of the arc spray gun used for the arc spraying method in pressure reduction, and its spraying method.

Next, an embodiment of the present invention will be described.
The arc spraying method in this embodiment uses an arc spray gun 10 shown in FIG. The basic configuration of the arc spray gun 10 is the same as that of a general arc spray gun. Two spray wires (wires W1, W2 and a thick one-dot chain line) are connected to a cylindrical outer tube 1A and a conical inner tube. Feeding from the rear side (the left side in the figure) to the front end (the right side in the figure) of the double-sprayed thermal spray nozzle unit 1 comprising the cylinder 1B, a high frequency current was applied between these two wires W1 and W2. In this state, they intersect at the front end position (the right end in the figure) of the cylindrical inner cylinder 1B to generate an arc (electric spark) between the ends (arc point P) of both wires.

  And the arc spraying method in this embodiment is the same as the generation | occurrence | production of the said arc, "Compressed atomizing gas" (thin line arrow) supplied from the bottom part side (the lower side and the back side of the paper surface of illustration) of the spray gun 10 In this example, compressed air) is ejected toward the front of the nozzle from a gap (an annular slit S for blowing out) provided between the outer cylinder 1A and the inner cylinder 1B of the nozzle unit 1 for thermal spraying. While the arc droplets of the wires W1 and W2 sucked out from the point P are put on the atomizing gas stream (thin line arrows) and are refined, an object to be irradiated (a workpiece to be processed) in front of the nozzle for spraying 1 is processed. This is the so-called “decompression arc spraying method”.

In particular, the interior (inner diameter side) of the inner cylinder 1B of the thermal spraying nozzle unit 1, the arc portion communicating from the nozzle rear side (the left side) to the front end small diameter portion of the inner cylinder 1B (arc point P near) A purge gas supply pipe 7 is provided. Through this arc portion purge gas supply pipe 7, a predetermined “negative” for relieving the negative pressure generated around the arc point P due to the injection of the atomizing gas. Separately from the atomizing gas, the pressure relief gas (hereinafter "arc purge gas", thick arrow, in this example) is supplied directly to the arc point P from the outside of the gun (nozzle). It has come to be. This is the greatest feature of the arc spraying method of the present invention.

  The arc spraying apparatus used in the above-described reduced pressure arc spraying method and the configuration of the arc spraying gun 10 will be described in more detail. As shown in FIG. 1A, the arc spraying apparatus used in this embodiment is an arc spraying gun ( An arc gun for thermal spraying) 10, a wire carriage (bobbin rack BR) for feeding the thermal spraying wire (wires W <b> 1 and W <b> 2) wound around a bobbin (reel) to the thermal spraying gun 10, and the thermal spraying gun 10 A thermal spraying power supply device (power supply PS) for supplying a high frequency current for application, an air compressor (compressor CP) with a dryer for supplying compressed air from which moisture has been removed to the thermal spraying gun 10, and the thermal spraying gun 10. Inert gas supply means (nitrogen gas cylinder GB) for supplying an inert gas (nitrogen gas) having a concentration of 90% or more to the arc generation site, and these It is composed of the channel (pipe) and a cable for connecting the.

As shown in the side view of FIG. 1B, the arc spray gun 10 includes a cylindrical outer cylinder 1A (rear end portion of the outer cylinder) and a front block 1C (outer cylinder) whose front end side is tapered. (A front end portion of the body) and a double nozzle nozzle 1 for spraying composed of a conical inner cylinder 1B having a reduced diameter toward the front side, and two spraying wires (left) A gun body 11 having a function of feeding the wire W1 and the right wire W2) to the nozzle part 1 at a predetermined speed (ratio), and a lower part (bottom part) of the gun body 11 to support the nozzle part 1 The gun grip 12 is mainly used.

The spray gun 10 includes two wire rods for spraying (bobbin rack BR) fed from a wire introduction port 11a provided on the rear side (the left side in the drawing) of the gun main body 11 from a wire carriage (bobbin rack BR). The wires W1 and W2) are supplied, and the high-pressure compressed dry air (atomizing gas) fed from the compressor CP is provided on the lower surface side (lower half of the outer peripheral surface) of the nozzle unit 1 It is filled between the outer cylinder 1A and the inner cylinder 1B of the nozzle portion 1 via the introduction port 2, and the filled atomizing gas is formed by the outer cylinder 1A and the front block 1C. From an annular blow-out port (slit S) provided between the cylinder and the front end of the inner cylinder 1B, it is ejected toward the front of the nozzle (right direction in the figure).

  A part of the compressed air is supplied to an air injector pipe (6A, 6B) to be described later on the front side (right side in the spraying direction) on the upper surface side (upper half of the outer peripheral surface) of the nozzle portion 1. An injector gas (injector gas) introduction port 4 is provided, and the arc portion purge gas is provided on the opposite side of the nozzle portion 1 on the far side in the drawing (left side in the spraying direction). A purge gas introduction port 3 connected to the supply pipe 7 is provided, and an inert gas (nitrogen gas) having a concentration of 90% or more is supplied to the purge gas introduction port 3 from the nitrogen gas tank GB. In addition, in the outer periphery of the front end side of the nozzle part 1 in FIG.1 (b), the thermal spray hood (cover) for preventing the atomizing gas (and metal droplets) after jetting from spreading too much [reference numeral 8, two-dot chain line] May be attached.

  As shown in the cross-sectional view of FIG. 2, the thermal spray nozzle portion 1 of the thermal spray gun 10 has a double-structure main comprising a cylindrical outer cylinder 1A and a conical inner cylinder 1B formed on the inner periphery thereof. The block is composed of three blocks: a front block 1C and a rear block 1D attached to the front and rear of the block.

The front block 1C disposed on the front side of the main block (the right side in the figure on the front end side) constitutes an outer cylinder together with the cylindrical outer cylinder 1A as described above. between, it forms a space (atomizing gas flow passage R) of the annular for circulating and filling the supplied compressed air, in its front end, between the outer peripheral surface of the inner cylinder 1B A slit S for emitting compressed air (atomizing air) is formed. The compressed air supplied from the atomizing gas inlet 2 on the lower surface side of the main block (the back surface side of the drawing paper) is filled in the annular gas flow path R and once stays, and then the nozzle portion. from the slit S provided on one front end, (the ring) uniformly over the entire periphery so that the blown at high speed towards the nozzle front.

The rear block 1D disposed on the rear side (the left side in the figure on the rear end side) of the main block is disposed so as to seal the rear side (rear end) opening of the main block. the block 1D has two wires (left W1, right W2) fed from the side of the gun body 11 after the nozzle portion 1, through the interior of itself in front of the front end nozzle section 1 (outside) Wire supply pipes (the left side 5A and the right side 5B) for guiding to reach the end are inserted.

In the present embodiment, these wire feed pipes 5A, 5B, respectively, in an arc shape to bend gently inward along the diameter of the upper Symbol inner cylinder 1B from the middle, and is bent. With this structure, when the wires W1 and W2 move in the wire supply pipes 5A and 5B, friction hardly occurs and the wires W1 and W2 can move smoothly. Further, in the present embodiment, the wire rod for thermal spraying (wire), which has a insertion limit of about 1.3 to 1.6 mmφ in the conventional wire supply pipe (see FIG. 4), is formed by the above arc-shaped bending process. It became possible to use a wire for thermal spraying of 6 to 2.4 mmφ. Thereby, the spraying speed and the spraying efficiency are improved as compared with the prior art.

  The rear block 1D of the nozzle unit 1 has a purge gas introduction port 3 connected to the arc part purge gas supply pipe 7 and an injector gas introduction port 4 connected to the air injector pipe (right side 6A, left side 6B). These are respectively drilled so as to open to the outer peripheral surface of the rear block 1D, and are supplied from the nitrogen gas cylinder GB through the purge gas introduction port 3 and introduced through the arc part purge gas supply pipe 7. The negative pressure reducing nitrogen gas (concentration of 90% or more) is directly supplied to the arc point P where the two wires W1 and W2 intersect.

  Further, a part (small amount) of high-pressure compressed dry air (atomizing gas) fed from the compressor CP is supplied to the injector gas inlet 4 of the rear block 1D. After branching to the injector pipes 6A and 6B, the wire supply pipes 5A and 5B are respectively supplied in the direction of the supply source of the wires W1 and W2 (that is, in the direction opposite to the flow of each wire, the left direction in the figure). It is designed to flow toward you. The compressed air introduced into the wire supply pipes 5A and 5B is caused by the flow of the air, the metal powder (friction powder) generated in the wire supply pipes 5A and 5B by the conveyance of the wires, and the gun Metal powder or the like generated by friction with the wire feed mechanism (pulley, drive device, etc.) in the main body 11 is pushed back to the wire insertion side (the base side and the left side in the drawing) of the wire supply pipes 5A and 5B and discharged. Demonstrate the effect of (cleaning the inside of the pipe).

According to the arc spraying method using the arc spray gun 10 having the above configuration (the arc spraying method under reduced pressure), the blowout port (slit S) provided between the outer cylinder 1A and the inner cylinder 1B of the nozzle unit 1 for thermal spraying. In order to eliminate the “negative pressure” at the arc point P generated when spraying compressed air (atomizing gas) for spraying from the front, an arc purge gas supply pipe located behind the nozzle 1 7, nitrogen gas having a concentration of 90% or more is introduced directly into the arc point P. Thereby, the production | generation of the oxide in the said arc point P is suppressed, and physical properties, such as the adhesiveness of the metal sprayed coating adhering to a to-be-photographed object, can be improved dramatically. Further, the arc spraying method suppresses the evaporation of the sprayed metal accompanying the oxidation or the like, and reduces the amount of the sprayed metal that is wasted without being fixed on the surface of the subject. Therefore, the arc spraying method of the present invention, in combination with improvement in workability and workability, can form a sprayed metal film having a required thickness efficiently and at low cost.

  In addition, as a wire for thermal spraying (cermet spraying material) that can be used in the arc spraying method of the present invention, aluminum (Al), zinc (Zn), molybdenum (Mo), copper (Cu), titanium (Ti), etc. In addition to the above single metals, low carbon steel, high carbon steel, austenitic stainless steel, martensitic stainless steel, ferritic stainless steel, galbarium (Al-Zn), rabar joule (Cu-Si-Mn-B), white copper (Cu-Ni) ), Brass (Cu—Zn), nickel aluminum (Ni—Al), nickel chromium (Ni—Cr), monel (Ni—Cu), etc., or a combination thereof, and used as a pseudoalloy spray coating be able to. Moreover, you may use the "core-type wire" of which material composition differs in what is called an outer layer and an inner layer (what is called a core-sheath structure). In the case of the above-mentioned cored type thermal spray material, a wire including a non-metallic material such as ceramic or rare earth as an inner layer can be used inside a metal tube (outer layer).

  Further, in the above embodiment, an example in which nitrogen gas is used as the inert gas for purging the arc portion is given as an example, but the “inert gas” in the present invention includes a rare gas group such as helium and argon. Elemental gases can be used alone or in admixture. Further, as a gas component of a portion other than the inert gas in the arc part purge gas (the remaining 10% or less of the “concentration of 90% or more”), a highly reducible gas having a concentration of 5 to 10% (for example, hydrogen Gas) may be added. If such a reducing gas is added, oxidation of the molten metal in the arc portion can be further prevented, which is preferable.

  Furthermore, the “nitrogen gas” used as the inert gas for purging the arc part is the one stored in the nitrogen gas cylinder (tank), but a larger amount is used by using a nitrogen gas generator or an air separator. When (large flow rate) nitrogen gas can be supplied, this nitrogen gas may also be used for the atomizing gas used for spraying. Thereby, the production | generation of the oxide in an arc point is suppressed more, and physical properties, such as the adhesiveness of the metal sprayed coating adhering to a to-be-projected body (processed object), can be improved more significantly. As the nitrogen gas to be used, it is preferable to use a high-purity grade having a concentration of 95% or more, more preferably nitrogen gas having a purity of 99.99% (four nines) or more.

The method of introducing (supplying) the inert gas for purging the arc around the arc is not limited to the arc purging gas supply pipe 7. For example, an arc portion purge gas supply pipe may be introduced rear side of the nozzle unit 1 from (gun body 11 side) in a straight line, but it may also be configured to introduce the other position.

  Next, the experimental results of “Example” for verifying the performance of the thermal spray coating obtained by using “inert gas having a concentration of 90% or more” as the arc part purge gas will be described by comparison with a comparative example. To do. However, the present invention is not limited to the following examples.

  In the following examples, the thermal spray coating is formed by performing arc spraying under the following processing conditions using the arc spray gun having the structure described in the above embodiment (see FIG. 1B). A “thermal spray coating” was prepared. And the obtained sample (sample) was subjected to <pinhole test> (porosity test) according to the ferroxyl test method described in JIS H 8617 (nickel plating and nickel-chromium plating) appendix 3. “Porosity per area” representing the denseness of the film was evaluated. Also, using the same sample, a <bending test> (three-point bending test) according to the “push bending method” described in JIS Z 2248 (metal material bending test method) was performed, and the “film” "Adhesion strength to the substrate" was evaluated.

[Preparation of thermal spray coating]
Using the arc spray gun of the present invention,
・ Base Rolled Steel SS400 (as defined in JIS G3101), 3 mm thickness In addition, the base (base) of the sprayed surface of the above-mentioned rolled steel is preliminarily defined as “Decorrosion Degree” Sa3 grade as defined in JIS Z 0313. (Without a magnifying glass, the surface has no visible mill scale, rust, paint film, foreign material, oil, grease and mud, and has a uniform metal color.)
・ Wires for thermal spraying Al (2.4mmφ) 2 ・ Spraying speed Wire 8m / min each [equivalent to thermal spraying amount (98g × 2) / min]
In addition, the negative pressure of an arc generation part is equivalent to 0.8 atmospheric pressure (811 hPa).
・ Spraying pattern Circular (Diffusion to diameter 100mmφ at 200mm distance from nozzle)
・ Applied voltage 24V320A (40kHz)
・ Gas consumption (flow rate)
Atomizing (injecting) gas: compressed air (0.7 MPa) 1.2 m ³ / min
Arc part purge gas: Nitrogen gas (0.3 MPa) 10 L / min
Injector gas: Compressed air (0.2 MPa) 2.0 L / min
・ Equipment used: High-speed inverter drive spraying equipment Arcboy A400 improved type (D-Tech)
In addition, the film thickness of the thermal spray coating was measured using an electromagnetic film thickness meter SL-120C (manufactured by Sanko Electronics Laboratory).

[Example 1]
Under the above processing conditions, arc spraying was performed on the sample substrate while supplying 90% concentration of nitrogen gas (0.3 MPa) at a rate of 10 L / min as an arc portion purge gas to be introduced into the arc generation site. . The film thickness of the thermal spray coating of the obtained “Example 1” sample was 120 μm.

[Example 2]
Under the above processing conditions, arc spraying was performed on the sample substrate while supplying 95% concentration of nitrogen gas (0.3 MPa) at a rate of 10 L / min as an arc purge gas to be introduced into the arc generation site. . The film thickness of the thermal spray coating of the obtained “Example 2” sample was 120 μm.

[Example 3]
Under the above processing conditions, arc spraying is performed on the sample substrate while supplying nitrogen gas (0.3 MPa) with a concentration of 99.99% at a rate of 10 L / min as an arc purge gas to be introduced into the arc generation site. went. The film thickness of the thermal spray coating of the obtained “Example 3” sample was 120 μm.

[Comparative Example 1]
Under the above processing conditions, while supplying normal compressed air (0.7 MPa, nitrogen concentration about 78%) at a rate of 10 L / min as an arc purge gas to be introduced into the arc generation site, an arc is formed on the sample substrate. Thermal spraying was performed. The film thickness of the sprayed coating of the obtained “Comparative Example 1” sample was 120 μm.

[Comparative Example 2]
Under the above processing conditions, arc spraying was performed on the sample substrate while supplying 85% nitrogen gas (0.3 MPa) at a rate of 10 L / min as the arc purge gas to be introduced into the arc generation site. . The film thickness of the sprayed coating of the obtained “Comparative Example 2” sample was 120 μm.

[Example 4]
Similar to “Example 1” except that nitrogen gas (0.7 MPa, 1.2 m ³ / min) with a concentration of 90% was used instead of compressed air for the “atomizing gas” for spraying (arc part) The purge gas was 90% concentration nitrogen gas), and arc spraying was performed on the sample substrate. The film thickness of the thermal spray coating of the obtained “Example 4” sample was 120 μm.

[Example 5]
Similar to “Example 2” except that nitrogen gas (0.7 MPa, 1.2 m ³ / min) with a concentration of 95% was used instead of compressed air as the “atomizing gas” for spraying (arc part) The purge gas was 95% concentration nitrogen gas), and arc spraying was performed on the sample substrate. The film thickness of the thermal spray coating of the obtained “Example 5” sample was 120 μm.

[Example 6]
The same as “Example 3” except that nitrogen gas (0.7 MPa, 1.2 m ³ / min) with a concentration of 99.99% was used instead of compressed air as the “atomizing gas” for spraying ( The arc purge gas was nitrogen gas having a concentration of 99.99%), and arc spraying was performed on the sample substrate. The film thickness of the thermal spray coating of the obtained “Example 6” sample was 120 μm.

<Pinhole test>
With the pinhole test, after attaching a qualitative filter paper soaked with a predetermined test solution to the test surface (sprayed coating surface) of the obtained sample (sample: 50 mm square), The filter paper is peeled off, and the number and size of colored spots (namely, “number and size of film defects”) generated on the filter paper are visually counted to obtain “the degree of opening”. The “denseness” or “porousness” of the film is evaluated by the size (somewhat) of “.”

(Preparation of test solution)
The test solution has the following composition. (Per 1L of test solution)
Component A. 10 g of potassium hexacyanoferrate (II) trihydrate
Component B. Hexacyanoferrate (III) potassium 10g
Component C. Sodium chloride 60g
After these are dissolved sequentially, the total volume is made up to 1000 ml with pure water.

(Test operation)
1. A qualitative filter paper (25 mm x 60 mm) pre-soaked with a test solution is placed on and closely adhered to the test surface of the sample whose surface (sprayed coating surface) has been cleaned, and tin that becomes the cathode is placed on it. A plate is placed, and a weight (200 g) for stabilizing the close contact of the qualitative filter paper is placed thereon.
2. The sample (anode) and tin plate (cathode) are electrically connected, and a current density of 0.2 A / dm ² (DC current) is applied for 5 minutes.
3. The weight and tin plate are removed, the qualitative filter paper is taken out, and the number and size of colored spots formed on the filter paper are measured.
4). The degree of openness (porosity) is calculated as “score” by calculation from the result of counting the colored spots. The “score” is integrated according to the following criteria.

(Accumulation method of openness)
Using the area of 1 cm ² of the test paper as a unit, the score is calculated as follows depending on the size of the diameter.
・ Spots with a diameter less than 1 mm have a score of 1 per piece.
-The number of spots with a diameter of 1 mm or more and less than 3 mm is 3 per piece.
-The number of spots with a diameter of 3 mm or more and less than 5 mm is 10 per piece.
However, if there are speckles with a diameter of 5 mm or more, the whole test is regarded as “uncountable” (failed).

  The results of each Example and each Comparative Example obtained by the above aggregation are shown in “Table 1” and “Table 2” below.

<Bending test> Three-point bending (applying force to the center of a test piece with free support at both ends) Test on one surface of the base material (the rolled steel SS400, width 13 mm × length 110 mm, 3 mm thickness, surface Sa3 grade) Under the thermal spraying conditions of Examples 1 to 6 and Comparative Examples 1 and 2, after forming the arc sprayed coating, the coating surface was polished, and the film thickness of each sample (test piece) was aligned to 120 μm. The surface was a flat “mirror surface” (the same applies to Examples 1 to 6 and Comparative Examples 1 and 2).

  Then, each test piece is set on a test stand (distance 60 mm between fulcrums XY) of a hydraulic servo type strength tester (servo pulser, manufactured by Shimadzu Corporation) with the above-mentioned film (polished mirror surface) facing downward [Fig. 3 (a)], while visually observing the coating surface from the lower surface (mirror surface) side, the indenter Z (the tip is a semicircular shape with a radius of 5 mm at the tip) from the upper side of the test piece (back surface and steel surface) When the center of the test piece (center between fulcrums) is pressed downward at a pressing speed of 1 mm / min depending on the cross-section), and abnormalities (cracks, cracks, peeling, etc.) are observed on the coating surface, pressing by the above indenter Z [See FIG. 3B].

  Next, the indenter Z is removed, and the inner angle α of the bending of each test piece in a state where it is bent downward in a “U” shape with the test load (a triangular shape with the base between the fulcrums and the lowest point of the bending as the apex) (Vertical angle) was measured with a protractor or the like to obtain the “bending angle” of each test piece.

  The results of each Example and each Comparative Example obtained by the above measurement are collectively shown in the following “Table 1” and “Table 2”.

  From the “openness per area” in the above tables, the arc spraying in reduced pressure in Examples 1 to 3 using nitrogen gas (inert gas) with a concentration of 90% or more as the arc purge gas has a concentration of 85%. Compared to arc spraying in reduced pressure of Comparative Examples 1 and 2 using the following nitrogen gas (or compressed air), the “denseness” of the sprayed coating adhered to and solidified on the subject (object) is improved. I can see. In particular, Examples 2 and 3 using a nitrogen gas with a concentration of 95% or more as the arc purge gas, and Examples 4 to 6 using nitrogen gas as the atomizing (injection) gas, It can be seen that the degree of opening is “3” or less, and the denseness of the film is greatly improved as compared with the conventional example (Comparative Example 1 = 10, Comparative Example 2 = 8).

  Further, from the results of the bending angle of the “bending test” (adhesion test) in each table above, the reduced pressure of Examples 1 to 3 using nitrogen gas (inert gas) with a concentration of 90% or more as the arc part purge gas. Inner arc spraying has improved adhesion to an object to be irradiated (particularly iron Fe) as compared with reduced pressure arc spraying in Comparative Examples 1 and 2 using nitrogen gas (or compressed air) having a concentration of 85% or less. I can see it. And in Examples 4-6 which use nitrogen gas also for the gas for atomizing (injection), in addition to the denseness of the said film | membrane improving, the adhesiveness of these films | membranes is also improving more. Therefore, according to the arc spraying method under reduced pressure according to the present invention, a dense sprayed coating having a dense and excellent adhesion can be formed by these synergistic effects.

  The arc spraying method of the present invention can be widely applied to form a sprayed coating used for rust / corrosion prevention, surface modification, electromagnetic wave shielding and the like. In particular, a corrosion-resistant film that is suitable for large-scale construction and covers the surface of large structures such as bridges and buildings can be made into a dense, long-life, highly weather-resistant film.

DESCRIPTION OF SYMBOLS 1 Nozzle part 1A Outer cylinder 1B Inner cylinder 1C Front block 1D Rear block 2 Atomizing gas introduction port 3 Purge gas introduction port 4 Injector gas introduction port 5A, 5B Wire supply pipe 6A, 6B Air injector pipe 7 Gas supply for arc part purge Pipe 8 Hood 10 Thermal spray gun 11 Gun body 11a Wire inlet 12 Gun grip W1, W2 Wire P Arc point S Slit (outlet)
R Atomizing gas flow path BR Bobbin rack GB Gas cylinder PS Power supply CP Compressor

Claims (7)

Two wire rods for thermal spraying are fed from the rear side of the nozzle for spraying consisting of a cylindrical outer end and a tapered outer tube and a conical inner tube toward the front end. A high-frequency current is applied between the wire rods, intersecting at the front end position of the inner cylinder to generate an arc between the tips of both wire rods, generating molten droplets of these wire rods, From the gap between the cylinder and the inner cylinder, compressed atomizing gas is ejected forward, and the droplets of the wire sucked out while generating a negative pressure at the arc generation position, the atomizing while finer put the airflow use gas, a arc spraying method of spraying toward the front of the morphism body of the spray nozzle,
Above Symbol spray nozzle, for delivering said two wires, respectively, the two wire feed pipe which is formed in an arc shape to bend gently from the middle to the inside along the reduced diameter of the inner cylinder Provided, let the wire feed pipe reach the outside of the front end of the inner cylinder through the wire,
To the respective wire feed pipe, by placing the air injector pipe, with flow portion of the gas for said atomizing toward the supply source direction of the introduced wire to the wire feed pipe,
In order to relieve the negative pressure generated at the arc generation position, an arc portion purge gas supply means is provided which communicates from the rear side of the inner cylinder to the front end small diameter portion of the inner cylinder through the inside of the inner cylinder , An arc spraying method characterized in that an inert gas having a concentration of 90% or more for purging an arc portion is supplied from the arc portion purging gas supply means.   The arc spraying method according to claim 1, wherein the inert gas having a concentration of 90% or more is also supplied between an outer cylinder and an inner cylinder of the thermal spray nozzle so as to be used also as the atomizing gas.   The arc spraying method according to claim 1 or 2, wherein a nitrogen gas having a concentration of 95% or more is used as the inert gas having a concentration of 90% or more. The nozzle part of the double structure consisting of a cylindrical cylinder on the rear end and a tapered outer cylinder on the front end side and a conical inner cylinder, and the gun body and gun grip that support the nozzle part, plus and minus, respectively the applied thermal spray wire, and two wires supply pipe for supplying to the intersection that is located in front end side of the nozzle portion through the inside of the inner cylinder of the nozzle portion from the gun body, the periphery of the intersection nozzle part of the front end surface, and an annular slit provided between the outer tube and the inner tube, placed on a stream of atomizing gas emitted forward from the annular slit, the arc generated by the intersection An arc spray gun that sprays droplets of the wire melted by the nozzle toward the subject in front of the nozzle part ,
The upper Symbol 2 wires supply pipe, respectively, are formed in an arc shape to bend gently inward along the reduced diameter of the upper Symbol inner tube from its middle, by passing the wire inside these wire feed pipe The wire is configured to reach the outside of the front end of the inner cylinder,
In each wire feed pipe, with an air injector pipe for flowing a part of the atomizing gas toward the supply source direction of the introduced wire to the wire feed pipe is arranged,
Arc portion purge gas supply means communicating to the front end small diameter portion of the inner cylinder through the inner side or al the inner cylinder is provided after the nozzle portion, said by emitted forward of the gas for the atomizing Arc spraying characterized in that an inert gas having a concentration of 90% or more for arc portion purge is supplied from the arc portion purge supply means corresponding to the negative pressure generated at the intersection. gun. The rear end of the inner tube of the nozzle portion is formed on hermetically, as the arc portion purge gas supply means, through the inside of the upper Symbol inner cylinder from the gas inlet port provided on the outer surface of the outer cylinder of the nozzle portion 5. An arc spray gun according to claim 4, further comprising an arc part purge gas supply pipe which communicates with the front end small diameter part of the inner cylinder and blows out the arc part purge gas toward the front crossing part.   The arc spray gun according to claim 4 or 5, wherein an inert gas having a concentration of 90% or more, which is the same as that for purging the arc portion, is supplied as the atomizing gas emitted toward the front of the nozzle portion. .   The arc spray gun according to any one of claims 4 to 6, wherein the inert gas having a concentration of 90% or more is nitrogen gas having a concentration of 95% or more.

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