JP2012162777A - Method and apparatus for plasma spraying - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the number of defective products produced in plasma spraying.SOLUTION: A plasma spraying apparatus starts feeding a wire 11 at a low speed, and generates a plasma arc 55 while a tip portion of the wire 11 is positioned ahead of a nozzle 37. With the generation of the plasma arc 55, the tip portion of the wire 11 is melted and turned into a jet flow 7 to be sprayed at an objected to be sprayed to thereby form a membrane. After the plasma arc 55 is generated and the wire 11 is melted, the feeding of the wire 11 is continued at an increased feeding speed.

Description

  The present invention relates to a plasma spraying method and a plasma in which a plasma arc is generated in the vicinity of a tip of a spray gun while feeding a wire to the spray gun, and a molten metal of the wire that is melted by the heat of the plasma arc is sprayed toward a sprayed object. It relates to a thermal spraying device.

  As a conventional plasma spraying apparatus, for example, the one described in Patent Document 1 below is known. This thermal spraying device generates a pilot arc by applying a high frequency and a high voltage with a nozzle side as an anode between a nozzle for discharging plasma gas and a cathode disposed in the nozzle.

  The generated pilot arc rides on a plasma gas flow flowing in the nozzle and moves to a wire that is an anode similar to the nozzle to form a plasma arc. The wire is melted by the heat of the plasma arc, and the molten metal of the melted wire is sprayed onto the object to be sprayed by the plasma gas flow.

US Pat. No. 5,938,944

  By the way, in the above-mentioned conventional thermal spraying apparatus, after generating a plasma arc, the wire is moved forward from the nozzle side toward the nozzle center. That is, in this case, when the pilot arc is transferred to the wire and the plasma arc is generated, the tip is melted while the wire is stopped, so that the tip side of the plasma arc is pulled to the tip of the melted wire. Will be displaced laterally.

  As a result, when the wire melts in this state, the molten metal is blown away in the direction deviating from the original plasma jet flow in front of the nozzle and adheres to and accumulates at other locations such as the side electrodes, and this deposit separates. As a result, it is sprayed on the object to be sprayed, resulting in the generation of defective products. In addition, the flow direction of the plasma gas is changed by the deposit attached to the nozzle, and the spraying direction is changed, so that defective products are generated without being sprayed at a required place.

    Therefore, an object of the present invention is to suppress generation of defective products due to plasma spraying.

  In the present invention, the wire is supplied while being moved forward in a state where the tip is in front of the nozzle, and a plasma arc is generated in this supply state to melt the tip of the wire, and the wire is moved after the plasma arc is generated. The speed is higher than that at the start of movement.

  According to the present invention, when the plasma arc is generated, since the tip of the wire is already at the nozzle front position, the plasma arc is formed toward the front position and can suppress lateral displacement. Occurrence can be suppressed.

It is a whole block diagram of the plasma spraying apparatus concerning one Embodiment of this invention. It is a block diagram which expands and shows the nozzle part periphery of the plasma spraying apparatus of FIG. It is a flowchart which shows operation | movement of the plasma spraying apparatus of FIG. It is operation | movement explanatory drawing which shows operation | movement of the plasma spraying apparatus of FIG. 1 in order with (a) and (b). FIG. 5 is an operation explanatory view illustrating the operation of the plasma spraying apparatus of FIG. 1 in order of (c) and (d) following FIG. 4. It is a graph which shows the wire supply rate change of the plasma spraying apparatus of FIG. It is operation | movement explanatory drawing by the plasma spraying apparatus of a comparative example, (a) shows the state which the plasma arc displaced to the contact tip side, (b) shows the state which the spraying direction changed with the deposit formed in the contact tip, respectively. . It is operation | movement explanatory drawing by the plasma spraying apparatus of another comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a plasma spraying apparatus according to an embodiment of the present invention includes a processing surface of a workpiece 5 on a side from a tip portion of a spraying gun 3 that protrudes downward from a gun body 1. A sprayed metal jet 7 is sprayed toward 5a to form a coating. In addition, the to-be-processed object 5 here is a cylinder block of an engine as an example, and the to-be-processed surface 5a is a cylinder bore.

  A wire 11 made of an iron-based metal material housed in a wire housing container 9 is sequentially supplied to the gun body 1 and the spray gun 3 via a wire feeding section 13 as a wire feeding means. The wire feeding unit 13 includes a wire feeding motor 15 (see FIG. 2) as a driving unit and a feeding roller 17 that is rotated by the wire feeding motor 15, and moves the wire 11 by the rotation of the feeding roller 17. The wire feed motor 15 is driven and controlled by a controller 19 as control means.

  The thermal spray gun 3 is connected at its base end portion (upper end portion in FIG. 1) to a rotation support portion 23 provided rotatably at the bottom portion in the housing 21 of the gun body 1. A gun rotation motor 27 provided in the housing 21 is connected to the rotation support portion 23 via a connecting belt 29 with a partition wall 25 therebetween.

  The wire 11 is movably inserted in the center of the rotation support portion 23, and the rotation support portion 23 rotates around the wire 11 and the wire 11 does not rotate. The thermal spray gun 3 is attached at a position eccentric with respect to the rotation center of the rotation support portion 23. Therefore, the thermal spray gun 3 rotates around the wire 11 so as to swivel around it. A cylindrical cover 30 is attached to the lower portion of the housing 21 so as to surround the periphery of the rotating spray gun 3 except the tip.

  A gas introduction part 31 is provided above the rotation support part 23. A plasma gas and an atomization air are supplied to the gas introduction part 31 from a plasma gas cylinder 33 and an atomization air cylinder 35, respectively. It ejects from the tip of 3. Therefore, although not particularly shown in FIG. 1, a plasma gas passage and an atomizing air passage through which the plasma gas and the atomizing air flow are formed from the gas introducing portion 31 to the rotation support portion 23 and the spray gun 3. It is.

  Here, a plasma gas passage and an atomizing air passage (not shown) in the gas introducing portion 31 and a plasma gas passage and an atomizing air (not shown) in the rotation support portion 23 rotating with respect to the gas introducing portion 31 are provided. It is necessary to communicate with each flow path.

  As a communication structure in this case, for example, each lower end portion of the plasma gas flow path and the atomizing air flow path in the gas introduction section 31 is an annular passage, and the plasma extending vertically in the rotation support section 23 is formed in the annular passage. It is conceivable to connect the upper ends of the gas flow path and the atomizing air flow path. Thereby, even if the rotation support part 23 rotates with respect to the gas introduction part 31, the plasma gas flow path and the atomization air flow path in the rotation support part 23 and the plasma gas flow path in the gas introduction part 31 and The atomizing air flow path is always in communication with each other.

  The thermal spray gun 3 is provided with a nozzle 37 at a portion protruding from the cover 30 at the tip (lower end). As shown in FIG. 2, the nozzle 37 has a discharge port 39 with a rotation center axis (wire). 11 (longitudinal direction of 11).

  The nozzle 37 includes a plasma gas discharge passage 41 through which plasma gas flows at the center, and a plurality of atomizing air discharge passages 43 through which atomizing air flows are formed around the plasma gas passage 41. The plasma gas discharge passage 41 and the atomizing air discharge passage 43 communicate with the plasma gas passage and the atomizing air passage (not shown), respectively.

  The plasma gas discharge passage 41 is formed in a tapered conical shape so that the inner diameter becomes smaller toward the tip side, and an atomizing air discharge passage 43 is formed along the outer peripheral side of the conical shape. That is, a plurality of discharge ports 39 of the nozzle 37 are formed at substantially equal intervals along the circumferential direction around the plasma gas discharge port 41a located at the center of the tip of the plasma gas discharge passage 41. And an atomizing air discharge port 43a at the tip of the atomizing air discharge passage 43.

  A cathode 45 is disposed as an electrode in the center of the plasma gas discharge passage 43, and a high voltage is applied between the cathode 45 and a nozzle 37 serving as an anode by a power supply device 47 serving as a power supply unit. In the vicinity of the nozzle 37 of the wire 11, a contact tip 49 serving as an anode similar to the nozzle 37 is provided, and this contact tip 49 is attached to be integrated with the thermal spray gun 3 (nozzle 37). Therefore, the contact chip 49 is electrically connected to the wire 11 while rotating as the nozzle 37 rotates.

  The wire 11 is guided between a contact tip 49 and the housing 21 by a wire guide (not shown) and sequentially fed forward.

  A high-frequency generator 51 as a high-frequency generator is connected between the power supply 47 and the cathode 45, and the high-frequency generator 51 and the power supply 47 constitute plasma generating means.

  Next, the operation will be described with reference to FIGS. First, the controller 19 simultaneously outputs a plasma generation on signal and a wire supply on signal (step S1). As a result, the wire feed motor 15 is driven, and the supply of the wire 11 is started at time T1 in FIG. 6 (FIG. 4A). At this time, as shown in FIG. 6, the feeding speed A of the wire 11 is a low speed of 3 m / min which is the first speed. At this time, it is assumed that the plasma gas and the atomizing air are previously discharged from the plasma gas discharge port 41a and the atomization air discharge port 43a at the tip of the nozzle 37, respectively.

  Thereafter, a high frequency / high voltage drive signal is output from the power supply device 47 to the high frequency generator 51 (step S2), whereby a pilot arc 53 (between the cathode 45 and the inner wall of the plasma gas passage 41 in the nozzle 37). 2) occurs. The generated pilot arc 53 rides on the plasma gas flow and moves to the tip of the wire 11 and becomes a plasma arc 55 at time T2 in FIG. 6 as shown in FIG. 4B.

  At the time when the plasma arc 55 is generated, the wire 11 is in a state where the tip slightly exceeds the center line 57 of the nozzle 37 from the position of FIG. 4A, as shown in FIG. 4B. Yes. Therefore, the plasma arc 55 is formed between the cathode 45 and the vicinity of the tip of the wire 11 in a state along the center line 57 of the nozzle 37.

  In this state, the tip of the wire 11 is melted by the heat of the plasma arc 55, and as shown in FIG. 5A, the droplet 59 is caused to flow by the plasma gas flow and the atomizing air flow, The sprayed surface 5a is sprayed to form a film.

  While the wire 11 is moving at a low speed A, the amount of heat of the plasma is excessive with respect to the wire moving speed, so that the wire 11 in the plasma arc 55 is melted as shown in FIG. It gradually becomes shorter.

  The generation of the plasma arc 55 is detected by a plasma generation detector (galvanometer) 61 provided in the power supply device 47, and this detection signal is output to the controller 19 as a plasma generation confirmation signal (step S3). . Upon receiving the plasma generation confirmation signal, the controller 19 outputs a drive signal so that the wire feed motor 15 increases from a low speed to a high speed (step S4). Start driving with. The feed speed B at a high speed of the wire 11 is set to 10 m / min which is the second speed as shown in FIG.

  When the feed speed B of the wire 11 is increased, as shown in FIG. 5B, a steady state is achieved in which the feed speed B and the amount of heat of the plasma arc 55 are balanced, and the spray gun 3 is rotated in this steady state. By being lowered, the sprayed coating is formed on the sprayed surface 5a.

  As described above, in the present embodiment, the plasma arc 55 is generated in a state where the wire 11 is moved at the low feed rate A to the front position of the nozzle 37, and then the moving speed of the wire 11 becomes the normal speed. I try to increase it. As a result, when the plasma arc 55 is generated, the tip of the wire 11 is positioned substantially corresponding to the front center line 57 of the nozzle 37, and the plasma arc 55 is formed toward the front position and displaced toward the contact tip 49 side. Can be suppressed.

  In contrast, as shown in FIG. 7A as a comparative example, when the supply of the wire 110 is started after the plasma arc 550 is generated, the wire 110 is stopped when the plasma arc 550 is generated. The melting of the tip proceeds. For this reason, the tip end side of the plasma arc 550 is displaced toward the side contact tip 490 so as to be pulled by the wire 110.

  As a result, when the wire 110 is melted in this state, the molten metal is blown away in the direction away from the original flow of the plasma jet and adheres and deposits around the contact chip 490, and the deposit 100 is eventually separated and sprayed. It will be thermally sprayed on the material and cause defective products.

  Further, as shown in FIG. 7B, the gas flow direction is changed by the deposit 100 attached to the contact tip 490, and the spraying direction is shifted from the center of the nozzle 370 from the original broken line position to the solid line position. Therefore, it is not sprayed on the necessary part of the sprayed object, and defective products are generated.

  In addition, when the plasma arc 550 is generated by supplying the wire 110 to a position beyond the nozzle 370 in advance as in the comparative example of FIG. 8, many wires 110 are generated before the plasma arc 550 is generated. As a result of the supply, the consumption of the wire 110 increases, and a defective product due to the adhesion of the surplus wire 110a to the sprayed object occurs.

  On the other hand, in the present embodiment, the plasma arc 55 is formed toward the front position of the nozzle 37 at the time of occurrence and suppresses displacement toward the contact tip 49 side. Therefore, the contact tip of the deposit 100 as shown in FIG. Adhesion to 49 can be suppressed. As a result, as shown in FIG. 4B, the plasma arc 55 spreads in a substantially conical shape centering on the center line 57 at the front position of the nozzle 37, and a uniform coating can be formed on the sprayed surface 5a. Therefore, the generation of defective products due to plasma spraying can be suppressed.

  Further, in order to avoid the lateral displacement of the plasma arc 550, the surplus wire 110a is generated as in the case where the plasma arc 550 is generated after the wire 110 is sufficiently supplied in advance as shown in FIG. It can also be suppressed.

  In the present embodiment, the controller 19 outputs a start signal simultaneously to the wire feed motor 15 and the power supply device 47. Thus, after the wire feed motor 15 is driven and the supply of the wire 11 is started, the high frequency generator 51 is delayed by a request signal from the power supply device 47 and the plasma arc 55 is delayed with respect to the wire 11 feed operation. Can be generated.

  In the above embodiment, the time (interval) from the time T1 when the supply of the wire 11 is started at a low feed rate A to the time T2 when the plasma arc 55 is generated is set to 20 msec to 100 msec, as shown in FIG. As a result, the deposit 100 could be prevented from adhering to the contact chip 490. Further, the feed rate A at a low speed of the wire 11 until the plasma arc 55 is generated is not limited to 3 m / min, and the generation of the deposit 100 can be suppressed in the range of 1.5 to 6.0 m / min. did it.

3 spray gun 5 spray object 11 wire 15 wire feed motor (drive unit, wire supply means)
17 Feed roller (wire supply means)
19 Control controller (control means)
37 Nozzle 45 Cathode (electrode)
47 Power supply (power supply unit, plasma generating means)
51 High-frequency generator (high-frequency generator, plasma generator)
55 Plasma Arc

Claims (4)

  A wire that is a material for thermal spraying is supplied toward the front of the nozzle at the tip of the spray gun, and the molten metal obtained by melting the wire by the heat of the plasma arc generated between the electrode in the nozzle and the wire is applied to the sprayed object. A plasma spraying method of spraying toward the nozzle, wherein the wire is supplied while being moved forward at a first speed in a state where the tip is in front of the nozzle, and the plasma arc is generated in this supply state. A plasma spraying method, wherein the tip of the wire is melted, and the moving speed of the wire after the generation of the plasma arc is set to a second speed higher than the first speed at the start of the movement.   The wire supply means for supplying the wire includes a drive unit for moving the wire, and the plasma generation means for generating the plasma arc generates a high frequency by receiving power supply from the power supply unit and the power supply unit. The plasma spraying method according to claim 1, further comprising: a high-frequency generator configured to output a start signal simultaneously to the drive unit and the power supply unit.   A wire that is a material for thermal spraying is supplied toward the front of the nozzle at the tip of the spray gun, and the molten metal obtained by melting the wire by the heat of the plasma arc generated between the electrode in the nozzle and the wire is applied to the sprayed object. A plasma spraying apparatus that injects toward the wire, wire supply means for supplying the wire while moving the wire forward, plasma generation means for generating a plasma arc between the electrode in the nozzle and the wire, and the plasma generation means And a control means for driving and controlling the wire supply means. The control means starts supply while the wire is moving forward at a first speed, and the tip of the wire is in the front position of the nozzle. The plasma arc is generated, and after the generation of the plasma arc, the moving speed of the wire becomes a second speed higher than the first speed at the start of the supply. Sea urchin, spray coating apparatus, characterized in that the drive control.   The wire supply unit includes a drive unit that moves the wire, and the plasma generation unit includes a power supply unit and a high-frequency generation unit that generates a high frequency upon receiving power supply from the power supply unit, The plasma spraying apparatus according to claim 3, wherein the control unit outputs a start signal simultaneously to the driving unit and the power supply unit.

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