Plasma spray gun for inner hole spraying and pipeline inner hole spraying method

Abstract

The invention discloses a plasma spray gun for inner hole spraying, which comprises a plasma spray gun body and a suction type dust removal cooling structure, and the suction type dust removal cooling structure is arranged on one side outside an inner hole spray gun head of the plasma spray gun body and comprises a suction type dust removal cooling part; a first reducing hole, a throat section and a second reducing hole which are communicated with one another are sequentially formed in the suction type dust removal cooling part in the axial direction of the suction type dust removal cooling part, the small opening end of the first reducing hole is connected with one end of the throat section, and the large opening end of the first reducing hole is communicated with a gun head cooling gas pipe; the small opening end of the second reducing hole is connected with the other end of the throat section, the large opening end of the second reducing hole is arranged in the direction opposite to the spraying direction of the inner hole spray gun head, and the throat section is communicated with a suction inlet. Compared with the prior art, in the spraying process, it can be guaranteed that a good dust removal effect and a good cooling effect are achieved in the pipeline, and the forming quality of a coating is improved.

Description

Technical Field

[0001] The invention relates to the technical field of inner hole spraying, and in particular to a plasma spray gun for inner hole spraying and a pipeline inner hole spraying method. Background Art

[0002] Photovoltaic power generation, as a clean and renewable new energy technology, has been vigorously developed in recent years. Both monocrystalline silicon and polycrystalline silicon can be used as raw materials for photovoltaic cells, but the power generation efficiency of monocrystalline silicon is much higher than that of polycrystalline silicon, and monocrystalline silicon is prepared from high-purity polycrystalline silicon. In order to increase the efficiency of crystal pulling, improve the quality of single crystal rods, and reduce the equipment damage rate, the CCz (Continuous-Cz) method (continuous feeding straight pulling method) is proposed to prepare single crystals. Due to the high hardness of polycrystalline silicon, the feeding process will cause surface wear of the feeding device and the conveying pipeline, and introduce impurities. The higher the purity of monocrystalline silicon, the better its electrical and thermal properties. This requires that the surfaces of components such as the feeding device and the conveying pipeline have high wear resistance and homogeneity to ensure the quality of the single crystal rod.

[0003] In order to ensure that the conveying pipeline has high wear resistance and homogeneity, a plasma spray gun is generally used to spray a layer of coating on the inner wall of the conveying pipeline; the plasma spray gun has a great influence on the forming quality of the coating during the spraying process.

[0004] Among them, CN115505864A discloses a small-sized axial powder feeding inner hole plasma spray gun, comprising:

[0005] A front gun body, which is provided with a first through hole;

[0006] A nozzle, one end of which is fixed to one side of the front gun body through a nozzle gland, and the other end of which extends through the first through hole to the other side of the front gun body;

[0007] Wherein, a spray channel is coaxially arranged in the nozzle;

[0008] rear gun body;

[0009] An insulator, which is disposed between the front gun body and the rear gun body and is fixedly connected to both the front gun body and the rear gun body;

[0010] Wherein, the insulator is provided with a second through hole, and the rear gun body is provided with a third through hole; the first through hole, the second through hole, and the third through hole are coaxially arranged;

[0011] A powder feeding frame is fixedly connected to the rear gun body; the powder feeding frame has a powder feeding channel inside, and a powder feeding joint is provided on one side of the powder feeding frame close to the rear gun body; the powder feeding channel is connected to the channel of the powder feeding joint;

[0012] A cathode, which is disposed in both the second through hole and the third through hole; a cathode seat of the cathode is connected to the powder feeding connector, a cathode head extends through the second through hole into the injection channel of the nozzle, and an annular cavity is formed between the cathode head and the inner wall of the injection channel;

[0013] Wherein, a powder delivery channel is coaxially arranged in the cathode, one end of the powder delivery channel is connected to the channel of the powder delivery joint, and the other end is connected to the injection channel; and the powder delivery channel and the injection channel are coaxially arranged; an air intake channel is opened on the front gun body and is connected to the annular cavity;

[0014] A cooling channel, wherein cooling water is passed through the interior thereof, so that the cooling water enters through the front gun body, flows through the nozzle outer area and the cathode outer area in a circular manner in sequence, and then flows out from the rear gun body;

[0015] Wherein, an annular heat sink is arranged on the outer side of the cathode at a position corresponding to the cooling channel.

[0016] The above-mentioned small-sized axial powder feeding inner hole plasma spraying gun is used for spraying small-sized axial powder feeding inner holes, but no coating cooling structure is provided, which causes heat accumulation in the pipeline and reduces the quality of the coating formed in the pipeline.

[0017] At the same time, CN217418794U discloses a rotary plasma spray gun, including a front gun shell, an intermediate insulator, a rear gun shell, an intermediate insulating connector and an insulating connector, the front gun shell and the rear gun shell are respectively arranged on both sides of the intermediate insulator, and an airflow distribution ring is arranged in the intermediate insulator, a nozzle is arranged in the front gun shell, and a water-proof sleeve is arranged between the nozzle and the front gun shell, a cathode head is arranged below the nozzle, and the cathode head is located in the rear gun shell and fixed to the rear gun shell through an electrode seat, a powder delivery needle is inserted in the nozzle, and the right end of the powder delivery needle is connected to the powder delivery pipe, and the other end of the powder delivery pipe is connected to the channel Z1 in the intermediate insulating connector, The front gun housing is connected with an anode water inlet pipe, the middle insulator is connected with a mixed air inlet pipe, and the rear gun housing is connected with a cathode water return pipe, wherein: the end of the anode water inlet pipe is connected with the channel Z2 in the middle insulating connector through a positive conductive ring, and the channel Z2 is connected with the channel J2 in the insulating connector, the end of the cathode water return pipe is connected with the channel Z3 in the middle insulating connector through a negative conductive ring, the end of the mixed air inlet pipe is connected with the channel Z6 in the middle insulating connector, an insulating connector is arranged on the right side of the middle insulating connector, a gas-liquid slip ring is arranged on the right side of the insulating connector, and the inner core of the gas-liquid slip ring is rotated by a motor.

[0018] The above-mentioned rotary plasma spray gun sprays the inner wall of the pipeline in a rotating manner, but no coating cooling structure is provided, which causes heat accumulation in the pipeline and reduces the quality of the coating formed in the pipeline.

[0019] In summary, the current plasma spray guns are not equipped with a coating cooling structure, which leads to heat accumulation in the pipeline during the spraying process, thereby reducing the quality of the coating formed in the pipeline. Summary of the invention

[0020] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a plasma spray gun for inner hole spraying and a method for inner hole spraying of a pipeline, so as to solve the problem in the prior art that heat accumulates in the pipeline during the spraying process of the plasma spray gun, which will reduce the quality of the coating formed in the pipeline.

[0021] To achieve the above-mentioned object, the first aspect of the present invention adopts the following technical solution: a plasma spray gun for inner hole spraying, comprising a plasma spray gun body, and also comprising a suction dust removal and cooling structure, wherein the suction dust removal and cooling structure is arranged on one side outside the inner hole spray gun head of the plasma spray gun body and comprises:

[0022] A suction-type dust removal and cooling part, wherein the suction-type dust removal and cooling part has a first reducing hole, a roaring mouth section and a second reducing hole connected in sequence along its axial direction, the small end of the first reducing hole is connected to one end of the roaring mouth section and its large end is connected to a gun head cooling air pipe, the small end of the second reducing hole is connected to the other end of the roaring mouth section and its large end is arranged in the opposite direction of the spraying direction of the inner hole spray gun head, and the roaring mouth section is connected to a suction port.

[0023] The second aspect of the present invention adopts the following technical solution: a method for spraying inner holes of a pipeline, in which the plasma spray gun for inner hole spraying described in the first aspect of the present invention is used to spray inside the pipeline.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. During the spraying process of the plasma spray gun for inner hole spraying, the cooling air introduced by the cooling air pipe of the gun head enters the suction dust removal cooling part, passes through the first reducing hole, the roar section and the second reducing hole in sequence, to form a suction force at the suction port, to draw the heat and dust accumulated in the spraying pipe into the roar section, and then spray into the pipe from the second reducing hole at a faster speed in the opposite direction of the spraying direction of the inner hole spray gun head and spray out from one end of the pipe. It can be used for inner hole spraying of pipes with a diameter of 145-200mm and a length of 4000mm, and can ensure good dust removal and cooling effects in the pipe during the spraying process, thereby improving the forming quality of the coating;

[0026] 2. The pipeline inner hole spraying method utilizes the plasma spray gun of the present invention for spraying, which can ensure good dust removal and cooling effects in the pipeline during the spraying process, thereby improving the molding quality of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a partial structure of an embodiment of the present invention;

[0028] Figure 2 for Figure 1 Structural schematic diagram of the medium suction dust removal and cooling structure;

[0029] Figure 3 for Figure 2 A cross-sectional view of

[0030] Figure 4 for Figure 1 Section view along line AA.

[0031] The figure marks in the drawings of the specification include: inner hole spray gun head 1, powder feeding needle 11, anode nozzle 12, suction dust removal cooling structure 2, suction dust removal cooling part 21, first reducing hole 22, roar mouth section 23, second reducing hole 24, suction port 25, inner hole spray gun barrel 3, powder feeding pipe 4, water inlet cable 5, mixed gas inlet pipe 6, water outlet cable 7, gun head cooling air pipe 8, reinforcing ribs 9, and barrel cooling air pipe 10. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below through specific embodiments:

[0033] Because the current plasma spray guns are not equipped with a coating cooling structure, heat accumulates in the pipeline during the spraying process, which will reduce the quality of the coating formed in the pipeline. In order to solve this problem, Figure 1 , Figure 2 as well as Figure 3 As shown, an embodiment of the present invention proposes a plasma spray gun for inner hole spraying, including a plasma spray gun body and a suction dust removal cooling structure 2, wherein the suction dust removal cooling structure 2 is arranged on the outer side of the inner hole spray gun head 1 of the plasma spray gun body and includes a suction dust removal cooling part 21, wherein the suction dust removal cooling part 21 has a first diameter reducing hole 22, a roaring mouth section 23 and a second diameter reducing hole 24 connected in sequence along its axial direction, the small mouth end of the first diameter reducing hole 22 is connected to one end of the roaring mouth section 23 and the large mouth end thereof is connected to a gun head cooling air pipe 8, the small mouth end of the second diameter reducing hole 24 is connected to the other end of the roaring mouth section 23 and the large mouth end thereof is arranged in the opposite direction of the spraying direction toward the inner hole spray gun head 1, and the roaring mouth section 23 is connected to a suction port 25.

[0034] During the spraying process of the plasma spray gun for inner hole spraying, the cooling air introduced by the gun head cooling air pipe 8 enters the suction dust removal cooling part 21, passes through the first reducing hole 22, the roar section 23 and the second reducing hole 24 in sequence, to form a suction force at the suction port 25, to draw the heat and dust accumulated in the pipe being sprayed into the roar section 23, and then spray into the pipe from the second reducing hole 24 at a faster speed in the opposite direction of the spraying direction of the inner hole spray gun head 1 and spray out from one end of the pipe. It can carry out inner hole spraying for pipes with a diameter of 145-200mm and a length of 4000mm, and can ensure good dust removal and cooling effects in the pipe during the spraying process, thereby improving the molding quality of the coating.

[0035] In this embodiment, there are two suction-type dust removal and cooling structures 2 and they are distributed on both sides outside the inner hole spray gun head 1. The large mouth ends of the first reducing holes 22 of the two suction-type dust removal and cooling structures 2 are connected to the gun head cooling air pipe 8 by a three-way pipe. The cooperation of the two suction-type dust removal and cooling structures 2 can more effectively cool the pipeline during the spraying process and discharge the generated dust, thereby improving the molding quality of the coating.

[0036] Among them, circular holes are formed at the separated ends of the first reducing hole 22 and the second reducing hole 24, and the diameter of the circular hole connected to the first reducing hole 22 is smaller than the diameter of the circular hole connected to the second reducing hole 24, so that the cooling air introduced into the suction dust removal cooling part 21 through the gun head cooling air pipe 8 can quickly flow through the circular holes, the first reducing hole 22, the roaring mouth section 23 and the second reducing hole 24, and form a suction force at the roaring mouth section 23 to draw the heat and dust accumulated in the pipeline into the roaring mouth section 23, and then discharge it.

[0037] In order to better understand the present solution, the plasma spray gun will be further optimized below.

[0038] like Figure 3 As shown, according to another embodiment of the present invention, the plasma spray gun for inner hole spraying, wherein the roaring mouth section 23 includes a straight hole section and a variable diameter hole section, and the straight hole section is connected to the suction port 25;

[0039] There are two reducing hole sections, and the small ends of the two reducing hole sections are connected to the two ends of the straight tube hole section in a one-to-one correspondence, and the large ends of the two reducing hole sections are connected to the small ends of the first reducing hole 22 and the small ends of the second reducing hole 24 in a one-to-one correspondence.

[0040] Here, the roaring mouth section 23 is designed to be composed of a straight hole section and two variable diameter hole sections, which is conducive to the cooling gas to flow quickly through the circular hole, the first variable diameter hole 22, the roaring mouth section 23 and the second variable diameter hole 24, to further enhance the suction force in the straight hole section, and further enhance the force to draw the heat and dust accumulated in the pipeline into the roaring mouth section 23. At the same time, it is also conducive to the heat and dust to flow faster to the outside of the pipeline after being discharged from the second variable diameter hole 24 with the cooling gas, and the heat and dust generated during the spraying process can be quickly and effectively discharged from the pipeline.

[0041] In this embodiment, the central axis of the suction port 25 is arranged perpendicular to the central axis of the straight bore section, which is conducive to drawing the heat and dust accumulated in the pipeline into the straight bore section, then flowing toward the second diameter-changing hole 24, and then flowing out of the pipeline.

[0042] In the prior art, the discharge port of the powder delivery needle 11 is connected to the inner side of the anode nozzle 12 through a channel arranged in the inner hole spray gun head 1. Therefore, during use, the powder delivered by the powder delivery needle 11 will adhere to the channel and the inner wall of the anode nozzle 12, which will greatly affect the process of the anode nozzle 12 and the cathode head cooperating to generate a plasma arc. The anode nozzle 12 and the cathode head may even fail to produce a plasma arc, causing the plasma spray gun to fail to operate normally. In order to solve this problem, Figure 1 As shown, according to another embodiment of the present invention, a plasma spray gun for inner hole spraying, wherein the inner hole spray gun head 1 includes a powder feeding needle 11 and an anode nozzle 12; the powder feeding needle 11 is arranged at the outer top of the inner hole spray gun head 1 in the horizontal direction, and the anode nozzle 12 is arranged inside the inner hole spray gun head 1 in the vertical direction, and the injection extension line of the anode nozzle 12 is arranged perpendicular to the powder feeding extension line of the powder feeding needle 11.

[0043] In this embodiment, there is no direct connection between the powder feeding needle 11 and the anode nozzle 12, and the powder transported by the powder feeding needle 11 will not enter the anode nozzle 12, and the powder will not adhere to the inner wall of the anode nozzle 12; specifically, the plasma arc generated by the cooperation between the anode nozzle 12 and the cathode head is ejected from the anode nozzle 12 to fully contact the powder ejected from the powder feeding needle 11, and the powder is melted and under the action of the plasma arc, the molten powder basically moves along the movement direction of the plasma arc to be sprayed onto the inner wall of the pipe to form a coating.

[0044] like Figure 1 and Figure 4As shown, according to another embodiment of the present invention, a plasma spray gun for inner hole spraying, wherein the plasma spray gun body also includes an inner hole spray gun barrel 3, the inner hole spray gun head 1 is arranged on the front end top of the inner hole spray gun barrel 3, and the inner hole spray gun barrel 3 is provided with a powder delivery pipe 4, a water inlet cable 5, a mixed gas inlet pipe 6, a water outlet cable 7 and a barrel cooling air pipe 10 that cooperate with the inner hole spray gun head 1, and the gun head cooling air pipe 8 is also arranged in the inner hole spray gun barrel 3.

[0045] In this embodiment, the inner hole spray gun barrel 3 serves as the installation support body of the inner hole spray gun head 1, and the powder delivery pipe 4, the water inlet cable 5, the mixed gas inlet pipe 6, the water outlet cable 7, the barrel cooling air pipe 10 and the gun head cooling air pipe 8 are also hiddenly installed, and the powder delivery pipe 4, the water inlet cable 5, the mixed gas inlet pipe 6, the water outlet cable 7, the barrel cooling air pipe 10 and the gun head cooling air pipe 8 are ensured to be installed in an orderly manner; at the same time, it is also convenient for the plasma spray gun to extend into a pipeline with a diameter of 145-200mm and a length of 4000mm to perform inner hole spraying.

[0046] In order to improve the structural strength of the inner bore spray gun barrel 3 and ensure that the inner bore spray gun barrel 3 can be used stably and safely during use; the inner wall of the inner bore spray gun barrel 3 is provided with a plurality of reinforcing ribs 9 along its circumferential direction, and each reinforcing rib 9 is arranged along the axial direction of the inner bore spray gun barrel 3.

[0047] It should be noted that the plasma spray gun mainly improves the design of the suction dust removal cooling structure 2, the arrangement of the powder feeding needle 11 and the inner bore spray gun barrel 3 to meet the requirements of efficient inner bore spraying for pipes with a diameter of 145-200mm and a length of 4000mm. The arrangement and connection of the remaining structures in the plasma spray gun are prior art and will not be further elaborated here. The corresponding structures in CN115505864A and CN217418794U can be referred to and adaptive changes can be made.

[0048] The present invention also proposes a method for spraying inner holes of a pipeline in combination with the above-mentioned plasma spray gun, comprising the following steps: placing the plasma spray gun in one end of the pipeline after the inner surface is roughened, starting the plasma spray gun to preheat the pipeline, during which the plasma spray gun moves in the pipeline along the axial direction of the pipeline and the pipeline rotates; after preheating, the plasma spray gun is used to spray a coating in the pipeline and the air supply pressure of the cooling air pipe of the gun head is controlled to be 0.3-0.5Mpa.

[0049] The pipeline inner hole spraying method utilizes the plasma spray gun of the present invention to perform spraying, and during the spraying process, it can ensure good dust removal and cooling effects in the pipeline, thereby improving the molding quality of the coating.

[0050] Wherein, when the coating is a single-layer pure silicon coating, the thickness does not exceed 150 μm; when the coating is a composite coating, the total thickness does not exceed 250 μm and the thickness of the pure silicon layer located on the surface is 140-160 μm.

[0051] In actual use, it is found that when the coating is too thin, it will lose its effect prematurely due to wear, and when the coating is too thick, it is easy for the coating to fall off in chunks due to impact.

[0052] The present pipe inner hole spraying method is described below with reference to a specific example.

[0053] Implementation 1

[0054] The 316 stainless steel pipe (φ180, wall thickness 4mm) with roughened inner surface was placed on the workpiece rack, and the preheating parameters of the plasma spray gun were set: preheating distance was 100mm, preheating current was 400A, main gas flow rate was 40L / min, steel pipe rotation speed was 50r / min, and plasma spray gun feed speed was 30mm / s.

[0055] Powder spraying parameters: spraying current 600A, main gas pressure 0.8Mpa, main gas flow 60L / min, auxiliary gas pressure 0.8Mpa, auxiliary gas flow 8L / min, steel pipe rotation speed 50r / min, plasma spray gun feed speed 2mm / s.

[0056] Two powder feeders are used to work together, each powder feeder has a powder feeding pipe, and the two powder feeding pipes are connected to the powder feeding pipe in the above-mentioned plasma spray gun by a T-type tee; the silicon powder is electronic grade polysilicon (grade one) with a particle size of 15-75μm, which is placed in the powder feeding tank of the 1# powder feeder; the metal powder is 316 stainless steel powder with a particle size of 15-45μm, which is placed in the powder feeding tank of the 2# powder feeder, and the powder feeding carrier gas pressure is 0.4Mpa; the powder feeding carrier gas flow rate of each powder feeder is 5L / min, and the powder feeding rate of each powder feeder is 20g / min.

[0057] Connect the gun tip cooling air pipe, the gun barrel cooling air pipe, and the workpiece rack cooling air exhaust to the nitrogen gas source with a gas supply pressure of 0.4Mpa.

[0058] During the spraying process, the spraying distance is 90mm, and the powder disc speed of each powder feeder is adjusted to control the powder feeding rate. The powder feeding amount of the powder feeding tank of the 2# powder feeder is set to 20g / min, and the powder feeding amount of the powder feeding tank of the 1# powder feeder is set to 0g / min. The first layer of coating is prepared with a thickness of 40μm; the powder feeding amount of the powder feeding tank of the 2# powder feeder is set to 15g / min, and the powder feeding amount of the powder feeding tank of the 1# powder feeder is set to 5g / min. The second layer of coating is prepared with a thickness of 30μm; the powder feeding amount of the powder feeding tank of the 2# powder feeder is set to 15g / min, and the powder feeding amount of the powder feeding tank of the 1# powder feeder is set to 5g / min. The powder feeding amount of the powder tank is 10g / min, the powder feeding amount of the powder tank of the 1# powder feeder is 10g / min, and the third layer of coating is prepared with a thickness of 20μm; the powder feeding amount of the 2# powder feeding tank of the powder feeder is set to 5g / min, and the powder feeding amount of the powder feeding tank of the 1# powder feeder is set to 15g / min, and the fourth layer of coating is prepared with a thickness of 20μm; the powder feeding amount of the powder feeding tank of the 2# powder feeder is set to 0g / min, and the powder feeding amount of the powder feeding tank of the 1# powder feeder is 20g / min, with a thickness of 140μm.

[0059] A composite coating with 5 layers is formed by spraying on the inner wall of the 316 stainless steel pipe.

[0060] According to testing, the Vickers hardness of stainless steel is 335HV, the hardness of the composite coating is 687HV, and the hardness of high-purity polysilicon is generally higher than 700HV. During the feeding process, it is easy to cause wear on the surface of the stainless steel pipeline, thereby introducing impurities during the feeding process.

[0061] Implementation 2

[0062] Place the 316 stainless steel tube (φ150, wall thickness 3mm) with roughened inner surface on the workpiece rack;

[0063] Set the preheating parameters: preheating distance is 75mm, preheating current is 400A, main gas flow rate is 40L / min, steel pipe rotation speed is 50r / min, plasma spray gun feed speed is 50mm / s;

[0064] Spraying powder parameters: electronic grade polysilicon (grade three), particle size 15-38μm, powder feeding carrier gas pressure 0.8Mpa, powder feeder powder feeding carrier gas flow 8L / min, powder feeding rate 25g / min, spraying current 500A, main gas pressure 0.8Mpa, main gas flow 55L / min, auxiliary gas pressure 0.8Mpa, auxiliary gas flow 2L / min;

[0065] A powder feeder is used to connect with the powder feed pipe in the plasma spray gun;

[0066] During the spraying process, the spraying distance is 80 mm, the steel pipe rotation speed is 30 r / min, the plasma spray gun feed speed is 2 mm / s, and the gun head cooling air pipe and the gun barrel cooling air pipe are connected to a nitrogen gas source.

[0067] A pure silicon coating having a layer is formed by spraying on the inner wall of the 316 stainless steel tube, and the thickness of the pure silicon coating is 150 μm.

[0068] After testing, the hardness of the pure silicon coating is 723HV.

[0069] Example 3

[0070] Place the 316 stainless steel tube (φ180, wall thickness 3mm) with roughened inner surface on the workpiece rack;

[0071] Set the preheating parameters: preheating distance is 130mm, preheating current is 400A, main gas flow rate is 40L / min, steel pipe rotation speed is 50r / min, plasma spray gun feed speed is 50mm / s;

[0072] Two powder feeders are used to work together, each of which has a powder feeding pipe, and the two powder feeding pipes are connected to the powder feeding pipe in the above-mentioned plasma spray gun by a T-type tee; the silicon powder is electronic grade polysilicon (first level), with a particle size of 15-45μm, and is placed in the powder feeding tank of the 1# powder feeder; the metal powder is NiAl powder, with a particle size of 45-75μm, and is placed in the powder feeding tank of the 2# powder feeder, and the powder feeding carrier gas pressure is 0.4Mpa; the powder feeding carrier gas flow rate of each powder feeder is 5L / min, and the powder feeding rate of each powder feeder is 20g / min;

[0073] Connect the cooling air pipe of the gun tip, the cooling air pipe of the gun barrel, and the cooling air exhaust of the workpiece rack to the nitrogen gas source with a gas supply pressure of 0.4Mpa;

[0074] During the spraying process, NiAl metal powder was sprayed first, the spraying current was 600A, the main gas pressure was 0.8Mpa, the main gas flow rate was 65L / min, the auxiliary gas pressure was 0.8Mpa, the auxiliary gas flow rate was 8L / min, the spraying distance was 120mm, the steel pipe rotation speed was 40r / min, the plasma spray gun feed speed was 3mm / s, the powder feeding amount of the powder feeding tank of the 2# powder feeder was set to 25g / min, and the powder feeding amount of the powder feeding tank of the 1# powder feeder was set to 0g / min, and the bottom coating preparation was completed, with a thickness of 85 μm; then spray pure Si powder, spraying current 560A, main gas pressure 0.8Mpa, main gas flow 60L / min, auxiliary gas pressure 0.8Mpa, auxiliary gas flow 2L / min, spraying distance 100mm, steel pipe rotation speed 30r / min, plasma spray gun feed speed 1.5mm / s, set the powder feeding amount of the powder feeding tank of 2# powder feeder to 0g / min, the powder feeding amount of the powder feeding tank of 1# powder feeder to 25g / min, complete the surface coating preparation, the thickness is 160μm.

[0075] A composite coating with two layers is formed by spraying on the inner wall of the 316 stainless steel pipe.

[0076] After testing, the hardness of the composite coating is 692HV.

[0077] Comparative Example 1

[0078] The only difference from Example 1 is that the plasma spray gun used is the plasma spray gun in CN115505864A.

[0079] After testing, the hardness of the composite coating is 486HV.

[0080] Comparative Example 2

[0081] The only difference from Example 2 is that the plasma spray gun used is the plasma spray gun in CN115505864A.

[0082] After testing, the hardness of the composite coating is 498HV.

[0083] It should be noted that the main gas mentioned above refers to argon, and the auxiliary gas refers to hydrogen.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A plasma spray gun for inner hole spraying, comprising a plasma spray gun body, characterized in that: It also includes a suction dust removal cooling structure, which is arranged on one side outside the inner hole spray gun head of the plasma spray gun body and includes: A suction-type dust removal and cooling part, wherein the suction-type dust removal and cooling part has a first reducing hole, a roaring mouth section and a second reducing hole connected in sequence along its axial direction, the small end of the first reducing hole is connected to one end of the roaring mouth section and its large end is connected to a gun head cooling air pipe, the small end of the second reducing hole is connected to the other end of the roaring mouth section and its large end is arranged in the opposite direction of the spraying direction of the inner hole spray gun head, and the roaring mouth section is connected to a suction port.

2. A plasma spray gun for inner hole spraying according to claim 1, characterized in that: There are two suction-type dust removal and cooling structures, which are distributed on both sides outside the inner hole spray gun head.

3. A plasma spray gun for inner hole spraying according to claim 1 or 2, characterized in that: The roar section comprises: A straight bore section, the straight bore section being in communication with the suction port; The variable diameter hole segments have two variable diameter hole segments, and the small ends of the two variable diameter hole segments are connected to the two ends of the straight tube hole segment in a one-to-one correspondence, and the large ends of the two variable diameter hole segments are connected to the small ends of the first variable diameter hole and the small ends of the second variable diameter hole in a one-to-one correspondence.

4. A plasma spray gun for inner hole spraying according to claim 3, characterized in that: The central axis of the suction port is arranged perpendicularly to the central axis of the straight cylinder hole section.

5. The plasma spray gun for inner hole spraying according to claim 1, characterized in that: The inner hole spray gun head comprises: A powder feeding needle, which is arranged horizontally on the outer top of the inner hole spray gun head; The anode nozzle is arranged in the inner hole spray gun head along the vertical direction, and the spray extension line of the anode nozzle is arranged perpendicular to the powder feeding extension line of the powder feeding needle.

6. The plasma spray gun for inner hole spraying according to claim 1, characterized in that: The plasma spray gun body also includes: An inner-hole spray gun barrel, wherein the inner-hole spray gun head is arranged at the top of the front end of the inner-hole spray gun barrel, and a powder delivery pipe, a water inlet cable, a mixed gas inlet pipe and a water outlet cable matching the inner-hole spray gun head are arranged in the inner-hole spray gun barrel, and a gun head cooling air pipe is also arranged in the inner-hole spray gun barrel.

7. A plasma spray gun for inner hole spraying according to claim 6, characterized in that: The inner wall of the inner bore spray gun barrel is provided with a plurality of reinforcing ribs along its circumferential direction, and each reinforcing rib is arranged along the axial direction of the inner bore spray gun barrel.

8. A method for spraying inner holes of a pipeline, characterized in that: The plasma spray gun for inner hole spraying according to any one of claims 1 to 7 is used to spray inside the pipeline.

9. A pipeline inner hole spraying method according to claim 8, characterized in that: The following steps are involved: Placing the plasma spray gun in one end of the pipeline after the inner surface is roughened, and starting the plasma spray gun to preheat the pipeline, during which the plasma spray gun moves in the pipeline along the axial direction of the pipeline and the pipeline rotates; After preheating, the plasma spray gun is used to spray the coating inside the pipeline and the air supply pressure of the cooling air pipe of the gun head is controlled to be 0.3-0.5 MPa.

10. A pipeline inner hole spraying method according to claim 9, characterized in that: When the coating is a single-layer pure silicon coating, the thickness does not exceed 150 μm; when the coating is a composite coating, the total thickness does not exceed 250 μm and the thickness of the pure silicon layer located on the surface is 140-160 μm.

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