A metal pipe fitting plasma cutting apparatus and method

Abstract

The application discloses a metal pipe fitting plasma cutting device and method, comprising a cutting nozzle, the cutting nozzle comprising a nozzle body and a nozzle head, the nozzle body being through in the axial direction and being detachably connected with a cutting torch, a center pipe being fixed in the nozzle body, the center pipe being detachably connected with the nozzle head; the inner hole of the center pipe and the internal passage of the nozzle head jointly constituting an inner cavity, an outer cavity being formed between the outer wall of the center pipe and the inner wall of the nozzle body; a flow guide cover being fixed on the end of the nozzle head close to the nozzle body, an annular reverse flow channel being formed between the flow guide cover and the nozzle body, the reverse flow channel being communicated with the outer cavity, the flow direction of the airflow in the reverse flow channel being opposite to the flow direction of the working airflow sprayed by the nozzle head, so as to form a reverse thrust; the problem that the continuous recoil thrust in the prior art easily causes the arm muscle fatigue of the operator, causes the decrease of the holding stability, and the slag is easily splashed upward and adhered to the outer wall of the cutting nozzle under the action of the airflow.

Description

Technical Field

[0001] This invention relates to the field of plasma cutting technology, and in particular to a plasma cutting device and method for metal pipe fittings. Background Technology

[0002] Plasma cutting technology, with its high efficiency and flexibility, is widely used in the on-site processing of metal pipes. Existing cutting nozzles are generally divided into two categories: contact nozzles and non-contact nozzles. Contact nozzles are suitable for thin-walled materials, while non-contact nozzles are mostly used for cutting thick-walled plates or large-diameter profiles.

[0003] However, there are significant technical bottlenecks when performing long-term handheld operations on thick-walled, large-diameter metal pipes (square or round pipes).

[0004] Firstly, during operation, the high-temperature plasma arc and compressed airflow are ejected at high speed from the nozzle using a non-contact cutting nozzle. According to the law of conservation of momentum, this generates a recoil thrust along the cutting direction. Since cutting thick-walled, large-diameter workpieces takes a long time, the continuous recoil thrust can easily cause muscle fatigue in the operator's arms, leading to decreased grip stability. This not only seriously affects the straightness and perpendicularity of the cut, but may even cause short circuits and backfire due to vibration, damaging the cutting torch.

[0005] Secondly, the molten residue (slag) generated during the cutting of thick-walled materials is large in quantity and extremely hot. Under the action of airflow, it is easy to splash upward and adhere to the outer wall of the cutting nozzle, causing the cutting nozzle to be in an abnormally high temperature environment for a long time. This accelerates the oxidation and thermal fatigue failure of the nozzle, significantly shortens the service life of consumables, and increases production costs.

[0006] To address this, we designed a plasma cutting device and method for metal pipe fittings. Summary of the Invention

[0007] The purpose of this invention is to solve the problems in the prior art where continuous recoil thrust easily causes operator arm muscle fatigue, leading to decreased grip stability, and molten slag easily splashes upward and adheres to the outer wall of the cutting nozzle under the action of airflow. Therefore, a plasma cutting device and method for metal pipes is proposed.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A plasma cutting device for metal pipe fittings includes a cutting nozzle, which includes a nozzle body and a nozzle head. The nozzle body extends axially and is detachably connected to a cutting torch. A central tube is fixed inside the nozzle body, and the central tube is detachably connected to the nozzle head. The inner hole of the central tube and the internal channel of the mouthpiece together form an inner cavity, and the outer wall of the central tube and the inner wall of the mouthpiece enclose each other to form an outer cavity; A flow guide is fixed to one end of the nozzle near the body of the nozzle. An annular reverse flow channel is formed between the flow guide and the body of the nozzle. The reverse flow channel is connected to the outer cavity. The airflow direction in the reverse flow channel is opposite to the working airflow direction ejected by the nozzle, so as to form a reverse thrust. The airflow in the reverse flow channel flows upward along the inner wall of the mouthpiece and forms an airflow protective cover for cooling on the outer periphery of the mouthpiece. The distance between the central tube and the nozzle is adjustable.

[0009] Preferably, the top of the mouthpiece is coaxially fixed with a radially outwardly protruding annular flange, and the mouthpiece as a whole has an inverted frustum-shaped structure, with its outer diameter gradually decreasing from top to bottom; The inner wall of the flow guide is parallel to the outer wall of the nozzle, so that the cross-sectional area of ​​the reverse flow channel along the airflow direction remains consistent, thereby maintaining the stability of the airflow velocity. The air guide cover has multiple annularly distributed airflow holes, and the airflow forms an annular airflow protection layer through the airflow holes.

[0010] Preferably, the top of the nozzle is coaxially integrally formed with a first threaded pipe connector for threaded connection with the output end of the cutting torch; The top of the nozzle is coaxially integrally formed with a second threaded pipe connector, which is threaded with the bottom of the central tube to enable the nozzle and the central tube to be detachable and the spacing to be adjusted. The top of the second threaded pipe joint is coaxially extended with a sealing tube. The outer diameter of the sealing tube is in clearance fit with the inner diameter of the central tube. At least two sealing grooves are circumferentially recessed on the outer peripheral wall of the sealing tube, and each sealing groove is fitted with a high-temperature resistant sealing ring. When tightened, the sealing tube is inserted into the inner hole of the central tube, and the high-temperature resistant sealing ring elastically abuts against the inner wall of the central tube to block fluid crosstalk between the inner and outer cavities and ensure the sealing of the reverse flow channel.

[0011] Preferably, the top of the flow guide is detachably connected to an annular plate, the annular plate comprising two arc-shaped plates, the inner diameter of the annular plate being smaller than the inner diameter of the flow guide, and an annular gap being left between the inner diameter of the annular plate and the outer wall of the nozzle. The lower edge of the inner ring of the ring plate has a slope.

[0012] Preferably, the nozzle body has a countersunk hole in the radial direction, the central tube has a through hole in the radial direction corresponding to the countersunk hole, and the countersunk hole is internally threaded with a countersunk bolt passing through the through hole.

[0013] Preferably, the outer wall of the central tube is fixed with a plurality of annularly distributed connecting plates, and the outer wall of the connecting plates is fixedly connected to the inner wall of the nozzle.

[0014] Preferably, the airflow hole axis is inclined from the inside out in a direction away from the cutting nozzle axis, and the axes of the plurality of airflow holes are coplanar.

[0015] Preferably, the axis of the airflow hole is inclined from the inside out in a direction away from the axis of the cutting nozzle, and the axes of the plurality of airflow holes are inclined outward.

[0016] Preferably, the flange and the mouthpiece are joined by a chamfer, and the flange and the mouthpiece are tangent to the chamfer.

[0017] A method of using a plasma cutting device for metal pipes includes the following steps: S1. Connect the first threaded pipe connector to the cutting torch threadedly, and insert the inner nozzle with the center electrode into the inner cavity. Leave a gap between the outer wall of the nozzle and the inner wall of the inner cavity for inert gas flow, and the nozzle body is connected to the inert gas of the cutting torch. S2. Screw the second threaded pipe fitting into the central pipe, and adjust the distance between the bottom of the nozzle and the top of the nozzle by rotating the nozzle. At the same time, adjust the distance between the inner wall of the guide shroud and the outer wall of the nozzle to adjust the size of the reverse flow channel and adjust the airflow in the reverse flow channel. S3. Turn on the plasma cutter and cutting torch. The equipment is running. Inert gas enters through the first threaded pipe joint and is split through the central pipe. Part of the inert gas flows out through the working airflow injected from the nozzle and flows downward. The other part of the inert gas enters the outer cavity and flows upward from the bottom of the nozzle body. Finally, it flows upward through the guide shroud, forming a cooling airflow protective shroud on the outer periphery of the nozzle body. At the same time, it forms a reverse thrust opposite to the working airflow injected from the nozzle. S4. Part of the inert gas flowing through the guide shroud is ejected outward through the airflow holes, thereby forming an airflow protection layer, which not only prevents the reverse airflow on the guide shroud side from sucking in the cutting slag, but also inhibits the cutting slag from splashing upward.

[0018] The beneficial effects of this invention are as follows: 1. This invention utilizes the annular reverse flow channel formed between the nozzle body and the nozzle tip by the flow guide. Based on the principle of fluid mechanics, it guides part of the high-pressure inert gas to flow in the opposite direction (upward). At the flow guide, a balanced thrust opposite to the cutting jet direction is generated. This reverse thrust can effectively counteract part of the recoil force generated by the plasma arc jet, greatly reduce the operator's hand load, improve the grip stability during long-term operation, thereby ensuring the straightness and perpendicularity of the cut, and reducing the risk of short circuit backfire caused by shaking. 2. This invention utilizes the rising airflow of the reverse flow channel to form a dense airflow protective shield (air curtain) around the outer periphery of the nozzle. The continuously flowing gas quickly carries away the heat conducted to the nozzle, significantly reducing the overall temperature of the cutting nozzle and preventing overheating and burn-out. This air curtain forms an invisible isolation wall between the cutting nozzle and the high-temperature cutting area, effectively blocking the splashing and adhesion of oxide scale and molten metal, fundamentally solving the problem of heat accumulation caused by slag adhesion, extending the service life of consumables, and reducing production costs. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure and plasma cutting torch installation of a metal pipe cutting device proposed in this invention. Figure 2 This is a schematic diagram of the overall structure of a plasma cutting device for metal pipes proposed in this invention. Figure 3 This invention provides a plasma cutting device for metal pipe fittings. Figure 2 Enlarged structural diagram at point A in the middle; Figure 4 This is a schematic diagram of the overall exploded structure of a plasma cutting device for metal pipes proposed in this invention. Figure 5 This is a schematic diagram of the overall cross-sectional structure of a plasma cutting device for metal pipes proposed in this invention. Figure 6 This invention provides a plasma cutting device for metal pipe fittings. Figure 5 Enlarged structural diagram at point B; Figure 7 This is a schematic diagram of the first embodiment of the airflow hole structure of the plasma cutting device for metal pipes proposed in this invention; Figure 8 This is a schematic diagram of the second embodiment of the airflow hole structure of the plasma cutting device for metal pipes proposed in this invention; Figure 9 This is a schematic diagram of the airflow through the airflow hole in a second embodiment of a plasma cutting device for metal pipes proposed in this invention.

[0020] In the diagram: 10. Nozzle; 11. First threaded pipe fitting; 12. Flange; 13. Countersunk hole; 14. Countersunk bolt; 20. Nozzle; 21. Flow deflector; 211. Airflow hole; 212. Reverse flow channel; 22. Second threaded pipe joint; 221. Sealing pipe; 23. Ring plate; 30. Central tube; 31. Outer cavity; 32. Inner cavity; 33. Connecting plate. Detailed Implementation

[0021] Example 1: Reference Figure 1- Figure 7 As shown, a plasma cutting device for metal pipes includes a cutting nozzle, which comprises a nozzle body 10 and a nozzle head 20. The nozzle body 10 extends axially and is detachably connected to the cutting torch for easy replacement after wear and routine maintenance. The upper end of the nozzle body 10 is connected to the electrode and inert gas path of the cutting torch. A central tube 30 is coaxially fixed inside the nozzle body 10. The central tube 30 is made of the same material as the cutting nozzle, using a metal material with excellent thermal conductivity (such as copper). The top of the central tube 30 (i.e., the inert gas inlet end) has a sloping structure to reduce the wind resistance when the inert gas is split. The lower end of the central tube 30 is detachably connected to the nozzle head 20. In particular, the distance between the central tube 30 and the nozzle head 20 is adjustable. By adjusting the nozzle head 20, the axial distance between it and the lower end of the central tube 30 can be precisely adjusted, thereby adjusting the size of the gap between them. The inner hole of the central tube 30 and the internal channel of the nozzle 20 together form a continuous and through inner cavity 32. At the same time, there is a certain gap between the outer wall of the central tube 30 and the inner wall of the nozzle 10. This gap encloses and forms an annular outer cavity 31 that communicates with the inner cavity 32. The bottom of the outer cavity 31 is open and connected to the outside (that is, it is connected through the gap between the bottom of the central tube 30 and the nozzle 20), so that some of the inert high-pressure gas can be ejected outward through the gap between the bottom of the central tube 30 and the nozzle 20. A flow guide 21 is integrally formed or fixedly welded to one end of the nozzle 20 near the nozzle body 10 (i.e., the upper end). The inner diameter of the flow guide 21 is larger than the outer diameter at the corresponding position of the nozzle body 10, thereby forming an annular reverse flow channel 212 between the flow guide 21 and the nozzle body 10. The reverse flow channel 212 is connected to the outer cavity 31 through the gap between the bottom of the central tube 30 and the nozzle 20. The airflow direction in the reverse flow channel 212 is opposite to the working airflow direction ejected by the nozzle 20, so as to form a reverse thrust. During operation, after the inert protective gas enters the nozzle 10, a portion of the gas flows upward through the reverse flow channel 212. This airflow direction is completely opposite to the working airflow direction (downward) ejected from the nozzle 20. According to the principles of fluid dynamics, this reverse airflow generates an upward reverse thrust at the guide shroud 21. This thrust can partially offset the outward thrust generated during the cutting process, reduce the fatigue of the operator's arm muscles, and improve the stability of the grip.

[0022] Furthermore, the rising airflow in the reverse flow channel 212 continues to flow upward along the inner wall of the nozzle body 10, forming a dense airflow protective shield around the outer periphery of the nozzle body 10. This airflow protective shield carries away the heat conducted to the nozzle body 10 through the continuous flow of gas, providing air cooling to the entire nozzle body 10 and preventing the cutting nozzle from burning due to overheating. This airflow protective shield can also isolate the high-temperature cutting area from the cutting nozzle body, further preventing the splashing of oxide scale and molten metal and its adhesion to the nozzle body 10, thus playing a protective effect similar to an "air curtain".

[0023] Reference Figure 2 , Figure 4 , Figure 5 As shown, the top of the nozzle body 10 is integrally formed or welded with a radially outward protruding annular flange 12. When the inert airflow flows upward along the nozzle body 10, it is guided by the annular flange 12, causing the airflow to flow radially outward along the flange 12, forming a second annular airflow protection layer, thereby improving the interception effect of upward splashing molten metal particles. To adapt to the airflow dynamics during the cutting process, the nozzle body 10 has an inverted frustum-shaped structure with its outer diameter gradually decreasing from top to bottom. This structure not only reduces the weight of the nozzle tip and lowers the load inertia of the cutting torch, but more importantly, it makes the outer wall of the nozzle body 10 form a "clearance zone" in the cutting area, reducing the contact area with the splashed slag. At the same time, it is beneficial for the reverse airflow to form a funnel-shaped coverage area when it diffuses. The inner wall of the deflector 21 is parallel to the outer wall of the nozzle 10. Since the nozzle 10 is frustoconical, the deflector 21 is also conical. This parallel arrangement ensures that the cross-sectional area of ​​the reverse flow channel 212 remains consistent along the airflow direction (from bottom to top). According to the fluid continuity equation, under constant flow rate, a constant cross-sectional area can maintain the stability of the airflow velocity and avoid eddies, throttling, or pressure loss caused by abrupt changes in the flow channel cross-section, thereby ensuring the uniformity of the protective gas shield and the stability of the thrust balance. The flow guide shroud 21 has multiple annularly distributed airflow holes 211, the axis of which is at a certain angle to the nozzle body 10. The airflow forms an annular airflow protection layer through the airflow holes 211, which is used to suppress the upward splashing of molten metal particles during plasma cutting operations and to prevent the reverse airflow guided by the flow guide shroud 21 from sucking in molten metal particles.

[0024] Reference Figure 4 , Figure 5 As shown, the top of the nozzle body 10 is coaxially integrally formed with a first threaded pipe connector 11, which is used for threaded connection with the output end of the cutting torch. The top of the nozzle 20 is coaxially integrally formed with a second threaded pipe connector 22, which is threadedly engaged with the bottom of the central tube 30. By rotating the nozzle 20, the relative axial displacement and disassembly / removal of the nozzle 20 and the central tube 30 can be achieved by utilizing the thread transmission principle. The top of the second threaded pipe joint 22 has a sealing tube 221 extending coaxially and integrally. The outer diameter of the sealing tube 221 is in clearance fit with the inner diameter of the central tube 30 to guide the sealing tube 221 to be smoothly inserted. On the outer peripheral wall of the sealing tube 221, at least two spaced sealing grooves are recessed circumferentially along the axial direction. Each sealing groove is fitted with a high-temperature resistant sealing ring (such as one made of fluororubber or graphite composite material). When tightened, the sealing tube 221 is inserted into the inner hole of the central tube 30. The high-temperature resistant sealing ring embedded in the sealing groove undergoes elastic deformation, and its outer ring tightly and elastically abuts against the inner wall of the central tube 30. In this way, a reliable dynamic sealing barrier is formed inside the central tube 30, which effectively blocks the fluid crosstalk between the inner cavity 32 and the outer cavity 31 and ensures the sealing of the reverse flow channel 212. Specifically, this sealing structure ensures that the high-temperature and high-pressure plasma working gas in the inner cavity 32 will not leak to the outer cavity 31 through the bottom, thus avoiding interference with the ionization process of the plasma arc.

[0025] Reference Figure 4 , Figure 6 As shown, the top of the flow guide 21 is detachably connected to an annular plate 23. The annular plate 23 includes two arc-shaped plates with multiple through holes. The top of the flow guide 21 has multiple threaded holes corresponding to the through holes. The annular plate 23 and the top of the flow guide 21 are detachably connected by bolts. Reference Figure 6 As shown, the inner diameter of the ring plate 23 is smaller than the inner diameter of the guide shroud 21. The inner diameter of the ring plate 23 and the outer wall of the nozzle body 10 have an annular gap. By fixing the ring plate 23 to the guide shroud 21, the ring plate 23 forms an airflow blocking part for the protruding part inside the guide shroud 21. Through this protruding blocking, the airflow rate out of the airflow hole 211 can be increased, so as to avoid the problem of weak annular airflow protective layer caused by insufficient airflow in the airflow hole 211. In order to ensure the air volume of the air outlet 211 and avoid the problem of the ring plate 23 affecting the flow of inert air (causing eddies), a slope is opened at the lower edge of the inner ring of the ring plate 23. This slope is used to guide the airflow to flow upward along the nozzle body 10.

[0026] Reference Figure 3 , Figure 4As shown, the nozzle body 10 has a countersunk hole 13 radially, and the central tube 30 has a through hole corresponding to the countersunk hole 13 radially. The countersunk hole 13 is internally threaded with a countersunk bolt 14 passing through the through hole. The countersunk bolt 14 is radially adjusted along the second threaded pipe joint 22. After the nozzle 20 is adjusted, the fixing reliability between the nozzle 20 and the central tube 30 is improved by the squeezing and / or frictional force of the countersunk bolt 14.

[0027] Reference Figure 4 , Figure 5 As shown, multiple annularly distributed connecting plates 33 are fixed to the outer wall of the central tube 30. The outer wall of the connecting plate 33 is welded and fixedly connected to the inner wall of the nozzle 10. The material of the connecting plate 33 is the same as that of the central tube 30 and the nozzle 20.

[0028] Reference Figure 7 As shown, the axis of the airflow hole 211 is inclined from the inside out in a direction away from the cutting nozzle axis. The axes of multiple airflow holes 211 are coplanar. The airflow is guided through the airflow hole 211 to form a horizontal vortex airflow layer. When the vortex is applied, a centripetal force is generated, which avoids the problem of molten metal particles splashing outward when they collide with the airflow layer.

[0029] Example 2: Refer to 8. Figure 9 As shown, based on Embodiment 1, in this embodiment, preferably, the axis of the airflow hole 211 is inclined from the inside out in a direction away from the cutting nozzle axis, and the axis of the multiple airflow holes 211 is inclined outward, that is, the axis of the airflow hole 211 is spirally inclined along the axis of the nozzle 20. When its axis is inclined outward toward the cutting nozzle axis, the inert airflow ejected from the multiple airflow holes 211 forms a trumpet-shaped pressing layer that is wider at the bottom and narrower at the top, so that the molten metal particles are suppressed within the trumpet-shaped pressing layer. When the axis of the airflow hole 211 is tilted inward and parallel to the tangent of the outer wall of the nozzle 20, the airflow ejected from the multiple airflow holes 211 forms an annular vortex airflow protective layer (vortex air curtain) to protect the nozzle 20, prevent molten metal particles from splashing and adhering to the nozzle 20, and improve the service life of the nozzle 20.

[0030] Reference Figure 5 As shown, the flange 12 and the mouthpiece 10 are joined by a chamfer. The flange 12 and the mouthpiece 10 are tangent to the chamfer, meaning that the outer periphery of the flange 12, the outer wall of the mouthpiece 10, and the chamfer satisfy a tangent transition geometric relationship. This tangent structure eliminates the problem of abrupt changes in cross-section (i.e., sharp angles) that exist in traditional right-angle connections or simple chamfer connections. When the rising airflow in the reverse flow channel 212 flows over the top of the mouthpiece 10 and overflows to form an airflow protective layer, the tangent chamfer constitutes a smooth guide surface for the airflow.

[0031] A method of using a plasma cutting device for metal pipes includes the following steps: S1. Connect the first threaded pipe connector 11 to the cutting torch threadedly, and insert the inner nozzle with the center electrode into the inner cavity 32. Leave a gap between the outer wall of the nozzle and the inner wall of the inner cavity 32 for inert gas flow. The nozzle body 10 is in communication with the inert gas of the cutting torch. S2. Screw the second threaded pipe connector 22 into the central pipe 30, and adjust the distance between the bottom of the nozzle 10 and the top of the nozzle 20 by rotating the nozzle 20. At the same time, adjust the distance between the inner wall of the guide shroud 21 and the outer wall of the nozzle 10 to adjust the size of the reverse flow channel 212 and adjust the airflow in the reverse flow channel 212. S3. Turn on the plasma cutter and cutting torch. The equipment is running. Inert gas enters through the first threaded pipe joint 11 and is split through the central pipe 30. Part of the inert gas is ejected through the working airflow injected by the nozzle 20 and flows downward. The other part of the inert gas enters the outer cavity 31 and then flows upward from the bottom of the nozzle body 10 through the guide shroud 21. It forms a cooling airflow protective shroud on the outer periphery of the nozzle body 10 and at the same time forms a reverse thrust opposite to the working airflow injected by the nozzle 20. S4. Part of the inert gas flowing through the guide shroud 21 is ejected outward through the airflow hole 211, thereby forming an airflow protection layer, which not only prevents the reverse airflow on the side of the guide shroud 21 from sucking in the cutting slag, but also inhibits the cutting slag from splashing upward.

[0032] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A plasma cutting device for metal pipe fittings, comprising a cutting nozzle, characterized in that, The cutting nozzle includes a nozzle body (10) and a nozzle head (20). The nozzle body (10) extends through the axial direction and is detachably connected to the cutting gun. A central tube (30) is fixed inside the nozzle body (10), and the central tube (30) is detachably connected to the nozzle head (20). The inner hole of the central tube (30) and the internal channel of the mouthpiece (20) together form an inner cavity (32), and the outer wall of the central tube (30) and the inner wall of the mouthpiece (10) enclose each other to form an outer cavity (31). A flow guide (21) is fixed at one end of the nozzle (20) near the nozzle body (10). An annular reverse flow channel (212) is formed between the flow guide (21) and the nozzle body (10). The reverse flow channel (212) is connected to the outer cavity (31). The airflow direction in the reverse flow channel (212) is opposite to the working airflow direction ejected by the nozzle (20) to form a reverse thrust. The airflow in the reverse flow channel (212) flows upward along the inner wall of the mouthpiece (10) and forms an airflow protective cover for cooling on the outer periphery of the mouthpiece (10). The distance between the central tube (30) and the nozzle (20) is adjustable.

2. The plasma cutting device for metal pipe fittings according to claim 1, characterized in that, The top of the mouth body (10) is coaxially fixed with a radially outwardly protruding annular flange (12). The mouth body (10) as a whole has an inverted frustum-shaped structure, and its outer diameter gradually decreases from top to bottom. The inner wall of the flow guide (21) and the outer wall of the nozzle (10) are set parallel to each other, so that the cross-sectional area of ​​the reverse flow channel (212) along the airflow direction remains consistent, so as to maintain the stability of the airflow velocity. The air guide cover (21) has multiple annularly distributed airflow holes (211), and the airflow forms an annular airflow protection layer through the airflow holes (211).

3. The plasma cutting device for metal pipe fittings according to claim 2, characterized in that, The top of the nozzle (10) is coaxially integrally formed with a first threaded pipe connector (11) for threaded connection with the output end of the cutting torch. The top of the nozzle (20) is integrally formed with a second threaded pipe connector (22) on the same axis. The second threaded pipe connector (22) is threaded with the bottom of the center tube (30) to realize the detachment of the nozzle (20) and the center tube (30) and the adjustment of the spacing. The top of the second threaded pipe joint (22) is coaxially extended with a sealing tube (221). The outer diameter of the sealing tube (221) is in clearance fit with the inner diameter of the central tube (30). At least two sealing grooves are recessed around the outer peripheral wall of the sealing tube (221), and each sealing groove is fitted with a high-temperature resistant sealing ring. When tightened, the sealing tube (221) is inserted into the inner hole of the central tube (30) and the high-temperature resistant sealing ring elastically abuts against the inner wall of the central tube (30) to block the fluid crosstalk between the inner cavity (32) and the outer cavity (31) and ensure the sealing of the reverse flow channel (212).

4. The plasma cutting device for metal pipe fittings according to claim 3, characterized in that, The top of the flow guide (21) is detachably connected to a ring plate (23). The ring plate (23) includes two arc-shaped plates. The inner diameter of the ring plate (23) is smaller than the inner diameter of the flow guide (21). The inner diameter of the ring plate (23) and the outer wall of the nozzle (10) have an annular gap. The inner lower edge of the ring plate (23) has a slope.

5. The plasma cutting device for metal pipe fittings according to claim 1, characterized in that, The mouthpiece (10) has a countersunk hole (13) in the radial direction, and the central tube (30) has a through hole in the radial direction corresponding to the countersunk hole (13). The countersunk hole (13) is internally threaded with a countersunk bolt (14) that passes through the through hole.

6. The plasma cutting device for metal pipe fittings according to claim 1, characterized in that, The outer wall of the central tube (30) is fixed with a plurality of annularly distributed connecting plates (33), and the outer wall of the connecting plates (33) is fixedly connected to the inner wall of the mouth body (10).

7. The plasma cutting device for metal pipe fittings according to claim 2, characterized in that, The axis of the airflow hole (211) is inclined from the inside out in a direction away from the axis of the cutting nozzle, and the axes of the plurality of airflow holes (211) are coplanar.

8. The plasma cutting device for metal pipe fittings according to claim 2, characterized in that, The axis of the airflow hole (211) is inclined from the inside out in a direction away from the axis of the cutting nozzle, and the axes of the plurality of airflow holes (211) are inclined outward.

9. A plasma cutting device for metal pipe fittings according to claim 2, characterized in that, The flange (12) and mouth body (10) are connected by a chamfer, and the flange (12) and mouth body (10) are tangent to the chamfer.

10. A method of using a plasma cutting device for metal pipe fittings, characterized in that, The application of the plasma cutting apparatus for metal pipes as described in claim 4 includes the following steps: S1. Connect the first threaded pipe connector (11) to the cutting torch threadedly, and insert the inner nozzle with the center electrode into the inner cavity (32). Leave a gap between the outer wall of the nozzle and the inner wall of the inner cavity (32) for inert gas flow, and the nozzle body (10) is connected to the inert gas of the cutting torch. S2. Screw the second threaded pipe connector (22) into the central pipe (30), and adjust the distance between the bottom of the nozzle (10) and the top of the nozzle (20) by rotating the nozzle (20). At the same time, adjust the distance between the inner wall of the guide shroud (21) and the outer wall of the nozzle (10) to adjust the size of the reverse flow channel (212) and adjust the airflow in the reverse flow channel (212). S3. Turn on the plasma cutter and the cutting torch. The equipment is running. Inert gas enters through the first threaded pipe joint (11) and is divided through the central pipe (30). Part of the inert gas flows out through the working airflow injected by the nozzle (20) and flows downward. The other part of the inert gas enters the outer cavity (31) and then flows upward from the bottom of the nozzle body (10) through the guide shroud (21). It forms a cooling airflow protection shroud on the outer periphery of the nozzle body (10) and at the same time forms a reverse thrust opposite to the working airflow injected by the nozzle (20). S4. Part of the inert gas flowing through the guide shroud (21) is ejected outward through the airflow hole (211), thereby forming an airflow protection layer, which prevents the reverse airflow on the side of the guide shroud (21) from sucking in the cutting slag, and also inhibits the cutting slag from splashing upward.

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