Method of cutting metal pipe without chips

Abstract

The application relates to a kind of uninterrupted chipless cutting metal pipe methods, adopt plasma arc cutting machine to cut aluminum alloy pipe, non-ferrous metal pipe, plasma arc cutting machine includes plasma torch, gas source, gas supplied by gas source is converted into plasma gas by plasma torch and is sprayed to form plasma gas flow, plasma gas flow carries out arc operation, perforation operation, cutting operation to aluminum alloy pipe or non-ferrous metal pipe.The uninterrupted chipless cutting metal pipe method can cut aluminum alloy pipe, non-ferrous metal pipe at high speed, cutting speed can reach 3-5 m / min, cutting efficiency is high, cutting effect is good, can continuously uninterrupted cutting operation 8h, cutting quality is high, and the cutting surface is not prone to produce corrugation, cross section slag and other defects.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of uninterrupted kerfless cutting metal pipe method, belong to metal pipe cutting processing technical field. BACKGROUND

[0002] In cutting metal pipe, the currently common high-speed cutting machining system is mainly composed of high-speed machining center that can meet high-speed cutting, high-performance tool clamping system, high-speed cutting tool, safe and reliable high-speed cutting cam software system and the like.

[0003] No matter how the current machining tool improves, it cannot avoid the problem of chip removal, and more or less affects the quality of the cutting surface. For high-precision machining of metal pipes, especially aluminum alloy pipes, it will seriously limit the improvement of product qualification rate.

[0004] Kerfless cutting is an advanced cutting technology that does not produce kerf or debris, unlike traditional cutting methods. This cutting technology is widely used in material processing fields such as metal cutting, glass cutting, semiconductor chip cutting, etc. Traditional cutting methods, such as mechanical cutting, generally require the use of a cutting method to achieve cutting, which produces cutting debris or cutting marks, causing damage to the surface of the material. In addition, traditional cutting methods have high requirements for the size accuracy and shape complexity of materials, which also limits their application in some special fields.

[0005] The principles and implementation methods of kerfless cutting are as follows:

[0006] 1. Laser decomposition cutting

[0007] Laser decomposition cutting irradiates the inside of the material with a high-energy laser beam, causing the local area to reach a high temperature and high pressure state, thereby triggering a decomposition reaction inside the material. This cutting method does not require direct contact with the surface of the workpiece, can achieve precise cutting, and will not produce residual cutting marks.

[0008] 2. Plasma cutting

[0009] Plasma cutting is a cutting method that converts gas or liquid into a plasma state and uses a high-energy plasma beam to cut the workpiece. Plasma cutting can cut materials at high temperatures and high pressures, and has good cutting effect on materials with small cutting marks.

[0010] 3. Induction heating cutting

[0011] Induction heating cutting generates a high-temperature area inside the workpiece through electromagnetic induction to achieve cutting. This cutting technology is commonly used in the field of metal cutting and can achieve efficient and precise cutting without contacting the surface of the workpiece.

[0012] In the field of non-waste cutting, plasma arc cutting is to pass mixed gas through high-frequency arc, and the gas can be air, or a mixed gas of hydrogen, argon and nitrogen. The high-frequency arc makes some gas "decompose" or ionize into basic atomic particles, thereby generating "plasma gas", which is blown out from the nozzle of the torch under the action of high-pressure gas. The heat cutting formed by adopting plasma arc cutting has similar working principle to plasma arc welding, and high-purity nitrogen is generally used as plasma gas in plasma arc cutting, but argon or mixed gas of argon and nitrogen, argon and hydrogen, etc. can also be used. Plasma arc cutting uses large current, and the outer sleeve of the torch has a ring-shaped water nozzle, and the sprayed water cover can reduce the smoke and noise generated during cutting, and improve the quality of the cut to a certain extent. However, once the plasma arc cutting is in uninterrupted high-speed cutting, for example, cutting an aluminum flat tube with a wall thickness of 1mm, the speed is usually limited to 1~1.7m / min, and it also needs to be paused every 10min of continuous cutting, otherwise the quality of the cut will be significantly reduced, for example, the cut surface will produce ripples, and the cross section will hang slag.

[0013] Based on this, the present application is proposed. SUMMARY

[0014] The present application provides a method for uninterrupted non-waste cutting of metal pipes to overcome the shortcomings of the prior art, and the specific technical solutions are as follows:

[0015] A method for uninterrupted non-waste cutting of metal pipes, comprising the following steps:

[0016] An aluminum alloy pipe or non-ferrous metal pipe is cut by using a plasma arc cutting machine, the plasma arc cutting machine comprises a plasma torch and a gas source for supplying gas to the plasma torch, the gas supplied by the gas source is converted into plasma gas by the plasma torch and sprayed to form a plasma gas flow, and the plasma gas flow performs arc maintaining operation, piercing operation and cutting operation on the aluminum alloy pipe or non-ferrous metal pipe;

[0017] During the cutting operation, the plasma torch is aimed at the edge of the aluminum alloy pipe or non-ferrous metal pipe, the distance between the plasma torch and the aluminum alloy pipe or non-ferrous metal pipe is adjusted to reach the designed cutting distance, and the aluminum alloy pipe or non-ferrous metal pipe cannot be cut open during edge cutting, and the actual current value connected by the plasma torch is 90~95% of the rated current value;

[0018] When the piercing operation is performed, the distance between the plasma torch and the aluminum alloy pipe or non-ferrous metal pipe is the piercing distance, and the ratio of the piercing distance to the designed cutting distance is 2.

[0019] Further improvement, the outer sleeve of the plasma torch is provided with a ring plate, the ring plate is fixedly connected with the plasma torch, a conical sleeve-shaped water nozzle is arranged below the ring plate, and the water nozzle is sleeved on the outer part of the plasma torch; the inner part of the water nozzle is provided with a water spraying cavity, the edge part of the ring plate is provided with a first annular groove, and the first annular groove is communicated with the water spraying cavity; the upper part of the ring plate is provided with two symmetrically-distributed water inlet pipes which are communicated with the first annular groove.

[0020] Further improvement, when the plasma torch is working, the water nozzle sprays a conical shell-shaped water cover to surround the plasma gas stream sprayed by the plasma torch; the ring plate is further provided with an air extraction mechanism for extracting smoke and waste gas in the water cover, the ring plate is sequentially provided with a screw hole, a second annular groove, a third annular groove and a fourth annular groove from top to bottom in a concentric manner, the screw hole, the second annular groove and the third annular groove are communicated, the screw hole is located at the upper end of the ring plate, the fourth annular groove is located at the lower end of the ring plate, the fourth annular groove is provided with a plurality of equidistantly-distributed circular first through holes between the groove bottom of the fourth annular groove and the groove bottom of the third annular groove; the air extraction mechanism comprises a permanent magnet ball arranged in the third annular groove, a plurality of electromagnets arranged in the second annular groove in an equidistant manner, a vertical plane where the third annular groove is located is a reference plane, the electromagnets are arranged in an inclined manner, and the included angle between the length direction of the electromagnets and the reference plane is γ, 20°≤γ≤30°; the screw hole is provided with a cover plate, the cover plate is threadedly connected with the screw hole, the cover plate is provided with two symmetrically-distributed second through holes, the upper part of the cover plate is provided with an air extraction pipe communicated with the second through holes, and the air extraction pipe is provided with an air pump.

[0021] Further improvement, the ring plate and the cover plate are made of aluminum alloy, and the gas source is one or more of nitrogen, argon, hydrogen, air, carbon dioxide, water vapor and gaseous alkane.

[0022] Further improvement, the permanent magnet ball and the third annular groove are gap-fitted, the minimum value of the distance between the upper end of the permanent magnet ball and the lower end of the electromagnet is x, 1.3cm≤x≤2.2cm, and the ratio of the diameter of the permanent magnet ball to the diameter of the first through hole is y, 2.5≤y≤3.6.

[0023] Further improvement, γ=27°, x=1.8cm, and y=2.9.

[0024] Further improvement, the second annular groove has an isosceles trapezoidal structure in cross section, the width of the lower end of the second annular groove is smaller than that of the upper end of the second annular groove, the edge of the electromagnet is matched with the lower end of the second annular groove, the electromagnet has at least six electromagnets, a connecting rod is connected between two adjacent electromagnets, and the electromagnet is glued to the inner wall of the second annular groove.

[0025] Further improvement, the plasma torch in the operation, the water nozzle spray cone shell-shaped water cover, air pump start, the water cover in the air extraction mechanism for air operation, each electromagnet in turn electrify generates repulsion with the permanent magnet ball magnetic force and push the permanent magnet ball along the third annular groove in clockwise or counterclockwise rotation; The permanent magnet ball rotates in the third annular groove, only one electromagnet is electrified.

[0026] Further improvement, the rotating speed of the permanent magnet ball in the third annular groove is 22r / min, and the vacuum degree of the air extraction end of the air pump is 5500±100Pa.

[0027] Further improvement, when using the plasma torch to cut the aluminum alloy pipe or non-ferrous metal pipe according to the designed trajectory, liquid nitrogen is sprayed on the aluminum alloy pipe or non-ferrous metal pipe along the designed trajectory; In the same area, the interval time between the end of liquid nitrogen spraying and the cutting by the plasma torch is t j , 2s≤t j ≤5s.

[0028] The beneficial effects of the present application are:

[0029] The uninterrupted chipless cutting method of metal pipe can cut aluminum alloy pipe and non-ferrous metal pipe at high speed, and the cutting speed can reach 3-5m / min, the cutting efficiency is high, the cutting effect is good, the continuous uninterrupted cutting operation can be carried out for 8h, the cutting quality is high, and the cutting surface is not easy to produce corrugation, broken section and other defects. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a structure diagram of the plasma torch, water nozzle and air extraction mechanism in the plasma arc cutting machine of the present application;

[0031] Figure 2 It is an internal schematic diagram of the plasma torch, water nozzle and air extraction mechanism in the plasma arc cutting machine of the present application;

[0032] Figure 3 It is a structure diagram of the air extraction mechanism of the present application;

[0033] Figure 4 It is a distribution diagram of the permanent magnet ball, electromagnet and first through hole of the present application;

[0034] Figure 5 It is a distribution diagram of the electromagnet in the second annular groove of the present application;

[0035] Figure 6 It is a relationship diagram between the rotating speed f of the permanent magnet ball in the third annular groove and the abnormal times e of the water cover surface. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0037] In the description of the present application, it should be noted that, unless otherwise specified, the meaning of "a plurality of" is two or more; the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail" and the like indicate the orientation or positional relationship shown in the drawings, which is only for the purpose of facilitating the description of the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0038] In the description of the present application, it should be noted that, unless otherwise specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. Embodiment 1

[0039] The uninterrupted chipless cutting method of metal pipe material, comprising the following steps:

[0040] The plasma arc cutting machine is used to cut aluminum alloy pipe material and non-ferrous metal pipe material, as shown in FIG. 1, the plasma arc cutting machine comprises a plasma torch 10, a gas source for supplying gas to the plasma torch 10, the gas supplied by the gas source is converted into plasma gas by the plasma torch 10 and sprayed to form a plasma gas flow, and the plasma gas flow performs arc maintaining operation, piercing operation and cutting operation on the aluminum alloy pipe material or non-ferrous metal pipe material. Figure 1 In the cutting operation, the plasma torch 10 is aimed at the edge of the aluminum alloy pipe material or non-ferrous metal pipe material, the distance between the plasma torch 10 and the aluminum alloy pipe material or non-ferrous metal pipe material is adjusted to reach the designed cutting distance, the aluminum alloy pipe material or non-ferrous metal pipe material cannot be cut open when cutting at the edge, the actual current value connected by the plasma torch 10 is 90-95% of the rated current value, to prevent overload and reduce service life.

[0041] ​

[0042] When in the piercing operation, the distance between the plasma torch 10 and the aluminum alloy pipe or non-ferrous pipe is a piercing distance, and the ratio of the piercing distance to the designed cutting distance is 2.

[0043] The arc maintaining device of the plasma arc cutting machine is a device for ensuring that the arc can be quickly reignited when the arc is extinguished due to some reason during cutting, and can also ensure that the energy consumption is reduced, the electrode is less burned, and the service life is prolonged during non-cutting work.

[0044] The gas source is one or more of nitrogen, argon, hydrogen, air, carbon dioxide, water vapor, and gaseous alkanes.

[0045] Taking the cutting of the aluminum alloy pipe by the plasma arc cutting machine as an example, the gas source is nitrogen. Example 2

[0046] As shown in Figure 1 , 2 The outer part of the plasma torch 10 is sleeved with a ring plate 20, the ring plate 20 is fixedly connected with the plasma torch 10, a conical sleeve-shaped water nozzle 30 is arranged below the ring plate 20, and the water nozzle 30 is sleeved on the outer part of the plasma torch 10; a water spraying cavity 31 is arranged in the inner part of the water nozzle 30, a first annular groove 32 is arranged on the edge of the ring plate 20, and the first annular groove 32 is in communication with the water spraying cavity 31; two water inlet pipes 33 symmetrically distributed are arranged on the upper part of the ring plate 20, and the water inlet pipes 33 are in communication with the first annular groove 32.

[0047] The water inlet pipe 33 is connected with a high-pressure water source, such as tap water with a water pressure of 0.6 MPa, and the water is finally sprayed out through the first annular groove 32 and the water spraying cavity 31 to form a conical shell-shaped water cover, which surrounds the plasma gas stream sprayed out by the plasma torch 10; the sprayed water cover can reduce the smoke and noise generated during cutting, and improve the cutting quality to a certain extent. However, during continuous cutting, the insoluble smoke in the water cover will continuously accumulate, which will eventually cause the cutting quality to decrease. Therefore, the insoluble smoke in the water cover needs to be timely removed. Example 3

[0048] During the operation of the plasma torch 10, the water nozzle 30 sprays a conical shell-shaped water cover to surround the plasma gas stream sprayed out by the plasma torch 10; as Figures 3-5As shown, the ring plate 20 is also provided with an air extraction mechanism 50 for extracting smoke and exhaust gas in the water cover, and the ring plate 20 is sequentially provided with a screw hole, a second annular groove 24, a third annular groove 23, and a fourth annular groove 21 from top to bottom, the screw hole, the second annular groove 24, and the third annular groove 23 are communicated, the screw hole is located at the upper end of the ring plate 20, the fourth annular groove 21 is located at the lower end of the ring plate 20, and the opening of the fourth annular groove 21 is downwardly arranged, a plurality of circular first through holes 22 are arranged between the groove bottom of the fourth annular groove 21 and the groove bottom of the third annular groove 23 at equal intervals; the air extraction mechanism 50 comprises a permanent magnet ball 51 arranged in the third annular groove 23, a plurality of electromagnets 52 are arranged in the second annular groove 24 at equal intervals, the vertical plane where the third annular groove 23 is located is a reference plane, the electromagnets 52 are arranged obliquely, and the included angle between the length direction of the electromagnets 52 and the reference plane is γ, 20°≤γ≤30°; the screw hole is provided with a cover plate 53, the cover plate 53 is threadedly connected with the screw hole, the cover plate 53 is provided with two second through holes 54 arranged symmetrically, an air extraction pipe 55 is arranged above the cover plate 53 and communicated with the second through holes 54, and an air pump is arranged outside the air extraction pipe 55.

[0049] Preferably, the ring plate 20 and the cover plate 53 are made of aluminum alloy to prevent magnetic interference. Embodiment 4

[0050] To ensure smooth rotation, the permanent magnet ball 51 and the third annular groove 23 are gap-fitted, the minimum value of the distance between the upper end of the permanent magnet ball 51 and the lower end of the electromagnet 52 is x, 1.3 cm≤x≤2.2 cm, and the ratio of the diameter of the permanent magnet ball 51 to the diameter of the first through hole 22 is y, 2.5≤y≤3.6. Most preferably, γ=27°, x=1.8 cm, and y=2.9. Embodiment 5

[0051] The second annular groove 24 has an isosceles trapezoidal structure in cross section, the width of the lower end of the second annular groove 24 is smaller than the width of the upper end of the second annular groove 24, the edge of the electromagnet 52 is matched with the lower end of the second annular groove 24, the electromagnet 52 has at least six electromagnets, a connecting rod 521 is connected between two adjacent electromagnets 52, and the electromagnet 52 is glued to the inner wall of the second annular groove 24.

[0052] All the electromagnets 52 and the connecting rods 521 constitute an electromagnetic disc, and the structure of the second annular groove 24 can facilitate the removal of the electromagnetic disc and subsequent cleaning, and can also provide buffering, so that the disturbed airflow in the third annular groove 23 is buffered by the second annular groove 24 and finally extracted by the air extraction pipe 55.

[0053] When the electromagnetic disk needs to be taken out, the adhesive layer near the electromagnet 52 is removed, and the electromagnetic disk can be taken out from the second annular groove 24. Example 6

[0054] When the plasma torch 10 is in operation, the water nozzle 30 sprays a conical water cover, the air pump is started, the air extraction mechanism 50 performs air extraction operation in the water cover, and each electromagnet 52 is sequentially powered to generate magnetic force repelling the permanent magnet ball 51 and pushing the permanent magnet ball 51 to rotate clockwise or counterclockwise in the third annular groove 23; during the rotation of the permanent magnet ball 51 in the third annular groove 23, only one electromagnet 52 is powered.

[0055] Among them, the rotating speed of the permanent magnet ball 51 in the third annular groove 23 is 22r / min, and the vacuum degree of the air extraction end of the air pump is 5500±100Pa.

[0056] For example, the first electromagnet 52 is powered to generate magnetic force repelling the permanent magnet ball 51 and pushing the permanent magnet ball 51 to advance clockwise in the third annular groove 23, and the electromagnet 52 is arranged in one-to-one correspondence with the first through hole 22; after the magnetic force generated by the first electromagnet 52 ends, the second electromagnet 52 is the electromagnet 52 adjacent to the first electromagnet 52 in the advancing direction of the permanent magnet ball 51, if the second electromagnet 52 does not generate magnetic force after the first electromagnet 52 is powered off, the speed of the permanent magnet ball 51 will decrease significantly when passing through the first through hole 22, therefore, the second electromagnet 52 is powered to generate magnetic force repelling the permanent magnet ball 51 and continue to push the permanent magnet ball 51 to advance clockwise in the third annular groove 23, thereby ensuring that the permanent magnet ball 51 can continuously rotate in the third annular groove 23.

[0057] Firstly, the air extraction mechanism 50 can extract the smoke and waste gas in the water cover, and the smoke and waste gas pass through the fourth annular groove 21, the first through hole 22, the third annular groove 23, the second annular groove 24, and the second through hole 54 in sequence, and finally are extracted by the air extraction pipe 55. During the air extraction process, if the vacuum degree of the air extraction end of the air pump is too large, the edge or cover structure of the water cover will be unstable, and occasionally water splashes will occur. During the process of water splashing, it is possible to cause some water splashes to interfere with the plasma gas flow, thereby affecting the plasma cutting efficiency and the quality of the cut. If the vacuum degree of the air extraction end of the air pump is too small, the air extraction effect will be limited.

[0058] Because the number of suction pipes 55 is limited, only two are provided; the closer to the first through hole 22 of the suction pipe 55, the greater the "suction force" generated, thereby existing a "suction force difference" between the suction force generated at the first through hole 22 far away from the suction pipe 55, the "suction force difference" reaches a certain degree, which destroys the balance of the water film on the surface of the water cover, and eventually causes the water splash to occur. In theory, the number of suction pipes 55 is the same as the number of first through holes 22 and is set one by one corresponding to the position, and finally converges, but the disadvantage of this method is that because the number of suction pipes 55 is too much, when the plasma torch 10 is walking during operation, some pipes are easily squeezed and bent, thereby causing "suction" to be not smooth, which may cause occasional water splash or a gap on the surface of the water cover.

[0059] In the present application, since the permanent magnet ball 51 rotates in the third annular groove 23, it is equivalent to "stirring" the airflow in the third annular groove 23, thereby making the airflow extracted from the fourth annular groove 21 uniformly distributed to a certain extent, and the force field in the water cover is stable, which is not easy to cause water splash on the surface of the water cover or a gap on the surface of the water cover.

[0060] If the rotating speed of the permanent magnet ball 51 in the third annular groove 23 is too slow, the "stirring" of the airflow in the third annular groove 23 is limited;

[0061] Through the suction mechanism 50 for suction operation in the water cover, the abnormal number of times of water splash on the surface of the water cover or the gap on the surface of the water cover is observed and counted for 8h of continuous operation, and e is the abnormal number of times of the surface of the water cover.

[0062] The rotating speed of the permanent magnet ball 51 in the third annular groove 23 is f, f changes in 0~38r / min, and the corresponding e value change is seen Figure 6 , and comprehensively considering, f is preferably 22r / min.

[0063] In addition, it should be noted that if γ is too large, a large part of the downward force will cause the permanent magnet ball 51 to generate a large impact on the surface of the first through hole 22 during rotation, thereby causing the plasma torch 10 to also vibrate at a low frequency, which seriously affects the quality of the cut. For example, γ=38°, the consequence is that the probability of waviness defects on the cut surface (calculated by counting the number of surface defects of 100 cutting pieces) will increase by 35%. If γ is too small, in order to ensure f=22r / min, the energy consumption of the electromagnet will increase by 5%.

[0064] In addition, if y is too large, the diameter of the first through hole 22 will be small with the volume of the permanent magnet ball 51 unchanged, which is not conducive to pumping. If y is too small, the permanent magnet ball 51 will also cause a large impact on the surface of the first through hole 22 during rotation, so that the plasma torch 10 will also vibrate at low frequency, which seriously affects the quality of the cut. Compared with y = 2.9, if y = 4, the probability of causing the cut surface to have a corrugated defect increases by 51%. Example 7

[0065] When the plasma torch 10 is used to cut an aluminum alloy pipe or a non-ferrous metal pipe according to a designed trajectory, a liquid nitrogen spray gun is used to spray liquid nitrogen on the aluminum alloy pipe or the non-ferrous metal pipe along the designed trajectory; in the same area, the interval time between the end of the liquid nitrogen spraying and the cutting by the plasma torch 10 is t j , 2s≤t j ≤5s.

[0066] If the liquid nitrogen freezing method of the present embodiment is not used, the probability of the metal pipe cutting method without interruption and without chips described in the present application having a slag defect on the cut surface is not more than 1% when the cutting speed is 2 m / min; when the cutting speed is 3 m / min, the probability of having a slag defect on the cut surface is 7%; when the cutting speed is 5 m / min, the probability of having a slag defect on the cut surface is 18%.

[0067] However, by using the method of the present embodiment, the pipe is first frozen by a liquid nitrogen spray gun, and then cut, and when the cutting speed is 5 m / min, the probability of having a slag defect on the cut surface is not more than 1%.

[0068] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for continuous, chip-free cutting of metal pipes, characterized in that, Includes the following steps: A plasma arc cutting machine is used to cut non-ferrous metal pipes. The plasma arc cutting machine includes a plasma spray gun (10) and a gas source for supplying gas to the plasma spray gun (10). The gas supplied by the gas source is converted into plasma gas through the plasma spray gun (10) and sprayed out to form a plasma gas flow. The plasma gas flow performs arc maintenance, piercing and cutting operations on the non-ferrous metal pipes. During the cutting operation, the plasma spray gun (10) is aligned with the edge of the non-ferrous metal pipe, and the distance between the plasma spray gun (10) and the non-ferrous metal pipe is adjusted to achieve the designed cutting distance. Starting from the edge of the non-ferrous metal pipe, the non-ferrous metal pipe should not be cut open during edge cutting. The actual current connected to the plasma spray gun (10) is 90-95% of the rated current value. During the perforation operation, the distance between the plasma spray gun (10) and the non-ferrous metal pipe is the perforation distance, and the ratio of the perforation distance to the design tangent is 2. The plasma spray gun (10) is fitted with an annular plate (20) on its outside. The annular plate (20) is fixedly connected to the plasma spray gun (10). A conical nozzle (30) is provided below the annular plate (20). The nozzle (30) is fitted on the outside of the plasma spray gun (10). A spray chamber (31) is provided inside the nozzle (30). A first annular groove (32) is provided on the edge of the annular plate (20). The first annular groove (32) is connected to the spray chamber (31). Two symmetrically distributed water inlet pipes (33) are provided on the upper part of the annular plate (20). The water inlet pipes (33) are connected to the first annular groove (32). When the plasma spray gun (10) is in operation, the spray nozzle (30) sprays out a conical water shield and surrounds the plasma gas flow sprayed by the plasma spray gun (10); the annular plate (20) is also provided with an air extraction mechanism (50) for removing the smoke and exhaust gas in the water shield. The annular plate (20) is provided with a screw hole, a second annular groove (24), a third annular groove (23), and a fourth annular groove (21) arranged concentrically from top to bottom. The screw hole, the second annular groove (24), and the third annular groove (23) are all connected. The screw hole is located at the upper end of the annular plate (20). The fourth annular groove (21) is located at the lower end of the annular plate (20) and the groove opening of the fourth annular groove (21) is set downward. Multiple grooves are arranged between the bottom of the fourth annular groove (21) and the bottom of the third annular groove (23). The first circular through holes (22) are evenly spaced; the air extraction mechanism (50) includes a permanent magnet ball (51) disposed inside the third annular groove (23), and a plurality of electromagnets (52) are evenly spaced inside the second annular groove (24). The vertical plane in which the radial direction of the third annular groove (23) is located is the reference plane. The electromagnets (52) are inclined and the angle between the length direction of the electromagnets (52) and the reference plane is γ, 20°≤γ≤30°; a cover plate (53) is provided at the screw hole, the cover plate (53) is threaded to the screw hole, and two second through holes (54) are provided at the cover plate (53) in a symmetrical arrangement. An air extraction pipe (55) connected to the second through holes (54) is provided above the cover plate (53), and an air pump is connected to the outside of the air extraction pipe (55).

2. The method for continuous, chip-free cutting of metal pipes according to claim 1, characterized in that: Both the ring plate (20) and the cover plate (53) are made of aluminum alloy, and the gas source is one or more of nitrogen, argon, hydrogen, air, carbon dioxide, water vapor, and gaseous alkanes.

3. The method for continuous, chip-free cutting of metal pipes according to claim 1, characterized in that: The permanent magnet ball (51) and the third annular groove (23) are in clearance fit. The minimum distance between the upper end of the permanent magnet ball (51) and the lower end of the electromagnet (52) is x, 1.3cm≤x≤2.2cm; the ratio of the diameter of the permanent magnet ball (51) to the diameter of the first through hole (22) is y, 2.5≤y≤3.

6.

4. The method for continuous, chip-free cutting of metal pipes according to claim 3, characterized in that: The values ​​are γ=27°, x=1.8cm, and y=2.

9.

5. The method for continuous, chip-free cutting of metal pipes according to claim 1, characterized in that: The cross-section of the second annular groove (24) is an isosceles trapezoidal structure. The width of the lower end of the second annular groove (24) is smaller than the width of the upper end of the second annular groove (24). The edge of the electromagnet (52) is adapted to the lower end of the second annular groove (24). There are at least 6 electromagnets (52). A connecting rod (521) connects two adjacent electromagnets (52). The electromagnets (52) are glued to the inner wall of the second annular groove (24).

6. The method for continuous, chip-free cutting of metal pipes according to claim 1, characterized in that: When the plasma spray gun (10) is in operation, the spray nozzle (30) sprays out a conical water cover, the air pump starts, and the air extraction mechanism (50) performs air extraction operation inside the water cover. Each electromagnet (52) is energized in sequence to generate a magnetic force that repels the permanent magnet ball (51) and pushes the permanent magnet ball (51) to rotate clockwise or counterclockwise along the third annular groove (23). During the rotation of the permanent magnet ball (51) in the third annular groove (23), only one electromagnet (52) is energized.

7. The method for continuous, chip-free cutting of metal pipes according to claim 6, characterized in that: The rotational speed of the permanent magnet ball (51) in the third annular groove (23) is 22 r / min, and the vacuum degree of the pump end is 5500±100 Pa.

8. The method for continuous, chip-free cutting of metal pipes according to claim 1, characterized in that: When cutting non-ferrous metal pipes according to the design trajectory using a plasma spray gun (10), a liquid nitrogen spray gun is used to spray liquid nitrogen onto the non-ferrous metal pipes along the design trajectory first; in the same area, the time interval between the end of liquid nitrogen spraying and the plasma spray gun (10) spraying out plasma gas for cutting is t. j 2s≤t j ≤5s.

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