JP2008212969A - Plasma torch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a plasma torch to use a large current by increasing the cooling capacity of an indirect water cooling system nozzle tip. <P>SOLUTION: The plasma torch provided with a nozzle tip 14 having an electrode rod 11, double cylindrical nozzle rests 5, 6 arranged with the electrode rod in a central position, and a nozzle 15 facing the pointed end of the electrode rod and a cooling medium flow passage for making a cooling medium flow in the front end side of the nozzle rest is provided with the nozzle tip 14 having a tapered male screw in an outer peripheral surface and tightened and coupled to the nozzle rest by the tapered male screw of the outer peripheral surface screwed into the female screw at the front end of the nozzle rest. There is a silver plating on the screw surface of at least either of the tapered male screw of the nozzle tip and the female screw at the front end of the nozzle rest. An inner tube 5 of the nozzle rest has a projected rim which bisects the circular cylindrical space for flowing of the cooling medium up to an annular space w2 of a nozzle tip coupling section of cooling medium flow passages 19-w1 to w4-20 to a lateral supply channel w1 and a drainage canal w3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a plasma torch, and more particularly to a mounting structure for a nozzle tip at the tip of a torch.

Japanese Utility Model Publication No. 57-176180 Japanese Patent Laid-Open No. 1-143776 Japanese Utility Model Publication No. 55-28032.

  A plasma torch in which a rod-shaped tungsten electrode is passed through a cylindrical nozzle base and a nozzle tip is attached to the lower end of the nozzle base generates plasma gas supplied to the space of the nozzle base through which the tungsten electrode passes at the tip of the tungsten electrode. Plasma ionized by arc is sprayed from the nozzle (nozzle port) of the nozzle tip, and the shield gas supplied to the space between the outer peripheral surface of the nozzle base and the shield cap is forward (processed) along the outer surface of the nozzle tip. The target material is injected. In order to cool and squeeze the plasma arc with the nozzle of the nozzle tip, cooling water is supplied to the flow path inside the nozzle stand to cool the nozzle stand and the nozzle tip.

  As described in Patent Document 1, the cooling method includes an indirect cooling method in which cooling water is allowed to flow only through the nozzle table, and as described in Patent Documents 2 and 3, the cooling water is passed through the nozzle table through the nozzle tip. There is a direct cooling system that flows. Furthermore, in order to increase the cooling capability of the nozzle tip, the plasma welding torch described in Patent Document 3 is provided with a partition wall that divides the nozzle tip into two parts on the left and right sides in the cooling water flow path of the nozzle tip so The structure that is folded back is adopted.

  The cooling effect of the nozzle tip is inferior to the indirect cooling method than the direct cooling method. Therefore, in plasma welding using an indirect cooling plasma torch, the maximum current that can be used is usually about 150 A, and use of a large current is impossible because the nozzle tip is damaged (nozzle melting). In addition, due to insufficient cooling of the nozzle tip, the thermal pinch effect of the arc is weak, the arc diameter is wider and the heat concentration is inferior than the direct water cooling method. On the other hand, in the direct cooling method, since there is a cooling water flow path between the nozzle base and the nozzle tip, when the nozzle tip is removed from the nozzle base, the internal cooling water flows out and the torch gets wet. Therefore, it is difficult to perform maintenance such as replacement, inspection and cleaning by removing the nozzle tip at the welding site.

  In an indirect water-cooled plasma torch, the heat of the nozzle tip is transferred to the nozzle base by heat transfer through the contact surface between the nozzle base and the nozzle tip and is absorbed by the cooling water, but the heat transfer capacity of the contact surface is low. . When the nozzle tip is screw-coupled to the nozzle base, the contact is better than in the case of contact, but conventionally, the contact is inadequate microscopically because it is screwed with a parallel screw. That is, when a parallel screw is tightened, a surface pressure is applied to one side of the screw thread on the screwing side, but the surface is in close contact with each other, but the opposite surface of the screw thread is not in contact, and therefore the heat transfer area is small. Even in a mode in which the nozzle tip is made into an umbrella shape and screwed so that the lower surface of the umbrella is pressed against the tip surface of the nozzle base (for example, Patent Document 1), microscopic unevenness (roughness) of the contact plane, dust, etc. are crushed. Since the surface pressure is not applied, the heat transfer effect of the contact plane portion is low. The same applies to the case of inclined surface contact where the tip of the nozzle base is a conical hole surface and the conical surface of the lower surface of the nozzle tip is fitted to the conical surface, and the contact may be incomplete due to the taper error of the conical surfaces of both members. High nature.

  An object of the present invention is to increase the cooling capacity of an indirect water-cooled nozzle tip to enable use of a large current.

(1) It has an electrode rod (11), a double cylindrical nozzle base (5, 6) with the electrode rod (11) arranged at the center, and a nozzle (15) facing the tip of the electrode rod (11). The cooling medium is passed through the nozzle tip (14) mounted at the tip of the double cylindrical nozzle base (5, 6) and the tip side inside the double cylindrical nozzle base (5, 6). In a plasma torch comprising a cooling medium flow path (19-w1 to w4-20),
A taper male screw is provided on the outer peripheral surface, and the taper male screw on the outer peripheral surface is screwed into the female screw at the tip of the double cylindrical nozzle base (5, 6) and tightened to the double cylindrical nozzle base (5, 6). A plasma torch comprising a combined nozzle tip (14).

  In addition, in order to make an understanding easy, the code | symbol of the corresponding element or the equivalent element of the Example which is shown in drawing and mentions later in parentheses is attached for reference by reference. The same applies to the following.

  In the taper screw, the entire screw thread (both slopes) is subjected to surface pressure, and the microscopic irregularities are crushed and contacted. There is little variation or deterioration in the heat transfer capacity of the contact surface between the nozzle tip and the nozzle base. Heat transfer from the nozzle tip to the nozzle base is improved. This enables welding with a large current.

  (2) The plasma according to (1) above, wherein the surface of at least one of the taper male screw of the nozzle tip (14) and the female screw at the tip of the double cylindrical nozzle base (5, 6) has silver plating. torch.

  Silver has a high thermal conductivity and is soft and fills fine irregularities to increase the adhesion, so by applying silver plating to the contact part between the nozzle tip and the nozzle base, the adhesion of the contact screw part increases, Conduction is improved. In the screwing of copper, one side is easy to bite the other, and the surface is damaged or it is difficult to come off. Silver adheres tightly and does not damage the copper part and improves the sliding property, so that heat conduction is improved and it is easy to remove.

  (3) The inner cylinder (5) of the double cylindrical nozzle base (5, 6) is a ring shape of the nozzle tip (14) coupling portion of the cooling medium flow path (19-w1 to w4-20). The above-mentioned (1) or (2) has a protruding portion in the radial direction that divides the cylindrical cooling medium flow space up to the space (w2) into a right and left water supply channel (w1) and a drainage channel (w3). The plasma torch described in). The cooling water that has entered the water supply channel (w1) enters the ring-shaped space (w2) of the nozzle tip (14) coupling part, enters the drainage channel (w3) after making a half turn around the outside of the nozzle chip (14) coupling part. Head to the drain. Since the cooling water makes a half turn around the outside of the nozzle tip (14) connecting portion, the heat removal effect at the nozzle tip (14) mounting portion of the nozzle base (5, 6) is high. That is, the cooling effect of the nozzle tip (14) is high.

  Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

  FIG. 1 shows a longitudinal section of one embodiment of the present invention. A cathode base 2, an insulating bush 3 and an anode base 4 are inserted into the cylindrical inner space of the plasma torch base 1, and these are integrally fixed to the base 1. A nozzle table inner cylinder 5 and a nozzle table 6 are inserted into the anode table 4. A nozzle tip 14 is attached to the lower end (tip) of the nozzle base 6. A connecting cylinder 7 is fixed to the nozzle base 6, and a shield cap 8 with a female thread that accepts the male screw is screwed into the connecting cylinder 7, and the shield cap 8 is rotated in the screwing direction, whereby a shield cap is provided. The end face 8 is fastened to the end face of the base 1.

  There is an electrode holder 9 inside the nozzle base inner cylinder 5 and a conductive chuck 10 inside. A tungsten electrode 11 passes through the conductive chuck 10. The tip of the conductive chuck 10 where the split groove is cut is squeezed in a direction toward the center of the tungsten electrode 11 to sandwich the tungsten electrode 11. Thereby, the tungsten electrode 11 is fixed to the electrode holder 9 via the conductive chuck 10 and the fastening chuck 12. The tungsten electrode 11 passes through the centering stone 13 and faces the nozzle 15 of the nozzle tip 14.

  An electrode holder 9 and a conductive chuck 10 are inserted in the cathode base 2, and the tungsten electrode 11 is electrically connected to the pilot power source 21 and the main power source 22 via the conductive chuck 10, the torch cap 16 and the cathode base 2. Is done.

  Plasma gas is supplied from the plasma gas tube 17 on the arm of the substrate 1 to the inner space of the electrode holder 9, reaches the center hole space of the centering stone 13, and is ionized by an arc at the tip of the tungsten electrode 11 to become plasma. , Ejected from the nozzle 15. The shield gas fed between the nozzle base 6 and the substrate 1 from the shield gas pipe 18 on the arm of the substrate 1 passes through the vent hole of the connecting cylinder 7 and reaches the inner space of the shield cap 8. Erupts forward from the torch.

  The anode pipe 19, which is a conductive water supply pipe, is connected to the anode base 4 through the arm of the base 1, that is, is electrically connected, and the cooling water (solid arrow) supplied to the anode pipe 19 is the anode base. 4 and through the water supply path w1 between the nozzle base 6 and the nozzle base inner cylinder 5, through the ring-shaped space w2 that goes around the nozzle tip mounting portion, and further through the drainage path w3, the insulating bush 3 It passes through the ring-shaped space w4 that is the inner space and exits to the cathode pipe 20 that is a conductive drainage pipe. The cathode pipe 20 is connected to the cathode table 2 through the arm of the base 1. That is, they are electrically connected.

  A cylindrical space is vertically divided into two semi-cylindrical spaces w1 and w3 by a protrusion (not shown) of the nozzle base inner cylinder 5 protruding in the radial direction x and extending in the axial direction z. The space is the water supply channel w1, and the other semi-cylindrical space is the drainage channel w3.

  The tip of the nozzle base 6 has a truncated conical shape, and further has a sleeve 6s with a flange 6f and has a double cylindrical shape. A taper female screw 6fs is provided at the base portion of the sleeve 6s, that is, at the tip of the nozzle base 6, and a taper male screw 14ms on the outer periphery of the nozzle tip 14 is screwed therein.

  In FIG. 2, the cross section (2A-2A line cross section on FIG. 1) of the flange 6f part of the nozzle stand 6 is shown. The flange 6f of the nozzle base 6 also has a shape protruding in the x direction so as to define a water supply inlet and a water discharge outlet continuous with the water supply path w1 and the water discharge path w3. The cross-sectional shape of the protrusion protruding in the radial direction x of the nozzle base inner cylinder 5 and extending in the axial direction z is also the same as the cross-sectional shape of the flange 6f shown in FIG. Since the space below the flange 6f, that is, the space on the nozzle 15 side is a ring-shaped space w2, the cooling water in the water supply channel w1 is split into two when it enters the space w2, and the outside of the taper male screw 14ms of the nozzle tip 14 is respectively separated. It flows through the ring-shaped space w2 so as to make a half turn and enters the drainage channel w3. Therefore, the cooling effect on the tip of the nozzle base 6, that is, the outer portion of the taper male screw 14ms of the nozzle tip 14 is high.

  FIG. 3A shows a longitudinal section of the contact thread portion between the taper female thread and the taper male thread. When the taper screw is screwed in, the entire screw thread (both sloped surfaces of the screw thread and the upper surface R portion and the lower surface R portion of the screw thread) are subjected to surface pressure, and are in good contact (the ruggedness on the micron scale is also crushed and contacted). Therefore, the adhesiveness of the contact screw part between the taper female screw 6fs of the nozzle base 6 and the taper male screw 14ms of the nozzle tip 14 is high, and the thermal conductivity is high. As shown in FIG. 3 (b), the contact thread portion using a conventional parallel screw, when tightened, is subjected to surface pressure only on one side of the thread on the screwing side, but is in close contact with the screw thread. Since the surface of this is not in contact, the heat transfer area is halved and the thermal conductivity is low. In addition, the contact area is small because there is not enough surface pressure strength to crush the unevenness on the micron level by the processing tool.

  In the present embodiment shown in FIG. 1, silver plating is applied to the outer peripheral surface portion of the nozzle tip 14, that is, the tapered male screw 14 ms, in order to further increase the thermal conductivity. Since this silver plating has high thermal conductivity and is soft and fills fine irregularities to increase the adhesion, the adhesion of the contact thread portion between the taper female screw 6fs of the nozzle base 6 and the taper male screw 14ms of the nozzle tip 14 is improved. And heat conduction is improved. In the screwing of copper, one side is easy to bite the other, and the surface is damaged or it is difficult to come off. Silver adheres tightly, and does not damage the copper part and increases the slipperiness, so that the heat conduction is improved and can be easily removed.

  Next, the experimental results of thermal conductivity will be described. The sample of the present invention (one example) is the plasma torch shown in FIG. 1, but neither the nozzle base 6 nor the nozzle tip 14 is plated, and the dimensions around the nozzle tip (unit is mm). Is shown in FIG. The taper screw is JIS standard R (PT) 1/4.

  Reference Example 1 shown in FIG. 4B in which an umbrella-shaped nozzle tip 14p1 having a horizontal contact surface is coupled to the nozzle base 6p1 with a parallel screw and a nozzle tip 14p2 having a conical contact surface shown in FIG. Reference Example 2 coupled to the nozzle base 6p2 with a parallel screw was used as a comparative example. The parallel screws of Reference Examples 1 and 2 are JIS standard M10xP1. Note that the tightening torque of the nozzle tip with respect to the nozzle base is the same in both the sample (a) of the present invention shown in FIG. 4 and Reference Example 1 (b) and Reference Example 2 (c). It is.

  FIG. 5 shows the screw dimensions (unit: JIS standard R (PT) 1/4) of the taper female screw 6fs of the nozzle base 6 and the taper male screw 14ms of the nozzle tip 14 of the sample of the present invention shown in FIG. Indicates mm).

FIG. 6 shows the results of thermal conductivity experiments. Reference Example 4 shown in FIG. 6D is of the direct cooling method described in Patent Document 2. The temperature difference Δt in FIG. 6 is the difference (° C.) between the drainage (return water) temperature and the supply water (incoming water) temperature in a cooling water circulation device (not shown) for supplying and discharging cooling water to and from the plasma torch. The amount of heat is the amount of heat absorbed from the plasma torch, and most of it is the amount of heat absorbed from the nozzle tip. The amount of heat is
Amount of heat (kcal / h) = temperature difference Δt (° C.) × flow rate (liter / min) × 60
It was calculated by.

  FIG. 7 is a graph showing the relationship between the welding current and the amount of heat (cooling amount) in the experimental results shown in FIG. In FIG. 7, reference examples 1 and 2 are shown with the heat amount reduced after 200A because the tip holes of the nozzle tips 14p1 and 14p2 are melted and become unusable up to a welding current of about 200A. It is the result of canceling. The sample of the present invention (one example: FIG. 4 (a)) shows a cooling characteristic close to the cooling characteristic of Reference Example 3 of the direct water cooling system, although it is an indirect water cooling system, and has a high current. It can be seen that welding is possible.

  FIG. 8 shows the evaluation when an arc is generated under the same experimental conditions shown in FIG. 8 for the three types of nozzle tip mounting structures shown in FIGS. 4 (a), 4 (b) and 4 (c). In the case of the plasma torch of the present invention (Example (a)), the nozzle 15 of the nozzle tip 14 was not deformed by melting damage up to about 300A. Accordingly, the welding current can be increased to about 300 A, which is higher than about 150 A, which is generally used in the conventional indirect water cooling method. In Reference Examples 1 and 2, the nozzle tip nozzle was not deformed due to melt damage up to about 150A, but at about 200A, the nozzle was deformed due to melt damage, so it must be used at about 150A or less. .

  In the embodiment shown in FIG. 1, the taper male thread portion 14ms of the nozzle tip 14 is silver-plated, but the female screw hole of the nozzle base 6 may be silver-plated, and the taper male thread portion of the nozzle tip 14 and the nozzle base Both of the female screw holes 6 may be plated with silver. Practically, it is practical and economical to apply silver plating to the tapered male thread portion 14ms of the nozzle tip 14 as in the embodiment shown in FIG. However, when silver plating is applied to the female screw hole of the nozzle base 6 instead of the nozzle tip 14, the silver plating is worn and the heat transfer contribution is reduced during repeated replacement of the nozzle tip. As an example, silver plating may be applied to the taper male thread portion 14 ms of the nozzle tip 14.

  According to the present invention, the taper female screw 6fs of the nozzle base 6 and the taper male screw 14ms of the nozzle tip 14 are provided with a taper angle of 0.5 ° to 45 °, a thread length L = 4 to 45 mm, and a screw pitch P = 0. By setting it within the range of 4 to 4 mm, the cooling capacity can be increased as compared with the case where parallel screws are employed. In addition, the taper screw is not limited to the triangular mountain shape, but the trapezoidal shape is not limited to the triangular mountain shape because the cooling capability is higher than when the parallel screw is used. When silver plating is applied to the male screw of the nozzle tip 14 and / or the female screw hole of the nozzle base, even if the screw thread is trapezoidal, the silver plating fills the gap between the screw coupling portions, so that the cooling capability is high.

  Further, the internal thread of the nozzle base 6 that receives the taper male thread of the nozzle tip 14 is not limited to the taper thread, and even if it is a parallel thread, both have higher cooling capacity than the parallel thread. In addition to a taper female, a parallel female screw can be employed. When silver plating is applied to the male screw of the nozzle tip 14 and / or the female screw hole of the nozzle base, even if the female screw hole is a parallel screw, the silver plating fills the gap in the screw coupling portion, so that the cooling capability is high.

It is a longitudinal cross-sectional view of one Example of this invention. It is a cross-sectional view in the 2A-2A line of FIG. (A) is an enlarged longitudinal cross-sectional view which expands and shows the taper screw coupling | bond part of the nozzle stand 6 and the nozzle tip 14 shown in FIG. (B) It is an expanded longitudinal cross-sectional view which expands and shows the screw coupling | bond part of the conventional parallel screw. (A) It is an expanded longitudinal cross-sectional view which shows the dimension of the coupling | bond part of the nozzle stand 6 and the nozzle tip 14 of the experimental sample of this invention. (B) And (c) is an expanded longitudinal cross-sectional view which shows the dimension of the coupling | bond part of the nozzle stand 6p1, 6p2 of the comparative example, and nozzle tip 14p1, 14p2. FIG. 2 is an enlarged longitudinal sectional view showing dimensions of taper screws of a nozzle base 6 and a nozzle tip 14 shown in FIG. 1. FIG. 5 is a chart showing a heat removal calorific value experimental result of each nozzle base / nozzle tip coupling structure and direct water cooling type nozzle tip cooling structure shown in FIG. 4. FIG. It is the graph which graphed the experimental result shown in FIG. FIG. 5 is a chart showing an evaluation of the results of a durable arc current experiment for each nozzle base / nozzle tip coupling structure shown in FIG. 4. FIG.

Explanation of symbols

1: Base body 2: Cathode base 3: Insulating bush 4: Anode base 5: Nozzle base inner cylinder 6: Nozzle base 6s: Sleeve 6f: Flange 6fs: Tapered female screw 7: Connecting cylinder 8: Shield cap 9: Electrode holder 10: Conductive Chuck 11: Tungsten electrode 13: Centering stone 14: Nozzle tip 14ms: Taper male screw 15: Nozzle 16: Torch cap 17: Plasma gas pipe 18: Shield gas pipe 19: Anode pipe (water supply pipe)
20: Cathode pipe (drain pipe)
21: Pilot power source 22: Main power source 23: Welding material w1: Water supply channel w2: Ring-shaped space w3: Drainage channel w4: Ring-shaped space

Claims (3)

An electrode rod, a double cylindrical nozzle base having the electrode bar disposed at a central position, a nozzle tip attached to the tip of the double cylindrical nozzle base, having a nozzle facing the tip of the electrode bar; and In a plasma torch comprising a cooling medium flow channel for allowing a cooling medium to flow inside the tip side of the double cylindrical nozzle base,
A nozzle tip having a taper male screw on the outer peripheral surface, and the taper male screw on the outer peripheral surface is screwed into the female screw at the tip of the double cylindrical nozzle base and is fastened to the double cylindrical nozzle base. A characteristic plasma torch.   2. The plasma torch according to claim 1, wherein at least one screw surface of the taper male screw of the nozzle tip and the female screw at the tip of the double cylindrical nozzle base has silver plating.   Cylindrical cooling medium flow space from the inner cylinder of the double cylindrical nozzle base to the ring-shaped space of the nozzle chip coupling portion of the cooling medium flow path is used as a left and right water supply channel and drainage channel. The plasma torch according to claim 1, wherein the plasma torch has a radially protruding portion that is divided into two.

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