JP2010120018A - Plasma welding torch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma welding torch capable of converging plasma arc without excessively increasing flow speed of plasma gas. <P>SOLUTION: The plasma welding torch includes: a bar-like non-consumptive electrode 1; a cylindrical plasma nozzle 2 which coaxially surrounds the non-consumptive electrode 1; and a cylindrical shield nozzle 3 which coaxially surrounds the plasma nozzle 2. The plasma welding torch A gushes plasma gas PG from a plasma gas passage 4 and gushes shield gas SG from a shield gas passage 5. A bypass passage 23 that introduces a part of the plasma gas PG from the plasma gas passage 4 to the shield gas passage 5 is arranged at the plasma nozzle 2. The plasma gas PG diverged from the bypass passage 23 further converges the plasma arc and avoids improper increase of the flow speed of the plasma gas PG. Accordingly, good welding with a suitable key hole is carried out to a welding base metal of relatively thick Al alloy. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a plasma welding torch particularly suitable for I-type butt welding of thick plates of Al alloy.

  2. Description of the Related Art Conventionally, plasma welding torches used for plasma welding with a welded base material abutted against aluminum plates have been proposed (see, for example, Patent Documents 1 to 3). FIG. 6 shows an example of such a plasma welding torch. The plasma welding torch X shown in the figure includes a non-consumable electrode 91, a plasma nozzle 92, and a shield nozzle 93. A plasma gas PG is supplied between the consumable electrode 91 and the plasma nozzle 92, and a shield gas SG is supplied between the plasma nozzle 92 and the shield nozzle 93. The non-consumable electrode 91 and the welding base material P are connected to a plasma power supply device (not shown), and a plasma voltage is applied. With this plasma voltage, the plasma gas PG becomes a plasma state, and a plasma arc PA is generated. In order to weld a thicker base metal P with the plasma arc PA, it is desirable to sufficiently contract the plasma arc PA with the shield gas SG and to increase the flow rate of the plasma gas PG.

  However, when the flow rate of the plasma gas PG is excessively increased, the molten metal that is a part of the weld base material P melted by the plasma arc PA is blown away. In such a case, as shown in FIG. 7, a good bead along the butt line WL was not formed, and welding could not be performed appropriately.

Japanese Patent Laid-Open No. 06-32825 Japanese Patent Laid-Open No. 10-058147 JP 2004-243374 A

  The present invention has been conceived under the circumstances described above, and its object is to provide a plasma welding torch capable of contracting a plasma arc without excessively increasing the flow velocity of the plasma gas. To do.

  A plasma welding torch provided by the present invention includes a rod-shaped non-consumable electrode, a cylindrical plasma nozzle that coaxially surrounds the non-consumable electrode, and a cylindrical shield nozzle that coaxially surrounds the plasma nozzle. A plasma welding torch that ejects a plasma gas from a plasma gas flow path that is a gap between the electrode and the plasma nozzle, and jets a shield gas from a shield gas flow path that is a gap between the plasma nozzle and the shield nozzle. The plasma nozzle is provided with one or more bypass channels for introducing a part of the plasma gas from the plasma gas channel to the shield gas channel.

  According to such a configuration, the plasma gas diverted from the bypass flow path to the shield gas flow path restrains the plasma arc generated by the plasma arc as a medium, and further contracts. Contribute to. Moreover, since a part of the plasma gas is diverted from the bypass channel, it is possible to avoid an excessive increase in the flow rate of the plasma gas remaining in the plasma gas channel. As a result, the plasma arc sufficiently contracted can be directed to the welding base material, and a sufficient penetration depth can be obtained. Furthermore, since there is little possibility that the wind pressure of the plasma gas becomes excessively high, it is possible to suppress the molten metal from being unfairly blown off. This makes it possible to perform good welding with an appropriate keyhole. According to such welding, a back bead having a sufficient width and amount can be formed, which is preferable for increasing the welding strength of the welding base material.

  In a preferred embodiment of the present invention, the plurality of bypass channels are arranged on the same circle centered on the non-consumable electrode. Such a configuration is preferable for contracting the plasma arc.

  In a preferred embodiment of the present invention, the plasma nozzle has a cone-shaped portion having a cross-sectional dimension that decreases toward the tip, and the plurality of bypass passages extend in a direction in which the non-consumable electrode extends. It penetrates the cone-shaped part. According to such a configuration, it is advantageous to eject the plasma gas so as to go to the welding base material while surrounding the non-consumable electrode well. Further, a part of the plasma gas can be ejected through the bypass flow path so as to flow in a direction along the plasma arc toward a position relatively close to the plasma arc. This is suitable for constricting the plasma arc.

  In a preferred embodiment of the present invention, the plasma gas contains Ar, and the shield gas contains Ar and He. Such a configuration is suitable for welding a welding base material made of an Al alloy having a relatively large plate thickness.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

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

  1 to 3 show a plasma welding torch according to the present invention. The illustrated plasma welding torch A includes a non-consumable electrode 1, a plasma nozzle 2, and a shield nozzle 3, and is held by, for example, an articulated robot (not shown). The plasma welding torch A is connected to a welding power source (not shown), and extends along a butt line WL with respect to a welding base material P on which a plate of an Al—Mg alloy having a thickness of 12 mm or more (for example, 15 mm) is butted. Used to perform plasma welding.

  The non-consumable electrode 1 is a metal rod made of tungsten, for example, and is an electrode for applying an AC arc voltage to the welding base material P.

  The plasma nozzle 2 is a cylindrical member made of a metal such as copper and has a water cooling structure as appropriate. The plasma nozzle 2 surrounds the non-consumable electrode 1 coaxially. A gap between the plasma nozzle 2 and the non-consumable electrode 1 is a plasma gas flow path 4. Plasma gas PG is supplied to the plasma gas channel 4 from, for example, a gas cylinder (not shown). The plasma gas PG is, for example, Ar, and its flow rate is about 3 L / min. This plasma gas PG flows out of the opening 21 after flowing so as to surround the non-consumable electrode 1. When the arc voltage is applied between the non-consumable electrode 1 and the welding base material P, a plasma arc PA is generated from the non-consumable electrode 1 using the plasma gas PG as a medium.

  The shield nozzle 3 is a cylindrical member made of a metal such as copper and has a water cooling structure as appropriate. The shield nozzle 3 surrounds the plasma nozzle 2 and the non-consumable electrode 1 coaxially. A gap between the shield nozzle 3 and the plasma gas nozzle 2 is a shield gas flow path 5. Shield gas SG is supplied to shield gas channel 5 from a gas cylinder outside the figure, for example. The shield gas SG is, for example, a mixed gas of 30% Ar-70% He, and its flow rate is about 15 L / min. The shield gas SG is ejected from the opening 31 of the shield nozzle 3 and functions to contract the plasma gas PG and the plasma arc PA.

  The plasma nozzle 2 has a cone portion 22. The cone-shaped portion 22 is a portion whose diameter becomes smaller toward the tip. Three bypass flow paths 23 are formed in the cone-shaped portion 22. The bypass channel 23 passes through the cone-shaped portion 22 in the axial direction of the non-consumable electrode 1 and connects the plasma gas channel 4 and the shield gas channel 5. By providing the bypass flow path 23, a part of the plasma gas PG flows into the shield gas flow path 5 and is ejected from the opening 31. As shown in FIG. 2, in the present embodiment, three bypass channels 23 are further arranged on the same circle with the non-consumable electrode 1 as the center.

  FIG. 3 shows an example of welding using the plasma welding torch A. In this embodiment, welding is performed obliquely upward with the plasma welding torch A and the welding base material P tilted so that the angle θ with respect to the vertical line VL is about 15 degrees. The welding current at this time is about 300 A, and the welding speed is about 13 cm / min. A keyhole KH, which is a very small hole, is formed in the molten metal melted by the plasma arc PA. Welding is performed by sequentially solidifying the molten metal.

  Next, the operation of the plasma welding torch A will be described.

  According to the present embodiment, the plasma gas PG that is diverted from the bypass flow path 23 to the shield gas flow path 5 contributes to restraining and further tightening the plasma arc PA. In addition, since a part of the plasma gas PG is diverted from the bypass channel 23, it is possible to avoid an excessive increase in the flow rate of the plasma gas PG remaining in the plasma gas channel 4. As a result, it is possible to direct a sufficiently contracted plasma arc PA toward the welding base material P, and to obtain a sufficient penetration depth with respect to the welding base material P made of a relatively thick Al alloy. Can do. Furthermore, since there is little possibility that the wind pressure of the plasma gas PG becomes excessively high, it is possible to suppress the molten metal from being blown off illegally. As a result, as shown in FIGS. 4 and 5, it is possible to favorably perform welding along the butt line WL while forming an appropriate keyhole KH. According to such welding, as shown in FIG. 5, the back bead RB having a sufficient width and amount can be formed, which is preferable for increasing the welding strength of the welding base material P.

  Arranging the three bypass flow paths 23 on the same circle centering on the non-consumable electrode 1 is preferable for contracting the plasma arc PA. The cone-shaped part 22 is advantageous for injecting the plasma gas PG so as to go toward the welding base material P while surrounding the non-consumable electrode 1 well. If a bypass channel 23 extending in the axial direction of the non-consumable electrode 1 is provided in the cone-shaped portion 22, the plasma flows so as to flow in a direction along the plasma arc PA toward a position relatively close to the plasma arc PA. A part of the gas PG can be ejected through the bypass channel 23. This is suitable for constricting the plasma arc PA. If plasma welding is performed while the plasma welding torch A and the welding base material P are tilted so that the angle θ with respect to the vertical line VL is about 15 degrees, it is possible to prevent the molten metal from being unduly dropped. This is preferred to form a good back bead RB.

  The plasma welding torch according to the present invention is not limited to the above-described embodiment. The specific configuration of each part of the plasma welding torch according to the present invention can be varied in design in various ways.

  The number and arrangement of the bypass passages 23 are not limited to the above-described embodiment, and any configuration may be used as long as the plasma arc PA is contracted and an inappropriate speed-up of the plasma gas PG can be avoided. The shape of the plasma nozzle 2 is not limited to the shape having the cone-shaped portion 22, and may be any shape as long as the plasma gas PG can be appropriately ejected.

It is principal part sectional drawing which shows an example of the plasma welding torch concerning this invention. It is a bottom view showing an example of a plasma welding torch according to the present invention. It is principal part sectional drawing which shows an example of the plasma welding using the plasma welding torch shown in FIG. It is the principal part top view which looked at the welding preform | base_material shown in FIG. 3 from the back surface. It is sectional drawing which follows the VV line of FIG. It is principal part sectional drawing which shows an example of the plasma welding using the conventional plasma welding torch. It is the principal part top view which looked at the welding preform | base_material shown in FIG. 6 from the back surface.

Explanation of symbols

A Plasma welding torch KH Keyhole P Welding base material PA Plasma arc PG Plasma gas RB Back bead SG Shield gas VL Vertical line WL Butting line 1 Electrode 2 Plasma nozzle 3 Shield nozzle 4 Plasma gas flow path 5 Shield gas flow path 21 Opening 22 Cone-shaped part 23 Bypass flow path 31 Opening

Claims (4)

A rod-shaped non-consumable electrode;
A cylindrical plasma nozzle that coaxially surrounds the non-consumable electrode;
A cylindrical shield nozzle that coaxially surrounds the plasma nozzle,
A plasma gas is ejected from a plasma gas flow path that is a gap between the non-consumable electrode and the plasma nozzle,
A plasma welding torch for injecting a shield gas from a shield gas flow path that is a gap between the plasma nozzle and the shield nozzle,
The plasma welding torch according to claim 1, wherein the plasma nozzle is provided with one or more bypass passages for introducing a part of the plasma gas from the plasma gas passage to the shield gas passage.   The plasma welding torch according to claim 1, wherein the plurality of bypass flow paths are arranged on the same circle centered on the non-consumable electrode. The plasma nozzle has a cone-shaped portion whose sectional dimension becomes smaller toward the tip,
The plasma welding torch according to claim 2, wherein the plurality of bypass flow paths penetrate the cone-shaped portion in a direction in which the non-consumable electrode extends.   The plasma welding torch according to any one of claims 1 to 3, wherein the plasma gas includes Ar, and the shield gas includes Ar and He.