JP2011235302A - Welding torch for gas shield welding and gas shield welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a welding torch including a gas nozzle with a simple circular cross section, capable of carrying out gas shield welding of a material with a deep groove or a material where a groove is not formed in an optimum condition without being restricted by a groove width relative to the structure of the welding torch used in the gas shield welding.SOLUTION: The welding torch includes a gas nozzle which is relatively movable in a torch axis direction to a torch body. A nozzle port is forwardly/backwardly movable by allowing the gas nozzle to be slidably fitted into a guide cylinder in the torch axis direction and by a bellows structure extendable and contractable in the axial direction or the like. The gas nozzle is coupled with a forward/backward drive device such as a servo cylinder which is stroke controllable by NC control and the nozzle port is moved and positioned. When a part of a bottom of a narrow deep groove is welded, welding is carried out while the gas nozzle is retreated and a welding wire is protruded long from the nozzle port.

Description

  The present invention relates to the structure of a welding torch used in gas shield welding, and more particularly to the above-described apparatus characterized by a gas nozzle for supplying a shielding gas to the tip of the torch.

  Gas shield welding is a welding method in which high-quality welding or special metal welding is performed by performing welding in an atmosphere of an inert gas or a special gas. A welding torch for gas shield welding includes a gas nozzle for supplying a shielding gas to the tip of the torch. The gas nozzle is a hollow pipe that covers the tip of the welding torch. The tip of the welding wire sent out from the welding torch protrudes from the nozzle port (opening end) of the gas nozzle by a predetermined length. However, if the nozzle port is too far from the surface of the base metal to be welded, it was supplied from the nozzle port. Since the shield gas diffuses and the weld cannot be shielded from the atmosphere, welding is performed with the nozzle opening close to the surface of the base metal.

  When the base metal to be welded has a thickness of a certain level or more, a groove is formed in the weld of the base metal and multilayer welding, that is, the welding torch is moved many times to the weld, to build up the multilayer overlay. Do. Further, in order to perform uniform overlaying on a welded portion having a certain width, welding is performed while weaving, that is, while reciprocating the tip of the welding torch in a direction perpendicular to the moving direction.

  As the thickness of the base metal to be welded increases, the depth of the groove also increases. If the groove width is unnecessarily wide, the amount of welding material required to fill the groove with a wide cross section increases, and welding takes time. Therefore, it is desirable that the width of the groove is as narrow as possible.

  In the gas shield welding of a thick material having a deep groove depth, there is a problem whether the nozzle opening is inserted into the groove for welding or not. When welding is performed by inserting the nozzle port into the groove in a state in which the protruding amount of the wire from the nozzle port is a normal protruding length, interference between the wall surface of the groove and the gas nozzle becomes a problem. That is, the width of the groove must be larger than the outer diameter of the gas nozzle, and when welding is performed while weaving, it is avoided that the weaving width is limited by the collision between the gas nozzle and the groove wall. There is a need. If a sufficient weaving width cannot be obtained due to interference between the gas nozzle and the groove wall, the welding wire cannot be brought close to the groove wall, and welding is incomplete. Therefore, welding is performed by attaching a thin gas nozzle or a flat gas nozzle.

  On the other hand, in welding in which the nozzle opening is not inserted into the groove, welding is performed on the groove bottom portion by causing the tip of the welding wire to protrude long from the nozzle opening. In this case, the deflection of the wire tip that protrudes long from the tip of the torch (displacement of the tip due to the inclination or bending of the wire) becomes a problem. Further, when the build-up progresses by multi-layer welding, the apparent groove depth becomes shallow, and it is necessary to retract the tip of the wire accordingly. Along with this retreating operation, the nozzle opening also retreats, the distance from the surface of the member metal becomes wide, and the shield gas diffuses.

  In order to cope with such a problem, the following Patent Documents 1 to 5 propose a structure of a welding torch for gas shield welding a thick material or a narrow portion.

JP 2008-200723 A Japanese Utility Model Laid-Open No. 5-18769 Japanese Utility Model Publication No. 6-574 JP 2009-297720 A JP-A-9-10944

  However, for example, in the structure described in Patent Document 1, there is a restriction that the groove width cannot be made smaller than the outer diameter of the gas nozzle. In the structure described in Patent Document 2, the surface of the member having an obstacle or a step is welded. There is a problem that cannot be adopted. Further, in the structures of Patent Documents 3 to 5, the gas nozzle has a special shape and structure. For this reason, the gas nozzle becomes expensive, a base material in which a groove is not taken, or a mother with a shallow groove depth. There are problems such as incompatibility with welding of materials, and there is a problem in terms of versatility.

  According to the present invention, gas shield welding can be performed under conditions suitable for both welding of a material having a deep groove and welding of a material having no groove without being restricted by the groove width. An object of the present invention is to obtain a welding torch capable of performing welding by supplying shield gas from a gas nozzle having a simple circular cross section having a thickness necessary for supplying gas.

  The welding torch of the present invention includes a gas nozzle 2 that can move relative to the torch body in the torch axial direction. The gas nozzle 2 is provided so as to be slidably fitted in the guide tube 13 in the torch axial direction or slidable in the axial direction, or the nozzle port 22 is advanced and retracted by a bellows-like cylindrical body that can expand and contract in the axial direction (torch axial direction It can be freely moved). The gas nozzle 2 is connected to an advancing / retreating drive device 5 such as a servo cylinder capable of stroke control by NC control, and the nozzle port 22 is moved and positioned. The distance from the tip of the torch to the tip of the welding wire 3 is maintained at a set predetermined distance, and the distance (protrusion amount) from the nozzle port to the tip of the welding wire changes due to the forward and backward movement of the nozzle port 22.

  When welding the bottom portion of the narrow and deep groove, welding is performed with the gas nozzle retracted and the welding wire protruding long from the nozzle port. At this time, the gas nozzle 2 is not inserted into the groove, and welding is performed with the tip of the welding wire reaching the bottom of the groove. Since only the welding wire is inserted into the groove and the nozzle port is located outside the groove, it is possible to perform the necessary weaving operation on the wire tip without causing interference between the gas nozzle and the wall of the groove. it can. It is also possible to make the groove width narrower than the outer diameter of the gas nozzle.

  As welding progresses, the welding material is built up on the bottom of the groove, the apparent depth of the groove becomes shallower, and the welding torch also retreats accordingly. When driven, the nozzle port 22 relatively moves forward to keep the distance between the nozzle port 22 and the base material surface 82 constant. Since the welding torch retraction amount is controlled by the NC device of the welding robot, controlling the advance / retreat driving device 5 with the same NC device relatively advances the nozzle port 22 by an amount equal to the retraction amount of the welding torch. Thus, the distance between the nozzle port 22 and the base metal surface 82 can be kept constant. Further, when there are obstacles or steps on the surface of the base material, the gas nozzle 2 can be moved backward to get over the obstacles or steps by a teaching or processing program.

  The advancing end of the nozzle port 22 is set so as to satisfy the condition for planar welding when the advancing end is advanced, that is, when the amount of projection of the welding wire from the nozzle port is the shortest. Thereby, the welding of the base material in which the groove is not provided or the base material in which the shallow groove is provided can be performed without any trouble. Also, in fillet welding in which the base material surfaces 82 and 82 cross each other at an acute angle as shown in FIG. 7, the gas nozzle 2 and the base material surface 82 are caused to interfere by appropriately retracting the nozzle port 22. Welding can be performed.

  According to the welding torch of the present invention, the shield from the base metal having a deep groove to the welding of the base metal having no groove without being limited by the groove depth or the groove width. Gas shield welding can be performed in a state in which the gap between the gas nozzle opening and the base metal surface and the gap between the welding wire tip and the base metal are maintained at the optimum intervals. Even in welding where the apparent groove depth gradually decreases due to welding progressing as the weld metal builds up, the distance between the nozzle opening and the base metal surface is always kept constant, and only the welding wire is retracted sequentially. Welding can be performed.

  Since the welding torch according to the present invention performs welding without inserting the gas nozzle into the groove, the groove width can be sufficiently narrowed as necessary, and the weaving of the wire tip into the groove is limited. It does not occur. Further, by the sensing operation for detecting the contact between the welding wire and the base metal, the depth of the groove and the width of the groove can be detected by the NC device, and the optimum nozzle opening position can be automatically set.

Side view of the welding torch shown attached to the welding robot Diagram showing groove width and groove depth measurement by wire touch sensing A perspective view explaining the weaving operation Illustration of weaving where nozzle and groove do not interfere Illustration of weaving where nozzle and groove interfere Flow chart showing an example of nozzle stroke control procedure Schematic showing fillet welding where the nozzle may interfere with the base metal

  Next, an embodiment of the present invention will be described with reference to the drawings. In the figure, 1 is a welding torch, 2 is a gas nozzle, 3 is a welding wire fed from the tip of the welding torch, 4 is a wrist provided at the arm tip of the welding robot, and 6 is a shock sensor.

  The wrist 4 of the welding robot is attached with a turning bracket 42 that turns by rotating around the wrist axis 41, and the torch holder 11 is attached to the tip of the turning bracket via a shock sensor 6. The welding torch 1 is attached with the neck portion 12 fixed to the torch holder 11. A guide inner cylinder 13 is fixed to the welding torch 1 on the tip side from the neck portion 12. A guide outer cylinder 14 is fitted into the guide inner cylinder 13 so as to be slidable in the axial direction. The gas nozzle 2 is fixed to the tip of the guide outer cylinder 14. Shield gas is supplied to the gas nozzle 2 through a hose 21 connected to the base end of the torch body, and the shield gas flows out from the nozzle port 22 at the lower end of the gas nozzle 2 during welding. The welding wire 3 passes through the hose 21 and is sent out from the tip 15 at the tip of the welding torch 1.

  A servo cylinder 5 is mounted on the torch holder 11 in parallel with the welding torch 1. The tip of the rod 51 of the servo cylinder is connected to a connecting plate 16 fixed to the base end of the guide outer cylinder 14. Therefore, the rod 51 of the servo cylinder and the gas nozzle 2 fixed to the guide outer cylinder 14 are integrally stroked (moved in the axial direction). The stroke position of the rod 51 is detected by a sensor built in the servo cylinder 5 and given as a feedback signal c to the NC device 7 of the welding robot. The NC device 7 controls the hydraulic oil a and b applied to the servo cylinder 5 by controlling the servo valve 52 so that the stroke amount of the rod 51 becomes the commanded value Ls.

  The stroke origin of the nozzle port 22 is the position of the nozzle port when welding a plane on which no groove is provided. At this time, the tip 15 protrudes from the nozzle port 22 by a length Lo, and further, the welding wire extends from the tip of the tip. 3 protrudes by a length L (see FIG. 2; FIG. 1 is an example when Lo <0). That is, at the stroke origin of the rod 51 of the servo cylinder, the nozzle port 22 is positioned above the tip of the welding wire 3 by L + Lo. In the stroke of the rod 51, the direction in which the rod 51 is drawn is defined as the positive direction. Therefore, the position of the nozzle port 22 when the rod 51 is stroked by Ls is L + Lo + Ls from the tip of the welding wire 3.

Next, a welding torch according to the present invention will be described by taking as an example a case where base metals 8 and 8 provided with parallel grooves, that is, grooves whose groove width W does not change from the groove bottom to the groove outlet, are multilayer welded. The welding operation using the will be described. First, prior to welding,
dn: outer diameter of gas nozzle 2 B: interference allowance including inclination of torch a: amplitude of weaving L: protruding length of welding wire from tip end Lo: protruding length of nozzle 15 from tip 15 at stroke origin Δ: Register the height of build-up per layer.

Next, in a state where the gas nozzle 2 is moved to the rising end, a low potential difference is applied between the welding wire 3 and the base metals 8 and 8 to bring the welding wire 3 into contact with the base metals 8 and 8. With wire touch sensing that detects current,
W: groove width H: groove depth is detected, and the detected value is stored in the NC device 7. The groove width W is measured by detecting the amount of horizontal movement of the welding torch by the NC device 7 when the wire tip is brought into contact with one wall of the groove 81 and then brought into contact with the opposite wall. it can. In addition, the groove depth H is the vertical direction of the welding torch when the wire tip is brought into contact with the surface of the base metal and then brought into contact with the bottom of the groove (the surface of the backing metal) at the center of the groove. It can be measured by detecting the amount of movement by the NC device 7.

Based on the measured groove width W and depth H, the stroke command value Ls given to the servo cylinder 5 is set as shown in the following (1) to (3). Here, Ls is a command value of a stroke (nozzle reverse stroke) given to the servo cylinder, and N is the number of welding layers.
(1) When the groove width W is larger than dn + 2a + 2B (FIG. 4), there is no possibility that the groove wall and the gas nozzle 2 interfere even if the nozzle port 22 is inserted into the groove. Weld in position. That is,
If W> dn + 2a + 2B,
All layers are welded at the command value Ls = 0 regardless of the groove depth.
(2) When the groove width is small, that is, when W ≦ dn + 2a + 2B (FIG. 5), the nozzle is raised according to the groove depth to prevent interference. That is,
If L + Lo> H + B, the command value Ls = 0.
If L + Lo ≦ H + B, welding of the first layer is started with the command value Ls = H− (L + Lo) + B.
(3) On the other hand, after the N-th layer welding is performed, the groove depth becomes shallower by the thickness of the weld overlay that has already been performed, so when performing the N + 1-th layer welding,
If L + Lo> H−N × δ + B, the command value Ls = 0.
If L + Lo ≦ H−N × δ + B, the command value Ls = H−N × δ− (L + Lo) + B
Weld with.

  FIG. 6 is a flowchart illustrating an example of a control procedure for controlling the stroke Ls of the servo cylinder so that welding is performed under the above-described conditions, where Hn = H−N × δ. Here, if the determination step S1 is Yes, even if the gas nozzle 2 is inserted into the groove and welding is performed, there is no possibility that the gas nozzle and the wall of the groove interfere with each other, so the gas nozzle 2 is set to the origin position Ls = 0. All the welding is performed (step S2).

  If the determination step S1 is No, if the gas nozzle 2 is inserted into the groove and welding is performed, the gas nozzle and the groove wall may interfere with each other. However, if the substantial groove depth Hn (= H−N × δ) is a depth at which the tip of the gas nozzle does not reach the base material surface even if the gas nozzle is at the origin position Ls = 0, it is necessary to compare the gas nozzle. Therefore, the determination is made in step S3. That is, if the dimension obtained by adding a margin B to the substantial groove depth Hn is smaller than the distance L + Lo from the nozzle opening to the wire tip when the gas nozzle is at the origin position (Yes in step S3), the nozzle opening Since there is a gap of more than the margin B between the surface of the base material and the number of layers N is increased, the substantial groove depth becomes shallower. Therefore, in the subsequent welding, the gas nozzle is moved to the origin position Ls = 0. All subsequent welding is performed (step S2).

  If the determination in step S3 is No, if the welding is performed with the gas nozzle as the origin position, the gas nozzle and the groove wall may interfere with each other. The gas nozzle is retracted by Ls = Hn− (L + Lo) + B so that a gap of only margin B is opened therebetween, and the layer is welded (step S5). In this case, since the substantial groove depth Hn becomes shallower as the build-up progresses, Hn is corrected in step S6 each time one layer of welding is completed, and the process returns to the determination in step S3.

  As can be understood from the above description of the embodiments, by using the welding torch according to the invention of the present application, when the groove width is narrow or the groove depth is deep, the substantial groove depth is increased by the progress of welding. In the case of gas shield welding under various conditions, such as when there is no groove, the gas nozzle is placed in an optimal position without causing interference between the gas nozzle supplying the shield gas and the wall of the groove. Welding can be performed.

DESCRIPTION OF SYMBOLS 1 Welding torch 2 Gas nozzle 3 Welding wire 5 Advance / retreat drive device (servo cylinder)
7 NC device of welding robot 8 Base material 13 Guide tube 22 Nozzle port 82 Base material surface

Claims (3)

  A welding torch comprising a gas nozzle capable of moving a nozzle port relative to the torch body in the torch axial direction, and an advance / retreat drive device for axially moving the nozzle port of the gas nozzle by an NC device of a welding robot.   A gas nozzle is mounted on a guide inner cylinder 13 in a torch axial direction provided in a torch main body so as to be slidable in the cylinder axial direction, and the advance / retreat driving device is a servo cylinder provided in parallel with the guide inner cylinder. Item 2. A welding torch according to item 1.   Using the welding torch according to claim 1 or 2, the width of the groove provided in the base metal to be welded is added to the diameter of the gas nozzle attached to the tip of the torch by twice the amplitude of the weaving during welding. If the width is larger than the added width, welding is performed with the position of the gas nozzle fixed, and the width of the groove is added to the diameter of the gas nozzle attached to the tip of the torch by adding twice the amplitude of the weaving during welding. If the width is smaller than the added width, the relative position in the axial direction of the gas nozzle with respect to the welding torch body is changed according to the substantial groove depth when performing the welding, and the nozzle opening and base material of the gas nozzle are changed. A gas shield welding method, wherein welding is performed while maintaining a constant distance from a metal surface.

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