Welding apparatus and welding method

Abstract

This aims to reduce the number of workers required in the manufacturing of welded parts that require back shielding, while also improving welding quality. [Solution] A welding apparatus 1 for welding a workpiece that requires back shielding, comprising: an arm portion 105 configured to be movable horizontally along the weld line of the workpiece; and a back shield support member 10 configured to be movable horizontally along the weld line of the workpiece below the arm portion 105, wherein the arm portion 105 and the back shield support member 10 move integrally and synchronously, a welding torch 110 for welding along the weld line of the workpiece is provided at the end of the arm portion 105, and a back shield portion 20 for supplying back shielding gas to the back surface of the welding area of ​​the workpiece is provided at the end of the back shield support member 10.

Description

Technical Field

[0001] The present invention relates to a welding apparatus and a welding method used for performing welding during manufacture of large tanks such as tank trucks and storage tanks for various liquids or gases, for example.

Background Art

[0002] In the manufacture of various pipes, tanks and the like, it is known that welding is performed by butt-welding metal plates and performing keyhole welding using a non-consumable electrode (plasma, TIG, laser, etc.). For example, in plasma keyhole welding, welding is performed while a plasma arc penetrates the metal plate in the plate thickness direction, so preventing oxidation of the back bead formed on the back side is important in terms of quality.

[0003] Accordingly, for example, Patent Document 1 discloses that when performing long-length welding of a large plate, a carriage equipped with a front-side welding torch and a back-side back shield supply mechanism are mounted on a self-propelled backing carriage, the light of the keyhole arc that has escaped to the back is detected by a plurality of sensors, and speed adjustment is performed so that the backing carriage is at the same position relative to the front carriage, while back shield gas is supplied to perform back shielding, whereby oxidation and the like of the back bead are suppressed, and welding quality is known to be improved.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] Incidentally, during normal welding, and especially in keyhole welding, a high-temperature arc is passed through to the back side of the metal plate, and a molten pool is formed on the back bead side as well. Therefore, it is highly susceptible to the influence of the atmosphere on the back side. For example, in an oxidizing atmosphere without back shielding, the molten pool on the back side of the metal plate undergoes an oxidation reaction, and the surface of the back bead is covered with a thick oxide film, leading to problems such as deterioration of corrosion resistance and insufficient strength due to the recessed shape of the back bead, resulting in a decline in quality.

[0006] For this reason, back shielding is particularly important in keyhole welding. As described in Patent Document 1 above, there is a method of performing back shielding by mounting a back shield supply mechanism on a back trolley and using a back-side plasma torch travel trolley and a back-through plasma arc light sensor for synchronized control. However, the mechanism using a back support travel trolley and the synchronized control with the front travel trolley have been complex and costly.

[0007] Furthermore, in the manufacture of tank trucks and large tanks, it is known that workers enter the tank, manually support the back shield supply mechanism against the back side, and move in accordance with the torch movement on the front side, performing welding while preventing oxidation of the back bead. In the manufacture of large tanks, welding is often performed using manipulator welding equipment, but even in that case, the oxidation prevention work inside the tank is performed by workers, and this work is arduous, involving lifting heavy objects in a confined space for long periods of time, so there is a need for further efficiency improvements, reduction of man-hours for workers, and improvement of the working environment.

[0008] In particular, plasma welding is a representative keyhole welding method, but there are also high-current TIG welding and laser welding methods. However, all of these methods have similar challenges because they involve through-welding.

[0009] This invention has been made in view of the above circumstances, and aims to provide a welding apparatus and welding method that can reduce equipment costs, reduce the man-hours required of workers and improve the working environment in the manufacture of large tanks, while also improving welding quality. [Means for solving the problem]

[0010] To achieve the above objective, the present invention provides a welding apparatus for welding a workpiece that requires back shielding, comprising: an arm configured to be movable horizontally along the weld line of the workpiece; and a back shield support member configured to be movable horizontally along the weld line of the workpiece below the arm, wherein the arm and the back shield support member move integrally and synchronously, a welding torch for welding along the weld line of the workpiece is provided at the end of the arm, and a back shield section for supplying back shielding gas to the back surface of the welding area of ​​the workpiece is provided at the end of the back shield support member.

[0011] The welding may be performed using a plasma welding method.

[0012] The plasma welding method may also be a keyhole welding method.

[0013] The back shield portion may include a back shield box positioned directly below the welding torch, sandwiching the workpiece during welding, and a pressing mechanism that presses the back shield box against the workpiece.

[0014] The back shield portion may include a back shield box located directly below the welding torch, sandwiching the workpiece during welding, and a monitoring camera for monitoring the inside of the back shield box.

[0015] The welding apparatus may be configured using a manipulator welding apparatus, and the arm portion and the back shield support member may be supported by the manipulator welding apparatus.

[0016] The workpiece to be welded may be a tank used in a large tank truck.

[0017] Further, according to the present invention from another aspect, there is provided a welding method for performing welding on a workpiece that requires back shielding, the welding method using a welding apparatus including an arm portion configured to be movable in the horizontal direction along a weld line of the workpiece, and a back shield support member disposed below the arm portion and configured to be movable in the horizontal direction along the weld line of the workpiece, the welding method being characterized by moving the arm portion and the back shield support member integrally in synchronization with each other, and pressing a back shield portion provided at an end of the back shield support member directly below a welding torch provided at an end of the arm portion across the workpiece to perform welding.

[0018] The welding may be a plasma welding method.

[0019] The plasma welding method may be a keyhole welding method. Effects of the Invention

[0020] According to the present invention, in the manufacture of large-sized tanks, it is possible to reduce equipment costs, cut down the number of man-hours for workers, improve the working environment, and achieve an improvement in welding quality. Brief Description of the Drawings

[0021] [Figure 1] It is a schematic explanatory view of a conventional welding apparatus. [Figure 2] It is a schematic explanatory view of a welding apparatus according to an embodiment of the present invention. [Figure 3] It is an enlarged view of a welded portion. Modes for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that in the present specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description thereof is omitted. Note that the embodiment of the present invention uses a plasma welding method which is one type of keyhole welding method, and therefore the following description will be given in the context of plasma welding.

[0023] <Conventional welding apparatus> First, the configuration of a conventional welding apparatus using a manipulator welding apparatus will be briefly described. FIG. 1 is a schematic explanatory view of a conventional welding apparatus 100 using a manipulator welding apparatus, and is a schematic cross-sectional view of the apparatus during welding as viewed from the side. As shown in FIG. 1, the conventional welding apparatus 100 includes a support column 102 and an arm portion 105 supported on the support column 102 via a support 103. The arm portion 105 extends in the horizontal direction (X direction in the figure), and is configured such that its height can be freely changed in the vertical direction (Y direction in the figure) along the support column 102.

[0024] The arm portion 105 is configured to be movable in the horizontal direction, and a welding torch 110 is provided at an end portion thereof (the end portion in the positive X-axis direction in the figure). The configuration of the welding torch 110 is arbitrary, and for example, a general plasma welding torch mechanism that performs keyhole welding while penetrating a metal plate in the plate thickness direction by a plasma arc may be used, and a detailed description thereof will be omitted.

[0025] At the time of keyhole welding, for example, a metal plate is formed into a cylindrical shape to constitute a workpiece H to be welded, and the operation is performed while moving the welding torch 110 along the weld line (welding traveling axis: X direction in the figure) with the butted ends as the weld line. The movement of the welding torch 110 is performed by moving the arm portion 105 in the horizontal direction. Normally, the right direction in FIG. 1 (positive X-axis direction: see the arrow in the figure) is the welding progressing direction.

[0026] Further, inside the workpiece H to be welded, a worker 124 having a back shield gas supply mechanism 120 for supplying a back shield gas to the back surface (inner surface) of the welded portion is arranged. As the worker 124 moves in accordance with the movement of the welding torch 110, the back shield gas supply mechanism 120 is also moved, and welding is performed while supplying the back shield gas to a desired position.

[0027] In conventional welding equipment 100, plasma welding is performed while a worker 124 supplies back shielding gas inside the workpiece H. At that time, the movement of the welding torch 110 and the back shielding gas supply mechanism 120 must be synchronized. In this case, the synchronization of the two was achieved by the movement of the worker 124, ensuring welding quality.

[0028] The inventors focused on the workload on workers 124 and the synchronization accuracy between the welding torch 110 and the back shielding gas supply mechanism 120 when using the conventional plasma welding apparatus 100 shown in Figure 1 during the manufacture of large tanks used in tank trucks and the like. To further reduce the workload on workers 124, improve the working environment, and enhance the synchronization accuracy between the welding torch 110 and the back shielding gas supply mechanism 120, they devised the following welding apparatus configuration. The configuration of the welding apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

[0029] In this specification, "large tank" refers to a cylindrical or rectangular tank with a diameter or side length of approximately 500 mm or more, where at least one side of the cylindrical shape is not covered, and there is an open or partially open section.

[0030] <Plasma welding apparatus according to an embodiment of the present invention> Figure 2 is a schematic diagram illustrating a welding apparatus 1 according to an embodiment of the present invention using a manipulator welding apparatus, and is a schematic cross-sectional view of the apparatus as seen from the side during welding. Figure 3 is an enlarged view of the welding area, and is a schematic diagram of the enlarged portion enclosed by the dashed line in Figure 2. In the following description, components having the same functional configuration as the conventional welding apparatus 100 described above are denoted by the same reference numerals and their descriptions may be omitted.

[0031] As shown in Figure 2, the welding apparatus 1 comprises a support column 102 and an arm portion 105 supported on the support column 102 via a support member 103. The arm portion 105 extends horizontally (X direction in the figure), and its height is adjustable vertically (Y direction in the figure) along the support column 102. The arm portion 105 is configured to be movable in the horizontal direction, and a welding torch 110 is provided at its end (the end in the positive X direction in the figure). The horizontal movement of the arm portion 105 is performed, for example, by a rack and pinion mechanism between the drive motor of a moving mechanism 104 provided on the support member 103 and the arm portion 105.

[0032] Furthermore, in the welding apparatus 1, a back shield support member 10 is provided below the arm portion 105 (negative Y-axis direction in the figure) and supported by a support column 103a via a support member 103. The back shield support member 10 extends horizontally (X-direction in the figure) below the arm portion 105 and in the same direction as the arm portion 105 in a plan view. The back shield support member 10 is configured to be movable in the horizontal direction, and a back shield portion 20 is provided at its end (positive X-axis end in the figure).

[0033] Here, the arm portion 105 and the back shield support member 10 are integrally constructed and supported by the column 102 via the support 103, moving integrally in the vertical direction. For example, the ends of the arm portion 105 and the back shield support member 10 (the ends in the negative direction of the X axis in the figure) are connected by a connecting member 11. The back shield support member 10 is also supported by a support member 103a that extends downward from the support 103. With this configuration, the back shield support member 10 moves integrally with the horizontal movement of the arm portion 105 (see arrow in the figure). That is, the welding torch 110 provided at the end of the arm portion 105 and the back shield portion 20 provided at the end of the back shield support member 10 are configured to move synchronously in both the X axis and Y axis directions. For example, the back shield portion 20 is always positioned directly below the welding torch 110, and both are configured to move synchronously along the same welding line.

[0034] Furthermore, as shown in Figure 3, the back shield section 20 includes a back shield box 22 located directly below the welding torch 110, sandwiching the workpiece H; a monitoring camera 24 for monitoring the inside of the back shield box 22; and a pressing mechanism 30 for pressing the back shield box 22 against the inner surface (back surface of the welding area) of the workpiece H. For example, the pressing mechanism 30 may be supported at the end of the back shield support member 10.

[0035] The monitoring camera 24 is mounted, for example, on the outside side of the back shield box 22, and can monitor the inside of the back shield box 22 through a window 26 provided on the side of the back shield box 22. That is, during keyhole welding, the state of the plasma arc that has penetrated to the back side of the workpiece H, and the shape and quality of the back bead immediately after solidification can be visually confirmed in real time. The window 26 may be made of, for example, heat-resistant quartz glass.

[0036] Furthermore, a back shielding gas hose (not shown) is connected to the back shielding box 22, which communicates with a gas supply source (not shown), and back shielding gas is supplied to the inside. The back shielding gas may be an inert gas, for example.

[0037] The pressing mechanism 30 includes an elastic member 32 that supports the back shield box 22, and a cylinder mechanism 34 for pressing the back shield box 22 upward by pressing the elastic member 32. The back shield box 22 has an opening 22a on its upper surface, and the back shield box 22 is pressed against the inner surface of the workpiece H by the drive of the cylinder mechanism 34, and is fixed to the inner surface of the workpiece H (the back surface of the weld area) so that there is no gap between the opening 22a and the workpiece H. Furthermore, by interposing an elastic member 32, such as a spring, between the cylinder mechanism 34 and the back shield box 22, it is possible to press the opening 22a of the back shield box 22 against the inner surface of the workpiece H without any gaps, even if there are irregularities or curves on the inner surface of the workpiece H. In addition, a gap-filling member (not shown) may be provided around the opening 22a of the back shield box 22 to further improve the adhesion.

[0038] Furthermore, a monitoring camera 40 may be provided near the welding torch 110 to monitor the plasma arc and the weld groove from outside the workpiece H. The monitoring camera 40 is used to check the plasma arc state from outside the workpiece H and to monitor whether the welding torch 110 is moving along the weld groove (welding axis: X direction in the figure). For example, when performing plasma keyhole welding, if a misalignment occurs between the plasma arc and the weld groove based on the image signal of the weld line from the monitoring camera 40 with an image sensor, the operator will perform welding while correcting the position of the welding torch 110 (in a direction perpendicular to the X axis) so that it is in a predetermined reference position, using a control device (not shown).

[0039] <Welding Method> Next, we will explain the keyhole welding method for the workpiece H, specifically plasma keyhole welding.

[0040] Before performing plasma keyhole welding, the arm portion 105 and the back shield support member 10 are positioned in a predetermined preparation location, as shown by the dashed line on the left side (negative X-axis direction) of Figure 2.

[0041] In this state, the arm portion 105 and the back shield support member 10 are moved integrally, welding the welding area along the weld line of the workpiece H. Specifically, a plasma arc from the welding torch 110 provided at the end of the arm portion 105 is applied to the groove formed on the outer circumference of the workpiece H. This creates a keyhole that penetrates the workpiece H. As welding progresses, this keyhole moves backward, and the molten metal also moves backward and solidifies, forming a continuous weld bead. In this way, the welding area of ​​the workpiece H is welded and becomes cylindrical.

[0042] When a plasma arc from the welding torch 110 is applied, the back shield section 20 is positioned on the inner surface of the workpiece H (the back side of the welding area), and the back shield box 22 is pressed against the back side of the welding area. As described above, the arm section 105 and the back shield support member 10 move integrally, so the back shield box 22 can be pressed against the back side of the welding area with high precision. In this way, when plasma welding is performed, back shield gas is supplied into the back shield box 22, gas-shielding the inner surface of the workpiece H with a back shield gas atmosphere. This suppresses oxidation of the back bead and prevents defects in the bead shape.

[0043] <Effects and Effects> According to the welding apparatus 1 of this embodiment, in a configuration using a manipulator welding apparatus, a back shield support member 10 is provided in addition to the arm portion 105, and back shield gas is supplied to the back shield portion 20 provided at the end of the back shield support member 10. Therefore, the operator 124 required in the conventional welding apparatus 100 (see Figure 1) is not needed, improving work efficiency, reducing the man-hours for the operator, and improving the working environment.

[0044] Furthermore, in the welding apparatus 1, the arm portion 105 and the back shield support member 10 are integrally configured and move together. That is, the welding torch 110 provided at the end of the arm portion 105 and the back shield portion 20 provided at the end of the back shield support member 10 move along the same welding line in high-precision synchronization. As a result, back shield gas can be accurately supplied to the area directly below the welding torch 110 on the inner surface of the workpiece H (the back surface of the weld area), preventing oxidation of the back bead and improving welding quality.

[0045] In addition, the back shield section 20 is equipped with a monitoring camera 24 that monitors the inside of the back shield box 22, allowing for visual confirmation of the state of the back-through plasma arc in the keyhole and the shape of the back bead, making it easy to perform welding while checking the quality of the back bead.

[0046] Furthermore, in addition to welding the workpiece H in the X-axis direction, circumferential welding is also possible by rotating the workpiece H in the circumferential direction using a turning roll (not shown). In this case, a rotation mechanism may be provided to rotate the welding torch 110 and the back shielding gas supply mechanism 120 by 90° in the circumferential direction.

[0047] Although embodiments of the present invention have been described above, the present invention is not limited to these examples. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these will naturally also fall within the technical scope of the present invention. [Industrial applicability]

[0048] The present invention can be applied, for example, to welding equipment and welding methods used for welding during the manufacture of large tanks such as tank trucks and storage tanks for various liquids or gases. [Explanation of Symbols]

[0049] 1... Welding equipment 10...Back shield support member 11…Connecting member 20...Back shield section 22... Back shield box 22a…Aperture 24... Surveillance cameras 26...Window section 30... Pressing mechanism 32...Elastic member 34... Cylinder 40… Surveillance cameras 100…(Conventional) welding equipment 102…post 103...Support 103a...Support member 104...Movement mechanism 105...Arm 110... Welding torch 120...Back shielding gas supply mechanism 124...Worker

Claims

1. A welding apparatus for welding workpieces that require back shielding, An arm portion configured to be movable horizontally along the weld line of the workpiece to be welded, It includes a back shield support member configured to be movable horizontally along the weld line of the workpiece below the arm, The arm portion and the back shield support member move synchronously as a single unit. A welding apparatus characterized in that the end of the arm portion is equipped with a welding torch for welding along the weld line of the workpiece, and the end of the back shield support member is equipped with a back shield portion for supplying back shield gas to the back surface of the welding area of ​​the workpiece.

2. The welding apparatus according to claim 1, characterized in that the welding is performed by a plasma welding method.

3. The welding apparatus according to claim 2, characterized in that the plasma welding method is a keyhole welding method.

4. The aforementioned back shield portion is During welding, a back shield box is located directly below the welding torch, sandwiching the workpiece, A welding apparatus according to any one of claims 1 to 3, characterized by including a pressing mechanism for pressing the back shield box against the workpiece to be welded.

5. The aforementioned back shield portion is During welding, a back shield box is located directly below the welding torch, sandwiching the workpiece, The welding apparatus according to any one of claims 1 to 3, further comprising a monitoring camera for monitoring the inside of the back shield box.

6. The welding apparatus is configured using a manipulator welding apparatus. The welding apparatus according to any one of claims 1 to 3, characterized in that the arm portion and the back shield support member are supported by the manipulator welding apparatus.

7. The welding apparatus according to claim 1 or 2, characterized in that the workpiece to be welded is a tank used in a large tank truck.

8. A welding method for welding workpieces that require back shielding, An arm portion configured to be movable horizontally along the weld line of the workpiece to be welded, A welding apparatus including a back shield support member configured to be movable horizontally along the weld line of the workpiece below the arm, The arm portion and the back shield support member are moved in a synchronized manner as a single unit. A welding method characterized by pressing a back shield portion, provided at the end of the back shield support member, against the area directly below the welding torch, provided at the end of the arm portion, with the workpiece to be welded in between.

9. The welding method according to claim 8, characterized in that the welding is performed by a plasma welding method.

10. The welding method according to claim 9, characterized in that the plasma welding method is a keyhole welding method.

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