JPS60210361A - Build-up welding method of inside surface of pipe - Google Patents

Abstract

PURPOSE:To perform defectless and stable build-up welding of the inside surface of a pipe by detecting the coincidence of the height displacement of a welding torch provided to the top end of an arm with a reference value, upsetting the torch and profiling the end face of a bead thereby obtaining the smooth beads. CONSTITUTION:The oscillating direction of the welding torch 2 attached to the top end of the arm 7 consisting of a slender pipe is checked in continuous build- up welding of the inside surface of a pipe in which an arc voltage is controlled. The height displacement eA of the torch 2 is detected if the oscillating direction is in the direction of the build-up bead 5. The upsetting signal for the torch 2 is detected where the displacement eA rises up to set reference potential er. A command for stopping oscillation is emitted after time TA(sec) and the torch 2 is upset upon lapse of stop time TB. A set oscillating width W is detected and the torch 2 is upset if the oscillating direction of the torch 2 is on the side where there is no bead 5. The generation of an undercut or the trough in the lap part of the bead is eliminated by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a welding method for overlaying the inner surface of a tube, for example, in which overlay is applied to the inner surface of the tube in order to improve the corrosion resistance of the inner surface of the tube.

[Prior art]

Conventionally, the spiral method or step-over method using MIG welding or TIG welding has been adopted for overlay welding, which builds up on the inner surface of a tube, for tubes with an outer diameter of 200 mm or more.

In the spiral method, as shown in Figure 1, the welding torch (2) is continuously moved in the direction of arrow B while swinging the welding torch (2) within the tube (1) rotating in the inner circumferential direction of arrow A. move,
As shown in FIG. 2, this is a method in which a bead (3) is wound spirally around the inner surface of a tube (1).

In the step-over method, the welding torch (2) is oscillated within the rotating tube (11) as shown in Figure 1.
) detects one rotation of the bead (3) as shown in Figure 3.
In this method, the welding torch (2) is moved intermittently by a width of .

In the spiral method and the step-over method, it is necessary to mechanically synchronize the rotation of the tube (1) and the movement of the welding torch (2), which requires a large gear box, and the rotation of the tube (1). It is necessary to install the rotation mechanism and welding equipment on the same bed. Therefore, the entire device becomes bulky and expensive.

In addition, the oscillation pitch of the welding torch R2+ is determined by the gear ratio of the gearbox and is fixed in stages, such as 6ta-9mm, 12m, etc., so the bead connection is not flat, and the welding conditions are adjusted to match the mechanical conditions. Because it is necessary, the tube (
1) There was a problem with the quality of the overlay on the inner surface of the tube (11) because it could not cope with changes in welding conditions when the material changed.

In addition, for pipes with an outer diameter of 200 mm or less, the spiral method or step-over method described above cannot be applied because the pipe diameter is small, and the linear welding method using plugged arc welding, which is performed by hand welding, is adopted. .

The straight line 9 method is a method in which a bead (3) is placed in the longitudinal direction of the inner surface of the tube (1) as shown in Figure 4, and then the next bead (3) is placed by shifting the bead width. .

According to this linear deposition method, since the welding torch is shifted by the bead width to perform internal deposition, there is a problem that the bead width cannot be completely controlled and unevenness is likely to occur on the bead surface. In addition, in the linear deposition method, since covered arc welding is performed, slag is generated, and it takes time to peel it off, and depending on the material, it may be difficult to peel it off, and the slag tends to become entangled. Furthermore, since this method is carried out by hand welding, the length of the pipe that can be overlaid is limited to the range that can be reached, and if a long tube is required, it is necessary to weld the inner surface of the pipe and weld it circumferentially. Moreover, there arises the problem that the number of man-hours increases and the straightness of the pipe deteriorates, resulting in an increase in deformation of the welded portion.

[Objective of the invention]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, it is an object of the present invention to provide a method for overlaying the inner surface of a pipe in which the swinging of a welding torch is controlled automatically.

[Summary of the invention]

The welding method for overlaying the inner surface of a tube according to the present invention uses a welding device that can vary the height of a welding torch provided at the tip of an elongated arm in order to control the arc voltage to keep the length of the welding arc constant. It is detected that the height displacement matches the reference value set in advance according to the bead height,
This is a method to obtain a smooth bead by reversing the welding torch to trace the end face of the sheave.

The reason why the swinging of the welding torch is controlled by detecting the height displacement of the welding torch in this invention is as follows.

When the welding torch (2) and filler wire (6) are swung as shown in the arrows as shown in Fig. 5 while controlling the arc voltage to keep the welding arc length constant, a bead (5) on the base metal (4) is formed. The height of the welding torch (2) increases according to the height of the welding torch (2), and the height displacement of the welding torch (2) and the welding torch (
When the oscillation of 2) is measured with a potentiometer, the waveform shown in FIG. 6 is obtained. In FIG. 6, the horizontal axis shows the time opening T and the vertical axis shows the potential e. In the figure, waveform e0 shows the oscillation waveform of the welding torch (2), and waveform em shows the waveform of the height displacement of the welding torch (2). As shown in the figure, there is a very good correspondence between the oscillation waveform eo of the welding torch (2) and the height displacement waveform em.

Therefore, while controlling the arc voltage, the welding torch (2
By detecting the height displacement of 1, the bead end face can be detected and the welding torch (2) can be swung.

[Example of invention]

7, 8 and 9 show one welding device used for carrying out the present invention, FIG. 7 is a front view, FIG. 8 is a plan view,
FIG. 9 is a sectional view taken along the line AA in FIG. 7. In the figure (7
) is an arm made of a long and thin tube with a welding torch (2) attached to the tip. (□□□ is the welding torch (2) where the arm (7) is attached and the shaft (9) made of trapezoidal screw
) is a holder that moves up and down.

aυ is a lifting motor that performs shear voltage control by rotating a shaft (9) through a gear group α. (13 is a swinging slider to which the above-mentioned lifting motor aυ etc. is fixed, and a swinging shaft consisting of a trapezoidal screw connected to swinging motor a3 (the welding torch (21) swings by the rotation of 141. a!9#i The guide tte is a raw slider equipped with a swing motor (13).
and nut αn. Nara) (17) is screwed onto the main shaft 08 made of a trapezoidal screw, and the rotation of the main shaft 0υ moves the slider <tS+ along the guide rail (11).t21 is the main motor with gear <211. The main shaft a81 is rotated via the clutch (22A) and the gear group (3) using a fast-forward motor.

Note that (C) is the nut that attaches the main shaft (18) to the bed (A). Using the welding device configured as described above, TrG welding is performed on the inner surface of the small diameter pipe (J) shown in Figure 10. When welding overlay on the pipe (
The main motor (2) is rotated by a rotating device (not shown).
is driven to automatically move the welding torch (2) in the direction of arrow B in the figure, while driving the oscillating motor to overlay a fixed width on the pipe (1). Thereafter, the welding torch (2) is oscillated to follow the end face of the bead (5) that has been overlaid, and the inner surface of the pipe (1) is continuously overlaid.

FIG. 11 shows a 70-chart when the welding torch (2) is oscillated. .

In step 101, confirm the swinging direction of the bath welding torch (2), and if the swinging direction of the welding torch (2) is in the direction of the previously built-up bead, the welding torch (2) shown in FIG. A height displacement 6A of the welding torch (2) is detected by a potentiometer (not shown) (step 102), and when this height displacement eA rises from the lowest potential to a reference potential ar set in advance according to the bead height, the welding torch (2) is When a reversal signal is detected (step 106), a predetermined time Tm seconds after that time (step 105), a swing stop command is issued (step 10).
6), and after the predetermined stop time TB has elapsed (step 107), the welding torch (2) is reversed (step 1).
00). If the welding torch (2) swings in the direction without the bead (5), a preset swing width W is detected (step 104) and the welding torch (2) is reversed.

〔Effect of the invention〕

This invention performs tactile welding on the inner surface of the tube in accordance with the through-bead end face described above, so the bead surface is extremely smooth and there are no undercuts or valleys in the bead overlap that were problems with manual welding. Non-destructive inspection after welding becomes easy. Furthermore, since the weld bead width and build-up thickness required for build-up welding can be selected more freely than in other welding methods, the optimum build-up conditions that match the specifications can be adopted. Furthermore, since the bead can be joined at any position, welding can be continued even if the arc breaks due to reasons such as on the welding side.

In addition, in this invention, since there is no need to synchronize the rotation of the welding torch with the rotation of the oscillating reciprocating tube, the device used is large and compact.
Light weight can be achieved and the price can be reduced.

Furthermore, since this invention swings the welding torch to follow the bead end surface, overlaying on the inner surface of the tube is performed automatically by TIG welding using inert gas, and can be applied to any material. In addition, since slag is not generated, slag entrainment and associated welding defects are eliminated, and stable build-up of high quality is possible.

Further, according to the present invention, since the welding torch can be oscillated by the welding device main body, the arm to which the welding torch is attached can be made elongated, and as a result, the inner diameter after internal filling can be reduced to 50 mm.
It is possible to internally weld pipes with a diameter as small as 1.0 m, and by using the inversion method, it is possible to weld pipes with a length of up to 1.2 m, which has a great effect on improving quality.

[Brief explanation of the drawing]

Figure 1 is a layout diagram of a pipe and welding torch when overlaying a pipe, Figure 2 is a schematic diagram of a bead made by the conventional spiral method, and Figure 3 is a Jl diagram of a bead made by a conventional step-over port.
[if diagram, H4 Zusha 1] (Schematic diagram of a build using the conventional straight line dust method, Figure 5 is a schematic diagram of bead formation by overlay welding, Figure 6 shows the height displacement and vibration of the welding torch. waveform diagram of motion,
7 to 9 are structural diagrams of a welding device used for carrying out the present invention, in which FIG. 7 is a front view, FIG. 8 is a plan view, and FIG. 9 is a sectional view taken along line A-A in FIG. FIG. 10 is a layout diagram of the bead and welding torch, and FIG. 11 is a 70-chart when the welding torch is oscillated in the embodiment of the present invention. (1)...Pipe, (2)...Welding torch, +31.
+5)...bead, (4)...base material, (7)...
Arm, (8)...Holder, (9)...Axis, (II
. (c)...Gear group, Uυ...lifting motor, (1z・
... Swinging slider, (13) ... Swinging motor, I...
・Swing axis, ASR...main sliver, wing...guide,
(17+...nut, (18)-...main axis, (to)...
...Guide rail, (澗...Main motor, (2υ...
Gear, Hl (22A)...Clutch, (2)...Fast forward simulator, (2e...Bed. Agent Patent Attorney Sanro Kimura Figure 1 - Figure 2 Figure 3 Figure 41! !5511 Figure 6 Figure 10

Claims (1)

[Claims] Arc 1. In order to control pressure, a welding device that can vary the height of a welding torch installed at the tip of a long and thin arm is used, and it is confirmed that the height displacement of the welding torch matches a reference value set in advance according to the bead straightness. A welding method for overlaying the inner surface of a tube, characterized in that the end face of the bead is traced by detecting the detection and reversing the welding torch.