JPS5970480A - One-side butt welding method of pipe by inert gas tungsten arc welding - Google Patents

Abstract

PURPOSE:To form a bead having no defect such as lack of penetration or the like by detecting the quantity of the light radiated from the weld zone in the 1st layer while welding the groove of butted pipes under weaving without feeding a wire in the stage of welding the 2nd layer in the groove thereby controlling the welding of the 2nd layer so that the detected quantity of light attains the set quantity of light. CONSTITUTION:The groove 2 of butted welding pipes 1, 1' is welded at the root pass by ordinary TIG welding. The 2nd layer is welded while a nonconsumable electrode 5 is weaved without feeding a wire 7. The radiant light emitted from the weld zone in the 1st layer heated by the arc of the 2nd layer is detected with a photoelectric photodetector 22 provided to a backing strip 10. At least one among welding current value, welding speed and the number of weaving of the electrode 5 are controlled during welding so that the quantity of the radiant light attains a preset reference quantity of light.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for butt single-sided welding of pipes by inert gas tungsten arc welding (hereinafter referred to as T-work G welding).

Conventionally, for single-sided butt welding of pipes made of stainless steel, nickel alloy steel, etc., a welding machine and a backing metal are synchronized along the groove of the pipe to be welded, whose end faces are butted and fixedly arranged. While moving, the welding machine generates an arc between the non-consumable electrode and the pipe to be welded in an inert gas atmosphere, and feeds the filler wire into the arc or into the molten weld metal. Then, the groove is welded in multiple layers.
IG welding was used.

This TIG welding method has the advantage of being able to automatically weld in vertical, upward, and downward tilted positions, but in the case of upward position welding during first layer welding, as shown in Figure 1. , the surface bead 3 of the weld formed in the groove 2 between the welded pipes 1, 1' becomes smooth, but a good bead 4 is formed at a position below the inner surface of the welded pipes 1, 1'. There was a problem.

In order to make the back bead 4 higher than the inner surface of the pipes 1, 1' to be welded, it is sufficient to increase the amount of filler wire fed into the arc or into the molten metal, but if the amount of filler wire fed is increased, As shown in FIG. 2, the front bead 3 begins to sag significantly, and if lamination is continued in this state, defects such as poor fusion may occur.

Conventionally, after welding the first layer, the protrusions caused by the sagging of the front bead 3 were ground down using a grinder, etc., and the second and subsequent layers were laminated after being formed into a flat shape, which resulted in a decrease in work efficiency. In addition, there were interruptions in the work environment due to the generation of noise and dust.

``l - This invention 1 solves the above-mentioned problems and provides a method for butt single-sided welding of pipes by inert gas tungsten arc welding, which can always form a bead of uniform shape even if the welding position changes. .

The present inventors previously discovered that in gas-shielded arc welding of fixed tubes, the radiant light from the molten pool formed by the arc of the welding electrode on the inner surface of the fixed tube was detected using four light-receiving lights provided on the backing metal. We have developed a method to detect the backing metal using an element and use the detection signal to control the position of the backing metal.

Therefore, the inventors conducted further research and found that by controlling the amount of arc radiation from the molten pool to a preset amount in the above method, a bead with a uniform shape could be formed. .

The present invention has been made based on the above findings, and includes the steps of moving a welding machine and a backing metal synchronously along the groove of a pipe to be welded whose end surfaces are butted and fixedly arranged. Generate an arc between the non-consumable electrode and the pipe to be welded,
In the method for butt single-sided welding of a pipe by inert tungsten arc welding, in which a filler wire is fed into the arc or into the molten weld metal to weld the pre-raised groove in multiple layers, the second layer of the groove is welded. Sometimes, welding is carried out while riving the non-consumable electrode without feeding the wire into the arc or into the weld metal, and at the same time welding is carried out while the non-consumable electrode is riving, and the welding part of the first layer heated by the arc by the non-consumable electrode is welded. The amount of radiated light is detected by a photoelectric light receiving element provided on the backing metal, and the welding current value, welding speed, and number of times of riving of the non-consumable electrode are adjusted so that the amount of radiated light becomes a preset amount of light. Both are characterized by controlling one of them.

Next, this invention will be explained with reference to the drawings.

Fig. 3 is a longitudinal cross-sectional view of a TIG welded portion of a fixed tube showing an embodiment of the method of the present invention, Fig. 4 is a cross-sectional view taken along the line mm--m in Fig. 3, and Fig. 5 is an enlarged cross-sectional view of the backing metal portion. , FIG. 6 is a plan view as well. In the drawing, 1゜1' indicates a pipe to be welded = 4-liquid pipe which is arranged facing each other by forming a groove 2, and 5 indicates a pipe to be welded 1 by a drive device (not shown).
, 1' is a non-consumable electrode that moves along the groove 2 and generates an arc in the inert gas ejected from the nozzle 6 at the groove 2, and 7 is a filler wire that is fed into the arc or into the molten metal. , 8 are filler wire feeding rollers driven by a motor 9.

10 is a backing metal 1.11 is a shaft provided in the tube 1.1' along its axis; 12 is a rotating body fitted into the shaft 11 at a position corresponding to the groove 2; 10 is provided on a mounting seat 13 fixed to a rotating body 12 via a lateral movement mechanism 14 and a push-up mechanism 15, and a roller 1 is attached to the outer edge of the mounting seat 13.
6, the groove 2 should not touch the inner surface of the pipe to be welded 1゜1'.
It can be rotated freely along the inner surface. 17 is a motor for rotating the backing metal fixed to the shaft 11, and 18 is a pinion 19.
This is a ring gear formed integrally with the rotating body 12 for transmitting the rotation of the motor 17 to the rotating body 12 via the rotary body 12. Further, 20 is a clamp mechanism provided on the shaft 11 so as to clamp the rotating body 12 fitted into the shaft 11.

As shown in FIGS. 5 and 6, the backing metal 10 is provided with an ejection hole 21 for an inert shielding gas such as argon in the center, and a hole 21 for detecting radiant light from the formed weld bead. Photodiode, photodiode, photodiode, c
A light-receiving element 22 such as ds is placed on the front left side (F■, ) of the backing metal 10 with the arc generation point as the center in the direction of movement of the backing metal 10.
, front right side (FTL), rear left side (BL), and rear right side (Brt).

In this invention, when welding the groove 2 of the pipe to be welded 1.1' fixedly butted together while moving the non-consumable electrode 5, the filler wire 7, and the backing metal 10 in synchronization, In the first layer welding, an arc is generated between the non-consumable electrode 5 and the pipes 1, 1' to be welded by normal TIG welding,
Welding is performed by feeding filler wire 7 into the arc.

Next, the second layer is welded without feeding the filler wire 7 into the arc, while riving the non-consumable electrode 5, so as not to remelt the back bead formed in the first layer welding. At this time, the radiant light emitted from the welded part of the first layer heated by the arc of the second layer is detected by the photoelectric light receiving element 22 provided on the backing metal 10 and converted into an electric signal. As shown in the block diagram of FIG. A comparator 25 compares the amount of light with the reference light amount for obtaining the optimum storage depth set in . Then, the difference signal is inputted to at least one of the welding current controller 26, welding speed controller 27, and riping controller 28, and the welding current value,
At least one of the welding speed and the number of rivings is controlled.

That is, if the amount of arc radiation light is greater than the set value, at least one of the following measures is taken: lowering the welding current, increasing the welding speed, or increasing the Leibitz number of times.

On the other hand, if the amount of radiant light is smaller than the set value, at least one of the following measures is taken: increasing the welding current, decreasing the welding speed, or decreasing the number of rivings.

By doing this, the bead shape is as shown in Fig. 8.
The front bead 3 does not have a convex shape due to drooping, and the back bead 4 formed by the first layer welding can also maintain its normal shape.

In order to synchronously move the welding machine provided with the non-consumable electrode 5 and the filler wire 7 and the backing metal 10, the backing metal 10 directs the radiant light from the welded part heated and melted by the arc to the backing metal. Four light receiving elements 22 (F
'L), (Fn,), (BT,), (BR
), and the position of the backing metal 10 is controlled by the backing metal rotation motor 17 and the lateral movement mechanism 14 so that the radiated light is located near the center of the four light receiving elements. , can be easily done.

Next, the present invention will be explained using examples.

A stainless steel pipe with a wall thickness of 12.7 m and a diameter of 559
．． Welding was performed under the following conditions using a 4 ttrm tungsten electrode and injecting argon gas at 10 t/min as a shielding gas and argon gas' (HIOt/min) as a pack shielding gas.

1. First layer (1) Welding current -90~140A (current control) (2
) Welding voltage: 10cm constant (3) Welding speed near cm 1 minute constant (4) Wire feeding speed: 40~60crn/min (
5) Wibinda Ni Gyoununa 2, 2nd layer (1) Welding current: 80-120A (current control) (2
) Welding voltage = 10V constant (3) Welding speed controller M/min constant (4) Riving number: 20 to 60 times/min (number of times control) (5) Riving width: 4 mm constant (6
) Filler wire: Weld the first and second layers as described above without feeding, and from the third layer onwards, filler wire is welded in the same way as the first layer.As a result of welding while feeding, a bead There were no defects such as poor fusion, and an extremely good bead shape could be produced.

As described above, according to the method of the present invention, defects such as poor fusion occur regardless of the welding posture when welding the groove of the pipe to be welded whose end surfaces are butted and fixedly arranged. Excellent industrial effects such as welding with good bead shape are often achieved.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams showing the bead shape in the case of welding in an upward position during first layer welding, and FIG. 4 is a sectional view taken along the line l1l-III in FIG. 3, FIG. 5 is an enlarged sectional view of the backing metal portion, FIG. 6 is a plan view, and FIG. 7 is a block diagram of the method of the invention, and FIG. 81 FIG. 2 is an explanatory diagram showing a bead shape during welding according to the method of the present invention. In the drawings, 1.1'... Pipe to be welded 2... Groove 3... Front bead 4... Back bead 5
...Non-consumable electrode 6 ...Nozzle 7 ...Filler wire 8 ...Roller 9 ...Motor
10...Backing money 11...Axis 1
2...Rotating body 13...Mounting seat 14...
Full travel mechanism 15...Push-up mechanism 16...Roller 17...Motor 18...Ring gear 1
9...-nion 20...clamp mechanism 2]
...Shield gas outlet 22...Photoelectric light receiving element 23...Adder 24...
・Reference optical position setting device 25... Comparator 26... Welding current controller 27... Welding speed controller 28... Living controller Applicant: Natsuo Shioya, agent of Nippon Kokan Co., Ltd. (and 2 others) name) 11- 12-

Claims (1)

[Claims] Generating an arc between the non-consumable electrode and the welding tube while simultaneously moving the welding machine and the backing metal along the groove of the welding tube whose end surfaces are butted and fixedly arranged, In the method for butt single-sided welding of pipes by inert gas tungsten arc welding, in which a filler wire is fed into the arc or into the molten weld metal to weld the groove in multiple layers, when welding the second layer of the groove. , welding is performed while riving the non-consumable electrode without feeding the wire into the arc or into the weld metal, and radiation from the welded part of the first layer heated by the arc by the non-consumable electrode. The amount of light is detected by a photoelectric light receiving element provided on the backing metal, and the welding current value, welding speed, and at least the number of times of riving of the non-consumable electrode are adjusted so that the amount of radiated light becomes a preset amount of light. A method for butt single-sided welding of pipes using an inert gas tungsten arc welding section, characterized in that one side of the pipe is controlled.