JPH0866771A - Build up welding method in narrow gap butt welding of fixed tube - Google Patents

Abstract

PURPOSE: To improve quality of weld zone by adapting a narrow gap joint for groove and using high speed arc in the butt welding of fixed tubes so as to increase welding efficiency, to reduce thermal strain and to prevent generation of defect due to lack of fusion and run out. CONSTITUTION: A first pass welding bead is formed by butting fixed tubes 1, 2 each other in the narrow gap 3 having 5-10mm gap width GW. Next, a welding wire 6 is placed in the narrow gap, while using a gas metal arc welding method which is executed in carbonic acid shield atmosphere with high speed rotating arc having 20-100Hz and 2-6mm arc rotating diameter, a welding bead 5 is formed. Height control of a welding torch and gap copying control are executed by a arc sensor which uses an electric current and voltage wave form of high speed rotating arc for sensor. Further, the welding condition corresponding to detected values of welding position and gap width is selected from the data base of the optimum welding condition set beforehand to respective welding position and gap width, the build up circumferential welding is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated welding method for narrow groove butt welding of fixed pipes.

[0002]

2. Description of the Related Art In the laminated welding after the first layer welding in the narrow groove butt welding of a fixed pipe, the weld beads of the groove side wall and the front layer are sufficiently melted to secure a stable penetration and achieve uniform welding. It is important to ensure the bead height and form a good weld bead.

Conventionally, in the narrow groove butt lamination welding of the fixed pipe described above, welding is performed while weaving the welding torch with the V groove. However, in the groove alignment work of the fixed pipe, it is difficult to keep the groove width of the joint uniform, and it takes a lot of time for the groove alignment work. Further, the fluctuation of the groove width has been considered to be a cause of defects such as poor fusion on the groove wall side and poor fusion due to molten metal flow.

Further, in the conventional V-groove welding, the larger the wall thickness of the pipe, the larger the groove cross-sectional area. Therefore, the cross-sectional area of the welded joint, that is, the required welding amount is increased and the welding efficiency is improved. In addition, there is a problem that thermal deformation due to welding is large because the required welding amount is large.

[0005]

From the above-mentioned problems of the prior art, there has been proposed a welding method for reducing the amount of deposition by a so-called narrow groove welding method with a small groove cross-sectional area to achieve high efficiency. However, there was a problem that the groove width fluctuated due to the setting error between the fixed pipes, resulting in defective fusion of the groove wall surface during laminated welding. The occurrence of welding defects due to the fluctuation of the groove width is more sensitive in the narrow groove joint than in the V groove,
It was a problem.

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned problems, a narrow groove joint having a groove width of 5 to 10 mm by abutting fixed tubes to each other is constructed, and an arc rotation speed is provided under an atmosphere of a carbon dioxide gas shield. Is 20 to 100 Hz, and the arc rotation diameter is 2 to 6
mm welding using a gas metal arc welding method with a high-speed rotating arc and using an arc sensor that uses the current and voltage waveforms of the high-speed rotating arc as a sensor while performing height control and groove tracking control of the welding torch during welding. Detects the welding posture and groove width variation, selects welding conditions according to the detected values of the welding posture and groove width from the optimum welding condition database preset for each welding posture and groove width, and selects the multi-layer circle. This is solved by a laminated welding method in narrow groove butt welding of a fixed pipe, which is characterized by performing circumferential welding.

[0007]

In the laminated welding by the narrow groove butt welding of the fixed pipe according to the present invention, the control of the welding torch height and the groove tracing are performed by the high speed rotating arc type arc sensor system.
Welding proceeds while ensuring sufficient penetration of the groove wall surface by high-speed rotating arc welding.

[0008] In the layered welding, the downward welding is performed separately for the right half and the left half of the fixed tube. The lower limit of the groove width is set to 5 mm, because if it is less than this, laminated welding of the next layer will not be performed well, and if it is 10 mm or more, it becomes difficult to secure the penetration of the groove side wall. is there.

The groove of the laminated portion may have a narrow groove shape with no groove angle, but since the groove tends to narrow in the upper layer due to thermal deformation, an angle of 1 ° to 2 ° on one side is usually used. This is achieved by setting a narrow groove.

Further, in the above-mentioned butt lamination welding of the fixed pipe, when the welding posture changes, the welding posture change is detected, and the welding condition is automatically selected from the preset optimum welding condition database. Welding is performed.

Further, the value of the groove width is detected with respect to the variation of the groove width, and an appropriate welding condition is automatically selected from the preset optimum welding condition database according to the detected value to perform welding. Be seen.

In the above welding position, that is, the welding position detector, the diameter of the fixed pipe is known, and the distance of a half circumference from 0 o'clock to 6 o'clock can be calculated. Therefore, the half circumference distance is meshed with the rack of the traveling rail. It can be detected by the encoder of the welding carriage running.

Further, the groove width value is detected by, for example, C
The image of the groove width can be easily detected by image processing with a CD camera or the like.

The rotation speed of the high-speed rotating arc is 20
If it is less than 100 Hz, the arc heat and the arc force are not effectively dispersed, and if it exceeds 100 Hz, on the contrary, a good weld cannot be obtained.

The arc rotating diameter of the high-speed rotating arc is set to 2
The reason why it is set to ˜6 mm is that if it is less than 2 mm, the performance as an arc sensor may not be obtained, and the groove wall surface may cause fusion failure, and if it exceeds 6 mm, the arc is excessively dispersed.

The control of the height of the welding torch by the high-speed rotating arc sensor is a method of controlling the height of the welding torch so that the average value of the welding current rotating at a high speed for each rotation matches the reference value.

In the groove contour control, the groove contour control of the welding torch is carried out by comparing the left and right integral values of the above-mentioned welding arc voltage rotating at a high speed and keeping the left and right integral values constant. .

The optimum welding condition database is: welding current 150 to 400 A, welding speed 20 to 120 cm / min,
The weld bead thickness preferably uses a value in the range of 2 to 5 mm.

If the welding current is less than 150 A, the arc pressure will be insufficient, and the penetration will be reduced, so that the fusion of the groove wall surface will be apt to cause the fusion failure. If it exceeds 400, on the contrary, the arc pressure will be excessively large. , In particular, it becomes difficult to hold the molten metal in the vertical welding position, causing molten metal flow and dripping,
Good weld beads are not formed.

The welding speed is determined by the relationship with the above-mentioned welding current value, but at 20 cm / min or less, the weld bead height becomes high, and the flow of molten metal, dripping, and cracking are likely to occur. If it is 120 cm / min or more, the penetration of heat tends to be insufficient due to insufficient heat input, and stable weld beads cannot be formed.

When the weld bead thickness is less than 2 mm, the welding heat input is insufficient when the welding speed is too high, and insufficient penetration easily occurs in the narrow groove side wall.

When the weld bead thickness exceeds 5 mm, the molten metal in the molten pool cannot be held by the arc and a molten metal flow occurs, which is remarkable especially in the vertical position, and the molten metal thickness immediately below the arc is generated. Is too large, the bottom of the groove just below the arc is not sufficiently melted, and fusion failure occurs.

In the present invention, adaptive control of the welding parameters is performed according to the change of the welding posture and the change of the groove width.

The appropriate conditions for each welding position and groove width are as follows:
It is obtained by experiments in advance and stored as a welding condition program.

During lamination welding of the butt intermediate layers of the fixed pipe, the welding position detector changes the welding position by C
A change in groove width is detected by a method such as image processing by a CD camera, and a preset welding condition program is read out based on both values to perform adaptive control of welding conditions.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a narrow groove according to a laminated welding method in the narrow groove butt welding of a fixed tube of the present invention.

In FIG. 1, 1 and 2 are fixed pipes to be welded. 3 is a narrow groove, and the thickness of the fixed tubes 1 and 2 is 12 mm.
On the other hand, the groove width GW is 5.5 mm, and the shape has a taper θ of 1 ° to 2 ° outward.

The reason why the taper is provided above the narrow groove 3 is that when the first-layer weld bead 4 is formed in the groove, the first-layer weld bead 4 undergoes thermal contraction during solidification and the upper part of the groove becomes narrow. ,
Since the welding wire 6 is prevented from rotating during the layered welding of the present invention, the problem of heat shrinkage of the groove can be solved if the welding wire 6 is tapered at the above-mentioned angle.

After the first layer weld bead 4 is formed, the welding wire 6 is arranged in the narrow groove 3 and the arc rotation speed is 20 to 100 H under a shield gas atmosphere of 100% CO _2.
The laminated welding bead 5 is formed by high-speed rotary arc welding with z and a rotary diameter of 2 to 6 mm.

The diameter of the welding wire 6 is, for example, 1.
2 mm was used. The thickness of the weld bead 5 to be laminated is about 3 mm, and this value is the height of the welding layer to be laminated.

Here, the weld bead thickness H is the difference (H ₂ -H ₁ ) between the average thickness H ₁ of the weld bead before lamination and the average thickness H ₂ of the weld bead after lamination. The thickness of the weld bead is expressed as H = S ₀ / GW, where S ₀ (mm ² ) is the welding cross-sectional area and GW is the groove width.

Further, the welding cross sectional area S ₀ is the wire deposition rate Vf (mm ³ / min), the welding speed and Vz (mm / ^{_{min), S 0 (mm 2)}} = Vf (mm 3 / min) / Vz
(Mm / min).

Wire welding speed Vf (mm ³ / min)
Is Vf (mm ² ) where SW (mm ² ) is the wire cross-sectional area, vf (mm / min) is the wire feeding speed, and α is the welding efficiency.
³ / min) = α × vf (mm / min) × SW (mm ² ). The wire feeding speed vf (mm / min) is proportional to the welding current value, and at a welding current of 150 A, it is 3.92 mm / min.
Min, and at 400 A, it is 17.42 mm / min. As described above, the present invention determines the thickness of the weld bead and performs the layered welding.

FIG. 2 is a side view of the laminated welding apparatus in the narrow groove butt welding of the fixed tubes 1 and 2 of the present invention.

In FIG. 2, fixed pipe 2 to be butt welded.
Along a traveling rail 7 set on the outer peripheral surface of the rotary arc torch 8, an angle control shaft 9 of the rotary arc torch 8,
A traveling carriage 12 having a height control shaft 10 of the rotary arc torch 8 and a groove contour control shaft 11 of the rotary arc torch 8 goes around the outer periphery of the fixed pipe 2 while stacking butt intermediate layers of the fixed pipes 1 and 2. Weld. In addition, 13 is a welding wire feeder, and 14 is a welding wire reel.

Since the welding is butt lamination welding of the fixed tubes 1 and 2, the welding postures are downward welding at the 0 o'clock position of the arc start, vertical welding at the 3 o'clock position, upward welding at 6 o'clock, and temporary postures. Since welding is performed while changing, good welding cannot be performed unless the welding conditions are changed.

Table 1 shows 0:00 to 2:00, 2:00 to 4:00 and 4:00 to
It shows the condition range of welding current and welding speed up to 6 o'clock. In actual welding, the welding conditions are according to the welding position,
Welding conditions are databased by subdividing by groove width.

[0038]

[Table 1]

FIG. 3 is a control block diagram in the laminated welding of the intermediate layer in the narrow groove butt welding of the fixed pipe of the present invention. The welding conditions are controlled in accordance with the change of the welding posture and the change of the groove width. To do.

In FIG. 3, 6 is a welding wire, 8 is a rotary arc torch, and 15 is a CCD camera. The image of the groove width of the narrow groove from the CCD camera 15 is taken into the image memory 17, and the CPU 16 takes it. The groove width WG is calculated.
The groove width is not limited to the method of processing the image of the CCD camera 15 described above, but also the laser scanning method, the magnetic sensor,
A method of detecting with an eddy current sensor or the like may be used.

Reference numeral 18 is a digital input / output circuit, and 19 is a welding control device for controlling the welding conditions of the rotary arc torch 8 and the welding wire 6. Reference numeral 20 is an optimum welding condition database in which the optimum welding conditions are set for each of the above-mentioned welding postures and groove widths, and 21 is a welding position detector that detects the welding posture from the movement amount of the welding carriage. The CPU 16 calculates the groove width value using the image memory 17 described above, outputs the data for each welding position and groove width from the optimum welding condition database 20, and outputs the data to the welding controller 19 to the digital input / output circuit 18. , And the control thereof is performed by timing with a signal from the welding position detector 21. As the welding posture position detecting method, there is also a method of detecting with a inclinometer as another method. Reference numeral 22 is a monitor TV.

In the present invention, narrow groove butt lamination welding of fixed pipes was carried out in the following examples. (1) Fixed tube outer diameter: 900 mm (API5LX-60) (2) 〃〃 plate thickness: 12 mm (3) Groove shape Taper θ: 2 ° Groove width B: 5.5 to 7.5 mm (4) High speed Rotating arc Arc rotating speed: 20 to 100 Hz variable Arc rotating diameter: 3 to 5 mm Arc sensor: Welding torch height control, groove tracing control (5) Welding wire: Solid type (6) Welding wire diameter: 1.2 mm (7 ) Shielding gas: CO ₂ 100% (8) Welding current: 150 to 400 A (9) Welding speed: 20 to 120 cm / min

According to the present invention, the laminated welding of the narrow groove 3 joints is performed under the above-mentioned welding condition by dividing the fixed pipes 1 and 2 from the upper position of 0 o'clock to the lower part of 6 o'clock position into left and right half portions of the circumference. Downward welding was performed, and fixed pipes 1 and 2 were circumferentially butt laminated welded. Further, by rotating the arc at a high speed, the arc was dispersed in the narrow groove, so the surface of the weld bead was smoothed, and the wall surface of the narrow groove was well melted to prevent fusion failure.

[0044]

As described above, according to the present invention, in butt welding of fixed pipes, by adopting a narrow groove joint for the groove, it is possible to improve welding efficiency and reduce thermal strain.

Further, by performing arc sensor groove profile control by a high-speed rotating arc and adaptively controlling welding conditions corresponding to variations in welding posture and groove width, fusion failure and molten metal due to groove width variation can be achieved. Since it is possible to prevent the occurrence of defects due to flow and facilitate the alignment of the fixed pipe groove *, automation of butt welding of fixed pipes, de-skilling, and high quality welding can be achieved.

[Brief description of drawings]

FIG. 1 is a narrow groove cross-sectional view showing laminated welding in narrow groove butt welding of a fixed tube of the present invention.

FIG. 2 is a side view of the laminated welding device in the narrow groove butt welding of the fixed pipe of the present invention.

FIG. 3 is a control block diagram in layered welding in narrow groove butt welding of a fixed tube of the present invention.

[Explanation of symbols]

 1.2 Fixed pipe 3 Narrow groove 4 Laminated welding bead 5 First layer welding bead 6 Welding wire 7 Traveling rail 8 Rotating arc torch 9 Rotating arc torch angle control axis 10 Rotating arc torch height control axis 11 Rotating arc torch Narrow groove profile control axis 12 Traveling carriage 13 Welding wire feeder 14 Welding wire reel 15 CCD camera 16 CPU 17 Image memory 18 Digital input / output circuit 19 Welding controller 20 Optimal welding condition database 21 Welding position detector 22 Monitor TV B Narrow opening Tip width θ Narrow groove taper angle

Claims (1)

[Claims] 1. The width of the groove is 5 to 1 by abutting fixed tubes with each other.
A narrow groove joint having a diameter of 0 mm is formed, and a gas metal arc welding method using a high-speed rotating arc having an arc rotation speed of 20 to 100 Hz and an arc rotation diameter of 2 to 6 mm in an atmosphere of a carbon dioxide gas shield, and the high speed is used. The welding torch height control and groove profile control are performed by an arc sensor that uses the current and voltage waveforms of the rotating arc as a sensor, while detecting the welding posture and groove width variation during welding, and preliminarily identifying the welding posture. Narrow groove butt welding of fixed pipes characterized by performing multi-layer circumferential welding by selecting welding conditions according to the detected values of the welding posture and groove width from the optimum welding condition database set for each Welding method in.