JPH08108271A - Narrow groove butt welding method for fixed pipe - Google Patents

Abstract

(57) [Abstract] [Purpose] In narrow-butt butt welding of fixed pipes, the first layer,
Welding of laminated and final layers is performed while appropriately controlling welding conditions against changes in root gap, groove width and welding position. [Structure] In narrow groove butt welding of fixed pipes, the first layer single-sided welding is performed with the ceramic backing material, and the changes in the root gap, groove width and welding position are made according to the welding conditions stored in the database in advance. While adaptively controlling, welding of the first layer, lamination and final layer is performed. [Effect] Even if the root gap and the welding position change, a good back bead of the first layer welding is formed, and even if the groove width and the welding position change, excellent lamination and final layer welding are performed.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Butt welding of fixed pipes is carried out in a process consisting of first layer welding, laminated welding, and final layer welding which is finish welding. Welding by a weaving method of a welding torch is generally used for the final layer.

On the other hand, there is an invention of the present applicant disclosed in Japanese Patent Laid-Open No. 4-200975, which uses a high-speed rotary arc welding method for butt welding fixed pipes.

In the invention disclosed in the above publication, a narrow groove having a V-shaped bottom is formed at the abutting portion of the fixed tube, and a ceramic backing material is arranged on the rear surface of the groove of the fixed tube. The single-sided first layer welding is performed by a high-speed rotating arc welding method with an arc rotation speed of 10 to 150 Hz and an arc rotation diameter of 1 to 4 mm under conditions of a welding current of 300 A or more and a welding speed of 150 cm / min or more.

[0005]

The welding method using the weaving method described above has a poor welding efficiency because the welding torch is weaved. In addition, since the groove is a V groove, as the plate thickness of the fixed tube increases, the groove cross-sectional area increases and the required amount of deposited metal increases, so that the welding efficiency decreases.

Further, the root gap of the groove portion cannot avoid fluctuations in the circumferential position due to the groove alignment error and thermal deformation. However, in any of the above-mentioned conventional techniques, welding conditions corresponding to the fluctuations are also present. Since the control is not performed, there is a problem that the back bead is not formed due to insufficient penetration, or the back bead is excessive due to excessive penetration.

Further, since the welding conditions are not controlled even with respect to the fluctuation of the groove width, defects such as fusion failure on the groove wall side are likely to occur in the laminated welding, and the welding is not performed in the final layer welding. There is a problem that welding defects such as insufficient penetration at both ends, undercut (insufficient amount of deposited metal), and excessive or insufficient extra beads are likely to occur.

In butt welding of fixed pipes, the welding position changes from 0 o'clock to 6 o'clock on the timepiece display, downward welding at 0 o'clock position, vertical welding at 3 o'clock (9 o'clock) position, 6 o'clock position. The welding posture changes with upward welding, but since the welding conditions are not controlled accordingly, the setting range of the welding conditions is narrow and welding defects easily occur due to disturbance.

For this reason, the butt welding of fixed pipes largely depends on the skill of the welding operator, and automation is delayed.

In recent years, there has been a problem of lack of manpower for welding experts, and automation, non-skill and high efficiency of the welding work have been earnestly desired.

[0011]

[Means for Solving the Problems] The above-mentioned problem is that in forming the narrow groove on the butt end face of the fixed pipe and performing the narrow groove butt welding of the fixed pipe by gas metal arc welding, in the first layer welding, A ceramic backing material is brought into contact with the back surface of the narrow groove, and a high-speed rotating arc welding method with an arc rotation speed of 20 to 100 Hz and an arc rotation diameter of 1 to 4 mm is used. The current and voltage waveforms of the high-speed rotation arc are used as sensors. Welding torch height control and groove tracing control are performed by the arc sensor used, and the welding current is 150 to 500 A and the welding speed is 50 to 50% depending on the welding position and the route gap in advance.
From the optimum welding condition database set in the range of 300 cm / min, circumferential downward welding is performed while selecting welding conditions according to the welding position and the value of the root gap detected during welding. 2 to 6 arc rotation diameter
Using the high-speed rotary arc welding method changed to mm, while performing the welding torch height control and groove tracking control,
Welding current 150 ~ for each welding position and groove width
Circumferential downward welding while selecting welding conditions according to the welding position and groove width values detected during welding from the optimum welding condition database set at 400 A and welding speed range of 20 to 120 cm / min. In the final layer welding, while weaving the welding torch with the groove width center position obtained by the groove profile control in the laminated welding as the center of the weaving, by welding position and groove width in advance,
From the optimum welding condition database set in the range of welding current 80 to 200 A and welding speed 10 to 40 cm / min, the circumference is selected while selecting the welding conditions according to the welding posture and the value of the groove width detected during welding. This is solved by a narrow groove butt welding method for a fixed pipe, which is characterized by performing downward welding.

[0012]

[Function] In the first layer welding and the layered welding, by using the high-speed rotating arc welding method, the fusion failure of the groove wall surface peculiar to the narrow groove welding can be eliminated by the arc dispersion effect, so that the narrow groove can be used. Thus, the welding efficiency can be dramatically improved by reducing the amount of deposited metal.

In the first layer welding process, the high-speed rotary arc welding method is used to perform the welding torch height control and the groove tracking control by the arc sensor, and at the same time, the welding attitude and the route gap are determined from the optimum welding condition database. By selecting the welding conditions according to the variation, a good first layer weld bead is formed on the entire circumference.

Also in the laminated welding process, the high-speed rotating arc welding method is used to perform the welding torch height control and the groove tracking control by the arc sensor, and to change the welding attitude and the groove width from the optimum welding condition database. By selecting welding conditions accordingly, a good laminated weld bead is formed on the entire circumference.

In the final layer welding step, the weaving welding method is used, and according to the variation of the welding position and the groove width,
By selecting welding conditions from the optimum welding condition database, a good final layer weld bead is formed on the entire circumference.

Further, since each welding process is performed by the downward welding, the molten pool moves smoothly and the welding efficiency is improved.

By using ceramics as the backing material, a high current can be used and the welding speed can be increased.

The arc rotation speed of the high-speed rotary arc welding method is set to 20 to 100 Hz. If it is less than 20 Hz, the arc heat and the arc force are not effectively dispersed, and if it exceeds 100 Hz, the opposite is true. This is because good welds cannot be obtained.

In the first layer welding process, the arc rotating diameter of the high speed rotating arc method is set to 1 to 4 mm.
This is because the arc disperses too much when it exceeds.

The reason why the arc rotating diameter of the high speed rotating arc method in the lamination welding process is set to 2 to 6 mm is that if the groove diameter is less than 2 mm, penetration of the groove wall surface cannot be obtained, and if it exceeds 6 mm, the arc is excessively dispersed. is there.

If the weaving speed of the weaving welding method in the final layer welding step is less than 5 mm / sec, the time to be located in the central portion of the groove becomes long and the molten metal flow easily occurs.
If it exceeds 0 mm / sec, the pressure and heat input of the arc will be excessively dispersed, and fusion defects will easily occur at both ends of the groove, so 5-40 mm / sec is preferable. Further, if the weaving width is less than 2 mm, defective fusion of both ends of the groove is likely to occur, and the welding bead width exceeding 6 mm is excessively large to easily cause molten metal flow, so that the weaving width is preferably 2 to 6 mm.

The height of the welding torch is controlled by the arc sensor in the above-mentioned first layer / lamination welding process so that the height of the welding torch is adjusted so that the average value of the welding current rotating at a high speed for each revolution coincides with the reference value. It is a control method. This allows
The weld bead height can be made uniform.

In addition, in the groove tracing control by the arc sensor, the left and right integrated values (average values) of the above-mentioned welding arc voltage rotating at high speed are compared, and the welding torch is adjusted so that the left and right integrated values become equal. This is a method of controlling the groove width direction position. This keeps the welding torch at the groove center position,
The welding line direction can be automatically followed.

In the final layer welding process, since the groove wall surface does not remain so much, it is difficult to control the groove profile by the arc sensor. Therefore, the central position of the groove width obtained by the groove profile control in the laminated welding process is stored. Then, by regenerating it as the center value of weaving and weaving the welding torch, the welding line direction can be automatically followed.

Regarding the detection of the welding posture, since the diameter of the fixed tube is known, the welding torch is measured by measuring the circumferential moving distance of the welding carriage running on the outer circumference of the fixed tube from the 0 o'clock position. The position of the clock face display can be known, and the welding posture can be detected.

The variation of the root gap or the groove width can be obtained by, for example, image-processing the root groove portion with a CCD camera or the like.

The welding conditions for each welding position and each groove root gap or each groove width are divided into the first layer welding, the layered welding and the final layer welding, and are obtained by experiments in advance and stored as an optimum welding condition database. .

The range of the welding current and welding speed in each welding process is limited for the following reasons.

If the initial layer welding current is less than 150 A, the penetration of the root portion tends to be insufficient, and a stable back bead is not formed. On the other hand, when it exceeds 500 A, the arc pressure becomes excessive and the back bead comes out too much, so that a good back bead is not formed.

The welding speed of the first layer is determined by the relationship with the above-mentioned welding current value. If the welding speed is less than 50 cm / min, the weld bead height becomes high and cracks are likely to occur. It is easy to occur. If it exceeds 300 cm / min, penetration will be insufficient due to insufficient heat input and a stable back bead will not be formed.

When the lamination welding current is less than 150 A, the penetration of the wall surface of the groove tends to be insufficient, fusion failure occurs and a stable back bead is not formed. On the other hand, when it exceeds 400 A, the arc pressure becomes excessively high and the weld bead is excessively produced, so that a good laminated bead is not formed.

The lamination welding speed is determined by the relationship with the above-mentioned welding current value. If it is less than 20 cm / min, the weld bead height becomes high and cracks easily occur, and in the vertical position, the welding bead drops. Cheap. If it exceeds 120 cm / min, penetration tends to be insufficient due to insufficient heat input, and stable laminated beads cannot be formed.

If the final layer welding current is less than 80 A, the penetration tends to be insufficient, and stable welding beads cannot be formed. On the other hand, if it exceeds 200 A, on the contrary, the arc pressure becomes excessively large, the weld bead is overexposed, the appearance of the weld bead is impaired, and the hardness of the weld metal becomes too high.

The final layer welding speed is determined by the relationship with the above-mentioned welding current value. If the welding speed is less than 10 cm / min, the weld bead height becomes high and cracks are likely to occur. It is easy to occur. If it exceeds 40 cm / min, penetration tends to be insufficient due to insufficient heat input, and stable finish weld beads cannot be formed.

As described above, in the present invention, the butt welding work of the fixed pipe is automated and highly efficient by adopting the narrow groove, using an appropriate welding method for each welding process, and implementing adaptive control during welding. , High quality is achieved.

[0036]

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 the narrow groove joint of the first layer weld portion in the butt welding of the fixed pipe of the present invention. In FIG. 1, 1 and 2 are a part of a fixed pipe, and the narrow groove 3 formed by the ends of the fixed pipes 1 and 2 has a root portion groove 3a of 75 ° at the bottom.
V-shaped with an angle θ _{1 of} ˜120 °. Further, a back groove 3b is provided on the back surface of the root groove 3a.

The root gap ΔG is abutted on the bottom so as to be 0, but the gap is unavoidable due to a setting error of the fixed pipes 1 and 2 and thermal deformation of welding.

Root portion groove angle θ ₁ is 75 ° to 120 °
The reason is that if it is less than 75 °, it is difficult to obtain sufficient penetration of the back bead, and if it exceeds 120 °, the back bead tends to come out too easily, which makes it difficult to respond to fluctuations in the route gap, and the arc sensor is used. This is because there is a risk of problems such as a decrease in detection sensitivity.

The reason why the root gap ΔG is not provided is that the groove alignment is easy and the groove alignment work can be performed in a short time.

WB indicates the width of the narrow groove, but it is preferably 5 mm or more in order to perform the laminated welding of the next layer well. For example, if the plate thickness of the fixed tubes 1 and 2 is 12 mm,
It is preferably about 5.5 mm.

The narrow groove 3 faces outward and is 1 ° to 2 ° on one side.
Has a taper angle θ ₂ . The reason for the tapered narrow groove is that the outer side of the narrow groove narrows due to heat contraction, so it is better to expand the outer side of the narrow groove beforehand according to the plate thickness and welding conditions. Because it will be done.

The root face r was 0 to 2 mm. Two
If it exceeds mm, a high welding current will result and it will be difficult to form a good back bead without defects. Therefore, it is desirable that the root face be close to zero.

CB is a ceramic backing material, which is supported by an internal clamp (not shown) on the back surface of the narrow groove 3 (inner surface of the tube), and is abutted while correcting the misalignment of the fixed tubes 1 and 2 to form a back bead. It has a forming groove CBa.

6 is a welding wire. The arc rotation speed is _{20 to} 10 in a shield gas atmosphere of 100% CO _2.
The first layer weld bead 4 is formed by rotating at high speed in the narrow groove 3 at 0 Hz and an arc rotation diameter D of 1 to 4 mm. The diameter of the welding wire 6 used 1.2 mm as an example.

FIG. 2 is a sectional view of the narrow groove joint of the laminated welded portion in the butt welding of the fixed pipe of the present invention. In FIG. 2, after the first layer welding bead 4 is formed in the narrow groove 3 of the fixed tubes 1 and 2, the welding wire 6 is arranged in the narrow groove 3,
In the same manner as the first layer welding, the arc rotation speed is _{20 to} 100 Hz, the arc rotation diameter D is 2 to 6 mm, the high speed rotation arc welding is performed and the laminated welding bead 5 is formed in the shield gas atmosphere of 100% CO _2. To be done. The diameter of the welding wire 6 used was 1.2 mm, which is the same as that of the first layer.

FIG. 3 shows the weaving locus of the welding torch in the final layer welding. WW is the weaving width, WT is the groove both ends stop time, and the slope WS is the weaving speed. The dotted line is the locus of the center of weaving. The center position of the groove width obtained by the arc sensor groove profile control during laminated welding of the previous layer is stored for each welding position, and it is reproduced as the center value of the weaving to weave the welding torch to perform welding. The line direction can be followed automatically.

FIG. 4 is a schematic side view of a welding apparatus used for welding the first layer, the laminated layer and the final layer in the butt welding of the fixed pipe of the present invention. In FIG. 4, a rotary arc torch 8, an angle control shaft 9 of the rotary arc torch 8, a height control of the rotary arc torch 8 are provided along a traveling rail 7 set on the outer peripheral surface of the fixed tube 2 to be butt-welded. A traveling bogie 12 having a shaft 10 and a groove-tracing control shaft 11 of the rotary arc torch 8 moves on the outer peripheral surface of the fixed pipe 2 and is circumferentially downward welded to form a single-side butt first layer of the fixed pipes 1 and 2. Weld, layer weld and final layer weld. CB is a ceramic backing material for the first layer welding, 13 is a welding wire feeder, and 14 is a welding wire reel. In the final layer welding,
The rotary arc torch 8 stops rotating, and the groove tracking control shaft 1
1 was driven to perform weaving welding.

Table 1 shows the range of welding conditions for the first layer. The ranges of the welding current and the welding speed for each welding position are 0:00 to 2:00, 2:00 to 4:00, and 4:00 to 6:00. . Actually, a database of further optimized welding conditions for each welding position and each root gap is stored.

[0050]

[Table 1]

Table 2 shows the range of the layered welding conditions, which is the range of the welding current and the welding speed for each welding position from 0:00 to 2:00, 2:00 to 4:00, and 4:00 to 6:00. Actually, a database of further optimized welding conditions for each welding position and groove width is stored.

[0052]

[Table 2]

FIG. 5 is a system diagram for controlling the welding conditions according to the above-mentioned welding posture and variation of the root gap or groove width according to the present invention.

In FIG. 5, 6 is a welding wire, 8 is a rotary arc torch, and 15 is a CCD camera. The image of the route gap or groove width from the CCD camera 15 is taken into the image memory 17 and routed by the CPU 16. The gap or groove width is calculated. The root gap or the groove width may be detected by a laser scanning method, a magnetic sensor, an eddy current sensor or the like, in addition to the method of processing the image of the CCD camera 15 described above.

Reference numeral 18 is a digital input / output circuit, and 19 is a welding control device which controls 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 welding conditions for each of the above-mentioned welding postures and root gaps or groove widths are preset, and 21 is a welding position detector for detecting the welding posture from the movement amount of the welding carriage. CPU1
6 calculates the root gap or groove width using the image memory 17 described above, and welds the welding position-specific data and root gap-specific data from the optimum welding condition database 20 via the digital input / output circuit 18. Output to the control device 19. Further, those controls are performed while timing is given by 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 23 denotes a welding line storage device for storing the center position of the groove width obtained at the time of layered welding for each welding position for controlling the welding line following in the final layer welding. Reference numeral 22 is a monitor TV.

Concrete welding conditions of the embodiment of the present invention are as follows. (1) Fixed tube outer diameter: 900 mm (2) Fixed tube plate thickness: 12 mm (3) Groove shape Root groove θ ₁ : 90 ° Back groove: Width 2 mm, depth 1 mm Root face: 1 mm Taper θ ₂ : 2 ° Groove width WB: 5.5 mm (4) Backing material: Ceramics (5) High-speed rotation arc welding method (first layer welding, laminated welding) Arc rotation speed: 20 to 100 Hz Arc rotation diameter: First layer ... 1 to 4 mm: Stacking ... 2 to 6 mm Arc sensor: Welding torch height control, groove profile control (6) Weaving welding method (final layer welding) Weaving speed: 5 to 40 mm / sec Weaving width: 2 to 6 mm (7 ) welding wire: solid type (8) welding wire diameter: 1.2 mm (9) shield gas: CO ₂ 100% (10) welding current: initial layer · 150～500A: stacking · 150 00A: final layer · 80~200A (11) Welding Speed: initial layer ·· 50~300cm / min: laminated ·· 20~120cm / min: final layer · 10 to 40 cm / min

Under the above welding conditions, first, the root face portion r of the narrow groove 3 was melted at once by the high-speed rotary arc welding method to form the back bead, and the fixed tubes 1 and 2 were formed. From 0 o'clock at the upper position to 6 o'clock at the bottom,
The entire circumference butt first layer welding of the fixed tubes 1 and 2 was performed by downward welding in which the circumference was divided into right and left halves.

Then, by downward welding in which the circumference was divided into left and right halves, laminated welding was performed on the first layer welding beads by a high-speed rotary arc welding method.

Finally, the final layer welding was performed by weaving a welding torch on the laminated welding beads by downward welding in which the circumference was divided into left and right halves.

[0060]

As described above, the present invention has the following effects. Since the initial layer welding and the layered welding are performed by the high-speed rotary arc welding method, the penetration of the groove wall surface is good, so that the defect of fusion failure does not occur. By using a narrow groove, the amount of deposited metal is small and highly efficient welding is performed. Even if the welding posture and groove root gap or groove width change, appropriate welding conditions are automatically selected according to the change value and welding is performed from the first layer welding to the final layer welding. In layer welding, a good back bead is obtained,
In the laminating and final layer welding, good penetration of the groove side wall can be obtained corresponding to the variation of the groove width, the welding quality is improved, and a special skill worker requiring skill is not required. Since ceramic is used for the backing material, high current can be used and welding speed can be increased.

[Brief description of drawings]

FIG. 1 is a sectional view of a narrow groove joint of a first layer weld portion in a narrow groove butt welding of a fixed pipe of the present invention.

FIG. 2 is a sectional view of a narrow groove joint of a laminated welded portion in the narrow groove butt welding of the fixed tube of the present invention.

FIG. 3 is a weaving locus diagram of the welding torch of the final layer welding in the narrow groove butt welding of the fixed tube of the present invention.

FIG. 4 is a schematic side view of a welding apparatus used for welding the first layer, the laminated layer, and the final layer in the butt welding of the fixed pipe of the present invention.

FIG. 5 is a control system diagram for controlling welding conditions in accordance with a variation of a welding posture and a root gap or a groove width according to the present invention.

[Explanation of symbols]

1 Fixed pipe 2 Fixed pipe 3 Narrow groove 4 First layer weld bead 5 Multilayer weld bead FB Final layer weld bead CB Ceramic backing material 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 Rotary arc torch 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 control device 20 Optimal welding condition database 21 Welding position detector 22 Monitor TV 23 Welding line memory WB Narrow groove width θ ₁ Root groove angle θ ₂ Narrow groove taper angle ΔG Root gap r Root face

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B23K 9/127 507 D 8315-4E 9/173 D 8315-4E

Claims (1)

[Claims] 1. When forming a narrow groove on the butt end surface of a fixed tube and performing narrow groove butt welding of the fixed tube by gas metal arc welding, in the first layer welding, a ceramic backing is applied to the back surface of the narrow groove. Abutting the material, the arc rotation speed is 20 to 10
The welding torch height control and the groove tracking control are performed in advance by using an arc sensor that uses the current and voltage waveforms of the high-speed rotating arc as a sensor, using a high-speed rotating arc welding method of 0 Hz and an arc rotating diameter of 1 to 4 mm. Welding current 150 to 50 depending on welding position and root gap
Circumferential downward welding is performed while selecting welding conditions according to the welding position and root gap value detected during welding from the optimum welding condition database set at 0 A and welding speed of 50 to 300 cm / min. In laminated welding, the high-speed rotary arc welding method in which the arc rotary diameter is changed to 2 to 6 mm is used to perform the welding torch height control and the groove profile control, and according to the welding posture and the groove width in advance. , Welding current 150-400A, welding speed 20-120
From the optimum welding condition database set in the range of cm / min, downward welding around the circumference is performed while selecting welding conditions according to the welding position and the value of the groove width detected during welding. Weaves the welding torch with the center of the groove width obtained by the groove profile control in the laminated welding as the center of the weaving. The welding current is 80 to 200 A and the welding speed is 10 in advance for each welding position and groove width. From the optimum welding condition database set in the range of up to 40 cm / min, circumferential downward welding is performed while selecting welding conditions according to the welding position and the value of the groove width detected during welding. Narrow groove butt welding method for fixed pipes.