JP3166512B2 - Narrow butt welding method for fixed pipe - Google Patents

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 tubes.

[0002]

2. Description of the Related Art Butt welding of fixed pipes is performed in a process consisting of initial layer welding, lamination welding, and final layer welding, which is finish welding. Welding of the welding torch by the weaving method is generally used for the last layer.

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

In the invention disclosed in the above-mentioned 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 back surface of the groove of the fixed tube. The single-layer 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 at a welding current of 300 A or more and a welding speed of 150 cm / min or more.

[0005]

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

Further, the root gap at the groove portion is inevitably fluctuated in the circumferential position due to an error in groove alignment and thermal deformation. Is not controlled, there is a problem that the back bead is not formed due to insufficient penetration, or the back bead is excessively projected due to excessive penetration.

Further, since the welding conditions are not controlled with respect to the variation of the groove width, defects such as poor fusion at the groove wall side are liable to occur in lamination welding. There is a problem that welding defects such as insufficient penetration at both ends of the tip, undercut (insufficient amount of deposited metal), and excessive or insufficient extra beads are likely to occur.

In the butt welding of fixed pipes, the welding position changes from 0 o'clock to 6 o'clock on a clock face display, downward welding at 0 o'clock position, vertical welding at 3 o'clock position (9 o'clock), and 6 o'clock position. In this case, the welding posture changes in the upward welding, but the welding conditions are not controlled correspondingly, so that the setting range of the welding conditions is narrow, and welding defects easily occur due to disturbance.

For these reasons, butt welding of a fixed pipe largely depends on the skill of a welding operator, and automation is delayed.

In recent years, there is also a problem of a shortage of skilled welding personnel, and there is a strong demand for automation, non-skilling and high efficiency of the welding operation.

[0011]

SUMMARY OF THE INVENTION The above-mentioned object is to form a narrow groove on the butt end face of the fixed pipe and perform the narrow groove butt welding of the fixed pipe by gas metal arc welding. A ceramic backing material is brought into contact with the back surface of the narrow groove, using 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. The current and voltage waveform of the high-speed rotating arc are used as sensors. Welding torch height control and groove tracking control are performed by the arc sensor used, and a welding current of 150 to 500 A and a welding speed of 50 to
Circumferential downward welding is performed while selecting welding conditions from the optimum welding condition database set in the range of 300 cm / min according to the welding posture and the value of the root gap detected during welding. Arc rotation diameter 2-6
mm, using the high-speed rotating arc welding method, while performing the welding torch height control and groove tracking control,
Welding current is 150 ~ in advance for each welding position and groove width.
Circumferential downward welding is performed while selecting welding conditions from the optimum welding condition database set at 400 A and a welding speed of 20 to 120 cm / min according to the values of the welding posture and the groove width detected during welding. In the final layer welding, the arc rotation speed is 1 to 10 Hz and the arc rotation diameter is 1 to 3 m.
m, the welding arc is rotated around the center of the groove width obtained by the groove profiling control in the lamination welding as a rotation center. ~ 300A, welding speed 3
From the optimal welding condition database set in the range of 0 to 120 cm / min, circumferential downward welding is performed while selecting welding conditions according to the values of the welding position and groove width detected during welding. And a narrow groove butt welding method for the fixed pipe.

[0012]

[Function] In the first layer welding and the lamination welding, the high-speed rotating arc welding method is used to eliminate the poor fusion of the groove wall surface peculiar to narrow groove welding due to the arc dispersion effect, so that narrow grooves can be used. Thus, a drastic improvement in welding efficiency can be achieved by reducing the amount of deposited metal.

[0013] In the first layer welding process, the high-speed rotating arc welding method is used to control the welding torch height and the groove tracing control using an arc sensor. By selecting the welding conditions according to the variation, a good initial layer weld bead is formed over the entire circumference.

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

In the lamination welding process, the high-speed rotating arc welding method is used to control the welding torch height and the groove copying control using an arc sensor, and to change the welding posture and the groove width from the optimum welding condition database. By selecting welding conditions accordingly, a good laminated weld bead is formed over the entire circumference.

In the final layer welding step, a rotary arc welding method is used, and a welding condition is selected from an optimum welding condition database according to a change in a welding position and a groove width, so that a good final layer is formed over the entire circumference. A weld bead is formed.

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

The reason why the arc rotation speed of the high-speed rotating arc method in the initial layer welding process is set to 20 to 100 Hz is that 20H
If it is less than z, arc heat and arc power will not be effectively dispersed, and if it exceeds 100 Hz, the reverse will occur, and a good weld cannot be obtained. In addition, the arc rotation diameter is 1
The reason for setting the thickness to ４4 mm is that if it is less than 1 mm, the function as an arc sensor cannot be obtained, and if it exceeds 4 mm, the arc is too dispersed.

The reason why the arc rotation speed of the high-speed rotating arc method in the lamination welding process is set to 20 to 100 Hz is that 20H
If it is less than z, arc heat and arc power will not be effectively dispersed, and if it exceeds 100 Hz, the reverse will occur, and a good weld cannot be obtained. In addition, the arc rotation diameter is 2
The reason for setting the thickness to 〜6 mm is that if it 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.

The reason why the arc rotation speed of the rotary arc welding method in the final layer welding process is set to 1 to 10 Hz is that if it is less than 1 Hz, the time of being located at the center of the groove becomes longer and the flow of the molten metal easily occurs, and exceeds 10 Hz. This is because the pressure and heat input of the arc are excessively dispersed, so that poor fusion is likely to occur at both ends of the groove. Also, the arc rotation diameter is 1-3mm
The reason for this is that if it is less than 1 mm, poor fusion at both ends of the groove is likely to occur, and if it exceeds 3 mm, the arc is excessively dispersed.

The control of the height of the welding torch by the arc sensor in the first layer and the lamination welding process described above is performed by adjusting the height of the welding torch so that the average value of the welding current rotating at a high speed per one rotation matches the reference value. How to control. This allows
The height of the weld bead can be made uniform.

The groove tracking control by the arc sensor compares the integrated value (average value) on the left side and the right side of the welding arc voltage rotating at high speed, and adjusts the welding torch so that the integrated values on the left and right become equal. This is a method for controlling the position in the groove width direction. This keeps the welding torch at the center of the groove width,
The welding line direction can be automatically followed.

In the final layer welding process, since there is not much groove wall left, it is difficult to control the groove tracing by the arc sensor. Therefore, the center position of the groove width obtained by the groove tracing control in the lamination welding process is stored. In addition, by rotating the arc with the rotation as the center of rotation, the welding line direction can be automatically followed.

As for the detection of the welding posture, the diameter of the fixed pipe is known, so that the distance from the 0 o'clock position of the welding bogie traveling on the outer circumference of the fixed pipe is measured to determine the welding torch. The position of the clock display can be known, and the welding posture can be detected.

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

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

The range of the welding current and welding speed in each welding step was 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, if it exceeds 500 A, on the contrary, the arc pressure becomes excessive, the back bead becomes excessive, and a good back bead is not formed.

The initial layer welding speed is determined by the relationship with the above-mentioned welding current value. If the welding speed is less than 50 cm / min, the height of the weld bead becomes high and cracks easily occur. Easy to occur. When it exceeds 300 cm / min, insufficient penetration tends to occur due to insufficient heat input, and a stable back bead is not formed.

If the lamination welding current is less than 150 A, the penetration of the groove wall surface tends to be insufficient, resulting in poor fusion and the formation of a stable back bead. On the other hand, if it exceeds 400 A, the arc pressure becomes excessively large, so that the weld bead becomes excessive, and a good laminated bead cannot be formed.

The lamination welding speed is determined by the relationship with the aforementioned welding current value. If the welding speed is less than 20 cm / min, the weld bead height increases and cracks are liable to occur. Cheap. If it exceeds 120 cm / min, the penetration will be insufficient due to insufficient heat input, and a stable laminated bead will not be formed.

If the final layer welding current is less than 200 A, penetration tends to be insufficient, and a stable welding bead is not formed. On the other hand, if it exceeds 300 A, the arc pressure becomes excessively large, and the weld bead is excessively formed, so that the beauty 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 30 cm / min, the weld bead height increases and cracks easily occur. Easy to occur. If it exceeds 120 cm / min, insufficient penetration tends to occur due to insufficient heat input, and a stable finish weld bead is not formed.

As described above, according to the present invention, the employment of a narrow groove, the use of an appropriate welding method for each welding step, and the execution of adaptive control during welding make it possible to automate and improve the efficiency of butt welding work of fixed pipes. , High quality is achieved.

[0035]

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 joint of a first layer welded portion in butt welding of a fixed pipe according to the present invention. In FIG. 1, reference numerals 1 and 2 denote a part of a fixed tube, and a narrow groove 3 formed by the ends of the fixed tubes 1 and 2 has a root groove 3a at the bottom at 75 °.
It has a V-shape with an angle θ _{1 of up} to 120 °. A back groove 3b is provided on the back surface of the root groove 3a.

The bottom portion is disposed in contact with the root gap ΔG so that the root gap ΔG becomes zero. However, a gap is inevitable due to a setting error of the fixed tubes 1 and 2 and thermal deformation of welding.

The root groove angle θ ₁ is 75 ° to 120 °
The reason is that if the angle is less than 75 °, sufficient penetration of the back bead is difficult to obtain, and if the angle exceeds 120 °, the back bead tends to be excessively formed, and it becomes difficult to cope with the fluctuation of the root gap, and the arc sensor is used. This is because there is a risk that a problem such as a decrease in detection sensitivity may occur.

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

Although WB indicates a narrow groove width, it is preferably 5 mm or more in order to perform lamination welding of the next layer satisfactorily. 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 is outwardly directed at 1 ° to 2 ° on one side.
Has a taper angle θ ₂ . The reason for using a tapered narrow groove is that the outside of the narrow groove becomes narrower due to heat shrinkage, so it is better to expand the outside of the narrow groove in advance according to the plate thickness and welding conditions. Because it can be done.

The root face r was 0 to 2 mm. 2
If it exceeds mm, it becomes difficult to form a good back bead without a defect due to a high welding current. Therefore, it is desirable that the root face is close to zero.

Reference numeral CB denotes a ceramic backing material, which is supported by an internal clamp (not shown) on the back surface (on the inner side of the tube) of the narrow groove 3 and is brought into contact with the fixed tubes 1 and 2 while correcting misalignment. It has a forming groove CBa.

Reference numeral 6 denotes a welding wire. Under a 100% CO ₂ shielding gas atmosphere, the arc rotation speed is 20 to 10
At 0 Hz, the arc rotation diameter D is 1 to 4 mm, and the inside of the narrow groove 3 is rotated at high speed to form the first layer weld bead 4. The diameter of the welding wire 6 was, for example, 1.2 mm.

FIG. 2 is a sectional view of a narrow groove joint of a laminated welded portion in butt welding of a fixed pipe according to the present invention. In FIG. 2, after an initial layer welding bead 4 is formed in the narrow groove 3 of the fixed pipes 1 and 2, a welding wire 6 is arranged in the narrow groove 3.
In the same way as the first-layer welding, a high-speed rotating arc welding is performed in a 100% CO ₂ shielding gas atmosphere at an arc rotation speed of _{20 to} 100 Hz, an arc rotation diameter D of 2 to 6 mm, and a laminated weld bead 5 is formed. Is 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 is a schematic side view of a welding apparatus used for welding the first layer, the lamination, and the last layer in the butt welding of fixed tubes according to the present invention. 3, a rotary arc torch 8, an angle control shaft 9 of the rotary arc torch 8, and a height control of the rotary arc torch 8 along a running rail 7 set on the outer peripheral surface of the fixed pipe 2 to be butt-welded. While the traveling carriage 12 having the shaft 10 and the groove tracing control shaft 11 of the rotary arc torch 8 moves on the outer peripheral surface of the fixed tube 2, the first layer of the single-sided butting of the fixed tubes 1 and 2 by circumferential downward welding Perform welding, lamination welding and final layer welding. CB is a ceramic backing material at the time of initial layer welding, 13 is a welding wire feeder, and 14 is a welding wire reel.

Table 1 shows the range of the initial layer welding conditions, that 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, the database is further divided into optimal welding conditions for each welding position and each route gap.

[0048]

[Table 1]

Table 2 shows the range of the lamination welding conditions, that is, the range of the welding current and the welding speed for each welding posture from 0:00 to 2:00, 2:00 to 4:00, and 4:00 to 6:00. Actually, the database is further divided into optimal welding conditions for each welding position and each groove width.

[0050]

[Table 2]

FIG. 4 is a system diagram for controlling welding conditions in accordance with the above-described changes in the welding position and root gap or groove width according to the present invention.

In FIG. 4, reference numeral 6 denotes a welding wire, 8 denotes a rotating arc torch, 15 denotes a CCD camera, and an image of a root gap or a groove width from the CCD camera 15 is taken into an image memory 17, and the CPU 16 executes a rooting operation. A 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.

Numeral 18 denotes a digital input / output circuit, and numeral 19 denotes a welding control device for controlling welding conditions of the rotary arc torch 8 and the welding wire 6. Reference numeral 20 denotes an optimal welding condition database in which welding conditions for each of the above-described welding positions and for each of the root gap or the groove width are preset, and reference numeral 21 denotes a welding position detector for detecting a welding position based on the amount of movement of the welding carriage. CPU1
6 calculates the root gap or the groove width using the above-mentioned image memory 17 and welds the data for each welding position and each root gap from the optimum welding condition database 20 via the digital input / output circuit 18. Output to the control device 19. In addition, these controls are performed while taking timing by a signal from the welding position detector 21. As another method for detecting the welding posture position, there is a method of detecting the position using an inclinometer. Reference numeral 23 denotes a welding line storage device that stores the center position of the groove width obtained at the time of lamination welding for each welding posture for welding line tracking control in final layer welding. Reference numeral 22 denotes a monitor TV.

The specific welding conditions in 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: 5.5mm (4) Backing material: Ceramics (5) High-speed rotating arc welding method (first layer welding, lamination welding) Arc rotation speed: 20 to 100Hz Arc rotation diameter: first layer ... Arc sensor: Welding torch height control, groove tracking control (6) Rotating arc welding method (final layer welding) Arc rotation speed: 1-10 Hz Arc rotation diameter: 1-3 mm ( 7) Welding wire: solid type (8) Welding wire diameter: 1.2 mm (9) Shielding gas: 100% CO ₂ (10) Welding current: first layer 150-500A: lamination 150-400A : Final layer · 200 to 300 A (11) Welding speed: Initial layer · · 50 to 300 cm / min: Lamination · · 20 to 120 cm / min: Final layer · 20 to 120 cm / min

Under the above welding conditions, first, the root face r of the narrow groove 3 is melted at a time by the high-speed rotary arc welding method to form the back bead while the back pipe is formed. From the upper position of 0 o'clock to the lower position of 6 o'clock,
By downward welding in which the circumference was divided into right and left halves, the first circumferential layer butt welding of the fixed pipes 1 and 2 was performed.

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

Finally, the final layer welding was performed on the laminated welding bead by rotary arc welding by downward welding in which the circumference was divided into right and left halves.

[0058]

As described above, the present invention has the following effects. Since the initial layer welding and the lamination welding are performed by the high-speed rotating arc welding method, the penetration of the groove wall is good, so that defects of poor fusion do not occur. By using a narrow groove, welding with a small amount of deposited metal and high efficiency is performed. Even if the welding position and groove root gap or groove width change, appropriate welding conditions are automatically selected according to the change values, and welding is performed from the first layer welding to the last layer welding. Good back bead is obtained in layer welding,
In lamination and final layer welding, a good penetration of the groove side wall corresponding to the variation of the groove width can be obtained, and the welding quality is improved, and a special skill worker who requires skill is not required. Since ceramic is used for the backing material, a high current can be used, and the welding speed can be increased.

[Brief description of the drawings]

FIG. 1 is a sectional view of a narrow groove joint of an initial layer welded portion in a narrow groove butt welding of a fixed pipe according to the present invention.

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

FIG. 3 is a schematic side view of a welding apparatus used for welding the first layer, the lamination, and the last layer in the butt welding of the fixed pipe according to the present invention.

FIG. 4 is a control system diagram according to the present invention for controlling welding conditions in response to variations in the welding position and the root gap or groove width.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fixed pipe 2 Fixed pipe 3 Narrow gap 4 Initial layer welding bead 5 Laminated welding bead FB Final layer welding bead CB Ceramic backing material 6 Welding wire 7 Running rail 8 Rotating arc torch 9 Angle control axis of rotating arc torch 10 Rotating arc Torch height control axis 11 Rotating arc torch groove tracking control axis 12 Traveling trolley 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 monitors TV 23 welding line memory WB narrow groove width theta ₁ root portion included angle theta ₂ narrow groove taper angle ΔG root gap r root face

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI B23K 9/173 B23K 9/173 D (56) References JP-A-4-200975 (JP, A) JP-A-59-70474 ( JP, A) JP-A-59-232671 (JP, A) JP-A-63-252671 (JP, A) JP-A-2-70384 (JP, A) JP-A-56-141971 (JP, A) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) B23K 9/095 B23K 9/028 B23K 9/035 B23K 9/12 B23K 9/127 B23K 9/173

Claims (1)

(57) [Claims] When a narrow groove is formed at a butt end face of a fixed pipe and the narrow groove is butt-welded to the fixed pipe by gas metal arc welding, a ceramic backing is provided on the back surface of the narrow groove in the first layer welding. Material is abutted and the arc rotation speed is 20 to 10
Using a high-speed rotating arc welding method of 0 Hz and an arc rotating diameter of 1 to 4 mm, a welding torch height control and a groove copying control are performed by an arc sensor using a current and a voltage waveform of the high-speed rotating arc as sensors, and Welding current of 150 to 50 by welding position and root gap
0A, from the optimum welding condition database set at a welding speed of 50 to 300 cm / min, perform circumferential downward welding while selecting welding conditions according to the welding posture and root gap value detected during welding. In the multilayer welding, the high-speed rotating arc welding method in which the arc rotating diameter is changed to 2 to 6 mm is used, and the welding torch height control and the groove profiling control are performed. , Welding current 150-400A, welding speed 20-120
Circumferential downward welding is performed while selecting welding conditions from the optimum welding condition database set in the range of cm / min according to the values of the welding position and groove width detected during welding, and performing the final layer welding. Uses a rotary arc welding method with an arc rotation speed of 1 to 10 Hz and an arc rotation diameter of 1 to 3 mm, and rotates the welding arc around the center position of the groove width obtained by the groove copying control in the lamination welding as a rotation center. Along with
Welding current 200 ~ in advance for each welding position and groove width
Circumferential downward welding is performed while selecting welding conditions from the optimum welding condition database set at a welding speed of 300 A and a welding speed of 30 to 120 cm / min according to the values of the welding position and the groove width detected during welding. A narrow groove butt welding method for a fixed pipe, which is performed.