JPS5837062B2 - Continuous overlay welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of continuously overlaying the inner surface of a substantially hemispherical body.

For example, pressure vessels for the chemical industry and pressure vessels for nuclear reactors, etc., tend to have various corrosion-resistant alloys welded overlay on their inner surfaces in order to cope with the high temperatures, high pressures, and even harsher corrosive environments in which they are used. .

Various welding methods are used for these build-up welds, but the submerged arc welding method using a strip electrode is superior in terms of welding efficiency.

The overlay welding method using a strip electrode is being adopted for overlay welding of the end plate of these pressure vessels, but since the inner surface of the end plate is a three-dimensional curved surface of a hemisphere, continuous automatic overlay welding has been long-awaited. Nevertheless, continuous automation using the strip electrode method was not possible.

Therefore, the only intermittent method for welding the inner surface of the end plate using a strip electrode is to weld in concentric circles, cut the arc after completing welding on one concentric circle, and reset the target position to the next concentric circle to weld. has been carried out.

In this method, welding defects occur at the discontinuous portions due to the discontinuation of welding, and this portion must be corrected.

Therefore, there has been a long-awaited continuous automation of end plate overlay welding using the strip electrode method in order to improve the quality and efficiency of welded parts.

The present invention relates to continuous automation of end plate overlay welding using this band electrode method.

By the way, in build-up welding, the overlap distance between one bead and the next bead is very important in order to avoid creating defects inside and on the surface of the overlapped portion.

Conventionally, in overlay welding of a hemisphere, the lap allowance was adjusted by visually observing the tip of the strip electrode to adjust the inclination of the hemisphere, making the adjustment extremely inaccurate and making continuous automation difficult. It was impossible.

In build-up welding in a concentric circle, when moving to the next concentric circle, as shown in FIG. Attempts have also been made to determine the movement angle Jθ by the product thereof.

However, when this so-called timer method is used, the movement angle and movement length P are determined by respectively, so the precision of the timer itself cannot be expected to be very high, and both 4θ and P are the relationship between speed N and time T. Since it is a product, accuracy cannot be expected.

The method of the present invention was developed in view of the above, and attempts to detect the angle of a substantially hemispherical body and determine the moving distance based on this angle.

In the method of the present invention, the inclination angle is constantly detected and the weld beads meet while rotating a substantially hemispherical body and sequentially performing automatic overlay welding in an arc shape and a partial spiral shape from the outer circumference to the inner circumference. At a previous predetermined time point, partial spiral welding is performed while moving and rotating the substantially hemispherical body by a preset angle in an arcuate direction in a vertical plane that includes the spherical center and the rotation axis, and then It is characterized by stopping in-plane movement and performing the next arcuate weld.

According to the present invention, it is possible to continuously automate the build-up welding of a hemisphere, and to precisely control the lap allowance, which is the lifeblood of build-up welding.

The wrap fee is the bead width minus the bead pitch.

In arc welding using a strip electrode, the bead width is equal to the strip electrode width.

Therefore, in order to control the lap allowance, it is sufficient to control the bead pitch.

The bead transfer on the inner surface of the hemisphere is performed by tilting the hemisphere.

In Fig. 1, the inclination angle Jθ for each time is is given by

In the formula, P represents the bead pitch. This lθ should be controlled accurately.

For this purpose, an angle detector is attached to the center of the tilt axis of the positioner that supports the hemisphere 1, and connected to an arithmetic control circuit.

At this time, Jθ is calculated and input using the above formula.

Alternatively, Jθ may be calculated by inputting P and D.

Welding is performed at the current inclination angle θ1, the inclination is started in response to the inclination command from Kira, and the inclination is continued until θ1-Jθ=θ2 is reached.

Since some angle detectors are highly accurate, Jθ can be made sufficiently accurate for welding.

There are two ways to give the inclination command depending on the build-up welding method:

However, although the second method is not preferable because it results in intermittent build-up as described above, it is possible to control the bead wrap distance more accurately than conventional visual inspection.

■ As shown in Fig. 2, after concentric build-up C1, partial spiral build-up S1, then concentric build-up C2, partial spiral build-up S2, etc.
When overlay welding is performed sequentially with
This is done by activating a limit switch, etc. attached to the rotary table of the positioner that rotates the positioner at a fixed point.

- Semi-automatic welding, that is, only concentric welding is performed automatically, and when the end point of the concentric welding is reached, the arc is cut and a tilting command is given by manual button operation to tilt the rotary table by Jθ.

Next, specific examples of the present invention will be explained based on FIGS. 3 to 10.

An overall view of the apparatus used to carry out the method of the present invention is shown in Figure 3, and an overall view of the welding positioner is shown in Figures 4 to 6.
They are shown in the figure.

This device mainly includes a positioner 30, a manipulator 5, a welding head 4, and a control device (not shown).

The positioner 30 includes a rotary table 3, an axle 23,
It is composed of a sector gear 6, an arm 7 and a frame 8.

A king pin (not shown) is fixed to the center of the table 3, and is supported by a flat bearing (not shown) attached to an axle 23.

When the rotation motor 9 attached to the axle 23 is driven, the coupling 10 and the rotation planetary gear reducer 11 are driven.
The pinion 13 is rotated via the rotational worm gear reducer 12, and the rotational gear 14 attached to the lower part of the table 3 meshes with the pinion 13, causing the table 3 to rotate around the shaft 2 of the king pin of the table. be done.

A sector gear 6 and an arm 7 are attached to both ends of the axle 23.

The arm 7 and the sector gear 6 are connected via a tilting pin 16,
They are respectively pivotally supported on the upper part of the frame 8.

When the tilting motor 17 is driven, the pinion 20 is rotated via the coupling 18 and the tilting reducer 19, and due to the rotation of the pinion 20 meshing with the sector gear 6, the table 3 is rotated through the sector gear 6 into the tilting pin. It is tilted around 16.

Furthermore, six types of workpiece holders 21 and six types of workpiece clamping jigs (not shown) are respectively attached to the upper surface of the table 3.

Furthermore, although not shown, a shaft encoder is attached to the end of the tilting pin 16 as a tilt angle detector, and a limit switch is attached to the axle 2 for detecting the tilt start position.
3, and its striker is attached to a rotating gear 14 at the bottom of the table 3.

The manipulator 5 can horizontally move, raise and lower, and rotate the boom by driving with an electric motor.

The welding head 4 is attached to the tip of the boom 22 of the manipulator 5, and is configured to feed a strip electrode to perform submerged arc welding.

During actual welding, the substantially hemispherical body 1 as the object to be welded has its spherical center aligned with the rotating shaft 2 of the rotary table 3 and the substantially hemispherical body 1.
The workpiece holder 21 and the clamping jig are aligned so that they coincide with the intersection with the center axis of the tilt pin 16 as the center axis of the tilt, and so that the table 3 and the end surface of the substantially hemispherical body 1 are parallel to each other. It is fixed on the table 3 using a tool.

The overlay welding is carried out in a concentric or arcuate shape from the outer circumference side to the inner circumference side of the substantially hemispherical body 1 (in FIGS. 8 and 9, for example, C1, C
2...Cn, Cn+1), and when moving to the adjacent inner concentric circle (for example, from C1 to C2 or from Cn to C
n+1) in a partially spiral manner (for example, S1...Sn).

Therefore, at the start of welding, the table 3 is tilted, and the boom 22 of the manipulator 5 is operated to create a substantially hemispherical shape.
The welding head 4 is positioned at a predetermined outermost circumferential position.

Here, the terms "outer circumferential side" and "inner circumferential side" refer to approximately hemisphere 1.
It means the inner position of

Before starting welding, the microcomputer of the control device is programmed with information such as the inner diameter of the approximately hemispherical body 1: D (mi) and the welding speed: S (mm).
/s), one-time tilt angle for moving from one concentric circle to the next concentric circle: Jθ(0), table tilt rotation speed: R (
rpm) is input using a digital switch.

Here, the control method during overlay welding will be explained based on FIGS. 7 to 10. The table rotation speed r (rpm) is given by:

Here, as shown in FIG. 7, the inclination angle θ is 90° when the table 3 is positioned horizontally, and O0 when the table 3 is positioned vertically.

The shaft encoder attached to the tilting pin 16 (
(not shown), the inclination angle θ is constantly detected.
The table rotation speed r is always controlled according to the table inclination angle θ by calculation control so that the welding speed S inputted in advance is maintained at a predetermined value.

Next, one inclination angle lθ to keep the lap distance constant
The beat pitch P is determined in advance, and the value of θ calculated based on the above formula is input into the computer.

Further, the table inclination rotation speed R is given by: The value of the locus change movement distance G is determined in advance, and the value of R calculated based on the above formula is input into the computer.

On the other hand, the position of the tilt start position detecting striker is set based on the value of the trajectory change movement distance G.

That is, the trajectory change movement distance G with the welding start point as the origin
The above-mentioned striker (not shown) is placed at a position X forward by the value of Welding of the shaped part S1 is performed, and the next concentric ring build-up (for example, C
At the starting point of 2), the trajectory is set to change exactly by the value of the beat pitch P.

By such a method, the inner surface of the substantially hemispherical body 1 as the object to be welded has concentric or arcuate portions C1, C2...Cn
, Cn+1... and spiral portion S1...Sn
Continuous overlay welding is performed by...

In terms of control performance, the shaft encoder has a resolution of 1/3000 from 0 to 90 degrees, and the table rotation control has a resolution of 1/3000.
The calculation is performed via a governor with a control range of 1:1, a speed of 1/50, and an accuracy of ±5% or less, and the calculated value is given to the governor.

As a result, the welding speed has an accuracy of ±5% or less at any position, and stable welding can be performed.

By the way, D: 150mm, welding speed: 180m
m/min, welding voltage = 26■, welding current: 700A
, strip electrode width: 50 am. Beat pitch: 44mm
, Partial spiral build-up length: 150 mm 1 Minimum build-up center diameter: 140 When welding was performed, very good build-up welding was obtained.

According to the method of the present invention, although continuous build-up welding is reliably controlled as described above, since the table inclination angle is detected, welding may be stopped midway due to power outage, replacement of the strip electrode, etc. It is possible to memorize the state even if the

Therefore, even if the tilting operation is stopped in the middle, only the remaining angle of lθ can be tilted after restarting.

In this respect, it is completely different from the timer method.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are both explanatory diagrams for explaining the method of the present invention, FIG. 3 is an explanatory diagram showing a specific example of an apparatus for carrying out the method of the present invention, and FIG. Fig. 5 is a front view, Fig. 6 is a side view, Fig. 7 is an explanatory diagram of the rotary table and a substantially hemispherical body, and Fig. 8 is an explanation of build-up welding on a substantially hemispherical body. 9 is an enlarged explanatory view of the main part of FIG. 8, and FIG. 10 is an explanatory view of each tilt angle of a substantially hemispherical body. 1...Approximately hemisphere, 2...Rotation axis, 3.
... Rotating table, 4... Welding head, C...
...Arc-shaped part, S1...Spiral-shaped part.

Claims (1)

[Claims] 1 In a method of continuous automatic overlay welding in circular arc shapes and partial spiral shapes from the outer circumference to the inner circumference while rotating a substantially hemisphere, welding is performed while constantly detecting the inclination angle of the rotation axis of the substantially hemisphere. A predetermined point in time before the beats meet is detected, and the substantially hemispherical body is moved in a circular arc direction by a preset angle within a vertical plane including the center of the sphere and the center of rotation, and is rotated to form a partially spiral shape. A continuous build-up welding method characterized by performing welding, then stopping movement in the vertical plane, and performing the next arcuate welding.