JPS6132113B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is useful for connecting a plurality of steel pipes in the axial direction, or when connecting a plurality of joint parts of a beam-through pipe column, etc. Concerning automatic welding methods.

Conventionally, when connecting a plurality of steel pipes 50 to 52 (hereinafter referred to as pipes) in the axial direction (Fig. 7), or when connecting a unit pipe 54 to which a bracket 53 is attached and a plurality of pipes 55 to 57 (Fig.
), the pipe 50 is
52 or 55 to 57 were welded in a downward position while rotating in the circumferential direction.

However, taking FIG. 7 as an example, each pipe 50
It is almost impossible to match the groove conditions of grooves 52 to 52, and variations occur in the cross-sectional area of each groove due to groove intervals, groove angles, mismatches, etc. Therefore, manually,
Regardless of whether it is semi-automatic or not, the welding speed between each welded joint will change, and the welding speed will not be able to correspond to the rotational speed of the pipe. If the two speeds do not correspond, defects such as slag entrainment and poor fusion will occur. In order to prevent this, conventional methods have been to rotate the pipe intermittently at a predetermined speed,
There were problems such as being forced to choose inefficient means such as stopping or reversing the welding process.

This invention was created in view of the above circumstances,
Rotate multiple tubes at the same set circumferential speed,
This was an automatic welding method in which multiple welding joints were electrogas welded in parallel at the same time.The wire feed amount was changed in stages for each welding joint, and the wire feed amount was set accordingly according to the standard wire protrusion length. The upper and lower limits of the standard welding current can be changed, and the welding current is detected at the set circumferential speed and compared with the upper and lower limits of the standard welding current to ensure that the detected welding current is within the range of the upper and lower limits. When the wire feed rate is , welding continues without changing the wire feed rate, and when the detected welding current is outside the range of the upper and lower limit values, the wire feed rate is changed to the next higher or lower wire feed rate. The purpose is to match the welding speed of multiple welded parts to the rotational speed of the pipe, so that they can be welded simultaneously in parallel. This paper proposes a gas welding method.

[Overview of Configuration] FIG. 1 shows a general configuration of an automatic welding device used in the present invention. This automatic welding device is an electrogas welding device, and is used when welding a plurality of pipes 1, 2, 3 in the axial direction while rotating them in the circumferential direction, etc.
When multiple weld joints 4 and 5 exist on multiple pipes, these weld joints 4 and 5 are welded simultaneously and in parallel by rotating pipes 1, 2, and 3 in principle in synchronization with a constant circumferential speed. It's becoming like that.

That is, the automatic welding device includes a pipe rotating device 7 using a turning roller 6, and a wire feeding device 10 that can feed welding wire 9 of a welding torch 8 individually corresponding to each welding joint 4, 5.
and a welding control device 11 that controls the welding state.
and a welding power source 12.

[Explanation of the principle of control operation] The feeding amount f [g/
The relationship (bearing capacity) between welding current I (A) and wire protrusion length l (mm) when [min] is constant is as shown in FIG. In addition, in FIG. 4, three sets of wires having different feeding amounts are shown by parallel lines. Further, as an example of the above-mentioned combination of appropriate welding conditions, I=300
[A], V = 36 [V] combination, I = 400 [A], V
There are =42 [V] combinations.

Furthermore, when the wire protrusion length l is constant, the melting rate m [g/min] (equal to the wire feeding amount).
The relationship between I(A) and welding current I(A) is as shown in FIG.

Now, when connecting pipes 1, 2, and 3,
Welding of the welding joints 4 and 5 is started simultaneously, but at this time, the rising speed of the molten pool 33 varies depending on the size of the groove cross-sectional area of the welding joints 4 and 5.

That is, since the pipes 1, 2, and 3 are rotated at the same set circumferential speed, the welded joint with a larger (or smaller) groove cross-sectional area will have a slower (or faster) rising speed of the molten pool 33. . Therefore, in a welded joint in which the groove cross-sectional area is large (or small), the protruding length l of the welding wire 9 increases (or decreases).

Therefore, in this invention, when welding is performed at a certain wire feed rate, the upper and lower limits of the standard wire protrusion length are set to the upper and lower limits of the standard welding current according to the wire feed rate, as shown in FIG. Therefore, by comparing the upper and lower limits of the reference welding current set in advance, when the protruding length l of the welding wire 9 increases (or decreases) and reaches the upper limit (or lower limit), the By increasing (or decreasing) the wire feed rate, which was set to be able to be changed to Welding can be carried out at an appropriate current and voltage within the range and with the wire feed amount within that range.

Note that the reference welding current value is set within the range of the upper and lower limits of the appropriate welding current.

Since the adjustment of appropriate welding conditions for each weld joint is the same, the adjustment of one joint will be explained next with reference to FIG.

First, at startup, the wire protrusion length is set to the optimum length l ₀ and welding is started. The tube body is rotated at a set circumferential speed, the optimum wire protrusion length is l ₀ (the value is between the lower limit l′ and the upper limit l″ of the wire protrusion length), and the reference welding current setting value mentioned above is I ₂ (point between the upper limit I ₂ ′ and the lower limit I ₂ ″), and assuming that the cross-sectional area of the groove between the pipes does not change as set and welding is performed with the appropriate wire feed rate. As is clear from the drawing, the welding current and the corresponding wire protrusion length are
It is located approximately at the midpoint between points P ₂ ′ and P ₂ ″, and is welded in that state.

If the groove cross-sectional area fluctuates and the fluctuation is small, the fluctuation of the molten pool surface will also be _{small .}
The wire feed rate varies along the P ₂ ′, P ₂ ″ lines, and welding can be continued with a constant wire feed rate.

However, in actual welding, if the wire feed rate remains constant, it is not possible to properly weld in response to fluctuations in the groove cross-sectional area.

Therefore, for example, initially within the range of wire protrusion lengths l' and l'', welding current I
Welding is performed with a constant wire feed rate at the initial stage (this is referred to as the first stage feed rate), where the wire feed rate changes in the range of I _{2 ′} to I ₂ ″, and this first stage feed rate is Corresponding to the cross-sectional area, the protruding length of the wire gradually increases when the feeding amount is small.

When the protruding length of the wire becomes longer than l'', it is detected that the detected current value I has become smaller than the lower limit _I2 '' of the standard welding current, and the stepping motor is driven to increase the wire feed rate. along with increasing
The welding current and welding voltage corresponding to the wire feed amount are sequentially increased along the P ₂ ″ and P ₃ ″ lines.

When the wire feed rate corresponding to the groove cross-sectional area is exceeded, the molten pool rises faster than the set circumferential speed and the wire protrusion length gradually becomes shorter.The wire protrusion length becomes shorter than l''. When the wire feed rate is increased, the increase in the wire feed rate is stopped and the wire feed rate is
The fixed feeding amount of the upper stage (second stage) is greater than the feeding amount of the first stage.

At this time, if the detected current value I is the lower limit I ₃ '' of the standard normal welding current I ₃ , then the relationship between the wire protrusion length l and the welding current I at the second stage feed rate is as follows: P ₃ ′ and P ₃ ″ If the feeding amount in the second stage corresponds to the cross-sectional area of the groove at that time, welding continues with the wire protruding length slightly shorter than l''. In addition, if the feed rate in the second stage is a small feed rate in relation to the groove cross-sectional area at the next point in time (if the groove cross-sectional area increases as welding progresses), , after reaching the second stage feed rate, the feed rate may become insufficient again), when the wire protrusion length becomes longer than l'', the wire feed rate is increased and the second stage feed rate is increased. The feed rate is set to the level higher than the stage. The principle of adjusting the wire feed rate at this time is the same as that for switching from the first stage feed rate to the second stage feed rate described above.

In addition, if the feed rate in the second stage is larger than the wire feed rate corresponding to the groove cross-sectional area at that point, the molten pool will rise faster, the wire protrusion length will gradually become shorter, and P ₃ ″, move on the P ₃ ′ line.

When the wire protrusion length becomes shorter than l', the detected current value I becomes the upper limit of the reference welding current _I3 .
It is detected that the welding current has become larger than I ₃ ′, and the stepping motor is driven to reduce the wire feed amount and sequentially reduce the welding current voltage along the P ₃ ′ and P ₁ ′ lines.

When the wire feeding amount decreases below the amount corresponding to the groove cross-sectional area, the wire protrusion length gradually increases.

When the wire protrusion length becomes longer than I', the decrease in wire feed rate is stopped, and the wire feed rate is set to a constant feed rate in the lower stage (third stage), which is smaller than the feed rate in the second stage.
The feed rate of each step).

At this time, the detected current value I is the upper limit of the reference welding current _I1.
I ₁ ′, the relationship between wire protrusion length l and welding current I at the feed rate in the third stage is expressed by a straight line connecting P ₁ ' and P _{1 '} ', and the feed rate in the third stage is If it corresponds to the groove cross-sectional area at the time, welding is continued with the wire protrusion length slightly longer than l'.

In addition, if the feed rate in the third stage is a large feed rate in relation to the groove cross-sectional area at the next point in time (if the groove cross-sectional area is decreasing as welding progresses), , after reaching the third stage feed rate,
In addition, the amount of feed may be excessive. ), when the wire protrusion length becomes shorter than l', the wire feed amount is reduced to a feed amount in a stage lower than the third stage.

The principle of adjusting the wire feed rate at this time is the same as that for switching from the second stage feed rate to the third stage feed rate described above.

In addition, if the feed rate in the third stage is less than the wire feed rate corresponding to the groove cross-sectional area at that time,
The protruding length of the wire gradually increases and moves along the P ₁ ′, P ₁ ″ lines.

When the wire protrusion length becomes longer than l'', the detected current value I becomes the lower limit of the reference welding current _I1 .
It detects that I is smaller than ₁ '', drives the stepping motor, increases the wire feed amount, and increases the welding current and welding voltage corresponding to the wire feed amount.The wire feed at this time The principle of adjusting the amount is the same as that when switching from the first stage feed amount to the second step feed amount described above.

In this way, welding is performed while increasing and decreasing the wire feed rate in stages while adjusting the circumferential speed and the rise in the molten pool.

Generally, the groove condition is not constant over the entire circumference of the pipes 1, 2, and 3, so the above-mentioned control is performed appropriately following the groove condition.

Note that if the groove condition is abnormal and the groove cross-sectional area cannot be adjusted to the set stage of the wire feed amount, the control mechanism may be attached to change the set circumferential speed of the tubular body as necessary.

Further, the welding current I and the welding voltage V are adjusted by a welding current voltage regulator 23. The above control state is summarized in FIG. 8.

[Description of Control System] As shown in FIG. 2, the welding control system is composed of a welding control device 11 and a welding current detector 13 that detects the welding current of each welding joint 4, 5. The device 11 includes a welding current controller 14 corresponding to the number of welding joints 4, 5, a wire feed controller 15, a pipe rotation speed setting device 16 for setting the rotation speed of the pipes 1, 2, 3, etc. .

Welding current detector 13 detects welding current using shaft 17 provided inside welding power source 12 as a sensor, and the detection signal is amplified to a predetermined level by amplifier 18 and output.

The output signal of the amplifier 18 is transmitted to the welding current controller 14.
is input as a detection signal. In this controller 14, a comparator 19 for detecting the upper limit value of the wire protrusion length and a comparator 19' for detecting the lower limit value of the wire protrusion length have a reference current set value when the wire protrusion length is at the upper limit.
A comparison is made between the detection signal and the reference welding current setting value In' when the wire protrusion length is at the lower limit.These In' and In' are set by the resistance values of variable resistors 28 and 28', which will be described later. Ru.

At the same time, a pulse signal with a predetermined number of oscillations is generated in the oscillator 21, and this pulse signal and the comparator 19,
The output signal of 19' is input to the logic circuit 59, and if there is an input signal from the comparator 19, a pulse to the left rotation side is generated, and if there is an input signal from the comparator 19', a pulse to the right rotation side is generated. The signal is input from the logic circuit 59 to the pulse motor drive circuit 22 .

The pulse motor drive circuit 22 is a so-called switching circuit that switches the pulse input direction for each phase of the field pole of the pulse motor 24 in accordance with the detected welding current value, and rotates the pulse motor 24 left or right.

Therefore, the welding current controller 14 (details are shown in FIG.
a), the pulse motor 24 is controlled by the pulse input direction by the pulse motor drive circuit 22.
The rotation angle is adjusted by the rotation direction of the input pulse and the number of input pulses.

By controlling the rotation of the pulse motor 24, the contactor 29 fixed to the rotating shaft 25 is interlocked to change the resistance values of the variable resistors 26, 27, 28, and 28'.

When the resistance value of the welding current variable resistor 26 changes in the welding current voltage regulator 23, the wire feeding amount is increased or decreased, the welding current is increased or decreased, and the resistance value of the welding voltage variable resistor 27 is changed. The change results in a voltage corresponding to the current. Also, a variable resistor 28 for setting the upper and lower limits of the reference welding current,
By changing the resistance value of 28', the reference welding current set values In' and In'' at the upper and lower limits of the wire protrusion length are switched to the set values corresponding to the wire feed rate of the next stage.

In this way, while rotating the entire pipe at a constant circumferential speed V [cm/min], the wire feed rate is increased or decreased in stages to perform standard welding within a certain range above and below the standard wire protrusion length. It is possible to weld with current I and voltage V.

Note that the variable resistors 26, 27, 28, and 28' rotate to the left or right within a range in which their resistance values cannot be changed by the rotation of the rotating shaft 25 of the pulse motor 24, making it impossible to control welding at the above-mentioned set pipe circumferential speed. When this occurs, the limit switches 30 and 31 are operated by a striker provided on the rotating shaft 25, and the limit switches are turned OFF and the pulse motor 24 is stopped.

When the pulse motor 24 stops, the signals from the limit switches 30 and 31 are combined with the signal from the oscillator 21 in the logic circuit 60 for driving the pulse motor for pipe rotation speed control, and the pulse for the right or left rotation signal is used to drive the pulse motor. It is input to the circuit 22' and rotates the pulse motor 24'.
As shown in FIG. 3b, the rotation of the pulse motor 24' causes the variable resistor 16 to change, thereby increasing or decreasing the rotational speed of the pipe.

In this way, the present invention is capable of controlling the rising speed of the molten pool of each weld joint when connecting a single pipe or a plurality of pipes having a plurality of weld joints with different groove cross-sectional areas by vertical welding while rotating in the circumferential direction. Since the rotational speed of the pipe and the pipe can be synchronized, welding can be started and finished at the same time.

Furthermore, since a plurality of welded joints can be simultaneously welded, it is possible to save the intermittent and inefficient work performed by a plurality of workers as in the past, and improve efficiency.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the configuration of the vertical automatic welding device, Figure 2 is a block diagram showing the configuration of the welding control device, Figure 3 a is the welding current controller, and b is the configuration of the pipe rotation speed controller. FIG. 4 is a partial perspective view showing the
5 is a characteristic curve showing the correlation between wire protrusion length l and welding current I, FIG. 5 is a characteristic curve showing the correlation between welding current I and melting rate m, and FIG. 6 is a flowchart showing a summary of control operations. 7 and 8 are explanatory diagrams of the prior art. 1, 2, 3...Pipe, 4, 5...Welded part, 6
... Turning roller, 7 ... Pipe rotation device,
8...Welding torch, 9...Welding wire, 10...
Wire feeding device, 11... Welding control device, 12...
...Welding power source, 13...Welding current detector, 14...
Welding current controller, 15...Wire feed controller, 1
6... Pipe rotation speed setting device, 19, 19'...
Comparator, 21... Oscillator, 22, 22'... Pulse motor drive circuit, 23... Welding current voltage regulator, 24, 24'... Pulse motor, 25, 2
5'... Rotating shaft, 26... Variable resistor for welding current, 27... Variable resistor for welding voltage, 28... Variable resistor for setting reference welding current, 28'... Variable resistor for setting reference welding current. Container, 29... Contact, 3
0,31...Limit switch, 33...Melting pool.

Claims (1)

[Claims] 1 An automatic welding method in which multiple pipes are rotated at the same circumferential speed and multiple welding joints are simultaneously electrogas welded in parallel, and the wire feed amount is changed in stages for each welding joint. The upper and lower limits of the standard welding current, which are set in accordance with the standard wire protrusion length, can be changed accordingly, and the welding current is detected at the set circumferential speed, and this is set as the upper and lower limits of the standard welding current. When the detected welding current is within the range of the upper and lower limits by comparison, welding is continued without changing the wire feed rate, and when the detected welding current is outside the range of the upper and lower limits. An electrogas automatic welding method for a tube body, characterized in that the wire feed rate is changed to a wire feed rate one level higher or lower to perform welding.