JPS6317553B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a narrow gap welding method performed using a gas shielded arc welding method such as MIG or TIG, and a method for keeping the weld bead height constant against groove fluctuations such as gaps. The purpose of this is to obtain a sound weld.

Gas-shielded arc welding methods such as MIG and TIG have been used to weld thick plate structures in narrow gaps. In these conventional narrow gap welding methods, if the groove width changes in the direction of the weld line, or if the bead of the previous layer is uneven, the weld bead of the next layer becomes uneven and the arc becomes unstable, resulting in unsatisfactory results. There was a risk that welding would not be possible. In order to avoid this, the unevenness of the bead in the previous layer is polished to make it smooth by using a grinder, or the groove width is detected by a detection means such as a television camera, and the welding conditions are controlled based on this. However, the method using a grinder is extremely difficult due to the narrow gap, while the method using a television camera, etc. has timing problems due to a discrepancy between the detection position of the groove width and the arc position, and the detection means equipment is There was a problem with control stability because it was easily damaged by arc heat and spatter.

The present invention was made in order to solve the various problems of the conventional welding methods as described above, and it is based on the electric signal of the arc generated between the molten metal and the electrode, and the arc that is set in advance. and a reference signal, the height of the welding torch is controlled so that the first difference signal thus calculated becomes zero, and an electric signal corresponding to the deformation in the height direction of the torch is detected. Then, the difference between the detected electric signal and a displacement reference signal corresponding to a preset reference height of the torch is calculated, and the welding cart is moved so that the second difference signal calculated in this way becomes zero. The feature is that the weld bead height is maintained constant by controlling the speed.

This invention will be explained by way of examples and with drawings. FIG. 1 is a perspective view showing a state in which welding is performed by the narrow gap welding method of the present invention.

In FIG. 1, 1 and 1' are materials to be welded with a predetermined narrow groove 2, 3 is a welding torch, and 4 is a molten metal pool. The welding torch 3 serves as a guide for a welding wire (consumable electrode) 5, and the welding wire 5 is guided by a feed roller 7 driven by a feed motor 6 into a weld metal pool 4 using the welding torch 3 as a guide. Welding is performed by generating an arc 8. Although FIG. 1 shows the case of a consumable electrode arc, the same applies to a non-consumable electrode arc (TIG). However, in that case, a feeding motor is not necessary, and instead of a wire, a non-consumable electrode can be used at the tip of the nozzle. A power source and the like for generating an arc between the welding wire 5 and the materials to be welded 1, 1' are not shown. The welding torch 3 is fixedly supported by an arm 9 supported by a welding cart 11 running along rails 10, 10 provided in the direction of the welding line, via a drive block to be described later. As the groove 2 advances, it simultaneously advances within the groove 2. 19 is a welding torch drive block, which is connected to the welding cart 11.
A welding torch height control motor 20 is mounted on an arm 9 horizontally fixed to the welding torch drive block 19, and a welding torch height control motor 20 for driving a screw shaft 21 is installed on the upper part of the welding torch drive block 19. The base 22 of the small arm 23 attached to the
can be moved up and down.
The welding torch height control motor 20 is provided with a potentiometer 24 for detecting the displacement output of the welding torch 3.

By the way, the causes of unevenness in the weld bead are often caused by, for example, when the width l of the groove 2 changes in the direction of welding progress, or when the initial layer bottom surface 12 of the arc is uneven. Therefore, when the groove width l increases or when the bottom surface 12 of the arc initial layer is low,
Since the welding wire 5 is melted at a constant amount, the molten metal pool 4 inevitably has a low molten metal pool surface.On the other hand, if the groove width l becomes narrower or the bottom surface 12 of the arc initial layer becomes higher. In this case, the molten metal pool surface will be higher.

Next, the method of the present invention will be explained with reference to the control system diagram shown in FIG.

In FIG. 2, 13 is a detector for detecting the arc electrical signal (arc current or arc voltage), 14 is a noise removal filter, and 15 is the arc electrical signal detected by the detector 13. , the first signal for calculating the difference from the reference signal, which will be described later.
A differential amplifier 16 is a reference signal generator for inputting an arc reference signal (arc current or arc voltage) to the differential amplifier 15 when the distance between the molten metal pool 4 and the welding electrode is a predetermined distance. , 20
24 is a welding torch height control motor for moving the welding torch 3 in the height direction so that the difference signal calculated by the first differential amplifier 15 becomes zero;
26 is a potentiometer for converting the displacement in the height direction of the welding torch 3 into an electric signal, and 26 is an electric signal corresponding to the displacement in the height direction of the welding torch 3 from the potentiometer 24, and A second differential amplifier 25 is a welding torch 3 for calculating a difference from a displacement reference signal, which will be described later, corresponding to a reference height.
a displacement reference signal generator for inputting a displacement reference signal corresponding to the reference height to the second differential amplifier 26;
Further, 27 is an acceleration/deceleration controller for controlling the rotation of the travel motor 17 of the welding cart 11 so that the difference signal calculated by the second differential amplifier 26 becomes zero.

A filter 14 removes noise from the arc electrical signal detected by the detector 13 . The first differential amplifier 15 calculates the difference between the reference signal from the reference signal generator 16 and the electrical signal of the arc from which the noise has been removed. Welding torch height control motor 20 moves welding torch 3 in the height direction so that the first difference signal calculated by first differential amplifier 15 becomes zero. For example, when the arc current value becomes low, the welding torch 3 is lowered, and when the arc current value becomes high, the welding torch 3 is raised to keep the arc current value constant. This maintains the arc length constant and stabilizes the arc. A second differential amplifier 26 calculates the difference between the electric signal from the potentiometer 24 corresponding to the displacement of the welding torch 3 in the height direction and the displacement reference signal from the displacement reference signal generator 25 . The acceleration/deceleration controller 27 controls the rotation of the travel motor 17 so that the second difference signal calculated by the second differential amplifier 26 becomes zero. For example, if the groove width becomes wider during welding and the molten metal pool surface becomes lower than the reference surface, the traveling speed of the welding cart 11 is reduced, i.e.
The melting amount of the welding wire 5 is increased to make the molten metal pool surface match the reference height.

In this way, the arc length is kept constant while the molten metal pool surface is made to match the reference height.

As explained above, according to the present invention, the weld bead surface can be made uniform by changes in the welding arc itself, which eliminates the need for grinding work using a grinder as in the past, and when using detection means such as a television camera. Since there is no risk of timing delay, arc heat, damage to the detection means due to spatter, etc., highly reliable control can be performed and the quality of the welded part can be further improved, which is an extremely useful effect. brought about.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a state in which welding is performed by the method of the present invention, and FIG. 2 is a control system diagram of the same embodiment. In the drawings, 1, 1'... Material to be welded, 2... Bevel, 3... Welding torch, 4... Molten metal pool, 5... Welding wire, 6... Feeding motor, 7... Feeding. Laura, 8
...Arc, 9...Arm, 10...Rail, 1
DESCRIPTION OF SYMBOLS 1...Welding trolley, 12...First layer bottom, 13...Detector, 14...Filter, 15...First differential amplifier, 16...Reference signal generator, 17...Travel motor, 18... Tacho generator, 19... Welding torch drive block, 20... Welding torch height control motor, 21... Screw shaft, 22... Base, 23...
...Small arm, 24...Potentiometer, 25...
...Displacement reference signal generator, 26...Second differential amplifier, 27...Acceleration/deceleration controller.

Claims (1)

[Claims] 1 Calculate the difference between the electrical signal of the arc generated between the molten metal and the electrode and the preset reference signal of the arc, and adjust the height of the welding torch so that the first difference signal calculated in this way becomes zero. controlling the height of the torch, detecting an electrical signal corresponding to a displacement in the height direction of the torch, and calculating a difference between the detected electrical signal and a displacement reference signal corresponding to a preset reference height of the torch; A narrow gap welding method characterized in that the traveling speed of the welding cart is controlled so that the second difference signal calculated in this manner becomes zero, thereby maintaining the weld bead height constant.