JPS6227911B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting burn-through of a molten pool in consumable electrode arc welding in which welding is performed by continuously feeding a consumable electrode wire.

When welding thin plates automatically using consumable electrode arc welding, the molten pool may melt down due to inappropriate changes in welding conditions or misalignment of the welding wire, causing the arc to break during welding and restart the arc. If this process is repeated, holes may be discontinuously formed in the welded part, or even if the arc continues to occur, the molten metal may drip down or be blown off by the arc, causing a fusion state and damaging the workpiece. There are things to do.

Therefore, it is necessary to change the welding conditions or stop the arc generation by detecting the burn-through of the molten pool as soon as possible to reduce damage to the welded object.

Now, in consumable electrode arc welding, when a normal arc is generated and satisfactory welding is being performed, if for some reason the molten pool melts down, the arc breaks and the voltage instantly drops from the welding power source. The no-load voltage rises to about 50V, and the welding current does not continue due to arc breakage and suddenly drops to zero.However, in automatic welding, the torch continues to move forward and feed the wire, so the next moment When a wire comes into contact with the edge of a melted hole and a short circuit current flows, there is a change in voltage and current.

The present invention has been made with attention to the above points, and in order to detect changes in arc voltage or welding current that occur simultaneously with melting of the molten pool,
Normal arc voltage under suitable welding conditions for welding,
Or, set upper and lower limit values to detect values that exceed the welding current fluctuation range.

That is, when the value is greater than or equal to the upper limit value or less than the lower limit value, it is assumed that an arc has broken if detected by arc voltage, or a short circuit if detected by welding current.
In addition, even during normal welding, arcing and short circuits occur repeatedly in the short arc region where the welding current is low, and even in other high current regions, instantaneous short circuits due to droplet transfer, etc., or instantaneous seek breaks due to poor wire feeding, etc. etc. are occurring.

Most of these usually occur alone. However, when the burn-through phenomenon occurs, a signal that exceeds the upper limit of the detected value and a signal that falls below the lower limit of the detected value are sure to occur within a certain period of time. In order to detect this phenomenon, when one of the signals is generated, this signal is held for a certain period of time, and by monitoring the presence or absence of the subsequent signal within this time, burn-through is detected, and this can be detected by changing the welding conditions. The purpose is to use it as a signal or an arc stop signal to eliminate welding defects.

Hereinafter, specific embodiments of the present invention will be described based on the drawings.

The figure is a block diagram, and for ease of understanding,
Each block is labeled with a device name representing its function.

Welding current is detected by shunt 1 and amplified by amplifier 2. When the welding current becomes less than a preset lower limit value due to arc breakage or burn-through of the molten pool, the comparison/discrimination circuit 3 operates and provides a low current detection pulse output to the holding circuit 4. The holding circuit 4 receives the input of this low current detection pulse and holds this low current detection pulse signal a for a certain period of time.

On the other hand, when burn-through of the molten pool occurs and the automatically fed wire comes into contact with the base metal after the arc breaks and the welding current exceeds the preset upper limit, the comparison discrimination circuit 5 is activated and the high current The detection pulse output is given to the holding circuit 6. The holding circuit 6 receives this high current detection pulse input and holds this high current detection pulse signal b for a certain period of time.

Due to the burn-through of the molten pool, the range of change in the welding current increases and becomes below the lower limit value, outputting a low current detection pulse signal a, and then within a certain period of time, exceeding the upper limit value and outputting a high current detection pulse signal b. Then, the matching circuit 7 operates and outputs the burn-through signal c, thereby appropriately changing the welding conditions.

It is assumed that the same function is achieved regardless of which of the low current detection pulse signal a and the high current detection pulse signal b is output first.

In this example, welding current is set as the welding condition.
220A, arc voltage 26V, upper limit of detection value 30V,
The lower limit value was 6V, and the signal retention time was 0.1 seconds.

Furthermore, it is of course possible to input only pulses that have lasted a certain period of time to the holding circuits 4 and 6.

Further, each block in the figure may be constructed using any known device, and does not need to have a structure specifically limited to the present invention.

As explained above, by carrying out the method of the present invention, it is possible to prevent the workpiece from penetrating or It is now possible to reliably detect defects such as fusing in the minimum amount of time, and by changing the welding conditions for a certain period of time based on this detection signal, welding defects can be eliminated and welding can be continued under the original welding conditions. It has the effect of allowing you to do it comfortably.

[Brief explanation of the drawing]

The drawing is a block diagram showing an embodiment of the invention. 1... Shunt, 2... Amplifier, 3... Comparison/discrimination circuit, 4... Holding circuit, 5... Comparison/discrimination circuit,
6...holding circuit, 7...matching circuit.

Claims (1)

[Claims] 1. In consumable electrode arc welding that continuously feeds the consumable electrode wire, the upper and lower limits of the arc voltage or welding current are set, the arc voltage or welding current during welding is detected, and the detected value is Generates an output signal when the upper limit value or lower limit value is exceeded, holds this signal for a certain period of time, and outputs a subsequent signal that exceeds the lower limit value or exceeds the upper limit value within this certain period of time. A method for detecting burn-through of molten metal during welding, characterized by outputting a burn-through signal when the burn-through signal is detected.