JPS6036860B2 - Wire position control device in welding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling the state of insertion of a welding wire into a welding pool in, for example, TIG (inert gas arc) welding.

In TIG welding, it is difficult to set the position of the filler wire relative to the molten pool.

In other words, it is not enough that the filler wire simply contacts the molten pool, but the depth at which it is inserted matters. This is because if the welding wire penetrates too deeply into the molten pool, it may hit the solid-liquid interface or stir up the molten pool, causing welding defects. Furthermore, if the filler wire is too loose, the arc will be disturbed and welding defects will occur, and the melted filler wire will tend to fall, especially in the case of upward welding. Therefore, in order to obtain a well-finished weld, it is necessary to set the filler wire in a precisely inserted state with respect to the molten pool. However, in the past, there was no established method for quantitatively and objectively determining the insertion state of the filler wire into the molten pool, and the insertion state had to be adjusted by a person after all.

Therefore, the present invention provides an apparatus that quantitatively determines the insertion state of the filler wire and controls the filler wire to an optimal position based on this.

It is known that in arc welding, a potential is generated in the space around the welding arc. An example of the potential distribution is shown in FIG. In this figure, reference numeral 1 indicates the base material of the electrode 2, the vertical axis represents the height position of the electrode 1 with respect to the base material 2, and the horizontal axis represents the position on the base material 2 with respect to the central axis of the electrode 1. The potential is based on the base material 2. Conventionally, the potential of the molten pool was naturally at a drop potential since it was on the base material 2, and the filler wire in contact with the molten pool was also considered to be at zero potential. However, when the inventors conducted measurements, it was found that a minute electric potential was generated in the filler wire. Moreover, the value changed depending on the state of insertion. When the values were measured under the same conditions as in FIG. 1, it was found that a potential as shown in FIG. 5 was generated in the filler wire 4 depending on the plunge depth of the filler wire 4 into the molten pool 3. That is, as shown in Fig. 2a, if the filler wire 4 is inserted too deeply into the molten pool 3 (nearly plunging), the voltage will be 0.035V, and if the filler wire 4 is inserted too shallow as shown in Fig. ) is 0.07
It was V. If they are completely separated, the voltage will be as high as several volts as shown in Figure 1, so compared to this, the voltage will be 1/1
It can be seen that the voltage is as small as 0.00. From the above, it is possible to control the state of insertion of the filler wire into the molten pool by using the minute potential of the filler wire.

In other words, an appropriate value between the potential of the filler wire when it is about to plunge and the potential of the filler wire when it is about to float is set as a reference potential, and the actual potential of the filler wire is detected.
If this detected value is larger than the above reference value, the welding wire is pushed into the molten pool, so the welding wire is driven in the direction of insertion into the molten pool, and if it is smaller than the reference value, it is pushed into the molten pool, so the welding wire is moved into the molten pool. By driving the welding wire in the direction of pulling it up from the welding point, the state of insertion of the filler wire into the welding pool can be automatically maintained at the optimum state at all times. An example of a device that performs such control is shown in FIG.

In FIG. 3, a welding DC power source 11 is connected between an electrode 1 at the tip of a welding torch 10 and a base material 2. The filler wire 4 is unwound from the wire reel 8 and fed into the melt pool 3 via the wire feeder a and the wire tip 5. The entire part for feeding the filler wire is attached to a welding torch via a screw 7.
By driving this screw rod 7 with the DC motor 6, it moves in the vertical direction. This vertical movement controls the insertion state of the filler wire 4 into the melt pool 3. The voltage detection unit 12 detects a minute voltage between the filler wire 4 and the base material 2.

This minute voltage is amplified by the wire voltage amplifier 14 and then by the comparator amplifier 14 and then applied to the comparator amplifier 15 . The reference voltage generator 16 generates an appropriate value (
For example, when the former is 0.035V and the latter is 0.07V, the voltage Vs corresponding to 0.045V is set as the reference voltage. Comparison amplifier 15 detects a difference voltage V^ between reference voltage Vs and detection voltage Vw, and amplifies this.

Figure 4 shows an example of the voltage waveforms of Vs, Vw, and V^.
The motor drive amplifier 17 further amplifies the differential voltage V^ and applies it to the DC motor 6. The DC motor 6 is driven by this voltage and rotates in a direction in which the detected voltage Vw matches the reference voltage Vs. As a result, the filler wire is set in the optimal insertion state into the melt pool 3. Incidentally, one of the items that a welder monitors and operates during all-position welding of pipes and the like is adjusting the insertion position of the filler wire 4 with respect to the molten pool 3.

One of the reasons why this adjustment is necessary is that the shape of the molten pool 3 differs due to changes in the welding posture (FIG. 6). Therefore, the relative positions of the electrode 1 and the molten pool 3 change as the welding posture changes. That is, as shown in FIG. 6, the molten pool 3 moves away from the electrode 1 when moving vertically, and the molten pool 3 approaches the electrode 1 when moving vertically, with the downward position as a reference. Therefore, if the insertion position of the filler wire 4 remains fixed relative to the electrode 1, it may float completely as shown in FIG. This can cause welding defects (see Figure 2a). Therefore, if the position of the filler wire 4 is adjusted by applying a small voltage between the filler wire 4 and the base metal 2 according to the present invention, the filler wire 4 can always be inserted at the proper position as shown in FIG. be able to.

Although the above explanation has been given for cases suitable for TIG welding, this invention is applicable to all welding methods ( For example, it can be applied to plasma welding). As explained above, according to the present invention, it is possible to detect the insertion state of the lacquer wire into the molten pool based on the wire voltage, and by utilizing this, it is possible to obtain uniform welding in automatic welding. I can do it.

[Brief explanation of drawings]

Figure 1 is a graph showing the potential distribution state around the welding arc.
FIG. 2a is a diagram showing the state in which the welding wire is inserted, FIG. 2b is a diagram showing the state in which the welding wire is floating, and FIG. 3 is a block diagram showing an embodiment of the present invention. 4 is a waveform diagram of the detection voltage Vw, reference voltage Vs, and differential voltage V^ in FIG. 3, and FIG. FIG. 6 is a diagram showing an example of the microvoltage characteristics, and is a diagram showing the relationship between the welding posture and the insertion position of the welding wire 4. 1... Electrode, 2... Base material, 3...
...Melting pool, 4...Filler wire, 5...Wire tip, 6...DC motor, 7...Vertical drive screw shank, 8...Wire reel, 9... Wire feeder, 10... Welding torch, 11... Welding power source. Figure 1 Figure 2 Figure 3 Figure 5 Figure 6

Claims (1)

[Claims] 1 A means for detecting a potential difference that is minute compared to the potential difference between the base metal and the filler wire when the filler wire is floating from the melt pool, and a means for detecting a potential difference that is minute compared to the potential difference between the base material and the filler wire when the filler wire is floating in the melt pool, and means for setting an appropriate value between the minute potential difference when it is about to float and the minute potential difference when it is about to push in as a reference potential difference; Compared to the potential difference,
A wire position control device in a welding machine, comprising a wire drive device that drives the filler wire in a direction to further insert it into the molten pool when the potential difference is larger than the reference potential difference, and drives it in a direction to pull it away from the molten pool when it is smaller than the reference potential difference. .