JPH0453625B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention uses gas-shielded arc welding,
This invention relates to a method for performing high-speed continuous welding with high quality and high efficiency.

[Prior Art] Conventionally, when performing gas-shielded arc high-speed welding, there has been a problem of welding defects. Therefore,
In the single electrode high speed carbon gas arc welding method, a consumable electrode with a diameter of 3.2 mm to 6.4 mm is used to
A technique is disclosed in which high-speed welding is performed at a speed of 3 m/min or more with a receding angle of 5° to 20° and a welding current of 600 A or more (Japanese Patent Publication No. 61-39152).

As a further improved method, by using multiple consumable electrodes and passing a pulsed current that creates a phase difference between adjacent consumable electrodes, bead formation is stabilized and continuous stable tack welding is achieved at high speed. A technique for performing this has been disclosed (Japanese Patent Application Laid-Open No. 61-49787).

[Problems to be Solved by the Invention] However, in the case of the former conventional technique, when the speed exceeds 5 m/min in the single-electrode high-speed carbon dioxide arc welding method, the pool of molten metal 4 recedes 8 as shown in FIG. As the size increases, there is a problem that poor fusion defects occur frequently, and in the case of the latter conventional technology, it is technically difficult to achieve a method of providing a phase difference between adjacent electrodes at a welding current of 600 A or more. There is a problem.

Figure 3 shows a welding speed of 3 to 12 with a V groove of 60 to 100°.
The results of the relationship between bead width and bead cross-sectional area based on actual measurements of weld bead cross-sections obtained in experiments of high-speed carbon gas arc welding at m/min are shown. As the speed increases, the condition in the region shown in FIG. 3 is reached, and the amount of welding is insufficient, resulting in discontinuous beads. When the welding current is increased to increase penetration, the amount of welding becomes excessive relative to the bead width, and humping is likely to occur (region I).

The present invention has been made in view of this problem, and by controlling the bead forming conditions so as to be within the range based on the knowledge obtained from the above-mentioned experiments, it is possible to achieve better results than before without causing irregular beads or welding defects. The object of the present invention is to provide a method that can achieve sufficient root penetration with a large root face groove while performing high-efficiency and high-quality welding while using a large current.

[Means for Solving the Problems] The gas-sealed arc high-speed welding method of the present invention uses two consumable electrode wires and inputs large arc energy in so-called one-pool tandem welding in the gas-sealed arc welding method. Also, the behavior of the arc and molten pool is controlled to prevent irregular beads such as puckering and humping, or welding defects such as cold laps, thereby improving the limits of welding heat input and welding speed.

That is, the gist of the present invention is that the consumable electrode wire is
In this case, the inclination angle of the leading electrode with respect to the vertical line is a receding angle of 0 to 30°, the inclination angle of the trailing electrode with respect to the vertical line is an advancing angle of 5 to 50°, the distance between the electrodes is 100 mm or less, and the leading electrode is The electrode wire diameter is 2 mmΦ or more, the welding current is 600 A or more, and the welding speed is 5
In the gas-shielded arc welding method performed at m/min or more, a DC welding power source is used as the leading electrode with electrode positive polarity, and a commercial frequency AC welding power source or transistor inverter, etc. equipped with a restriking pulse generator is used as the trailing electrode. Switching characteristics of 50Hz
This is a gas-shielded arc high-speed welding method using an oscillating current of ~100 KHz, making the wire diameter of the trailing electrode smaller than that of the leading electrode, and making the trailing current less than half of the leading current.

The present invention will be explained in detail below.

[Function] Figure 1 is a model showing an embodiment of the present invention using a two-electrode gas-shielded arc welding method using a leading electrode 1 and a trailing electrode 2.
4 is the base material, 4 is the molten metal, 5 is the arc of the leading electrode 1, and 6 is the arc of the trailing electrode 2. This welding method reduces the inter-electrode distance 7 and uses a large current particularly for the leading electrode, so arc breakage is likely to occur due to electromagnetic interference. In order to prevent this, the current phase for the trailing electrode is changed periodically, and the trailing current is set to one-half or less of the leading current. The leading current is a DC wire positive polarity, and the trailing current is a commercial frequency AC with a restriking pulse applied or an oscillating current with switching characteristics of 50Hz to 100KHz using a transistor inverter or the like. This oscillating current can be an alternating current with a center of O volts (Fig. 4 a, d), a direct current with a positive wire polarity (Fig. 4 b, e), or a direct current with a negative polarity (Fig. 4 c, f). But either is fine.

Next, the reason for limiting the method of the present invention as described above will be explained.

The reason why two consumable electrode wires are used is that in single electrode welding, if the welding speed exceeds 5 m/min, poor fusion defects will occur frequently.

The inclination angle of the leading electrode with respect to the vertical line is 0 to 30°.
The reason for setting a receding angle of It's for a reason.

The inclination angle of the trailing electrode to the vertical line is 5 to 50°.
The reason why we set the advancing angle to 100mm or less and the distance between the electrodes is that the arc of the trailing electrode is sprayed diagonally above the pool formed by the leading electrode, and the arc pressure is most effective in preventing the pool from retreating and increasing the pool width. Because there is.

The reason why the wire diameter of the leading electrode is 2 mmΦ or more is as follows.
This is because if welding is carried out at a welding speed of 5 m/min or more with a wire less than 2 mmΦ, the bead width will become extremely narrow and humping beads will easily occur.
The reason why it is set to 600A or more is that 600A is the lower limit current that does not cause arc breakage in a 2 mmΦ wire.

The reason why the welding speed was set to 5 m/min or more is that welding speeds of less than 5 m/min can be achieved using conventional techniques. The reason why a DC welding power source is used as the leading electrode with positive electrode polarity is that penetration and arc stability are good.

Switching characteristics of 50Hz to 100K using a commercial frequency AC welding power source with a restriking pulse generator on the trailing electrode or a transistor inverter, etc.
The reason for using Hz oscillating current is that it is effective in preventing arc breakage due to electromagnetic interference with the preceding electrode. Commercial frequency AC welding power sources require a restriking pulse generator to maintain arc stability. In the case of 50Hz to 100KHz oscillating current with switching characteristics caused by a transistor inverter, etc.,
Since the waveform is a rectangular wave with a steep rise, a pulse generator is unnecessary, but the higher the frequency, the better the arc stability, which is advantageous in preventing arc breakage due to electromagnetic interference. However, there is an upper limit due to device manufacturing technology, and it is difficult to put an oscillating current of over 100 KHz into practical use.

The wire diameter of the trailing electrode is made smaller than that of the leading electrode.
The reason why the trailing current is set to be one-half or less of the leading current is that it is necessary to prevent arc breakage due to electromagnetic interference. Even if alternating current or oscillating current is used as the trailing current, if high-speed welding is performed at a welding speed of 5 m/min or more with an electrode distance of 100 mm or less, arc breakage due to electromagnetic interference is extremely likely to occur.
If the trailing current exceeds one-half of the leading current, the arc cannot be maintained stably. On the other hand, in order to maintain arc stability, it is necessary to make the wire diameter of the trailing electrode smaller than that of the leading electrode in order not to lower the current density too much.

Figure 3 compares the experimental results of the relationship (area) between bead width and bead cross-sectional area without humping beads and discontinuous beads that can be achieved with the method of the present invention using a CO ₂ -based shielding gas with the conventional method (area). This is what is shown. From this figure, it can be seen that the method of the present invention can form beads with a good large cross-sectional area compared to the conventional method. This means that it is possible to prevent humping even if a large current is used to increase penetration, for example.
This makes it possible to perform gas-shielded arc high-speed welding in a high efficiency range, which was previously impossible, and expands its practical range. Further, as will be explained in the examples below, it becomes possible to obtain a large penetration that could not be obtained with the conventional method.

Note that efficiency can be further improved by performing the one-pool tandem arc welding of the present invention in plural at arbitrary distance intervals. The present invention can also be applied to narrow gap welding of thick plates.

[Example] A more detailed explanation will be given below using specific Examples 1 and 2. The welding conditions and results are as follows. FIG. 5 shows each size of the bead cross section.

Example 1 [Leading electrode] DC power supply: Constant voltage characteristics Wire: Plain steel solid 4mmΦ Gas: CO ₂ , 150 per minute Torch angle: 15 degrees backward, Ext 35mm Current: 1400A Voltage: 24V Interpolation distance: 28mm [Trailing electrode] AC electrode: Drooping characteristics, 50Hz Wire: Plain steel solid 2mmΦ Gas: 80% Ar + CO ₂ , 25 min Torch angle: 27 degrees forward, Ext 25 mm Current: 600 A Voltage: 35 V [Glove shape] 70°, 8 mm deep V opening Tip, common steel 20mm thick [Welding speed] 9m/min [Test results] Good bead appearance, no defects, penetration 1.6mm,
Throat thickness 4.5mm Example 2 [Advanced electrode] DC power supply: Constant voltage characteristics Wire: Plain steel solid 4.8mmΦ Gas: CO ₂ , 200 per minute Torch angle: 7 degrees retreat, Ext 30mm Current: 2000A Voltage: 25V Interpole spacing: 45mm [Trailing electrode] DC power supply: Constant voltage characteristics, 20KHz inverter Wire: Flux-cored 1.6mmΦ Gas: CO ₂ , 20 per minute Torch angle: 15 degrees forward, Ext20mm Current: 450A Voltage: 37V [Group shape] 90°V Bevel, SM50 material 25mm thick [Welding speed] 12m/min [Test results] Good bead appearance, no defects, penetration 2.6mm,
Throat thickness: 5 mm [Effects of the invention] As shown in Examples 1 and 2, when the gas-shielded arc high-speed welding method according to the present invention is performed, the above-mentioned welding speed can be achieved even at a welding speed of 10 m/min, which is twice the conventional welding speed. A good weld bead with large penetration and throat thickness and no weld defects can be obtained, and a welded joint with much higher efficiency and higher quality than conventional methods can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the vicinity of a welding electrode for carrying out the present invention, FIG. 2 is a schematic diagram of the vicinity of a welding electrode according to a conventional method, and FIG. 3 is a diagram showing the relationship between bead width and bead cross-sectional area. FIG. 4 shows a waveform diagram of an oscillating current, and FIG. 5 shows a sectional view of a weld bead. 1... Leading electrode wire, 2... Trailing electrode wire, 3... Base metal, 4... Welding pool, 5... Leading arc, 6... Trailing arc, 7... Distance between electrodes,
8...Pool retreat distance, 9...Bead width, 10...
...Bead (welding) cross-sectional area, 11...Penetration, 12
...Thick throat.

Claims (1)

[Claims] 1 Use two consumable electrode wires, set the inclination angle of the leading electrode to the vertical line at a receding angle of 0 to 30°,
The inclination angle of the trailing electrode with respect to the vertical line is an advancing angle of 5 to 50 degrees, the distance between the electrodes is 100 mm or less, the wire diameter of the leading electrode is 2 mmΦ or more, the welding current is 600 A or more, and the welding speed is 5 m/min or more. In the gas-shielded arc welding method, a DC welding power source with electrode positive polarity is used as the leading electrode, and a commercial frequency AC welding power source equipped with a restriking pulse generator or a transistor inverter with switching characteristics of 50 Hz is used as the trailing electrode. A gas-shielded arc high-speed welding method characterized by using an oscillating current of ~100KHz, making the wire diameter of the trailing electrode smaller than that of the leading electrode, and making the trailing current less than half of the leading current.