JPS6160270A - High speed tack welding - Google Patents

Abstract

PURPOSE:To perform tack welding to form a continuous and stable bead by lowering an arc voltage of a succeeding electrode when a plural weld electrode is approached at the edge of base metal to carry out gas shield arc welding. CONSTITUTION:In gas shield arc welding to carry out tack welding of base metal using a plural consumable electrode, molten metal 4 from an arc 3 of a proceeding electrode 1 is intercepted by an arc 5 of a succeeding electrode 2 to form a weld bead. When the weld electrode approaches at the edge of base metal, the voltage of the succeeding electrode 2 is lowered and arc length of an arc 5 is shortened to carry out tack welding. Therefore, the decrease of arc power by magnetic blow are prevented to show the sufficient effects of interception a molten metal 4 and a continuous weld bead is formed to prevent the occurrence of weld defects in this welding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-speed tack welding method in which tack welding is performed continuously at high speed prior to main welding.

[Conventional technology]

Continuous tack welding performed at a welding speed of 8 m/min or higher using the two-electrode MIG welding method uses a leading electrode 1 and a trailing electrode 2 as shown in Fig. 4, and the molten metal 4 generated by the arc B of the leading electrode 1 is This is done by forming a welding bead while blocking the outflow to the rear of the trailing electrode 2 with the arc 5 of the trailing electrode 2.

In conventional welding methods, welding parameters such as arc voltage, welding current, and welding speed are maintained under the same conditions even when the electrode reaches the end of the welded part of the base metal.

[Problem that the invention seeks to solve]

However, when tack welding is performed at high speed, a very high welding current is used for the preceding electrode 1 in order to obtain the required amount of welding. Therefore, when tack welding approaches the end of the base metal, the magnetic blow caused by this welding current becomes stronger, and the arc is strongly attracted backward. When the arc 3 of the leading electrode 1 is attracted to the rear by the magnetic blower, the molten metal 3 flows quickly along with the arc, and the molten metal 3 that flows quickly becomes the arc of the trailing electrode 2. The weld bead cannot be held down by force and flows backwards, resulting in an irregular weld bead with a markedly uneven weld bead shape as shown in Figures 5 to 7.
humping bead).

Here, FIG. 5 shows a plan view of the welded part, 6 is the groove surface, 7
Weld beads 7A and 7B are irregular bead shapes of weld bead 7. FIG. 6 shows the AA cross section of FIG.
The figure shows the BB cross section in FIG. 5, and 8 is the base material.

As shown in the figure, if the weld bead 7 of the tack weld becomes an irregular bead with significant irregularities, there is also the problem that slag entrainment and poor fusion occur during the main welding, making welding defects more likely to occur.

[Means for solving problems]

The high-speed tack welding method of this invention uses a plurality of consumable electrodes to perform tack welding of base metals by gas-shielded arc welding, and when the welding electrode approaches the end of the base metal, the trailing electrode This is a method of performing tack welding by lowering the atmospheric pressure of the arc.

[Effect]

As mentioned above, when the welding electrode approaches the end of the base metal, the arc is attracted backwards by magnetic blowing, and if the arc voltage setting of the finishing electrode is kept constant, the arc length of the dohyo-row electrode becomes longer, leading to It is often difficult to stop the molten metal with the electrode, the hot water flows backwards, the pool disappears, and the weld bead is extremely irregular and uneven in shape.

However, if the arc voltage setting of the trailing electrode is set lower when welding approaches the end of the base metal, and the arc length of the trailing electrode is shortened, magnetic blowing will occur, causing the arc of the trailing electrode to move backward. However, the amount of molten metal drawn by the leading electrode that had flowed under the trailing electrode is pushed to both sides of the arc column of the trailing electrode, causing the hot water seen in the normal bead area t, b. The same hot water pool is formed, and this hot water pool can be maintained continuously.

〔Example〕

FIG. 1 is a diagram showing arc voltage characteristics of a trailing electrode according to an embodiment of the present invention in comparison with conventional arc voltage characteristics. In the conventional tack welding method, the base metal end is tack welded at the same arc voltage v1 as the trailing electrode arc voltage (E) in the normal bead area, but in this invention, welding is performed at the base metal end E. , the position is detected by a limit switch, etc., and the arc voltage ■i is gradually lowered by this position detection signal to a predetermined arc voltage V! This arc voltage V is used to perform tack welding near the end of the base material.

As shown in the figure, tack welding near the edge of the base metal is performed at an arc voltage V that is lower than the arc voltage Vl in the normal bead area, so the arc length is shortened, and even if magnetic blow occurs, the arc force will Molten metal can be blocked and a continuous and smooth weld bead can be obtained.

In the above example, the welding current in the bead normal area [pole arc voltage 1 is 22v1, trailing electrode welding current e400A
When tack welding is performed at a high welding speed of 8 wL/min9, the distance from the base metal end E is approximately 50 to 60 cm.
When tack welding is performed by lowering the arc voltage from position m to 20 to 21 V, the bead width of weld bead 7 will be reduced as shown in the plan view of the weld part in Fig. 2 and the side sectional view in Fig. 3. Welding can be performed continuously under constant conditions. In the case of force-welding, tack welding is performed with the arc voltage of the leading electrode being constant IT.

Therefore, when performing tack welding at a high welding speed of 8 WL/min9 or higher, the arc voltage should be lowered at a position approximately 50 to 60 cm from the edge of the base metal to shorten the arc length. C,
The influence of magnetic blowing on weld bead formation can be eliminated.

° [Effects of the Invention] As explained above, the present invention is capable of performing tack welding by reducing the arc voltage of the trailing electrode to shorten the arc length when welding approaches the end of the base metal. It is possible to prevent a decrease in arc force due to magnetic blowing, to exhibit a sufficient effect of blocking molten metal, and to form a continuous weld bead. Therefore, it is possible to prevent welding defects from occurring during main welding.

[Brief Description of the Drawings] Fig. 1 is a diagram of the arc voltage characteristics of the trailing electrode according to the embodiment of the present invention, Fig. 2 is a plan view of the weld bead according to the above embodiment, and Fig. 3 is a weld bead according to the above embodiment. side sectional view of
Figure 4: Arc morphology diagram in two-electrode MIG welding method, Figure 5
The figure shows a plan view of a conventional weld bead, FIGS. 6 and 7 show side views of a conventional weld bead, and FIG.
A sectional view and FIG. 7 are BB sectional views of FIG. 5. 1... Advance'! it pole, 2... Trailing electrode, 3.5.
... Arc, 4... Molten metal, 6... Groove surface, 7.
...Welding peed, 8...Base metal, E...Base metal end, V
,,V,... Arc voltage of trailing electrode. Agent Patent Attorney Sanro Kimura Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] In gas-shielded arc welding in which base metals are tack welded using multiple consumable electrodes, this high-speed tack welding method is characterized by reducing the arc voltage of the trailing electrode when the welding electrode approaches the end of the base metal. Attached welding method.