JPH0329502B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a TIG arc welding method.

TIG welding is a method that uses the heat of an arc generated between a tungsten electrode and a base metal to perform welding while surrounding the electrode and base metal with an inert gas atmosphere. Since the heat for melting and the supply of filler metal for welding are independently controllable, it can be used not only for steel-based materials such as ordinary steel, special steel, and stainless steel, but also for aluminum, aluminum alloys, Welding of structural members using various industrial metal materials such as copper and its alloys, titanium and its alloys has become increasingly necessary.

As mentioned above, in the Teig welding method, the control of the arc between the tungsten electrode and the base metal and the amount of welding from the filler metal are performed independently and relatively easily, and the bead is smooth and almost no spatter occurs. On the other hand, compared to normal arc welding, the amount of welding is small, and care must be taken to prevent defects when welding relatively thick plates of 10 mm or more.
Although there are disadvantages such as low welding speed, 10mm
In welding of materials of lower quality, it has come to be used more and more frequently because of its good bead appearance and good efficiency.

Components of industrial machinery itself, jigs and tools used to manufacture those machines, etc. Carbon steel, low alloy steel, medium alloy steel,
There are many applications in which welding is used to join plates and tubes with a thickness of approximately 10 mm or less using steel types such as high-strength steel and ferritic heat-resistant steel. Materials for use are set.

When forming butt welded joints and fillet welded joints using the Teig welding method, first process the appropriate groove shape according to conditions such as plate thickness, welding position, backing material, base metal, filler metal, etc. After removing dirt, etc., tack welding is performed as necessary, and then actual welding is performed.

In Teigue arc welding, the arc is extremely stable once welding has started and it has transitioned to steady welding, but the arc becomes stable at the start and end of the arc, causing burn-through and craters at the ends. , the appearance of the bead becomes poor,
This will lead to other welding defects.

To prevent these defects, when starting the arc, use a scrap plate to generate the arc before starting the actual welding, or start the arc on the weld line inward from the starting end. A method is adopted in which the melting torch is moved forward by returning it from the starting position to the starting position to form a molten pool, and then inserting a filler rod.

Further, as a type of the above-mentioned waste plate, a welding method is adopted in which end tabs are attached to the start and end portions of welding to restrain the base material and prevent welding defects at the ends.

In the conventional technology using end tabs, as shown in FIG. 1, when welding base materials 1 and 2, tabs 3 and 4, which are the same or have the same thickness as base materials 1 and 2, are placed at the welding start end, respectively. and the end of the tungsten electrode, place it on the backing metal (back bar), generate an arc on the start tab 3, and start with the tungsten electrode red-hot to ensure that the arc is generated and welding is performed. By doing this and finishing welding on the end tab 4, defects such as burn-through at the welding start and end portions were prevented.

However, in such a method, tabs 3 and 4 burn out after each welding and must be replaced, and if the lengths of base metals 1 and 2 in the welding direction are different, tabs 3 or 4 4 was damaged by adhesion to the base material, resulting in the disadvantage that the tab could no longer exhibit its effectiveness.

Some welded joints allow unwelded parts of about 1 mm or less to remain at the welding start and end ends of the base metals 1 and 2.

The present invention provides such a welded joint that is not affected by the uneconomical effects of burnout of the tabs 3 and 4 and by the difference in welding length between the base materials 1 and 2.
The purpose of this invention is to provide a welding method using the tab 3.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 is a perspective view showing an embodiment of the present invention, in which reference numerals 1 and 2 indicate base materials to be welded, which are placed on a back bar 5. 6 is a welding torch located at the welding start end. Reference numeral 13 is a start type that is closely attached to the welding start end and has a sufficiently larger heat capacity than the base metals 1 and 2. Reference numeral 14 is a small metal piece placed at the expected welding end position, and the welding torch is placed at the welding end position. Even if the electrode at the tip of the torch comes into contact with the small metal piece, the torch is heavy enough to be moved without giving a substantial impact to the electrode.

In the welding method of the present invention using such a start tab metal piece, an arc is first generated on the start tab 13 to proceed with welding.
When the torch reaches the expected welding end position and the electrode at the tip of the torch contacts the small metal piece 14 and short-circuits, the arc between the electrode and the base metal disappears and the arc voltage becomes zero. Detects this voltage drop and turns off the welding current
It would be even more effective if a cutoff circuit is provided to terminate welding.

According to this method, a small metal piece 14 corresponding to an end tab is placed on the welding end of the base metals 1 and 2, and the welding torch 6 reaches the end and contacts the metal piece 14, causing a short circuit and extinguishing the arc. Since the current is then cut off, the arc extinguishing point can be set accurately, the arc is extinguished just before the welding end, and defects such as burn-through at the end can be prevented.

Further, it is not necessary to bring the small metal piece 14 into close contact with the welding end, and it is simply placed on the welding end position, and the small metal piece 14 is moved to the rear of the welding line by contact with the welding torch 6. Since the welding current is turned off, there is no need to replace the tab each time you weld. Furthermore, even if the welding lengths of the base materials 1 and 2 are different, the effectiveness of the tab is not lost.

[Brief explanation of the drawing]

1 is a schematic perspective view illustrating the operation of downward butt welding of plates according to the prior art, and FIG. 2 is a schematic perspective view illustrating the same welding operation according to the method of the present invention. The correspondence between reference numerals and constituent members in the drawings is shown below. 1, 2...Base metal (material to be welded), 13...Start tab, 14...Small metal piece, 5...Back bar,
6...Welding torch.

Claims (1)

[Claims] 1. In the TIG arc welding method in which welding is performed by arc starting with a start tab; a small metal piece movable by contact with a welding torch is placed at the expected welding end position; A welding method in which when the welding torch reaches the scheduled welding end position, the welding arc is extinguished by contact short-circuiting with the small metal piece, and then the welding current is cut off to prevent burn-through at the welding end. 2. In the welding method according to claim 1; in cutting off the welding current, a drop in arc voltage accompanying extinction of the welding arc is detected and the welding current is cut off. welding method.