JPS5978779A - Welding method for preventing melt-down in end part of welding in tig welding - Google Patents

Abstract

PURPOSE:To interrupt welding current and to prevent melt-down of the terminal end part of welding by placing a small metallic piece on the position intended for ending the welding and extinguishing the arc when short-circuiting arises upon contact of a torch with the small metallic piece. CONSTITUTION:A small metallic piece 14 is not required to be held in tight contact with the terminal end part of welding and is required simply to be placed on the position intended for ending the welding. There is no need for exchanging the tab at each welding as the piece 14 is moved backward of the weld line by contact with a welding torch 6 and the welding current is turned off. The effect of the tab is maintained as it is even if the welding length of base materials 1, 2 is different.

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. The heat for melting the welding material and the supply of filler metal to the welding pot are independently controllable, so it can be used for copper-based materials such as ordinary steel, special steel, and stainless steel, aluminum, aluminum alloys, etc. It has come to be widely used in welding structural members using various industrial metal materials such as copper and its alloys, titanium and its alloys.

As mentioned above, in the TIG welding method, the arc between the tungsten electrode and the base metal and the amount of welding from the filler metal can be controlled independently and relatively easily, and the welding process is smooth and generates almost no spatter. On the other hand, compared to normal arc welding, the amount of welding is small and the thickness IOttr
When welding relatively thick plates of 10 m or more, care must be taken to prevent defects, and there are disadvantages such as a slow welding speed, but when welding materials with a thickness of 10 m or more, the bead appearance is good and the efficiency is good. It has come to be used more and more frequently.

Components of industrial machines themselves, jigs and tools used to manufacture these machines, etc. Steel types such as carbon steel, low alloy steel, metal alloy steel, high tensile steel, and ferritic heat-resistant steel, such as plate materials with a thickness of about 10 mm or less, There are many applications for joining pipe materials by welding.
Appropriate filler rod materials are available for each steel type and base metal combination.

When forming butt weld joints and fillet joints using the TIG welding method, first, an appropriate groove shape is processed based on nine conditions such as plate thickness, welding position, backing material, base material, and bath filler material. However, after removing dirt, etc., temporary attachment will be done by welding, etc. depending on the membership fee, and then heathering will be performed.

In TIG arc welding, the arc becomes extremely stable once welding has started and the state has shifted to steady welding, but the arc becomes stable at the start and end of the arc, and the melt at the end does not fall off or create a crater. This can lead to poor bead appearance and other weld 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 inside welding line from the end where it is started. The melting torch is then moved back to the starting position to form a molten pool, and a filler rod is inserted to advance the melting torch.

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 ends, respectively. The tungsten electrode is placed in close contact with the terminal end, placed on the back bar, and an arc is generated on the start tab 3. By starting with the tungsten electrode red-hot, an arc is generated reliably. By performing welding at the welding point and finishing the welding on the end tab 4, defects such as melt drop at the welding start and end portions are prevented.

However, in such a method, tabs 3 and 4 burn out after each welding and must be replaced, and if the lengths of the base metals l 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 are allowed to have an unwelded portion of approximately 1 mg or less remaining at the welding start and end of base metals 1 and 2.

The present invention provides a welding method using tabs in such welded joints, which is not affected by the uneconomical effects associated with burnout of the tabs 3.4 and by differences in welding lengths of the base metals 1.2. The purpose is to

Hereinafter, nine examples of the present invention will be described 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 the back bar 5. 6 is a bath welding torch located at the m-junction end. 13
1 is a start tab which is closely attached to the bath welding end and has a heat capacity sufficiently larger than that of the base metal 1.2, and 14 is a small piece of the remaining end placed at the expected welding end position, so that the welding torch can The torch is heavy enough to move even if the electrode at the tip of the torch reaches the contact end position Im and is moved by a small metal piece without giving a substantial impact to the electrode.

In the welding method of the present invention using such a start tab and a small 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 area piece 14 and short-circuits, the arc between the electrode and the base metal disappears and the arc voltage becomes zero.

It would be even more effective to provide a cutoff circuit that detects this voltage drop and sets the bath current to (J F i ) to terminate welding.

According to this method, a small metal piece 14 corresponding to an end tough is placed on the bath welding end portions of the base materials 1 and 2, and a bath welding torch 6 is placed on the base metals 1 and 2.
The current is cut off by the arc extinguishing when it reaches the welding end and contacts the gold plate small piece 14, causing a short circuit. Therefore, by setting the arc extinguishing point accurately, the arc is extinguished just before the welding end, and the current is cut off. Melting can prevent defects such as dropping.

In addition, it is not necessary to bring the small metal piece 14 into close contact with the welding end; it is simply placed on the welding end position.) By contact with the welding torch 6, the metal piece 14 is moved to the rear of the welding line and then welded. Since the current is turned off, there is no need to replace the tab each time weld. Furthermore, even if the welding lengths of the base materials 1 and 2 are different, the tab does not lose its effectiveness.

[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. Agent Patent Attorney Isao Fujimoto

Claims (1)

[Claims] (1) In the TIG arc welding method in which welding is performed by arc starting with a start tab; a small piece of metal that can be moved by contact with the welding torch is placed at the scheduled welding end position, and the welding torch starts the welding at the scheduled welding end position. A welding method in which the welding arc is extinguished by contact short-circuiting with the small metal piece when the welding position is reached, and then the welding current is cut off to prevent the melt from dripping 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 that is designed to be used.