JPH0639541A - Arc spot welding method - Google Patents

Abstract

PURPOSE:To obviate deposition of a lower side plate on a backing apparatus and to weld upper and lower plates together on a sufficient deposition area by abutting the backing apparatus on the lower surface of the lower side plate of superposed works, performing cladding by welding with droplets of a welding wire and then, increasing welding electric power to extend the arc width. CONSTITUTION:The backing apparatus 2 is abutted on the lower surface of the lower side plate 1b of the superposed works. An arc is generated from a torch to melt the welding wire 31. The droplets are transferred on the lower side plate 1b part of a hole 11 bottom part for welding to form cladding 4 by welding. A welding current is then increased to extend the arc width, melting of base metals and melting of the welding wire 31 are proceeded to increase the quantity of molten metal (m) and proper arc spot welding is performed. Since the thickness of the lower side plate part 10b on the hole 11 bottom part for welding is increased due to cladding 4 by welding, even if the depth H of penetration from the hole bottom 110 for welding is increased, the abnormal situation of deposition on the backing apparatus 2 of the lower side plate 1b can be obviated. Accordingly, the welding current can be increased and the deposition range can be B extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of arc spot welding an upper plate having a hole for welding to a lower plate.

[0002]

2. Description of the Related Art In the case of arc spot welding of an upper plate and a lower plate, an upper plate having a hole for welding preliminarily formed thereon is placed on the lower plate, and a welding torch is placed directly above the center of the welding hole. Set,
It is known to arc-weld the base material portion near the welding hole by melting it with an arc.

In this case, a backing device is brought into contact with the lower surface of the lower plate to prevent the melted portion of the lower plate from falling off.

[0004]

In the above arc spot welding, in order to widen the welding range and increase the welding area, it is necessary to increase the welding current and widen the arc width. When the welding current is increased (therefore, the welding range is widened), the penetration depth of the base metal is correspondingly increased. Therefore, if the welding range is widened, the penetration depth of the lower plate will exceed the lower surface of the lower plate, and the lower plate will be welded to the backing device, and the backing device will be detached from the welding end work. This may cause troubles, especially in the case of automatic welding, which causes a failure.

On the other hand, if the welding current is reduced in order to eliminate such a problem, the welding range is reduced, and it becomes impossible to secure a predetermined welding strength. An object of the present invention is to back-cover a lower plate when performing arc spot welding in a state where a backing tool is in contact with a lower plate of a stacking work of an upper plate and a lower plate having a hole for welding. It is an object of the present invention to provide an arc spot welding method capable of eliminating welding to a device and welding the upper and lower plates thereof with a sufficient welding area.

[0006]

According to the arc spot welding method of the present invention, a backing device is applied to the lower surface of a lower plate of a work in which an upper plate having a welding hole is superposed on the lower plate. Contact, the lower plate part of the bottom part of the welding hole is built up with droplets of the welding wire, and then the welding power is increased and the arc width is expanded to expand the welding range between the upper and lower plates. The configuration is characterized by.

[0007]

Operation The build-up can be performed with a minimum welding current that can transfer the droplets of the welding wire. Therefore, the current during build-up can be made sufficiently small to make the penetration depth of the base metal sufficiently shallow. As a result, it is possible to prevent the lower plate from being welded to the backing device during the buildup.

As a result of this buildup, the thickness of the lower plate portion at the bottom portion of the welding hole is substantially increased. As a result, the welding current is increased during the original arc spot welding, and the penetration depth of the lower plate is correspondingly increased. Even if the depth is deepened, the lower plate is prevented from being welded to the backing device during the arc spot welding.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A shows the state immediately before the start of arc spot welding.

In FIG. 1 (a), reference numeral 1a is an upper plate on which a welding hole 11 is preliminarily formed. Reference numeral 1b denotes a lower plate, which is stacked on the upper plate 1a to form a stacking work. A backing device 2 is in contact with the lower surface of the lower plate 1b of the stacking work.

Reference numeral 3 denotes an arc welding torch, which is a welding hole 1
It is set just above the center of 1. 31 is a welding wire. In order to perform arc spot welding of the above-described lap work according to the present invention, an electric current is passed through the welding machine to generate an arc from the torch 3, the welding wire 31 is melted, and the droplets are formed. The welding hole 11 is moved to the lower plate portion of the bottom surface portion, and the buildup 4 is formed as shown in FIG.

Since the droplet transfer of the welding wire can be performed with a minimum welding current (critical current) (below this current value, the droplet cannot be transferred and welding cannot be performed). It is possible to make the penetration depth h of the base material sufficiently shallow by making the electric current at the time of build-up small and sufficiently prevent the lower plate 1b from being welded to the backing device 2 at the time of the build-up.

After forming the built-up portion having a predetermined thickness, the welding current is increased to widen the arc width as shown in FIG. 1 (c) to melt the base metal and the welding wire. Proceeding to increase the amount of molten metal m, the original arc spot welding is performed.

At the time of this original welding, the thickness of the lower plate portion 10b at the bottom portion of the welding hole is substantially increased due to the above-mentioned buildup 4, so that the substantial bottom surface 110 of the welding hole is formed.
Even if the penetration depth H from the bottom is increased, the abnormal situation of welding the lower plate 1b to the backing device 2 can be eliminated, and therefore the welding current can be increased and the arc width can be widened to increase the welding range B. It can be expanded well.

In the above, switching from the welding condition at the time of overlaying to the original welding condition at the time of arc spot welding is performed by applying a low current and low voltage for a fixed time set according to the plate thickness and the welded area. After that, a time control method that automatically switches between high-current and high-voltage energization for a certain period of time (for example, in the case of a steel sheet for housing construction with an upper plate having a thickness of 4 mm and a lower plate having a thickness of 2 mm, 200 amperes and 1.5 V for 23 seconds). Is energized at 500 amperes and 45 volts for 1.0 sec), the rise of the molten metal is detected from changes in the arc current, etc., and when the rise height reaches a predetermined value,
A method of automatically switching can be used.

[0016]

The arc spot welding method of the present invention is constructed as described above, and in the case where the upper plate having the welding holes and the thin lower plate are subjected to the arc spot welding in the welding holes. Even if the welding power is increased and the arc width is increased to increase the welding area, the lower plate can be well prevented from welding to the backing device, and the upper and lower plates have excellent welding strength, and after welding It is possible to perform arc spot welding satisfactorily while ensuring the workability of detaching the backing device.

[Brief description of drawings]

FIG. 1 is an explanatory view showing each work step of an arc spot welding method of the present invention, in which (a) of FIG. 1 shows a state immediately before starting welding, and (b) of FIG. 1 shows a state immediately after overlaying. Shows the original state during welding.

[Explanation of symbols]

 1a Upper plate 11 Hole for welding 1b Lower plate 2 Backing device 3 Welding torch 31 Welding wire-4 Overlay

Claims (1)

[Claims] 1. A backing device is brought into contact with a lower surface of a lower plate of a work in which an upper plate having a hole for welding is laid on a lower plate, and a lower plate portion of a bottom portion of the welding hole is welded to a welding wire. The arc spot welding method is characterized by increasing the welding electric power and expanding the arc width to expand the welding range between the upper and lower plates.