JPS58159973A - Method and device of dc arc welding - Google Patents

Abstract

PURPOSE:To perform DC arc welding of thin sheets with a wire of a large diameter without overmelting of base materials, by supplying electric current to the welding load only for the specified time after short-circuiting of the wire which is fed at a specified speed and the base materials and the generation of the arc. CONSTITUTION:In a DC arc welding machine, a series circuit of a reactor 3 and a welding load 4 which is an arc generating part is connected to the output terminal of a rectifier circuit 1 through a power transistor (TR)2 as a switching element. A diode 5 for commutation is connected in parallel with said circuit and a diode 6 is connected in parallel with said reactor 3. The arc is interrupted by turning the TR2 off after a specified time t1 since the generation of the arc. Relatively high voltage is maintained with the leakage current in this stage, and when the output is short-circuited in this state, short-circuiting current is flowed by the energy released from the reactor 3. When the TR2 is turned on after the specified time t2 upon lapse of the t1, the larger short-circuiting current flows, and the arc is regenerated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses Joule heat when a welding wire (hereinafter simply referred to as wire) as a consumable electrode and the base metal is short-circuited and arc heat when the wire short-circuits are opened to cause the welding wire to This relates to the DC arc welding method and welding machine that performs welding while melting the materials. Conventionally, when welding thin plates, the no-load voltage and current capacity of the welding machine used for welding thick plates are reduced. By the way, I was gone. That is, the conventional method for welding thin plates was to weld by passing a small current through a small diameter wire. Figures 1a and 1b show output waveforms in this conventional DC arc welding.

However, when welding such thin plates, the problem is that the base metal melts too much.

The present invention was developed in view of the current situation, and it is an object of the present invention to enable welding of thin plates using a large diameter wire without causing excessive melting of the base metal.

In order to achieve this objective, the present invention supplies current to the welding load only for a certain period of time after the short circuit between the wire and the base metal and the occurrence of an arc, so that the wire melts more than the base metal melts. This increases the ratio. Hereinafter, the DC arc welding method and welding machine according to the present invention will be explained using the drawings of FIGS. 2 to 17.

2 to 6 each show an electric circuit of a DC arc welding machine according to an embodiment of the present invention. In the figures, 1 is a rectifier circuit, 2 is a power transistor as a switching element, 3 is a reactor, and 4 is a A welding load is an arc generating part, 6 is a commutation diode, and 6 is a diode connected in parallel to the reactor 3.

That is, in the DC arc welding machine of the present invention, a series circuit of a reactor 3 and a welding load 4 is connected to the output end of a rectifier circuit via a power transistor 2, and a series circuit of a reactor 3 and a welding load 4 is Showa 58-159973 (
2) A commutating diode 5 is connected in parallel to the series circuit, and a diode 6 is connected in parallel to the reactor 3 so that the same polarity side is connected to the commutating diode 6.

Figures 6a-C show the output waveforms in the welding method of the present invention. That is, in the present invention, a certain period of time tl (tl is 2m5e in the experiment) after the arc is generated.
c) Afterwards, turn off the power transistor 2 and turn it OFF.
j, for a fixed time of 12 (t2 is am!1e in the experiment)
c) The power transistor 2 is turned on later.

In this way, if the power transistor 2 is turned off tl after the arc occurs, arc breakage occurs. At this time, the leakage current of power transistor 2 and diode 6
Reverse leakage current generates a relatively high voltage at the output. Then, when the output is short-circuited with the power transistor 2 in the OFF state, a short-circuit current flows due to the energy release of the reactor 3.
Afterwards, after a certain period of time t2, the power transistor 2 is turned off.
When N is applied, a larger short-circuit current of 61·- flows, and arc regeneration is performed.

Figures 7a and b show the state of the fusion zone when thin plates are welded by the welding method according to the present invention and the conventional welding method. can be reduced. In addition, Fig. 7a, ]? Smell, 7
is the base material, and 8 is the molten metal.

Here, according to the melting method of the present invention, the average arc voltage is 2
It becomes 12V at 0OA, which is lower than the normal 24V,
As a result, the number of short circuits is 130 times/at an output current of 20OA.
seconds and become very high. Furthermore, although the heat input during a short circuit is the same as before, the heat input when an arc occurs can be reduced, so melting of the base material can be reduced. Furthermore, in the present invention, arc current can also be controlled by allowing the base current of power transistor 2 to flow through a separate path.

As described above, according to the DC arc welding method and welding machine of the present invention, it is possible to reduce the heat input to the base metal, so that
Thin plates can be welded using a large diameter wire, and the base metal can be welded without excessive melting.

[Brief explanation of drawings]

1a and 1b are waveform diagrams showing output waveforms in the conventional DC arc welding method, FIGS. 2 to 6 are electric circuit diagrams of a DC arc welding machine according to an embodiment of the present invention, and FIG. 6a
7-c is a timing chart showing a control method in the DC arc welding method of the present invention, and FIGS. 7a and 7b are schematic diagrams showing welding results in the welding method of the present invention and the conventional welding method. 1... Rectifier circuit, 2... Power transistor, 3... Reactor, 4...
Welding load, 6... Commutation diode, 6...-
·diode. Name of agent: Patent attorney Toshio Nakao and 1 other person
ail Unpublished → 414 figure

Claims (2)

[Claims] (1) When welding is performed while the welding wire and base metal are melted by Joule heat when the welding wire as a consumable electrode and the base metal are short-circuited and arc heat when the wire short-circuit is opened, the welding A direct current arc welding method characterized by keeping the wire feeding speed substantially constant and supplying current to the welding load only during a short-circuit period between the welding wire and the base metal and for a certain period of time after arc generation. (2) Connect a series circuit of a reactor and welding load to the output end of the rectifier circuit via a switching element, connect a commutation diode in parallel to the series circuit of the reactor and welding load, and connect a commutation diode in parallel to the series circuit of the reactor and welding load. - A diode is connected in parallel to the reactor so that the side of the same polarity as the diode is connected, and the switching element is turned off a certain time after an arc occurs, and turned on a certain time after the switching element is turned off. DC arc welding machine controlled as follows.