JPS596745B2 - Arc fusion welding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an arc fusion welding device for TIG welding.

A number of welding machines have been developed for so-called TIG welding, in particular for welding a plurality of heat exchanger tubes end-to-end and for welding the ends of heat exchanger tubes at the openings into the tubesheet.

In many types of heat exchangers, it is necessary to keep variables within limits, particularly relevant for welding small diameter tubes, under conditions of difficult access to each welding location and during welding. Thus, a large number of welds can be made. To meet such requirements, machines of compact design have been proposed that are automated and operate with a series of pre-programmed welding operations. After proper positioning of the machine with respect to the part to be welded, one of the series of operations to be carried out by automatic welding equipment is an arcing operation, and for this purpose usually A high-frequency voltage oscillation wave is applied across the arc gap, and this high-frequency voltage oscillation wave breaks down the arc gap and ionizes it first, and the electrode supported by the welding head is connected to the electric motor controlled by the welding programmer. The low voltage direct current arc needed to effect the weld can be generated when the tube is caused to swirl around the tube. The power supply for automatic TIG welding of tube end-to-end or tube-to-tubesheet may be a rectifier controlled by the programmer to produce a programmable steady current as much as possible; It may also be a power supply that generates a programmed pulsating direct current according to instructions.

Both devices are arranged for high frequency generation of DC arc,
And high frequency arc generation can also be used in arc fusion welding equipment using AC power supplies and sometimes equipment using consumable electrodes. The invention generally finds application in arc fusion welding equipment for pipe welding or other purposes with a programmer-controlled electric motor and using high frequency termination generation. This invention is
An electric motor that rotates the welding electrode and the workpiece relative to each other, a device that controls the electric motor according to instructions from a programmer, a power source that generates an arc, and an arc that is generated between the welding electrode and the workpiece. It has a device for applying high-frequency voltage oscillation waves, and is set in parallel with the main arc gap through which inert gas passes, and is set larger than the main arc gap, so that when the main arc is not generated, discharge occurs under high-frequency oscillation. It is characterized in that an auxiliary arc gear device is provided with an auxiliary arc gear through which an inert gas is passed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings as an example.
Referring to the drawing, an automatic TIG welding machine for welding two pipes 1 and 2 end to end together is driven by an electric motor 4 to rotate around the joint between the two pipes. It has an arranged welding head 3, a rectifier 5 forming a power source for supplying direct current to the arc, a programmer 6 for monitoring and controlling the welding according to the expected sequence of the welding operations.

The welding head 3 has a non-consumable electrode 7 made of, for example, thoriated tungsten, and a ceramic sleeve 8 on its axis.
(The tip of the electrode 7 protrudes from this sleeve 8.) Inside this sleeve 8 is a gas supply conduit 9.
An inert gas such as argon gas for the welding operation is supplied through the sleeve 8, and the supplied inert gas is discharged from the inside of the sleeve 8 around the tip of the electrode 7 and the tube junction. so that an arc is formed between the two.

The axis of the electrode 7 of the welding head 3 is always aligned with the tube 1 during the pivoting movement.
, 2 are oriented perpendicularly to the common axis of the two. The electric motor 4 for rotating the welding head 3 is controlled by a motor control device 10.
can control the starting and stopping of the electric motor 4 as well as its speed. The welding current circuit has a conductor 11 and a conductor 12 connecting the metal of the tubes 1, 2 and the rectifier 5, the conductor 12 being normally made negative with respect to the conductor 11 in this type of welding and connected to the electrode 7. It is connected between the power source 5 and the power source 5. DC voltmeter 13 and ammeter 14 measure welding voltage and welding current, respectively. A coil 21 is provided on the conducting wire 12,
This coil 21 is the coil 22 of the spark gap oscillator 23.
This oscillator 23 is connected to an alternating current power source via a conductor 25 inserted in a contact 26 and can generate periodic bursts of high-frequency oscillations. The auxiliary arc gap device 27 has a cathode 28 which can be a tungsten welding electrode.
and an anode 29 in the form of a solid copper plate, the cathode 28 and the anode 29 being placed in a chamber with a length of fire-resistant glass tube 30 as a wall, the interior of this chamber being a gas discharge conduit from the chamber. A flow of inert gas drawn from the gas supply conduit 9 is passed through the conduit 31 under the control of a valve 32 provided in the gas supply conduit 9 .

Alternatively, the inert gas flow caused to flow through the chamber may be the inert gas flow in the passage to the welding head 3. Cathode 28 is electrically connected via fuse 33, anode 29 is connected to the negative side of conductors 11 and 12, and anode 29 is connected to the other of the conductors. The fuse 33 can be tested by a circuit connected across the fuse 33 and including another fuse 34, a power supply 35, a normally open contact 36, and a lamp 37 in series. programmer 6
Information regarding the welding head position is supplied from the electric motor 4 through a signal line 104, and information regarding the welding voltage and welding current is supplied through signal lines 113 and 114, respectively.

The programmer 6 connects to the motor control device 1 via a control line 110.
0, and controls the output of the power supply 5 via a control line 105. Signal lines 104, 113, 11
In response to the signal 4, the programmer 6 adjusts the speed and speed of the motor 4 in a predetermined manner to meet the requirements at various welding conditions and at various angular positions of the trajectory of the welding head during the main part of the welding operation. (or) welding voltage and (
or) adjust the welding current. Furthermore, the programmer 6
This is done to ensure a low motor speed for a specified period of time for arc ignition and initial tube joint heating before the start of the main part of the welding operation, and generally to keep the residual arc crater in the weld relatively small. In order to do this, the main part of the welding operation is followed by ensuring low motor speed and low arc current, and finally by stopping the motor and extinguishing the arc. - The programmer 6, which is capable of controlling the contacts 26 via the control line 126, is adapted to hold the contacts 26 in the conductor 25 normally open, but presses a start button (not shown) to start the welding operation. When pressed, the contact 26 is closed until the DC voltage applied to the welding voltage information line 113 falls below a predetermined value due to the formation of a required arc, or until a predetermined short period of time has elapsed. Ru.

Before starting the welding operation, it is necessary to momentarily close the contact 36 and turn on the lamp 37 to confirm that the fuse 33 is completely routed.

At the stage of preparing the machine for performing a welding operation,
It is necessary to open the valve 32 to fill the chamber of the auxiliary arc device 27 with inert gas, and then to maintain the flow of inert gas through that chamber, and of course the inert gas continuously discharged from this chamber. needs to be returned. To start the welding operation, when the start button is pressed, the power supply 5, under the control of the programmer 6, connects the electrode 7 of the welding head 3 to the pipes 1 and 2 between the pipes 1 and 2 to be welded end to end. A DC voltage is applied to the arc gap between the junction and, by closing the contact 26, a high-frequency, high-amplitude voltage is superimposed on said DC voltage, whereby said arc gap is dielectrically broken down and firstly ionized, thus A state is reached in which the DC arc required for welding operation can be generated. When a DC arc is generated in this way,
Information for reducing the output voltage of the power supply 5 from the open circuit voltage to the operating voltage is sent from the voltmeter 13 to the programmer 6, thereby opening the contacts 26 and thereby stopping the application of high frequency voltage to the DC welding circuit. . The auxiliary arc gap in the auxiliary arc gap device 27 is set, for example, 25% larger than the suitably set main arc gap, so that the auxiliary arc gap does not break down under high frequency voltage even if the main arc occurs. Ru. In particular, the main arc gap setting may be incorrect,
Among many reasons, such as a defect in the connection between the tube and the power source 5 via the conductor 11, or a defect in the welding head that causes air to enter the arc gap mixed with the inert gas. For either of these reasons, if a main arc is not generated even when a high frequency voltage is applied from the oscillator 23, the high frequency voltage will discharge across the auxiliary arc gear to the auxiliary arc gear device 27.

When ionization of the gas occurs due to the discharge of the auxiliary arc gap, the programmer 6, in response to information from the voltmeter 13, reopens the contacts 26 to cut off the oscillator 23 and stop applying the high frequency voltage. In this case, even if the application of the high frequency voltage is stopped, a DC arc current may flow through the auxiliary arc gap device 21 due to the ionization of gas due to the discharge of the auxiliary arc gear, but the fuse 33 will melt before that, so such DC arc current will Overheating and damage to the auxiliary arc gap device 27 is thus prevented. If an auxiliary arc is generated under high-frequency oscillation when the main arc is not generated, the high-frequency voltage will cause tracking and signal transmission across the insulator between the electrode 7, the motor 4 and the motor control device 10, for example. The formation of a return path from line 104 and/or control line 110 through programmer 6 and power supply 5 ensures that it is well absorbed and does not endanger the equipment. Such stray high-frequency currents can be introduced not only by themselves but also by the opening of low-resistance paths to direct current from the power supply 5, e.g. in complex and sensitive circuits using printed circuits and transistors in the programmer and the power supply. It will be appreciated that damage to the equipment may occur. When such damage occurs, it can be extremely time consuming to repair, as it can be accompanied by component breakage as well as failure.
The welding head is also protected by the auxiliary arc gap from damage that may ensue if the high frequency oscillations are unable to discharge across the main arc gap.

This invention can be implemented as follows.

(1) The auxiliary arc gap is formed by an electrode placed in a chamber through which an inert gas passes. (
2) The cathode of the auxiliary arc gap electrode is a tungsten welding electrode, and the anode is a solid copper plate.

(3) The chamber is equipped with a length of fireproof glass tube as a wall. (4) The auxiliary arc gap circuit includes a fuse.

(5) A circuit connected to both ends of the fuse and with normally open contacts forms a device for testing the integrity of the fuse.

(6) The arc fusion welding equipment for TIG welding includes a motor for the welding electrode, a programmer, a power source consisting of a rectifier, a high frequency arc starter, and a second arc gap device.

[Brief explanation of the drawing]

The drawing shows the main parts of a TIG welding machine for welding ends of a plurality of tubes. In the drawing, 11 and 2 are pipes (processed parts), 3 is a welding head, and 4
is an electric motor, 5 is a rectifier (power supply), 6 is a programmer, 7 is an electrode, and 27 is an auxiliary arc gap.

Claims (1)

[Claims] 1. An electric motor that rotates the welding electrode and the workpiece relative to each other, a device that controls the motor according to instructions from a programmer, a power source that generates an arc, and an electric motor that generates an arc between the welding electrode and the workpiece. It has a device that applies a high-frequency voltage oscillation wave that causes the inert gas to pass through, and is set larger than the main arc gap in parallel with the main arc gap through which inert gas passes. 1. An arc fusion welding device for TIG welding, characterized in that an auxiliary arc gap device is provided having an auxiliary arc gap through which an inert gas passes for discharge.