JPH07116836A - Backing gas supply device of tig welding - Google Patents

Abstract

PURPOSE:To speedily and efficiently execute inert gas substitution at TIG welding of piping, etc. CONSTITUTION:The device is provided with a first supply means 21 to set the prescribed gas supply flow rate to the inside space 1b formed by tube bodies to be welded 1, 1a, a second supplying means 22 set to the backing gas supply flow rate lower than the former and an oxygen detecting means 23 to detect an oxygen concentration of the discharged gas from the inside space 1b. Further it is provided with a control means 24 to switch backing gas supply to the inside space 1b from the first supply means 21 to the second supply means 22 by the signal detected that an oxygen concentration from the oxygen detecting means 23 is lowered less than the prescribed value. The device speedily and efficiently executes precharge to the inside space, further surely executing substitution of inert gas and suppressing is consumption.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a gas supply port for supplying a back gas to an internal space of a pipe to be welded such as a pipe, and a gas exhaust port for discharging a gas from the internal space to perform TIG welding. It relates to a back gas supply device used for carrying out.

[0002]

2. Description of the Related Art Conventionally, when welding pipes made of stainless steel, aluminum or the like, TIG welding has been carried out for the purpose of avoiding welding defects due to oxygen around the welded portion and improving the characteristics of the welded portion. . In this TIG welding, for example, in order to weld and connect the pipes, first, the grooves that will be the welded portions of the pipes are butted together, the pipe ends are closed to form an internal space inside the pipe, and one of the closed ends A gas supply port is provided on the other side, and a gas discharge port is provided on the other side. Next, while supplying an inert gas such as argon gas from the gas supply port and discharging the gas from the gas discharge port, the air in the internal space is purged and replaced with an inert gas, and then the electric welding machine is started and piping is started. Weld from the outer peripheral surface.

[0003]

However, in the above-mentioned conventional method, since the replacement of the internal space with the inert gas is performed depending on the experience and feeling, the replacement failure often occurs.
There have been problems such as poor welding and uneven welding. Further, when excessive purging is performed to avoid such an accident, an extremely expensive gas such as argon gas is unnecessarily discharged and the consumption amount increases. Further, when welding a large-diameter or long pipe, there is a problem that it takes a long time to replace the inert gas. Therefore, an object of the present invention is to provide a new back gas supply device that solves such a problem in the back gas supply in the conventional TIG welding.

[0004]

That is, the present invention provides a gas supply port for supplying back gas to the inner space of a pair of pipes to be welded to be welded to each other, and a gas for discharging gas from the inner space. It is a device that supplies a back gas for TIG welding by providing an outlet. This apparatus is configured such that a first supply unit that is in communication with the gas supply port and supplies a predetermined flow rate of back gas, and a predetermined flow rate that is in communication with the gas supply port and is smaller than the first supply unit. And a second supply means for supplying the back gas, and an oxygen detection means for detecting the oxygen concentration of the gas discharged from the gas discharge port. Further, this apparatus supplies back gas from the first gas supply means to the gas supply port in response to a start command, and supplies the back gas from the first supply means to the second gas by the oxygen concentration decrease signal from the oxygen detection means. A control means for switching to the supply means is provided,
It is characterized by that.

In a preferred embodiment of the above device,
The oxygen concentration decrease signal causes the control means to output a command to automatically start the welding machine. In another preferred embodiment of the above-mentioned device, the oxygen detecting means is capable of setting two different oxygen concentrations, and outputs different detection signals when the measured oxygen concentration becomes less than or equal to each set value. The first setting of the oxygen concentration value that is slightly higher than the oxygen concentration value that allows the welding work to start, and the second setting of the oxygen concentration value that allows the welding work to start. The first supply means is switched to the second supply means by the value detection signal, and the start command is issued to the welding machine 3 by the second set value detection signal. In still another preferred embodiment of the above apparatus, flow rate detecting means for detecting the back gas supply flow rate after the start of welding is further provided, and the flow rate of the back gas supplied by the detecting means has fallen below a predetermined value. Is detected and an alarm is issued.

[0006]

According to the back gas supply device of the present invention, since a large flow rate of the back gas is supplied to the internal space of the welded portion by the first supply means for precharging, replacement of the inert gas in the internal space is promptly performed. Can be done. Then, the oxygen concentration in the internal space is equal to or lower than the set predetermined value, that is, the initial replacement is sufficiently detected by the oxygen detecting means, and the signal is used to supply the back gas from the first supplying means at least during welding. It is arranged to switch to the second supply means set to the minimum flow rate. Therefore, it is possible to surely perform the inert gas replacement without excess and deficiency, and it is possible to suppress the consumption of the back gas at the time of welding to a necessary minimum.

[0007]

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1 is an explanatory view showing a state in which TIG welding is performed using the back gas supply device of the present invention. Grooves to be welded in the pipes 1 and 1a to be welded, which are shown as a pair of pipes, are brought into contact with each other to form a welded portion 2, and a welder head 4 of a welder 3 is arranged in the welded portion 2. . An operation switch 5 for manually starting and stopping the welding machine 3 is connected to the welding machine 3. In the example shown in the figure, two sets of pipes to be welded are set at one time, and they can be continuously TIG-welded one after another. However, one set of pipes to be welded is set at one time. It may be configured as follows.

The sealed body 6 seals the end of the welded pipe 1 and the sealed body 7 seals the end of the welded body 1a to form an internal space 1b. A gas supply port 17 and a gas discharge port 15 are respectively provided in the closed bodies 6 and 7, as will be described later, and the gas supply port 17 has a pipe 8 for supplying gas.
A gas exhaust pipe 15 is connected to the gas exhaust port 15. Further, a sample pipe 10 for oxygen detecting means is connected to the gas outlet 15. As shown in FIG. 2, the sealing body 7 has a tapered cylindrical body 11 made of a flexible material such as rubber, a ring-shaped band 12, and a flange 13. One end of the cylindrical body 11 having a large diameter is airtightly connected to the outer peripheral end of the welding pipe 1a by the band 12, and the other end of the cylindrical body 11 is airtightly connected to the surface of the flange 13 by adhesion or the like.

The pipe 9 is airtightly connected to the outer periphery of the flange 13, a hole 14 is provided in the center of the shaft of the flange 13, and a cylindrical gas outlet 15 is connected to the periphery of the hole 14. . The sample pipe 10 is connected to the tip of the gas outlet 15. Gas outlet 1
A plurality of through holes 16 are provided in the peripheral wall of the gas discharge port 1,
Since the inside of the pipe 5 and the inside of the pipe 9 are communicated with each other, the gas discharged from the internal space 1b is
A part is extracted by the sample pipe 10, but most is discharged into the pipe 9. Although the details of the sealing body 6 shown in FIG. 1 are not shown, the sealing body 6 has the same structure as the cylindrical body 11, the band 12, and the flange 13 having a hole in the center of the shaft shown in FIG. The pipe 8 is airtightly connected. Then, the hole of the flange serves as a gas supply port (reference numeral 17 shown in FIG. 1).

In FIG. 1, the back gas supply device 20 comprises a first supply means 21, a second supply means 22, and an oxygen detection means 2.
3, and a control means 24. The first supply means 21 has a flow rate setting means 25 such as a manual valve, a control valve 26 such as an electromagnetic valve, and a flow rate detecting means 27. The flow rate setting means 25 is set so as to supply the back gas having a relatively large flow rate to the gas supply port 17, and the flow rate is determined by the flow rate detecting means 2
Monitored by 7. The second supply means 22 has a flow rate setting means 28 such as a manual valve, a control valve 29 such as an electromagnetic valve, and a flow rate detecting means 30. The flow rate setting means 28 is set to the gas supply port 17 to a smaller amount than that set by the flow rate setting means 25, preferably to the minimum back gas flow rate required during welding. The flow rate is monitored by the flow rate detecting means 30.

The flow rate detecting means 27 is provided with a flow rate lower limit detecting means 31 for notifying that the back gas supplied to the internal space 1b during welding has decreased below a predetermined value. Then, according to the output signal, the control means 24 issues a drive command for driving alarm means such as a lamp or a buzzer (not shown). If necessary, the flow rate upper limit detecting means 32 may be further provided to notify that excess back gas is being supplied. The downstream side of each of the first supply means 21 and the second supply means 22 is a pipe 8
And each upstream side is connected to the header 33.
It is connected to the. The back gas is supplied to the header 33 from a supply source (not shown) through the pipe 34 and the main valve 35. The first supply means 21, the second supply means 22, the header 33, the main valve 35, the control means 24, etc. are attached to the box (A) as shown in the drawing for the purpose of protection, and are housed therein. ing.

The oxygen detecting means 23 measures the oxygen concentration in the gas introduced through the sample pipe 10, and outputs a detection signal when the measured value drops to a preset oxygen concentration. The output signal is control means 2
4 is input. The gas from the two sample pipes 10 is switched by the solenoid valve 36 and the oxygen detection means 2
Introduced in 3. These solenoid valves 36 are controlled by a switching command from the control means 24. The oxygen detecting means 23, the electromagnetic valve 36 and the like are also attached to the box (B) and housed therein, as shown in the figure, for protection and the like. The oxygen detecting means 23 may be configured to set one oxygen concentration as described above, but it is possible to set two different oxygen concentrations, and the measured oxygen concentration values are below the respective set values. At this time, each detection signal can be output.

The control means 24 may be composed of a sequencer or may be made to perform a required control by a program using a computer, but since these means are well known and commonly used in this field, a detailed description thereof will be given. Is omitted. The control means 24 is adapted to receive a start command, a stop command, etc. from the remote switch device 37.

Next, the operation of the above apparatus will be described with reference to FIG. 3. First, in order to prepare for welding, two sets of welded pipe bodies 1 and 1a are butted to each other as shown in FIG. Both ends thereof are sealed with the sealing bodies 6 and 7, respectively. Further, the box (A) and the gas supply port 17 are connected by a pipe 8, the box (B) and the gas discharge port 15 are connected by a sample pipe 10, and the gas discharge port 15 is connected by a pipe 9. Further, a welding machine head 4 which is connected to the welding machine 3 by an electric cable is arranged in the welding portion 2 where the welding is performed first, and the back gas is supplied from the back gas supply source to the header 33. Next, the remote switch device 37 issues a selection command for the pipes to be welded (the pipes 1 and 1a to be welded on the lower side of FIG. 1) to be welded to the control means 24 to select the solenoid valve 36 provided in the sample pipe 10. To do. Further, from the remote switch device 37 to the control means 24
When a start command is issued to the device, the control valve 26 of the first supply means 21 located on the left side of FIG. It is supplied to the supply port 17 and precharge (large flow rate purge) is performed. The flow rate can be known by the flow rate detecting means 27.

When a predetermined precharge is carried out and the oxygen concentration of the gas discharged from the gas discharge port 15 becomes equal to or lower than a preset value, a detection signal is output from the oxygen detection means 23, whereby the control means 24 is operated. , First supply means 2
A switching command from 1 to the second supply means 22 is output.
That is, the control valve 26 of the first supply means 21 is closed to stop the back gas supply, and the control valve 29 of the second supply means 22 is opened to supply the back gas at the flow rate set by the flow rate setting means 28. Is started. Further, if desired, a display signal is output to display the fact that this switching has been performed by a lamp or the like. When the oxygen detecting means 23 sets the value of the oxygen concentration when the interior space 1b is sufficiently replaced with the inert gas, that is, the value of the oxygen concentration at which the welding operation can be started, the switching command is issued from the control means 24. At the same time, a start command is issued to the welding machine 3. When setting such an oxygen concentration value, after the detection signal is output from the oxygen detection means 23 in order to further enhance the stability of the oxygen concentration detection,
It is also possible to delay the time set by a timer means or the like and issue the switching command and the welding machine start-up command.

The control flow shown in FIG. 3 is not the above-described configuration but the case where the oxygen detecting means 23 is configured to be able to set two different oxygen concentration values, and these settings are set to start the welding operation. This is an example of a case in which there are two stages: a first setting of an oxygen concentration value that is slightly higher than the oxygen concentration value that enables the welding operation and a second setting of an oxygen concentration value that allows the welding operation to start. In this example, when the oxygen concentration reaches the first set value, the oxygen detection means 23 outputs a first detection signal, and the control means 24 transfers the first supply means 21 to the second supply means 22. Is issued to switch from a large flow rate precharge to a small flow rate purge, that is, a work (welding) purge, and when the oxygen concentration reaches the second set value, the oxygen detection means 23 The second detection signal is output, and the control means 24 issues a start command to the welding machine 3. With this configuration, the inert gas replacement can be performed more reliably.

Even when the oxygen concentration is set in two steps as described above, after the second detection signal is output from the oxygen detection means 23, the oxygen detection means 23 outputs the second detection signal in order to further enhance the stability of the oxygen concentration detection. It is also possible to delay the time set by a timer means or the like and issue a welding machine start command.
As shown in FIG. 3, when the flow rate of the back gas supplied to the gas supply port 17 drops below a predetermined value after the start of welding, an alarm signal for driving the alarm means is output from the control means 24, and if necessary. Further, a stop signal is output to the welding machine 3. After the predetermined welding is completed, the remote switch device 3
By issuing a stop command from 7, the control means 24 outputs a signal to stop the welding machine 3 and also a signal to stop the back gas supply by the second supply means 22. Next, the same operation as above is repeated for the remaining pipes to be welded.

[0018]

In the back gas supply device of the present invention configured as described above, a large amount of back gas is supplied and precharged by the first supply means, so that the inert gas in the internal space of the welded portion is supplied. The replacement can be performed quickly and efficiently. Then, the oxygen concentration in the internal space is detected to be equal to or lower than a preset value by the oxygen detection means, that is, it is detected that the replacement is sufficiently performed. A switch is made to the second supply means set to the required minimum flow rate. Therefore, it is possible to surely perform the inert gas replacement without excess and deficiency, and it is possible to suppress the consumption of the back gas at the time of welding to a necessary minimum. Further, by automatically starting the welding machine together with switching from the first supplying means to the second supplying means, the precharge and the starting of the welding machine can be linked.

Further, the oxygen detecting means is configured so that two different oxygen concentrations can be set, and when the measured oxygen concentration values are below the respective set values, respective detection signals are output, The first setting value is detected by setting the first setting value of the oxygen concentration value slightly higher than the oxygen concentration value at which welding work can be started and the second setting of the oxygen concentration value at which welding work can be started. A signal is used to switch from the first supply means to the second supply means, and a start command is issued to the welding machine 3 by the detection signal of the second set value, so that the inert gas replacement can be performed more reliably. Can be done. Further, a flow rate detecting means for detecting the back gas supply flow rate after the start of welding is further provided, and an alarm and / or a welding machine is detected by detecting that the flow rate of the back gas supplied by the detecting means has dropped below a predetermined value. It is possible to prevent the occurrence of welding defects and the like in advance by stopping.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a state in which TIG welding is performed using the back gas supply device of the present invention.

FIG. 2 is a partial cross-sectional view showing in detail a portion of the closed body 7 in FIG.

FIG. 3 is a flowchart illustrating the operation of the apparatus shown in FIG.

[Explanation of symbols]

 1 Welded Pipe 1a Welded Pipe 1b Internal Space 2 Welding Part 3 Welder 4 Welder Head 5 Operation Switch 6 Blocking Body 7 Blocking Body 8 Piping 9 Piping 10 Sample Piping 11 Cylinder 12 Band 13 Flange 14 Hole 15 Gas Outlet port 16 Through hole 17 Gas supply port 20 Back gas supply device 21 First supply means 22 Second supply means 23 Oxygen detection means 24 Control means 25 Flow rate setting means 26 Control valve 27 Flow rate detection means 28 Flow rate setting means 29 Control Valve 30 Flow rate detecting means 31 Flow rate lower limit detecting means 32 Flow rate upper limit detecting means 33 Header 34 Piping 35 Main valve 36 Solenoid valve 37 Remote switch device

Claims (1)

[Claims] 1. A pair of welded pipe bodies 1, which are welded to each other,
Gas supply port 17 for supplying back gas to the internal space 1b of 1a
In the apparatus for performing TIG welding by providing the gas discharge port 15 for discharging the gas from the internal space 1b thereof, the first supply which communicates with the gas supply port 17 and supplies the back gas at a set predetermined flow rate. Means 21, a second supply means 22 communicating with the gas supply port 17 and supplying a smaller amount of back gas than the first supply means 21 at a set predetermined flow rate, and a gas discharged from the gas discharge port 15. And an oxygen detecting means 23 for detecting the oxygen concentration of the backside gas is supplied from the first gas supplying means 21 to the gas supply port 17 by a start command, and the oxygen concentration decreasing signal from the oxygen detecting means 23 A back gas supply device for TIG welding, comprising a control means 24 for switching the back gas supply from the first supply means 21 to the second supply means 22.