JP2604696B2 - Welding method for stainless steel pipes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates, in the welding of the pipe joint, such as stainless steel or titanium, relates to a pipe welding how to reasonably achieve the prevention of oxidation of the pipe inner peripheral surface.

[0002]

It should be noted on the welding BACKGROUND OF THE INVENTION Stainless steel is first antioxidant of the molten metal, preventing in particular refractory chromium oxide (Fe0 · Cr ₂ 0 _3, mp 1,900-2,180 ° C.) the occurrence or To remove inert gas,
It is necessary to protect the molten metal with a non-oxidizing gas or flux. In this regard, protection of the arc with an inert gas, such as TIG welding or plasma arc welding, is significantly better than with covered arc welding.

[0003] An important application of TIG welding is first layer welding of pipe butt joints. In the butt welding of small and thin pipes, the backing ring was conventionally welded inside the joint, but this hinders the smoothness of the inner peripheral surface,
Further, there is a disadvantage that a root crack is easily generated. In order to eliminate these disadvantages, the inner peripheral surface is shielded with an inert gas so as to obtain a smooth molten metal on the inner peripheral surface.

[0004]

In order to shield the inner peripheral surface of the pipe with an inert gas, it is necessary to seal a certain concentration of the inert gas inside the pipe such as stainless steel. For this reason, conventionally, an oxygen concentration meter or the like is attached and the both end surfaces of the pipe are closed, and then the inert gas is sent into the pipe and the concentration is measured by the oxygen concentration meter. After confirming that it has risen above the value, welding work has started.

In the above-described apparatus, since the inert gas is fed by closing both end surfaces of the pipe, a large amount of the inert gas is required when the pipe is long, and the gas concentration increases to a certain value or more. It takes a long time before the welding operation becomes very inefficient. In addition, to measure the concentration of inert gas with an oximeter or the like, expensive measuring instruments must be carefully installed, and the installation and removal of measuring instruments must be performed for each pipe to be welded. Is significantly worse.

The present invention has been proposed to improve the conventional problems relating to welding of butt joints such as stainless steel pipes. In the present invention, an inert gas is filled only in a necessary area inside a pipe at the time of joint welding. It is an object of the present invention to provide a pipe welding method for effectively preventing oxidation of the inner peripheral surface of the pipe. Another object of the present invention, pipes welded
The is to provide a method for efficiently and inexpensively achieved.

[0007]

In order to achieve the above object, a pipe welding apparatus 1 according to the present invention, as shown in FIG. 1, comprises a TIG or plasma arc welding machine 3 having a torch 2 and a weldable state. And a timer 5 for turning on the indicator light after a predetermined time elapses, and a solenoid valve 6 for controlling gas supply between the two disks on the inner peripheral surface of the pipe. . This welding device 1 may be any of full-automatic welding, semi-automatic welding or pipe-fixed manual welding of a rotating pipe, and the torch 2 and the solenoid valve 6 are piped from a gas cylinder 7 or a centralized gas piping facility in a factory.

As is apparent from FIG. 2, the pipe welding apparatus 1 includes a pair of sectioning disks 11, 11 having a diameter slightly smaller than the inner diameter of the pipe 10 to be welded, and a flexible tube for vertically supporting both disks. And preferably 12. Disks 11 and 1 made of aluminum etc.
1 can be closely attached to the inner peripheral surface of the pipe by attaching an elastic material 13 such as rubber to the periphery thereof, and may be appropriately replaced with one having a different diameter according to the inner diameter of the pipe to be welded.

The flexible tube 12 usually extends through the center of both disks 11, 11, and has a plurality of gas flow holes 14 in a peripheral wall between the disks. The tube 12 has one end 15 connected to the gas cylinder 7 via the electromagnetic valve 6 and the other end 16 closed when the apparatus is operated, so that the inert gas in the cylinder 7 passes through the flow hole 14. The space between the two disks 11 is filled.

In the pipe welding method according to the present invention, a pair of divided discs 11, 11 are arranged at a predetermined interval in order to fill an inert gas only in a necessary area inside a pipe 10 (FIG. 1) such as stainless steel or titanium. And make close contact with the inner peripheral surface of the pipe. The inert gas used in the method of the present invention is a welding machine 3
Argon, helium, nitrogen gas, carbon dioxide gas or a mixed gas of these and air may be used as the shielding gas sent to the torch 2.

In the method of the present invention, the power switch is turned on and the solenoid valve 6
Is activated and the timer 5 is excited. The inert gas passes through the solenoid valve 6 and the two discs 1 inside the pipe.
After a predetermined time has passed from the gas supply, the timer 5 is operated and the welding operation can be started. Timer 5
Is set, for example, to 60 seconds, and this set time may be appropriately adjusted according to the wall thickness and diameter of the pipe 10 to be welded.

[0012]

According to the pipe welding method of the present invention, when welding a butt joint such as a stainless steel pipe 10, an inert gas is filled only between the pair of partitioning disks 11 inside the pipe so that the inner peripheral surface of the pipe can be sealed. Prevent oxidation. Even if the pipe 10 is long or the elbow 17 (FIG. 3), the inert gas is fed only between the disks 11 and 11, so that the filling amount is small, and the gas concentration on the inner peripheral surface of the weld is more than a certain value. The time it takes to rise to becomes shorter.

In the pipe welding apparatus 1 of the present invention, when welding a joint, the concentration of an inert gas capable of achieving prevention of oxidation of the inner peripheral surface of the weld is determined not only by visual inspection but also by a patlite (trade name).
Can be accurately confirmed by the indicator lamp 4. Moreover, in the apparatus 1 of the present invention, only the inexpensive indicator lamp 4 is installed for checking the concentration of the inert gas, and there is no need to attach or remove a measuring instrument or the like for each pipe to be welded.

[0014]

Next, the present invention will be described based on embodiments.
The pipe welding apparatus 1 according to the present invention is a fully-rotating pipe welding apparatus. As shown in FIG. 1, a TIG welding machine 3 having a torch 2 and a gas cylinder 7 are mounted on a frame 20. It is installed movably along the positioner 21. An indicator light 4 such as a patrol light (trade name) indicating a weldable state is attached to the upper part of the frame 20, and a known timer 5 and a solenoid valve 6 are provided on the side of the frame.
Attach.

Although not shown, a reel of a filler wire, a wire speed governor, a wire feed / feed motor and the like are installed in the TIG welding machine 3, and a wire guide (not shown) is formed in the torch 2. The torch 2 is a pipe 1 to be welded.
According to the diameter of 0, the torch support plate 18 can be moved in the front-back direction, and the plate can be further horizontally moved in the up-down direction.

Further, as apparent from FIG. 2, the pipe welding apparatus 1 includes a pair of aluminum discs 11,
11 and a flexible tube 12 for vertically supporting both disks. The disks 11, 11 have a diameter slightly smaller than the inner diameter of the pipe 10 to be welded, and the periphery thereof is surrounded by an annular rubber material 13, so that the disks can be in close contact with the inner peripheral surface of the pipe 10. Plural sets of disks 11, 11 having different diameters according to the inner diameter of the pipe 10 to be welded are prepared.

The discs 11 may be folded in two or formed into a disc spring shape so as to be easily inserted into the pipe 10. In this case, the disks 11, 11 are slightly deformed by the pressurization with the inert gas, and come into close contact with the inner peripheral surface of the pipe. Further, the periphery of the disk may be surrounded by a specially shaped annular rubber material 13 so that the disk is brought into close contact with the inner peripheral surface of the pipe by pressurization with an inert gas.

The flexible tube 12 extends through the centers of the disks 11, 11 and forms a plurality of gas flow holes 14 in a peripheral wall between the disks. The tube 12 is piped such that one end 15 thereof is connected to the gas cylinder 7 via the electromagnetic valve 6 (see a two-dot chain line in FIG. 2).
Further, the other end 16 is closed when the apparatus is operated. Cylinder 7
The inert gas therein is a mixed gas of argon and air, which is a shielding gas sent to the torch 2 of the welding machine 3,
From the disc 1 through the flow hole 14 of the tube 12
Flow between 1 and 11 to fill.

FIG. 4 is a circuit diagram schematically showing electric wiring in the pipe welding apparatus 1. The power switch 22 is, for example, a known push button switch. When the switch is turned on, the gas electromagnetic valve 6 and The relay 23 operates, and the timer 5 is excited by the relay. The timer 5 is operated, for example, after 60 seconds to turn on the indicator lamp 4. On the other hand, when the switch 22 is turned off, another relay operates to excite the timer 24. The timer 24 is activated, for example, after 60 seconds, and closes the gas solenoid valve 6 and turns off the indicator light 4.

The stainless steel pipe 10 to be butt-welded is set horizontally by the chuck 25 of the positioner 21 so that the joint portion 19 of the normal V-shape is completely aligned.
The pair of partitioning disks 11, 11 are arranged perpendicularly to the pipe axis near the joint 19 to seal the inside 10a of the pipe in order to fill the inert gas only in a necessary area inside the pipe.

Next, the frame 20 is appropriately moved,
The torch 2 of the TIG welding machine 3 is positioned at the joint 19. When the power switch 22 is turned on, the gas solenoid valve 6 and the relay 23 operate, and the inert gas is transferred from the cylinder 7 through the solenoid valve 6, the piping and the tube 12 to both the disks 11 and 1.
At the same time, the timer 5 is excited by the relay 23.

The timer 5 detects that the inert gas
It is activated after a set time between 1 and 11 is filled. By the operation of the timer, the indicator lamp 4 is turned on and the positioner 21 is butt-welded with the torch 2 of the TIG welding machine 3.
To rotate the pipe 10. When the pipe 10 completes one rotation and the welding is completed, the switch 22 is turned off, which activates another relay to excite the timer 24.

Immediately after the completion of the joint welding, the pipe 1
Since the amount of oxygen in the internal space 0 is increasing, the timer 24
While the solenoid valve 6 is open, the supply of the inert gas is continued while the solenoid valve 6 is opened, and at the same time, the joint welding point is rapidly cooled by air or the like. 60 seconds after the cooling is completed, the timer 2
4 operates to close the electromagnetic valve 6, stop the supply of the inert gas, and turn off the indicator light 4. Thereafter, the other end of the tube 12 may be opened to release the inert gas inside the pipe into the air, and the partition disks 11, 11
Remove from inside the pipe.

When this welding apparatus is a semi-automatic pipe rotating type welding by the positioner 21, the switch 22
Is turned on, and waits until the indicator light 4 is turned on. After the indicator light is turned on, the butt welding with the torch 2 of the TIG welding machine 3 may be started. When the predetermined manual welding is completed, the switch 22 is turned off, and after the indicator lamp 4 is turned off, the other end 16 of the tube 12 is opened to release the inert gas in the pipe into the air.

When a pipe having an elbow 17 as shown in FIG. 3 is butt-welded, the pipe is fixed horizontally on a table (not shown), and the tube 12 is bent along the elbow 17 of the pipe. A pair of sorting disks 11, 11 are fitted into the pipe. Disk 11,
In order to fill the inert gas only in a necessary area inside the pipe, the pipe 11 is arranged perpendicular to the pipe axis near the elbow at the joint 19 to seal the inside 10b of the pipe.

[0026]

According to the pipe welding method of the present invention, when welding a butt joint such as a stainless steel pipe, an inert gas is filled only between a pair of partition disks inside the pipe to oxidize the inner peripheral surface of the pipe. Effectively prevent. In the method of the present invention, even when the pipe to be welded is long or an elbow, the amount of the inert gas is small, and the time required for the gas concentration to rise to a certain value or more on the inner circumferential surface of the weld is shortened, and the welding operation is shortened. The efficiency is high and it is very economically advantageous.

In the pipe welding apparatus of the present invention, the concentration of the inert gas for preventing the inside of the pipe from being oxidized when the joint is welded can be accurately confirmed not only by visual inspection but also by an indicator light such as a patrol light. When the pipe welding apparatus is semi-automatic or manual welding, welding is started by turning on the indicator light, gas is efficiently released by turning off the indicator light, and oxidation during joint welding can be reliably prevented.

Moreover, in the apparatus of the present invention, only an inexpensive indicator light such as a patrol light is installed, and there is no need to attach or remove a measuring instrument or the like for each pipe to be welded. The apparatus of the present invention is economical because an expensive measuring instrument is not required, and the work efficiency is increased because it is not necessary to attach and detach the measuring instrument and the like for each pipe.

[Brief description of the drawings]

FIG. 1 is a schematic side view illustrating a pipe welding apparatus according to the present invention.

FIG. 2 is a schematic plan view showing a pipe to be welded in the pipe welding apparatus of FIG.

FIG. 3 is a schematic sectional view showing another example of use of the pipe welding apparatus.

FIG. 4 is a circuit diagram schematically showing electric wiring in the pipe welding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pipe welding apparatus 2 Torch 3 Welder 4 Indicator 5 Timer 6 Solenoid valve 7 Gas cylinder 10 Stainless steel pipe 11, 11 Separation disk 12 Flexible tube 14 Gas circulation hole

Claims (2)

(57) [Claims] 1. A pair of sorting disks are fixed inside a pipe made of stainless steel or titanium at a predetermined interval, and then a power switch of a welding machine is turned on to activate an electromagnetic valve and to excite a timer. It forced in an inert gas to between the divided disk inside the pipe through a valve, inert
Inert inside the pipe after a specified time has passed since the gas was introduced
When the gas is full, the timer is activated and the indicator lights up to indicate that the welding operation can be started, while the welding operation is completed and the power switch of the welding machine is turned off to activate another timer.
Inactive with the solenoid valve open and the indicator light on
Oxidizing gas inside the pipe to prevent oxidation
Stop and cool the welded area with air, etc.
Then, when another timer is activated at the time when the cooling is completed, the solenoid valve is closed to stop the supply of the inert gas, and at the same time, the indicator lamp is turned off to inform the user that the welding pipe can be removed. Welding method. 2. In order to fill an inert gas only in a necessary area inside the pipe, a pair of partitioning disks are brought into close contact with the inner peripheral surface of the pipe at a predetermined interval, and both disks are vertically supported by a flexible tube. In the flexible tube, a plurality of gas flow holes are formed in a peripheral wall between both disks, and by connecting the tube to a gas cylinder via an electromagnetic valve , an inert gas passes through the gas flow holes.
2. The method according to claim 1, wherein the flow is filled between the two discs .