JPS5927982Y2 - Inner side gas shield device for ERW pipe making - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a gas shield device that creates an inert gas atmosphere in a welded area during the manufacture of an electric resistance welded pipe.

There are many oxide defects in the welds of conventional ERW pipes.

This is because oxides generated during melting were not squeezed out and remained in the weld.

Because of these defects, conventional electrical resistance welded tubes were generally considered to be unreliable.

Therefore, when manufacturing high-grade line pipes and the like, it is necessary to create an inert gas atmosphere in the welded area during electric resistance welding to prevent the formation of oxides.

Conventionally, in order to create an inert gas atmosphere in the welded part, inert gas is supplied to the welded part from the outer surface of the electric resistance welded pipe or from both the inner and outer surfaces.

Gas is normally supplied from the outside through the electric resistance welded pipe 1 as shown in Figure 1.
A gas shield device 3 is provided on the outside surface of the squeeze roll 2, close to the squeeze roll 2, and on the inlet side thereof.

However, when gas is supplied only from the outside surface, a large amount of gas is required to replace the inside surface with inert gas, which can cause harmful effects, so a gas shield device is also installed on the inside surface. It is considered preferable to supply

Note that supplying gas only from the inner surface is not carried out due to reasons such as the high specific gravity of the normally used inert gas.

Conventional inner side gas shield devices have drawbacks such as being easily damaged by welding spatter and being unable to be used continuously for long periods of time due to the accumulation of spatter, making it difficult to stably produce high-quality ERW pipes. It was unfit to do so.

The present invention provides an inner side gas shield device that is inserted into the pipe during welding of ERW pipes to create an inert gas atmosphere in the welded area, and is not damaged by welding spatter and does not accumulate welding spatter. The purpose is to stably obtain high quality ERW pipes.

The inner side gas shield device of the present invention has an upper skirt fixed to the upper part of the shield box which is open at the top and bottom, and a lower skirt attached to the pipe to be welded at the bottom so that the height can be adjusted freely. It is characterized in that inert gas blow-off ports are provided on both sides of the weld line, and a curtain gas blow-off nozzle is further provided on the side surface of the welded pipe on the unwelded side.

The device of the present invention will be explained in detail below with reference to the drawings.

As shown in FIG. 2, an upper skirt 5 and a lower skirt 6 are provided at the top and bottom of a shield box 4 that is open at the top and bottom.

Each skirt is made of heat-resistant flexible materials such as quartz tape and asbestos.

The lower skirt 6 is attached closely to the shield box 4 so that its height can be adjusted.

In the upper part of the inside of the shield box 4, two gas outlets 8 connected to the inert gas introduction pipe 7 are installed in the opposite direction.

Further, a curtain gas blowing nozzle 9 is provided on the side surface of the shield box 4.

The installation position is the entrance side of the welded pipe, that is, the side surface that is the unwelded side when the device is set in the welded part as shown in FIG.

10 is a curtain gas inlet, and 11 is a set metal fitting.

The device of the present invention has a welding point 12 as shown in FIGS. 3 and 4.
It is attached to the frame 14 provided in the middle of the mandrel 13 using a set metal fitting 11 and a set bolt 15 so as to cover the welded pipe, and the upper and lower skirts 5° and 6 are respectively in appropriate contact with the inner surface of the pipe depending on the inner diameter of the welded pipe to improve airtightness. Then, adjust the attachment position of the lower skirt 6 to the shield box 4.

Note that the mandrel 13 is already provided for mounting an inner bead cutting device or the like.

During electric resistance welding, an inert gas such as Ar is introduced into the gas introduction pipes 7 and 10, and the inert gas is blown out from the gas outlet 8 and the curtain gas outlet nozzle 9.

The gas outlet 8 is preferably a slit, but may also be a porous nozzle.

By filling the area around the gas outlet 8 with a fibrous material such as steel wool, glass wool, or asbestos, or a porous granular material such as alumina or silica, the inert gas blown onto the welding area can be It becomes a laminar flow.

The same gas may be introduced into the gas introduction pipes 7 and 10 from the same pipe, or a gas with inferior purity may be introduced into the gas introduction pipe 10 through separate pipes.

Since the inner side gas shield device of the present invention is open at the top and bottom, welding spatter 16 will not accumulate inside the device and will not damage the device or reduce the shielding performance.

Since the contact area with the inner surface of the welded pipe is made of a flexible skirt, airtightness is improved, there is no breakage due to welding spatter, and the welded area can be kept in a stable inert gas atmosphere.

As described above, the device of the present invention reliably creates an inert gas atmosphere in the welded part of the electric resistance welded pipe and its vicinity, prevents oxidation of the welded part, and makes it possible to obtain a highly reliable welded pipe with a high yield.

[Brief explanation of the drawing]

Figure 1 shows a conventional external gas shield device, Figure 2
The figure is a perspective view of the inner side gas shield device of the present invention, FIG. 3 is a longitudinal cross-sectional view showing the device of the present invention in a set state, and FIG. 4 is a perspective view of the same. 1...Erw tube, 2...Squeeze roll, 3...Gas shield device, 4...Shield box, 5...Top Skirt, 6...
...Lower skirt, 7...Gas introduction pipe, 8
......Gas outlet, 9...Curtain gas blowout nozzle, 10...Gas introduction pipe, 11.
...Set metal fittings, 12...Welding points, 13
...Mandrel, 14...Frame, 15.
...Set bolt, 16...Spatter, 17...Contact tip.

Claims (1)

[Scope of utility model registration request] An upper skirt is fixed around the entire upper part of the shield box, which has an open top and bottom, and a lower skirt is installed around the entire lower part in close contact with the pipe to be welded so that the height can be adjusted freely, and the welding line of the ERW pipe is installed inside. An inner side gas shield device for an electric resistance welded pipe, characterized in that an inert gas outlet is provided on both sides, and a curtain gas outlet nozzle is further provided on the unwelded side of the external welded pipe.