JPS6328710B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to dry underwater welding for preventing components harmful to the human body from diffusing into the working atmosphere during dry underwater welding.

Generally, a dry method using a chamber is used for underwater welding at high water depths. FIG. 1 shows an example of the chamber. The chamber 1 has a water passage plate such as a punching plate attached to the bottom and communicates with the water, and the pressure inside the chamber is high enough to correspond to the depth of the water. The welder and the welding base material are placed in a working environment completely free of water. If the gas sent into chamber 1 is air, when the welder returns to land from chamber 1, the nitrogen dissolved in the blood in the body will boil due to the sudden change in atmospheric pressure, and there is a risk of diving sickness. be.

Therefore, air can be sent directly into the chamber up to a depth of about 30 meters, but at deeper water depths, the rate of absorption and excretion into the human body is increased, the solubility is reduced, and the anesthetic effect of nitrogen is prevented, reducing respiratory resistance. In order to do this, the gas inside the chamber is a mixed gas of (helium + oxygen) or (helium + nitrogen + oxygen). The amount of oxygen is 2.8% at a depth of 100m, 300
Since the concentration in M is as low as 1%, every possible care must be taken to control the components. For this reason, welding is performed in helium gas, but if welding is performed in an atmosphere containing a large amount of helium gas,
Welding methods that use tungsten electrodes cause abnormal wear on the electrodes, and the arc becomes unstable and rough. Furthermore, welding and cutting of underwater structures targeted by underwater welding require a powerful arc or plasma, which is accompanied by a large amount of exhaust gas. Of course, contamination can be reduced by opening a gas suction pipe, which is also used on the ground, near the arc, but if the suction is strong enough to prevent any exhaust gas from escaping, the welding arc and welding metal will be removed just like welding in strong winds. This will have an adverse effect on
Therefore, in the past, it was common to leave exhaust gas treatment, along with carbon dioxide gas etc. discharged by the operator, to the control of the atmosphere inside the chamber.

However, as mentioned above, even if there is no contamination due to welding, adding an additional burden to the difficult chamber atmosphere control is a problem that cannot be ignored in terms of health management of workers. This invention solved that problem.

The present invention will be explained below with reference to the drawings.

In the dry underwater welding method of the present invention, the underwater structure, in the illustrated example, the welded portion W of the underwater pipeline 4a, must be placed into the chamber 1, but this is in accordance with well-known technology. The welding method is arc or plasma welding, which uses an inert shielding gas, without using a covered arc welding rod that contains a lot of harmful gas. Conventional welding equipment may be used as is. As an example
FIG. 2 shows conventional TIG welding equipment, and FIG. 3 shows the same equipment with only a torch to which the present invention is applied.

The welding power source 2 has drooping characteristics, and its (+) side terminal is connected to the welding base material 4 via the earth cable 3, and its (-) side terminal is connected to the electrode 6 via the torch cable 5. ing. 7 is an arc generated between the electrode 6 and the base material 4, and 8 is molten metal. In Japan, argon is generally used as the shielding gas S, and from the inlet 9, the shielding gas nozzle of the torch 10', only the tip of which is shown in the figure.
10a′ and is discharged into the weld area to protect the molten pool.

The torch 10 shown in FIG. 3 to which this invention is applied differs from the torch 10' shown in FIG. or consisting of a group of fibers,
This is the addition of an absorption nozzle 11 having a skirt-shaped flexible brush (annular brush-shaped nozzle) 14 at its tip that allows a minute amount of arc light to pass through. The suction part is located between the shield gas nozzle 10a and the flexible wall,
Of course, the suction nozzle 11 has its exhaust port 13 connected to the vacuum pump 12, and the exhaust gas is discharged into or onto the water and is not collected.

The torch 10 may be operated semi-automatically by gripping the peripheral handle (not shown) as shown in FIG. 1, or in this case, it may be fixed to an automatic pipe welding device for fully automatic welding. . During welding, the torch 10 is pressed against the surface of the base material 4 on the outer periphery of the welding part so that the skirt-shaped flexible brush 14 is slightly bent, even if the hand holding the torch 10 shakes a little or even if there are heights on the surface of the base material. The tip of the flexible brush 14 is always in contact with the base material 4 so as not to lose its partitioning effect. Therefore, the positions of the tip of the electrode 6 and the tip of the flexible brush 14 are adjusted appropriately so that an appropriate arc length is maintained in the upper state.

In addition, the exhaust volume of the suction nozzle 11 is reduced so that the entire amount of the supplied shield gas S, the gas generated by the arc heat, and the metal vapor is exhausted, and the flexible brush 14 itself and the gap between the flexible brush 14 and the base material 4 are reduced. The pump or fan 12, conduit, discharge port 13, etc. are designed to draw in and discharge an appropriate amount of gas from the chamber. In the experiment, as shown in Figure 6, as an example, the distance between the nozzle and the base material was set to 20 mm.
If the feed shield gas flow rate Q ₁ is set to 30Nl/min, the ratio of the displacement amount Q ₂ to the feed shield gas flow rate is
The relationship between Q ₂ /Q ₁ and the amount of gas released into the chamber Q ₃ is that the larger Q ₂ /Q ₁ is, the smaller Q ₃ is.
Flexible wall even if Q ₂ /Q ₁ are the same (annular brush type nozzle)
The effect of the flexible wall is remarkable. A in the figure shows the current flow without a flexible wall.
When 100A flows, a uses a flexible wall to carry the current.
When 100 A is applied, B is the case where there is no flexible wall and no current is passed, and b is the case where the flexible wall is used and no current is passed. The amount of Q ₃ released into the chamber varies depending on the flow rate of the shield gas supplied and the current value, but usually the exhaust volume Q ₂ is equal to the flow rate Q ₁ of the shield gas supplied.
If the volume was increased by 1.5 to 3 times, harmful substances generated by the arc, such as argon gas, ozone, and fume, would not be emitted into chamber 1, but it is necessary to conduct a simple test and adjust the exhaust volume to an appropriate value. Bye.

The air permeability of the flexible brush 14 used in the experiment varies depending on the conditions of use, but is at a level that causes a flow path resistance of 20 to 150 mm at the water head. Airtightness and flexibility tend to be contradictory, and the lack of airtightness can be compensated for by the displacement. In order to prevent harmful gases from leaking to the outside, the exhaust amount only needs to be able to reduce the pressure inside the flexible brush 14 so as to suck in the external gas G, and there is no need to suck in excess gas.

Under atmospheric pressure, the shielding gas is either argon or helium.However, the deeper you go underwater and the higher the pressure, the higher the required arc voltage for helium. If the pressure inside the chamber exceeds 30 bar, the arc voltage will approach 60 V in the case of helium, making it impossible to use an ordinary arc welding machine as a power source. Furthermore, the higher the atmospheric pressure, the more the arc contracts and tends to concentrate at the tip of the electrode, which is more pronounced in helium than in argon.

In experiments, when helium was used, the electrode tip began to burn out at a pressure of 8 bar, arc became unstable at 16 bar, and welding failed at 32 bar.

Therefore, when carrying out operations deep underwater, argon is decisively superior to helium as it is less affected by atmospheric pressure as a shielding gas.

Argon, like nitrogen, is not toxic in itself, but it has a significantly higher solubility in water (blood, etc.) than nitrogen or helium, and is excreted from the human body at a slower rate, so there is a high risk of promoting diving disease. . Therefore, when using argon in the chamber, instead of dissipating it into the chamber and then exhausting it through ventilation (because it is difficult to separate argon from the helium in the chamber), it is removed from around the arc as in this invention. It is desirable to capture and discharge them immediately.

Next, the welding apparatus of the present invention will be explained. For either arc or plasma welding, conventional welding equipment can be used as is, simply adding a suction nozzle with a skirt-shaped flexible brush around the outer circumference of the torch's gas nozzle, and arranging an exhaust device to connect to this. . The TIG welding torch 10 in Figure 3 is for MIG,
It can be thought of as a plasma welding torch, and the point is that a suction nozzle 11 with a flexible brush 14 is attached to the outer periphery of the shield gas nozzle 10a in an airtight manner at the upper part, so that exhaust can be exhausted by a pump or fan 12. It is. Since the exhaust device is based on well-known technology, the features of the welding device of the present invention are focused on the suction nozzle 11 with the flexible brush 14.

As mentioned above, if the harmful gas used as a shielding gas during welding and the harmful gas and metal vapor generated during welding are completely exhausted by conventional suction and exhaust devices, the suction wind will make the arc unstable. The suction nozzle 11 of the present invention surrounds the outer periphery of the shield gas nozzle 10a of the torch, maintains contact with the surface of the base material by means of a skirt-shaped flexible brush 14, and temporarily isolates the vicinity of the arc from the outside air. Therefore, harmful gases and metal vapors generated near the arc are silently drawn radially to the outer periphery.
Central arc (sensitive to wind due to plasma-like gas body)
is discharged without affecting the

The skirt-shaped flexible brush 14 has flexible elasticity, so if you move it while lightly pressing it against the base material, it will bend and expand according to the undulations of the base material surface and the shaking of the hand holding the torch. and generated gas,
Maintains a barrier effect that traps vapor. Furthermore, as the flexible brush 14, one made of thin metal wires, non-metallic fibers, or both bundled into an annular brush shape has the property of allowing a small amount of arc light to pass through, so it is possible to block intense arc and plasma light without using safety glass. This has the great advantage of being able to proceed with welding while monitoring. The metal wire mentioned above is 0.1 to 0.2 mm of heat-resistant stainless steel.
diameter, carbon fiber is used as the non-metallic fiber,
Good results have been obtained, but there are probably many other suitable methods as well.

The means for binding the upper parts of the thin wires or fibers arranged in the shape of an annular brush may be any method such as welding, brazing, braiding, or clamping, and the connection method to the end of the suction nozzle 11 may be brazing in the illustrated example, but screws may be used. It is also good to make it removable by stopping it. Deep welding groove 1 as shown in Figure 4
5, a flexible brush 14 that matches the shape
When performing fillet welding using a square fillet welding brush, it is convenient to make it replaceable, such as using a square flexible brush for fillet welding. However, as shown in FIG. 5, for a relatively shallow development 15, the flexible brush 14
By making the skirt slightly longer, whether the groove shape is V-shaped or U-shaped, it will fit in as if the brush was pressed into the groove. And weld bead 1 that forms at the rear
Since the flexible brush 14 naturally adapts to the protrusion 6, the partition effect of the flexible brush 14 is maintained.

Since some of the thin wires of the flexible brush 14 enter the groove 15, the gap between the thin wires increases in some parts, and the blocking effect may be weakened, but if you allow some margin for the displacement of the suction nozzle 11. , the amount of exhaust gas will only temporarily increase, but there is no risk that the generated gas will escape to the outside. Since the flexible brush 14 itself has a function of permeating gas to a certain extent, a small amount of external gas is always present.
The pump is sucked and discharged, so even if the gap between the base material and the flexible brush increases temporarily, the displacement will not change suddenly. This contributes to stabilizing the atmosphere within the flexible brush 14 and, in turn, stabilizing the arc.

Although the present invention has been described above with reference to the illustrated embodiments, it is possible for engineers to make various changes and applications using known techniques without changing the gist of the invention. For example, the method of this invention can be used for welding inside chambers that maintain internal pressure at atmospheric pressure, spacecraft, and other closed containers, or it can be used for general welding parts to prevent air contamination and danger from arc light. It is easy to think of ways to completely prevent this, and also make it possible to perform arc welding in strong winds, or change the welding torch to a heating or cutting torch.

This invention has achieved the treatment of generated gas and metal vapor, which are problems in chamber welding in deep sea, etc., without compromising welding quality or workability, by simply adding a special suction and exhaust device to the welding torch. That is, since a suction nozzle with a skirt-shaped flexible brush is simply added to the outer periphery of the gas nozzle of the torch and connected to the exhaust device, the equipment is simple and the lightness of the torch is not impaired. The skirt-shaped flexible brush is flexible and highly elastic, so even unskilled workers can weld by pressing the brush onto the weld line while advancing the torch without being affected by hand movement or the unevenness of the base material. The flexible brush weakens the internal arc light enough to be visible to the naked eye and transmits it, allowing the welding condition to be detected without passing through dark safety glass.

In addition, this skirt-shaped flexible brush can radially suck shielding gas, generated gas, and metal vapor from the outer periphery of the arc, and constantly sucks in outside air from the slits around the entire circumference, temporarily Even if the outside air inlet is enlarged, there is little fluctuation in the suction gas flow, and this is the suction method that has the least effect on the sensitive arc. Furthermore, since the outer periphery of the arc is temporarily isolated from the outside air, the amount of expensive shielding gas such as argon used is significantly reduced compared to the conventional method, and the exhaust device can also be of small capacity.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of underwater welding according to the present invention, Fig. 2 is an explanatory diagram of a conventional TIG welding device, and Fig. 3
The figure is an explanatory diagram of the main parts of the torch in the welding device of the present invention, and Figure 4 is a welding situation of a deep V-shaped groove.
FIG. 5 is an explanatory diagram of the welding situation of a shallow V-shaped groove. Figure 6 shows the amount released into the chamber Q ₃ and Q ₂ /
This shows the relationship between Q ₁ (Q ₂ : displacement volume, Q ₁ : supply shield gas flow rate), and in the figure, A, a, B, and b are respectively (no flexible wall, current 100 A) and (flexible wall). Yes, current 100A), (without flexible wall, current 0), (with flexible wall,
The current is 0). 10, 10′...Welding torch, 11...Suction nozzle,
14...Skirt-shaped flexible brush.

Claims (1)

[Claims] 1. In dry underwater welding in which the welding part of an underwater structure is placed in a chamber and welded, the welding method used is an arc or plasma welding method using shielding gas, and the welding torch is used to Further, around the outer periphery of the shielding gas nozzle, one or both of thin metal wires and non-metallic fibers having flexible elasticity and heat resistance are bundled into an annular brush shape, and a skirt can be formed to transmit a small amount of arc light. The structure includes a suction nozzle with a flexible brush at the tip, and during welding, the torch is pressed against the surface of the base material around the welding part so that the flexible brush is slightly bent, and the flexible brush is driven while always in contact with the base material. By doing so, the entire amount of harmful components such as shielding gas, gas generated by welding, and metal vapor is discharged from the suction nozzle,
Dry underwater welding is further characterized in that environmental pollution within the chamber is prevented by discharging a small amount of gas sucked into the chamber from the gap between the flexible brushes and the gap between the flexible brush and the base material. Method. 2. In the dry underwater welding method according to claim 1, the gas in the chamber is (helium + oxygen) or (helium + nitrogen + oxygen), and the torch shield gas is mainly argon.