JP2003053543A - Tig welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit high-efficiency TIG welding of shielding a welding arc with gaseous He and shielding a weld metal with gaseous Ar even in narrow groove welding and to make it possible to stably perform high-frequency and high-voltage discharge process start in spite of shielding with the gaseous He. SOLUTION: This TIG welding equipment has a shielding box 4 for blowing the inert gases into the groove from outside the groove, a welding torch 1 for performing TIG welding by being inserted into the groove, an electrode 3 at the front end of the welding torch and gas nozzles 2a and 2b which are arranged on both sides of the electrode and blow off the inert gases. The blow- off directions of the gases are directions opposing each other and the gases blown off from the gas nozzles collide against each other, forming the gaseous streams of an ascending component and a descending component. The gaseous Ar is adopted for the inert gas blown off from the shielding box 4 and the gaseous He is adopted for the inert gases blown off from the gas nozzles 2a and 2b.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a welding apparatus,
Especially in a groove with a very narrow groove width, TIG (Tungst
en Inert Gas Arc) Welding equipment effective for performing welding.

[0002]

2. Description of the Related Art Main piping for power generation boilers, R for nuclear power generation
PV (Reactor Pressure Vesse)
The pressure vessel such as l) is a thick plate structure having a thickness of 30 mm to 150 mm, and has a large number of welding points. For example, the main piping that forms part of the power generation boiler is a main steam pipe, high-temperature reheat steam pipe, low-temperature reheat steam pipe, main water supply pipe, etc. It has a structure of. The main piping has a high-temperature, high-pressure piping structure in which high-temperature, high-pressure steam heated by a coil is sent from a boiler to a turbine, and steam that has finished work in the turbine is returned to the boiler coil again.

Further, since the piping itself is at high temperature and high pressure, the expansion and contraction amount at the time of starting and stopping the boiler is large, and stress concentrates on the welded joint, so that a high quality weld is required for the main piping from the boiler to the turbine. To be done. In this welding, the heat input to the base metal is suppressed to reduce welding distortion and thermal effects,
Further, a narrow groove arc welding method with a groove width of 8 mm to 12 mm is applied because the welding can be performed efficiently.

The welding method is stainless steel, and in the case of high alloy steel, non-consumable electrode type TIG (Tungsten In) is used.
ert Gas Arc welding method is also used for low alloy and mild steel, the consumable electrode type GMA (Gas Metal) is used.
Arc) welding method is often applied.

Here, as a technique related to the present invention, a narrow groove TIG welding method will be described with reference to FIG. A narrow groove 14 having a width of 8 mm to 12 mm between the base materials 5a and 5b facing each other.
Is processed, and the long welding torch 1 and wire torch 9 thinner than the groove width are inserted into the narrow groove 14. An electrode 3 made of tungsten is attached to the tip of the welding torch 1, and the electrode 3 is used as a negative electrode and the base materials 5a and 5b while shielding the weld from air by an inert gas (Ar gas) blown from the torch tip. The arc 6 is formed as a positive electrode, the additive wire 8 guided by the wire torch 9 is fed to the welding portion for welding, and the narrow groove 14 is filled with the weld metal to join the base materials 5a and 5b.

FIG. 12 shows a state in which welding is performed while moving the welding device in the groove direction by means of a moving device such as a carriage, which is not shown. The addition wire 8 is wound around a wire reel 24 and guided by a wire feeder 23 to a welding portion via a conduit cable 22 and a wire torch 9.

Further, since only the shielding gas blown from the tip of the welding torch 1 entrains the air around the welding torch 1 and the shield of the welded portion is incomplete, the shield box 4 is placed outside the narrow groove 14 above the welding torch 1. Generally, a method of installing and flowing a shield gas in the direction of the narrow groove 14 to create an inert gas atmosphere inside the narrow groove 14 is generally adopted.

This narrow groove TIG welding method is a multi-layer welding of one layer and one pass, and since one layer has a laminated thickness of about 2 to 3 mm, if the plate thickness becomes thick, it becomes a continuous welding for a long time of several hours. It was desired to further improve efficiency and ensure quality.

As a technique for increasing the efficiency of TIG welding, Japanese Patent Application Laid-Open No. 7-227673 proposes a method of using He gas as a shield gas. When He gas is used as the shield gas, the arc pressure drops,
On the contrary, as can be seen from the graph of FIG. 5 showing the influence of the He amount in the Ar / He mixed gas on the arc voltage, it has the effect of increasing the arc voltage. Naturally, the amount of heat input into the base metal (welding current x arc voltage ÷ welding speed) also increases, and high efficiency welding can be performed.

However, the method of using He gas deteriorates the shield property against the weld metal. Further, in the method using the mixed gas of He and Ar, as can be seen from FIG. 5,
Since the arc voltage of the pure Ar gas is almost reached by mixing only 25% of the Ar gas with the pure He gas, the He gas effect cannot be exhibited at a higher Ar mixing ratio. on the other hand,
On the other hand, if the Ar mixing ratio is less than this, the He concentration will be too high and the shielding property will deteriorate.

Therefore, in the double shield method of the conventional example as shown in FIG. 11, by flowing He gas as the center gas and Ar gas as the outer gas, the welding arc is shielded by the He gas as the center gas and melted. By shielding the metal with Ar gas as the outer gas, high efficiency TIG welding is realized by utilizing the high potential gradient of pure He while maintaining the shielding property against the molten metal.

On the other hand, when TIG welding is performed with a very narrow groove having a groove width of 7 mm or less, both side groove walls can be melted by an arc without weaving the electrode left and right in the groove,
Since the amount of deposited metal can be small, TIG welding can be performed in a short time, and welding deformation and residual stress are extremely small, and various technological developments are underway.

For example, as shown in FIG. 11, a shield nozzle 18 is arranged on the surfaces of the base materials 5a and 5b by using the double shield torch described above, and a long round tungsten electrode 3 reaching the groove bottom. Is mounted on the electrode holder 16d, and welding is performed while Ar gas is strongly flown from the shield nozzle 18 and He gas is strongly flown from the center gas nozzle 17 provided in the shield nozzle 18. In this shield method from the surface of the base material, the reach depth of the center gas is limited to about 40 mm, and the groove depth is 100 mm.
Not applicable to deep groove welding.

An example of a conventional narrow groove TIG welding torch (Japanese Patent Publication No. 3-69629) is shown in FIGS. 9 and 10. An electrode 3 is attached to the tip of the welding torch, and it is necessary to shield the periphery with Ar gas, which is an inert gas, and the Ar gas is blown out toward the tip of the torch by the gas nozzles 2c and 2d to perform welding. Generally, the gas nozzles 2c and 2d are attached to the left and right of the electrode 3 in order to reduce the width of the torch, and are installed near the electrode 3. In particular, when a very narrow groove having a groove width of 7 mm or less is targeted, it is very difficult to install the gas nozzle so as to surround the electrode 3 because the torch width is desired to be minimized.

[0015]

Using the conventional narrow groove TIG welding torch shown in FIGS. 9 and 10, the welding torch 1 is inserted into the narrow groove as shown in FIG. He gas was blown out from the gas nozzles 2c and 2d as Ar gas, and a test was conducted to confirm whether the same effect as the double shield method could be obtained. Although the arc voltage was measured and the shield state was confirmed, the arc voltage in the He gas shield was not obtained, and the same effect as the double shield method was not recognized.

This is because the Ar gas blown into the groove from the shield box 4 is entrained by the He gas ejected from the gas nozzles on both sides of the electrode 3, as shown in FIG. It is considered that this is particularly large at the electrode portion where the He gas blown out from the gas nozzle of (1) overlaps.

Further, as a problem when welding with He gas shield, there is a problem that the starting property is poor. As a method for starting TIG welding, there are a high frequency discharge method, a high voltage discharge method, and a touch start method. Since He has a higher ionization voltage than Ar and is less likely to be plasmatized, it is known that the He shield is difficult to ionize even if a high frequency or a high voltage is applied between the electrode and the base material, and the startability is extremely poor. . Therefore, countermeasures such as starting with an extremely short distance between the electrode and the base material have been taken.

However, this method requires a sequence such as pulling up the torch after arc firing. Also, since narrow groove welding requires work at the bottom of a narrow and deep groove,
There were problems such as difficult position adjustment.

As described above, in the prior art, in order to realize the high-efficiency TIG welding in which the welding arc is shielded by He gas and the molten metal is shielded in Ar gas by the narrow groove TIG welding, the base metal outside the groove is used. Even if Ar gas is blown into the groove from the shield box installed on the surface of the material and He gas is blown from the gas nozzles whose outlets on both sides of the electrode face the groove bottom direction, the He gas will still entrap Ar gas. High efficiency T
IG welding could not be realized.

Further, there is a problem that the startability is poor in the case of the high frequency discharge system start and the high voltage discharge system start with the He shield.

The object of the present invention is also to achieve narrow groove welding.
Welding arc is shielded by He gas, molten metal is Ar
It is an object of the present invention to provide a TIG welding apparatus that enables high-efficiency TIG welding with gas shielding and that can stably start a high-frequency discharge method and a high-voltage discharge method even with a He gas shield.

[0022]

In order to solve the above problems, the present invention adopts the following configurations. A shield box that blows an inert gas into the groove from outside the groove, a welding torch that inserts into the groove and performs TIG welding, an electrode at the tip of the welding torch, and an inert gas placed on both sides of the electrode. A TIG welding apparatus including a gas nozzle that blows out gas, wherein the blowing directions of the gas nozzles are opposite to each other, and the gases blown out from the gas nozzles collide with each other to generate a gas flow of an ascending component and a descending component. TIG welding equipment.

In the TIG welding apparatus, the gas nozzle has a blow-out target position slightly above the tip of the electrode.

In the TIG welding apparatus, the inert gas blown from the shield box is Ar gas, and the inert gas blown from the gas nozzle is He gas.

Further, the TIG welding apparatus shields the electrode at the tip of the welding torch for performing TIG welding and the arc formed between the electrode and the base material with He gas, which is 20 He gas at the start of welding. % Of Ar gas is added, and the TIG welding device cuts off the Ar gas after the arc is ignited.

By adopting such a configuration,
The present invention can have the following functions and actions. That is, Ar from the shield box on the surface of the base material outside the groove
By blowing the gas into the groove, the specific gravity of Ar gas is heavy, so that the inside of the groove becomes an Ar gas environment and the molten metal being welded can be shielded by Ar gas. Then, by making the blowing directions of the gas nozzles arranged on both sides of the electrodes face each other and causing the He gases blown from the gas nozzles to collide with each other to generate a gas flow of an ascending component and a descending component, Ar gas from the upper part of the groove is formed. The arc can be shielded with He gas without being involved. At this time, the gas nozzles 2a, 2b
Although the Ar gas is slightly entrained in the direction, the entrained Ar gas is entrained in a direction that spreads with respect to the blowing direction, so the arc is hardly affected by the Ar gas.

The arc generated between the electrode tip and the base material is generated from the narrow surface of the electrode tip to the wide base material.
That is, the arc spreads from the electrode tip toward the base metal, and comparing the current densities at points P and Q (see FIG. 8), P
The current density at the point is higher, and the plasma airflow is generated in the directions of arrows A and B. That is, the He gas is selectively sent into the flow of the plasma air flow by aiming the gas nozzle blowout position slightly above the electrode tip.
The arc can be completely shielded by He gas, and high efficiency TIG welding in narrow groove welding is achieved.

Further, the high frequency discharge system start and the high voltage discharge system start with the He gas shield are performed by adding 20% or more of Ar gas to the He gas at the time of welding start, thereby improving arc startability in an Ar gas environment. It becomes the same, and stable arc start can be performed. Then, by cutting off the Ar gas after the arc is ignited, high efficiency TIG welding is achieved.

[0029]

DETAILED DESCRIPTION OF THE INVENTION A TIG welding apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of the TIG welding torch according to the embodiment of the present invention inserted into the groove, and FIG. 2 is a side view of the TIG welding torch according to the embodiment inserted into the groove. It is a figure. FIG. 4 illustrates the T according to the embodiment of the present invention.
He gas and Ar at the start of welding in the IG welding machine
It is a flowchart figure which shows the gas flow of gas.

In FIG. 1, 1 is a welding torch for narrow groove, 2a and 2b are gas nozzles for spraying He gas to the tip of the electrode, 3 is an electrode made of tungsten for generating an arc, and 4 is outside the groove. A shield box for blowing Ar gas from the surface of the base metal toward the groove 14, 5, 5a, 5b are base materials of the workpiece, 6 is an arc, 7 is a weld pool, 8 is an additive wire, 9 is an additive wire 8 Wire torch that guides the
Reference numeral 10 is a mounting base for mounting the welding torch 1, the gas nozzles 2a and 2b, and the wire torch 9, and 11a and 11b.
Is a welding bead after welding, 12 is a welding control device for controlling welding equipment, 13a, 13b and 13c are solenoid valves for opening and closing Ar gas and He gas, 14 is a groove, and 25 is a flow rate for adjusting gas flow rate. The adjusting valve is shown.

Next, the operation, function and action of the TIG welding apparatus according to this embodiment will be described. The non-consumable electrode type arc welding method and the welding procedure are the same as those in the conventional method, and the description thereof will be omitted.

In order to improve the efficiency of TIG welding, naturally, it is necessary to increase the welding current, but if the welding current is increased, the concentration of the arc increases and the arc pressure increases. That is, as shown in FIG. 8, the arc generated between the tip of the electrode 3 and the base material 5 is generated from the narrow surface of the tip of the electrode 3 to the wide base material. The arc spreads from the tip of the electrode 3 in the direction of the base material 5, and comparing the current densities at points P and Q, the current density at point P is higher, and the plasma flow is in the direction of arrows A and B in the figure. Arc pressure is generated.

Thus, when the welding current is increased, the P point and the Q point
The current density difference at the point becomes large and the arc pressure also becomes large.
When this arc pressure becomes large, the force for digging the base material 5 becomes strong, a pore is generated at the center of the welding bead, and a humping bead that breaks the bead is generated, resulting in a welding defect.
This arc pressure can be reduced to 1/4 or less in the He gas shield as compared with the Ar gas shield. This is H
This is because the arc shape of the e-gas shield and the arc of the Ar shield have different arc shapes, and a difference in current density at the electrode tip can cause a difference in pressure between A and B.

He in the mixed gas of Ar and He shown in FIG.
As can be seen from the graph showing the effect of the amount on the arc voltage, the arc voltage in He gas is 1.5 times or more higher than the arc voltage in Ar gas, and naturally the heat input to the base metal (welding current x The arc voltage / welding speed) is also higher in the He gas shield. By welding with the He gas shield in this way, highly efficient TIG welding can be performed. However, since He gas is light, a problem occurs in the shield property. Further, when mixed with Ar gas having a good shielding property, as shown in FIG. 5, unless He gas is 80% or more, the influence of Ar gas is strongly exerted.

From the above, it can be said that the technique of shielding the arc with He gas and flowing the Ar gas around it to shield the molten metal realizes ideal high-efficiency TIG welding. This high-efficiency TIG welding technique is applied to narrow groove welding in the TI according to the present embodiment.
This is a G welding device and will be specifically described with reference to FIGS. 1 and 2. First, in order to shield the entire inside of the groove 14 with an inert gas, Ar gas is caused to flow toward the groove 14 by the shield box 4. Then, He gas is sprayed onto the upper end of the tip of the electrode 3 by the gas nozzles 2a and 2b on both sides of the welding torch.

When shielding the arc with He gas,
As shown in FIG. 8, the origins of the plasma airflows A and B,
That is, it is an effective method to spray He gas slightly upward from the tip of the electrode 3. In other words, as shown in FIG. 6, the gas nozzles 2a and 2b are installed in opposite directions from both sides of the electrode 3, and the He gas is blown out so that the target position of the gas nozzle is slightly above the electrode tip. To do.
In the narrow groove, the He gases collide with each other to generate a gas flow of an ascending component and a descending component.
The arc can be shielded with He gas without involving the r gas.

Although the Ar gas is slightly entrained in the gas nozzles 2a, 2b direction, the entrained Ar gas is entrained in a direction that spreads with respect to the blowing direction, so that the arc is hardly affected by the Ar gas. That is, since the arc can be completely shielded by He gas and the molten metal can be shielded by Ar gas, high efficiency TIG welding can be achieved even in narrow groove welding.

A welding test was carried out in a deep groove of 50 mm or more, and the arc voltage in this embodiment and H in which He gas was made to flow from the shield box 4 with a shallow groove of approximately 20 mm were used.
It was confirmed that the arc voltage was the same for only e gas, and it was confirmed that high efficiency welding was realized.

Next, the arc start method with the He gas shield will be described. Since He has a higher ionization voltage than Ar and does not easily turn into plasma, it is known that the He shield is difficult to ionize even if a high frequency or a high voltage is applied between the electrode and the base material, and the startability is extremely poor. . Therefore, by adding 20% or more of Ar gas to He gas at the welding start of the high-frequency discharge method start and the high-voltage discharge method start, the arc startability becomes the same as in the Ar gas environment, and a stable arc start is achieved. It can be carried out. Then, by cutting off the Ar gas after the arc is ignited, high efficiency TIG welding can be achieved.

As can be seen from the graph showing the effect of the He amount in the Ar / He mixed gas on the arc voltage in FIG. 5, almost 25% of the Ar gas is mixed with the pure He gas, the arc voltage of the pure Ar gas is almost the same. turn into. That is Ar
If the gas content is 20% or more, the properties are close to those of pure Ar gas.

Solenoid valves 13a, 13b, 13c are provided in the welding control device 12 shown in FIG. 1, and He gas guided to the gas nozzles 2a, 2b by the solenoid valve 13a is
The solenoid valve 13b opens and closes the Ar gas guided to the gas nozzles 2a and 2b, and the solenoid valve 13c opens and closes the Ar gas guided to the shield box 4. Ar gas that has passed through the solenoid valve 13b has a flow rate adjusting valve 25.
The flow rate of He gas can be adjusted to 20 to 30%.

Next, the starting sequence will be described with reference to FIG. For the start preflow time, the solenoid valves 13a, 13b, 13c are opened. The gas blown out from the gas nozzles 2a and 2b has Ar of 20% or more.
Contains gas. Here, a high frequency or high voltage is applied between the electrode 3 and the base material 5 to ignite an arc. At this time, since the He gas contains the Ar gas, the start is performed well. After the arc is ignited, the solenoid valve 13b is closed to shut off the Ar gas contained in the He gas. In addition, although a method of flowing only Ar gas in the shield box 4 at the time of starting and starting He gas after arc ignition was also examined, since gas is projected when the solenoid valve is opened,
It cannot be used to cause the phenomenon of extinguishing an arc.

Next, a TIG according to another embodiment of the present invention.
The welding device will be described below with reference to FIG. In FIG. 3, 1 is a welding tip torch for narrow groove, 2a and 2b are gas nozzles for spraying He gas to the electrode tip portion, 3
Is an electrode that is made of tungsten and is inclined and attached to the welding torch 1 to generate an arc, 4 is a shield box that blows Ar gas from the surface of the groove outer base material toward the groove 14, and 5 is a mother of the workpiece. Material, 6 is arc, 7 is molten pool, 8
Is a wire torch, 9 is a wire torch that guides the wire 8 to the weld, 10 is a welding torch 1 and gas nozzles 2a, 2b.
And a mounting base for mounting the wire torch 9, 11
a and 11b are weld beads after welding, 15 is a gas nozzle 2
and b is an attachment for attaching and fixing the wire to the torch 9.

In the case of TIG welding, the electrode 3 is used as the base material 5 (see FIG.
Then, it may be installed at an angle to the groove bottom).
This is used when it is desired to utilize the spread of the arc rather than prioritizing vertical penetration to obtain lateral groove wall penetration. Further, the welding torch 1, the wire torch 9, the gas nozzle 2 are made by inserting the additive wire into the welded portion vertically.
The widths of a and 2b are also narrowed. In this case, the wire torch 9 is installed between the welding torch 1 and the gas nozzle 2b. Thus, in either case of oblique electrode or vertical insertion of the additive wire, Ar gas is blown into the groove from the shield box 4 outside the groove, the inside of the groove is shielded by Ar gas, and the electrodes are arranged on both sides of the electrode. The blowing directions of the gas nozzles are set to face each other, and the He gas blown from the gas nozzles collides with each other to generate a gas flow of an ascending component and a descending component, and the ejection target position of the gas nozzles arranged on both sides of the electrode is the electrode tip. High efficiency TIG welding can be achieved by aiming a little higher.

When the wire torch 9 is installed between the welding torch 1 and the gas nozzle 2b, the distance between the outlet of the gas nozzle 2b and the electrode 3 is larger than that of the gas nozzle 2a. It is necessary to make the amount larger than that of the gas nozzle 2a.

[0046]

According to the present invention, even in a deep groove having a groove width of 7 mm or less and a groove depth of 40 mm or more, Ar gas flowing from the shield box toward the inside of the groove. The molten metal is shielded by the He gas and the arc is shielded by the He gas blown out from the gas nozzles on both sides of the electrode. Therefore, the high shielding property of Ar gas and the high welding arc potential gradient of He gas are effectively used to perform narrow groove welding. However, highly efficient TIG welding can be realized.

Further, at the time of starting the welding of the high frequency discharge method and the high voltage discharge method when the arc is shielded by He gas, by adding 20% or more of Ar gas to He gas, the arc start in an Ar gas environment is performed. It becomes similar to the sex, and a stable arc start can be performed. After the arc is ignited, H gas is cut off by cutting off the Ar gas.
High efficiency TIG because the arc is shielded by e-gas
Welding can be achieved.

[Brief description of drawings]

FIG. 1 is a front view of a TIG welding torch according to an embodiment of the present invention inserted into a groove.

FIG. 2 is a side view showing a state in which the TIG welding torch according to the present embodiment is inserted into a groove.

FIG. 3 is a front view of the TIG welding torch according to another embodiment of the present invention when it is inserted into the groove.

FIG. 4 is a flowchart showing a gas flow of He gas and Ar gas at the start of welding of the TIG welding apparatus according to the embodiment of the present invention.

FIG. 5 is a graph showing the influence of the amount of He in an Ar / He mixed gas on the arc voltage.

FIG. 6 is an explanatory diagram showing a shield state when He gas is blown out in a direction facing from gas nozzles on both sides of an electrode according to the present embodiment.

FIG. 7: H from the gas nozzles on both sides of the upper electrode downward
It is explanatory drawing showing the shield state at the time of blowing out e gas.

FIG. 8 is an explanatory diagram showing a generation mechanism of a plasma airflow generated in an arc portion.

FIG. 9 is a front view of a TIG welding torch according to the related art.

FIG. 10 is a side view of a TIG welding torch related to the prior art.

FIG. 11 is a double shielded TIG according to the prior art.
It is sectional drawing of the welding part which shows the welding method using a torch.

FIG. 12 is an explanatory view showing a welding method of narrow groove welding.

[Explanation of symbols]

1 welding torch 2a, 2b, 2c, 2d gas nozzle 3 electrodes 4 shield box 5,5a, 5b Base material 6 arc 7 molten pool 8 additive wire 9 wire torch 10 Mounting base 11, 11a, 11b Weld beads 12 Welding control device 13a, 13b, 13c Solenoid valve 14 bevel 15 Fixture 16a, 16b, 16c, 16d Electrode holder 17 Center gas nozzle 18 Shield gas nozzle 19 Additive wire conduit 20 Cooling water conduit 21 Electrode fixing block 22 conduit cable 23 Wire feeder 24 wire reel 25 Flow control valve

Claims (4)

[Claims] 1. A shield box for spraying an inert gas into the groove from outside the groove, a welding torch for inserting into the groove to perform TIG welding, an electrode at the tip of the welding torch, and both sides of the electrode. And a gas nozzle that blows out an inert gas, and the blowing directions of the gas nozzles are opposite to each other, and the gases blown out from the gas nozzles collide with each other and rise component and fall component. A TIG welding device characterized by generating a gas flow of 2. The TIG welding apparatus according to claim 1, wherein the gas nozzle has a blowout target position slightly above the tip of the electrode. 3. The TIG welding apparatus according to claim 1, wherein the inert gas blown out from the shield box is Ar gas, and the inert gas blown out from the gas nozzle is He gas. TIG welding equipment. 4. An electrode at the tip of a welding torch for performing TIG welding, and an arc formed between the electrode and the base material are He.
A gas-shielded TIG welding apparatus, characterized in that 20% or more of Ar gas is added to He gas at the start of welding, and the Ar gas is shut off after arc ignition.
IG welding equipment.