JP2595066B2 - Plasma gas welding equipment and welding torch - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plasma gas welding apparatus and a welding torch, and in particular, to a key for melting a material to be welded through and forming a keyhole for welding. The present invention relates to a plasma gas welding apparatus suitable for hole welding and a torch for welding.

[Conventional technology]

In plasma welding, in particular, the keyhole welding method in which the relevant part of the material to be welded is melted through and welded while forming a keyhole, since a uniform back beat shape can be obtained, for example, in pipe joining work, etc. It has been used in conjunction with the automation of welding operations.

This type of plasma welding is capable of high heat input and has a high energy concentration, which has the effect of shortening the welding work time and improving the finish of the welded parts. In some cases, control for measuring automation is not easy. Conventionally, for the purpose of performing automated plasma welding without the need for specialized skills of this kind, for example, as described in Japanese Patent Application Laid-Open No. 62-61777 previously proposed by the applicant, the welding current value There is a method of performing welding while adjusting the welding speed and the gas amount.

[Problems to be solved by the invention]

The principle of the plasma welding method is to convert the gas ejected from the nozzle into plasma by an arc, electrically guide the plasma to the surface of the material to be welded, melt the material to be welded, and perform fusion welding. is there. In such a plasma welding method, the plasma for fusion-bonding the material to be welded is:
Theoretically, the amount of gas supplied to generate it,
The magnitude and energy density are determined based on the value of the applied current. Therefore, as described above, the welding current value, welding speed,
Therefore, a control method that performs automatic welding while adjusting at least two items of the gas amount is necessary. However, even if such control is performed, the plasma welding performed by adopting the keyhole welding technique requires a control method. If the thickness of the welding material becomes larger than a certain limit, a part that cannot be controlled is generated.

It is the occurrence of blowholes. This is a phenomenon in which the gas is welded to the welded portion of the melted welded material with the gas remaining, and a void remains, and this phenomenon is likely to occur particularly during plasma welding of a thick material to be welded. As a result of various studies of the cause, the following has been solved.

First, the base material melted by the plasma generates a keyhole along the plasma flow. At the next moment, the current for plasma generation is reduced to reduce the plasma and close the keyhole during that time. Try to make it work. However, if the gas flow rate for plasma generation increases, simply reducing the current value will result in spraying the material to be welded at a high gas flow rate, and this gas flow will cause a keyhole. It is thought to affect the closing action.

Second, as the thickness of the material to be welded increases, the amount of the base material dissolved increases, so that the melted base material increases its fluidity due to its own weight, and the first cause also overlaps to block the keyhole. It is also conceivable that they may be solidified without doing so.

SUMMARY OF THE INVENTION The present invention has been made by investigating a method of controlling a gas flow rate for plasma generation with the object of solving the occurrence of blowholes which is considered to be based on the above-described cause.

[Means for solving the problem]

As a means for achieving the above object, the plasma welding apparatus of the present invention is provided with a gas flow rate control device capable of intermittently controlling a gas flow rate for plasma generation integrally with a torch.

Further, the present invention proposes a method for controlling a plasma welding apparatus having the gas flow control device by a control device provided at a remote place.

In addition, the gas flow control device proposes a structure that is useful for the configuration because it is easier to control the gas flow control device in synchronism with the applied pulse current if it is as close as possible to the gas ejection port of the torch that generates plasma. It is.

Furthermore, the present invention proposes a welding torch in which a gas flow control device is integrally formed.

[Action]

Plasma welding that can control the gas flow rate as described above can control the gas flow rate that is thought to affect the blockage of the keyhole. The occurrence of blowholes in the melting part can be prevented. Moreover,
Since the gas flow rate is controlled in synchronism with the pulse current value for plasma generation, it is possible to finely control the gas flow, which is considered to have an adverse effect when the keyhole melts through and closes.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a plasma welding apparatus according to the present invention.

On the welding line of the work 1 to be subjected to keyhole welding,
Plasma jet (hereinafter referred to as nozzle) 4p
A torch 4 fixed to a moving bed (not shown) has a gas flow control device 5 according to the present invention integrally attached to a part thereof. The torch 4 is provided with a pulse current, a plasma generation gas,
A sealing gas and a control signal transmission cable are guided.

A control device 3 controls the entire welding device. 8 is a gas cylinder, 9 is a power transformer. The plasma welding apparatus of the present invention further includes a signal line 10 for controlling a gas flow control device 5 integrally attached to the torch 4 from the power supply device 2. It goes without saying that this control is linked with the control device 3.

This signal line 10 controls the gas flow supplied to the torch for plasma generation by the gas flow control device 5 attached to the torch 4, which will be described in detail later, in synchronization with the pulse current value for plasma generation. This is for operating the valve mechanism.

This kind of plasma welding apparatus of the present invention automatically sets keyhole welding while setting a torch 4 on a workpiece 1 and controlling a gas flow rate in synchronization with a pulse current value based on an operation from a control device 3. Can be done.

Next, an embodiment of the torch 4, which is a main component of the present invention, and a gas flow control device 5 integrated therewith will be described.

FIG. 2 (a) shows an embodiment in which the torch 4 is shown in cross section. The electrode 4a is configured to wrap around the electrode 4a.
And a skirt 4d which surrounds the outer periphery of the nozzle cylinder 4b and is provided so as to blow out the shielding gas B around the nozzle 4p.

 The description of the electrical configuration is omitted.

The gas flow controller 5 is inserted in series on the torch side of the supply port 4e of the plasma generation gas A sent between the electrode 4a and the nozzle tube 4b. 4f is a supply port of the shielding gas B. At the time of welding work, first, a pilot arc is generated at the end of the electrode 4a and the end of the nozzle 4p with the amount of gas A restricted.
Thereafter, a current path is formed between the electrode and the workpiece 1 and then the gas A is increased to a predetermined flow rate to thereby increase the nozzle.
Plasma p from 4p to the material to be welded is generated.

Gas flow controller 5 in torch 4 of the present invention
Synchronizes with a pulse current value applied between the electrode 4a and the workpiece 1 and performs a splitting operation of the gas A therein. The gas A 'diverted based on this diverting operation passes through a conduit 15 shown in FIG. 2 (b), and a jet ring 16 provided at the tip of the nozzle 4p, that is, between the nozzle 4p and the material 1 to be welded. It is led to. FIG. 2 (b) shows a drawing of the ejection ring 16 as viewed from below. Squirt ring 16
Is provided with a plurality of small holes 16a through which gas A 'can be blown out toward the material 1 to be welded. This configuration combines the split gas A 'with the shielding gas B to exhibit the effect of wrapping around the keyhole. The gas A' split in synchronization with the pulse current value is , Which are intermittently sprayed from the ejection ring 16 onto the surface of the workpiece 1.

In this manner, the time course of the gas A being divided by the gas flow controller 5 is controlled as shown in the graph of FIG. That is, when the pulse current is at the peak value (T _p ), the gas flow control device 5 does not perform the branching operation as shown in the present embodiment, and the entire amount of gas A introduced from the supply port 4e is changed to the electrode 4a. And is converted to plasma energy. In this state, a plasma having sufficient heat input energy and ejection energy to generate a keyhole is generated by melting the material 1 to be welded. Next, when the keyhole is completed and the keyhole is closed as the next step, the pulse current becomes the base value (T _B ). The gas flow control device 5
Upon receiving the change in the pulse current value as a signal, a part of the gas A is divided and flows to the ejection ring 16 side. In this state, as shown in the graph, a shield gas flow in which the divided gas A 'is synergized with the shield gas B which is constantly supplied and supplied is generated. This is because the energy of the plasma decreases due to the change in the pulse current value,
When the keyhole is closed, the strength of the gas A blown to the keyhole is reduced, and conversely, the shielding gas acting to wrap the keyhole from the surroundings is increased. .

In this way, the amount of gas A for plasma generation is
As an example, it is considered that the gas flow control device to be controlled in the vicinity of the above has a structure as shown in FIG. 4, for example.

The drawing shows a supply port 4e for supplying the gas A for plasma generation to the torch 4, which is directly attached to the supply port 4e. A branch port 5b is formed at right angles to the main flow path 5a through which the gas A flows. The port 5b is provided with a valve mechanism 5c that is normally closed and is opened and closed based on a control signal issued in synchronization with the pulse current value. 5d is a flexible pipe for supplying gas A. The gas flow control device 5 of this kind has a structure
Since it is directly attached to the main body of the torch 4, the valve mechanism 5c opens and closes based on the control signal, and when the flow rate of the gas A flowing through the nozzle is controlled, the gas A reaches the above-described nozzle 4p. Time delay until the gas flow reaches the nozzle is short, and there is no phenomenon that the pressure decreases in the flow path. It can be easily taken. In the figure, an electromagnetic valve configuration using a spring and an electromagnet is used, but this kind of gas flow control device configured for the purpose of diverting the gas A is not limited to this if the purpose can be achieved. Absent. In the case of an electromagnetic valve mechanism, if there is room for improvement in that sound is inevitably emitted, adopting a flow path switching method without a valve, a throttle valve method, or the like is a content that can be easily improved. .

Further, whether the path for guiding the gas A for plasma generation to the nozzle 4p is formed by a single flow path or a plurality of flow paths is determined by determining the split ratio of the gas A or by determining the plasma flow rate. This is a very important choice in maintaining stability.

FIG. 5 shows another embodiment of the gas flow control device 5, in which gas A is divided into two flow paths in the device,
4p, and a valve mechanism 5c is provided in one of the two gas flow paths. In the figure, the same parts as those already described are denoted by the same reference numerals. In the gas flow control device having this kind of structure, when the gas A enters from the inlet 5e, it is divided into the flow path 5k and the flow path 51. Each flow path is provided with a gas flow rate adjusting function 5 m so that the flow rate of gas A flowing through each flow path can be determined.

The control of the gas flow rate adjusting function 5m can be adjusted based on a command from the control device. Further, a valve mechanism 5c is provided in one flow path 51. After configuring the valve mechanism 5c, the flow paths 5k and 5l are united again and connected to the nozzle 4p of the torch 4.

The purpose of adopting the configuration in which the gas A flow path is divided in this way is to firstly reduce the pressure fluctuation caused by the change in the flow rate of the gas A due to the operation of the gas flow control device in order to maintain the stability of the plasma. It is effective when necessary. Secondly, the present invention is effective when the gas flow control at the time of setting welding conditions, which has been conventionally performed on the power supply device side, is performed by a torch to improve responsiveness.

Although FIG. 5 has been described as an embodiment of the gas flow control device, the torch itself can have this kind of structure as long as it has a valve mechanism and can form a gas flow control device and a branch channel. Needless to say.

6 and 7 are sectional views showing another embodiment of the torch integrally provided with the gas flow control device 5 of the present invention.

FIG. 6 shows a configuration in which the diverted gas A 'is joined to the skirt 4d where the shielding gas B flows when the pulse current has the base value described in FIG.

FIG. 7 shows a configuration in which the gas A 'split in the other example of FIG. 6 is discharged to the outside.

Each of the above torches is an embodiment that can be structurally adopted in selecting an application range of the plasma welding apparatus.

〔The invention's effect〕

Since the present invention is configured as described above,
The following effects are obtained.

By providing control means for controlling the gas flow rate for plasma generation in the torch, the responsiveness of the control of the plasma gas flow rate is improved, and the plasma gas flow rate control synchronized with the pulse current value when performing keyhole welding is realized. Will be possible.

The welding apparatus provided with this kind of gas flow rate control apparatus is applied to plasma keyhole welding in order to enable welding without the occurrence of blowholes, even with a material to be welded having a thickness that has been impossible so far. The range can be greatly expanded, and in combination with automation, a device that can greatly contribute to industrial development can be provided.

[Brief description of the drawings]

FIG. 1 is a drawing showing the configuration of a plasma welding apparatus of the present invention, and FIGS. 2 (a) and 2 (b) are cross-sectional views showing one embodiment of a torch of the present invention, and a downward view, and FIG. FIG. 4 is a graph showing the relationship between the pulse current of the plasma welding apparatus of the present invention and the gas flow rate for plasma generation, FIG. 4 is a sectional view showing an embodiment of the gas flow control apparatus of the present invention, and FIG. , A conceptual diagram showing another embodiment of the gas flow control device, FIG.
FIG. 7 is a sectional view showing another embodiment of the torch of the present invention. DESCRIPTION OF SYMBOLS 1 ... Material to be welded, 2 ... Power supply device, 3 ... Control device, 4
... torch, 5 ... gas flow control device, A ... plasma generation gas, B ... shield gas, 4a ... electrode, 4p ...
Nozzle, 5a …… Flow path, 5b …… Branch, 5c …… Valve mechanism, 5m
... gas flow adjustment function, 16 ... spout ring.

Continuation of the front page (72) Inventor Shinichi Kurita 3-1-1 Sachimachi, Hitachi City, Ibaraki Prefecture Inside the Hitachi Works, Hitachi, Ltd. (56) References JP-A-62-176685 (JP, A) Jpn. -20777 (JP, U)

Claims (3)

(57) [Claims] 1. A plasma gas welding torch having a plasma generating electrode and a nozzle surrounding the plasma generating electrode and discharging a plasma generating gas, wherein a valve capable of controlling a discharge amount of the plasma generating gas from the nozzle. A torch for plasma gas welding, comprising a mechanism, wherein the valve mechanism operates in conjunction with a pulse current value applied to the nozzle. 2. A plasma gas welding torch has a plurality of plasma generating gas flow paths, each of which has a gas flow rate adjusting function, and at least one of the flow paths has a plasma generating gas flow function. A torch for plasma gas welding, comprising a gas flow control means capable of controlling a gas flow in synchronization with a pulse current for plasma generation. A means for supplying a pulse current for generating plasma to the torch; a means for supplying a gas for generating plasma to the torch; and a flow rate of the gas for generating plasma supplied to the torch is tuned to the pulse current. The plasma gas welding apparatus is provided with a flow rate control means for controlling the flow rate and a control means for controlling the respective means.