JPS5947632B2 - All position TIG welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a TIG welding method capable of successfully welding steel plates, particularly thick steel plates, at a high welding speed in any position.

Extremely high quality is required for welded parts of penstocks, tanks, etc. in hydroelectric power plants.

Therefore, although it is generally not as good as the consumable electrode type MIG welding method in terms of welding efficiency, it has superior aspects that other welding methods cannot easily match in terms of weld quality and adaptability to all-position welding. Because of this, the non-consumable electrode type TIG welding method is used for welding penstocks, etc. General pulse T
In the IG welding method, the arc generating current pulse frequency is several H2), the average current value is about 200 A, and the welding speed of the filler wire, which determines the welding efficiency, is 10 fl/77ZZ7Z!
This is far from the welding speed of I■MIG welding, which is 35g/77ZZ7l. For this reason, when welding thick-walled, large-diameter pipes, as shown in Figure 9, it is necessary to increase the number of welding baths, resulting in so-called multi-pass welding in which each layer is divided into D. The final welding efficiency is extremely poor. In addition, in all-position welding, it is common for the penetration shape of the weld bead and the external shape of the bead to change considerably in response to changes in the welding position, and as the number of welding buses increases, the weld bead Adjusting the shape is a big problem.D) In addition, the influence of groove errors that are unavoidable in on-site joints etc. will be added, so controlling the lamination becomes an even more difficult problem, which in turn prevents the performance of fully automated welding. It turns out. Therefore, the general pulse TIG welding method is MI
Like the G welding method, it is unsuitable for application to all-position welding of thick-walled, large-diameter pipes. In recent years, attempts have been made to improve the welding efficiency of the TIG welding method so that thick steel plates can be welded economically.One example is the hot wire TIG welding method, which uses an appropriate auxiliary power source to heat the filler wire with electricity. be. In this method, the welding speed can be easily increased by appropriately increasing the welding current and filler wire heating current, so welding efficiency can be greatly increased compared to normal TIG welding. However, because of the high welding accuracy and volume of welding, the molten metal flows down or falls in horizontal or upward welding positions, making it impossible to achieve good welding, and its range of application is extremely limited.

Another example is a high-frequency pulsed TIG welding method in which the pulse frequency is about 150 KHz. This method has a welding speed of 30g/Mm, which is almost comparable to the MIG welding method, and the high frequency generates an ultrasonic high-frequency vibration phenomenon generated in the welding arc, which has the effect of holding the molten metal on the base metal, making it possible to weld in all positions. possible, and the welding efficiency has been significantly improved. However, in order to implement this method, it is necessary to manufacture a power source for generating high-frequency pulses and an automatic control device that does not malfunction due to noise caused by high-frequency pulses. Questions also remain regarding gender. The present invention eliminates the above-mentioned drawbacks, and also uses MIG welding method, high frequency type TI
The purpose of this method is to achieve a welding speed (welding efficiency) that is sufficiently higher than that of the G welding method, as well as the stable welding quality inherent to the TIG welding method, using a uniquely selected appropriate frequency and amplitude. A combination of an arc with a pulsating electromagnetic pressure effect generated using a strong pulsed current with an alternating magnetic field generation mechanism that produces an extremely effective electromagnetic stirring effect on the high-temperature molten metal formed by the arc. This is the basic configuration.

More specifically, TIG uses a powerful pulse current with a uniquely selected frequency, that is, a frequency range of several tens of Hz to several hundred Hz.
By employing welding, it is possible to heat the molten metal more rapidly and effectively without using excessive welding heat input, and even with a relatively low level of welding heat input, the molten metal can be heated even at a relatively low level of welding heat input. This greatly increases the fluidity of the material and easily causes electromagnetic stirring phenomena that could not be expected at low heat input levels. It is possible to create the conditions for In addition, the arc generated by the above-mentioned pulsed current of several + Hz to several hundred Hz generates pulsating electromagnetic pressure, and this pressure has the effect of pressing the surface of the molten metal flat against the base material (thick steel plate). . Therefore, the TIG.
If welding is performed, even if a large amount of molten metal is generated, the pressure will prevent the molten metal from flowing down or falling, making it possible to weld in all positions. It can be formed flat along the mother plate surface. Another aspect of the present invention is a magnetic field generating mechanism in which a magnetic field generated by energizing a filler wire acts on a magnetic field generated by a welding arc. The current flowing through the filler wire may be direct current or alternating current of about 50 Hz. By appropriately selecting the frequencies of the welding current applied to the welding electrode and the frequency of the current applied to the filler wire, it is possible to produce the aforementioned strong electromagnetic stirring phenomenon in the high temperature molten metal. Furthermore, supplying electricity to the filler wire 1 also serves to heat the filler wire 1, and heating the filler wire 1 further improves welding efficiency. As described above, the TIG welding method of the present invention dramatically improves welding efficiency as shown in Table 1 due to the synergistic effect of selecting the welding current pulse frequency, applying electricity to the filler wire, and heating the filler wire. It is something.

Let us now consider the significance of frequency limitation in the present invention.

When the filler wire is heated using the high-frequency pulsed TIG welding method described above, in the high-frequency pulsed TIG welding method, as in the present invention, electromagnetic pressure is generated in the arc, which has the effect of pressing the molten metal against the base metal. Since it is an arc, the molten metal temperature is also high.

Therefore, the question arises as to whether heating and supplying the filler wire would further improve the electromagnetic stirring phenomenon and the welding efficiency shown in Table 1. However, because the pulse frequency of the welding current is extremely high compared to the frequency of the filler wire heating current, the magnetic fields generated by both currents interfere with each other, reducing the electromagnetic pressure of the arc and electromagnetic stirring phenomenon that is inherent in the high-frequency pulsed TIG welding method itself. Unfortunately, it is not possible to achieve the welding efficiency achieved by the present invention. In addition, the pulse welding current of several tens to one hundred Hz limited by the present invention is 50 Hz)6
Although it can be synthesized and supplied extremely easily from a 0Hz commercial power source, when supplying a pulsed welding current with a frequency of around 1000Hz or higher, a special power supply must be prepared, and pulsating electromagnetic pressure and electromagnetic stirring effects are also required. The present invention does not exceed the range of pulsed welding current at a limited frequency. Therefore, the limited frequency has sufficient pulsating electromagnetic pressure and electromagnetic stirring action necessary to achieve the object of the invention described above, and is extremely economically advantageous. Embodiments of the present invention will be described below with reference to the drawings. This embodiment is applicable to a situation where the welding position changes as welding progresses, and is applied to an inclined pipe which is more complex than a vertical or horizontal pipe.

1 to 3 schematically show a TIG welding machine implementing the present invention.

Reference numeral 1 denotes a thick-walled, large-diameter steel pipe, and a running track rail 3 is provided near a joint 2 of the steel pipe 1 in parallel to the joint, and a running truck 4 is disposed on the running track rail 3.

The traveling trolley 4 includes a wire reel 5 for storing the filler wire 7 in a coiled form, an arc voltage control device 6, a wire guide 8 for feeding the filler wire 7 to the welding part after stretching it.
A welding torch section 9 is provided. Fig. 4 shows the welding position in 45, and is a partial model diagram when welding one side from the inner surface of the pipe, and the welding torch part 9 moves along the welding line 10 while performing welding in all positions 1. conduct.

FIG. 5 is a detailed view showing the torch section.

The torch 11 is connected to a main power supply (not shown), and the main power supply is connected to a tungsten electrode 1 included in the torch 11.
A pulsed arc generating current of 50 to 500 Hz, 1200 A to 600 A is supplied to No. 2. Due to the generation of the pulse arc 13, a metal molten pool 14 is formed on the inner wall of the steel pipe 1, and the molten pool 1
4 is supplied with filler wire 7. The filler wire 7 is connected to an auxiliary power source (not shown) that heats the wire 7. The auxiliary power source may be a commercial 100-220 VAC power source or a DC power source as long as it can heat the filler wire 7. While supplying the filler wire 7 which is generated by the main power supply unit and heated by the auxiliary power supply, the torch 11 is swung in the width direction of the welding part as shown in FIG. If the rod is moved as shown in the trajectory 15 shown in the figure, it is possible to form a welded part shown in FIG. 8 in which each layer is parallel and the number of passes is small.

Table 1 shows a comparison of each welding method, and the medium pulse type TIG welding method in Category 3 is the one according to the present invention.

Table 2 shows welding conditions and welding records for welding a circumferential joint of a large-diameter, thick-walled steel pipe inclined at an angle of -1.45° according to the present invention.

The steel plate thickness is 35 mm, the pipe diameter is 4200 mm, the welding groove is 30°, and the welding current pulse frequency is 50 Hz.

Also, the numbers 1 to ▲7 of the laminated sections correspond to the numbers written on the bead portions in Fig. 8. As described above, the present invention exhibits the following excellent effects.

The welding efficiency in the ITIG welding method is dramatically improved as shown in Table 1.

11 The entire width of the welding groove can be laminated in one pass for each layer, and at the same time, the bead of each layer can be made uniformly thick, and the number of welding passes can be greatly reduced, making it possible to weld large-diameter, thick-walled pipe circumferential joints with extremely high quality. It can be done in a short time.

The welding current pulse frequency is relatively low at several tens to hundreds of Hz, so there is no need to take special noise countermeasures like the control device in high-frequency TIG welding, and the pulse welding current at this frequency can be easily applied using a commercial power supply. Since it can be synthesized, a device for carrying out the present invention can be manufactured at low cost and can be carried out on-site.

It has been confirmed that even when the filler wire is not energized during the above-mentioned process, a welding speed of 40 f1/min can be obtained by welding with a welding current pulse frequency of several + Hz to several hundred Hz, and in the construction example of the present invention. Although the welding groove was set to a 30° V-shaped groove, it has been confirmed that substantially stable welding can be performed using a 20° V-shaped groove to further improve welding efficiency.

Furthermore, it goes without saying that the present invention can be applied to aluminum plates, stainless steel, etc. other than steel plates.

[Brief explanation of the drawing]

1 to 3 show a TIG welding machine implementing the present invention, in which FIG. 1 is a front view, FIG. 2 is a side view, and FIG. 3 is a perspective view.
Figure 4 is an explanatory diagram of the welding position in inclined large diameter steel pipes, Figure 5
The figure is a detailed diagram showing the torch part of the TIG welding method, Figure 6 is an explanatory diagram regarding the movement of the torch with respect to the groove, Figure T is a diagram showing the trajectory of the torch, and Figure 8 is a welded part welded according to the present invention. FIG. 9 is a cross-sectional view of a welded part by the conventional TIG welding method. 1 is an iron pipe, 7 is a filler wire, 9 is a torch part, 11
12 is a torch, 12 is an electrode, 13 is an arc, and 14 is a molten metal pool.

Claims (1)

[Claims] 1 In the TIG welding method, the welding current is applied to the electrode from several tens to
It is characterized by supplying a pulsed current of several hundred Hz to generate an arc in a pulsed manner at the frequency, and supplying the heated filler metal to the molten metal pool by passing a current of 0 to several tens of Hz through the filler metal. All position TIG welding method.