JPH0747215B2 - TIG automatic welding method for thin corrugated joints - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a TIG automatic welding method for thin-walled corrugated joints, for example, a large expansion tube used for sealing a piping part of a nuclear power plant and a special heat exchanger. It is suitable for use in welding such as.

<Prior Art> As shown in FIG.
A large bellows-shaped telescopic tube consisting of 1 and 12 butts
In the welding of the thin-walled corrugated joint formed at the 3 butt portion, for example, in the case of being used for sealing the piping portion of a nuclear power plant, it is required to form the back bead in one pass.

Conventionally, there are few examples of such butt welding of waveform
This kind of welding was performed by manual TIG welding which relied on the worker's skill. In FIG. 8, reference numeral 14 is a welding bead and 15 is a TIG welding torch.

<Problems to be Solved by the Invention> When welding the corrugated joint in a state where such a bellows-shaped expansion tube 13 is erected, the welding position of the welding torch 15 is vertical and upward as the welding progresses. , Downward and various changes.

In this case, if the plate thickness is extremely thin (about 1.5 mm or less), there is no problem in terms of welding, but if the plate thickness reaches about 2 to 4 mm, the back bead is formed in one pass. Requires a large amount of heat input, so the amount of molten metal also becomes large, so depending on the welding position, the molten metal whose surface tension lost to gravity fell, and there were problems that the bead 14 had a concave defect, etc. .

The present invention solves the problems in such thin-walled corrugated joint welding, and provides a TIG automatic welding method that enables all-posture one-pass backside welding of a butt joint having a plate thickness of 2 to 4 mm. is there.

<Means for Solving the Problems> The TIG automatic welding method according to the present invention for solving the above-mentioned problems is a tungsten welding in welding of a corrugated joint in which corrugated plate-shaped members are butted against each other at a surface intersecting the wave. As a welding current between the electrode and the corrugated member to be welded, a slope-down type pulse train current consisting of multiple pulsed currents whose current value gradually decreases from the preceding pulse is repeatedly applied as the welding progresses. Is characterized by.

<Operation> When the welding current value gradually decreases after the back surface of the joint is melted by the high current, the molten metal solidifies and shrinks to some extent.
After that, when the welding current becomes high again, the back surface is melted again, and by repeating the repeated change of the welding current and the welding speed, the back bead formed on the back surface is connected and becomes continuous.

<Examples> Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a graph showing the change over time of the welding current according to one embodiment of the method of the present invention, and FIG. 2 is a schematic perspective view of the welded portion obtained thereby.

According to the method of the present invention, as shown in FIG. 1, the welding current A is made into a pulsed pulsating current, and the current value is gradually reduced from a plurality of (4 in this embodiment) pulsed currents which are gradually reduced from the pulse preceding in time. The slope-down type pulse train current 16 is repeatedly applied between the tungsten welding electrode and the corrugated plate member to be welded as the welding progresses. That is, while maintaining the minimum current required to sustain the arc, the pulse width t ₀
Pulsed high current is applied in a predetermined cycle. Moreover, this pulse-like high current is made into a set of a plurality of slope-down types that gradually decreases from the high current value for each pulse, and this is repeated.

In this way, as shown in FIG. 2, a molten pool is formed for each pulse train current 16 and adjacent molten pools are connected to form a continuous weld bead 14. The second
In the figure, 17 is a tungsten welding electrode, 18 is a welding arc, and 19 is a material to be welded.

Next, looking specifically at the welding line of the expansion tube 13, as shown in FIG. 3 which is an explanatory view of the changing state of the welding line,
In the case of upward welding, the welding follows the waveform of the expansion tube 13 and first stands up → upward corresponding to the inside welding of the pipe → upward →
The process is upward-downward, which corresponds to the outer welding of the pipe, and is repeated until the corrugated shape ends. In order to perform this welding, a fourth diagram showing the positional relationship diagram of the welding torch is shown.
As shown in the figure, the welding torch 15 is formed in a small size so that it can be inserted into the narrow valley of the corrugated shape of the expansion tube 13 and can be swung there. The position is adjustable in the X-axis direction (the direction of the depth of the waveform), the Y-axis direction that is the longitudinal direction of the expandable tube 13 that is orthogonal thereto, the Z-axis direction that is orthogonal thereto, and the θ-axis direction around the Z-axis. . That is, the welding torch 15 is moved along the Y axis in the vertical welding, is rotated about the θ axis in the upward welding corresponding to the inner welding of the pipe, and is moved along the X axis in the upward welding and the downward welding. Further, in the upward welding corresponding to the outer welding of the pipe, the X-axis, the Y-axis, and the θ-axis are interlocked to move the welding torch 15 in an arc shape on the XY plane and maintain the required welding posture. Furthermore, the welding torch 15 is aligned with the groove by the Z-axis movement, and the arc voltage is automatically set to move the welding torch 15 toward and away from the base metal so that the arc height can be made constant at any welding position. A control slide shaft is also provided.

By the way, in such a welding process, the bead formation state differs depending on whether it corresponds to the inner welding of the pipe or the outer welding of the pipe.

That is, the penetration shape of the weld bead 14 is generally wide on the side of the welding arc 18 and narrow on the side of the rear surface, as shown in FIG. That is, the width of the front bead is W ₁ and the width of the back bead is
If W ₂ , then W ₁ > W ₂ . This tendency is particularly large in the method of using a high current for a short time like the method of the present invention. Therefore, in welding in the case of being equivalent to the inner welding of the pipe, as shown in FIG. 6, since the circumferential length on the back surface side is longer than the circumferential length on the welding arc 18 side, adjacent back bead beads are not connected. Otherwise, the gap Δl may be opened. On the other hand, as shown in FIG. 7, in the case of the outside welding of the pipe, the peripheral length relationship between the welding arc 18 side and the back side is opposite, so that the risk is small.

Therefore, as a welding condition, the ratio of the high current use time t ₀ shown in FIG. 1 and the use time t ₁ at the minimum current required to maintain the welding arc 18 is automatically changed in the above cases. preferable. That is, in the welding in the case where it corresponds to the inner welding of the pipe in which the back bead is difficult to be connected in terms of shape, the high current application time t ₀ is set to be 0.1 to 0.2 sec longer than the others. By doing so, the amount of molten metal in that portion is increased, and it becomes possible to reliably make the back bead continuous.

<Effects of the Invention> As described above in detail with reference to the embodiment, according to the present invention, it is possible to reduce the heat input as a whole to reduce the amount of molten metal and to make the back bead continuous. Thus, for example, all-position one-pass backside automatic welding of a butt joint having a plate thickness of 2 to 4 mm such as a long joint of a bellows-shaped large expansion tube can be performed.

[Brief description of drawings]

FIG. 1 is a graph showing the change over time of the welding current according to one embodiment of the method of the present invention, FIG. 2 is a perspective view showing the outline of the welded portion obtained thereby, and FIG. 3 is the change in the welding line of the expansion tube. Fig. 4 is an explanatory view of the situation, Fig. 4 is a positional relationship diagram of the welding torch in the welding, Figs. 5 to 7 are explanatory views showing the weld bead penetration state, and Fig. 8 is a welding condition of the expansion tube. It is a partially broken perspective view showing. In the drawing, 13 is an expansion tube, 14 is a welding bead, 15 is a welding torch, 16 is a pulse train current, 17 is a tungsten welding electrode, 18 is a welding arc, and 19 is a work material.

Front page continuation (71) Applicant 999999999 Chubu Electric Power Co., Inc. 1 Higashishinmachi, Higashi-ku, Nagoya, Aichi Prefecture (71) Applicant 999999999 Hokuriku Electric Power Co., Inc. 15-1 Ushijima-cho, Toyama City, Toyama Prefecture (71) Applicant 999999999 China Electric Power Co., Ltd. 4-33 Komachi, Naka-ku, Hiroshima City, Hiroshima Prefecture (71) Applicant 999999999 Shikoku Electric Power Co., Inc. 2-5 Marunouchi, Takamatsu City, Kagawa Prefecture (71) Applicant 999999999 Kyushu Electric Power Co., Ltd. Watanabe Dori, Chuo-ku, Fukuoka City, Fukuoka Prefecture 2-82-82 (71) Applicant 999999999 Japan Atomic Power Company 1-6-1, Otemachi, Chiyoda-ku, Tokyo (71) Applicant 999999999 2-5-1 Marunouchi, Chiyoda-ku, Tokyo (72) Inventor Noboru Nishiyama 3-3-22 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture Kansai Electric Power Co., Inc. (72) Shinji Igarashi 1-3-1, Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Company ( 72) Inventor Yoichi Jizaki 15-1 Ushijimacho, Toyama City, Toyama Prefecture Inland Electric Power Company (72) Inventor Masahiko Konishi 2-82 Watanabe-dori, Chuo-ku, Fukuoka-shi, Fukuoka Within Kyushu Electric Power Co., Inc. (72) Inatsuka Tatsutoshi 1-6 Otemachi, Chiyoda-ku, Tokyo No. 1 in Nihon Nuclear Power Co., Ltd. (72) Inventor Genta Takano 2-1-1, Niihama, Arai-cho, Takasago-shi, Hyogo Prefecture (1) Inside Takasago Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor, Kisaburo Tanaka 2 Niihama, Arai-machi, Takasago-shi 1-1-1 Mitsubishi Heavy Industries, Ltd. Takasago Laboratory (72) Inventor Hiromasa Kamei 2-1-1, Niihama, Arai-cho, Takasago-shi, Hyogo Prefecture 2-1 Mitsubishi Heavy Industries Ltd. Takasago Laboratory (72) Inventor Yoshihisa Nishikawa Arai-cho, Takasago-shi, Hyogo Prefecture 2-1-1 Nihama, Takasago Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor, Shoji Kushimoto 2-1-1, Niihama, Arai-cho, Takasago-shi, Hyogo Prefecture, Takasago Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor, Michito Sakamoto, Hyogo Prefecture 2-1-1 Niihama, Arai-cho, Takasago-shi Mitsubishi Heavy Takasago Research Institute (72) Inventor Yoshio Hashimoto 2-1-1 Niihama, Arai-cho, Takasago, Hyogo Prefecture Mitsubishi Heavy Industries, Ltd. Takasago Research Institute (72) Inventor Katsuhiko Hamada 1-1, Wadazaki-cho, Hyogo-ku, Kobe-shi, Hyogo No. 1 No. 1 in Mitsubishi Heavy Industries, Ltd. Kobe Shipyard (56) Reference JP-A-50-97551 (JP, A)

Claims (1)

[Claims] 1. In welding a corrugated joint in which corrugated members are butted against each other at a surface intersecting with the wave, a welding current between the tungsten welding electrode and the corrugated plate member to be welded is used as a welding current value higher than that of the preceding pulse. A TIG automatic welding method for thin-walled corrugated joints, characterized in that a slope-down type pulse train current consisting of a plurality of gradually decreasing pulse currents is repeatedly applied as the welding progresses.