JP4687453B2 - UOE steel pipe manufacturing method - Google Patents

Description

  The present invention relates to a method of manufacturing a UOE steel pipe.

  The UOE steel pipe is a steel pipe mainly used for transportation of oil or natural gas. In the production, first, groove processing is performed on both edge portions of the thick steel plate, which is a raw material, and then formed into an open pipe by a C press, U press, and O press machine. After that, seam welding is performed by tack welding by gas shield welding, inner surface welding by submerged arc welding, and outer surface welding, and finally, the tube is finished to a predetermined size by a pipe expander.

  By the way, the tack welding serves as a backing metal for the next submerged arc welding, and is generally welded from the outer surface side of the open pipe in order to simplify the equipment configuration and operability. It is. For this reason, in submerged arc welding, internal welding is performed in advance using a bead of tack welding formed on the outer surface side of the open pipe as a backing metal, and then outer surface welding is performed from the outer surface side. It is customary.

  Here, when carrying out inner surface welding, (1) if there is a fusion failure between the tack welding and the base metal part, (2) if there is a defect such as cracks, blowholes in the tack welding itself, (3) If the heat input is excessive during construction of the inner surface welding, the weld metal may flow out to the outer surface side beyond the tack welding that is the backing metal, which may cause poor welding.

  Such weld defects are referred to as “blown-out” of internal welds. When this burn-through is slight, it is permitted to remove the defective portion where the burn-out has occurred by the grinder, recreate the groove, and resume the internal welding. On the other hand, when the length of the defective part exceeds 50 mm, or when the weld metal that has melted down damages the base metal, it is not allowed to care for, and the steel pipe becomes a defective product, resulting in significant cost deterioration. Invite.

  Therefore, in order to prevent such burn-out during internal welding, visual inspection after tack welding is performed, and defective parts of tack welding are carried out by overlaying, and no burn-off occurs. Measures such as lowering heat input conditions of internal welding to a certain extent are taken.

  However, in practice, it is difficult to visually inspect all the pipes over the entire length of the weld bead after provisional attachment in terms of production efficiency hindrance, inspection personnel costs, and the like. In addition, there is a limit to reducing the heat input of the inner surface welding from the viewpoint of preventing a poor coupling with the outer surface welding to be performed later.

For these reasons, it is difficult to completely prevent burn-out during internal welding.
Therefore, in order to stop the inner surface welding while this burn-off is slight, the welding worker currently monitors the vicinity of the welding position visually from the outer surface of the steel pipe, or uses a camera attached to the inner surface welding machine to determine the welding position. Monitoring.

  However, in visual monitoring from the outer surface of the steel pipe, the backing metal that supports the steel pipe from the outer surface of the steel pipe blocks the field of view, so that even if a burn-out occurs, it is difficult to detect until a large amount of weld metal flows out.

  In addition, since the position of the inner surface welding is covered with the flux used for submerged arc welding, in the image of the camera attached to the inner surface welding machine, the change in the welding arc when the burnout occurs, or the weld metal It is difficult to confirm the spill situation.

  Thus, with the conventional method, it is impossible to completely prevent the melt-down during the inner surface welding, and it has been difficult to make the discovery in a slight manner.

  The problem to be solved by the present invention is that, in the past, it was not possible to find out the burn-out during inner surface welding.

The manufacturing method of the UOE steel pipe of the present invention is as follows:
In order to detect the burn-through during the inner or outer surface welding construction,
In the manufacturing method of UOE steel pipe,
Temporarily weld the outer surface of the open pipe,
Place a backing metal on the outer surface side of the open pipe in which a groove having the same width as the groove on the outer surface is formed,
Install a light-sensitive sensor and a heat-sensitive sensor on the opposite side of the backing metal facing the open pipe,
While welding the inner surface of the open pipe, the weld metal passing through the groove is detected by the sensor,
If the burn-is detected is the most important feature to stop the person the weld.

  In the present invention, in the manufacture of a UOE steel pipe, when a burn-out occurs during the construction of inner surface welding or outer surface welding, the outflow of the weld metal is quickly detected from the outside of the backing metal, and the welding is immediately stopped. Therefore, it is possible to suppress the melt-off length within a repairable range, and it is possible to prevent a decrease in yield and a deterioration in manufacturing cost.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing a basic configuration of a welding monitoring apparatus used in the method for manufacturing a UOE steel pipe of the present invention.

  In FIG. 1, 1 is a steel pipe which is a material to be welded, and an open pipe is tack-welded from the outer surface side. 2 shows an inner surface welding machine and its head for submerged arc welding of the tack welded portion 1a from the inner surface side of the steel pipe 1, and 3 shows a shielding flux for the submerged arc welding.

  Reference numeral 4 denotes a backing metal installed on the outer surface side of the tack welded portion 1a when inner surface welding is performed. In the UOE steel pipe manufacturing method of the present invention, the outer side of the backing metal 4, that is, the steel pipe. For example, a light-sensitive sensor 5 and a heat-sensitive sensor 6 are installed on the side opposite to the side facing 1 to detect weld metal that has melted during welding. In addition, 9 in FIG. 1 is a frame for the backing metal 4.

  In FIG. 1, a groove 4a having the same width as the groove on the outer surface side of the steel pipe 1 is formed on the backing metal 4, for example, so that the weld metal melted down during the welding can be reliably detected. One photo-sensitive sensor 5 that can detect the inside of the groove 4a and a heat-sensitive sensor 6 corresponding to the required length are arranged in the direction along the weld line.

  The light-sensitive sensor 5 detects a change in luminance due to weld metal that has melted during internal welding. Further, the heat-sensitive sensor 6 detects a heat change due to the weld metal that has melted. And if the change resulting from the weld metal which at least any one of these sensors 5 and 6 melted is detected, welding will be stopped automatically.

  In the example of FIG. 1, the detection of the burnout using both the light-sensitive sensor 5 and the heat-sensitive sensor 6 is shown. However, only one of them may be used to detect the burnout. Needless to say.

  A photo sensor is representative as the light-sensitive sensor 5, but any type can be used as long as it can detect a change in luminance. In addition to a sensor such as an air expansion tube, the heat sensing sensor 6 may be a sensor that senses heat by melting and disconnecting with the heat of the weld metal, such as a solder wire, piano wire, or chemical fiber.

Hereinafter, the results of tests conducted to confirm the effects of the present invention will be described in detail.
The steel pipe used for the test had an outer diameter of 762 mm and a wall thickness of 6 mm, 25.4 mm, and 40 mm.

  In order to confirm the effect of the method of the present invention, use a material that does not carry out defect care such as cracking of a welded part and blowhole, and intentionally burns out by changing the heat input conditions of internal welding. And compared with the conventional method.

  In the embodiment of the present invention, as shown in FIG. 1, a groove was formed in the backing metal, and the burn-off was detected by a light-sensitive sensor or a heat-sensitive sensor provided on the back side of the backing metal. In the comparative example, the burn-through was detected by visual observation from the side surface of the steel pipe as before. The implementation conditions and results are shown in Table 1 below.

The form of the inner surface welding melt-off in the comparative examples and the examples is shown in FIGS.
FIGS. 2 and 3 show the state during the inner surface welding of the comparative example, and the state shown in FIG. 3 is obtained when the burn-out occurs with respect to the normal inner surface welding shown in FIG. In FIG. 2 and FIG. 3, 7 indicates an inner surface weld bead.

  In the case of the comparative example, the weld metal 8 that has flowed out and flowed to the outer surface side is obstructed by the outer surface of the steel pipe 1 and the backing metal 4 as shown in FIG. is there. Accordingly, it can be detected only when the amount of the weld metal 8 that has flowed out and has flowed out increases.

  As a result, in the conventional method for visually detecting the burn-off, the length of the burn-off portion was 50 mm or more regardless of the wall thickness condition as in Comparative Example 1 to Comparative Example 3. Therefore, since repair by repair is impossible, it becomes a second-class product, resulting in a decrease in yield and a decrease in manufacturing cost. In the comparative example, the reason why the burn-out length after detection is longer as the inner wall welding is thinner and the heat input condition is lower is because the welding speed is faster.

  On the other hand, in the embodiment of the method of the present invention, the weld metal 8 that has been burned out and has flowed out to the outer surface side, as shown in FIG. It is detected by a light-sensitive sensor in the middle of dropping the groove 4 a of the pad 4, or detected by contacting the heat-sensitive sensor 6.

  Therefore, in the examples of the present invention, in any of the examples, it was possible to detect the burn-out at an early stage regardless of the wall thickness, and thus it was possible to suppress the burn-out length after detection to less than 50 mm. It was.

The present invention is not limited to the above example, within the scope of the technical idea described in 請 Motomeko may of course also be changed as appropriate embodiment.

It is the figure which showed the basic composition of the welding monitoring apparatus used for the manufacturing method of the UOE steel pipe of this invention. It is the figure which showed the state at the time of the inner surface welding of a comparative example, and showed the state of normal inner surface welding. It is the figure which showed the state at the time of the inner surface welding of a comparative example, and showed the state which the burn-through generate | occur | produced. It is the figure which showed the state at the time of the inner surface welding of the Example of this invention, and showed the state of normal inner surface welding. It is the figure which showed the state at the time of the inner surface welding of the Example of this invention, and showed the state which the burn-through generate | occur | produced.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel pipe 1a Tack weld 2 Internal welder and head 4 Backing metal 4a Groove 5 Optical sensor 6 Thermal sensor 7 Internal weld bead 8 Outflow molten metal

Claims (1)

In the manufacturing method of UOE steel pipe,
Temporarily weld the outer surface of the open pipe,
Place a backing metal on the outer surface side of the open pipe in which a groove having the same width as the groove on the outer surface is formed,
Install a light-sensitive sensor and a heat-sensitive sensor on the opposite side of the backing metal facing the open pipe,
While welding the inner surface of the open pipe, the weld metal passing through the groove is detected by the sensor,
Manufacturing method of the case where burn-is detected UOE steel pipe characterized in that to stop the person the weld.

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