JP5726549B2 - Structural materials for plug-in welded pipe fittings - Google Patents

Description

  The present invention relates to a structural material for insertion welded pipe joints that can reduce the occurrence of poor penetration.

  The quality of a plug-welded pipe joint such as a socket-welded joint is ensured by sufficiently melting the intersecting corner portion (right-angle corner portion) between the socket end surface (vertical surface) and the pipe outer surface.

  Socket welded joints have been used in many joints since work setup is easy. In ordinary butt welding of pipes, it is necessary to produce a back wave, and advanced techniques and skills are required as welding techniques, but socket welded joints do not require such techniques and skills.

  FIG. 3 is a diagram showing an axial cross-section of a socket welded joint in which good penetration has been performed. The pipe 2 is inserted into the socket 1, and there is no welding defect (poor penetration) between the end face of the socket 1 and the surface of the pipe 2, and a fillet weld A is formed.

  FIG. 4 is a diagram showing an axial cross section of a socket weld joint in which a weld defect (poor penetration) occurs. The fillet weld B is welded between the end face of the socket 1 and the surface of the pipe 2, but a defect C is generated.

  If there is such a penetration failure, the planned strength is not ensured, and there is a possibility of leakage during use, so it is necessary to suppress the occurrence of the penetration failure.

  In general, penetration defects can be detected by performing a radiographic inspection. However, if a radiation transmission test is used for a plug-in welded pipe joint, the effect of using this joint, which is a simple joint, will not be achieved, so it is better to perform a radiation transmission test using butt welding. It is done. In general, the liquid penetration inspection or the magnetic particle inspection is applied to the nondestructive inspection for the insertion welded pipe joint. Since this is a surface inspection, as shown in the defect portion C in FIG. No internal defects can be detected.

  In general, after the welding is completed, the pressure resistance test is performed. However, when the internal defect as shown in the defect portion C in FIG. 4 is small, the pressure resistance test is often passed. Thereafter, it is considered that defects often develop as cracks during use, leading to leakage. Therefore, it is important how to manage the internal defects so as not to occur.

  FIG. 2 is a diagram showing a conventional socket welding mode. The tip portion (tungsten electrode) of the torch 13 enters the corner portion where the end surface 11a of the socket 11 and the outer surface 12a of the pipe 12 intersect at an angle of approximately 45 °.

In the figure, when the distance between the tip of the torch 13 and the end surface 11a of the socket 11 is l _A ′, and the distance between the tip of the torch 13 and the outer surface 12a of the pipe 12 is l _B ′, l _A ′ = l _B In the case of ′, the distance l _C ′ between the tip of the torch 13, the end surface 11 a of the socket 11, and the corner portion where the outer surface 12 a of the pipe 12 intersects is l _C ′ = √2l _A ′ (or = √2l _B ′). It becomes. Accordingly, the l _C ′ dimension in this case is √2 times (about 1.4 times) l _A ′ or l _B ′.

  In FIG. 2, the direction (position) where an arc is likely to occur is assumed as follows. First, as arc characteristics, there is arc rigidity, and there is a tendency that the arc tends to be emitted in the direction in which the electrodes are facing. However, generally, the direction in which an arc is likely to occur tends to be easily generated at a position where the distance between the electrode and the base material is the smallest.

  Therefore, it is preferable that an arc is generated at a corner portion where the end surface 11a of the socket 11 and the outer surface 12a of the pipe 12 intersect, but actually, the end surface 11a of the socket 11 having the smallest distance from the tip of the torch 13 to the base material An arc is likely to occur toward the outer surface 12 a of the pipe 12.

  Usually, it is covered with the skill of the welder, and the torch 13 is moved and covered so as to melt the corner. However, if the cover is insufficient, there is a high possibility that it will lead to poor melting of the corner portion, which may lead to a defect of poor welding at the corner portion.

  The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a structural material for a plug-welded pipe joint that can reduce the occurrence of poor penetration.

The structural material for a welded-type pipe joint according to the present invention is a corner portion in which a pipe is inserted into a substantially hollow cylindrical insertion port, and the end of the welding torch is formed by the end surface of the insertion port and the outer surface of the pipe. a plug weld type pipe joint for structural materials to be fillet welding enters toward the end face of the insertion port is substantially Ri frustoconical inclined surfaces der, plug weld type pipe joint for construction central axis angle between the cross section perpendicular the generally frustoconical shape of the inclined surface of the wood is characterized der Rukoto 30 ° or more.

  According to the structural material for a plug-welded type pipe joint of the present invention, it is possible to provide a socket weld joint in which a lack of penetration of the corner portion is unlikely to occur.

It is a figure which shows the shape of the structural material for insertion welding type pipe joints of embodiment of this invention, and the aspect of socket welding. It is a figure which shows the aspect of the conventional socket welding. It is a figure which shows the axial direction cross section of the socket welded joint in which favorable penetration was performed. It is a figure which shows the axial direction cross section of the socket welded joint in which the welding defect (poor penetration defect) has arisen.

  Hereinafter, a structure material for a plug-welded pipe joint according to an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, a socket welded joint will be described as an example, but the present invention can also be applied to a general insertion welded joint.

  Drawing 1 is a figure showing the shape of the structural material for insertion welding type pipe joints of the embodiment of the present invention.

  In the socket weld joint 100 in which the pipe 102 is inserted into the substantially hollow cylindrical insertion port 101b of the socket (insertion welded pipe joint structural member) 101 of the present embodiment, the end surface 101a of the socket 101 has a substantially truncated cone. It becomes the shape inclined surface.

As shown in FIG. 1, the distance between the tip of the torch 103 and the socket end surface 101a is l _A , the distance between the tip of the torch 103 and the pipe outer surface 102a is l _B, and the distance between the tip of the torch 103 and the corner is l _C. To do.

An entrance angle α of the torch 103 (an angle formed between the central axis of the torch 103 and the pipe outer surface 102a) is 60 °, and an angle β of the socket end surface 101a (a cross section perpendicular to the central axis of the socket 101 and a substantially frustoconical end surface 101a). Is 30 °, the distance l _A = distance l _B and l _C becomes l _C = (2 / √3) l _A (about 1.15 times), l _A and l _B , And l _C are almost the same length. Therefore, it can be seen that the arc is generated uniformly on the socket end surface, the outer surface of the pipe, and the corners thereof, and defects are less likely to occur.

The angle β of the socket end surface 101a is preferably 30 ° or more in the figure, but by making the angle larger than 0 °, the distance between the tip of the torch 103 and the socket end surface 101a is l _A , Since the difference between the distance between the tip of the torch 103 and the pipe outer surface 102a is 1 _B and the distance between the tip of the torch 103 and the corner is 1 _C , the occurrence of defects can be reduced.

  As described above, according to the socket of the present embodiment, the socket end surface of the socket joint has a substantially truncated cone shape that is tilted to the wide angle side, and the distance between the electrode tip and the base material is approximately equal, so that the socket corner portion The structure is easy to reach the arc. This makes it easier for the arc to come out uniformly on the pipe, the socket end face and the corner thereof, and insufficient corner penetration is unlikely to occur. Therefore, defects on the end face are less likely to occur, leading to improved reliability of the joint.

100: Socket weld joint 101: Socket (structure material for plug-in welded pipe joint)
102: Piping

Claims (1)

The pipe is inserted into the substantially hollow cylindrical insertion port, and the tip of the welding torch enters the corner portion formed by the end surface of the insertion port and the outer surface of the pipe and is fillet welded. It is a structural material for buried welded pipe joints,
The end surface of the insertion port, Ri substantially frustoconical inclined surfaces der,
Angle between a section perpendicular the generally frustoconical inclined surface to the central axis of the plug weld type pipe joint for construction materials, for plug welding type pipe joint according to claim der Rukoto least 30 ° Structural material.

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