JP2012236216A - Structural material for socket welding pipe fitting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a socket welding joint difficult to generate insufficient welding of a corner part.SOLUTION: A pipe is inserted into a nearly hollow cylindrical insertion hole, and the tip of a welding torch moves toward the corner part formed by the end face of the insertion hole and the outer face of the pipe, so that this structural material for a socket welding pipe fitting is fillet-welded. A corner part on the inside diameter side of the insertion hole is not chamfered.

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. 7 is a diagram showing an axial cross section of a socket weld 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. 8 is a view 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 surface of the socket 1 and the surface of the pipe 2, but a defect C is generated in the chamfer D.

  If there is such a penetration failure, it is easily affected by stress in the direction perpendicular to the pipe axis caused by vibration of the pipe, etc., and the strength as planned cannot be secured, and there is a possibility of causing leakage during use. is there. Therefore, it is necessary to suppress the occurrence of poor penetration.

  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. However, since this is a surface inspection, the defect 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. 8 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.

  One possible reason for the occurrence of the defective portion C shown in FIG. 8 is that the end face of the socket component is chamfered. In general, the edge of a machine part is chamfered for reasons such as preventing injury. However, when the socket and the pipe are fitted to each other due to the chamfered portion, a triangular cross-section space exists at the intersecting corner portion (right-angle corner portion) between the socket end surface (vertical surface) and the pipe outer surface. The presence of this space portion is considered to increase the possibility of poor penetration.

  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.

  In the present invention, a pipe is inserted into a substantially hollow cylindrical insertion port, and the tip of the welding torch enters a corner portion formed by the end surface of the insertion port and the outer surface of the pipe, and is fillet welded. This is a structural material for insertion welded pipe joints, characterized in that the inner diameter side corner of the insertion port is not chamfered.

  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 observation direction in the welding conditions of chamfering existence of this Example, and no chamfering. It is a cross-sectional photograph which shows the result of chamfering of a present Example. It is a cross-sectional photograph which shows the result of chamfering of a present Example. It is a cross-sectional photograph which shows the result of no chamfering of a present Example. It is a cross-sectional photograph which shows the result of no chamfering of a present Example. 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 having a structure in which the pipe 102 is inserted into the substantially hollow cylindrical insertion port 101b of the socket (insertion welded pipe joint structure) 101 of the present embodiment, the pipe 102 of the end surface 101a of the socket 101 is The periphery of the insertion opening is not chamfered and has a substantially right-angled cross section.

  As a manufacturing method of the socket 101 of this embodiment, for example, a pipe is cut by a pipe cutter such as a pipe cutter or a band saw to expose an end face, and a corner on the inner diameter side of the insertion port is chamfered and finished. That's fine.

  As described above, since the periphery of the insertion port of the pipe 102 on the end face 101a of the socket 101 is not chamfered, a cross section is formed at a crossing corner (right angle corner) between the socket end face (vertical face) and the pipe outer face as in the prior art. There is no space on the triangle, and it is possible to reduce the penetration failure by deleting this space portion.

  Examples of the present invention will be described below. In addition, this invention is not limited to a following example.

  In order to confirm the effect of the socket without chamfering of the present embodiment, welding experiments were performed on sockets with and without chamfering, and the weld cross section was confirmed.

(Welding conditions)
Fig.2 (a) is a figure which shows the observation direction in the welding conditions with chamfering. The welding conditions with chamfering are as follows. The torch (angle) was fixed, and the pipe and socket were rotated and welded.
・ Torch (tungsten electrode) angle: 62 degrees
・ Tungsten electrode tip position: ε (distance from socket end face) = 2 mm, δ (distance from pipe end face) = 4 mm
・ Filler wire (filler material) diameter: 1.6φ
・ Welding heat input: about 1000 J / mm

FIG. 2B is a diagram showing an observation direction under a welding condition without chamfering. The welding conditions without chamfering are as follows, and the welding conditions are the same as those with chamfering.
・ Torch (tungsten electrode) angle: 62 degrees
・ Tungsten electrode tip position: ε (distance from socket end face) = 2 mm, δ (distance from pipe end face) = 4 mm
・ Filler wire (filler material) diameter: 1.6φ
・ Welding heat input: about 1000 J / mm

(Experimental result)
3 and 4 are cross-sectional photographs showing the results of chamfering (cross-sectional macro observation photograph of welded part: enlarged 10 times). 3 and 4 both show that the chamfered portion has a defect (A portion in FIG. 3 and B portion in FIG. 4).

  5 and 6 are cross-sectional photographs showing the results without chamfering (cross-sectional macro observation photograph of the welded part: enlarged 10 times). No defects are recognized in FIG. 5, and defects (C in the figure) are recognized in FIG. 6, but the size is small compared to defects A and B with chamfers (FIGS. 3 and 4). Become. Therefore, the effect of the present invention was confirmed.

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 corner portion on the inner diameter side of the insertion port is not chamfered, and is a structural material for insertion welded pipe joints.