JP6026727B2 - Structural materials for plug-in welded pipe fittings - Google Patents

Description

  The present invention relates to a structural material for a plug-in welded pipe joint that can reduce the occurrence of poor penetration by providing a minute projection at the tip.

  Plug-welded pipe joints such as socket weld joints have been used in many joints since work setup has been easy (see, for example, Patent Document 1). In ordinary butt welding of pipes, it is necessary to produce a back wave, and high technology and skill are required as welding techniques. On the other hand, socket welded joints are not required to have the skills and skills.

  FIG. 5 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.

  Socket welded joints are generally used for small-diameter pipes with an inner diameter of about 11.0 mm to 90.0 mm, but it is judged that there is no need for the welding operator to produce a back wave like butt welding. For welding technology management, if the welding heat input is too large for a small-diameter pipe, there is a thermal effect on the inner surface of the pipe and material deterioration. Done.

  FIG. 6 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. Since the parts to be welded, that is, the socket 1 and the pipe 2 have a large heat capacity, defects such as poor penetration as shown in FIG. 6 occur if the welding heat input suitable for the heat capacity is not given.

  In general, a surface inspection such as a liquid penetrant inspection is performed as a method for inspecting a socket-welded joint. However, this inspection method cannot detect defects inside the weld such as a penetration failure. Such a defect can be detected by using a radiation transmission test. However, because radiation is used, it is necessary to set up a management area, etc. In consideration of the difficulty and cost of preparation, it is generally adopted as a simple joint. It is difficult to adopt for existing socket welded joints. In the pressure resistance test, a slight penetration failure may pass the inspection.

  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.

Japanese Patent Laid-Open No. 11-118074

  As described above, socket welded joints are often used for small diameter pipes. For this reason, the installation location of the pipe is often a narrow portion or is installed in a location close to the wall or floor of the room, and the welding operation is often performed in a location where the welding posture is bad. For this reason, variations in welding heat input are likely to occur. If the heat input is insufficient (becomes too low) due to variations in welding heat input, the possibility of the above-mentioned poor penetration increases. Therefore, sufficient penetration is possible even for slight heat input variations. It is necessary to design a joint that provides

  The present invention has been made to solve such a conventional problem, and it is possible to obtain a sufficient penetration even when the welding heat input varies. Is to provide.

The present invention relates to a structure for a plug-in welded pipe joint in which a pipe is inserted into a slot and is fillet welded, and welded during fillet welding around the inner diameter side of the end face of the slot. Provided with a minute projection having a predetermined axial length in the insertion port for melting by heat input, and when the piping is inserted into the insertion port around the inner diameter side of the tip of the minute projection A separation portion having a length in the insertion axial direction equal to or less than the length in the insertion axial direction of the micro-projections for separating from the surface of the metal to prevent escape of welding heat input is provided.

  According to the structural material for a plug-welded type pipe joint of the present invention, by providing a small projection having a separation portion on the end face to which the structural material is welded, even if the welding heat input varies and a small projection portion is obtained, It is possible to provide a joint that is sufficiently melted to reduce the occurrence of a problem of penetration failure.

It is sectional drawing which shows the structure of the structural material for insertion welding type pipe joints of embodiment of this invention. It is sectional drawing which shows the example of the other separation part shape of embodiment of this invention. It is a figure which shows the microprotrusion shape provided with the separation part of a present Example, and the microprotrusion shape of a comparative example. It is a figure which shows the quality criteria of the welding state of a present Example. It is a figure which shows the axial direction cross section of the example of the socket welded joint in which favorable penetration was performed. It is a figure which shows the axial direction cross section of the example of the socket welding joint in which the 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 welded joint 100 having a structure in which the pipe 102 is inserted into the insertion port 101 b of the socket 101, a minute protrusion 103 is formed around the inner diameter side of the end surface of the insertion port 101 b of the socket 101.

  A socket (insertion welded pipe joint structure material) 101 according to the present embodiment includes a microprojection portion 103 that is a portion having a small heat capacity locally at a portion to be welded of the socket weld joint 100, and has a heat input during welding. Even if the welding heat input becomes small due to variations, the microprojection 103 itself melts sufficiently with the welding heat input during fillet welding to suppress the occurrence of defects, thereby reducing the possibility of poor penetration. Thus, a good weld joint can be obtained.

  Further, a chamfered separation portion 103 a is formed on the inner diameter side of the tip portion of the microprojection portion 103. When the intersecting corner portion of the socket 101 and the pipe 102 is in close contact, the welding heat input escapes to the pipe side having a large heat capacity, and the variation in the welding heat input may not be absorbed. In the present embodiment, by providing the separation portion 103a, escape of welding heat input to the pipe 102 is prevented. As a result, even when the welding heat input varies and decreases during the first layer welding, the minute protrusions are easily melted, so that the first layer is sufficiently melted, and the occurrence of poor penetration can be reduced.

  Further, before the first layer welding is performed, in order to temporarily fix the positions of the socket 101 and the pipe 102, some locations are tack welded, and then the entire circumference is welded. At the time of the temporary fixing, the pipe is drawn to the side where the first welding is performed, and the socket inner surface 101b and the outer surface of the pipe 102 are brought into close contact with each other. Such a close contact portion always exists at one place in the joint. However, in the present invention, by providing the separation portion 103a, the escape of welding heat input to the pipe 102 is prevented, and a poor penetration occurs. Great effect on reduction.

  In the case of the present embodiment, the cross-sectional shape of the microprojection 103 is preferably a square, but it may not be a square, or may be a rectangle or a semicircle due to workability and weldability. .

  Further, in the present embodiment, the separation portion 103a of the microprojection portion 103 has a chamfered shape, but is not limited thereto, and may have a shape that can be separated from the outer surface of the pipe 102. For example, a step shape 203b as shown in FIG. 2 (a) or a curved shape 303b as shown in FIG. 2 (b) may be provided. Since the end face of the socket part is originally chamfered, the chamfered shape is preferable in that a desired shape can be obtained by simply cutting the outer peripheral side of the socket end face.

  As described above, according to the structure for insertion welded pipe joints of each embodiment of the present invention, by providing a minute protrusion having a separation portion at the tip of the socket insertion port, welding heat input can be achieved. Even with slight variations, a joint with good penetration can be obtained, and the possibility of occurrence of leakage of liquid or gas inside the pipe in use can be reduced. Moreover, although the triangle and the quadrangle were mentioned as an example of the cross-sectional shape of the minute protrusion, the cross-sectional shape is not limited to these, and any shape that can be processed may be used.

  Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

  In order to confirm the effect of the separation portion of the present embodiment, a socket having a minute projection provided with a separation portion as an example (FIG. 3A) and a socket having a minute projection without a separation portion as a comparative example (Fig. 3 (b)) was actually welded, and the cross-section of the cross section was confirmed by macrophotograph observation. The external dimensions of the microprojections were 1 mm × 1 mm, and the chamfering was C0.5 mm. In this example, in order to effectively check the influence of the separation portion, welding was performed in a state in which the socket inner surface 101b and the outer surface of the pipe 102 were in close contact over the entire circumference.

  FIG. 4 shows the criteria for determining whether the welding state is good or bad. As shown in the figure, the penetration amount was compared by calculating from the macro photograph the penetration insufficiency height indicating the penetration amount of the fillet weld C. In this figure, when the amount of penetration is negative, it has melted to the pipe side, and it is judged as “good”, and when the amount of minus is larger, it is judged that sufficient penetration has occurred.

The test conditions are as follows. In this test, the conditions under which welding defects are likely to occur were set, the torch was fixed, and the socket and piping were rotated and welded.
・ Set current: 98A (standard)
・ Aperture: 25A
・ Piping: sch40 (Material SUS304)
・ Socket: sch80 (Material: SUS304)
・ Heat input (target): 1000J / mm
・ Ground: Socket side ground ・ Torch angle: 52 ° (fixed)
・ Filler wire: φ1.2

The measurement results are shown in Table 1.

  As can be seen from the table, both the socket with the minute protrusions with the separation part and the socket with the minute protrusions without the separation part have a negative penetration shortage, and there is no occurrence of poor penetration. Welding was performed. However, for sockets having microprotrusions provided with a separation part of this embodiment, compared with sockets having microprotrusions not provided with a separation part, the negative value of the insufficient penetration height is increased and better penetration is achieved. Has been confirmed. Therefore, the effect of this example was confirmed.

100: Insertion welding type pipe joint 101 according to an embodiment of the present invention 101: Socket 102: Pipe 103: Minute protrusion 103a: Separation part

Claims (3)

A construction material for a plug-in welded pipe joint for pipe insertion into the insertion port and fillet welding,
Provided around the inner diameter side of the end surface of the insertion port is a micro projection having a predetermined length in the axial direction of the insertion port for melting by welding heat input during fillet welding, and the tip of the micro projection In the periphery of the inner diameter side, when the pipe is inserted into the insertion port, the axial length of the insertion port in the insertion port is separated from the surface of the piping to prevent escape of welding heat input. A structure material for a plug-welded pipe joint, comprising a separation portion having the following axial length in the insertion port .   2. The structural material for a plug-in welded pipe joint according to claim 1, wherein the separation portion has a chamfered shape formed around the inner diameter side of the tip end portion of the microprojection portion. The plug-in welded pipe joint structural material according to claim 1, wherein the separation portion has a stepped shape or a curved shape formed around the inner diameter side of the tip end portion of the microprojection portion.