JP7410646B2 - How to form protrusions on iron pipes - Google Patents

Description

The present invention relates to a method for forming a protrusion on the outer circumferential surface of an iron pipe, such as an insertion port of a ductile cast iron pipe having an earthquake-resistant joint structure, and an iron pipe having the protrusion.

For example, as shown in FIG. 4, a cast iron pipe has a cylindrical straight part with constant inner and outer diameters, with one end serving as a socket 1 and the other end serving as a socket 2, and an inner surface of the socket 1. There is a tube into which a lock ring 3 is loaded and which has a protrusion 4 on the outer peripheral surface of the insertion port 2. This pipe P is constructed by inserting the insertion port 2 of one pipe P into the socket 1 of the other pipe P over the lock ring 3, and the protrusion 4 is locked to the lock ring 3 (dotted chain line state). This prevents the insertion port 2 of one pipe P from coming out of the other pipe P from the socket 1, and the tip of the insertion port 2 comes into contact with the end wall 1a on the inner surface of the socket 1 (as indicated by the two-dot chain line). ) to form an earthquake-resistant joint structure that prevents further insertion. In the figure, 5 is a lock ring holder and 6 is a rubber ring.

This type of pipe P is usually cast by centrifugal casting, but the protrusion 4 on the outer surface of the insertion port 2 may be formed by fitting a ring into the insertion port 2 and welding it, or by forming the ring as shown in FIG. As shown in a), it is formed with a weld bead a by build-up welding over the entire outer circumference of the insertion port 2 (see Patent Documents 1 to 4). The protrusion 4 formed by the weld bead a is finished by cutting into the desired cross-sectional shape shown in FIGS. 4 and 5(b).

Conventionally, in the build-up welding of the weld bead a, a protrusion is formed by one-round build-up welding (Patent Document 1, FIG. 2, FIG. 3, Patent Document 2, FIG. 7, Patent Document 3, FIG. 1, (See Patent Document 4, FIG. 3, etc.). There is a technical limit to the shape and strength of the protrusion 4 that can be formed by this one-round build-up, and it is not easy to form the protrusion 4 into the required cross-sectional shape shown in FIG. 5(b). For this reason, skill is required to form the protrusion 4 of the required height and width with this one-round build-up.
From this point, as shown in FIG. 6, the overlay welds a ₁ , a ₂ , a ₃ of one circumference are overlapped multiple times in the radial direction of the cast iron pipe P to form a plurality of weld beads a ₁ , a ₂ on the outer circumferential surface. , a ₃ may be formed (see FIG. 5(a)).

Japanese Patent Application Publication No. 2013-158792 Japanese Patent Application Publication No. 2008-185114 Japanese Patent Application Publication No. 09-189388 Patent No. 6082087

At this time, the build-up start position and end position are overlapped parts s ₁ , s ₂ , and s ₃ where the build-up welds a overlap. The overlapping portions are overlapped portions, and hereinafter will simply be referred to as “wrap portions s ₁ , s ₂ , s ₃ ” as appropriate. When the lap parts s ₁ , s ₂ , and s ₃ overlap as shown in FIG. 7 (on the same line in the radial direction), the lap parts s ₁ , s ₂ , and s ₃ are at the same position (overlapping). Therefore, the lap portion becomes more raised than the other portions (only that portion is thicker). This bulge may cause the welded shape to collapse, resulting in failure to form a good weld bead a, or the finishing process of cutting the bulge may become complicated (requires time and effort).

In view of the above-mentioned circumstances, an object of the present invention is to facilitate the formation of a protrusion having a desired cross-sectional shape by the build-up welding.

In order to achieve the above object, the present invention first involves overlaying each build-up weld around the outer surface of the iron pipe multiple times in the radial direction of the iron pipe and forming a protrusion from the plurality of weld beads. The protrusion made of the ring is formed by fillet welding, which is a plurality of layers of build-up welding over the entire circumference of the side surface of the ring and the outer peripheral surface of the iron pipe.
With these multiple weld beads, it is easier to form the build-up weld into the desired shape and size, and the width and height of the protrusion formed by the weld bead is greater than that formed by one weld. It is easy to adjust the size to the required size, and no skill is required.
At this time, the lap portions at the start and end of one circumference of build-up welding can have substantially the same height and width as other portions (the height and width can be made substantially uniform over the entire circumference).

Next, in the present invention, the lap portions at which the build-up welding of each weld bead starts and ends are shifted to different positions in the outer circumferential direction of the iron pipe.
In this way, if the lap parts at the start and end of the build-up welding on each circumference shift in the circumferential direction, the height and width of the lap parts of the build-up welding on one circumference will be almost the same as the other parts, as described above. As a result, the built-up lap portions do not overlap as in the conventional case, and the swelling of the lap portions is also suppressed. In other words, it is possible to approximate the shape of a continuous welded portion when the build-up of each circumference is performed continuously.

One specific method is to perform build-up welding around the entire circumference of the outer surface of the iron pipe, and overlap each build-up weld around the outer surface of the iron pipe multiple times in the radial direction of the iron pipe to form a protrusion consisting of a plurality of weld beads on the outer circumferential surface of the iron pipe. A method for forming a protrusion on an iron pipe forming a part, the overlay welding around the outer surface of the iron pipe is started and ended overlappingly , and the lap part (overlapping part) of the start and end of the overlay welding of each weld bead is formed. , we adopted a configuration in which they are located at different positions on the outer circumferential direction of the iron pipe.

Another specific method is to fit a ring onto the outer surface of the iron pipe, and make the ring into a protrusion by fillet welding in which multiple layers are built up over the entire circumference of the side surface of the ring and the outer peripheral surface of the iron pipe. In the method for forming a protrusion in an iron pipe, the build-up welding between the ring side surface and the outer circumferential surface of the iron pipe is started and finished repeatedly , and the lap portions at the start and end of the build-up welding of each weld bead are formed in the direction of the outer circumference of the iron pipe. They adopted a configuration in which they are placed in different positions.
By these methods of forming protrusions on iron pipes, it is possible to obtain iron pipes having protrusions on the outer circumferential surface.

In the present invention, with the above-described configuration, the start and end lap portions of one weld bead are shifted, so that the build-up welding of the lap portions is suppressed. Therefore, the welded shape is less likely to collapse in that area, resulting in a good weld bead layer (the shape of the protrusion is stabilized), and the finishing process for the bulge is also easy (simplified).

A sectional view of a main part of an iron pipe according to an embodiment of the method for forming a protrusion on an iron pipe according to the present invention A partial perspective view of an iron pipe according to another embodiment Cutaway front view of each example of the embodiment A ductile cast iron pipe for earthquake-resistant joints is shown, (a) is a partially cutaway sectional view of the connected state, and (b) is a partially perspective view. A method of forming a protrusion by build-up welding is shown; (a) is a partial cross-sectional view after welding, and (b) is a partial cross-sectional view after cutting and finishing. An explanatory diagram of a method of forming a protrusion by build-up welding Cross-sectional view for explaining an effect of the protrusion forming method

An embodiment of the method for forming a protrusion on an iron pipe according to the present invention is shown in FIG. 1, and this method restricts the outer peripheral surface of the insertion port 2 of the ductile cast iron pipe P for earthquake-resistant joints in the width direction, as shown in FIG. This is a case where the retaining protrusion 4 is formed by the weld bead a without any slippage. Note that the width direction regulation is achieved by arranging a pair of backing plates on both sides of the weld bead a, as described in, for example, Japanese Patent Laid-Open No. 2007-229800.
In the same manner as described above, the cast iron pipe P is formed by welding one round of build-up over the entire outer circumference of the cast iron pipe P by arc welding, and then repeating this one round of build-up welding multiple times in the radial direction of the cast iron pipe P. A protrusion 4 consisting of a plurality of weld beads a1, a2, and a3 is formed on the outer peripheral surface of the pipe P.
During welding, one build-up welding on the outer circumference of the cast iron pipe P goes around the outer surface of the iron pipe P from the start to the end, and the start and end are overlapped to form a lap part s, as shown in Figure 1. As shown, the lap portions s (s1, s2, s3) of each weld bead a1, a2, a3 are located at different positions in the outer circumferential direction of the cast iron pipe P (insertion port 2).
The number of weld beads a and the interval t between the lap portions s are appropriately determined by experiments or the like, taking into account the height and width of the protrusion 4 so that it can effectively exert its function. In this embodiment, the number of weld beads a: 3, and the lap portions s (s1, s2, s3) were made not to overlap in the radial direction (not to be on the same line in the radial direction).

In this way, forming the protrusion 4 using a plurality of weld beads a (a ₁ , a ₂ , a ₃ ) makes it easier to adjust the width and height to the required dimensions, compared to forming the protrusion 4 by one welding. Easy and does not require skill.
In addition, if the lap portions s (s ₁ , s ₂ , s ₃ ) at the start and end of the build-up welding are shifted in the direction of the outer circumference of the cast iron pipe P, the build-up of the wrap portions s will be shifted. , each of the overlays will not overlap and the bulges will also be suppressed.
From the above, the welding shape in the welded part (protrusion 4) is unlikely to collapse, resulting in a good weld bead a (the shape of the protrusion 4 is stable), and the multiple welds shown in FIG. 5(b) The finishing process by cutting the protrusion 4 into a desired shape using the beads a ₁ , a ₂ , and a ₃ is also facilitated (simplified).

The method for forming protrusions on iron pipes according to the present invention can be employed to form protrusions on the outer peripheral surface of various iron pipes P using multiple layers of weld beads, in addition to ductile cast iron pipes P. At this time, it goes without saying that it is not limited to the insertion port 2. The number of layers of each weld bead a is arbitrary. Furthermore, it goes without saying that the cast iron pipe P is not limited to the cast iron pipe of the above-described embodiment type, but can be employed in various cast iron pipes having a protrusion on the outer circumferential surface in which the protrusion is formed by overlay welding.

The idea of shifting the lap portion of each weld bead in the length direction of the bead according to the present invention can also be adopted in various welding processes in which the lap portions of each weld bead overlap when a plurality of weld beads are overlapped. For example, as shown in FIGS. 2 and 3 showing other embodiments of the present invention, a ring 14 is fitted onto the outer surface of the iron pipe P, and the diameter of the iron pipe P is adjusted over the entire circumference between the side surface of the ring 14 and the outer peripheral surface of the iron pipe P. In a method for forming a protrusion of an iron pipe in which the ring 14 is a protrusion by fillet welding of a plurality of layers overlapping in a direction , the sides of the ring 14 of the weld beads a ₁ , a ₂ , a ₃ of the overlapping fillet welds. Similarly, the start and end of the build-up welding a around the outer peripheral surface of the iron pipe P overlap in the circumferential direction of the iron pipe, and the start and end of the build-up welding of each of the overlapping weld beads a ₁ , a ₂ , a ₃ The ending lap portions are located at different positions on the outer circumferential direction of the iron pipe. In this case, it goes without saying that it can also be adopted when the protrusion 4 is provided with a ring 14.
At this time, the side surfaces of the ring 14 may be welded in multiple layers on both sides (FIG. 3(a)), or may be welded in multiple layers on only one side (FIG. 3(b)). The side surface can be welded in multiple layers (a ₁ , a ₂ , a ₃ ), and the other side surface can be welded in a single layer (FIG. (c)).

Furthermore, the present invention can also be adopted in the formation of the protrusion shown in FIG. 11 of Patent Document 4, and can be applied not only to the cast iron pipe P but also to the formation of the protrusion in various iron pipes that can be overlay welded. It goes without saying that the present invention can also be used when fillet welding various rings 14 to iron pipes.
In this way, the embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of this invention is indicated by the claims, and it is intended that all changes within the meaning and range equivalent to the claims are included.

P Cast iron pipe (iron pipe)
a, a ₁ , a ₂ , a ₃ weld bead (overlay welding)
s, s ₁ , s ₂ , s ₃ Overlay welding lap part (welding/end position)
1 Socket for cast iron pipe 2 Socket 4 Projection 14 Ring

Claims (1)

Overlay welding is performed over the entire circumference of the outer surface of the iron pipe (P), and each overlay weld around the outer surface of the iron pipe (P) is overlapped multiple times in the radial direction of the iron pipe (P), so that a plurality of overlapping weld beads ( a1, a2, a3) to form a protrusion (4) without restricting the width direction, the method comprises:
Each build-up welding around the outer surface of the iron pipe (P) of the overlapping welding beats (a1, a2, a3) is performed from the start to the end after going around the outer surface of the iron pipe (P). An iron pipe in which the overlapping parts (s1, s2, s3) of the start and end of overlay welding of each overlapping weld bead (a1, a2, a3) are at different positions in the outer circumferential direction of the iron pipe (P). How to form protrusions.

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