JP2020133792A - Welding method of ring-shaped object to iron pipe end - Google Patents

Abstract

To make it hard to cause breakage in a weld part, when mounting a flange 2 to an iron pipe 1 such as a ductile cast iron pipe by welding.SOLUTION: A method is provided for welding a flange 2 to an end of an iron pipe 1. The flange has a sleeve 10 being fit into the iron pipe end. The sleeve and the flange are fitted into the iron pipe end with the sleeve as the inside. The sleeve is welded ato the iron pipe end, and then an inner end of the sleeve and the flange are welded a, ato the iron pipe side face. When the sleeve is welded ato the pipe earlier, even if portions of both sides sandwiching the weld part aof the sleeve are welded a, a, the contractive force is prevented by the weld part aof the sleeve even if the weld part aof one side makes thermal contraction by the weld part of the sleeve. Accordingly, the contractive force is not applied to the weld part aof the other side, and therefore the breakage of the weld part of the other side is hard to occur. The sleeve is configured such that a groove 11 is formed in an outer circumferential surface and the welding to the iron pipe can be performed in the groove. When performed in this way, the welding of the sleeve becomes smooth.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method of welding a ring-shaped object such as a flange to an end of a metal pipe used for fluid transportation such as water and fixed transportation such as powder and combustion ash.

A method of attaching a ring-shaped flange to an iron pipe by welding is described in JIS B 2220: 2012 Annex (Reference) “Details of Welded Part of Welded Flange”. According to this method, for example, as shown in FIGS. 13 and 14, in a state where the iron pipe 1 is inserted into the flange 2 (the flange 2 is fitted into the end portion of the iron pipe 1), the same back surface as the end face side of the flange 2. has a circumferential portion of the side to be welded a ₀ to iron pipe 1. FIG. 14 shows a case where the transported object in the steel pipe 1 is required not to come into contact with the weld bead or the flange 2, and FIG. 13 shows a case where there is no such requirement.
As shown in FIG. 15, the iron pipe 1 with the flange 2 is connected by fastening both flanges 2 and 2 facing each other with a gasket 3 interposed at the end faces of the iron pipes 1 and 1 to be connected by bolts and nuts 4. See Patent Document 1, Fig. 2 etc.).

Further, as shown in FIG. 17, rings 5 are provided on the outer periphery of the ends of the iron pipes 1 and 1 connected on the same axis, and the protrusions 7 protruding inward of the two-piece annular housing 6 are ringed on both rings 5 and 5. The annular housing 6 is provided over both ends of both iron pipes 1 and 1 by locking on the end surface of 5 and interposing rubber rings 8 extending over both ends of both iron pipes 1 and 1. There is a pipe joint structure in which the housing is fastened with bolts and nuts (see Patent Document 2, FIG. 1, etc., and in FIG. 6 of this document, the housing is locked in the groove instead of the protrusion 7).

Special Fair 6-56232 Gazette Japanese Unexamined Patent Publication No. 2003-42360

In any of these means, when the flange 2 or the ring 5 is welded to the iron pipe 1, the welded portion has a characteristic of shrinking due to a temperature difference when cooled.
Therefore, as shown in FIG. 16, when the flange 2 (ring 5) is welded a ₀ (fillet welding a ₀₁ , a ₀₂ ) on both sides of the inner peripheral surface (the end surface side and the same back surface side), it precedes. When the welded portion, for example, the a ₀₁ portion in the figure is welded first, the a ₀₁ portion is subjected to a tensile action due to heat shrinkage of the welded portion a _{02 due} to cooling. When the iron pipe 1 contains a large amount of carbon such as ductile cast iron, when welding is performed, a layer (hereinafter referred to as heat-affected zone) containing cementite, which is hard and does not stretch, is formed on the iron part during cooling. Will be done. If an excessive tensile force acts on the heat-affected zone, the heat-affected zone does not stretch, so that problems such as cracking may occur.

An object of the present invention is to make it difficult for cracks to occur in a welded portion when a ring-shaped object (member) such as a flange is attached to an iron pipe such as a ductile cast iron pipe by welding under the above-mentioned actual conditions.

In order to achieve the above object, in the present invention, the sleeve is integrated with the flange in advance by welding or the like, the sleeve is fitted to the iron pipe and welded, and then the flange is welded to the iron pipe.
In this way, if the sleeve is welded to the iron pipe first, even if the parts on both sides of the sleeve that sandwich the welded portion are welded, even if the welded portion of the sleeve attempts to heat-shrink the welded portion on one side. Since the contraction force is blocked by the welded portion of the sleeve, the contraction force does not reach the welded portion on the other side, and cracking of the welded portion on the other side is unlikely to occur.

A specific method for welding a ring-shaped object to an iron pipe end portion of the present invention is a method of welding a ring-shaped flange to the iron pipe end portion, and the flange has a sleeve that fits into the iron pipe end portion. , Fit the sleeve and flange into the iron pipe end with the sleeve inside, weld the sleeve to the iron pipe end, then weld the inner end of the sleeve to the iron pipe, and weld the flange to the iron pipe end. It was adopted.

Another specific method of welding a ring-shaped object to the end of a steel pipe is to fit a ring with a sleeve on the outer peripheral surfaces of both ends of both steel pipes butted on the same axis with the sleeve inside. In a pipe joint structure in which an annular housing is provided over both ends of both steel pipes by locking an inwardly projecting protrusion to the ring and interposing rubber rings extending over both ends of both steel pipes, the sleeve is attached to the steel pipe. After welding to the end portion, the inner end portion of the sleeve is welded to the iron pipe, and the ring is welded to the iron pipe end portion and the sleeved ring is welded to the iron pipe end portion.

In both of these configurations, the sleeve is formed with a groove on the outer peripheral surface thereof, and welding to the iron pipe can be performed in the groove. By doing so, since the welding position becomes a groove and is clear, the welding of the sleeve becomes smooth.

Further, in the structure in which a flange, which is a ring-shaped object, is welded to the specific iron pipe end portion of the present invention, the flange has a sleeve that fits into the iron pipe end portion, and the sleeve and the sleeve and the sleeve with the sleeve inside the iron pipe end portion It is possible to adopt a configuration in which a flange is fitted, the sleeve is welded to the end of the iron pipe, the inner end of the sleeve is welded to the iron pipe, and the flange is also welded to the end of the iron pipe.

Further, in the structure in which a ring-shaped object is welded to the end of another concrete steel pipe, a ring with a sleeve is fitted on the outer peripheral surfaces of both ends of both steel pipes butted on the same axis with the sleeve inside, and the ring shape is formed. In a pipe joint structure in which the annular housing is provided over both ends of both steel pipes by locking a protrusion protruding inward of the housing to the ring and interposing a rubber ring extending over both ends of both steel pipes, the sleeve thereof. Is welded to the end of the iron pipe, and the inner end of the sleeve is also welded to the iron pipe. The ring adopts a configuration in which the ring with a sleeve welded to the end of the iron pipe is welded to the end of the iron pipe. obtain.
In this configuration, the sleeve may be configured such that a groove is formed on the outer peripheral surface thereof and welding is performed to the iron pipe in the groove.

Since the present invention is configured as described above, it is possible to solve the problem of cracking of the welded portion that occurs when a ring-shaped object such as a flange is welded to a pipe containing a large amount of carbon such as a ductile cast iron pipe. Further, when manufacturing a tube with protrusions for a housing joint, it is possible to prevent cracking of the welded portion when both sides of the ring-shaped member are welded.

Top half cut front view of a flange with a sleeve in one embodiment of a method of welding a flange which is a ring-shaped object to an iron pipe end according to the present invention and a welding structure thereof. Top half cut front view of the flange with sleeve of the same embodiment welded to the pipe end Top half cut front view of the pipe joint structure of the same embodiment Top half cut front view of a flange with a sleeve in a method of welding a flange which is a ring-shaped object to an iron pipe end according to the present invention and another embodiment of the welded structure. Top half cut front view of the flange with sleeve of the same embodiment welded to the pipe end Top half cut front view of a ring-shaped object welded to the end of an iron pipe according to the present invention and a ring with a sleeve welded to the pipe in one embodiment of the welded structure. Top half cut front view of the pipe joint structure of the same embodiment Top half cut front view of a ring-shaped object welded to an iron pipe end according to the present invention and a ring with a sleeve welded to the pipe in another embodiment of the welded structure. Top half cut front view of the pipe joint structure of the same embodiment Top half cut front view of a method for welding a ring-shaped object to an iron pipe end according to the present invention and a ring with a sleeve welded to the pipe in still another embodiment of the welded structure. Top half cut front view of welded pipe of another example of ring with sleeve in the same embodiment Top half cut front view of the pipe joint structure of the same embodiment Cutting front view of an example in which a conventional flange is welded to the pipe end Cutting front view of another example in which a conventional flange is welded to the pipe end Top half cut front view of pipe joint structure with conventional flange Enlarged view of the flange welded portion of FIG. Top half cut front view of pipe joint structure with conventional annular housing Front view of the cut with the annular housing and the like removed in FIG.

A method of welding a flange 2 which is a ring-shaped object to an iron pipe end portion according to the present invention and an embodiment of the welded structure thereof are shown in FIGS. 1 to 3, and this embodiment shows the connected ductile cast iron shown in FIG. This is a case of a pipe joint structure in which RF flanges 2 are provided at the ends of pipes 1 and 1, and both flanges 2 and 2 are fastened with bolts and nuts 4 via a gasket 3.
The feature is that the flange 2 has an iron cylindrical sleeve 10 as shown in FIGS. 1 to 3. The sleeve 10 in this embodiment is welded a ₀ to the flange 2 in advance, but the flange 2 and the sleeve 10 may be integrally molded (see Patent Document 1, FIG. 1).
A groove 11 is formed in the sleeve 10 in the axial direction thereof. The width and length of the groove 11 are arbitrary as long as the effect can be obtained. The number of grooves 11 is also arbitrary around the outer peripheral surface of the sleeve 10, but in the case of a plurality of grooves 11, equidistant perimeter is preferable. In this embodiment, three lines are used at equal intervals around the perimeter. The groove 11 may be intermittent in the axial direction.

The flange 2 with the sleeve 10, as shown in FIG. 2, fitted to the ends of the ductile cast iron pipes 1, first, in the groove 11, (welded) attaching the sleeve 10 to the tube 1 by welding a _1. Thereafter, with the outer inner periphery of the flange 2 is welded a ₂ to the tube 1, to weld a ₃ to tube 1 (the opposite end of the flange 2) the end of the sleeve 10. And welding a ₂ of the outer inner periphery of the flange 2, welding a ₃ end of the sleeve 10 may either even after at first.

At this time, since the sleeve 10 is welded a ₁ before the tube 1, the welding portion of one side groove 11 of the shrinkage force sleeve 10 also welds a ₃ of (sleeve end side) trying to heat shrinkage because it is blocked in a _1, the contraction force is not inferior to weld a ₂ on the other side (flange 2 side), cracks of the weld a ₂ of other side hardly occurs.

Although the groove 11 is in the axial direction, it can also be in the circumferential direction as shown in FIGS. 4 and 5. The number of the grooves 11 is also arbitrary in the axial direction of the sleeve 10, but in the case of a plurality of grooves 11, equidistant perimeter is preferable. In this embodiment, the number is one. Further, the groove 11 does not need to be formed over the entire circumference and may be intermittent.
The flange 2 with a sleeve 10 of this embodiment is also used as a pipe joint (see FIG. 3).

A method of welding a ring-shaped object to an iron pipe end portion according to the present invention and another embodiment of the welded structure thereof are shown in FIGS. 6 and 7, and this embodiment is abutted (connected) as shown in FIG. A ring 5 is provided on the outer periphery of the ends of the ductile cast iron pipes 1 and 1, and an annular housing 6 divided into two is locked to both rings 5 and 5 with a protrusion 7 on the inner side interposed therebetween. This is a case of a pipe joint structure in which the two-piece housing 6 is fastened with bolts and nuts.

The feature is that the ring 5 has an iron cylindrical sleeve 10 as shown in FIG. Although the sleeve 10 is integrally cast to the ring 5, the sleeve 10 may be welded to the ring 5. Similarly, the sleeve 10 is formed with a groove 11 in the axial direction thereof. The width and length of the groove 11 are arbitrary as long as the effect can be obtained. The number of grooves 11 is also arbitrary, but in the case of a plurality of grooves 11, equal spacing around them is preferable. In this embodiment, three lines are used at equal intervals around the perimeter. The groove 11 may be intermittent in the axial direction.

The ring 5 with the sleeve 10, as shown in FIG. 6, fitted to the ends of the ductile cast iron pipes 1, first, in the groove 11, (welded a ₁₎ attached to the sleeve 10 tube 1 by welding. Thereafter, the welded a ₂ outer inner periphery of the ring 5 to the tube 1, to weld a ₃ to tube 1 (the opposite end of the ring 5) end of the sleeve 10. And welding a ₂ of the outer inner periphery of the ring 5, welding a ₃ end of the sleeve 10 may either even after at first.

At this time, since the sleeve 10 is welded a ₁ before the tube 1, also blocked by the weld a ₁ of the contractile force of the sleeve as the weld a ₃ on one side (sleeve end side) tries to heat shrinkage to be, the shrinkage force can not reach the weld a ₂ on the other side (the ring 5 side), cracks of the weld a ₂ of other side hardly occurs.
As shown in FIG. 7, the iron pipe 1 to which the ring 5 with the sleeve 10 is attached has an annular housing 6 divided into two on both rings 5 and 5 with a protrusion 7 protruding inward via a rubber ring 8. Lock and fasten the two-piece annular housing 6 with bolts and nuts.
The ring 5 with the sleeve 10 may be divided in the circumferential direction. In this case, the welding to the pipe 1 on the divided surface can be substituted for the welding of the groove 11.

As shown in FIG. 8, the ring 5 with the sleeve 10 can be fitted into the groove 15 formed on the outer surface of the pipe 1 in contact with one of the groove walls, and the ring 5 or the sleeve 10 can be welded in that state. it can. In this case, the connection mode shown in FIG. 9 is used. At this time, the ring 5 and the sleeve 10 can be fitted into the groove 15 as at least one split shape in the circumferential direction. The order of welding, performs welding _{a 1} through the groove 11 of the sleeve 10, subsequently, performs welding _{a 3} end of the welding _{a 2,} the sleeve 10 of the ring 5 side. The welding a ₂ and welding a ₃ may be in either the first. The split surface b of the ring 5 and the sleeve 10 can be welded, and the welding of the split surface b with the pipe 1 can be replaced with the welding of the groove 11 portion.

Further, the groove 11 is not limited to the axial direction, but may be in the circumferential direction as shown in FIGS. 10 and 11. At this time, the grooves 11 may be intermittent, but it is preferable that the grooves 11 extend over the entire circumference at equal intervals.
As shown in FIG. 12, the iron pipe 1 to which the ring 5 with the sleeve 10 is attached has an annular housing 6 divided into two on both rings 5 and 5 with a protrusion 7 protruding inward via a rubber ring 8. Lock and fasten the two-piece annular housing 6 with bolts and nuts.

In the above embodiment, the method of welding the flange 2 to the sleeve 10 includes a case of welding to the end face of the sleeve 10 (FIG. 1) and a case of welding to the end portion (see FIGS. 13 and 14). Further, the iron pipe 1 for welding the flange 2 may have an insertion port shape at both ends or a socket shape at one end. When both ends have an insertion port shape, one flange 2 can be integrally cast with the pipe by centrifugal casting.
In each embodiment, if the welding a ₁ is properly carried out, the groove 11 may be omitted, also the grooves 11 may also be through, the circumferential direction of the through grooves 11 is intermittently provided If so. Further, the depth of the groove 11 is also arbitrary. When the groove 11 is not provided, the thickness of the sleeve 10 at the welded portion is appropriately set (thinned) by an experiment or the like so that the sleeve 10 and the pipe 1 can be melted by the heat of welding.

Further, it goes without saying that the present invention can be adopted not only for the above-mentioned RF flange pipe joint but also for various flange pipe joints such as other FF flanges, and the welding method (welding structure) according to the present invention is water. Applicable not only to water and sewage and industrial water pipelines, but also to wear-resistant pipes used for fixed transportation of powder, combustion ash, etc., and metal pipelines that require abrasion resistance, such as fire extinguishing pipes in tunnels. can do. Further, the iron pipe 1 is not limited to the ductile cast iron pipe, and can be various metal pipes that can be welded.
Thus, it should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is indicated by the scope of claims and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Ductile cast iron pipe 2 Flange 3 Gasket 4 Fastening bolt / nut 5 Ring 6 Ring housing 7 Protrusion 8 Rubber ring 10 Sleeve 11 Groove a ₀ , a ₀₁ , a ₀₂ , a ₁ , a ₂ , a ₃ Weld (welded part)

Claims (3)

A method of welding a ring-shaped flange (2) to the end of an iron pipe (1), the flange (2) having a sleeve (10) that fits into the end of the iron pipe, and a sleeve at the end of the iron pipe. The flange (2) and the sleeve (10) are fitted with the (10) inside, the sleeve (10) is welded to the end of the iron pipe (a ₁ ), and then the inner end of the sleeve (10) is attached to the iron pipe (10). A method of welding a ring-shaped object to the end of an iron pipe by welding (a ₃ ) to the end of the iron pipe and welding the flange (2) to the end of the iron pipe (a ₂ ). Rings (5) with sleeves (10) are fitted on the outer peripheral surfaces of both ends of both steel pipes (1, 1) butted on the same shaft with the sleeve (10) inside, and inside the annular housing (6). The annular housing (6) is attached to both iron pipes (6) by locking the protrusion (7) protruding from the ring (5) to the ring (5) and interposing rubber rings (8) extending over both ends of both iron pipes (1, 1). In the pipe joint structure provided over both ends of 1 and 1),
After the sleeve (10) is welded to the end of the iron pipe (a ₁ ), the inner end of the sleeve (10) is welded to the iron pipe (1) (a ₃ ), and the ring (5) is attached to the end of the iron pipe. A method of welding a ring-shaped object to an iron pipe end by welding (a ₂ ) to the iron pipe end and welding the ring (5) with the sleeve (10) to the iron pipe end. The ring-shaped object according to claim 1 or 2, wherein a groove (11) is formed on the outer peripheral surface of the sleeve (10), and welding (a ₁ ) is performed on the iron pipe (1) in the groove (11). Method.

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