JP5198366B2 - Manufacturing method of steel pipe for threaded piping - Google Patents

Description

The present invention relates to a steel pipe for piping with a screw used for low-pressure piping.

Piping steel pipes used for piping of steam, water, gas, air, etc., whose working pressure is relatively low, are defined in JIS G 3452 as carbon steel pipes for piping (SGP).
Conventionally, when this type of piping steel pipe is threaded, male threads (taper male threads) are formed at both ends. And when connecting this steel pipe for piping with a thread, the socket is attached to the edge part of one piping steel pipe, and the external thread part of the edge part of the other piping steel pipe is screwed in and connected to this socket.

By the way, it is practiced to apply a compressive force in the longitudinal direction of the tube while the metal tube is partially heated to increase a part of the metal tube (that is, to increase the thickness of a part of the plate).
For example, Patent Document 1 and Patent Document 2 (Metal tube thickening method) describe that only a portion requiring strength is increased as a metal tube used in an automobile or the like.
As shown in FIG. 11 (a), this metal tube has an outer diameter at the end of the metal tube 21 that is the same as the outer diameter of the material metal tube, and is thickened on the inner surface side. The thickened portion is indicated by 21a.

Patent Document 3 (metal tube thickening method) includes, for example, a metal tube made of an oxide dispersion strengthened Fe-based superalloy used in a U-shaped reaction tube of a cracking furnace for purifying and separating ethylene. The method of increasing the thickness of the is described. For the case where it is necessary to provide a male screw on the outer surface near the end of this metal tube, as shown in FIG. A metal tube 31 having the same diameter as the portion (no step on the inner surface) but a larger outer diameter is shown (claims 2, 3 and paragraphs [0002], [0005], [0019] of Patent Document 3). ], [0022]).
In patent document 3, it seems that it is assumed that after cutting at the BB position in FIG. The thickened portion is indicated by 31a.

In Patent Document 4 (circular steel pipe having a joint portion and manufacturing method thereof), as shown in FIG. 11 (C), the steel pipe pillars for buildings or steel pipe piles for civil engineering are thickened on the inner surface side at both ends. A steel pipe 41 having a joint portion having a thick portion 41a and having an outer peripheral surface threaded or tapered is described.
The steel pipe 41 having the joint portion is a large steel pipe having an outer diameter of 600 mm, a thin portion having a thickness of 40 mm, an end thick portion 41a having a thickness of 80 mm, etc., and a stepped steel plate is formed by the UOE method. It is assumed to be tubed. The UOE pipe making method is a pipe making method in which a steel plate having a width corresponding to the circumferential length of a pipe is formed into a U shape by pressing, and then formed into a circular shape, and then an edge is welded to form a pipe.

  In Patent Document 5 (slurry transporting steel pipe and manufacturing method thereof), as shown in FIG. 11 (D), the end of the pipe is formed on the outer surface side by a hot upsetting process as shown in FIG. The steel pipe 51 which increased in thickness and formed the flange part 51a is described.

JP-A-7-214148 JP-A-9-327723 JP2002-160015 JP-A-8-302901 JP-A-11-333537

  As mentioned above, conventional threaded pipe steel pipes have male threads on the outer circumferences at both ends. When connecting these threaded pipe steel pipes, the end of one pipe steel pipe is connected. Although sockets are attached and connected, it is cumbersome to prepare a separate socket. Also, the work of attaching the socket is complicated.

  The present invention has been made based on the above background, and an object of the present invention is to provide a threaded pipe steel pipe that can directly connect pipe steel pipes without attaching a socket.

The invention of claim 1 which solves the above-mentioned problem is a method for producing a threaded pipe steel pipe for producing a threaded pipe steel pipe having a female thread at one end in the longitudinal direction of the pipe and a male thread at the other end. And
One end of the material steel pipe, which is a carbon steel pipe for piping specified in JIS G 3452 with a nominal diameter of 15A to 100A, is heated by a high-frequency induction heating coil, and then the one end is expanded. Next, it has a diameter expansion / thickening step of compressing in the longitudinal direction of the tube to increase the thickness of this one end,
The diameter expansion / thickening process for expanding the diameter of the one end is as follows:
It consists of two divided pieces 7a and 7b, and when the two are combined, a two-stage structure comprising a large inner diameter portion whose inner diameter is larger than the inner diameter of the material steel pipe and a smaller inner diameter portion that serves as a chuck portion for chucking the material steel pipe A die 7 with a chucking function that has a cylindrical inner surface and serves as a die that regulates the outer diameter of the pipe when expanding the diameter and a function of chucking the material steel pipe, and a conical tip portion 9b at the tip of the cylindrical portion 9a. Using the punch 9 provided with a flange portion 9c that pushes the end surface of the material steel pipe 1 ′ at the rear end of the holding cylindrical portion 9a,
By inserting and pushing the punch 9 into the pipe while the raw steel pipe is chucked by the small inner diameter portion of the die having the chuck function, the inner diameter of the one end portion of the punch becomes larger than the inner diameter of the raw steel pipe. Then, the one end is compressed in the longitudinal direction of the pipe by the flange 9c of the punch 9, and the one end is larger than the outer diameter of the raw steel pipe and the plate thickness is thicker than the raw steel pipe thickness. Is to increase the meat
A male screw is formed on the outer surface of the other end portion of the steel pipe whose one end portion is enlarged and thickened by a chaser, and the male screw of the other end portion is screwed to the inner surface of the one end portion which is enlarged and thickened. A size female screw is formed by a cutting tap.
Here, the female screw on the inner surface of one end and the male screw on the outer surface of the other end are taper screws.
Claim 2 is a method of manufacturing a steel pipe for threaded piping according to claim 1,
The outer diameter D, the inner diameter d, and the plate thickness t of the enlarged diameter / thickened portion 5 are respectively set at one end of the material steel pipe.
t ₀ <t <1.5 t ₀
D ₀ -1.5t ₀ <d <D ₀ -0.5t ₀
D ₀ + 0.8t ₀ <D <D ₀ + 3t ₀
And characterized in that the meat up Zo径, so as to be in the range.

According to the present invention, since pipes for piping can be directly connected without attaching a separate socket, the workability of pipe connection is improved.
In addition, it is not necessary to prepare a socket for a separate part, and the number of parts is reduced, so that handling related to pipe connection work is simplified and the cost is reduced.

It is a partially notched side view of the steel pipe for piping of one Example of this invention. (A) is a longitudinal cross-sectional view of the raw material steel pipe used for manufacture of the steel pipe for piping with a screw of FIG. 1, (b) is a cross-sectional view. When manufacturing the steel pipe for pipes with a screw of Drawing 1, it is a figure explaining the situation where one end part of a raw material steel pipe is heated as a pre-process which expands the diameter of one end part of a raw steel pipe. (A) is a diagram for explaining the process following FIG. 3, and is a diagram for explaining the initial stage of the process for expanding and increasing the thickness of one end of the raw steel pipe. (B) is a cross-sectional view taken along the line AA in (A). It is. FIG. 5 is a diagram for explaining a stage in the middle of expanding and increasing the diameter of one end of the raw steel pipe in a process subsequent to FIG. FIG. 6 is a diagram for explaining a stage where the diameter expansion / thickening of one end portion of the material steel pipe is completed following FIG. 5. It is sectional drawing of the steel pipe obtained by the said diameter expansion / thickening process. It is a figure explaining the point which forms a male screw in the outer surface of the other end part of the steel pipe of FIG. FIG. 9 is a diagram for explaining a procedure for forming a female screw at one end of a steel pipe whose diameter has been increased, following the step of FIG. 8. It is sectional drawing which showed the state which connected the steel pipe for pipes with a screw of FIG. (A), (B), (C), and (D) are diagrams showing a conventional example of a metal tube having a thickened end.

  Hereinafter, embodiments of the steel pipe for threaded piping of the present invention will be described with reference to FIGS.

FIG. 1 is a partially cutaway side view of a threaded steel pipe 1 according to an embodiment of the present invention.
The threaded pipe for steel pipe 1 has one end (left end in FIG. 1), by compressing the pipe longitudinal direction one end portion of the material steel pipe in a heated state, the outer diameter D is higher than the material steel pipe outer diameter D ₀ large in an enlarged diameter, thickening as the thickness t becomes thicker than the material steel plate thickness t _0, and the female thread 2 is formed on the inner surface, the male thread on the outer surface of the other end (right end in FIG. 1) 3 is formed.
The female screw 2 is sized to be screwed onto the male screw 3, and both are tapered screws. In the drawing, the taper is omitted. Reference numeral 5 denotes a portion where the diameter has been increased or increased (the increased diameter / increased portion).

FIG. 2 (a) is a longitudinal sectional view of a raw steel pipe 1 ′ used for manufacturing the threaded piping steel pipe 1 of FIG. 1, and (b) is a transverse sectional view.
This material steel pipe 1 ′ is a so-called gas pipe defined as a carbon steel pipe for piping (SGP) in JIS G 3453, and is used for piping of steam, water, gas, air, etc., whose working pressure is relatively low. Steel pipe.
Either a white tube (galvanized tube) or a black tube (non-plated tube) may be used.
The present invention is directed to a steel pipe for piping having a nominal diameter of 15A to 100A .
The outer diameter of the material steel pipe 1 ′ is represented by D ₀ , the inner diameter is represented by d ₀ , and the plate thickness is represented by t ₀ .

A method for manufacturing the steel pipe 1 with a screw in FIG. 1 will be described.
First, as shown in FIG. 3, for example, one end portion of the material steel pipe 1 ′ to be expanded and thickened is heated by the high frequency induction heating coil 4 disposed at one end portion of the material steel pipe 1 ′. The heating range is, for example, about twice the outer diameter D ₀ of the material steel pipe 1 ′. The heating temperature is preferably heated until the tube surface becomes orange (approximately 700 to 800 °). In the figure, 6 is a receiving roller.

Next, as shown in FIG. 4 to FIG. 6, one end of the raw steel pipe 1 ′ heated to 700 to 800 ° and to be expanded and thickened is compressed in the longitudinal direction of the pipe while the temperature is maintained. Then, this one end is enlarged and thickened.
In these drawings, reference numeral 7 denotes a die with a chuck function which has both a function as a mold (hole mold) for defining the outer diameter of the pipe when the diameter is expanded and a function of chucking the material steel pipe 1 ′. 7b, and when both 7a and 7b are combined, two-stage cylindrical inner surfaces 7c and 7d are formed. The large inner diameter portion is the hole mold portion 7c, and the small inner diameter portion is the chuck portion 7d. The inner diameter of the hole mold portion 7c is equal to the outer diameter D of the expanded / thickened portion 5 of the target threaded steel pipe 1 for piping.
Reference numeral 9 denotes a special punch that is pushed into the one end of the material steel pipe 1 'by the force of a hydraulic cylinder (not shown). This punch 9 has a conical tip portion 9b at the tip of the cylindrical portion 9a, and a collar portion 9c that pushes the end surface of the material steel pipe 1 'at the rear end of the cylindrical portion 9a.

When the punch 9 is pushed into the end portion of the material steel pipe 1 ′ with hydraulic pressure in a state where the material steel pipe 1 ′ is chucked by the die 7 with a chuck function as shown in FIG. 4, the end portion of the pipe becomes as shown in FIG. The diameter is expanded. At this stage, the diameter is increased while the plate thickness is decreased. A steel pipe at the stage where the processing has progressed from the raw steel pipe 1 ′ (the stage until the finished product in FIG. 1 is reached) is denoted by reference numeral 1 ″.
When the punch 9 is further pushed in, as shown in FIG. 6, the flange 9c of the punch 9 hits the end surface of the steel pipe "1 and pushes it to increase the plate thickness at one end. At this time, the outer diameter of the pipe also increases. Then, when the outer peripheral surface of the pipe hits the inner surface of the hole mold portion 7c, the diameter expansion / thickening process is completed.
FIG. 7 shows a steel pipe 1 ″ obtained by this diameter expansion / thickening process.
The diameter expansion / thickening process of this steel pipe is carried out with the outer diameter D, inner diameter d, and plate thickness t of the expanded diameter / thickened portion 5 being respectively
t ₀ <t <1.5 t ₀
D ₀ -1.5t ₀ <d <D ₀ -0.5t ₀
D ₀ + 0.8t ₀ <D <D ₀ + 3t ₀
It is appropriate to increase the diameter and increase the thickness so that it falls within the range.

Next, a male screw 3 is formed on the outer peripheral surface of the other end portion of the steel pipe 1 ″ having the enlarged diameter / thickened portion 5 at one end portion. It can be done with a threading machine.
In FIG. 8, the chesers 13 fixed to the plurality of cheser blocks 12 attached to the die head 11 of the die head threading machine 10 rotate together with the die head 11 and the chesser block 12, and the outer periphery of the other end portion of the steel pipe 1 ″ Perform threading.

Next, a female screw is formed on the inner surface of the enlarged diameter / thickened portion 5. This female thread machining can be performed using a general means such as a tap 15 as shown in FIG.
Thereby, the steel pipe 1 with a screw shown in FIG. 1 is obtained.
FIG. 10 shows a state where the threaded steel pipes 1 are connected. The male screw portion 3 at the other end is screwed into the female screw portion 2 at the one end (expanded diameter / thickened portion 5).

In the case of a conventional steel pipe for piping, male threads are formed at both ends, so a socket is attached to one end of one pipe steel pipe, and the male thread at the other end of the other steel pipe is screwed in and connected Therefore, since it is necessary to prepare a socket of another part, it is cumbersome and the work of attaching the socket is also complicated. Since the steel pipes 1 for piping can be directly connected without attaching a socket, the workability of pipe connection is improved.
In addition, it is not necessary to prepare a socket for a separate part, and the number of parts is reduced, so that handling related to pipe connection work is simplified and the cost is reduced.

DESCRIPTION OF SYMBOLS 1 Steel pipe for pipes 1 'material steel pipe 1 "Steel pipe 2 in the middle of processing 2 Female thread part 3 Male thread part 5 Diameter expansion and thickening part 7 Die with chuck function 9 Punch 10 Threading machine 13 Chester 15 Tap t ₀ Thickness D of material steel pipe ₀ Outer diameter of material steel pipe d ₀ Inner diameter t of material steel pipe Thickness D ₀ of the expanded and thickened part (for steel pipe for threaded piping) Outer diameter d ₀ of the expanded and thickened part (for steel pipe for threaded pipe) Internal diameter of meat part

Claims (2)

A method for producing a threaded pipe steel pipe for producing a threaded pipe steel pipe having a female thread at one end in the longitudinal direction of the pipe and a male thread at the other end,
One end of the material steel pipe, which is a carbon steel pipe for piping specified in JIS G 3452 with a nominal diameter of 15A to 100A, is heated by a high-frequency induction heating coil, and then the one end is expanded. Next, it has a diameter expansion / thickening step of compressing in the longitudinal direction of the tube to increase the thickness of this one end,
The diameter expansion / thickening process for expanding the diameter of the one end is as follows:
It consists of two divided pieces 7a and 7b, and when the two are combined, a two-stage structure comprising a large inner diameter portion whose inner diameter is larger than the inner diameter of the material steel pipe and a smaller inner diameter portion that serves as a chuck portion for chucking the material steel pipe A die 7 with a chucking function that has a cylindrical inner surface and serves as a die that regulates the outer diameter of the pipe when expanding the diameter and a function of chucking the material steel pipe, and a conical tip portion 9b at the tip of the cylindrical portion 9a. Using the punch 9 provided with a flange portion 9c that pushes the end surface of the material steel pipe 1 ′ at the rear end of the holding cylindrical portion 9a,
By inserting and pushing the punch 9 into the pipe while the raw steel pipe is chucked by the small inner diameter portion of the die having the chuck function, the inner diameter of the one end portion of the punch becomes larger than the inner diameter of the raw steel pipe. Then, the one end is compressed in the longitudinal direction of the pipe by the flange 9c of the punch 9, and the one end is larger than the outer diameter of the raw steel pipe and the plate thickness is thicker than the raw steel pipe thickness. Is to increase the meat
A male screw is formed on the outer surface of the other end portion of the steel pipe whose one end portion is enlarged and thickened by a chaser, and the male screw of the other end portion is screwed to the inner surface of the one end portion which is enlarged and thickened. A method of manufacturing a steel pipe for threaded piping, wherein a female screw of a size is formed by a cutting tap. The outer diameter D, the inner diameter d, and the plate thickness t of the enlarged diameter / thickened portion 5 are respectively set at one end of the material steel pipe.
t ₀ <t <1.5 t ₀
D ₀ -1.5t ₀ <d <D ₀ -0.5t ₀
D ₀ + 0.8t ₀ <D <D ₀ + 3t ₀
The method for manufacturing a steel pipe for threaded piping according to claim 1, wherein the diameter is increased and the thickness is increased so as to satisfy the following range.

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