JP2010142810A - Method of treating pipe end of metallic pipe material and plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of treating the end of a metallic pipe material by which a thread portion having a more proper inside diameter is formed while preventing the occurrence of flaws on the inside of the pipe end part when forming the thread portion in the end part of the metallic pipe material and a plug used therefor. <P>SOLUTION: Before forming the thread portion on the inside of the end part of the metallic pipe material 2, pipe expanding process is performed by using the plug 1 which has a tapered surface S and the diameter of the cross section of which becomes a smaller diameter toward the top from a position X (D) in the axial direction, where the diameter of the cross section is the maximum diameter D and in which a cone angle θ to the axial center M of a tapered surface S is θ≤3.5°between a position X (0.7D) where the diameter of the cross section becomes 0.7D on the tapered surface S and a position X (D) in the axial direction. In this pipe expanding process, the contact angle α (that is, it is equal to the cone angle θ) when the tapered surface S of the plug 1 is brought into contact with the pipe end part of the pipe material 2 made of the metal is ≤3.5°. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a tube end processing method for forming a threaded portion in a tube end portion of a metal tube material, and a plug used in the method.

A pipe end treatment is generally performed in which a thread portion for connection is provided at a pipe end portion of a metal pipe material.
In general, the dimensional tolerance for the threaded portion requires higher precision than the dimensional tolerance for the outer diameter of the metal tube material. If the dimensional tolerance of the threaded portion is preferentially matched, the dimensional tolerance of the metal tube material becomes smaller. It may be out of direction. For this reason, the outer diameter of the metal pipe member and the threaded portion have dimensional tolerances separately.
In other words, after forming the outer diameter of the metal tube so as to be within the dimensional tolerance for the metal tube, a threaded portion that is within the dimensional tolerance for the screw is formed at the tube end of the metal tube. Yes.
In such a metal tube forming method, in order to ensure the inner diameter of the threaded portion (to fit within the dimensional tolerance), conventionally, before forming the threaded portion of the tube end portion, the tube end portion is moved up and down using a die. Shrinkage processing (swedge processing) has been performed in which the inner diameter is shrunk by crimping from the left and right sides (see Patent Documents 1 and 2, for example).

However, in the above method, since the tube end is caulked from the outside, it is difficult to make the inside of the tube end a perfect circle, and there is a problem that the accuracy of the threaded portion is not good. In addition, there is a case where scratches are generated on the inner surface of the metallic pipe material by performing the contraction treatment.
On the other hand, pipe expansion processing for correcting the bending of the pipe end and the like is also known (see, for example, Patent Document 3), but scratches may occur inside the pipe end after the pipe expansion processing. It has been difficult to apply the conventional tube expansion treatment as it is as the tube end treatment before formation.
In particular, in order to increase the working accuracy of the threaded portion of the metal pipe material, there is a case where descaling is performed before the threaded portion is formed. In addition, there is a problem that the inner surface of the metal pipe material is easily scratched due to the absence of scale lubrication during the pipe expansion process.
JP-A-8-267168 JP-A-11-114640 International Publication No. 2006/033376 Pamphlet

  The present invention has been made in view of such prior art, and when forming a threaded portion at the tube end portion of a metal tube material, a threaded portion having a more appropriate inner diameter is formed while preventing the occurrence of scratches inside the tube end portion. It is an object of the present invention to provide a method for treating a pipe end of a metal pipe material and a plug used therefor.

In order to solve the above-mentioned problems, the inventors of the present invention perform a tube expansion process using a plug having a substantially circular cross section in the axial direction on the tube end portion of the metal tube material before forming the screw portion. Various investigations were made on the conditions of the plug used for the tube expansion process. As a result, in the plug having a tapered surface whose diameter decreases from the axial center position X (D) where the sectional diameter becomes the maximum diameter D toward the tip, the axial center which is the tapered surface and has a sectional diameter of 0.7D. By defining the taper angle θ of the tapered surface with respect to the axial center between the directional position X (0.7D) and the axial direction position X (D) as 3.5 ° or less, It has been found that the generation of scratches is prevented.
The present invention has been completed based on these new findings of the present inventors.

  That is, the pipe end processing method for a metal pipe according to the present invention is a pipe end processing method for forming a threaded portion inside a pipe end of a metal tube, and the axial center cross section is formed before the threaded portion is formed. A step of expanding the tube end using a substantially circular plug, and the plug has a tapered surface whose diameter decreases from the axial center position X (D) where the cross-sectional diameter is the maximum diameter D toward the tip; The axial center of the tapered surface between the axial position X (0.7D) and the axial position X (D), which is the tapered surface and has a sectional diameter of 0.7D The taper angle θ with respect to is θ ≦ 3.5 °.

  According to the pipe end processing method for a metal pipe having the above-described configuration, the pipe expansion process using the plug under the above conditions is performed before the threaded portion is formed inside the pipe end of the metal pipe. , The contact angle (ie, equal to the taper angle θ) when the taper surface of the plug contacts the pipe end of the metal pipe is 3.5 ° or less, and the plug slides in the pipe end. The contact angle between the tube end and the taper surface of the plug is also 3.5 ° or less. For this reason, it is possible to form a threaded portion that does not cause scratches on the inner side of the tube end, and that is within the dimensional tolerance for the threaded portion, in addition to the dimensional tolerance for the metallic tube material. Therefore, when forming the threaded portion at the tube end portion of the metal tube material, it is possible to form the threaded portion having a more appropriate inner diameter while preventing the occurrence of scratches inside the tube end portion.

  Preferably, the tube expansion process is performed after descaling the inner surface of the metal pipe.

In this case, after descaling the inner surface of the metal tube material, the tube end portion of the metal tube material is expanded using the plug, and then a thread portion is formed.
By removing the scale from the inner surface of the metallic tube material, the lubrication of the scale is eliminated. However, by performing the tube expansion process using the plug, it is possible to effectively prevent the occurrence of scratches inside the tube end portion. Therefore, when forming a screw part with respect to the metal pipe material which descaled the inner surface before screw part formation, the pipe end processing method of the metal pipe material of the present invention can be used suitably.

  Further, the plug according to the present invention is a plug for expanding the pipe end after descaling the inner surface of the metal pipe and before forming a threaded portion inside the pipe end of the metal pipe. And having a substantially circular shape in cross section in the axial direction, and a tapered surface having a small diameter from the axial position X (D) where the cross sectional diameter is the maximum diameter D toward the tip. The taper angle θ of the tapered surface with respect to the axial center between the axial position X (0.7D) where the sectional diameter becomes 0.7D and the axial position X (D) is θ ≦ 3. It is characterized by being 5 °.

  As described above, by using the plug having the above-described configuration, it is possible to effectively prevent the occurrence of a flaw on the inner side of the pipe end in the pipe expansion process.

Preferably, the taper angle θ is 3.0 ° ≦ θ ≦ 3.5 °.
In this case, the lower limit value of the taper angle θ in the range is defined as 3.0 °. By setting the taper angle θ to 3.0 ° or more, the axial length of the plug can be shortened as much as possible, so that an increase in the weight of the plug and an increase in the size of the equipment can be prevented.

  According to the pipe end processing method and the plug of the metal pipe according to the present invention, before the threaded portion is formed inside the pipe end of the metal pipe, the pipe expansion process using the plug of the above condition is performed. In the pipe expansion process, the contact angle (ie, equal to the taper angle θ) when the tapered surface of the plug contacts the pipe end of the metal pipe is 3.5 ° or less, and the plug slides inside the pipe end. The contact angle between the tube end and the taper surface of the plug while moving is also 3.5 ° or less. For this reason, it is possible to form a threaded portion that does not cause scratches on the inner side of the tube end, and that is within the dimensional tolerance for the threaded portion, in addition to the dimensional tolerance for the metallic tube material. Therefore, when forming the threaded portion at the tube end portion of the metal tube material, it is possible to form the threaded portion having a more appropriate inner diameter while preventing the occurrence of scratches inside the tube end portion.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view passing through the axis of a plug used in the pipe end processing method for a metal pipe according to the present invention. FIG. 2 is an enlarged view of region A in FIG.
First, the plug used in the pipe end processing method for a metal pipe in the present embodiment will be described.

As shown in FIGS. 1 and 2, the plug 1 according to the present embodiment has a substantially circular cross section perpendicular to the axis M, and the cross sectional diameter (diameter of the cross section perpendicular to the axis M) is the maximum diameter D. An axial center position X (0.7D) having a tapered surface S having a smaller diameter from the axial center position X (D) to the tip, the tapered surface S having a cross-sectional diameter of 0.7D. A taper angle θ of the taper surface S with respect to the axis M between the axial direction position X (D) is θ ≦ 3.5 °.
More specifically, the taper angle θ in the present embodiment is 3.0 ° ≦ θ ≦ 3.5 °.

In the present embodiment, the plug 1 includes a sliding portion 1a having the tapered surface S, and an axial position X where the cross-sectional diameter of the sliding portion 1a is 0.7D further on the distal end side of the sliding portion 1a. A tip portion 1b having a smaller diameter from (0.7D) to the tip, and an axial position X (D) where the cross-sectional shape of the sliding portion 1a is the maximum diameter D on the rear end side of the sliding portion 1a. And a rear end portion 1c having a smaller diameter toward the rear end. In the present embodiment, the tapered surface S is formed in a curved shape that protrudes outward in a sectional view passing through the axis M. Therefore, in the present embodiment, the taper angle θ decreases within the above range as it approaches X (D) along the direction of the axis M, and the taper angle θ decreases within the above range as it approaches X (0.7D). Grows within. Moreover, it connects so that the surface of the sliding part 1a and the front-end | tip part 1b may become a smooth curve.
A cylinder 3 is attached to the rear end 1c of the plug 1, and the plug 1 is configured to be movable in the direction of the axis M via the cylinder 3. The plug 1 is made of, for example, a cemented carbide (WC) It is formed by surface coating on the production) by sintering the powder.

  The plug 1 is used for pipe expansion processing of a metal tube 2 having an inner diameter d (diameter) of 0.7D ≦ d <D. That is, when the plug 1 is inserted into the pipe end of the metal pipe 2 by the cylinder 3 with the axis M of the plug 1 being substantially collinear with the axis of the metal pipe 2, the pipe end The part comes into contact with the tapered surface S of the sliding part 1a.

Then, the contact angle α (that is, equal to the taper angle θ) when the tapered surface S of the plug 1 contacts the tube end of the metal pipe 2 is within the above range, and the plug 1 is inside the tube end. The contact angle between the tube end and the tapered surface S while sliding is also within the above range. For this reason, it is possible to expand the tube end portion to have an inner diameter within a desired dimensional tolerance without causing scratches inside the tube end portion.
Moreover, in the plug 1 of the present embodiment, the lower limit value of the taper angle θ in the range is defined as 3.0 °. By setting the taper angle θ to 3.0 ° or more, the length in the axial direction of the plug 1 can be shortened as much as possible, thereby preventing an increase in the weight of the plug 1 and an increase in the size of the equipment. it can.

  In addition, the taper surface S in the present embodiment has a curved shape protruding outward in a cross-sectional view passing through the axis M as shown in FIGS. 1 and 2, but is not limited thereto, and passes through the axis M. The cross-sectional view may be linear.

Next, the pipe end processing method of the metal pipe 2 in the present embodiment will be described.
First, the metal pipe 2 is processed into a desired outer diameter (within dimensional tolerance). Here, the metal pipe material is not particularly limited. For example, martensitic stainless steel [(12-13) Cr- (2.5-6) Ni- (0.3-2.5) Mo] is used. .

Next, if necessary, the inner surface of the metal pipe 2 is descaled. When the metal pipe 2 is produced as an oil well steel pipe, the API (American Petroleum Institute) standard stipulates that martensitic stainless steel pipes remove the scale on the inner surface of the pipe. There must be.
Examples of descaling include shot blasting, pickling, polishing, and the like.

Subsequently, a tube expansion process is performed to expand the tube end portion of the metal tube 2 using the plug 1. First, the metal pipe 2 is fixed to an expanding device (not shown). And it adjusts so that the axial center of the metal pipe material 2 may become substantially the same as the axial center M of the plug 1.
After aligning the axis M, the plug 1 is pushed from the end of the metal tube 1 to a predetermined distance by the cylinder 3. At this time, the pipe end of the metal pipe 2 is expanded by the plug 1. After the plug 1 is pushed to a predetermined distance, it is pulled out in the direction opposite to the direction in which the plug 1 is pushed by the cylinder 3.

  After performing such pipe expansion processing, cutting is performed on the inner side of the pipe end portion of the processed metal pipe material 2 to form a thread portion (female screw portion).

As described above, before the threaded portion is formed inside the tube end portion of the metal pipe member 2, the tube expansion processing using the plug 1 of the above condition is performed, so that in the tube expansion processing step, the tube end portion is scratched. In addition to the dimensional tolerance with respect to the metal pipe member 2, it is possible to form a threaded portion that is within the dimensional tolerance with respect to the threaded portion. Therefore, when forming a thread part in the pipe end part of the metal pipe member 2, it is possible to form a thread part having a more appropriate inner diameter while preventing generation of a flaw inside the pipe end part.
In addition, in this embodiment, since the inner surface of the metal tube 2 is descaled, the scale is not lubricated in the pipe expansion process, but the use of the plug 1 makes the scale less lubricated. Further, it is possible to effectively prevent the occurrence of scratches inside the tube end. Therefore, when forming a screw part with respect to the metal pipe material 3 which descaled the inner surface before forming a screw part, the pipe end processing method of the metal pipe material 2 of this invention can be used suitably.

  In the pipe end processing method described above, the descaling and the pipe expansion process were performed after the outer diameter dimension processing of the metal pipe material 2, but after the outer diameter dimension processing, the bending of the metal tube material 2 in the axial direction is corrected. It is good also as performing a descaling and a pipe expansion process after performing the correction process aiming at the improvement of roundness. The correction process is performed using, for example, a straightener. Moreover, in order to adjust characteristics, such as the intensity | strength and toughness of the metal pipe material 2, you may implement heat processing before a correction process. Moreover, in order to remove the processing distortion and residual stress which generate | occur | produced in the metal pipe material 2 by the pipe expansion process, you may heat-process the expanded part. Moreover, in order to adjust the mechanical characteristics of the metal pipe member 2 such as strength and toughness, heat treatment may be performed after the pipe expansion process.

  The embodiment according to the present invention has been described above, but the present invention is not limited to the above embodiment, and various improvements, changes, and modifications can be made without departing from the spirit of the present invention.

Next, examples of the plug and tube end processing method according to the present invention will be described.
In this embodiment, a plug having a taper surface having an arc shape with a curvature radius R = 300 mm is used as a plug, and the pipe ends of metal pipes (steel pipes) having various outer diameters and wall thicknesses (inner diameters) are in contact with each other. The contact angle α and the quality of the inner surface at that time (visual observation) were verified. A plurality of plugs having different outer diameters depending on the inner diameter of the metal tube material was used.
Below, the quality result of the inner surface quality of the metal pipe in the present example is shown.

  As shown in the above table, when the contact angle α exceeds 3.5 °, the inside of the tube end is scratched, resulting in deterioration of the inner surface quality. On the other hand, when the contact angle α was 3.5 ° or less, it was confirmed that good inner surface quality was maintained without causing scratches inside the tube end.

It is a schematic axial sectional view showing a plug used in a pipe end processing method for a metal pipe according to the present invention. It is the area A enlarged view of FIG.

Explanation of symbols

1 Plug 2 Metal pipe material D Maximum diameter M Axial center S Tapered surface X Axial direction position θ Taper angle

Claims (4)

A pipe end processing method for forming a threaded portion inside a pipe end of a metal pipe,
Before the formation of the threaded portion, the step of expanding the tube end portion using a plug having a substantially circular cross section in the axial direction,
The plug has a tapered surface having a small diameter from the axial direction position X (D) where the cross-sectional diameter is the maximum diameter D toward the tip, and the axial center where the cross-sectional diameter is 0.7D. A taper angle θ of the tapered surface with respect to the axis between the direction position X (0.7D) and the axis direction X (D) is θ ≦ 3.5 °. Pipe end processing method for pipe materials.   2. The pipe end treatment method for a metal pipe according to claim 1, wherein the step of expanding the pipe is performed after descaling the inner surface of the metal pipe. A plug for expanding the pipe end after descaling the inner surface of the metal pipe and before forming a threaded portion inside the pipe end of the metal pipe,
The taper surface has a substantially circular shape in cross section in the axial direction, and has a tapered surface having a small diameter from the axial center position X (D) where the cross sectional diameter is the maximum diameter D toward the tip, and the cross sectional diameter is the tapered surface. A taper angle θ of the taper surface with respect to the shaft center is θ ≦ 3.5 ° between the shaft center direction position X (0.7D) of 0.7 D and the shaft center direction position X (D). Plug characterized by that.   The plug according to claim 3, wherein the taper angle θ is 3.0 ° ≦ θ ≦ 3.5 °.

Images