Form rolling method for joint portion of fluid supply pipe and fluid supply pipe

Abstract

Provided is a method of forming a locking ridge for a case of forming the locking ridge on an outer peripheral surface of a joint portion by form rolling, the method realizing a joint portion structure which is superior in pipe detachment prevention performance when pipes with locking ridges are connected by fixing pipe ends with a housing. Using a convex roller arranged inside the workpiece pipe body and a forming circular groove arranged outside the pipe body, the locking ridge is form-rolled such that an upright wall portion thereof is raised at an angle of at least 65 and no greater than 90 with respect to the outer peripheral surface in the pipe axis direction, and that a height of the locking ridge from the outer peripheral surface to the apex of the tip portion is at least a total of curvature radii of faces of the processing means in contact with the pipe body.

Claims

1. A form rolling method of a joint portion of a fluid supply pipe, the form rolling method forming a locking ridge having an upright wall portion on an outer peripheral surface of a workpiece pipe body, wherein: the locking ridge includes a curved basal portion extending from the outer peripheral surface, the upright wall portion extending from the basal portion, a curved portion extending from the upright wall portion, and a tip portion extending from the curved portion; and the form rolling method comprising: providing processing means comprising a convex roller arranged inside the pipe body and a forming circular groove arranged outside the pipe body, wherein a clearance between the convex roller and the forming circular groove is greater than plate thickness of the pipe body; processing the pipe body using the processing means to form a convex portion on the outer peripheral surface; moving the forming circular groove along a direction of longitudinal axis of the pipe to press the convex portion against the convex roller thereby forming the locking ridge, wherein the upright wall portion of the locking ridge is raised at an angle of at least 65 and no greater than 90 with respect to the outer peripheral surface in a direction along longitudinal axis of the pipe, and a height of the locking ridge from the outer peripheral surface to an apex of the tip portion is at least equal to a total of curvature radii of faces of the processing means arranged inside and outside in contact with the pipe body.

2. The form rolling method for a joint portion of a fluid supply pipe according to claim 1, wherein the convex roller has a curve of a curvature radius R.sub.I at a contact portion between an apical surface thereof and the upright wall surface.

3. The form rolling method for a joint portion of a fluid supply pipe according to claim 1, wherein the forming circular groove has a curve of a curvature radius R.sub.U at a contact portion between a tip surface thereof and an inner upright wall surface.

4. The form rolling method for a joint portion of a fluid supply pipe according to claim 1, wherein the locking ridge is formed while pressure is applied to the pipe body in the pipe axis direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagram illustrating a method of forming the locking ridge by using the convex roller and the forming circular groove, regarding the form rolling method of the present invention;

(2) FIG. 2 is a diagram illustrating a relationship between the convex roller and the forming circular groove in the case of using a processing means having a clearance between the convex roller and the forming circular groove that is smaller than a plate thickness of the workpiece pipe body, regarding the form rolling method of the present invention;

(3) FIG. 3 is a diagram illustrating a method of forming the locking ridge by using a processing means having a clearance between the convex roller and the forming circular groove that is greater than a plate thickness of the workpiece pipe body, regarding the form rolling method of the present invention;

(4) FIG. 4 is a diagram illustrating a method of forming an upright wall portion in the convex portion being formed, by using a processing means having a clearance between the convex roller and the forming circular groove that is greater than a plate thickness of the workpiece pipe body, regarding the form rolling method of the present invention;

(5) FIG. 5 is a diagram illustrating a method of forming the locking ridge by using a ring having the convex roller and the forming circular groove, regarding the form rolling method of the present invention;

(6) FIG. 6 is a diagram illustrating a locking ridge having an upright wall portion raised at a predetermined angle with respect to an outer peripheral surface of the pipe body, formed according to the form rolling method of the present invention;

(7) FIG. 7 is a diagram illustrating a detachment prevention effect of a joint portion employing the locking ridge formed according to the form rolling method of the present invention;

(8) FIG. 8 is a diagram illustrating a measured position in a hardness test in Example of the present invention;

(9) FIG. 9 is a diagram illustrating a housing-type pipe joint structure employing a common locking ridge;

(10) FIG. 10 is a diagram illustrating a method of forming a locking ridge by a common form rolling method;

(11) FIG. 11 is a diagram illustrating a structure in which a circular groove is formed on an outer peripheral surface of a pipe body;

(12) FIG. 12 is a diagram illustrating a structure in which a circular locking member is welded onto an outer peripheral surface of a pipe body; and

(13) FIG. 13 is a diagram illustrating a defective state of a joint portion employing a common locking ridge.

PREFERRED MODE FOR CARRYING OUT THE INVENTION

(14) The present inventors etc. have conducted extensive research on ways to improve detachment prevention performance of a joint portion in a case of using pipe bodies having locking ridges, which are formed by the form rolling method disclosed in Patent Document 1, on outer peripheral surfaces with a joint portion in which a housing fixes pipe ends as a fluid supply pipe.

(15) During which they have achieved the present invention.

(16) Details thereof will be described hereinafter, including study processes.

(17) A detachment prevention force at a joint portion, i.e. tensile strength F in the pipe axis direction (kN)nominal diameter3 is required as a part of earthquake resistant performance of a joint portion (Chika Maisetsu Kanro Taishin Tsugite no Gijutu Kijun (An) (Technical Standard for Earthquake Resistant Joint of Buried Pipelines (Draft)), Japan Institute of Country-ology and Engineering, 1977). For example, in the case of a steel pipe of nominal diameter 80 (90 mm in outer diameter and 3 mm in plate thickness), a tensile strength in the pipe axis direction of at least 240 kN is required.

(18) Given the above, the present invention supposed that it would be possible to improve the detachment prevention performance by changing a contact state between the housing and the locking ridge illustrated in FIG. 9 from line contact to surface contact.

(19) First, a form rolling method of a locking ridge having a vertical upright wall surface raised at an angle of 90 with respect to the outer peripheral surface of the pipe body, as illustrated in FIG. 6(a), was reviewed.

(20) When a tensile load in the pipe axis direction is applied to a joint portion for ends of the pipe bodies having locking ridges, of which cross-sectional shape has the upright wall surface, being covered by a housing for fixing, the contact relationship between the housing and the locking ridge is surface contact state, thereby lowering surface pressure, suppressing deformation of the locking ridge, and making the tensile load act only in the pipe axis direction, as illustrated in FIG. 7. As a result, it is expected that superior fastening performance is exerted on the pipe bodies, and the detachment prevention performance is thus improved.

(21) Based on such idea, a method for forming the locking ridge of which cross-sectional shape has the upright wall surface on the outer peripheral surface of the pipe body was reviewed.

(22) Formation of the locking ridge by the form rolling method is realized by rotating in a circumferential direction of a workpiece pipe body 2 while pressurizing in directions of approaching each other a convex roller 10 arranged inside the workpiece pipe body 2 and a forming circular groove 12 arranged outside the workpiece pipe body 2, as illustrated in FIG. 1.

(23) As illustrated in FIG. 2, with an inner width of the forming circular groove 12 being WU and a width of the convex roller 10 being WI, if a clearance therebetween ((WUWI)/2) is smaller than an initial plate thickness of the workpiece pipe body 2, the workpiece pipe body 2 is compressed between the rollers and deforms. As a result, the vertical upright wall portion 6 raised at an angle of 90 with respect to the outer peripheral surface 3 of the pipe body is formed at a site of the deformation. In order to form the upright wall portion 6, a convex height 9 must be at least equal to a total of RI at a contact portion between a tip surface 15 and the upright wall surface 16 of the convex roller 10 and RU at a contact portion between a tip surface 17 of the forming circular groove 12 of the concave roller 11 and an inner upright wall surface 18.

(24) After the compression processing, a high degree of work was applied to and work-hardening was caused at the site of the deformation, and therefore the locking ridge thus processed had great hardness and a characteristic of suppressing deformation under a tensile load. However, in the case of the convex height being too large, a proportion of decrease in plate thickness becomes too large and the plate thickness is reduced, and the deformation resistance against the tensile load tends to be reduced.

(25) Next, a case of manufacturing with the clearance at least equal to the plate thickness was reviewed. In this case, the upright wall portion which is inclined with respect to the pipe axis direction of the workpiece pipe body is formed. For making the upright wall portion into a vertical shape at an angle of 90, a method of forming the locking ridge while applying pressure in the pipe axis direction is effective. A vertical upright wall portion can be formed by, for example, first forming a convex portion (overhanging portion) 4 by form rolling as illustrated in FIG. 3, followed by shaping the convex portion 4 such that the angle 19 of the upright wall portion 6 increases by moving the forming circular groove 12 in the pipe axis direction and pressing the convex portion 4 against the convex roller 10 as illustrated in FIG. 4.

(26) Since processing of pressing against the convex roller applies a high degree of work to and work-hardening is caused at a shaped site, the locking ridge thus processed had great hardness and a superior characteristic of preventing detachment of the pipe under a tensile load.

(27) Such a characteristic is not limited to the locking ridge with the upright wall portion made to be vertical. Even in a case with the upright wall portion shaped with an angle smaller than 90, the locking ridge had great hardness and a superior characteristic of preventing detachment of the pipe under a tensile load. More specifically, the locking ridge having the upright wall portion shaped with an angle of at least 65 was preferable.

(28) Even the locking ridge having the upright wall portion extending at an angle smaller than 90, when a tensile load is applied to the joint portion provided with such a locking ridge, deforms at a site of contact with the housing and a surface contact state with an inner wall of the housing is obtained, thereby lowering surface pressure and providing superior detachment prevention performance.

(29) The convex height 9 of the convex portion must be at least equal to a total of RI and RU. However, in the case of the convex height being too large, a proportion of decrease in plate thickness becomes too large and the plate thickness is reduced, and the deformation resistance against the tensile load tends to be reduced.

(30) As a material for the pipe body, a steel pipe is preferably used. Supposing use as a water supplying pipe, a steel pipe of high durability is preferred. As the steel pipe of high durability, a plated steel pipe that is superior in corrosion resistance is preferable. As the plated steel pipe, a steel pipe with ZnAlMg alloy plating that is superior in corrosion resistance is preferable. If further improvement in corrosion resistance is sought, it is preferable to use a steel pipe made of stainless steel such as SUS304.

(31) By using such a steel pipe having a plate thickness of approx. 3 mm, a joint portion satisfying the abovementioned earthquake resistant performance of the joint portion can be obtained.

(32) The present invention can also be applied to a fluid supply pipe used for supply of fluid such as liquid, gas, etc. The present invention can be applied to any joint portion of pipes of which ends are fixedly connected by a housing, and is preferably applied to a joint portion of a water supply pipe.

(33) The present invention is described more in detail hereafter by means of Examples; however, the present invention is not limited thereto.

EXAMPLES

Manufacturing Example 1

(34) Using a SUS304 steel pipe of nominal diameter 80 (90 mm in outer diameter and 3 mm in plate thickness) as a pipe body material, a locking ridge was formed on an outer peripheral surface.

(35) In a case of processing under a condition that a clearance between the inner convex roller and the outer concave roller is smaller than a plate thickness (3 mm) of the pipe body, a form rolling roller having a dimension of 80 mm in outer diameter, 5.0 mm in WI, and 2.5 mm in RI was used as the convex roller 10 illustrated in FIG. 2 and a form rolling roller having a dimension of 117 mm in outer diameter, 17 mm in groove depth, 9.0 mm in WU, and 2.5 mm in RU was used as the concave roller 11. The clearance therebetween was 2.0 mm and smaller than the plate thickness. Under such a condition, a locking ridge of which convex height 9 was approx. 3.5 to 12.0 mm was formed.

(36) In a case of processing under a condition that a clearance between the inner convex roller and the forming circular groove of the outer concave roller is greater than a plate thickness of the pipe body, a form rolling roller having a dimension of 80 mm in outer diameter, 5.0 mm in WI, and 2.5 mm in RI was used as the convex roller 10 illustrated in FIG. 3 and a form rolling roller having a dimension of 117 mm in outer diameter, 17 mm in groove depth, 13.0 mm in WU, and 2.5 mm in RU was used as the concave roller 11. The form rolling was further performed while applying pressure in a pipe axis direction of the pipe body. The clearance therebetween was 4.0 mm and greater than the plate thickness.

(37) Under such a condition, locking ridges of which convex height was: approx. 4.0 mm, which is smaller than a total of RI at a tip of the convex roller and RU at a contact portion between a tip of the forming circular groove of the concave roller and an inner upright wall surface; approx. 6.0 mm; approx. 12.0 mm; and approx. 15.0 mm, which are greater than the total of RI and RU, were formed.

Manufacturing Example 2

(38) Using a SUS304 steel pipe of nominal diameter 150 (165 mm in outer diameter and 3.5 mm in plate thickness) as a pipe body material, a locking ridge was formed on an outer peripheral surface.

(39) In a case of processing under a condition that a clearance between the inner convex roller and the outer concave roller is smaller than a plate thickness (3.5 mm) of the pipe body, a form rolling roller having a dimension of 110 mm in outer diameter, 6.0 mm in WI, and 3.0 mm in RI was used as the convex roller and a form rolling roller having a dimension of 117 mm in outer diameter, 17 mm in groove depth, 10.0 mm in WU, and 2.5 mm in RU was used as the concave roller. The clearance therebetween was 2.0 mm. Under such a condition, a locking ridge of which convex height was approx. 4.0 to 18.0 mm was formed.

(40) In a case of processing under a condition that a clearance between the inner convex roller and the outer concave roller is greater than the plate thickness of the pipe body, a form rolling roller having a dimension of 110 mm in outer diameter, 6.0 mm in WI, and 3.0 mm in RI was used as the convex roller and a form rolling roller having a dimension of 117 mm in outer diameter, 17 mm in groove depth, 18.0 mm in WU, and 2.5 mm in RU was used as the concave roller. The form rolling was further performed while applying pressure in a pipe axis direction of the pipe body. The clearance therebetween was 6.0 mm and greater than the plate thickness.

(41) Under such a condition, locking ridges of which convex height was: approx. 4.0 mm, which is smaller than a total of RI of the convex roller and RU of the forming circular groove of the concave roller (5.5 mm); and approx. 8.0 mm, which is greater than the total.

Manufacturing Example 3

(42) Using a SUS304 steel pipe of nominal diameter 250 (267 mm in outer diameter and 4.0 mm in plate thickness) as a pipe body material, a locking ridge was formed on an outer peripheral surface.

(43) In a case of processing under a condition that a clearance between the inner convex roller and the outer concave roller is smaller than a plate thickness (4.0 mm) of the pipe body, a form rolling roller having a dimension of 110 mm in outer diameter, 6.0 mm in WI, and 3.0 mm in RI was used as the convex roller and a form rolling roller having a dimension of 117 mm in outer diameter, 17 mm in groove depth, 10.0 mm in WU, and 2.5 mm in RU was used as the concave roller. The clearance therebetween was 2.0 mm. Under such a condition, a locking ridge of which convex height was approx. 4.0 to 20.0 mm was formed.

(44) In a case of processing under a condition that a clearance between the inner convex roller and the outer concave roller is greater than the plate thickness of the pipe body, a form rolling roller having a dimension of 110 mm in outer diameter, 6.0 mm in WI, and 3.0 mm in RI was used as the convex roller and a form rolling roller having a dimension of 117 mm in outer diameter, 17 mm in groove depth, 20.0 mm in WU, and 2.5 mm in RU was used as the concave roller. The form rolling was further performed while applying pressure in a pipe axis direction of the pipe body. The clearance therebetween was 7.0 mm and greater than the plate thickness.

(45) Under such a condition, a locking ridge of which convex height was approx. 9.0 mm, which is greater than the total of RI of the convex roller and RU of the forming circular groove of the concave roller (5.5 mm) were formed.

(46) <Evaluation 1> Cross-Sectional Observation

(47) The form-rolled portion of the stainless steel pipe thus formed was cut along a longitudinal direction of the workpiece pipe body and a cross-section thereof was observed. A minimum plate thickness of the basal portion and a length of the upright wall portion of the locking ridge were measured. The cross-section thus cut was embedded in resin, a surface was polished, and measured with a length measuring microscope. In addition, an angle at which the upright wall portion of the locking ridge was raised from the outer peripheral surface of the pipe body was measured. A cross-sectional shape was measured with a laser displacement meter, and an angle of an intersection between a baseline extending from the outer peripheral surface and a straight line extending from an outer surface of the convex portion was calculated.

(48) In a case of form rolling under a condition that a clearance between the convex roller and the forming circular groove is smaller than a plate thickness, the locking ridges obtained in Manufacturing Examples 1 to 3 had cross-sectional shape including a curved basal portion extending from the outer peripheral surface of the pipe body, an upright wall portion extending vertically at an angle of 90 with respect to the outer peripheral surface in the pipe axis direction, a curved portion formed continuously therefrom, and a tip portion as illustrated in FIG. 6(a). For example in Test Example 4 having a convex height of approx. 7.0 mm obtained in Manufacturing Example 1, the plate thickness of each portion of the locking ridge has been reduced to approx. 1.8 mm at the basal portion. The reduction rate of plate thickness at the basal portion was approx. 40%.

(49) As described above, by using form rolling rollers with a clearance that is smaller than the plate thickness of the pipe body, a locking ridge having the vertically extending upright wall portion was obtained in such a way that the locking ridge was protruding in an outer diameter direction while the plate thickness at a side wall portion was being reduced by compression processing.

(50) In a case of form rolling under a condition that a clearance between the convex roller and the forming circular groove is greater than the plate thickness of the pipe body, cross-sectional shapes of the locking ridges obtained in Manufacturing Examples 1 to 3 includes the upright wall portion vertically extending at an angle of 90 with respect to the pipe axis direction as illustrated in FIG. 6(a), depending on the convex height. Alternatively, the locking ridge includes an inclined upright wall portion extending at an angle of at least 65 as illustrated in FIG. 6(b).

(51) <Evaluation 2> Tensile Test in Pipe Axis Direction

(52) Using test samples obtained in Manufacturing Examples 1 to 3, a tensile test in the pipe axis direction was conducted to measure the detachment prevention performance of the joint portion. The form-rolled locking ridge was fixed by a housing and measurement was performed with a universal tester under a maximum load. The measurement results are shown in Table 1 (Manufacturing Example 1), Table 2 (Manufacturing Example 2), and Table 3 (Manufacturing Example 3).

(53) As discussed above, the joint portion is required to have tensile strength F (kN)nominal diameter3 in the pipe axis direction. For example, for the joint portion of the pipe body of nominal diameter 80, a standard load of earthquake resistant performance is at least 240 kN, and maximum load must be at least the standard load. The maximum load obtained in the measurement being at least the standard load was considered as pass () and the maximum load being smaller than the standard load was considered as fail (x).

(54) <Evaluation 2-1> (in the Case of Clearance Between the Inner Convex Roller and the Outer Concave Roller being Smaller than a Plate Thickness of a Workpiece Pipe Body)

(55) Test samples processed under a condition of clearance between the convex roller and the forming circular groove of the concave roller being approx. 2.0 mm were used in: Test Examples 1 to 6 for Manufacturing Example 1; Test Examples 15 to 19 for Manufacturing Example 2; and Test Examples 23 to 27 Manufacturing Example 3.

(56) For Manufacturing Example 1, Test Examples 2 to 5 exhibited maximum loads of at least the standard load as shown in Table 1. For example, Test Example 3 with a convex height of 6.0 mm exhibited a maximum load of 275 kN. Meanwhile, Test Example 1 with a convex height of 3.5 mm, which was smaller than the total of RI and Ru (5.0 mm), exhibited the smallest maximum load. Test Example 6 with an extremely large convex height had a drastically reduced plate thickness (50%) at the basal portion, and exhibited decreased maximum load.

(57) For Manufacturing Example 2, Test Examples 16 to 18 exhibited maximum loads of at least the standard load as shown in Table 2. Meanwhile, for example Test Example 15 with a convex height of approx. 4.0 mm, which was smaller than the total of RI and Ru (5.5 mm), exhibited the smallest maximum load. Test Example 19 with an extremely large convex height had a drastically reduced plate thickness (54%) at the basal portion, and exhibited decreased maximum load.

(58) For Manufacturing Example 3, Test Examples 24 to 26 exhibited maximum loads of at least the standard load as shown in Table 3. Meanwhile, for example Test Example 23 with a convex height of 4.0 mm, which is smaller than the total of RI and Ru (5.5 mm), exhibited the smallest maximum load. Test Example 27 with an extremely large convex height had a drastically reduced plate thickness (55%) at the basal portion, and exhibited decreased maximum load.

(59) <Evaluation 2-2> (in the Case of Clearance Between the Inner Convex Roller and the Outer Concave Roller being Greater than a Plate Thickness of a Workpiece Pipe Body)

(60) As shown in Table 1, test samples processed under a condition of the clearance being approx. 4.0 mm in Manufacturing Example 1 were used in Test Examples 7 to 14. Among these, Test Example 7 with a convex height smaller than the total of RI and Ru (5.0 mm) exhibited a maximum load of 230 kN, which was smaller than the standard load. Among Test Examples with a convex height being at least equal to the total, Test Examples 9, 10, 12 and 13 of which upright wall portions were at 70 and 90 with respect to the pipe axis direction exhibited maximum loads of at least the standard load. For example, Test Example 13 (convex height of approx. 12.0 mm and angle of 90) exhibited 255 kN. Meanwhile, Test Examples 8 and 11 having an angle of 60 exhibited maximum loads smaller than the standard load. Test Example 14 with an extremely large convex height had a drastically reduced plate thickness (50%) at the basal portion, and exhibited decreased maximum load.

(61) As shown in Table 2, test samples processed under a condition of the clearance being approx. 6.0 mm in Manufacturing Example 2 were used in Test Examples 20 to 22. The convex heights were 8.0 mm, which was greater than the total of RI and Ru (5.5 mm), and Test Examples 21 and 22 of which upright wall portions were at 70 and 90 with respect to the pipe axis direction exhibited maximum loads of at least the standard load. Meanwhile, Test Example 20 having an angle of 60 exhibited maximum loads smaller than the standard load.

(62) As shown in Table 3, test samples processed under a condition of the clearance being approx. 7.0 mm in Manufacturing Example 3 were used in Test Examples 28 to 30. The convex heights were 9.0 mm, which was greater than the total of RI and Ru (5.5 mm), and Test Examples 29 and 30 of which upright wall portions were at 70 and 90 with respect to the pipe axis direction exhibited maximum loads of at least the standard load. Meanwhile, Test Example 28 having an angle of 60 exhibited maximum loads smaller than the standard load.

(63) <Evaluation 3> (Hardness Test)

(64) Using a test piece with a locking ridge, hardness at the basal portion, the upright wall portion, and the tip portion was measured. The test piece being cut was embedded in resin, a cross-section was polished, and hardness was measured by a micro Vickers hardness test. Hardness of the pipe body material was 152 HV. The measurement results are shown in Tables 1 to 3. As illustrated in FIG. 8, Positions A and E show results of measurement in the basal portion; Positions B and D show results of measurement in the upright wall portion; and Position C shows results of measurement in the tip portion.

(65) In Manufacturing Examples 1 to 3, Test Examples having the maximum load of at least the standard load exhibited high hardness of at least 300 HV, as shown in Tables 1 to 3. The hardness was more than approx. twice as high as the hardness of the pipe body material. Meanwhile, Test Examples having a maximum load smaller than the standard load exhibited low hardness of no greater than approx. 230 HV. Test Examples obtained by the method of the present invention had increased hardness, as a result of the compression processing during formation of the convex portion applying a high degree of work and realizing work-hardening. Consequently, deformation of the locking ridge due to the tensile load was suppressed, thereby increasing the maximum load of the test piece.

(66) Given the above results, it has been proven that the joint portion manufactured by the form rolling method of the present invention has high maximum load, suppresses deformation of the locking ridge, and has superior pipe detachment prevention performance. It has been confirmed that the most of the tensile load acts in the pipe axis direction and superior engaging performance between pipe bodies can be exerted. Especially the locking ridge having the upright wall portion vertically extending at 90 with respect to the pipe axis direction and in surface contact with the housing had low surface pressure and could suppress deformation of the locking ridge.

(67) TABLE-US-00001 TABLE 1 Test Results for Test Samples Obtained in Manufacturing Example 1 (Pipe Body of Nominal Diameter 80) Upright Wall Nominal Convex Portion Max. Diameter Clearance Height Angle Hardness (HV) (Material: 152 HV) Load (mm) (mm) (mm) () Position A Position B Position C Position D Position E (kN) 80 2.0 3.5 225 (90 5.0 90 255 t3.0) 6.0 328 385 352 394 335 275 7.0 260 10.0 245 12.0 230 4.0 4.0 90 230 6.0 60 210 208 224 205 226 225 70 240 90 386 354 312 364 397 285 12.0 60 235 70 245 90 384 362 310 355 391 255 15.0 90 225 Basal Basal Portion Portion Plate Vertical Determination Min. Thickness Upright Nominal Convex (Standard Test Plate Reduction Wall Diameter Clearance Height Load) Example Thickness Rate Length (mm) (mm) (mm) 240 kN No. (mm) (%) (mm) 80 2.0 3.5 x 1 2.8 7 0 (90 5.0 2 2.3 23 1.5 t3.0) 6.0 3 2.1 30 2.5 7.0 4 1.8 40 3.5 10.0 5 1.6 47 6.5 12.0 x 6 1.5 50 8.5 4.0 4.0 x 7 2.7 10 0.5 6.0 x 8 2.3 23 9 2.2 27 10 2.2 27 2.5 12.0 x 11 1.8 40 12 1.6 47 13 1.6 47 8.5 15.0 x 14 1.5 50 11.5

(68) TABLE-US-00002 TABLE 2 Test Results for Test Samples Obtained in Manufacturing Example 2 (Pipe Body of Nominal Diameter 150) Nominal Convex Max. Diameter Clearance Height Angle Hardness (HV) (Material: 152 HV) Load (mm) (mm) (mm) () Position A Position B Position C Position D Position E (kN) 150 2.0 4.0 90 430 (165 6.0 490 t3.5) 8.0 328 412 366 401 331 540 10.0 520 18.0 445 6.0 8.0 60 209 199 212 200 211 430 70 520 90 388 365 314 372 391 555 Basal Basal Portion Portion Plate Vertical Determination Min. Thickness Upright Nominal Convex (Standard Test Plate Reduction Wall Diameter Clearance Height Load) Example Thickness Rate Length (mm) (mm) (mm) 450 kN No. (mm) (%) (mm) 150 2.0 4.0 x 15 3.2 9 0.4 (165 6.0 16 2.7 23 2.4 t3.5) 8.0 17 2.3 34 4.4 10.0 18 2.1 40 6.4 18.0 x 19 1.6 54 14.4 6.0 8.0 x 20 2.7 23 21 2.6 26 22 2.5 29 4.4

(69) TABLE-US-00003 TABLE 3 Test Results for Test Samples Obtained in Manufacturing Example 3 (Pipe Body of Nominal Diameter 250) Nominal Convex Max. Diameter Clearance Height Angle Hardness (HV) (Material: 152 HV) Load (mm) (mm) (mm) () Position A Position B Position C Position D Position E (kN) 250 2.0 4.0 90 710 (267 6.0 760 t4.0) 9.0 335 399 361 411 341 910 15.0 770 20.0 700 7.0 9.0 60 215 201 220 198 230 720 70 900 90 390 371 318 369 401 935 Basal Basal Portion Portion Plate Vertical Determination Min. Thickness Upright Nominal Convex (Standard Test Plate Reduction Wall Diameter Clearance Height Load) Example Thickness Rate Length (mm) (mm) (mm) 750 kN No. (mm) (%) (mm) 250 2.0 4.0 x 23 3.6 10 0.7 (267 6.0 24 3.2 20 2.7 t4.0) 9.0 25 2.6 35 5.7 15.0 26 2.4 40 11.7 20.0 x 27 1.8 55 16.7 7.0 9.0 x 28 2.9 28 29 2.8 30 30 2.7 33 5.7

EXPLANATION OF REFERENCE NUMERALS

(70) 1 Joint portion

(71) 2 Workpiece pipe body

(72) 3 Outer peripheral surface

(73) 4 Locking ridge

(74) 4 Convex portion

(75) 5 Basal portion

(76) 6 Upright wall portion

(77) 7 Curved portion

(78) 8 Tip portion

(79) 9 Convex height

(80) 10 Convex roller

(81) 11 Concave roller

(82) 12 Forming circular groove

(83) 13 Ring

(84) 14 Housing

(85) 15 Tip surface (Convex roller)

(86) 16 Upright wall surface (Convex roller)

(87) 17 Tip surface (Forming circular groove)

(88) 18 Inner upright wall surface (Forming circular groove)

(89) 19a Angle

(90) 19b Baseline

(91) 19c Straight line

(92) 20 Pipe joint

(93) 21 Locking ridge

(94) 22 Pipe body

(95) 23 Housing

(96) 24 Inner peripheral opening edge

(97) 25 Inner form rolling roller

(98) 26 Forming ridge

(99) 27 Outer form rolling roller

(100) 28 Forming circular groove

(101) 29 Circular groove

(102) 30 Locking member

(103) 31 Welded portion