JPS6137015B2 - - Google Patents
Info
- Publication number
- JPS6137015B2 JPS6137015B2 JP12409981A JP12409981A JPS6137015B2 JP S6137015 B2 JPS6137015 B2 JP S6137015B2 JP 12409981 A JP12409981 A JP 12409981A JP 12409981 A JP12409981 A JP 12409981A JP S6137015 B2 JPS6137015 B2 JP S6137015B2
- Authority
- JP
- Japan
- Prior art keywords
- tube
- diameter
- expansion
- tubes
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000007788 liquid Substances 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 238000006073 displacement reaction Methods 0.000 claims description 5
- 238000001816 cooling Methods 0.000 claims description 2
- 238000005260 corrosion Methods 0.000 description 8
- 230000007797 corrosion Effects 0.000 description 8
- 238000005336 cracking Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- 239000008399 tap water Substances 0.000 description 5
- 235000020679 tap water Nutrition 0.000 description 5
- 230000007423 decrease Effects 0.000 description 4
- 229910000975 Carbon steel Inorganic materials 0.000 description 3
- 239000010962 carbon steel Substances 0.000 description 3
- 239000010935 stainless steel Substances 0.000 description 3
- 229910001220 stainless steel Inorganic materials 0.000 description 3
- 239000012530 fluid Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 238000013459 approach Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D39/00—Application of procedures in order to connect objects or parts, e.g. coating with sheet metal otherwise than by plating; Tube expanders
- B21D39/08—Tube expanders
- B21D39/20—Tube expanders with mandrels, e.g. expandable
- B21D39/203—Tube expanders with mandrels, e.g. expandable expandable by fluid or elastic material
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Pressure Welding/Diffusion-Bonding (AREA)
- Heat Treatment Of Articles (AREA)
- Non-Disconnectible Joints And Screw-Threaded Joints (AREA)
Description
【発明の詳細な説明】
開示技術は油井管等の耐蝕二重管の軸方向圧縮
残留応力を形成させて製造する技術分野に属す
る。DETAILED DESCRIPTION OF THE INVENTION The disclosed technology belongs to the technical field of producing corrosion-resistant double pipes such as oil country tubular goods by forming axial compressive residual stress.
而して、この発明は予め外管を加熱増径してお
き、これに対して相対冷却状態の耐蝕内管を相対
重層嵌合させ、その状態で該内管内に拡管液圧を
印加して内管を拡管降伏させ塑性変形して外管に
一体化させ、更に、両管の体増径を図り、設定増
径状態に至つた後該拡管液を除去して両管縮径さ
せ、大きな締め代を得て自緊二重管を得る様にし
た製造方法に関するものであり、特に、両管を上
記設定増径状態に達せしめた時点で、両管の温度
差が小さくなるまで当該拡管状態を維持して摩擦
限界面圧以上の充分な軸方向嵌合力を生ぜしめた
後に拡管液を除去し両管縮管し、径方向内管昇温
増径、外管冷却縮径して大きな嵌合力を得、軸方
向外管縮少により内管に圧縮残留応力を付与する
様にした自緊二重管の製造方法に係るものであ
る。 Therefore, in this invention, the diameter of the outer tube is increased by heating in advance, and a corrosion-resistant inner tube in a relatively cooled state is fitted in a relatively overlapping manner to the outer tube, and in this state, a tube expansion liquid pressure is applied to the inside of the inner tube. The inner tube is expanded and yielded, plastically deformed and integrated with the outer tube, and the diameter of both tubes is increased. After reaching the set diameter increase state, the expansion liquid is removed and both tubes are reduced in diameter to create a larger diameter. This relates to a manufacturing method that obtains a self-sealing double pipe by obtaining a tightness margin, and in particular, when both pipes reach the set diameter increase state, the pipe is expanded until the temperature difference between the two pipes becomes small. After maintaining the condition and generating sufficient axial fitting force that exceeds the friction limit surface pressure, the tube expansion liquid is removed and both tubes are contracted.The inner tube is heated to increase its diameter, and the outer tube is cooled and contracted to create a larger diameter. The present invention relates to a method of manufacturing a self-tightening double pipe in which a fitting force is obtained and a compressive residual stress is applied to the inner pipe by shrinking the outer pipe in the axial direction.
周知の如く、油井管、原子力プラント配管等に
於ては耐圧、耐熱機能とを耐蝕機能とを具備せさ
せるべく、外管を、例えば、炭素鋼管、内管をス
テンレス鋼管にした二重管が採用される様になつ
て来ている。 As is well known, in oil country tubular goods, nuclear power plant piping, etc., in order to provide pressure resistance, heat resistance, and corrosion resistance, double-layered pipes with an outer tube made of carbon steel and an inner tube made of stainless steel, for example, are used. It is starting to be adopted.
而して、該種二重管の稼動中に於ける境界面ズ
レ、エロージヨンを防止するべく内外管の結合力
を強く付与することが必要であるが、嵌合度の均
一さ、製造のし易さ等のさまざまなメリツトから
出願人の先願の多くの発明に示される様に所謂熱
拡管法が開発され採用される様になつて来てい
る。 Therefore, it is necessary to provide strong bonding force between the inner and outer tubes in order to prevent boundary surface displacement and erosion during operation of the seed double tube, but it is necessary to provide a strong bonding force between the inner and outer tubes, and to ensure uniformity of fit and ease of manufacturing. Due to its various merits, the so-called thermal tube expansion method has been developed and has come to be adopted, as shown in many of the inventions of the applicant's earlier applications.
即ち、第1,2図に略示する様に炭素鋼外管1
をイからロまで予め加熱増径させておき、これに
水道水の温度までに水浸してハからニまで冷却縮
径させたステンレス内管2を相対重層嵌合させ、
該内管2の両端に所定シールプラグ3,3′を装
着し、一方のシールプラグ3から水道水4を拡管
液として送給して加圧させ、第2図、歪ε、応力
F曲線に沿つて内管2を拡管していき、内管2は
降伏して外管1の内面に当接し、更に塑性変形し
て増径し、内外管2,1がそれぞれ設定径ホ、ヘ
に達した後該拡管水を除去し、両管1,2を縮径
ト、チさせ、大気温に戻して外管1は冷却縮径リ
させ、内管2は昇温ヌして両管1,2に大きな締
め代ΔDを形成させ嵌合力を強く付与して自緊二
重管を得る様にしていた。 That is, as schematically shown in FIGS. 1 and 2, a carbon steel outer tube 1
The stainless steel inner tube 2, which has been previously heated to increase its diameter from A to B, is immersed in water up to the temperature of tap water and cooled and reduced in diameter from C to D, is fitted in a relative layer.
Predetermined seal plugs 3, 3' are attached to both ends of the inner pipe 2, and tap water 4 is fed as a pipe expansion liquid from one seal plug 3 to pressurize it, and the strain ε and stress F curves shown in FIG. The inner tube 2 is expanded along the line, and the inner tube 2 yields and comes into contact with the inner surface of the outer tube 1, and further plastically deforms and increases in diameter, and the inner and outer tubes 2 and 1 reach the set diameters E and F, respectively. After that, the expanded pipe water is removed, both pipes 1 and 2 are reduced in diameter, and the temperature is returned to the ambient temperature. A large interference margin ΔD was formed in 2 and a strong fitting force was applied to obtain a self-tightening double pipe.
さりながら、該種製造方法では上記設定径まで
両管1,2を増径した後直ちに拡管液圧を除去す
るため、外管1は横軸に外管温T、縦軸に内外管
1,2の面圧fをとるとC1で示す直線の様に拡
管液圧除去開始時まだ内管2に対し高温であるた
め、温度降下を続けて大気温に近づいていき、一
方、内管2は温度上昇していく。 However, in this type of manufacturing method, the expansion hydraulic pressure is immediately removed after increasing the diameter of both tubes 1 and 2 to the above-mentioned set diameter, so the outer tube 1 has an outer tube temperature T on the horizontal axis and an inner and outer tube 1 on the vertical axis. If we take the surface pressure f of 2, as shown by the straight line C 1 , since the inner pipe 2 is still at a high temperature when the pipe expansion starts to remove the hydraulic pressure, the temperature continues to drop and approaches the atmospheric temperature, while the inner pipe 2 temperature increases.
従つて、軸方向からみると、第4図に示す様に
外管1は短縮され、内管2は伸張していくことに
なり、第3図の摩擦限界面圧f0に達する温度に外
管1の温度が下降すると初めて軸方向ズレが内外
管間の摩擦によつて阻止されることになるが、こ
の時の軸方向の内管圧縮残留応力は十分に形成さ
れない恐れがある。 Therefore, when viewed from the axial direction, the outer tube 1 is shortened and the inner tube 2 is expanded, as shown in FIG . Only when the temperature of the tube 1 decreases will the axial displacement be prevented by the friction between the inner and outer tubes, but at this time there is a risk that sufficient compressive residual stress in the inner tube in the axial direction will not be formed.
そのため、潜在的に軸方向に於て応力腐蝕割れ
の危険性がある欠点があり、特に、油井管等に於
ては稼動中に自重により大きな軸方向引張応力が
印加され、加えて厳しい腐蝕環境下におかれるた
め、応力腐蝕割れ限界応力下での使用応力に制限
が与えられざるを得ない難点があつた。 Therefore, there is a potential risk of stress corrosion cracking in the axial direction, and in particular, in oil country tubular goods, large axial tensile stress is applied due to their own weight during operation, and in addition, they are exposed to harsh corrosive environments. However, there was a problem in that the stress that could be used under the critical stress for stress corrosion cracking had to be limited.
これに対処するに拡管中、及び、その後も内管
2に軸方向圧縮力を印加することも可能である
が、装置的に極めて複雑になり、管理、制御が煩
瑣でコスト高になる不利点があつた。 To deal with this, it is possible to apply an axial compressive force to the inner tube 2 during and after the tube expansion, but the disadvantage is that the equipment is extremely complicated, and management and control are complicated and costly. It was hot.
この発明の目的は上述従来技術に基づく熱拡管
法に基づく自緊二重管の軸方向圧縮残留応力に係
る問題点に鑑み、液圧拡管プロセスに於て設定拡
管状態を停止、維持することによりズレの生じな
い充分な軸方向嵌合力を得さしめて後液圧除去し
内管に軸方向圧縮残留応力を大きく付与すること
が出来る優れた自緊二重管製造方法を提供せんと
するものである。 The purpose of this invention is to solve the problem of axial compressive residual stress in self-stressing double pipes based on the thermal expansion method based on the prior art, and to stop and maintain the set expansion state in the hydraulic expansion process. It is an object of the present invention to provide an excellent self-tensioning double pipe manufacturing method that can obtain sufficient axial fitting force without causing any misalignment, remove hydraulic pressure afterward, and apply a large axial compressive residual stress to the inner pipe. be.
上述目的に沿うこの発明の構成は予め加熱増径
した外管に冷却縮管した内管を相対重層嵌合し、
低温液により内管を拡管し塑性変形増径して外管
に当接させ、更に、内外管共に増径して設定径に
達すると増径を停止してその状態を保ち、内外管
の温度差を小さくして外管を縮径して径方向は勿
論、軸方向面圧も充分に上げて摩擦力を上げ、軸
方向ズレが生じない様にしてから拡管液を除去し
て両管を縮径し、そのため、上記軸方向摩擦力に
より内管昇温伸張が阻止され、外管短縮により内
管が随伴短縮し、該内管に高い軸方向圧縮残留応
力が付与され、内管昇温増径、外管冷却による縮
径を介し高い締め代が得られ、充分な嵌合力が付
与される様にしたことを要旨とするものである。 The structure of the present invention in accordance with the above-mentioned object is to fit an inner tube which has been cooled and contracted into an outer tube whose diameter has been increased by heating in advance in a relatively overlapping manner,
The inner tube is expanded with a low-temperature liquid, plastically deformed to increase its diameter, and brought into contact with the outer tube.The diameter of both the inner and outer tubes is further increased, and when the set diameter is reached, the diameter increase is stopped and the state is maintained, thereby reducing the temperature of the inner and outer tubes. Reduce the difference and reduce the diameter of the outer pipe to increase the friction force by sufficiently increasing the surface pressure not only in the radial direction but also in the axial direction. After making sure that no axial deviation occurs, remove the tube expansion liquid and connect both tubes. As a result, the temperature increase and expansion of the inner tube is prevented by the above-mentioned axial frictional force, and the inner tube is concomitantly shortened due to the shortening of the outer tube, and a high axial compressive residual stress is applied to the inner tube, causing the inner tube to increase in temperature. The gist is to obtain a high interference margin through diameter increase and diameter reduction by cooling the outer tube, and to apply sufficient fitting force.
次にこの発明の実施例を第1,2,3図を参照
して第5図に従つて説明すれば以下の通りであ
る。尚、第1,4図と同一態様部分については同
一符号を用いて説明するものである。 Next, an embodiment of the present invention will be described below with reference to FIGS. 1, 2, and 3, and according to FIG. 5. Note that the same parts as in FIGS. 1 and 4 will be described using the same reference numerals.
前述同様設定長炭素鋼外管1を予め設定温度に
加熱して増径しておき、一方、ステンレス鋼内管
2を水道水浸けにより冷却縮径して第2図に示す
様にそれぞれ、イ、ロ、及びハ、ニに初期径にし
て相対重層嵌合し、シールプラグ3,3′を介し
て水道水4を内管2内に送給して加圧し、該第2
図ε―Fの応力、歪曲線に沿つて拡管していく。 As described above, the carbon steel outer tube 1 of a set length is heated to a set temperature in advance to increase its diameter, and the stainless steel inner tube 2 is cooled and reduced in diameter by immersion in tap water, as shown in Fig. 2. , B, C, and D are set to the initial diameter and are relatively overlappingly fitted, and the tap water 4 is fed into the inner pipe 2 through the seal plugs 3, 3' and pressurized.
The tube expands along the stress and strain curve shown in Figure ε-F.
而して、内管2が増径、降伏して外管1に一体
化して塑性変形し、更に両管1,2が増径され、
設定径ヘ、ホに達すると、拡管圧力印加を停止
し、その加圧力を維持させ、両管の温度差が小さ
くなるまで待つ。 As a result, the inner tube 2 increases in diameter, yields, integrates with the outer tube 1, and undergoes plastic deformation, and both tubes 1 and 2 further increase in diameter,
When the set diameter reaches the set diameter, stop applying pressure to expand the tube, maintain the pressure, and wait until the temperature difference between the two tubes becomes small.
この時、液圧拡管状態は維持されているため、
第3図C2折れ線グラフに示す様に外管1の降温
開始時は既に充分に内管2に対し限界摩擦面圧f0
を越えた内外管1,2の面圧f1を有する様になる
ので両管1,2の軸方向ズレは発生しなくなる。 At this time, the hydraulic pipe expansion state is maintained, so
As shown in the C2 line graph in Figure 3, when the temperature of the outer tube 1 starts to decrease, the critical friction surface pressure f 0 against the inner tube 2 is already sufficiently high.
Since the surface pressure f 1 of the inner and outer tubes 1 and 2 exceeds 1, axial displacement between the tubes 1 and 2 will not occur.
そして、外管温度がT0まで降下した時に拡管
圧を除去すると、この時には既にそれまでの温度
降下による限界摩擦面圧を越えた充分なる内外管
の面圧が得られているので、それ以後の外管温度
下降の間にも更に軸方向には内外管のズレは生じ
ず、外管の軸方向温度収縮により内管に軸方向圧
縮応力が導入されることになる。 If the tube expansion pressure is removed when the outer tube temperature drops to T 0 , by this time sufficient contact pressure between the inner and outer tubes has already been obtained that exceeds the limit frictional surface pressure due to the temperature drop up to that point. Even during the temperature drop of the outer tube, no deviation occurs between the inner and outer tubes in the axial direction, and axial compressive stress is introduced into the inner tube due to the axial temperature contraction of the outer tube.
この拡管圧を除去すべき温度T0は実験、理論
により設計的に求められており、当該設計時間経
過後拡管水道水4をシールプラグ3を介して除去
排出する。 The temperature T 0 at which this pipe expansion pressure should be removed is determined experimentally and theoretically, and after the designed time has elapsed, the pipe expansion tap water 4 is removed and discharged through the seal plug 3.
すると、両管1,2は第2図に示す様にト、チ
に縮管し、径方向に一応の締め代が得られるが、
放置することにより、外管1は大気温まで降温し
てトからリに縮径し、一方、内管2は大気温まで
チからヌに増径し、従つて、ΔDの大きな締め代
が得られ、強力な嵌合力が付与された自緊二重管
5が得られる。 Then, both pipes 1 and 2 contract to T and C as shown in Fig. 2, and a certain amount of interference is obtained in the radial direction, but
By leaving it as it is, the outer tube 1 cools down to the ambient temperature and its diameter decreases from T to E, while the inner tube 2 increases in diameter from T to N until it reaches the ambient temperature, and therefore a large interference of ΔD is obtained. A self-tightening double pipe 5 to which a strong fitting force is applied is obtained.
而して、上記プロセスに於て、外管1は第5図
に示す様に軸方向降温短縮されていくが、上述充
分な両管面圧嵌合力により随伴短縮されるが、軸
方向潜在昇温伸張との相対応力により大きな軸方
向圧縮残留応力を付与されることになる。 In the above process, the outer tube 1 is shortened as the temperature decreases in the axial direction as shown in FIG. A large compressive residual stress in the axial direction is imparted due to the stress relative to the warm stretching.
従つて、軸方向応力腐蝕割れ限界応力は大きく
設定される。 Therefore, the critical stress for axial stress corrosion cracking is set large.
そのため、前述油井管に使用して自重引張応力
が大きく作用しても、厳しい腐蝕環境下でも応力
腐蝕割れが生じない。 Therefore, even if it is used in the oil country tubular goods mentioned above and is subjected to large tensile stress due to its own weight, stress corrosion cracking will not occur even in a severe corrosive environment.
尚、この発明の実施態様は上述実施例に限るも
のでないことは勿論であり、例えば、拡管プロセ
スに於て外管も塑性変形させる様にしても良く、
又、内管も予め冷却縮管させておく必要はない等
種々の態様が採用可能である。 It should be noted that the embodiments of the present invention are of course not limited to the above-mentioned embodiments; for example, the outer tube may also be plastically deformed during the tube expansion process.
Further, various embodiments can be adopted, such as the need not to pre-cool the inner pipe to shrink the inner pipe.
上述の如く、この発明によれば、熱拡管法によ
つて内外管を液圧拡管し、設定径で拡管を停止す
ると共に該拡管液圧印加を維持して内外管の温度
差を小さくして後拡管液を除去する様にしたこと
により、基本的に予め高温にされた外管が内管に
対して降温していくプロセスで充分に両管の面圧
が軸方向ズレを生じさせない限界摩擦面圧を越え
て付与されるため、拡管液を除去しても、両管の
軸方向ズレは生ぜず、外管の軸方向短縮に伴い、
内管には充分大きな軸方向圧縮残留応力が付与さ
れ、従つて、径方向の高い嵌合力付与と共に応力
腐蝕割れに対する抗力の強い自緊二重管が得られ
る優れた効果が奏される。 As described above, according to the present invention, the inner and outer tubes are hydraulically expanded by a thermal tube expansion method, the tube expansion is stopped at a set diameter, and the expansion hydraulic pressure is maintained to reduce the temperature difference between the inner and outer tubes. By removing the liquid after tube expansion, the process in which the outer tube, which has been previously heated to a high temperature, cools down relative to the inner tube, creates enough contact pressure between the two tubes to reach the limit of friction that does not cause axial deviation. Since it is applied in excess of the surface pressure, even if the tube expansion liquid is removed, there will be no axial displacement of the two tubes, and as the outer tube is shortened in the axial direction,
A sufficiently large compressive residual stress in the axial direction is imparted to the inner tube, and therefore, an excellent effect is achieved in that a self-tightening double tube with high radial fitting force and strong resistance to stress corrosion cracking can be obtained.
又、上記軸方向圧縮残留応力付与は拡管液圧の
設定時間停止というプロセスだけで得られるた
め、何ら複雑な装置はいらず、操作も簡単であ
り、動力も必要としないメリツトがあり、コスト
にはね返りがない利点がある。 In addition, since the above-mentioned axial compressive residual stress can be obtained by simply stopping the pipe expansion hydraulic pressure for a set time, there is no need for any complicated equipment, the operation is simple, and there is no need for power, which has the advantage of reducing costs. There is no advantage.
第1図は拡管の概略説明図、第2図は拡管の応
力歪曲線説明図、第3図は外管温度と内外管面圧
との関係の従来及びこの発明の態様比較説明図、
第4図は従来技術に基づく内管外管の軸方向ズレ
の説明図、第5図はこの発明の実施例の内管圧縮
残留応力付与説明図である。
1…外管、2…内管、4…拡管液、F…拡管液
圧、ΔD…締め代、5…二重管、f0…摩擦限界面
圧。
FIG. 1 is a schematic explanatory diagram of tube expansion, FIG. 2 is an explanatory diagram of stress strain curves of tube expansion, and FIG. 3 is a comparative explanatory diagram of the relationship between the outer tube temperature and the inner and outer tube surface pressures between the conventional and the present invention.
FIG. 4 is an explanatory diagram of the axial deviation of the inner tube and the outer tube based on the prior art, and FIG. 5 is an explanatory diagram of applying compressive residual stress to the inner tube according to an embodiment of the present invention. 1...Outer pipe, 2...Inner pipe, 4...Tube expansion fluid, F...Tube expansion fluid pressure, ΔD...Clamping margin, 5...Double pipe, f0 ...Friction limit surface pressure.
Claims (1)
後拡管液圧を該内管内に印加し内管を拡管して両
管を一体拡管し所定径に増径後拡管液を除去して
締め代を介し自緊二重管を製造する方法におい
て、上記内外管一体拡管の所定径に増径した状態
を該内外管の温度差が小さくなるまで保持し、軸
方向ズレ摩擦限界面圧を越える面圧を内外管間に
得た後に該拡管液を除去する様にしたことを特徴
とす自緊二重管製造方法。1 Layer the cooling inner tube over the heated diameter-increasing outer tube, then apply expansion liquid pressure to the inner tube to expand the inner tube, expand both tubes together, and after increasing the diameter to a specified diameter, remove the expansion liquid and tighten. In a method for manufacturing a self-contained double-pipe tube through a process, the state in which the inner and outer tubes are integrally expanded to a predetermined diameter is maintained until the temperature difference between the inner and outer tubes becomes small, and the axial displacement friction limit surface pressure is exceeded. A method for manufacturing a self-contained double tube, characterized in that the tube expansion liquid is removed after surface pressure is obtained between the inner and outer tubes.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP12409981A JPS5825819A (en) | 1981-08-10 | 1981-08-10 | Manufacture of self-tightening double-wall tube |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP12409981A JPS5825819A (en) | 1981-08-10 | 1981-08-10 | Manufacture of self-tightening double-wall tube |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS5825819A JPS5825819A (en) | 1983-02-16 |
JPS6137015B2 true JPS6137015B2 (en) | 1986-08-21 |
Family
ID=14876895
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP12409981A Granted JPS5825819A (en) | 1981-08-10 | 1981-08-10 | Manufacture of self-tightening double-wall tube |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS5825819A (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE4406726A1 (en) * | 1994-03-02 | 1995-09-07 | Balcke Duerr Ag | Method and device for producing composite pipes |
-
1981
- 1981-08-10 JP JP12409981A patent/JPS5825819A/en active Granted
Also Published As
Publication number | Publication date |
---|---|
JPS5825819A (en) | 1983-02-16 |
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