【発明の詳細な説明】
く産業上の利用分野〉
本発明は、石油やガスの輸送用パイプおよび化学プラン
トでの配管として用いる耐食二重管の管端防鯖方法に関
するものである．
く従来の技術〉
従来、機械的接合による耐食二重管は、管端を切断した
ままの状態で、すなわち、内管と外管が未接着のままで
樹脂製のキャップ等でふたをして輸送や保管をしていた
．
また、耐食二重管そのものの技術としては、第１１８回
日本鉄鋼協会講演大会論文集Ｖｏｌ．２，Ｎａ６（１９
Ｂ９）の＃６８７および＃６８８に焼ばめ方式の技術が
例示されているが、輸送や保管に関する従来技術は殆ど
見当たらない．
〈発明が解決しようとする課題〉
機械的接合による耐食二重管では、内管と外管とが冶金
的に接合されておらず、ξクロ的には例えば１００倍の
顕微鏡観察では界面に空隙が存在しているため、管端で
は外気の湿気により鯖が発生し、使用に際し管端を廃却
することが多かった．二重管の構威要素の外管もしくは
内管に安価な材料を用いているとはいえ、管端を廃却す
ることはコストアップにつながり、その使用上の重要な
問題点であった．
〈課題を解決するための手段〉
本発明は、機械的接合による耐食二重管の管端部の内管
と外管との界面をあらかじめ肉盛熔接しておくことを特
徴とする耐食二重管管端の防錆方法である．
〈作 用〉
発明者らは、機械的接合による耐食二重管の管端の防錆
について種々研究した結果、管端の内管と外管との界面
を溶接しておけば、その後の輸送、保管に際して、界面
に鯖が発生せず、管端を廃却することがなくなるという
知見を得、その知見に基づいて本発明をなし得た．
すなわち、第１図（ａ）に示すように、外管１と内管２
とからなる耐食二重管の界面３の管端部を溶接によって
肉盛し、ビード４を形威し、外気の湿気による錆の発生
を防止できる．また、第１図（ｂ）に示すように予め開
先加工した場合も同様にビードを形威し鯖の発生を肪止
できる．しかも、この場合はビード４は突合わせ円周溶
接施工時にそのまま残せるという利点もある．
なお、肉盛溶接材料としては鯖を防ぐという目的を達威
できるものであれば何でもよいが、合わせ材戒分の保証
淳という観点からは合わせ材と共金もしくはより高合金
成分のものが望ましい．く実施例〉
寸法が外径： １４２．９ｍ、厚：２．５−である内
管として第１表に示す合金の鋼管を、寸法が外径：１６
８．３ｍ，厚： １２．７閣である外管として同じく第
１表に示す威分の炭素鋼管を有する機械的接合の耐食二
重管を、１個は管端はそのまま、別の１個は管端を共金
ティグ溶接によって肉盛し、３０日間室内に放置した．
従来法の二重管では内管と外管との界面には管端より１
４一にわた，て錆が発生したが、本発明に係る二重管で
は全く錆の発生がなく健全であった．鯖の発生状況は、
本発明に係る二重管については＊ａにて肉盛熔接部を除
去後、従来法の二重管についてはそのままで、内管のみ
をダイスにて押し抜いて、外管の炭素鋼管を肉眼にて観
察した．〈発明の効果〉
本発明方法によると、従来のように管端に外気の湿気に
よる鯖の発生を防止することができ、管端を廃却せずに
済みコストダウンを図れる．４，DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for protecting the ends of corrosion-resistant double pipes used as pipes for transporting oil and gas and piping in chemical plants. Conventional technology: Conventionally, mechanically bonded corrosion-resistant double pipes have been produced with the pipe ends cut, that is, with the inner pipe and outer pipe unbonded, and covered with a resin cap, etc. It was transported and stored. In addition, as for the technology of the corrosion-resistant double pipe itself, the 118th Japan Iron and Steel Institute Lecture Conference Proceedings Vol. 2, Na6(19
Shrink fit technology is exemplified in #687 and #688 of B9), but almost no prior art related to transportation or storage can be found. <Problem to be solved by the invention> In a mechanically joined corrosion-resistant double pipe, the inner pipe and the outer pipe are not metallurgically joined, and from a ξchromatic perspective, for example, microscopic observation at 100x magnification shows that there are voids at the interface. Because of the presence of molten metal, mackerel occurs at the ends of the pipes due to the moisture in the outside air, and the ends of the pipes are often discarded after use. Although inexpensive materials are used for the outer and inner tubes of the double-pipe structure, discarding the tube ends leads to increased costs, which is an important problem in its use. <Means for Solving the Problems> The present invention provides a corrosion-resistant double-walled pipe characterized in that the interface between the inner pipe and the outer pipe at the pipe end of the corrosion-resistant double-walled pipe is welded overlay in advance by mechanical joining. This is a method of preventing rust at the ends of pipes. <Function> As a result of various studies on rust prevention of the pipe ends of corrosion-resistant double pipes by mechanical joining, the inventors found that if the interface between the inner pipe and the outer pipe at the pipe ends is welded, subsequent transportation will be easier. The present invention was based on the knowledge that no mackerel is generated at the interface during storage and the end of the tube is not discarded. That is, as shown in FIG. 1(a), an outer tube 1 and an inner tube 2
The pipe end of the interface 3 of the corrosion-resistant double pipe made of is overlaid by welding to form a bead 4, which can prevent rust from forming due to moisture in the outside air. Furthermore, as shown in Fig. 1(b), if the bevel is prepared in advance, the bead can be shaped in the same way and the occurrence of mackerel can be prevented. Moreover, in this case, there is an advantage that the bead 4 can be left as is during butt circumferential welding. Any material may be used as the overlay welding material as long as it can achieve the purpose of preventing welding, but from the viewpoint of ensuring the safety of the laminated material, it is preferable to use the same metal as the laminated material or one with a higher alloy content. ．． Example> A steel pipe made of the alloy shown in Table 1 was used as the inner pipe having an outer diameter of 142.9 m and a thickness of 2.5 m, and an outer diameter of 16 m in outer diameter.
8.3 m, thickness: 12.7 mm As the outer pipe, a mechanically bonded corrosion-resistant double pipe with the same carbon steel pipe shown in Table 1 was used, one with the pipe end intact, and the other with the same pipe end. The tube end was overlaid by matching TIG welding and left indoors for 30 days. In the conventional double pipe, the interface between the inner pipe and the outer pipe is
However, the double pipe according to the present invention had no rust at all and was in good health. The occurrence status of mackerel is
For the double pipe according to the present invention, after removing the overlay welded part in *a, for the double pipe using the conventional method, only the inner pipe is punched out with a die, and the outer carbon steel pipe is removed with the naked eye. Observed at. <Effects of the Invention> According to the method of the present invention, it is possible to prevent the occurrence of mackerel at the tube end due to moisture in the outside air, unlike in the conventional method, and it is possible to reduce costs by eliminating the need to dispose of the tube end. 4,
【図面の簡単な説明】[Brief explanation of the drawing]
第１図は、本発明方法を説明する二重管の断面図である
．
１・・・外
管、
２・・・内
管、
３・・・界
面、
４・・・肉盛ビード．FIG. 1 is a sectional view of a double pipe explaining the method of the present invention. 1... Outer tube, 2... Inner tube, 3... Interface, 4... Overlay bead.