JPH0996386A - Manufacture of removal preventive tube joint of ductile cast iron pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a mass production in a simple process, by heating the spigot of a ductile cast iron pipe to a specific temperature, surrounding and compressing the pipe from the whole surface leaving the end forming the spigot projection lines, copying the spigot projection line section form to the end, moving a cut circular metal mold on the axial line, and swaging casting the pipe. SOLUTION: The spigot 3 of a ductile cast iron pipe P is inserted to a high-frequency heating device 6, an it is heated by controlling so that the whole thickness of the spigot 3 is made even to the temperature lower 80 to 100 deg.C than the solid phase line of the material. By leaving the height to form the projection lines 31 of the spigot 3, the clamp dies 41 of a horizontal casting presses are moved from both side squarely to the pipe axis O, and the pipe is held and pressure contacted from the whole periphery so as to be fixed. Then, a sliding mandrel 42 cutting a notch 40 where the form of a specific spigot projection line is copied is slide parallel to the pipe axis, a small diameter cylinder 44 is inserted to the inner surface of the cast iron pipe P, the pipe body is held by the clamp dies 41, and the pipe body is made in the form of the notch 43 by advancing the pipe while deforming it on an area surface 45. Consequently, the stock products can be processed easily, and a high productivity can be realized.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【発明の属する技術分野】本発明はダクタイル鋳鉄管の
離脱防止管継手、特に挿口に突条を突設して継合する他
管の受口に装着したロックリング２と係合させて管の離
脱を防止する型式の管継手に係る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separation preventing pipe joint for a ductile cast iron pipe, and more particularly to a pipe which is engaged with a lock ring 2 attached to the receiving end of another pipe which is formed by projecting a ridge on the insertion port. The present invention relates to a pipe joint of a type that prevents separation of the pipe.

【０００２】[0002]

【従来の技術】水道管路は都市、農村を問わず、およそ
人間が居住し生活を営む箇所を網羅して地中に管路を形
成し、必須の水を送給する役割を果たすものであり、ラ
イフラインの代表とされるものである。したがって如何
なる天変地異に遭遇しても管路の損傷がなく、常に送水
機能を維持する保証が強く求められる。交通の発達に伴
って種々の外圧が頻々と埋設管に加わり、たとえば、地
上を通過する重車両に伴う振動、衝撃はますます頻繁と
なる一方、我が国の地理的な特異性として地震による激
烈な地殻の震動、揺動なども避けられないから、それに
対して容易に管と管とが離脱しないような継手部が社会
的に求められることは当然である。2. Description of the Related Art A water pipeline serves to form a pipeline in the ground to cover the places where people live and live, regardless of whether it is a city or a rural area, and to play an essential role in supplying water. Yes, it is the representative of the lifeline. Therefore, no matter what kind of catastrophic event is encountered, there is a strong demand for assurance that the pipeline will not be damaged and the water supply function will always be maintained. With the development of traffic, various external pressures are frequently applied to the buried pipe, and, for example, vibrations and shocks associated with heavy vehicles passing over the ground are becoming more frequent. Since it is inevitable that the earth's crust will vibrate and oscillate, it is natural that there is a social demand for a joint that prevents the pipes from separating from each other.

【０００３】ダクタイル鋳鉄管の継合は管端の受口へ挿
口を挿入する継手方式を特徴とし、溶接などによる鋼管
より遥かに継合作業が手軽で容易な点が水道管路敷設用
の主力として採用する決め手となっているが、受口、挿
口間の離脱を特に防止する継手構造として、図５に示す
ような構成がＪＩＳ規格（Ｇ５５２６）によって標準化
されている。この規格はＳII型と呼ばれるダクタイル鋳
鉄管の継手部であり、呼び径によってそれぞれの寸法は
当然異なるが、たとえば呼び径１００ｍｍ（実外径１１
８．０ｍｍ）のダクタイル鋳鉄管であれば挿口に突設し
た突条３１ａの高さは挿口３ａ外周面から９ｍｍ、呼び
径３００ｍｍ（実外径３２２．８ｍｍ）の管であれば１
０ｍｍと定められている。図でも明らかなように、この
突条はダクタイル鋳鉄又は鋼材で製作した環状体（リン
グ）を挿口の所定の先端近くに嵌合し、環状体の側面と
管の外周面との間を隅肉溶接１０１を全周から行なって
固定する方式が採られている。The splicing of ductile cast iron pipes is characterized by a joint system in which an insertion port is inserted into the receiving end of the pipe end, and the point that splicing work is much easier and easier than with steel pipes by welding, etc. Although it is a decisive factor for adoption as a main force, a structure as shown in FIG. 5 is standardized by the JIS standard (G5526) as a joint structure that particularly prevents separation between the receiving opening and the insertion opening. This standard is a joint part of a ductile cast iron pipe called SII type, and each size naturally varies depending on the nominal diameter, but for example, a nominal diameter of 100 mm (actual outer diameter 11
In the case of a ductile cast iron pipe of 8.0 mm), the height of the protrusion 31a protruding from the insertion port is 9 mm from the outer peripheral surface of the insertion port 3a, and is 1 if the pipe has a nominal diameter of 300 mm (actual outer diameter 322.8 mm).
It is set to 0 mm. As is clear from the figure, this ridge is made by fitting an annular body (ring) made of ductile cast iron or steel near the prescribed tip of the insertion slot, and forming a corner between the side surface of the annular body and the outer peripheral surface of the pipe. A method is employed in which the meat welding 101 is performed from the entire circumference and fixed.

【０００４】この離脱防止方式の施工手順としては、あ
らかじめ挿口に鋼材またはダクタイル鋳鉄で成形したリ
ングを外嵌して全周の隅肉溶接を施した後、その先端に
一つ割りのロックリング２ａを遊嵌して受口１ａ内へ挿
入し、さらに受口内周面と挿口外周面の間に生じる環状
の狭い隙間からハサミ状の押圧器具によって欠円部を押
し縮めて縮径したロックリング２ａを挿入し、受口１ａ
内へ刻設したロックリング収容溝１１ａの位置に届く
と、押圧していた外力を緩めて弾性でロックリング２ａ
を元の形状に拡径し溝の中へ嵌合する。この結果、ロッ
クリング２ａの内周面は受口１ａの内周面より突出した
突条となるから、挿口３ａの突条３１ａと相互に係合す
る関係を成立して離脱を防止する。[0004] As a construction procedure of the detachment prevention system, a ring formed of steel or ductile cast iron is externally fitted to the insertion port in advance, and fillet welding is performed on the entire circumference, and then a split lock ring is provided at the tip. The lock 2a is loosely fitted and inserted into the receiving opening 1a, and the diameter of the lock is reduced by compressing the truncated circle portion with a scissor-like pressing device from a narrow annular gap formed between the inner peripheral surface of the receiving opening and the outer peripheral surface of the insertion opening. Insert the ring 2a and make the socket 1a
When it reaches the position of the lock ring receiving groove 11a engraved inward, the pressing external force is relaxed to elastically move the lock ring 2a.
Expand to the original shape and fit into the groove. As a result, the inner peripheral surface of the lock ring 2a becomes a protrusion protruding from the inner peripheral surface of the receiving opening 1a, so that the engagement with the protruding protrusion 31a of the insertion opening 3a is established to prevent separation.

【０００５】しかし、この方式ではロックリング２ａの
現地における受口内への嵌合がきわめて煩わしく、また
一時的にロックリング２ａを押し縮めるという器具も必
要であり、必ずしも能率の高い作業であるとは言い難
い。そのために比較的簡単な継合作業が進行されるスリ
ップ・オン・タイプと呼ばれる方式が開発された。この
方式は受口内のロックリング収容溝の中へ弾性体とロッ
クリングとを初めから収容した状態で前管の挿口内へ挿
入し、挿口に突設した突条に衝き当たると弾性体を弾性
変形させてロックリングを溝の内側方向へ押し込みなが
ら挿口突条を乗り越えて正しい継合位置まで前進すると
いう方式である。この方式であれば煩瑣で困難、非能率
でもあった継合後のロックリングの溝への填め込みとい
う作業がなくなり、離脱防止タイプの管継手を高能率で
施工できる利点が享受される。However, in this method, it is extremely troublesome to fit the lock ring 2a into the receiving port at the site, and a device for temporarily pressing the lock ring 2a is required, which is not always efficient. Hard to say. For that reason, a method called a slip-on type has been developed in which a relatively simple joining operation proceeds. This method inserts the elastic body and the lock ring into the lock ring accommodating groove in the receiving port from the beginning, and inserts the elastic body and the lock ring into the insertion port of the front pipe. This is a method of elastically deforming and pushing the lock ring toward the inside of the groove, overcoming the insertion ridge and advancing to the correct joining position. With this method, the work of fitting the lock ring into the groove after joining, which was cumbersome, difficult, and inefficient, is eliminated, and the advantage of being able to construct a disconnection prevention type pipe joint with high efficiency is enjoyed.

【０００６】スリップ・オン・タイプの特徴は図６に示
すように、ロックリング２が挿口３の外周面から突出し
た突条３１を乗り越えて継合するのであるから、必然的
に従来のＪＩＳで規定された離脱防止タイプよりも挿口
突条の高さを低く抑えることが条件の一つであり、ま
た、突条の形状も挿口端部に亘って緩やかな傾斜面を形
成してロックリング２の摺動と退入を容易にする後面
と、外周面上に直立してロックリング２との係合を確実
に維持する前面の両面で形成することが別の条件とな
る。この要件を満たす形状であれば従来（図５）のよう
に単に溶接によってリング材を挿口面上に溶着するだけ
では現地での実施は困難である。そのためにスリップ・
オン・タイプの施工を円滑に進行するために、挿口突条
の形状や受口内へ嵌合するロックリングの形状などにつ
いて幾つかの先駆的な提示が見出される。As shown in FIG. 6, the feature of the slip-on type is that the lock ring 2 passes over the projection 31 protruding from the outer peripheral surface of the insertion port 3 and is joined, so that the conventional JIS is inevitable. One of the conditions is to keep the height of the insertion ridge lower than that of the detachment prevention type specified in 1), and the shape of the ridge must also be formed with a gentle sloping surface over the end of the insertion opening. Another condition is that the lock ring 2 is formed with both a rear surface that facilitates sliding and retreat, and a front surface that stands upright on the outer peripheral surface and securely maintains the engagement with the lock ring 2. If the shape meets this requirement, it is difficult to carry out the work at the site simply by welding the ring material onto the insertion surface by welding as in the conventional case (FIG. 5). Therefore slip
In order to smoothly proceed the on-type construction, some pioneering presentations have been found on the shape of the insertion ridge and the shape of the lock ring fitted into the receiving opening.

【０００７】図７に示す従来技術は特開平７−２７２６
５号公報に係るスリップ・オン・タイプの離脱防止管継
手であって、図（Ａ）が全体図である。図（Ｂ）は挿口
３ｂの外周面上に挿口突条３１ｂを形成するために挿口
端部に穿設した挿口溝１０２に嵌入する挿口リング１０
３であり、図の通り一部を切り欠いた欠円状に製作さ
れ、欠円部に段差１０４と、段差に貫通するリベット孔
１０５を具えている。図（Ｃ）はリング材の欠円部の段
差上に嵌合する接合ピース１０６であり、弓形の断面と
リベット孔１０７を具えている。挿口突条を挿口外周面
上へ固定する手順は、挿口溝１０２へ挿口リング１０３
を嵌め込み、挿口リングの欠円部に連続する段差１０４
へ接合ピース１０６を架橋し、両部材のリベット孔１０
５と１０７とを合せてリベットを打ち込んで締結するこ
とによって簡単に完了すると謳っている。The prior art shown in FIG. 7 is disclosed in JP-A-7-2726.
The slip-on type separation prevention pipe joint according to Japanese Patent Laid-Open No. 5 is a general view. FIG. 1B shows an insertion ring 10 which is fitted into an insertion groove 102 formed at the end of the insertion opening to form an insertion protrusion ridge 31b on the outer peripheral surface of the insertion opening 3b.
As shown in the figure, it is manufactured in the shape of an open circle, a part of which is cut away, and the open circle has a step 104 and a rivet hole 105 penetrating the step. FIG. 3C shows a joining piece 106 that fits on the step of the circular portion of the ring material, and has a bow-shaped cross section and a rivet hole 107. To fix the insertion ridge on the outer peripheral surface of the insertion hole, insert the insertion ring 103 into the insertion groove 102.
Step 104 that is continuous with the missing circle of the insertion ring
The joining piece 106 is bridged to the rivet holes 10 of both members.
It is said to be completed simply by setting 5 and 107 together and driving and fastening the rivets.

【０００８】また、図８に示す従来技術は特開平５−２
３１５７２号公報に係る離脱防止管継手であり、この発
明の要旨はスリップ・オン・タイプを円滑に進行するた
めにロックリング２ｃの形状と、ロックリング２ｃを収
容する受口１ｃの内周面の形状を特に改変した点にあ
り、挿口突条に関しては特別な記載があるわけではない
が、図で見る限り、挿口突条３１ｃを形成するために挿
口端部近くに突条収容溝１０８を切り込んで挿口リング
１０９を嵌入し、挿口リングの挿口端部側は挿口外周面
上に傾斜面を形成するように隅肉溶接１１０を行なう一
方、反対側は挿口外周面から切り込んだ傾斜面の開先１
１１を形成して溶接する構成を示唆している。この方式
によって従来のＪＩＳの規定よりも挿口突条の高さを低
く抑え、端部を傾斜面、内部側を直角面となるスリップ
・オン・タイプ用の突条としての要件を満たしたものと
考えられる。The prior art shown in FIG. 8 is disclosed in Japanese Patent Laid-Open No. 5-2.
The detachment prevention pipe joint according to Japanese Patent No. 31572, and the gist of the present invention is the shape of the lock ring 2c and the inner peripheral surface of the receiving port 1c that accommodates the lock ring 2c in order to smoothly advance the slip-on type. Although there is no special description about the insertion ridge, it is in the point that the shape is particularly modified, but as shown in the figure, in order to form the insertion ridge 31c, the ridge receiving groove is formed near the end of the insertion ridge. 108 is cut in and the insertion ring 109 is inserted, and fillet welding 110 is performed so that the insertion end portion side of the insertion ring forms an inclined surface on the insertion opening outer peripheral surface, while the opposite side is the insertion opening outer peripheral surface. Groove 1 of the inclined surface cut from
It suggests a structure in which 11 is formed and welded. By this method, the height of the insertion ridge is kept lower than the conventional JIS standard, and the requirements for a slip-on type ridge with an inclined surface at the end and a right-angled surface on the inside are satisfied. it is conceivable that.

【０００９】スリップ・オン・タイプ用の挿口突条を形
成することは、突条の高さを低く抑制するほど技術的な
困難さが増長することは常識的にも予想できる。たとえ
ば従来技術であるＪＩＳ規定では突条の高さは約１０ｍ
ｍとされているが、スリップ・オン・タイプであれば３
ｍｍ程度に設定することが理想である。とすれば肉薄の
リング材を直接外周面上へ溶接することは殆ど望み得な
いし、溝内へ嵌合して溶接したとしても、一方の溶接の
盛り肉を加工で削除しなければ直立した係合側面を形成
することができない。このことは溶接強度を著しく低下
させるから事実上は不可能な処置である。It is common sense that forming a slip-on type spigot ridge increases in technical difficulty as the height of the ridge is reduced. For example, the height of the ridge is about 10 m according to the JIS regulation which is a conventional technique.
m, but 3 for slip-on type
The ideal setting is about mm. If so, it is almost impossible to weld a thin ring material directly onto the outer peripheral surface, and even if the thin ring material is fitted into the groove and welded, the upright part of one weld must be removed by machining. No mating surface can be formed. This is a virtually impossible measure because it significantly reduces the weld strength.

【００１０】一方、スリップ・オン・タイプ用に特に適
応できるように改善された図７、図８の挿口突条の形態
が課題解決の上で明らかに有効であることは評価され
る。しかし、現場的な諸条件から見て万全の手段である
とは必ずしも言い切れない。たとえば図７について言え
ば、挿口リングは段差とリベット孔を具えた欠円状の環
状体であり、形状がきわめて簡単であるとは言えない
し、この挿口リングに嵌合する接合ピースについても同
様である。すなわち部材の個数も多く、加工も煩瑣であ
るから製作に対する負担は看過できない程度に嵩むし、
現地における継合施工時に必ずリベットによる締結を要
件とする点も作業能率の点で負の効果をもたらす懸念が
残る。図８の挿口突条の形態は溶接、またはそれに変わ
る接合方式を想定したものであると見られるが、リング
材の外周面上へ突出する全高が小さい限り、傾斜面を形
成する肉盛高さも低く制限されざるを得ず、水平方向へ
負荷する離脱力に十分対抗するだけの溶着強度が得られ
るか、特に溶け込み量の不足が起こらないかなどの意見
が分れるところである。また、内部側の直角側面を形成
するために挿口外周面に開先面を加工する点も負担の一
つと言わざるを得ないし、その溶着力が如何ほどの離脱
防止に有効であるかもなお、検討の余地があるのではな
いか。On the other hand, it is appreciated that the form of the insertion ridges of FIGS. 7 and 8 improved so as to be particularly adapted to the slip-on type is obviously effective in solving the problem. However, it cannot always be said that it is a perfect means in view of various conditions on the spot. For example, referring to FIG. 7, the insertion ring is a ring-shaped annular body having a step and a rivet hole, and it cannot be said that the shape is extremely simple. It is the same. In other words, since the number of members is large and the processing is complicated, the burden on the production increases to the extent that it cannot be overlooked.
There is a concern that workability will also be negatively affected by the fact that rivets must always be fastened when jointing locally. The shape of the insertion ridge in FIG. 8 seems to be assumed to be welding or a joining method that changes to that, but as long as the total height protruding above the outer peripheral surface of the ring material is small, the build-up height forming an inclined surface However, there is no choice but to limit it to a low level, and it is possible to obtain an opinion as to whether a welding strength sufficient to counter the detaching force applied in the horizontal direction can be obtained, and in particular, whether the penetration amount is insufficient. In addition, it must be said that one of the burdens is to process the groove surface on the outer peripheral surface of the insertion opening to form the right-angled side surface on the inner side, and the welding force may be effective in preventing separation. I think there is room for consideration.

【００１１】阪神大震災においては被災地の水道管路は
瞬間的に支離滅裂の状態に破壊され、次いで発生した火
災に対しても消火用水が得られないために延焼するまま
に傍観する他なかったという深刻な教訓が残るが、管路
を構成するダクタイル鋳鉄管自体の破壊は殆ど現われ
ず、大部分が管継手からの離脱によることが確認されて
いる。以後、全国の自治体は水道管路の防災に重点目標
を絞り、特に離脱防止型の管継手への変換を主たる対応
策に挙げているが、本発明は以上に述べた離脱防止型の
管継手の抱える課題を解決するために、従来よりも遥か
に簡単な工程で、かつ量産体制に馴染み経済的に有利な
製造方法を提供することを目的とする。In the Great Hanshin Earthquake, the water pipes in the disaster area were instantly destroyed in a state of incoherence, and there was no way to obtain fire extinguishing water for the next fire, so there was no choice but to look around as it spread the fire. Although a serious lesson remains, it has been confirmed that the ductile cast iron pipe itself that constitutes the pipeline hardly breaks, and most of it is due to detachment from the pipe joint. Since then, local governments throughout the country have focused their efforts on disaster prevention of water pipes, and in particular listed conversion to a separation prevention type pipe joint as a main countermeasure, but the present invention describes the separation prevention pipe joint described above. An object of the present invention is to provide a manufacturing method which is economically advantageous in that it has a much simpler process than in the past and is familiar with a mass production system in order to solve the problem of the above.

【００１２】[0012]

【課題を解決するための手段】本発明に係るダクタイル
鋳鉄管の離脱防止管継手はダクタイル鋳鉄管の受口１の
内周面に刻設したロックリング収容溝１１に装着したロ
ックリング２と、継合するダクタイル鋳鉄管の挿口３の
先端に突設した突条３１が係合して両管の離脱を防止す
る基本構成を前提とし、ダクタイル鋳鉄管Ｐの全部、ま
たは少なくとも挿口３を最高でダクタイル鋳鉄材の固相
線より８０〜１００℃低い鍛造成形可能な温度まで加熱
昇温し、ダクタイル鋳鉄管Ｐの外周面のうち、挿口突条
３１を形成すべき長さの端部を残して全面より囲繞圧迫
して固定し、該露呈した端部へ所定の挿口突条３１の断
面形状を転写した切欠きを設けた環状の金型を管軸と同
軸線上で移動しつつ、該切欠きに倣う据え込み鍛造を行
なう手順を特徴とする。この手順は、ダクタイル鋳鉄管
が具えた冶金的な固有の熱間変形能力を活用して、従来
技術よりも遥かに簡単に、かつ、既に生産された在庫品
も含めて最も大量に離脱機能を保有するダクタイル鋳鉄
管に変換できるから、全国的な耐震性のライフラインを
容易に再構築でき、課題を一挙に解決する。DISCLOSURE OF THE INVENTION A separation prevention pipe joint for a ductile cast iron pipe according to the present invention includes a lock ring 2 mounted in a lock ring accommodating groove 11 formed in an inner peripheral surface of a socket 1 of the ductile cast iron pipe, Assuming a basic structure in which a projection 31 protruding from the tip of the insertion port 3 of the ductile cast iron pipe to be joined is engaged to prevent the two pipes from being separated from each other, the entire ductile cast iron pipe P, or at least the insertion port 3 is The end of the outer peripheral surface of the ductile cast iron pipe P, the length of which is to be formed, is the temperature at which the temperature can be forged by 80 to 100 ° C. lower than the solidus line of the ductile cast iron material at the maximum, to form the insertion protrusion 31. While pressing and fixing the surrounding area from the entire surface, the annular die provided with a notch in which the cross-sectional shape of the predetermined insertion protrusion ridge 31 is transferred to the exposed end is moved coaxially with the tube axis. , Characterized by the procedure of upsetting forging following the notch That. This procedure takes advantage of the metallurgical's inherent hot-deformability of ductile cast iron pipes, making it much easier than the prior art and providing the largest amount of detachment capability, including inventory already produced. Since it can be converted to the existing ductile cast iron pipe, it is possible to easily rebuild the nationwide earthquake-resistant lifeline and solve the problems at once.

【００１３】前記の基本的な手順のうち、ダクタイル鋳
鉄管Ｐの挿口３の外周面上を巻き回した加熱コイルを励
磁して誘起する渦電流で加熱する高周波加熱装置６を使
用することがエネルギー経済性の上からはきわめて望ま
しい態様であり、課題解決の上でコスト的に有利であ
る。Of the basic procedures described above, it is possible to use the high-frequency heating device 6 which heats the heating coil wound around the outer peripheral surface of the insertion port 3 of the ductile cast iron pipe P by the eddy current induced by exciting it. This is a very desirable mode from the viewpoint of energy economy, and is cost effective in solving the problems.

【００１４】ダクタイル鋳鉄管挿口の据え込み鍛造につ
いては、横型の鍛造プレス４による態様が望ましく、挿
口３の外周面を成形すべき挿口突条３１の容積に相当す
る長さの端部を残して二つ割りの環状体であるクランプ
ダイス４１を作動して全面から挟持して固定し、該露呈
した端部へ水平方向に滑動するスライディングマンドレ
ル４２を移動し、該スライディングマンドレル４２に刻
設した挿口突条３１と同形の切欠き４３の前進と共に所
望の形状に成形する手順が課題解決のために合理的であ
る。The upsetting forging of the ductile cast iron pipe insertion is preferably performed by a horizontal forging press 4, and the outer peripheral surface of the insertion opening 3 has an end portion having a length corresponding to the volume of the insertion protrusion 31 to be formed. The clamp die 41, which is an annular body divided into two parts, is operated and clamped and fixed from the entire surface, and the sliding mandrel 42 that slides in the horizontal direction is moved to the exposed end portion, and is engraved on the sliding mandrel 42. The procedure of forming the desired shape with the advance of the notch 43 having the same shape as the insertion ridge 31 is rational for solving the problem.

【００１５】あるいは前記の横型に代えて、ダクタイル
鋳鉄管挿口の据え込み鍛造が竪型の鍛造プレス５による
ものであり、受圧台５７の上面へ載置したダクタイル鋳
鉄管内へ円筒状のマンドレル５１を嵌合すると共に、挿
口３の先端における突条３１の所定長さを残してその他
の外周面を囲繞する下金型５２を前記マンドレル５１の
軸線と直角方向から挾圧して管体を固定し、該下金型５
２の上方でマンドレルの外周面上に滑動自在に外嵌する
上金型５４を降下して下金型５２の上面５３から露呈す
る前記挿口の先端に達し、上金型５４に切り込んだ所定
形状を転写した切欠き５５が接触する管体を押圧して塑
性変形を加えながら降下を続け、上金型５４の下面５６
と下金型５２の上面５３とが会合して停止する手順であ
ってもよい。Alternatively, instead of the horizontal type, upsetting of the ductile cast iron pipe inlet is performed by the vertical forging press 5, and the cylindrical mandrel 51 is inserted into the ductile cast iron pipe placed on the upper surface of the pressure receiving base 57. The lower die 52 surrounding the other outer peripheral surface of the mandrel 51 with a predetermined length of the projection 31 at the tip of the insertion opening 3 fixed from the direction perpendicular to the axis of the mandrel 51 to fix the tubular body. And the lower die 5
The upper die 54, which is slidably fitted over the outer peripheral surface of the mandrel, descends above 2 to reach the tip of the opening exposed from the upper surface 53 of the lower die 52 and cut into the upper die 54. The notch 55 whose shape has been transferred presses the tube body with which it comes into contact and continues to descend while applying plastic deformation to the lower surface 56 of the upper mold 54.
The procedure may be such that the above and the upper surface 53 of the lower mold 52 meet and stop.

【００１６】[0016]

【発明の実施の形態】図１は本発明の実施の形態を示す
工程毎の略図である。図（Ａ）は対象であるダクタイル
鋳鉄管Ｐを所望の成形加工が可能な温度まで昇温する加
熱工程である。ダクタイル鋳鉄管Ｐの全体を加熱炉内へ
装入して昇温する方法もあるが、成形する挿口付近だけ
を局部的に加熱する方式を採る方が経済的に有利である
ことは言うまでもない。局部加熱としては図２に例示す
るような高周波加熱装置６の適用が望ましく、挿口３の
所望の範囲に亘って螺旋状に巻き回した加熱コイル６１
の軸心に管軸を一致させて挿入し、高周波発振器６２に
通電して挿口内部に誘起する渦電流によるジュール熱と
ヒステリシス熱で管体を加熱する。挿口３の端部にＰｔ
−ＰｔＲｈよりなる熱電対６３を装着して温度上昇を温
度計６４へ伝え、温度計６４から温度調整用の制御器に
入力する。制御器の例としてはＣＰＵ６５が典型的であ
り、あらかじめ入力して記憶した初期条件と現実の温度
との差を演算して高周波発信器６２へ指令する。たとえ
ば設定温度を１１００℃とし、上下の比例帯を±３０℃
に設定し、１１００℃までは比例制御で表面温度を上昇
させる。一般に高周波加熱においては材料表面がＡ₂変
態点以上に達すると表面に集中していた渦電流が減少し
て内部に移行するのが通則である。最高加熱温度の設定
は事前の実験によって確認することが望ましいが、材料
の固相線よりも８０〜１００℃低い温度とすることが推
奨されている。この温度に達した後は積分制御に切り替
えて挿口３の全肉厚が均等に設定温度に達するまで制御
しつつ加熱を続ける。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of each step showing an embodiment of the present invention. FIG. (A) shows a heating step of raising the temperature of the target ductile cast iron pipe P to a temperature at which desired molding can be performed. There is also a method of charging the entire ductile cast iron pipe P into the heating furnace to raise the temperature, but it goes without saying that it is economically advantageous to locally heat only the vicinity of the molding opening. . As the local heating, it is desirable to apply the high-frequency heating device 6 as illustrated in FIG. 2, and the heating coil 61 spirally wound over the desired range of the insertion slot 3.
The tube is inserted with its axis aligned with the axis of, and the tube is heated by the Joule heat and the hysteresis heat due to the eddy current induced in the insertion slot by energizing the high-frequency oscillator 62. Pt at the end of the insertion slot 3
A thermocouple 63 made of -PtRh is attached to convey a temperature rise to the thermometer 64, and the thermometer 64 inputs the temperature rise to a controller for temperature adjustment. A typical example of the controller is the CPU 65, which calculates the difference between the actual temperature and the initial condition that is input and stored in advance, and issues the command to the high-frequency oscillator 62. For example, the set temperature is 1100 ° C and the upper and lower proportional bands are ± 30 ° C.
And the surface temperature is raised by proportional control up to 1100 ° C. Generally, in high-frequency heating, when the surface of the material reaches the A ₂ transformation point or higher, it is a general rule that the eddy current concentrated on the surface decreases and moves to the inside. It is desirable to confirm the setting of the maximum heating temperature by an experiment in advance, but it is recommended to set the temperature to 80 to 100 ° C. lower than the solidus of the material. After reaching this temperature, the control is switched to integral control, and heating is continued while controlling until the total thickness of the insertion slot 3 reaches the set temperature evenly.

【００１７】ダクタイル鋳鉄管の高温における加工性に
ついては幾つかの実験報告が認められるが、その一部を
引用すると、豊橋技科大・山田伸弥他の「球状黒鉛鋳鉄
の力学的特性に及ぼす加工熱処理の影響」（日本鋳物協
会・第１０１回講演会・１９８２、５・東京）によれ
ば、オーステナイト化温度内で加工すれば靱性は圧下率
の増加と共に向上し、組織観察した結果、γプールの消
滅に起因する延性の増加が原因と見られること、さらに
オーステナイト化温度とオーステンパー温度の両域で加
工した試料は、圧下率の増加と共に靱性が増加し、圧下
率が約２０％で最高値を示した後低下することを報告し
ている。Although some experimental reports have been found on the workability of ductile cast iron pipes at high temperatures, a part of them is cited as "Hydraulic heat treatment on mechanical properties of spheroidal graphite cast iron" by Shinya Yamada et al. According to "Effects of the Castings of Japan" (101st Lecture Meeting, 1982, 5, Tokyo), the toughness was improved with the increase of the rolling reduction when processed within the austenitizing temperature. It is thought that the increase in ductility due to disappearance is the cause. Further, the samples processed at both the austenitizing temperature and the austempering temperature increase the toughness as the rolling reduction increases, and the rolling reduction reaches the maximum value at about 20%. It has been reported that it will decrease after that.

【００１８】エル・エー・ノイメア他の「ダクタイル鋳
鉄の熱間圧延、鍛造の実験」（アメリカ合衆国鉱山局研
究報告）（L.A.Neumeier et−Experiments in Hot-Roll
ingand Forging of Ductile Cast Iron−Report of In
vestigations ・U.S.BUREAUof MINES 8448）によれば１
９５０°Ｆでは７０％の圧下率（高さ）で僅か１試料だ
けに亀裂があり、１７５０°Ｆでは３個（うち１個は重
大）、１５５０°Ｆでは１０個のうち５個に亀裂が認め
られた。しかし、鍛造中にも当然温度の低下が伴うから
再加熱を施さない限り１７５０°Ｆにおける７０％圧下
率の鍛造性は若干低下する。１５５０°Ｆにおける鍛造
で最も深刻な亀裂の生じた３試料は０．４％のＮｉを含
み、一方、無傷であった２試料は銑鉄の配合がなかっ
た。１７５０°Ｆで亀裂の入った３個のうち２個はＮｉ
を含み、この試料は１９５０°Ｆで亀裂の入った唯一の
試料でもある。Ｎｉ以外でオーステナイト内へ固溶され
る他の成分の影響は認められなかった。Ｓｉはオーステ
ナイトに固溶され強力な黒鉛化成分であるから低温にお
ける鍛造性の向上に貢献する。その他、Ｍｎ，Ｓ，Ｐの
影響などの影響を報告している。このような従来技術の
成分的な、また成形温度に関する研究報告は詳細に検討
して最適の鍛造条件を選定することがより優れた鍛造成
形を実施するうえで有効であることは言うまでもない。L. A. Noumea et al., "Experiments on hot rolling and forging of ductile cast iron" (Ministry of the United States Research Report) (LANeumeier et-Experiments in Hot-Roll)
ingand Forging of Ductile Cast Iron−Report of In
vestigations ・ 1 according to USBUREAU of MINES 8448)
At 950 ° F there was only one sample cracking at 70% reduction (height), at 1750 ° F there were 3 cracks (1 of which was severe) and at 1550 ° F there were 5 cracks out of 10. Admitted. However, since the temperature is naturally lowered during forging, the forgeability of 70% reduction at 1750 ° F is slightly reduced unless reheating is performed. The three most severely cracked samples at 1550 ° F forged contained 0.4% Ni, while the two intact samples had no pig iron formulation. Two of the three cracked at 1750 ° F were Ni
, Which is also the only sample that cracked at 1950 ° F. Other than Ni, no influence of other components dissolved in austenite was observed. Since Si is a solid solution in austenite and is a strong graphitizing component, Si contributes to improvement in forgeability at low temperatures. In addition, the effects such as Mn, S, and P are reported. Needless to say, it is effective to conduct a detailed study on the component and forming temperature of the prior art and to select the optimum forging condition in order to perform better forging.

【００１９】図１（Ｂ）は加熱したダクタイル鋳鉄管Ｐ
の挿口３のうち、突条３１を形成すべき長さを残して管
軸と平行位置を保ったままで横型鍛造プレスのクランプ
ダイス４１が両側（図の上下）から管軸Ｏと直角方向に
移動して管を全周から抱持し圧接して固定した状態であ
る。次に図（Ｃ）のように所定の挿口突条の形状を転写
した切欠き４３を切り込んだスライディングマンドレル
４２を管軸方向と平行にスライドして管の挿口先端から
接近し、ついに材料に到達した後は小径円筒部４４はダ
クタイル鋳鉄管Ｐの内面へ嵌入して前記のクランプダイ
ス４１とで管体を挾圧し、管肉と衝き当る傾斜面４５は
変形を強制しながら前進して切欠き４３の形状通りの形
状に成形する。スライディングマンドレル４２の前進は
傾斜面４５の端部となる先端面４６がクランプダイス４
１の側面４７に会合して停止し、この位置が下死点とな
る。図（Ｄ）は成形を完了したマンドレルが水平に移動
してダクタイル鋳鉄管Ｐから離脱し、一方、全周を被覆
して拘束していたクランプダイス４１も直角方向に上下
に離脱し、成形したダクタイル鋳鉄管Ｐを開放した状態
である。FIG. 1B shows a heated ductile cast iron pipe P.
The clamp die 41 of the horizontal forging press is moved in the direction perpendicular to the pipe axis O from both sides (upper and lower in the figure) while keeping the position parallel to the pipe axis while leaving the length for forming the ridge 31 in the insertion opening 3 of FIG. It is in a state of moving, holding the tube from the entire circumference, and pressing and fixing it. Next, as shown in FIG. 3C, a sliding mandrel 42 having a notch 43 formed by transferring the shape of a predetermined insertion opening ridge is slid in parallel with the pipe axis direction to approach from the tip of the insertion end of the pipe, and finally the material. After reaching, the small-diameter cylindrical portion 44 is fitted into the inner surface of the ductile cast iron pipe P, and the clamp die 41 presses the pipe body, and the inclined surface 45 that collides with the pipe meat moves forward while forcing deformation. The notch 43 is molded into the same shape as that of the notch 43. When the sliding mandrel 42 is advanced, the tip end surface 46, which is the end of the inclined surface 45, is clamped by the clamp die 4.
It comes to the side 47 of 1 and stops, and this position becomes the bottom dead center. In the figure (D), the mandrel which has completed the molding moves horizontally and separates from the ductile cast iron pipe P, while the clamp die 41 that covers and restrains the entire circumference also separates vertically in the vertical direction and molds. The ductile cast iron pipe P is open.

【００２０】図３は鍛造成形の別の実施形態を示したも
のであり、縦向けに受圧台５７の上へ載置したダクタイ
ル鋳鉄管Ｐの内部へマンドレル５１を挿通し、水平方向
に滑動する下金型５２を移動して外周面を拘束して固定
し、その下金型５２の上面５３から形成すべき挿口突条
に相当する長さの端部だけを外部に露呈させる。成形用
の上金型５４はマンドレル５１の外周面に添って降下
し、その切欠き５５が挿口３の管肉に衝き当って押圧し
て変形する。上金型５４の降下が成形作用と共に続き下
金型の上面５３に会合して停止する。FIG. 3 shows another embodiment of forging, in which the mandrel 51 is inserted into the inside of the ductile cast iron pipe P which is vertically mounted on the pressure receiving base 57, and is slid horizontally. The lower die 52 is moved to constrain and fix the outer peripheral surface of the lower die 52, and only the end portion having a length corresponding to the insertion protrusion to be formed from the upper surface 53 of the lower die 52 is exposed to the outside. The upper mold 54 for molding descends along the outer peripheral surface of the mandrel 51, and the notch 55 hits the tube meat of the insertion port 3 and presses it to deform it. The lowering of the upper mold 54 continues with the molding action and meets the upper surface 53 of the lower mold to stop.

【００２１】クランプダイスの熱間成形は液圧の鍛造プ
レスが好適である。挿口突条の成形は全周に亘る塑性変
形であり、一種の据え込み鍛造と言えるから強力な押圧
力を継続的に加えることが必要であり、機械式のクラン
クプレスより適当である。ダクタイル鋳鉄管の口径によ
って必要な能力は変わるが、口径１００ｍｍのダクタイ
ル鋳鉄管を対象とする場合には、クランプダイスを作動
するクランプシリンダの能力は５０〜１００Ｔ、また、
マンドレルを作動するメインシリンダの能力は２００Ｔ
で正常な成形をすることが確認されたが、なお、鍛造プ
レスの形態については検討する余地がある。鍛造プレス
の概略のフローを図４に例示するが、比較的少量の作動
油（または作動水でもよい）を循環する貯槽７と小能力
の加圧ポンプ７１で対応できるようにアキュムレータ７
２を具え、逆止弁７３、バイパス弁７４を管路に介装し
た油圧回路を採用している。For hot forming of the clamp die, a hydraulic forging press is suitable. The molding of the spigot ridge is a plastic deformation over the entire circumference, and since it can be said that it is a kind of upset forging, it is necessary to continuously apply a strong pressing force, which is more suitable than a mechanical crank press. The required capacity varies depending on the diameter of the ductile cast iron pipe, but when targeting a ductile cast iron pipe with a diameter of 100 mm, the capacity of the clamp cylinder that operates the clamp die is 50 to 100T, and
The capacity of the main cylinder that operates the mandrel is 200T.
Although it was confirmed that the normal molding was carried out, the form of the forging press still has room for consideration. A schematic flow of the forging press is illustrated in FIG. 4, but the accumulator 7 is provided so that the storage tank 7 that circulates a relatively small amount of hydraulic oil (or hydraulic water may be used) and the pressurizing pump 71 with a small capacity.
2, a hydraulic circuit in which a check valve 73 and a bypass valve 74 are provided in a pipe line is adopted.

【００２２】[0022]

【発明の効果】本発明は以上に述べたようにダクタイル
鋳鉄管の工場生産の段階ですべての管種に対応した挿口
突条を成形加工し、離脱防止の機能をすべての管路にそ
なえたいという最近の耐震性の深刻なニーズに応えるこ
とができる。また、現に生産中のダクタイル鋳鉄管に留
まらず、既に在庫中の製品についても容易に実施して耐
震性を新たに付与できるから、全国の自治体からの過大
な要求に対しても即座に応答できる高生産性、量産体制
を可能とする効果が著しい。また、この効果は経済的な
利点とも結び付くから、物心両面において得られる膨大
なメリットに比べて、生産コストの高騰は受忍の限度内
に含まれると解することが妥当である。請求項２に係る
効果としては、エネルギーコストの低減という見地で当
然期待される効果が得られるし、請求項３と請求項４に
ついては一概に優劣が決められないが、成形加工に要す
るストロークの割りには製品である鋳鉄管が長大である
から、設備を設置する位置や専用面積、製品の搬入、排
出などの点から見れば横型の方が有利である場合が多い
のではないか。しかし、あらかじめマンドレルを管内に
挿通して挟持した上で管肉に外圧を掛ける竪型の方式
も、欠陥の防止、品質の向上の点では看過できないメリ
ットを生む場合も考えられるから、今後なお、研究の余
地が残されている。As described above, according to the present invention, at the stage of the factory production of ductile cast iron pipes, the insertion protrusions corresponding to all pipe types are formed and processed, and the function of preventing separation is provided to all pipe lines. It can meet the recent serious needs for earthquake resistance. In addition, it is possible to add new earthquake resistance by easily implementing products that are already in stock, not limited to the ductile cast iron pipes that are currently being produced, so it is possible to immediately respond to excessive demands from local governments nationwide. The effect of enabling high productivity and mass production is remarkable. In addition, this effect is also associated with economic advantages, so it is appropriate to understand that the rise in production costs is within the permissible limits, as compared to the enormous merits obtained in both physical and mental aspects. As the effect according to claim 2, the effect naturally expected from the viewpoint of energy cost reduction can be obtained, and the superiority and inferiority cannot be unconditionally determined for claim 3 and claim 4, but the stroke required for the molding process The cast iron pipes, which are products, are relatively long, so the horizontal type is often more advantageous in terms of the location where equipment is installed, the dedicated area, and the loading and unloading of products. However, the vertical method in which the mandrel is inserted through the tube in advance and clamped and then the external pressure is applied to the tube meat may also bring advantages that cannot be overlooked in terms of preventing defects and improving quality, so in the future, There is room for research.

【図面の簡単な説明】[Brief description of drawings]

【図１】本発明に係る製造工程の実施形態を（Ａ）〜
（Ｄ）の一部縦断正面図によって例示する。FIG. 1 shows an embodiment of a manufacturing process according to the present invention (A).
This is illustrated by a partially longitudinal front view of (D).

【図２】本発明の実施に使用する加熱装置の一形態を示
す配置図（Ａ）と制御方法の関係を示す図（Ｂ）であ
る。FIG. 2 is a layout diagram (A) showing an embodiment of a heating device used for implementing the present invention and a diagram (B) showing a relationship between control methods.

【図３】本発明の別形態の成形方法を示す縦断正面図で
ある。FIG. 3 is a vertical sectional front view showing a molding method according to another embodiment of the present invention.

【図４】本発明の実施に使用する鍛造プレスのフローの
一形態である。FIG. 4 is a form of a flow of a forging press used for carrying out the present invention.

【図５】従来技術（ＪＩＳ規格）の縦断正面図である。FIG. 5 is a vertical sectional front view of a conventional technique (JIS standard).

【図６】スリップ・オン・タイプの標準的な縦断正面図
である。FIG. 6 is a standard vertical sectional front view of a slip-on type.

【図７】スリップ・オン・タイプに係る従来技術の一例
を示す縦断正面図(Ａ）と挿口リングの縦断正面図
（Ｂ）と結合ピースの縦断正面図（Ｃ）である。FIG. 7 is a vertical sectional front view (A) showing an example of a conventional technique related to a slip-on type, a vertical sectional front view (B) of an insertion ring, and a vertical sectional front view (C) of a connecting piece.

【図８】別のスリップ・オン・タイプに係る従来技術の
縦断正面図である。FIG. 8 is a vertical cross-sectional front view of a conventional technique related to another slip-on type.

【符号の説明】[Explanation of symbols]

１ 受口 ２ ロックリング ３ 挿口 ４ 横型鍛造プレス ５ 竪型鍛造プレス ６ 高周波加熱装置 11 ロックリング収容溝 31 挿口突条 41 クランプダイス 42 スライディングマンドレル 43 切欠き 51 マンドレル 52 下金型 53 上面 54 上金型 55 切欠き 56 下面 57 受圧台 61 加熱コイル 62 高周波発振器 Ｐ ダクタイル鋳鉄管 1 Receptacle 2 Lock ring 3 Insert 4 Horizontal type forging press 5 Vertical type forging press 6 High frequency heating device 11 Lock ring accommodating groove 31 Insertion ridge 41 Clamping die 42 Sliding mandrel 43 Notch 51 Mandrel 52 Lower die 53 Upper surface 54 Upper mold 55 Notch 56 Lower surface 57 Pressure receiving table 61 Heating coil 62 High frequency oscillator P Ductile cast iron pipe

Claims (4)

【特許請求の範囲】[Claims] 【請求項１】 ダクタイル鋳鉄管の受口１の内周面に刻
設したロックリング収容溝１１に装着したロックリング
２と、継合するダクタイル鋳鉄管の挿口３の先端に突設
した突条３１が係合して両管の離脱を防止するダクタイ
ル鋳鉄管の離脱防止管継手において、ダクタイル鋳鉄管
Ｐの全部、または少なくとも挿口３を最高でダクタイル
鋳鉄材の固相線より８０〜１００℃低い鍛造成形可能な
温度まで加熱昇温し、ダクタイル鋳鉄管Ｐの外周面のう
ち、挿口突条３１を形成すべき長さの端部を残して全面
より囲繞圧迫して固定し、該露呈した端部へ所定の挿口
突条３１の断面形状を転写して切欠いた環状の金型を管
軸Ｏと同軸線上で移動しつつ、該切欠きに倣う据え込み
鍛造を行なうことを特徴とするダクタイル鋳鉄管の離脱
防止管継手の製造方法。1. A projection formed at a tip of a lock ring 2 fitted in a lock ring housing groove 11 formed in an inner peripheral surface of a receptacle 1 of a ductile cast iron pipe, and a tip of an insertion port 3 of the ductile cast iron pipe to be joined. In the detachment prevention pipe joint of the ductile cast iron pipe in which the strip 31 is engaged to prevent the detachment of both pipes, all of the ductile cast iron pipe P, or at least the insertion port 3 is at most 80 to 100 from the solidus line of the ductile cast iron material. The temperature of the ductile cast iron pipe P is increased by heating to a temperature that allows forging at a low temperature of ℃, and is fixed by surrounding the entire surface of the ductile cast iron pipe P, leaving the end portion of the length at which the insertion ridge 31 should be formed. Characterized by upsetting forging that follows the notch while moving the notched annular die on the coaxial line with the pipe axis O by transferring the cross-sectional shape of the predetermined insertion opening projection 31 to the exposed end portion. To manufacture a pipe joint for preventing separation of ductile cast iron pipes Law. 【請求項２】 請求項１において、ダクタイル鋳鉄管Ｐ
の加熱のために挿口３の外周面上を巻き回した加熱コイ
ル６１を励磁して誘起する渦電流で加熱する高周波加熱
装置６を使用することを特徴とするダクタイル鋳鉄管の
離脱防止管継手の製造方法。2. The ductile cast iron pipe P according to claim 1,
For removing the ductile cast iron pipe by using a high-frequency heating device 6 for exciting a heating coil 61 wound on the outer peripheral surface of the insertion port 3 to heat the same with an eddy current induced. Manufacturing method. 【請求項３】 請求項１または２において、ダクタイル
鋳鉄管挿口の据え込み鍛造が横型の鍛造プレス４による
ものであり、挿口３の外周面を成形すべき挿口突条３１
の長さに相当する端部を残して二つ割りの環状体である
クランプダイス４１を作動して全面から水平に挟持して
固定し、該露呈した端部へ水平方向に滑動するスライデ
ィングマンドレル４２を移動し、該スライディングマン
ドレル４２に刻設した挿口突条３１と同形の切欠き４３
の前進と共に所望の形状に成形することを特徴とするダ
クタイル鋳鉄管の離脱防止管継手の製造方法。3. The upset forging of the ductile cast iron pipe insertion opening according to claim 1 or 2, wherein the upsetting forging is performed by a horizontal forging press 4, and the outer peripheral surface of the insertion opening 3 is to be formed.
The clamp die 41, which is an annular body divided into two parts, is actuated to leave an end corresponding to the length of the above, and is horizontally clamped and fixed from the entire surface, and the sliding mandrel 42 that slides horizontally to the exposed end is moved. Then, a notch 43 having the same shape as the insertion ridge 31 formed on the sliding mandrel 42 is formed.
A method for manufacturing a pipe joint for preventing separation of a ductile cast iron pipe, characterized in that the pipe joint is formed into a desired shape with the advance of the. 【請求項４】 請求項１または２において、ダクタイル
鋳鉄管挿口の据え込み鍛造が竪型の鍛造プレス５による
ものであり、受圧台５７の上面へ管軸Ｏを垂直に載置し
たダクタイル鋳鉄管Ｐの中へ円筒状のマンドレル５１を
嵌合すると共に、挿口３の先端における突条３１の所定
長さを残してその他の外周面を囲繞する下金型５２を前
記マンドレル５１の軸線と直角方向から挾圧して管体を
固定し、該下金型５２の上方でマンドレルの外周面上に
滑動自在に外嵌する上金型５４を降下して下金型５２の
上面５３から露呈する前記挿口の先端に達し、上金型５
４に切り込んだ所定形状を転写した切欠き５５が接触す
る管体を押圧して塑性変形を加えながら降下を続け、上
金型５４の下面５６と下金型５２の上面５３とが会合し
て停止することを特徴とするダクタイル鋳鉄管の離脱防
止管継手の製造方法。4. The ductile cast iron pipe as set forth in claim 1 or 2, wherein the upset forging of the ductile cast iron pipe inlet is performed by a vertical forging press 5, and the pipe axis O is vertically mounted on the upper surface of the pressure receiving base 57. A cylindrical mandrel 51 is fitted into the pipe P, and a lower die 52 that surrounds the other outer peripheral surface while leaving a predetermined length of the protrusion 31 at the tip of the insertion port 3 is used as the axis of the mandrel 51. The tube body is fixed by pressing it in a right angle direction, and the upper die 54, which is slidably fitted over the outer peripheral surface of the mandrel above the lower die 52, is lowered to be exposed from the upper surface 53 of the lower die 52. Reaching the tip of the insertion slot, the upper die 5
The notch 55 having the predetermined shape cut in 4 presses the tube body in contact with the notch 55 and continues descending while applying plastic deformation, and the lower surface 56 of the upper mold 54 and the upper surface 53 of the lower mold 52 meet. A method for manufacturing a pipe joint for preventing separation of a ductile cast iron pipe, characterized by stopping.