JP6165478B2 - Recessed steel pipe joint, bonded steel pipe, and method of joining steel pipes - Google Patents
Recessed steel pipe joint, bonded steel pipe, and method of joining steel pipes Download PDFInfo
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Description
本発明は、建築構造物の基礎杭、地盤改良、山岳トンネルや擁壁の補強工事などに使用される窪み付き鋼管の機械式継手、その継手を用いて接合された接合鋼管及び鋼管の接合方法に関する。 The present invention relates to a mechanical joint of a hollow steel pipe used for foundation pile of a building structure, ground improvement, mountain tunnel or retaining wall, a jointed steel pipe joined using the joint, and a method of joining the steel pipe About.
建築構造物の基礎杭工事、地盤改良、山岳トンネルや擁壁の補強工事には、安価で、かつ信頼性の高い材料および工法が求められている。例えば、特許文献１には、地盤改良や土木建築構造物の基礎として用いられる杭の支持力を向上させる方法として、杭と地盤との間に生じる摩擦力を向上させるために、鋼管表面に窪みをつけた鋼管が開示されている。また、特許文献２には、山岳トンネル補強工事において、セメント系あるいはレジン系などの固結材を用いて地山との付着力を向上することを目的として、鋼管表面にらせん状の凹部を有する鋼管、縞状に凸部と凹部を有する鋼管を用いる工法が開示されている。
For building foundation pile construction, ground improvement, mountain tunnel and retaining wall reinforcement work, inexpensive and reliable materials and construction methods are required. For example, in
さらに、特許文献３には、複数の地山補強用鋼管を直列に連結させて打設して地山を補強する工法として、鋼管端部の外径が拡径され、かつその内周面に雌ねじ部が形成されるとともに、他端部の外周面に雄ねじ部が形成された継手を有する地山補強工法が開示されている。また、特許文献４には、鋼管端部の外径が縮径され、かつその外周面に雄ねじ部が形成されるとともに、他端部の内周面に雌ねじが形成された継手を有する地山補強工法が開示されている。
Furthermore, in
建築構造物の基礎杭工事、地盤改良、山岳トンネルや擁壁の補強工事における現場施工時の接合で適用される効率的な機械式継手には、上記に示したように鋼管に直接加工する方式や、あらかじめ加工した継手を溶接、摩擦圧接、液相拡散接合などにより、管本体に取り付ける方式がある。特許文献５に示すように、摩擦圧接は継手の信頼性が高いことから自動車部品などに使用されている。
Efficient mechanical joints that are applied in the field construction for foundation pile construction, ground improvement, mountain tunnel and retaining wall reinforcement work for building structures are directly processed into steel pipes as shown above. In addition, there is a method of attaching a pre-processed joint to the pipe body by welding, friction welding, liquid phase diffusion bonding, or the like. As shown in
上記特許文献１に記載の鋼管および複合杭においては、窪みにより固化部材に対する十分な付着力が確保される。ただし、現場施工において、機械式継手により窪み付き鋼管を効率的に連結する方法として、例えば、特許文献３、あるいは特許文献４に示すように、鋼管端部に、直接、ネジ切り加工する方法がある。しかしながら、窪み付き鋼管の表面には連続的に凹みがあるので、ネジ切り加工するためには窪み付き鋼管の鋼管厚みを厚くする必要があることから、継手を含む鋼管全体の重量が大きくなり、経済性の観点から課題があった。
In the steel pipe and the composite pile described in
一方、あらかじめ、ネジ切り加工した厚肉の鋼管を窪み付き鋼管と溶接する方法も考えられる。しかしながら、窪み付き鋼管は低コスト化の観点から、合金元素の添加量が少なくなっており、また、ネジ切り加工した鋼管よりも厚みが薄いため、アーク溶接時の溶接熱影響部の軟化が大きく、継手性能（引張強度、曲げ強度）が低下するという課題があった。 On the other hand, a method of welding a thick-walled steel pipe that has been threaded in advance to a steel pipe with a recess is also conceivable. However, from the viewpoint of cost reduction, hollow steel pipes have less alloying elements added and are thinner than threaded steel pipes, so the heat affected zone during arc welding is greatly softened. There was a problem that joint performance (tensile strength, bending strength) was lowered.
そこで、上記事情に鑑み、本発明の目的は、窪み付き鋼管の鋼管厚みを厚くすることなく、優れた継手強度を発揮出来る窪み付き鋼管継手を提供することにある。 Therefore, in view of the above circumstances, an object of the present invention is to provide a hollow steel pipe joint that can exhibit excellent joint strength without increasing the thickness of the hollow steel pipe.
本発明の要旨は、以下の通りである。
（１）継手用鋼管と、鋼管表面に窪みが形成された窪み付き鋼管とが摩擦圧接により接合され、前記窪み付き鋼管が、質量％で、Ｃ ：０．０５〜０．２０、Ｓｉ：０．６以下、Ｍｎ：０．５〜２．０、Ｐ：０．０３以下、Ｓ：０．０３以下、Ａｌ：０．０５以下、Ｎ：０．００１〜０．００６、Ｏ：０．００６以下を含有し、残部が鉄および不可避的不純物からなり、かつ、下記（式１）で定義されるＣＥ値が０．１５〜０．４５、かつ、引張強度が４００Ｎ／ｍｍ ２ 以上であることを特徴とする窪み付き鋼管継手。
ＣＥ＝Ｃ＋Ｓｉ／２４＋Ｍｎ／６＋Ｎｉ／４０＋Ｃｒ／５＋Ｍｏ／４＋Ｖ／１４・・・（式１）
（２）前記継手用鋼管の肉厚が前記窪み付き鋼管の肉厚よりも大きいことを特徴とする（１）記載の窪み付き鋼管継手。
（３）前記継手用鋼管の外径と前記窪み付き鋼管の外径が同じであることを特徴とする（２）記載の窪み付き鋼管継手。
（４）前記窪み付き鋼管における摩擦圧接部近傍の最軟化部の硬度と、当該窪み付き鋼管の母材硬度との硬度差が１５％以下であることを特徴とする（１）乃至（３）のいずれかに記載の窪み付き鋼管継手。
（５）前記窪み付き鋼管が、質量％で、さらに、Ｎｂ：０．００３〜０．０５、Ｔｉ：０．００３〜０．０３０、Ｃｒ：０．０５〜０．２０のうち一種または二種以上を含有することを特徴とする（１）乃至（４）のいずれかに記載の窪み付き鋼管継手。
（６）前記窪み付き鋼管が、ディンプル鋼管あるいは段付き鋼管であることを特徴とする（１）乃至（５）のいずれかに記載の窪み付き鋼管継手。
（７）継手用鋼管と、鋼管表面に窪みが形成された窪み付き鋼管とが摩擦圧接により接合された窪み付き鋼管継手と、表面に窪みが形成されていない他の鋼管とを有し、前記窪み付き鋼管継手の継手用鋼管と、前記他の鋼管とが機械加工により接合されたことを特徴とする接合鋼管。
（８）継手用鋼管と、鋼管表面に窪みが形成された窪み付き鋼管とが摩擦圧接により接合された窪み付き鋼管継手を少なくとも２本有し、前記窪み付き鋼管継手の継手用鋼管同士が機械加工により接合されたことを特徴とする接合鋼管。
（９）前記継手用鋼管の肉厚が前記窪み付き鋼管の肉厚よりも大きいことを特徴とする（７）乃至（８）のいずれかに記載の接合鋼管。
（１０）前記継手用鋼管の外径と前記窪み付き鋼管の外径が同じであることを特徴とする（９）記載の接合鋼管。
（１１）前記窪み付き鋼管における摩擦圧接部近傍の最軟化部の硬度と、当該窪み付き鋼管の母材硬度との硬度差が１５％以下であることを特徴とする（７）乃至（１０）のいずれかに記載の接合鋼管。
（１２）前記窪み付き鋼管が、質量％で、Ｃ ：０．０５〜０．２０、Ｓｉ：０．６以下、Ｍｎ：０．５〜２．０、Ｐ：０．０３以下、Ｓ：０．０３以下、Ａｌ：０．０５以下、Ｎ：０．００１〜０．００６、Ｏ：０．００６以下を含有し、残部が鉄および不可避的不純物からなり、かつ、下記（式１）で定義されるＣＥ値が０．１５〜０．４５、かつ、引張強度が４００Ｎ／ｍｍ ２ 以上であることを特徴とする（７）乃至（１１）のいずれかに記載の接合鋼管。
ＣＥ＝Ｃ＋Ｓｉ／２４＋Ｍｎ／６＋Ｎｉ／４０＋Ｃｒ／５＋Ｍｏ／４＋Ｖ／１４・・・（式１）
（１３）前記窪み付き鋼管が、質量％で、さらに、Ｎｂ：０．００３〜０．０５、Ｔｉ：０．００３〜０．０３０、Ｃｒ：０．０５〜０．２０のうち一種または二種以上を含有することを特徴とする（１２）記載の接合鋼管。
（１４）前記窪み付き鋼管が、ディンプル鋼管あるいは段付き鋼管であることを特徴とする（７）乃至（１３）のいずれかに記載の接合鋼管。
（１５）継手用鋼管の一端部に機械加工を施し、当該継手用鋼管の他端に窪み付き鋼管を摩擦圧接により接合し、その後、前記機械加工を施した側に、予め機械加工を施した、表面に窪みが形成されていない他の鋼管を接合することを特徴とする鋼管の接合方法。
（１６）継手用鋼管の一端部に機械加工を施し、当該継手用鋼管の他端に窪み付き鋼管を摩擦圧接により接合した窪み付き鋼管継手を少なくとも２本製造し、その後、各接合鋼管の前記継手用鋼管の機械加工を施した側の端部同士を接合することを特徴とする鋼管の接合方法。
（１７）前記窪み付き鋼管が、質量％で、Ｃ ：０．０５〜０．２０、Ｓｉ：０．６以下、Ｍｎ：０．５〜２．０、Ｐ：０．０３以下、Ｓ：０．０３以下、Ａｌ：０．０５以下、Ｎ：０．００１〜０．００６、Ｏ：０．００６以下を含有し、残部が鉄および不可避的不純物からなり、かつ、下記（式１）で定義されるＣＥ値が０．１５〜０．４５の範囲にある鋼板を９００℃以上に加熱した後、管状に成形し、さらに鋼管表面に連続的に凹みを成形し、７００℃以上で成形工程を終了させて前記窪み付き鋼管を製造することを特徴とする（１５）乃至（１６）のいずれかに記載の鋼管の接合方法。
ＣＥ＝Ｃ＋Ｓｉ／２４＋Ｍｎ／６＋Ｎｉ／４０＋Ｃｒ／５＋Ｍｏ／４＋Ｖ／１４・・・（式１）
（１８）前記窪み付き鋼管が、質量％で、さらに、Ｎｂ：０．００３〜０．０５、Ｔｉ：０．００３〜０．０３０、Ｃｒ：０．０５〜０．２０のうち一種または二種以上を含有したことを特徴とする（１７）記載の鋼管の接合方法。
The gist of the present invention is as follows.
(1) A steel pipe for a joint and a steel pipe with a dent with a dent formed on the surface of the steel pipe are joined by friction welding, and the steel pipe with a dent is in mass%, C: 0.05 to 0.20, Si: 0 .6 or less, Mn: 0.5 to 2.0, P: 0.03 or less, S: 0.03 or less, Al: 0.05 or less, N: 0.001 to 0.006, O: 0.006 The following is contained, the balance is made of iron and inevitable impurities, the CE value defined by the following (Formula 1) is 0.15 to 0.45, and the tensile strength is 400 N / mm 2 or more. Recessed steel pipe joint.
CE = C + Si / 24 + Mn / 6 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14 (Formula 1)
(2) The hollow steel pipe joint according to (1), wherein the thickness of the joint steel pipe is larger than the thickness of the hollow steel pipe.
(3) The hollow steel pipe joint according to (2), wherein an outer diameter of the steel pipe for joint and an outer diameter of the steel pipe with the depression are the same.
(4) The hardness difference between the hardness of the softest portion near the friction welded portion in the steel pipe with the depression and the base material hardness of the steel pipe with the depression is 15% or less (1) to (3) A steel pipe joint with a recess according to any one of the above.
( 5 ) The hollow steel pipe is mass%, and further, one or two of Nb: 0.003 to 0.05, Ti: 0.003 to 0.030, and Cr: 0.05 to 0.20. The steel pipe joint with a recess according to any one of (1) to (4), characterized by containing the above.
( 6 ) The hollow steel pipe joint according to any one of (1) to ( 5 ), wherein the hollow steel pipe is a dimple steel pipe or a stepped steel pipe.
(7) comprises a steel tube for joint, and the steel pipe joint with a recess with depression depression in the steel pipe surface is formed steel tube and are joined by friction welding, and the other steel pipe depressions on the surface are not formed, the A jointed steel pipe, characterized in that a steel pipe for joint of a steel pipe joint with a recess and the other steel pipe are joined by machining.
( 8 ) It has at least two steel pipe joints with dents in which a steel pipe for joints and a steel pipe with dents with dents formed on the steel pipe surface are joined by friction welding, and the steel pipes for joints of the steel pipe joints with dents are machines Joined steel pipe characterized by being joined by processing.
(9) The bonded steel pipe according to any one of (7) to (8), wherein a thickness of the steel pipe for joint is larger than a thickness of the steel pipe with a recess.
(10) The bonded steel pipe according to (9), wherein an outer diameter of the joint steel pipe and an outer diameter of the hollow steel pipe are the same.
(11) The hardness difference between the hardness of the softest portion in the vicinity of the friction welded portion in the steel pipe with the depression and the base material hardness of the steel pipe with the depression is 15% or less (7) to (10) The bonded steel pipe according to any one of the above.
(12) The hollow steel pipe is in mass%, C: 0.05 to 0.20, Si: 0.6 or less, Mn: 0.5 to 2.0, P: 0.03 or less, S: 0 0.03 or less, Al: 0.05 or less, N: 0.001 to 0.006, O: 0.006 or less, the balance being iron and inevitable impurities, and defined by the following (formula 1) The bonded steel pipe according to any one of (7) to (11), wherein the CE value is 0.15 to 0.45 and the tensile strength is 400 N / mm 2 or more.
CE = C + Si / 24 + Mn / 6 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14 (Formula 1)
(13) The steel pipe with a dent is in mass%, and one or two of Nb: 0.003 to 0.05, Ti: 0.003 to 0.030, and Cr: 0.05 to 0.20. The bonded steel pipe according to (12), comprising the above.
(14) The bonded steel pipe according to any one of (7) to (13), wherein the hollow steel pipe is a dimple steel pipe or a stepped steel pipe.
( 15 ) One end of the joint steel pipe is machined, and a hollow steel pipe is joined to the other end of the joint steel pipe by friction welding, and then the machined side is pre-machined. A method for joining steel pipes, comprising joining other steel pipes having no depressions on the surface.
( 16 ) One end of the joint steel pipe is machined, and at least two hollow steel pipe joints are formed by joining the hollow steel pipe to the other end of the joint steel pipe by friction welding. A method of joining steel pipes, characterized in that the ends of the jointed steel pipes subjected to machining are joined together.
( 17 ) The hollow steel pipe is in mass%, C: 0.05 to 0.20, Si: 0.6 or less, Mn: 0.5 to 2.0, P: 0.03 or less, S: 0 0.03 or less, Al: 0.05 or less, N: 0.001 to 0.006, O: 0.006 or less, the balance being iron and inevitable impurities, and defined by the following (formula 1) After heating a steel plate having a CE value in the range of 0.15 to 0.45 to 900 ° C. or higher, it is formed into a tubular shape, and further a recess is formed on the surface of the steel pipe, and the forming step is performed at 700 ° C. or higher. The method for joining steel pipes according to any one of ( 15 ) to ( 16 ), wherein the steel pipe with recesses is manufactured by finishing.
CE = C + Si / 24 + Mn / 6 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14 (Formula 1)
( 18 ) The steel tube with a dent is in mass%, and further, one or two of Nb: 0.003 to 0.05, Ti: 0.003 to 0.030, and Cr: 0.05 to 0.20. The steel pipe joining method according to ( 17 ), which contains the above.
なお、本発明における「窪み付き鋼管継手」とは、継手用鋼管と窪み付き鋼管が接合されたものを指す。この「窪み付き鋼管継手」には、窪み付き鋼管の一端に継手用鋼管が接合されたものだけでなく、両端に継手用鋼管が接合されたものも含まれる。また、本発明における「接合鋼管」とは、窪み付き鋼管継手と他の鋼管とが接合された鋼管や、窪み付き鋼管継手同士が接合された鋼管を指す。 In addition, the "steel pipe joint with a dent" in this invention refers to what the steel pipe for joints and the steel pipe with a dent were joined. This “steel pipe joint with a recess” includes not only a steel pipe with a joint joined to one end of the steel pipe with a recess, but also a joint with a steel pipe for joint at both ends. In addition, the “joined steel pipe” in the present invention refers to a steel pipe in which a steel pipe joint with a recess and another steel pipe are joined, or a steel pipe in which steel pipe joints with a recess are joined together.
本発明によれば、建築構造物の基礎杭、地盤改良、山岳トンネルや擁壁の補強工事などに使用される窪み付き鋼管の厚さを厚くすることなく、他の鋼管を連結することができる。これにより、安価でかつ、優れた継手性能を得ることができる。その結果、建築土木構造物の安全性が向上する。 According to the present invention, other steel pipes can be connected without increasing the thickness of the hollow steel pipes used for foundation piles, ground improvement, mountain tunnels and retaining walls of building structures, etc. . Thereby, it is cheap and can obtain excellent joint performance. As a result, the safety of the architectural civil structure is improved.
以下に、本発明の窪み付き鋼管継手について詳細に説明する。 Below, the steel pipe joint with a hollow of this invention is demonstrated in detail.
現場施工において、窪み付き鋼管を効率的に連結するために、あらかじめ、ネジ切り加工した厚肉の継手用鋼管と窪み付き鋼管とを溶接する方法がある。しかしながら、窪み付き鋼管は低コスト化の観点から、合金元素の添加量が少なくなっており、また、ネジ切り加工した継手用鋼管よりも厚みが薄いため、アーク溶接で接合した場合、溶接熱影響部の軟化が大きくなり、継手性能が低下する。すなわち、施工後に継手用鋼管を含む窪み付き鋼管に荷重が作用した場合、鋼管厚みの薄い、窪み付き鋼管側の軟化部にひずみが集中することにより、窪み付き鋼管の軟化部から容易に破断し、継手性能が低下する。 In field construction, there is a method of welding a thickened steel pipe for a joint and a steel pipe with a recess in advance in order to efficiently connect the steel pipe with a recess. However, from the viewpoint of cost reduction, hollow steel pipes have a smaller amount of alloying elements and are thinner than threaded steel pipes for joints. The softening of the part increases, and the joint performance decreases. In other words, when a load is applied to a hollow steel pipe including a steel pipe for joints after construction, the strain concentrates on the softened part on the side of the hollowed steel pipe with a thin steel pipe, thereby easily breaking from the softened part of the hollowed steel pipe. , Joint performance will be reduced.
そこで、本願発明者らは、図１に示す通り、窪み付き鋼管２と継手用鋼管３を接合する際に摩擦圧接することを見出した。摩擦圧接であれば、アーク溶接に比較して短時間で接合することが可能となり、接合時に発生する熱もアーク溶接に比較して低くすることができる。このため、摩擦圧接部ＦＷＰの周囲の熱影響部の軟化を小さくすることができ、継手性能の低下を防ぐことが可能となる。
Therefore, the inventors of the present application have found that, as shown in FIG. 1, friction welding is performed when the
すなわち、本発明によれば、窪み付き鋼管２にネジ切り加工を施さずに継手用鋼管３を接合することが可能となるため、窪み付き鋼管２の鋼管厚みを厚くすることなく、優れた継手強度を有する窪み付き鋼管継手１を得ることができる。なお、図面では、窪み付き鋼管２の一例としてディンプル鋼管を図示している。ただし、窪み付き鋼管２は、ディンプル鋼管に限定されるものではなく、例えば段付き鋼管であっても良い。
That is, according to the present invention, since it becomes possible to join the
窪み付き鋼管継手１に鋼管表面に窪みが形成されていない他の鋼管４を接合する場合には、図２に示す通り、継手用鋼管３の肉厚を窪み付き鋼管２の肉厚よりも大きくしておくことが好ましい。そうすれば、窪み付き鋼管継手１の継手用鋼管３の一端部にネジ切り加工をすることが可能となり、同様にネジ切り加工された他の鋼管４を接合することができる。なお、継手用鋼管３と他の鋼管４を接合するためのネジ切り加工は、加工例の一例であって、鋼管同士を接合できれば他の機械加工を施しても良い。
When joining the other steel pipe 4 in which the hollow is not formed in the steel pipe surface to the steel pipe joint 1 with a hollow, as shown in FIG. 2, the thickness of the
このとき、継手用鋼管３と窪み付き鋼管２が同じ外径を有していることが好ましい。そうすれば、窪み付き鋼管継手１を用いて接合された接合鋼管に段差が生じないため、接合鋼管をスムーズに地盤に挿入することができる。これにより、建築構造物の基礎杭工事、地盤改良、山岳トンネルや擁壁の補強工事を効率的に行うことができる。
At this time, it is preferable that the
ただし、継手用鋼管３の肉厚が厚い場合には、摩擦圧接時に生ずる摩擦熱による温度上昇が緩やかになり、鋼管の溶融温度に到達するまでに時間がかかってしまう。この場合、鋼管が溶融温度に到達するまで摩擦圧接を続けるか、あるいは継手用鋼管３の回転速度を上げて温度上昇を促すことが必要となる。しかしながら、いずれにしても通常の摩擦圧接時よりも多くのエネルギーを投入することになるため、エネルギー効率が悪化してしまう。そのような場合には、図３に示す削り部５のように、摩擦圧接部ＦＷＰ近傍の継手用鋼管３の内周面を窪み付き鋼管２の肉厚に合わせて削ることが好ましい。そうすれば、エネルギー効率を落とすことなく、窪み付き鋼管２と継手用鋼管３を摩擦圧接により接合することができ、かつ、継手用鋼管３の摩擦圧接部ＦＷＰの反対側の端部にネジ切り加工等の機械加工を施すことができる。
However, when the thickness of the
また、窪み付き鋼管２の肉厚と継手用鋼管３の肉厚が異なる場合であって、かつ、外径も異なる場合には、図４に示す削り部６のように、継手用鋼管３の摩擦圧接部ＦＷＰ近傍の継手用鋼管３の外周面を窪み付き鋼管２の肉厚に合わせて削っても良い。この場合も、エネルギー効率の悪化を防ぐことができる。
When the thickness of the
上記の窪み付き鋼管継手１の説明では、窪み付き鋼管継手１に鋼管表面に窪みが形成されていない他の鋼管４を接合することとしたが、接合対象はこれに限定されるものではない。例えば、図５に示すように、窪み付き鋼管継手１を少なくとも２本製造し、窪み付き鋼管継手１同士を接合しても良い。この場合には、継手用鋼管３のネジ切り加工等の機械加工を施した側の端部同士を接合する。これにより、窪み付き鋼管２の鋼管厚みを厚くすることなく、継手用鋼管３を介して窪み付き鋼管２同士を接合することができる。
In the description of the steel pipe joint 1 with a dent described above, the other steel pipe 4 with no dent formed on the steel pipe surface is joined to the steel pipe joint 1 with a dent, but the joining target is not limited to this. For example, as shown in FIG. 5, at least two
以上に示した窪み付き鋼管継手１を用いれば、鋼管の表面形状に関わらず、複数の鋼管を連結することができる。例えば、図６に示すように、窪みが形成されていない他の鋼管４と窪み付き鋼管継手１を連結し、その窪み付き鋼管継手１と他の窪み付き鋼管継手１を連結することも可能である。このように窪み付き鋼管継手１を用いれば、様々な鋼管を連結することができ、連結の組み合わせは無数に存在する。 If the steel pipe joint 1 with a dent shown above is used, a some steel pipe can be connected irrespective of the surface shape of a steel pipe. For example, as shown in FIG. 6, it is also possible to connect the other steel pipe 4 in which the dent is not formed and the steel pipe joint 1 with the dent, and to connect the steel pipe joint 1 with the dent and the other steel pipe joint 1 with the dent. is there. Thus, if the steel pipe joint 1 with a dent is used, various steel pipes can be connected and there are countless combinations of connections.
また、本願発明者らは、窪み付き鋼管継手の継手性能をさらに向上させることについて鋭意検討した。 In addition, the inventors of the present application have earnestly studied to further improve the joint performance of the hollow steel pipe joint.
通常、摩擦圧接により接合された鋼管においては、熱影響部にある程度の軟化が生じる。軟化対策として、例えば、特許文献５には、ＮｂとＭｏを複合添加することにより、自動車部品に使用される高強度鋼管の熱影響部の軟化を抑制する製造方法が開示されている。
Usually, in a steel pipe joined by friction welding, a certain amount of softening occurs in the heat affected zone. As a countermeasure against softening, for example,
しかしながら、窪み付き鋼管継手の摩擦圧接部において、窪み付き鋼管側は厚みが薄いので、摩擦圧接時に投入された熱量が窪み付き鋼管側に滞留し、軟化しやすくなる。また、薄肉の窪み付き鋼管にＮｂとＭｏを複合添加した場合、摩擦圧接部で1300℃以上の高温に加熱された部分の硬さが著しく上昇し、割れが発生しやすくなるとともに継手のコストが増加する。そこで、本願発明者らは安価で、かつ摩擦圧接部の継手性能を向上させるためには、摩擦圧接部の最高硬さの上昇を抑制しつつ、窪み付き鋼管側の最軟化部と窪み付き鋼管母材との平均硬さの差を１５％以内にすることが好ましいことを見出した。 However, in the friction welded portion of the steel pipe joint with a recess, the thickness of the steel pipe with the recess is thin, so that the amount of heat input during the friction welding stays on the steel pipe side with the recess and is easily softened. In addition, when Nb and Mo are added in combination to a thin-walled hollow steel pipe, the hardness of the portion heated to a high temperature of 1300 ° C or higher at the friction welded portion is significantly increased, cracking is likely to occur, and the cost of the joint is reduced. To increase. Therefore, in order to improve the joint performance of the friction welded part, the inventors of the present application have reduced the maximum hardness of the friction welded part while suppressing the increase in the maximum hardness of the friction welded part and the softened part on the side of the recessed steel pipe and the steel pipe with the recessed part. It has been found that the difference in average hardness from the base material is preferably within 15%.
また、熱影響部の軟化を抑制するために合金添加量を増加させると、摩擦圧接後の硬さが著しく増加し、割れが発生しやすくなるとともに継手の鋼管のコストが増加してしまう。そこで、本願発明者らは、窪み付き鋼管の炭素当量および合金元素添加量を抑制し、かつ鋼管の製造において、鋼を９００℃以上１３５０℃以下に加熱した後、管状に成形し、さらに鋼管表面に連続的に凹みを成形し、７００℃以上で成形工程を終了して製造される４００Ｎ／ｍｍ２以上の引張強度を有する窪み付き鋼管を摩擦圧接することにより、摩擦圧接部の熱影響部の軟化が抑制され、優れた性能を有する継手が得られることを見出した。 Further, when the amount of alloy addition is increased in order to suppress softening of the heat affected zone, the hardness after friction welding is remarkably increased, cracking is likely to occur, and the cost of the steel pipe of the joint is increased. Therefore, the inventors of the present invention suppress the carbon equivalent of the hollow steel pipe and the amount of alloy element added, and in the production of the steel pipe, the steel is heated to 900 ° C. or higher and 1350 ° C. or lower, and then formed into a tubular shape. By continuously welding a hollow steel pipe having a tensile strength of 400 N / mm 2 or more, which is manufactured by continuously forming a dent and finishing the molding process at 700 ° C. or higher, the heat affected zone of the friction welded portion It has been found that softening is suppressed and a joint having excellent performance can be obtained.
また、本願発明者らは、窪み付き鋼管の化学成分を調整することや、一定条件下で窪み付き鋼管を製造することにより、窪み付き鋼管継手の継手性能をさらに向上させることが可能なことを見出した。以下、窪み付き鋼管の化学成分の限定理由について述べる。 In addition, the inventors of the present application can further improve the joint performance of a steel pipe joint with a recess by adjusting the chemical composition of the steel pipe with a recess or manufacturing a steel pipe with a recess under a certain condition. I found it. Hereinafter, the reason for limiting the chemical composition of the steel pipe with a recess will be described.
Ｃの下限０．０５％は、強度の確保ならびにＮｂ添加による析出硬化、結晶粒の微細化効果を発揮させるための最小量である。しかしＣ量が多過ぎると摩擦圧接部の硬さが著しく上昇し、割れが発生するので、上限を０．２０％とした。 The lower limit of 0.05% of C is a minimum amount for ensuring the strength, precipitation hardening by adding Nb, and effect of refining crystal grains. However, if the amount of C is too large, the hardness of the friction welded portion is remarkably increased and cracking occurs, so the upper limit was made 0.20%.
Ｓｉは脱酸や強度向上のため添加する元素であるが、多く添加すると摩擦圧接部の硬さが上昇し割れが発生するので、上限を０．６％とした。 Si is an element added for deoxidation and strength improvement, but if added in large amounts, the hardness of the friction welded portion increases and cracks occur, so the upper limit was made 0.6%.
Ｍｎは強度を確保する上で不可欠な元素であり、その下限は０．５％である。しかし、Ｍｎが多すぎると鋼の焼入性が増加して溶接性を低下させるので、上限を２．０％とした。 Mn is an element indispensable for securing strength, and its lower limit is 0.5%. However, if there is too much Mn, the hardenability of the steel increases and the weldability decreases, so the upper limit was made 2.0%.
本発明において、不可避的不純物であるＰ量を０．０３％以下とする。この主たる理由は、摩擦圧接部の性能をより一層向上させるためである。Ｐ量の低減は、連続鋳造スラブの中心偏析を低減させて、粒界破壊を防止させる。またＳ量を０．０３％以下とする。Ｓ量の低減は、延伸化したＭｎＳを低減して延靱性を向上させる効果がある。 In the present invention, the amount of P, which is an inevitable impurity, is set to 0.03% or less. The main reason for this is to further improve the performance of the friction welding portion. The reduction of the P amount reduces the center segregation of the continuously cast slab and prevents the grain boundary fracture. Further, the S amount is set to 0.03% or less. The reduction of the amount of S has the effect of improving the ductility by reducing the stretched MnS.
Ｎｂは結晶粒の微細化や析出硬化に寄与し、鋼の強靱化および熱影響部の軟化抑制の作用を有する。この効果を発揮させるための最小量として、その下限を０．００３％とした。しかし、Ｎｂ量が０．０５０％超えると、摩擦圧接部で割れが発生するので、その上限を０．０５０％とした。 Nb contributes to refinement of crystal grains and precipitation hardening, and has the effect of toughening steel and suppressing softening of the heat-affected zone. As a minimum amount for exhibiting this effect, the lower limit was set to 0.003%. However, if the Nb content exceeds 0.050%, cracks occur at the friction welded portion, so the upper limit was made 0.050%.
Ａｌは通常脱酸剤として鋼に含まれる元素で、組織の微細化にも効果を有する。しかしＡｌ量が０．０６％を超えるとＡｌ系非金属介在物が増加して割れが発生するので、その上限を０．０６％とした。 Al is an element usually contained in steel as a deoxidizer, and has an effect on refining the structure. However, if the Al content exceeds 0.06%, Al-based nonmetallic inclusions increase and cracks occur, so the upper limit was made 0.06%.
ＮはＴｉＮを形成してスラブ再加熱時および熱影響部のオ−ステナイト粒の粗大化を抑制して低温靱性を向上させる。しかし、多過ぎるとスラブ表面疵の原因となるので、その上限を０．００６％以下とした。 N forms TiN and suppresses the coarsening of the austenite grains at the time of slab reheating and in the heat-affected zone, thereby improving the low temperature toughness. However, too much will cause slab surface flaws, so the upper limit was made 0.006% or less.
Ｏ量の低減は鋼中の酸化物を少なくして、延靱性の改善に効果があるので、その上限を０．００６％以下とした。 Since the reduction of the amount of O reduces the amount of oxide in the steel and is effective in improving the ductility, the upper limit is made 0.006% or less.
さらにＴｉ、Ｃｒを添加する理由について説明する。基本成分にさらにこれらの元素を添加する主たる目的は、本発明鋼の特徴を損なうことなく、強度・低温靭性などの特性の向上をはかるためである。したがって、その添加量は自ら制限されるべき性質のものである。 Further, the reason for adding Ti and Cr will be described. The main purpose of adding these elements to the basic component is to improve the properties such as strength and low temperature toughness without impairing the characteristics of the steel of the present invention. Therefore, the amount of addition is a property that should be restricted by itself.
Ｔｉ添加は微細なＴｉＮを形成し、スラブ再加熱時および摩擦圧接部のオ−ステナイト粒の粗大化を抑制してミクロ組織を微細化し、低温靱性を改善する。このようなＴｉＮの効果を発現させるためには、最低０．００３％のＴｉ添加が必要である。しかしＴｉ量が多過ぎると、ＴｉＮの粗大化やＴｉＣによる析出硬化が生じ、低温靱性が低下するので、その上限を０．０３０％とした。 Addition of Ti forms fine TiN, suppresses coarsening of austenite grains during slab reheating and friction welding, refines the microstructure, and improves low-temperature toughness. In order to exhibit such an effect of TiN, at least 0.003% of Ti should be added. However, if the amount of Ti is too large, TiN coarsening and precipitation hardening due to TiC occur and the low-temperature toughness decreases, so the upper limit was made 0.030%.
Ｃｒは母材の強度増加や熱影響部の軟化抑制をさせる効果があり、この効果を発揮させるためには０．０５％以上の添加が必要である。しかし、多過ぎると摩擦圧接部の最高硬さが著しく上昇し、割れを発生させる。このためＣｒ量の上限は０．２％である。 Cr has the effect of increasing the strength of the base material and suppressing the softening of the heat-affected zone. In order to exhibit this effect, 0.05% or more must be added. However, when the amount is too large, the maximum hardness of the friction welded portion is remarkably increased and cracks are generated. For this reason, the upper limit of Cr amount is 0.2%.
さらに、下記（式１）で定義されるＣＥ値を０．１５〜０．４５の範囲に限定する。ＣＥ値が０．１５未満では十分な強度が得られない。またＣＥ値が０．４５を超えると、溶接性が低下し、割れが発生する。
ＣＥ＝Ｃ＋Ｓｉ／２４＋Ｍｎ／６＋Ｎｉ／４０＋Ｃｒ／５＋Ｍｏ／４＋Ｖ／１４・・・（式１）
Furthermore, the CE value defined by the following (formula 1) is limited to the range of 0.15 to 0.45. If the CE value is less than 0.15, sufficient strength cannot be obtained. On the other hand, when the CE value exceeds 0.45, the weldability is lowered and cracking occurs.
CE = C + Si / 24 + Mn / 6 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14 (Formula 1)
つぎに、窪み付き鋼管の製造条件の限定理由について説明する。 Below, the reason for limitation of the manufacturing conditions of the steel pipe with a dent is demonstrated.
本発明では、上記の成分を有する鋼を９００℃以上１３５０℃以下に加熱した後、管状に成形し、さらに鋼管表面に連続的に凹みを成形し、７００℃以上で成形工程を終了して窪み付き鋼管を製造する。このように製造した窪み付き鋼管は、摩擦圧接時の軟化部の低下度合いが少なく、優れた継手性能が得られる。 In the present invention, the steel having the above components is heated to 900 ° C. or more and 1350 ° C. or less, then formed into a tubular shape, further formed into a recess on the surface of the steel pipe, and the forming process is completed at 700 ° C. or more to form a recess. Manufactured steel pipes. The steel pipe with dents manufactured in this way has a low degree of lowering of the softened part at the time of friction welding, and excellent joint performance can be obtained.
鋼の加熱温度を９００℃以上とする理由は、オ−ステナイト域で合金元素を十分に溶体化させ、強度を向上させるためである。しかし加熱温度が１３５０℃を超えると、鋼板強度が著しく低下し、鋼管の成形ができなくなる。このため、加熱温度の上限は１３５０℃とした。 The reason why the heating temperature of the steel is set to 900 ° C. or higher is to sufficiently dissolve the alloy elements in the austenite region and improve the strength. However, when the heating temperature exceeds 1350 ° C., the strength of the steel sheet is remarkably lowered and the steel pipe cannot be formed. For this reason, the upper limit of heating temperature was 1350 degreeC.
さらに、鋼管表面に連続的に凹みを成形する際、７００℃以上で成形工程を終了する必要がある。凹みの成形を含めた鋼管の成形を７００℃以上で終了する理由は、摩擦圧接時の軟化を抑制するためである。７００℃未満で成形した場合、鋼管の強度が上昇し、窪み付き鋼管側の最軟化部と窪み付き鋼管母材の平均硬さの差が大きくなり、継手の性能が低下するためである。 Furthermore, when forming a dent continuously on the steel pipe surface, it is necessary to finish the forming process at 700 ° C. or higher. The reason for finishing the forming of the steel pipe including the forming of the dent at 700 ° C. or more is to suppress softening during the friction welding. This is because when the molding is performed at a temperature lower than 700 ° C., the strength of the steel pipe increases, the difference in average hardness between the most softened portion on the steel pipe side with the depression and the steel pipe base material with the depression becomes large, and the performance of the joint decreases.
なお、本実施形に係る窪み付き鋼管は、例えば、（１）成形ロールユニットにおいて、加熱された鋼板を丸めて管状に成形するとともに鋼板の端部同士を接合することにより鋼管を成形する方法、（２）加熱された丸ビレットを穿孔して管状に成形し、成形ロールで鋼管を定形する方法、において、突起部を表面に有する鋼管造形用ロールを鋼管の外表面に押圧することにより窪みを付与することにより製造される。 In addition, the hollow steel pipe according to the present embodiment is, for example, (1) a method of forming a steel pipe by rounding a heated steel sheet into a tubular shape and joining ends of the steel sheet in a forming roll unit, (2) In a method in which a heated round billet is perforated and formed into a tubular shape, and a steel pipe is shaped with a forming roll, a depression is formed by pressing a steel pipe forming roll having protrusions on the outer surface of the steel pipe. It is manufactured by giving.
摩擦圧接により窪み付き鋼管継手を製造する場合、窪み付き鋼管より厚みが厚く、かつ、機械加工を施した継手用鋼管を摩擦圧接により接合し、窪み付き鋼管側の最軟化部と窪み付き鋼管母材との平均硬さの差を１５％以内とする必要がある。機械加工した継手用鋼管を窪み付き鋼管よりも厚くする理由は、機械加工として例えばネジ切り加工を施した後の肉厚を確保するためである。また、窪み付き鋼管側の最軟化部と窪み付き鋼管母材の平均硬さの差がビッカース硬さで１５％以内とする理由は、摩擦圧接部の引張強度および曲げ強度を母材のそれと同等以上にするためである。 When manufacturing hollow steel pipe joints by friction welding, the steel pipe for joints, which is thicker than the hollow steel pipe and machined, is joined by friction welding, and the softened part on the hollow steel pipe side and the hollow steel pipe mother The difference in average hardness with the material needs to be within 15%. The reason why the machined steel pipe for the joint is made thicker than the steel pipe with a recess is to ensure the thickness after machining, for example, threading. The reason why the difference in average hardness between the softened part on the steel pipe side with the dent and the steel pipe base material with the dent is within 15% in terms of Vickers hardness is that the tensile strength and bending strength of the friction welded part are the same as that of the base material This is because of the above.
本発明の実施例について述べる。種々の成分を有する、厚さ３．２ｍｍ厚の鋼板を種々の条件で加熱、成形した後、直径（外径）７６．３ｍｍの４００Ｎ／ｍｍ２級以上の引張強度を有する窪み付き鋼管を製造した。また、ネジ切り加工を施した厚さ５．５ｍｍ、外径７６．３ｍｍの継手用鋼管と窪み付き鋼管を摩擦圧接して窪み付き鋼管継手を作成し、その性能を評価した。摩擦圧接部の硬さは、摩擦圧接部を含むサンプルを切り出した後、板厚中心において、窪み付き鋼管継手の長手方向にビッカース硬度計を用いて測定した。測定データは５点の平均値をとり代表データとした。 Examples of the present invention will be described. After a 3.2 mm thick steel plate having various components is heated and formed under various conditions, a steel tube with a recess having a diameter (outer diameter) of 76.3 mm and a tensile strength of 400 N / mm grade 2 or higher is manufactured. did. Moreover, the steel pipe joint with a hollow was produced by friction-welding the steel pipe for joints with the thickness of 5.5 mm which gave the threading process, and the outer diameter 76.3 mm, and the steel pipe with a hollow, and the performance was evaluated. The hardness of the friction welded part was measured using a Vickers hardness tester in the longitudinal direction of the steel pipe joint with a recess at the center of the plate thickness after cutting out a sample including the friction welded part. The measurement data was an average of 5 points and used as representative data.
本発明が規定する化学成分組成を有する本発明鋼Ｎｏ．１〜８、および、本発明の範囲から外れた条件を有する比較鋼Ｎｏ．９〜２３の化学成分組成、製造条件、継手引張強度を、それぞれ表１に示す。また、表１にそれぞれの母材からなる窪み付き鋼管の製造時の鋼板加熱温度、成形終了温度および諸性質を示す。なお、表１において、本発明の範囲から外れている条件または性質を示す欄に下線を引いた。 The present invention steel No. having the chemical composition defined by the present invention. Comparative Steel Nos. 1 to 8 and conditions outside the scope of the present invention. Table 1 shows the chemical composition, production conditions, and joint tensile strength of 9-23. Table 1 shows the steel plate heating temperature, forming end temperature, and various properties at the time of manufacturing the hollow steel pipe made of each base material. In Table 1, the columns indicating conditions or properties that are out of the scope of the present invention are underlined.
表１に示すように、本発明鋼であるＮｏ．１〜８の窪み付き鋼管継手は、優れた特性を有していた。これに対して、比較鋼Ｎｏ．９〜２３は、窪み付き鋼管の成分組成、鋼管の製造条件あるいは摩擦圧接部の最軟化部の硬さが適切でなく、いずれかの特性が劣っていた。
As shown in Table 1, no. The steel pipe joints with
Ｎｏ．９は窪み付き鋼管母材のＣ量が多いため、摩擦圧接部の硬さが著しく上昇し、割れが発生した。Ｎｏ．１０は窪み付き鋼管母材のＣ量が少ないため、摩擦圧接部の引張強度が低い。Ｎｏ．１１は窪み付き鋼管母材のＳｉ量が多いため、摩擦圧接部の硬さが著しく上昇し、割れが発生した。Ｎｏ．１２は窪み付き鋼管母材のＭｎ量が多いため、摩擦圧接部の硬さが著しく上昇し、割れが発生した。Ｎｏ．１３は窪み付き鋼管母材のＮｂ量が多すぎるため、摩擦圧接部で割れが発生した。Ｎｏ．１４は窪み付き鋼管母材のＡｌ量が多いため、鋼管母材部に割れが発生した。Ｎｏ．１５は窪み付き鋼管母材のＯ量が多いため、摩擦圧接部に割れが発生した。Ｎｏ．１６は窪み付き鋼管母材のＴｉ量が多すぎるため、摩擦圧接部で割れが発生した。Ｎｏ．１７は窪み付き鋼管母材のＣｒ量が多すぎるため、摩擦圧接部の最高硬さが高く、割れが発生した。 No. No. 9 had a large amount of C in the hollow steel pipe base material, so that the hardness of the friction welded part was remarkably increased and cracking occurred. No. No. 10 has a small amount of C in the hollow steel pipe base material, and hence the tensile strength of the friction welded portion is low. No. Since No. 11 had a large amount of Si in the hollow steel pipe base material, the hardness of the friction welded portion was remarkably increased and cracking occurred. No. No. 12 had a large amount of Mn in the hollow steel pipe base material, so that the hardness of the friction welded portion was remarkably increased and cracking occurred. No. Since No. 13 had too much Nb content of the hollow steel pipe base material, cracks occurred at the friction welding part. No. No. 14 has a large amount of Al in the hollow steel pipe base material, and therefore cracks occurred in the steel pipe base material part. No. Since No. 15 had a large amount of O in the hollow steel pipe base material, cracks occurred in the friction welding portion. No. In No. 16, since the amount of Ti in the hollow steel pipe base material was too large, cracks occurred at the friction welding portion. No. Since No. 17 had too much Cr in the hollow steel pipe base material, the maximum hardness of the friction welded portion was high, and cracking occurred.
Ｎｏ．１８はＣＥ値が大きいため、摩擦圧接部の最高硬さが高く、割れが発生した。Ｎｏ．１９はＣＥ値が低いため、十分な摩擦圧接部の引張強度が得られない。Ｎｏ．２０は鋼管製造時の鋼板の加熱温度が低いため、十分な強度が得られない。Ｎｏ．２１は鋼管製造時の鋼板の加熱温度が高いため、鋼管の成形ができない。Ｎｏ．２２は鋼管製造時の成形終了温度が低いため、鋼管母材の強度が著しく上昇し、窪み付き鋼管側の最軟化部と窪み付き鋼管母材の平均硬さの差が大きくなり、継手強度が低い。Ｎｏ．２３は窪み付き鋼管側の最軟化部と窪み付き鋼管母材の平均硬さの差が１５％を超えるため、引張強度が低い。 No. No. 18 had a large CE value, so the maximum hardness of the friction welded part was high, and cracking occurred. No. Since 19 has a low CE value, sufficient tensile strength of the friction welded portion cannot be obtained. No. No. 20 cannot obtain sufficient strength because the heating temperature of the steel sheet during the production of the steel pipe is low. No. No. 21 cannot form a steel pipe because the heating temperature of the steel sheet at the time of manufacturing the steel pipe is high. No. No. 22 has a low forming end temperature at the time of manufacturing the steel pipe, so that the strength of the steel pipe base material is remarkably increased, and the difference in average hardness between the softened part on the side of the steel pipe with the depression and the steel pipe base material with the depression becomes large, and the joint strength is reduced. Low. No. No. 23 has a low tensile strength because the difference in average hardness between the most softened portion on the steel pipe side with the depression and the steel pipe base material with the depression exceeds 15%.
以上のように、本発明で規定する条件のうち、いずれかの条件から外れると、優れた性能を有する窪み付き鋼管継手が得られないのに対し、本発明で規定する条件を満たすことにより、優れた継手性能を有する窪み付き鋼管継手が安定して製造できた。 As described above, out of any of the conditions defined in the present invention, a hollow steel pipe joint having an excellent performance cannot be obtained, whereas by satisfying the conditions defined in the present invention, A hollow steel pipe joint having excellent joint performance could be stably produced.
本発明は、建築構造物の基礎杭、地盤改良、山岳トンネルや擁壁の補強工事などに使用される窪み付き鋼管継手に適用できる。その結果、建築土木構造物の安全性が向上する。 INDUSTRIAL APPLICABILITY The present invention can be applied to a hollow steel pipe joint used for a foundation pile of a building structure, ground improvement, a mountain tunnel or a retaining wall reinforcement work, and the like. As a result, the safety of the architectural civil structure is improved.
１ 溶接鋼管継手
２ 窪み付き鋼管
３ 継手用鋼管
４ 鋼管
５ 削り部
６ 削り部
ＦＷＰ 摩擦圧接部
DESCRIPTION OF
Claims (18)
前記窪み付き鋼管が、
質量％で、Ｃ ：０．０５〜０．２０、Ｓｉ：０．６以下、Ｍｎ：０．５〜２．０、Ｐ：０．０３以下、Ｓ：０．０３以下、Ａｌ：０．０５以下、Ｎ：０．００１〜０．００６、Ｏ：０．００６以下を含有し、残部が鉄および不可避的不純物からなり、かつ、下記（式１）で定義されるＣＥ値が０．１５〜０．４５、かつ、引張強度が４００Ｎ／ｍｍ ２ 以上であることを特徴とする窪み付き鋼管継手。
ＣＥ＝Ｃ＋Ｓｉ／２４＋Ｍｎ／６＋Ｎｉ／４０＋Ｃｒ／５＋Ｍｏ／４＋Ｖ／１４・・・（式１） A fitting for steel pipes, with depression depression in the steel pipe surface is formed steel tube and are joined by friction welding,
The hollow steel pipe is
In mass%, C: 0.05 to 0.20, Si: 0.6 or less, Mn: 0.5 to 2.0, P: 0.03 or less, S: 0.03 or less, Al: 0.05 Hereinafter, N: 0.001 to 0.006, O: 0.006 or less is contained, the balance is made of iron and inevitable impurities, and the CE value defined by the following (Formula 1) is 0.15 to A steel pipe joint with a recess, which is 0.45 and has a tensile strength of 400 N / mm 2 or more .
CE = C + Si / 24 + Mn / 6 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14 (Formula 1)
表面に窪みが形成されていない他の鋼管とを有し、
前記窪み付き鋼管継手の継手用鋼管と、前記他の鋼管とが機械加工により接合されたことを特徴とする接合鋼管。 A steel pipe joint with a recess in which a steel pipe for a joint and a steel pipe with a recess having a recess formed on the surface of the steel pipe are joined by friction welding,
Having other steel pipes with no depressions on the surface ,
A steel pipe for joint of the steel pipe joint with a recess and the other steel pipe are joined by machining.
質量％で、Ｃ ：０．０５〜０．２０、Ｓｉ：０．６以下、Ｍｎ：０．５〜２．０、Ｐ：０．０３以下、Ｓ：０．０３以下、Ａｌ：０．０５以下、Ｎ：０．００１〜０．００６、Ｏ：０．００６以下を含有し、残部が鉄および不可避的不純物からなり、かつ、下記（式１）で定義されるＣＥ値が０．１５〜０．４５、かつ、引張強度が４００Ｎ／ｍｍIn mass%, C: 0.05 to 0.20, Si: 0.6 or less, Mn: 0.5 to 2.0, P: 0.03 or less, S: 0.03 or less, Al: 0.05 Hereinafter, N: 0.001 to 0.006, O: 0.006 or less is contained, the balance is made of iron and inevitable impurities, and the CE value defined by the following (Formula 1) is 0.15 to 0.45 and tensile strength of 400 N / mm ２2 以上であることを特徴とする請求項７乃至１１のいずれかに記載の接合鋼管。It is the above, The joining steel pipe in any one of Claims 7 thru | or 11 characterized by the above-mentioned.
ＣＥ＝Ｃ＋Ｓｉ／２４＋Ｍｎ／６＋Ｎｉ／４０＋Ｃｒ／５＋Ｍｏ／４＋Ｖ／１４・・・（式１）CE = C + Si / 24 + Mn / 6 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14 (Formula 1)
当該継手用鋼管の他端に窪み付き鋼管を摩擦圧接により接合し、
その後、前記機械加工を施した側に、予め機械加工を施した、表面に窪みが形成されていない他の鋼管を接合することを特徴とする鋼管の接合方法。 Machine one end of the steel pipe for joints,
A steel pipe with a recess is joined to the other end of the steel pipe for joint by friction welding,
Then, the steel pipe joining method characterized by joining another steel pipe which has been machined in advance and has no depressions on the surface thereof on the machined side.
当該継手用鋼管の他端に窪み付き鋼管を摩擦圧接により接合した窪み付き鋼管継手を少なくとも２本製造し、
その後、各接合鋼管の前記継手用鋼管の機械加工を施した側の端部同士を接合することを特徴とする鋼管の接合方法。 Machine one end of the steel pipe for joints,
Producing at least two steel pipe joints with a recess in which a steel pipe with a recess is joined to the other end of the steel pipe for joint by friction welding,
Then, the edge part of the side which gave the machining of the said steel pipe for joints of each joining steel pipe is joined, The joining method of the steel pipe characterized by the above-mentioned.
質量％で、 Ｃ ：０．０５〜０．２０、Ｓｉ：０．６以下、Ｍｎ：０．５〜２．０、Ｐ：０．０３以下、Ｓ：０．０３以下、Ａｌ：０．０５以下、Ｎ：０．００１〜０．００６、Ｏ：０．００６以下を含有し、残部が鉄および不可避的不純物からなり、かつ、下記（式１）で定義されるＣＥ値が０．１５〜０．４５の範囲にある鋼板を９００℃以上に加熱した後、管状に成形し、さらに鋼管表面に連続的に凹みを成形し、７００℃以上で成形工程を終了させて前記窪み付き鋼管を製造することを特徴とする請求項１５乃至１６のいずれかに記載の鋼管の接合方法。
ＣＥ＝Ｃ＋Ｓｉ／２４＋Ｍｎ／６＋Ｎｉ／４０＋Ｃｒ／５＋Ｍｏ／４＋Ｖ／１４・・・（式１） The hollow steel pipe is
C: 0.05 to 0.20, Si: 0.6 or less, Mn: 0.5 to 2.0, P: 0.03 or less, S: 0.03 or less, Al: 0.05 Hereinafter, N: 0.001 to 0.006, O: 0.006 or less is contained, the balance is made of iron and inevitable impurities, and the CE value defined by the following (Formula 1) is 0.15 to After heating the steel sheet in the range of 0.45 to 900 ° C. or higher, it is formed into a tubular shape, and a recess is continuously formed on the surface of the steel pipe, and the forming step is completed at 700 ° C. or higher to produce the steel tube with the recess. The steel pipe joining method according to any one of claims 15 to 16 , wherein:
CE = C + Si / 24 + Mn / 6 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14 (Formula 1)
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