JP2010179338A - Forge-welded pipe excellent in workability - Google Patents
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- JP2010179338A JP2010179338A JP2009025259A JP2009025259A JP2010179338A JP 2010179338 A JP2010179338 A JP 2010179338A JP 2009025259 A JP2009025259 A JP 2009025259A JP 2009025259 A JP2009025259 A JP 2009025259A JP 2010179338 A JP2010179338 A JP 2010179338A
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- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 238000000034 method Methods 0.000 abstract description 5
- 238000005242 forging Methods 0.000 description 9
- 229910000831 Steel Inorganic materials 0.000 description 8
- 239000010959 steel Substances 0.000 description 8
- 210000003205 muscle Anatomy 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 5
- 239000011324 bead Substances 0.000 description 3
- 238000005336 cracking Methods 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 238000005304 joining Methods 0.000 description 3
- 238000003466 welding Methods 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000007665 sagging Methods 0.000 description 1
- 238000009751 slip forming Methods 0.000 description 1
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Abstract
Description
本発明は、フレア加工などの強加工に供されても、接合部に割れが発生しにくい、加工性に優れた鍛接管に関する。 The present invention relates to a forged pipe having excellent workability, in which cracks are unlikely to occur in a joint even when subjected to strong processing such as flare processing.
近年、配管は、その継手部分を兼ね備えるものとして、フレア加工のような管端部への強加工を施されたものが増えている。この強加工に耐える性能を有するものとして電縫管が適用されているが、電縫管は高価なため、廉価な鍛接管の適用が図られている。
従来の鍛接管は、接合部の強度が低くて、強加工すると接合部を起点として割れが発生しやすいため、フレア加工のような用途に適用するには不十分な性能と言われてきた。
In recent years, pipes that have been subjected to strong processing such as flare processing on the pipe end have been increasing as having joint portions. Although the electric resistance welded tube is applied as having the ability to withstand this strong work, since the electric resistance welded pipe is expensive, an inexpensive forged welded pipe is applied.
Conventional forged pipes have been said to have insufficient performance for applications such as flaring because the strength of the joint is low and cracking tends to occur when the steel is strongly processed.
鍛接管の製造においては、図１に一例を示すとおり、スリットした鋼帯２を、エッジ成形機４でエッジ部（幅端部）を成形（エッジ成形）し、加熱炉５にて全幅を加熱し、該加熱後の鋼帯を成形鍛接機６で管状に連続成形しつつ、エッジ部にノズル７で酸素または空気を吹き付けて酸化熱により融点直下近傍の温度まで昇温させ、エッジ衝合・鍛接して接合し、場合によっては絞り圧延を行って、管８に仕上げている。なお、図示していないが、スリットした鋼帯のエッジ部を切削してからエッジ成形する場合もある。
In the production of forged pipes, as shown in FIG. 1, the slit steel strip 2 is formed with the edge forming machine 4 at the edge (width end) (edge forming), and the entire width is heated in the
製造した鍛接管は、接合部に酸化物などが残留しやすく、また、接合部の外面側および内面側に筋が発生し、これらに起因して、フレア加工のような強加工において接合部に割れが発生していた。接合部の外面側の筋は、鋼帯をスリットしてエッジ部に発生したダレが鍛接時に残留したものである。また、内面側の筋は、接合時にエッジ衝合部が盛り上がってビード部を形成し、この谷間が筋となったものである。 In the manufactured welded pipe, oxides and the like are likely to remain in the joint, and streaks are generated on the outer surface side and inner surface side of the joint, resulting in strong joints such as flare processing. Cracks occurred. The streaks on the outer surface side of the joint portion are formed by slitting the steel strip and the sagging generated at the edge portion remaining during forging. Further, the inner surface side streaks are formed by forming the bead portion by rising the edge abutting portion at the time of joining, and this valley is a streak.
そこで、従来は、特許文献１〜３に示されるように、外面側の筋深さ、内面側のビード高さ、内面側の筋深さ、接合部の介在物などを特定の範囲に規制することによって、接合部の強度向上を図った鍛接管を提供していた。
Therefore, conventionally, as shown in
しかし、本発明者らの検討では、前記従来の技術に則って外面側の筋深さ、内面側のビード高さ、内面側の筋深さ、接合部の介在物を特定範囲に規制しても、鍛接管の接合部の強度を充分に向上できず、フレア加工で接合部が割れてしまう場合が多いという課題があることを把握した。すなわち、外面側の筋深さ、内面側の筋深さなどが接合部の強度に及ぼす影響は見掛けの現象であり、真の現象を把握できず本質的な解決になっていなかったわけである。 However, in the examination by the present inventors, in accordance with the above-mentioned conventional technology, the outer surface side muscle depth, the inner surface side bead height, the inner surface side muscle depth, and the inclusions in the joint are regulated to a specific range. However, it has been understood that there is a problem that the strength of the joint portion of the forged pipe cannot be sufficiently improved and the joint portion is often cracked by flare processing. In other words, the influence of the outer surface side muscle depth, the inner surface side muscle depth, and the like on the strength of the joint is an apparent phenomenon, and the true phenomenon cannot be grasped and has not been an essential solution.
本発明は、上述の課題を解決し、フレア加工のような強加工を行なっても、接合部から割れることのない鍛接管を提供することを目的としてなされたものであり、その要旨は次のとおりである。
(1) 鍛接管の接合部を押し潰し方向の一端部近傍とした偏平試験による偏平高さ比（Ｈ）が、管肉厚に対する接合部肉厚方向長さの比（Ｒ）を用いて下記＜１＞式で定義される限界偏平高さ比（ＨＬ）以下であることを特徴とする加工性に優れた鍛接管。
The present invention has been made for the purpose of providing a forged pipe that solves the above-described problems and does not break from the joint even when performing strong processing such as flare processing. It is as follows.
(1) The flat height ratio (H) in the flattening test with the joint part of the forged weld pipe near one end in the crushing direction is shown below using the ratio (R) of the joint thickness direction to the pipe wall thickness. A forged welded tube excellent in workability, characterized by being below the limit flat height ratio (HL) defined by the formula <1>.
ＨＬ＝−１．５×Ｒ＋１．７ ‥‥＜１＞ HL = −1.5 × R + 1.7 <1>
本発明によれば、フレア加工などの強加工に供されても、接合部に割れを発生させない鍛接管が得られる。 ADVANTAGE OF THE INVENTION According to this invention, even if it uses for strong processes, such as a flare process, the forge welded pipe which does not generate | occur | produce a crack in a junction part is obtained.
鍛接管をフレア加工のような強加工に供する場合、従来から接合部に割れが発生して問題であるため、鍛接管製造段階において、接合部が良好であるか確認して品質を確保しておく必要がある。
そこで、接合部の強度を評価する方法として、管の偏平試験を採用した。すなわち、フレア加工は接合部を含めて管内面を拡管して広げる加工であることから、偏平試験においても管内面側の接合部に張力を付与する評価方法が必要である。そこで、図２に示すとおり、鍛接管の接合部を押し潰し方向の一端部近傍とした偏平試験（例えば管の接合部を試験台上のほぼ真上またはほぼ真下に配置して管を上下から押し潰す０度偏平試験）を採用し、押し潰しによって接合部内面に張力を加える評価を行った。鍛接管の接合部を押し潰し方向の一端部近傍とすることによって、管を押し潰すと接合部近傍は円形形状から平坦化するために、接合部外面側に圧縮力が作用し、接合部内面側に張力が作用する。したがって、フレア加工で管内面側に加わる張力を偏平試験で代替することができて、割れ評価が可能なわけである。
When the forged pipe is subjected to strong processing such as flaring, cracks have conventionally occurred in the joints, so it is a problem in the forged pipe manufacturing stage to ensure that the joints are good and to ensure quality. It is necessary to keep.
Therefore, a tube flatness test was adopted as a method for evaluating the strength of the joint. That is, since the flare processing is a process of expanding and expanding the inner surface of the pipe including the joint, an evaluation method for applying tension to the joint on the inner surface of the pipe is also required in the flattening test. Therefore, as shown in FIG. 2, a flattening test in which the joint portion of the forged tube is near one end in the crushing direction (for example, the joint portion of the tube is disposed almost directly above or almost directly below the test table and the tube is viewed from above and below. A 0 degree flattening test for crushing was employed, and evaluation was performed by applying tension to the inner surface of the joint by crushing. By making the joint part of the forged pipe near the one end in the crushing direction, when the pipe is crushed, the vicinity of the joint part is flattened from a circular shape, so that a compressive force acts on the outer surface side of the joint part, and the inner surface of the joint part Tension acts on the side. Therefore, the tension applied to the inner surface of the tube by flare processing can be replaced by a flat test, and crack evaluation is possible.
そこで、押し潰した際に接合部に割れが発生する押し潰し高さ比（押し潰し高さ比＝（試験前の管外径−押し潰し量）／試験前の管外径）を、偏平高さ比（Ｈ）と定義し、これを求めた。偏平高さ比（Ｈ）は、値が大きいほど割れに至る押し潰し量が小さいため接合部が割れやすいことを示し、値が小さいほど割れに至る押し潰し量が大きくて接合部が割れにくいことを示す。 Therefore, the crushing height ratio (crushing height ratio = (pipe outer diameter before test-crushing amount) / pipe outer diameter before test) at which the joint is cracked when crushing is calculated as the flat height This was defined as the thickness ratio (H) and obtained. The flat height ratio (H) indicates that the larger the value, the smaller the amount of crushing that leads to cracking, so the joint is more likely to break. Indicates.
一方、鍛接管にフレア加工のような強加工を施す場合に接合部が割れやすい理由として、鍛接管の製造時に、接合部に酸化物などが残留しやすく、また、接合部の内外面両側に筋状の疵が発生すると考えられていた。すなわち、接合部に残留した酸化物や接合部の内外面両側の筋状疵が割れ発生の起点となりやすいと考えられてきたわけである。したがって、これら接合部が割れる原因に基づいて、過去に、特許文献１〜３に記載されるように、接合部の介在物を低減させ、また、外面側または内面側の筋を低減させた鍛接管の提供がなされてきた。しかし、これらを適切に管理するだけでは、充分な接合部強度が得られず、問題となっていた。
On the other hand, the reason why joints are easily cracked when performing strong processing such as flaring on forged pipes is that oxides, etc. tend to remain at the joints during the manufacture of forged pipes, It was thought that streak was generated. That is, it has been considered that the oxide remaining in the joint and the streaks on both the inner and outer surfaces of the joint are likely to start cracks. Therefore, based on the cause of the breakage of these joints, as described in
そこで、本発明者らは、接合部肉厚方向長さに着目した。従来の接合部強度が低い鍛接管を詳細に観察すると、接合部肉厚方向長さがいずれも短くて、フレア加工のような強加工における管円周方向に作用する強い張力に対して、接合部強度が不足していることを見出したわけである。
接合部強度についてさらに詳細に述べると、管肉厚に比べて接合部肉厚方向長さが短くなると接合部強度が低くなり、長くなると接合部強度が向上するわけである。すなわち、フレア加工のような強加工においては、管端部およびその周辺が拡管されつつ円周方向に拡がっていく。その際、管端部およびその周辺では、円周方向に過大な張力が作用する。この張力は、管の肉厚が薄い部分に応力集中を起こさせやすいため、接合部の肉厚が薄い場合、すなわち、接合部肉厚方向長さが管肉厚より短い場合、接合部に応力集中して割れやすくなるわけである。
Therefore, the present inventors paid attention to the length in the junction thickness direction. When observing in detail the conventional welded pipe with low joint strength, the joint thickness direction length is short, and the joint is against strong tension acting in the pipe circumferential direction in strong processing such as flare processing. It has been found that the strength of the part is insufficient.
The joint strength will be described in more detail. When the length in the joint thickness direction is shorter than the tube thickness, the joint strength is lowered, and when the length is longer, the joint strength is improved. That is, in strong processing such as flare processing, the tube end portion and the periphery thereof are expanded in the circumferential direction while being expanded. At that time, excessive tension acts in the circumferential direction at the pipe end and its periphery. This tension tends to cause stress concentration in the thin part of the tube, so if the thickness of the joint is thin, that is, if the length in the joint thickness direction is shorter than the pipe thickness, the stress is applied to the joint. It is easy to concentrate and break.
従来は、この過大な張力による応力集中に着目できなかったため、単に接合部の介在物や内外面側の筋状疵を割れの起点として考え、これらのみを捉えてそれに応じた対策を取った結果、接合部に充分な強度が得られなかった。
そこで、まず、フレア加工に供して割れが発生しない鍛接管について、フレア加工部に隣接する原管部分を採取し、その原管の偏平試験を行って接合部の割れを観察した。その結果の一例を図３に示す。接合部の状態によって割れが発生する押し潰し高さ比すなわち偏平高さ比（Ｈ）にバラツキが発生するが、試験に供した全数の管がフレア加工で接合部に割れを発生しないことから、その中で最も偏平高さ比（Ｈ）が大きい値がフレア加工の接合部の割れ発生限界に対応する限界偏平高さ比（ＨＬ）と考えられる。この原管を用いて限界偏平高さ比（ＨＬ）を求めておいて、製造した他の鍛接管が、偏平試験においてこの値以下の偏平高さ比（Ｈ）となれば、フレア加工に供しても接合部に割れは発生せず、良好な接合部であることがわかる。
In the past, it was impossible to focus on the stress concentration due to this excessive tension. A sufficient strength could not be obtained at the joint.
Therefore, first, for a forged welded tube that was subjected to flare processing and no cracks occurred, a portion of the original tube adjacent to the flare-processed portion was sampled, and a flattening test of the original tube was performed to observe cracks in the joint. An example of the result is shown in FIG. Variations occur in the crushing height ratio, that is, the flat height ratio (H), where cracks occur depending on the state of the joint, but because all the tubes used in the test do not crack in the joints due to flare processing, Among them, the value with the largest flat height ratio (H) is considered as the limit flat height ratio (HL) corresponding to the crack occurrence limit of the flared joint. The limit flat height ratio (HL) is obtained using this original pipe, and if the other forged welded pipes produced have a flat height ratio (H) below this value in the flat test, they are subjected to flare processing. Even if it does not generate | occur | produce a crack in a junction part, it turns out that it is a favorable junction part.
本発明者らが、フレア加工に供しても割れが発生せず最も偏平高さ比（Ｈ）が大きい鍛接管Ｂについて、この限界偏平高さ比（ＨＬ）を用いて、管肉厚に対する接合部肉厚方向長さの比（Ｒ）との関係を検討したところ、管肉厚に対する接合部肉厚方向長さの比（Ｒ）が０．９５以下の領域で割れが発生しやすい。そこで、限界偏平高さ比（ＨＬ）と、管肉厚に対する接合部肉厚方向長さの比（Ｒ）との関係を調べると、図４に示すとおりである。図中の直線ＨＬは、限界偏平高さ比（ＨＬ）に対応し、下記＜１＞式で表される。 For the welded pipe B that has the largest flat height ratio (H) without cracking even when subjected to flare processing, the present inventors use this limit flat height ratio (HL) to join the pipe thickness. When the relationship with the ratio (R) of the thickness in the thickness direction of the part is examined, cracks tend to occur in the region where the ratio (R) of the length in the thickness direction of the joint to the tube thickness is 0.95 or less. Therefore, when the relationship between the limit flat height ratio (HL) and the ratio (R) of the tube thickness direction length to the tube thickness is examined, it is as shown in FIG. The straight line HL in the figure corresponds to the limit flat height ratio (HL) and is expressed by the following <1> equation.
ＨＬ＝−１．５×Ｒ＋１．７ ‥‥＜１＞
したがって、製造した鍛接管の接合部を押し潰し方向の一端部近傍とした偏平試験による偏平高さ比（Ｈ）が、管肉厚に対する接合部肉厚方向長さの比（Ｒ）を用いて前記＜１＞式で定義される限界偏平高さ比（ＨＬ）以下、すなわちＨ≦ＨＬであれば、接合部に割れの発生しない鍛接管としてフレア加工に供しうることがわかった。
HL = −1.5 × R + 1.7 <1>
Therefore, the flatness ratio (H) by the flattening test in which the joint portion of the manufactured welded pipe is near one end in the crushing direction is calculated by using the ratio (R) of the joint thickness direction to the pipe wall thickness. It was found that if it is equal to or less than the limit flat height ratio (HL) defined by the above formula (1), that is, H ≦ HL, it can be subjected to flaring as a forged welded tube in which no crack occurs in the joint.
なお、管肉厚とは、鍛接管の円周方向の平均肉厚でもよく、管の接合部とは反対側に位置する部分の肉厚でもよく、接合部周辺で肉厚がほぼ同等となる特定位置、例えば接合部肉厚方向長さ相当の距離分だけ接合部から離した位置の肉厚、接合部を挟んで管円周方向１／４の範囲で平均した肉厚など、としてもよい。 The pipe wall thickness may be an average wall thickness in the circumferential direction of the welded pipe, or may be a wall thickness of a portion located on the opposite side of the pipe joint, and the wall thickness is substantially equal around the joint. It may be a specific position, for example, a thickness at a position separated from the joint by a distance corresponding to the length in the joint thickness direction, a thickness averaged in a range of ¼ of the pipe circumferential direction across the joint, and the like. .
図１に一例を示した製造工程で鍛接管を製造した。すなわち、スリットした鋼帯２を、エッジ成形機４でエッジ部（幅端部）を成形（エッジ成形）し、加熱炉５にて全幅を加熱し、該加熱後の鋼帯を成形鍛接機６で管状に連続成形しつつ、エッジ部にノズル７で酸素または空気を吹き付けて酸化熱により融点直下近傍の温度まで昇温させ、エッジ衝合・鍛接して接合し、絞り圧延を行って鍛接管を製造した。
A forged pipe was manufactured in the manufacturing process shown in FIG. That is, the slit steel strip 2 is formed at the edge portion (width end portion) by the edge forming machine 4 (edge forming), the entire width is heated in the
上記製造工程で製造した鍛接管について、管肉厚に対する接合部肉厚方向長さの比（Ｒ）を測定し、そのＲを用いて＜１＞式から限界偏平高さ比（ＨＬ）を計算した。一方、図２に一例を示す０度偏平試験（接合部をほぼ真上として）を行い、偏平高さ比（Ｈ）を求めた。また、フレア加工を行なって接合部の割れ発生の有無を調べた。それらの結果を表１に示す。 For the welded pipe manufactured in the above manufacturing process, measure the ratio (R) of the length in the joint thickness direction to the pipe wall thickness, and use that R to calculate the limit flat height ratio (HL) from the formula <1>. did. On the other hand, the flatness ratio (H) was obtained by conducting a 0-degree flattening test (with the joint portion almost directly above) as an example shown in FIG. Further, flare processing was performed to examine whether or not the joint was cracked. The results are shown in Table 1.
表１より、本発明例Ｎｏ．１〜６では、いずれの鍛接管もＨ≦ＨＬであり、フレア加工において接合部に割れが発生せずに良好であった。これに対し、比較例（従来例）Ｎｏ．７〜10では、いずれの鍛接管もＨ＞ＨＬであり、フレア加工において接合部に割れが発生し、接合部強度は低くて満足できる結果ではなかった。 From Table 1, Example No. of the present invention. In Nos. 1 to 6, all of the welded welded pipes were H ≦ HL, and were satisfactory without causing cracks at the joints in the flare processing. In contrast, the comparative example (conventional example) No. In 7 to 10, all of the welded pipes were H> HL, cracks were generated in the joint in the flare processing, and the joint strength was low, which was not a satisfactory result.
本発明に係る鍛接管は、接合部強度が良好であり、フレア加工のような強加工に供しても接合部が割れることがなく、著しく良好な性能を有しており、廉価な鍛接管への厳しい要求にも充分耐えるものであって、その産業上の利用可能性は極めて大きいものである。 The forged welded pipe according to the present invention has good joint strength, and the joint does not crack even when subjected to strong processing such as flare processing, has remarkably good performance, and is an inexpensive forged welded pipe. Therefore, the industrial applicability is extremely large.
１ コイラー
２ スリットした鋼帯
３ ルーパー
４ エッジ成形機
５ 加熱炉
６ 成形鍛接機
７ ノズル
８ 鍛接管（管）
９ 鍛接管の接合部
10 押し潰し力
11 接合部内面側に作用する張力
12 接合部外面側に作用する圧縮力
DESCRIPTION OF
9 Joints of forged pipes
10 Crushing force
11 Tension acting on the inner surface of the joint
12 Compression force acting on the outer surface of the joint
Claims (1)
ＨＬ＝−１．５×Ｒ＋１．７ ‥‥＜１＞ The flat height ratio (H) in the flattening test in which the joint portion of the forged pipe is in the vicinity of one end portion in the crushing direction is the following <1> using the ratio (R) of the joint thickness direction to the pipe wall thickness. Forged welded tube excellent in workability, characterized by being not more than the limit flat height ratio (HL) defined by the formula.
HL = −1.5 × R + 1.7 <1>
Priority Applications (1)
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| JPH04270009A (en) * | 1991-02-20 | 1992-09-25 | Kawasaki Steel Corp | Method for forming edge of hoop for butt welded tube |
| JPH09108729A (en) * | 1995-10-23 | 1997-04-28 | Nippon Steel Corp | Production of forge welded steel tube excellent in quality |
| JPH10211586A (en) * | 1996-05-29 | 1998-08-11 | Kawasaki Steel Corp | Manufacture of steel pipe |
| JPH10263846A (en) * | 1997-03-21 | 1998-10-06 | Nippon Steel Corp | Manufacture of butt-welded steel tube with superior workability |
| JP2001170779A (en) * | 1999-12-13 | 2001-06-26 | Kawasaki Steel Corp | Steel tube manufacturing method |
| JP2007152430A (en) * | 2005-11-11 | 2007-06-21 | Nippon Steel Corp | Forged steel pipe with excellent workability, manufacturing method, and manufacturing equipment line |
| JP2008208417A (en) * | 2007-02-26 | 2008-09-11 | Jfe Steel Kk | Resistance welded steel tube for heat treatment, and its manufacturing method |
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Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04270009A (en) * | 1991-02-20 | 1992-09-25 | Kawasaki Steel Corp | Method for forming edge of hoop for butt welded tube |
| JPH09108729A (en) * | 1995-10-23 | 1997-04-28 | Nippon Steel Corp | Production of forge welded steel tube excellent in quality |
| JPH10211586A (en) * | 1996-05-29 | 1998-08-11 | Kawasaki Steel Corp | Manufacture of steel pipe |
| JPH10263846A (en) * | 1997-03-21 | 1998-10-06 | Nippon Steel Corp | Manufacture of butt-welded steel tube with superior workability |
| JP2001170779A (en) * | 1999-12-13 | 2001-06-26 | Kawasaki Steel Corp | Steel tube manufacturing method |
| JP2007152430A (en) * | 2005-11-11 | 2007-06-21 | Nippon Steel Corp | Forged steel pipe with excellent workability, manufacturing method, and manufacturing equipment line |
| JP2008208417A (en) * | 2007-02-26 | 2008-09-11 | Jfe Steel Kk | Resistance welded steel tube for heat treatment, and its manufacturing method |
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