JP2017129517A - Torsion fatigue test method of steel pipe, and test piece used therefor - Google Patents
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本発明は、電縫鋼管、シームレス鋼管などの焼き入れ鋼管母材のねじり疲労試験方法及びそれに用いる試験体に関するものである。 The present invention relates to a torsional fatigue test method for hardened steel pipe base materials such as ERW steel pipes and seamless steel pipes, and a test body used therefor.
鋼管を機械構造用に使用する場合、特に回転方向のトルクによって繰り返し荷重がかけられる部材に用いられることがあり、鋼管のねじり疲労特性を把握することは重要である。一般的にねじり疲労特性は、管端にフランジ部材を溶接し、フランジ部材を試験装置にボルト締結して管端を繰り返し強制的に回転方向の力を加える試験が行われる。このとき母材を適正に評価するためには、母材より強度の低い部位をなくさねばならない。これは負荷応力が低強度部に集中し、母材が破壊するより以前に低強度部が破壊するためである。 When a steel pipe is used for a machine structure, it is sometimes used for a member that is repeatedly subjected to a load by a rotational torque, and it is important to grasp the torsional fatigue characteristics of the steel pipe. In general, the torsional fatigue characteristic is a test in which a flange member is welded to a pipe end, the flange member is bolted to a test apparatus, and a force in the rotational direction is forcibly repeated at the pipe end. At this time, in order to properly evaluate the base material, a portion having lower strength than the base material must be eliminated. This is because the load stress concentrates on the low strength portion and the low strength portion breaks before the base material breaks.
ねじり疲労試験時は、管端とフランジ治具は表面に凹凸がないように滑らかに接合する必要があるが、鋼管を溶接以外の方法で接合、例えばチャック締結であればチャック端に、ボルト締結であればボルト穴端に応力が集中し、そこから疲労破壊する。そのため、ねじり疲労試験では管端とフランジ治具とを溶接することが不可欠になるが、溶接には必ず熱影響（HAZ）による軟化を伴うため、母材より低強度部が発生する問題があった。この溶接過程は母材にとって焼鈍と等価な熱履歴となり、特に近年開発中の高強度焼入れ鋼管の場合は軟化部の強度が母材に比べて著しく低下することから、評価を実現する接合法がなかった。 During the torsional fatigue test, the pipe end and flange jig must be smoothly joined so that there are no irregularities on the surface, but steel pipes are joined by methods other than welding. If so, stress concentrates on the bolt hole end, and fatigue failure occurs from there. Therefore, in the torsional fatigue test, it is indispensable to weld the pipe end to the flange jig. However, since welding is always accompanied by softening due to thermal influence (HAZ), there is a problem that a lower strength part is generated than the base metal. It was. This welding process has a thermal history equivalent to annealing for the base metal, and especially in the case of high-strength hardened steel pipes being developed in recent years, the strength of the softened part is significantly lower than that of the base metal. There wasn't.
従来、特許文献１にあるように、捻り疲労試験時に鋼管を試験装置ブラケットへ接続する際、鋼管の外径より最大0.6mm小さい内径のブラケット孔へ挿入した後に溶接することで、外圧による圧縮残留応力の発生に伴う摩擦力を増加させ、ねじり疲労特性を評価する手法が提案されている。しかし、本手法でも溶接が不可欠であり、溶接によって著しく軟化した部位が発生する高強度焼き入れ鋼管では、溶接部がほぼ同径であり、軟化部から破壊するため、適用は困難であった。また特許文献２の方法では、管端部を拡管してフランジと接合するので、溶接による軟化部が生じても径の大きさでカバーできる可能性がある。しかし、高強度材を所定の径まで拡管することは技術的に容易ではなく、拡管時に座屈や割れが発生する懸念が大きいため、やはり適用が難しい。特に５ｍｍ以上の厚手材を均質に拡管することは困難であり、比較的薄手材に有効な方法であった。 Conventionally, as disclosed in Patent Document 1, when connecting a steel pipe to a test equipment bracket during a torsional fatigue test, it is welded after being inserted into a bracket hole whose inner diameter is 0.6 mm smaller than the outer diameter of the steel pipe, thereby compressing residual due to external pressure. A method for increasing the frictional force accompanying the generation of stress and evaluating torsional fatigue characteristics has been proposed. However, welding is indispensable also in this method, and in a high-strength hardened steel pipe in which a portion softened significantly by welding is generated, the welded portion has almost the same diameter, and it is difficult to apply because it breaks from the softened portion. Moreover, in the method of patent document 2, since a pipe end part is expanded and it joins with a flange, even if the softened part by welding arises, there exists a possibility that it can cover with the magnitude | size of a diameter. However, it is not technically easy to expand a high-strength material to a predetermined diameter, and it is still difficult to apply because there is a great concern that buckling or cracking will occur during expansion. In particular, it is difficult to uniformly expand a thick material of 5 mm or more, which is an effective method for a relatively thin material.
こうした問題から従来は、鋼管単体でのねじり疲労試験は実施できず、鋼管を機械構造に組み込んだ状態で試験するしかなかった。しかし、試験体の準備に時間やコストがかかり、様々な形状に依存する特殊な締結治具が必要になる問題がある上、鋼管自体の疲労特性が評価できないまま部品設計をするため、形状の検討が不十分となり易く、ねじり疲労試験後に設計への手戻りが生じるといった開発の遅延にも繋がっていた。こうした背景から、鋼管の母材自体のねじり疲労特性を評価する手法が強く望まれていた。 Conventionally, the torsional fatigue test with a single steel pipe could not be performed because of these problems, and the test had to be performed with the steel pipe incorporated in the mechanical structure. However, it takes time and cost to prepare the test specimen, and there is a problem that a special fastening jig that depends on various shapes is required.In addition, the design of the parts cannot be performed without evaluating the fatigue characteristics of the steel pipe itself. This has led to delays in development, such as the possibility of insufficient studies, and the return to design after a torsional fatigue test. Against this background, a method for evaluating the torsional fatigue characteristics of the steel pipe base metal itself has been strongly desired.
以上の問題を踏まえた本発明の目的は、高強度な焼き入れ鋼管であってもフランジ部材と適正に接合し、鋼管母材自体のねじり疲労特性を正確に評価することができるねじり評価試験方法とそれに用いる試験体を提供することである。 The object of the present invention based on the above problems is torsion evaluation test method capable of accurately joining torsional fatigue characteristics of a steel pipe base material itself by properly joining to a flange member even in a high-strength hardened steel pipe And a specimen used for the same.
上記の課題を解決するためになされた本発明のねじり疲労試験方法は、フランジ継手を評価母材と同等以上の焼き入れ性を有する成分で製作し、試験体である鋼管の両端に摩擦接合した後に焼き入れ、ねじり疲労試験を行うことを特徴とするものである。 In the torsional fatigue test method of the present invention made to solve the above-mentioned problems, a flange joint is manufactured with a component having a hardenability equal to or higher than that of the evaluation base material, and friction bonded to both ends of a steel pipe as a test body. It is characterized by performing a quenching and a torsional fatigue test later.
上記した本発明における評価母材と同等以上の焼き入れ性を有する成分とは、フランジ継手のカーボン量が評価母材と同量以上且つその他の選択元素の含有量が次の評価指標（１）で表されるＶＣ９０以下であることが好ましい。
ＶＣ９０＝１０＾（２．９４−０．７５＊（２．７［Ｃ］＋０．４［Ｓｉ］＋［Ｍｎ］＋０．４５［Ｎｉ］＋０．４５［Ｃｕ］＋０．８［Ｃｒ］＋２［Ｍｏ］）） （１）
The component having a hardenability equivalent to or higher than that of the evaluation base material in the present invention is the following evaluation index (1) in which the carbon amount of the flange joint is equal to or more than that of the evaluation base material and the content of other selective elements is It is preferable that it is below VC90 represented by these.
V C90 = 10 ^ (2.94−0.75 * (2.7 [C] +0.4 [Si] + [Mn] +0.45 [Ni] +0.45 [Cu] +0.8 [Cr] +2 [Mo])) (1)
また本発明においてフランジ継手は、母材外径＋5mm≧フランジ継手外径≧母材外径、母材内径≧フランジ継手内径≧母材外径−5mmとすることが好ましい。 In the present invention, the flange joint preferably has a base material outer diameter + 5 mm ≧ flange joint outer diameter ≧ base material outer diameter, base material inner diameter ≧ flange joint inner diameter ≧ base material outer diameter−5 mm.
上記の課題を解決するためになされた本発明のねじり疲労試験体は、評価母材と同等以上の焼き入れ性を有する成分で製作されたフランジ継手が試験体である鋼管の両端に摩擦接合され、当該フランジ継手及び当該試験体が焼き入れされていることを特徴とする。 The torsional fatigue test body of the present invention, which has been made to solve the above-mentioned problems, has a flange joint manufactured with a component having a hardenability equivalent to or higher than that of the evaluation base material, and is friction bonded to both ends of a steel pipe as a test body. The flange joint and the specimen are quenched.
評価母材と同等以上の焼き入れ性を有する成分とは、カーボン量が評価母材と同量以上且つその他の選択元素の含有量が次の評価値で母材以下であることを特徴とする。
ＶＣ９０＝１０＾（２．９４−０．７５＊（２．７［Ｃ］＋０．４［Ｓｉ］＋［Ｍｎ］＋０．４５［Ｎｉ］＋０．４５［Ｃｕ］＋０．８［Ｃｒ］＋２［Ｍｏ］））
The component having a hardenability equivalent to or higher than that of the evaluation base material is characterized in that the amount of carbon is equal to or higher than that of the evaluation base material and the content of other selected elements is equal to or lower than the base material in the following evaluation value. .
V C90 = 10 ^ (2.94−0.75 * (2.7 [C] +0.4 [Si] + [Mn] +0.45 [Ni] +0.45 [Cu] +0.8 [Cr] +2 [Mo]))
またその試験体は、母材外径＋5mm≧フランジ継手外径≧母材外径、母材内径≧フランジ継手内径≧母材外径−5mmであることを特徴とする。 The test specimen is characterized in that the outer diameter of the base material + 5 mm ≧ the outer diameter of the flange joint ≧ the outer diameter of the base material, the inner diameter of the base material ≧ the inner diameter of the flange joint ≧ the outer diameter of the base material−5 mm.
本発明のねじり疲労試験方法及びそれに用いる試験体によれば、従来実現できなかった母材自体のねじり疲労試験を実施でき、部品の設計前に特性を把握できるため、大幅な開発リソースの削減が可能となる。 According to the torsional fatigue test method of the present invention and the specimen used therefor, the torsional fatigue test of the base metal itself, which could not be realized in the past, can be carried out and the characteristics can be grasped before the design of the parts, which greatly reduces the development resources. It becomes possible.
以下に本発明の実施形態を説明する。
溶接部の特性は母材焼き入れ後強度に依存しており、高強度材では必然的に溶接部位の軟化を伴う。これに対し本発明では、フランジ継手を評価母材と焼き入れ後強度が同じ或いは高い成分で製作し、試験体である鋼管の両端に取り付け、摩擦圧接後に全体を焼き入れることによって母材部のねじり疲労評価を実現する。尚、ここで焼き入れ性が同じ或いは高い成分としては、例えば、焼き入れ後強度に最も効くカーボン量が評価母材と同量以上、且つその他の選択元素については焼き入れ速度の評価指標である下記式（１）
ＶＣ９０＝１０＾（２．９４−０．７５＊（２．７［Ｃ］＋０．４［Ｓｉ］＋［Ｍｎ］＋０．４５［Ｎｉ］＋０．４５［Ｃｕ］＋０．８［Ｃｒ］＋２［Ｍｏ］）） （１）
が母材以下である成分とすることが好ましい。尚、これ以外に焼き入れ後強度が同じ或いは高い成分を判断するには、例えば実際にサンプル試作と硬度測定による方法がある。この判断方法は、上記式に含まれていないNb、Ti、Vなどの析出強化元素も考慮して設計した成分をラボ溶解して試験片を製作し、炉でA3点（オーステナイト域）以上まで加熱後、急冷する。その後、試験片を切断して汎用的な硬度測定器で硬度を測定する。例えば、ビッカース硬度計を用い、試験片断面の表層から１００μｍ深さの部位及び中心付近の部位をそれぞれ５点ずつ測定し、平均値を取る。部位によって硬度が異なる場合は、同時に母材成分も試作し、部位ごとに直接硬度を比較することが好ましい。
Embodiments of the present invention will be described below.
The characteristics of the welded part depend on the strength after quenching the base metal, and a high-strength material inevitably involves softening of the welded part. On the other hand, in the present invention, the flange joint is manufactured with a component having the same or high strength after quenching as the evaluation base material, attached to both ends of the steel pipe as a test body, and the whole base portion is quenched by friction welding. Realize torsional fatigue evaluation. Here, as the components having the same or high hardenability, for example, the amount of carbon most effective for the strength after quenching is equal to or more than the evaluation base material, and other selective elements are evaluation indexes of the quenching rate. Following formula (1)
V C90 = 10 ^ (2.94−0.75 * (2.7 [C] +0.4 [Si] + [Mn] +0.45 [Ni] +0.45 [Cu] +0.8 [Cr] +2 [Mo])) (1)
Is preferably a component that is equal to or less than the base material. In addition, in order to determine a component having the same or high strength after quenching, for example, there are actually a method of sample trial manufacture and hardness measurement. This judgment method is to lab-dissolve the components designed considering precipitation strengthening elements such as Nb, Ti, V, etc. that are not included in the above formula, and manufacture test specimens up to A3 point (austenite region) or higher in the furnace Cool quickly after heating. Thereafter, the test piece is cut and the hardness is measured with a general-purpose hardness measuring instrument. For example, a Vickers hardness tester is used to measure five points each at a depth of 100 μm and a portion near the center from the surface layer of the test piece cross section, and take the average value. In the case where the hardness varies depending on the part, it is preferable to make a prototype of the base material component at the same time and directly compare the hardness for each part.
図１にねじり疲労試験体の構造を示す。試験体１の両端にフランジ部材２ａ、２ｂが３の位置で摩擦圧接されている。この場合、拡管加工などで評価母材の管端外径を極端に大きくする必要がないという特徴がある。また固溶拡散による摩擦圧接では接続部の鋼材成分が変化せず、焼き入れによって母材同等の強度になることも初めて検証された。なお実用上、フランジに別成分の材料を使っても、評価母材よりも外径を大きくしておくことでねじり疲労試験を実現できる。 FIG. 1 shows the structure of a torsional fatigue test body. Flange members 2 a and 2 b are friction-welded to both ends of the test body 1 at the position 3. In this case, there is a feature that it is not necessary to extremely increase the pipe end outer diameter of the evaluation base material by pipe expansion processing or the like. It was also verified for the first time that the steel components of the joints did not change during friction welding by solid solution diffusion, and that the strength was equal to that of the base material by quenching. In practice, a torsional fatigue test can be realized by using a different component material for the flange by making the outer diameter larger than the evaluation base material.
また、フランジの内外径は評価母材と完全に同じである必要はなく、摩擦圧接の接合性確保の観点から、内径については、母材内径≧フランジ継手内径、外径については、母材外径≦フランジ継手外径であればよい一方、焼き入れ冷速が大きく異ならないことが望ましく、内径側は母材内径−5mm≦フランジ継手内径、外形側は母材外径＋5mm≧フランジ継手外径とすることが望ましい。
以下に本発明の実施例を示す。
Also, the inner and outer diameters of the flange need not be exactly the same as the evaluation base material. From the viewpoint of ensuring the weldability of friction welding, the inner diameter of the base material is equal to or greater than the inner diameter of the flange joint, and the outer diameter of the flange joint. While it is sufficient if the diameter ≤ flange joint outer diameter, it is desirable that the quenching and cooling speed should not be significantly different. Is desirable.
Examples of the present invention are shown below.
評価母材は150ksiクラス、φ38.1×t7.0×400mmLの高強度鋼管であり、フランジ材料には評価指標（１）を満足するSCM440を用いた。フランジの評価母材との接続部は内径φ25、外径φ40の円筒形とし、反対側の端部には試験装置とボルト１２本で接続するためのフランジが形成されている一体型の加工品である。 The evaluation base material was a 150 ksi class, high strength steel pipe of φ38.1 × t7.0 × 400 mmL, and SCM440 satisfying the evaluation index (1) was used as the flange material. The connection part of the flange to the evaluation base material is a cylindrical shape with an inner diameter of φ25 and an outer diameter of φ40, and the end of the opposite side is an integrated work product in which a flange is formed to connect the test device with 12 bolts It is.
これらを余熱圧力：２kg/mm2、余熱時間：５秒、摩擦圧力：５．０kg/mm2、摩擦より代：３mm、アプセット圧力：１０kg/mm2、アプセット時間：５秒、回転数：１０００rpm及び、より代：５mmで摩擦圧接した。その後、加熱炉にて９５０℃で１０分間保持し、水冷を行った。 Preheating pressure: 2 kg / mm 2 , Preheating time: 5 seconds, Friction pressure: 5.0 kg / mm 2 , Frictional allowance: 3 mm, Upset pressure: 10 kg / mm 2 , Upset time: 5 seconds, Rotation speed: 1000 rpm And more: Friction welding at 5 mm. Then, it hold | maintained at 950 degreeC for 10 minute (s) with the heating furnace, and water-cooled.
図２は上記の方法で製作した試験体の溶接部から２０mmまでの焼き入れ前の硬さ（３倍すると強度に変換できる）を示している。溶接ままではHAZ部の硬度が評価母材部の半分以下に低下していることが分かる。この状態で試験をすると、硬度の低い（低強度）部位が先行して割れ、母材評価に至らなかった。一方、図３は上記条件で焼入れた後の硬さを示しており、焼き入れることで母材と同じ硬度に回復したことが分かる。本試験体を用いてねじり疲労試験を行ったところ、溶接部及び溶接部近傍で破壊することなく、母材自体のねじり特性を評価できるようになった。 FIG. 2 shows the hardness before quenching up to 20 mm from the welded portion of the test specimen manufactured by the above method (can be converted to strength when tripled). It can be seen that the hardness of the HAZ part is reduced to less than half of the evaluation base metal part as it is welded. When the test was conducted in this state, the low hardness (low strength) part was cracked first, and the evaluation of the base material was not achieved. On the other hand, FIG. 3 shows the hardness after quenching under the above-mentioned conditions, and it can be seen that the hardness is recovered to the same as that of the base material by quenching. When the torsional fatigue test was performed using this test body, the torsional characteristics of the base metal itself could be evaluated without breaking near the welded part and the welded part.
１：評価母材
２ａ、２ｂ：フランジ部材
３：摩擦圧接部
1: Evaluation base materials 2a, 2b: Flange member 3: Friction welding part
Claims (6)
ＶＣ９０＝１０＾（２．９４−０．７５＊（２．７［Ｃ］＋０．４［Ｓｉ］＋［Ｍｎ］＋０．４５［Ｎｉ］＋０．４５［Ｃｕ］＋０．８［Ｃｒ］＋２［Ｍｏ］）） The component having the strength after quenching equal to or higher than that of the evaluation base material means that the carbon amount is equal to or higher than that of the evaluation base material, and the content of other selected elements is equal to or lower than the base material in the following evaluation values. The torsional fatigue test method for steel pipes according to claim 1, wherein
V C90 = 10 ^ (2.94−0.75 * (2.7 [C] +0.4 [Si] + [Mn] +0.45 [Ni] +0.45 [Cu] +0.8 [Cr] +2 [Mo]))
ＶＣ９０＝１０＾（２．９４−０．７５＊（２．７［Ｃ］＋０．４［Ｓｉ］＋［Ｍｎ］＋０．４５［Ｎｉ］＋０．４５［Ｃｕ］＋０．８［Ｃｒ］＋２［Ｍｏ］）） The component having a hardenability equivalent to or higher than that of the evaluation base material is characterized in that the amount of carbon is equal to or higher than that of the evaluation base material and the content of other selected elements is equal to or lower than the base material in the following evaluation value. The test body used for the torsional fatigue test method of the steel pipe of Claim 4.
V C90 = 10 ^ (2.94−0.75 * (2.7 [C] +0.4 [Si] + [Mn] +0.45 [Ni] +0.45 [Cu] +0.8 [Cr] +2 [Mo]))
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113324862A (en) * | 2021-07-13 | 2021-08-31 | 广东省医疗器械质量监督检验所 | Simulated clinical fatigue resistance testing method and device for peritoneal dialysis external connection tube |
| CN114813332A (en) * | 2021-06-02 | 2022-07-29 | 天津大学 | Flexible joint usability evaluation method for pipeline steel pipe girth welding joint based on bending strain |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114813332A (en) * | 2021-06-02 | 2022-07-29 | 天津大学 | Flexible joint usability evaluation method for pipeline steel pipe girth welding joint based on bending strain |
| CN114813332B (en) * | 2021-06-02 | 2024-03-19 | 天津大学 | Pipeline steel pipe ring-welded joint softening fit usability evaluation method based on bending strain |
| CN113324862A (en) * | 2021-07-13 | 2021-08-31 | 广东省医疗器械质量监督检验所 | Simulated clinical fatigue resistance testing method and device for peritoneal dialysis external connection tube |
| CN113324862B (en) * | 2021-07-13 | 2022-05-06 | 广东省医疗器械质量监督检验所 | Simulated clinical fatigue resistance testing method and device for peritoneal dialysis external connection tube |
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