JP2020071149A - Brittle crack propagation stopping characteristics test method and test piece - Google Patents
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- 229910000831 Steel Inorganic materials 0.000 description 21
- 239000010959 steel Substances 0.000 description 21
- 239000000463 material Substances 0.000 description 18
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Abstract
Description
本発明は、鋼材の脆性亀裂伝播停止特性（脆性亀裂アレスト靭性）試験方法及び当該試験に供する試験片に関するものである。 TECHNICAL FIELD The present invention relates to a brittle crack propagation arresting characteristic (brittle crack arrest toughness) test method for steel materials and a test piece to be subjected to the test.
脆性破壊は、大規模な塑性変形を伴わず、材料の降伏強度以下の低応力で亀裂が発生し、高速で長距離を伝播して構造物が破壊に至る現象である。大規模構造物に使用される鋼材には、脆性破壊が発生した際に亀裂の伝播が途中で停止する、優れた脆性亀裂伝播停止特性（アレスト性）が要求される。 Brittle fracture is a phenomenon that does not involve large-scale plastic deformation, causes a crack at a low stress equal to or lower than the yield strength of a material, propagates over a long distance at high speed, and causes a structure to fracture. Steel materials used for large-scale structures are required to have excellent brittle crack propagation stopping characteristics (arrestability), in which crack propagation stops halfway when brittle fracture occurs.
脆性亀裂伝播停止特性は、日本溶接協会が制定した規格（例えば、非特許文献１）に準じて評価することができる。日本溶接協会規格ＷＥＳ２８１５の脆性亀裂伝播停止特性試験方法のうち、温度勾配を持たせた試験片の低温側から脆性亀裂を発生させ、亀裂の停止位置を確認し、評価するものを温度勾配型アレスト試験という。 The brittle crack propagation stopping property can be evaluated according to a standard established by the Japan Welding Association (for example, Non-Patent Document 1). Of the brittle crack propagation arresting characteristic test methods of the Japan Welding Association standard WES2815, a brittle crack is generated from the low temperature side of a test piece having a temperature gradient, the crack stop position is confirmed, and the one to be evaluated is a temperature gradient type arrest. It is called an examination.
ＷＥＳ２８１５では、脆性亀裂伝播停止特性試験に用いられる試験片の幅を３５０〜１０００ｍｍとしている。試験片の幅は、亀裂を発生させる試験片の一端から他端までの距離である。脆性亀裂伝播停止特性試験では、脆性亀裂を発生させるための打撃エネルギーと伝播させるための引張ひずみエネルギーとを試験片に載荷し、亀裂を試験片の幅方向に伝播させる。 In WES2815, the width of the test piece used for the brittle crack propagation termination property test is set to 350 to 1000 mm. The width of the test piece is the distance from one end to the other end of the test piece that causes a crack. In the brittle crack propagation stop property test, the impact energy for generating the brittle crack and the tensile strain energy for propagating the brittle crack are loaded on the test piece, and the crack is propagated in the width direction of the test piece.
このうち、打撃エネルギーは、亀裂の発生だけでなく、亀裂の伝播にも影響し、その影響が及ぶ範囲（影響範囲）はエネルギーの大きさに比例して大きくなり、亀裂の伝播に影響を及ぼすエネルギーの量（影響量）は亀裂が発生した部位から離れるほど小さくなる。打撃エネルギーの載荷は、脆性亀裂伝播停止特性試験では、脆性亀裂を発生させることだけが目的である。したがって、脆性亀裂伝播停止特性を正しく評価するには、打撃エネルギーの影響を無視できる部位で亀裂を停止させる必要があり、試験片の幅を大きくすることが望ましく、ＷＥＳ２８１５では試験片の幅を３５０ｍｍ以上としている。 Of these, the impact energy affects not only the occurrence of cracks but also the propagation of the cracks, and the range (influence range) of the impact increases in proportion to the magnitude of the energy, affecting the propagation of the cracks. The amount of energy (influence amount) becomes smaller as the distance from the cracked portion increases. Impact energy loading is only intended to generate brittle cracks in a brittle crack propagation arrest property test. Therefore, in order to correctly evaluate the brittle crack propagation stopping property, it is necessary to stop the crack at a site where the influence of impact energy can be ignored, and it is desirable to increase the width of the test piece. In WES2815, the width of the test piece is 350 mm. That is all.
非特許文献２には、ＷＥＳ２８１５よりも幅が狭く、幅３００ｍｍである試験片を用いて温度勾配型アレスト試験を行った例が示されている。非特許文献２では、アレスト性を数値解析するモデルを検証するために、温度勾配型アレスト試験を実施している。 Non-Patent Document 2 shows an example in which a temperature gradient arrest test is performed using a test piece having a width narrower than WES2815 and a width of 300 mm. In Non-Patent Document 2, a temperature gradient arrest test is carried out in order to verify a model for numerically analyzing arrestability.
脆性亀裂伝播停止特性を評価する際には、確実に脆性亀裂を発生させるため、載荷する打撃エネルギーを大きくすることが望ましい。この場合、打撃エネルギーが亀裂伝播に影響する範囲が大きくなり、亀裂が発生した部位から亀裂を停止させる部位までの距離を大きくする必要が生じることから、大型の試験片が必要になる。しかし、試験片が大型になると大規模な試験装置が必要になるだけでなく、試験片自体の重量が大きくなりその取扱いが困難になる。さらに、供試材のサイズによっては幅が３５０ｍｍ以上の試験片を採取することが困難な場合もある。 When evaluating the brittle crack propagation stopping property, it is desirable to increase the impact energy to be loaded in order to surely generate the brittle crack. In this case, the range in which the impact energy affects the crack propagation becomes large, and it becomes necessary to increase the distance from the site where the crack is generated to the site where the crack is stopped. Therefore, a large test piece is required. However, when the test piece becomes large, not only a large-scale test device is required, but also the weight of the test piece itself becomes large, which makes its handling difficult. Furthermore, depending on the size of the test material, it may be difficult to collect a test piece having a width of 350 mm or more.
非特許文献２のように試験片の幅を狭くすると、試験片幅に対して打撃エネルギーの影響範囲が大きくなり、脆性亀裂が適正な部位で停止するような試験条件を設定することが難しくなる。一方、打撃エネルギーを小さくすると、脆性亀裂が発生しない場合や、亀裂が発生しても打撃部近傍で停止しまう場合があり、適正な評価ができない場合がある。そこで、従来よりも試験片幅の小さい小型試験片を用いて脆性亀裂伝播停止特性試験を行う際には、小さな打撃エネルギーで脆性亀裂を発生させることが求められる。 When the width of the test piece is narrowed as in Non-Patent Document 2, the impact range of the impact energy is increased with respect to the width of the test piece, and it becomes difficult to set the test conditions such that the brittle crack stops at an appropriate portion. . On the other hand, if the impact energy is reduced, a brittle crack may not occur, or even if a crack occurs, it may stop in the vicinity of the impact area, and proper evaluation may not be possible. Therefore, when carrying out a brittle crack propagation stopping property test using a small test piece having a smaller test piece width than before, it is required to generate a brittle crack with a small impact energy.
本発明はこのような実情に鑑みて、小型の試験片を用いて、脆性亀裂伝播停止特性を適正に評価できる試験方法及び試験片を提供することを課題とする。 In view of such circumstances, it is an object of the present invention to provide a test method and a test piece that can appropriately evaluate the brittle crack propagation arresting property by using a small test piece.
本発明者らは、脆性亀裂の発生に要する打撃エネルギーを小さくするために検討を行った。その結果、脆性亀裂が発生する部分だけを脆化させることにより、亀裂を発生し易くし、伝播した亀裂が停止する部分は脆化させることなく元の材質のままにすることにより、打撃エネルギーを小さくしても、脆性亀裂伝搬停止特性を評価できることを見出した。即ち、打撃エネルギーを加える試験片の切欠きの近傍に脆化部を設け、適正な温度勾配を与えることにより、小型の試験片を用いても脆性亀裂伝播停止特性を適正に評価することができた。本発明は、このような知見に基づいてなされたものであり、その要旨は以下のとおりである。 The present inventors have conducted studies to reduce the impact energy required to generate brittle cracks. As a result, by embrittlement only the part where the brittle crack occurs, it is easy to generate the crack, and the part where the propagated crack stops is left as it is in the original material without embrittlement. It has been found that the brittle crack propagation arresting property can be evaluated even if it is made small. That is, by providing an embrittlement portion in the vicinity of the notch of the test piece to which impact energy is applied, and by providing an appropriate temperature gradient, it is possible to properly evaluate the brittle crack propagation stopping property even with a small test piece. It was The present invention has been made based on such findings, and the gist thereof is as follows.
［１］試験片の一端に切欠きを設け、当該切欠きに打撃エネルギーを負荷し、亀裂を発生させる脆性亀裂伝播停止特性試験方法において、
前記試験片の厚さｔが１００ｍｍ以下であり、
前記試験片の一端と他端との距離である試験片の幅Ｗが２００ｍｍ以上３５０ｍｍ未満であり、
前記試験片が、前記切欠きの先端に隣接する部分に脆化部を有する脆性亀裂伝播停止特性試験方法。
［２］前記試験片幅方向の前記脆化部の長さが５０ｍｍ以下であり、
前記試験片幅方向と直交する前記脆化部の幅が１ｍｍ以上３０ｍｍ以下である
上記［１］に記載の脆性亀裂伝播停止特性試験方法。
［３］前記脆化部がアーク溶接によって形成される
上記［１］又は［２］に記載の脆性亀裂伝播停止特性試験方法。
［４］前記脆化部が電子ビーム溶接によって形成される
上記［１］又は［２］に記載の脆性亀裂伝播停止特性試験方法。
［５］前記試験片の一端から他端に向けて温度Ｔが上昇しており、
前記試験片の一端からの距離Ｘに対する前記温度Ｔの変化率である温度勾配ｄＴ／ｄＸ［℃／ｍｍ］が下記（式１）を満足する、［１］〜［４］のいずれか一項に記載の脆性亀裂伝播停止特性試験方法。
０．７６−０．０００８Ｗ≦ｄＴ／ｄＸ≦０．６４−０．０００２Ｗ ・・・（式１）
［６］脆性亀裂伝播停止特性試験方法の試験片であって、
一端に切欠きを有し、
厚さが１００ｍｍ以下であり、
前記一端と他端との距離である幅Ｗが２００ｍｍ以上３５０ｍｍ未満であり、
前記切欠きの先端に隣接する部分に脆化部を有する脆性亀裂伝播停止特性試験片。
［７］前記脆化部の長さが５０ｍｍ以下、前記脆化部の幅が１ｍｍ以上３０ｍｍ以下である上記［６］に記載の脆性亀裂伝播停止特性試験片。
［８］前記脆化部が表面のアーク溶接ビードと熱影響部とからなる上記［６］又は［７］に記載の脆性亀裂伝播停止特性試験片。
［９］前記脆化部が電子ビーム溶接ビードである上記［６］又は［７］に記載の脆性亀裂伝播停止特性試験片。
[1] In a brittle crack propagation stopping property test method in which a notch is provided at one end of a test piece, impact energy is applied to the notch, and a crack is generated,
The thickness t of the test piece is 100 mm or less,
The width W of the test piece, which is the distance between one end and the other end of the test piece, is 200 mm or more and less than 350 mm,
The brittle crack propagation stopping property test method, wherein the test piece has an embrittlement portion in a portion adjacent to the tip of the notch.
[2] The length of the embrittled portion in the width direction of the test piece is 50 mm or less,
The brittle crack propagation stopping property test method according to the above [1], wherein the width of the embrittled portion orthogonal to the width direction of the test piece is 1 mm or more and 30 mm or less.
[3] The brittle crack propagation stopping property test method according to the above [1] or [2], wherein the embrittled portion is formed by arc welding.
[4] The brittle crack propagation stopping property test method according to the above [1] or [2], wherein the embrittled portion is formed by electron beam welding.
[5] The temperature T increases from one end of the test piece to the other end,
The temperature gradient dT / dX [° C / mm], which is the rate of change of the temperature T with respect to the distance X from one end of the test piece, satisfies the following (Equation 1), [1] to [4]. The brittle crack propagation arresting property test method described in.
0.76-0.0008W ≦ dT / dX ≦ 0.64-0.0002W (Equation 1)
[6] A test piece of a brittle crack propagation stopping property test method,
Has a notch at one end,
The thickness is 100 mm or less,
The width W, which is the distance between the one end and the other end, is 200 mm or more and less than 350 mm,
A brittle crack propagation stopping property test piece having an embrittlement portion in a portion adjacent to the tip of the notch.
[7] The brittle crack propagation stopping property test piece according to the above [6], wherein the length of the embrittled portion is 50 mm or less and the width of the embrittled portion is 1 mm or more and 30 mm or less.
[8] The brittle crack propagation stopping property test piece according to the above [6] or [7], wherein the embrittled portion is composed of a surface arc weld bead and a heat-affected zone.
[9] The brittle crack propagation stopping property test piece according to the above [6] or [7], wherein the brittle portion is an electron beam weld bead.
本発明によれば、従来よりも小型の試験片を用いて、脆性亀裂伝播停止特性を適正に評価することができる。したがって、試験片の作製が容易になり、また、適正な試験条件を容易に定めることができるため、材料開発に要する期間及びコストを削減することができる。 According to the present invention, it is possible to properly evaluate the brittle crack propagation stopping property by using a test piece smaller than the conventional one. Therefore, the test piece can be easily manufactured, and appropriate test conditions can be easily determined, so that the period and cost required for material development can be reduced.
１．本発明に係る試験方法の概要
本発明に係る脆性亀裂伝播停止特性試験方法は、試験片の一端から他端に向けて亀裂を進展させ、前記亀裂を停止させる鋼板の特性を評価する試験方法である。図１の試験片では、試験片の一端は図面中上方の辺を、他端は下方の辺を指す。本発明に係る試験片１は、図１に示すように、その一端に切欠き３０及び切欠き先端に隣接する脆化部４０を有している。ここで、切欠き先端とは、試験片幅方向の切欠きの頂点を指す。図２に示すように、切欠き３０には楔７を設置し、打撃エネルギーを負荷して脆性亀裂を発生させる。脆性亀裂が進展する試験片幅方向と直交する試験片長さ方向には、構造体に作用する引張応力を再現するために、弾性変形の範囲内で引張荷重が載荷される。例えば、試験片に接合されたタブ板２１（図中では、２１Ａ、２１Ｂと表示。）に設けたピンチャック２２を介して、試験片の長さ方向に引張荷重を付加することができる。
1. Outline of the test method according to the present invention, the brittle crack propagation stop characteristics test method according to the present invention is a test method for evaluating the characteristics of a steel sheet that propagates a crack from one end of the test piece toward the other end and stops the crack. is there. In the test piece of FIG. 1, one end of the test piece indicates an upper side in the drawing, and the other end indicates a lower side. As shown in FIG. 1, the test piece 1 according to the present invention has a notch 30 at one end thereof and an embrittled portion 40 adjacent to the tip of the notch. Here, the notch tip refers to the apex of the notch in the width direction of the test piece. As shown in FIG. 2, the wedge 7 is installed in the notch 30 and impact energy is applied to generate a brittle crack. A tensile load is applied within the elastic deformation range in order to reproduce the tensile stress acting on the structure in the length direction of the test piece orthogonal to the width direction of the test piece in which the brittle crack propagates. For example, a tensile load can be applied in the length direction of the test piece via the pin chuck 22 provided on the tab plate 21 (indicated by 21A and 21B in the figure) joined to the test piece.
脆性亀裂は、例えば図２に示すように、試験片の一端に設けた切欠きに切欠きの開き角よりも先端角が大きい楔を設置し、楔へ打撃エネルギーを載荷することによって発生させる。打撃エネルギーは、切欠きを開口させるために与えており、例えばＷＥＳ２８１５と同様に、自由落下や圧縮ガスなどによって発生させることができる。 The brittle crack is generated, for example, as shown in FIG. 2, by installing a wedge having a tip angle larger than the opening angle of the notch in a notch provided at one end of the test piece and applying impact energy to the wedge. The impact energy is given to open the notch, and can be generated by free fall, compressed gas, or the like as in the case of WES2815, for example.
楔に載荷された打撃エネルギーは、試験片の切欠きを開口し、切欠きの先端ではひずみエネルギー（弾塑性ひずみ）となって脆性亀裂を発生させ、一部は亀裂伝播にも作用する。そのため、脆性亀裂は、試験片の長さ方向に作用する引張応力に起因するひずみエネルギー（弾性ひずみ）によって試験片の幅方向に伝播する。 The impact energy loaded on the wedge opens the notch of the test piece and becomes strain energy (elasto-plastic strain) at the tip of the notch to generate a brittle crack, and a part also acts on crack propagation. Therefore, the brittle crack propagates in the width direction of the test piece due to strain energy (elastic strain) caused by the tensile stress acting in the length direction of the test piece.
試験片の一端では、亀裂の発生を容易にするため、冷却等によって温度を低下させている。試験片には温度勾配が付与されており、試験片の一端から亀裂が進展する他端に向けて温度を上げている。また、打撃エネルギーに起因する弾塑性ひずみエネルギーの影響も試験片の一端から離れるに従って小さくなる。したがって、試験片の一端から発生した亀裂は、他端に向けて距離が離れるほど伝播し難くなり、停止に至る。 At one end of the test piece, the temperature is lowered by cooling or the like in order to facilitate the generation of cracks. A temperature gradient is applied to the test piece, and the temperature is increased from one end of the test piece toward the other end where the crack propagates. Further, the influence of the elasto-plastic strain energy resulting from the impact energy becomes smaller as the distance from the one end of the test piece increases. Therefore, the crack generated from one end of the test piece becomes more difficult to propagate as the distance increases toward the other end, and the crack stops.
試験後、ＷＥＳ２８１５に準拠して、（ａ）亀裂伝播経路の条件、（ｂ）アレスト亀裂長さの条件、（ｃ）亀裂直進性の条件、（ｄ）亀裂分岐の条件、（ｅ）打撃エネルギーの条件を満足した場合、アレスト靭性を算定する。このような試験方法は、温度勾配型アレスト試験と称される。 After the test, according to WES2815, (a) crack propagation path conditions, (b) arrest crack length conditions, (c) crack straightness conditions, (d) crack branch conditions, (e) impact energy If the condition of is satisfied, the arrest toughness is calculated. Such a test method is called a temperature gradient arrest test.
２．試験片のサイズ及び形状
本発明に係る脆性亀裂伝播停止特性試験方法に使用する試験片の厚さｔは１００ｍｍ以下にするとよい。これは、試験片の厚さｔが１００ｍｍを超えると、試験片の幅を大きくしなければ脆性亀裂伝播停止特性の評価が難しくなるためである。板厚の下限は特に限定しない。試験片の厚さは脆性亀裂伝播停止特性を評価する鋼板の板厚と同じでもよい。例えば、溶接構造物に適用される厚鋼板の板厚は６ｍｍ以上の場合が多く、このような場合試験片の厚さｔも６ｍｍ以上とすればよい。
2. Size and shape of test piece The thickness t of the test piece used in the brittle crack propagation arrest property test method according to the present invention is preferably 100 mm or less. This is because if the thickness t of the test piece exceeds 100 mm, it becomes difficult to evaluate the brittle crack propagation arresting property unless the width of the test piece is increased. The lower limit of the plate thickness is not particularly limited. The thickness of the test piece may be the same as the thickness of the steel sheet for evaluating the brittle crack propagation arresting property. For example, the plate thickness of the thick steel plate applied to the welded structure is often 6 mm or more, and in such a case, the thickness t of the test piece may be 6 mm or more.
本発明に係る試験片は、試験片の採取が可能な供試材の入手の容易さ、費用等の観点から、試験片の一端と他端との距離である試験片の幅Ｗを３５０ｍｍ未満とすることができる。一方、試験片の幅Ｗが小さすぎると上記のＷＥＳ２８１５に係る条件（ａ）〜（ｅ）を満足するように脆性亀裂を停止させることが難しくなる。アレスト靭性を安定的に算定するために、試験片の幅Ｗを２００ｍｍ以上とするとよい。 The test piece according to the present invention has a width W of the test piece, which is a distance between one end and the other end of the test piece, of less than 350 mm, from the viewpoint of easy availability of the test material from which the test piece can be collected, cost, and the like. Can be On the other hand, if the width W of the test piece is too small, it becomes difficult to stop the brittle crack so as to satisfy the conditions (a) to (e) relating to the above WES2815. In order to stably calculate the arrest toughness, the width W of the test piece may be 200 mm or more.
また、試験片の厚さｔが大きくなると、脆性亀裂の発生に要する打撃エネルギーが大きくなる。後述するように、脆性亀裂伝播停止特性を評価する際には、試験片の長さ方向における打撃エネルギーの影響を無視できる部位で亀裂を停止させることが必要である。試験片の厚さｔを大きくすると、打撃エネルギーの影響が及ぶ距離が長くなるので、試験片の幅Ｗは一定以上を確保することが好ましい。このような観点から、試験片幅Ｗと試験片の厚さｔとの比Ｗ／ｔは２以上であることが好ましい。脆性亀裂が進展する方向を制御するためにサイドグルーブを設けてもよい。 Further, as the thickness t of the test piece increases, the impact energy required to generate brittle cracks increases. As will be described later, when evaluating the brittle crack propagation stopping property, it is necessary to stop the crack at a site where the influence of impact energy in the length direction of the test piece can be ignored. When the thickness t of the test piece is increased, the distance affected by the impact energy becomes longer, so it is preferable to secure the width W of the test piece to be a certain value or more. From such a viewpoint, it is preferable that the ratio W / t of the width W of the test piece to the thickness t of the test piece is 2 or more. Side grooves may be provided to control the direction in which brittle cracks propagate.
３．脆化部
本発明に係る試験片は、その一端に、亀裂を発生させる切欠きを有しており、試験片の、切欠きの先端（試験片の幅の方向の切欠きの頂点）に隣接する部分を脆化させることが特徴である。この脆化させた部分を脆化部と呼ぶ。脆化部は、脆性亀裂を発生させるために必要な打撃エネルギーを減少させるために設けられている。なお、試験片に設ける切欠きの形成方法は特に限定されないが、ＷＥＳ２８１５において推奨される機械切欠き、プレス切欠きのいずれかを採用することが好ましい。
3. Embrittlement part The test piece according to the present invention has a notch that causes a crack at one end thereof, and is adjacent to the tip of the notch (the apex of the notch in the width direction of the test piece) of the test piece. The feature is that the part to be embrittled is made brittle. This embrittled portion is called an embrittlement portion. The embrittlement portion is provided to reduce the impact energy required to generate a brittle crack. The method of forming the notch provided in the test piece is not particularly limited, but it is preferable to employ either the mechanical notch recommended in WES2815 or the press notch.
脆性亀裂伝播停止特性を評価するためには、亀裂発生のために負荷された打撃エネルギーが亀裂伝播に及ぼす影響を無視できる部位で亀裂を停止させることが必要になる。脆性亀裂伝播停止特性試験では、打撃エネルギーによる亀裂伝播への影響が、試験片の一端から離れるに従って小さくなることを考慮して、亀裂が停止する範囲（試験片の一端から幅方向の距離）を概ね０．３Ｗ〜０．７Ｗ（Ｗは試験片の幅）になるようにするとよい。亀裂が停止する範囲が脆化部にならないようにするため、脆化部の長さは、長くても０．３Ｗ以下にすることが好ましい。ここで、脆化部の長さとは、脆化部の試験片幅方向における長さのことをいう。 In order to evaluate the brittle crack propagation stopping property, it is necessary to stop the crack at a site where the impact of the impact energy applied for crack initiation on the crack propagation can be ignored. In the brittle crack propagation stop property test, considering that the impact of impact energy on crack propagation decreases with increasing distance from one end of the test piece, the range where the crack stops (distance in the width direction from one end of the test piece) is considered. It is preferable that the width is approximately 0.3 W to 0.7 W (W is the width of the test piece). The length of the embrittlement portion is preferably 0.3 W or less at the longest so that the range where the crack stops does not become the embrittlement portion. Here, the length of the embrittled portion means the length of the embrittled portion in the width direction of the test piece.
本発明に係る試験片の幅Ｗの最小値は２００ｍｍであるので、亀裂を停止させる範囲を、試験片の一端から他端に向けて６０〜１４０ｍｍの範囲とするとよいことになる。亀裂を停止させる範囲に脆化部を設けることは好ましくないため、試験片の一端から、脆化部の、試験片幅の方向の端部までの長さは５０ｍｍ以下にすることが好ましい。さらに好ましくは、切欠き長さと脆化部長さとの和を５０ｍｍ以下にすることが好ましい。 Since the minimum value of the width W of the test piece according to the present invention is 200 mm, it is advisable to set the range in which cracks are stopped from the one end to the other end of the test piece in the range of 60 to 140 mm. Since it is not preferable to provide the embrittled portion in the range where the crack is stopped, the length from one end of the test piece to the end of the embrittled portion in the width direction of the test piece is preferably 50 mm or less. More preferably, the sum of the notch length and the embrittled portion length is preferably 50 mm or less.
試験片の、脆性亀裂を発生させる部位に脆化部を設けることにより亀裂が発生し易くなるため、脆化部の長さの下限は特に限定しない。脆化部の形成方法により異なるが、例えばアーク溶接ビードであれば１ｍｍ以上であることが好ましく、電子ビーム溶接であれば０．１ｍｍ以上であることが好ましい。 By providing an embrittled portion in a portion of the test piece where the brittle crack is generated, the crack is likely to occur. Therefore, the lower limit of the length of the embrittled portion is not particularly limited. Although it depends on the method of forming the embrittled portion, it is preferably 1 mm or more for an arc welding bead and 0.1 mm or more for electron beam welding.
また、脆化部は、板厚方向に全面にわたって形成されていることが望ましいが、板厚方向の一部に形成されていてもよい。例えば、試験片の表面にアーク溶接によって脆化部を形成する場合、試験片の表面近傍に形成されたアーク溶接ビード及び熱影響部の直下にしか脆化部が形成されておらず、脆化部が板厚方向に貫通していない場合がある。板厚方向の一部に脆化部がある場合、脆化部の板厚方向深さの下限は特に限定しないが、１ｍｍ以上であることが好ましい。さらに好ましくは２ｍｍ以上であり、上記したように全面にわたって形成されることが理想的である。 The embrittlement portion is preferably formed over the entire surface in the plate thickness direction, but may be formed in a part in the plate thickness direction. For example, when forming an embrittlement portion by arc welding on the surface of the test piece, the embrittlement portion is formed only directly below the arc-welded beads and the heat-affected zone formed near the surface of the test piece, and the embrittlement occurs. The part may not penetrate in the plate thickness direction. When the embrittlement part exists in a part in the plate thickness direction, the lower limit of the depth of the embrittlement part in the plate thickness direction is not particularly limited, but is preferably 1 mm or more. It is more preferably 2 mm or more, and ideally formed over the entire surface as described above.
また、脆化部の長さと直交する脆化部の幅は、機械切欠きと同様、０．２ｍｍ以上であればよい。電子ビームなどの高エネルギービームによって溶融、凝固させて脆化部を形成する場合などでは、１ｍｍ以上であってもよい。アーク溶接によって脆化部を形成する場合などでは、２ｍｍ以上であってもよい。脆化部の幅は広くても効果は変わらないため、脆化部の上限は特に限定されないが、コストの上昇を抑えるためには３０ｍｍ以下であることが好ましい。 Further, the width of the embrittled portion, which is orthogonal to the length of the embrittled portion, may be 0.2 mm or more, similar to the mechanical notch. In the case of melting and solidifying with a high-energy beam such as an electron beam to form an embrittlement portion, it may be 1 mm or more. In the case where the embrittlement portion is formed by arc welding, it may be 2 mm or more. Since the effect does not change even if the width of the embrittlement portion is wide, the upper limit of the embrittlement portion is not particularly limited, but it is preferably 30 mm or less in order to suppress an increase in cost.
脆化部の形成方法は特に限定されない。
脆化部は、例えば、アーク溶接によって形成することができる。また、例えば、硬化肉盛溶接によって形成されるビードや、クラックスタータビードであってもよい。アーク溶接によって形成された脆化部の例を図３に示す。図３は、試験片の両面に、試験片の幅方向に延びるアーク溶接ビード４２（図中では４２Ａ、４２Ｂと表示。）が形成されており、その直下部分に熱影響部４３（図中では４３Ａ、４３Ｂと表示。）が形成される。この場合、脆化部は、アーク溶接ビード４２と熱影響部４３とによって構成されており、板厚方向に貫通してはいない。ただし、アーク溶接条件によっては、脆化部を板厚方向に貫通させることもできる。溶接ワイヤは、例えば、硬化肉盛溶接用フラックス入りワイヤやクラックスタータビード用溶接棒を用いることができる。
The method for forming the embrittlement portion is not particularly limited.
The brittle portion can be formed by, for example, arc welding. Further, for example, a bead formed by hardfacing welding or a crack starter bead may be used. FIG. 3 shows an example of the embrittled portion formed by arc welding. In FIG. 3, arc-welded beads 42 (indicated by 42A and 42B in the drawing) extending in the width direction of the test piece are formed on both sides of the test piece, and a heat-affected zone 43 (in the drawing, by a portion directly below it). 43A and 43B) are formed. In this case, the embrittlement portion is composed of the arc weld bead 42 and the heat-affected zone 43 and does not penetrate in the plate thickness direction. However, depending on the arc welding conditions, the embrittlement portion can be penetrated in the plate thickness direction. As the welding wire, for example, a flux-cored wire for hardfacing welding or a welding rod for crack starter beads can be used.
また、脆化部は、電子ビーム溶接（電子ビーム照射も含む）によって形成してもよい。電子ビーム溶接によって形成された脆化部の例を図４に示す。図４は、試験片の片側から厚さ方向に貫通する電子ビーム溶接を行った例であり、試験片の厚さ方向を貫通して幅方向に延びる脆化部４４が形成されている。なお、電子ビーム溶接は真空チャンバー内で、３００ｍｍ程度の対物距離を確保した状態で、約７０ｋＶの加速電圧と約２００ｍＡの電流を用いた電子ビームを試験片に照射しながら、幅方向に速度４００ｍｍ／ｍｉｎ程度で移動させることで、所定の脆化部を形成させることができる。
サイドグルーブを設けた場合、サイドグルーブに沿うように脆化部を形成すればよい。例えば、図１１（ａ）に試験片の両面に設けたサイドグルーブ５０に沿ってアーク溶接４２を施し、脆化部を形成した例を示す。また、例えば、片方のサイドグルーブにだけアーク溶接を施し、脆化部を形成してもよい。また、例えば、試験片の片方の面にのみサイドグルーブを形成し、そのサイドグルーブに沿ってアーク溶接を施し、脆化部を形成してもよいし、サイドグルーブを形成していない面にのみアーク溶接を施し、脆化部を形成してもよい。
例えば、図１１（ｂ）に試験片の両面に設けたサイドグルーブ５０に沿って電子ビーム溶接を施し、脆化部４４を形成した例を示す。上記したアーク溶接により脆化部を形成した例と同様、電子ビーム溶接による脆化部の形成も、片面にサイドグルーブを形成した場合など、サイドグルーブの形態に限定されない。
The embrittlement portion may be formed by electron beam welding (including electron beam irradiation). An example of the embrittled portion formed by electron beam welding is shown in FIG. FIG. 4 is an example in which electron beam welding is performed to penetrate the test piece from one side in the thickness direction, and an embrittlement portion 44 that penetrates the thickness direction of the test piece and extends in the width direction is formed. Electron beam welding is performed in a vacuum chamber with an objective distance of about 300 mm secured, while irradiating the test piece with an electron beam using an acceleration voltage of about 70 kV and a current of about 200 mA, and a speed of 400 mm in the width direction. A predetermined embrittlement portion can be formed by moving at a speed of about / min.
When the side groove is provided, the embrittlement portion may be formed along the side groove. For example, FIG. 11A shows an example in which arc welding 42 is performed along the side grooves 50 provided on both sides of the test piece to form the embrittlement portion. Further, for example, the embrittlement portion may be formed by performing arc welding on only one of the side grooves. Further, for example, a side groove may be formed only on one surface of the test piece, arc welding may be performed along the side groove to form an embrittlement portion, or only on a surface where the side groove is not formed. The embrittlement may be formed by performing arc welding.
For example, FIG. 11B shows an example in which the embrittlement portion 44 is formed by performing electron beam welding along the side grooves 50 provided on both surfaces of the test piece. Similar to the example in which the embrittled portion is formed by arc welding described above, the formation of the embrittled portion by electron beam welding is not limited to the form of the side groove, such as the case where the side groove is formed on one surface.
４．温度勾配
本発明に係る脆性亀裂伝播停止特性試験方法では、亀裂の発生を容易にするため、試験片の一端の温度を低下させるとよい。一方、亀裂を停止させるため、亀裂の進行方向に向けて温度を上昇させるとよい。試験片に付与される温度勾配ｄＴ／ｄＸ［℃／ｍｍ］は、試験片の一端からの幅方向の距離Ｘに対する温度Ｔの変化率であり、温度勾配ｄＴ／ｄＸは、ＷＥＳ２８１５に準拠して設定するとよい。温度勾配ｄＴ／ｄＸは、試験片の幅Ｗ（ｍｍ）によって、下記式（式１）を満足するように上限及び下限を設定することが好ましい。
０．７６−０．０００８Ｗ≦ｄＴ／ｄＸ≦０．６４−０．０００２Ｗ ・・・ （式１）
4. Temperature Gradient In the brittle crack propagation arrest property test method of the present invention, the temperature at one end of the test piece may be lowered in order to facilitate the occurrence of cracks. On the other hand, in order to stop the crack, it is preferable to raise the temperature in the traveling direction of the crack. The temperature gradient dT / dX [° C./mm] applied to the test piece is the rate of change of the temperature T with respect to the distance X in the width direction from one end of the test piece, and the temperature gradient dT / dX is based on WES2815. Good to set. Regarding the temperature gradient dT / dX, it is preferable to set the upper limit and the lower limit so as to satisfy the following formula (Formula 1) depending on the width W (mm) of the test piece.
0.76-0.0008W ≦ dT / dX ≦ 0.64-0.0002W (Equation 1)
脆性亀裂伝播停止特性試験方法に幅が５００ｍｍの試験片（以下、５００ｍｍ幅と称する場合がある。同様に、幅が３００ｍｍの試験片を３００ｍｍ幅と称する場合がある。）を使用する場合、脆性亀裂を発生させる試験片の一端の温度は、試験片の幅方向における中央の温度に対して、−８０℃〜−１２０℃になるよう温度勾配が付与されるとよい。また、試験片には、一端に設けた切欠き３０（例えば長さ２９ｍｍ）と対向する他端に、応力分布を均一にするための切込み（例えば長さ２９ｍｍ）を設けてもよく、この場合、温度勾配は、０．３６〜０．５４℃／ｍｍに相当する。 When a test piece having a width of 500 mm (hereinafter, may be referred to as 500 mm width. Similarly, a test piece having a width of 300 mm may be referred to as 300 mm width) is used in the brittle crack propagation stopping property test method, A temperature gradient may be applied such that the temperature at one end of the test piece that causes cracks is −80 ° C. to −120 ° C. with respect to the center temperature in the width direction of the test piece. Further, the test piece may be provided with a notch 30 (for example, length 29 mm) provided at one end and a notch (for example, length 29 mm) for equalizing stress distribution at the other end facing the notch 30. , The temperature gradient corresponds to 0.36-0.54 ° C./mm.
脆性亀裂伝播停止特性試験方法では、亀裂長さａ＝Ｗ／２でアレストさせるのが理想的な条件である。試験片が５００ｍｍ幅の場合と３００ｍｍ幅の場合とで、亀裂長さａ＝Ｗ／２における亀裂伝播の駆動力Ｋ値が等しくなるように試験条件を設定するためには、３００ｍｍ幅の試験応力（試験片の長さ方向の引張応力）は５００ｍｍ幅の１．２９倍（＝√(５００／３００)）にするとよい。すなわち５００ｍｍ幅の時に１００ＭＰａであれば３００ｍｍ幅では１２９ＭＰａとなる。 In the brittle crack propagation arrest property test method, the ideal condition is to arrest the crack length a = W / 2. In order to set the test conditions such that the crack propagation driving force K values at the crack length a = W / 2 are equal when the test piece has a width of 500 mm and when the test piece has a width of 300 mm, a test stress of a width of 300 mm is used. The (tensile stress in the length direction of the test piece) may be 1.29 times the width of 500 mm (= √ (500/300)). That is, if the pressure is 100 MPa when the width is 500 mm, it becomes 129 MPa when the width is 300 mm.
試験片が５００ｍｍ幅と３００ｍｍ幅で、温度勾配を０．３６℃／ｍｍと同一にして脆性亀裂伝播停止特性試験方法を行うと仮定した場合の温度とＫ値の関係を図５に記号「＋」（５００ｍｍ幅）及び「×」（３００ｍｍ幅）で示す。温度変化に対するＫ値の傾きは、５００ｍｍ幅と比較して３００ｍｍ幅が大きくなっている。
図５には、亀裂伝播停止特性であるアレスト靭性Ｋｃａ値と温度との関係も実線で示している。亀裂伝播停止特性のＫｃａ値が、Ｋ値を上回ると亀裂の伝播が停止する。したがって、材料特性のＫｃａ値の温度変化を示す図中の実線と、Ｋ値の温度変化を示す線（記号「＋」及び「×」で示す線）とが交差するところで亀裂が停止することになる。
The relationship between the temperature and the K value is shown in FIG. 5 in the case where it is assumed that the brittle crack propagation arresting property test method is performed with the test pieces having a width of 500 mm and a width of 300 mm and the temperature gradient being the same as 0.36 ° C./mm. "(500 mm width) and" x "(300 mm width). The slope of the K value with respect to temperature change is larger in the width of 300 mm than in the width of 500 mm.
FIG. 5 also shows the relationship between the arrest toughness Kca value, which is a crack propagation stopping characteristic, and the temperature with a solid line. When the Kca value of the crack propagation stop characteristic exceeds the K value, the crack propagation stops. Therefore, the crack stops at the intersection of the solid line in the figure showing the temperature change of the Kca value of the material property and the line showing the temperature change of the K value (lines indicated by symbols “+” and “x”). Become.
しかし、図５に示すように、試験片の幅を３００ｍｍにすると、亀裂が伝播したときのＫ値の変化（Ｋ値の温度に対する傾き）が、アレスト靭性Ｋｃａ値の温度依存性（Ｋｃａ値の温度に対する傾き）に近くなることがわかる。また、Ｋｃａ値の温度依存性が板厚でも変化することなどから、試験条件を適正に設定しないとＫｃａ値及びＫ値の温度変化を示す線が交差せず、亀裂伝播が停止し難くなる。（Ｋ値≦Ｋｃａ値になったときに亀裂伝搬が停止するため。）これが、試験片を小型にしたときにデータ採取が困難になる原因の一つであると考えられる。 However, as shown in FIG. 5, when the width of the test piece was set to 300 mm, the change in the K value when the crack propagated (the slope of the K value with respect to the temperature) depended on the temperature dependence of the arrest toughness Kca value (of the Kca value). It can be seen that the slope is close to the temperature). Further, since the temperature dependence of the Kca value changes even with the plate thickness, unless the test conditions are properly set, the Kca value and the line indicating the temperature change of the K value do not intersect, and it becomes difficult to stop the crack propagation. (Because crack propagation stops when K value ≦ Kca value.) This is considered to be one of the reasons why data collection becomes difficult when the test piece is made small.
次に、試験片を５００ｍｍ幅と３００ｍｍ幅で試験片の一端及び他端の温度が同じにした場合と、温度勾配を試験片の幅に応じて変化させた場合について検討する。５００ｍｍ幅で試験応力を１００ＭＰａとした場合と同じＫ値の温度変化を３００ｍｍ幅で得る場合、３００ｍｍ幅の温度勾配は５００ｍｍ幅の１．６７(＝５／３)倍になるため、亀裂長さ、温度の計測誤差が大きくなることが予想される。また、このように温度勾配が大きくなると、亀裂が停止し難くなり、Ｋｃａ値が低く評価される可能性がある。 Next, a case where the test piece has a width of 500 mm and a width of 300 mm and the temperature of one end and the other end of the test piece are the same and a case where the temperature gradient is changed according to the width of the test piece will be examined. When the temperature change of the same K value is obtained with a width of 300 mm and a test stress of 500 MPa with a width of 500 mm, the temperature gradient of the width of 300 mm is 1.67 (= 5/3) times that of the width of 500 mm. It is expected that the temperature measurement error will increase. Further, when the temperature gradient becomes large as described above, it becomes difficult for the crack to stop, and the Kca value may be evaluated to be low.
図５の検討結果から、脆性亀裂伝播停止特性試験方法では、試験片を３００ｍｍ幅とした場合は、５００ｍｍ幅とした場合よりも強い温度勾配にすべきであることがわかる。一方、試験片を３００ｍｍ幅とした場合、５００ｍｍ幅の場合よりも温度勾配を大きくしすぎないことが好ましい。
また、試験片のＫｃａ値の温度依存性は、試験片の厚さによっても変化する。図５では、同じ材料の試験片で厚さが２５ｍｍ、５０ｍｍ、７０ｍｍの例を示す。
なお、図５における試験片「３００−１」は、幅３００ｍｍの試験片の一例を示す。また試験片「ＫＥ３６（５０ｍｍ）」は、ＮＫ規格で降伏強度３５５ＭＰａ以上、−４０℃でのシャルピー吸収エネルギーが２７Ｊ以上の鋼材で板厚が５０ｍｍのものの例を示す。
これらの知見に基づいて、種々の試験片幅Ｗを有する試験片を用いて適正なＫｃａ値が得られる条件について検討を行い、温度勾配ｄＴ／ｄＸ（℃／ｍｍ）を上記（式１）のように試験片幅Ｗ（ｍｍ）に応じて変化させることとした。
From the examination result of FIG. 5, it is understood that in the brittle crack propagation arresting characteristic test method, the temperature gradient should be stronger when the test piece has a width of 300 mm than when it has a width of 500 mm. On the other hand, when the test piece has a width of 300 mm, it is preferable that the temperature gradient is not too large as compared with the case of a width of 500 mm.
The temperature dependence of the Kca value of the test piece also changes depending on the thickness of the test piece. FIG. 5 shows examples of test pieces made of the same material and having thicknesses of 25 mm, 50 mm, and 70 mm.
The test piece “300-1” in FIG. 5 is an example of a test piece having a width of 300 mm. The test piece “KE36 (50 mm)” is an example of a steel material having a yield strength of 355 MPa or more according to NK standard, a Charpy absorbed energy at −40 ° C. of 27 J or more, and a plate thickness of 50 mm.
Based on these findings, the conditions for obtaining an appropriate Kca value using test pieces having various test piece widths W were examined, and the temperature gradient dT / dX (° C / mm) was determined by As described above, the width is changed according to the width W (mm) of the test piece.
５．打撃エネルギーについて
上述のように、脆性亀裂伝播停止特性を正しく評価するためには、打撃エネルギーの影響を無視できる部位で亀裂を停止させることが必要になる。本発明に係る試験片の形状はＷＥＳ２８１５とは異なるが、ＷＥＳ２８１５で推奨される打撃エネルギーを参考にして、亀裂を発生させるために載荷する打撃エネルギーを決定することができる。
5. Hitting Energy As described above, in order to correctly evaluate the brittle crack propagation stopping property, it is necessary to stop the crack at a portion where the influence of the hitting energy can be ignored. Although the shape of the test piece according to the present invention is different from that of WES2815, the impact energy to be loaded to generate a crack can be determined by referring to the impact energy recommended by WES2815.
ＷＥＳ２８１５では、試験片の幅が５００ｍｍである場合に推奨される打撃エネルギーＥｉ［Ｊ］を、板厚ｔ［ｍｍ］、引張応力σ［Ｎ／ｍｍ２］との関係式で表している。
Ｅｉ／ｔ≦min（１．２σ−４０，２００） ・・・ （式２）
ここで、右辺のmin（１．２σ−４０，２００）は２数値（１．２σ−４０）又は（２００）のどちらか最小値を意味する。
In WES2815, the impact energy E i [J] recommended when the width of the test piece is 500 mm is expressed by the relational expression between the plate thickness t [mm] and the tensile stress σ [N / mm 2 ].
E i / t ≦ min (1.2σ−40,200) (Equation 2)
Here, min (1.2σ−40,200) on the right side means the minimum value of either two numerical values (1.2σ−40) or (200).
試験片の幅が２００ｍｍの場合、５００／２００＝２．５であるから、上記（式２）に替えて、下記（式３）によって求められる打撃エネルギーＥｉ［Ｊ］が推奨される。
Ｅｉ／ｔ≦min（１．２σ−４０，２００）／２．５ ・・ （式３）
ここで、min（１．２σ−４０，２００）は２つの数値（１．２σ−４０）又は（２００）のどちらか最小値を意味する。
When the width of the test piece is 200 mm, since 500/200 = 2.5, the impact energy E i [J] obtained by the following (Equation 3) is recommended instead of the above (Equation 2).
E i / t ≦ min (1.2σ−40,200) /2.5 ··· (Equation 3)
Here, min (1.2σ-40,200) means the minimum value of either of the two numerical values (1.2σ-40) or (200).
上記（式２）又は（式３）によって試験条件から求められる打撃エネルギーの上限を付与し、亀裂が発生しない場合は打撃エネルギーを大きくし、亀裂が停止しない場合は打撃エネルギーを小さくすればよい。本発明に係る脆性亀裂伝播停止特性試験方法では、上記（式２）によって求められる打撃エネルギーを参考にして、試験片の一端から幅方向の距離が０．３Ｗ〜０．７Ｗ（Ｗは試験片の幅）の範囲内で亀裂が停止するように、打撃エネルギーを決定するとよい。 The upper limit of the striking energy obtained from the test conditions is given by (Equation 2) or (Equation 3), and the striking energy is increased when the crack does not occur, and the striking energy is decreased when the crack does not stop. In the brittle crack propagation termination property test method according to the present invention, the distance in the width direction from one end of the test piece is 0.3 W to 0.7 W (W is the test piece, with reference to the impact energy obtained by the above (Equation 2). The impact energy may be determined so that the crack stops within the range of (width).
６．供試材について
本発明が対象とする鋼材は、特に限定されない。例えば、一般の溶接構造用厚鋼板を一般の溶接構造物に適用する場合、鋼板の厚さは６．０ｍｍ以上であることが多い。
6. Regarding the sample material The steel material targeted by the present invention is not particularly limited. For example, when a general thick steel plate for welded structure is applied to a general welded structure, the thickness of the steel plate is often 6.0 mm or more.
鋼材の製造方法も特に制限されない。例えば、常法で鋼を溶製し、成分の調整後、鋳造して得られた鋳片を熱間圧延して製造することができる。熱間圧延後は、そのまま水冷するか、又は空冷した後、熱処理を施してもよい。熱間圧延後、冷間圧延して、さらに熱処理を施してもよい。 The method for manufacturing the steel material is also not particularly limited. For example, it can be manufactured by melting steel by a conventional method, adjusting the components, and then hot rolling a cast piece obtained by casting. After hot rolling, it may be water-cooled as it is, or air-cooled and then heat-treated. After hot rolling, cold rolling may be performed and further heat treatment may be performed.
試験片を採取した供試鋼（鋼材Ａ）の板厚、降伏強度、引張強度を表１に示す。 Table 1 shows the plate thickness, yield strength, and tensile strength of the sample steel (steel material A) from which the test piece was sampled.
［実施例１］
鋼材Ａから、アーク溶接によって形成された脆化部（長さ３０ｍｍ、幅５ｍｍ）を設けた３００ｍｍ幅試験片（長さも３００ｍｍ）と、脆化部を設けていない５００ｍｍ幅の試験片（長さも５００ｍｍ）とを準備した。ＷＥＳ２８１５に準拠して、どちらも温度勾配が０．５５℃／ｍｍになるようにして温度勾配型アレスト試験を実施した。結果を図６に示す。ＷＥＳ２８１５規格に準拠する５００ｍｍ幅試験片のデータ（●）に比べて、３００ｍｍ幅試験片のデータ（□）は若干低めの数値（−８％程度）を示しているが、ＷＥＳ２８１５でもデータばらつきの範囲とされている±１５％以内には十分入っており、本発明の試験法の有効性が確認された。
[Example 1]
From steel material A, a 300 mm width test piece (length is also 300 mm) provided with an embrittlement portion (length 30 mm, width 5 mm) formed by arc welding, and a 500 mm width test piece without an embrittlement portion (also length) 500 mm) was prepared. According to WES2815, the temperature gradient type arrest test was carried out so that the temperature gradient was 0.55 ° C./mm in both cases. Results are shown in FIG. Compared to the data (●) of the 500 mm width test piece conforming to the WES2815 standard, the data (□) of the 300 mm width test piece shows a slightly lower numerical value (about -8%), but the range of data variation is also in WES2815. The content is sufficiently within ± 15%, which is said to be, and the effectiveness of the test method of the present invention was confirmed.
［実施例２］
鋼材Ａから、実施例１の３００ｍｍ幅試験片と同形状で、脆化部を設けていない試験片を準備し、実施例１と同じ条件で温度勾配型アレスト試験を実施した。結果を図７に示す。脆化部を付与しない場合、打撃エネルギーが低いと亀裂が発生しなかったため、試験データを１点しか採取できなかった。また、亀裂を発生させるために打撃エネルギーを大きくする必要があり、亀裂が停止し難くなるため、Ｋｃａ値が低めに評価されていることが確認された。
[Example 2]
From steel material A, a test piece having the same shape as the 300 mm width test piece of Example 1 and having no embrittlement portion was prepared, and a temperature gradient arrest test was performed under the same conditions as in Example 1. The results are shown in Fig. 7. In the case where the embrittlement portion was not provided, cracks did not occur when the impact energy was low, so that only one piece of test data could be collected. It was also confirmed that the Kca value was evaluated to be low because it is necessary to increase the impact energy in order to generate cracks and it becomes difficult for the cracks to stop.
［実施例３］
鋼材Ａから、実施例１と同様の脆化部を付与した３００ｍｍ幅試験片を準備し、温度勾配（ｄＴ／ｄＸ）を０．４５℃／ｍｍとし、下限（０．７６−０．０００８Ｗ＝０．５２℃／ｍｍ）よりも低い条件で温度勾配型アレスト試験を実施した。結果を図８に示す。温度勾配が低いと、亀裂が停止しやすくなるため、Ｋｃａ値が高めに評価されることが確認できた。
[Example 3]
A 300 mm width test piece provided with an embrittled portion similar to that of Example 1 was prepared from steel material A, the temperature gradient (dT / dX) was set to 0.45 ° C./mm, and the lower limit (0.76−0.0008W = The temperature gradient type arrest test was carried out under conditions lower than 0.52 ° C./mm). The results are shown in Fig. 8. It can be confirmed that the Kca value is evaluated higher because the crack tends to stop when the temperature gradient is low.
［実施例４］
実施例１と同様の３００ｍｍ幅試験片で、脆化部の長さを５０ｍｍ、幅を５ｍｍにした試験片を用いて、実施例１と同条件で温度勾配型アレスト試験を実施した。結果を図９に示す。脆化部長さが長いと、亀裂長さが長くなりやすいため、Ｋｃａ値を低めに評価され易くなることがわかる。ただし、脆化部長さ５０ｍｍの場合、ＷＥＳ２８１５でデータばらつきの範囲とされている±１５％程度である。
[Example 4]
A temperature gradient type arrest test was performed under the same conditions as in Example 1, using the same 300 mm width test piece as in Example 1 with the embrittlement portion having a length of 50 mm and a width of 5 mm. The results are shown in Fig. 9. It can be seen that when the length of the embrittled portion is long, the crack length is likely to be long, and therefore the Kca value is likely to be evaluated low. However, when the length of the embrittled portion is 50 mm, it is about ± 15% which is the range of data variation in WES2815.
［実施例５］
実施例１と同様の３００ｍｍ幅試験片で脆化部を電子ビーム（長さ３０ｍｍ、幅２ｍｍ）で形成した試験片を用いて、実施例１と同条件で温度勾配型アレスト試験を実施した。結果を図１０に示す。脆化部をアーク溶接で形成した場合と同程度のＫｃａ値評価ができることが確認された。
[Example 5]
A temperature gradient arrest test was carried out under the same conditions as in Example 1 using the same 300 mm width test piece as in Example 1 with the embrittlement portion formed with an electron beam (length 30 mm, width 2 mm). The results are shown in Fig. 10. It was confirmed that the Kca value could be evaluated to the same extent as when the brittle portion was formed by arc welding.
以上、本発明について説明したが、本発明は、本明細書にて説明した態様に限定されることはなく、本発明の記載に当てはまるものであれば本発明の技術的範囲に含まれる。 Although the present invention has been described above, the present invention is not limited to the embodiments described in the present specification and is included in the technical scope of the present invention as long as it is applicable to the description of the present invention.
本発明は、あらゆる産業における鋼材の脆性亀裂伝播停止特性試験において利用することができる。特に、脆性亀裂伝播停止特性が必要とされる、造船、建築物などの溶接構造物に使用される鋼板が要求特性を満足しているか否かの評価や材料開発に有用である。 INDUSTRIAL APPLICABILITY The present invention can be used in brittle crack propagation arrest property tests of steel materials in all industries. In particular, it is useful for evaluating whether or not a steel sheet used for a welded structure such as a shipbuilding or a building, which requires brittle crack propagation stopping characteristics, satisfies required characteristics, and develops materials.
１ 試験片
７ 楔
２１ タブ板
２２ ピンチャック
３０ 切欠き
４０ 脆化部
４２ アーク溶接ビード
４３ 熱影響部
４４ 電子ビーム溶接による脆化部
５０ サイドグルーブ
Ｌ 試験片の長さ
Ｗ 試験片の幅
ｔ 試験片の厚さ
1 Specimen 7 Wedge 21 Tab Plate 22 Pin Chuck 30 Notch 40 Embrittlement 42 Arc Weld Bead 43 Heat Affected Zone 44 Embrittlement by Electron Beam Welding 50 Side Groove L Specimen Length W Specimen Width t Test Piece thickness
Claims (9)
前記試験片の厚さｔが１００ｍｍ以下であり、
前記試験片の一端と他端との距離である試験片の幅Ｗが２００ｍｍ以上３５０ｍｍ未満であり、
前記試験片が、前記切欠きの先端に隣接する部分に脆化部を有する脆性亀裂伝播停止特性試験方法。 A notch is provided at one end of the test piece, and the notch is loaded with impact energy to generate a crack, and in a brittle crack propagation stopping property test method,
The thickness t of the test piece is 100 mm or less,
The width W of the test piece, which is the distance between one end and the other end of the test piece, is 200 mm or more and less than 350 mm,
The brittle crack propagation stopping property test method, wherein the test piece has an embrittlement portion in a portion adjacent to the tip of the notch.
前記試験片幅方向と直交する前記脆化部の幅が１ｍｍ以上３０ｍｍ以下である
請求項１に記載の脆性亀裂伝播停止特性試験方法。 The length of the embrittled portion in the width direction of the test piece is 50 mm or less,
The brittle crack propagation stopping property test method according to claim 1, wherein the width of the embrittled portion orthogonal to the width direction of the test piece is 1 mm or more and 30 mm or less.
請求項１又は２に記載の脆性亀裂伝播停止特性試験方法。 The brittle crack propagation stopping property test method according to claim 1, wherein the embrittled portion is formed by arc welding.
請求項１又は２に記載の脆性亀裂伝播停止特性試験方法。 The brittle crack propagation stopping property test method according to claim 1 or 2, wherein the embrittled portion is formed by electron beam welding.
前記試験片の一端からの距離Ｘに対する前記温度Ｔの変化率である温度勾配ｄＴ／ｄＸ［℃／ｍｍ］が下記（式１）を満足する請求項１〜４のいずれか一項に記載の脆性亀裂伝播停止特性試験方法。
０．７６−０．０００８Ｗ≦ｄＴ／ｄＸ≦０．６４−０．０００２Ｗ ・・・（式１） The temperature T is increasing from one end of the test piece to the other end,
The temperature gradient dT / dX [° C / mm], which is the rate of change of the temperature T with respect to the distance X from one end of the test piece, satisfies the following (formula 1): Brittle crack propagation arrest property test method.
0.76-0.0008W ≦ dT / dX ≦ 0.64-0.0002W (Equation 1)
一端に切欠きを有し、
厚さｔが１００ｍｍ以下であり、
前記一端と他端との距離である幅Ｗが２００ｍｍ以上３５０ｍｍ未満であり、
前記切欠きの先端に隣接する部分に脆化部を有する脆性亀裂伝播停止特性試験片。 A test piece of a brittle crack propagation termination property test method,
Has a notch at one end,
The thickness t is 100 mm or less,
The width W, which is the distance between the one end and the other end, is 200 mm or more and less than 350 mm,
A brittle crack propagation stopping property test piece having an embrittlement portion in a portion adjacent to the tip of the notch.
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| CN115659867A (en) * | 2022-10-31 | 2023-01-31 | 中国石油大学(北京) | Multilayer system three-dimensional well pattern fracturing fracture propagation simulation method |
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