JP2000180324A - Method for determining creep embrittlement in low alloy steel - Google Patents
Method for determining creep embrittlement in low alloy steelInfo
- Publication number
- JP2000180324A JP2000180324A JP35668998A JP35668998A JP2000180324A JP 2000180324 A JP2000180324 A JP 2000180324A JP 35668998 A JP35668998 A JP 35668998A JP 35668998 A JP35668998 A JP 35668998A JP 2000180324 A JP2000180324 A JP 2000180324A
- Authority
- JP
- Japan
- Prior art keywords
- alloy steel
- grain boundary
- low alloy
- test piece
- creep embrittlement
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
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- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、石油精製、石油化学プ
ラント等の高温で運転される装置に使用される低合金鋼
のクリープ脆化判定方法に関し、詳しくは、クリープ脆
化を簡便且つ迅速に判定できる低合金鋼のクリープ脆化
判定方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for judging creep embrittlement of low alloy steel used in equipment operated at a high temperature, such as a petroleum refinery or a petrochemical plant. The present invention relates to a method for judging creep embrittlement of a low alloy steel which can be judged at a time.
【０００２】[0002]
【従来の技術】石油精製、石油化学プラント等の装置で
高温用材料として使用される低合金鋼の長時間使用に伴
う加熱脆化として焼戻し脆化、クリープ脆化がその代表
として揚げられる。2. Description of the Related Art Temper embrittlement and creep embrittlement are typical heat embrittlement associated with long-term use of low alloy steel used as a material for high temperature in equipment such as petroleum refining and petrochemical plants.
【０００３】焼戻し脆化は、低合金鋼を３７５〜５７５
℃の温度領域で長時間使用することにより常温での材料
の靱性が低下する現象であり、機器の停止時における水
圧試験、気密試験時に脆性破壊を主体とする事故をもた
らし、設備の安全面から問題視されている。焼戻し脆化
は、鋼中の残留不純物元素（Ｐ，Ｓｎ、Ｓｂ，Ａｓ等）
の旧オーステナイト粒界での偏析に伴う粒界結合力の低
下に起因することが知られている。[0003] Temper embrittlement occurs when a low alloy steel is used.
This is a phenomenon in which the toughness of the material at room temperature decreases due to prolonged use in the temperature range of ℃, causing accidents mainly due to brittle fracture during water pressure tests and airtight tests when equipment is stopped, and from the viewpoint of equipment safety. It is viewed as a problem. Temper embrittlement is caused by residual impurity elements (P, Sn, Sb, As, etc.) in steel.
It is known that this is caused by a decrease in grain boundary bonding force due to segregation at the former austenite grain boundary.
【０００４】また、クリープ脆化は、材料を高温で使用
する時、作用する応力が一定であっても経時的に組織変
化が進行して、クリープ延性を消失し、結晶粒界でボイ
ド（Void：空孔）更に粒界割れが発生し、ついには破断
に至る現象である。このクリープ脆化は、構造物に付属
物等が取り付けられ応力集中構造となる溶接部の熱影響
部で粒界割れとしてしばしば検出されている。クリープ
脆化は、使用温度・応力に基づく脆化であるが、鋼中の
不純物元素（Ｐ，Ｃｕ，Ａｓ，Ｓｎ，Ｓｂ）、製作時の
溶接後熱処理条件も脆化に大きな影響を与える。Also, creep embrittlement occurs when a material is used at a high temperature, even if the applied stress is constant, the structure changes with time, the creep ductility is lost, and voids are formed at the grain boundaries. : Void) This is a phenomenon in which grain boundary cracks further occur and eventually break. This creep embrittlement is often detected as a grain boundary crack in a heat-affected zone of a welded portion where an accessory or the like is attached to a structure to form a stress concentration structure. Although creep embrittlement is embrittlement based on operating temperature and stress, impurity elements (P, Cu, As, Sn, and Sb) in steel, and post-weld heat treatment conditions at the time of fabrication also have a large effect on embrittlement.
【０００５】上記の材料の脆化の内、焼き戻し脆化は装
置運転中に破壊を生ずる危険性は少ないと考えられる
が、クリープ脆化は装置運転中に発生し進行して破壊を
生ずる可能性があり、クリープ脆化の判定は装置の安全
操業上、重要な問題である。[0005] Of the above embrittlement of materials, temper embrittlement is considered to have a low risk of causing breakage during operation of the apparatus, but creep embrittlement occurs during operation of the apparatus and can proceed to cause breakage. Therefore, the determination of creep embrittlement is an important issue in the safe operation of the equipment.
【０００６】従って、実装置で高温・長時間使用された
低合金鋼製圧力容器等を開放点検した際に、溶接熱影響
部にボイド或いは微少割れを検出することがあれば、こ
れらの欠陥はクリープ脆化割れと推定され、グラインダ
ーによる研削、溶接補修等が実施される。しかも、この
種の割れが検出される事は、圧力容器材料はかなり脆化
が進行していると考えられるので、割れ検出部をサンプ
リングして切り出し、材料の脆化の進行度を調査するこ
とが行われる。Therefore, if a void or a small crack is detected in the weld heat affected zone when an open inspection of a low-alloy steel pressure vessel or the like that has been used for a long time at a high temperature in an actual apparatus is detected, these defects are considered. Presumed to be creep embrittlement cracking, grinding by a grinder, welding repair, etc. are performed. In addition, the fact that this kind of crack is detected means that the material of the pressure vessel is considered to be considerably embrittled, so it is necessary to sample and cut out the crack detection part and investigate the degree of embrittlement of the material. Is performed.
【０００７】このようなことから、プラント装置等にお
いては、高温長時間使用に伴うクリープ脆化の進行度を
予め把握しておくことは、機器の安全上非常に重要なこ
とである。For this reason, in plant equipment and the like, it is very important for the safety of equipment to grasp in advance the degree of creep embrittlement associated with long-term use at high temperatures.
【０００８】[0008]
【発明が解決しようとする課題】従来、クリープ脆化の
判定法としては、クリープ試験、ＳＳＲＴ試験等の機械
的試験方法と金属組織を顕微鏡観察するミクロ組織試験
方法があるが、これらの試験方法には次のような短所が
ある。 （１）機械試験方法の場合 試験の時間が長い。通常、数十時間（ＳＳＲＴ）から
数万時間（クリープ）も要する。 試験片のサイズにより、実機からの試験片採取に制約
がある。 一般的に試験時間が長期に亘るため、試験費用が高
い。 板厚方向に対する脆化の進行分布状況の評価ができな
い。 （２）ミクロ組織試験の場合 クリープ脆化の特徴であるボイドを検出できる範囲
は、試験片の観察面に限られ、試験片の内部は検出でき
ない。 従って、例えば板厚方向に対する脆化進行度を調査す
るには、数多くの試験片を採取して組織の観察を行わな
ければならず、多大な労力を必要とする。 断面組織の観察に熟練を要す。Conventionally, as methods for determining creep embrittlement, there are a mechanical test method such as a creep test and an SSRT test, and a microstructure test method for observing a metal structure with a microscope. Has the following disadvantages: (1) Mechanical test method The test time is long. Usually, it takes tens of hours (SSRT) to tens of thousands of hours (creep). Depending on the size of the test piece, there is a restriction on collecting the test piece from the actual machine. In general, the test cost is high because the test time is long. It is not possible to evaluate the progress distribution of embrittlement in the thickness direction. (2) In the case of microstructure test The range in which voids, which is a feature of creep embrittlement, can be detected is limited to the observation surface of the test piece, and the inside of the test piece cannot be detected. Therefore, for example, in order to investigate the degree of embrittlement in the thickness direction, a large number of test pieces must be collected and the structure must be observed, which requires a great deal of labor. Observation of the cross-sectional structure requires skill.
【０００９】本発明は、上記の問題点に鑑みてなされた
もので、クリープ脆化を迅速・簡便に判定する方法を提
供することを目的とする。The present invention has been made in view of the above problems, and has as its object to provide a method for quickly and easily determining creep embrittlement.
【００１０】[0010]
【課題を解決するための手段】請求項１に係る発明の低
合金鋼のクリープ脆化判定方法は、低合金鋼からなる材
料から採取した試験片を、該材料のエネルギー遷移温度
以下の温度で衝撃破壊して、その破面に粒界破面が生じ
ているか否かを調べ、前記粒界破面があればクリープ脆
化が生じていると判定することを特徴とする。According to a first aspect of the present invention, there is provided a method for judging creep embrittlement of a low-alloy steel, comprising the steps of: (a) preparing a test piece taken from a material made of a low-alloy steel at a temperature lower than the energy transition temperature of the material; It is characterized in that it is examined whether or not the fracture surface has been subjected to impact fracture and has a grain boundary fracture surface, and if the fracture surface is present, it is determined that creep embrittlement has occurred.
【００１１】請求項２に係る発明の低合金鋼のクリープ
脆化判定方法は、低合金鋼からなる材料から採取した試
験片を、該材料のエネルギー遷移温度以下の温度で衝撃
破壊して、その破面から、 粒界破面率＝（粒界破面の面積／測定範囲の総面積）×
100 ％ の式により粒界破面率を求め、この粒界破面率に基づい
てクリープ脆化の有無を判定することを特徴とする。According to a second aspect of the present invention, there is provided a method for judging creep embrittlement of a low-alloy steel, comprising: From the fracture surface, Grain boundary fracture surface ratio = (Area of grain boundary fracture surface / Total area of measurement range) x
The method is characterized in that the grain boundary fracture ratio is determined by the formula of 100%, and the presence or absence of creep embrittlement is determined based on the grain boundary fracture ratio.
【００１２】尚、本発明の低合金鋼とは、高温強度増大
元素であるＣｒを０．５０〜３．２５重量％又はＭｏを
０．１５〜１．１０重量％を含む鋼及びその溶接部を言
う。請求項３に係る発明の低合金鋼のクリープ脆化判定
方法は、請求項１又は２において、前記試験片が、材料
のボイドが検出された箇所の近傍から採取したものであ
る。The low-alloy steel of the present invention refers to a steel containing 0.50 to 3.25% by weight of Cr or 0.15 to 1.10% by weight of Mo, which is an element for increasing high-temperature strength, and a welded portion thereof. Say According to a third aspect of the invention, there is provided the method for judging creep embrittlement of a low alloy steel according to the first or second aspect, wherein the test piece is collected from a vicinity of a location where a void of the material is detected.
【００１３】請求項４に係る発明の低合金鋼のクリープ
脆化判定方法は、請求項１〜３のうちいずれか１つにお
いて、前記低合金鋼がＣｒを０．８０〜１．５０重量％
及びＭｏを０．４５〜０．６５重量％含む鋼であること
を特徴とする。According to a fourth aspect of the present invention, there is provided the method for judging creep embrittlement of a low alloy steel according to any one of the first to third aspects, wherein the low alloy steel contains 0.80 to 1.50% by weight of Cr.
And Mo containing 0.45 to 0.65% by weight of Mo.
【００１４】請求項５に係る発明の鋼材のクリープ脆化
判定方法は、請求項１〜４のうちいずれか１つにおい
て、前記試験片の切欠き部形成位置が、所望の粒界破面
測定部位になるよう試験片を採取することを特徴とす
る。According to a fifth aspect of the present invention, there is provided a method for judging creep embrittlement of a steel material according to any one of the first to fourth aspects, wherein the notch forming position of the test piece is a desired grain boundary fracture surface measurement. It is characterized in that a test piece is collected so as to be a site.
【００１５】請求項６に係る発明の鋼材のクリープ脆化
判定方法は、請求項１〜５のうちいずれか１つにおい
て、前記衝撃破壊する際の試験片の温度が、前記材料の
吸収エネルギー遷移曲線の下部棚肩部の高温側温度以下
であることを特徴とする。According to a sixth aspect of the present invention, there is provided the method for judging creep embrittlement of a steel material according to any one of the first to fifth aspects, wherein the temperature of the test piece at the time of the impact fracture is determined by a change in the energy absorption of the material. It is characterized in that the temperature is lower than or equal to the high temperature side of the lower shelf of the curve.
【００１６】請求項７に係る発明の鋼材のクリープ脆化
判定方法は、請求項１又は３〜６のうちいずれか１つに
おいて、低合金鋼溶接継手の板厚方向に沿って複数の試
験片を採取し、各試験片における破面の粒界破面の有無
を求めること特徴とする。According to a seventh aspect of the present invention, there is provided the method for judging creep embrittlement of a steel material according to any one of the first to third aspects, wherein a plurality of test pieces are provided along a thickness direction of the low alloy steel welded joint. And the presence or absence of a grain boundary fracture surface in each specimen is determined.
【００１７】請求項８に係る発明の鋼材のクリープ脆化
判定方法は、請求項２〜６のうちいずれか１つにおい
て、低合金鋼溶接継手の板厚方向に沿って複数の試験片
を採取し、各試験片における破面の粒界破面率を求める
こと特徴とする。According to a eighth aspect of the present invention, in the method for judging creep embrittlement of a steel material according to any one of the second to sixth aspects, a plurality of test pieces are sampled along a thickness direction of the low alloy steel welded joint. Then, a feature is to obtain a grain boundary fracture surface ratio of a fracture surface in each test piece.
【００１８】請求項９に係る発明の鋼材のクリープ脆化
判定方法は、請求項７又は８おいて、前記試験片が、前
記低合金鋼溶接継手の溶接熱影響部粗粒域の板厚方向に
切欠き部が入れられていることを特徴とする。According to a ninth aspect of the present invention, in the method for judging creep embrittlement of a steel material according to the ninth or eighth aspect, the test piece may be such that the test piece has a thickness direction in a coarse grain area of a weld heat affected zone of the low alloy steel welded joint. A notch portion is provided in the hole.
【００１９】かかる請求項１〜９に係わる発明の作用に
ついて説明する。従来、高温領域でクリープ破壊を起こ
すと粒界破面が観察されることは知られているが、これ
とは異なり、クリープ脆化を起こしている低合金鋼を低
温でシャルピー衝撃試験を行うとその破面に粒界破面が
観察されることを知見した。そこで、請求項１に係る発
明においては、試験片の衝撃破壊による破面に粒界破面
が生じていない場合は、クリープ脆化が起きていないと
判断される。そして、この粒界破面が生じている場合
は、クリープ脆化があると判断される。従って、粒界破
面の有無を調べれば、クリープ脆化の有無を定性的に迅
速且つ簡便に判定できるようになる。The operation of the invention according to the first to ninth aspects will be described. Conventionally, it is known that a grain boundary fracture surface is observed when creep fracture occurs in a high temperature region, but unlike this, when a Charpy impact test is performed on a low alloy steel that has caused creep embrittlement at low temperature. It was found that a grain boundary fracture surface was observed on the fracture surface. Therefore, in the invention according to claim 1, when no grain boundary fracture surface occurs in the fracture surface due to impact fracture of the test piece, it is determined that creep embrittlement has not occurred. When this grain boundary fracture surface occurs, it is determined that there is creep embrittlement. Therefore, by examining the presence or absence of a grain boundary fracture surface, the presence or absence of creep embrittlement can be determined qualitatively quickly and easily.
【００２０】さらに、請求項２に係る発明においては、
試験片の衝撃破壊による破面から上述の式で測定された
粒界破面率が０％の場合は、クリープ脆化が起きていな
いと判断される。そして、この粒界破面率の値が０％で
ない場合は、クリープ脆化があると判断され、その値が
高い程クリープ脆化が進行している傾向にある。このよ
うに、粒界破面率を用いれば、クリープ脆化の有無を定
性的に又は略定量的に迅速且つ簡便に判定できるように
なる。Further, in the invention according to claim 2,
If the grain boundary fracture rate measured by the above equation from the fracture surface due to impact fracture of the test piece is 0%, it is determined that creep embrittlement has not occurred. When the value of the grain boundary fracture ratio is not 0%, it is determined that there is creep embrittlement, and the higher the value, the more the creep embrittlement tends to progress. As described above, the use of the grain boundary fracture ratio makes it possible to quickly and easily determine the presence or absence of creep embrittlement qualitatively or almost quantitatively.
【００２１】請求項３に係る発明においては、ボイドが
検出されてクリープ脆化があることが判明している場所
を基点としてその近傍を調査することで、確実にクリー
プ脆化の判定ができ、簡便にその近傍のクリープ脆化の
分布状態を確実に把握できる。即ち、粒界破面がある場
合、つまり粒界破面率の値０％を超えている場合にあっ
ても、クリープ脆化以外の焼戻し脆化の虞れがなくはな
いが、顕微鏡観察によってボイドが検出されてクリープ
脆化があることが判明している場所を基点として、その
近傍を調査する場合にあっては、本判定方法より簡便に
その近傍のクリープ脆化の分布状態を確実に把握され
る。According to the third aspect of the present invention, creep embrittlement can be determined with certainty by investigating the vicinity of a place where a void is detected and it is known that there is creep embrittlement, as a base point. The distribution state of creep embrittlement in the vicinity can be easily and reliably grasped. That is, even when there is a grain boundary fracture surface, that is, even when the value of the grain boundary fracture surface ratio exceeds 0%, there is no danger of tempering embrittlement other than creep embrittlement, but by microscopic observation. In the case of investigating the vicinity of a location where a void is detected and it is known that there is creep embrittlement, the distribution state of creep embrittlement in the vicinity can be more easily determined by the present determination method. Be grasped.
【００２２】請求項４に係る発明においては、前記低合
金鋼がいわゆる１Ｃｒ−１／２Ｍｏ鋼ないし１・１／４
Ｃｒ−１／２Ｍｏ鋼である場合、その低合金鋼はクリー
プ脆化の感受性が高く、的確にクリープ脆化の判定が行
える。In the invention according to claim 4, the low alloy steel is a so-called 1Cr-1 / 2Mo steel or 1.1 / 4.
In the case of a Cr-1 / 2Mo steel, the low alloy steel has a high susceptibility to creep embrittlement, and can accurately determine creep embrittlement.
【００２３】請求項５に係る発明においては、一般にク
リープ脆化は、溶接熱影響部の粗粒域というごく限られ
た狭い部分に発生するので、その部分に試験片の切欠き
部の底部を一致させることにより、確実にその部分を衝
撃破壊することができて、信頼性の高いデータを得るこ
とができる。In the invention according to claim 5, since the creep embrittlement generally occurs in a very limited narrow portion such as a coarse grain region of the weld heat affected zone, the bottom of the notch portion of the test piece is formed in that portion. By making them coincide with each other, the portion can be reliably destroyed by impact, and highly reliable data can be obtained.
【００２４】請求項６に係る発明においては、吸収エネ
ルギー遷移曲線の下部棚肩部の高温側温度以下で衝撃破
壊することにより、粒界破面の明確な現出が行え、その
後の粒界破面の計測が精度よく行える。In the invention according to claim 6, the impact fracture is performed at a temperature lower than the high-temperature side of the lower shelf shoulder of the absorption energy transition curve, so that a grain boundary fracture surface can clearly appear, and the subsequent grain boundary fracture occurs. Surface measurement can be performed with high accuracy.
【００２５】請求項７及び８に係る発明においては、本
判定方法がボイドが検出されてクリープ脆化があること
が判明している表面を基点として、板厚方向のクリープ
脆化の進行度分布を簡便に確実に把握することができ、
例えば、設計上の必要板厚と板厚方向のクリープ脆化の
進行深さとを比較して機器の安全性を検討・評価するこ
とができる。According to the seventh and eighth aspects of the present invention, the degree of progression of creep embrittlement in the sheet thickness direction starts from the surface where voids are detected and it is known that there is creep embrittlement. Can be easily and reliably grasped,
For example, the safety of equipment can be examined and evaluated by comparing the required thickness in design with the progression of creep embrittlement in the thickness direction.
【００２６】請求項９に係る発明においては、一般にク
リープ脆化が生ずる溶接熱影響部粗粒域に対して板厚方
向に切欠き部を入れることにより、確実に各位置に対応
する溶接熱影響部粗粒域部分を衝撃破壊することができ
て、信頼性の高いデータを得ることができる。According to the ninth aspect of the present invention, a notch is formed in the thickness direction of the weld heat affected zone where the creep embrittlement generally occurs, so that the weld heat affected zone corresponding to each position is surely ensured. The part of the coarse grain region can be broken by impact, so that highly reliable data can be obtained.
【００２７】[0027]
【発明の実施の形態】以下に、本発明のクリープ脆化判
定方法の実施形態について、低合金鋼製圧力容器の場合
について説明する。BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the method for judging creep embrittlement of the present invention will be described in the case of a pressure vessel made of a low alloy steel.
【００２８】実装置で高温・長時間使用された低合金鋼
製圧力容器は厚板の場合が多く、板厚方向に若干の温度
差が考えられる。また、厚板のため溶接部は多層盛溶接
されるため溶接熱影響部は繰り返し熱影響を受ける。こ
のような状況から表面からどの程度の距離まで板厚方向
にクリープ脆化が生じているかを知ることは重要なこと
である。A low-alloy steel pressure vessel which has been used for a long time at a high temperature in an actual apparatus is often a thick plate, and a slight temperature difference in the thickness direction is conceivable. Further, since the welded portion is formed by multi-layer welding because of the thick plate, the heat affected zone is repeatedly affected by heat. From such a situation, it is important to know how far from the surface the creep embrittlement occurs in the thickness direction.
【００２９】本実施形態は、かかる低合金鋼の実機材の
板厚方向に対する脆化分布状態を把握する場合の例を示
すもので、試験材（サンプリング材）からその板厚方向
に沿って複数の試験片を切り出し、板厚方向に切欠き溝
を加工した小型シャルピー衝撃試験片を作成し、シャル
ピー衝撃試験を行ってそれぞれの破面を観察し、粒界破
面率を測定することによって板厚方向のどの位置までク
リープ脆化が生じているかを判断する。This embodiment shows an example in which the state of embrittlement distribution in the sheet thickness direction of the actual low-alloy steel material is grasped, and a plurality of specimens are sampled from the test material (sampling material) along the sheet thickness direction. A small Charpy impact test specimen with a notch groove machined in the plate thickness direction was prepared, a Charpy impact test was performed, and each fracture surface was observed. It is determined at which position in the thickness direction creep embrittlement has occurred.
【００３０】前記低合金鋼とは、高温強度増大元素であ
るＣｒを０．５０〜３．２５重量％又はＭｏを０．１５
〜１．１０重量％を含む鋼及びその溶接部を言うが、本
方法においては、特に、前記低合金鋼がいわゆる１Ｃｒ
−１／２Ｍｏ鋼ないし１・１／４Ｃｒ−１／２Ｍｏ鋼で
ある場合、即ち、Ｃｒを０．８０〜１．５０重量％及び
Ｍｏを０．４５〜０．６５重量％含む鋼である場合、そ
の低合金鋼はクリープ脆化の感受性が高く、きわめて的
確にクリープ脆化の判定が行える。 １）試験片の採取、加工、製作条件 図１に示すように、低合金鋼製圧力容器の材料Ａと材料
Ｂの溶接部分をサンプリングした試験材１から、溶接ビ
ード部分をまたいでその肉厚方向（板厚方向）に対して
等間隔に且つできる限り多く試験片２を採取する。この
場合、図示のように溶接熱影響部が各試験片２の略中央
部のノッチ形成位置となるように採取する。このような
採取方法によって、試験材の肉厚方向の各箇所に対する
脆化度を精度良く評価できるようになる。そして、ＪＩ
Ｓ Ｚ ２２０２（１９９８）において、Ｖノッチ試験
片として標準サイズ（10×10×55mm）が規定されおり、
実機材の一点だけを測定する場合はその寸法で差支えな
い。しかし、本実施形態の如く実機材の肉厚方向に対す
る脆化分布状態を把握する場合は、出来る限り多くの試
験片を採取するのが好ましく、試験片の幅（試験片に触
れた衝撃刃の刃縁に沿った方向）が1/2 サイズ（５×10
×55mm）のサブサイズ試験片がよく、更に好ましくは、
図２の如き1/4 サイズ（2.5 ×10×55mm）の寸法のサブ
サイズ試験片とするのが良い。[0030] The low-alloy steel is a high-temperature-strength-enhancing element such as 0.50 to 3.25% by weight of Cr or 0.15% of Mo.
In the present method, especially the low alloy steel is a so-called 1Cr steel.
-When the steel is 1/2 Mo steel to 1.1 / 4 Cr-1 / 2 Mo steel, that is, when the steel contains 0.80 to 1.50% by weight of Cr and 0.45 to 0.65% by weight of Mo. The low-alloy steel has a high susceptibility to creep embrittlement, and can determine creep embrittlement very accurately. 1) Sampling, Processing, and Manufacturing Conditions for Test Specimen As shown in FIG. 1, the thickness of a test material 1 obtained by sampling a welded portion of a material A and a material B of a low alloy steel pressure vessel over a weld bead portion. The test pieces 2 are sampled at equal intervals in the direction (plate thickness direction) and as much as possible. In this case, the specimen is sampled so that the weld heat affected zone is located at the notch forming position substantially at the center of each test piece 2 as shown. By such a sampling method, the degree of embrittlement at each location in the thickness direction of the test material can be accurately evaluated. And JI
In SZ 2202 (1998), a standard size (10 × 10 × 55 mm) is specified as a V notch test piece,
If only one point of the actual equipment is measured, its dimensions can be used. However, when grasping the state of embrittlement distribution in the thickness direction of the actual equipment as in the present embodiment, it is preferable to collect as many test pieces as possible, and the width of the test pieces (the impact blade that touches the test pieces). The size along the edge is 1/2 size (5 × 10
× 55 mm) sub-size test piece is better, more preferably,
It is preferable to use a sub-size test piece having a size of 1/4 size (2.5 × 10 × 55 mm) as shown in FIG.
【００３１】試験片の加工は、図１の如く切欠き部（切
欠き溝又はノッチ）加工方向を実機材の板厚方向（実機
材の表面と直交する方向）とし、切欠き部は溶接熱影響
部をエッチングしてから加工する。板厚方向に切欠き部
を設けることによって、衝撃試験の衝撃刃の触れる面が
実機材の板厚方向に相当することになる。As shown in FIG. 1, the processing direction of the test piece is such that the notch (notch groove or notch) processing direction is the thickness direction of the actual machine (the direction orthogonal to the surface of the actual machine), and the notch is the welding heat. The affected part is etched before processing. By providing the notch in the plate thickness direction, the contact surface of the impact blade in the impact test corresponds to the plate thickness direction of the actual machine.
【００３２】このような加工方法によって、切欠き部の
底部をクリープ脆化が最も生じやすい溶接熱影響部の粗
粒域に正確に当たるようにする。一般にクリープ脆化
は、溶接熱影響部の粗粒域というごく限られた狭い部分
に発生するので、その部分に試験片の切欠き部の底部を
一致させることにより、確実にその部分で衝撃破壊する
ことができ、信頼性の高いデータを得ることができる。
切欠き部の底部の曲率半径Ｒは、図２の如く0.25mmであ
る。 ２）シャルピー衝撃試験 実機材から採取し加工した前記試験片についてシャルピ
ー衝撃試験を行う際の試験温度は、実機材と同材質の材
料で予備衝撃試験を行って得られる図３の試験温度と吸
収エネルギーの関係を示す遷移曲線で示されるエネルギ
ー遷移温度（Energy Transion Temperature)以下の低温
であればよいが、好ましくは粒界破面がもっとも現出し
やすい図３に示す試験片の吸収エネルギー遷移曲線の下
部棚（Lower Shelf)肩部の高温側温度以下、更に好まし
くは下部棚肩部の温度範囲から選択して行う。By such a working method, the bottom of the notch is made to exactly hit the coarse grain area of the weld heat affected zone where creep embrittlement is most likely to occur. In general, creep embrittlement occurs in a very limited narrow part of the weld heat-affected zone, such as the coarse-grained area. And highly reliable data can be obtained.
The radius of curvature R at the bottom of the notch is 0.25 mm as shown in FIG. 2) Charpy impact test The test temperature at the time of conducting the Charpy impact test on the test piece sampled and processed from the actual equipment is the test temperature and absorption shown in FIG. 3 obtained by performing a preliminary impact test using the same material as the actual equipment. The temperature may be lower than the energy transition temperature shown by the transition curve showing the energy relationship, but it is preferable that the grain boundary fracture surface appears most easily. The temperature is selected from the high temperature side of the lower shelf shoulder portion, more preferably from the temperature range of the lower shelf shoulder portion.
【００３３】尚、試験材料と同材質のエネルギー遷移温
度や下部棚温度範囲が文献等で既知であれば、そのデー
タを採用して予備衝撃試験を省略することができる。ま
た、前記エネルギー遷移温度は、延性破面率100 ％とな
る最低温度に対応する吸収エネルギーと、脆性破面率10
0 ％となる最高温度に対応する吸収エネルギーとの、平
均吸収エネルギーに相当する温度で、簡便な方法とし
て、延性破面率100 ％となる最低温度における吸収エネ
ルギーの1/2 の値に相当する温度として求めることがで
きる。前記下部棚の肩部温度範囲は、具体的には、例え
ば１Ｃｒ−１／２Ｍｏ鋼においては、図３に示すよう
に、遷移点が約０℃であり、通常−４０℃〜−６０℃の
範囲であるため、予めこの範囲を選定し、好ましくは、
−５０℃をシャルピー衝撃試験温度とするとよい。If the energy transition temperature and the lower shelf temperature range of the same material as the test material are known in the literature, the data can be used to omit the preliminary impact test. Further, the energy transition temperature is determined based on the absorbed energy corresponding to the lowest temperature at which the ductile fracture rate becomes 100% and the brittle fracture rate of 10%.
A temperature equivalent to the average absorbed energy with the absorbed energy corresponding to the highest temperature of 0%, and, as a simple method, equivalent to half the value of the absorbed energy at the lowest temperature at which the ductile fracture rate is 100%. It can be obtained as temperature. The shoulder temperature range of the lower shelf is specifically, for example, in the case of 1Cr-1 / 2Mo steel, as shown in FIG. 3, the transition point is about 0 ° C., and is usually −40 ° C. to −60 ° C. Because it is a range, this range is selected in advance, preferably,
-50 ° C may be set as the Charpy impact test temperature.
【００３４】そして、上記で定めたシャルピー衝撃試験
温度でＪＩＳ Ｚ ２２４２に従ってシャルピー衝撃試
験を行う。具体的には試験片の切欠き部がない側が試験
機のハンマーに接するように、該試験片の切欠き部中央
と試験片支持台間の中央とを所定の精度で一致させて固
定し、衝撃試験を行なう。 ３）粒界破面率の測定 シャルピー衝撃試験によって得られた破面について、粒
界破面測定を行う。 ＜測定範囲＞図４に示すように、破面の測定範囲は、粒
界破面がもっとも現出しやすい切欠き部の底部の直下部
とし、試験片全幅（2.5 mm）に亘って、溶接熱影響部の
粗粒域である切欠き部の深さ方向に0.2 mm〜0.3 mm、好
ましくは0.25mmに亘って測定する（図中のハッチング部
分）。 ＜測定方法＞金属結晶粒の集合体が破壊する時、破面が
結晶粒内を貫通する粒内破面と結晶粒界に沿って生ずる
粒界破面とが、金属結晶の粒内及び粒界の強度状態に応
じて生ずる。本実施形態の測定方法は、この粒界破面の
面積を測定する。粒界破面は、図６に示す写真の如く滑
らかな破面（図６の写真の粒界破面部分をスキャナーで
読取りパソコンで画像処理してハッチングした図７の画
像を参照）であり、電子顕微鏡写真により判別できる。
具体的には、電子顕微鏡で前記測定範囲を３００〜４０
０倍、好ましくは３５０倍程度に拡大して測定する。粒
界破面を算出するには、図７に示すように、測定範囲に
おける粒界破面をトレーシング方眼紙に敷き写し、その
面積を算出すればよい。また、例えば商品名Image-Pro
Plus、商品名Meterials-Pro 等の市販画像解析・計測ソ
フトウェアを使用することによって、パソコンで簡単に
効率よく行うことができる。 ＜粒界破面率の計算＞次に、下記式に従って粒界破面率
を求める。Then, a Charpy impact test is performed at the Charpy impact test temperature determined above in accordance with JIS Z 2242. Specifically, the center of the notch of the test piece and the center between the test piece supports are fixed with a predetermined accuracy so that the side of the test piece without the notch is in contact with the hammer of the tester, and fixed. Perform an impact test. 3) Measurement of grain boundary fracture surface The grain boundary fracture surface is measured for the fracture surface obtained by the Charpy impact test. <Measurement range> As shown in Fig. 4, the measurement range of the fracture surface was set just below the bottom of the notch where the grain boundary fracture surface was most likely to appear, and the welding heat was measured over the entire width (2.5 mm) of the test piece. The measurement is performed in the depth direction of the notch portion, which is the coarse-grained area of the affected portion, in a range of 0.2 mm to 0.3 mm, preferably 0.25 mm (hatched portion in the figure). <Measurement method> When an aggregate of metal crystal grains breaks, the intragranular fracture surface where the fracture surface penetrates through the crystal grain and the grain boundary fracture surface that occurs along the crystal grain boundary are within and within the metal crystal grain. It occurs depending on the strength state of the field. The measurement method of the present embodiment measures the area of the grain boundary fracture surface. The grain boundary fracture surface is a smooth fracture surface as shown in the photograph of FIG. 6 (see the image of FIG. 7 in which the grain boundary fracture surface portion in the photograph of FIG. 6 is read by a scanner and image-processed by a personal computer and hatched). It can be determined from an electron micrograph.
Specifically, the measurement range is 300 to 40 with an electron microscope.
The measurement is performed at a magnification of 0 times, preferably about 350 times. In order to calculate the grain boundary fracture surface, as shown in FIG. 7, the grain boundary fracture surface in the measurement range may be laid on a tracing graph paper and the area thereof may be calculated. Also, for example, the product name Image-Pro
By using commercially available image analysis / measurement software such as Plus, trade name Meterials-Pro, etc., it can be easily and efficiently performed on a personal computer. <Calculation of Grain Boundary Surface Fraction> Next, the grain boundary fracture surface ratio is determined according to the following equation.
【００３５】粒界破面率＝（粒界破面の面積／測定範囲
の総面積）×100 ％ ４）試験結果の判定 以上の測定によって、粒界破面率が算出され、粒界破面
の占める割合により、クリープ脆化の有無を判定するこ
とができる。Grain boundary fracture surface ratio = (area of grain boundary fracture surface / total area of measurement range) × 100% 4) Judgment of test result By the above measurement, the grain boundary fracture surface ratio is calculated, and the grain boundary fracture surface is calculated. , The presence or absence of creep embrittlement can be determined.
【００３６】即ち、試験片の衝撃破壊で破面に粒界破面
が生じていない場合、つまり試験片の衝撃破壊で測定さ
れた粒界破面率の値が０％の場合は、クリープ脆化が起
きていないと判断される。そして、粒界破面が生じてい
る場合、つまり、粒界破面率の値が０％でない場合は、
クリープ脆化があると判断され、その値が高い程クリー
プ脆化が進行している傾向にある。That is, when no intergranular fracture surface is generated on the fracture surface due to impact fracture of the test piece, that is, when the value of the grain boundary fracture surface ratio measured by impact fracture of the test piece is 0%, creep embrittlement occurs. It is determined that no conversion has occurred. When a grain boundary fracture surface has occurred, that is, when the value of the grain boundary fracture surface ratio is not 0%,
It is determined that there is creep embrittlement, and the higher the value is, the more creep embrittlement tends to progress.
【００３７】尚、粒界破面率の値が０％でない場合にあ
っても、クリープ脆化以外の焼戻し脆化の虞れがなくは
ない。しかし、顕微鏡観察によってボイドが検出されて
クリープ脆化があることが判明している場所を基点とし
て、その近傍を調査する場合にあっては、本判定方法よ
り簡便にその近傍のクリープ脆化の分布状態を確実に把
握できる。従って、前記試験片を採取する前の実機材の
表面や板厚断面を、事前にミクロ観察により、溶接熱影
響部粗粒域にボイドがあるかどうか確認することが好ま
しい。ボイドがあることが判明すれば、実機材の該部分
においてはクリープ脆化が起きていると判定できる。こ
のような状況において、板厚方向に対し等間隔に採取し
た各試験片から得られた「粒界破面率と肉厚方向位置の
関係」をプロットすることにより、板厚方向におけるク
リープ脆化の分布状況がよく解る。このクリープ脆化の
進行度分布を知ることによって、例えば、設計上の必要
板厚と板厚方向のクリープ脆化の進行深さとを比較して
機器の安全性を検討・評価することができる。Incidentally, even when the value of the grain boundary fracture ratio is not 0%, there is still a risk of tempering embrittlement other than creep embrittlement. However, in the case of investigating the vicinity of a place where the void is detected by microscopic observation and it is known that there is creep embrittlement, the creep embrittlement in the vicinity is more easily performed by the present determination method. The distribution state can be grasped reliably. Therefore, it is preferable to confirm by microscopic observation in advance whether or not there are any voids in the weld heat affected zone coarse grain region by observing the surface and the thickness cross section of the actual machine before collecting the test piece. If it is found that there is a void, it can be determined that creep embrittlement has occurred in this portion of the actual machine. In this situation, creep embrittlement in the sheet thickness direction was plotted by plotting the "relationship between grain boundary fracture ratio and position in the thickness direction" obtained from each test piece sampled at equal intervals in the sheet thickness direction. I understand the distribution situation. By knowing the progress distribution of the creep embrittlement, for example, the safety of the equipment can be examined and evaluated by comparing the required thickness in design with the progress depth of the creep embrittlement in the thickness direction.
【００３８】［実施例］ （１）試験片の仕様と採取位置並びに形状 試験材は、圧力容器の胴板円周継手から採取した板厚１
９．５mmt の低合金鋼（ＡＳＴＭ Ａ３８７ Ｇｒ．１
２Ｃｌ．２：１．０Ｃｒ−１／２Ｍｏ鋼）で、運転温度
約５００℃で２００，０００時間以上使用された材料で
ある。当該材料は顕微鏡観察により、胴板円周継手内外
面の溶接熱影響部粗粒域の結晶粒界にボイドが確認され
た材料である。当該試験材からの衝撃試験片の採取は、
図１に示すように、1/4 サイズ［JIS Z 2202(1998)Ｖノ
ッチ試験片］のサブサイズ試験片とし、試験材の厚さを
ｔとすると、試験片の厚さ中心位置が外表面側から、1/
12t,3/12t,5/12t,7/12t,9/12t,11/12tの位置になるよう
にして、試験片を６本採取した。衝撃試験片の溶接部を
バフ研磨し、３〜５％ナイタル（硝酸アルコール液）を
塗布してエッチング処理を施し溶接熱影響部の粗粒域を
明確にした。その粗粒域に切欠き部の底部がくるよう
に、切欠き部を板厚方向に機械加工で形成した。 （２）シャルピー衝撃試験 衝撃試験条件を表１に示す。試験温度は試験材料の脆性
領域である下部棚温度の肩部に位置する−５０℃とし
た。[Examples] (1) Specifications, sampling position and shape of test piece The test material was a sheet thickness 1 sampled from the circumferential joint of the body plate of the pressure vessel.
9.5 mmt low alloy steel (ASTM A387 Gr.1)
2Cl. 2: 1.0Cr-1 / 2Mo steel), which has been used at an operating temperature of about 500 ° C. for 200,000 hours or more. This material is a material in which voids have been confirmed by microscopic observation at crystal grain boundaries in the coarse grain region of the weld heat affected zone on the inner and outer surfaces of the body plate circumferential joint. The collection of impact test specimens from the test material
As shown in FIG. 1, a sub-size test piece of 1/4 size [JIS Z 2202 (1998) V notch test piece] and a thickness of the test material as t, the thickness center position of the test piece is the outer surface. From the side, 1 /
Six test pieces were collected at the positions of 12t, 3 / 12t, 5 / 12t, 7 / 12t, 9 / 12t, and 11 / 12t. The welded portion of the impact test piece was buff-polished, and 3-5% nital (a nitric acid alcohol solution) was applied and subjected to an etching treatment to clarify the coarse grain area of the weld heat affected zone. The notch was machined in the plate thickness direction so that the bottom of the notch was located in the coarse grain area. (2) Charpy impact test Table 1 shows the impact test conditions. The test temperature was −50 ° C. located at the shoulder of the lower shelf temperature, which is the brittle region of the test material.
【００３９】[0039]
【表１】 （３）破面観察条件 衝撃試験後の破面観察はすべての試験について共通に、
切欠き部の底部直下部の全幅について、走査型電子顕微
鏡にて観察し、３５０倍で撮影した。粒界破面の判定に
ついては、図６の写真に示すように、粒界に沿って平坦
に破壊され、その内部は滑らかな破面を粒界破面と判定
し計測した。低温域で特徴的に観察される劈開破面（リ
バー・パターン）、また、ディンプルは計測より除外し
た。粒界破面の測定は、図７に示すように破面写真上に
１cm四方の格子を設けた透明な方眼紙を置き、計測・集
計することにより粒界破面の面積率を得た。 （４）試験結果 上記の粒界破面の面積の測定結果を基に、下記に従い粒
界破面率を求めた。[Table 1] (3) Fracture surface observation conditions Fracture surface observation after the impact test is common for all tests.
The entire width immediately below the cutout was observed with a scanning electron microscope and photographed at a magnification of 350 times. Regarding the determination of the grain boundary fracture surface, as shown in the photograph of FIG. 6, the surface was broken flat along the grain boundary, and a smooth fracture surface inside was determined as the grain boundary fracture surface and measured. Cleavage fracture surfaces (river patterns) and dimples characteristically observed at low temperatures are excluded from the measurement. In the measurement of the grain boundary fracture surface, as shown in FIG. 7, a transparent graph paper having a 1 cm square grid was placed on the fracture surface photograph, and the area ratio of the grain boundary fracture surface was obtained by measuring and totaling. (4) Test Results Based on the measurement results of the area of the grain boundary fracture surface, the grain boundary fracture surface ratio was determined as follows.
【００４０】粒界破面率＝（粒界破面の面積／測定範囲
の総面積）×100 ％ 板厚方向について衝撃試験を行なった結果を表２及び図
５に示す。Grain boundary fracture rate = (area of grain boundary fracture surface / total area of measurement range) × 100% Table 2 and FIG. 5 show the results of an impact test conducted in the sheet thickness direction.
【００４１】[0041]
【表２】 試験の結果、表２に示すように、板厚の中央部とその内
外表面において相違が認められ、中央部では粒界破面は
認められず、外面側では２１％、内面側では９〜２２％
と、内外面側において粒界破面が多く観察され、後述す
るミクロ組織観察の結果と一致していた。[Table 2] As a result of the test, as shown in Table 2, a difference was observed between the central portion of the sheet thickness and the inner and outer surfaces, no grain boundary fracture surface was observed at the central portion, 21% on the outer surface side, and 9 to 22 on the inner surface side. %
And many grain boundary fracture surfaces were observed on the inner and outer surfaces, which was consistent with the results of microstructure observation described later.
【００４２】以上の粒界破面率に基づくクリープ脆化分
布状況の評価から、クリープ脆化は実機材の内外表面よ
り同時に進行し全板厚の１／２程度（外表面〜3/12t と
9/12t 〜内表面）脆化していると判断された。 （５）ミクロ組織観察 前記粒界破面率によるクリープ脆化の有無の判定を検証
するために、試験片のミクロ組織観察を行い、クリープ
脆化を示すボイドの有無を調べた。From the above evaluation of the creep embrittlement distribution based on the grain boundary fracture ratio, it was found that creep embrittlement progressed simultaneously from the inner and outer surfaces of the actual machine, and was about 1/2 of the total sheet thickness (outer surface to 3/12 ton).
9 / 12t ~ inner surface) It was judged to be embrittled. (5) Microstructure Observation In order to verify the determination of the presence or absence of creep embrittlement based on the grain boundary fracture ratio, the microstructure of the test piece was observed and the presence or absence of voids indicating creep embrittlement was examined.
【００４３】（イ）観察位置 図８に示すように、前記粒界破面率を求めた衝撃試験片
を採取した残りの試験材で、その採取した前記衝撃試験
片の切欠き部（ノッチ）に隣接した材料断面の溶接熱影
響部粗粒域の観察箇所（ａ，ｂ，ｃ）を含むように試験
片を採取してミクロ観察を行った。(A) Observation position As shown in FIG. 8, a notch portion (notch) of the impact test piece obtained from the remaining test material from which the impact test piece for which the grain boundary fracture rate was determined was obtained. The test specimen was sampled so as to include the observation point (a, b, c) in the coarse grained area of the weld heat-affected zone of the material section adjacent to, and microscopic observation was performed.
【００４４】尚、図８は、前記粒界破面率を求めた衝撃
試験片を採取した試験材部分とミクロ組織観察のための
試験材部分との断面を、解りやすいように９０度回転移
動して表示したものである。また、図５のＸ軸方向に前
記溶接熱影響部粗粒域の観察箇所（ａ，ｂ，ｃ）の位置
を参考として示した。FIG. 8 shows the cross section of the test material portion from which the impact test piece for which the grain boundary fracture ratio was determined and the test material portion for microstructure observation are rotated by 90 ° so that the cross section can be easily understood. It is displayed. Further, the positions of the observation points (a, b, c) in the coarse zone of the weld heat affected zone in the X-axis direction in FIG. 5 are shown for reference.
【００４５】（ロ）観察作業手順 前記溶接熱影響部粗粒域を含むように採取したミクロ組
織観察用試験片を、研磨処理しやすくするために、熱硬
化性樹脂に埋込んだ後、カービメットペーパー80# 〜15
00# で研磨した。洗浄後再び、ポリッシング用バフ5 〜
0.05μm で鏡面研磨した。(B) Observation work procedure A microstructure observation specimen taken so as to include the coarse zone of the heat affected zone is embedded in a thermosetting resin to facilitate polishing treatment. Met paper 80 # 〜15
Polished with 00 #. After cleaning, polishing buff 5 ~ again
Mirror polishing at 0.05 μm.
【００４６】前記処理後、図８に示すように、光学顕微
鏡の５０〜２００倍で、試験材の外表面近傍（ａ）、中
央部（ｂ）及び内表面近傍（ｃ）のそれぞれ３mm×３mm
の範囲を観察箇所として位置決めし、４００〜９００倍
の高倍率で観察した。After the above-mentioned treatment, as shown in FIG. 8, at a magnification of 50 to 200 times using an optical microscope, each of the test material near the outer surface (a), the center (b) and the inner surface (c) has a size of 3 mm × 3 mm.
Were positioned as observation points, and observed at a high magnification of 400 to 900 times.
【００４７】前記観察の後、３〜５％ナイタルでエッチ
ング処理して組織を明瞭に出現させ、再び顕微鏡観察
し、最終的に９００倍の倍率で写真記録を取った。 （ハ）観察結果 ミクロ観察により、前記観察箇所ａと前記観察箇所ｃと
にボイドの存在が確認され、クリープ脆化があることが
認められた。一方、前記観察箇所ｂにはボイドがなくク
リープ脆化がないことが認められた。このミクロ観察結
果は、前項（４）で示した本実施形態の方法を用いた粒
界破面率に基づくクリープ脆化分布状況の評価とよく一
致した。After the above observation, the structure was clearly exposed by etching with 3 to 5% nital, and the structure was again observed with a microscope. Finally, a photograph was recorded at a magnification of 900 times. (C) Observation results Microscopic observation confirmed the existence of voids at the observation points a and c, and confirmed that there was creep embrittlement. On the other hand, it was confirmed that there was no void and no creep embrittlement at the observation point b. This micro-observation result agreed well with the evaluation of the creep embrittlement distribution based on the grain boundary fracture ratio using the method of the present embodiment described in (4) above.
【００４８】今回のミクロ組織観察は、溶接熱影響部粗
粒域の板厚方向について全面に亘って高倍率観察をせず
に、外表面側、中央部、内表面側の３箇所の観察とした
が、前記顕微鏡観察だけで約１２時間を要した。尚、板
厚方向について全面に亘って高倍率観察する場合は、試
料調整の時間の約８時間を含めると、ミクロ組織観察に
計約３３時間要することになる。In this microstructure observation, three high-magnification observations were performed on the outer surface side, the center portion, and the inner surface side without performing high-magnification observation over the entire surface in the thickness direction of the coarse zone of the weld heat affected zone. However, it took about 12 hours only for the microscope observation. When high magnification observation is performed over the entire surface in the plate thickness direction, a total of about 33 hours are required for microstructure observation, including about 8 hours for sample preparation.
【００４９】一方、本実施例で行った前記粒界破面率を
求めた衝撃試験方法では、衝撃試験と粒界破面率の測定
に要する時間は、全板厚方向全面を対象とした試験片６
本すべてを行っても概略１５時間程度で済む。従って、
本実施形態の低合金鋼のクリープ脆化判定方法は、従来
のミクロ組織観察方法よりきわめて省力できる方法であ
る。On the other hand, according to the impact test method for determining the grain boundary fracture ratio performed in the present embodiment, the time required for the impact test and the measurement of the grain boundary fracture ratio is determined by the test for the entire surface in the entire thickness direction. Piece 6
It takes only about 15 hours to do all of this. Therefore,
The method for judging creep embrittlement of a low-alloy steel according to the present embodiment is a method that can save much labor compared to a conventional microstructure observation method.
【００５０】以上、前記実施形態においては、肉厚方向
のどの位置までクリープ脆化が生じているかを判断をす
るために、肉厚方向に試験片を採取したが、表面のどの
範囲までクリープ脆化が生じているかを判断をするため
に、表面に沿って試験片を採取し、実施形態の如く粒界
破面率の測定を行ってもよいのはむろんである。その場
合、図９の如く試験片２の切欠き部（ノッチ）底部の方
向は溶接部に沿って設けるとよい。As described above, in the above embodiment, the test piece was sampled in the thickness direction in order to determine the position in the thickness direction where the creep embrittlement occurred. It is a matter of course that a test piece may be taken along the surface to determine whether or not the cracking has occurred, and the grain boundary fracture ratio may be measured as in the embodiment. In this case, the bottom of the notch (notch) of the test piece 2 may be provided along the welded portion as shown in FIG.
【００５１】[0051]
【発明の効果】以上説明したように、請求項１及び２に
係わる本発明によれば、石油精製、石油化学プラント装
置等で使用される装置材料等の高温環境で使用される材
料のクリープ脆化の有無を衝撃試験での破面観察による
粒界破面の有無又は粒界破面率の測定により行うので、
従来のミクロ組織観察試験等によるクリープ脆化の判定
方法に比べて、試験片加工も安価にでき、試験時間も大
幅に短縮され、また、労力も少なくて済み、安価、迅
速、簡便にできる。特に請求項２に係わる発明によれ
ば、粒界破面率の値が高い程クリープ脆化が進行してい
る傾向にあり、定量的に近い状態でその材料の状態を把
握できる利点がある。As described above, according to the first and second aspects of the present invention, creep embrittlement of materials used in a high-temperature environment, such as equipment materials used in petroleum refining and petrochemical plant equipment, and the like. Since the presence or absence of the formation is determined by measuring the presence or absence of grain boundary fracture surface by observing the fracture surface in the impact test,
Compared with the conventional method of judging creep embrittlement by a microstructure observation test or the like, test piece processing can be performed at a lower cost, the test time can be significantly reduced, and labor can be reduced, and the cost can be reduced, quickly, and simply. In particular, according to the second aspect of the present invention, as the value of the grain boundary fracture ratio increases, the creep embrittlement tends to progress, and there is an advantage that the state of the material can be grasped in a nearly quantitative state.
【００５２】請求項３に係わる発明によれば、本判定方
法がボイドが検出されてクリープ脆化があることが判明
している場所を基点として、その近傍を簡便に調査で
き、クリープ脆化を確実に把握できる。According to the third aspect of the present invention, the present method can easily investigate the vicinity of a location where a void is detected and it is known that there is creep embrittlement, and the creep embrittlement can be reduced. Can be grasped reliably.
【００５３】請求項４に係る発明においては、前記低合
金鋼がいわゆる１Ｃｒ−１／２Ｍｏ鋼ないし１・１／４
Ｃｒ−１／２Ｍｏ鋼である場合、クリープ脆化の感受性
が高く、的確にクリープ脆化の判定を行うことができ
る。In the invention according to claim 4, the low alloy steel is so-called 1Cr-1 / 2Mo steel to 1.1 / 4.
In the case of a Cr-1 / 2Mo steel, the susceptibility to creep embrittlement is high, and it is possible to accurately determine creep embrittlement.
【００５４】請求項５に係る発明においては、クリープ
脆化判定のための破面観察部位、例えば溶接熱影響部の
粗粒域等に試験片の切欠き部の底部を一致させること
で、確実にその部分を衝撃破壊できその部分の破面が得
られるので、信頼性の高いクリープ脆化のデータを得る
ことができる。According to the fifth aspect of the present invention, the bottom of the cutout portion of the test piece is made coincident with the fracture surface observation site for judging creep embrittlement, for example, the coarse grain region of the weld heat affected zone. Then, the portion can be subjected to impact fracture and a fracture surface of the portion can be obtained, so that highly reliable creep embrittlement data can be obtained.
【００５５】請求項６に係る発明においては、吸収エネ
ルギー遷移曲線の下部棚肩部の高温側温度以下で衝撃破
壊することにより、試験片の変形等の外乱を伴わず、粒
界破面の明確な現出が行え、その後の粒界破面の計測が
精度よく行える。In the invention according to claim 6, the impact fracture is performed at a temperature lower than the high-temperature side of the lower shelf shoulder of the absorption energy transition curve, so that the grain boundary fracture surface can be clearly defined without disturbance such as deformation of the test piece. And the subsequent measurement of the grain boundary fracture surface can be performed with high accuracy.
【００５６】請求項７又は８に係る発明においては、ク
リープ脆化があることが判明している表面を基点とし
て、板厚方向のクリープ脆化の進行度分布を簡便に確実
に把握することができ、例えば、低合金鋼溶接継手にお
いて設計上の必要板厚と板厚方向のクリープ脆化の進行
度合とを比較して機器の安全性を検討・評価することが
できる。In the invention according to claim 7 or 8, it is possible to easily and reliably grasp the progress distribution of the creep embrittlement in the thickness direction, based on the surface known to have creep embrittlement. For example, it is possible to examine and evaluate the safety of equipment by comparing the required thickness in design and the degree of progress of creep embrittlement in the thickness direction in a low-alloy steel welded joint.
【００５７】請求項９に係る発明においては、溶接熱影
響部粗粒域に対して板厚方向に切欠き部を入れるので、
確実に各位置に対応する溶接熱影響部粗粒域部分を衝撃
破壊することができて、信頼性の高いデータを得ること
ができる。According to the ninth aspect of the present invention, the notch is formed in the thickness direction in the coarse zone of the weld heat affected zone.
The coarse grained area of the weld heat affected zone corresponding to each position can be reliably destroyed by impact, and highly reliable data can be obtained.
【図１】本発明に係るクリープ脆化判定方法の実施形態
の試験片採取の説明図FIG. 1 is an explanatory diagram of specimen collection in an embodiment of a creep embrittlement determination method according to the present invention.
【図２】採取した試験片形状を示す図FIG. 2 is a diagram showing the shape of a test piece taken out.
【図３】試験材料の遷移温度曲線FIG. 3 Transition temperature curve of test material
【図４】粒界破面の測定位置を示す図FIG. 4 is a view showing a measurement position of a grain boundary fracture surface.
【図５】試験材の脆化分布状況を示す図FIG. 5 is a view showing a state of embrittlement distribution of a test material.
【図６】粒界破面の観察例を示す電子顕微鏡写真FIG. 6 is an electron micrograph showing an example of observation of a grain boundary fracture surface.
【図７】図６のパソコンによる処理画像の図7 is a diagram of an image processed by the personal computer in FIG. 6;
【図８】ミクロ観察位置を示す図FIG. 8 is a diagram showing a micro observation position.
【図９】試験材の表面の脆化分布を測定する場合の試験
片採取の説明図FIG. 9 is an explanatory view of sample collection when measuring embrittlement distribution on the surface of a test material.
１ 試験材 ２ 試験片 1 Test material 2 Test piece
───────────────────────────────────────────────────── フロントページの続き (72)発明者 赤澤 由郎 神奈川県茅ヶ崎市浜之郷331−１ (72)発明者 池上 宏平 東京都大田区蒲田本町１丁目９番３号 株 式会社新潟鉄工所エンジニアリングセンタ ー内 (72)発明者 西坂 幸人 東京都大田区蒲田本町１丁目９番３号 株 式会社新潟鉄工所エンジニアリングセンタ ー内 (72)発明者 原 泰弘 神奈川県横浜市磯子区新磯子町27番地５ 新潟工事株式会社内 (72)発明者 志賀 啓介 神奈川県横浜市磯子区新磯子町27番地５ 新潟工事株式会社内 (72)発明者 中本 龍一 神奈川県横浜市磯子区新磯子町27番地５ 新潟工事株式会社内 Ｆターム(参考） 2G061 AA14 AB04 AC04 CA01 CB08 CB19 EB10 EC05 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuro Akazawa 331-1 Hamanosato, Chigasaki City, Kanagawa Prefecture (72) Inventor Kohei Ikegami 1-9-3 Kamata Honcho, Ota-ku, Tokyo Niigata Iron Works Engineering Center Co., Ltd. (72) Inventor Yukito Nishisaka 1-9-3 Kamata Honcho, Ota-ku, Tokyo Inside the Niigata Ironworks Engineering Center Co., Ltd. (72) Inventor Yasuhiro Hara 27-5 Shinisogocho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Niigata Construction Co., Ltd. (72) Inventor Keisuke Shiga 27-5 Shinisogocho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Niigata Construction Co., Ltd. (72) Ryuichi Nakamoto 27-5 Shinisogocho, Isogo-ku, Yokohama-shi, Kanagawa Niigata Construction F term in reference (reference) 2G061 AA14 AB04 AC04 CA01 CB08 CB19 EB10 EC05
Claims (9)
を、該材料のエネルギー遷移温度以下の温度で衝撃破壊
して、その破面に粒界破面が生じているか否かを調べ、
前記粒界破面があればクリープ脆化が生じていると判定
することを特徴とする低合金鋼のクリープ脆化判定方
法。A test piece taken from a material made of a low alloy steel is subjected to impact fracture at a temperature equal to or lower than the energy transition temperature of the material, and it is examined whether or not a fracture surface has a grain boundary fracture surface.
A method for judging creep embrittlement of low alloy steel, wherein it is judged that creep embrittlement has occurred if the grain boundary fracture surface is present.
を、該材料のエネルギー遷移温度以下の温度で衝撃破壊
して、その破面から下記の式による粒界破面率を求め、 粒界破面率＝（粒界破面の面積／測定範囲の総面積）×
100 ％ 前記粒界破面率に基づいてクリープ脆化の有無を判定す
ることを特徴とする低合金鋼のクリープ脆化判定方法。2. A test piece taken from a material made of a low alloy steel is subjected to impact fracture at a temperature lower than the energy transition temperature of the material, and a grain boundary fracture rate is calculated from the fracture surface by the following equation. Boundary fracture rate = (Area of grain boundary fracture surface / Total area of measurement range) x
100% A method for judging creep embrittlement of low alloy steel, which judges the presence or absence of creep embrittlement based on the grain boundary fracture ratio.
れた箇所の近傍から採取したものであることを特徴とす
る請求項１又は２に記載の低合金鋼のクリープ脆化判定
方法。3. The method for judging creep embrittlement of a low alloy steel according to claim 1, wherein the test piece is obtained from the vicinity of a location where a void of the material is detected.
０重量％及びＭｏを０．４５〜０．６５重量％含む鋼で
あることを特徴とする請求項１〜３いずれか１つに記載
の低合金鋼のクリープ脆化判定方法。4. The low alloy steel according to claim 1, wherein the Cr content is 0.80 to 1.5.
The method for determining creep embrittlement of a low alloy steel according to any one of claims 1 to 3, wherein the steel contains 0% by weight and 0.45 to 0.65% by weight of Mo.
粒界破面測定部位になるよう試験片を採取することを特
徴とする請求項１〜４のいずれか１つに記載の低合金鋼
のクリープ脆化判定方法。5. The test piece according to any one of claims 1 to 4, wherein the test piece is sampled so that the notch forming position of the test piece is a desired grain boundary fracture surface measurement site. Method for judging creep embrittlement of low alloy steel.
記材料の吸収エネルギー遷移曲線の下部棚肩部の高温側
温度以下であることを特徴とする請求項１〜５のいずれ
か１つに記載の低合金鋼のクリープ脆化判定方法。6. The method according to claim 1, wherein the temperature of the test piece at the time of the impact fracture is equal to or lower than the high temperature side of the lower shelf shoulder of the absorption energy transition curve of the material. 4. A method for judging creep embrittlement of a low alloy steel according to any one of the above.
の試験片を採取し、各試験片における前記粒界破面の有
無を求めることを特徴とする請求項１又は３〜６のいず
れか１つに記載の低合金鋼のクリープ脆化判定方法。7. The method according to claim 1, wherein a plurality of test pieces are sampled along the thickness direction of the low alloy steel welded joint, and the presence or absence of the grain boundary fracture surface in each test piece is determined. The method for judging creep embrittlement of a low alloy steel according to any one of the above.
の試験片を採取し、各試験片における前記粒界破面率を
求めることを特徴とする請求項２〜６のいずれか１つに
記載の低合金鋼のクリープ脆化判定方法。8. The method according to claim 2, wherein a plurality of test pieces are sampled along a thickness direction of the low alloy steel welded joint, and the grain boundary fracture rate in each test piece is obtained. The method for judging creep embrittlement of a low alloy steel according to one of the above aspects.
接熱影響部粗粒域の板厚方向に切欠き部が入れられてい
ることを特徴とする請求項７又は８に記載の低合金鋼の
クリープ脆化判定方法。9. The test piece according to claim 7, wherein a cutout portion is formed in a thickness direction of a coarse grained area of the weld heat affected zone of the low alloy steel welded joint. Method for judging creep embrittlement of low alloy steel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35668998A JP2000180324A (en) | 1998-12-15 | 1998-12-15 | Method for determining creep embrittlement in low alloy steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35668998A JP2000180324A (en) | 1998-12-15 | 1998-12-15 | Method for determining creep embrittlement in low alloy steel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2000180324A true JP2000180324A (en) | 2000-06-30 |
Family
ID=18450294
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP35668998A Pending JP2000180324A (en) | 1998-12-15 | 1998-12-15 | Method for determining creep embrittlement in low alloy steel |
Country Status (1)
| Country | Link |
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| JP (1) | JP2000180324A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014202730A (en) * | 2013-04-10 | 2014-10-27 | 新日鐵住金株式会社 | Test piece for evaluating brittle crack propagation stop characteristics and method for evaluating brittle crack propagation stop characteristics of thick steel plate |
| KR101910630B1 (en) * | 2016-12-23 | 2018-12-28 | 주식회사 포스코 | Method for deciding effectiveness of a measured fracture toughness value |
-
1998
- 1998-12-15 JP JP35668998A patent/JP2000180324A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014202730A (en) * | 2013-04-10 | 2014-10-27 | 新日鐵住金株式会社 | Test piece for evaluating brittle crack propagation stop characteristics and method for evaluating brittle crack propagation stop characteristics of thick steel plate |
| KR101910630B1 (en) * | 2016-12-23 | 2018-12-28 | 주식회사 포스코 | Method for deciding effectiveness of a measured fracture toughness value |
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