JP2014142304A - Life evaluation method for austenite stainless steel - Google Patents
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本発明は、高温及び応力負荷環境下に置かれたオーステナイト系ステンレス鋼の予寿命を精度良く推定可能な寿命評価方法に関する。 The present invention relates to a life evaluation method capable of accurately estimating the pre-life of an austenitic stainless steel placed under a high temperature and stress load environment.
オーステナイト系ステンレス鋼は、低温から高温までの温度域で、強度、靱性などの機械的性質及び溶接性などに優れており、幅広い用途に使用されている。火力プラントのボイラなど、６００℃以上の高温条件下で使用される機器の構成材料としても、オーステナイト系ステンレス鋼が広く使用されている。火力プラントのボイラ等は、高温高圧環境下で運転されるので、ボイラ等を構成するオーステナイト系ステンレス鋼は、長期に亘る運転によりクリープ損傷が蓄積されることがある。 Austenitic stainless steel is excellent in mechanical properties such as strength and toughness and weldability in a temperature range from a low temperature to a high temperature, and is used in a wide range of applications. Austenitic stainless steel is also widely used as a constituent material of equipment used under high-temperature conditions of 600 ° C. or higher, such as boilers in thermal power plants. Since boilers and the like of thermal power plants are operated in a high-temperature and high-pressure environment, creep damage may accumulate in austenitic stainless steel constituting the boiler and the like due to long-term operation.
クリープ損傷とは、高温及び応力負荷環境下で放置しておくと、材料の引張強度以下の応力でも歪が発生し、これによって、クリープボイド（微小な空洞）や結晶粒の粗大化、さらには微視き裂が発生する現象である。微視き裂が大きくなると、ついには破断に至る場合もある。そのため、オーステナイト系ステンレス鋼の寿命評価を精度良く行うことで、機器の安全な運転を確保する必要がある。図３は、機械部品の表面に発生したクリープボイドの一例を示す。 Creep damage means that if left under high temperature and stress load environment, distortion occurs even under stress below the tensile strength of the material, which causes creep voids (fine cavities) and coarsening of crystal grains. This is a phenomenon in which microcracks are generated. When the microcrack becomes large, it may eventually break. Therefore, it is necessary to ensure safe operation of the equipment by accurately evaluating the life of austenitic stainless steel. FIG. 3 shows an example of creep voids generated on the surface of the machine part.
従来、オーステナイト系ステンレス鋼のクリープ損傷度を評価する方法として、以下の手法を行っている。一つの手法として、評価対象となる材料を切り出してクリープ破断試験等の破壊試験法を用い、クリープ損傷度を評価している。別な手法として、評価対象となる材料の使用された温度、圧力、時間から、強度低下前の未使用材の強度を用い、応力解析法によってクリープ損傷度を推定する手法がある。 Conventionally, as a method for evaluating the degree of creep damage of austenitic stainless steel, the following method is used. As one method, a material to be evaluated is cut out and a creep test such as a creep rupture test is used to evaluate the degree of creep damage. As another method, there is a method of estimating the degree of creep damage by a stress analysis method using the strength of an unused material before strength reduction from the temperature, pressure, and time used for the material to be evaluated.
さらに、別な手法として、まず、レプリカ法によって評価対象となる材料の表面の金属組織を観察し、発生したクリープボイドの個数密度を計測する。次に、計測した個数密度を、実験室で取得したクリープボイドの個数密度とクリープによる寿命消費率（破断までの時間を１００％とする寿命消費率）との関係線図（図４）に当てはめることで、寿命消費率を非破壊的に評価する手法がある。 As another method, first, the metal structure of the surface of the material to be evaluated is observed by the replica method, and the number density of the generated creep voids is measured. Next, the measured number density is applied to a relationship diagram (Fig. 4) between the number density of creep voids obtained in the laboratory and the life consumption rate due to creep (lifetime consumption rate when the time to fracture is 100%). Thus, there is a method for nondestructively evaluating the lifetime consumption rate.
特許文献１には、オーステナイト系ステンレス鋼の表面のクリープボイド及び粒界析出物の結晶粒界方向の長さを計測し、粒界損傷線密度（単位面積当たりのクリープボイドの結晶粒界方向長さの合計値）、及び粒界損傷率（単位面積当たりの粒界析出物の結晶粒界方向長さの合計値）を求め、予め実験室での試験によって求めてあるこれらの値と寿命消費率との関係を示す線図に、計測値を当てはめることで、オーステナイト系ステンレス鋼の寿命消費率を求めている。 In Patent Document 1, the length of creep voids on the surface of austenitic stainless steel and the grain boundary direction of grain boundary precipitates are measured, and the grain boundary damage linear density (the length of creep voids per unit area in the grain boundary direction) is measured. Total value), and grain boundary damage rate (total value of grain boundary direction length of grain boundary precipitates per unit area), and these values and lifetime consumption obtained in advance by laboratory tests The lifetime consumption rate of austenitic stainless steel is obtained by applying the measured value to a diagram showing the relationship with the rate.
オーステナイト系ステンレス鋼は、高温に曝されると、しばしば低温靱性が低下する。これは、ＦｅとＣｒの金属間化合物であるσ相や炭化物が析出することが主な原因である。このσ相や炭化物の析出がオーステナイト系ステンレス鋼の寿命消費率を増加させることが知られている。特許文献２には、オーステナイト系ステンレス鋼のσ相の析出量と、高周波領域における超音波の減衰率との間に相関があることに着目し、超音波探傷法を用いて非破壊的に寿命消費率を予測する手法が開示されている。 Austenitic stainless steels often have low temperature toughness when exposed to high temperatures. This is mainly due to the precipitation of σ phase and carbide which are intermetallic compounds of Fe and Cr. It is known that precipitation of this σ phase and carbide increases the life consumption rate of austenitic stainless steel. Patent Document 2 pays attention to the fact that there is a correlation between the precipitation amount of σ phase of austenitic stainless steel and the attenuation factor of ultrasonic waves in a high frequency region. A method for predicting the consumption rate is disclosed.
破壊試験法は評価対象となる機械部品の強度を低下させると共に、機械部品の補修が必要となるので、なるべく避けたい評価方法である。応力解析法はほぼ確立された手法であるが、精度はさほど良くない。
近年、オーステナイト系ステンレス鋼の寿命評価を短期間で非破壊的に行うニーズが増えている。しかし、従来の非破壊的評価方法は、一定温度、一定応力下での静的な環境で行われる実験室での試験の結果に基づいて評価を行っている点に問題がある。実際に用いられている機械部品では、温度分布（熱勾配）や温度変動等があり、このような環境下で発生するクリープ損傷は、静的な環境での実験結果とは必ずしも一致しない。そのため、実際に機械部品が置かれた温度及び応力負荷の環境を加味した試験を行うことで、寿命評価の精度を向上させる必要がある。
The destructive test method is an evaluation method that should be avoided as much as possible because it reduces the strength of the machine part to be evaluated and requires repair of the machine part. The stress analysis method is an almost established method, but the accuracy is not so good.
In recent years, there has been an increasing need for non-destructive evaluation of the life of austenitic stainless steel in a short period of time. However, the conventional non-destructive evaluation method has a problem in that the evaluation is performed based on the result of a test in a laboratory performed in a static environment under a constant temperature and a constant stress. Actually used mechanical parts have temperature distribution (thermal gradient), temperature fluctuation, and the like, and the creep damage that occurs in such an environment does not necessarily match the experimental results in a static environment. Therefore, it is necessary to improve the accuracy of life evaluation by performing a test in consideration of the temperature and stress load environment where the machine parts are actually placed.
特許文献１に開示された非破壊的評価方法も、静的な環境で行われる実験室試験の結果に基づいて、粒界損傷線密度や粒界損傷率を求めており、機械部品が実際に置かれた環境下での実験結果とは一致しないという問題がある。特許文献２に開示された非破壊的評価方法も、同様に、静的な実験室試験の結果であり、また、超音波の減衰率とクリープによる寿命消費率との相関は、特許文献２中の図３に示すように、バラツキがあり、さらに精度が低下するという問題がある。 The non-destructive evaluation method disclosed in Patent Document 1 also obtains the grain boundary damage linear density and grain boundary damage rate based on the results of laboratory tests performed in a static environment, and the machine parts are actually used. There is a problem that it does not agree with the experimental results in the environment in which it was placed. The non-destructive evaluation method disclosed in Patent Document 2 is also the result of a static laboratory test, and the correlation between the attenuation rate of ultrasonic waves and the life consumption rate due to creep is disclosed in Patent Document 2. As shown in FIG. 3, there is a problem in that there is variation and the accuracy is further reduced.
本発明は、かかる従来技術の課題に鑑み、オーステナイト系ステンレス鋼で構成される機械部品が置かれる環境を考慮した寿命評価とすることで、該機械部品の寿命評価の精度を向上させることを目的とする。 In view of the problems of the prior art, the present invention aims to improve the accuracy of the life evaluation of the mechanical part by considering the life in consideration of the environment where the mechanical part made of austenitic stainless steel is placed. And
かかる目的を達成するため、本発明のオーステナイト系ステンレス鋼の寿命評価方法は、高温及び応力負荷環境下で運転される機械部品を構成するオーステナイト系ステンレス鋼の寿命評価方法であって、オーステナイト系ステンレス鋼からなり、複数の異なる温度及び応力環境に対応したσ相や炭化物等の析出物の析出量を有する複数のサンプル片を用意する準備工程と、これら複数のサンプル片を用い、クリープボイド個数密度とクリープによる寿命消費率との関係を示す第１の関係線図を作成する第１の線図作成工程と、寿命評価対象となる機械部品の析出物析出量を計測する計測工程と、計測した前記機械部品の析出物析出量に対し、対応する析出物析出量を有するサンプル片を選択する選択工程と、機械部品のクリープボイド個数密度を計測し、このクリープボイド個数密度と選択されたサンプル片の第１の関係線図から機械部品のクリープによる寿命消費率を求める寿命評価工程とからなる。 In order to achieve this object, the life evaluation method for austenitic stainless steel according to the present invention is a method for evaluating the life of austenitic stainless steel constituting a machine part operated under a high temperature and stress load environment. Preparatory steps for preparing multiple sample pieces made of steel and having precipitation amounts of precipitates such as sigma phase and carbide corresponding to multiple different temperatures and stress environments, and using these multiple sample pieces, creep void number density A first diagram for creating a first relationship diagram showing a relationship between the life consumption rate due to creep and a creep, a measuring step for measuring the amount of precipitates deposited on a machine part to be evaluated for life, and a measurement A selection step of selecting a sample piece having a corresponding precipitation amount with respect to the precipitation amount of the mechanical component, and the number of creep voids of the mechanical component Degrees was measured, and a life evaluation step of determining the life consumption rate due to creep machine parts from the first relational diagram of the creep void number density and the selected sample piece.
オーステナイト系ステンレス鋼の寿命消費過程は、前半で、結晶粒界にσ相や炭化物が析出し、後半で、σ相や炭化物に隣接してクリープボイドが形成される。本発明方法は、機械部品を構成するオーステナイト系ステンレス鋼のクリープ損傷の進行程度が組織の状態により異なること、及び組織の変化が機械部品が置かれた温度及び応力負荷の環境下で異なることを考慮した寿命評価を行う。本発明者等は、厳しい温度及び応力環境にあるオーステナイト系ステンレス鋼ほど、σ相や炭化物等の析出物の析出の進行が早くなることを見い出した。そのため、機械部品の置かれた温度及び応力負荷の環境の違いを、一義的に析出物析出量の違いに置き換えるようにしている。即ち、寿命消費の初期の段階で機械部品の析出物析出量を計測し、この析出物析出量からその後の寿命消費の推移を複数のパターンに分けて推定する。 In the first half of the life consumption process of austenitic stainless steel, σ phase and carbide precipitate at the grain boundaries, and in the second half, creep voids are formed adjacent to the σ phase and carbide. According to the method of the present invention, the degree of progress of creep damage of austenitic stainless steel constituting a machine part varies depending on the state of the structure, and the change in structure varies depending on the temperature and stress load environment where the machine part is placed. Perform life evaluation in consideration. The present inventors have found that the austenitic stainless steel in a severe temperature and stress environment is accelerated in the precipitation of precipitates such as σ phase and carbide. For this reason, the difference in temperature and stress load environment where the machine parts are placed is uniquely replaced by the difference in the amount of precipitates deposited. That is, the amount of precipitates deposited on the machine parts is measured at an early stage of life consumption, and the transition of life consumption thereafter is estimated from the amount of precipitates divided into a plurality of patterns.
まず、準備工程で、複数の異なる温度及び応力負荷の環境に対応した析出物析出量を有する複数のサンプル片を用意する。次に、これらのサンプル片を用いて、クリープボイド個数密度とクリープによる寿命消費率（以下「寿命消費率」という。）との関係を示す第１の関係線図を作成する。一方、寿命評価対象となる機械部品の析出物析出量を計測し、この析出物析出量に対応した析出物析出量を有するサンプル片を選択する。次に、選択されたサンプル片の第１の関係線図から機械部品の寿命消費率を求める。 First, in the preparation step, a plurality of sample pieces having a precipitation amount corresponding to a plurality of different temperature and stress load environments are prepared. Next, using these sample pieces, a first relationship diagram showing the relationship between the number density of creep voids and the life consumption rate by creep (hereinafter referred to as “lifetime consumption rate”) is created. On the other hand, the amount of precipitate deposited on the machine part to be evaluated for life is measured, and a sample piece having a deposit deposited corresponding to the amount of deposited precipitate is selected. Next, the lifetime consumption rate of the machine part is obtained from the first relationship diagram of the selected sample piece.
このように、機械部品が置かれた温度及び応力負荷の環境を一義的に析出物析出量に置き換えることで、簡便な手法で、機械部品が置かれた温度及び応力負荷の環境を考慮した寿命消費率を求めることができる。そのため、寿命消費率の精度を向上できる。 In this way, by simply replacing the temperature and stress load environment where the machine part is placed with the amount of precipitates deposited, the lifetime considering the temperature and stress load environment where the machine part is placed is simplified. The consumption rate can be determined. Therefore, the accuracy of the life consumption rate can be improved.
本発明の一態様として、複数の温度及び応力環境を、時間経過に伴って温度勾配があり、かつ応力が負荷される高負荷環境と、一定温度でかつ応力が負荷される中負荷環境と、一定温度で応力が負荷されない低負荷環境とに分類し、低負荷環境に対応した析出物析出量から高負荷環境に対応した析出物析出量に向かって、順々に高い析出物析出量を設定する。
前記３つの負荷環境は、通常、機械部品が置かれると思われる負荷環境である。これによって、通常の負荷環境において、精度良い寿命消費率を求めることができる。
As one aspect of the present invention, a plurality of temperatures and stress environments are divided into a high load environment in which there is a temperature gradient with time and stress is applied, and a medium load environment in which stress is applied at a constant temperature, Categorized as a low load environment where stress is not applied at a constant temperature, and gradually increases the precipitation amount from the precipitation amount corresponding to the low load environment to the precipitation amount corresponding to the high load environment. To do.
The three load environments are usually load environments in which machine parts are supposed to be placed. This makes it possible to obtain an accurate lifetime consumption rate in a normal load environment.
また、本発明者等は、時効時間及び温度に基づいて設定された時効パラメータを用いることで、複数のサンプル片の析出物析出量を決定するのが容易になることを見い出した。即ち、本発明の一態様として、この時効パラメータとオーステナイト系ステンレス鋼の析出物析出量との関係を示す第２の関係線図を形成し、準備工程において、第２の関係線図から複数のサンプル片の析出物析出量を決定するようにする。これによって、実際の負荷環境に即した析出物析出量を設定できる。 In addition, the present inventors have found that it is easy to determine the precipitation amount of a plurality of sample pieces by using aging parameters set based on aging time and temperature. That is, as one aspect of the present invention, a second relationship diagram showing the relationship between the aging parameter and the precipitation amount of the austenitic stainless steel is formed. The amount of precipitate deposited on the sample piece is determined. This makes it possible to set the amount of precipitate deposited in accordance with the actual load environment.
本発明によれば、寿命消費の前半段階で析出する析出物の析出量に基づいて、寿命消費の後半段階で発生するクリープボイドと寿命消費率との相関を表す線図を選択することで、オーステナイト系ステンレス鋼が置かれた温度及び応力負荷環境を考慮した精度良い寿命予測が可能になる。 According to the present invention, on the basis of the amount of precipitates deposited in the first half of the life consumption, by selecting a diagram representing the correlation between the creep void generated in the second half of the life consumption and the life consumption rate, It is possible to accurately predict the life considering the temperature and stress load environment where the austenitic stainless steel is placed.
以下、本発明を図に示した実施形態を用いて詳細に説明する。但し、この実施形態に記載されている構成部品の寸法、材質、形状、その相対配置などは特に特定的な記載がない限り、この発明の範囲をそれのみに限定する趣旨ではない。 Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.
本発明の一実施形態を図１及び図２に基づいて説明する。本実施形態では、オーステナイト系ステンレス鋼で構成される機械部品のクリープ損傷の進行程度が、結晶粒界に析出する析出物の析出量によって異なること、及び析出物析出量が機械部品が置かれた温度及び応力環境によって異なることを考慮し、クリープ損傷の指標としてのクリープボイドの形成状況と寿命消費率との相関を表す線図を作成する。特許文献２のように、従来の寿命評価でも、析出物の影響を加味する例があるが、これは等温度状態の実験室での試験で評価したものであり、実際の温度及び応力負荷環境を考慮していない。 An embodiment of the present invention will be described with reference to FIGS. In this embodiment, the degree of progress of creep damage of mechanical parts made of austenitic stainless steel differs depending on the amount of precipitates precipitated at the grain boundaries, and the amount of precipitates deposited is the mechanical parts. Considering the difference depending on the temperature and stress environment, a diagram showing the correlation between the formation of creep voids as an indicator of creep damage and the lifetime consumption rate is created. As in Patent Document 2, even in the conventional life evaluation, there is an example in which the influence of precipitates is taken into account, but this is evaluated by a test in an isothermal laboratory, and the actual temperature and stress load environment Is not considered.
図１に、析出物の析出量と時効パラメータとの関係を示す線図である。ここで、横軸となる時効パラメータは、「Ｔ×（Ｃ＋ｌｏｇ（ｔ））」で示され、Ｔは温度（Ｋ）、Ｃは定数、ｔは時間（ｈ）である。図１において、縦軸は、析出物の析出量を示し、析出物の析出量を領域イ、領域ロ及び領域ハに区分する。領域イと領域ロとの境界は、例えば、析出物の形成が主に粒界にある場合で粒界の交点を中心とする領域イと粒界全体で形成される領域ロのように設定する。また、領域ロと領域ハとの境界は、例えば、析出物の形成が粒内でも明瞭に生じる領域ハのようにして設定する。 FIG. 1 is a diagram showing the relationship between the amount of precipitates and aging parameters. Here, the aging parameter on the horizontal axis is represented by “T × (C + log (t))”, where T is temperature (K), C is a constant, and t is time (h). In FIG. 1, the vertical axis indicates the amount of precipitates deposited, and the amount of precipitates is divided into region a, region b, and region c. The boundary between the area A and the area B is set, for example, as in the area B formed by the entire area of the grain boundary and the area B centering on the intersection of the grain boundaries when the formation of precipitates is mainly at the grain boundary. . In addition, the boundary between the region B and the region C is set, for example, as in the region C in which the formation of precipitates clearly occurs in the grains.
曲線Ａは、一定温度及び応力無負荷状態の環境下で行った実験結果を示し、曲線Ｂは、一定温度及び応力負荷状態の環境下で行った実験結果を示し、曲線Ｃは、時間経過と共に一定の温度勾配を有し、かつ応力負荷状態の環境下で行った実験結果を示している。 Curve A shows the result of an experiment conducted in an environment of constant temperature and no stress load, curve B shows the result of an experiment conducted in an environment of constant temperature and stress load, and curve C shows the result over time. The experimental result which carried out in the environment of having a fixed temperature gradient and a stress load state is shown.
次に、領域イ、領域ロ及び領域ハの夫々に属する析出物析出量を有するサンプル片を用意する。この場合、図１の関係線図を目安に、これらサンプル片の析出物析出量を選定する。次に、これらサンプル片のクリープボイド個数密度（一定面積中に発生したクリープボイドの個数）を計測しながら、クリープ試験及び中途止め状態における検査を行う。これらの試験及び検査により、図２に示す、クリープボイド個数密度と寿命消費率との関係線図を作成する。図２において、寿命曲線Ｘは、領域イの析出物析出量を有するサンプル片の試験結果であり、寿命曲線Ｙは、領域ロの析出物析出量を有するサンプル片の試験結果であり、寿命曲線Ｚは、領域ハの析出物析出量を有するサンプル片の試験結果である。 Next, a sample piece having a deposit amount belonging to each of the region A, the region B, and the region C is prepared. In this case, the precipitation amount of these sample pieces is selected based on the relationship diagram of FIG. Next, while measuring the number density of creep voids of these sample pieces (the number of creep voids generated in a certain area), the creep test and the inspection in the suspended state are performed. By these tests and inspections, the relationship diagram between the creep void number density and the life consumption rate shown in FIG. 2 is created. In FIG. 2, the life curve X is a test result of a sample piece having a precipitation amount of region A, and the life curve Y is a test result of a sample piece having a precipitation amount of region B. Z is a test result of a sample piece having a deposit amount of region C.
なお、クリープボイド個数密度の計測は、機械部品が薄肉材の場合、レプリカ法等を用いて、表面のクリープボイド個数を計測すればよい。しかし、厚肉材の場合、内部のクリープボイド個数を計測しないと、正確な寿命消費率を予測できない。 The creep void number density may be measured by measuring the number of creep voids on the surface using a replica method or the like when the machine part is a thin-walled material. However, in the case of a thick material, an accurate lifetime consumption rate cannot be predicted unless the number of internal creep voids is measured.
次に、オーステナイト系ステンレス鋼で構成され、寿命評価対象となる機械部品の析出物析出量を計測する。そして、この機械部品の析出物析出量が領域イ、ロ又はハのうち、どの領域に属するかを確認する。次に、この機械部品が属する領域に対応したサンプル片及び該サンプル片の寿命曲線を選択する。そして、この機械部品のクリープボイド個数密度を計測し、図２から、この機械部品の寿命消費率を求める。 Next, the precipitation amount of the mechanical part which consists of austenitic stainless steel and is a life evaluation object is measured. And it confirms to which area | region the deposit deposition amount of this machine part belongs to the area | region a, b, or c. Next, a sample piece corresponding to the region to which the mechanical part belongs and a life curve of the sample piece are selected. And the creep void number density of this machine part is measured, and the lifetime consumption rate of this machine part is calculated | required from FIG.
時効試験のような静的状態（一定温度及び応力無負荷状態）での試験と比べて、クリープ試験のような応力負荷の状況では、析出物の析出は促進される傾向がある。そのため、従来行った等温状態での寿命評価は、温度勾配や温度変動があり、かつ応力が負荷された環境下にある機械部品の寿命評価においては、これらの影響を反映していない。 Compared with a test in a static state (a constant temperature and no stress load state) such as an aging test, precipitation of the precipitate tends to be accelerated in a stress load situation such as a creep test. For this reason, the conventional life evaluation in an isothermal state does not reflect these effects in the life evaluation of mechanical parts in an environment where there is a temperature gradient or temperature fluctuation and stress is applied.
理想的には、温度勾配をもたせた試験片を用いてクリープ試験を行い、中途止め状態での検査結果を反映させた評価線図を作成するとよい。しかし、このような試験は実施が困難であり、現実的ではない。そこで、本実施形態では、予め析出物を析出させた状態でクリープ試験や中途止め状態での検査を行う。これによって、温度及び応力環境が異なる環境下での寿命曲線を得ることができる。 Ideally, a creep test is performed using a test piece having a temperature gradient, and an evaluation diagram reflecting an inspection result in a suspended state is created. However, such tests are difficult to implement and are not realistic. Therefore, in the present embodiment, a creep test or an inspection in a suspended state is performed in a state where precipitates are deposited in advance. As a result, it is possible to obtain life curves under different environments of temperature and stress.
本実施形態によれば、寿命評価対象となる機械部品が置かれた温度及び応力環境の違いを、析出物の析出量の違いに置き換え、この機械部品の寿命消費の初期の段階で計測した析出物析出量に基づいて、この機械部品が置かれた温度及び応力環境を考慮した寿命評価が可能になる。従って、精度良い寿命消費率を予測できる。また、図２に示すように、時効パラメータと析出物析出量との相関を示す相関線図を作成することで、実際に機械部品が置かれた温度及び応力環境に対応した析出物析出領域の設定が容易になる。さらに、寿命消費率を精度良く推定できるので、機械部品の残存寿命を精度良く推定できるため、機械部品の保守管理に貢献できる。 According to the present embodiment, the difference in temperature and stress environment where the machine part to be subjected to life evaluation is placed is replaced with the difference in the amount of precipitates deposited, and the precipitation measured in the initial stage of the life consumption of this machine part. Based on the amount of deposited matter, it is possible to evaluate the life in consideration of the temperature and stress environment where the mechanical component is placed. Accordingly, it is possible to predict the life consumption rate with high accuracy. In addition, as shown in FIG. 2, by creating a correlation diagram showing the correlation between the aging parameter and the precipitation amount, the precipitate precipitation region corresponding to the temperature and stress environment where the machine part is actually placed Easy to set up. Furthermore, since the life consumption rate can be estimated with high accuracy, the remaining life of the machine component can be estimated with high accuracy, thereby contributing to maintenance management of the machine component.
実際に、ボイラプラントに組み込まれ、オーステナイト系ステンレス鋼（１８Ｃｒ系鋼）で構成された蒸気配管の寿命評価を、本実施形態の方法によって行った。この結果から、本発明方法によれば、従来の寿命評価方法と比べて、精度良い寿命予測結果を得ることができた。 Actually, the life evaluation of the steam pipe built in the boiler plant and made of austenitic stainless steel (18Cr steel) was performed by the method of this embodiment. From this result, according to the method of the present invention, it was possible to obtain a life prediction result with higher accuracy than the conventional life evaluation method.
なお、前記実施形態では、温度及び時効時間のみを考慮し、機械部品に負荷される応力を考慮しない時効パラメータを用いたが、負荷応力も考慮した時効パラメータを用いるようにしてもよい。これによって、さらに実際の温度及び応力負荷環境に即した寿命評価が可能になる。 In the embodiment, only the temperature and the aging time are considered and the aging parameter not considering the stress applied to the machine part is used. However, the aging parameter considering the load stress may be used. This makes it possible to evaluate the life according to the actual temperature and stress load environment.
本発明によれば、オーステナイト系ステンレス鋼で構成される機械部品が置かれる環境を考慮した寿命評価が可能になり、機械部品の寿命評価の精度を向上できる。 ADVANTAGE OF THE INVENTION According to this invention, the lifetime evaluation in consideration of the environment where the machine component comprised with austenitic stainless steel is placed is attained, and the precision of the lifetime evaluation of a machine component can be improved.
イ、ロ、ハ 析出物析出量領域
Ｃｖ クリープボイド
Ｘ、Ｙ、Ｚ 寿命曲線
A, B, C Precipitate precipitation area Cv Creep void X, Y, Z Life curve
Claims (3)
オーステナイト系ステンレス鋼からなり、複数の異なる温度及び応力環境に対応した析出物析出量を有する複数のサンプル片を用意する準備工程と、
前記複数のサンプル片を用い、クリープボイド個数密度とクリープによる寿命消費率との関係を示す第１の関係線図を作成する第１の線図作成工程と、
寿命評価対象となる機械部品の析出物析出量を計測する計測工程と、
計測した前記機械部品の析出物析出量に対し、対応する析出物析出量を有するサンプル片を選択する選択工程と、
前記機械部品のクリープボイド個数密度を計測し、このクリープボイド個数密度と選択されたサンプル片の前記第１の関係線図から前記機械部品のクリープによる寿命消費率を求める寿命評価工程とからなることを特徴とするオーステナイト系ステンレス鋼の寿命評価方法。 In the life evaluation method of austenitic stainless steel constituting machine parts operated under high temperature and stress load environment,
A preparatory step of preparing a plurality of sample pieces made of austenitic stainless steel and having a precipitation amount corresponding to a plurality of different temperatures and stress environments;
Using the plurality of sample pieces, a first diagram creating step for creating a first relationship diagram showing a relationship between a creep void number density and a lifetime consumption rate by creep;
A measurement process for measuring the amount of precipitates deposited on the machine parts subject to life evaluation;
A selection step of selecting a sample piece having a corresponding deposit amount with respect to the measured deposit amount of the machine part,
It comprises a life evaluation step of measuring the creep void number density of the machine part and obtaining the life consumption rate by creep of the machine part from the creep void number density and the first relation diagram of the selected sample piece. A life evaluation method for austenitic stainless steel characterized by
前記低負荷環境から前記高負荷環境に向かって、対応する析出物析出量として順々に高い析出物析出量を設定することを特徴とする請求項１に記載のオーステナイト系ステンレス鋼の寿命評価方法。 The plurality of temperature and stress environments have a temperature gradient with time and a high load environment in which stress is applied, a medium load environment in which stress is applied at a constant temperature, and stress is applied at a constant temperature. Is classified as a low-load environment
The life evaluation method for austenitic stainless steel according to claim 1, wherein a high precipitation amount is sequentially set as the corresponding precipitation amount from the low load environment to the high load environment. .
前記準備工程において、前記第２の関係線図から前記複数のサンプル片の析出物析出量を決定することを特徴とする請求項１又は２に記載のオーステナイト系ステンレス鋼の寿命評価方法。 A second diagram creation step of creating a second relationship diagram showing a relationship between an aging parameter set based on the aging time and temperature and a precipitation amount of the austenitic stainless steel;
The life evaluation method for austenitic stainless steel according to claim 1 or 2, wherein, in the preparation step, the amount of precipitates of the plurality of sample pieces is determined from the second relationship diagram.
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| JP2016142591A (en) * | 2015-01-30 | 2016-08-08 | 三菱日立パワーシステムズ株式会社 | Service temperature estimation method and creep life estimation method |
| JP6448724B1 (en) * | 2017-08-10 | 2019-01-09 | 九州電力株式会社 | Remaining life evaluation method |
| CN113111507A (en) * | 2021-04-08 | 2021-07-13 | 西安热工研究院有限公司 | Method for evaluating material safety of steam system after serious overtemperature of boiler |
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| JP2016142591A (en) * | 2015-01-30 | 2016-08-08 | 三菱日立パワーシステムズ株式会社 | Service temperature estimation method and creep life estimation method |
| JP6448724B1 (en) * | 2017-08-10 | 2019-01-09 | 九州電力株式会社 | Remaining life evaluation method |
| JP2019035597A (en) * | 2017-08-10 | 2019-03-07 | 九州電力株式会社 | Residual lifetime evaluation method |
| CN113111507A (en) * | 2021-04-08 | 2021-07-13 | 西安热工研究院有限公司 | Method for evaluating material safety of steam system after serious overtemperature of boiler |
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