JPH085535A - Method for diagnosing remaining life expectancy of steel product with creep damage caused - Google Patents
Method for diagnosing remaining life expectancy of steel product with creep damage causedInfo
- Publication number
- JPH085535A JPH085535A JP13473494A JP13473494A JPH085535A JP H085535 A JPH085535 A JP H085535A JP 13473494 A JP13473494 A JP 13473494A JP 13473494 A JP13473494 A JP 13473494A JP H085535 A JPH085535 A JP H085535A
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- Prior art keywords
- hardness
- creep damage
- remaining life
- steel material
- diagnosing
- 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.)
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- Investigating And Analyzing Materials By Characteristic Methods (AREA)
- 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、高温下で長時間応力を
受け続けてクリープ損傷が生じる鋼材の余寿命診断方法
に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for diagnosing a remaining life of a steel material which is subjected to stress for a long time at high temperature to cause creep damage.
【０００２】[0002]
【従来の技術】ボイラ等の高温部には、高温における許
容応力が高いクロムモリブデン鋼（Ｆｅ、Ｃｒ、Ｍｏを
含む鋼材）が広く用いられている。しかし、クロムモリ
ブデン鋼は、高温下で長時間応力を受け続けるとクリー
プ損傷が進行し、ボイドや亀裂等が発生することが知ら
れている。2. Description of the Related Art Chromium-molybdenum steel (steel material containing Fe, Cr, Mo) having a high allowable stress at high temperatures is widely used for high temperature parts such as boilers. However, it is known that when chromium molybdenum steel is subjected to stress for a long time at high temperature, creep damage progresses and voids and cracks occur.
【０００３】このため、従来から使用中の鋼材の余寿命
を正確に診断する手段が強く要望されており、各種非破
壊法による手段の開発が行われてきた。その１つとして
表面のビッカース硬さを計測し、これから余寿命を診断
する手段が提案され一部で使用されていた。これは、対
面角が１３６度のダイヤモンド四角すい圧子を用い、試
験面に窪みをつけたときの試験荷重と、窪みの対角線長
さから求めた窪みの表面積とから、所定の式でビッカー
ス硬さを算出するものであり（ＪＩＳ−Ｚ−２２４
４）、クリープ損傷が進むとビッカース硬さが低下する
特性に基づくものである。For this reason, there has been a strong demand for a means for accurately diagnosing the remaining life of a steel material in use, and various nondestructive methods have been developed. As one of them, a means for measuring the Vickers hardness of the surface and diagnosing the remaining life from this has been proposed and used in part. This is a Vickers hardness according to a predetermined formula from the test load when a dent was made on the test surface and the surface area of the dent obtained from the diagonal length of the dent, using a diamond quadrangular cone indenter with a facing angle of 136 degrees. To calculate (JIS-Z-224
4) It is based on the characteristic that the Vickers hardness decreases as creep damage progresses.
【０００４】[0004]
【発明が解決しようとする課題】しかし、実験の結果、
ビッカース硬さは、無負荷で長時間高熱に晒された場合
でも低下し、クリープ損傷による低下と区別しにくい問
題点があった。そのため、上述した従来の手段では、正
確な余寿命の診断ができなかった。However, as a result of the experiment,
The Vickers hardness decreases even when exposed to high heat for a long time without any load, and there is a problem that it is difficult to distinguish it from the decrease due to creep damage. Therefore, the conventional means described above cannot accurately diagnose the remaining life.
【０００５】本発明はかかる問題点を解決するために創
案されたものである。すなわち、本発明の目的は、クリ
ープ損傷が生じる鋼材の余寿命を非破壊で正確に診断で
きる鋼材の余寿命診断方法を提供することにある。The present invention was devised to solve such problems. That is, an object of the present invention is to provide a method for diagnosing the remaining life of a steel product that can accurately and nondestructively diagnose the remaining life of a steel product in which creep damage occurs.
【０００６】[0006]
【課題を解決するための手段】本発明によれば、鋼材の
クリープ損傷率と炭化物部分の硬さとの関係を予め求
め、使用中の鋼材の表面を拡大して炭化物部分のみの硬
さを計測し、この硬さから前記関係により鋼材の余寿命
を診断することを特徴とするクリープ損傷が生じる鋼材
の余寿命診断方法が提供される。According to the present invention, the relationship between the creep damage rate of a steel material and the hardness of a carbide portion is obtained in advance, and the hardness of only the carbide portion is measured by enlarging the surface of the steel material in use. However, there is provided a method for diagnosing the remaining life of a steel product in which creep damage occurs, which is characterized by diagnosing the remaining life of the steel product based on the above relationship from this hardness.
【０００７】本発明の好ましい実施例によれば、前記炭
化物部分は、ベイナイトである。また、前記炭化物部分
はパーライトであることが好ましい。また、前記硬さ計
測は、小型の四角すい圧子を用い、２００ｇ以下の試験
荷重により、試験面に最大径５０μｍ以下の窪みをつけ
る微小硬度計によるのがよい。更に、前記硬さは、マイ
クロビッカース硬さであるのがよい。According to a preferred embodiment of the present invention, the carbide portion is bainite. Further, the carbide portion is preferably pearlite. In addition, the hardness measurement is preferably performed by using a small square indenter and a micro hardness meter that forms a depression having a maximum diameter of 50 μm or less on a test surface under a test load of 200 g or less. Further, the hardness is preferably micro Vickers hardness.
【０００８】[0008]
【作用】クロムモリブデン鋼の母材は、フェライトとベ
イナイト（又はパーライト）の二層組織となっており、
高温下で長時間応力を受けてクリープ損傷が進行する
と、ベイナイトの炭化物が分解し、球状化する。この分
解球状化した炭化物は、高温下で長時間応力を受けた場
合ほど、その部分の硬度が低くなることが実験によりわ
かった。本発明は、かかる新規の知見に基づくものであ
る。[Function] The base material of chromium molybdenum steel has a two-layer structure of ferrite and bainite (or pearlite),
When creep damage progresses under stress at high temperature for a long time, bainite carbide decomposes and becomes spherical. It was found from experiments that the decomposed and spheroidized carbide had a lower hardness at that portion as it was subjected to stress for a long time at high temperature. The present invention is based on this novel finding.
【０００９】従来のビッカース硬さ計は、試験荷重が１
ｋｇ以上であり、クロムモリブデン鋼の表面に一辺２０
０μｍ角以上の大きい窪み（圧痕）ができてしまう。こ
のため、表面にできた鋼材のフェライト部とベイナイト
部（炭化物）の硬さが平均化された値となり、新材とク
リープで損傷した材料との硬さ値に明確な差がなく、正
確な寿命診断には適用できなかった。しかし、鋼材の表
面を拡大し、炭化物部分のみの硬さを計測することによ
り、無負荷で長時間高熱に晒された場合の単なる熱疲労
と明確に区別できることがわかった。The conventional Vickers hardness meter has a test load of 1
20 kg / kg or more on the surface of chromium molybdenum steel
Large depressions (indentations) of 0 μm square or more are formed. Therefore, the hardness of the ferrite part and bainite part (carbide) of the steel material formed on the surface becomes an averaged value, and there is no clear difference in the hardness value between the new material and the material damaged by creep, and it is accurate. It was not applicable to life diagnosis. However, by expanding the surface of the steel material and measuring the hardness of only the carbide part, it was found that it can be clearly distinguished from mere thermal fatigue when exposed to high heat for a long time with no load.
【００１０】すなわち、上述した本発明の方法によれ
ば、鋼材のクリープ損傷率と炭化物部分の硬さとの関係
を予め求め、使用中の鋼材の表面を拡大して炭化物部分
のみの硬さを計測し、この硬さから前記関係により鋼材
の余寿命を診断することにより、クリープ損傷の程度と
その余寿命を正確に診断することができる。That is, according to the above-described method of the present invention, the relationship between the creep damage rate of the steel material and the hardness of the carbide portion is obtained in advance, the surface of the steel material in use is enlarged, and the hardness of only the carbide portion is measured. However, by diagnosing the remaining life of the steel material from this hardness based on the above relationship, the degree of creep damage and its remaining life can be accurately diagnosed.
【００１１】[0011]
【実施例】以下、本発明の好ましい実施例を従来例と比
較して説明する。図６は、前述した従来の余寿命診断に
適用するための材料表面のビッカース硬さ（Ｈv ）と熱
履歴との関係を示す図である。この図において、横軸
は、熱履歴を代表するラーソンミラーパラメータＰであ
り、温度Ｔ℃にＬ時間晒された場合、Ｐ＝（Ｔ＋２７
３）（２０＋ｌｏｇＬ）．．．式の関係がある。ま
た、図中無負荷で長時間高温に晒された場合を●（符号
１）で示し、応力下で高温に晒されるクリープ損傷の場
合をその他の記号○他（符号３〜５）で示している。ま
た、図中の２本の線は、無負荷で長時間高温に晒された
場合の範囲を示す。EXAMPLES Preferred examples of the present invention will be described below in comparison with conventional examples. FIG. 6 is a diagram showing the relationship between the Vickers hardness (Hv) of the material surface and the thermal history, which is applied to the above-mentioned conventional residual life diagnosis. In this figure, the horizontal axis is the Larson-Miller parameter P representing the thermal history, and when exposed to the temperature T ° C. for L hours, P = (T + 27
3) (20 + logL). ． ． There is an expression relationship. Also, in the figure, the case of high temperature without load for a long time is indicated by ● (symbol 1), and the case of creep damage exposed to high temperature under stress is indicated by other symbols ○ and others (symbols 3 to 5). There is. Further, the two lines in the figure show the range when exposed to high temperature for a long time with no load.
【００１２】図６から明らかなように、ビッカース硬さ
（Ｈv ）は、無負荷で長時間高温に晒された場合（●：
符号１）でも低下し、クリープ損傷による低下（○他：
符号３〜５）とほとんど区別できない。従って、クリー
プ損傷の場合に単なる加熱との相違はあるが、これから
正確な余寿命の診断はできないことがわかる。As is apparent from FIG. 6, the Vickers hardness (Hv) is that when exposed to high temperature for a long time without load (●:
It also decreases with the code 1) and decreases due to creep damage (○ other:
Almost indistinguishable from symbols 3-5). Therefore, in the case of creep damage, there is a difference from mere heating, but it can be understood from this that accurate residual life cannot be diagnosed.
【００１３】図７は、クリープ損傷が生じる鋼材（２．
２５Ｃｒ−１Ｍｏ）の材料表面の拡大図である。図中、
左は新材であり、右はクリープ損傷を受けた材料であ
る。また、各図で白い部分はフェライト、黒い部分はベ
イナイト（又はパーライト）である。フェライトは鋼組
織中のα鉄であり、９１０℃以下で安定な純鉄相であ
る。また、ベイナイト（又はパーライト）は、フェライ
トとセメンタイト（Ｆe3Ｃ）との層状共析混合物であ
る。図７から新材に比べ、クリープ損傷材では、ベイナ
イトの炭化物が分解し、球状化しているのがわかる。FIG. 7 shows a steel material (2.
25Cr-1Mo) is an enlarged view of the material surface. In the figure,
Left is new material and right is creep damaged material. In each figure, the white part is ferrite and the black part is bainite (or pearlite). Ferrite is α iron in the steel structure and is a pure iron phase stable at 910 ° C or lower. Bainite (or pearlite) is a layered eutectoid mixture of ferrite and cementite (Fe3C). It can be seen from FIG. 7 that in the creep-damaged material, the bainite carbide is decomposed and spheroidized in the creep-damaged material.
【００１４】また図７の中央部の矩形は、ビッカース硬
さの計測の際にできる圧痕であり、図中の縦の線分は１
００μｍの長さを示している。後述するように、ベイナ
イトの硬さは、クリープ損傷が進行するにつれて低下す
るが、この図からわかるように、従来のビッカース硬さ
計は、試験荷重が１ｋｇ以上であり、クロムモリブデン
鋼の表面に一辺２００μｍ角以上の大きい窪み（圧痕）
ができてしまうため、表面にできた鋼材のフェライト部
とベイナイト（炭化物）の硬さが平均化された値とな
り、新材とクリープで損傷した材料との硬さ値に明確な
差がなく、正確な寿命診断には適用できないことがわか
る。Further, the rectangle in the center of FIG. 7 is an indentation formed when the Vickers hardness is measured, and the vertical line segment in the figure is 1.
A length of 00 μm is shown. As will be described later, the hardness of bainite decreases as creep damage progresses, but as can be seen from this figure, the conventional Vickers hardness tester has a test load of 1 kg or more, Large depression (indentation) with a side of 200 μm square or more
Therefore, the hardness of the ferrite part of the steel material formed on the surface and the hardness of bainite (carbide) become an averaged value, there is no clear difference in hardness value between the new material and the material damaged by creep, It can be seen that it cannot be applied to accurate life diagnosis.
【００１５】図１は、本発明によるクリープ損傷が生じ
る鋼材の余寿命診断方法を示すフロー図である。この図
に示すように、本発明の余寿命診断方法は、鋼材のクリ
ープ損傷率と炭化物部分の硬さとの関係を予め求める第
１ステップＳ１と、使用中の鋼材の表面を拡大して炭化
物部分のみの硬さを計測する第２ステップＳ２と、この
硬さから前記関係により鋼材の余寿命を診断する第３ス
テップＳ３とからなる。FIG. 1 is a flow chart showing a method for diagnosing the remaining life of a steel material in which creep damage occurs according to the present invention. As shown in this figure, the residual life diagnosis method of the present invention comprises a first step S1 in which the relationship between the creep damage rate of a steel material and the hardness of a carbide portion is determined in advance, and the surface of the steel material in use is enlarged to enlarge the carbide portion. It consists of a second step S2 of measuring the hardness of the steel and a third step S3 of diagnosing the remaining life of the steel material from the hardness based on the above relationship.
【００１６】本発明の方法では、鋼材の硬さ計測は、小
型の四角すい圧子を用い、２００ｇ以下の試験荷重によ
り、試験面に最大径５０μｍ以下の窪みをつける微小硬
度計による。硬さは、マイクロビッカース硬さ（Ｈmv）
で表示される。図２は、本発明の方法による図７と同様
の図であり、クリープ損傷が生じる同一鋼材（２．２５
Ｃｒ−１Ｍｏ）の材料表面の拡大図である。図中、左は
新材であり、右はクリープ損傷を受けた材料である。ま
た、図２における縦の線分は５０μｍの長さを示してい
る。更に、図３は、図２の左図中央を模写したものであ
る。In the method of the present invention, the hardness of the steel material is measured by using a small square indenter and a microhardness meter which makes a dent having a maximum diameter of 50 μm or less on the test surface under a test load of 200 g or less. Hardness is Micro Vickers hardness (Hmv)
Is displayed. FIG. 2 is a view similar to FIG. 7 according to the method of the present invention, showing the same steel material (2.25
It is an enlarged view of the material surface of (Cr-1Mo). In the figure, the left is the new material and the right is the material that has been damaged by creep. The vertical line segment in FIG. 2 has a length of 50 μm. Further, FIG. 3 is a copy of the center of the left diagram of FIG.
【００１７】図２及び図３において、白い部分がフェラ
イト６、黒い炭化物部分は、ベイナイト７（又はパーラ
イト）である。図１における試験荷重は５０ｇであり、
圧痕８の大きさは、約１５μｍ角である。従って、この
方法によりベイライト７すなわち炭化物部分のみの硬さ
を計測することができる。In FIGS. 2 and 3, the white portion is ferrite 6 and the black carbide portion is bainite 7 (or pearlite). The test load in FIG. 1 is 50 g,
The size of the indentation 8 is about 15 μm square. Therefore, by this method, the hardness of only bayite 7, that is, the carbide portion can be measured.
【００１８】本発明の方法では、鋼材のクリープ損傷率
と炭化物部分の硬さとの関係を予め求める。図４は、図
６と同様の本発明の方法による材料表面のマイクロビッ
カース硬さ（Ｈmv）と熱履歴との関係を示す図である。
この図において、横軸は、ラーソンミラーパラメータＰ
であり、縦軸はマイクロビッカース硬さ（Ｈmv）であ
る。また、図中無負荷で長時間高温に晒された場合を●
（符号１）と斜めの■（符号２）で示し、応力下で高温
に晒されるクリープ損傷の場合をその他の記号○等（符
号３〜５）で示している。また、図中の２本の線は、無
負荷で長時間高温に晒された場合の範囲である。In the method of the present invention, the relationship between the creep damage rate of steel and the hardness of the carbide portion is obtained in advance. FIG. 4 is a diagram showing the relationship between the micro-Vickers hardness (Hmv) of the material surface and the thermal history by the method of the present invention similar to FIG.
In this figure, the horizontal axis represents the Larson Miller parameter P.
And the vertical axis represents the micro Vickers hardness (Hmv). In addition, in the figure, if the product is exposed to high temperature for a long time with no load,
The symbol (1) and the diagonal symbol (2) are shown, and the case of creep damage that is exposed to high temperature under stress is indicated by other symbols such as O (symbols 3 to 5). Also, the two lines in the figure are the ranges when exposed to high temperature for a long time with no load.
【００１９】図４に示すように、マイクロビッカース硬
さも、無負荷で長時間高熱に晒された場合（符号１、
２）に低下するが、クリープ損傷による低下○等（符号
３〜５）はこれと明確に相違する直線上にほぼ分布す
る。従って、この結果から予め図５に模式的に示すよう
な、クリープ損傷率と硬度の低下率との関係を求め、使
用中の鋼材の表面を拡大して炭化物部分のみの硬さを計
測し、この硬さから前記関係により鋼材の余寿命を診断
することができる。As shown in FIG. 4, the micro Vickers hardness is also high when exposed to high heat for a long time without load (reference numeral 1,
2), but decrease due to creep damage, etc. (reference numerals 3 to 5) are almost distributed on a straight line which is clearly different from this. Therefore, from this result, the relationship between the creep damage rate and the rate of decrease in hardness, as schematically shown in FIG. 5, is obtained in advance, the surface of the steel material in use is enlarged, and the hardness of only the carbide portion is measured, From this hardness, the remaining life of the steel material can be diagnosed from the above relationship.
【００２０】なお、本発明は上述した実施例に限定され
ず、本発明の要旨を逸脱しない範囲で自由に変更できる
ことは勿論である。The present invention is not limited to the above-described embodiments, and it goes without saying that the present invention can be freely modified without departing from the gist of the present invention.
【００２１】[0021]
【発明の効果】上述したように、本発明による余寿命診
断方法は、クリープ損傷が生じる鋼材の余寿命を非破壊
で正確に診断できる、優れた効果を有する。As described above, the residual life diagnosing method according to the present invention has an excellent effect that the residual life of a steel material in which creep damage occurs can be accurately diagnosed nondestructively.
【図１】本発明によるクリープ損傷が生じる鋼材の余寿
命診断方法を示すフロー図である。FIG. 1 is a flow chart showing a method of diagnosing a remaining life of a steel product in which creep damage occurs according to the present invention.
【図２】マイクロビッカース硬さを計測した鋼材の材料
表面の拡大図である。FIG. 2 is an enlarged view of a material surface of a steel material on which micro Vickers hardness is measured.
【図３】図２の左図中央の説明図である。FIG. 3 is an explanatory diagram of the center of the left diagram of FIG.
【図４】材料表面のマイクロビッカース硬さと熱履歴と
の関係を示す図である。FIG. 4 is a diagram showing the relationship between the micro Vickers hardness of the material surface and the thermal history.
【図５】クリープ損傷率と硬度の低下率との関係図であ
る。FIG. 5 is a relationship diagram between a creep damage rate and a hardness decrease rate.
【図６】材料表面のビッカース硬さと熱履歴との関係を
示す図である。FIG. 6 is a diagram showing a relationship between Vickers hardness of a material surface and thermal history.
【図７】ビッカース硬さを計測した鋼材の材料表面の拡
大図である。FIG. 7 is an enlarged view of a material surface of a steel material whose Vickers hardness is measured.
【符号の説明】 １、２ 無負荷で長時間高温に晒された場合の実験結果 ３〜５ 応力下で高温に晒されるクリープ損傷の場合の
実験結果 ６ フェライト部 ７ ベイナイト（又はパーライト） ８ 圧痕[Explanation of symbols] 1, 2 Experimental results when exposed to high temperature for a long time with no load 3-5 Experimental results when creep damage is exposed to high temperature under stress 6 Ferrite part 7 Bainite (or pearlite) 8 Indentation
Claims (5)
さとの関係を予め求め、使用中の鋼材の表面を拡大して
炭化物部分のみの硬さを計測し、この硬さから前記関係
により鋼材の余寿命を診断する、ことを特徴とするクリ
ープ損傷が生じる鋼材の余寿命診断方法。1. A relationship between the creep damage rate of a steel material and the hardness of a carbide portion is obtained in advance, the surface of the steel material in use is enlarged to measure the hardness of only the carbide portion, and from this hardness, the steel material is obtained from the above relation. A method for diagnosing the remaining life of a steel product in which creep damage occurs, which is characterized by diagnosing the remaining life.
とを特徴とする請求項１に記載のクリープ損傷が生じる
鋼材の余寿命診断方法。2. The method for diagnosing the remaining life of a steel material causing creep damage according to claim 1, wherein the carbide portion is bainite.
とを特徴とする請求項１に記載のクリープ損傷が生じる
鋼材の余寿命診断方法。3. The method for diagnosing the remaining life of a steel material causing creep damage according to claim 1, wherein the carbide portion is pearlite.
用い、２００ｇ以下の試験荷重により、試験面に最大径
５０μｍ以下の窪みをつける微小硬度計による、ことを
特徴とする請求項１に記載のクリープ損傷が生じる鋼材
の余寿命診断方法。4. The hardness measurement is performed by using a small square indenter, and a micro hardness meter that forms a depression having a maximum diameter of 50 μm or less on a test surface under a test load of 200 g or less. A method for diagnosing the remaining life of a steel material causing creep damage as described in.
ある、ことを特徴とする請求項１に記載のクリープ損傷
が生じる鋼材の余寿命診断方法。5. The method for diagnosing residual life of a steel material causing creep damage according to claim 1, wherein the hardness is a micro Vickers hardness.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13473494A JPH085535A (en) | 1994-06-17 | 1994-06-17 | Method for diagnosing remaining life expectancy of steel product with creep damage caused |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13473494A JPH085535A (en) | 1994-06-17 | 1994-06-17 | Method for diagnosing remaining life expectancy of steel product with creep damage caused |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH085535A true JPH085535A (en) | 1996-01-12 |
Family
ID=15135347
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13473494A Pending JPH085535A (en) | 1994-06-17 | 1994-06-17 | Method for diagnosing remaining life expectancy of steel product with creep damage caused |
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| Country | Link |
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| JP (1) | JPH085535A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104165815A (en) * | 2014-08-13 | 2014-11-26 | 武汉钢铁(集团)公司 | Method for discriminating punching performance of silicon steel sheet by measuring microhardness |
| JP2016006389A (en) * | 2014-06-20 | 2016-01-14 | 株式会社Ihi | Ferrite steel creep remaining life evaluation method |
-
1994
- 1994-06-17 JP JP13473494A patent/JPH085535A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016006389A (en) * | 2014-06-20 | 2016-01-14 | 株式会社Ihi | Ferrite steel creep remaining life evaluation method |
| CN104165815A (en) * | 2014-08-13 | 2014-11-26 | 武汉钢铁(集团)公司 | Method for discriminating punching performance of silicon steel sheet by measuring microhardness |
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