WO2022259957A1 - Method for evaluating brittle crack arrest performance of thick steel plate - Google Patents

Method for evaluating brittle crack arrest performance of thick steel plate Download PDF

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WO2022259957A1
WO2022259957A1 PCT/JP2022/022514 JP2022022514W WO2022259957A1 WO 2022259957 A1 WO2022259957 A1 WO 2022259957A1 JP 2022022514 W JP2022022514 W JP 2022022514W WO 2022259957 A1 WO2022259957 A1 WO 2022259957A1
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transition temperature
test
plate thickness
brittle crack
charpy impact
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PCT/JP2022/022514
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French (fr)
Japanese (ja)
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久和 田近
恒久 半田
哲哉 田川
涼太 長尾
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Ｊｆｅスチール株式会社
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Priority to KR1020237036291A priority Critical patent/KR20230159710A/en
Priority to CN202280030516.3A priority patent/CN117321402A/en
Priority to JP2022549693A priority patent/JP7188655B1/en
Publication of WO2022259957A1 publication Critical patent/WO2022259957A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/30—Investigating strength properties of solid materials by application of mechanical stress by applying a single impulsive force, e.g. by falling weight
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/42—Low-temperature sample treatment, e.g. cryofixation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/30—Investigating strength properties of solid materials by application of mechanical stress by applying a single impulsive force, e.g. by falling weight
    • G01N3/31—Investigating strength properties of solid materials by application of mechanical stress by applying a single impulsive force, e.g. by falling weight generated by a rotating fly-wheel

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  • the present invention relates to an evaluation method for easily evaluating the brittle crack arrestability of thick steel plates with a thickness of 40 mm or more using a small test piece.
  • Patent Document 1 a Charpy impact test was performed using a Charpy impact test piece in which a press notch was introduced from the center of the plate thickness and the position of 1/4 of the plate thickness from the surface, and the brittleness obtained respectively
  • a method for evaluating the brittle fracture arrestability of steel plates is described, which evaluates the brittle fracture arrestability based on the fracture surface transition temperature at which the fracture surface ratio becomes 75%.
  • Patent Document 2 in evaluating the brittle fracture propagation stopping performance of a thick steel plate of 50 mm or more in a small test, a rectangular cross section taken from the center position of the thickness of the thick steel plate is a deformed press notch Charpy A Charpy impact test is performed using a test piece, and based on the transition temperature pTE at which the obtained absorbed energy shows a specific value, or the transition temperature BATT at which the brittle fracture surface ratio shows a specific value, the brittle fracture propagation arrest performance A method for evaluating the brittle fracture arrestability of thick steel plates is described.
  • Non-Patent Document 1 there is a distribution of toughness at each position in the plate thickness direction, and considering that the brittle fracture arrestability Kca value obtained by the ESSO test is strongly affected by the low toughness region, A technique for evaluating the brittle fracture arrestability by taking the toughness value at each position as the area average value of the steel plate and weighting the value at the center of the plate thickness is described.
  • Patent Document 1 uses press-notched Charpy impact test specimens taken from the center of the plate thickness of a thick steel plate and the position of 1/4 of the plate thickness from the surface to evaluate brittle fracture propagation arrest performance.
  • the correlation with the brittle crack arrest toughness value Kca is low.
  • the correlation with the brittle crack arrest toughness value Kca is low in a thick steel plate in which the fracture mode in the plate thickness direction is greatly different.
  • the thick steel plate targeted by the present invention has a thickness of 40 mm or more, and is a thick steel plate in which the mode of brittle crack propagation changes between the central portion of the thickness and the intermediate position of the thickness.
  • the "thickness central portion” referred to here is defined as a range from 3/8 to 5/8 of the plate thickness centering on the 1/2 position of the plate thickness.
  • “thickness middle position” refers to the position symmetrically distant from the plate thickness center of 1/6 to 3/8 of the plate thickness and 5/8 to 5/6 of the plate thickness.
  • the press notch Charpy impact test used a test piece taken from one central position of the plate thickness. The obtained results are shown in FIG.
  • FIG. 1 schematically shows the fracture surface morphology of the test piece.
  • the brittle crack arrestability of thick steel plates strongly affects not only the toughness at the center of the plate thickness, but also the toughness at the part (intermediate position) where the fracture surface is formed, which is different from the center of the plate thickness. It can be said that From the observation of the non-penetrating test piece of this thick steel plate, in the brittle crack arrest test, the crack propagates deeply at the center and intermediate positions of the plate thickness when crack propagation stops, but the progress near the surface layer is relative. Shallow. From this fracture morphology, it is considered that the crack propagation behavior at the sheet thickness center and intermediate positions rather than the surface layer controls the propagation of brittle cracks in the entire steel sheet. Therefore, in this kind of thick steel plate, it was found that the vicinity of the surface layer has little effect on the brittle crack arrestability.
  • the fracture surface morphology at a thickness direction position other than the plate thickness center position is different from that at the plate thickness center position, and if the fracture surface morphology exhibits many ductile cracks and ligaments, the crack leading edge The dynamic stress intensity factor decreases, and crack propagation is likely to stop. Therefore, it is presumed that the toughness at the position in the plate thickness direction, which presents a fracture surface morphology different from that at the plate center position, greatly affects the brittle crack arrestability of the entire steel plate.
  • the temperatures exhibiting predetermined characteristic values were evaluated by a small-scale test at the plate thickness center position and at positions in the plate thickness direction showing fracture surface morphologies different from the plate thickness center position.
  • the plate thickness 1/4 Charpy impact test specimens (10 mm square ⁇ 55 mm length) were also collected from 4 positions (hereinafter, the 1/4 plate thickness position is indicated by the subscript q in the symbols).
  • a V notch was introduced into the Charpy impact test piece from the plate thickness 1/4 position, and the V notch Charpy impact test was performed. asked.
  • the temperature p T E40Jh (° C.) at which the absorbed energy in the press notch Charpy impact test at the above-mentioned plate thickness center position (hereinafter, the plate thickness center position is indicated by the subscript h in the symbol) is 40 J.
  • the obtained temperature v T rsq (° C.) at which the brittle fracture surface ratio in the V-notch Charpy impact test at the 1/4 position of the plate thickness is 50% is combined to obtain the combined transition temperature T w (° C.) by the small-scale test.
  • temperature T Kca 8000 (° C.) and temperature T w (° C.).
  • the transition temperature at each position in the plate thickness direction was weighted and averaged as a contribution according to the effect on the brittle crack arrestability in the entire thickness. .
  • T w ⁇ 89.1° C.
  • the present invention has been completed based on the above findings and further studies. That is, the gist of the present invention is as follows. [1] A method for evaluating the brittle crack arrestability of a thick steel plate, in evaluating the brittle crack arrestability obtained by a large test from a temperature showing a predetermined characteristic value obtained using a small test, A brittle crack propagation arrest test was performed using a full-thickness test piece of the thick steel plate, and from the observation of the morphology of the obtained fracture surface, the position range in the plate thickness direction showing a different fracture surface morphology from the plate thickness center position was identified as a position, The temperature indicating the predetermined characteristic value obtained using the small-sized test is combined with the transition temperature of the press notch Charpy impact test at the center thickness position and the transition temperature of the V notch Charpy impact test at the middle thickness position.
  • a method for evaluating the brittle crack arrestability of a thick steel plate wherein the brittle crack arrestability of the thick steel plate is evaluated from the combination transition temperature.
  • a method for evaluating the brittle crack arrestability of a thick steel plate in evaluating the brittle crack arrestability obtained by a large test from a temperature showing a predetermined characteristic value obtained using a small test, A brittle crack propagation arrest test was performed using a full-thickness test piece of the thick steel plate, and from the observation of the morphology of the obtained fracture surface, the position range in the plate thickness direction showing a different fracture surface morphology from the plate thickness center position was identified as a position, The temperature indicating the predetermined characteristic value obtained using the small test is the transition temperature T ct of the press notch Charpy impact test at the plate thickness center position, and the transition temperature of the V notch Charpy impact test at the plate thickness middle position.
  • the brittle crack arrest toughness Kca is k1 (N /mm 3/2 ), and evaluating the brittle crack arrestability of a thick steel plate.
  • Tw Tmt + B1 ⁇ Tct (1)
  • T w the combined transition temperature (°C) obtained using a compact test
  • T mt transition temperature (°C) of V-notch Charpy impact test at plate thickness intermediate position
  • T ct Transition temperature (° C.) in press notch Charpy impact test at the center of the plate thickness
  • A1, B1, C1 Coefficient [3]
  • a method for evaluating the brittle crack arrestability of a thick steel plate in which the brittle crack arrestability obtained by a large-scale test is changed from the temperature indicating a predetermined characteristic value obtained by using a small-scale test.
  • a brittle crack propagation arrest test was performed using a full-thickness test piece of the thick steel plate, and from the observation of the morphology of the obtained fracture surface, the position range in the plate thickness direction showing a different fracture surface morphology from the plate thickness center position was identified as a position,
  • the temperature indicating the predetermined characteristic value obtained using the small test is the transition temperature T ct of the press notch Charpy impact test at the plate thickness center position, and the transition temperature of the V notch Charpy impact test at the plate thickness middle position.
  • T w the combined transition temperature (°C) obtained using a compact test
  • T mt transition temperature (°C) of V-notch Charpy impact test at plate thickness intermediate position
  • T ct Transition temperature (° C.) in press notch Charpy impact test at the center of the plate thickness
  • A2, B2, C2 Coefficient [4]
  • the mid-thickness position is the 1/4-thickness position
  • the transition temperature Tct is the transition temperature at which the absorbed energy in the press-notch Charpy impact test at the mid-thickness position shows 40 J.
  • the transition temperature T mt is the transition temperature v T rsq at which the brittle fracture surface ratio in the V notch Charpy impact test at the 1/4 position of the plate thickness is 50%,
  • the following formula (5) is The evaluation method for brittle crack arrestability of a steel plate according to [2], wherein the following formula (6) is used instead of the formula (2).
  • Tw 1.12 x (pTE40Jh + vTrsq ) / 2 + 0.44 x (pTE40Jh - vTrsq ) (7)
  • v T rsq Transition temperature (° C.) at which the brittle fracture surface ratio in the V-notch Charpy impact test at the 1/4 plate thickness position is 50%
  • p T E40Jh Transition temperature (°C) at which the absorbed energy in the press notch Charpy impact test at the plate thickness center position shows 40 J [6]
  • a method for evaluating the brittle crack arrestability of a thick steel plate in evaluating the brittle crack arrestability obtained by a large test from a temperature showing a predetermined characteristic value obtained using a small test, A brittle crack propagation arrest test was performed using a
  • Tmt is a combination transition temperature Tw obtained by combining the transition temperature Tct and the transition temperature Tmt defined by the following equation (1a), and from the combination transition temperature Tw , the following equation (2a) is obtained.
  • a method for evaluating the brittle crack arrestability of a thick steel plate which estimates the temperature CAT at which brittle cracks do not propagate in the CAT test, and evaluates the brittle crack arrestability of the steel plate.
  • Tw Tmt + E1 ⁇ Tct (1a)
  • CAT D1 ⁇ Tw +F1 (2a)
  • D1, E1, F1: coefficient [7] A method for evaluating the brittle crack arrestability of a thick steel plate, in which the brittleness obtained by a large-scale test from the temperature exhibiting a predetermined characteristic value obtained using a small-scale test
  • a brittle crack propagation arrest test was performed using a full-thickness test piece of the thick steel plate, and from the observation of the morphology of the obtained fracture surface, the position range in the plate thickness direction showing a different fracture surface morphology from the plate thickness center position was identified as a position
  • the temperature indicating the predetermined characteristic value obtained using the small test is the transition temperature T ct of the press notch Charpy impact test at the plate thickness center position, and the transition temperature of the V notch Charpy impact test at the plate thickness middle position.
  • Tmt is a combined transition temperature Tw that is a combination of the transition temperature Tct and the transition temperature Tmt defined by the following equation (3a), and from the combined transition temperature Tw , the following equation (4a) is A method for evaluating the brittle crack arrestability of a thick steel plate, which estimates the temperature CAT at which brittle cracks do not propagate in the CAT test, and evaluates the brittle crack arrestability of the steel plate.
  • T w (T mt + T ct )/2 + E2 ⁇ (T ct - T mt ) (3a)
  • CAT D2 ⁇ Tw +F2 (4a)
  • T mt transition temperature (° C.) of V-notch Charpy impact test at plate thickness intermediate position
  • T ct Transition temperature (° C.) in press notch Charpy impact test at the center of the plate thickness
  • D2, E2, F2 Coefficients
  • a full-thickness large-scale brittle crack arrest test such as the ESSO test is used only to identify the test position, and toughness evaluation is performed by a small test using a test piece of the same size as the Charpy impact test. From the results, it is possible to easily and accurately evaluate the brittle crack arrestability of steel plates, which is very effective in industry.
  • the temperature T Kca 8000 obtained by the ESSO test, the energy transition temperature p T E40Jh in the press notch Charpy impact test at the plate thickness center position, and the fracture surface transition temperature v T rsq in the V notch Charpy impact test at the plate thickness 1/4 position and the combined transition temperature Tw.
  • a temperature indicating a predetermined characteristic value obtained using a small-scale test is used. This is a method for evaluating propagation stop performance. Further, the upper limit of the plate thickness in the present invention is preferably 120 mm or less.
  • a steel plate having high brittle crack arrestability is subjected to a brittle crack arrest test and the morphology of the fracture surface is observed.
  • a main crack (brittle crack) 3 propagates in an oblique direction of 35° from the embrittlement portion 2 adjacent to the notch 1 and then stops (brittle crack arrest 4).
  • the toughness at the thickness direction position (hereinafter referred to as the plate thickness intermediate position) that forms a fracture surface different from the plate thickness center position. It is speculated that this has a large effect on the brittle crack arrestability of From the observation of the non-penetrating test piece of this thick steel plate, in the brittle crack arrest test, the crack propagates deeply at the center and intermediate positions of the plate thickness when crack propagation stops, but the progress near the surface layer is relative. Shallow. From this fracture morphology, it is considered that the crack propagation behavior at the sheet thickness center and intermediate positions rather than the surface layer controls the propagation of brittle cracks in the entire steel sheet. Therefore, in this type of steel plate, it can be said that the vicinity of the surface layer has little effect on the brittle crack arrestability.
  • a large-scale brittle crack arrest test is performed at an appropriate test temperature using several, preferably 3 to 5, full-thickness test pieces of a target thick steel plate. Furthermore, the fracture surface morphology of the obtained test piece is observed, and the position range in the plate thickness direction exhibiting a fracture surface morphology different from that at the plate thickness center position is specified as the plate thickness intermediate position.
  • the plate thickness intermediate position is often located in the range of (1/6 to 3/8) t from the front and back surfaces. often good. For "thickness center position" and "thickness 1/4 position", a range of ⁇ 5% of the thickness is allowed.
  • the plate thickness 1/4 position includes the range of (1.05t/4) to (0.95t/4).
  • the plate thickness 1/2 is defined as "t /2"
  • 1/4 of the thickness is "t/4”
  • the thickness may be replaced with t.
  • full-thickness large-scale tests include ESSO tests, CAT tests, and press notch bending tests, but the present invention is not limited to these.
  • an ESSO test, a CAT test, a press notch bending test, etc. using a reduced thickness test piece may be used. It is important to have a test piece thickness that includes If a small-sized test can be performed at a plurality of plate thickness positions and a characteristic change region can be found, fracture surface observation using a large-sized test piece may be omitted.
  • the small-sized test used in the present invention is the Charpy impact test, and the test piece size used is the commonly used size (for example, 10 mm square). Also, the notch introduced into the test piece is a V notch or a press notch.
  • the brittle crack propagation arrestability of a thick steel plate is determined by the temperature at which a predetermined characteristic value is obtained at the central position of the plate thickness, and the predetermined temperature at the intermediate position of the plate thickness, which indicates a fracture surface morphology different from that at the central position of the plate thickness. Considering that the temperature that indicates the characteristic value is greatly affected, we decided to conduct the small-scale test at the plate thickness center position and the plate thickness intermediate position of the thick steel plate.
  • a Charpy impact test is performed at the plate thickness center position of the thick steel plate, and the obtained energy transition temperature or fracture surface transition temperature Tct is taken as the temperature (transition temperature) indicating a predetermined characteristic value at the plate thickness center position.
  • the conventional press notch Charpy impact test was carried out.
  • the press notch Charpy impact test it is possible to reproduce the phenomenon in which a brittle crack initiates from the part embrittled by the press notch and stops, and this phenomenon is similar to the actual brittle crack arrest behavior. This is because it is a phenomenon.
  • the transition temperature Tct at the central position of the plate thickness the temperature pTE40J ( °C).
  • the energy transition temperature or the fracture surface transition temperature Tmt obtained by conducting the Charpy impact test is the temperature (transition temperature) that indicates a predetermined characteristic value at the plate thickness direction intermediate position.
  • the ductile crack to the brittle crack exhibiting the same fracture mode It was assumed that the V-notch Charpy impact test, in which .
  • the V-notch Charpy impact test piece is easy to process and can be tested immediately after processing, so there is an advantage that the test process can be simplified.
  • the press notch Charpy impact test piece requires press processing, which requires extra work.
  • high-toughness steel sheets when the region immediately below the notch becomes embrittled by introducing a press notch, brittle cracks do not stably occur during the test. As a result, a stable test cannot be performed because it may not stop. Therefore, as the transition temperature T mt at the mid-thickness position, it is possible to use the fracture surface transition temperature v T rs (°C) at which the brittle fracture surface ratio is 50% in the V notch Charpy impact test, which is easy to obtain stable test results. Simple and preferable.
  • the transition temperature T ct at the center position of the plate thickness which is obtained at two positions in the plate thickness direction
  • the plate A combined transition temperature Tw is used in combination with the transition temperature Tmt at the mid-thickness position.
  • the transition temperature pTE40Jh is used as Tct
  • the transition temperature vTrsq is used as Tmt
  • the temperature indicating the toughness of the entire plate thickness may be used.
  • the toughness of the entire plate thickness it is preferable to combine the average toughness at each plate thickness position (toughness average) and the toughness difference at each plate thickness position (toughness difference).
  • the combined transition temperature T w is defined as: This is because the toughness of the entire plate thickness is the average of toughness (toughness average) at each position of the plate (T mt +T ct )/2, and in addition, it is affected by a stepped step as shown in FIG. This is because it is thought that the factors that are present, that is, (T ct ⁇ T mt ), which is the difference in toughness (difference in toughness) at each position of the sheet thickness, contribute greatly.
  • the temperature T Kca k1 (°C) at which the brittle crack arrest toughness Kca becomes k1 (N/mm 3/2 ) as the brittle fracture arrestability of the steel plate.
  • T w 1.12 ⁇ ( pTE40Jh + vT rsq ) /2 + 0.44 ⁇ (pTE40Jh - vT rsq ) ( 7 )
  • a CAT test may be used as the large-scale test. In that case, it is preferable to use the temperature CAT (° C.) at which brittle cracks do not propagate as the brittle fracture arrestability of the steel plate.
  • a temperature gradient type ESSO test was performed using a full-thickness test piece to determine the brittle crack arrest performance of the thick steel plate, and the brittle crack arrest was determined.
  • a temperature T Kca 8000 at which the toughness K ca is 8000 N/mm 3/2 was calculated.
  • the fracture surface morphology was observed, and the range of plate thickness positions showing fracture surface morphology different from the fracture surface at the plate thickness center position was specified as the plate thickness intermediate position. Then, it was confirmed that in the tested thick steel plates, the plate thickness intermediate position may be represented by the plate thickness t/4 position.
  • a Charpy impact test piece (10 mm square) was collected from the L direction at the plate thickness center position and the plate thickness t / 4 position as the plate thickness intermediate position, and a Charpy impact test was performed as a small test. was obtained to obtain a predetermined characteristic value.
  • a press notch Charpy impact test was performed at the central position of the plate thickness, and the transition temperature Tct (°C) was determined as the temperature pTE40Jh at which the absorbed energy is 40J.
  • Tct the transition temperature
  • a V notch Charpy impact test was performed, and the fracture surface transition temperature v T rsq at which the brittle fracture surface ratio was 50% was used as the transition temperature T mt (°C). asked.
  • the large-scale test is used only to specify the test position, and two thickness intermediate positions, the plate thickness center position and the plate thickness center position where the fracture surface morphology is different from the plate thickness center position, are used. From the results of the small-scale test at the position, the brittle crack arrestability of the thick steel plate could be easily evaluated with high accuracy, and the usefulness of the evaluation method of the present invention was confirmed.
  • notch 2 embrittlement part 3: main crack (brittle crack) 4: Brittle crack arrest 5: Flat fracture surface 6: Stepped step s: Brittle crack growth direction

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Abstract

Provided is a method for evaluating the brittle crack arrest performance of a thick steel plate.　The thick steel plate brittle crack arrest performance that would be obtained using a large-scale test is estimated by using a Charpy impact test, which is a small-scale test, to evaluate a characteristic value at each of a plate-thickness central position and a plate-thickness intermediate position exhibiting a fracture surface morphology different to that at the plate-thickness central position, and combining temperatures (transition temperatures) at which the obtained predetermined characteristic values are exhibited. An evaluation is performed at the plate-thickness central position using an energy transition temperature Tct of a press-notch Charpy impact test, and an evaluation is performed at the plate-thickness intermediate position using a fracture surface transition temperature Tmt of a V-notch Charpy impact test, and a transition temperature Tw (=Ymt+B1×Tct) obtained by combining these transition temperatures is used to estimate the brittle crack arrest performance of the thick steel plate. The brittle crack arrest performance of the thick steel plate can thus be evaluated simply and accurately. It should be noted that Tw=(Tmt+Tct)/2+B2×(Tct-Tmt) may be used as the combined transition temperature Tw.

Description

厚鋼板の脆性亀裂伝播停止性能の評価方法Evaluation method of brittle crack arrestability of steel plate
　本発明は、板厚が４０ｍｍ以上の厚鋼板の脆性亀裂伝播停止性能を、小型試験片を用いて簡便に評価する評価方法に関する。 The present invention relates to an evaluation method for easily evaluating the brittle crack arrestability of thick steel plates with a thickness of 40 mm or more using a small test piece.
　船舶、海洋構造物、低温貯蔵タンクおよび建築・土木構造物等の大型構造物において、脆性破壊に伴う事故が発生すると、経済や環境に大きな影響を及ぼす。そのため、特に大型構造物に対しては構造物の安全性向上が求められている。使用される鋼材は、使用温度における、優れた靭性や優れた脆性破壊伝播停止性能を有することが要求されている。 　In large-scale structures such as ships, offshore structures, low-temperature storage tanks, and architectural/civil engineering structures, if an accident due to brittle fracture occurs, it will have a major impact on the economy and the environment. Therefore, it is required to improve the safety of structures, especially for large structures. The steel materials used are required to have excellent toughness and excellent brittle fracture arrestability at service temperatures.
　脆性破壊伝播停止性能の評価は、従来から、ＥＳＳＯ試験や二重引張試験に代表される大型試験によって行われている。しかし、これらの大型試験は、多くの日数や多大の費用を要するため、簡便に行うことが難しいという問題がある。そのため、ＷＥＳ　３００３－１９９５（日本溶接協会規格）には、Ｖノッチシャルピー衝撃試験の破面遷移温度ｖＴｒｓから脆性破壊伝播停止性能を予測する手法が制定されている。しかし、近年開発された、板厚５０mmを超える鋼材に適用する場合、予測精度が悪く、簡便に評価を行うことが難しい。 Evaluation of brittle fracture arrestability has conventionally been carried out by large-scale tests such as ESSO tests and double tension tests. However, these large-scale tests require many days and cost a lot of money, so there is a problem that they are difficult to carry out easily. Therefore, WES 3003-1995 (the standard of the Japan Welding Society) establishes a method for predicting brittle fracture arrestability from the fracture surface transition temperature v Trs in a V-notch Charpy impact test. However, when it is applied to steel materials with a plate thickness exceeding 50 mm, which have been developed in recent years, the prediction accuracy is poor and it is difficult to easily evaluate.
　例えば、特許文献１には、板厚中心部および表面から板厚の１／４の位置から採取しプレスノッチを導入したシャルピー衝撃試験片を用いて、シャルピー衝撃試験を行い、それぞれ得られた脆性破面率が７５％となる破面遷移温度に基づいて、脆性破壊伝播停止性能を評価する、厚鋼板の脆性破壊伝播停止性能の評価方法が記載されている。 For example, in Patent Document 1, a Charpy impact test was performed using a Charpy impact test piece in which a press notch was introduced from the center of the plate thickness and the position of 1/4 of the plate thickness from the surface, and the brittleness obtained respectively A method for evaluating the brittle fracture arrestability of steel plates is described, which evaluates the brittle fracture arrestability based on the fracture surface transition temperature at which the fracture surface ratio becomes 75%.
　また、特許文献２には、５０ｍｍ以上の厚鋼板の脆性破壊伝播停止性能を小型試験で評価するにあたり、厚鋼板の板厚の中心部位置から採取した矩形断面が１００ｍｍ２超えの変形プレスノッチシャルピー試験片を用いてシャルピー衝撃試験を実施し、得られた吸収エネルギーが特定値を示す遷移温度ｐＴＥ、あるいは脆性破面率が特定値を示す遷移温度ＢＡＴＴに基づいて、脆性破壊伝播停止性能を評価する、厚鋼板の脆性破壊伝播停止性能の評価方法が記載されている。 In addition, in Patent Document 2, in evaluating the brittle fracture propagation stopping performance of a thick steel plate of 50 mm or more in a small test, a rectangular cross section taken from the center position of the thickness of the thick steel plate is a deformed press notch Charpy A Charpy impact test is performed using a test piece, and based on the transition temperature pTE at which the obtained absorbed energy shows a specific value, or the transition temperature BATT at which the brittle fracture surface ratio shows a specific value, the brittle fracture propagation arrest performance A method for evaluating the brittle fracture arrestability of thick steel plates is described.
　また、非特許文献１には、板厚方向各位置で靭性に分布があり、ＥＳＳＯ試験によって求まる脆性破壊伝播停止性能Ｋｃａ値が低靭性領域の影響を強く受けることを考慮し、板厚方向各位置における靭性値をその鋼板の面積平均値とし、板厚中央部の値を重み付けした脆性破壊伝播停止性能を評価する技術が記載されている。 In addition, in Non-Patent Document 1, there is a distribution of toughness at each position in the plate thickness direction, and considering that the brittle fracture arrestability Kca value obtained by the ESSO test is strongly affected by the low toughness region, A technique for evaluating the brittle fracture arrestability by taking the toughness value at each position as the area average value of the steel plate and weighting the value at the center of the plate thickness is described.
特開２０１１－３３４５７号公報JP 2011-33457 A 国際公開２０１４／２０８０７２号WO2014/208072
　特許文献１に記載された技術は、厚鋼板の板厚中心部および表面から板厚の１／４の位置から採取したプレスノッチシャルピー衝撃試験片を用いて、脆性破壊伝播停止性能を評価している。しかしながら、表層の靭性値が反映されておらず、表層におけるシアリップ発生が脆性き裂伝播停止に大きく影響するような厚鋼板では、脆性き裂伝播停止靭性値Ｋcaとの相関性が低くなる。また、シアリップ発生が少ない場合でも、板厚方向での破壊形態が大きく異なるような厚鋼板では、脆性き裂伝播停止靭性値Ｋcaとの相関性が低くなるという問題がある。さらに、脆性破壊伝播停止性能が高い鋼板では、板厚１／４位置でのプレスノッチシャルピー衝撃試験において、ノッチ底からの脆性亀裂の発生が困難な場合があるため、適正なプレスノッチシャルピー衝撃試験結果を得ることが難しいという問題があった。 The technique described in Patent Document 1 uses press-notched Charpy impact test specimens taken from the center of the plate thickness of a thick steel plate and the position of 1/4 of the plate thickness from the surface to evaluate brittle fracture propagation arrest performance. there is However, in a thick steel plate in which the toughness value of the surface layer is not reflected and the occurrence of shear lip in the surface layer greatly affects brittle crack arrest, the correlation with the brittle crack arrest toughness value Kca is low. In addition, even if the occurrence of shear lip is small, there is a problem that the correlation with the brittle crack arrest toughness value Kca is low in a thick steel plate in which the fracture mode in the plate thickness direction is greatly different. Furthermore, in a steel plate with high brittle fracture arrestability, it may be difficult to generate a brittle crack from the notch bottom in a press notch Charpy impact test at the 1/4 position of the plate thickness, so an appropriate press notch Charpy impact test The problem was that it was difficult to obtain results.
　また、特許文献２に記載された技術では、通常のシャルピー衝撃試験と同様のサイズのプレスノッチシャルピー衝撃試験片を用いて、試験片を板厚中央部１箇所から採取して、厚鋼板の脆性亀裂伝播停止性能を評価している。しかし、板厚６０～８０ｍｍの厚鋼板においては、プレスノッチシャルピー衝撃試験を用いた小型試験結果により得られた特性値と厚鋼版の脆性亀裂伝播停止性能の間には高い相関性が見られる一方で、板厚が８０ｍｍを超えてさらに厚くなる場合には、精度が低下する場合があるという問題があった。 In addition, in the technique described in Patent Document 2, a press notch Charpy impact test piece of the same size as a normal Charpy impact test is used to collect the test piece from one central part of the plate thickness, and the brittleness of the thick steel plate is measured. Crack propagation arrest performance is evaluated. However, for thick steel plates with a plate thickness of 60 to 80 mm, a high correlation can be seen between the characteristic values obtained from the results of the small test using the press notch Charpy impact test and the brittle crack arrestability of the thick steel plates. On the other hand, if the plate thickness exceeds 80 mm and becomes even thicker, there is a problem that the accuracy may decrease.
　そこで、本発明は、全厚の大型試験は試験位置を特定することのみに使用し、小型試験を用いる簡便な方法で、厚鋼板の脆性亀裂伝播停止性能を精度高く評価できる、厚鋼板の脆性亀裂伝播停止性能の評価方法を提供することを目的とする。なお、本発明が対象とする厚鋼板は、板厚４０ｍｍ以上とし、板厚中央部と板厚中間位置で脆性亀裂伝播形態が変化する厚鋼板とする。ここでいう「板厚中央部」は、板厚の１／２位置を中心として、板厚の３／８～５／８位置の範囲というものとする。また、「板厚中間位置」は、板厚の１／６～３／８位置、および板厚の５／８～５／６位置の、板厚中央部から対称的に離れた位置をいうものとする。 Therefore, the present invention uses a full-thickness large-scale test only to specify the test position, and a simple method using a small-scale test to evaluate the brittle crack arrestability of the steel plate with high accuracy. It is an object of the present invention to provide a method for evaluating crack arrestability. The thick steel plate targeted by the present invention has a thickness of 40 mm or more, and is a thick steel plate in which the mode of brittle crack propagation changes between the central portion of the thickness and the intermediate position of the thickness. The "thickness central portion" referred to here is defined as a range from 3/8 to 5/8 of the plate thickness centering on the 1/2 position of the plate thickness. In addition, "thickness middle position" refers to the position symmetrically distant from the plate thickness center of 1/6 to 3/8 of the plate thickness and 5/8 to 5/6 of the plate thickness. and
　本発明者らは、上記した目的を達成するため、まず、厚鋼板１９種（板厚１００ｍｍ）について、大型試験であるＥＳＳＯ試験を実施しＫcaが８０００Ｎ／ｍｍ３／２となる温度ＴＫｃａ＝８０００（℃)を求め、同時に小型試験であるプレスノッチシャルピー衝撃試験（試験片：１０ｍｍ角×５５ｍｍ長さ）を実施し、吸収エネルギーが４０Ｊとなる温度ｐＴＥ４０Ｊ（℃）を求めた。なお、プレスノッチシャルピー衝撃試験は、板厚中央位置１箇所から採取した試験片を用いた。
得られた結果を、温度ＴＫｃａ＝８０００（℃)と温度ｐＴＥ４０Ｊ（℃）との関係で図２に示す。得られたＴＫｃａ＝８０００とｐＴＥ４０Ｊとの相関関係から、回帰式である次（ａ）式
　ＴＫｃａ＝８０００＝０．１７×ｐＴＥ４０Ｊ－２３．２５　…（ａ）
　（ここで、回帰残差ｕ：１０．６１）
を得た。そして、温度ＴＫｃａ＝８０００（℃)の上限値の推定式として次（ｂ）式
　ＴＫｃａ＝８０００＝０．１７×ｐＴＥ４０Ｊ－２．０３　…（ｂ）
を得た。そして、この推定式から、ＴＫｃａ＝８０００を－１０℃とするに必要なｐＴＥ４０Ｊを推定すると、ｐＴＥ４０Ｊ＝－４６．９℃となる。図２から、ｐＴＥ４０Ｊ＝－４６．９℃を超える値を示す厚鋼板は９種となっている。推定値以下となる比率は１０／１９（５３％）で、推定精度が低いことがわかる。このような、板厚中央位置１箇所から採取した試験片によるプレスノッチシャルピー衝撃試験結果を用いる小型試験による厚鋼板の脆性亀裂伝播停止性能の評価方法では、板厚の厚い厚鋼板においては、相関性に乏しい評価結果しか得られないことがわかる。相関性が低いため、安全側の検討に設定される２σが大きくなり、大型試験を実施すれば所望の脆性亀裂伝播停止性能を有している鋼板まで、小型試験おいては「推定値を超える」と評価されることになる。 In order to achieve the above-described object, the present inventors first conducted an ESSO test, which is a large-scale test, on 19 types of thick steel plates (plate thickness 100 mm), and measured the temperature T Kca at which K ca became 8000 N / mm 3/2 . = 8000 (°C), and at the same time, a press notch Charpy impact test (test piece: 10 mm square x 55 mm length), which is a small test, was performed to determine the temperature p T E40J (°C) at which the absorbed energy becomes 40J. In addition, the press notch Charpy impact test used a test piece taken from one central position of the plate thickness.
The obtained results are shown in FIG. 2 as a relationship between the temperature T Kca=8000 (° C.) and the temperature p T E40J (° C.). From the correlation between the obtained T Kca = 8000 and p T E40J , the following regression equation (a) T Kca = 8000 = 0.17 x p T E40J -23.25 (a)
(Here, regression residual u: 10.61)
got Then, as an estimation formula for the upper limit of the temperature T Kca = 8000 (°C), the following equation (b) T Kca = 8000 = 0.17 x pT E40J -2.03 (b)
got From this estimation formula, p T E40J required to set T Kca=8000 to −10° C. is estimated to be p T E40J =−46.9° C. From FIG. 2, there are 9 types of steel plates exhibiting a value exceeding p T E40J =−46.9°C. The ratio of values below the estimated value is 10/19 (53%), indicating that the estimation accuracy is low. In such a method for evaluating the brittle crack arrestability of a thick steel plate by a small-scale test using the results of a press notch Charpy impact test using a test piece taken from one place at the center of the plate thickness, in a thick steel plate, the correlation It can be seen that only poor evaluation results can be obtained. Since the correlation is low, 2σ, which is set for consideration on the safe side, is large, and if a large-scale test is performed, the steel plate will have the desired brittle crack arrestability. ” will be evaluated.
　そこで、高い脆性亀裂伝播停止性能を有する厚鋼板（板厚：１００ｍｍ、ＥＨ４０～４７級）について大型試験である脆性亀裂伝播停止試験（ＣＡＴ試験、試験温度：－３０℃）を実施し、試験後、得られた試験片の破面形態を観察した。図１に、試験片の破面形態を模式的に示す。 Therefore, a brittle crack arrest test (CAT test, test temperature: -30 ° C.), which is a large-scale test, was performed on a thick steel plate (plate thickness: 100 mm, EH40 to 47 grade) having high brittle crack arrest performance. , the fracture surface morphology of the obtained test piece was observed. FIG. 1 schematically shows the fracture surface morphology of the test piece.
　切欠１・脆化処理域で発生した脆性亀裂は、試験部に突入してから、板厚中央部では、主亀裂（脆性亀裂）３が斜め３５°方向に進展したのち停止（脆性亀裂停止４）する破面形態を示している。さらに、斜め方向に進展する主亀裂３の端では、表面から板厚方向に３５％の位置から１５％の位置まで、および、表面から板厚方向に６５％の位置から８５％の位置まで、所定の間隔ごとに比較的平坦に進展して停止する亀裂（平坦破面５）と階段状の段差６（延性破面）が複数、形成された破面形態を示している。これら平坦破面５は、各亀裂の発生位置の高さが異なっており、かなり大きなリガメントを有する階段状の段差を形成している。 The brittle crack generated in the notch 1 and the embrittlement treated area entered the test section, and in the central part of the plate thickness, the main crack (brittle crack) 3 propagated in an oblique 35 ° direction and then stopped (brittle crack arrest 4 ) shows the fracture surface morphology. Furthermore, at the edge of the main crack 3 that develops in an oblique direction, from the 35% position to the 15% position in the plate thickness direction from the surface, and from the 65% position to the 85% position in the plate thickness direction from the surface, It shows a fracture surface configuration in which a plurality of cracks (flat fracture surfaces 5) that develop and stop relatively flatly at predetermined intervals and a plurality of stepped steps 6 (ductile fracture surfaces) are formed. These flat fracture surfaces 5 have different heights at which cracks are generated, forming step-like steps having considerably large ligaments.
　このような破面形態から、厚鋼板の脆性亀裂伝播停止性能は、板厚中央部の靭性に加えて、板厚中央部とは異なる破面を形成する部位（中間位置）の靭性に強く影響されていると言える。なお、この厚鋼板の非貫通の試験片の観察から、脆性亀裂伝播停止試験において、亀裂伝播停止時には板厚中心ならびに中間位置では亀裂が深く進展しているが、表層近傍はその進展が相対的に浅い。この破壊形態から表層よりも板厚中心ならびに中間位置での亀裂伝播挙動が鋼板全体の脆性亀裂の進展を支配するものと考えられる。したがって、この種の厚鋼板では、表層近傍は、脆性亀裂伝播停止性能への影響は少ないとの知見を得た。 From this fracture surface morphology, the brittle crack arrestability of thick steel plates strongly affects not only the toughness at the center of the plate thickness, but also the toughness at the part (intermediate position) where the fracture surface is formed, which is different from the center of the plate thickness. It can be said that From the observation of the non-penetrating test piece of this thick steel plate, in the brittle crack arrest test, the crack propagates deeply at the center and intermediate positions of the plate thickness when crack propagation stops, but the progress near the surface layer is relative. Shallow. From this fracture morphology, it is considered that the crack propagation behavior at the sheet thickness center and intermediate positions rather than the surface layer controls the propagation of brittle cracks in the entire steel sheet. Therefore, in this kind of thick steel plate, it was found that the vicinity of the surface layer has little effect on the brittle crack arrestability.
　このような板厚中央位置以外の板厚方向位置において板厚中央位置とは異なる破面形態を呈し、延性亀裂やリガメントが多く存在する破面形態を示している場合には、亀裂前縁の動的応力拡大係数が低下し、亀裂伝播停止しやすい状況になる。そのため、板厚中央位置とは異なる破面形態を呈する板厚方向位置の靭性が、厚鋼板全体の脆性亀裂伝播停止性能に大きく影響すると推察される。 If the fracture surface morphology at a thickness direction position other than the plate thickness center position is different from that at the plate thickness center position, and if the fracture surface morphology exhibits many ductile cracks and ligaments, the crack leading edge The dynamic stress intensity factor decreases, and crack propagation is likely to stop. Therefore, it is presumed that the toughness at the position in the plate thickness direction, which presents a fracture surface morphology different from that at the plate center position, greatly affects the brittle crack arrestability of the entire steel plate.
　このようなことから、板厚中央位置および板厚中央位置とは異なる破面形態を示す板厚方向位置での、所定の特性値を示す温度を小型試験でそれぞれ評価し、得られた所定の特性値を示す温度を組み合わせて厚鋼板の脆性亀裂伝播停止性能を推定すれば、厚鋼板の脆性亀裂伝播停止性能を、精度高く、信頼性高く評価できることに想到した。 For this reason, the temperatures exhibiting predetermined characteristic values were evaluated by a small-scale test at the plate thickness center position and at positions in the plate thickness direction showing fracture surface morphologies different from the plate thickness center position. By estimating the brittle crack arrestability of a thick steel plate by combining the temperatures indicating the characteristic values, the inventors conceived that the brittle crack arrestability of the steel plate can be evaluated with high accuracy and high reliability.
　そこで、板厚中央位置の破面形態と異なる破面形態を示す位置が板厚１／４位置であることから、上記した板厚中央位置でのプレスノッチシャルピー試験に加えて、板厚１／４位置（以下、記号中において板厚１／４位置のことをｑの下付き文字で示す。）からもシャルピー衝撃試験片（１０ｍｍ角×５５ｍｍ長さ）を採取した。板厚１／４位置からもシャルピー衝撃試験片にはＶノッチを導入して、Ｖノッチシャルピー衝撃試験を実施し、脆性破面率が５０％となる破面遷移温度ｖＴｒｓｑ（℃）を求めた。上述した板厚中央位置（以下、記号中において板厚中央位置のことをｈの下付き文字で示す。）でのプレスノッチシャルピー衝撃試験の吸収エネルギーが４０Ｊとなる温度ｐＴＥ４０Ｊｈ（℃）と、得られた板厚１／４位置でのＶノッチシャルピー衝撃試験の脆性破面率が５０％を示す温度ｖＴｒｓｑ(℃)を組み合わせて、小型試験による組合せ遷移温度Ｔｗ（℃）とし、温度ＴＫｃａ＝８０００（℃)と温度Ｔｗ（℃）との相関関係を求めた。なお、小型試験による板厚方向各位置での遷移温度を組み合わせるに当たり、板厚方向各位置での遷移温度を、全厚での脆性亀裂伝播停止性能に与える影響に応じた寄与分として加重平均した。加重平均は１２：１００とした。したがって、小型試験による組合せ遷移温度Ｔｗ（℃）は、Ｔｗ＝ｖＴｒｓｑ＋０．１２×ｐＴＥ４０Ｊｈと表される。 Therefore, since the position showing the fracture surface morphology different from the fracture surface morphology at the plate thickness center position is the plate thickness 1/4 position, in addition to the press notch Charpy test at the plate thickness center position described above, the plate thickness 1/4 Charpy impact test specimens (10 mm square×55 mm length) were also collected from 4 positions (hereinafter, the 1/4 plate thickness position is indicated by the subscript q in the symbols). A V notch was introduced into the Charpy impact test piece from the plate thickness 1/4 position, and the V notch Charpy impact test was performed. asked. The temperature p T E40Jh (° C.) at which the absorbed energy in the press notch Charpy impact test at the above-mentioned plate thickness center position (hereinafter, the plate thickness center position is indicated by the subscript h in the symbol) is 40 J. , the obtained temperature v T rsq (° C.) at which the brittle fracture surface ratio in the V-notch Charpy impact test at the 1/4 position of the plate thickness is 50% is combined to obtain the combined transition temperature T w (° C.) by the small-scale test. , temperature T Kca=8000 (° C.) and temperature T w (° C.). In addition, when combining the transition temperatures at each position in the plate thickness direction obtained by the small-scale test, the transition temperature at each position in the plate thickness direction was weighted and averaged as a contribution according to the effect on the brittle crack arrestability in the entire thickness. . The weighted average was 12:100. Therefore, the combined transition temperature T w (° C.) from the compact test is expressed as T w = v T rsq +0.12× p T E40Jh .
　得られた温度ＴＫｃａ＝８０００（℃)と組合せ遷移温度Ｔｗ（℃）との関係を図３に示す。温度ＴＫｃａ＝８０００（℃)と温度Ｔｗ（℃）との相関関係は、回帰式として、次（ｃ）式
　　　　　　　ＴＫｃａ＝８０００＝０．３６×Ｔｗ－３．２７　…（ｃ）
　　　　　　　（ここで、回帰残差ｕ：９．５１）
で表される。この回帰式をもとに、バラツキの範囲内でＴＫｃａ＝８０００（℃)の上限値を推定する推定式を、次（ｄ）式
　ＴＫｃａ＝８０００（℃)＝０．３６×Ｔｗ＋２２．２９  …（ｄ）
とした。この推定式から、ＴＫｃａ＝８０００が－１０℃となるために必要なＴｗを推定すると、Ｔｗ＝－８９．１℃となる。図３から、Ｔｗ＝－８９．１℃を超える値を示す厚鋼板は４種であり、１５／１９（８０％）が推定値以下となっており、図２に示す場合にくらべ、推定誤差は小さくなっていることがわかる。このため、安全側の検討に設定された２σが小さくなり、大型試験を実施した場合に所望の脆性亀裂伝播停止性能を有することを示すことができる鋼板の多くが、小型試験による推定値以下となるため、合理的に推定することが可能となった。 FIG. 3 shows the relationship between the obtained temperature T Kca=8000 (° C.) and the combined transition temperature T w (° C.). The correlation between the temperature T Kca = 8000 (°C) and the temperature T w (°C) is expressed by the following regression equation (c): T Kca = 8000 = 0.36 x T w -3.27 (c)
(Here, regression residual u: 9.51)
is represented by Based on this regression formula, the estimation formula for estimating the upper limit of T Kca = 8000 (°C) within the range of variation is the following equation (d) T Kca = 8000 (°C) = 0.36 × T w +22 .29 (d)
and From this estimation formula, when T w necessary for T Kca =8000 to become −10° C. is estimated, T w =−89.1° C. is obtained. From FIG. 3, there are four types of steel plates exhibiting a value exceeding T w = -89.1 ° C., and 15/19 (80%) are below the estimated value. It can be seen that the error is small. For this reason, 2σ, which was set for consideration on the safe side, becomes small, and many of the steel sheets that can be shown to have the desired brittle crack arrestability when a large-scale test is performed are below the value estimated by the small-scale test. Therefore, it is possible to make a reasonable estimate.
　本発明は、上記した知見に基づき、さらに検討を加えて完成されたものである。すなわち、本発明の要旨は次のとおりである。
［１］厚鋼板の脆性亀裂伝播停止性能の評価方法であって、小型試験を用いて得られた所定の特性値を示す温度から大型試験により得られる脆性亀裂伝播停止性能を評価するに当たり、
前記厚鋼板の全厚試験片を用いた脆性亀裂伝播停止試験を行い、得られた破面の形態観察から、板厚中央位置と異なる破面形態を示す板厚方向の位置範囲を板厚中間位置として特定し、
前記小型試験を用いて得られた所定の特性値を示す温度を、前記板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度と前記板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度とを組み合わせた、組合せ遷移温度として、
前記組合せ遷移温度から、前記厚鋼板の脆性亀裂伝播停止性能を評価する、厚鋼板の脆性亀裂伝播停止性能の評価方法。
［２］厚鋼板の脆性亀裂伝播停止性能の評価方法であって、小型試験を用いて得られた所定の特性値を示す温度から大型試験により得られる脆性亀裂伝播停止性能を評価するに当たり、
前記厚鋼板の全厚試験片を用いた脆性亀裂伝播停止試験を行い、得られた破面の形態観察から、板厚中央位置と異なる破面形態を示す板厚方向の位置範囲を板厚中間位置として特定し、
前記小型試験を用いて得られた所定の特性値を示す温度を、前記板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度Ｔｃｔと、前記板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度Ｔｍｔとを組み合わせた、下記（１）式で定義される組合せ遷移温度Ｔｗとして、該組合せ遷移温度Ｔｗから、下記（２）式を用いて脆性亀裂伝播停止靭性Ｋｃａがｋ１（Ｎ／ｍｍ３／２）となる温度ＴＫｃａ＝ｋ１（℃）を推定し、厚鋼板の脆性亀裂伝播停止性能を評価する、厚鋼板の脆性亀裂伝播停止性能の評価方法。
　　　　　　　　　　　　　　　　　　　記
　　　　　　　　Ｔｗ＝Ｔｍｔ＋Ｂ１×Ｔｃｔ　　　…（１）
　　　　　　　　ＴＫｃａ＝ｋ１＝Ａ１×Ｔｗ＋Ｃ１　　　…（２）
ここで、Ｔｗ：小型試験を用いて得られた組合せ遷移温度（℃）、
　　　　Ｔｍｔ：板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度（℃)、
　　　　Ｔｃｔ：板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度（℃）、
　　　　Ａ１、Ｂ１、Ｃ１：係数
［３］　厚鋼板の脆性亀裂伝播停止性能の評価方法であって、小型試験を用いて得られた所定の特性値を示す温度から大型試験により得られる脆性亀裂伝播停止性能を評価するに当たり、
前記厚鋼板の全厚試験片を用いた脆性亀裂伝播停止試験を行い、得られた破面の形態観察から、板厚中央位置と異なる破面形態を示す板厚方向の位置範囲を板厚中間位置として特定し、
前記小型試験を用いて得られた所定の特性値を示す温度を、前記板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度Ｔｃｔと、前記板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度Ｔｍｔとを組み合わせた、下記（３）式で定義される組合せ遷移温度Ｔｗとして、該組合せ遷移温度Ｔｗから、下記（４）式を用いて脆性亀裂伝播停止靭性Ｋｃａがｋ１（Ｎ／ｍｍ３／２）となる温度ＴＫｃａ＝ｋ１を（℃）推定し、厚鋼板の脆性亀裂伝播停止性能を評価する、厚鋼板の脆性亀裂伝播停止性能の評価方法。
　　　　　　　　　　　　　　　　　　　　記
　　　　Ｔｗ＝（Ｔｍｔ＋Ｔｃｔ）／２＋Ｂ２×(Ｔｃｔ－Ｔｍｔ)　　　…（３）
　　　　ＴＫｃａ＝ｋ１＝Ａ２×Ｔｗ＋Ｃ２　　　…（４）
ここで、Ｔｗ：小型試験を用いて得られた組合せ遷移温度（℃)、
　　　　Ｔｍｔ：板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度（℃)、
　　　　Ｔｃｔ：板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度（℃）、
　　　　Ａ２、Ｂ２、Ｃ２：係数
［４］前記板厚中間位置を板厚１／４位置とし、前記遷移温度Ｔｃｔを、板厚中央位置におけるプレスノッチシャルピー衝撃試験の吸収エネルギーが４０Ｊを示す遷移温度ｐＴＥ４０Ｊｈとし、前記遷移温度Ｔｍｔを、板厚１／４位置におけるＶノッチシャルピー衝撃試験の脆性破面率が５０％である遷移温度ｖＴｒｓｑとし、
前記（１）式に代えて、下記（５）式を、
前記（２）式に代えて、下記（６）式を用いる、［２］に記載の厚鋼板の脆性亀裂伝播停止性能の評価方法。
　　　　　　　　　　　　　　　　　　　　記
　　　　Ｔｗ＝ｖＴｒｓｑ＋０．１２×ｐＴＥ４０Ｊｈ　　　…（５）
　　　　ＴＫｃａ＝８０００＝０．３６×Ｔｗ＋２２．３　　　…（６）
　　　　ｖＴｒｓｑ：板厚１／４位置におけるＶノッチシャルピー衝撃試験の脆性破面率が５０％である遷移温度（℃）、
　　　　ｐＴＥ４０Ｊｈ：板厚中央位置におけるプレスノッチシャルピー衝撃試験の吸収エネルギーが４０Ｊを示す遷移温度（℃)
［５］前記板厚中間位置を板厚１／４位置とし、前記遷移温度Ｔｃｔを、板厚中央位置におけるプレスノッチシャルピー衝撃試験の吸収エネルギーが４０Ｊを示す遷移温度ｐＴＥ４０Ｊｈとし、前記遷移温度Ｔｍｔを、板厚１／４位置におけるＶノッチシャルピー衝撃試験の脆性破面率が５０％である遷移温度ｖＴｒｓｑとし、
前記（３）式に代えて、下記（７）式を、
前記（４）式に代えて、下記（８）式を用いる、［３］に記載の厚鋼板の脆性亀裂伝播停止性能の評価方法。
　　　　　　　　　　　　　　　　　　　　記
　　　　Ｔｗ＝１．１２×(ｐＴＥ４０Ｊｈ＋ｖＴｒｓｑ)／２＋０．４４×(ｐＴＥ４０Ｊｈ－ｖＴｒｓｑ)　　　…（７）
　　　　ＴＫｃａ＝８０００＝０．４０×(ｐＴＥ４０Ｊｈ＋ｖＴｒｓｑ) ／２＋０．１６×(ｐＴＥ４０Ｊｈ－ｖＴｒｓｑ)＋２２．３　　　…（８）
　　　　ｖＴｒｓｑ：板厚１／４位置におけるＶノッチシャルピー衝撃試験の脆性破面率が５０％である遷移温度（℃）、
　　　　ｐＴＥ４０Ｊｈ：板厚中央位置におけるプレスノッチシャルピー衝撃試験の吸収エネルギーが４０Ｊを示す遷移温度（℃)
［６］厚鋼板の脆性亀裂伝播停止性能の評価方法であって、小型試験を用いて得られた所定の特性値を示す温度から大型試験により得られる脆性亀裂伝播停止性能を評価するに当たり、
前記厚鋼板の全厚試験片を用いた脆性亀裂伝播停止試験を行い、得られた破面の形態観察から、板厚中央位置と異なる破面形態を示す板厚方向の位置範囲を板厚中間位置として特定し、
前記小型試験を用いて得られた所定の特性値を示す温度を、前記板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度Ｔｃｔと、前記板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度Ｔｍｔとを、下記（１ａ）式で定義される前記遷移温度Ｔｃｔと前記遷移温度Ｔｍｔとを組み合わせた組合せ遷移温度Ｔｗとして、該組合せ遷移温度Ｔｗから、下記（２ａ）式を用いて、ＣＡＴ試験における脆性亀裂が伝播しない温度ＣＡＴを推定し、厚鋼板の脆性亀裂伝播停止性能を評価する、厚鋼板の脆性亀裂伝播停止性能の評価方法。
　　　　　　　　　　　　　　　　記
　　　Ｔｗ＝Ｔｍｔ＋Ｅ１×Ｔｃｔ　　　…（１ａ）
　　　ＣＡＴ＝Ｄ１×Ｔｗ＋Ｆ１　　　…（２ａ）
ここで、Ｄ１、Ｅ１、Ｆ１：係数
［７］厚鋼板の脆性亀裂伝播停止性能の評価方法であって、小型試験を用いて得られた所定の特性値を示す温度から大型試験により得られる脆性亀裂伝播停止性能を評価するに当たり、
前記厚鋼板の全厚試験片を用いた脆性亀裂伝播停止試験を行い、得られた破面の形態観察から、板厚中央位置と異なる破面形態を示す板厚方向の位置範囲を板厚中間位置として特定し、
前記小型試験を用いて得られた所定の特性値を示す温度を、前記板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度Ｔｃｔと、前記板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度Ｔｍｔとを、下記（３ａ）式で定義される前記遷移温度Ｔｃｔと前記遷移温度Ｔｍｔとを組み合わせた組合せ遷移温度Ｔｗとして、該組合せ遷移温度Ｔｗから、下記（４ａ）式を用いて、ＣＡＴ試験における脆性亀裂が伝播しない温度ＣＡＴを推定し、厚鋼板の脆性亀裂伝播停止性能を評価する、厚鋼板の脆性亀裂伝播停止性能の評価方法。
　　　　　　　　　　　　　　　　記
　　　Ｔｗ＝（Ｔｍｔ＋Ｔｃｔ）／２＋Ｅ２×(Ｔｃｔ－Ｔｍｔ) 　　　…（３ａ）
　　　ＣＡＴ＝Ｄ２×Ｔｗ＋Ｆ２　　　…（４ａ）
ここで、Ｔｍｔ：板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度（℃）、
　　　　Ｔｃｔ：板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度（℃）、
　　　　Ｄ２、Ｅ２、Ｆ２：係数 The present invention has been completed based on the above findings and further studies. That is, the gist of the present invention is as follows.
[1] A method for evaluating the brittle crack arrestability of a thick steel plate, in evaluating the brittle crack arrestability obtained by a large test from a temperature showing a predetermined characteristic value obtained using a small test,
A brittle crack propagation arrest test was performed using a full-thickness test piece of the thick steel plate, and from the observation of the morphology of the obtained fracture surface, the position range in the plate thickness direction showing a different fracture surface morphology from the plate thickness center position was identified as a position,
The temperature indicating the predetermined characteristic value obtained using the small-sized test is combined with the transition temperature of the press notch Charpy impact test at the center thickness position and the transition temperature of the V notch Charpy impact test at the middle thickness position. Also, as the combined transition temperature,
A method for evaluating the brittle crack arrestability of a thick steel plate, wherein the brittle crack arrestability of the thick steel plate is evaluated from the combination transition temperature.
[2] A method for evaluating the brittle crack arrestability of a thick steel plate, in evaluating the brittle crack arrestability obtained by a large test from a temperature showing a predetermined characteristic value obtained using a small test,
A brittle crack propagation arrest test was performed using a full-thickness test piece of the thick steel plate, and from the observation of the morphology of the obtained fracture surface, the position range in the plate thickness direction showing a different fracture surface morphology from the plate thickness center position was identified as a position,
The temperature indicating the predetermined characteristic value obtained using the small test is the transition temperature T ct of the press notch Charpy impact test at the plate thickness center position, and the transition temperature of the V notch Charpy impact test at the plate thickness middle position. As a combination transition temperature Tw defined by the following formula (1), which is combined with Tmt , the brittle crack arrest toughness Kca is k1 (N /mm 3/2 ), and evaluating the brittle crack arrestability of a thick steel plate.
Note Tw=Tmt + B1× Tct (1)
TKca=k1 =A1× Tw +C1 (2)
where T w : the combined transition temperature (°C) obtained using a compact test;
T mt : transition temperature (°C) of V-notch Charpy impact test at plate thickness intermediate position,
T ct : Transition temperature (° C.) in press notch Charpy impact test at the center of the plate thickness,
A1, B1, C1: Coefficient [3] A method for evaluating the brittle crack arrestability of a thick steel plate, in which the brittle crack arrestability obtained by a large-scale test is changed from the temperature indicating a predetermined characteristic value obtained by using a small-scale test. In evaluating performance,
A brittle crack propagation arrest test was performed using a full-thickness test piece of the thick steel plate, and from the observation of the morphology of the obtained fracture surface, the position range in the plate thickness direction showing a different fracture surface morphology from the plate thickness center position was identified as a position,
The temperature indicating the predetermined characteristic value obtained using the small test is the transition temperature T ct of the press notch Charpy impact test at the plate thickness center position, and the transition temperature of the V notch Charpy impact test at the plate thickness middle position. As the combined transition temperature Tw defined by the following formula (3), which is combined with Tmt , the brittle crack arrest toughness Kca is k1 (N A method for evaluating the brittle crack arrestability of a thick steel plate by estimating the temperature T Kca=k1 (° C.) at which the steel plate becomes brittle crack arrestability/mm 3/2 ).
Note T w = (T mt + T ct )/2 + B2 × (T ct - T mt ) (3)
TKca=k1 =A2× Tw +C2 (4)
where T w : the combined transition temperature (°C) obtained using a compact test;
T mt : transition temperature (°C) of V-notch Charpy impact test at plate thickness intermediate position,
T ct : Transition temperature (° C.) in press notch Charpy impact test at the center of the plate thickness,
A2, B2, C2: Coefficient [4] The mid-thickness position is the 1/4-thickness position, and the transition temperature Tct is the transition temperature at which the absorbed energy in the press-notch Charpy impact test at the mid-thickness position shows 40 J. The transition temperature T mt is the transition temperature v T rsq at which the brittle fracture surface ratio in the V notch Charpy impact test at the 1/4 position of the plate thickness is 50%,
Instead of the above formula (1), the following formula (5) is
The evaluation method for brittle crack arrestability of a steel plate according to [2], wherein the following formula (6) is used instead of the formula (2).
Note T w = v T rsq + 0.12 x p T E40Jh (5)
TKca =8000 =0.36×Tw+22.3 (6)
v T rsq : Transition temperature (° C.) at which the brittle fracture surface ratio in the V-notch Charpy impact test at the 1/4 plate thickness position is 50%,
p T E40Jh : Transition temperature (°C) at which the absorbed energy in the press notch Charpy impact test at the plate thickness center position shows 40 J
[5] The plate thickness middle position is the plate thickness 1/4 position, the transition temperature Tct is the transition temperature pTE40Jh at which the absorbed energy in the press notch Charpy impact test at the plate thickness center position is 40 J , and the transition The temperature Tmt is the transition temperature v T rsq at which the brittle fracture surface rate in the V notch Charpy impact test at the 1/4 position of the plate thickness is 50%,
Instead of the above formula (3), the following formula (7) is
The method for evaluating the brittle crack arrestability of a steel plate according to [3], wherein the following formula (8) is used instead of the formula (4).
Note Tw = 1.12 x (pTE40Jh + vTrsq ) / 2 + 0.44 x (pTE40Jh - vTrsq ) (7)
TKca =8000 =0.40×( pTE40Jh + vTrsq ) /2+0.16× ( pTE40Jh -vTrsq ) +22.3 (8)
v T rsq : Transition temperature (° C.) at which the brittle fracture surface ratio in the V-notch Charpy impact test at the 1/4 plate thickness position is 50%,
p T E40Jh : Transition temperature (°C) at which the absorbed energy in the press notch Charpy impact test at the plate thickness center position shows 40 J
[6] A method for evaluating the brittle crack arrestability of a thick steel plate, in evaluating the brittle crack arrestability obtained by a large test from a temperature showing a predetermined characteristic value obtained using a small test,
A brittle crack propagation arrest test was performed using a full-thickness test piece of the thick steel plate, and from the observation of the morphology of the obtained fracture surface, the position range in the plate thickness direction showing a different fracture surface morphology from the plate thickness center position was identified as a position,
The temperature indicating the predetermined characteristic value obtained using the small test is the transition temperature T ct of the press notch Charpy impact test at the plate thickness center position, and the transition temperature of the V notch Charpy impact test at the plate thickness middle position. Tmt is a combination transition temperature Tw obtained by combining the transition temperature Tct and the transition temperature Tmt defined by the following equation (1a), and from the combination transition temperature Tw , the following equation (2a) is obtained. A method for evaluating the brittle crack arrestability of a thick steel plate, which estimates the temperature CAT at which brittle cracks do not propagate in the CAT test, and evaluates the brittle crack arrestability of the steel plate.
Note Tw=Tmt + E1× Tct (1a)
CAT=D1× Tw +F1 (2a)
Here, D1, E1, F1: coefficient [7] A method for evaluating the brittle crack arrestability of a thick steel plate, in which the brittleness obtained by a large-scale test from the temperature exhibiting a predetermined characteristic value obtained using a small-scale test In evaluating the crack arrestability,
A brittle crack propagation arrest test was performed using a full-thickness test piece of the thick steel plate, and from the observation of the morphology of the obtained fracture surface, the position range in the plate thickness direction showing a different fracture surface morphology from the plate thickness center position was identified as a position,
The temperature indicating the predetermined characteristic value obtained using the small test is the transition temperature T ct of the press notch Charpy impact test at the plate thickness center position, and the transition temperature of the V notch Charpy impact test at the plate thickness middle position. Tmt is a combined transition temperature Tw that is a combination of the transition temperature Tct and the transition temperature Tmt defined by the following equation (3a), and from the combined transition temperature Tw , the following equation (4a) is A method for evaluating the brittle crack arrestability of a thick steel plate, which estimates the temperature CAT at which brittle cracks do not propagate in the CAT test, and evaluates the brittle crack arrestability of the steel plate.
Note T w = (T mt + T ct )/2 + E2 × (T ct - T mt ) (3a)
CAT=D2× Tw +F2 (4a)
Here, T mt : transition temperature (° C.) of V-notch Charpy impact test at plate thickness intermediate position;
T ct : Transition temperature (° C.) in press notch Charpy impact test at the center of the plate thickness,
D2, E2, F2: Coefficients
　本発明によれば、ＥＳＳＯ試験等の全厚の大型の脆性亀裂伝播停止試験は試験位置を特定することのみに使用し、シャルピー衝撃試験等と同様なサイズの試験片を用いる小型試験による靭性評価結果から、厚鋼板の脆性亀裂伝播停止性能を、簡便かつ精度よく評価することができ、産業上格段の効果を奏する。 According to the present invention, a full-thickness large-scale brittle crack arrest test such as the ESSO test is used only to identify the test position, and toughness evaluation is performed by a small test using a test piece of the same size as the Charpy impact test. From the results, it is possible to easily and accurately evaluate the brittle crack arrestability of steel plates, which is very effective in industry.
脆性亀裂伝播停止試験（ＣＡＴ試験）後のＣＡＴ全厚試験片の破面形態の一例を模式的に示す説明図である。FIG. 3 is an explanatory view schematically showing an example of a fracture surface morphology of a CAT full-thickness test piece after a brittle crack arrest test (CAT test). ＥＳＳＯ試験により求めた温度ＴＫｃａ＝８０００と板厚中央位置におけるプレスノッチシャルピー衝撃試験のエネルギー遷移温度ｐＴＥ４０Ｊとの関係を示すグラフである。It is a graph which shows the relationship between temperature TKca =8000 calculated| required by the ESSO test, and the energy transition temperature pTE40J of the press notch Charpy impact test in the plate|board thickness center position. ＥＳＳＯ試験により求めた温度ＴＫｃａ＝８０００と、板厚中央位置におけるプレスノッチシャルピー衝撃試験のエネルギー遷移温度ｐＴＥ４０Ｊｈと板厚１／４位置におけるＶノッチシャルピー衝撃試験の破面遷移温度ｖＴｒｓｑとを組み合わせた組合せ遷移温度Ｔｗとの関係を示すグラフである。The temperature T Kca = 8000 obtained by the ESSO test, the energy transition temperature p T E40Jh in the press notch Charpy impact test at the plate thickness center position, and the fracture surface transition temperature v T rsq in the V notch Charpy impact test at the plate thickness 1/4 position and the combined transition temperature Tw. ＥＳＳＯ試験により求めた温度ＴＫｃａ＝８０００と、小型試験結果から求めた予測温度（推定温度）ＴＫｃａ＝８０００ ＊との関係を示すグラフである。5 is a graph showing the relationship between a temperature T Kca=8000 obtained from an ESSO test and a predicted temperature (estimated temperature) T Kca=8000 * obtained from a small-sized test result.
　本発明は、板厚４０ｍｍ以上、好ましくは５０ｍｍ以上の厚鋼板の脆性亀裂伝播停止性能を評価するに当たり、小型試験を用いて得られた所定の特性値を示す温度を用いる、厚鋼板の脆性亀裂伝播停止性能の評価方法である。また、本発明における板厚の上限は１２０ｍｍ以下とすることが好ましい。 In the present invention, in evaluating the brittle crack arrestability of a thick steel plate having a thickness of 40 mm or more, preferably 50 mm or more, a temperature indicating a predetermined characteristic value obtained using a small-scale test is used. This is a method for evaluating propagation stop performance. Further, the upper limit of the plate thickness in the present invention is preferably 120 mm or less.
　高い脆性亀裂伝播停止性能を有する厚鋼板について、脆性亀裂伝播停止試験を実施し破面を形態観察すると、図１に模式的に示すような破面形態を呈する。板厚中央部では、切欠１に隣接する脆化部２から主亀裂（脆性亀裂）３が斜め３５°方向に進展したのち停止（脆性亀裂停止４）している。また、斜め方向に進展する主亀裂３の端では、表面から板厚方向に３５％の位置から１５％の位置まで、および、表面から板厚方向に６５％の位置から８５％の位置まで、所定の間隔ごとに比較的平坦に進展して停止する平坦な亀裂（平坦破面５）と階段状の段差６（延性破面）が複数形成された破面形態を示している。
これら平坦破面５は、斜めに進展している主亀裂３の異なる位置から発生しており、これら平坦破面５の間かなり大きなリガメントを有する階段状の段差６（延性破面）を形成している。 A steel plate having high brittle crack arrestability is subjected to a brittle crack arrest test and the morphology of the fracture surface is observed. At the central portion of the plate thickness, a main crack (brittle crack) 3 propagates in an oblique direction of 35° from the embrittlement portion 2 adjacent to the notch 1 and then stops (brittle crack arrest 4). In addition, at the edge of the main crack 3 that progresses in the oblique direction, from the 35% position to the 15% position in the plate thickness direction from the surface, and from the 65% position to the 85% position in the plate thickness direction from the surface, It shows a fracture surface configuration in which a plurality of flat cracks (flat fracture surfaces 5) that develop and stop relatively flatly at predetermined intervals and a plurality of stepped steps 6 (ductile fracture surfaces) are formed.
These flat fracture surfaces 5 are generated from different positions of the obliquely propagating main crack 3, and form stepped steps 6 (ductile fracture surfaces) having considerably large ligaments between these flat fracture surfaces 5. ing.
　このような破面形態から、板厚中央位置の靭性に加えて、板厚中央位置とは異なる破面を形成する板厚方向位置（以下、板厚中間位置と称する）の靭性が厚鋼板全体の脆性亀裂伝播停止性能に大きく影響していることが推察される。
なお、この厚鋼板の非貫通の試験片の観察から、脆性亀裂伝播停止試験において、亀裂伝播停止時には板厚中心ならびに中間位置では亀裂が深く進展しているが、表層近傍はその進展が相対的に浅い。この破壊形態から表層よりも板厚中心ならびに中間位置での亀裂伝播挙動が鋼板全体の脆性亀裂の進展を支配するものと考えられる。したがって、この種の厚鋼板では、表層近傍は、脆性亀裂伝播停止性能への影響は少ないといえる。 From such a fracture surface morphology, in addition to the toughness at the thickness center position, the toughness at the thickness direction position (hereinafter referred to as the plate thickness intermediate position) that forms a fracture surface different from the plate thickness center position. It is speculated that this has a large effect on the brittle crack arrestability of
From the observation of the non-penetrating test piece of this thick steel plate, in the brittle crack arrest test, the crack propagates deeply at the center and intermediate positions of the plate thickness when crack propagation stops, but the progress near the surface layer is relative. Shallow. From this fracture morphology, it is considered that the crack propagation behavior at the sheet thickness center and intermediate positions rather than the surface layer controls the propagation of brittle cracks in the entire steel sheet. Therefore, in this type of steel plate, it can be said that the vicinity of the surface layer has little effect on the brittle crack arrestability.
　そこで、本発明では、まず、対象とする厚鋼板について、数枚、好ましくは３～５枚の全厚試験片を用いて、適切な試験温度で大型試験の脆性亀裂伝播停止試験を実施する。さらに、得られた試験片の破面形態を観察し、板厚中央位置と異なる破面形態を示す板厚方向の位置範囲を板厚中間位置として特定する。なお、この種の厚鋼板では、板厚中間位置は、表裏面から（１／６～３／８）ｔの範囲の位置となることが多く、表裏面からｔ／４位置で代表してもよい場合が多い。なお、「板厚中央位置」、「板厚１／４位置」は、板厚の±5％の範囲を許容するものとする。（すなわち、「板厚１／４位置」は、（１．０５ｔ／４）～（０．９５ｔ／４）の範囲を含むものとする。）また、本発明において、例えば板厚１／２を「ｔ／２」、板厚１／４を「ｔ／４」とするように、板厚をｔと置き換えて記載する場合がある。
　全厚の大型試験としては、ＥＳＳＯ試験、ＣＡＴ試験、プレスノッチ曲げ試験等が例示されるが、本発明ではこれに限定されない。例えば、減厚試験片を用いるＥＳＳＯ試験、ＣＡＴ試験、プレスノッチ曲げ試験等としてもよいが、その場合には、板厚中央位置とは異なる破面形態を示す特性変化領域である板厚中間位置を含む試験片厚さとすることが肝要となる。なお、複数の板厚位置で小型試験を実施して、特性変化領域を見出すことができれば、大型試験片による破面観察を省略しても良い。 Therefore, in the present invention, first, a large-scale brittle crack arrest test is performed at an appropriate test temperature using several, preferably 3 to 5, full-thickness test pieces of a target thick steel plate. Furthermore, the fracture surface morphology of the obtained test piece is observed, and the position range in the plate thickness direction exhibiting a fracture surface morphology different from that at the plate thickness center position is specified as the plate thickness intermediate position. In addition, in this type of thick steel plate, the plate thickness intermediate position is often located in the range of (1/6 to 3/8) t from the front and back surfaces. often good. For "thickness center position" and "thickness 1/4 position", a range of ±5% of the thickness is allowed. (That is, the "plate thickness 1/4 position" includes the range of (1.05t/4) to (0.95t/4).) In addition, in the present invention, for example, the plate thickness 1/2 is defined as "t /2", and 1/4 of the thickness is "t/4", the thickness may be replaced with t.
Examples of full-thickness large-scale tests include ESSO tests, CAT tests, and press notch bending tests, but the present invention is not limited to these. For example, an ESSO test, a CAT test, a press notch bending test, etc. using a reduced thickness test piece may be used. It is important to have a test piece thickness that includes If a small-sized test can be performed at a plurality of plate thickness positions and a characteristic change region can be found, fracture surface observation using a large-sized test piece may be omitted.
　なお、本発明で使用する小型試験は、シャルピー衝撃試験とし、使用する試験片サイズは常用（例えば１０ｍｍ角）のサイズとする。また、試験片に導入するノッチは、Ｖノッチまたはプレスノッチとする。 The small-sized test used in the present invention is the Charpy impact test, and the test piece size used is the commonly used size (for example, 10 mm square). Also, the notch introduced into the test piece is a V notch or a press notch.
　そして、本発明では、厚鋼板の脆性亀裂伝播停止性能は、板厚中央位置の所定の特性値を示す温度、および、板厚中央位置とは異なる破面形態を示す板厚中間位置の所定の特性値を示す温度に、大きく影響されていると考え、小型試験は、厚鋼板の板厚中央位置および板厚中間位置で行うこととした。 In the present invention, the brittle crack propagation arrestability of a thick steel plate is determined by the temperature at which a predetermined characteristic value is obtained at the central position of the plate thickness, and the predetermined temperature at the intermediate position of the plate thickness, which indicates a fracture surface morphology different from that at the central position of the plate thickness. Considering that the temperature that indicates the characteristic value is greatly affected, we decided to conduct the small-scale test at the plate thickness center position and the plate thickness intermediate position of the thick steel plate.
　厚鋼板の板厚中央位置では、シャルピー衝撃試験を実施し、得られたエネルギー遷移温度または破面遷移温度Ｔｃｔを、板厚中央位置の所定の特性値を示す温度（遷移温度）とする。なお、板厚中央位置では、従来から行われてきたプレスノッチシャルピー衝撃試験を実施することとした。プレスノッチシャルピー衝撃試験では、プレスノッチにより脆化した部位から脆性亀裂が発生して、それが停止する現象を再現することが可能であり、この現象は、実際の脆性亀裂伝播停止挙動と同様の現象であるためである。なお、板厚中央位置の遷移温度Ｔｃｔとしては、鋼板板厚が薄い場合に脆性亀裂伝播停止性能と高い相関性を示す、プレスノッチシャルピー衝撃試験の吸収エネルギーが４０Ｊを示す温度ｐＴＥ４０Ｊ（℃）とすることが好ましい。 A Charpy impact test is performed at the plate thickness center position of the thick steel plate, and the obtained energy transition temperature or fracture surface transition temperature Tct is taken as the temperature (transition temperature) indicating a predetermined characteristic value at the plate thickness center position. At the central position of the plate thickness, the conventional press notch Charpy impact test was carried out. In the press notch Charpy impact test, it is possible to reproduce the phenomenon in which a brittle crack initiates from the part embrittled by the press notch and stops, and this phenomenon is similar to the actual brittle crack arrest behavior. This is because it is a phenomenon. As the transition temperature Tct at the central position of the plate thickness, the temperature pTE40J ( °C).
　また、厚鋼板の板厚中間位置では、シャルピー衝撃試験を実施して得られたエネルギー遷移温度または破面遷移温度Ｔｍｔを、板厚方向中間位置の所定の特性値を示す温度（遷移温度）とする。なお、厚鋼板の板厚中間位置では、亀裂が荷重の作用により延性破壊端から再度脆性亀裂が発生して停止しているため、本発明では、同様な破壊形態を呈する、延性亀裂から脆性亀裂が発生するＶノッチシャルピー衝撃試験を小型試験として実施するとした。
また、Ｖノッチシャルピー衝撃試験片は、加工が容易であるとともに、加工直後に試験を行うことが可能であるため、試験工程を簡素化できるという利点がある。プレスノッチシャルピー衝撃試験片ではプレス加工を施す必要があり、余分な手間を要する。高靭性鋼板では、プレスノッチ導入により、ノッチ直下の領域が脆化された場合に、試験時に脆性亀裂が安定して発生せず、また、脆性亀裂が安定して発生する温度では、脆性亀裂が停止しない可能性があるため、結果として安定した試験を実施できない。そのため、板厚中間位置の遷移温度Ｔｍｔとしては、安定した試験結果が得やすいＶノッチシャルピー衝撃試験において脆性破面率が５０％となる破面遷移温度ｖＴｒｓ（℃）を用いることが簡便で好ましい。 In addition, at the plate thickness intermediate position of the thick steel plate, the energy transition temperature or the fracture surface transition temperature Tmt obtained by conducting the Charpy impact test is the temperature (transition temperature) that indicates a predetermined characteristic value at the plate thickness direction intermediate position. and In addition, at the plate thickness intermediate position of the thick steel plate, since the crack is generated again from the ductile fracture edge by the action of the load and stopped, in the present invention, the ductile crack to the brittle crack exhibiting the same fracture mode It was assumed that the V-notch Charpy impact test, in which .
In addition, the V-notch Charpy impact test piece is easy to process and can be tested immediately after processing, so there is an advantage that the test process can be simplified. The press notch Charpy impact test piece requires press processing, which requires extra work. In high-toughness steel sheets, when the region immediately below the notch becomes embrittled by introducing a press notch, brittle cracks do not stably occur during the test. As a result, a stable test cannot be performed because it may not stop. Therefore, as the transition temperature T mt at the mid-thickness position, it is possible to use the fracture surface transition temperature v T rs (°C) at which the brittle fracture surface ratio is 50% in the V notch Charpy impact test, which is easy to obtain stable test results. Simple and preferable.
　本発明では、小型試験を用いて得られた所定の特性値を示す温度（遷移温度）として、板厚方向の２位置で求めた、上記した板厚中央位置の遷移温度Ｔｃｔと上記した板厚中間位置の遷移温度Ｔｍｔとを組み合わせた組合せ遷移温度Ｔｗを用いる。Ｔｗは、次（１）式および（１ａ）式
　　　Ｔｗ＝Ｔｍｔ＋Ｂ１×Ｔｃｔ　　　　　…（１）
　　　（ここで、Ｂ１：係数）
　　　Ｔｗ＝Ｔｍｔ＋Ｅ１×Ｔｃｔ　　　…（１ａ）
　　　（ここで、Ｅ１：係数）
で表せる。これは、上記の厚鋼板の破面形態の観察から、厚鋼板の脆性亀裂伝播停止性能には、板厚中央位置の靭性および板厚中間位置の靭性が強く影響していることに基づく。なお、全厚での脆性亀裂伝播停止性能への影響の程度に応じて、ＴｍｔとＴｃｔの加重平均としてもよい。具体的には、板厚中間位置を板厚１／４位置とした場合には、Ｔｃｔとして遷移温度ｐＴＥ４０Ｊｈを、Ｔｍｔとして遷移温度ｖＴｒｓｑを用い、加重平均の比として、１２：１００を適用し、次（５）式
　　　Ｔｗ＝ｖＴｒｓｑ＋０．１２×ｐＴＥ４０Ｊｈ　　　　…（５）
とすることが好ましい。なお、加重平均の比として１２：１００を適用するのは、板厚中間位置で得られる階段状の破面形態が、脆性亀裂伝播停止性能を著しく向上させること、およびこの加重平均の配分を用いることにより、大型試験結果と小型試験結果の相関性が高くなることに基づく。なお、本発明では、上記した加重平均に限定されることはない。 In the present invention, as the temperature (transition temperature) indicating a predetermined characteristic value obtained using a small-sized test, the transition temperature T ct at the center position of the plate thickness, which is obtained at two positions in the plate thickness direction, and the plate A combined transition temperature Tw is used in combination with the transition temperature Tmt at the mid-thickness position. T w is expressed by the following equations (1) and (1a): T w =T mt +B1×T ct (1)
(Here, B1: coefficient)
Tw=Tmt + E1× Tct (1a)
(Here, E1: coefficient)
can be expressed as This is based on the fact that the brittle crack arrestability of a thick steel plate is strongly influenced by the toughness at the mid-thickness position and the toughness at the mid-thickness position, based on the above observation of the fracture surface morphology of the thick steel plate. A weighted average of Tmt and Tct may be used depending on the degree of influence on brittle crack arrestability in the entire thickness. Specifically, when the plate thickness intermediate position is the plate thickness 1/4 position, the transition temperature pTE40Jh is used as Tct , the transition temperature vTrsq is used as Tmt , and the weighted average ratio is 12 : 100 is applied, and the following equation (5) T w = v T rsq + 0.12 x p T E40Jh (5)
It is preferable to The weighted average ratio of 12:100 is applied because the stepped fracture surface morphology obtained at the plate thickness intermediate position significantly improves the brittle crack arrestability, and this weighted average distribution is used. This is based on the fact that the correlation between the large-scale test results and the small-scale test results is enhanced. Note that the present invention is not limited to the above-described weighted average.
　また、小型試験を用いて得られた所定の特性値を示す温度として、板厚全体の靭性を表すものを用いても良い。板厚全体の靭性を表すものとしては、各板厚位置の靭性の平均（靭性平均）と、板厚各位置の靭性の差（靭性差）と、を組み合わせたものとするのが好ましい。板厚方向の代表位置を、板厚中央位置と板厚中間位置とした場合には、板厚中央位置のシャルピー衝撃試験の遷移温度Ｔｃｔと板厚中間位置のシャルピー衝撃試験の遷移温度Ｔｍｔとを用いて、次（３）式
　　　Ｔｗ＝（Ｔｍｔ＋Ｔｃｔ）／２＋Ｂ２×（Ｔｃｔ－Ｔｍｔ）    …（３）
　　　（ここで、Ｂ２：係数）
で定義される組合せ遷移温度Ｔｗとすることが好ましい。なぜなら、板厚全体の靭性は、板厚各位置の靭性の平均（靭性平均）である（Ｔｍｔ＋Ｔｃｔ）／２、に加えて、図１に示すような階段状の段差に影響している要素、すなわち板厚各位置の靭性の差（靭性差）である（Ｔｃｔ－Ｔｍｔ）が大きく寄与していると考えられるからである。 Further, as the temperature indicating the predetermined characteristic value obtained using the small-scale test, the temperature indicating the toughness of the entire plate thickness may be used. As a representation of the toughness of the entire plate thickness, it is preferable to combine the average toughness at each plate thickness position (toughness average) and the toughness difference at each plate thickness position (toughness difference). When the representative positions in the plate thickness direction are the plate thickness center position and the plate thickness intermediate position, the transition temperature T ct of the Charpy impact test at the plate thickness center position and the transition temperature T mt of the Charpy impact test at the plate thickness intermediate position Using the following equation (3) T w = (T mt + T ct )/2 + B2 × (T ct - T mt ) (3)
(Here, B2: coefficient)
Preferably, the combined transition temperature T w is defined as: This is because the toughness of the entire plate thickness is the average of toughness (toughness average) at each position of the plate (T mt +T ct )/2, and in addition, it is affected by a stepped step as shown in FIG. This is because it is thought that the factors that are present, that is, (T ct −T mt ), which is the difference in toughness (difference in toughness) at each position of the sheet thickness, contribute greatly.
　そして、小型試験を用いて得られた組合せ遷移温度Ｔｗと大型試験により得られた厚鋼板の脆性破壊伝播停止性能との相関関係を、予め求めておく。 Then, the correlation between the combined transition temperature Tw obtained by using the small-scale test and the brittle fracture arrestability of the steel plate obtained by the large-scale test is obtained in advance.
　大型試験として、ＥＳＳＯ試験を用いた場合には、厚鋼板の脆性破壊伝播停止性能として、脆性亀裂伝播停止靭性Ｋｃａがｋ１（Ｎ／ｍｍ３／２）となる温度ＴＫｃａ＝ｋ１（℃）を用いる。 When the ESSO test is used as the large-scale test, the temperature T Kca = k1 (°C) at which the brittle crack arrest toughness Kca becomes k1 (N/mm 3/2 ) as the brittle fracture arrestability of the steel plate. Use
　そのような相関関係式は、次（２）式、および次（４）式
　　　ＴＫｃａ＝ｋ１＝Ａ１×Ｔｗ＋Ｃ１　　　　　…（２）
　　　（ここで、Ａ１、Ｃ１：係数）
　　　ＴＫｃａ＝ｋ１＝Ａ２×Ｔｗ＋Ｃ２　　　　　…（４）
　　　（ここで、Ａ２、Ｃ２：係数）
で表される。小型試験を用いて得られた組合せ遷移温度Ｔｗから、（２）式または（４）式を用いて、脆性亀裂伝播停止靭性Ｋｃａがｋ１となる温度ＴＫｃａ＝ｋ１を推定する。 Such correlation formulas are the following formula (2) and the following formula (4) T Kca=k1 =A1×T w +C1 (2)
(Here, A1, C1: coefficients)
TKca=k1 =A2× Tw +C2 (4)
(Here, A2, C2: coefficients)
is represented by From the combined transition temperature Tw obtained using the small-scale test, the temperature T Kca =k1 at which the brittle crack arrest toughness Kca becomes k1 is estimated using the equation (2) or (4).
　なお、Ｔｗ＝ｖＴｒｓｑ＋０．１２×ｐＴＥ４０Ｊｈとした場合には、ＴｗとＴＫｃａ＝８０００と
の関係は、具体的に、次式
　　　ＴＫｃａ＝８０００＝０．３６×（ｖＴｒｓｑ＋０．１２×ｐＴＥ４０Ｊｈ）＋２２．３
または、次（６）式
　　　ＴＫｃａ＝８０００＝０．３６×Ｔｗ＋２２．３　　　…（６）
で表せる。 When T w = v T rsq + 0.12 x p T E40Jh , the relationship between T w and T Kca = 8000 is specifically expressed by the following formula T Kca = 8000 = 0.36 x ( v T rsq +0.12× pT E40Jh ) +22.3
Or, the following equation (6) T Kca =8000 =0.36×T w +22.3 (6)
can be expressed as
　また、（３）式にかえて下記（７）式
Ｔｗ＝１．１２×（ｐＴＥ４０Ｊｈ＋ｖＴｒｓｑ）／２＋０．４４×（ｐＴＥ４０Ｊｈ－ｖＴｒｓｑ）　　　…（７）
とした場合には、下記（８）式
　　　ＴＫｃａ＝８０００＝０．４０×(ｐＴＥ４０Ｊｈ＋ｖＴｒｓｑ) ／２＋０．１６×(ｐＴＥ４０Ｊｈ－ｖＴｒｓｑ)＋２２．３　　　…（８）
で表せる。 Also, instead of the equation (3), the following equation (7) T w = 1.12 × ( pTE40Jh + vT rsq ) /2 + 0.44 × (pTE40Jh - vT rsq ) ( 7 )
In the case of the following formula (8) T Kca = 8000 = 0.40 × ( p T E40Jh + v T rsq ) / 2 + 0.16 × ( p T E40 Jh - v T rsq ) + 22.3 (8)
can be expressed as
　なお、大型試験として、ＣＡＴ試験を用いても良い。その場合、厚鋼板の脆性破壊伝播
停止性能として、脆性亀裂が伝播しない温度ＣＡＴ（℃）を用いることが好ましい。 A CAT test may be used as the large-scale test. In that case, it is preferable to use the temperature CAT (° C.) at which brittle cracks do not propagate as the brittle fracture arrestability of the steel plate.
　そのような相関関係式は、次（２ａ）式および次（４ａ）式
　　　　ＣＡＴ＝Ｄ１×Ｔｗ＋Ｆ１　　　…（２ａ）
　　　（ここで、Ｄ１、Ｆ１：係数）
　　　　ＣＡＴ＝Ｄ２×Ｔｗ＋Ｆ２　　　…（４ａ）
　　　（ここで、Ｄ２、Ｆ２：係数）
で表せる。小型試験を用いて得られた組合せ遷移温度Ｔｗから、（２ａ）式を用いて、ＣＡＴ試験における脆性亀裂が伝播しない温度ＣＡＴ（℃）を推定する。 Such correlation equations are the following equations (2a) and (4a): CAT=D1×T w +F1 (2a)
(where D1 and F1 are coefficients)
CAT=D2× Tw +F2 (4a)
(Here, D2, F2: coefficients)
can be expressed as From the combination transition temperature Tw obtained using the small-scale test, the temperature CAT (° C.) at which the brittle crack does not propagate in the CAT test is estimated using equation (2a).
　（２ａ）式において、遷移温度Ｔｗを板厚全体の靭性を表すものとして、各板厚位置の靭性の平均（靭性平均）と、板厚各位置の靭性の差（靭性差）と、を組み合わせたものとする場合、下記（３ａ）式が導かれる。
　　　　Ｔｗ＝（Ｔｍｔ＋Ｔｃｔ）／２＋Ｅ２×(Ｔｃｔ－Ｔｍｔ)　　　…（３ａ）
　　　（ここで、Ｅ２：係数）
　この場合上記（４ａ）式にてＣＡＴ試験における脆性亀裂が伝播しない温度ＣＡＴ（℃）を推定する。 In formula (2a), the transition temperature Tw represents the toughness of the entire plate thickness, and the average toughness at each plate thickness position (toughness average) and the toughness difference at each plate thickness position (toughness difference) are When they are combined, the following formula (3a) is derived.
Tw=(Tmt + Tct )/2+E2×( Tct - Tmt ) (3a)
(Here, E2: coefficient)
In this case, the temperature CAT (°C) at which the brittle crack does not propagate in the CAT test is estimated by the above equation (4a).
　以下、さらに実施例を用いて本発明について説明する。 The present invention will be further described below using examples.
　板厚７０～１００ｍｍの厚鋼板（ＥＨ４０～４７級厚鋼板）について、全厚試験片を用いて温度勾配型ＥＳＳＯ試験を実施して、厚鋼板の脆性亀裂伝播停止性能を求め、脆性亀裂伝播停止靭性Ｋｃａが８０００Ｎ／ｍｍ３／２を示す温度ＴＫｃａ＝８０００を算出した。また、試験後、破面形態を観察し、板厚中央位置の破面とは異なる破面形態を示す板厚位置の範囲を板厚中間位置として特定した。そして、試験した厚鋼板では、板厚中間位置は板厚ｔ／４位置で代表してもよいことを確認した。 For thick steel plates (EH40 to 47 grade thick steel plates) with a thickness of 70 to 100 mm, a temperature gradient type ESSO test was performed using a full-thickness test piece to determine the brittle crack arrest performance of the thick steel plate, and the brittle crack arrest was determined. A temperature T Kca = 8000 at which the toughness K ca is 8000 N/mm 3/2 was calculated. Further, after the test, the fracture surface morphology was observed, and the range of plate thickness positions showing fracture surface morphology different from the fracture surface at the plate thickness center position was specified as the plate thickness intermediate position. Then, it was confirmed that in the tested thick steel plates, the plate thickness intermediate position may be represented by the plate thickness t/4 position.
　一方、板厚中央位置、および、板厚中間位置としての板厚ｔ／４位置のＬ方向からシャルピー衝撃試験片（１０ｍｍ角）を採取して、小型試験としてシャルピー衝撃試験を実施し、小型試験を用いた所定の特性値を示す温度を求めた。 On the other hand, a Charpy impact test piece (10 mm square) was collected from the L direction at the plate thickness center position and the plate thickness t / 4 position as the plate thickness intermediate position, and a Charpy impact test was performed as a small test. was obtained to obtain a predetermined characteristic value.
　板厚中央位置では、プレスノッチシャルピー衝撃試験を実施し、遷移温度Ｔｃｔ（℃）として吸収エネルギーが４０Ｊを示す温度ｐＴＥ４０Ｊｈを求めた。また、板厚中間位置（板厚１／４位置）では、Ｖノッチシャルピー衝撃試験を実施し、遷移温度Ｔｍｔ（℃）として脆性破面率が５０％となる破面遷移温度ｖＴｒｓｑを求めた。 A press notch Charpy impact test was performed at the central position of the plate thickness, and the transition temperature Tct (°C) was determined as the temperature pTE40Jh at which the absorbed energy is 40J. In addition, at the plate thickness intermediate position (plate thickness 1/4 position), a V notch Charpy impact test was performed, and the fracture surface transition temperature v T rsq at which the brittle fracture surface ratio was 50% was used as the transition temperature T mt (°C). asked.
　そして、得られたＴｃｔとＴｍｔとを組み合わせて、小型試験により得られた組合せ遷移温度Ｔｗとし、予め求められた相関関係式から温度ＴＫｃａ＝８０００を求めた。 Then, the obtained Tct and Tmt were combined to obtain the combined transition temperature Tw obtained by the small-scale test, and the temperature TKca =8000 was obtained from the correlation formula obtained in advance.
　また、小型試験により得られた組合せ遷移温度Ｔｗ（℃）をＴｗ＝１．１２×（ｐＴＥ４０Ｊｈ＋ｖＴｒｓｑ）／２＋０．４４×（ｐＴＥ４０Ｊｈ－ｖＴｒｓｑ）とし、次式
ＴＫｃａ＝８０００ ＊＝０．４０×（ｐＴＥ４０Ｊｈ＋ｖＴｒｓｑ）／２＋０．１６×（ｐＴＥ４０Ｊｈ－ｖＴｒｓｑ）＋２２．３
を用いて、温度ＴＫｃａ＝８０００ ＊を予測（推定）した。 In addition, the combination transition temperature T w (° C.) obtained by the small-scale test is T w =1.12×( pT E40Jh + vT rsq ) /2+0.44×( pT E40Jh − vT rsq ) . Formula T Kca = 8000 * = 0.40 x ( pT E40Jh + vT rsq )/2 + 0.16 x ( pT E40Jh - vT rsq ) + 22.3
was used to predict (estimate) the temperature T Kca =8000 * .
　得られた結果を、温度ＴＫｃａ＝８０００と推定（予測）温度ＴＫｃａ＝８０００ ＊との関係で図４に示す。
　図４から、本発明の評価方法による推定温度ＴＫｃａ＝８０００ ＊はＴＫｃａ＝８０００と相関性も高く、２σは２０℃以下であり、温度ＴＫｃａ＝８０００を小さい推定誤差で推定可能であることがわかる。 The obtained results are shown in FIG. 4 in relation to the temperature T Kca=8000 and the estimated (predicted) temperature T Kca=8000 * .
From FIG. 4, the estimated temperature T Kca = 8000 * by the evaluation method of the present invention has a high correlation with T Kca = 8000 , 2σ is 20 ° C. or less, and the temperature T Kca = 8000 can be estimated with a small estimation error. I understand.
　このように、本発明の評価方法によれば、大型試験は試験位置を特定することのみに使用し、板厚中央位置と、板厚中央位置とは破面形態が異なる板厚中間位置の２位置での小型試験結果から簡便に、厚鋼板の脆性亀裂伝播停止性能を精度高く評価でき、本発明評価方法の有用性が確認できた。 Thus, according to the evaluation method of the present invention, the large-scale test is used only to specify the test position, and two thickness intermediate positions, the plate thickness center position and the plate thickness center position where the fracture surface morphology is different from the plate thickness center position, are used. From the results of the small-scale test at the position, the brittle crack arrestability of the thick steel plate could be easily evaluated with high accuracy, and the usefulness of the evaluation method of the present invention was confirmed.
１：切欠
２：脆化部
３：主亀裂（脆性亀裂）
４：脆性亀裂停止
５：平坦破面
６：階段状の段差
ｓ：脆性亀裂進展方向 1: notch 2: embrittlement part 3: main crack (brittle crack)
4: Brittle crack arrest 5: Flat fracture surface 6: Stepped step s: Brittle crack growth direction

Claims (7)

  1. 　厚鋼板の脆性亀裂伝播停止性能の評価方法であって、小型試験を用いて得られた所定の特性値を示す温度から大型試験により得られる脆性亀裂伝播停止性能を評価するに当たり、
    前記厚鋼板の全厚試験片を用いた脆性亀裂伝播停止試験を行い、得られた破面の形態観察から、板厚中央位置と異なる破面形態を示す板厚方向の位置範囲を板厚中間位置として特定し、
    前記小型試験を用いて得られた所定の特性値を示す温度を、前記板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度と前記板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度とを組み合わせた、組合せ遷移温度として、
    前記組合せ遷移温度から、前記厚鋼板の脆性亀裂伝播停止性能を評価する、厚鋼板の脆性亀裂伝播停止性能の評価方法。     A method for evaluating the brittle crack arrestability of a thick steel plate, in evaluating the brittle crack arrestability obtained by a large-scale test from a temperature indicating a predetermined characteristic value obtained using a small-scale test,
    A brittle crack propagation arrest test was performed using a full-thickness test piece of the thick steel plate, and from the observation of the morphology of the obtained fracture surface, the position range in the plate thickness direction showing a different fracture surface morphology from the plate thickness center position was identified as a position,
    The temperature indicating the predetermined characteristic value obtained using the small-sized test is combined with the transition temperature of the press notch Charpy impact test at the center thickness position and the transition temperature of the V notch Charpy impact test at the middle thickness position. Also, as the combined transition temperature,
    A method for evaluating the brittle crack arrestability of a thick steel plate, wherein the brittle crack arrestability of the thick steel plate is evaluated from the combination transition temperature.
  2. 　厚鋼板の脆性亀裂伝播停止性能の評価方法であって、小型試験を用いて得られた所定の特性値を示す温度から大型試験により得られる脆性亀裂伝播停止性能を評価するに当たり、
    前記厚鋼板の全厚試験片を用いた脆性亀裂伝播停止試験を行い、得られた破面の形態観察から、板厚中央位置と異なる破面形態を示す板厚方向の位置範囲を板厚中間位置として特定し、
    前記小型試験を用いて得られた所定の特性値を示す温度を、前記板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度Ｔｃｔと、前記板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度Ｔｍｔとを組み合わせた、下記（１）式で定義される組合せ遷移温度Ｔｗとして、該組合せ遷移温度Ｔｗから、下記（２）式を用いて脆性亀裂伝播停止靭性Ｋｃａがｋ１（Ｎ／ｍｍ３／２）となる温度ＴＫｃａ＝ｋ１（℃）を推定し、厚鋼板の脆性亀裂伝播停止性能を評価する、厚鋼板の脆性亀裂伝播停止性能の評価方法。
    　　　　　　　　　　　　　　　　　　　記
    　　　　　　　　Ｔｗ＝Ｔｍｔ＋Ｂ１×Ｔｃｔ　　　…（１）
    　　　　　　　　ＴＫｃａ＝ｋ１＝Ａ１×Ｔｗ＋Ｃ１　　　…（２）
    ここで、Ｔｗ：小型試験を用いて得られた組合せ遷移温度（℃）、
    　　　　Ｔｍｔ：板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度（℃)、
    　　　　Ｔｃｔ：板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度（℃）、
    　　　　Ａ１、Ｂ１、Ｃ１：係数     A method for evaluating the brittle crack arrestability of a thick steel plate, in evaluating the brittle crack arrestability obtained by a large-scale test from a temperature indicating a predetermined characteristic value obtained using a small-scale test,
    A brittle crack propagation arrest test was performed using a full-thickness test piece of the thick steel plate, and from the observation of the morphology of the obtained fracture surface, the position range in the plate thickness direction showing a different fracture surface morphology from the plate thickness center position was identified as a position,
    The temperature indicating the predetermined characteristic value obtained using the small test is the transition temperature T ct of the press notch Charpy impact test at the plate thickness center position, and the transition temperature of the V notch Charpy impact test at the plate thickness middle position. As a combination transition temperature Tw defined by the following formula (1), which is combined with Tmt , the brittle crack arrest toughness Kca is k1 (N /mm 3/2 ), and evaluating the brittle crack arrestability of a thick steel plate.
    Note Tw=Tmt + B1× Tct (1)
    TKca=k1 =A1× Tw +C1 (2)
    where T w : the combined transition temperature (°C) obtained using a compact test;
    T mt : transition temperature (°C) of V-notch Charpy impact test at plate thickness intermediate position,
    T ct : Transition temperature (° C.) in press notch Charpy impact test at the center of the plate thickness,
    A1, B1, C1: coefficients
  3. 　厚鋼板の脆性亀裂伝播停止性能の評価方法であって、小型試験を用いて得られた所定の特性値を示す温度から大型試験により得られる脆性亀裂伝播停止性能を評価するに当たり、
    前記厚鋼板の全厚試験片を用いた脆性亀裂伝播停止試験を行い、得られた破面の形態観察から、板厚中央位置と異なる破面形態を示す板厚方向の位置範囲を板厚中間位置として特定し、
    前記小型試験を用いて得られた所定の特性値を示す温度を、前記板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度Ｔｃｔと、前記板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度Ｔｍｔとを組み合わせた、下記（３）式で定義される組合せ遷移温度Ｔｗとして、該組合せ遷移温度Ｔｗから、下記（４）式を用いて脆性亀裂伝播停止靭性Ｋｃａがｋ１（Ｎ／ｍｍ３／２）となる温度ＴＫｃａ＝ｋ１（℃）を推定し、厚鋼板の脆性亀裂伝播停止性能を評価する、厚鋼板の脆性亀裂伝播停止性能の評価方法。
    　　　　　　　　　　　　　　　　　　　　記
    　　　　Ｔｗ＝（Ｔｍｔ＋Ｔｃｔ）／２＋Ｂ２×(Ｔｃｔ－Ｔｍｔ)　　　…（３）
    　　　　ＴＫｃａ＝ｋ１＝Ａ２×Ｔｗ＋Ｃ２　　　…（４）
    ここで、Ｔｗ：小型試験を用いて得られた組合せ遷移温度（℃)、
    　　　　Ｔｍｔ：板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度（℃)、
    　　　　Ｔｃｔ：板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度（℃）、
    　　　　Ａ２、Ｂ２、Ｃ２：係数     A method for evaluating the brittle crack arrestability of a thick steel plate, in evaluating the brittle crack arrestability obtained by a large-scale test from a temperature indicating a predetermined characteristic value obtained using a small-scale test,
    A brittle crack propagation arrest test was performed using a full-thickness test piece of the thick steel plate, and from the observation of the morphology of the obtained fracture surface, the position range in the plate thickness direction showing a different fracture surface morphology from the plate thickness center position was identified as a position,
    The temperature indicating the predetermined characteristic value obtained using the small test is the transition temperature T ct of the press notch Charpy impact test at the plate thickness center position, and the transition temperature of the V notch Charpy impact test at the plate thickness middle position. As the combined transition temperature Tw defined by the following formula (3), which is combined with Tmt , the brittle crack arrest toughness Kca is k1 (N /mm 3/2 ), and evaluating the brittle crack arrestability of a thick steel plate.
    Note T w = (T mt + T ct )/2 + B2 × (T ct - T mt ) (3)
    TKca=k1 =A2× Tw +C2 (4)
    where T w : the combined transition temperature (°C) obtained using a compact test;
    T mt : transition temperature (°C) of V-notch Charpy impact test at plate thickness intermediate position,
    T ct : Transition temperature (° C.) in press notch Charpy impact test at the center of the plate thickness,
    A2, B2, C2: Coefficients
  4. 　前記板厚中間位置を板厚１／４位置とし、前記遷移温度Ｔｃｔを、板厚中央位置におけるプレスノッチシャルピー衝撃試験の吸収エネルギーが４０Ｊを示す遷移温度ｐＴＥ４０Ｊｈとし、前記遷移温度Ｔｍｔを、板厚１／４位置におけるＶノッチシャルピー衝撃試験の脆性破面率が５０％である遷移温度ｖＴｒｓｑとし、
    前記（１）式に代えて、下記（５）式を、
    前記（２）式に代えて、下記（６）式を用いる、請求項２に記載の厚鋼板の脆性亀裂伝播停止性能の評価方法。
    　　　　　　　　　　　　　　　　　　　　記
    　　　　Ｔｗ＝ｖＴｒｓｑ＋０．１２×ｐＴＥ４０Ｊｈ　　　…（５）
    　　　　ＴＫｃａ＝８０００＝０．３６×Ｔｗ＋２２．３　　　…（６）
    　　　　ｖＴｒｓｑ：板厚１／４位置におけるＶノッチシャルピー衝撃試験の脆性破面率が５０％である遷移温度（℃）、
    　　　　ｐＴＥ４０Ｊｈ：板厚中央位置におけるプレスノッチシャルピー衝撃試験の吸収エネルギーが４０Ｊを示す遷移温度（℃)     The plate thickness middle position is the plate thickness 1/4 position, the transition temperature Tct is the transition temperature pTE40Jh at which the absorbed energy in the press notch Charpy impact test at the plate thickness center position is 40 J, and the transition temperature Tmt is the transition temperature v T rsq at which the brittle fracture surface rate in the V notch Charpy impact test at the 1/4 position of the plate thickness is 50%,
    Instead of the above formula (1), the following formula (5) is
    The evaluation method for brittle crack arrestability of a steel plate according to claim 2, wherein the following formula (6) is used instead of the formula (2).
    Note T w = v T rsq + 0.12 x p T E40Jh (5)
    TKca =8000 =0.36×Tw+22.3 (6)
    v T rsq : Transition temperature (° C.) at which the brittle fracture surface ratio in the V-notch Charpy impact test at the 1/4 plate thickness position is 50%,
    p T E40Jh : Transition temperature (°C) at which the absorbed energy in the press notch Charpy impact test at the plate thickness center position shows 40 J
  5. 　前記板厚中間位置を板厚１／４位置とし、前記遷移温度Ｔｃｔを、板厚中央位置におけるプレスノッチシャルピー衝撃試験の吸収エネルギーが４０Ｊを示す遷移温度ｐＴＥ４０Ｊｈとし、前記遷移温度Ｔｍｔを、板厚１／４位置におけるＶノッチシャルピー衝撃試験の脆性破面率が５０％である遷移温度ｖＴｒｓｑとし、
    前記（３）式に代えて、下記（７）式を、
    前記（４）式に代えて、下記（８）式を用いる、請求項３に記載の厚鋼板の脆性亀裂伝播停止性能の評価方法。
    　　　　　　　　　　　　　　　　　　　　記
    　　　　Ｔｗ＝１．１２×(ｐＴＥ４０Ｊｈ＋ｖＴｒｓｑ)／２＋０．４４×(ｐＴＥ４０Ｊｈ－ｖＴｒｓｑ)　　　…（７）
    　　　　ＴＫｃａ＝８０００＝０．４０×(ｐＴＥ４０Ｊｈ＋ｖＴｒｓｑ) ／２＋０．１６×(ｐＴＥ４０Ｊｈ－ｖＴｒｓｑ)＋２２．３　　　…（８）
    　　　　ｖＴｒｓｑ：板厚１／４位置におけるＶノッチシャルピー衝撃試験の脆性破面率が５０％である遷移温度（℃）、
    　　　　ｐＴＥ４０Ｊｈ：板厚中央位置におけるプレスノッチシャルピー衝撃試験の吸収エネルギーが４０Ｊを示す遷移温度（℃)     The plate thickness middle position is the plate thickness 1/4 position, the transition temperature Tct is the transition temperature pTE40Jh at which the absorbed energy in the press notch Charpy impact test at the plate thickness center position is 40 J, and the transition temperature Tmt is the transition temperature v T rsq at which the brittle fracture surface rate in the V notch Charpy impact test at the 1/4 position of the plate thickness is 50%,
    Instead of the above formula (3), the following formula (7) is
    The evaluation method for brittle crack arrestability of a steel plate according to claim 3, wherein the following formula (8) is used instead of the formula (4).
    Note Tw = 1.12 x (pTE40Jh + vTrsq ) / 2 + 0.44 x (pTE40Jh - vTrsq ) (7)
    TKca =8000 =0.40×( pTE40Jh + vTrsq ) /2+0.16× ( pTE40Jh -vTrsq ) +22.3 (8)
    v T rsq : Transition temperature (° C.) at which the brittle fracture surface ratio in the V-notch Charpy impact test at the 1/4 plate thickness position is 50%,
    p T E40Jh : Transition temperature (°C) at which the absorbed energy in the press notch Charpy impact test at the plate thickness center position shows 40 J
  6. 　厚鋼板の脆性亀裂伝播停止性能の評価方法であって、小型試験を用いて得られた所定の特性値を示す温度から大型試験により得られる脆性亀裂伝播停止性能を評価するに当たり、
    前記厚鋼板の全厚試験片を用いた脆性亀裂伝播停止試験を行い、得られた破面の形態観察から、板厚中央位置と異なる破面形態を示す板厚方向の位置範囲を板厚中間位置として特定し、
    前記小型試験を用いて得られた所定の特性値を示す温度を、前記板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度Ｔｃｔと、前記板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度Ｔｍｔとを、下記（１ａ）式で定義される前記遷移温度Ｔｃｔと前記遷移温度Ｔｍｔとを組み合わせた組合せ遷移温度Ｔｗとして、該組合せ遷移温度Ｔｗから、下記（２ａ）式を用いて、ＣＡＴ試験における脆性亀裂が伝播しない温度ＣＡＴ（℃）を推定し、厚鋼板の脆性亀裂伝播停止性能を評価する、厚鋼板の脆性亀裂伝播停止性能の評価方法。
    　　　　　　　　　　　　　　　　記
    　　　　Ｔｗ＝Ｔｍｔ＋Ｅ１×Ｔｃｔ　　　…（１ａ）
    　　　　ＣＡＴ＝Ｄ１×Ｔｗ＋Ｆ１　　　…（２ａ）
    ここで、Ｄ１、Ｅ１、Ｆ１：係数     A method for evaluating the brittle crack arrestability of a thick steel plate, in evaluating the brittle crack arrestability obtained by a large-scale test from a temperature indicating a predetermined characteristic value obtained using a small-scale test,
    A brittle crack propagation arrest test was performed using a full-thickness test piece of the thick steel plate, and from the observation of the morphology of the obtained fracture surface, the position range in the plate thickness direction showing a different fracture surface morphology from the plate thickness center position was identified as a position,
    The temperature indicating the predetermined characteristic value obtained using the small test is the transition temperature T ct of the press notch Charpy impact test at the plate thickness center position, and the transition temperature of the V notch Charpy impact test at the plate thickness middle position. Tmt is a combination transition temperature Tw obtained by combining the transition temperature Tct and the transition temperature Tmt defined by the following equation (1a), and from the combination transition temperature Tw , the following equation (2a) is obtained. A method for evaluating the brittle crack arrestability of thick steel plates by estimating the temperature CAT (° C.) at which brittle cracks do not propagate in the CAT test, and evaluating the brittle crack arrestability of steel plates.
    Note Tw=Tmt + E1× Tct (1a)
    CAT=D1× Tw +F1 (2a)
    where D1, E1, F1: coefficients
  7. 　厚鋼板の脆性亀裂伝播停止性能の評価方法であって、小型試験を用いて得られた所定の特性値を示す温度から大型試験により得られる脆性亀裂伝播停止性能を評価するに当たり、
    前記厚鋼板の全厚試験片を用いた脆性亀裂伝播停止試験を行い、得られた破面の形態観察から、板厚中央位置と異なる破面形態を示す板厚方向の位置範囲を板厚中間位置として特定し、
    前記小型試験を用いて得られた所定の特性値を示す温度を、前記板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度Ｔｃｔと、前記板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度Ｔｍｔとを、下記（３ａ）式で定義される前記遷移温度Ｔｃｔと前記遷移温度Ｔｍｔとを組み合わせた組合せ遷移温度Ｔｗとして、該組合せ遷移温度Ｔｗから、下記（４ａ）式を用いて、ＣＡＴ試験における脆性亀裂が伝播しない温度ＣＡＴ（℃）を推定し、厚鋼板の脆性亀裂伝播停止性能を評価する、厚鋼板の脆性亀裂伝播停止性能の評価方法。
    　　　　　　　　　　　　　　　　記
    　　　　Ｔｗ＝（Ｔｍｔ＋Ｔｃｔ）／２＋Ｅ２×(Ｔｃｔ－Ｔｍｔ)　　　…（３ａ）
    　　　　ＣＡＴ＝Ｄ２×Ｔｗ＋Ｆ２　　　…（４ａ）
    ここで、Ｔｍｔ：板厚中間位置におけるＶノッチシャルピー衝撃試験の遷移温度（℃）、
    　　　　Ｔｃｔ：板厚中央位置におけるプレスノッチシャルピー衝撃試験の遷移温度（℃）、
    　　　　Ｄ２、Ｅ２、Ｆ２：係数     A method for evaluating the brittle crack arrestability of a thick steel plate, in evaluating the brittle crack arrestability obtained by a large-scale test from a temperature indicating a predetermined characteristic value obtained using a small-scale test,
    A brittle crack propagation arrest test was performed using a full-thickness test piece of the thick steel plate, and from the observation of the morphology of the obtained fracture surface, the position range in the plate thickness direction showing a different fracture surface morphology from the plate thickness center position was identified as a position,
    The temperature indicating the predetermined characteristic value obtained using the small test is the transition temperature T ct of the press notch Charpy impact test at the plate thickness center position, and the transition temperature of the V notch Charpy impact test at the plate thickness middle position. Tmt is a combined transition temperature Tw that is a combination of the transition temperature Tct and the transition temperature Tmt defined by the following equation (3a), and from the combined transition temperature Tw , the following equation (4a) is A method for evaluating the brittle crack arrestability of thick steel plates by estimating the temperature CAT (° C.) at which brittle cracks do not propagate in the CAT test, and evaluating the brittle crack arrestability of steel plates.
    Note T w = (T mt + T ct )/2 + E2 × (T ct - T mt ) (3a)
    CAT=D2× Tw +F2 (4a)
    Here, T mt : transition temperature (° C.) of V-notch Charpy impact test at plate thickness intermediate position;
    T ct : Transition temperature (° C.) in press notch Charpy impact test at the center of the plate thickness,
    D2, E2, F2: Coefficients
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