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 PDFInfo
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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
Description
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 (
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.
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.
[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
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.
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.
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.
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.
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.
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.
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).
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
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
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.
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).
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).
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 * .
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.
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)
- 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. - 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 - 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 - 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 - 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 - 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 - 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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