JP4782084B2 - Judgment method of brittle crack propagation stop property of thick steel plate - Google Patents
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本発明は、例えば、船舶、低温タンク、及び発電用水圧鉄管などの大型構造物に用いられる厚鋼板の脆性き裂伝播停止特性の判定方法に関する。 The present invention relates to a method for determining brittle crack propagation stopping characteristics of a thick steel plate used for large structures such as ships, low-temperature tanks, and hydraulic iron pipes for power generation.
脆性破壊は、鉄鋼材料等の構造材料において、時として大規模な塑性変形を伴わず、材料の降伏強度以下の低応力で発生し、１０００ｍ／ｓ程度の高速で長距離伝播して、構造物を一瞬のうちに破壊させるので、安全上極めて重要な現象である。
この脆性破壊の発生を防止するための手法としては、例えば、非特許文献１に規定されるＣＴＯＤ（Ｃｒａｃｋ−Ｔｉｐ Ｏｐｅｎｉｎｇ Ｄｉｓｐｌａｃｅｍｅｎｔ）試験等の評価試験を用いた防止案（非特許文献２参照）が提案され、これらが各種規格に取り入れられるなどして、脆性破壊の発生防止が可能になってきている。
特に、大規模構造物では、万が一脆性破壊が発生した場合でも、き裂の伝播を防止することができれば、安全性を格段に向上させることが可能になる。実際に、ＬＮＧ（Ｌｉｑｕｅｆｉｅｄ Ｎａｔｕｒａｌ Ｇａｓ）又はＬＰＧ（Ｌｉｑｕｅｆｉｅｄ Ｐｅｔｒｏｌｅｕｍ Ｇａｓ）等の低温タンクに用いられる低温用鋼材、水圧鉄管用鋼材、又は造船用鋼材等では、非特許文献３に規定される脆性破壊伝播停止試験のような大型破壊試験で測定される脆性破壊伝播停止特性Ｋｃａ値に対する要求値が規定されている。
Brittle fracture occurs in structural materials such as steel materials, sometimes with low-scale stress below the yield strength of the material, without large-scale plastic deformation, and propagates over a long distance at a high speed of about 1000 m / s. Is an extremely important phenomenon in terms of safety.
As a method for preventing the occurrence of this brittle fracture, for example, there is a prevention plan using an evaluation test such as a CTOD (Crac-Tip Opening Displacement) test defined in Non-Patent Document 1 (see Non-Patent Document 2). Proposed and incorporated into various standards, it has become possible to prevent the occurrence of brittle fracture.
In particular, in a large-scale structure, even if a brittle fracture occurs, if the propagation of a crack can be prevented, the safety can be significantly improved. In fact, brittle fracture propagation defined in Non-Patent Document 3 is used for low-temperature steel, hydraulic iron pipe steel, or shipbuilding steel used in low-temperature tanks such as LNG (Liquid Natural Gas) or LPG (Liquid Petroleum Gas). A required value for the brittle fracture propagation stop characteristic Kca value measured in a large-scale fracture test such as a stop test is defined.
ところが、これらの試験は、大型の試験片を使用するため、試験実施のための工期を要し、コストがかかるので、一般に品質管理のための試験としては適当ではない。
そこで、代表的な簡易評価試験であるシャルピー試験法と脆性破壊伝播停止特性を用いた相関式が提案され（非特許文献４〜６参照）、シャルピー試験を規定して脆性き裂伝播停止特性を判定する手法が、従来採用されてきた。なお、脆性き裂伝播停止特性は、板厚依存性があるため、非特許文献４、５では、板厚依存性についても考慮している。
また、非特許文献４にあるプレスノッチシャルピー試験法、ＡＳＴＭ（Ａｍｅｒｉｃａｎ Ｓｔａｎｄａｒｄ ｏｆ Ｔｅｓｔｉｎｇ ａｎｄ Ｍａｔｅｒｉａｌｓ）規格Ｅ−２０８に規定されているＮＲＬ落重試験法や、非特許文献６にあるような切欠き付き曲げ試験法（ロシア規格ＧＯＳＴ−２２７１７６ ＴＫＢ試験法）等による脆性き裂伝播停止特性の評価も検討されてきた。
However, since these tests use large test pieces, they require a work period for performing the tests and are costly, so they are generally not suitable as tests for quality control.
Therefore, a correlation equation using the Charpy test method, which is a typical simple evaluation test, and the brittle fracture propagation stop characteristics has been proposed (see Non-Patent Documents 4 to 6). A method of determining has been conventionally employed. In addition, since the brittle crack propagation stop characteristic has a plate thickness dependency, Non-Patent Documents 4 and 5 also consider the plate thickness dependency.
Further, the press notch Charpy test method described in Non-Patent Document 4, the NRL drop weight test method defined in ASTM (American Standard of Testing and Materials) standard E-208, and the notch as described in Non-Patent
しかしながら、シャルピー試験は、脆性破壊の発生特性の影響を強く受けるため、非特許文献４〜６に示す脆性破壊伝播停止特性との対応関係には、大きなばらつきを含んでおり、測定精度上大きな問題があった。
また、プレスノッチシャルピー試験法、ＮＲＬ落重試験法、及びＴＫＢ試験法でも、例えば、非特許文献４、６に示すように、板厚依存性や板厚方向靱性分布の取り扱いを含め、十分な測定精度を与える手法は存在しなかった。
However, since the Charpy test is strongly influenced by the characteristics of occurrence of brittle fracture, the correspondence with the brittle fracture propagation stop characteristics shown in Non-Patent Documents 4 to 6 includes a large variation, which is a big problem in measurement accuracy. was there.
Further, even in the press notch Charpy test method, the NRL drop weight test method, and the TKB test method, for example, as shown in
本発明はかかる事情に鑑みてなされたもので、厚鋼板の脆性破壊伝播停止特性を簡易に評価することのできる厚鋼板の脆性き裂伝播停止特性の判定方法を提供することを目的とする。 This invention is made | formed in view of this situation, and it aims at providing the determination method of the brittle crack propagation stop characteristic of the thick steel plate which can evaluate the brittle fracture propagation stop characteristic of a thick steel plate easily.
本発明は上記課題を解決するためのものであり、その手段（１）は、脆性破壊伝播停止試験で使用する一辺が５００ｍｍの大型試験片の代わりに複数の小型試験片を使用して、厚鋼板の脆性き裂伝播停止特性を判定する方法であって、
前記各小型試験片が、厚さが１６ｍｍ以上２５ｍｍ以下、幅が５０ｍｍ以上９０ｍｍ以下、長さが１３０ｍｍ以上３６０ｍｍ以下で、かつ長手方向中央部にそれぞれノッチを有し、該各小型試験片を予め設定した各温度に冷却して、該各小型試験片を動的３点曲げ負荷により破断し、発生する脆性破壊が前記小型試験片の幅方向両端部に到達する限界温度である遷移温度を求め、
前記求めた遷移温度が、要求される保証温度Ｔ０（℃）と、要求される脆性破壊伝播停止性能Ｋｃａ値Ａ（Ｎ／ｍｍ１．５）と、前記厚鋼板の板厚ｔ（ｍｍ）とで表される換算式から得られる温度Ｔ（℃）以下である場合に、前記要求される脆性破壊伝播停止性能Ｋｃａ値を満足すると判定する。
The present invention is for solving the above-mentioned problems. The means (1) is a method in which a plurality of small test pieces are used instead of a large test piece having a side of 500 mm used in the brittle fracture propagation stop test. A method for determining the brittle crack propagation stopping characteristics of a steel sheet,
Each of the small test pieces has a thickness of 16 mm or more and 25 mm or less, a width of 50 mm or more and 90 mm or less, a length of 130 mm or more and 360 mm or less, and a notch at the center in the longitudinal direction. After cooling to each set temperature, each small test piece is broken by a dynamic three-point bending load, and a transition temperature that is the limit temperature at which the brittle fracture that occurs reaches both ends in the width direction of the small test piece is obtained. ,
The obtained transition temperature is the required guaranteed temperature T 0 (° C.), the required brittle fracture propagation stop performance Kca value A (N / mm 1.5 ), and the thickness t (mm) of the thick steel plate. It is determined that the required brittle fracture propagation stop performance Kca value is satisfied when the temperature is equal to or lower than the temperature T (° C.) obtained from the conversion formula expressed as follows.
手段（２）は、手段（１）において、前記温度Ｔは式（１）で求める。
Ｔ＝１／｛１／（Ｔ０＋２７３）＋０．０００６２５×ｌｎ（Ａ／Ｘ）
−０．０００１８１×（１−ｔ／２５）｝−２７３ ・・・（１）
ここで、Ｘは厚鋼板の鋼種で決定される定数である。
手段（３）は、手段（２）において、前記小型試験片は、厚さが１６ｍｍ、幅が５０ｍｍ、長さが１３０ｍｍであって、前記定数Ｘは２０００である。
In the means (2), in the means (1), the temperature T is obtained by the equation (1).
T = 1 / {1 / (T 0 +273) + 0.000625 × ln (A / X)
-0.000181 × (1-t / 25)}-273 (1)
Here, X is a constant determined by the steel type of the thick steel plate.
The means (3) is the means (2), wherein the small test piece has a thickness of 16 mm, a width of 50 mm, a length of 130 mm, and the constant X is 2000.
手段（４）は、手段（１）〜（３）において、前記厚鋼板の板厚は２５ｍｍ以上５０ｍｍ未満であって、前記小型試験片を前記厚鋼板の表層側から採取し、該小型試験片の測定温度を前記遷移温度とする。
手段（５）は、手段（１）〜（３）において、前記厚鋼板の板厚は５０ｍｍ以上１００ｍｍ未満であって、前記小型試験片を前記厚鋼板の表層側及び厚み方向中央部から採取し、該各小型試験片の測定温度の平均値を前記遷移温度とする。
The means (4) is the means (1) to (3), wherein the plate thickness of the thick steel plate is 25 mm or more and less than 50 mm, the small test piece is taken from the surface layer side of the thick steel plate, and the small test piece The measured temperature is defined as the transition temperature.
Means (5) is the means (1) to (3), wherein the plate thickness of the thick steel plate is 50 mm or more and less than 100 mm, and the small test piece is collected from the surface layer side of the thick steel plate and the central portion in the thickness direction. The average value of the measurement temperatures of the small test pieces is defined as the transition temperature.
本発明に係る厚鋼板の脆性き裂伝播停止特性の判定方法は、換算式を使用するので、日本溶接協会規格「ＷＥＳ鋼種認定試験方法」（１９９５年）に準拠した大型試験片の脆性破壊伝播停止試験で求められるべき脆性破壊伝播停止特性Ｋｃａ値を保証する際に、小型試験片の遷移温度を、大型試験片で得られる脆性破壊伝播停止性能Ｋｃａ値に結び付けることができる。
また、小型試験片の遷移温度は、動的３点曲げ負荷により求めるため、シャルピー試験のような脆性破壊の発生特性の影響を受けることがない。更に、換算式には、厚鋼板の板厚が用いられているため、板厚依存性も考慮されている。
これにより、脆性破壊伝播停止試験のような大型試験片を使用することなく、簡易で精度良い判定が可能となるなど、産業上有用な著しい効果を奏する。
The method for determining the brittle crack propagation stop property of the thick steel plate according to the present invention uses a conversion formula, so that the brittle fracture propagation of a large specimen conforming to the Japan Welding Association Standard "WES Steel Grade Certification Test Method" (1995). When guaranteeing the brittle fracture propagation stop characteristic Kca value to be obtained in the stop test, the transition temperature of the small test piece can be linked to the brittle fracture propagation stop performance Kca value obtained with the large test piece.
Further, since the transition temperature of the small test piece is obtained by a dynamic three-point bending load, it is not affected by the occurrence characteristics of brittle fracture as in the Charpy test. Furthermore, since the plate thickness of the thick steel plate is used in the conversion formula, the plate thickness dependency is also taken into consideration.
Thus, there are significant industrially useful effects such as simple and accurate determination without using a large test piece such as a brittle fracture propagation stop test.
また、換算式を特定した場合には、小型試験片の遷移温度から、要求される脆性破壊伝播停止性能Ｋｃａ値を満足するか否かを瞬時に判定できるので、作業性が良好である。
そして、小型試験片に、厚さが１６ｍｍ、幅が５０ｍｍ、長さが１３０ｍｍのものを使用した場合、大型試験片とは異なり、持ち運びが便利で、しかも試験の際の作業性も良好である。また、厚鋼板の鋼種で決定される定数として、最下限値となる２０００を使用する場合、脆性破壊伝播停止性能Ｋｃａ値の安全率が十分に高められた評価ができる。
Further, when the conversion formula is specified, it is possible to instantaneously determine whether or not the required brittle fracture propagation stop performance Kca value is satisfied from the transition temperature of the small test piece, so that workability is good.
When a small test piece having a thickness of 16 mm, a width of 50 mm, and a length of 130 mm is used, unlike a large-size test piece, it is easy to carry and also has good workability during testing. . Further, when 2000, which is the lower limit value, is used as a constant determined by the steel type of the thick steel plate, an evaluation can be made in which the safety factor of the brittle fracture propagation stopping performance Kca value is sufficiently increased.
更に、厚鋼板の板厚が２５ｍｍ以上５０ｍｍ未満の場合、厚鋼板の板厚依存性による影響は小さいため、その影響を考慮する必要がなく、厚鋼板の表層側から採取した小型試験片の測定温度を遷移温度として使用できる。
また、厚鋼板の板厚が５０ｍｍ以上１００ｍｍ未満の場合、厚鋼板の板厚依存性による影響があるため、その影響を考慮する必要があり、厚鋼板の表層側及び厚み方向中央部から採取した各小型試験片の測定温度の平均値を遷移温度とすることで、その精度を高めることができる。
Furthermore, when the plate thickness of the steel plate is 25 mm or more and less than 50 mm, since the influence due to the plate thickness dependency of the steel plate is small, there is no need to consider the influence, and measurement of a small test piece taken from the surface layer side of the steel plate Temperature can be used as the transition temperature.
In addition, when the plate thickness of the thick steel plate is 50 mm or more and less than 100 mm, there is an influence due to the plate thickness dependency of the thick steel plate, so it is necessary to consider the influence, and the sample was taken from the surface layer side of the thick steel plate and the central portion in the thickness direction. By setting the average value of the measurement temperatures of each small test piece as the transition temperature, the accuracy can be increased.
続いて、添付した図面を参照しつつ、本発明を具体化した実施の形態につき説明し、本発明の理解に供する。
ここで、図１は本発明の一実施の形態に係る厚鋼板の脆性き裂伝播停止特性の判定方法の説明図、図２は脆性破壊伝播停止試験から求められる脆性破壊伝播停止特性Ｋｃａ値とＮＲＬ落重試験法から求められる遷移温度ＴＮＤＴとの関係を示す説明図、図３は厚鋼板の板厚効果の説明図、図４は脆性破壊伝播停止試験によるＫｃａ値の温度依存性を示す説明図である。
Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIG. 1 is an explanatory view of a method for determining brittle crack propagation stop characteristics of a thick steel plate according to one embodiment of the present invention, and FIG. 2 is a diagram showing brittle fracture propagation stop characteristics Kca value obtained from a brittle fracture propagation stop test. FIG. 3 is an explanatory diagram showing the relationship with the transition temperature TNDT obtained from the NRL drop weight test method, FIG. 3 is an explanatory diagram of the plate thickness effect of the thick steel plate, and FIG. 4 is an explanatory diagram showing the temperature dependence of the Kca value by the brittle fracture propagation stop test. FIG.
図１に示すように、本発明の一実施の形態に係る厚鋼板の脆性き裂伝播停止特性の判定方法は、脆性破壊伝播停止試験（「ＷＥＳ鋼種認定試験方法（１９９５年）」日本溶接協会規格）で使用する一辺が５００ｍｍの大型試験片の代わりに複数の小型試験片を使用する方法であり、各小型試験片として、厚さが１６ｍｍ以上２５ｍｍ、幅が５０ｍｍ以上９０ｍｍ以下、長さが１３０ｍｍ以上３６０ｍｍ以下のものを使用して、例えば、厚鋼板の需要者が要求する脆性破壊伝播停止性能Ｋｃａ値（以下、単にＫｃａ値ともいう）を満足するか否かを判定する方法である。以下、詳しく説明する。 As shown in FIG. 1, the method for determining the brittle crack propagation stop property of a thick steel plate according to an embodiment of the present invention is the brittle fracture propagation stop test ("WES steel type qualification test method (1995)" Japan Welding Association. In this method, a plurality of small test pieces are used instead of a large test piece having a side of 500 mm, and each small test piece has a thickness of 16 mm to 25 mm, a width of 50 mm to 90 mm, and a length. This is a method for determining whether or not a brittle fracture propagation stop performance Kca value (hereinafter also simply referred to as a Kca value) required by a demander of a thick steel plate is satisfied by using a steel sheet having a thickness of 130 mm to 360 mm. This will be described in detail below.
本発明者らは、鋭意検討した結果、ＮＲＬ落重試験片（米国規格 ＡＳＴＭ規格Ｅ−２０８）である小型試験片から求まる遷移温度ＴＮＤＴ（以下、単に遷移温度、又はＴＮＤＴともいう）から、例えば、板厚が２５ｍｍ以上１００ｍｍ以下の厚鋼板のＫｃａ値を推定する手法を確立し、本発明をなしたものである。
本発明では、脆性破壊伝播停止性能Ｋｃａ値を満足するか否かの判定に際し、小型試験片から求めた遷移温度を、大型試験片で得られる脆性破壊伝播停止性能Ｋｃａ値に結び付ける換算式を使用する。なお、この換算式は、厚鋼板の需要者が要求する保証温度Ｔ０（℃）、及び要求される脆性破壊伝播停止性能Ｋｃａ値Ａ（Ｎ／ｍｍ１．５）と、厚鋼板の板厚ｔ（ｍｍ）を用いて表されるものであり、具体的には、以下に示す式（１）を使用して、温度Ｔ（℃）を求めることが好ましい。
Ｔ＝１／｛１／（Ｔ０＋２７３）＋０．０００６２５×ｌｎ（Ａ／Ｘ）
−０．０００１８１×（１−ｔ／２５）｝−２７３ ・・・（１）
ここで、Ｘは厚鋼板の鋼種で決定される定数である。
以下、換算式である式（１）の導出方法について説明する。
As a result of intensive studies, the present inventors have determined from a transition temperature TNDT (hereinafter also simply referred to as a transition temperature or TNDT) obtained from a small test piece which is an NRL drop weight test piece (US standard ASTM standard E-208), for example. The present invention has been established by establishing a method for estimating the Kca value of a thick steel plate having a thickness of 25 mm or more and 100 mm or less.
In the present invention, when determining whether or not the brittle fracture propagation stop performance Kca value is satisfied, a conversion formula that links the transition temperature obtained from the small test piece to the brittle fracture propagation stop performance Kca value obtained from the large test piece is used. To do. In addition, this conversion formula is the guaranteed temperature T 0 (° C.) required by the customer of the thick steel plate, the required brittle fracture propagation stop performance Kca value A (N / mm 1.5 ), and the plate thickness of the thick steel plate. It is expressed using t (mm). Specifically, it is preferable to obtain the temperature T (° C.) using the following formula (1).
T = 1 / {1 / (T 0 +273) + 0.000625 × ln (A / X)
-0.000181 × (1-t / 25)}-273 (1)
Here, X is a constant determined by the steel type of the thick steel plate.
Hereinafter, the derivation method of Formula (1) which is a conversion formula is demonstrated.
本発明者らは、ＮＲＬ落重試験により、脆性破壊特性を評価する簡易試験法を、一定厚みの小型試験片を使用して実施することで検討した。
まず、板厚２５ｍｍでの降伏強さが３３５ＭＰａ級から５１０ＭＰａ級の強度レベルの鋼材について、非特許文献３に規定される脆性破壊伝播停止試験（標準ＥＳＳＯ試験）から求められる脆性破壊伝播停止特性Ｋｃａ値と、ＡＳＴＭ規格Ｅ−２０８のＮＲＬ落重試験法から求められる遷移温度ＴＮＤＴとの対応関係を調査した。その結果、図２に示すように、遷移温度ＴＮＤＴがＫｃａ値２０００〜３０００Ｎ／ｍｍ１．５に対応することを見出した。なお、図２に示す３つの鋼種Ａ〜Ｃは、表１に示す化学組成を有している。
The present inventors examined a simple test method for evaluating brittle fracture characteristics by an NRL drop weight test using a small test piece having a constant thickness.
First, brittle fracture propagation stop characteristics Kca obtained from a brittle fracture propagation stop test (standard ESSO test) defined in Non-Patent Document 3 for steel materials having a yield strength of 335 MPa class to 510 MPa class with a plate thickness of 25 mm. The relationship between the value and the transition temperature TNDT obtained from the NRL drop weight test method of ASTM standard E-208 was investigated. As a result, as shown in FIG. 2, it was found that the transition temperature TNDT corresponds to a Kca value of 2000 to 3000 N / mm 1.5 . Note that the three steel types A to C shown in FIG. 2 have chemical compositions shown in Table 1.
また、厚鋼板は、板厚が厚くなれば、脆くなるという特性を有している。
そこで、上記した結果を、種々の板厚に拡張するため、板厚が４０〜１００ｍｍの厚鋼板を減厚して脆性破壊伝播停止試験を行い、その板厚効果を調査した結果について説明する。
前記した非特許文献４に示された板厚効果は、板厚が３５ｍｍ以上で小さくなっており、特に板厚が４０〜１００ｍｍの範囲では、板厚効果が過小評価されていた。
また、非特許文献５では、シャルピー試験とＫｃａ値との相関式が与えられているが、ｖＴｒｓを材料特性として板厚ｔを変数と考えれば、Ｋｃａ値の板厚効果に関する式と解釈できる。なお、非特許文献５の式では、Ｋｃａ値が４０００Ｎ／ｍｍ１．５以上の高い側で板厚効果を過小評価し、板厚が８０ｍｍ以上の厚手材では、板厚効果を過大評価することが明らかになった。
Moreover, a thick steel plate has the characteristic of becoming brittle as the plate thickness increases.
Therefore, in order to extend the above-described results to various plate thicknesses, a thickness steel plate having a thickness of 40 to 100 mm is reduced, a brittle fracture propagation stop test is performed, and the results of examining the plate thickness effect will be described.
The plate thickness effect shown in Non-Patent Document 4 described above is small when the plate thickness is 35 mm or more, and the plate thickness effect is underestimated particularly in the range of 40 to 100 mm.
Further, in Non-Patent Document 5, a correlation formula between the Charpy test and the Kca value is given. However, if the plate thickness t is regarded as a variable with vTrs as a material characteristic, it can be interpreted as a formula relating to the plate thickness effect of the Kca value. In the formula of Non-Patent Document 5, the plate thickness effect is underestimated on the high side with a Kca value of 4000 N / mm 1.5 or higher, and the plate thickness effect is overestimated with a thick material with a plate thickness of 80 mm or higher. Became clear.
得られたデータを詳細に検討した結果、下記式（２）のような板厚効果を導出した。
Ｋｃａ（ｔ）＝Ｋｃａ（２５ｍｍ）×ｅｘｐ｛０．２９×（１−ｔ／２５）｝ ・・・（２）
この式（２）は、図３に示すように、厚鋼板の板厚が厚くなることで、Ｋｃａ値が低下することを意味している。
一方、板厚２５ｍｍでの脆性破壊伝播停止試験によるＫｃａ値の温度依存性は、Ｋｃａ値の対数と絶対温度の逆数が、一定の傾きの１次の相関を持ち、下記式（３）で表されることを見出した。
ｌｎ（Ｋｃａ´）−ｌｎ（Ｋｃａ）
＝−１６００×｛１／（２７３＋Ｔ´）−１／（２７３＋Ｔ０）｝ ・・・（３）
なお、この式（３）の関係は、図４に図示される。
As a result of examining the obtained data in detail, a plate thickness effect like the following formula (2) was derived.
Kca (t) = Kca (25 mm) × exp {0.29 × (1-t / 25)} (2)
This equation (2) means that the Kca value decreases as the plate thickness of the thick steel plate increases as shown in FIG.
On the other hand, the temperature dependence of the Kca value in the brittle fracture propagation stop test at a plate thickness of 25 mm is expressed by the following equation (3), where the logarithm of the Kca value and the reciprocal of the absolute temperature have a linear correlation with a certain slope. I found out that
ln (Kca ')-ln (Kca)
= −1600 × {1 / (273 + T ′) − 1 / (273 + T 0 )} (3)
The relationship of this equation (3) is illustrated in FIG.
上記した式（３）に、Ｋｃａ´としてＸを代入する。なお、Ｘは厚鋼板の鋼種で決定される定数である。
また、Ｔ´は、目標となる遷移温度ＴＮＤＴであり、これを温度Ｔ（℃）として代入する。
そして、Ｔ０は、需要者が要求する保証温度（℃）である。
更に、Ｋｃａは、需要者が要求する脆性破壊伝播停止性能であり、Ａ（Ｎ／ｍｍ１．５）を代入する。
これにより、上記した式（３）は、以下に示す式となる。
ｌｎＸ−ｌｎＡ＝−１６００×｛１／（２７３＋Ｔ）−１／（２７３＋Ｔ０）｝
これを、温度Ｔについて解くことで、前記した式（１）が得られる。
X is substituted as Kca ′ in the above equation (3). X is a constant determined by the steel type of the thick steel plate.
T ′ is a target transition temperature TNDT, which is substituted as a temperature T (° C.).
T 0 is the guaranteed temperature (° C.) requested by the consumer.
Furthermore, Kca is the brittle fracture propagation stop performance requested by the consumer, and A (N / mm 1.5 ) is substituted.
Thereby, the above-described formula (3) becomes the following formula.
lnX−lnA = −1600 × {1 / (273 + T) −1 / (273 + T 0 )}
By solving this with respect to the temperature T, the above-described equation (1) is obtained.
以上の方法により得られた式（１）を使用して、厚鋼板の脆性き裂伝播停止特性の判定を行う。
まず、使用する厚鋼板の種類の選択に際し、需要者が要求する保証温度Ｔ０（℃）、及び脆性破壊伝播停止性能Ｋｃａ値Ａ（Ｎ／ｍｍ１．５）と、厚鋼板の板厚ｔ（ｍｍ）を、式（１）に代入する。これにより、換算式である式（１）から温度Ｔが得られる。
厚鋼板が、この温度Ｔ（℃）以下の遷移温度ＴＮＤＴを有する場合、この厚鋼板が脆性破壊伝播停止性能Ｋｃａ値を満足すると判定されるため、換算式から得られた温度Ｔに基づいて、例えば、過去のデータ等を使用し、厚鋼板の種類を幾つかの種類に絞り込む。
そして、各厚鋼板から、小型試験片を採取する。
Using the formula (1) obtained by the above method, the brittle crack propagation stop characteristic of the thick steel plate is determined.
First, when selecting the type of thick steel plate to be used, the guarantee temperature T 0 (° C.) required by the customer, the brittle fracture propagation stop performance Kca value A (N / mm 1.5 ), and the thickness t of the thick steel plate (Mm) is substituted into equation (1). Thereby, the temperature T is obtained from the conversion formula (1).
When the thick steel plate has a transition temperature TNDT below this temperature T (° C.), it is determined that this thick steel plate satisfies the brittle fracture propagation stop performance Kca value. Therefore, based on the temperature T obtained from the conversion formula, For example, past data or the like is used to narrow down the types of thick steel plates into several types.
And a small test piece is extract | collected from each thick steel plate.
この小型試験片は、直方体となっており、厚さが１６ｍｍ以上２５ｍｍ以下、幅が５０ｍｍ以上９０ｍｍ以下、長さが１３０ｍｍ以上３６０ｍｍ以下のものであればよく、具体的には、以下のものを使用できる。
・厚さ：１６ｍｍ、幅：５０ｍｍ、長さ：１３０ｍｍ
・厚さ：１９ｍｍ、幅：５０ｍｍ、長さ：１３０ｍｍ
・厚さ：２５ｍｍ、幅：９０ｍｍ、長さ：３６０ｍｍ
なお、これら小型試験片の寸法は、ＡＳＴＭに規定された規格であるが、この寸法に限定されるものではなく、持ち運び等を考慮すれば、厚さが１６ｍｍの小型試験片を使用することが好ましい。
The small test piece has a rectangular parallelepiped shape, and may have a thickness of 16 mm to 25 mm, a width of 50 mm to 90 mm, and a length of 130 mm to 360 mm. Can be used.
・ Thickness: 16mm, width: 50mm, length: 130mm
・ Thickness: 19 mm, width: 50 mm, length: 130 mm
・ Thickness: 25 mm, width: 90 mm, length: 360 mm
The dimensions of these small test pieces are standards stipulated in ASTM, but are not limited to these dimensions, and considering carrying around, it is possible to use small test pieces with a thickness of 16 mm. preferable.
ここで、厚鋼板の板厚が２５ｍｍ以上５０ｍｍ未満の場合は、小型試験片を厚鋼板の表層側から複数本採取する。また、厚鋼板の板厚が５０ｍｍ以上１００ｍｍ未満の場合、小型試験片を厚鋼板の表層側及び厚み方向中央部から複数本採取する。
小型試験片の長手方向中央部にノッチを形成し、ノッチを形成した複数の小型試験片を予め設定した各温度にそれぞれ冷却する。そして、ＮＲＬ落重試験法を使用し、各小型試験片を動的３点曲げ負荷により破断し、発生する脆性破壊が小型試験片の幅方向両端部に到達する限界温度である遷移温度ＴＮＤＴを求める。
なお、厚鋼板の板厚が２５ｍｍ以上５０ｍｍ未満の場合は、小型試験片の測定温度を遷移温度ＴＮＤＴとする。また、厚鋼板の板厚が５０ｍｍ以上１００ｍｍ未満の場合は、厚鋼板の表層側及び厚み方向中央部から採取した各小型試験片の測定温度の平均値を遷移温度ＴＮＤＴとする。
Here, when the plate thickness of the thick steel plate is 25 mm or more and less than 50 mm, a plurality of small test pieces are collected from the surface layer side of the thick steel plate. Moreover, when the plate | board thickness of a thick steel plate is 50 mm or more and less than 100 mm, multiple small test pieces are extract | collected from the surface layer side and thickness direction center part of a thick steel plate.
A notch is formed in the central portion in the longitudinal direction of the small test piece, and the plurality of small test pieces having the notch are cooled to respective preset temperatures. Then, using the NRL drop weight test method, each small test piece is broken by a dynamic three-point bending load, and a transition temperature TNDT, which is a limit temperature at which the generated brittle fracture reaches both ends in the width direction of the small test piece, is set. Ask.
In addition, when the plate | board thickness of a thick steel plate is 25 mm or more and less than 50 mm, let the measurement temperature of a small test piece be transition temperature TNDT. Moreover, when the plate | board thickness of a thick steel plate is 50 mm or more and less than 100 mm, let the transition temperature TNDT be the average value of the measurement temperature of each small test piece extract | collected from the surface layer side and thickness direction center part of the thick steel plate.
以上の方法で求めた小型試験片の遷移温度ＴＮＤＴが、前記した換算式である式（１）から得られる温度Ｔ（℃）以下である場合に、需要者が要求する脆性破壊伝播停止性能Ｋｃａ値を満足すると判定する。
なお、小型試験片として、厚さが１６ｍｍ、幅が５０ｍｍ、長さが１３０ｍｍのものを使用した場合は、式（１）のＸに２０００を代入する。これは、前記した図２からも明らかなように、２０００が遷移温度ＴＮＤＴと対応する最も低い（安全率が高い）Ｋｃａ値であることによる。
従って、小型試験片の寸法が他の寸法であっても、Ｘに２０００を代入すれば、十分に対応できる。
このようにして得られた結果から、需要者が要求する厚鋼板を提供するので、厚鋼板の脆性破壊伝播停止特性を簡易に評価できる。
The brittle fracture propagation stoppage performance Kca required by the customer when the transition temperature TNDT of the small test piece obtained by the above method is equal to or lower than the temperature T (° C.) obtained from the equation (1) which is the conversion formula described above. It is determined that the value is satisfied.
When a small test piece having a thickness of 16 mm, a width of 50 mm, and a length of 130 mm is used, 2000 is substituted for X in formula (1). This is because 2000 is the lowest (high safety factor) Kca value corresponding to the transition temperature TNDT, as is apparent from FIG.
Therefore, even if the size of the small test piece is another size, it can be sufficiently handled by substituting 2000 for X.
Thus, since the thick steel plate which a consumer demands is provided from the result obtained in this way, the brittle fracture propagation stop characteristic of a thick steel plate can be evaluated easily.
次に、本発明の作用効果を確認するために行った実施例について説明する。
ここでは、前記した表１に示すＡ〜Ｃの３種類の厚鋼板を使用した。なお、使用した３種類の各鋼材の板厚、強度（ＹＰ：降伏点、ＴＳ：引張り）、伸び（ＥＬ：弾性伸び）、及びシャルピー衝撃特性を表２に、それぞれ示す。
Next, examples carried out for confirming the effects of the present invention will be described.
Here, three types of thick steel plates A to C shown in Table 1 were used. Table 2 shows the thickness, strength (YP: yield point, TS: tensile), elongation (EL: elastic elongation), and Charpy impact characteristics of each of the three types of steel materials used.
判定を行うに際し、まず、ＮＲＬ落重試験での遷移温度ＴＮＤＴ（以下、単にＴＮＤＴともいう）と、脆性破壊伝播停止性能Ｋｃａ値（以下、単にＫｃａ値ともいう）との対応について検討した。
ここでは、表２に示す厚鋼板Ｎｏ．２、３、５〜９の板厚中央部から、厚み２５ｍｍの試験片を採取し、日本溶接協会規格「ＷＥＳ鋼種認定試験方法」（２０００年）に準拠した脆性破壊伝播停止試験、及びＡＳＴＭ規格Ｅ−２０８に準拠したＮＲＬ落重試験を実施した。
試験で得られた同一温度でのＫｃａ値とＴＮＤＴとの関係を、図５に示す。
図５から明らかなように、ＮＲＬ落重試験での遷移温度ＴＮＤＴは、Ｋｃａ値で２０００〜３０００Ｎ／ｍｍ１．５に対応することが確認できた。
In making the determination, first, the correspondence between the transition temperature TNDT (hereinafter also simply referred to as TNDT) in the NRL drop weight test and the brittle fracture propagation stopping performance Kca value (hereinafter also simply referred to as Kca value) was examined.
Here, thick steel plates No. 1 shown in Table 2 are used. Test specimens with a thickness of 25 mm were collected from the center of the plate thickness of 2, 3, 5-9, and the brittle fracture propagation stop test according to the Japan Welding Association standard "WES steel type certification test method" (2000), and the ASTM standard. An NRL drop weight test according to E-208 was performed.
FIG. 5 shows the relationship between the Kca value at the same temperature obtained in the test and TNDT.
As is clear from FIG. 5, it was confirmed that the transition temperature TNDT in the NRL drop weight test corresponds to 2000 to 3000 N / mm 1.5 in terms of Kca value.
次に、表２に示す厚鋼板Ｎｏ．３、４、９を用いて、Ｋｃａ値の板厚効果を検討した。
なお、厚鋼板Ｎｏ．３からは、厚さが、２５ｍｍ、４０ｍｍ、６０ｍｍ、及び８０ｍｍの試験片を、また厚鋼板Ｎｏ．４からは、厚さが、２５ｍｍ及び４０ｍｍの試験片を、そして、厚鋼板Ｎｏ．９からは、厚さが、２５ｍ、５０ｍｍ、７０ｍｍ、及び１００ｍｍの試験片をそれぞれ切り出して、脆性破壊伝播停止試験を実施した。
それぞれ元厚でのＫｃａ値が４０００Ｎ／ｍｍ１．５となる温度におけるＫｃａ値を、２５ｍｍ厚でのＫｃａ値に対する比で表し、横軸を板厚にしてプロットした図６により、Ｋｃａ値の板厚依存性を求め、下記に示す式を得た。
Ｋｃａ（ｔ）＝Ｋｃａ（２５ｍｍ）×ｅｘｐ｛０．２９×（１−ｔ／２５）｝
このように、Ｋｃａ値が板厚に依存することを確認できた。
Next, thick steel plates No. 1 shown in Table 2 were used. Using 3, 4 and 9, the plate thickness effect of the Kca value was examined.
In addition, thick steel plate No. From No. 3, test pieces having thicknesses of 25 mm, 40 mm, 60 mm, and 80 mm were used. From No. 4, test pieces having thicknesses of 25 mm and 40 mm, and thick steel plate No. 4 were used. From No. 9, test pieces having a thickness of 25 m, 50 mm, 70 mm, and 100 mm were cut out and subjected to a brittle fracture propagation stop test.
The Kca value at a temperature at which the Kca value at the original thickness is 4000 N / mm 1.5 is expressed as a ratio with respect to the Kca value at a thickness of 25 mm, and the horizontal axis represents the plate thickness. The thickness dependency was determined, and the following formula was obtained.
Kca (t) = Kca (25 mm) × exp {0.29 × (1-t / 25)}
Thus, it was confirmed that the Kca value depends on the plate thickness.
次に、表２に示す厚鋼板Ｎｏ．１〜９から採取した小型試験片（厚さ：１６ｍｍ、幅：５０ｍｍ、長さ：１３０ｍｍ）を用いて、これらの鋼材が、需要者が要求する保証温度Ｔ０＝−１０℃で、脆性破壊伝播停止性能Ｋｃａ≧４０００Ｎ／ｍｍ１．５を満足するかを検討した。この結果を表３に示す。 Next, thick steel plates No. 1 shown in Table 2 were used. Using small test specimens (thickness: 16 mm, width: 50 mm, length: 130 mm) collected from 1 to 9, these steel materials are brittle fracture at the guaranteed temperature T 0 = −10 ° C. required by the customer. Whether the propagation stop performance Kca ≧ 4000 N / mm 1.5 was satisfied was examined. The results are shown in Table 3.
表３に示すように、厚鋼板Ｎｏ．２、４、９から採取した小型試験片は、遷移温度ＴＮＤＴが、本発明の換算式から得られる温度Ｔより高温であった。このとき、Ｋｃａ値が４０００となる実際の温度は、いずれも−１０℃を超えていた。
一方、それ以外の厚鋼板Ｎｏ．１、３、５〜８から採取した小型試験片は、遷移温度ＴＮＤＴが、本発明の換算式で与えられる温度Ｔより低温であった。このとき、Ｋｃａ値が４０００となる実際の温度は、いずれも−１０℃以下であった。
以上のことから、本発明の判定方法を使用した試験結果は、従来行っていた大型試験片を使用した場合と同じ結果であり、本発明の判定式の有効性が確認された。
As shown in Table 3, thick steel plate No. The small test pieces collected from 2, 4, and 9 had a transition temperature TNDT higher than the temperature T obtained from the conversion formula of the present invention. At this time, the actual temperature at which the Kca value was 4000 exceeded -10 ° C.
On the other hand, other thick steel plates No. The small test pieces collected from 1, 3, and 5-8 had a transition temperature TNDT lower than the temperature T given by the conversion formula of the present invention. At this time, the actual temperatures at which the Kca value was 4000 were all −10 ° C. or lower.
From the above, the test result using the determination method of the present invention is the same result as the case of using a large test piece which has been conventionally performed, and the effectiveness of the determination formula of the present invention was confirmed.
以上、本発明を、実施の形態を参照して説明してきたが、本発明は何ら上記した実施の形態に記載の構成に限定されるものではなく、特許請求の範囲に記載されている事項の範囲内で考えられるその他の実施の形態や変形例も含むものである。例えば、前記したそれぞれの実施の形態や変形例の一部又は全部を組合せて本発明の厚鋼板の脆性き裂伝播停止特性の判定方法を構成する場合も本発明の権利範囲に含まれる。
また、前記実施の形態においては、１つの換算式についてのみ示しているが、この換算式の各係数は、前記した数値に限定されるものではなく、小型試験片の形状に応じて変更できる。
As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, the case where the method for determining the brittle crack propagation stopping property of a thick steel plate according to the present invention is configured by combining some or all of the above-described embodiments and modifications is also included in the scope of the right of the present invention.
Moreover, in the said embodiment, although it has shown about only one conversion formula, each coefficient of this conversion formula is not limited to an above-described numerical value, It can change according to the shape of a small test piece.
Claims (5)
前記各小型試験片が、厚さが１６ｍｍ以上２５ｍｍ以下、幅が５０ｍｍ以上９０ｍｍ以下、長さが１３０ｍｍ以上３６０ｍｍ以下で、かつ長手方向中央部にそれぞれノッチを有し、該各小型試験片を予め設定した各温度に冷却して、該各小型試験片を動的３点曲げ負荷により破断し、発生する脆性破壊が前記小型試験片の幅方向両端部に到達する限界温度である遷移温度を求め、
前記求めた遷移温度が、要求される保証温度Ｔ０（℃）と、要求される脆性破壊伝播停止性能Ｋｃａ値Ａ（Ｎ／ｍｍ１．５）と、前記厚鋼板の板厚ｔ（ｍｍ）とで表される換算式から得られる温度Ｔ（℃）以下である場合に、前記要求される脆性破壊伝播停止性能Ｋｃａ値を満足すると判定することを特徴とする厚鋼板の脆性き裂伝播停止特性の判定方法。 A method for determining the brittle crack propagation stop characteristic of a thick steel plate using a plurality of small test pieces instead of a large test piece having a side of 500 mm used in the brittle fracture propagation stop test,
Each of the small test pieces has a thickness of 16 mm or more and 25 mm or less, a width of 50 mm or more and 90 mm or less, a length of 130 mm or more and 360 mm or less, and a notch at the center in the longitudinal direction. After cooling to each set temperature, each small test piece is broken by a dynamic three-point bending load, and a transition temperature that is the limit temperature at which the brittle fracture that occurs reaches both ends in the width direction of the small test piece is obtained. ,
The obtained transition temperature is the required guaranteed temperature T 0 (° C.), the required brittle fracture propagation stop performance Kca value A (N / mm 1.5 ), and the thickness t (mm) of the thick steel plate. It is determined that the required brittle fracture propagation stop performance Kca value is satisfied when the temperature is equal to or lower than the temperature T (° C.) obtained from the conversion formula expressed by the following: How to determine characteristics.
Ｔ＝１／｛１／（Ｔ０＋２７３）＋０．０００６２５×ｌｎ（Ａ／Ｘ）
−０．０００１８１×（１−ｔ／２５）｝−２７３ ・・・（１）
ここで、Ｘは厚鋼板の鋼種で決定される定数である。 The method for determining the brittle crack propagation stop characteristic of a thick steel plate according to claim 1, wherein the temperature T is obtained by the equation (1).
T = 1 / {1 / (T 0 +273) + 0.000625 × ln (A / X)
-0.000181 × (1-t / 25)}-273 (1)
Here, X is a constant determined by the steel type of the thick steel plate.
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| JP6686951B2 (en) * | 2017-03-27 | 2020-04-22 | Ｊｆｅスチール株式会社 | Evaluation method for brittle crack propagation arresting performance of thick steel plate |
| JP7119805B2 (en) * | 2018-09-13 | 2022-08-17 | 日本製鉄株式会社 | Thick steel plate quality evaluation method |
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