JP5061649B2 - Thick steel plate with a thickness of 50 mm or more with excellent brittle crack propagation stopping characteristics - Google Patents
Thick steel plate with a thickness of 50 mm or more with excellent brittle crack propagation stopping characteristics Download PDFInfo
- Publication number
- JP5061649B2 JP5061649B2 JP2007049384A JP2007049384A JP5061649B2 JP 5061649 B2 JP5061649 B2 JP 5061649B2 JP 2007049384 A JP2007049384 A JP 2007049384A JP 2007049384 A JP2007049384 A JP 2007049384A JP 5061649 B2 JP5061649 B2 JP 5061649B2
- Authority
- JP
- Japan
- Prior art keywords
- thickness
- crack propagation
- brittle crack
- steel plate
- less
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 229910000831 Steel Inorganic materials 0.000 title claims description 82
- 239000010959 steel Substances 0.000 title claims description 82
- 238000005096 rolling process Methods 0.000 claims description 36
- 239000000203 mixture Substances 0.000 claims description 5
- 229910052759 nickel Inorganic materials 0.000 claims description 5
- 229910052717 sulfur Inorganic materials 0.000 claims description 5
- 229910052796 boron Inorganic materials 0.000 claims description 4
- 229910052802 copper Inorganic materials 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 229910052720 vanadium Inorganic materials 0.000 claims description 4
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims description 3
- 229910052748 manganese Inorganic materials 0.000 claims description 2
- 229910052758 niobium Inorganic materials 0.000 claims description 2
- 239000000463 material Substances 0.000 description 26
- 238000000034 method Methods 0.000 description 15
- 229910000859 α-Fe Inorganic materials 0.000 description 13
- 230000000694 effects Effects 0.000 description 12
- 239000010410 layer Substances 0.000 description 10
- 238000012360 testing method Methods 0.000 description 10
- 238000001816 cooling Methods 0.000 description 9
- 239000002344 surface layer Substances 0.000 description 8
- 230000009467 reduction Effects 0.000 description 6
- 239000013078 crystal Substances 0.000 description 5
- 238000009864 tensile test Methods 0.000 description 5
- 230000007704 transition Effects 0.000 description 5
- 229910052804 chromium Inorganic materials 0.000 description 4
- 230000001186 cumulative effect Effects 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 238000003860 storage Methods 0.000 description 4
- 239000010953 base metal Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000003303 reheating Methods 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- 229910001566 austenite Inorganic materials 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 230000001771 impaired effect Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000001902 propagating effect Effects 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- RMLPZKRPSQVRAB-UHFFFAOYSA-N tris(3-methylphenyl) phosphate Chemical compound CC1=CC=CC(OP(=O)(OC=2C=C(C)C=CC=2)OC=2C=C(C)C=CC=2)=C1 RMLPZKRPSQVRAB-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- -1 but P exceeds 0.03% Inorganic materials 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 238000009863 impact test Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 230000002040 relaxant effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Images
Landscapes
- Heat Treatment Of Steel (AREA)
Description
本発明は、船舶、海洋構造物、低温貯蔵タンク、建築・土木構造物等の大型構造物に使用される脆性き裂伝播停止特性に優れた、厚さ５０ｍｍ以上の厚鋼板に関する。 The present invention relates to a thick steel plate having a thickness of 50 mm or more and excellent in brittle crack propagation stopping characteristics used for large structures such as ships, marine structures, low-temperature storage tanks, and construction / civil engineering structures.
船舶、海洋構造物、低温貯蔵タンク、建築・土木構造物等の大型構造物においては、脆性破壊に伴う事故が経済や環境に及ぼす影響が大きいため、安全性の向上が常に求められている。 In large structures such as ships, offshore structures, low-temperature storage tanks, and construction / civil engineering structures, accidents associated with brittle fractures have a large impact on the economy and the environment, and therefore safety is always required to be improved.
したがって、この様な構造物に使用される鋼材に対しては、低温靭性が要求されることが多く、最近では、不慮の事故等で構造物にき裂が発生した場合においても破壊に至ることを防止する観点から、低温における脆性き裂伝播停止特性が要求されている。 Therefore, low-temperature toughness is often required for steel materials used in such structures, and recently, even if a crack occurs in the structure due to an accident, etc., it can lead to failure. From the viewpoint of preventing cracking, brittle crack propagation stopping characteristics at low temperatures are required.
一般に、鋼板のアレスト性は高強度あるいは厚肉材ほど劣化する傾向がある。このため、コンテナ船やバルクキャリアーなどの船舶においてはその構造上、船体外板に高強度の厚肉材を使用される場合が多く、船舶の安全性確保の点から材料に対する脆性き裂伝播停止特性の要求も一段と高度化している。 In general, the arrestability of a steel sheet tends to deteriorate as the strength or thickness of the material increases. For this reason, vessels such as container ships and bulk carriers often use high-strength thick materials for the outer skin of the hull due to their structure, and stop the propagation of brittle cracks to materials from the standpoint of ensuring ship safety. The requirements for characteristics are becoming more sophisticated.
鋼材の脆性き裂伝播停止特性を向上させる手段として、従来からＮｉ含有量を増加させる方法が知られており、液化天然ガス（ＬＮＧ）の貯槽タンクにおいては、９％Ｎｉ鋼が商業規模で使用されている。しかし、Ｎｉ量の増加はコストの大幅な上昇を余儀なくさせるため、ＬＮＧ貯槽タンク以外の用途には適用が難しい。 As a means of improving the brittle crack propagation stopping characteristics of steel materials, a method of increasing the Ni content has been conventionally known. In a LNG storage tank, 9% Ni steel is used on a commercial scale. Has been. However, since the increase in the amount of Ni necessitates a significant increase in cost, it is difficult to apply to applications other than the LNG storage tank.
一方、ＬＮＧのような極低温まで至らない、船舶やラインパイプに使用される鋼板の板厚が５０ｍｍ以下の比較的薄手の鋼材に対しては、ＴＭＣＰ法により細粒化を図り、低温靭性を向上させて、優れた脆性き裂伝播停止特性を付与することができる。 On the other hand, for thin steel materials with a plate thickness of 50 mm or less, such as LNG, that do not reach cryogenic temperatures, the steel plate used for ships and line pipes is refined by the TMCP method to achieve low temperature toughness. It can be improved to give excellent brittle crack propagation stopping properties.
さらに、制御圧延において、変態したフェライトに圧下を加えて集合組織を発達させることにより、脆性き裂伝播停止特性の向上を図る方法も知られている。これは、鋼材の破壊面上にセパレーションを板厚方向と平行な方向に生ぜしめ、脆性き裂先端の応力を緩和させることにより、脆性破壊に対する抵抗を高める方法である。 Furthermore, in controlled rolling, a method of improving the brittle crack propagation stopping property is also known by developing a texture by reducing the transformed ferrite. This is a method of increasing resistance to brittle fracture by causing separation on the fracture surface of the steel material in a direction parallel to the plate thickness direction and relaxing stress at the tip of the brittle crack.
例えば、特許文献１では、制御圧延により（１１０）面Ｘ線強度比を２以上とし、かつ円相当径２０μｍ以上の粗大粒を１０％以下とすることにより、耐脆性破壊特性を向上させている。しかし、鋼材の板厚の増加に伴いアレスト性能は低下しており、特に板厚５０ｍｍを超えるような厚肉材において所定の耐脆性破壊特性が得られるかどうかは不明である。 For example, in Patent Literature 1, brittle fracture resistance is improved by controlling the (110) plane X-ray intensity ratio to 2 or more and controlling coarse grains having an equivalent circle diameter of 20 μm or more to 10% or less by controlled rolling. . However, the arrest performance decreases with an increase in the thickness of the steel material, and it is unclear whether a predetermined brittle fracture resistance can be obtained particularly in a thick material exceeding 50 mm in thickness.
一方、近年、合金コストを上昇させることなく、鋼材の表層部の組織を超微細化する技術が、脆性き裂伝播停止特性を向上させる手段として提案されている。例えば、特許文献２では、脆性き裂が伝播する際に、鋼材表層部に発生するシアリップ（塑性変形領域）が脆性き裂伝播停止特性の向上に効果があることに着目し、シアリップ部分の結晶粒を微細化させて、伝播する脆性き裂が有する伝播エネルギーを吸収させる方法が開示されている。 On the other hand, in recent years, a technique for making the structure of the surface layer portion of a steel material ultrafine without increasing the alloy cost has been proposed as a means for improving the brittle crack propagation stopping property. For example, in Patent Document 2, when a brittle crack propagates, attention is paid to the fact that shear lip (plastic deformation region) generated in the steel surface layer portion is effective in improving the brittle crack propagation stop characteristic. A method is disclosed in which the grains are refined to absorb the propagating energy of the propagating brittle crack.
この製造方法としては、熱間圧延後の制御冷却により表層部分をＡｒ３変態点以下に冷却し、その後制御冷却を停止して表層部分を変態点以上に復熱させる工程を１回以上繰り返して行い、この間に鋼材に圧下を加えることにより、繰り返し変態させ又は加工再結晶させて、表層部分に超微細なフェライト組織又はベイナイト組織を生成させるものである。 As this manufacturing method, the process of cooling the surface layer portion below the Ar3 transformation point by controlled cooling after hot rolling, and then stopping the controlled cooling to reheat the surface layer portion above the transformation point is repeated one or more times. In the meantime, by rolling down the steel material, it is repeatedly transformed or processed and recrystallized to generate an ultrafine ferrite structure or bainite structure in the surface layer portion.
さらに、特許文献３では、フェライト−パーライトを主体のミクロ組織とする鋼材において脆性き裂伝播停止特性を向上させるには、両表面部は円相当粒径：５μｍ以下、アスペクト比：２以上のフェライト粒を有するフェライト組織を５０％以上有する層で構成し、フェライト粒径のバラツキを抑えることが重要であることが開示されている。 Furthermore, in Patent Document 3, in order to improve the brittle crack propagation stopping characteristics in a steel material mainly composed of ferrite-pearlite, both surface portions have a ferrite equivalent particle diameter of 5 μm or less and an aspect ratio of 2 or more. It is disclosed that it is important to form a layer having a ferrite structure having grains of 50% or more and to suppress variations in ferrite grain size.
このバラツキを抑える方法として仕上げ圧延中の１パス当りの最大圧下率を１２％以下にすることで局所的な再結晶現象が抑制されるとしている。しかし、これらの開示された発明は、鋼材表層部のみを一旦冷却した後に復熱させ、かつ復熱中に加工を加えることによって、脆性き裂伝播停止特性に効果のある組織を得るものであり、実生産規模では制御が容易ではないと考えられるプロセスである。また、板厚が５０ｍｍを超える厚肉材での記載もないため、厚肉材への適用は不明である。 As a method for suppressing this variation, the local recrystallization phenomenon is suppressed by setting the maximum rolling reduction per pass during finish rolling to 12% or less. However, these disclosed inventions are intended to obtain a structure effective in brittle crack propagation stop characteristics by reheating after cooling only the steel surface layer part and adding processing during reheating, This is a process that is considered to be difficult to control at the actual production scale. Moreover, since there is no description with a thick material exceeding 50 mm in thickness, the application to a thick material is unknown.
このような問題を解決する方法として、特許文献４において、フェライト結晶粒の微細化のみならずフェライト結晶粒内に形成されるサブグレインに着目しＴＭＣＰ法の延長技術が提供されている。 As a method for solving such a problem, Patent Document 4 provides a technique for extending the TMCP method by paying attention not only to refinement of ferrite crystal grains but also to subgrains formed in ferrite crystal grains.
具体的には、板厚３０〜４０ｍｍにおいて、鋼板表層の冷却および復熱などの複雑な温度制御を必要とせずに、（ａ）微細なフェライト結晶粒を確保する圧延条件、（ｂ）鋼材板厚の５％以上の部分に微細フェライト組織を生成する圧延条件、（ｃ）微細フェライトに集合組織を発達させるとともに加工（圧延）により導入した転位を熱的エネルギーにより再配置しサブグレインを形成させる圧延条件、（ｄ）形成した微細なフェライト結晶粒と微細なサブグレイン粒の粗大化を抑制する冷却条件、によって脆性き裂伝播停止特性を向上させる方法を提供している。 Specifically, in a plate thickness of 30 to 40 mm, without requiring complicated temperature control such as cooling and recuperation of the steel sheet surface layer, (a) rolling conditions for securing fine ferrite crystal grains, (b) steel plate Rolling conditions for generating a fine ferrite structure in a portion of 5% or more of the thickness, (c) A texture is developed in the fine ferrite, and dislocations introduced by processing (rolling) are rearranged by thermal energy to form subgrains. The present invention provides a method for improving brittle crack propagation stopping characteristics by rolling conditions and (d) cooling conditions for suppressing coarsening of formed fine ferrite crystal grains and fine subgrain grains.
しかし、この発明では、板厚５０ｍｍ超えの厚肉材での記載がなく、板厚５０ｍｍ超えの厚肉材において所定の脆性き裂伝播停止特性が得られるかどうか不明である。
一方、最近の６，０００ＴＥＵを越える大型コンテナ船では鋼板の板厚は５０ｍｍ以上となっている。脆性き裂伝播停止特性の向上のためには、前述のように細粒化による母材靭性の向上、鋼材の表層部のシアリップ生成、板厚内部に圧延面での（１００）面の集合組織の発達による応力付加方向とき裂伝播方向に角度のずれ生成等が有効であることが知られている。 On the other hand, in the recent large container ships exceeding 6,000 TEU, the thickness of the steel sheet is 50 mm or more. In order to improve the brittle crack propagation stopping characteristics, as described above, improvement of the base metal toughness by fine graining, generation of shear lip in the surface layer portion of the steel material, texture of the (100) surface on the rolling surface inside the plate thickness It is known that it is effective to generate an angle shift in the direction of stress application and the direction of crack propagation due to the development of cracks.
しかしながら、最近の６，０００ＴＥＵを越える大型コンテナ船で用いられるような板厚５０ｍｍ以上の厚鋼板では、細粒化による母材靭性の向上が難しくなること、鋼材表層部のシアリップが板厚全体に占める割合が小さくなること等から、十分な脆性き裂伝播停止効果が得にくくなる。 However, it is difficult to improve the toughness of the base metal by refining with a thick steel plate with a thickness of 50 mm or more as used in large container ships exceeding 6,000 TEU. Since the ratio occupied becomes small, it becomes difficult to obtain a sufficient brittle crack propagation stopping effect.
そこで、本発明は、板厚５０ｍｍ以上の厚鋼板において、万一脆性破壊が発生した場合でも、大規模破壊に至る前に脆性き裂を停止させるのに適した鋼板を提供することを目的とする。なお、この技術は、板厚が５０ｍｍ未満であっても効果を有する。 Therefore, an object of the present invention is to provide a steel plate suitable for stopping a brittle crack before reaching a large-scale fracture even if a brittle fracture occurs in a thick steel plate having a thickness of 50 mm or more. To do. This technique is effective even when the plate thickness is less than 50 mm.
本発明者らは、上記課題の達成に向けて鋭意研究を重ねた結果、板厚内の位置（例えば、板厚中央部と板厚１／４部、等）によって脆性き裂の伝播方向を相違させた場合、板厚全体でのき裂伝播抵抗が著しく増加し、優れた脆性き裂伝播停止性能を得ることが可能であることを見出した。 As a result of intensive research aimed at achieving the above-mentioned problems, the present inventors determined the propagation direction of the brittle crack depending on the position within the plate thickness (for example, the plate thickness center portion and the plate thickness ¼ portion, etc.). It has been found that when the difference is made, the crack propagation resistance in the entire plate thickness is remarkably increased, and excellent brittle crack propagation stopping performance can be obtained.
さらに、このような優れた脆性き裂伝播停止性能を得るために適切な集合組織の状態お
よび鋼板の成分範囲を見出した。本発明は上記知見を基に更に検討を加えてなされたもの
で、すなわち、本発明は、
（１）脆性き裂伝播方向が一定方向となる層状の領域を板厚断面方向に複数有する厚鋼板であって、隣接する層状の領域の脆性き裂伝播方向の差が３０°以上であることを特徴とする脆性き裂伝播停止特性に優れた厚さ５０ｍｍ以上の厚鋼板。
（２）脆性き裂伝播方向が一定方向となる層状の領域が、３層以上であることを特徴とする（１）記載の脆性き裂伝播停止特性に優れた厚さ５０ｍｍ以上の厚鋼板。
（３）圧延面での（１００）面Ｘ線強度比が２．０以上の層状の領域と、圧延面での（１１０）面Ｘ線強度比が１．５以上の層状の領域を板厚方向に交互にｎ層（但し、ｎは３以上の奇数）重ねた構造を特徴とする（１）に記載の脆性き裂伝播停止特性に優れた厚さ５０ｍｍ以上の厚鋼板。
（４）ｎが３で、板厚中央部を含む層状の領域の、板厚における圧延面での（１００）面Ｘ線強度比が２．０以上であることを特徴とする（３）記載の脆性き裂伝播停止特性に優れた厚さ５０ｍｍ以上の厚鋼板。
（５）鋼組成が、質量％で、Ｃ：０．０３〜０．２％、Ｓｉ：０．０３〜０．５％、Ｍｎ：０．５〜２．０％、Ａｌ：０．００５〜０．０８％、Ｐ：０．０３％以下，Ｓ：０．０１％以下、Ｎ：０．００６０％以下を含有し、残部がＦｅおよび不可避的不純物からなる（１）〜（４）のいずれかに記載の脆性き裂伝播停止特性に優れた厚さ５０ｍｍ以上の厚鋼板。
（６）鋼組成が、上記成分に加えてさらに、質量％で、Ｎｂ：０．００５〜０．０５％、Ｔｉ：０．００５〜０．０３％、Ｃｕ：０．０１〜０．５％、Ｎｉ：０．０１〜１．０％、Ｃｒ：０．０１〜０．５％、Ｍｏ：０．０１〜０．５％、Ｖ：０．００１〜０．１％、Ｂ：、０．００３％以下、Ｃａ：０．００５％以下、ＲＥＭ：０．０１％以下のいずれか１種、または２種以上を含有することを特徴とする（５）に記載の脆性き裂伝播停止特性に優れた厚さ５０ｍｍ以上の厚鋼板。
Furthermore, in order to obtain such excellent brittle crack propagation stopping performance, an appropriate texture state and component range of the steel sheet were found. The present invention has been made by further study based on the above knowledge, that is, the present invention,
(1) A thick steel plate having a plurality of layered regions in the plate thickness cross-sectional direction in which the direction of brittle crack propagation is constant, and the difference in the direction of brittle crack propagation between adjacent layered regions is 30 ° or more. A steel plate having a thickness of 50 mm or more and excellent in brittle crack propagation stopping characteristics.
(2) The thick steel plate having a thickness of 50 mm or more having excellent brittle crack propagation stopping characteristics as described in (1), wherein the layered region in which the brittle crack propagation direction is a constant direction is three or more layers.
(3) Thickness of a layered region having a (100) plane X-ray intensity ratio of 2.0 or more on the rolled surface and a layered region having a (110) plane X-ray intensity ratio of 1.5 or more on the rolled surface A thick steel sheet having a thickness of 50 mm or more and excellent in brittle crack propagation stopping characteristics as described in (1), wherein n layers (where n is an odd number of 3 or more) are alternately stacked in a direction.
(4) n is 3, and the (100) plane X-ray intensity ratio at the rolled surface in the plate thickness of the layered region including the center portion of the plate thickness is 2.0 or more. A steel plate with a thickness of 50 mm or more, which has excellent brittle crack propagation stopping characteristics.
(5) Steel composition is mass%, C: 0.03-0.2%, Si: 0.03-0.5%, Mn: 0.5-2.0%, Al: 0.005- Any of (1) to (4), containing 0.08%, P: 0.03% or less, S: 0.01% or less, N: 0.0060% or less, the balance being Fe and inevitable impurities A thick steel plate having a thickness of 50 mm or more which is excellent in the brittle crack propagation stopping property described in Crab.
(6) In addition to the above components, the steel composition is further mass%, Nb: 0.005-0.05%, Ti: 0.005-0.03%, Cu: 0.01-0.5% , Ni: 0.01 to 1.0%, Cr: 0.01 to 0.5%, Mo: 0.01 to 0.5%, V: 0.001 to 0.1%, B: In the brittle crack propagation stopping property as described in (5), which contains any one or more of 003% or less, Ca: 0.005% or less, REM: 0.01% or less Excellent steel plate with a thickness of 50 mm or more.
本発明によれば鋼板の圧延方向もしくは圧延方向に直角方向に板厚全体にわたり脆性き裂が伝播する場合において、優れた脆性き裂伝播停止性能を備えた板厚５０ｍｍ以上の厚鋼板が得られ、産業上極めて有用である。 According to the present invention, when a brittle crack propagates over the entire thickness in the rolling direction of the steel plate or in a direction perpendicular to the rolling direction, a thick steel plate having a thickness of 50 mm or more with excellent brittle crack propagation stopping performance is obtained. It is extremely useful in industry.
本発明は、脆性き裂伝播方向が一定方向となる層状の領域を板厚断面方向に複数有し、隣接する層状の領域間で脆性き裂伝播方向が異なることを特徴とする。以下に本発明の限定理由について説明する。 The present invention is characterized in that a plurality of layered regions having a constant direction of brittle crack propagation are provided in the cross-sectional direction of the plate thickness, and the direction of brittle crack propagation differs between adjacent layered regions. The reason for limiting the present invention will be described below.
本発明に係る厚鋼板は、板厚方向の隣接する層状の領域間で異なる脆性き裂伝播方向を有する。 The steel plate according to the present invention has different brittle crack propagation directions between adjacent layered regions in the plate thickness direction.
鋼板の圧延方向もしくは圧延方向に直角方向に板厚全体にわたり脆性き裂が伝播する場合、例えば、板厚中央部と板厚１／４部でき裂の伝播方向が異なると、付加応力のうちき裂伝播に作用する方向の成分が小さくなる効果に加え、板厚全体に脆性き裂が伝播するために板厚中央部と板厚１／４部で異なる方向に生じたき裂が連結する必要があり、同一方向、すなわち同一面上をき裂が伝播する場合に較べき裂伝播の抵抗が著しく大きくなる。 When a brittle crack propagates over the entire plate thickness in the rolling direction of the steel plate or in a direction perpendicular to the rolling direction, for example, if the propagation direction of the crack is different at the center of the plate thickness and the 1/4 thickness, In addition to the effect of reducing the component in the direction acting on crack propagation, a brittle crack propagates throughout the plate thickness, so it is necessary to connect cracks generated in different directions at the plate thickness center and plate thickness 1/4. Yes, the resistance to crack propagation is significantly greater when cracks propagate in the same direction, that is, on the same plane.
き裂伝播方向の差が３０°未満であれば比較的き裂伝播抵抗の増大効果が小さいため、き裂伝播方向の差は３０°以上とすることが好ましい。尚、板厚中央部と板厚３／４部でも同じことであるが、ここでは板厚中央部と板厚１／４部で説明する。 If the difference in the crack propagation direction is less than 30 °, the effect of increasing the crack propagation resistance is relatively small. Therefore, the difference in the crack propagation direction is preferably 30 ° or more. The same applies to the central portion of the plate thickness and the ¾ portion of the plate thickness. Here, the central portion of the plate thickness and the ¼ portion of the plate thickness are described.
板厚中央部と板厚１／４部での亀裂伝播方向の相違は後述する圧延組織の差によるもので、板厚中央部や、板厚１／４部での亀裂伝播方向は当該位置を中心に、特定の圧延組織が形成されている層状の領域内では一定であり、本発明に係る厚鋼板は、隣接する層状の領域間で異なる脆性き裂伝播方向を有するものである。 The difference in the crack propagation direction between the center portion of the plate thickness and the 1/4 portion of the plate thickness is due to the difference in the rolling structure described later. In the center, the thickness is constant in a layered region where a specific rolling structure is formed, and the thick steel plate according to the present invention has a brittle crack propagation direction that is different between adjacent layered regions.
また、層状の領域は板厚方向に３層以上重なった構造とする。板厚全体の脆性き裂伝播方向がほぼ同じである場合は従来鋼と変わらず、また脆性き裂伝播方向の差が３０°以上の部分が板厚方向に２層の場合には、板厚各部で生じたき裂の連結に必要な抵抗が小さい。 The layered region has a structure in which three or more layers are overlapped in the thickness direction. If the brittle crack propagation direction of the entire plate is almost the same, it is not different from conventional steel, and if the portion where the difference in brittle crack propagation direction is 30 ° or more is two layers in the plate thickness direction, the plate thickness The resistance required to connect cracks generated in each part is small.
従って、本発明に係る厚鋼板は、層状の領域が、板厚方向に３層以上重なった構造で、隣接する層状の領域間の、脆性き裂伝播方向の差が３０°以上とすることが好ましい。 Therefore, the thick steel plate according to the present invention has a structure in which the layered regions overlap three or more layers in the plate thickness direction, and the difference in the brittle crack propagation direction between adjacent layered regions may be 30 ° or more. preferable.
尚、板厚中央部を含む層状の領域と、隣接する、板厚１／４部を含む層状の領域との間で、脆性き裂伝播方向の差が３０°以上となる場合、圧延組織は板厚中央部における圧延面での（１００）面Ｘ線強度比が２．０以上、かつ板厚１／４部における圧延面での（１１０）面Ｘ線強度比が１．５以上であった。 When the difference in brittle crack propagation direction is 30 ° or more between the layered region including the center portion of the plate thickness and the adjacent layered region including the plate thickness of ¼ part, the rolling structure is The (100) plane X-ray intensity ratio at the rolled surface at the center of the plate thickness was 2.0 or more, and the (110) plane X-ray intensity ratio at the rolled surface at the 1/4 thickness portion was 1.5 or more. It was.
本発明は板厚中央部と板厚１／４部のき裂伝播方向に十分な差が生じれば良く、板厚中央部における圧延面での（１１０）面Ｘ線強度比が１．５以上、板厚１／４部における圧延面での（１００）面Ｘ線強度比が２．０以上としても良い。 In the present invention, it suffices if a sufficient difference occurs in the crack propagation direction between the central portion of the plate thickness and the 1/4 portion of the plate thickness, and the (110) plane X-ray intensity ratio at the rolling surface in the central portion of the plate thickness is 1.5. As described above, the (100) plane X-ray intensity ratio on the rolled surface at the 1/4 thickness portion may be 2.0 or more.
尚、圧延材の圧延組織は、板厚中央部を中心に上下対象の組織となるので、本発明に係る厚鋼板の板厚方向断面組織は、板厚中央部を含む層状の領域に対して、上下方向に層状の領域が同数形成された、板厚方向にｎ層（但し、ｎは３以上の奇数）の層状の領域を有する。 In addition, since the rolling structure of the rolled material is the structure of the upper and lower objects centering on the central part of the plate thickness, the cross-sectional structure in the thickness direction of the thick steel plate according to the present invention is relative to the layered region including the central part of the thickness. The same number of layered regions are formed in the vertical direction, and there are n layered layers (where n is an odd number of 3 or more) in the thickness direction.
板厚中央部を含む層状の領域を挟んで対向する層状の領域、例えば、板厚１／４部と板厚３／４部は同じ脆性亀裂伝播停止特性を有する。 The layered regions facing each other across the layered region including the central part of the plate thickness, for example, the plate thickness of ¼ part and the plate thickness of 3/4 part have the same brittle crack propagation stop characteristics.
また、本発明の層状の領域とは、当該領域内の圧延組織、脆性亀裂伝播方向が一定の、圧延方向、圧延直角方向に層状に形成される領域で、例えば、板厚中央部を含む層状の領域の場合、当該領域内では、圧延面の（１１０）面Ｘ線強度比が１．５以上で、脆性亀裂伝播方向は一定方向である。 In addition, the layered region of the present invention is a region formed in layers in the rolling direction and the direction perpendicular to the rolling direction, in which the rolling structure in the region, the brittle crack propagation direction is constant, for example, the layered shape including the central portion of the plate thickness In this region, the (110) plane X-ray intensity ratio of the rolled surface is 1.5 or more and the brittle crack propagation direction is a constant direction in the region.
厚鋼板としての良好な特性と、優れた脆性き裂伝播停止特性を得るために、好ましい化学成分は以下の様である。 In order to obtain good properties as a thick steel plate and excellent brittle crack propagation stopping properties, preferred chemical components are as follows.
Ｃ：０．０３〜０．２０％
Ｃは鋼の強度を向上する元素であり、本発明では、所望の強度を確保するためには０．０３％以上の含有を必要とするが、０．２０％を超えると、溶接性が劣化するばかりか靭性にも悪影響がある。このため、Ｃは、０．０３〜０．２０％の範囲に規定した。なお、好ましくは０．０５〜０．１５％である。
C: 0.03-0.20%
C is an element that improves the strength of steel. In the present invention, it is necessary to contain 0.03% or more in order to ensure a desired strength, but if it exceeds 0.20%, the weldability deteriorates. As well as adversely affecting toughness. For this reason, C was specified in the range of 0.03 to 0.20%. In addition, Preferably it is 0.05 to 0.15%.
Ｓｉ：０．０３〜０．５％
Ｓｉは脱酸元素として、また、鋼の強化元素として有効であるが、０．０３％未満の含有量ではその効果がない。一方、０．５％を越えると鋼の表面性状を損なうばかりか靭性が極端に劣化する。従ってその添加量を０．０３〜０．５％とする。
Si: 0.03-0.5%
Si is effective as a deoxidizing element and as a strengthening element for steel, but if its content is less than 0.03%, it has no effect. On the other hand, if it exceeds 0.5%, not only the surface properties of the steel are impaired, but also the toughness is extremely deteriorated. Therefore, the addition amount is 0.03 to 0.5%.
Ｍｎ：０．５〜２．０％
Ｍｎは、強化元素として添加する。０．５％より少ないとその効果が十分でなく、２．０％を超えると溶接性が劣化し、鋼材コストも上昇するため、０．５〜２．０％とする。
Mn: 0.5 to 2.0%
Mn is added as a strengthening element. If the content is less than 0.5%, the effect is not sufficient. If the content exceeds 2.0%, the weldability deteriorates and the steel material cost increases, so the content is made 0.5 to 2.0%.
Ａｌ：０．００５〜０．０８％
Ａｌは、脱酸剤として作用し、このためには０．００５％以上の含有を必要とするが、０．０８％を超えて含有すると、靭性を低下させるとともに、溶接した場合に、溶接金属部の靭性を低下させる。このため、Ａｌは、０．００５〜０．０８％の範囲に規定した。なお、好ましくは、０．０２〜０．０５％である。
Al: 0.005 to 0.08%
Al acts as a deoxidizer, and for this purpose, it needs to contain 0.005% or more. However, if it contains more than 0.08%, it reduces the toughness and, when welded, weld metal Reduce the toughness of the part. For this reason, Al was specified in the range of 0.005 to 0.08%. In addition, Preferably, it is 0.02 to 0.05%.
Ｐ：０．０３％以下、Ｓ：０．０１％以下、Ｎ：０．００６０％以下
Ｐ，Ｓ、Ｎは、鋼中の不可避不純物であるが、Ｐは０．０３％を超え、Ｓは０．０１％を超え、Ｎは０．００６０％を超えると靭性が劣化するため、それぞれ、０．０３％以下、０．０２％以下、０．００６０％以下が望ましい。
P: 0.03% or less, S: 0.01% or less, N: 0.0060% or less P, S, and N are inevitable impurities in steel, but P exceeds 0.03%, and S is If it exceeds 0.01% and N exceeds 0.0060%, the toughness deteriorates. Therefore, 0.03% or less, 0.02% or less, and 0.0060% or less are desirable, respectively.
本発明においては、以上の元素に加え、母材の強度を高め、あるいは靭性を向上させるために、以下の元素を添加してもよい。 In the present invention, in addition to the above elements, the following elements may be added in order to increase the strength of the base material or improve the toughness.
Ｎｂ：０．００５〜０．０５％
Ｎｂは、ＮｂＣとしてフェライト変態時あるいは再加熱時に析出し、高強度化に寄与する。また、オーステナイト域の圧延において未再結晶域を拡大させる効果をもち、フェライトの細粒化に寄与するので、靭性の改善にも有効である。その効果を得るためには０．００５％以上の添加が必要であるが０．０５％を超えて添加すると、粗大なＮｂＣが析出し逆に、靭性の低下を招くのでその上限は０．０５％とするのが好ましい。
Nb: 0.005 to 0.05%
Nb precipitates as NbC during ferrite transformation or reheating, and contributes to increasing the strength. In addition, it has the effect of expanding the non-recrystallized region in rolling in the austenite region, and contributes to the refinement of ferrite, so it is also effective in improving toughness. In order to obtain the effect, addition of 0.005% or more is necessary, but if added over 0.05%, coarse NbC precipitates and conversely causes a decrease in toughness, so the upper limit is 0.05. % Is preferable.
Ｔｉ：０．００５〜０．０３％、
Ｔｉは微量の添加により、窒化物、炭化物、あるいは炭窒化物を形成し、結晶粒を微細化して母材靭性を向上させる効果を有する。その効果は０．００５％以上の添加によって得られるが、０．０３％を超える含有は、母材および溶接熱影響部の靭性を低下させるので、Ｔｉは、０．００５〜０．０３％の範囲にするのが好ましい。
Ti: 0.005 to 0.03%,
Ti has the effect of forming nitrides, carbides, or carbonitrides by adding a small amount, and refining crystal grains to improve the base material toughness. The effect is obtained by addition of 0.005% or more, but the content exceeding 0.03% lowers the toughness of the base metal and the weld heat affected zone, so Ti is 0.005 to 0.03%. The range is preferable.
Ｃｕ：０．０１〜０．５％、Ｎｉ：０．０１〜１．０％、Ｃｒ：０．０１〜０．５％
Ｍｏ：０．０１〜０．５％、Ｖ：０．００１〜０．１％、Ｂ：、０．００３％以下、Ｃａ：０．００５％以下、ＲＥＭ：０．０１％以下
Ｃｕ，Ｎｉ、Ｃｒ、Ｍｏ、Ｖ、Ｂはいずれも鋼の焼入れ性を高める元素である。圧延後の強度アップに直接寄与するとともに、靭性、高温強度、あるいは耐候性などの機能向上のために添加するが、過度の添加は靭性や溶接性を劣化させるため、それぞれ上限を０．５％、１．０％、０．５％、０．５％、０．１％、０．００３％とする。
Cu: 0.01-0.5%, Ni: 0.01-1.0%, Cr: 0.01-0.5%
Mo: 0.01 to 0.5%, V: 0.001 to 0.1%, B :, 0.003% or less, Ca: 0.005% or less, REM: 0.01% or less Cu, Ni, Cr, Mo, V, and B are all elements that enhance the hardenability of steel. It contributes directly to strength improvement after rolling, and is added to improve functions such as toughness, high-temperature strength, or weather resistance, but excessive addition degrades toughness and weldability, so the upper limit is 0.5% respectively. 1.0%, 0.5%, 0.5%, 0.1%, 0.003%.
一方、Ｃｕ，Ｎｉ、Ｃｒ、Ｍｏは添加量が０．０１％未満であるとその効果が現れないため、０．０１％以上の添加とする。また、Ｖは０．００１％未満であるとその効果が現れないため、０．００１％以上の添加とする。 On the other hand, if Cu, Ni, Cr, and Mo are added in an amount of less than 0.01%, the effect does not appear, so 0.01% or more is added. Further, if V is less than 0.001%, the effect does not appear, so 0.001% or more is added.
Ｃａ：０．００５％以下、ＲＥＭ：０．０１％以下
Ｃａ，ＲＥＭは溶接熱影響部の組織は微細化し靭性を向上させる、添加しても本発明の効果が損なわれることはないので必要に応じて添加してもよい。しかし、過度に添加すると、粗大な介在物を形成し母材の靭性を劣化させるので、添加量の上限をそれぞれ０．００５％、０．０１％とする。
Ca: 0.005% or less, REM: 0.01% or less Ca, REM is necessary because the structure of the weld heat-affected zone is refined to improve toughness, and even if added, the effect of the present invention is not impaired. It may be added accordingly. However, if added excessively, coarse inclusions are formed and the toughness of the base material is deteriorated, so the upper limits of the addition amount are made 0.005% and 0.01%, respectively.
本発明鋼を得るための製造条件については特に限定しないが、例えば、３層の場合、上記成分系の鋼素材を９００〜１２００℃の温度に加熱し、板厚中央部がＡｒ３点以上の温度で累積圧下率３０％以上、Ａｒ３点以下Ａｒ３点―６０℃以上の温度域において累積圧下率３０％以上の圧延を行った後、２℃／ｓ以上の冷却速度にて６００℃以下まで冷却することによって、脆性き裂伝播停止特性に優れた厚さ５０ｍｍ以上の厚鋼板を得ることができる。 The production conditions for obtaining the steel of the present invention are not particularly limited. For example, in the case of three layers, the steel material of the above component system is heated to a temperature of 900 to 1200 ° C., and the central portion of the plate thickness is Ar 3 or more Rolling at a cumulative reduction rate of 30% or more at a temperature, Ar 3 points or less, Ar 3 points at a temperature range of 60 ° C or more, and then rolling at a cumulative reduction rate of 30% or more, and 600 ° C or less at a cooling rate of 2 ° C / s or more. By cooling to 50 mm, a thick steel plate having a thickness of 50 mm or more excellent in brittle crack propagation stopping characteristics can be obtained.
ここで、鋼素材の加熱温度を９００〜１２００℃としたのは、加熱温度が９００℃以下であると圧延能率が低下し、加熱温度が１２００℃以上であるとオーステナイト粒が粗大化し、靭性の低下を招くためである。 Here, the heating temperature of the steel material is set to 900 to 1200 ° C., when the heating temperature is 900 ° C. or less, the rolling efficiency is lowered, and when the heating temperature is 1200 ° C. or more, the austenite grains are coarsened and the toughness is increased. This is to cause a decrease.
また、板厚中央部がＡｒ３点以上の温度で累積圧下率３０％以上、Ａｒ３点以下Ａｒ３点―６０℃以上の温度域において累積圧下率３０％以上の圧延を行うのは、所望の集合組織を得るためである。 In addition, it is desirable to perform rolling with a cumulative reduction ratio of 30% or more at a temperature of the central part of the sheet thickness of Ar 3 points or more and a cumulative reduction ratio of 30% or more in a temperature range of Ar 3 points or less, Ar 3 points to 60 ° C. or more. It is for obtaining the texture of.
この圧延を行うことにより、板厚中央部における圧延面での（１００）面Ｘ線強度比が２．０以上で、かつ板厚１／４における圧延面での（１１０）面Ｘ線強度比が１．５以上の集合組織を得ることができる。 By performing this rolling, the (100) plane X-ray intensity ratio at the rolled surface at the center of the sheet thickness is 2.0 or more, and the (110) plane X-ray intensity ratio at the rolled surface at the sheet thickness ¼. A texture of 1.5 or more can be obtained.
なお、上の条件はＡｒ３点―６０℃以下の圧延を行うことを制限するものではなく、圧延温度が規定の温度域より低下しても規定する温度域で３０％以上の圧下がおこなわれていればよい。 Note that the above conditions do not limit the rolling of Ar 3 point-60 ° C or lower, and even if the rolling temperature falls below the specified temperature range, a reduction of 30% or more is performed in the specified temperature range. It only has to be.
さらに、圧延が終了した鋼板を２℃／ｓ以上の冷却速度にて６００℃以下まで冷却するのは、２相域圧延によって導入された加工集合組織が再結晶するのを防ぐためである。 Furthermore, the steel sheet that has been rolled is cooled to 600 ° C. or less at a cooling rate of 2 ° C./s or more in order to prevent the work texture introduced by the two-phase region rolling from being recrystallized.
尚、板厚５０ｍｍ未満では本発明の鋼板を適用しなくても脆性き裂の伝播を停止させることが可能であるので本発明は対象を板厚５０ｍｍ以上の厚鋼板とする。いうまでもなく、本発明を適用する鋼板は、板厚５０ｍｍ未満であっても優れた脆性亀裂伝播停止特性を有する。 In addition, if the thickness is less than 50 mm, it is possible to stop the propagation of a brittle crack without applying the steel plate of the present invention, and therefore the present invention targets a thick steel plate having a thickness of 50 mm or more. Needless to say, the steel sheet to which the present invention is applied has excellent brittle crack propagation stopping characteristics even when the thickness is less than 50 mm.
表１に示す各組成の鋼を、転炉で溶製し、連続鋳造法で厚さ２８０ｍｍの鋼素材（スラブ）とした（鋼Ｎｏ．Ａ〜Ｉ）。これらの鋼素材を用いて板厚５０〜７０ｍｍの鋼板に熱間圧延し、板Ｎｏ．１〜３０の供試鋼を得た。 Steels having respective compositions shown in Table 1 were melted in a converter and used as a steel material (slab) having a thickness of 280 mm by a continuous casting method (steel Nos. A to I). These steel materials were hot-rolled to a steel plate having a thickness of 50 to 70 mm. 1-30 test steels were obtained.
これらの厚鋼板について、板厚の１／４部よりΦ１４のＪＩＳ１４Ａ号試験片を採取し、引張試験を行い、降伏点（ＹＳ）、引張強さ（ＴＳ）を測定した。また、板厚の１／４ｔ部よりＪＩＳ４号衝撃試験片を採取し、シャルピー試験を行って、破面遷移温度（ｖＴｒｓ）を求めた。 About these thick steel plates, the JIS14A test piece of (PHI) 14 was extract | collected from 1/4 part of plate | board thickness, the tensile test was done, and the yield point (YS) and the tensile strength (TS) were measured. Further, a JIS No. 4 impact test piece was collected from a 1/4 t portion of the plate thickness, and a Charpy test was performed to determine the fracture surface transition temperature (vTrs).
また、鋼板の集合組織を評価するため、所定の位置における圧延面での（１００）面Ｘ線強度比および（１１０）面Ｘ線強度比を測定した。ここで、面強度比とはランダム方位標準サンプルとの指定方位面のＸ線強度比である。 Further, in order to evaluate the texture of the steel sheet, the (100) plane X-ray intensity ratio and the (110) plane X-ray intensity ratio at the rolling surface at predetermined positions were measured. Here, the plane intensity ratio is the X-ray intensity ratio of the designated azimuth plane with the random azimuth standard sample.
さらに、これらの厚鋼板の板厚方向の脆性き裂伝播停止特性を評価するため、図１に示す温度勾配型ＥＳＳＯ試験を行い、−１０℃における脆性き裂伝播停止靭性Ｋｃａを求めた。 Furthermore, in order to evaluate the brittle crack propagation stopping characteristics in the plate thickness direction of these thick steel plates, the temperature gradient type ESSO test shown in FIG. 1 was conducted to determine the brittle crack propagation stopping toughness Kca at −10 ° C.
なお、以下の温度勾配型ＥＳＳＯ試験結果において、従来より脆性き裂の伝播を停止可能とされているＫｃａ値が６０００Ｎ／ｍｍ３／２以上の場合に優れた脆性き裂伝播停止特性を有するとした。 In addition, in the following temperature gradient type ESSO test results, when the Kca value, which is conventionally capable of stopping the propagation of a brittle crack, has excellent brittle crack propagation stopping characteristics when the Kca value is 6000 N / mm 3/2 or more, did.
表２に鋼板の引張試験結果、シャルピー破面遷移温度、および温度勾配型ＥＳＳＯ試験時の板厚内位置によるき裂伝播方向の角度の差、および−１０℃におけるＫｃａ値を示す。き裂伝播方向の角度の差が本発明の範囲内の鋼板では、良好なＫｃａ値を示した。 Table 2 shows the tensile test results of the steel sheet, the Charpy fracture surface transition temperature, the angle difference in the crack propagation direction depending on the position within the thickness during the temperature gradient type ESSO test, and the Kca value at -10 ° C. A steel plate having an angle difference in the crack propagation direction within the range of the present invention showed a good Kca value.
表３に鋼板の引張試験結果、シャルピー破面遷移温度、板厚中央部の（１００）面Ｘ線強度比、板厚１／４部の（１１０）Ｘ線強度比、および温度勾配型ＥＳＳＯ試験時の板厚中央部および１／４部のき裂伝播方向の角度の差、および−１０℃におけるＫｃａ値を示す。 Table 3 shows steel plate tensile test results, Charpy fracture surface transition temperature, (100) plane X-ray intensity ratio at the center of the plate thickness, (110) X-ray intensity ratio at ¼ zone, and temperature gradient type ESSO test. The difference in the angle of the crack propagation direction at the center of the plate thickness and ¼ part at the time and the Kca value at −10 ° C.
Ｘ線強度比およびき裂伝播方向の角度の差が本発明の範囲内の鋼板では、良好なＫｃａ値を示した。 The steel sheet in which the difference in the X-ray intensity ratio and the crack propagation direction angle is within the range of the present invention showed a good Kca value.
表４に鋼板の引張試験結果、シャルピー破面遷移温度、板厚中央部の（１１０）面Ｘ線強度比、板厚１／４部の（１００）Ｘ線強度比、および温度勾配型ＥＳＳＯ試験時の板厚中央部および１／４部のき裂伝播方向の角度の差、および−１０℃におけるＫｃａ値を示す。 Table 4 shows steel plate tensile test results, Charpy fracture surface transition temperature, (110) plane X-ray intensity ratio at the center of the plate thickness, (100) X-ray intensity ratio at 1/4 plate thickness, and temperature gradient type ESSO test. The difference in the angle of the crack propagation direction at the center of the plate thickness and ¼ part at the time and the Kca value at −10 ° C.
Ｘ線強度比およびき裂伝播方向の角度の差が本発明の範囲内の鋼板では、良好なＫｃａ値を示した。 The steel sheet in which the difference in the X-ray intensity ratio and the crack propagation direction angle is within the range of the present invention showed a good Kca value.
表５に鋼板の引張試験結果、シャルピー破面遷移温度、（１１０）面および（１００）面のＸ線強度比ならびにそれぞれの強度比を示す位置、および温度勾配型ＥＳＳＯ試験時のき裂伝播方向の角度の差、および−１０℃におけるＫｃａ値を示す。 Table 5 shows steel plate tensile test results, Charpy fracture surface transition temperature, X-ray intensity ratio of (110) plane and (100) plane, positions indicating the respective strength ratios, and crack propagation direction during temperature gradient type ESSO test The difference of the angle of and Kca value in -10 degreeC are shown.
Ｘ線強度比およびき裂伝播方向の角度の差が本発明の範囲内の鋼板では、良好なＫｃａ値を示した。 The steel sheet in which the difference in the X-ray intensity ratio and the crack propagation direction angle is within the range of the present invention showed a good Kca value.
本発明鋼は、板厚中央部を含み、板厚中央部での圧延面での（１００）面Ｘ線強度比が２．０以上の層状の領域を板厚中央部とし、その上下に、板厚１／４部（板厚３／４部）を含み、当該位置での圧延面での（１１０）面Ｘ線強度比が１．５以上の層状の領域を有する、当該領域内では、板厚方向に脆性亀裂伝播方向が一定で、隣接する層状領域間では脆性亀裂伝播方向が相違する、３層を重ねた構造のものである。 The steel of the present invention includes a plate thickness central portion, and a (100) plane X-ray intensity ratio at the rolled surface at the plate thickness central portion is a layered region having a thickness of 2.0 or more as a plate thickness central portion. In the said area | region which has plate | board thickness 1/4 part (plate | board thickness 3/4 part) and has the layered area | region whose (110) plane X-ray intensity ratio in the rolling surface in the said position is 1.5 or more, The structure has a three-layer structure in which the brittle crack propagation direction is constant in the plate thickness direction and the brittle crack propagation direction is different between adjacent layered regions.
Claims (6)
求項１記載の脆性き裂伝播停止特性に優れた厚さ５０ｍｍ以上の厚鋼板。 The thick steel plate having a thickness of 50 mm or more and excellent in brittle crack propagation stopping characteristics according to claim 1, wherein the layered region in which the brittle crack propagation direction is a constant direction is three or more layers.
）面Ｘ線強度比が１．５以上の層状の領域を板厚方向に交互にｎ層（但し、ｎは３以上の
奇数）重ねた構造を特徴とする請求項１に記載の脆性き裂伝播停止特性に優れた厚さ５０
ｍｍ以上の厚鋼板。 A layered region having a (100) plane X-ray intensity ratio of 2.0 or more on the rolling surface and (110) on the rolling surface
2) A brittle crack according to claim 1, wherein a layered region having an in-plane X-ray intensity ratio of 1.5 or more is alternately stacked in the thickness direction by n layers (where n is an odd number of 3 or more). Thickness 50 with excellent propagation stop characteristics
Thick steel plate of mm or more.
強度比が２．０以上であることを特徴とする請求項３記載の脆性き裂伝播停止特性に優れ
た厚さ５０ｍｍ以上の厚鋼板。 4. The brittleness according to claim 3, wherein n is 3 and the (100) plane X-ray intensity ratio at the rolled surface in the sheet thickness of the layered region including the center part of the sheet thickness is 2.0 or more. A steel plate with a thickness of 50 mm or more with excellent crack propagation stopping characteristics
．５〜２．０％、Ａｌ：０．００５〜０．０８％、Ｐ：０．０３％以下，Ｓ：０．０１％
以下、Ｎ：０．００６０％以下を含有し、残部がＦｅおよび不可避的不純物からなる請求
項１〜４のいずれかに記載の脆性き裂伝播停止特性に優れた厚さ５０ｍｍ以上の厚鋼板。 Steel composition is mass%, C: 0.03-0.2%, Si: 0.03-0.5%, Mn: 0
. 5 to 2.0%, Al: 0.005 to 0.08%, P: 0.03% or less, S: 0.01%
The thick steel plate having a thickness of 50 mm or more excellent in brittle crack propagation stopping property according to any one of claims 1 to 4, wherein N: 0.0060% or less, and the balance is Fe and inevitable impurities.
：０．００５〜０．０３％、Ｃｕ：０．０１〜０．５％、Ｎｉ：０．０１〜１．０％、Ｃ
ｒ：０．０１〜０．５％、Ｍｏ：０．０１〜０．５％、Ｖ：０．００１〜０．１％、Ｂ：
、０．００３％以下、Ｃａ：０．００５％以下、ＲＥＭ：０．０１％以下のいずれか１種
、または２種以上を含有することを特徴とする請求項５に記載の脆性き裂伝播停止特性に
優れた厚さ５０ｍｍ以上の厚鋼板。 In addition to the above components, the steel composition is further mass%, Nb: 0.005 to 0.05%, Ti
: 0.005-0.03%, Cu: 0.01-0.5%, Ni: 0.01-1.0%, C
r: 0.01-0.5%, Mo: 0.01-0.5%, V: 0.001-0.1%, B:
, 0.003% or less, Ca: 0.005% or less, REM: 0.01% or less, or two or more kinds of fragile crack propagation according to claim 5 A steel plate with a thickness of 50 mm or more with excellent stopping characteristics.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2007049384A JP5061649B2 (en) | 2007-02-28 | 2007-02-28 | Thick steel plate with a thickness of 50 mm or more with excellent brittle crack propagation stopping characteristics |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2007049384A JP5061649B2 (en) | 2007-02-28 | 2007-02-28 | Thick steel plate with a thickness of 50 mm or more with excellent brittle crack propagation stopping characteristics |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2008214654A JP2008214654A (en) | 2008-09-18 |
| JP5061649B2 true JP5061649B2 (en) | 2012-10-31 |
Family
ID=39835064
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2007049384A Active JP5061649B2 (en) | 2007-02-28 | 2007-02-28 | Thick steel plate with a thickness of 50 mm or more with excellent brittle crack propagation stopping characteristics |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP5061649B2 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5304520B2 (en) * | 2009-07-31 | 2013-10-02 | Ｊｆｅスチール株式会社 | Evaluation method of brittle fracture propagation stop performance of thick steel plate |
| JP5949114B2 (en) * | 2011-11-28 | 2016-07-06 | Ｊｆｅスチール株式会社 | Manufacturing method of structural high strength thick steel plate with excellent brittle crack propagation stopping characteristics |
| JP5713135B1 (en) | 2013-11-19 | 2015-05-07 | 新日鐵住金株式会社 | steel sheet |
| KR101523229B1 (en) * | 2013-11-28 | 2015-05-28 | 한국생산기술연구원 | Metal material with improved low temperature property and manufacturing method thereof |
| CN112501504B (en) * | 2020-11-13 | 2022-03-01 | 南京钢铁股份有限公司 | BCA 2-grade container ship crack arrest steel plate and manufacturing method thereof |
| WO2022259957A1 (en) * | 2021-06-10 | 2022-12-15 | Ｊｆｅスチール株式会社 | Method for evaluating brittle crack arrest performance of thick steel plate |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3548349B2 (en) * | 1996-09-18 | 2004-07-28 | 新日本製鐵株式会社 | Structural steel sheet with excellent brittle fracture resistance after plastic deformation |
| JP5064150B2 (en) * | 2006-12-14 | 2012-10-31 | 新日本製鐵株式会社 | High strength steel plate with excellent brittle crack propagation stopping performance |
-
2007
- 2007-02-28 JP JP2007049384A patent/JP5061649B2/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| JP2008214654A (en) | 2008-09-18 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP5445720B1 (en) | High strength steel plate with excellent arrestability | |
| JP5574059B2 (en) | High-strength H-section steel with excellent low-temperature toughness and method for producing the same | |
| JP5733425B2 (en) | High-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same | |
| JP5304925B2 (en) | Structural high-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same | |
| JP5434145B2 (en) | Structural high-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same | |
| JP5151090B2 (en) | Structural high-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same | |
| JP5598617B1 (en) | High strength thick steel plate for high heat input welding with excellent brittle crack propagation stopping characteristics and method for producing the same | |
| JP4946512B2 (en) | Structural high-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same | |
| JP5304924B2 (en) | Structural high-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same | |
| JP5181496B2 (en) | Structural high-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same | |
| JP2018024905A (en) | Structural high strength thick steel plate excellent in brittle crack arrest property and production method thereof | |
| JP5061649B2 (en) | Thick steel plate with a thickness of 50 mm or more with excellent brittle crack propagation stopping characteristics | |
| JP5181460B2 (en) | Structural high-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same | |
| JP5035199B2 (en) | Structural high-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same | |
| JP5034392B2 (en) | Structural high-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same | |
| JP5812193B2 (en) | Structural high-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same | |
| JP2008111166A (en) | High strength thick steel plate for structural use having excellent brittle crack arrest property, and its production method | |
| JP6112265B2 (en) | High-strength extra heavy steel plate and method for producing the same | |
| JP5733424B2 (en) | Structural high-strength thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same | |
| JP6477743B2 (en) | High-strength ultra-thick steel plate excellent in brittle crack propagation stopping characteristics and weld heat-affected zone toughness and method for producing the same | |
| JP6338022B2 (en) | High-strength extra-thick steel plate with excellent brittle crack propagation stopping characteristics and method for producing the same | |
| JP7468800B2 (en) | Steel plate and its manufacturing method | |
| JP5949114B2 (en) | Manufacturing method of structural high strength thick steel plate with excellent brittle crack propagation stopping characteristics |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20090821 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20100519 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20111028 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20111108 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20120105 |
|
| RD03 | Notification of appointment of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7423 Effective date: 20120321 |
|
| RD04 | Notification of resignation of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7424 Effective date: 20120327 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20120710 |
|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20120723 |
|
| R150 | Certificate of patent or registration of utility model |
Ref document number: 5061649 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20150817 Year of fee payment: 3 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |