JP4969275B2 - High tensile steel plate with excellent toughness of weld heat affected zone - Google Patents
High tensile steel plate with excellent toughness of weld heat affected zone Download PDFInfo
- Publication number
- JP4969275B2 JP4969275B2 JP2007062471A JP2007062471A JP4969275B2 JP 4969275 B2 JP4969275 B2 JP 4969275B2 JP 2007062471 A JP2007062471 A JP 2007062471A JP 2007062471 A JP2007062471 A JP 2007062471A JP 4969275 B2 JP4969275 B2 JP 4969275B2
- Authority
- JP
- Japan
- Prior art keywords
- steel plate
- inclusions
- tensile
- thick steel
- 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
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Description
本発明は、橋梁や高層建造物、船舶などの溶接構造物に適用される鋼板に関し、殊に大入熱溶接後の溶接熱影響部（以下、単に「ＨＡＺ」と呼ぶことがある）の靭性に優れた厚鋼板に関するものである。 The present invention relates to a steel sheet applied to a welded structure such as a bridge, a high-rise building, or a ship, and in particular, the toughness of a weld heat affected zone (hereinafter sometimes simply referred to as “HAZ”) after high heat input welding. It is related to the thick steel plate excellent in.
近年、上記各種溶接構造物の大型化に伴い、板厚が５０ｍｍ以上である厚鋼板の溶接が不可避となっている。このため、あらゆる分野において、溶接施工効率の向上や施工コストの低減を目的として、大入熱溶接が指向される状況である。 In recent years, with the increase in size of the above various welded structures, it is inevitable to weld thick steel plates having a plate thickness of 50 mm or more. For this reason, in all fields, high heat input welding is aimed at for the purpose of improving welding construction efficiency and reducing construction costs.
しかしながら、大入熱溶接を行うと、ＨＡＺが高温のオーステナイト領域まで加熱されてから徐冷されるので、加熱時にオーステナイト粒成長、徐冷時におけるオーステナイト粒界からの粒界フェライト生成に起因してＨＡＺの組織が粗大化し、その部分の靭性が劣化しやすいという問題がある。こうしたことから、大入熱溶接を実施しても、ＨＡＺにおける靭性（以下、「ＨＡＺ靭性」と呼ぶことがある）を高い水準に保つ技術の確立が望まれている。 However, when high heat input welding is performed, the HAZ is heated to the high temperature austenite region and then gradually cooled. Therefore, it is caused by austenite grain growth during heating and generation of grain boundary ferrite from the austenite grain boundary during annealing. There is a problem that the structure of the HAZ becomes coarse and the toughness of the portion tends to deteriorate. For these reasons, it is desired to establish a technique for maintaining the toughness in HAZ (hereinafter sometimes referred to as “HAZ toughness”) at a high level even when high heat input welding is performed.
大入熱溶接時におけるＨＡＺ靭性を確保するために適用される代表的な技術として、酸化物、硫化物或いは窒化物といった介在物を起点とした粒内変態促進による組織微細化技術が挙げられる。この技術は、溶接終了後の冷却時において、粒内に存在する介在物によって微細な変態組織を発達させ、粗大な粒界フェライト生成を抑制し、これによってＨＡＺ靭性を確保するものである。 A typical technique applied to ensure HAZ toughness during high heat input welding is a structure refinement technique by promoting intragranular transformation starting from inclusions such as oxides, sulfides or nitrides. In this technique, during the cooling after the end of welding, a fine transformation structure is developed by inclusions present in the grains, thereby suppressing the formation of coarse grain boundary ferrite, thereby ensuring the HAZ toughness.
こうした技術のうち、例えば酸化物を活用した技術として、特許文献１には、Ｏ濃度とＣａ濃度を制御することによって、ＭｎＳを複合析出させたＴｉ含有酸化物を微細に分散させ、それを核とする粒内フェライト変態を促進する（即ち、粗大な粒界フェライト生成を抑制する）技術が提案されている。また、特許文献２では、ＴｉとＭｇとを複合添加した系で、粒内フェライト核となるＴｉ含有酸化物とＭｎＳの複合体を生成させることによって、ＨＡＺ靭性に優れた溶接用高張力鋼を得る技術が開示されている。 Among these techniques, for example, as a technique utilizing an oxide, Patent Document 1 discloses that a Ti-containing oxide in which MnS is complex-precipitated is finely dispersed by controlling an O concentration and a Ca concentration, and is used as a nucleus. A technique for promoting the intragranular ferrite transformation (that is, suppressing the formation of coarse grain boundary ferrite) has been proposed. Further, in Patent Document 2, a high strength steel for welding excellent in HAZ toughness is produced by generating a composite of Ti-containing oxide and MnS that becomes an intragranular ferrite nucleus in a system in which Ti and Mg are added in combination. Obtaining techniques are disclosed.
また硫化物を活用した技術として、例えば特許文献３には、Ｃａを１〜４９原子％含むＭｎ硫化物を分散させ、粒内フェライト変態を促進することによって、ＨＡＺ靭性に優れた溶接用高張力鋼を得る技術が提案されている。 As a technique utilizing sulfide, for example, Patent Document 3 discloses a high tensile strength for welding excellent in HAZ toughness by dispersing Mn sulfide containing 1 to 49 atomic% of Ca and promoting intragranular ferrite transformation. Techniques for obtaining steel have been proposed.
更に、窒化物を活用した技術として、例えば特許文献４には、ＴｉＮ等を複合析出させたＢＮをフェライト変態の核として利用し、ＨＡＺ靭性を改善させる技術が提案されている。 Further, as a technique using nitride, for example, Patent Document 4 proposes a technique for improving HAZ toughness by using BN obtained by composite precipitation of TiN or the like as a nucleus of ferrite transformation.
酸化物、硫化物、窒化物等の介在物が粒内変態の核として機能するためには、直径が大きい方が有利であり、比較的直径が小さい介在物では粒内変態に寄与しないことになる。しかしながら、これまで提案されている技術では、粒内変態の核として機能する介在物が十分に存在しているとは言えず、必要なＨＡＺ靭性が必ずしも得られていないというのが実情である。
本発明は上記の様な事情に着目してなされたものであって、その目的は、化学成分組成を適切に調整すると共に、酸化物、硫化物或いは窒化物等の介在物の形態および個数を適切に制御することによって、大入熱溶接においても良好なＨＡＺ靭性を確保することのできる高張力厚鋼板を提供することにある。 The present invention has been made paying attention to the circumstances as described above, and its purpose is to appropriately adjust the chemical composition and to change the form and number of inclusions such as oxides, sulfides or nitrides. An object of the present invention is to provide a high-strength thick steel plate capable of ensuring good HAZ toughness even in high heat input welding by appropriately controlling.
上記目的を達成し得た本発明の高張力厚鋼板とは、Ｃ：０．０３〜０．１２％（「質量％」の意味。以下同じ）、Ｓｉ：０．４０％以下（０％を含まない）、Ｍｎ：１．０〜２．０％、Ｐ：０．０３％以下（０％を含まない）、Ｓ：０．００１〜０．０２５％、Ａｌ：０．０５％以下（０％を含まない）、Ｔｉ：０．００５〜０．１０％、Ｎ：０．００４０〜０．０３０％およびＯ：０．０００５〜０．０１０％を夫々含有し、残部が鉄および不可避的不純物からなる厚鋼板であって、表面に多数の凹凸を有する介在物のうち、凹部の最小曲率半径が０．１〜２．０μｍであって、円相当直径で０．２〜５μｍの酸化物、硫化物および窒化物の１種または２種以上からなる介在物が、観察視野１ｍｍ2当りで１００個以上存在する点に要旨を有するものである。 The high-tensile steel plate of the present invention that has achieved the above-mentioned object is C: 0.03 to 0.12% (meaning “mass%”, the same applies hereinafter), Si: 0.40% or less (0% Not included), Mn: 1.0 to 2.0%, P: 0.03% or less (not including 0%), S: 0.001 to 0.025%, Al: 0.05% or less (0 %), Ti: 0.005 to 0.10%, N: 0.0040 to 0.030% and O: 0.0005 to 0.010%, respectively, the balance being iron and inevitable impurities An oxide having a minimum curvature radius of 0.1 to 2.0 μm and an equivalent circle diameter of 0.2 to 5 μm. sulfides and inclusions consisting of one or more nitride, have a gist in that there more than 100 in the observation field of view 1 mm 2 per Is shall.
尚、上記「円相当直径」とは、酸化物、硫化物或いは窒化物等の介在物の大きさに着目して、その面積が等しくなる様に想定した円の直径を求めたものである。また本発明で対象とする介在物は、酸化物、硫化物、或いは窒化物のいずれかの単体からなる介在物は勿論のこと、これらの２種以上が複合析出したものをも含むものである。 The “equivalent circle diameter” refers to the diameter of a circle that is assumed to have the same area by paying attention to the size of inclusions such as oxide, sulfide, or nitride. The inclusions targeted in the present invention include not only inclusions consisting of any one of oxides, sulfides, and nitrides, but also those in which two or more of these are complex precipitated.
本発明の高張力厚鋼板においては、下記（１）式の関係を満足するものであることが好ましく、こうした要件を満足させることによって、上記のような形態の介在物を容易に分散させることができる。
０．０５≦９×［Ｏ］／（［Ｓ］＋１０×［Ｎ］）≦１．２０…（１）
但し、［Ｏ］，［Ｓ］および［Ｎ］は、夫々Ｏ，ＳおよびＮの含有量（質量％）を示す。
In the high-tensile thick steel plate of the present invention, it is preferable that the relationship of the following formula (1) is satisfied. By satisfying these requirements, inclusions of the above-described form can be easily dispersed. it can.
0.05 ≦ 9 × [O] / ([S] + 10 × [N]) ≦ 1.20 (1)
However, [O], [S] and [N] indicate the contents (mass%) of O, S and N, respectively.
本発明の高張力厚鋼板には、必要によって、更に（ａ）ＲＥＭ：０．０００１〜０．０５％、（ｂ）Ｚｒ：０．０００１〜０．０５％、（ｃ）Ｍｇ０．０００１〜０．００５％および／またはＣａ：０．０００１〜０．００５％、（ｄ）Ｃｕ：０．１〜１．５％、Ｎｉ：０．１〜１．５％、Ｃｒ：０．１〜１．５％およびＭｏ：０．１〜１．５％よりなる群から選ばれる１種以上、（ｅ）Ｎｂ：０．０１〜０．０６および／またはＶ：０．０１〜０．１％、（ｆ）Ｂ：０．００１〜０．００５％、等を含有させることも有用であり、こうした元素を含有させることによってその種類に応じて厚鋼板の特性が更に改善されることになる。 In the high-tensile thick steel plate of the present invention, if necessary, (a) REM: 0.0001 to 0.05%, (b) Zr: 0.0001 to 0.05%, (c) Mg 0.0001 to 0 0.005% and / or Ca: 0.0001-0.005%, (d) Cu: 0.1-1.5%, Ni: 0.1-1.5%, Cr: 0.1-1. 1 or more types selected from the group consisting of 5% and Mo: 0.1-1.5%, (e) Nb: 0.01-0.06 and / or V: 0.01-0.1%, ( f) It is also useful to contain B: 0.001 to 0.005%, etc., and the inclusion of such an element will further improve the properties of the thick steel plate depending on the type.
本発明によれば、鋼板の化学成分組成を適切な範囲内に収めると共に、酸化物、硫化物或いは窒化物を少なくとも含む介在物の形態、およびその個数を適切に制御することによって、粒内変態に寄与する介在物個数を増大でき、ＨＡＺの靭性改善を図った高張力厚鋼板が実現できた。 According to the present invention, the chemical composition of the steel sheet falls within an appropriate range, and the form of inclusions containing at least an oxide, sulfide or nitride, and the number of the inclusions are controlled appropriately, thereby allowing intragranular transformation. The number of inclusions contributing to the increase in the thickness of the steel sheet can be increased, and a high-tensile steel plate with improved HAZ toughness can be realized.
一般的には、介在物を起点とした粒内変態には、直径の大きい介在物の存在が有利であるため、直径が比較的小さい介在物は粒内変態に寄与せず、十分なＨＡＺ靭性が得られないことになる。本発明者らは、こうした着想の下で、大入熱溶接において、優れたＨＡＺ靭性を実現するために、酸化物、硫化物或いは窒化物等の介在物の形態と粒内変態との関係について、様々な角度から検討した。 In general, inclusions having a large diameter are advantageous for intragranular transformation starting from inclusions. Therefore, inclusions having a relatively small diameter do not contribute to intragranular transformation, and have sufficient HAZ toughness. Will not be obtained. Under such an idea, the inventors of the present invention are concerned with the relationship between the form of inclusions such as oxides, sulfides, and nitrides and intragranular transformation in order to achieve excellent HAZ toughness in high heat input welding. Considered from various angles.
その結果、鋳造時に生成する酸化物、硫化物、窒化物といった二次介在物の複合析出によって、表面に多数の凹凸が形成される介在物のうち、凹部の最小曲率半径が０．１〜２．０μｍであって、円相当直径で０．２〜５μｍの介在物は、粒内変態の起点として効果的に機能することが判明した。そして、こうした介在物が所定量存在するように制御したものでは、優れたＨＡＺ靭性を発揮する溶接用高張力厚鋼板が実現できることを見出し、本発明を完成した。 As a result, the minimum curvature radius of the concave portion is 0.1 to 2 among the inclusions in which many irregularities are formed on the surface by complex precipitation of secondary inclusions such as oxides, sulfides, and nitrides generated during casting. It was found that inclusions with a diameter of 0.0 μm and an equivalent circle diameter of 0.2 to 5 μm function effectively as the starting point of intragranular transformation. And what controlled so that these inclusions existed in predetermined amount discovered that the high-tensile steel plate for welding which exhibits the outstanding HAZ toughness was realizable, and completed this invention.
介在物の表面に上記のような凹凸を形成させるには、鋳造時の凝固過程で酸化物、硫化物、窒化物等の介在物の表面に複合析出する硫化物、窒化物といった二次介在物を利用することが効果的であり、こうした観点から、鋳造時に凝固が進行する１４５０〜１５００℃の温度範囲における冷却時間を６０〜３００秒に制御すればよい。即ち、上記温度範囲を所定の時間内で冷却することによって、二次介在物の複合析出形態が制御され、凹凸が効果的に形成される。冷却時間が６０秒よりも短いと、十分な複合析出量を確保できず、３００秒より長いと、二次析出物が酸化物、硫化物、窒化物といった介在物を均一に覆うように複合析出し、凹凸が得られなくなる。 In order to form the above irregularities on the surface of inclusions, secondary inclusions such as sulfides and nitrides that are complex-precipitated on the surface of inclusions such as oxides, sulfides and nitrides during the solidification process during casting. From such a viewpoint, the cooling time in the temperature range of 1450 to 1500 ° C. where solidification proceeds during casting may be controlled to 60 to 300 seconds. That is, by cooling the temperature range within a predetermined time, the complex precipitation form of secondary inclusions is controlled, and irregularities are effectively formed. If the cooling time is shorter than 60 seconds, a sufficient amount of composite precipitation cannot be secured, and if it is longer than 300 seconds, the composite precipitates so that secondary precipitates uniformly cover inclusions such as oxides, sulfides, and nitrides. And unevenness cannot be obtained.
ＨＡＺ靭性に優れた高張力厚鋼板を得るためには、上記のような形態の介在物を、鋼中に観察視野１ｍｍ2当り１００個（以下、「１００個／ｍｍ2」と記すことがある）以上存在させる必要がある。本発明で対象とする介在物の大きさは、円相当直径で０．２〜５．０μｍのものであるが、この大きさが０．２μｍより小さいと、必要な凹部が十分に形成されない。一方、５．０μｍを超えると、脆性破壊の起点となってＨＡＺ靭性を却って低下させることになる。また凹凸を有する介在物が、鋼中に１００個／ｍｍ2未満しか存在しない場合には、十分な粒内変態組織が得られず、ＨＡＺ靭性が低下することになる。 In order to obtain a high-tensile thick steel plate having excellent HAZ toughness, the inclusions having the above-described form may be described as 100 pieces in the steel per 1 mm 2 observation field (hereinafter referred to as “100 pieces / mm 2 ”). ) It is necessary to exist above. The size of the inclusions targeted in the present invention is a circle equivalent diameter of 0.2 to 5.0 [mu] m, but if this size is smaller than 0.2 [mu] m, the necessary recesses are not sufficiently formed. On the other hand, if it exceeds 5.0 μm, it becomes the starting point of brittle fracture and decreases the HAZ toughness. In addition, when there are less than 100 inclusions / mm 2 in the steel having irregularities, a sufficient intragranular transformation structure cannot be obtained, and the HAZ toughness is lowered.
上記のような凹部を有する介在物が粒内変態の促進に有効に機能する理由については、その全てを解明し得た訳ではないが、おそらく凹部でのフェライト変態核生成エネルギーの低下と考えることができた。またこうした観点から、凹部の最小曲率半径は０．１μｍ以上と規定したのである。しかしながら、凹部の最小曲率半径は２．０μｍを超えると、平滑な表面に近いものとなって凹部の効果が減少する。尚、凹部の最小曲率半径とは、後述の方法で測定される形状パラメータを意味し、この値が大きいと凹凸の形態が平坦になるものである。またこうした凹部は、曲率半径が小さいほどフェライト変態を促進するという理由から、「最小」の曲率半径が問題となるので、本発明では対象とする介在物の凹部の最小曲率半径を規定したのである。 The reason why inclusions with recesses as described above function effectively in promoting intragranular transformation has not been fully elucidated, but it is probably thought that the ferrite transformation nucleation energy in the recesses is reduced. I was able to. From this point of view, the minimum radius of curvature of the recess is defined as 0.1 μm or more. However, when the minimum radius of curvature of the recess exceeds 2.0 μm, the effect of the recess is reduced because it is close to a smooth surface. In addition, the minimum curvature radius of a recessed part means the shape parameter measured by the below-mentioned method, and when this value is large, the form of an unevenness | corrugation will become flat. In addition, since the concave portion has a problem that the minimum radius of curvature becomes a problem because the smaller the radius of curvature promotes ferrite transformation, the present invention defines the minimum radius of curvature of the concave portion of the target inclusion. .
本発明で対象とする介在物は上記した形態を有するものであるが、上記した要件を満足しないものでは、ＨＡＺ靭性には直接関係しないものとなる。即ち、介在物の表面に多数の凹凸があっても、上記要件を満足しないものではＨＡＺ靭性向上に大きな効果をもたらさないので、本発明で対象とする介在物とはならないのである。 The inclusions targeted in the present invention have the above-described form, but those that do not satisfy the above-described requirements are not directly related to the HAZ toughness. That is, even if there are many irregularities on the surface of the inclusions, those that do not satisfy the above requirements do not have a significant effect on improving the HAZ toughness, and therefore do not become inclusions targeted in the present invention.
次に、本発明の鋼板における成分組成について説明する。上記のように、本発明の鋼板は、介在物の形態や個数が上記の要件を満足していても、化学成分組成が適正範囲内になければ、ＨＡＺにおける優れた靭性を達成することができない。従って、本発明の厚鋼板では、介在物の分布状況が良好であることに加えて、夫々の化学成分の量が、以下に記載するような適正範囲内にあることも必要である。これらの成分の範囲限定理由は、下記の通りである。 Next, the component composition in the steel plate of the present invention will be described. As described above, the steel sheet of the present invention cannot achieve excellent toughness in HAZ unless the chemical composition is within an appropriate range even if the form and number of inclusions satisfy the above requirements. . Therefore, in the thick steel plate of the present invention, in addition to the good distribution of inclusions, the amount of each chemical component must be within an appropriate range as described below. The reasons for limiting the ranges of these components are as follows.
［Ｃ：０．０３〜０．１２％］
Ｃは、鋼板の強度を確保するために欠くことのできない元素であり、こうした効果を発揮させるためには０．０３％以上含有させる必要がある。好ましくは０．０４％以上である。しかしながら、Ｃ含有量が０．１２％を超えると、溶接時にＨＡＺに島状マルテンサイト相（ＭＡ相）が多く生成してＨＡＺの靭性劣化を招くことになる。従って、Ｃは０．１２％以下（好ましくは０．１０％以下）に抑える必要がある。
[C: 0.03-0.12%]
C is an element indispensable for securing the strength of the steel sheet, and in order to exert such effects, it is necessary to contain 0.03% or more. Preferably it is 0.04% or more. However, if the C content exceeds 0.12%, a large number of island martensite phases (MA phases) are generated in the HAZ during welding, leading to deterioration of the toughness of the HAZ. Therefore, C must be suppressed to 0.12% or less (preferably 0.10% or less).
［Ｓｉ：０．４０％以下（０％を含まない）］
Ｓｉは、固溶強化によって鋼板の強度を確保するのに有用な元素であるが、過剰に含有させると、溶接時にＨＡＺに島状マルテンサイト相（ＭＡ相）が多く生成してＨＡＺの靭性劣化を招くことになる。こうした観点から、Ｓｉ含有量は０．４０％以下にする必要があり、好ましくは０．３５％以下に抑える。
[Si: 0.40% or less (excluding 0%)]
Si is an element useful for securing the strength of a steel sheet by solid solution strengthening. However, if it is excessively contained, a large amount of island martensite phase (MA phase) is generated in the HAZ during welding, and the toughness of the HAZ deteriorates. Will be invited. From such a viewpoint, the Si content needs to be 0.40% or less, and is preferably suppressed to 0.35% or less.
［Ｍｎ：１．０〜２．０％］
Ｍｎは、鋼板の強度を確保する上で有用な元素であり、こうした効果を有効に発揮させるには、１．０％以上含有させる必要がある。好ましくは１．４％以上である。しかし、２．０％を超えて過剰に含有させるとＨＡＺの強度が上昇し過ぎて靭性が劣化するので、Ｍｎ含有量は２．０％以下とする。好ましくは１．８％以下である。
[Mn: 1.0 to 2.0%]
Mn is an element useful for ensuring the strength of the steel sheet, and in order to effectively exhibit such effects, it is necessary to contain 1.0% or more. Preferably it is 1.4% or more. However, if the content exceeds 2.0% excessively, the strength of the HAZ increases excessively and the toughness deteriorates, so the Mn content is set to 2.0% or less. Preferably it is 1.8% or less.
［Ｐ：０．０３％以下（０％を含まない）］
不純物元素であるＰは、粒界破壊を起こし易く靭性に悪影響を及ぼすので、その量はできるだけ少ないことが好ましい。靭性を確保するという観点からして、Ｐ含有量は０．０３％以下に抑制する必要があり、好ましくは０．０２％以下とする。しかし、工業的に、鋼中のＰを０％にすることは困難である。
[P: 0.03% or less (excluding 0%)]
P, which is an impurity element, easily causes grain boundary fracture, and adversely affects toughness. Therefore, the amount is preferably as small as possible. From the viewpoint of securing toughness, the P content needs to be suppressed to 0.03% or less, preferably 0.02% or less. However, industrially, it is difficult to make P in steel 0%.
［Ｓ：０．００１〜０．０２５％］
Ｓは、硫化物の生成に必須の元素であり、特に鋳造時の凝固過程で酸化物、硫化物、窒化物等の介在物の表面に硫化物として複合析出することにより、介在物表面の凹凸を形成する上で有効である。Ｓ含有量が０．００１％よりも少なくなると、必要な凹凸を形成するのに十分な複合析出量が得られないため、下限を０．００１％とした。また、Ｓ含有量が０．０２５％を超えると、介在物表面を均一に覆うよう硫化物が複合析出し、凹部の曲率半径が増大するため、粒内変態の促進効果が得られなくなる。こうしたことがら、Ｓ含有量の上限を０．０２５％とした。尚、Ｓ含有量の好ましい下限は０．００２％であり、好ましい上限は０．０２０％である。
[S: 0.001 to 0.025%]
S is an element indispensable for the formation of sulfides. In particular, unevenness on the surface of inclusions is caused by complex precipitation as sulfides on the surface of inclusions such as oxides, sulfides and nitrides during the solidification process during casting. It is effective in forming. If the S content is less than 0.001%, a composite precipitation amount sufficient to form the necessary irregularities cannot be obtained, so the lower limit was made 0.001%. On the other hand, if the S content exceeds 0.025%, sulfides are complex-precipitated so as to uniformly cover the inclusion surface, and the radius of curvature of the recesses increases, so that the effect of promoting intragranular transformation cannot be obtained. For these reasons, the upper limit of the S content was set to 0.025%. In addition, the minimum with preferable S content is 0.002%, and a preferable upper limit is 0.020%.
［Ａｌ：０．０５０％以下（０％を含まない）］
Ａｌは、脱酸元素として有効であるが、その含有量が過剰になると、粗大な酸化物系介在物を形成してＨＡＺ靭性を却って低下させるため、上限を０．０５０％とした。尚、Ａｌ含有量の好ましい上限は０．０４０％である。
[Al: 0.050% or less (excluding 0%)]
Al is effective as a deoxidizing element, but if its content is excessive, coarse oxide inclusions are formed and the HAZ toughness is reduced, so the upper limit was made 0.050%. In addition, the upper limit with preferable Al content is 0.040%.
［Ｔｉ：０．００５〜０．１０％］
Ｔｉは、窒化物または酸化物を形成してＨＡＺの靭性向上に寄与する元素である。こうした効果を有効に発揮させるには、Ｔｉは０．００５％以上含有させることが必要であり、好ましくは０．０１０％以上とする。しかしながら、Ｔｉ含有量が過剰になると、窒化物または酸化物が粗大になってＨＡＺの靭性を劣化させるため、０．１０％以下に抑えるべきである。好ましくは０．０８０％以下とする。
[Ti: 0.005 to 0.10%]
Ti is an element that forms nitrides or oxides and contributes to improving the toughness of HAZ. In order to exhibit such an effect effectively, it is necessary to contain Ti 0.005% or more, preferably 0.010% or more. However, if the Ti content is excessive, the nitride or oxide becomes coarse and deteriorates the toughness of the HAZ, so it should be suppressed to 0.10% or less. Preferably it is 0.080% or less.
［Ｎ：０．００４０〜０．０３０％］
Ｎは、窒化物の生成に必要な元素であり、特に鋳造時の凝固過程で酸化物、硫化物、窒化物等の介在物の表面に窒化物として複合析出することにより、介在物表面の凹凸を形成する上で有効である。Ｎ含有量が０．００４０％よりも少ないと、必要な凹凸を形成するのに十分な複合析出量が得られないため、下限を０．００４０％とした。また、Ｎ含有量が０．０３０％を超えて過剰になると、介在物表面を均一に覆うように窒化物が複合析出し、凹部の曲率半径が増大するため、粒内変態の促進効果が得られなくなる。こうしたことから、Ｎ含有量の上限は０．０３０％とする必要がある。尚、Ｎ含有量の好ましい下限は０．００５０％であり、好ましい上限は０．０２５％である。
[N: 0.0040 to 0.030%]
N is an element necessary for the formation of nitrides. In particular, the precipitates are unevenly formed on the surface of inclusions by being deposited as nitrides on the surface of inclusions such as oxides, sulfides and nitrides during the solidification process during casting. It is effective in forming. If the N content is less than 0.0040%, a composite precipitation amount sufficient to form the necessary unevenness cannot be obtained, so the lower limit was made 0.0040%. Further, when the N content exceeds 0.030% and excessive, nitride is complex-precipitated so as to uniformly cover the inclusion surface, and the radius of curvature of the concave portion increases, so that the effect of promoting intragranular transformation is obtained. It becomes impossible. For these reasons, the upper limit of the N content needs to be 0.030%. In addition, the minimum with preferable N content is 0.0050%, and a preferable upper limit is 0.025%.
［Ｏ：０．０００５〜０．０１０％］
Ｏは、酸化物の生成に必要な元素であり、Ｏ含有量が０．０００５％よりも小さいと、十分な量の酸化物が得られないため、下限を０．０００５％とした。また、Ｏ含有量が０．０１０％を超えて過剰になると、酸化物の粗大化によりＨＡＺ靭性の低下を招くので、その上限を０．０１０％とした。尚、Ｏ含有量に好ましい下限は０．００１％であり、好ましい上限は０．００８％である。
[O: 0.0005 to 0.010%]
O is an element necessary for the generation of an oxide. If the O content is less than 0.0005%, a sufficient amount of oxide cannot be obtained, so the lower limit was made 0.0005%. Further, if the O content exceeds 0.010% and becomes excessive, the HAZ toughness is reduced due to the coarsening of the oxide, so the upper limit was made 0.010%. In addition, the minimum with preferable O content is 0.001%, and a preferable upper limit is 0.008%.
本発明で規定する含有元素は上記の通りであって、残部は鉄および不可避的不純物であり、該不可避的不純物として、原料、資材、製造設備等の状況によって持ち込まれる元素（例えば、Ｓｎ，Ａｓ，Ｐｂ等）の混入が許容され得る。また上記のように化学成分組成の範囲内で下記（１）式を満足させることも有効である。更に、必要によって、下記各種元素を積極的に含有させることも有効であり、こうした元素を含有させることによってその種類に応じて厚鋼板の特性が更に改善されることになる。
０．０５≦９×［Ｏ］／（［Ｓ］＋１０×［Ｎ］）≦１．２０…（１）
但し、［Ｏ］，［Ｓ］および［Ｎ］は、夫々Ｏ，ＳおよびＮの含有量（質量％）を示す。
The contained elements specified in the present invention are as described above, and the balance is iron and unavoidable impurities, and elements brought in depending on the situation of raw materials, materials, manufacturing equipment, etc. (for example, Sn, As) , Pb, etc.) can be permitted. It is also effective to satisfy the following formula (1) within the range of the chemical component composition as described above. Furthermore, it is also effective to positively contain the following various elements as necessary, and the inclusion of such elements further improves the characteristics of the thick steel plate depending on the type.
0.05 ≦ 9 × [O] / ([S] + 10 × [N]) ≦ 1.20 (1)
However, [O], [S] and [N] indicate the contents (mass%) of O, S and N, respectively.
上記（１）式の関係は、酸化物、硫化物および窒化物等の生成に影響を与える元素として、Ｏ，ＳおよびＮを選び、実験に基づいて求めたものである。［９×［Ｏ］／（［Ｓ］＋１０×［Ｎ］）の値（以下、「Ｚ値」と呼ぶことがある）が０．０５より小さくなると、硫化物、窒化物が介在物表面を均一に覆うように複合析出し、凹部の曲率半径が増大するため、粒内変態の促進効果が得られにくくなる。また、Ｚ値が１．２０を超えると、酸化物、硫化物、窒化物等の介在物の表面に、必要な凹凸を形成するのに十分な硫化物、窒化物の複合析出が得られにくくなる。尚、Ｚ値のより好ましい下限は０．２０であり、より好ましい上限は１．０である。 The relationship of the above formula (1) is obtained based on experiments by selecting O, S, and N as elements that affect the generation of oxides, sulfides, nitrides, and the like. When the value of [9 × [O] / ([S] + 10 × [N]) (hereinafter sometimes referred to as “Z value”) is less than 0.05, sulfides and nitrides cause the inclusion surface to move. Since the composite precipitation is performed so as to cover uniformly, and the radius of curvature of the concave portion increases, it is difficult to obtain the effect of promoting intragranular transformation. When the Z value exceeds 1.20, it is difficult to obtain sufficient sulfide and nitride composite precipitates to form necessary irregularities on the surface of inclusions such as oxides, sulfides and nitrides. Become. A more preferable lower limit of the Z value is 0.20, and a more preferable upper limit is 1.0.
［ＲＥＭ：０．０００１〜０．０５％］
ＲＥＭ（希土類元素）は、酸化物または硫化物として析出することによって、粒内変態を促進する元素であり、その含有量が０．０００１％よりも少ないと、粒内変態の促進効果が十分に得られないため、好ましい下限を０．０００１％とした。また、ＲＥＭの好ましい含有量が０．０５％を超えて過剰になると、酸化物または硫化物の粗大化によってＨＡＺ靭性の低下を招くため、好ましい上限を０．０５％とした。ＲＥＭ含有量のより好ましい下限は０．０００５％であり、より好ましい上限は０．０４％である。尚、本発明において、ＲＥＭ（希土類元素）とは、ランタノイド元素（ＬａからＬｕまでの１５元素）およびＳｃ（スカンジウム）とＹ（イットリウム）を含む意味である。
[REM: 0.0001 to 0.05%]
REM (rare earth element) is an element that promotes intragranular transformation by precipitating as an oxide or sulfide. If its content is less than 0.0001%, the effect of promoting intragranular transformation is sufficient. Since it was not obtained, the preferable lower limit was made 0.0001%. Moreover, when the preferable content of REM exceeds 0.05% and becomes excessive, the HAZ toughness is lowered due to the coarsening of oxides or sulfides, so the preferable upper limit was made 0.05%. A more preferable lower limit of the REM content is 0.0005%, and a more preferable upper limit is 0.04%. In the present invention, REM (rare earth element) means a lanthanoid element (15 elements from La to Lu), Sc (scandium) and Y (yttrium).
［Ｚｒ：０．０００１〜０．０５％］
Ｚｒは、酸化物として析出することによって、粒内変態を促進するのに有効な元素であり、こうした効果を発揮させるためには０．０００１％以上含有させることが好ましい。しかしながら、Ｚｒの含有量が０．０５％を超えると、酸化物の粗大化によりＨＡＺ靭性の低下を招くため、０．０５％以下とすることが好ましい。尚、Ｚｒのより好ましい下限は０．０００５％であり、より好ましい上限は０．０４％である。
[Zr: 0.0001 to 0.05%]
Zr is an element effective for promoting intragranular transformation by precipitating as an oxide, and in order to exert such effects, it is preferably contained in an amount of 0.0001% or more. However, if the Zr content exceeds 0.05%, the HAZ toughness is reduced due to the coarsening of the oxide, so 0.05% or less is preferable. A more preferable lower limit of Zr is 0.0005%, and a more preferable upper limit is 0.04%.
［Ｍｇ：０．０００１〜０．００５％および／またはＣａ：０．０００１〜０．００５％］
ＭｇおよびＣａは、いずれも酸化物の微細分散に有効な元素であり、いずれも含有量が０．０００１％よりも少なくなると、微細分散の効果が十分に得られないため、好ましい下限を０．０００１％とした。また、いずれも含有量が０．００５０％を超えると、酸化物の粗大化により微細分散の効果が低下するため、いずれもその上限を０．００５０％とした。尚、これらの元素含有量のより好ましい下限は０．０００５％であり、より好ましい上限は０．００３０％である。
[Mg: 0.0001 to 0.005% and / or Ca: 0.0001 to 0.005%]
Mg and Ca are both effective elements for fine dispersion of oxides, and if the content is less than 0.0001%, the effect of fine dispersion cannot be obtained sufficiently. 0001%. Moreover, since the effect of fine dispersion | distribution will fall by coarsening of an oxide when content exceeds 0.0050% in all, all made the upper limit 0.0050%. In addition, the more preferable minimum of these element content is 0.0005%, and a more preferable upper limit is 0.0030%.
［Ｃｕ：０．１〜１．５％、Ｎｉ：０．１〜１．５％、Ｃｒ：０．１〜１．５％およびＭｏ：０．１〜１．５％よりなる群から選ばれる１種以上］
Ｃｕ、Ｎｉ、ＣｒおよびＭｏは、いずれも鋼板(母材)の高強度化に有効な元素であり、こうした効果を発揮させるためには、いずれも０．１％以上含有させることが好ましい。しかしながら、これらの元素の含有量が過剰になると、ＨＡＺ靭性の低下を招くため、いずれも１．５％以下とすることが好ましい。尚、これらの元素のより好ましい下限は０．２％であり、より好ましい上限は１．２％である。
[Selected from the group consisting of Cu: 0.1-1.5%, Ni: 0.1-1.5%, Cr: 0.1-1.5% and Mo: 0.1-1.5% One or more]
Cu, Ni, Cr, and Mo are all effective elements for increasing the strength of the steel sheet (base material), and in order to exert such effects, it is preferable that all of them be contained in an amount of 0.1% or more. However, if the content of these elements is excessive, the HAZ toughness is lowered, so that it is preferable that both be 1.5% or less. In addition, the more preferable lower limit of these elements is 0.2%, and the more preferable upper limit is 1.2%.
［Ｎｂ：０．０１〜０．０６および／またはＶ：０．０１〜０．１％］
ＮｂおよびＶは、炭窒化物として析出し、オーステナイト粒粗大化を抑制することでＨＡＺ靭性を改善する元素である。こうした効果を発揮させるには、いずれも０．０１％以上含有させることが好ましい。しかしながら、これらの含有量が過剰になると、粗大な炭窒化物が生成してＨＡＺ靭性の低下を招くため、Ｎｂで０．０６％以下、Ｖで０．１％以下とすることが好ましい。尚、より好ましい下限はＮｂ、Ｖいずれも０．０２％であり、より好ましい上限はＮｂで０．０５％、Ｖで０．０８％である。
[Nb: 0.01 to 0.06 and / or V: 0.01 to 0.1%]
Nb and V are elements that precipitate as carbonitride and improve HAZ toughness by suppressing austenite grain coarsening. In order to exhibit such an effect, it is preferable to contain all 0.01% or more. However, if these contents are excessive, coarse carbonitrides are generated and the HAZ toughness is lowered, so that Nb is preferably 0.06% or less and V is 0.1% or less. A more preferable lower limit is 0.02% for both Nb and V, and a more preferable upper limit is 0.05% for Nb and 0.08% for V.
［Ｂ：０．００１〜０．００５％］
Ｂは、粒界フェライト生成を抑制することで、ＨＡＺ靭性を向上させる元素であり、その効果を発揮させるためには０．００１％以上含有させることが好ましい。しかしながら、Ｂ含有量が過剰になって０．００５％を超えると、ＢＮとしてオーステナイト粒界に析出し、ＨＡＺ靭性の低下を招くため、０．００５％以下とすることが好ましい。尚、Ｂ含有量のより好ましい下限は０．００１５％であり、より好ましい上限は０．００４％である。
[B: 0.001 to 0.005%]
B is an element that improves the HAZ toughness by suppressing the formation of intergranular ferrite, and is preferably contained in an amount of 0.001% or more in order to exert its effect. However, if the B content becomes excessive and exceeds 0.005%, BN precipitates at the austenite grain boundary and causes a reduction in HAZ toughness, so 0.005% or less is preferable. A more preferable lower limit of the B content is 0.0015%, and a more preferable upper limit is 0.004%.
本発明は厚鋼板に関するものであり、該分野において厚鋼板とは、ＪＩＳで定義されるように、一般に板厚が３．０ｍｍ以上であるものを指す。しかし、本発明の厚鋼板の板厚は、８０ｍｍ以上であることが好ましい。即ち、本発明の厚鋼板は、板厚が８０ｍｍ以上となるような鋼板で、大入熱溶接を行っても良好なＨＡＺ靭性を示すものである。但し、本発明の鋼板の厚みは８０ｍｍ以上のものに限定されず、５０ｍｍ以上或いは、それ未満となるような鋼板への適用を排除するものではない。 The present invention relates to a thick steel plate. In this field, a thick steel plate generally refers to one having a plate thickness of 3.0 mm or more as defined by JIS. However, the thickness of the steel plate of the present invention is preferably 80 mm or more. That is, the steel plate of the present invention is a steel plate having a plate thickness of 80 mm or more, and exhibits good HAZ toughness even when high heat input welding is performed. However, the thickness of the steel sheet of the present invention is not limited to 80 mm or more, and does not exclude application to a steel sheet that is 50 mm or more or less.
こうして得られる本発明の厚鋼板は、例えば橋梁や高層建造物、船舶などの構造物の材料として使用でき、小〜中入熱溶接はもとより大入熱溶接においても、溶接熱影響部の靭性劣化を防ぐことができる。 The steel plate of the present invention thus obtained can be used as a material for structures such as bridges, high-rise buildings, ships, etc., and deteriorates the toughness of the weld heat affected zone not only in small to medium heat input welding but also in large heat input welding. Can be prevented.
以下、実施例を挙げて本発明をより具体的に説明するが、本発明はもとより下記実施例によって制限を受けるものではなく、前・後記の趣旨に適合し得る範囲で適当に変更を加えて実施することも勿論可能であり、それらはいずれも本発明の技術的範囲に包含される。 EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.
［実施例１］
下記表１、２に示す組成の鋼を、真空溶解炉(１５０ｋｇ)を用い、鋳造時の凝固過程が進行する１４５０〜１５００℃の冷却時間Ｔ(秒)を変化させながら溶製してスラブ（断面形状：２００ｍｍ×２５０ｍｍ）とした後、１１００℃に加熱して最終圧延温度が８８０℃となるように熱間圧延を施し、板厚：８０ｍｍの厚鋼板を製造した。各厚鋼板の化学成分組成、冷却時間Ｔ(秒)、およびＺ値を下記表１に示す。尚、表１、２において、ＲＥＭはＬａを５０％程度とＣｅを２５％程度含有するミッシュメタルの形態で添加した。また表１、２中「−」は元素を添加していないことを示している。
[Example 1]
The steels having the compositions shown in Tables 1 and 2 below were melted using a vacuum melting furnace (150 kg) while changing the cooling time T (seconds) of 1450 to 1500 ° C. during which the solidification process during casting progressed, and the slab ( (Cross-sectional shape: 200 mm × 250 mm) After heating to 1100 ° C. and hot rolling so that the final rolling temperature was 880 ° C., a steel plate having a plate thickness of 80 mm was produced. The chemical component composition, cooling time T (seconds), and Z value of each thick steel plate are shown in Table 1 below. In Tables 1 and 2, REM was added in the form of a misch metal containing about 50% La and about 25% Ce. In Tables 1 and 2, “-” indicates that no element is added.
得られた各厚鋼板から、溶接継手作製用試験片を採取し、各試験片のＨＡＺにおけるシャルピー衝撃試験を下記の要領で実施した。まず各溶接継手作製用試験片に、Ｖ開先を加工し、入熱量５０ｋＪ／ｍｍにてエレクトロガスアーク溶接を施し、溶接継手を得た。これら溶接継手から、溶接金属部近傍のＨＡＺに切欠を加工した、シャルピー衝撃試験片（ＪＩＳ Ｚ ２２０１の４号試験片）を採取し、ＨＡＺ靭性を評価した。そしてＪＩＳ Ｚ ２２４２に準拠して、−４０℃でシャルピー衝撃試験を行い、吸収エネルギー（ｖＥ-40）を測定した。このとき３本の試験片について吸収エネルギー（ｖＥ-40）を測定し、その平均値を求めた。そして、ｖＥ-40の値が１８０Ｊを超えるものをＨＡＺ靭性に優れると評価した。
Test pieces for producing welded joints were collected from the obtained thick steel plates, and a Charpy impact test in the HAZ of each test piece was performed as follows. First, V-grooves were processed into each welded joint preparation test piece, and electrogas arc welding was performed at a heat input of 50 kJ / mm to obtain welded joints. From these welded joints, Charpy impact test pieces (No. 4 test piece of JIS Z 2201) in which notches were machined in the HAZ near the weld metal part were collected and evaluated for HAZ toughness. And based on JISZ2242, the Charpy impact test was done at -40 degreeC and the absorbed energy (vE- 40 ) was measured. At this time, the absorbed energy (vE -40 ) was measured for the three test pieces, and the average value was obtained. And it evaluated that the value of vE- 40 exceeding 180J was excellent in HAZ toughness.
シャルピー衝撃試験終了後、各厚鋼板の試験片について、破断面から２〜６ｍｍ離れた、試験片中央部のＨＡＺを、電界放射式走査型電子顕微鏡（ＦＥ−ＳＥＭ）［「ＳＵＰＲＡ３５」（商品名）：Ｃａｒｌ Ｚｅｉｓｓ社製］を用いて観察（断面観察）し、表面に多数の凹凸が存在する介在物のうち、凹部の最小曲率半径が０．１〜２．０μｍであって、円相当直径が０．２〜５．０μｍの酸化物、硫化物および窒化物の１種または２種以上からなる介在物の個数密度（以下、「ＮＡ（個／ｍｍ2）」と表記する）を下記の方法で測定した。 After completion of the Charpy impact test, the HAZ in the center of the test piece, 2-6 mm away from the fracture surface, was measured for each thick steel plate using a field emission scanning electron microscope (FE-SEM) ["SUPRA35" (trade name ): Manufactured by Carl Zeiss Co., Ltd.] (of cross section observation), among inclusions having a large number of irregularities on the surface, the minimum radius of curvature of the concave portion is 0.1 to 2.0 μm, and the equivalent circle diameter Is the number density of inclusions (hereinafter referred to as “N A (pieces / mm 2 )”) consisting of one or more of oxides, sulfides and nitrides of 0.2 to 5.0 μm. It measured by the method of.
〈介在物の個数密度ＮＡ（個／ｍｍ2）の測定方法〉
（ｉ）まず上記ＦＥ−ＳＥＭの観察倍率を５０００倍に設定し、０．００２４ｍｍ2の面積に相当する観察視野を無作為に２０視野を選択し、各観察視野の画像を撮影した。同時に、各視野に含まれる、個々の介在物粒子についてＥＤＸ（エネルギー分散形Ｘ線分析）を実施し、構成元素に酸素、窒素および硫黄のうち一種あるいは二種以上が含まれる介在物粒子の画像を、倍率：１００００倍で撮影した。得られた１００００倍の画像に存在する、酸化物、窒化物、硫化物等の介在物のうち、表面形状が凹凸のものを選び、表面の凹部曲率半径を下記（ｉｉ）の手順によって測定した。
<Measurement method of inclusion number density N A (pieces / mm 2 )>
(I) First, the observation magnification of the FE-SEM was set to 5000 times, 20 observation fields corresponding to an area of 0.0024 mm 2 were randomly selected, and images of each observation field were taken. At the same time, EDX (energy dispersive X-ray analysis) is performed on each inclusion particle included in each field of view, and an image of inclusion particles containing one or more of oxygen, nitrogen and sulfur as constituent elements Was taken at a magnification of 10,000. Among inclusions such as oxides, nitrides and sulfides present in the obtained 10,000 times image, those having an uneven surface shape were selected, and the concave curvature radius of the surface was measured by the following procedure (ii). .
（ｉｉ）画像中の介在物の輪郭で、介在物凹部両側の凸部に共通接線Ｌ１を引き（図１）、接点を２点（図中Ａ、Ｂ）得た。次に、前記共通接線と平行な凹部の接線Ｌ2を引き、接点Ｃを得、「Image-Pro Plus」（ソフト名：Media Cybernetic社製）を用いた画像解析により、これら３接点（Ａ，Ｂ，Ｃ）を通る円を描き、その円の半径を介在物表面の凹部の曲率半径Ｒと定義した。 (Ii) the contour of the inclusions in the images, inclusions recesses on both sides of the draw common tangent L 1 on the convex portion (Fig. 1), 2-point contact (figure A, B) were obtained. Then, a tangent is drawn L 2 of the common tangent parallel to the recess, to give the contact C, "Image-Pro Plus": by image analysis using a (software name Media Cybernetic, Inc.), these three contacts (A, A circle passing through B, C) was drawn, and the radius of the circle was defined as the curvature radius R of the concave portion of the inclusion surface.
（ｉｉｉ）個々の介在物表面に存在する凹部のうち、上記の方法で測定した最小曲率半径が、０．１〜２．０μｍとなるような介在物粒子を選び、画像解析により、円相当直径を求めた。そのうちで、円相当径が０．２〜５．０μｍである介在物の個数を、５０００倍で２０視野の画像にてカウントし、観察視野１ｍｍ2に換算した個数密度ＮＡ（個／ｍｍ2）を求めた。 (Iii) Among the recesses existing on the surface of each inclusion, inclusion particles whose minimum radius of curvature measured by the above method is 0.1 to 2.0 μm are selected, and the equivalent circle diameter is determined by image analysis. Asked. Among them, circle the number of equivalent diameter inclusions is 0.2 to 5.0 .mu.m, and counted by 20 field of view of the image at 5000 times, number density in terms of the observation field of view 1 mm 2 N A (pieces / mm 2 )
上記のようにして得られた個数密度ＮＡを、各厚鋼板のＨＡＺ試験結果（ｖＥ-40の値）とともに下記表３、４に示す。 The number density N A obtained as described above are shown in the following Tables 3 and 4 together with the HAZ test results of the steel plate (the value of vE -40).
これらの結果から、次のように考察できる。まず本発明で規定する要件を満足する厚鋼板（表１，３の試験Ｎｏ．１〜２１）のものでは、所定の形態の介在物の個数密度ＮＡが高くなっており、優れたＨＡＺ靭性が達成されていることが分かる。 From these results, it can be considered as follows. Intended thick steel plate satisfying the requirements specified in the present invention (Test Table 1,3 No.1~21) First, the number density N A of inclusions of a given form becomes high with excellent HAZ toughness It can be seen that is achieved.
これに対して、本発明で規定する要件のいずれかを欠く厚鋼板（表２，４の試験Ｎｏ．２２〜３６）では、いずれも良好なＨＡＺ靭性が得られていないことが分かる。 On the other hand, it is understood that none of the thick steel plates lacking any of the requirements defined in the present invention (test Nos. 22 to 36 in Tables 2 and 4) have good HAZ toughness.
具体的には、試験Ｎｏ．２２〜２５のものでは、好ましい要件であるＺ値［９×[Ｏ]／(［Ｓ］+１０×[Ｎ])］、或いは鋳造時の凝固過程が進行する１４５０〜１５００℃の温度範囲での冷却時間Ｔが、適正な範囲内にないため、所定の形態を有する介在物の個数密度ＮＡが１００個／ｍｍ2に満たず、良好なＨＡＺ靭性が得られていない。 Specifically, Test No. In the case of 22 to 25, Z value [9 × [O] / ([S] + 10 × [N])], which is a preferable requirement, or a temperature range of 1450 to 1500 ° C. at which the solidification process during casting proceeds. cooling time T of, for not within the proper range, the number density N a of the inclusions having a predetermined shape are 100 / mm 2 without satisfied, not good HAZ toughness is obtained.
試験Ｎｏ．２６のものでは、Ｓｉ含有量が過剰になっており、硬質のＭＡ組織が増加していることが予想され、これによってＨＡＺ靭性が低下している。試験Ｎｏ．２７、２８のものでは、Ａｌ含有量、Ｏ含有量が夫々過剰になっており、粗大介在物が増加していることが予想され、ＨＡＺ靭性が低下している。 Test No. In the case of No. 26, the Si content is excessive, and it is expected that the hard MA structure is increased, thereby reducing the HAZ toughness. Test No. In the samples of Nos. 27 and 28, the Al content and the O content are excessive, and it is expected that coarse inclusions are increased, and the HAZ toughness is reduced.
試験Ｎｏ．２９〜３６のものでは、いずれかの元素の含有量が、適正な範囲から外れているため、所定の形態を有する介在物の個数密度ＮＡが１００個／ｍｍ2未満となっており、ＨＡＺ靭性が低下している。 Test No. Those of 29 to 36, the content of any element, because is out of the appropriate range, the number density N A of the inclusions having a predetermined shape has become less than 100 / mm 2, HAZ Toughness is reduced.
Claims (8)
０．０５≦９×［Ｏ］／（［Ｓ］＋１０×［Ｎ］）≦１．２０…（１）
但し、［Ｏ］，［Ｓ］および［Ｎ］は、夫々Ｏ，ＳおよびＮの含有量（質量％）を示す。 The high-tensile thick steel plate according to claim 1, which satisfies the relationship of the following formula (1).
0.05 ≦ 9 × [O] / ([S] + 10 × [N]) ≦ 1.20 (1)
However, [O], [S] and [N] indicate the contents (mass%) of O, S and N, respectively.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2007062471A JP4969275B2 (en) | 2007-03-12 | 2007-03-12 | High tensile steel plate with excellent toughness of weld heat affected zone |
| CN2008100807354A CN101265552B (en) | 2007-03-12 | 2008-02-18 | High-tension thick steel plate with excellent toughness of welding heat infection part |
| KR1020080022322A KR100983140B1 (en) | 2007-03-12 | 2008-03-11 | High tensile steel plate with excellent toughness of weld heat affected zone |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2007062471A JP4969275B2 (en) | 2007-03-12 | 2007-03-12 | High tensile steel plate with excellent toughness of weld heat affected zone |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2008223081A JP2008223081A (en) | 2008-09-25 |
| JP4969275B2 true JP4969275B2 (en) | 2012-07-04 |
Family
ID=39842036
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2007062471A Active JP4969275B2 (en) | 2007-03-12 | 2007-03-12 | High tensile steel plate with excellent toughness of weld heat affected zone |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JP4969275B2 (en) |
| KR (1) | KR100983140B1 (en) |
| CN (1) | CN101265552B (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5432539B2 (en) | 2009-01-28 | 2014-03-05 | 株式会社神戸製鋼所 | Steel with excellent toughness in weld heat affected zone |
| CN101956132B (en) * | 2009-07-15 | 2012-07-25 | 株式会社神户制钢所 | Steel having excellent toughness in welding heat affected zone, and manufacturing method thereof |
| JP5668588B2 (en) * | 2011-04-19 | 2015-02-12 | 新日鐵住金株式会社 | High-strength hot-rolled steel sheet excellent in formability and fracture characteristics and method for producing the same |
| CN102400045B (en) * | 2011-12-29 | 2013-03-20 | 钢铁研究总院 | Large-specification and high-strength D40 hot-rolled flat-bulb steel for ships and production process for hot-rolled flat-bulb steel |
| JP5883369B2 (en) | 2012-09-19 | 2016-03-15 | 株式会社神戸製鋼所 | Thick steel plate with excellent toughness in weld heat affected zone |
| CN104911485B (en) * | 2015-07-06 | 2017-07-21 | 武汉钢铁(集团)公司 | High high intensity structural steel for bridge of impact fracture fiber rate and preparation method thereof |
| KR20180132909A (en) * | 2016-04-21 | 2018-12-12 | 신닛테츠스미킨 카부시키카이샤 | Post-steel plate |
| CN106222548B (en) * | 2016-07-25 | 2017-11-10 | 武汉钢铁有限公司 | The low yield strength ratio structural steel for bridge and its production method of normalizing rolling |
| EP3533891A1 (en) * | 2016-10-27 | 2019-09-04 | JFE Steel Corporation | Steel for high heat input welding |
| CN112126851B (en) * | 2020-08-30 | 2021-11-02 | 五矿营口中板有限责任公司 | high-Ti-content micro-Al easy-welding low-alloy structural steel in ultra-fast cooling mode and manufacturing method thereof |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS589815B2 (en) * | 1977-10-11 | 1983-02-23 | 新日本製鐵株式会社 | Manufacturing method of high-strength steel plate with excellent low-temperature toughness and weldability |
| JPS61229461A (en) * | 1985-04-04 | 1986-10-13 | Nippon Steel Corp | Production of steel dispersed uniformly with resulted product of secondary deoxidation |
| JPH07266005A (en) * | 1994-03-31 | 1995-10-17 | Nippon Steel Corp | Production of steel having excellent toughness to welded heat affected part by synchronized belt type continuous casting method |
| JPH08104943A (en) * | 1994-10-06 | 1996-04-23 | Nippon Steel Corp | Steel for pressure vessel excellent in high temperature strength and its production |
| JP2005048265A (en) | 2003-07-31 | 2005-02-24 | Kobe Steel Ltd | Steel material superior in toughness of weld heat-affected zone, and manufacturing method therefor |
| JP4341395B2 (en) | 2003-12-09 | 2009-10-07 | 住友金属工業株式会社 | High strength steel and weld metal for high heat input welding |
| JP2005200716A (en) | 2004-01-16 | 2005-07-28 | Kobe Steel Ltd | Steel material superior in toughness of weld heat-affected zone |
| KR100892385B1 (en) * | 2004-07-21 | 2009-04-10 | 신닛뽄세이테쯔 카부시키카이샤 | Steel for welded structure excellent in low temperature toughness of heat affected zone of welded part, and method for production thereof |
-
2007
- 2007-03-12 JP JP2007062471A patent/JP4969275B2/en active Active
-
2008
- 2008-02-18 CN CN2008100807354A patent/CN101265552B/en not_active Expired - Fee Related
- 2008-03-11 KR KR1020080022322A patent/KR100983140B1/en active IP Right Grant
Also Published As
| Publication number | Publication date |
|---|---|
| CN101265552B (en) | 2010-06-09 |
| CN101265552A (en) | 2008-09-17 |
| JP2008223081A (en) | 2008-09-25 |
| KR20080083584A (en) | 2008-09-18 |
| KR100983140B1 (en) | 2010-09-20 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP4969275B2 (en) | High tensile steel plate with excellent toughness of weld heat affected zone | |
| JP5162382B2 (en) | Low yield ratio high toughness steel plate | |
| JP4660250B2 (en) | Thick high-strength steel sheet with excellent low-temperature toughness in the heat affected zone by high heat input welding | |
| JP5397363B2 (en) | Thick high-strength steel sheet with excellent low-temperature toughness in the heat affected zone by high heat input welding | |
| JP5425702B2 (en) | High-strength thick steel plate with excellent drop weight characteristics | |
| JP5207914B2 (en) | Thick steel plate with excellent toughness of base metal and weld heat affected zone | |
| JP4515430B2 (en) | Steel with excellent toughness and base metal toughness of weld heat affected zone and its manufacturing method | |
| WO2011142172A1 (en) | High-strength thick steel plate with excellent drop weight characteristics | |
| JP4311740B2 (en) | Thick steel plate with high heat input welded joint toughness | |
| JP5172391B2 (en) | Steel sheet with excellent toughness and uniform elongation of weld heat affected zone | |
| WO2012108517A1 (en) | Weld metal with excellent creep characteristics | |
| JP3699657B2 (en) | Thick steel plate with yield strength of 460 MPa or more with excellent CTOD characteristics of the heat affected zone | |
| JP4356949B2 (en) | Thick steel plate with excellent toughness in weld heat affected zone | |
| JP5394785B2 (en) | Thick steel plate with excellent weld heat affected zone toughness and low temperature base metal toughness | |
| JP5394849B2 (en) | Thick steel plate with excellent toughness in weld heat affected zone | |
| KR20080099789A (en) | Steel plate excellent in toughness of large heat-input weld heat affected zone | |
| JP5818343B2 (en) | Thick steel plate with excellent toughness in weld heat affected zone | |
| JP2005105322A (en) | Thick steel plate excellent in toughness of welded joint subjected to large heat input welding, and its production method | |
| JP5103037B2 (en) | Thick steel plate with excellent toughness of base metal and weld heat affected zone | |
| JP4276576B2 (en) | Thick high-strength steel sheet with excellent heat input and heat-affected zone toughness | |
| KR101151577B1 (en) | Steel plate | |
| JP2017053028A (en) | Ferrite-martensite two-phase stainless steel and manufacturing method therefor | |
| JP3854543B2 (en) | Steel and structures with excellent weld toughness | |
| JP2009179868A (en) | High tensile strength steel plate having excellent weldability | |
| WO2000075388A1 (en) | High-tension steel material with excellent suitability for welding with high-energy-density heat source and welded structure thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20090929 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20111124 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20111129 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20120125 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A821 Effective date: 20120125 |
|
| 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: 20120327 |
|
| 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: 20120403 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20150413 Year of fee payment: 3 |
|
| R150 | Certificate of patent or registration of utility model |
Free format text: JAPANESE INTERMEDIATE CODE: R150 |