JP4571915B2 - Refractory thick steel plate and manufacturing method thereof - Google Patents
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本発明は、建築、土木、海洋構造物、造船及び貯槽タンク等の分野で、溶接構造物の構造用部材として使用される耐火厚鋼板及びその製造方法に関する。 The present invention relates to a refractory thick steel plate used as a structural member of a welded structure in the fields of architecture, civil engineering, offshore structures, shipbuilding, storage tanks, and the like, and a method for manufacturing the same.
一般に、建築鋼構造物は、昭和６２年に報告された建設省総合技術開発プロジェクト「建築物の防火設計法の開発」（防火総プロ）の成果を受け、火災時の安全性を確保するため、鋼材の高温強度及び建築鋼構造物自体に実際に加わっている荷重から、鋼材の耐火性能を考慮した設計が必要とされている。 In general, building steel structures are designed to ensure safety in the event of a fire in response to the results of the Ministry of Construction's comprehensive technology development project “Development of fire prevention design methods for buildings” (Fire Protection General Professional) reported in 1987. In view of the high temperature strength of steel and the load actually applied to the construction steel structure itself, the design considering the fire resistance of the steel is required.
このような理由から、建築鋼構造物用の鋼材としては、建築鋼構造物の耐火設計において、鋼材表面へのロックウール等の耐火被覆施工に要する費用低減及びその施工工程の省略、更には外観上の観点から耐火被覆施工を省略でき、一般鋼よりも高温での耐力が高く、耐火性能に優れた耐火鋼の使用が拡がっている。 For these reasons, as steel materials for building steel structures, in the fireproof design of building steel structures, the cost reduction required for fireproof coating such as rock wool on the steel material surface, the omission of the construction process, and the appearance From the above point of view, fireproofing can be omitted, and the use of refractory steel, which has higher proof stress at a higher temperature than ordinary steel and has excellent fireproof performance, is expanding.
各建築鋼構造物の設計思想にもよるが、耐火用途には、通常、高温において規格降伏点（常温時降伏点）の（１／２）〜（２／３）以上の降伏強度又は耐力を有する鋼材の使用が有用である。そこで、従来、６００℃の温度域における短時間高温強度を高めた建築用低降伏比鋼材の製造方法が開発され（例えば、特許文献１参照。）、適用されている。この特許文献１に記載の建築用低降伏比鋼材の製造方法においては、質量％で、Ｃ：０．０４〜０．１５％、Ｓｉ：０．６％以下、Ｍｎ：０．５〜１．６％、Ｎｂ０．００５〜０．０４％、Ｍｏ：０．４〜０．７％、Ａｌ：０．１％以下及びＮ：０．００１〜０．００６％を含有し、残部がＦｅ及び不可避的不純物からなる鋼片を１１００〜１３００℃の温度域で加熱後、終了温度を８００〜１０００℃にして熱間圧延を行うことにより、無被覆又は従来の耐火被覆の２０〜５０％の被覆厚さで耐火目的を達成できる鋼材を得ている。 Depending on the design philosophy of each building steel structure, for fireproof applications, the yield strength or yield strength is usually (1/2) to (2/3) or more of the standard yield point (room temperature yield point) at high temperatures. Use of the steel material which has is useful. Therefore, conventionally, a method for producing a low yield ratio steel material for construction with an increased short-time high-temperature strength in a temperature range of 600 ° C. has been developed (see, for example, Patent Document 1) and applied. In the manufacturing method of the low yield ratio steel for construction described in Patent Document 1, C: 0.04-0.15%, Si: 0.6% or less, Mn: 0.5-1. 6%, Nb 0.005 to 0.04%, Mo: 0.4 to 0.7%, Al: 0.1% or less and N: 0.001 to 0.006%, the balance being Fe and inevitable After heating a steel slab composed of mechanical impurities in a temperature range of 1100 to 1300 ° C. and performing hot rolling at an end temperature of 800 to 1000 ° C., a coating thickness of 20 to 50% of the uncoated or conventional fireproof coating Now we have a steel that can achieve the fireproof purpose.
また、近時、８００℃までのより高温の温度域において耐火特性を有する耐火鋼が提案されている（例えば、特許文献２参照。）。この特許文献２に記載の４９０ＭＰａ級高張力鋼は、６００〜８００℃の温度範囲において優れた高温強度及び溶接性を得るため、鋼成分をＣ：０．００５％以上０．０４％未満、Ｓｉ：０．５％以下、Ｍｎ：０．１〜０．５％、Ｐ：０．０２％以下、Ｓ：０．０１％以下、Ｍｏ：０．３〜１．５％、Ｎｂ：０．０３〜０．１５％、Ｂ：０．０００５〜０．００３％、Ａｌ：０．０６％以下及びＮ：０．００６％以下を含有し、残部がＦｅ及び不可避的不純物からなる組成とし、鋼材温度Ｔが６００〜８００℃の範囲において、常温の降伏応力により高温時の降伏応力を無次元化した高温常温降伏応力比ｐ（＝高温降伏応力／常温降伏応力）が下記数式（１）を満たすようにしている。 Recently, a refractory steel having refractory characteristics in a higher temperature range up to 800 ° C. has been proposed (see, for example, Patent Document 2). The 490 MPa class high-strength steel described in Patent Document 2 has a steel component of C: 0.005% or more and less than 0.04% in order to obtain excellent high-temperature strength and weldability in a temperature range of 600 to 800 ° C., Si : 0.5% or less, Mn: 0.1 to 0.5%, P: 0.02% or less, S: 0.01% or less, Mo: 0.3 to 1.5%, Nb: 0.03 -0.15%, B: 0.0005-0.003%, Al: 0.06% or less and N: 0.006% or less, with the balance being Fe and inevitable impurities, steel temperature When T is in the range of 600 to 800 ° C., the high temperature normal temperature yield stress ratio p (= high temperature yield stress / normal temperature yield stress) obtained by making the yield stress at high temperature dimensionless by the normal temperature yield stress satisfies the following formula (1). I have to.
しかしながら、前述した従来の耐火鋼はいずれも、目的とする耐火特性を得るために、鋼にＭｏを１％前後（特許文献１に記載の鋼では０．４〜０．７％、特許文献２に記載の鋼では０．３〜１．５％）含有させているが、Ｍｏは高価な元素であり、また、Ｍｏを多量に添加すると、鋼材の靱性、特に溶接熱影響部（ＨＡＺ：Heat Affected Zone）の靭性に悪影響を及ぼすという問題点がある。このため、製造コストの低減及びＨＡＺ靱性の確保の点から、Ｍｏを添加しなくても、優れた耐火特性が得られ、高温強度に優れた厚鋼板の開発が望まれている。 However, all of the above-described conventional refractory steels have a Mo content of about 1% (0.4 to 0.7% for the steel described in Patent Document 1 and Patent Document 2) in order to obtain the desired fire resistance characteristics. However, Mo is an expensive element, and when a large amount of Mo is added, the toughness of the steel material, particularly the weld heat affected zone (HAZ: Heat) Affected Zone) has the problem of adversely affecting the toughness. For this reason, from the viewpoint of reducing manufacturing costs and securing HAZ toughness, it is desired to develop a thick steel plate that has excellent fire resistance characteristics and excellent high-temperature strength without adding Mo.
本発明は、上述した問題点に鑑みて案出されたものであり、Ｍｏを添加しなくても、７００℃以下の温度範囲において優れた短時間高温強度が得られ、かつ母材靭性及び溶接熱影響部靱性が良好な耐火厚鋼板及びその製造方法を提供することを目的とする。 The present invention has been devised in view of the above-mentioned problems, and an excellent short-time high-temperature strength can be obtained in a temperature range of 700 ° C. or less without adding Mo, and the base material toughness and welding can be achieved. It aims at providing the fire-resistant thick steel plate with favorable heat-affected zone toughness, and its manufacturing method.
本発明に係る耐火厚鋼板は、質量％で、Ｃ：０．０２〜０．２％、Ｓｉ：０．０３〜１％、Ｍｎ：０．３〜２％、Ａｌ：０．００１〜０．０５％、Ｎｂ：０．００５〜０．２％、Ｖ：０．０３〜０．３％及びＮ：０．００５〜０．０３％を含有すると共に、Ｐ：０．０２％以下及びＳ：０．０１％以下に制限し、残部がＦｅ及び不可避不純物からなり、ミクロ組織におけるベイナイト及びマルテンサイトの体積分率が合計で２０％以上であることを特徴とする。 The refractory thick steel plate according to the present invention is in mass%, C: 0.02 to 0.2%, Si: 0.03 to 1%, Mn: 0.3 to 2%, Al: 0.001 to 0.00. 05%, Nb: 0.005 to 0.2%, V: 0.03 to 0.3% and N: 0.005 to 0.03%, P: 0.02% or less, and S: It is limited to 0.01% or less, and the balance is Fe and inevitable impurities, and the volume fraction of bainite and martensite in the microstructure is 20% or more in total.
本発明においては、鋼組成を最適化すると共に、ミクロ組織におけるベイナイト及びマルテンサイトの体積分率を合計で２０％以上にしているため、Ｖ炭窒化物による析出強化によって高温強度を向上させることができると共に、室温強度を溶接構造用鋼材としての所望のレベルに維持することができる。これにより、Ｍｏを添加しなくても、短時間高温強度を向上することができると共に、母材靭性及び溶接熱影響部靱性の両方を良好にすることができる。 In the present invention, the steel composition is optimized, and the total volume fraction of bainite and martensite in the microstructure is 20% or more, so that the high temperature strength can be improved by precipitation strengthening with V carbonitride. In addition, the room temperature strength can be maintained at a desired level as a welded structural steel material. Thereby, even if it does not add Mo, while being able to improve high temperature strength for a short time, both base material toughness and welding heat affected zone toughness can be made favorable.
この耐火厚鋼板は、質量％で、Ｔｉ：０．００２〜０．０２％、Ｔａ：０．００２〜０．２％及びＺｒ：０．００２〜０．２％からなる群から選択された１種又は２種以上の元素を含有していてもよい。 This refractory thick steel plate is 1% selected from the group consisting of Ti: 0.002 to 0.02%, Ta: 0.002 to 0.2% and Zr: 0.002 to 0.2% by mass%. It may contain seeds or two or more elements.
また、質量％で、Ｃｒ：０．０１〜３％、Ｗ：０．０１〜３％、Ｎｉ：０．０１〜３％、Ｃｕ：０．０１〜１．５％及びＢ：０．０００３〜０．００５％からなる群から選択された１種又は２種以上の元素を含有することもできる。 Further, in terms of mass%, Cr: 0.01 to 3%, W: 0.01 to 3%, Ni: 0.01 to 3%, Cu: 0.01 to 1.5%, and B: 0.0003 to One or two or more elements selected from the group consisting of 0.005% can also be contained.
更に、質量％で、Ｍｇ：０．０００５〜０．０１％、Ｃａ：０．０００５〜０．０１％及びＲＥＭ（希土類元素）：０．０００５〜０．０５％からなる群から選択された１種又は２種以上の元素を含有していてもよい。 Furthermore, 1% selected from the group consisting of Mg: 0.0005 to 0.01%, Ca: 0.0005 to 0.01%, and REM (rare earth element): 0.0005 to 0.05% by mass%. It may contain seeds or two or more elements.
本発明に係る耐火厚鋼板の製造方法は、質量％で、Ｃ：０．０２〜０．２％、Ｓｉ：０．０３〜１％、Ｍｎ：０．３〜２％、Ａｌ：０．００１〜０．０５％、Ｎｂ：０．００５〜０．２％、Ｖ：０．０３〜０．３％及びＮ：０．００５〜０．０３％を含有すると共に、Ｐ：０．０２％以下及びＳ：０．０１％以下に制限し、残部がＦｅ及び不可避不純物からなる組成の鋼片又は鋳片を、１１５０〜１３００℃に加熱した後、１１００℃以下での累積圧下率を１０〜９０％、圧延終了温度をＡｒ３変態点以上として熱間圧延を施すことを特徴とする。 The manufacturing method of the fire-resistant thick steel plate which concerns on this invention is the mass%, C: 0.02-0.2%, Si: 0.03-1%, Mn: 0.3-2%, Al: 0.001. -0.05%, Nb: 0.005-0.2%, V: 0.03-0.3% and N: 0.005-0.03%, P: 0.02% or less And S: After restricting to 0.01% or less, the steel slab or slab of the composition which the remainder consists of Fe and an inevitable impurity is heated to 1150-1300 degreeC, The cumulative reduction rate in 1100 degrees C or less is 10-90. %, Hot rolling is performed at a rolling end temperature of Ar3 transformation point or higher.
本発明においては、鋼片又は鋳片の組成を最適化すると共に、１１５０〜１３００℃に加熱した後、１１００℃以下での累積圧下率を１０〜９０％、圧延終了温度をＡｒ３変態点以上として熱間圧延しているため、厚鋼板のミクロ組織におけるベイナイト及びマルテンサイトの体積分率を合計で２０％以上にすることができる。これにより、Ｖ炭窒化物による析出強化によって高温強度を向上させることができると共に、室温強度を溶接構造用鋼材としての所望のレベルに維持することができるため、Ｍｏを添加しなくても、７００℃以下の温度範囲において優れた短時間高温強度が得られ、かつ母材靭性及び溶接熱影響部靱性が良好な厚鋼板を製造することができる。 In the present invention, the composition of the steel slab or slab is optimized, and after heating to 1150 to 1300 ° C., the cumulative rolling reduction at 1100 ° C. or lower is set to 10 to 90%, and the rolling end temperature is set to the Ar3 transformation point or higher. Since it is hot-rolled, the volume fraction of bainite and martensite in the microstructure of the thick steel plate can be made 20% or more in total. Accordingly, the high temperature strength can be improved by precipitation strengthening with V carbonitride, and the room temperature strength can be maintained at a desired level as a steel material for welded structure. It is possible to produce a thick steel plate having excellent high-temperature strength for a short time in a temperature range of 0 ° C. or less and excellent base material toughness and weld heat affected zone toughness.
この耐火厚鋼板の製造方法では、前記熱間圧延後に、４００〜６５０℃で焼戻しを行うことができる。 In this method for producing a refractory thick steel plate, tempering can be performed at 400 to 650 ° C. after the hot rolling.
又は、前記熱間圧延後に、３〜１００℃／秒の冷却速度で、前記圧延終了温度から５５０℃以下の温度域まで加速冷却してもよい。その場合、前記加速冷却後に、４００〜６５０℃で焼戻しすることもできる。 Alternatively, after the hot rolling, accelerated cooling may be performed from the rolling end temperature to a temperature range of 550 ° C. or lower at a cooling rate of 3 to 100 ° C./second. In that case, it can also temper at 400-650 degreeC after the said accelerated cooling.
また、前記鋼片及び前記鋳片は、更に、質量％で、Ｔｉ：０．００２〜０．０２％、Ｔａ：０．００２〜０．２％及びＺｒ：０．００２〜０．２％からなる群から選択された１種又は２種以上の元素を含有していてもよい。 Further, the steel slab and the slab are further in mass%, from Ti: 0.002 to 0.02%, Ta: 0.002 to 0.2%, and Zr: 0.002 to 0.2%. One or two or more elements selected from the group may be contained.
更に、前記鋼片及び前記鋳片は、質量％で、Ｃｒ：０．０１〜３％、Ｗ：０．０１〜３％、Ｎｉ：０．０１〜３％、Ｃｕ：０．０１〜１．５％及びＢ：０．０００３〜０．００５％からなる群から選択された１種又は２種以上の元素が添加されていてもよい。 Furthermore, the said steel slab and the said slab are the mass%, Cr: 0.01-3%, W: 0.01-3%, Ni: 0.01-3%, Cu: 0.01-1. One or two or more elements selected from the group consisting of 5% and B: 0.0003 to 0.005% may be added.
更にまた、前記鋼片及び前記鋳片は、質量％で、Ｍｇ：０．０００５〜０．０１％、Ｃａ：０．０００５〜０．０１％及びＲＥＭ：０．０００５〜０．０５％からなる群から選択された１種又は２種以上の元素を含有することができる。 Still further, the steel slab and the slab are composed of Mg: 0.0005 to 0.01%, Ca: 0.0005 to 0.01%, and REM: 0.0005 to 0.05% by mass. One or more elements selected from the group can be contained.
本発明によれば、鋼組成を最適化すると共に、ミクロ組織におけるベイナイト及びマルテンサイトの体積分率を合計で２０％以上にしているため、高価なＭｏを含有させることなく、室温強度等の溶接構造用厚鋼板としての十分な特性が得られ、７００℃以下での短時間高温強度に優れ、かつ良好な母材靭性及びＨＡＺ靱性を有するＭｏ無添加型の耐火厚鋼板が得られる。 According to the present invention, since the steel composition is optimized and the volume fraction of bainite and martensite in the microstructure is 20% or more in total, welding with room temperature strength and the like without containing expensive Mo is performed. Sufficient characteristics as a structural steel plate can be obtained, and a Mo-free refractory steel plate having excellent base metal toughness and HAZ toughness with excellent short-time high-temperature strength at 700 ° C. or less can be obtained.
以下、本発明を実施するための最良の形態について、詳細に説明する。耐火鋼を建築鋼構造物等に使用される溶接構造用厚鋼板として利用する場合は、所望の室温強度及び良好な靱性を確保した上で、十分に高い高温強度を確保する必要がある。従来の耐火鋼においては、Ｍｏ及びＮｂ等の析出強化元素を適量添加することにより、これらの析出強化元素による室温強度の過度な上昇並びに母材靭性及びＨＡＺ靱性の劣化を抑制しつつ、高温強度を向上させる方法が採られている。これらの析出強化元素のうち、特にＭｏはそのほとんどが室温で固溶状態にあるため、室温強度の過度な上昇を招かず、耐火特性が必要な６００〜７００℃の高温域で析出量が増加して高温強度を発現する。このため、従来の耐火鋼では、室温強度及び高温強度の両立の観点から、Ｍｏを必須元素としている。 Hereinafter, the best mode for carrying out the present invention will be described in detail. When using refractory steel as a thick steel plate for welded structures used in construction steel structures, etc., it is necessary to ensure a sufficiently high high-temperature strength after ensuring the desired room temperature strength and good toughness. In conventional refractory steels, by adding appropriate amounts of precipitation strengthening elements such as Mo and Nb, high temperature strength is suppressed while suppressing excessive rise in room temperature strength and deterioration of base metal toughness and HAZ toughness due to these precipitation strengthening elements. The method of improving is taken. Among these precipitation strengthening elements, especially Mo is in a solid solution state at room temperature, so it does not cause an excessive increase in room temperature strength, and the amount of precipitation increases in the high temperature range of 600 to 700 ° C., which requires fire resistance. High strength. For this reason, in conventional fireproof steel, Mo is an essential element from the viewpoint of achieving both room temperature strength and high temperature strength.
しかしながら、本発明者は、従来の耐火鋼において必須元素として添加されているＭｏの高温強化機構について検討したところ、Ｍｏによる析出強化では６００℃以下の温度域における効果は十分であるが、６００℃を超え７００℃程度までの温度域における鋼材の高温強度を高めるためには、従来の添加量では不十分であり、更にＭｏを多量に添加して主としてＭｏの固溶強化による強化機構を高める必要があることを見出した。また、本発明者は、Ｍｏは他の析出強化元素に比べて焼入性が高く、特にＨＡＺを著しく硬化させるため、７００℃程度までの温度域における鋼材の高温強度を向上させるためにＭｏを添加すると、ＨＡＺ靭性及び溶接性が劣化するという問題があることも確認した。 However, the present inventor examined the high-temperature strengthening mechanism of Mo added as an essential element in the conventional refractory steel, and the precipitation strengthening by Mo is sufficient in the temperature range of 600 ° C. or lower, but 600 ° C. In order to increase the high temperature strength of the steel material in the temperature range exceeding about 700 ° C., the conventional addition amount is insufficient, and it is necessary to add a large amount of Mo and to enhance the strengthening mechanism mainly by solid solution strengthening of Mo Found that there is. Further, the inventor of the present invention has high hardenability compared to other precipitation strengthening elements. In particular, in order to significantly harden HAZ, Mo is used to improve the high temperature strength of the steel material in a temperature range up to about 700 ° C. It was also confirmed that there is a problem that the HAZ toughness and weldability deteriorate when added.
そこで、本発明者は、Ｍｏを添加しなくても室温強度と高温強度との両立が可能で、かつ良好なＨＡＺ靱性が達成できる高温強化機構を利用したＭｏ無添加型の耐火鋼について鋭意検討を行った。その結果、ミクロ組織中に高い転位密度を有するベイナイト相及びマルテンサイト相を所定量以上含有させることにより、Ｍｏによる高温強度発現機構を利用しなくても、主としてＶ炭窒化物による析出強化によって、室温強度を溶接構造用鋼材としての所望のレベルに維持しつつ、７００℃までの温度範囲において高温強度を向上することができ、かつ靱性も向上できることを見出した。なお、Ｖ及びＮｂは、純粋な炭化物及び窒化物以外に、ＣとＮとが固溶しあった炭窒化物をも形成し、更に、これらの析出物のいずれかを析出核として、別の析出物が析出する複合析出物も形成するが、鋼板の材質に対する作用効果はいずれの析出物であってもほぼ同等であるため、以下の説明においては、これら全てを炭窒化物又は析出物と総称する。 Therefore, the present inventor diligently investigated Mo-free refractory steel using a high-temperature strengthening mechanism that can achieve both room temperature strength and high-temperature strength without adding Mo and can achieve good HAZ toughness. Went. As a result, by including a predetermined amount or more of a bainite phase and a martensite phase having a high dislocation density in the microstructure, precipitation strengthening mainly by V carbonitride without using a high temperature strength development mechanism by Mo, It has been found that high temperature strength can be improved and toughness can be improved in a temperature range up to 700 ° C. while maintaining room temperature strength at a desired level as a steel material for welded structures. V and Nb form not only pure carbides and nitrides but also carbonitrides in which C and N are dissolved, and further, any one of these precipitates is used as a precipitation nucleus. A composite precipitate is also formed in which precipitates are deposited, but the effect on the material of the steel sheet is almost the same for any precipitate. Therefore, in the following explanation, all of these are referred to as carbonitrides or precipitates. Collectively.
本発明の耐火厚鋼板（以下、単に厚鋼板ともいう）は、これらの知見を基になされたものであって、質量％で、Ｃ：０．０２〜０．２％、Ｓｉ：０．０３〜１％、Ｍｎ：０．３〜２％、Ａｌ：０．００１〜０．０５％、Ｎｂ：０．００５〜０．２％、Ｖ：０．０３〜０．３％及びＮ：０．００５〜０．０３％を含有すると共に、Ｐ：０．０２％以下及びＳ：０．０１％以下に制限し、残部がＦｅ及び不可避不純物からなる組成であり、かつ、ミクロ組織におけるベイナイト及びマルテンサイトの体積分率が合計で２０％以上となっている。 The refractory thick steel plate (hereinafter, also simply referred to as a thick steel plate) of the present invention is based on these findings, and is in mass%, C: 0.02 to 0.2%, Si: 0.03. -1%, Mn: 0.3-2%, Al: 0.001-0.05%, Nb: 0.005-0.2%, V: 0.03-0.3% and N: 0.00. 005 to 0.03%, P: 0.02% or less and S: 0.01% or less, the balance is composed of Fe and inevitable impurities, and bainite and marten in the microstructure The volume fraction of the site is over 20% in total.
先ず、本発明の厚鋼板における成分組成の限定理由について説明する。以下に示す「％」は特に説明がない限り、「質量％」を意味するものとする。 First, the reason for limiting the component composition in the thick steel plate of the present invention will be described. Unless otherwise specified, “%” shown below means “% by mass”.
本発明の厚鋼板は、基本化学成分として、Ｃ：０．０２〜０．２％、Ｓｉ：０．０３〜１％、Ｍｎ：０．３〜２％、Ａｌ：０．００１〜０．０５％、Ｎｂ：０．００５〜０．２％、Ｖ：０．０３〜０．３％及びＮ：０．００５〜０．０３％を含有している。また、不純物であるＰは０．０２％以下及びＳは０．０１％以下に制限しており、残部はＦｅ及び不可避不純物である。 The thick steel plate of the present invention has C: 0.02 to 0.2%, Si: 0.03 to 1%, Mn: 0.3 to 2%, Al: 0.001 to 0.05 as basic chemical components. %, Nb: 0.005 to 0.2%, V: 0.03 to 0.3% and N: 0.005 to 0.03%. Further, P, which is an impurity, is limited to 0.02% or less and S is limited to 0.01% or less, and the balance is Fe and inevitable impurities.
Ｃ：０．０２〜０．２％
Ｃは、厚鋼板の強度及び靭性に大きな影響を及ぼす元素であるが、Ｃ含有量が０．０２％未満の場合、厚鋼板の室温強度及び高温強度のいずれも十分に高くすることができない。一方、厚鋼板中のＣ含有量が０．２％を超えると、母材及びＨＡＺの靭性が著しく劣化すると共に、溶接性も劣化するため、溶接構造用厚鋼板としては好ましくない。このため、本発明においては、厚鋼板中のＣ含有量は０．０２〜０．２％に限定する。
C: 0.02-0.2%
C is an element that greatly affects the strength and toughness of the thick steel plate. However, when the C content is less than 0.02%, neither the room temperature strength nor the high temperature strength of the thick steel plate can be sufficiently increased. On the other hand, when the C content in the thick steel plate exceeds 0.2%, the toughness of the base material and the HAZ is remarkably deteriorated and the weldability is also deteriorated. For this reason, in this invention, C content in a thick steel plate is limited to 0.02-0.2%.
Ｓｉ：０．０３〜１％
Ｓｉは脱酸元素であり、鋼の健全性を保つ上で重要な元素である。また、Ｓｉは、固溶強化により厚鋼板の強度を高める効果も有する。しかしながら、厚鋼板中のＳｉ含有量が０．０３％未満であると、脱酸が不十分となり、厚鋼板の清浄度を損ねて靭性を劣化させる可能性が大きくなり、更に強度の上昇も不明確となる。一方、Ｓｉ含有量が１％を超えると、特にＨＡＺ靭性の劣化が大きくなるため、好ましくない。従って、本発明の厚鋼板においては、Ｓｉ含有量を０．０３〜１％に制限する。
Si: 0.03 to 1%
Si is a deoxidizing element and is an important element for maintaining the soundness of steel. Si also has the effect of increasing the strength of the thick steel plate by solid solution strengthening. However, if the Si content in the thick steel sheet is less than 0.03%, deoxidation becomes insufficient, and the possibility of degrading the toughness by degrading the cleanliness of the thick steel sheet is increased, and further, the increase in strength is not increased. It becomes clear. On the other hand, if the Si content exceeds 1%, the HAZ toughness is particularly deteriorated, which is not preferable. Therefore, in the thick steel plate of the present invention, the Si content is limited to 0.03 to 1%.
Ｍｎ：０．３〜２％
Ｍｎは、適正に使用すれば、組織微細化を通して厚鋼板の強度と靭性とを同時に向上できる元素である。しかしながら、Ｍｎ含有量が０．３％未満であると、組織微細化が十分でなく、強度・靭性の向上が明確に現れない。一方、Ｍｎ含有量が２％を超えると、焼入性が過剰となって厚鋼板の強度が過大となり、母材靭性を劣化させると共に、ＨＡＺ靭性及び溶接性も劣化させるため、好ましくない。このため、本発明の厚鋼板においては、Ｍｎ含有量は０．３〜２％の範囲とする。
Mn: 0.3-2%
If used properly, Mn is an element that can simultaneously improve the strength and toughness of a thick steel plate through refinement of the structure. However, if the Mn content is less than 0.3%, the structure is not sufficiently refined and the improvement of strength and toughness does not appear clearly. On the other hand, if the Mn content exceeds 2%, the hardenability becomes excessive, the strength of the thick steel plate becomes excessive, the base material toughness is deteriorated, and the HAZ toughness and weldability are also deteriorated. For this reason, in the thick steel plate of this invention, Mn content shall be 0.3 to 2% of range.
Ａｌ：０．００１〜０．０５％
Ａｌは、Ｓｉと同様に脱酸元素であり、厚鋼板の清浄度を保つためには、０．００１％以上含有させる必要がある。一方、Ａｌは窒化物を形成してＮを固定するため、後述するＶ炭窒化物の析出強化を利用する本発明の厚鋼板においては、その添加量を制限すべきである。具体的には、Ａｌ含有量が０．０５％を超えると、Ａｌ窒化物の形成により、Ｖ炭窒化物による析出強化効果が大幅に低減する。よって、本発明の厚鋼板においては、Ａｌ含有量を０．００１％〜０．０５％とする。なお、Ｓｉ含有量が十分で、脱酸不足によって鋼の健全性が損なわれる虞がない場合は、Ｖの析出強化を有効活用するため、Ａｌ含有量を０．００１〜０．０１％に制限することがより好ましい。
Al: 0.001 to 0.05%
Al is a deoxidizing element like Si, and in order to maintain the cleanliness of the thick steel plate, it is necessary to contain 0.001% or more. On the other hand, since Al forms a nitride and fixes N, the amount of addition should be limited in the steel plate of the present invention that uses precipitation strengthening of V carbonitride described later. Specifically, when the Al content exceeds 0.05%, the precipitation strengthening effect by V carbonitride is significantly reduced due to the formation of Al nitride. Therefore, in the thick steel plate of the present invention, the Al content is set to 0.001% to 0.05%. In addition, when the Si content is sufficient and there is no possibility that the soundness of the steel is impaired due to insufficient deoxidation, the Al content is limited to 0.001 to 0.01% in order to effectively use the precipitation strengthening of V. More preferably.
Ｎｂ：０．００５〜０．２％
Ｎｂは、微量を添加することにより、室温から高温までの広い温度範囲で変態強化及び析出強化による高強度化を安定的に発現させる効果があり、後述するＶと同様に高温強度発現のために添加される基本元素である。しかしながら、厚鋼板中のＮｂ含有量が０．００５％未満であると、７００℃までの温度域における高温強度を十分に向上させることができない。また、Ｎｂには室温強度も高める作用があり、Ｎｂ添加により室温強度も高温強度と同程度向上する。このため、厚鋼板中のＮｂ含有量が０．２％を超えると、室温強度が過度に高くなり、母材及びＨＡＺの靭性が著しく劣化する。従って、本発明の厚鋼板においてはＮｂ含有量を０．００５〜０．２％の範囲とする。
Nb: 0.005 to 0.2%
Nb has the effect of stably developing high strength by transformation strengthening and precipitation strengthening in a wide temperature range from room temperature to high temperature by adding a trace amount. It is a basic element added. However, if the Nb content in the thick steel plate is less than 0.005%, the high temperature strength in the temperature range up to 700 ° C. cannot be sufficiently improved. Nb also has the effect of increasing the room temperature strength, and the addition of Nb improves the room temperature strength to the same extent as the high temperature strength. For this reason, when the Nb content in the thick steel plate exceeds 0.2%, the room temperature strength becomes excessively high, and the toughness of the base material and the HAZ is significantly deteriorated. Therefore, in the thick steel plate of the present invention, the Nb content is in the range of 0.005 to 0.2%.
Ｖ：０．０３〜０．３％
Ｖは、本発明の厚鋼板、即ち、Ｍｏ無添加型の耐火鋼において、前述のＮｂと同様に、７００℃までの温度域における高温強度を十分に発現させるために添加される必須の元素である。また、本発明の厚鋼板におけるＮ含有量の範囲内、即ち、Ｎの含有量が０．００５〜０．０３％である場合に、６００〜７００℃の温度範囲において短時間でＶ炭窒化物を形成させて、主としてＶ炭窒化物の析出強化により高温強度を発現させるためには、Ｖを０．０３％以上含有させることが必要である。Ｖ含有量が０．０３％未満であると、６００〜７００℃におけるＶ炭窒化物の析出速度が十分でなく、火災時の耐火性確保の前提である短時間加熱での強度発現に至らない。また、仮に、長時間加熱・保持したとしても、Ｖ炭窒化物の析出量が少ないため、高温強度の大幅な向上は期待できない。
V: 0.03-0.3%
V is an essential element that is added to sufficiently develop high-temperature strength in a temperature range up to 700 ° C. in the thick steel plate of the present invention, that is, Mo-free refractory steel, like Nb described above. is there. Further, in the range of the N content in the steel plate of the present invention, that is, when the N content is 0.005 to 0.03%, V carbonitride in a temperature range of 600 to 700 ° C. in a short time. In order to develop high temperature strength mainly by precipitation strengthening of V carbonitride, it is necessary to contain V by 0.03% or more. When the V content is less than 0.03%, the deposition rate of V carbonitride at 600 to 700 ° C. is not sufficient, and the strength is not manifested by short-time heating, which is a premise for ensuring fire resistance in a fire. . Moreover, even if heated and held for a long time, the amount of precipitation of V carbonitride is small, so a significant improvement in high temperature strength cannot be expected.
一方、Ｖ含有量は、０．０３％以上であれば多ければ多い程、高い高温強度が達成されるが、０．３％を超えてＶを過剰に含有させると、下記に示すような問題が生じる。即ち、第１の問題は、室温においても製品鋼中にＶ炭窒化物が析出するため、鋼板の室温強度が過大となり、更に母材靭性も劣化し、建築物等の溶接構造物用厚鋼板としての特性を確保できなくなるということである。第２の問題は、室温において製品鋼中に析出したＶ炭窒化物が粗大化しやすく、これにより靭性劣化が著しくなるということである。第３の問題は、ＨＡＺを著しく硬化させるため、ＨＡＺ靭性及び溶接性の両方を大幅に劣化させるということである。以上の理由から、本発明の厚鋼板においては、Ｖ含有量を０．０３〜０．３％に制限する。 On the other hand, if the V content is 0.03% or more, the higher the strength is, the higher the high temperature strength is. However, if V is excessively contained exceeding 0.3%, the following problems occur. Occurs. That is, the first problem is that V carbonitride precipitates in the product steel even at room temperature, so the room temperature strength of the steel sheet becomes excessive and the base material toughness deteriorates, and the steel plate for welded structures such as buildings. It is that it becomes impossible to secure the characteristics as. The second problem is that V carbonitrides precipitated in the product steel at room temperature are likely to be coarsened, resulting in significant deterioration in toughness. The third problem is that both HAZ toughness and weldability are significantly degraded because the HAZ is hardened significantly. For the above reasons, in the thick steel plate of the present invention, the V content is limited to 0.03 to 0.3%.
Ｎ：０．００５〜０．０３％
Ｎは、鋼中で上述したＶと結合して析出強化に有効なＶ炭窒化物を生成する。このように、Ｎは析出強化を利用して７００℃までの温度域における高温強度を発現するために重要な元素であるが、室温下では製品鋼材中にＶ炭窒化物を不必要に析出させず、６００〜７００℃での短時間加熱において迅速にＶ炭窒化物を析出させて高温強度を発現するためには、Ｖ含有量に対してＮ含有量を適正化する必要がある。具体的には、厚鋼板中のＮ含有量が０．００５％未満であると、Ｖ炭窒化物の溶解度積が小さくなり、６００〜７００℃での析出量及び析出速度が不十分となる。一方、厚鋼板中のＮ含有量が０．０３％を超えると、室温の段階でＶ炭窒化物が析出してしまうため、室温強度が過大となったり、室温で析出したＶ炭窒化物がその後粗大化して靭性が著しく劣化したり、ＨＡＺを著しく硬化させて、ＨＡＺ靭性及び溶接性が大幅に劣化したりする等の悪影響が許容できなくなる。このため、本発明の厚鋼板におけるＮ含有量は０．００５〜０．０３％とする。なお、安定的に６００〜７００℃で高温強度を向上させるためには、Ｎ含有量範囲を０．００７〜０．０２％とすることが好ましい。
N: 0.005 to 0.03%
N combines with V described above in the steel to produce V carbonitride effective for precipitation strengthening. Thus, N is an important element for developing high-temperature strength in the temperature range up to 700 ° C. using precipitation strengthening, but V carbonitride is unnecessarily precipitated in the product steel at room temperature. First, in order to quickly deposit V carbonitride and develop high temperature strength by short-time heating at 600 to 700 ° C., it is necessary to optimize the N content with respect to the V content. Specifically, when the N content in the thick steel plate is less than 0.005%, the solubility product of V carbonitride becomes small, and the precipitation amount and precipitation rate at 600 to 700 ° C. become insufficient. On the other hand, when the N content in the thick steel plate exceeds 0.03%, V carbonitride precipitates at the room temperature stage, so that the room temperature strength becomes excessive or the V carbonitride precipitated at room temperature After that, adverse effects such as coarsening and severe deterioration of toughness, or significant hardening of HAZ toughness and weldability due to remarkable hardening of HAZ become unacceptable. For this reason, N content in the thick steel plate of this invention shall be 0.005-0.03%. In order to stably improve the high temperature strength at 600 to 700 ° C., the N content range is preferably 0.007 to 0.02%.
Ｐ：０．０２％以下
Ｐは、不純物元素であり、靱性を阻害するため、その含有量は極力低減する必要がある。特に、厚鋼板中のＰ含有量が０．０２％を超えると、靱性への悪影響が許容できる範囲を超えるため、本発明の厚鋼板ではＰ含有量を０．０２％以下に規制する。
P: 0.02% or less P is an impurity element and inhibits toughness, so its content needs to be reduced as much as possible. In particular, if the P content in the thick steel plate exceeds 0.02%, the adverse effect on toughness exceeds the allowable range, so the P content is regulated to 0.02% or less in the thick steel plate of the present invention.
Ｓ：０．０１％以下
Ｓは、前述のＰと同様に不純物元素であり、鋼板中に過大に存在すると靱性及び延性を劣化させるため、その含有量は極力低減することが好ましい。特に、厚鋼板中のＳ含有量が０．０１％を超えると、靱性及び延性への悪影響が許容できる範囲を超えるため、本発明の厚鋼板ではＳ含有量を０．０１％以下に規制する。
S: 0.01% or less S is an impurity element as in the above-described P, and if it is excessively present in the steel sheet, the toughness and ductility are deteriorated. Therefore, the content is preferably reduced as much as possible. In particular, if the S content in the thick steel plate exceeds 0.01%, the adverse effects on toughness and ductility exceed the allowable range. Therefore, in the thick steel plate of the present invention, the S content is restricted to 0.01% or less. .
以上が、本発明の厚鋼板における基本化学組成であるが、本発明の厚鋼板においては、析出強化により鋼板の高温強度を高めるために、必要に応じて、これらの基本成分に加えて、更に、Ｔｉ：０．００２〜０．０２％、Ｔａ：０．００２〜０．２％及びＺｒ：０．００２〜０．２％からなる群から選択された１種又は２種以上の元素を含有させることができる。 The above is the basic chemical composition in the thick steel plate of the present invention.In the thick steel plate of the present invention, in order to increase the high-temperature strength of the steel plate by precipitation strengthening, in addition to these basic components, if necessary, Ti: 0.002-0.02%, Ta: 0.002-0.2% and Zr: One or more elements selected from the group consisting of 0.002-0.2% Can be made.
Ｔｉ：０．００２〜０．０２％
Ｔｉは、析出強化により強度を高める効果があり、更にＴｉＮを生成してピン止め効果によりＨＡＺ組織を微細化する効果もあり、ＨＡＺ靭性の向上に有効な元素である。Ｔｉを厚鋼板に含有させる場合、その含有量が０．００２％未満であると上記効果が明確に現れないため、Ｔｉ含有量は０．００２％以上とするのが好ましい。一方、ＴｉはＡｌと同様に、ＶよりもＮとの親和力が強く、Ｔｉ窒化物を形成しやすいため、０．０２％を超えてＴｉを過剰に含有させると、７００℃までの温度域において上述したＶ炭窒化物の析出を抑制するため、好ましくない。従って、本発明の厚鋼板においては、Ｔｉを厚鋼板に含有させる場合は、０．００２〜０．０２％の範囲とすることが好ましい。なお、Ａｌ及びＴｉは共にＮと結合して窒化物を生成し、高温におけるＶ炭窒化物の生成及び析出を抑制するため、Ｔｉを添加する場合は、Ａｌ及びＴｉの合計量を０．０１％以下に規制することがより好ましい。
Ti: 0.002 to 0.02%
Ti has an effect of increasing the strength by precipitation strengthening, and further has an effect of generating TiN and refining the HAZ structure by the pinning effect, and is an element effective for improving the HAZ toughness. When Ti is contained in the thick steel plate, if the content is less than 0.002%, the above effect does not appear clearly. Therefore, the Ti content is preferably 0.002% or more. On the other hand, Ti, like Al, has a stronger affinity with N than V and easily forms Ti nitrides. Therefore, when Ti is contained excessively in excess of 0.02%, in the temperature range up to 700 ° C. This is not preferable because the above-described precipitation of V carbonitride is suppressed. Therefore, in the thick steel plate of the present invention, when Ti is contained in the thick steel plate, it is preferable to be in the range of 0.002 to 0.02%. In addition, in order to suppress the production | generation and precipitation of V carbonitride at high temperature, both Al and Ti couple | bond with N and produce | generate a nitride, When adding Ti, the total amount of Al and Ti is 0.01. It is more preferable to regulate to not more than%.
Ｔａ：０．００２〜０．２％，Ｚｒ：０．００２〜０．２％
Ｔａ及びＺｒは、ＮｂとＶとの中間的な固溶析出挙動を示し、適量を添加すると、Ｎｂ及びＶと同様の効果を発揮する。Ｔａ及び／又はＺｒを添加する場合、高温強度を高めるためには夫々０．００２％以上含有させる必要がある。一方、Ｔａ含有量又はＺｒ含有量が０．２％を超えると、室温強度の過度な上昇、並びに母材靭性及びＨＡＺ靭性の劣化を招く。よって、Ｔａ及び／又はＺｒを添加する場合は、その含有量を夫々０．００２〜０．２％とする。
Ta: 0.002-0.2%, Zr: 0.002-0.2%
Ta and Zr exhibit an intermediate solid solution precipitation behavior between Nb and V, and when the appropriate amount is added, the same effect as Nb and V is exhibited. When adding Ta and / or Zr, it is necessary to contain 0.002% or more in order to increase the high temperature strength. On the other hand, when the Ta content or the Zr content exceeds 0.2%, an excessive increase in the room temperature strength and deterioration of the base metal toughness and the HAZ toughness are caused. Therefore, when adding Ta and / or Zr, the content is made 0.002 to 0.2%, respectively.
また、本発明の厚鋼板においては、室温強度及び靱性の調整、並びにその他の特性付与等の目的で、必要に応じて、上記各成分に加えて、更に、Ｃｒ：０．０１〜３％、Ｗ：０．０１〜３％、Ｎｉ：０．０１〜３％、Ｃｕ：０．０１〜１．５％及びＢ：０．０００３〜０．００５％からなる群から選択された１種又は２種以上の元素を含有させることができる。 In addition, in the thick steel plate of the present invention, for the purpose of adjusting the room temperature strength and toughness, and imparting other properties, as necessary, in addition to the above components, Cr: 0.01 to 3%, One or two selected from the group consisting of W: 0.01 to 3%, Ni: 0.01 to 3%, Cu: 0.01 to 1.5% and B: 0.0003 to 0.005% More than seed elements can be contained.
Ｃｒ：０．０１〜３％
Ｃｒは、焼入性を高めて室温強度を向上させる効果がある。また、Ｃｒを比較的多量に含有させると、加熱変態点が上昇するため、高温での組織安定性が向上し、７００℃以上の高温強度が向上する。しかしながら、Ｃｒ含有量が０．０１％未満では、これらの効果が明確に発揮されない。一方、Ｃｒ含有量が３％を超えると、母材及びＨＡＺの靭性が劣化するため好ましくない。そのため、本発明の厚鋼板においては、Ｃｒを含有させる場合は、その含有量を０．０１〜３％とする。
Cr: 0.01 to 3%
Cr has the effect of improving hardenability and improving room temperature strength. Further, when a relatively large amount of Cr is contained, the heating transformation point is increased, so that the structural stability at high temperature is improved and the high temperature strength of 700 ° C. or higher is improved. However, when the Cr content is less than 0.01%, these effects are not clearly exhibited. On the other hand, if the Cr content exceeds 3%, the toughness of the base material and the HAZ deteriorates, which is not preferable. Therefore, in the thick steel plate of the present invention, when Cr is contained, the content is set to 0.01 to 3%.
Ｗ：０．０１〜３％
Ｗは、Ｃｒにほぼ類似した効果を有する。従って、厚鋼板中にＷを含有させる場合は、前述したＣｒと同様の理由から、その含有量を０．０１〜３％に限定する。
W: 0.01 to 3%
W has an effect almost similar to Cr. Therefore, when W is contained in the thick steel plate, the content is limited to 0.01 to 3% for the same reason as Cr described above.
Ｎｉ：０．０１〜３％
Ｎｉは、適量添加することにより、厚鋼板の強度と靭性とを同時に向上することができ、ＨＡＺ靭性確保にも有効な元素である。しかしながら、Ｎｉ含有量が０．０１％未満の場合、これらの効果が得られない。また、３％を超えてＮｉを過剰に含有させると、母材及びＨＡＺが過度に硬化して却って靭性を劣化させることがある。よって、本発明の厚鋼板においては、Ｎｉを含有させる場合は、その含有量を０．０１〜３％に限定する。
Ni: 0.01 to 3%
By adding an appropriate amount of Ni, the strength and toughness of the thick steel plate can be improved at the same time, and Ni is an element effective for securing HAZ toughness. However, when the Ni content is less than 0.01%, these effects cannot be obtained. Moreover, when Ni is contained excessively exceeding 3%, a base material and HAZ may harden | cure excessively and may deteriorate toughness on the contrary. Therefore, in the thick steel plate of the present invention, when Ni is contained, the content is limited to 0.01 to 3%.
Ｃｕ：０．０１〜１．５％
Ｃｕは、主として焼入性を高めることにより、厚鋼板の強度向上に有効な元素である。しかしながら、Ｃｕ含有量が０．０１％未満の場合、明確な効果が得られない。一方、１．５％を超えてＣｕを過剰に含有させると、母材及びＨＡＺの靭性が劣化すると共に、熱間加工性が劣化して厚鋼板の製造性に問題が生じる。よって、本発明の厚鋼板にＣｕを含有させる場合は、その含有量を０．０１〜１．５％の範囲とする。
Cu: 0.01 to 1.5%
Cu is an element effective for improving the strength of the thick steel sheet mainly by improving hardenability. However, when the Cu content is less than 0.01%, a clear effect cannot be obtained. On the other hand, when Cu is contained excessively exceeding 1.5%, the toughness of the base material and the HAZ deteriorates, and hot workability deteriorates, resulting in a problem in the productivity of the thick steel plate. Therefore, when making the thick steel plate of this invention contain Cu, the content shall be 0.01 to 1.5% of range.
Ｂ：０．０００３〜０．００５％
Ｂは、微量の添加で焼入性を大幅に高められるため、厚鋼板の高強度化に非常に有効な元素である。しかしながら、厚鋼板の高強度化を目的として含有させる場合は、Ｂ含有量を０．０００３％以上にする必要がある。一方、０．００５％を超えてＢを過剰に含有させると、ＨＡＺが異常に硬化して、ＨＡＺ靭性及び溶接性が著しく劣化すると共に、ＨＡＺの再熱脆化及び再熱割れ感受性が高まるため、好ましくない。よって、本発明の厚鋼板において、Ｂを含有させる場合は、その含有量を０．０００３〜０．００５％に限定する。
B: 0.0003 to 0.005%
B is an element that is very effective for increasing the strength of thick steel plates, since the hardenability can be greatly enhanced by adding a small amount. However, when it is contained for the purpose of increasing the strength of the thick steel plate, the B content needs to be 0.0003% or more. On the other hand, if B exceeds 0.005% and HA is excessively contained, HAZ hardens abnormally, and HAZ toughness and weldability are remarkably deteriorated, and HAZ reheat embrittlement and reheat cracking susceptibility increase. It is not preferable. Therefore, in the thick steel plate of the present invention, when B is contained, the content is limited to 0.0003 to 0.005%.
更に、本発明の厚鋼板においては、鋼板の延性向上及びＨＡＺ靱性向上の目的で、必要に応じて、上記各成分に加えて、Ｍｇ：０．０００５〜０．０１％、Ｃａ：０．０００５〜０．０１％及びＲＥＭ（希土類元素）：０．０００５〜０．０５％からなる群から選択された１種又は２種以上の元素を含有させることができる。 Furthermore, in the thick steel plate of the present invention, Mg: 0.0005 to 0.01%, Ca: 0.0005, in addition to the above components, as necessary, for the purpose of improving the ductility of the steel plate and improving the HAZ toughness. ˜0.01% and REM (rare earth element): One or more elements selected from the group consisting of 0.0005 to 0.05% can be contained.
Ｍｇ、Ｃａ及びＲＥＭは、いずれもＳを含む介在物を形成して鋼中のＳを無害化する効果があり、適量添加により介在物制御することができ、特に、介在物の微細分散化に寄与する。しかしながら、その添加効果を確実に発揮させるためには、夫々０．０００５％以上含有させる必要がある。一方、Ｍｇ含有量又はＣａ含有量が０．０１％を超えるか、又はＲＥＭ含有量が０．０５％を超えると、粗大な介在物が生成し、延性及び靱性が劣化する。よって、Ｍｇ、Ｃａ及び／又はＲＥＭを添加する場合は、Ｍｇ含有量は０．０００５〜０．０１％に、Ｃａ含有量は０．０００５〜０．０１％に、ＲＥＭ含有量は０．０００５〜０．０５％に限定する。なお、複数のＲＥＭを添加する場合は、その総含有量を上記範囲とする。 Mg, Ca, and REM all have the effect of forming inclusions containing S to render S in the steel harmless, and inclusions can be controlled by adding an appropriate amount, especially for fine dispersion of inclusions. Contribute. However, in order to ensure the effect of addition, it is necessary to contain 0.0005% or more of each. On the other hand, if the Mg content or Ca content exceeds 0.01%, or the REM content exceeds 0.05%, coarse inclusions are generated, and ductility and toughness deteriorate. Therefore, when adding Mg, Ca and / or REM, the Mg content is 0.0005 to 0.01%, the Ca content is 0.0005 to 0.01%, and the REM content is 0.0005. Limited to ~ 0.05%. In addition, when adding several REM, let the total content be the said range.
なお、本発明の厚鋼板におけるミクロ組織中のベイナイト及びマルテンサイトの体積分率を、安定的に後述する範囲内にするためには、上述した成分組成を満足した上で、さらに、下記数式（２）で定義される炭素当量（Ｃｅｑ．）を０．３〜０．５％とすることがより好ましい。なお、下記数式（２）における［Ｃ］はＣ含有量（％）を、［Ｓｉ］はＳｉ含有量（％）を、［Ｍｎ］はＭｎ含有量（％）を、［Ｎｉ］はＮｉ含有量（％）を、［Ｃｒ］はＣｒ含有量（％）を、［Ｍｏ］はＭｏ含有量（％）を、［Ｖ］はＶ含有量（％）を夫々示す。 In addition, in order to make the volume fraction of bainite and martensite in the microstructure in the steel plate of the present invention stably within the range described later, after satisfying the above-described component composition, the following formula ( The carbon equivalent (Ceq.) Defined in 2) is more preferably 0.3 to 0.5%. In the following formula (2), [C] is the C content (%), [Si] is the Si content (%), [Mn] is the Mn content (%), and [Ni] is Ni content. The amount (%), [Cr] indicates the Cr content (%), [Mo] indicates the Mo content (%), and [V] indicates the V content (%).
上記数式（２）で定義される炭素当量（Ｃｅｑ．）が０．３％未満の場合、十分な焼入性が得られず、ベイナイト及びマルテンサイトを合計で２０体積％以上含有するミクロ組織が安定的に得られないことがある。一方、上記数式（２）で定義される炭素当量（Ｃｅｑ．）が０．５％を超えると、特にＨＡＺの硬化が無視できなくなり、ＨＡＺ靭性及び溶接性の劣化を招く場合がある。よって、上記数式（２）で定義される炭素当量（Ｃｅｑ．）は０．３〜０．５％とすることが好ましい。 When the carbon equivalent (Ceq.) Defined by the above formula (2) is less than 0.3%, sufficient hardenability cannot be obtained, and a microstructure containing 20% by volume or more of bainite and martensite in total. It may not be obtained stably. On the other hand, when the carbon equivalent (Ceq.) Defined by the above formula (2) exceeds 0.5%, the hardening of HAZ cannot be ignored, and the HAZ toughness and weldability may be deteriorated. Therefore, the carbon equivalent (Ceq.) Defined by the above formula (2) is preferably 0.3 to 0.5%.
次に、本発明の厚鋼板におけるミクロ組織について説明する。鋼板中にＭｏを添加せず、主として、Ｖの炭窒化物の析出強化により高温強度を高めるためには、各鋼成分を上述した範囲に限定すると共に、ミクロ組織におけるベイナイト及びマルテンサイトの体積分率を合計で２０％以上にする必要がある。 Next, the microstructure in the thick steel plate of the present invention will be described. In order to increase the high-temperature strength mainly by precipitation strengthening of V carbonitride without adding Mo to the steel sheet, each steel component is limited to the above-described range, and the volume fraction of bainite and martensite in the microstructure. The rate needs to be 20% or more in total.
本発明の厚鋼板において、ミクロ組織中のベイナイト及びマルテンサイトは、フェライト及びパーライトに比べて転位密度が高いため、転位を核として６００〜７００℃の温度域において、短時間でもＶとＮとが結合して炭窒化物を形成し、析出しやすくなる。また、転位密度による生成核が多いことにより、Ｖ炭窒化物が微細に析出しやすくなる。このＶ炭窒化物の析出強化により、６００〜７００℃における高温強度を向上させることができる。更に、厚鋼板の製造において、ベイナイト及びマルテンサイト変態はフェライト及びパーライトに比べて低温で開始するため、鋼板製造後の室温時の鋼板製品中ではＶが固溶状態で存在しやすく、鋼板の室温強度を過度に高めること、及び母材靭性が低下することを抑制する作用がある。また、Ｖ以外のＮｂ等の析出強化元素の高温での微細析出にも有利であり、析出強化元素全般の高温強度発現効果が有効に発揮される。更にまた、ベイナイト及びマルテンサイト中の転位は可動転位が多いため、建築用鋼として要求される低降伏比の特性を維持する作用もある。 In the thick steel plate of the present invention, bainite and martensite in the microstructure have a higher dislocation density than ferrite and pearlite, and therefore V and N are present even in a short time in the temperature range of 600 to 700 ° C. with dislocations as the core. Bonds to form a carbonitride and is likely to precipitate. Moreover, since there are many production nuclei by a dislocation density, V carbonitride tends to precipitate finely. The precipitation strengthening of the V carbonitride can improve the high-temperature strength at 600 to 700 ° C. Furthermore, in the manufacture of thick steel plates, bainite and martensitic transformations start at a lower temperature than ferrite and pearlite, so V tends to exist in a solid solution state in steel plate products at room temperature after steel plate manufacture, There exists an effect | action which suppresses raising a intensity | strength too much and a base material toughness falling. Further, it is advantageous for fine precipitation at high temperatures of precipitation strengthening elements such as Nb other than V, and the high temperature strength expression effect of the precipitation strengthening elements in general is effectively exhibited. Furthermore, since dislocations in bainite and martensite have many movable dislocations, they also have the effect of maintaining the characteristics of a low yield ratio required for construction steel.
本発明の厚鋼板において、上述した効果が十分に発揮されるためには、ミクロ組織中のベイナイト及びマルテンサイトの体積分率を合計で２０％以上にする必要がある。ミクロ組織中のベイナイト及びマルテンサイトの体積分率が合計で２０％未満であると、転位密度の低いフェライト及びパーライトが多くなり、火災時等のように６００〜７００℃の高温下でかつ短時間に、鋼板製造後の鋼板製品において室温下で固溶していたＶ量が十分に析出することができなくなる。 In the thick steel plate of the present invention, in order to sufficiently exhibit the above-described effects, the total volume fraction of bainite and martensite in the microstructure needs to be 20% or more. When the volume fraction of bainite and martensite in the microstructure is less than 20% in total, ferrite and pearlite with low dislocation density increase, and at a high temperature of 600 to 700 ° C. for a short time, such as in a fire. In addition, the amount of V dissolved in room temperature in the steel plate product after manufacturing the steel plate cannot be sufficiently precipitated.
なお、Ｖ含有量及びＮ含有量が上述した適性範囲から外れている場合、製造時に鋼板中にＶ炭窒化物が粗大析出しやすくなり、室温時の鋼板製品中の固溶Ｖが十分確保されないため、鋼板のミクロ組織中のベイナイト及びマルテンサイトの体積分率の合計が上記範囲内であっても、６００〜７００℃の高温下で短時間に析出するＶ炭窒化物の量が減少し、室温強度に比べて高温強度の向上効果が低減し、靭性が劣化する場合が生じることはいうまでもない。 In addition, when the V content and the N content are outside the above-described suitable ranges, V carbonitrides are likely to be coarsely precipitated in the steel sheet during production, and the solid solution V in the steel sheet product at room temperature is not sufficiently secured. Therefore, even if the total volume fraction of bainite and martensite in the microstructure of the steel sheet is within the above range, the amount of V carbonitride that precipitates in a short time at a high temperature of 600 to 700 ° C. is reduced. Needless to say, the effect of improving the high-temperature strength is reduced compared to the room temperature strength, and the toughness is deteriorated.
従って、本発明の厚鋼板においては、Ｍｏを含有せずに、主として、Ｖの炭窒化物の析出強化により高温強度を高めるために、上述した範囲に成分組成を限定し、更にミクロ組織におけるベイナイト及びマルテンサイトの体積分率を合計で２０％以上とする。なお、Ｖの固溶・析出挙動に対する効果は、ベイナイトとマルテンサイトとで大きな違いはないため、ベイナイト及びマルテンサイトの体積分率が合計で２０％以上であれば、フェライト及びパーライト以外の組織が、ベイナイト単独でも、また、マルテンサイト単独でも、又は両者の混合組織でも、上記効果は有効に発揮される。 Therefore, in the thick steel plate of the present invention, in order to increase the high temperature strength mainly by precipitation strengthening of V carbonitride without containing Mo, the component composition is limited to the above-described range, and further, the bainite in the microstructure. And the volume fraction of martensite is 20% or more in total. In addition, since the effect on the solid solution / precipitation behavior of V is not significantly different between bainite and martensite, if the volume fraction of bainite and martensite is 20% or more in total, the structure other than ferrite and pearlite In addition, the above-described effects can be effectively exhibited by bainite alone, martensite alone, or a mixed structure of both.
また、上記効果は、ベイナイト及びマルテンサイトの体積分率が合計で２０〜１００％の範囲で十分発揮されるが、引張強度レベルを５７０ＭＰａ級以下にする必要がある場合、建築用途等で安定的に低降伏比化したい場合には、ベイナイト及びマルテンサイトの体積分率の合計値の上限を９０％に制限することが好ましい。 In addition, the above effect is sufficiently exhibited when the total volume fraction of bainite and martensite is in the range of 20 to 100%. However, when the tensile strength level needs to be 570 MPa class or less, it is stable for architectural use. When it is desired to lower the yield ratio, the upper limit of the total volume fraction of bainite and martensite is preferably limited to 90%.
以上が本発明の耐火厚鋼板における成分組成及び組織の構成要件並びに限定理由である。上述の如く、本発明の厚鋼板においては、鋼組成を最適化すると共に、ミクロ組織中に高い転位密度を有するベイナイト及びマルテンサイトを所定量以上含有させているため、Ｍｏを添加しなくても、Ｖ炭窒化物による析出強化によって高温強度を向上させることができると共に、室温強度を溶接構造用鋼材としての所望のレベルに維持することができる。 The above is the component composition in the refractory thick steel sheet of the present invention, the structural requirements of the structure, and the reasons for limitation. As described above, in the thick steel sheet of the present invention, the steel composition is optimized, and since bainite and martensite having a high dislocation density is contained in a microstructure, a predetermined amount or more is contained, so that Mo is not added. Further, the high temperature strength can be improved by precipitation strengthening with V carbonitride, and the room temperature strength can be maintained at a desired level as a steel material for welded structure.
次に、上述の如く構成された本発明の耐火厚鋼板の製造方法について説明する。 Next, the manufacturing method of the refractory thick steel plate of the present invention configured as described above will be described.
本発明の厚鋼板の製造方法においては、Ｃ：０．０２〜０．２％、Ｓｉ：０．０３〜１％、Ｍｎ：０．３〜２％、Ａｌ：０．００１〜０．０５％、Ｎｂ：０．００５〜０．２％、Ｖ：０．０３〜０．３％及びＮ：０．００５〜０．０３％を含有すると共に、Ｐ：０．０２％以下及びＳ：０．０１％以下に制限し、更に必要に応じて、Ｔｉ：０．００２〜０．０２％、Ｔａ：０．００２〜０．２％、Ｚｒ：０．００２〜０．２％、Ｃｒ：０．０１〜３％、Ｗ：０．０１〜３％、Ｎｉ：０．０１〜３％、Ｃｕ：０．０１〜１．５％、Ｂ：０．０００３〜０．００５％、Ｍｇ：０．０００５〜０．０１％、Ｃａ：０．０００５〜０．０１％及びＲＥＭ：０．０００５〜０．０５％からなる群から選択された１種又は２種以上の元素を含有し、残部がＦｅ及び不可避不純物からなる組成の鋼片又は鋳片を、１１５０〜１３００℃に加熱した後、１１００℃以下での累積圧下率を１０〜９０％、圧延終了温度をＡｒ３変態点以上として熱間圧延を施すことを基本的要件とする。 In the method for producing a thick steel plate of the present invention, C: 0.02 to 0.2%, Si: 0.03 to 1%, Mn: 0.3 to 2%, Al: 0.001 to 0.05% , Nb: 0.005 to 0.2%, V: 0.03 to 0.3% and N: 0.005 to 0.03%, P: 0.02% or less, and S: 0.0. It is limited to not more than 01%, and further, if necessary, Ti: 0.002 to 0.02%, Ta: 0.002 to 0.2%, Zr: 0.002 to 0.2%, Cr: 0.00. 01-3%, W: 0.01-3%, Ni: 0.01-3%, Cu: 0.01-1.5%, B: 0.0003-0.005%, Mg: 0.0005 -0.01%, Ca: 0.0005-0.01% and REM: One or two or more elements selected from the group consisting of 0.0005-0.05%, the balance being After heating the steel slab or slab of the composition consisting of e and inevitable impurities to 1150 to 1300 ° C., hot rolling at a cumulative reduction rate of 1 to 100 ° C. or less at 10 to 90% and a rolling end temperature of Ar 3 transformation point or higher Is a basic requirement.
以下、本発明の厚鋼板の製造方法における各条件の数値限定理由について説明する。 Hereinafter, the reason for limiting the numerical value of each condition in the method for producing a thick steel plate of the present invention will be described.
加熱温度：１１５０〜１３００℃
熱間圧延前に行う鋼片又は鋳片の加熱において、その加熱温度が１１５０℃未満であると、圧延終了後に室温下で厚鋼板中にＮｂ及びＶ等の析出物形成元素の一部が未固溶のまま粗大析出物として残るため、室温強度及び高温強度が共に十分に高くならず、更に母材靭性が劣化する虞もある。一方、加熱温度が１３００℃を超えると、元素の溶体化は十分となるが、加熱オーステナイトの粒径が極端に粗大となり、その後の熱間圧延でも均一に微細化されないため、オーステナイトの粒径が均一にならず、厚鋼板における母材靭性が劣化する可能性が大きい。また、厚鋼板の表面性状も劣化する。以上の理由から、鋼片又は鋳片の加熱温度は１１５０〜１３００℃とする。
Heating temperature: 1150-1300 ° C
When heating the steel slab or slab before hot rolling, if the heating temperature is less than 1150 ° C., some of the precipitate-forming elements such as Nb and V are not present in the thick steel plate at room temperature after the end of rolling. Since it remains as a coarse precipitate as a solid solution, both the room temperature strength and the high temperature strength are not sufficiently high, and the base material toughness may further deteriorate. On the other hand, when the heating temperature exceeds 1300 ° C., the solution of the element is sufficient, but the grain size of the heated austenite becomes extremely coarse and is not uniformly refined even in the subsequent hot rolling. There is a high possibility that the base material toughness of the thick steel plate is not uniform and deteriorates. Further, the surface properties of the thick steel plate are also deteriorated. For the above reasons, the heating temperature of the steel slab or slab is 1150 to 1300 ° C.
１１００℃以下での累積圧下率：１０〜９０％，圧延終了温度：Ａｒ３変態点以上
鋼片又は鋳片の加熱後に所望の板厚の厚鋼板とする熱間圧延は、オーステナイトの再結晶による均一微細化、及びオーステナイトへの転位導入（未再結晶域圧延）を介して変態組織の微細化を図り、厚鋼板の強度・靭性向上するために、特に１１００℃以下での累積圧下率を１０〜９０％とし、かつ圧延終了温度をＡｒ３変態点以上とする必要がある。
Cumulative rolling reduction at 1100 ° C. or lower: 10 to 90%, rolling finish temperature: Ar3 transformation point or higher Hot rolling to obtain a thick steel plate with a desired thickness after heating a steel slab or cast slab is uniform by recrystallization of austenite In order to refine the transformation structure through refinement and introduction of dislocations into the austenite (non-recrystallization zone rolling), and to improve the strength and toughness of the thick steel plate, the cumulative rolling reduction particularly at 1100 ° C. or less is 10 to 10%. It is necessary to set it to 90% and to make the rolling end temperature equal to or higher than the Ar3 transformation point.
１１００℃を超えた温度では、オーステナイトが再結晶後に急速に粒成長するため、オーステナイト粒径の微細化に寄与しない。そこで、本発明の厚鋼板の製造方法においては、オーステナイト粒径の微細化に関係する１１００℃以下の温度範囲における累積圧下率を規定する。この１００℃以下の温度範囲における累積圧下率が１０％未満の場合、鋼中のオーステナイトを再結晶により効果的に微細化することができない。また、１１００℃以下での累積圧下率が大きい程オーステナイトは微細化されるが、この温度域での累積圧下率が９０％を超えると、オーステナイトを微細化する効果が飽和すると共に圧延時間が長時間となるため、生産性が低下し、圧延機にも負荷がかかる。更に、鋼片又は鋳片の厚さと厚鋼板の板厚の関係からも、９０％を超える累積圧下率を設定することは実用上の問題が生じる。よって、１１００℃以下での累積圧下率は１０〜９０％とする。 At temperatures exceeding 1100 ° C., austenite grows rapidly after recrystallization, so it does not contribute to the refinement of the austenite grain size. Therefore, in the method for producing a thick steel plate of the present invention, the cumulative rolling reduction in the temperature range of 1100 ° C. or less related to the refinement of the austenite grain size is specified. When the cumulative rolling reduction in the temperature range of 100 ° C. or lower is less than 10%, austenite in the steel cannot be effectively refined by recrystallization. In addition, austenite is refined as the cumulative rolling reduction at 1100 ° C. or less increases. However, if the cumulative rolling reduction in this temperature range exceeds 90%, the effect of refining austenite is saturated and the rolling time is long. Since time is spent, productivity is reduced and the rolling mill is loaded. Furthermore, from the relationship between the thickness of the steel slab or cast slab and the thickness of the thick steel plate, setting a cumulative reduction ratio exceeding 90% causes a practical problem. Therefore, the cumulative rolling reduction at 1100 ° C. or lower is set to 10 to 90%.
一方、熱間圧延において、圧延終了温度がＡｒ３変態点未満の低温圧延になると、鋼板中の未再結晶オーステナイトの割合、及びこのオーステナイト中への転位の導入が過度となるため、Ｎｂ及びＶの一部が圧延中又は圧延後に過度に析出し、高温強度が十分高くならない虞がある。また、圧延終了温度がＡｒ３変態点未満では、鋼板中の変態組織が過度に微細化されて降伏比（降伏応力／引張強さ）が過度に高くなるため、建築用途として好ましくない場合もある。このため、本発明の厚鋼板の製造方法においては、熱間圧延において、圧延終了温度をＡｒ３変態点以上に限定する。なお、熱間圧延において、加工転位の導入による鋼板中へのＮｂ及びＶの一部の析出、及び材質の異方性を安定して抑制し、高温強度を十分に高めるためには、圧延終了温度を８５０℃以上とすることが好ましい。 On the other hand, in hot rolling, when the rolling end temperature is low temperature rolling less than the Ar3 transformation point, the ratio of unrecrystallized austenite in the steel sheet and the introduction of dislocations in this austenite become excessive, so Nb and V There is a possibility that a part of the precipitate is excessively precipitated during or after rolling and the high-temperature strength is not sufficiently increased. In addition, when the rolling end temperature is lower than the Ar3 transformation point, the transformation structure in the steel sheet is excessively refined and the yield ratio (yield stress / tensile strength) becomes excessively high, which may not be preferable for architectural use. For this reason, in the manufacturing method of the thick steel plate of this invention, in hot rolling, rolling completion temperature is limited to an Ar3 transformation point or more. In hot rolling, in order to stably suppress the precipitation of part of Nb and V in the steel sheet due to the introduction of work dislocations and the anisotropy of the material and sufficiently increase the high temperature strength, the rolling is completed. The temperature is preferably 850 ° C. or higher.
本発明の厚鋼板の製造方法においては、熱間圧延時に一部１１００℃超での圧延が行なわれても、上述した熱間圧延条件を満足していれば、厚鋼板の特性に悪影響はない。従って、鋼片又は鋳片の厚さと厚鋼板の板厚との関係の都合で、１１００℃以下での累積圧下率を１０〜９０％、圧延終了温度をＡｒ３変態点以上とした熱間圧延以外に、１１００℃を超えた温度での圧延を施すことには何ら問題はない。また、熱間圧延前に、インゴット及びスラブ等からなる鋼片又は鋳片に対して、形状調整等を目的とした分塊圧延及び偏析拡散等を目的とした熱処理を施してもよく、これらの処理により上述した本発明の効果が損なわれることはない。 In the method for producing a thick steel plate of the present invention, even if some of the rolling is performed at a temperature exceeding 1100 ° C. during the hot rolling, the properties of the thick steel plate are not adversely affected as long as the above-described hot rolling conditions are satisfied. . Therefore, for the convenience of the relationship between the thickness of the steel slab or cast slab and the thickness of the thick steel plate, other than hot rolling where the cumulative rolling reduction at 1100 ° C. or less is 10 to 90% and the rolling end temperature is not less than the Ar3 transformation point In addition, there is no problem in performing rolling at a temperature exceeding 1100 ° C. In addition, before hot rolling, steel pieces or cast slabs made of ingots, slabs, etc. may be subjected to heat treatment for the purpose of partial rolling and segregation diffusion for the purpose of shape adjustment, etc. The effect of the present invention described above is not impaired by the treatment.
また、上述した熱間圧延工程後の冷却条件については、特に限定する必要はないが、厚鋼板製造後に室温下において鋼板製品中に含有されているＮｂ及びＶ等の析出強化元素を極力固溶状態とすると共に、ミクロ組織中のベイナイト及びマルテンサイトの体積分率を合計で２０％以上にするためには、空冷以上の冷却速度で冷却することが好ましい。具体的には、圧延終了後から４００℃までの平均冷却速度が０．５℃／秒以上となる条件で冷却することがより好ましい。 In addition, the cooling conditions after the hot rolling step described above need not be particularly limited, but precipitation strengthening elements such as Nb and V contained in the steel plate product at room temperature after the production of the thick steel plate are dissolved as much as possible. In order to obtain a state and a total volume fraction of bainite and martensite in the microstructure is 20% or more, it is preferable to cool at a cooling rate equal to or higher than air cooling. Specifically, it is more preferable to cool under the condition that the average cooling rate from the end of rolling to 400 ° C. is 0.5 ° C./second or more.
更に、本発明の厚鋼板の製造方法においては、熱間圧延後に、Ａｒ３変態点以上の冷却開始温度から５５０℃以下の冷却終了温度までの間を、３〜１００℃／秒の冷却速度で加速冷却することが好ましい。このように、熱間圧延後に、Ａｒ３変態点以上の温度域（冷却開始温度）から加速冷却することによって、鋼板中の組織変態が全体的に低温側となり、Ｎｂ及びＶ等の析出が抑制されるため、熱間圧延をより低温で行った場合でも、その後室温下において鋼板製品中に含有されるＮｂ及びＶ等の析出強化元素を固溶状態で保持することができるため、鋼板の高温強度を安定的に向上させることができる。 Furthermore, in the method for producing a thick steel plate of the present invention, after hot rolling, the cooling is accelerated at a cooling rate of 3 to 100 ° C./second from the cooling start temperature not lower than the Ar3 transformation point to the cooling end temperature not higher than 550 ° C. It is preferable to cool. Thus, after hot rolling, by accelerated cooling from a temperature range (cooling start temperature) above the Ar3 transformation point, the structural transformation in the steel sheet becomes the entire low temperature side, and precipitation of Nb, V, etc. is suppressed. Therefore, even when hot rolling is performed at a lower temperature, precipitation strengthening elements such as Nb and V contained in the steel plate product can be held in a solid solution state at room temperature thereafter, so that the high temperature strength of the steel plate Can be improved stably.
このとき、熱間圧延後の加速冷却時の冷却速度が３℃／秒未満であると、加速冷却による変態点低下又は組織微細化の効果が十分でなく、鋼板中に適正なベイナイト及び／又はマルテンサイトを上述した体積分率で生成することが困難となると共に、鋼板中でのＮｂ炭窒化物及びＶ炭窒化物の析出を十分抑制することが困難になる。一方、冷却速度が大きい程、加速冷却による組織制御が図られるが、１００℃／秒を超える程冷却速度を早くしても上述した効果は飽和し、更にこのような過大な冷却速度で冷却することは製造コストの上昇及び鋼板形状の悪化を招く。従って、本発明の厚鋼板の製造方法においては、熱間圧延後に加速冷却する場合は、冷却速度を３〜１００℃／秒とすることが好ましい。 At this time, if the cooling rate at the time of accelerated cooling after hot rolling is less than 3 ° C./second, the effect of transformation point reduction or microstructure refinement due to accelerated cooling is not sufficient, and appropriate bainite and / or in the steel sheet It becomes difficult to generate martensite at the above-described volume fraction, and it becomes difficult to sufficiently suppress precipitation of Nb carbonitride and V carbonitride in the steel sheet. On the other hand, as the cooling rate increases, the structure control by accelerated cooling is achieved. However, even if the cooling rate is increased as it exceeds 100 ° C./second, the above-described effect is saturated, and further cooling is performed at such an excessive cooling rate. This leads to an increase in manufacturing cost and deterioration of the steel plate shape. Therefore, in the manufacturing method of the thick steel plate of the present invention, when accelerated cooling is performed after hot rolling, the cooling rate is preferably 3 to 100 ° C./second.
また、熱間圧延後の加速冷却は、冷却開始温度がＡｒ３変態点未満の場合には、加速冷却開始までにＮｂ及びＶ等の析出元素が析出してしまい、高温強度の上昇に寄与できなくなる虞がある。一方、加速冷却終了温度（停止温度）が５５０℃を超えると、加速冷却停止後にＮｂ及びＶ等の析出元素が析出してしまう虞がある。従って、熱間圧延後に加速冷却を行なう場合は、冷却開始温度をＡｒ３変態点以上とし、加速冷却終了温度（停止温度）を５５０℃以下とするのが好ましい。 Further, in the accelerated cooling after hot rolling, when the cooling start temperature is lower than the Ar3 transformation point, precipitation elements such as Nb and V are precipitated before the start of accelerated cooling, and cannot contribute to the increase in the high temperature strength. There is a fear. On the other hand, if the accelerated cooling end temperature (stop temperature) exceeds 550 ° C., precipitation elements such as Nb and V may be deposited after the accelerated cooling is stopped. Therefore, when accelerated cooling is performed after hot rolling, it is preferable that the cooling start temperature is not lower than the Ar3 transformation point and the accelerated cooling end temperature (stop temperature) is not higher than 550 ° C.
更に、熱間圧延終了後又は加速冷却後に、必要に応じて、厚鋼板の室温強度の調整、靭性の向上及び残留応力の解放等を目的として、厚鋼板に対して加熱温度が４００〜６５０℃の焼戻しを施してもよい。厚鋼板に焼戻しを施す場合、焼戻し温度が４００℃未満であると、この焼戻し処理が材質調整及び残留応力解放に対してほとんど効果を発揮しない。一方、焼戻し温度が６５０℃を超えると、焼戻し段階で析出が生じて厚鋼板の室温強度が過度に上昇することがあり、これにより靭性が劣化する場合もある。また、炭窒化物が過時効析出状態となって、高温強度が有効に上昇しない可能性もあり、好ましくない。 Furthermore, after completion of hot rolling or after accelerated cooling, the heating temperature is 400 to 650 ° C. with respect to the thick steel plate for the purpose of adjusting the room temperature strength of the thick steel plate, improving toughness, releasing residual stress, and the like. May be tempered. When tempering a thick steel plate, if the tempering temperature is less than 400 ° C., this tempering treatment has little effect on material adjustment and residual stress release. On the other hand, when the tempering temperature exceeds 650 ° C., precipitation occurs in the tempering stage, and the room temperature strength of the thick steel plate may excessively increase, which may deteriorate the toughness. Moreover, carbonitride may be in an over-aged precipitation state, and high temperature strength may not increase effectively, which is not preferable.
なお、焼戻しの保持時間及び冷却条件については、加熱温度に比べて材質への影響が極めて小さいため、現実的及び工業的な条件範囲であれば特に規定する必要はないが、析出元素の固溶量を多くして粗大析出を抑制する観点から、焼戻しにおける保持時間は、加熱温度が５００℃以下の場合は４８時間以下、５００℃を超える場合は４時間以下とすることが好ましく、また冷却条件については、空冷又は空冷以上の冷却速度とすることが好ましい。 The tempering holding time and cooling conditions need not be specified as long as they are in practical and industrial conditions because the influence on the material is extremely small compared to the heating temperature. From the viewpoint of suppressing coarse precipitation by increasing the amount, the holding time in tempering is preferably 48 hours or less when the heating temperature is 500 ° C. or less, and 4 hours or less when the heating temperature exceeds 500 ° C., and cooling conditions About, it is preferable to set it as the cooling rate more than air cooling or air cooling.
上述の如く、本発明の厚鋼板の製造方法においては、組成が最適化された鋼片又は鋳片を、１１５０〜１３００℃に加熱した後、１１００℃以下での累積圧下率を１０〜９０％、圧延終了温度をＡｒ３変態点以上として熱間圧延しているため、圧鋼板のミクロ組織中のベイナイト及びマルテンサイトの体積分率を合計で２０％以上とすることができる。これにより、Ｖ炭窒化物による析出強化によって高温強度を向上させることができると共に、室温強度を溶接構造用鋼材としての所望のレベルに維持することができる。その結果、Ｍｏを添加しなくても、７００℃以下の温度範囲において短時間高温強度が優れ、かつ母材靭性及び溶接熱影響部靱性が良好な厚鋼板を得ることができる。 As described above, in the method for producing a thick steel plate according to the present invention, a steel slab or cast slab whose composition is optimized is heated to 1150 to 1300 ° C., and then the cumulative rolling reduction at 1100 ° C. or less is 10 to 90%. In addition, since hot rolling is performed at a rolling end temperature of Ar3 transformation point or higher, the volume fraction of bainite and martensite in the microstructure of the pressed steel sheet can be made 20% or more in total. Thereby, while high temperature strength can be improved by precipitation strengthening by V carbonitride, room temperature strength can be maintained at a desired level as a steel material for welded structure. As a result, it is possible to obtain a thick steel plate having excellent high-temperature strength for a short time in the temperature range of 700 ° C. or less and excellent base material toughness and weld heat affected zone toughness without adding Mo.
以下、本発明の実施例により、本発明の効果を詳細に説明する。本実施例においては、下記表１に示す化学組成の鋼片を使用し、板厚が２５ｍｍ又は５０ｍｍの鋼板を作製した。なお、下記表１に示すＮｏ.１〜Ｎｏ．８の鋼片は、化学組成が本発明の範囲内のものであり、Ｎｏ．９〜Ｎｏ．１７の鋼片は、化学組成が本発明の範囲から外れているものである。また、下記表１に示す化学組成における残部は、Ｆｅ及び不可避的不純物である。 Hereinafter, the effects of the present invention will be described in detail by way of examples of the present invention. In this example, steel pieces having a chemical composition shown in Table 1 below were used to produce steel plates having a plate thickness of 25 mm or 50 mm. In addition, No. 1-No. No. 8 steel slab has a chemical composition within the scope of the present invention. 9-No. The steel slab of 17 has a chemical composition outside the scope of the present invention. Further, the balance in the chemical composition shown in Table 1 below is Fe and inevitable impurities.
鋼片は、真空溶解又は転炉により溶製したインゴット又はスラブを、そのままか又は一旦分塊圧延を行うことにより作製した。そして、熱間圧延により、厚さが１００〜２００ｍｍの鋼片を、板厚が２５ｍｍ又は５０ｍｍの厚鋼板にした。このとき、熱間圧延後に、空冷又は水冷による加速冷却を行い、その後、必要に応じて、焼戻し処理を施した。その際の条件としては、いずれも室温強度が、引張強度４９０〜５７０ＭＰａ級鋼の範囲に入ることを意図した条件を選定したが、比較例の一部では、化学組成が本発明の範囲から外れているため、室温強度が引張強度４９０〜５７０ＭＰａ級鋼の範囲を逸脱したものもあった。下記表２に各厚鋼板の製造条件、並びに鋼板のミクロ組織中のベイナイト及びマルテンサイトの体積分率の合計量合計量を示す。なお、下記表２に示すミクロ組織におけるベイナイト及びマルテンサイトの体積分率の合計量は、圧延方向に垂直な板厚方向の断面におけるナイタール腐食組織を、倍率１００〜５００倍の光学顕微鏡により観察し、その面積率を求めた。そして、表面から２ｍｍの位置、板厚の１／４の位置及び板厚中心部の各々の位置で最低５視野ずつ観察し、それらの平均の面積率を採用した。また、Ａｒ３変態点は、加工フォーマスターによる小型試験を使用し、実際の圧延工程をシミュレート温度履歴及び加工条件の下で測定した。 The steel slab was produced by subjecting an ingot or slab melted by vacuum melting or a converter as it was or once to rolling in pieces. And the steel piece whose thickness is 100-200 mm was made into the thick steel plate whose plate | board thickness is 25 mm or 50 mm by hot rolling. At this time, after hot rolling, accelerated cooling by air cooling or water cooling was performed, and then tempering treatment was performed as necessary. As conditions at that time, conditions were selected in which the room temperature strength was intended to fall within the range of tensile strength of 490 to 570 MPa class steel, but in some of the comparative examples, the chemical composition deviated from the scope of the present invention. Therefore, some of the room temperature strengths deviated from the range of tensile strength of 490 to 570 MPa grade steel. Table 2 below shows the manufacturing conditions for each thick steel plate and the total amount of the volume fractions of bainite and martensite in the microstructure of the steel plate. In addition, the total amount of the volume fraction of bainite and martensite in the microstructure shown in Table 2 below was determined by observing the Nital corrosion structure in the cross section in the thickness direction perpendicular to the rolling direction with an optical microscope with a magnification of 100 to 500 times. The area ratio was obtained. Then, at least 5 visual fields were observed at a position of 2 mm from the surface, a position of 1/4 of the plate thickness, and a position of the center portion of the plate thickness, and an average area ratio thereof was adopted. In addition, the Ar3 transformation point was measured under a simulated temperature history and processing conditions using a small test by a processing for master and an actual rolling process.
また、上記表２に示すＮｏ．Ａ１〜Ｎｏ．Ａ１２の鋼板は、化学組成及び組織形態共に本発明の範囲内である実施例の厚鋼板でありＮｏ．Ｂ１〜Ｎｏ．Ｂ１０の鋼板は、化学組成又は組織形態のいずれかが、本発明の範囲から外れている比較例の厚鋼板である。 In addition, No. 2 shown in Table 2 above. A1-No. The steel plate of A12 is a thick steel plate according to an example in which both the chemical composition and the structure form are within the scope of the present invention. B1-No. The steel plate of B10 is a thick steel plate of a comparative example in which either the chemical composition or the structure form is out of the scope of the present invention.
次に、これらの厚鋼板の板厚中心部より、試験片の長手方向が厚鋼板の圧延方向と直交する方向になるように、丸棒引張試験片及び２ｍｍＶノッチシャルピー衝撃試験片を採取し、母材の機械的性質を調査した。その際、引張特性は室温、６００℃及び７００℃で試験を行い、２ｍｍＶノッチシャルピー衝撃特性は０℃で行った。なお、高温での引張試験は、ＪＩＳ Ｇ０５６７に従って実施した。 Next, a round bar tensile test piece and a 2 mm V notch Charpy impact test piece are collected so that the longitudinal direction of the test piece is in a direction orthogonal to the rolling direction of the thick steel plate from the center of the plate thickness of these thick steel plates, The mechanical properties of the base material were investigated. At that time, the tensile properties were tested at room temperature, 600 ° C. and 700 ° C., and the 2 mm V notch Charpy impact properties were conducted at 0 ° C. The tensile test at high temperature was performed according to JIS G0567.
また、ＨＡＺ靭性については、２５ｍｍ厚鋼板についてはそのまま、５０ｍｍ厚鋼板については２５ｍｍに減厚し、銅当金を使用して、入熱が約１５ｋＪ／ｍｍの片面１パスサブマージアーク溶接で継手を作製した。そして、各継手の鋼板板厚中心部における溶接金属とＨＡＺの境界（融合部：ＦＬ）がノッチ位置となり、ノッチが鋼板表面に垂直な面に入るようにして２ｍｍＶノッチシャルピー衝撃試験片を採取し、母材と同様に０℃で試験を実施した。なお、本実施例で行った１パスサブマージアーク溶接は、大入熱溶接であり、８００℃から５００℃までの冷却時間は、約２５０秒以上となる。以上の結果、即ち、母材の機械的性質及びＨＡＺ靭性を下記表３にまとめて示す。なお、下記表３に示す母材靭性及びＨＡＺ靭性は、試験片３本の０℃吸収エネルギーの平均値である。 As for HAZ toughness, the thickness of the 25 mm thick steel plate is reduced as it is, the thickness of the 50 mm thick steel plate is reduced to 25 mm, and the joint is formed by single-sided one-pass submerged arc welding with a heat input of about 15 kJ / mm using copper alloy. Produced. Then, a 2 mm V notch Charpy impact test specimen was taken so that the boundary between the weld metal and the HAZ at the center of the steel plate thickness of each joint (fusion part: FL) was the notch position, and the notch entered a plane perpendicular to the steel plate surface. The test was performed at 0 ° C. in the same manner as the base material. The one-pass submerged arc welding performed in this example is a high heat input welding, and the cooling time from 800 ° C. to 500 ° C. is about 250 seconds or more. The above results, that is, the mechanical properties and HAZ toughness of the base material are summarized in Table 3 below. In addition, the base material toughness and the HAZ toughness shown in Table 3 below are average values of 0 ° C. absorbed energy of three test pieces.
上記表３に示す実施例Ｎｏ．Ａ１〜Ｎｏ．Ａ１２の鋼板は、６００℃及び７００℃における高温強度が引張強度４９０〜５７０ＭＰａ級鋼用として十分高く、かつ、母材並びにＨＡＺ靭性も全て２００Ｊ以上を十分満足していた。この結果からも、実施例Ｎｏ．Ａ１〜Ｎｏ．Ａ１２の鋼板は、Ｍｏを含有させることなく、耐火用厚鋼板としての十分な特性を有していることが明らかになった。 Example No. shown in Table 3 above. A1-No. The steel sheet of A12 had a high temperature strength at 600 ° C. and 700 ° C. sufficiently high for a tensile strength of 490 to 570 MPa class steel, and the base material and HAZ toughness were all sufficiently satisfying 200J or more. From this result, Example No. A1-No. It became clear that the steel plate of A12 has sufficient characteristics as a fire-resistant thick steel plate without containing Mo.
一方、上記表３に示す比較例Ｎｏ．Ｂ１〜Ｎｏ．Ｂ１０の鋼板は、前述の実施例Ｎｏ．Ａ１〜Ｎｏ．Ａ１２の鋼板と比べて、特性が劣っていた。具体的には、比較例Ｎｏ．Ｂ１の鋼板は、Ｖを含有していないため、引張強度４９０ＭＰａ級鋼としては高温強度が低く、特に７００℃における降伏強度が低かった。比較例Ｎｏ．Ｂ２の鋼板は、Ｖ含有量が過剰なため、引張強度５７０ＭＰａ級鋼としても室温強度が過大であり、その上、母材靭性及びＨＡＺ靭性が共に顕著に劣化していたため、溶接構造用厚鋼板としては好ましくないものであった。 On the other hand, the comparative example No. shown in Table 3 above. B1-No. The steel plate of B10 is the above-mentioned Example No. A1-No. The characteristics were inferior compared to the A12 steel plate. Specifically, Comparative Example No. Since the steel plate of B1 does not contain V, the high-temperature strength is low as a tensile strength 490 MPa class steel, and particularly the yield strength at 700 ° C. is low. Comparative Example No. Since the steel sheet of B2 has an excessive V content, the room temperature strength is excessive even as a steel having a tensile strength of 570 MPa, and furthermore, both the base metal toughness and the HAZ toughness are significantly deteriorated. It was not preferable.
比較例Ｎｏ．Ｂ３の鋼板は、Ｎ含有量が過小なため、高温でのＶ炭窒化物の析出が十分でなく、そのため、高温強度が同様の室温強度レベルの実施例の鋼板に比べて低く、耐火用の引張強度５７０ＭＰａ級鋼としては高温強度が不十分であった。比較例Ｎｏ．Ｂ４の鋼板は、逆にＮ含有量が過大なため、Ｖが早期に粗大析出して、高温強度が低く、特に７００℃における高温強度の低下が顕著であった。また、比較例Ｎｏ．Ｂ４の鋼板は、固溶Ｎの増加及び粗大Ｖ炭窒化物のために、母材靭性及びＨＡＺ靭性が共に極めて低かった。比較例Ｎｏ．Ｂ５の鋼板は、Ｎｂが含有されていないため、Ｖ及びＮの含有量が本発明の範囲内であるにもかかわらず、高温強度が十分でなかった。比較例Ｎｏ．Ｂ６の鋼板は、逆にＮｂ含有量が過大なため、引張強度５７０ＭＰａ級鋼としても室温強度が過大であり、その上、母材靭性及びＨＡＺ靭性が共に顕著に劣化しいたため、溶接構造用厚鋼板としては好ましくないものであった。 Comparative Example No. The B3 steel sheet has an excessively low N content, so the precipitation of V carbonitride at high temperatures is not sufficient. Therefore, the high temperature strength is lower than that of the steel sheets of the same room temperature strength level, and is refractory. High-temperature strength was insufficient as a tensile strength 570 MPa class steel. Comparative Example No. On the contrary, in the steel sheet of B4, since the N content was excessive, V was coarsely precipitated at an early stage, and the high temperature strength was low, and the decrease in the high temperature strength particularly at 700 ° C. was remarkable. Comparative Example No. The steel plate of B4 had extremely low base metal toughness and HAZ toughness due to an increase in solute N and coarse V carbonitride. Comparative Example No. Since the steel sheet of B5 does not contain Nb, the high-temperature strength was not sufficient even though the contents of V and N were within the scope of the present invention. Comparative Example No. On the contrary, the steel sheet of B6 has an excessive Nb content, so that the room temperature strength is excessive as a tensile strength 570 MPa grade steel, and furthermore, both the base metal toughness and the HAZ toughness have been significantly deteriorated. It was not preferable as a thick steel plate.
比較例Ｎｏ．Ｂ７の鋼板は、Ｃ含有量が過大なため、また、比較例Ｎｏ．Ｂ８の鋼板は、Ｍｎ含有量が過大なため、母材靭性及びＨＡＺ靭性が共に顕著に劣化しており、溶接構造用厚鋼板としては好ましくないものであった。比較例Ｎｏ．Ｂ９の鋼板は、本発明の範囲外となるＭｏ含有鋼の例である。この比較例Ｎｏ．Ｂ９の鋼板は、高温強度については特に問題はないが、大入熱ＨＡＺ靭性は前述した実施例の鋼板に比べて明らかに劣っていた。比較例Ｎｏ．Ｂ１０の鋼板は、ミクロ組織中のベイナイト及びマルテンサイトの体積分率の合計量が過小であるため、引張強度４９０ＭＰａ級鋼としては高温強度が不十分であった。 Comparative Example No. The steel sheet of B7 has an excessive C content. Since the steel plate of B8 has an excessive Mn content, both the base metal toughness and the HAZ toughness are remarkably deteriorated, which is not preferable as a thick steel plate for welded structure. Comparative Example No. The steel plate of B9 is an example of Mo-containing steel that is outside the scope of the present invention. This Comparative Example No. The steel plate of B9 has no particular problem with respect to the high temperature strength, but the high heat input HAZ toughness was clearly inferior to the steel plates of the above-described examples. Comparative Example No. Since the total amount of the bainite and martensite volume fractions in the microstructure of the steel sheet B10 was too small, the high-temperature strength was insufficient as a tensile strength 490 MPa grade steel.
以上の実施例によっても、本発明により、Ｍｏを含有させることなく、引張強度４９０〜５７０ＭＰａ級の溶接構造用厚鋼板において、６００℃では規格降伏点の２／３程度以上、７００℃では規格降伏点の１／２以上の降伏強度を有し、母材及び大入熱溶接継手のＨＡＺ靭性が、２ｍｍＶノッチシャルピー衝撃試験の０℃における吸収エネルギーで７０Ｊ以上である厚鋼板を提供することが可能であり、産業上の効果は極めて大きい。 Also according to the above examples, according to the present invention, in the thick steel plate for welded structure having a tensile strength of 490 to 570 MPa without containing Mo, about 2/3 or more of the standard yield point at 600 ° C., and standard yield at 700 ° C. It is possible to provide a thick steel plate having a yield strength of 1/2 or more of the point and having a HAZ toughness of the base metal and the high heat input welded joint of 70 J or more in absorbed energy at 0 ° C. in a 2 mmV notch Charpy impact test. Therefore, the industrial effect is extremely large.
Claims (11)
Ｃ：０．０２〜０．２％、
Ｓｉ：０．０３〜１％、
Ｍｎ：０．３〜２％、
Ａｌ：０．００１〜０．０５％、
Ｎｂ：０．００５〜０．２％、
Ｖ：０．０３〜０．３％及び
Ｎ：０．００５〜０．０３％を含有すると共に、
Ｐ：０．０２％以下及び
Ｓ：０．０１％以下に制限し、
残部がＦｅ及び不可避不純物からなり、
ミクロ組織におけるベイナイト及びマルテンサイトの体積分率が合計で２０％以上であることを特徴とする耐火厚鋼板。 % By mass
C: 0.02 to 0.2%,
Si: 0.03 to 1%,
Mn: 0.3-2%,
Al: 0.001 to 0.05%,
Nb: 0.005 to 0.2%,
V: 0.03-0.3% and N: 0.005-0.03%,
P: 0.02% or less and S: 0.01% or less,
The balance consists of Fe and inevitable impurities,
A refractory thick steel sheet having a total volume fraction of bainite and martensite of 20% or more in a microstructure.
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| CN101849026B (en) | 2009-01-15 | 2012-07-04 | 新日本制铁株式会社 | Steel for weld construction having excellent high-temperature strength and low-temperature toughness and process for producing the steel |
| JP5347824B2 (en) * | 2009-08-10 | 2013-11-20 | 新日鐵住金株式会社 | Refractory steel material excellent in high-temperature strength of base metal and high-temperature ductility of weld heat-affected zone and its manufacturing method |
| EP2557184A1 (en) * | 2011-08-10 | 2013-02-13 | Swiss Steel AG | Hot-rolled profiled steel reinforcement for reinforced concrete with improved fire resistance and method for producing same |
| WO2014132627A1 (en) * | 2013-02-28 | 2014-09-04 | Ｊｆｅスチール株式会社 | Thick steel plate and production method for thick steel plate |
| CN114351045A (en) * | 2021-12-02 | 2022-04-15 | 包头钢铁（集团）有限责任公司 | Economical refractory hot-rolled steel plate with yield strength of 420MPa and preparation method thereof |
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| JP2005060835A (en) * | 2003-07-31 | 2005-03-10 | Jfe Steel Kk | Low-yield-ratio high-strength steel sheet excellent in toughness of welding-heat-affected part and its production method |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2003160835A (en) * | 2001-11-26 | 2003-06-06 | Kobe Steel Ltd | High-tension thick steel plate superior in weldability and uniform elongation |
| JP2004043961A (en) * | 2002-05-20 | 2004-02-12 | Nippon Steel Corp | 490 MPa CLASS HIGH TENSILE STRENGTH STEEL HAVING EXCELLENT HIGH TEMPERATURE STRENGTH AND METHOD OF PRODUCING THE SAME |
| JP2005060835A (en) * | 2003-07-31 | 2005-03-10 | Jfe Steel Kk | Low-yield-ratio high-strength steel sheet excellent in toughness of welding-heat-affected part and its production method |
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