JP2002294338A - Method for producing low yield ratio steel having excellent fire resistance - Google Patents
Method for producing low yield ratio steel having excellent fire resistanceInfo
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- JP2002294338A JP2002294338A JP2001101666A JP2001101666A JP2002294338A JP 2002294338 A JP2002294338 A JP 2002294338A JP 2001101666 A JP2001101666 A JP 2001101666A JP 2001101666 A JP2001101666 A JP 2001101666A JP 2002294338 A JP2002294338 A JP 2002294338A
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、建築、土木等の鋼
構造物に用いられる低降伏比鋼の製造方法に関し、特に
耐火強度に優れた鋼の製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing low yield ratio steel used for steel structures such as buildings and civil engineering, and more particularly to a method for producing steel having excellent fire resistance.
【０００２】[0002]
【従来の技術】高層建築構造物に用いられる鋼材は、Ｔ
Ｓ４９０Ｎ／ｍｍ2級高張力鋼からＴＳ５９０Ｎ／ｍｍ2
級高張力鋼へと高強度化が進展しているが、降伏比も上
昇するため、二相焼入れ焼戻し法により降伏比を低減さ
せる技術が特開平７−９０３６５号公報等で提案されて
いる。2. Description of the Related Art Steel materials used for high-rise building structures are T
From S490N / mm2 class high tensile steel to TS590N / mm2
Although high-strength steel has been developed to have high strength, the yield ratio also increases. Therefore, a technique for reducing the yield ratio by a two-phase quenching and tempering method has been proposed in Japanese Patent Laid-Open No. 7-90365.
【０００３】低降伏比に加えて更に耐火性の要求される
ことが多い、最近の建築用鋼に関しては、母材靭性を十
分確保しがたいという問題点はあるもののＮｂ，Ｍｏを
固溶させる技術が、特開平７−２５８７８９号公報等で
提案されている。[0003] In recent construction steels, in addition to a low yield ratio, there is often a need for fire resistance, although there is a problem in that it is difficult to ensure sufficient base material toughness, but Nb and Mo are dissolved. A technique has been proposed in Japanese Patent Application Laid-Open No. 7-258789.
【０００４】そして、特開２０００−１９２１４２号公
報には、母材靭性を向上させ、更に降伏比を低化させ、
耐火性を向上させるため、所定の化学成分の鋼板を熱間
圧延後、２℃／ｓｅｃ以上で加速冷却する際、Ａｒ3−
１００℃以上、Ａｒ3以下の二相域温度で待機し、その
後、４００〜６５０℃の温度範囲まで冷却を行うことが
記載されている。[0004] Japanese Patent Application Laid-Open No. 2000-192142 discloses that the base material toughness is improved and the yield ratio is further reduced.
In order to improve the fire resistance, after hot rolling a steel plate having a predetermined chemical composition, when accelerated cooling at 2 ° C./sec or more, Ar 3 −
It is described that the process waits at a two-phase region temperature of 100 ° C. or more and Ar 3 or less, and then cools to a temperature range of 400 to 650 ° C.
【０００５】しかし、高温強度に関して教えられること
は少なく、また、低降伏比とするため、二相域での待機
時間が１５０ｓｅｃと長く、生産性の低下することが懸
念される。However, there is little to be taught about the high-temperature strength, and in order to obtain a low yield ratio, the standby time in the two-phase region is as long as 150 seconds, and there is a concern that productivity may be reduced.
【０００６】[0006]
【発明が解決しようとする課題】そこで、本発明では、
建築用鋼として十分な母材靭性、低降伏比と共に耐火性
を兼ね備えた鋼として、常温での引張特性が、ＹＰ≧４
４０ＭＰａ，ＴＳ≧５９０ＭＰａ，ＹＲ≦８０％、シャ
ルピー衝撃特性がｖＥ０≧２００Ｊ及び高温強度がＹＰ
≧２９３ＭＰａ（ａｔ６００℃）を満足する鋼を生産性
良く製造する方法を提供することを目的とする。Therefore, in the present invention,
As a steel having sufficient base metal toughness and low yield ratio as a building steel, and having fire resistance, its tensile properties at room temperature is YP ≧ 4.
40MPa, TS ≧ 590MPa, YR ≦ 80%, Charpy impact characteristics are vE0 ≧ 200J, and high temperature strength is YP
It is an object of the present invention to provide a method for producing steel satisfying ≧ 293 MPa (at 600 ° C.) with high productivity.
【０００７】[0007]
【課題を解決するための手段】本発明者等は、上記課題
を解決するため、耐火性能の確保を前提に、二相域加熱
条件について詳細に検討し、低降伏比化と母材靭性の向
上に有効な軟質相の形成に関し、以下の知見を得た。Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have studied the heating conditions in the two-phase region in detail on the premise of ensuring the fireproof performance, and have obtained a low yield ratio and a base metal toughness. The following findings were obtained regarding the formation of a soft phase effective for improvement.
【０００８】（１）低降伏比化には、ミクロ組織を軟質
相と硬質相の混合組織とすることが有効である。(1) To reduce the yield ratio, it is effective to make the microstructure a mixed structure of a soft phase and a hard phase.
【０００９】（２）そのためには、二相域での保持（待
機）が有効であるが、長時間保持（待機）では、生産
性、強度が低下し、更に、Ｍｏ，Ｎｂ等の炭窒化物の析
出により降伏比が上昇する。(2) To this end, holding (standby) in a two-phase region is effective. However, holding (standby) for a long time reduces productivity and strength, and furthermore, carbonitriding of Mo, Nb, etc. The yield ratio increases due to the precipitation of the material.
【００１０】一方、短時間保持（待機）では、軟質相の
形成が不足し、十分な低降伏比が得られない。On the other hand, if the material is held for a short time (standby), formation of a soft phase is insufficient, and a sufficiently low yield ratio cannot be obtained.
【００１１】（３）短時間保持において、十分な軟質相
を形成する方法として、制御圧延によるミクロ組織の微
細化および展伸化によるフェライト変態サイトの増加が
有効である。(3) As a method of forming a sufficient soft phase in holding for a short time, it is effective to refine the microstructure by controlled rolling and increase the number of ferrite transformation sites by spreading.
【００１２】Ｎｂは、オーステナイト再結晶温度を上昇
させ、未再結晶温度域を高温側にするため、圧延効率を
損ねず、組織展伸化が可能となる。Nb raises the austenite recrystallization temperature and raises the non-recrystallization temperature range to a higher temperature side, so that the structure can be expanded without impairing the rolling efficiency.
【００１３】（４）二相域温度の低温側での保持（待
機）が、フェライト変態駆動力を大きくし、短時間での
保持（待機）で軟質相の形成を容易とする。(4) Holding (standby) on the low temperature side of the two-phase region temperature increases ferrite transformation driving force, and facilitates formation of a soft phase by holding (standby) in a short time.
【００１４】尚、高温強度は、火災等で加熱されたとき
Ｍｏ，Ｎｂ等を炭窒化物として析出させることがその向
上に有効で、二相域温度での保持が長時間になると二相
域温度において既に析出する量が過大となり、これら元
素の固溶が寄与する常温強度や高温強度が損なわれるた
め、二相域温度の低温側で短時間保持（待機）すること
が好ましい。The high-temperature strength can be effectively improved by precipitating Mo, Nb, etc. as carbonitrides when heated in a fire or the like. Since the amount already precipitated at the temperature becomes excessive and the room-temperature strength and the high-temperature strength to which solid solution of these elements contributes are impaired, it is preferable to hold (stand by) for a short time at the low temperature side of the two-phase region temperature.
【００１５】本発明はこれらの知見に更に検討を加えて
なされたものであり、すなわち、本発明は、 １．下記の工程を具備したことを特徴とする耐火特性に
優れた低降伏比鋼の製造方法。The present invention has been made by further studying these findings. That is, the present invention provides: A method for producing a low-yield-ratio steel having excellent fire resistance characteristics, comprising the following steps.
【００１６】（１）質量％で、Ｃ：０．０６〜０．１１
％、Ｓｉ：０．０５〜１．０％、Ｍｎ：０．５〜１．６
％、Ｐ：０．０１５％以下、Ｓ：０．０１％以下、Ｍ
ｏ：０．１５〜０．５％未満、Ａｌ：０．００５〜０．
１％、Ｎ：０．００５％以下、残部が実質的に鉄および
不可避的不純物からなる鋼を、１０００〜１２５０℃に
加熱する工程。(1) In mass%, C: 0.06 to 0.11
%, Si: 0.05 to 1.0%, Mn: 0.5 to 1.6
%, P: 0.015% or less, S: 0.01% or less, M
o: 0.15 to less than 0.5%, Al: 0.005 to 0.5%.
1%, N: 0.005% or less, the balance being a step of heating steel consisting essentially of iron and unavoidable impurities to 1000 to 1250 ° C.
【００１７】（２）１０００℃以下で、２０％以上の累
積圧下を行う圧延工程。(2) A rolling step of performing a cumulative reduction of 20% or more at a temperature of 1000 ° C. or less.
【００１８】（３）Ａｒ3点以上より２℃／ｓｅｃ以
上、冷却停止温度Ａｒ3−１５０〜Ａｒ3−１００℃で加
速冷却する一次冷却工程。(3) A primary cooling step of accelerated cooling at 2 ° C./sec or more from the Ar 3 point or more and at a cooling stop temperature Ar 3 -150 to Ar 3 -100 ° C.
【００１９】（４）該冷却停止温度で５〜１００ｓｅｃ
保持後、更に２℃／ｓｅｃ以上、冷却停止温度４００〜
６５０℃で加速冷却する二次冷却工程。(4) 5-100 seconds at the cooling stop temperature
After holding, furthermore, 2 ° C / sec or more, cooling stop temperature 400 ~
Secondary cooling step of accelerated cooling at 650 ° C.
【００２０】２． 更に、Ｎｂ：０．００５〜０．０５
％を含有する１記載の耐火特性に優れた低降伏比鋼の製
造方法。2. Further, Nb: 0.005 to 0.05
The method for producing a low-yield-ratio steel excellent in refractory properties according to 1 above, wherein
【００２１】３． 更に、Ｃｕ：０．０５〜０．５％、
Ｎｉ：０．０５〜０．５％、Ｃｒ：０．０５〜０．５
％、Ｖ：０．０１〜０．１％の一種又は二種以上を含有
する１または２記載の耐火特性に優れた低降伏比鋼の製
造方法。3. Further, Cu: 0.05 to 0.5%,
Ni: 0.05 to 0.5%, Cr: 0.05 to 0.5
%, V: The method for producing a low-yield-ratio steel excellent in refractory properties according to 1 or 2, which contains one or more of 0.01 to 0.1%.
【００２２】[0022]
【発明の実施の形態】本発明での、成分組成、製造条件
の限定理由について説明する。BEST MODE FOR CARRYING OUT THE INVENTION The reasons for limiting the component composition and the production conditions in the present invention will be described.
【００２３】Ｃ：０．０６〜０．１１％ Ｃは、鋼の常温強度、高温強度を安定して確保するため
有効で、０．０６％以上添加する。０．１１％を超えて
添加すると靭性、溶接性が劣化するため、０．０６〜
０．１１％（０．０６％以上、０．１１％以下）とす
る。C: 0.06% to 0.11% C is effective for stably securing the normal-temperature strength and high-temperature strength of steel, and is added in an amount of 0.06% or more. If added in excess of 0.11%, toughness and weldability deteriorate, so
0.11% (not less than 0.06% and not more than 0.11%).
【００２４】Ｓｉ：０．０５〜１．０％ Ｓｉは、脱酸元素として、０．０５％以上添加する。一
方、１．０％を超えて添加すると、延靭性が低下し、所
望の強度を超えるため、０．０５〜１．０％とする。Si: 0.05 to 1.0% Si is added in an amount of 0.05% or more as a deoxidizing element. On the other hand, if it is added in excess of 1.0%, the ductility decreases, and the desired strength is exceeded.
【００２５】Ｍｎ：０．５〜１．６％ Ｍｎは、母材及び溶接溶接継手の強度及び靭性向上に有
効で、０．５％以上添加する。一方、１．６％を超える
と溶接性が劣化し、母材及び溶接溶接継手の靭性を劣化
させるため、０．５〜１．６％とする。Mn: 0.5 to 1.6% Mn is effective for improving the strength and toughness of the base metal and the welded joint, and is added in an amount of 0.5% or more. On the other hand, if it exceeds 1.6%, the weldability deteriorates, and the toughness of the base metal and the welded joint deteriorates.
【００２６】Ｐ≦０．０１５％、Ｓ≦０．０１％ Ｐ，Ｓは、不純物元素であり、延靭性、加工性、および
溶接性を低下させるため、Ｐ≦０．０１５％、Ｓ≦０．
０１％とする。P ≦ 0.015%, S ≦ 0.01% P and S are impurity elements, which reduce the ductility, workability and weldability. .
01%.
【００２７】Ｍｏ：０．１５〜０．５％ Ｍｏは、鋼の強度を向上させ、特に高温強度の向上に有
効であり、０．１５％以上添加する。一方、０．５％超
えでは、溶接性及び溶接継手靭性を劣化させるため、
０．１５〜０．５％とする。Mo: 0.15 to 0.5% Mo improves the strength of the steel, and is particularly effective in improving the high-temperature strength. Mo is added in an amount of 0.15% or more. On the other hand, if it exceeds 0.5%, the weldability and weld joint toughness deteriorate, so
0.15 to 0.5%.
【００２８】Ａｌ：０．００５〜０．１％ Ａｌは、脱酸のため、０．００５％以上添加する。一
方、０．１％を超えると、母材靭性を劣化させるため、
０．１％以下とする。Al: 0.005 to 0.1% Al is added in an amount of 0.005% or more for deoxidation. On the other hand, if it exceeds 0.1%, the base material toughness deteriorates.
0.1% or less.
【００２９】Ｎ：０．００５％以下 Ｎは、ＡｌＮとして析出し、結晶粒の微細化により母材
靭性を向上させる。しかし、過剰に含まれると母材、溶
接部の靭性を劣化させるため、０．００５％以下とす
る。N: 0.005% or less N precipitates as AlN, and improves the base material toughness by making crystal grains fine. However, if it is excessively contained, the toughness of the base metal and the welded portion is deteriorated.
【００３０】以上が、本発明の基本成分組成であるが、
更にその特性を向上させるため、Ｎｂ，Ｃｕ，Ｎｉ，Ｃ
ｒ、Ｖの一種または二種以上を添加することが出来る。The above is the basic component composition of the present invention.
In order to further improve the characteristics, Nb, Cu, Ni, C
One or more of r and V can be added.
【００３１】Ｎｂ：０．００５〜０．０５％ Ｎｂは、加熱時に固溶状態のＮｂが焼入れ性を向上さ
せ、また、炭化物の析出強化により鋼の常温、高温強度
を向上させるため、０．００５％以上添加する。一方、
０．０５％を超えると靭性を劣化させるため、０．００
５〜０．０５％とする。Nb: 0.005 to 0.05% Nb is used in a solid solution state during heating to improve the quenchability, and to enhance the normal temperature and high temperature strength of steel by strengthening the precipitation of carbides. Add 005% or more. on the other hand,
If it exceeds 0.05%, the toughness deteriorates.
5 to 0.05%.
【００３２】Ｃｕ，Ｃｒ，Ｎｉ：０．０５〜０．５％ Ｃｕ，Ｃｒ，Ｎｉは、鋼および溶接継手の強度を向上さ
せ、Ｎｉは更に靭性を向上させるため、０．０５％以上
添加する。一方、０．５％を超えると、溶接性が劣化す
るため、０．０５〜０．５％とする。Cu, Cr, Ni: 0.05 to 0.5% Cu, Cr, Ni is added in an amount of 0.05% or more in order to improve the strength of steel and welded joints, and Ni to further improve toughness. . On the other hand, if it exceeds 0.5%, the weldability deteriorates.
【００３３】Ｖ：０．０１〜０．１％ Ｖは、析出強化により強度を上昇させるため、０．０１
％以上添加する。一方、多量に添加すると靭性が劣化す
るため、０．０１〜０．１％とする。V: 0.01-0.1% V increases the strength by precipitation strengthening.
% Or more. On the other hand, if added in a large amount, the toughness deteriorates, so the content is made 0.01 to 0.1%.
【００３４】２．製造条件 スラブ加熱温度：１０００〜１２５０℃ スラブ加熱温度は、合金元素を均質に固溶させるため、
１０００℃以上とする。しかし、１２５０℃を超えると
粗大組織となり、靭性が劣化するため、１０００〜１２
５０℃とする。2. Manufacturing conditions Slab heating temperature: 1000-1250 ° C. Slab heating temperature is to uniformly dissolve alloying elements.
1000 ° C. or higher. However, when the temperature exceeds 1250 ° C., a coarse structure is formed, and the toughness is deteriorated.
50 ° C.
【００３５】圧延条件：１０００℃以下で累積圧下率２
０％以上 熱間圧延後の二相域温度保持でのフェライト変態を促進
するため、熱間圧延において１０００℃以下での累積圧
下率を２０％以上とする。図１は、常温引張特性に及ぼ
す本規定の効果を示すもので、待機時間（保持時間）に
よらず８０％以下の低降伏比が得られている。Rolling conditions: Cumulative rolling reduction 2 at 1000 ° C. or less
0% or more In order to promote ferrite transformation while maintaining the temperature in the two-phase region after hot rolling, the cumulative rolling reduction at 1000 ° C or less in hot rolling is made 20% or more. FIG. 1 shows the effect of the present specification on the room temperature tensile properties, and a low yield ratio of 80% or less is obtained regardless of the standby time (holding time).
【００３６】冷却速度：２℃／ｓｅｃ以上 火災などで６００℃に加熱された際に、常温強度（ＹＰ
４４０Ｎ／ｍｍ2）の２／３であるＹＰ２９３Ｎ／ｍｍ2
級強度を確保できるよう、圧延後の冷却過程でのＭｏ，
Ｎｂの析出を抑制するため、冷却速度：２℃／ｓｅｃ以
上とする。Cooling rate: 2 ° C./sec or more When heated to 600 ° C. in a fire or the like, the room temperature strength (YP
YP293N / mm2 which is 2/3 of 440N / mm2)
Mo, Mo in the cooling process after rolling to ensure the class strength
In order to suppress the precipitation of Nb, the cooling rate is set to 2 ° C./sec or more.
【００３７】待機温度（保持温度）：Ａｒ3−１５０℃
〜Ａｒ3−１００℃ 低降伏比化、高靭化のため、二相域温度での待機（保
持）によりフェライト析出を促進する。待機温度（保持
温度）は、フェライト変態の駆動力の大きなＡｒ3−１
００℃以下とする。一方、Ａｒ3−１５０℃未満では、
軟質な第二相の生成が損なわれる場合があるため、Ａｒ
3−１５０℃〜Ａｒ3−１００℃とする。Stand-by temperature (holding temperature): Ar 3 -150 ° C.
~ Ar3-100 ° C To reduce the yield ratio and increase toughness, ferrite precipitation is promoted by waiting (holding) at a temperature in the two-phase region. The standby temperature (holding temperature) is Ar3-1 which has a large driving force for ferrite transformation.
It should be below 00 ° C. On the other hand, if Ar3 is less than -150 ° C,
Since the formation of the soft second phase may be impaired, Ar
The temperature is from 3 to 150 ° C to Ar3 to 100 ° C.
【００３８】尚、本発明では、Ａｒ3変態点として、Ｔ
ｒａｎｓ．ＩＳＩＪ、２２（１９８２）、Ｐ２１４
（Ｃ．Ｏｕｃｈｉ、Ｔ．Ｓａｍｐｅｉ、ａｎｄＩ．Ｋｏ
ｚａｓｕ）に記載されているＡｒ3＝９１０−３１０Ｃ
−８０Ｍｎ−２０Ｃｕ−１５Ｃｒ−５５Ｎｉ−８０Ｍｏ
＋０．３５（ｔ−８）によるものを用いた。但し、ｔ：
板厚（ｍｍ）とする。In the present invention, the Ar3 transformation point is T
rans. ISIJ, 22 (1982), P214
(C. Ouchi, T. Sampei, and I. Ko
Za3) Ar3 = 910-310C
-80Mn-20Cu-15Cr-55Ni-80Mo
+0.35 (t-8) was used. Where t:
Plate thickness (mm).
【００３９】待機時間（保持時間）：５〜１００秒 低降伏比化に有効な軟質相を生成し、且つ生産性を損ね
ないよう、二相域温度での保持時間を５〜１００秒とす
る。Stand-by time (holding time): 5 to 100 seconds The holding time at the temperature in the two-phase region is set to 5 to 100 seconds so that a soft phase effective for lowering the yield ratio is produced and productivity is not impaired. .
【００４０】冷却停止温度：４００〜６５０℃ ２相域温度での待機後（保持後）の冷却停止温度は、４
００℃未満では、靭性が劣化し、一方、６５０℃より高
温では強度が低下するため、４００〜６５０℃とする。Cooling stop temperature: 400 to 650 ° C. After cooling (after holding) at the two-phase region temperature, the cooling stop temperature is 4
If the temperature is lower than 00 ° C., the toughness is deteriorated. On the other hand, if the temperature is higher than 650 ° C., the strength is reduced.
【００４１】[0041]
【実施例】表１に示す化学成分の鋼を、表２に示す製造
条件により低降伏比耐火鋼板とした。表２に、母材につ
いて、常温引張特性、シャルピー衝撃特性及び６００℃
での高温引張特性を調査した結果を合わせて示す。EXAMPLES Steels having the chemical components shown in Table 1 were made into low yield ratio refractory steel sheets under the production conditions shown in Table 2. Table 2 shows the room temperature tensile properties, Charpy impact properties and 600 ° C.
The results obtained by examining the high-temperature tensile properties at the same time are also shown.
【００４２】本発明鋼であるＡ−１〜Ｈの各鋼板は、常
温での引張特性が、ＹＰ≧４４０ＭＰａ，ＴＳ≧５９０
ＭＰａ，ＹＲ≦８０％、シャルピー衝撃特性がｖＥ０≧
２００Ｊ及び高温強度がＹＰ≧２９３ＭＰａ（ａｔ６０
０℃）と優れた特性が得られている。Each of the steel sheets A-1 to H of the present invention has a tensile property at room temperature of YP ≧ 440 MPa and TS ≧ 590.
MPa, YR ≦ 80%, Charpy impact characteristic is vE0 ≧
200J and high temperature strength is YP ≧ 293MPa (at60
0 ° C.).
【００４３】一方、鋼Ｉ〜Ｏは比較鋼であり、これらの
うち鋼Ｉ〜Ｍは成分組成が本発明範囲内であるが製造条
件のいくつかが本発明範囲外となっている。鋼Ｎ，Ｏは
製造条件が本発明範囲内であるが、成分組成が本発明範
囲外である。On the other hand, steels I to O are comparative steels. Among them, steels I to M have component compositions within the scope of the present invention, but some production conditions are outside the scope of the present invention. The production conditions of steels N and O are within the scope of the present invention, but the component compositions are outside the scope of the present invention.
【００４４】比較鋼Ｉ〜Ｏは、常温引張特性、シャルピ
ー衝撃特性及び６００℃での高温引張特性のいずれかが
本発明鋼に対し劣っている。The comparative steels I to O are inferior to any of the steels of the present invention in any of the room-temperature tensile properties, the Charpy impact properties and the high-temperature tensile properties at 600 ° C.
【００４５】鋼Ｉは、二相域温度での保持時間が１０６
ｓｅｃと長く、保持中にＭｏが析出し、高温強度に劣
る。鋼Ｊは、冷却速度が１．８℃／ｓｅｃと長く、常温
及び高温強度に劣る。The steel I has a retention time at the two-phase region temperature of 106
sec, Mo precipitates during holding, and is inferior in high-temperature strength. Steel J has a long cooling rate of 1.8 ° C./sec, and is inferior in normal temperature and high temperature strength.
【００４６】鋼Ｋは、待機後の冷却停止温度が３６０℃
と低く、０℃におけるシャルピー吸収エネルギーが低
い。鋼Ｌは、１０００℃以下の圧下量が１５％と少ない
ため、低降伏比化が十分でない。Steel K has a cooling stop temperature of 360 ° C. after standby.
And the Charpy absorbed energy at 0 ° C. is low. Since the reduction amount of steel L at 1000 ° C. or less is as small as 15%, the reduction in yield ratio is not sufficient.
【００４７】鋼Ｍは、二相域温度での待機後の冷却停止
温度が６５５℃と高く、ＴＳ５９０Ｎ／ｍｍ2級の強度
が得られない。鋼Ｎは、Ｍｏ量が少なく、高温強度が低
い。鋼Ｏは、Ｃ量が少なく、常温、高温強度が低い。Steel M has a high cooling stop temperature of 655 ° C. after standby at the two-phase region temperature, and does not have a strength of TS590 N / mm 2 class. Steel N has a low Mo content and a low high-temperature strength. Steel O has a low C content and low strength at normal temperature and high temperature.
【００４８】[0048]
【表１】 [Table 1]
【００４９】[0049]
【表２】 [Table 2]
【００５０】[0050]
【発明の効果】本発明によれば、低降伏比建築用鋼とし
ての強度、靭性を備え、且つ６００℃での高温強度に優
れた耐火鋼を安価に生産性良く得ることが可能である。According to the present invention, it is possible to obtain inexpensively and with good productivity, fire-resistant steel having strength and toughness as a low yield ratio building steel, and excellent in high-temperature strength at 600 ° C.
【図１】常温引張特性に及ぼす１０００℃以下２０％以
上の累積圧下率及び待機時間の影響を示す図。FIG. 1 is a graph showing the influence of a cumulative rolling reduction of not more than 20% at 1000 ° C. or less and a waiting time on tensile properties at room temperature.
フロントページの続き Ｆターム(参考） 4K032 AA01 AA04 AA05 AA11 AA14 AA16 AA19 AA21 AA22 AA23 AA27 AA29 AA31 AA36 BA01 CA02 CA03 CB01 CB02 CC02 CC03 CC04 CD02 CD03 Continued on the front page F term (reference) 4K032 AA01 AA04 AA05 AA11 AA14 AA16 AA19 AA21 AA22 AA23 AA27 AA29 AA31 AA36 BA01 CA02 CA03 CB01 CB02 CC02 CC03 CC04 CD02 CD03
Claims (3)
耐火特性に優れた低降伏比鋼の製造方法。 （１）質量％で、Ｃ：０．０６〜０．１１％、Ｓｉ：
０．０５〜１．０％、Ｍｎ：０．５〜１．６％、Ｐ：
０．０１５％以下、Ｓ：０．０１％以下、Ｍｏ：０．１
５〜０．５％未満、Ａｌ：０．００５〜０．１％、Ｎ：
０．００５％以下、残部が実質的に鉄および不可避的不
純物からなる鋼を、１０００〜１２５０℃に加熱する工
程。 （２）１０００℃以下で、２０％以上の累積圧下を行う
圧延工程。 （３）Ａｒ3点以上より２℃／ｓｅｃ以上、冷却停止温
度Ａｒ3−１５０〜Ａｒ3−１００℃で加速冷却する一次
冷却工程。 （４）該冷却停止温度で５〜１００ｓｅｃ保持後、更に
２℃／ｓｅｃ以上、冷却停止温度４００〜６５０℃で加
速冷却する二次冷却工程。1. A method for producing a low-yield-ratio steel having excellent refractory properties, comprising the following steps. (1) In mass%, C: 0.06 to 0.11%, Si:
0.05-1.0%, Mn: 0.5-1.6%, P:
0.015% or less, S: 0.01% or less, Mo: 0.1
5 to less than 0.5%, Al: 0.005 to 0.1%, N:
A step of heating steel, which is 0.005% or less, with the balance substantially consisting of iron and unavoidable impurities, at 1000 to 1250 ° C. (2) A rolling step of performing a cumulative reduction of 20% or more at 1000 ° C. or less. (3) A primary cooling step of accelerated cooling at a cooling stop temperature of Ar3 -150 to Ar3-100 ° C at a temperature of 2 ° C / sec or more from the Ar3 point or more. (4) A secondary cooling step in which after maintaining the cooling stop temperature for 5 to 100 seconds, accelerated cooling is further performed at a cooling stop temperature of 400 to 650 ° C. at 2 ° C./sec or more.
含有する請求項１記載の耐火特性に優れた低降伏比鋼の
製造方法。2. The method according to claim 1, further comprising Nb: 0.005 to 0.05%.
ｉ：０．０５〜０．５％、Ｃｒ：０．０５〜０．５％、
Ｖ：０．０１〜０．１％の一種又は二種以上を含有する
請求項１または２記載の耐火特性に優れた低降伏比鋼の
製造方法。3. Further, Cu: 0.05 to 0.5%, N
i: 0.05 to 0.5%, Cr: 0.05 to 0.5%,
The method for producing a low-yield-ratio steel having excellent fire resistance according to claim 1 or 2, which contains one or more of V: 0.01 to 0.1%.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006093282A1 (en) * | 2005-03-04 | 2006-09-08 | Nippon Steel Corporation | High tensile and fire-resistant steel excellent in weldability and gas cutting property and method for production thereof |
| JP2006249468A (en) * | 2005-03-09 | 2006-09-21 | Jfe Steel Kk | Method for producing low yield ratio high tensile strength steel |
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|---|---|---|---|---|
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| JP2000192142A (en) * | 1998-12-25 | 2000-07-11 | Nkk Corp | Production of low yield ratio fire resistant steel |
| JP2000248317A (en) * | 1999-03-01 | 2000-09-12 | Nkk Corp | Production of low yield ratio fire resistant shape steel |
| JP2000256737A (en) * | 1999-03-05 | 2000-09-19 | Nkk Corp | Production of low yield ratio high tensile thick steel |
| JP2000256736A (en) * | 1999-03-05 | 2000-09-19 | Nkk Corp | Production of low yield ratio high tensile strength thick steel |
-
2001
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Patent Citations (5)
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|---|---|---|---|---|
| JPH036322A (en) * | 1989-06-02 | 1991-01-11 | Nippon Steel Corp | Production of low yield ratio steel products for building having excellent fire resistivity and steel material for building formed by using these steel products |
| JP2000192142A (en) * | 1998-12-25 | 2000-07-11 | Nkk Corp | Production of low yield ratio fire resistant steel |
| JP2000248317A (en) * | 1999-03-01 | 2000-09-12 | Nkk Corp | Production of low yield ratio fire resistant shape steel |
| JP2000256737A (en) * | 1999-03-05 | 2000-09-19 | Nkk Corp | Production of low yield ratio high tensile thick steel |
| JP2000256736A (en) * | 1999-03-05 | 2000-09-19 | Nkk Corp | Production of low yield ratio high tensile strength thick steel |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006093282A1 (en) * | 2005-03-04 | 2006-09-08 | Nippon Steel Corporation | High tensile and fire-resistant steel excellent in weldability and gas cutting property and method for production thereof |
| JP2006249468A (en) * | 2005-03-09 | 2006-09-21 | Jfe Steel Kk | Method for producing low yield ratio high tensile strength steel |
| JP4687153B2 (en) * | 2005-03-09 | 2011-05-25 | Ｊｆｅスチール株式会社 | Production method of low yield ratio high strength steel |
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