JPH0579744B2 - - Google Patents

Description

【発明の詳細な説明】[Detailed description of the invention]

〔産業上の利用分野〕 本発明は建築、土木および海洋構造物等の分野
において、各種建造物に用いる耐火性の優れた低
降伏比鋼材及びその製造方法に関する。 〔従来の技術〕 周知の通り建築、土木および海洋構造物などの
分野における各種建造物用構築材として、一般構
造用圧延鋼材（JIS Ｇ 3101）、溶接構造用圧延
鋼材（JIS Ｇ 3106）、溶接構造用耐候性熱間圧
延鋼材（JIS Ｇ 3114）、高耐候性圧延鋼材（JIS
Ｇ 3125）および一般構造用炭素鋼鋼管（JIS Ｇ
3444）、一般構造用角形鋼管（JIS Ｇ 3466）
などが広く利用されている。これらの鋼材は、通
常高炉によつて得られた溶銑を、脱Ｓ、脱Ｐした
のち転炉精練を行ない、連続鋳造もしくは分塊工
程において鋼片とし、ついで熱間塑性加工するこ
とにより、所望の特性を備えたものとして製品化
される。 ところで、各種建造物のうち、特に生活に密着
したビルや事務所および住居などの建造物に前記
鋼材を用いる場合、火災における安全性を確保す
るため、十分な耐火被覆を施すことが義務ずけら
れており、建築関係諸法令では、火災時に鋼材温
度が350℃以上にならぬよう規定している。つま
り、前記鋼材は、建造物に使用する場合350℃程
度で耐力（降伏強度）が常温時の60〜70％にな
り、建造物の倒壊を引き起こす恐れがあるため、
火災時における熱的損傷により該鋼材が載荷力を
失うことのないようにして利用しなければならな
い。たとえば、一般構造用圧延鋼材（JIS Ｇ
3101）に規定される形鋼を柱材とする建造物の例
では、その表面にスラグウール、ロツクウール、
ガラスウール、アスベストなどを基材とする吹き
付け材やフエルトを展着するほか、防火モルタル
で包被する方法および前記断熱材層の上に、さら
に金属薄板即ちアルミニユウムやステンレススチ
ール薄板で保護する方法など耐火被覆を入念に施
す必要がある。そのため、鋼材費用に比し耐火被
覆施工費が高額になり、建設コストが大幅に上昇
することを避けることが出来ない。そこで、建築
材として丸あるいは角鋼管を用い、冷却水が循環
するように構成し、火災時における温度上昇を防
止し載荷力を低下させない技術が提案され、ビル
の建設コストの引き下げと利用空間の拡大が図ら
れている。たとえば、実公昭52−16021号公報に
は、建築物の上部に水タンクを置き、中空鋼管か
らなる柱材に冷却水を供給する耐火構造建造物が
開示されている。また、特願昭63−143740では、
鋼材の基本成分として、適当量のMoとNbを複合
添加し、高温加熱−高温圧延法により600℃の高
温耐力が常温耐力の70％以上確保出来ることが示
されている。しかしながら、この発明の鋼板製造
法は圧延ままのため、常温と600℃の耐力確保は
Mo，Nb等の合金元素の添加に頼らざるを得ず、
合金添加量が多くなり、建築用鋼材として重要な
溶接性、溶接熱影響部（HAZ）靭性などの特性
が阻害されるという問題を有していた。 〔発明が解決しようとする課題） 前述のように建造物に従来の鋼材を利用する場
合、価格は安いが、高温特性が低いため無被覆や
軽被覆で利用することが出来ず、割高な耐火被覆
を施さねばならない。このため建設コストが高く
なると共に建造物の利用空間が狭くなり、経済効
率を低下させると云う課題がある。一方耐火性能
の向上をねらいとして、中空鋼材を用いて強制冷
却する方法は、構造が複雑になるため設計、施工
費に加えて設備費が嵩むことと、保守整備費も高
額になると云う課題がある。 また、ステンレススチールに代表されるような
耐熱鋼材は価格が非常に高いため、高温特性は良
好であるが、生産技術や施工技術面に加えて経済
的な面で建築材としての利用は非常に困難であ
る。 而して、近年建築物の高層化が進展し、設計技
術の向上とその信頼性の高さから、耐火設計につ
いて見直しが行われ、昭和62年建築物の新耐火設
計法が法定されるに至つた。その結果前述の350
℃の温度制限によることなく、鋼材の高温強度と
建物に実際に加わつている荷重により、耐火被覆
の能力を決定出来るようになり、場合によつては
無被覆で鋼材を使用することも可能になつた。 しかしながら、耐火性の優れた建築用鋼材とし
て、経済的価格で市場に供給できるような鋼材は
現在存在しない。 本発明の目的は、高温特性が優れ、かつ経済的
価格で市場に供給しうる耐火性の優れた鋼材及び
その製造方法並びに耐火性能を付与した鋼材料を
提供することにある。 〔課題を解決するための手段〕 本発明は前述の課題を克服し、目的を達成する
もので、その具体的手段を次に示す。すなわち本
発明は重量比でC0.04〜0.15％、Si0.6％以下、
Mn0.5〜1.6％、Mo0.2〜0.7％、Al0.1％以下、
N0.006％以下、又は必要によりさらに、Nb0.005
〜0.04％ Ti0.005〜0.10％ Zr0.005〜0.03％
V0.005〜0.10％ Ni0.05〜0.5％ Cu0.05〜1.0％
B0.0003〜0.002％ Ca0.0005〜0.005％
REM0.001〜0.02％のうち１種または２種以上を
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℃の温度域で加熱し、熱間圧延
を800℃〜1000℃の温度範囲で終了した後、得ら
れた鋼板をAr₃−20℃〜Ar₃−100℃まで空冷して
該鋼板組織のフエライト分率を20〜50％にし、続
いてこの温度から３〜40℃／秒の冷却速度で550
℃以下の任意の温度まで水冷し、その後放冷する
ことにより耐火性の優れた建築用低降伏比鋼材を
提供するものであり、さらに該鋼材を使用した建
築用鋼材料を提供するものである。 〔作用〕 さて、本発明者らは、火災時における鋼材強度
について研究の結果、無被覆使用を目標とした場
合、火災時の最高到達温度が1000℃であることか
ら、鋼材が該温度で常温耐力の70％以上の耐力を
備えるためには、やはり高価な金属元素を多量に
添加せねばならず、経済性を失することを知つ
た。つまり、従来の鋼材費とそれに加え耐火被覆
を施工する費用以上に鋼材単価が高くなり、その
ような鋼材は実際的に利用することが出来ない。
そこで、さらに研究を進めた結果、600℃での高
温耐力が常温時の70％（略々2/3）以上となる鋼
材が最も経済的であることをつきとめ、高価な添
加元素の量を少なくし、かつ耐火被覆を薄くする
ことが可能で、火災荷重が小さい場合は、無被覆
で使用することが出来る鋼材の製造方法及び耐火
性能を付与した鋼材料を開発した。さて、本発明
の特徴は、低Ｃ−低Mn鋼にMoを添加した成分
組成の鋼片を、高温で加熱したのち、比較的高温
で圧延を終了し、その後空冷過程でオーステナイ
トからフエライトへの変態途中であるフエライト
分率20〜50％（Ar₃−20℃〜Ar₃−100℃の温度範
囲）まで空冷し、この温度域から550℃以下の任
意の温度（550℃から室温までの温度範囲）まで
水冷して、その後、放冷する方法で、本発明法に
よつて製造した鋼材は、適当な常温耐力を有する
とともに、高温耐力が高いという特性を備えてい
る。つまり、常温耐力に対し600℃の温度域にお
ける耐力の割合が大きい。この理由は適当量の
Moを添加した鋼のミクロ組織が比較的大きなフ
エライトとベイナイトの混合組織とするためであ
る。これに対しベイナイト主体鋼では、600℃の
温度域における耐力に比して常温耐力が高くなり
常温での規格を満足させることが出来ない。ま
た、フエライト主体鋼では、常温と高温の耐力バ
ランスは比較的良好であるが、本発明鋼に比較し
てMoなど強度を高める元素の添加量を多くしな
ければならないという欠点がある。すなわち、本
発明者らはミクロ組織のフエライト−ベイナイト
化が高温耐力の向上に役立つことを見い出した。
本発明にかかる鋼は常温における降伏比が低く、
耐震性に優れているが、これもミクロ組織が20〜
50％の比較的大きなフエライトとベイナイトの混
合組織からなるためである。つぎに、本発明にか
かる特徴的な成分元素とその添加量について説明
する。 Moは微細な炭化物による析出硬化と固溶強化
によつて高温耐力を増加させる。必要な高温耐力
を得るためのMo量は他のベース成分やミクロ組
織によつて異なるが、本発明鋼の合金成分やプロ
セスを前提とすると、0.2％未満ではその効果は
小さく、Moの下限は0.2％以下である。しかしな
がら、Mo量が高すぎると、溶接性が悪くなり、
さらにHAZの靭性が劣化するので、Mo量の上限
は0.7％とする必要がある。 つぎに、本発明におけるMo以外の成分限定理
由について詳細に説明する。Ｃは母材および溶接
部の強度確保ならびにMoの添加効果を発揮させ
るために必要であり、0.04％未満では効果が薄れ
るので下限を0.04％とする。さらにＣ量が多過ぎ
るとHAZの低温靭性に悪影響をおよぼすだけで
なく、母材靭性、溶接性をも劣化させるので、
0.15％が上限となる。 Siは脱酸上鋼に含まれる元素で、Siが多くなる
と溶接性、HAZ靭性が劣化するため、その上限
を0.6％とした。 本発明鋼ではAl脱酸で十分であり、さらにTi
脱酸でも良い。SiについてHAZ靭性の点からは
含有量を0.15％とすることが望ましい。 つぎに、Mnは強度、靭性を確保する上で不可
欠の元素であり、その下限は0.5％である。しか
しMn量が多過ぎると焼入性が増加して溶接性、
HAZ靭性が劣化するだけでなく、目標とする規
格に適合する母材強度を得ることが出来ない。こ
のためMnの上限を1.6％とした。 Alは一般に脱酸上鋼に含まれる元素であるが、
SiおよびTiによつても脱酸は行なわれるので、
本発明鋼ではAlについて下限を限定しない。し
かしAl量が多くなると鋼の清浄度が悪くなり、
溶接部の靭性が劣化するので上限を0.1％とした。 Ｎは一般に不可避的不純物として鋼中に含まれ
るものであるが、Ｎ量が多くなるとHAZ靭性の
劣化や連続鋳造スラブの表面疵の発生などを助長
するので、その上限を0.006％とした。なお、本
発明鋼材は、不可避的不純物としてＰおよびＳを
含有する。Ｐ，Ｓは高温強度に与える影響は小さ
いので、その量について特に限定はしないが、一
般に靭性、板厚方向強度などに関する鋼の特性
は、Ｓ，Ｐ量が少ないほど向上する。望ましい
Ｐ，Ｓ量はそれぞれ0.02％、0.005％以下である。 本発明鋼の基本成分は以上のとおりであり、十
分に目的を達成出来るが、さらに以下に述べる元
素即ちNb，Ti，Zr，Ｖ，Ni，Cr，Ｂ，REMを
選択的に添加すると強度、靭性の向上について、
さらに好ましい結果が得られる。 つぎに、前記添加元素とその添加量について説
明する。NbはＮと結合して炭窒化物Nb（CN）を
形成し高温耐力の向上に効果を発揮する。しかし
ながら0.005％未満では、その効果は認められず、
0.04％超では溶接性などに害をおよぼすため
0.005〜0.04％の範囲とした。 Tiは前述のNbとほぼ同じ効果を持つ元素であ
り、0.005〜0.02％においてAl量が少ない場合Ti
の酸化物、炭窒化物を形成し、HAZ靭性を向上
させるが、0.005％未満では効果がなく、0.10％
を超えると溶接性などで悪影響がでて好ましくな
い。 ＶもNb，Tiとほぼ同じ効果を持つ元素であ
り、高温耐力に対する効果はNb，Tiに比較して
小さいが0.005〜0.10％の範囲において強度を向
上させる。しかし0.005％未満では効果が無く
0.10％を超えるとHAZ靭性に好ましくない影響
がある。 つぎに、Niは溶接性、HAZ靭性に悪影響をお
よぼすことなく、母材の強度、靭性を向上させる
が、0.05％未満では効果が薄く、0.5％超の添加
は建築用鋼として、極めて高価になるため経済性
を失うので、0.05〜0.5％の範囲とした。 CuはNiとほぼ同様な効果を持つほか、Cu析出
物による高温耐力の増加や耐食性、耐候性の向上
にも効果を有する。しかし、Cu量が1.0％を超え
ると熱間圧延時にCu割れが発生し製造が困難に
なり、また0.05％未満では効果がないのでCu量は
0.05〜1.0％に限定する。 Ｂは鋼の焼入性を増大させ強度を大きくする元
素であり、Ｎと結合したBNはフエライト発生核
として作用し、HAZ組織を微細化する。このよ
うなＢの効果を得るためには、最小限0.0003％の
Ｂ量が必要で、それ未満では効果が無く、またＢ
量が多過ぎると粗大なＢ−constituentがHAZの
旧オーステナイト粒界に析出して低温靭性を劣化
させるのでＢ量の上限は0.002％に制限する。 Ca，REMは硫化物（MnS）の形態を制御し、
シヤルピー吸収エネルギーを増加させ低温靭性を
向上させるほか、耐水素誘起割れ性の改善にも効
果を発揮する。しかしCa量は0.0005％未満では実
用上効果がなく、また、0.005％を超えるとCaO，
CaSが多量に生成して大形介在物となり、鋼の靭
性のみならず清浄度も害し、さらに溶接性にも悪
影響を与えるので、Ca添加量の範囲を0.0005〜
0.005％とする。また、REMについてもCaと同様
な効果があり、添加量を多くするとCaと同様な
問題が生じ、さらに、経済性も悪くなるので、
REM量の下限を0.001％、上限を0.02％とした。 さて、常温において、溶接構造用圧延鋼材
（JIS Ｇ 3106）に規定する性能を満足し、かつ
600℃の高温において高い耐力を維持せしめるた
めには、鋼成分と共に鋼の加熱および圧延、冷却
条件が重要である。特に前述のMoの添加による
高温耐力の増大を図るには、加熱時にMoを十分
溶体化させる必要があり、このため前述した成分
よりなる鋼片を加熱するときの温度の下限を1100
℃とする。また、加熱温度が高すぎると結晶粒が
大きくなつて低温靭性が劣化するので、その上限
は1300℃にせねばならない。次に、熱間圧延を施
すが、圧延終了温度を800℃以上の高温とする。
その理由は、圧延中にMoの炭窒化物を析出させ
ないためであり、γ域で、Moが析出すると、析
出物サイズが大きくなり、高温耐力が著しく低下
する。前記温度の上限は1000℃であり、これを越
える温度では圧延に支障をきたす。800℃以上で
圧延を終了し、空冷する方法を採用すると、常温
耐力と600℃の高温耐力のバランスは良好である。
しかしながら、圧延後に空冷する方法では、強度
の絶対値がやや不十分となる。このためMo添加
量を増加する必要があり、過度のMo添加による
溶接性などの問題があつた。この問題を解決する
ため、本発明者らは種々研究した結果、圧延終了
後、Ar₃−20℃〜Ar₃−100℃まで空冷し、続いて
この温度から３〜40℃／秒の冷却速度で550℃以
下の任意の温度まで水冷し、その後放冷する方法
が有効であることを見出したのである。すなわ
ち、圧延直後に冷却すると高強度は得られるが常
温耐力と600℃での高温耐力のバランスが不十分
となり、600℃の強度を確保しようとすれば、常
温の耐力が規格値をオーバする。圧延終了後に
Ar₃−20℃〜Ar₃−100℃まで冷却すると、オース
テナイトからフエライトが析出し20〜50％に達す
る。この温度より水冷を開始し、550℃以下の任
意の温度で水冷を停止することにより、ミクロ組
織が20〜50％のフエライトとベイナイトの混合組
織となり、常温と600℃の耐力バランスを良好と
しながら高耐力を達成し、かつ降伏比も低く抑え
ることが出来ることを見い出した。また圧延終了
後、Ar₃−20℃〜Ar₃−100℃まで空冷し、続いて
この温度から３〜40℃／秒の冷却速度で550℃以
下の任意の温度まで水冷し、その後放冷する方法
により、低い炭素当量（C_eq）で強度を維持する
ことができるだけでなく、炭素当量を低くするこ
とができるために本発明の目的の一つである溶接
性を改善し、溶接熱影響部（HAZ）の靭性等の
特性が阻害されなことを見出した。 なお、本発明鋼材を製造後、脱水素などの目的
でAc₁変態点以下の温度に再加熱しても、本発明
鋼材の特徴は何等損なわれることは無い。 また、本発明では、前述のように鋼片を加熱
し、ついで熱間圧延することにより製品とする
が、その後さらに所望の鋼材を製造するため、前
記製品を熱間又は冷間でさらに塑性加工してもよ
い。 たとえば、鋼材をブルーム、ビレツトとしたの
ち熱間で形鋼とするほか、前記製品を素材とし、
冷間加工して所望の鋼材たとえば形鋼や鋼管を製
造しても良い。その際、必要に応じて、熱処理を
適宜に実施する。 さて、次に本発明鋼の機械的性質を周知鋼材と
比較して詳細に説明する。 第１表は本発明鋼材とJIS Ｇ 3106溶接構造用
圧延鋼材（SM50A）との成分比較を示す。 なお、本発明の鋼材は上記表に示す成分の鋼片
を1150℃に加熱し、熱間圧延を仕上圧延温度836
℃で終了した後、760℃まで空冷し、次いでこの
温度より冷却速度27℃／secで急冷して454℃で冷
却を停止して製造された。 [Field of Industrial Application] The present invention relates to a low yield ratio steel material with excellent fire resistance used in various buildings in the fields of architecture, civil engineering, marine structures, etc., and a method for manufacturing the same. [Prior art] As is well known, rolled steel for general structures (JIS G 3101), rolled steel for welded structures (JIS G 3106), and welded steel are used as construction materials for various buildings in the fields of architecture, civil engineering, and marine structures. Structural weather resistant hot rolled steel materials (JIS G 3114), high weather resistant rolled steel materials (JIS G 3114)
G 3125) and general structural carbon steel pipes (JIS G
3444), square steel pipes for general structures (JIS G 3466)
etc. are widely used. These steel materials are usually produced by removing S and P from hot metal obtained in a blast furnace, smelting it in a converter, turning it into billets in a continuous casting or blooming process, and then subjecting it to hot plastic working. It is commercialized as having the following characteristics. By the way, when using the above-mentioned steel materials for buildings such as buildings, offices, and residences that are closely connected to daily life, it is mandatory to apply sufficient fireproof coating to ensure safety in the event of a fire. Building-related laws and regulations stipulate that the temperature of steel materials should not exceed 350℃ in the event of a fire. In other words, when the above-mentioned steel materials are used in buildings, the yield strength (yield strength) at around 350°C becomes 60 to 70% of that at room temperature, which may cause the building to collapse.
The steel must be used in such a way that it does not lose its load-bearing capacity due to thermal damage during a fire. For example, general structural rolled steel materials (JIS G
3101), the surface of which is coated with slag wool, rock wool,
In addition to spreading sprayed material or felt based on glass wool or asbestos, there are also methods of covering with fireproof mortar, and methods of further protecting the heat insulating material layer with a thin metal plate, such as aluminum or stainless steel thin plate. It is necessary to carefully apply fireproof coating. Therefore, the construction cost of fireproof coating becomes high compared to the cost of steel materials, and it is impossible to avoid a significant increase in construction cost. Therefore, a technology has been proposed that uses round or square steel pipes as construction materials to allow cooling water to circulate, thereby preventing temperature rises and reducing load capacity in the event of a fire. Expansion is being planned. For example, Japanese Utility Model Publication No. Sho 52-16021 discloses a fireproof structure in which a water tank is placed on top of the building to supply cooling water to pillars made of hollow steel pipes. In addition, in the patent application No. 63-143740,
It has been shown that by adding appropriate amounts of Mo and Nb as the basic components of steel materials and using a high-temperature heating-high-temperature rolling method, it is possible to secure a high-temperature yield strength of 600°C that is 70% or more of the room-temperature yield strength. However, since the steel sheet manufacturing method of this invention uses rolling as it is, it is difficult to ensure proof strength at room temperature and 600℃.
We have no choice but to rely on the addition of alloying elements such as Mo and Nb,
The problem was that the amount of alloy added was large, impeding properties such as weldability and weld heat-affected zone (HAZ) toughness, which are important for architectural steel materials. [Problem to be solved by the invention] As mentioned above, when conventional steel materials are used in buildings, the price is low, but due to their low high-temperature properties, they cannot be used uncoated or lightly coated, and they require relatively expensive fire resistance. Must be covered. Therefore, there are problems in that the construction cost increases and the usable space of the building becomes narrower, reducing economic efficiency. On the other hand, the method of forced cooling using hollow steel materials with the aim of improving fire resistance has the problem of a complicated structure, which increases equipment costs in addition to design and construction costs, and high maintenance costs. be. In addition, heat-resistant steel materials such as stainless steel are very expensive, and although they have good high-temperature properties, their use as construction materials is extremely difficult due to production technology, construction technology, and economical aspects. Have difficulty. In recent years, as buildings have become taller, fire-resistant design has been reviewed due to improvements in design technology and its reliability, and in 1988, a new fire-resistant design law for buildings was enacted. I've reached it. As a result, the aforementioned 350
The ability of fireproof coating can now be determined based on the high-temperature strength of the steel material and the load actually applied to the building, without being limited by the temperature limit of °C, and in some cases it is also possible to use steel without coating. Summer. However, there is currently no steel material that can be supplied to the market at an economical price as a structural steel material with excellent fire resistance. An object of the present invention is to provide a steel material with excellent high-temperature properties and excellent fire resistance that can be supplied to the market at an economical price, a method for producing the same, and a steel material imparted with fire resistance. [Means for Solving the Problems] The present invention overcomes the above-mentioned problems and achieves the objects, and specific means thereof are shown below. In other words, the present invention has a weight ratio of C0.04 to 0.15%, Si0.6% or less,
Mn0.5~1.6%, Mo0.2~0.7%, Al0.1% or less,
N0.006% or less, or further if necessary, Nb0.005
~0.04% Ti0.005~0.10% Zr0.005~0.03%
V0.005~0.10% Ni0.05~0.5% Cu0.05~1.0%
B0.0003~0.002% Ca0.0005~0.005%
A steel billet containing one or more of REM0.001~0.02% with the balance consisting of Fe and unavoidable impurities is heated in a temperature range of 1100~1300℃, and hot rolled at 800~1000℃. After the _temperature range _of 550 at a cooling rate of °C/sec
The present invention provides a low-yield-ratio steel material for construction with excellent fire resistance by water-cooling to an arbitrary temperature below ℃ and then allowing it to cool, and further provides a steel material for construction using the steel material. . [Function] As a result of research on the strength of steel materials in the event of a fire, the inventors of the present invention found that when uncoated use is targeted, the maximum temperature reached in the event of a fire is 1000°C. I learned that in order to have a yield strength of 70% or more, it would be necessary to add a large amount of expensive metal elements, which would be uneconomical. In other words, the unit price of the steel material becomes higher than the cost of the conventional steel material and the cost of installing a fireproof coating in addition to the cost of the conventional steel material, and such steel material cannot be practically used.
Therefore, as a result of further research, we found that the most economical steel material is one whose high-temperature yield strength at 600℃ is more than 70% (approximately 2/3) of that at room temperature, and by reducing the amount of expensive additive elements. In addition, we have developed a method for manufacturing steel materials that can be used without coating if the fire load is small, and a steel material with fire resistance properties. Now, the feature of the present invention is that a steel billet with a composition of low C-low Mn steel with Mo added is heated at a high temperature, then rolled at a relatively high temperature, and then in an air cooling process, austenite is converted to ferrite. Air cool to a ferrite fraction of 20 to 50% (temperature range from Ar ₃ -20℃ to Ar ₃ -100℃), which is in the middle of transformation, and then cool at any temperature from this temperature range to 550℃ or less (temperature from 550℃ to room temperature). The steel material manufactured by the method of the present invention, which is water-cooled to a temperature of 100% or less, and then left to cool, has the characteristics of having an appropriate room temperature yield strength and high high temperature yield strength. In other words, the ratio of proof stress in the temperature range of 600°C to normal temperature proof stress is large. The reason for this is that an appropriate amount
This is because the microstructure of the steel to which Mo is added is a mixed structure of relatively large ferrite and bainite. On the other hand, with bainite-based steel, the yield strength at room temperature is higher than the yield strength in the 600°C temperature range, making it impossible to satisfy the specifications at room temperature. In addition, although ferrite-based steel has a relatively good balance of yield strength between room temperature and high temperature, it has the disadvantage that it requires a larger amount of elements to increase strength, such as Mo, than the steel of the present invention. That is, the present inventors have found that changing the microstructure to ferrite-bainite is useful for improving high-temperature yield strength.
The steel according to the present invention has a low yield ratio at room temperature,
It has excellent earthquake resistance, but also has a microstructure of 20~
This is because it consists of a mixed structure of 50% relatively large ferrite and bainite. Next, characteristic component elements according to the present invention and their addition amounts will be explained. Mo increases high-temperature yield strength through precipitation hardening and solid solution strengthening due to fine carbides. The amount of Mo to obtain the necessary high-temperature yield strength varies depending on other base components and the microstructure, but assuming the alloy components and process of the steel of the present invention, the effect is small if it is less than 0.2%, and the lower limit of Mo is Less than 0.2%. However, if the amount of Mo is too high, weldability will deteriorate,
Furthermore, since the toughness of the HAZ deteriorates, the upper limit of the amount of Mo needs to be 0.7%. Next, the reason for limiting components other than Mo in the present invention will be explained in detail. C is necessary to ensure the strength of the base metal and the welded part and to exhibit the effect of adding Mo. If it is less than 0.04%, the effect will be weakened, so the lower limit is set at 0.04%. Furthermore, too much C not only adversely affects the low-temperature toughness of the HAZ, but also deteriorates the base metal toughness and weldability.
The upper limit is 0.15%. Si is an element contained in deoxidized steel, and as Si increases, weldability and HAZ toughness deteriorate, so the upper limit was set at 0.6%. In the steel of the present invention, Al deoxidation is sufficient, and Ti
It may also be deoxidized. From the viewpoint of HAZ toughness, it is desirable that the Si content be 0.15%. Next, Mn is an essential element for ensuring strength and toughness, and its lower limit is 0.5%. However, if the amount of Mn is too large, the hardenability will increase and the weldability will deteriorate.
Not only does HAZ toughness deteriorate, but the base material strength that meets the target standards cannot be obtained. For this reason, the upper limit of Mn was set at 1.6%. Al is an element generally included in deoxidized steel,
Deoxidation is also carried out by Si and Ti, so
In the steel of the present invention, there is no lower limit for Al. However, as the amount of Al increases, the cleanliness of the steel deteriorates.
Since the toughness of the weld zone deteriorates, the upper limit was set at 0.1%. N is generally contained in steel as an unavoidable impurity, but if the amount of N increases, it promotes deterioration of HAZ toughness and occurrence of surface flaws in continuously cast slabs, so the upper limit was set at 0.006%. Note that the steel material of the present invention contains P and S as inevitable impurities. Since P and S have a small effect on high temperature strength, their amounts are not particularly limited, but generally the properties of steel, such as toughness and strength in the thickness direction, improve as the S and P amounts decrease. Desirable amounts of P and S are 0.02% and 0.005% or less, respectively. The basic components of the steel of the present invention are as described above, and the purpose can be fully achieved, but if the following elements, namely Nb, Ti, Zr, V, Ni, Cr, B, and REM are selectively added, the strength can be improved. Regarding the improvement of toughness,
More favorable results are obtained. Next, the additive elements and their amounts will be explained. Nb combines with N to form carbonitride Nb (CN), which is effective in improving high-temperature yield strength. However, if the concentration is less than 0.005%, no effect is observed.
If it exceeds 0.04%, it will harm weldability etc.
The range was 0.005 to 0.04%. Ti is an element that has almost the same effect as Nb mentioned above, and when the amount of Al is small at 0.005 to 0.02%, Ti
forms oxides and carbonitrides, improving HAZ toughness, but has no effect below 0.005%, and 0.10%
Exceeding this is not preferable as it will adversely affect weldability. V is also an element that has almost the same effect as Nb and Ti, and although its effect on high temperature proof strength is smaller than that of Nb and Ti, it improves strength within the range of 0.005 to 0.10%. However, it has no effect at less than 0.005%.
If it exceeds 0.10%, it will have an unfavorable effect on HAZ toughness. Next, Ni improves the strength and toughness of the base metal without adversely affecting weldability and HAZ toughness, but if it is less than 0.05%, the effect is weak, and if it is added in excess of 0.5%, it becomes extremely expensive for construction steel. Therefore, it is set in the range of 0.05 to 0.5%. In addition to having almost the same effects as Ni, Cu also has the effect of increasing high-temperature yield strength and improving corrosion resistance and weather resistance due to Cu precipitates. However, if the Cu content exceeds 1.0%, Cu cracking occurs during hot rolling, making manufacturing difficult, and if it is less than 0.05%, there is no effect, so the Cu content is
Limited to 0.05-1.0%. B is an element that increases the hardenability and strength of steel, and BN combined with N acts as a ferrite generation nucleus and refines the HAZ structure. In order to obtain this effect of B, a minimum amount of B of 0.0003% is required; anything less than that has no effect, and B
If the amount is too large, coarse B-constituent will precipitate at the prior austenite grain boundaries of the HAZ and deteriorate the low temperature toughness, so the upper limit of the B amount is limited to 0.002%. Ca, REM controls the morphology of sulfide (MnS),
In addition to increasing the Charpy absorbed energy and improving low-temperature toughness, it is also effective in improving hydrogen-induced cracking resistance. However, if the amount of Ca is less than 0.0005%, it has no practical effect, and if it exceeds 0.005%, CaO,
A large amount of CaS is generated and becomes large inclusions, which impairs not only the toughness but also the cleanliness of the steel, and also has a negative effect on weldability.
It shall be 0.005%. In addition, REM has the same effect as Ca, and increasing the amount added causes the same problems as Ca, and furthermore, it becomes less economical.
The lower limit of REM amount was set to 0.001% and the upper limit was set to 0.02%. Now, at room temperature, it satisfies the performance specified in rolled steel materials for welded structures (JIS G 3106), and
In order to maintain high yield strength at a high temperature of 600°C, the heating, rolling, and cooling conditions of the steel are important as well as the steel composition. In particular, in order to increase the high-temperature yield strength through the addition of Mo mentioned above, it is necessary to sufficiently dissolve Mo during heating, and for this reason, the lower limit of the temperature when heating a steel billet made of the above-mentioned components is set at 1100°C.
℃. Furthermore, if the heating temperature is too high, the crystal grains will become large and the low temperature toughness will deteriorate, so the upper limit must be set at 1300°C. Next, hot rolling is performed, and the rolling end temperature is set to a high temperature of 800°C or higher.
The reason for this is to prevent Mo carbonitride from precipitating during rolling. When Mo precipitates in the γ region, the precipitate size increases and the high temperature yield strength significantly decreases. The upper limit of the temperature is 1000°C, and temperatures exceeding this will cause problems in rolling. If rolling is finished at 800°C or higher and then air cooled, the balance between room temperature yield strength and high temperature yield strength at 600°C is good.
However, in the method of air cooling after rolling, the absolute value of the strength is somewhat insufficient. Therefore, it was necessary to increase the amount of Mo added, and excessive Mo addition caused problems such as weldability. In order to solve this problem, the present inventors conducted various studies and found that after finishing rolling, air cooling was performed from Ar ₃ -20°C to _{Ar 3} -100°C, followed by cooling at a rate of 3 to 40°C/sec from this temperature. They discovered that it is effective to water-cool the material to any temperature below 550°C and then let it cool. In other words, if it is cooled immediately after rolling, high strength can be obtained, but the balance between room temperature yield strength and high temperature yield strength at 600°C is insufficient, and if an attempt is made to ensure strength at 600°C, the room temperature yield strength will exceed the standard value. After rolling
When cooled to Ar ₃ −20°C to Ar ₃ −100°C, ferrite precipitates from austenite and reaches 20 to 50%. By starting water cooling from this temperature and stopping water cooling at an arbitrary temperature below 550℃, the microstructure becomes a mixed structure of 20 to 50% ferrite and bainite, while maintaining a good yield strength balance between room temperature and 600℃. It has been discovered that high yield strength can be achieved and the yield ratio can be kept low. After rolling, the product is air cooled to Ar ₃ -20℃ to _{Ar 3} -100℃, then water cooled from this temperature to any temperature below 550℃ at a cooling rate of 3 to 40℃/second, and then left to cool. The method not only makes it possible to maintain strength with a low carbon equivalent (C _eq ), but also improves weldability, which is one of the objectives of the present invention, since the carbon equivalent can be lowered, and the weld heat-affected zone It was found that properties such as toughness of (HAZ) were inhibited. Note that even if the steel of the present invention is reheated to a temperature below the Ac ₁ transformation point for the purpose of dehydrogenation or the like after production, the characteristics of the steel of the present invention will not be impaired in any way. Furthermore, in the present invention, the steel billet is heated and then hot-rolled to produce a product as described above, and after that, in order to further manufacture a desired steel material, the product is further subjected to hot or cold plastic processing. You may. For example, in addition to forming steel materials into blooms and billets and then hot forming them into sections, we also use the above products as raw materials.
A desired steel material, such as a section steel or a steel pipe, may be produced by cold working. At that time, heat treatment is appropriately performed as necessary. Next, the mechanical properties of the steel of the present invention will be explained in detail in comparison with known steel materials. Table 1 shows a compositional comparison between the steel of the present invention and JIS G 3106 rolled steel for welded structures (SM50A). The steel material of the present invention is produced by heating a steel billet with the components shown in the table above to 1150°C, and then hot rolling it at a finish rolling temperature of 836°C.
℃, air-cooled to 760°C, then rapidly cooled from this temperature at a cooling rate of 27°C/sec, and the cooling was stopped at 454°C to produce the product.

【表】 第１図は、縦軸に応力度（Kgｆ／mm²）、横軸に
温度（℃）をとつたもので、実線で示す折線１が
本発明鋼材、破線で示す折線２が比較鋼材
（SM50A）の変化を示す。なお、TSは引張強さ、
YPは降伏点を示す。 第１図から明らかなように、800℃を超える温
度では、差がなくなるが、本発明鋼は600℃〜700
℃においてSM50Aの２倍の耐力を保持しており、
建築用鋼材として優れた特性を備えていることが
判る。 第２図は、縦軸に弾性係数（Kgｆ／mm²）、横軸
に温度（℃）をとつたもので、実線で示す折線１
が本発明鋼、破線で示す折線２がSM50Aの変化
を示す。また、第３図は、縦軸にクリープ歪
（％）、横軸に時間（分）をとり、試験片に加わる
600℃における応力度（Kgｆ／mm²）をパラメータ
ーとしており本発明鋼材の変化を折線で示し、第
４図は、同様にSM50Aの変化を折線で示してい
る。 第２図から明らかなように、本発明鋼材は、
700℃を超える温度で弾性係数が急激に低下する
のに対して、SM50Aは、600℃近辺で弾性係数が
急激に低下している。また、第３図および第４図
から明らかなように、本発明鋼材は、600℃の温
度で通常建物の柱・はりなど構造部材に作用する
応力度15Kgｆ／mm²に対し、通常の火災の最大継続
時間である３時間においてもクリープ歪の進行は
著しく少ないが、SM50Aは、600℃の温度で応力
度10Kgｆ／mm²が加わるとクリープ歪の進行が著し
く大きい。弾性係数が高温まで低下しないこと、
クリープ歪の進行が少ないことは、火災時に建物
の変形を少なくするため、本発明鋼材は、
SM50Aと比較して、建築用鋼材として優れた特
性を備えていることが判る。 本発明者らは、比較鋼材SS41との比較におい
ても同様な結果を得た。 このことから、本発明鋼材は、SM50AやSS41
に比し火災荷重が等しい場合、耐火被覆がより薄
いものでよいことが明らかであり、火災荷重が大
きくないときには、無被覆で済むことも、また明
らかである。 つぎに、本発明鋼材に無機系繊維質耐火薄層材
を展着した例について説明する。 第２表は耐火被覆厚さに関する実施例で、JIS
Ａ 1304で規定される実験において、鋼材温度が
350℃を超えないようにするため、必要な耐火材
別の被覆厚さを示す。 ところで、本発明鋼材の場合は、600℃を超え
るまで鋼材温度が上昇しても良いので、前述のと
おりその耐火被覆の厚さは第３表のように薄くて
済む。 第２表、第３表の比較から明らかなように本発
明鋼を利用する場合、耐火被覆の材料費、施工費
が大幅に軽減できる。[Table] In Figure 1, the vertical axis shows the stress (Kgf/mm ² ) and the horizontal axis shows the temperature (°C). The solid line 1 shows the steel of the present invention, and the broken line 2 shows the comparison. Shows changes in steel material (SM50A). In addition, TS is tensile strength,
YP indicates yield point. As is clear from Fig. 1, the difference disappears at temperatures exceeding 800°C, but the steel of the present invention
It maintains twice the proof strength of SM50A at ℃,
It can be seen that it has excellent properties as a building steel material. Figure 2 shows the elastic modulus (Kgf/mm ² ) on the vertical axis and the temperature (℃) on the horizontal axis.
indicates the steel of the present invention, and broken line 2 indicates the change in SM50A. In addition, Figure 3 shows the creep strain (%) on the vertical axis and the time (minutes) on the horizontal axis, and shows the creep strain (%) applied to the test piece.
The stress degree (Kgf/mm ² ) at 600° C. is used as a parameter, and the change in the steel material of the present invention is shown by a broken line, and FIG. 4 similarly shows the change in SM50A by a broken line. As is clear from FIG. 2, the steel material of the present invention is
The elastic modulus of SM50A rapidly decreases at temperatures above 700°C, whereas the elastic modulus of SM50A rapidly decreases at temperatures around 600°C. Furthermore, as is clear from Figures 3 and 4, the steel of the present invention has a stress level of 15 kgf/mm ² that acts on structural members such as pillars and beams of ordinary buildings at a temperature of 600°C, compared to that of a normal fire. Even at the maximum duration of 3 hours, the progress of creep strain is extremely small, but when a stress level of 10 Kgf/mm ² is applied to SM50A at a temperature of 600°C, the progress of creep strain is extremely large. The elastic modulus does not decrease at high temperatures,
The less progression of creep strain reduces the deformation of the building in the event of a fire, so the steel of the present invention
Compared to SM50A, it can be seen that it has superior properties as a construction steel material. The present inventors obtained similar results in comparison with comparative steel material SS41. From this, the steel materials of the present invention are suitable for SM50A and SS41.
When the fire load is the same, it is clear that the fireproof coating can be thinner, and it is also clear that when the fire load is not large, no coating can be used. Next, an example in which an inorganic fibrous refractory thin layer material is spread on the steel material of the present invention will be described. Table 2 is an example regarding the thickness of fireproof coating, JIS
In the experiment specified in A 1304, the steel temperature was
Indicates the required coating thickness for each type of refractory material in order to prevent temperatures from exceeding 350℃. By the way, in the case of the steel material of the present invention, the temperature of the steel material may rise to over 600°C, so as mentioned above, the thickness of the fireproof coating can be as thin as shown in Table 3. As is clear from the comparison of Tables 2 and 3, when the steel of the present invention is used, the material cost and construction cost of the fireproof coating can be significantly reduced.

【表】【table】

【表】【table】

【表】 つぎに、第５図は本発明にかかるＨ形鋼１
（300×300×10×15）に第３表における吹き付け
ロツクウール（湿式）２を展着した柱の概略立面
図およびＡ−Ａ断面図である。 第６図は、前記Ｈ形鋼柱に、JIS Ａ 1304で規
定される加熱を行い、通常建物の柱が支持する荷
重を加えて、破壊する時間を求めた試験結果であ
り、縦軸に温度（℃）、横軸に時間（分）をとつ
たもので、実線で示す折線１は柱の鋼材温度、破
線で示す折線２は加熱温度の変化を示す。また、
第７図は、縦軸に変形（cm）、横軸に温度（℃）
及び時間（分）をとつたもので、実線で示す折線
は柱の変形を示す。第６図および第７図から明ら
かなように、10mmの厚さの吹き付けロツクウール
（湿式）を施すことで、本発明鋼材で製造した柱
は600℃を超えるまで破壊を起こさず、１時間耐
火以上の性能を発揮していることが判る。 同様に、第８図は、本発明にかかるＨ形鋼はり
３（400×200×８×13）に、第３表における吹き
付けロツクウール（湿式）４を展着したはりの概
略立面図およびＡ−Ａ断面図である。 第９図は、前記Ｈ形鋼はりに、JIS Ａ 1304で
規定される加熱を行い、通常建物のはりが支持す
る荷重を加えて、破壊する時間を求めた試験結果
であり、縦軸に温度（℃）、横軸に（分）をとつ
たもので、実線で示す折線１ははり上側フランジ
５、折線２ははり下側フランジ６、折線３はウエ
ブ７の各温度を、破線で示す折線４は加熱温度の
変化を示す。また、第１０図は、縦軸に変形（鉛
直たわみ）（cm）、横軸に温度（℃）及び時間
（分）をとつたもので、実線で示す折線は、はり
各点の変形を示す。第８図および第９図から明ら
かなように、10mmの厚さの吹き付けロツクウール
（湿式）施すことで、本発明鋼材で製造したはり
は、600℃を超えるまで破壊を起こさず、１時間
耐火以上の性能を発揮していることが判る。又、
600℃における変形量も変形許容値以下であるこ
とが判る。 本発明者らは、他の耐火材についても試験を行
つたが同様な結果を得た。 つぎに、本発明鋼材について高耐熱性塗料を被
着し、試験した結果を第４表に示す。[Table] Next, FIG. 5 shows the H-section steel 1 according to the present invention.
They are a schematic elevational view and an AA sectional view of a column (300 x 300 x 10 x 15) on which sprayed rock wool (wet type) 2 in Table 3 is spread. Figure 6 shows the test results of heating the H-shaped steel column specified in JIS A 1304, applying a load normally supported by building columns, and determining the time to failure.The vertical axis shows the temperature. (°C), and time (minutes) is plotted on the horizontal axis, where the solid line 1 shows the steel temperature of the column, and the broken line 2 shows the change in heating temperature. Also,
Figure 7 shows deformation (cm) on the vertical axis and temperature (℃) on the horizontal axis.
and time (minutes), and the solid broken line indicates the deformation of the column. As is clear from Figures 6 and 7, by applying 10 mm thick sprayed rock wool (wet process), the columns made of the steel of the present invention do not break even at temperatures exceeding 600°C, and are fire resistant for more than 1 hour. It can be seen that the performance is demonstrated. Similarly, FIG. 8 is a schematic elevational view of an H-shaped steel beam 3 (400 x 200 x 8 x 13) according to the present invention and a beam in which sprayed rock wool (wet type) 4 in Table 3 is spread. -A sectional view. Figure 9 shows the test results of heating the H-shaped steel beam specified in JIS A 1304, applying a load normally supported by a building beam, and determining the time to failure.The vertical axis shows the temperature. (°C) and (minutes) on the horizontal axis, where the solid line 1 represents the temperature of the upper flange 5 of the beam, the 2nd line represents the lower flange 6 of the beam, and the 3rd broken line represents the temperature of the web 7. 4 indicates a change in heating temperature. In addition, in Figure 10, the vertical axis shows deformation (vertical deflection) (cm), and the horizontal axis shows temperature (°C) and time (minutes), and the solid broken line shows the deformation at each point of the beam. . As is clear from Figures 8 and 9, by applying sprayed rock wool (wet process) to a thickness of 10 mm, the beam made of the steel of the present invention does not break even at temperatures exceeding 600°C, and is fire resistant for more than 1 hour. It can be seen that the performance is demonstrated. or,
It can be seen that the amount of deformation at 600°C is also below the allowable deformation value. The present inventors also conducted tests on other refractory materials and obtained similar results. Next, the steel materials of the present invention were coated with a highly heat-resistant paint and tested, and the results are shown in Table 4.

【表】 塗料１、塗料２は発泡性高耐熱性塗料（***デ
ゾパツク社製、商品名パイロテクト、種別S30お
よびF60）で、試験鋼板は厚さ16mm、220mm角の
本発明鋼板を用いた。 従来の鋼材は、鋼材温度が350℃以下とされて
いたため、第４表に示す従来の塗料１、塗料２の
塗装によつても30分、60分しか耐火時間が確保で
きなかつたが、上記表に示すように本発明の鋼材
では600℃まで降伏強度が確保できるため、塗料
１、塗料２による塗装によつても60分、120分の
耐火時間が確保される。言い換えれば従来の耐火
時間を確保するのであれば塗装を簡略化しうるメ
リツトがある。 即ち本発明鋼に高耐熱性塗料を被着した鋼材
は、経済性が高く建設費を低減出来る。 つぎに、第１１図は本発明にかかるＨ形鋼８を
薄鋼板（SS41又はステンレス）９で囲んだ梁１
０の概略断面図で前記薄鋼板９は取付金具１１に
より、Ｈ形鋼８から10〜50mmの間隔を隔てて固定
されており、梁１０はコンクリート床１２を支承
している。 第１２図は、第１１図に示す試験体にJIS Ａ
1304に規定する加熱を行つた場合の鋼材温度の変
化を示し、縦軸に温度（℃）、横軸に時間（分）
をとつたものである。破線で示す折線１は加熱温
度を、折線２は薄鋼板（SS41）を取付けていな
いＨ形鋼の鋼材温度を、折線３は薄鋼板（SS41）
で囲んだＨ形鋼の鋼材温度を、折線４は薄鋼板
（SS41）の内側に軽微な耐火被覆を施した場合の
Ｈ形鋼の鋼材温度を、折線５は薄鋼板（ステンレ
ス）の内側に軽微な耐火被覆を施した場合のＨ形
鋼の鋼材温度を示す。 第１２図から明らかなように、薄鋼板（SS41）
で囲んだＨ形鋼の鋼材温度は、薄鋼板（SS41）
を取付けていないＨ形鋼の鋼材温度と比較して、
時間30分までの温度上昇が少なく、本発明鋼が
600℃を越える温度の上昇まで強度を保持するこ
とから、火災荷重が少なく耐火時間の短い火災に
対しては、薄鋼板（SS41）で囲むことにより、
無被覆が可能である。また、火災荷重が多く耐火
時間が長い場合も、薄鋼板（SS41）の内側に軽
微な耐火被覆を施すことで、Ｈ形鋼は無被覆とす
ることができる。なお、前述の薄鋼板９を含み、
防熱効果のある金属板たとえばステンレス薄鋼
板、チタン薄板、アルミニウム板を防熱盾板と総
称する。 前記防熱盾板を装着した本発明にかかる鋼材
は、建築現場における耐火物の吹き付けのような
困難な作業の必要がなく、容易に取り付けができ
るので、経済的な使用が可能である。 つぎに、第１３図のグラフは、本発明にかかる
角鋼管にコンクリートを充填し、表面に湿式吹き
付けによつてロツクウールを基材とする繊維質耐
火材を５mm厚に被着せしめ、１時間耐火試験
（JIS Ａ 1304準拠）を行なつて得られた角鋼管
の温度変化を示すもので、かかる耐火薄層でも、
本発明の鋼材は充分その目的を達成できる。 さらに、第１４図のグラフは、本発明の鋼板を
デツキプレートに加工し、裏面に7.5mm厚にロツ
クウールを基材とする繊維質耐火材を湿式法によ
つて吹き付けたものを、１時間耐火試験（JIS Ａ
1304準拠）して得られた結果を示すもので、デ
ツキプレート自体の温度は600℃を超えないので、
有効な耐火鋼材として本発明鋼材が使用できるこ
とが確認された。 つぎに、第１５図、第１６図は無被覆鉄骨の火
災試験において放射率が0.7および0.4の場合の昇
温曲線を示すグラフで、Ｔは板厚である。 第１５図、第１６図から明らかなように、板厚
が100mmであれば本発明の鋼材は無被覆で１時間
耐火において、まつたく問題が無い。 さらに、本発明者らの研究では、放射率が0.7
でも板厚が70mm以上あれば１時間耐火で問題が無
く、アルミニウム箔などの極薄金属を展着した本
発明鋼材であれば、板厚40mmまでは断熱耐火材を
被覆すること無く使用出来ることが判つた。 また、本発明鋼材を建築用鋼材料の一例として
ビルドアツプ形鋼の構造部材の一部に用いると、
設計要求に対し、圧延形鋼のような寸法制限が無
く、寸法裕度が広く柔軟な対応が可能なうえに、
加えて耐火性能が優れ、経済性に富む建築用鋼材
料を得ることができる。以下その実施例について
説明する。 第１７図ａ〜ｆは、本発明にかかるビルドアツ
プ耐熱形鋼の実施例にかかる概略断面図で、ａは
Ｉ形鋼１３の断面図で、フランジ１４は本発明鋼
材、フランジ１５ａ、およびウエブ１５ｂはJIS
Ｇ 3101にかかる一般構造用圧延鋼材から構成さ
れている。 ｂは溝形鋼１６の断面図で、フランジ１７は本
発明鋼材、フランジ１８ａ、ウエブ１８ｂはJIS
Ｇ 3106にかかる溶接構造用圧延鋼材から構成さ
れている。 ｃは山形鋼１９の断面図で、フランジ２０は本
発明鋼材、フランジ２１は溶接構造用耐候性熱間
圧延鋼材JIS Ｇ 3114から構成されている。 ｄは角鋼管２２の断面図で、溝形鋼２３は本発
明鋼材、溝形鋼２４は高耐候性圧延鋼材JIS Ｇ
3125から構成されている。 ｅは柱材２５の断面図で、リツプ溝形鋼２６は
本発明鋼材、リツプ溝形鋼２７は一般構造用鋼材
JIS Ｇ 3101から構成されている。 ｆはＨ形鋼２８の断面図で、フランジ２９ａ、
ウエブ２９ｂは本発明鋼材、フランジ３０は一般
構造用鋼材JIS Ｇ 3101から構成されている。 さて、第１８図は、前記Ｈ形鋼２８を梁に用い
て、コンクリート床版３１を支承した実施例にか
かる部分断面図で、フランジ２９ａ、ウエブ２９
ｂは本発明鋼材で構成され火災荷重が小さい場合
は、耐火被覆を施す必要がないため、耐火断熱層
３２の厚さT₂は該耐火断熱層３２の表面を示す
破線３３で示すようにフランジ３０を覆うにたる
保護厚さで充分であり、火災荷重の大きい場合で
も、その耐火断熱層の厚さは従来の半分以下で済
む。 従来のＨ形鋼では一点鎖線３４で囲われた厚さ
T₁の耐火被覆が必要であつたが、本発明にかゝ
る鋼材の場合節減出来る耐火被覆量は前述の差と
なるため、その経費節減量は多大である。 次に、第１９図は柱材３５に外壁コンクリート
３６を取付けた実施例にかかる概略断面図で、３
７は内装ボード、３８は支持梁を示す。前記柱材
３５は本発明鋼材からなるリツプ溝形鋼３９と一
般構造用鋼材JIS Ｇ 3101からなるリツプ溝形鋼
４０から構成されている。 従来であれば一点鎖線４１で示す耐火被覆厚さ
が必要であるが、前記柱材３５の露出表面３９ａ
は本発明鋼材なので、耐火被覆材４２は符号T₃
で示す如く、最大の厚さでも前記露出表面３９ａ
と同一で済み、火災荷重が大きい場合でも、符号
T₄で示すようにやや厚い耐火被覆層でよいため、
耐火被覆材の節減量は多大である。 次に、第２０図は下側フランジ４３のみが本発
明鋼材からなるＨ形鋼４４を用いて床版４５を支
承し、コンクリート充填材４６を前記Ｈ形鋼４４
のフランジ間に充填した部分断面図で、従来はＨ
形鋼全体をコンクリートで厚く包む必要があつた
が、本発明では、図に示すように簡略化すること
が可能になる。 第２１図は、Ｈ形鋼を建築物の柱材に用いた例
にかかり、内側フランジ４７のみが本発明鋼材で
あるＨ形鋼４８を用いて外壁材４９を支持してい
る部分断面図で、両フランジ間には第２０図のコ
ンクリートの代りに繊維質耐熱材５０の充填を行
なうが、従来のように、Ｈ形鋼４８を厚く繊維質
耐熱材もしくはコンクリートで包み込む必要は無
い。 第２２図は同様に、Ｈ形鋼を建築物の柱材に用
いた例にかかり、内側フランジ５１のみが本発明
鋼材であるＨ形鋼５２を用いてブロツク壁材５３
を支持している部分断面図で、前記ブロツク壁材
５３と内側フランジ５１間にコンクリートもしく
は繊維質耐熱材５４を充填する。従来では内側フ
ランジ５１を含めて厚くコンクリートで包み込ん
でいたが、本発明では図のように、簡単な耐火構
造とすることが可能である。 勿論、この例でも火災荷重が大きい場合には、
内側フランジ５１を露出しないように、耐火被覆
することは当然であるが、その場合も従来に比し
て、大幅に薄くたとえば半分の厚さにしても良
い。 次に、第２３図ａ，ｂは一般構造用鋼材JIS Ｇ
3101からなるＨ形鋼５５と本発明鋼材からなる
Ｈ形鋼５６の概略断面図で、それぞれのウエブを
鋸歯状に切断し、第２４図に示すようにそれぞれ
の半截体５５ａ，５６ａを互いに溶接５７ａ，５
７ｂし、ハニカムウエブ形鋼５８を形成すると、
耐力の優れた有用な梁材が得られる。 前記ハニカムウエブ形鋼５８は、従来のものと
異なり、下側が本発明鋼材なので、前述の如く耐
火被覆を軽減もしくは無くすことが可能であり、
また貫通孔５９，６０，６１は配管用として利用
度が高く、したがつて高層建築物用の構造材とし
て空間容積を大きくすることが出来、前記各種配
管の設備費を低減出来るため経済効率の良い部材
として、広い範囲で活用出来る。 第２５図は、前記ハニカムウエブ形鋼５８を第
２０図の例のように梁材として用いる例にかか
り、コンクリート６２の充填を実施する際には、
前記貫通孔５９，６０，６１があるため、コンク
リート充填作業を非常に高能率に実施することが
出来る。 この場合、前記ハニカムウエブ形鋼５８につい
て前述のとおり耐火被覆を軽減もしくは無くすこ
とが可能なので、その経済効果は多大である。 〔実施例〕 周知の転炉、連続鋳造、厚板工程で種々の鋼成
分の鋼板（厚み15を75mm）を製造し、常温耐力
（降伏強度）、高温耐力（降伏強度）などを調査し
た。第５表のNo.１〜No.19に本発明鋼を、No.20〜No.
29に比較鋼の化学成分を示す。続いて第６表に本
発明鋼と比較鋼について、加熱、圧延、冷却条件
別に機械的特性を示す。第６表の本発明例No.１〜
No.19の例では、すべて良好な常温及び高温耐力を
有している。これに対し、比較例のNo.４では、圧
延後の水冷開始温度がAr3温度以上であるため常
温耐力が高く、600℃の耐力との比が70％を満足
出来ず、No.６では、加熱温度が低く、圧延温度も
低いため常温耐力が高くなり、600℃の耐力との
比（以下耐力比）が70％を満足出来ず、No.８は圧
延ままで製造し、且つ800℃を切る温度で圧延し
たため、常温の耐力は高いが600℃での耐力が低
く、耐力比を満足出来なかつた。また、No.９で
は、No.４と同様に水冷開始温度が高いため耐力比
を満足出来ず、No.10の焼入、焼き戻しのプロセス
でも同様で耐力比が満足出来ず、No.15ではNo.６と
同様の理由で耐力比が満足出来なかつた。さら
に、比較例のNo.20〜No.29は化学成分がいずれも本
発明鋼の範囲から外れているため耐力比を満足出
来なかつた。すなわち、No.20では、Moが低く、
No.21では、Mnが低く、No.22では、Moが無添加
であるため、No.23では、Mo量が多過ぎ且つ水冷
開始温度が高過ぎのため、No.24〜No.29では、Mo
が少なく、耐力比が満足出来なかつた。[Table] Paint 1 and Paint 2 were foaming highly heat-resistant paints (manufactured by West German Dezopak, trade name: Pyrotect, types S30 and F60), and the steel plate of the present invention with a thickness of 16 mm and a square of 220 mm was used as the test steel plate. Conventional steel materials were designed to have a steel material temperature of 350°C or lower, so even with the conventional coatings 1 and 2 shown in Table 4, a fire resistance time of only 30 or 60 minutes could be ensured. As shown in the table, since the steel material of the present invention can maintain yield strength up to 600°C, fire resistance times of 60 minutes and 120 minutes can be ensured even when painted with Paint 1 and Paint 2. In other words, it has the advantage of simplifying the painting process as long as it maintains the conventional fire resistance time. That is, the steel material of the present invention coated with a highly heat-resistant paint is highly economical and can reduce construction costs. Next, FIG. 11 shows a beam 1 in which an H-beam 8 according to the present invention is surrounded by a thin steel plate (SS41 or stainless steel) 9.
0, the thin steel plate 9 is fixed to the H-beam 8 by a mounting bracket 11 at a distance of 10 to 50 mm, and the beam 10 supports a concrete floor 12. Figure 12 shows the JIS A test specimen shown in Figure 11.
Shows the change in steel temperature when heated according to 1304, with temperature (°C) on the vertical axis and time (minutes) on the horizontal axis.
It was taken from The broken line 1 shows the heating temperature, the 2nd broken line shows the steel temperature of the H-beam without the thin steel plate (SS41), and the 3rd broken line shows the steel temperature of the thin steel plate (SS41).
The temperature of the H-beam steel surrounded by the lines 4 is the temperature of the H-beam steel when a light fireproof coating is applied on the inside of the thin steel plate (SS41). The temperature of H-beam steel with a slight fireproof coating is shown. As is clear from Figure 12, thin steel plate (SS41)
The steel material temperature of the H-shaped steel enclosed in is the thin steel plate (SS41).
Compared to the temperature of the H-beam without the
The steel of the present invention has a small temperature rise up to 30 minutes.
It maintains its strength even when the temperature rises above 600℃, so by surrounding it with thin steel plates (SS41), it is possible to protect against fires with a small fire load and a short fire resistance time.
Can be left uncoated. Furthermore, even if the fire load is large and the fire resistance time is long, the H-shaped steel can be left uncoated by applying a light fireproof coating to the inside of the thin steel plate (SS41). In addition, including the above-mentioned thin steel plate 9,
Metal plates that have a heat-insulating effect, such as stainless thin steel plates, titanium thin plates, and aluminum plates, are collectively called heat-shield plates. The steel material according to the present invention equipped with the heat shield plate can be easily installed without the need for difficult work such as spraying fireproofing at a construction site, and therefore can be used economically. Next, the graph in Fig. 13 shows that the square steel pipe according to the present invention is filled with concrete, and a fibrous refractory material based on rock wool is applied to the surface to a thickness of 5 mm by wet spraying. It shows the temperature change of square steel pipes obtained by testing (according to JIS A 1304), and even with such a thin fireproof layer,
The steel material of the present invention can fully achieve its purpose. Furthermore, the graph in Figure 14 shows that the steel plate of the present invention is processed into a deck plate, and the back side is sprayed with a fibrous refractory material based on rock wool to a thickness of 7.5 mm using a wet method. Test (JIS A
1304), and the temperature of the deck plate itself does not exceed 600℃.
It was confirmed that the steel material of the present invention can be used as an effective fire-resistant steel material. Next, FIGS. 15 and 16 are graphs showing temperature rise curves when the emissivity is 0.7 and 0.4 in a fire test of an uncoated steel frame, where T is the plate thickness. As is clear from FIGS. 15 and 16, if the plate thickness is 100 mm, the steel material of the present invention can be fire-resistant for one hour without coating without any problem. Furthermore, in our research, the emissivity was 0.7
However, if the plate thickness is 70 mm or more, there is no problem with fire resistance for one hour, and if the steel material of the present invention is coated with ultra-thin metal such as aluminum foil, it can be used up to a thickness of 40 mm without covering it with heat-insulating and fire-resistant material. I found out. In addition, when the steel material of the present invention is used as a part of a structural member of a build-up section steel as an example of a steel material for construction,
It has no dimensional restrictions like rolled section steel, has a wide dimensional tolerance, and can respond flexibly to design requirements.
In addition, a steel material for construction that has excellent fire resistance and is highly economical can be obtained. Examples thereof will be described below. 17a to 17f are schematic cross-sectional views of embodiments of the build-up heat-resistant steel section according to the present invention, in which a is a cross-sectional view of the I-section steel 13, the flange 14 is the steel material of the present invention, the flange 15a, and the web 15b. is JIS
Constructed from general structural rolled steel according to G 3101. b is a cross-sectional view of the channel steel 16, the flange 17 is made of the steel of the present invention, the flange 18a and the web 18b are made of JIS steel.
Constructed from rolled steel for welded structures according to G 3106. c is a cross-sectional view of the angle iron 19, in which the flange 20 is made of the steel material of the present invention, and the flange 21 is made of a weather-resistant hot-rolled steel material JIS G 3114 for welded structures. d is a cross-sectional view of the square steel pipe 22, where the channel steel 23 is the steel material of the present invention and the channel steel 24 is the highly weather resistant rolled steel material JIS G.
Consists of 3125. e is a cross-sectional view of the column 25, the lip channel steel 26 is a steel material of the present invention, and the lip channel steel 27 is a general structural steel material.
It is composed of JIS G 3101. f is a cross-sectional view of the H-beam 28, with flanges 29a,
The web 29b is made of a steel material according to the present invention, and the flange 30 is made of a general structural steel material JIS G 3101. Now, FIG. 18 is a partial cross-sectional view of an embodiment in which the H-shaped steel 28 is used as a beam to support a concrete slab 31, in which the flange 29a, web 29
If b is made of the steel of the present invention and the fire load is small, there is no need to apply a fireproof coating, so the thickness T ₂ of the fireproof heat insulating layer 32 is as shown by the broken line 33 indicating the surface of the fireproof heat insulating layer 32. 30 is sufficient, and even when the fire load is large, the thickness of the fireproof insulation layer can be less than half that of the conventional one. For conventional H-beam steel, the thickness is surrounded by the dashed line 34.
Although a fire-resistant coating of _T1 was required, the amount of fire-resistant coating that can be saved in the case of the steel according to the present invention is the above-mentioned difference, so the cost savings are significant. Next, FIG. 19 is a schematic cross-sectional view of an embodiment in which external wall concrete 36 is attached to pillar material 35.
7 indicates an interior board, and 38 indicates a support beam. The column 35 is composed of a lip channel steel 39 made of the steel of the present invention and a lip channel steel 40 made of general structural steel JIS G 3101. Conventionally, the thickness of the fireproof coating indicated by the dashed line 41 is required, but the exposed surface 39a of the pillar material 35 is
is the steel material of the present invention, so the fireproof covering material 42 has the code T ₃
As shown in , even at the maximum thickness, the exposed surface 39a
Even if the fire load is large, the sign
As shown in T ₄ , a slightly thicker fireproof coating layer is sufficient;
The savings in fireproof cladding are significant. Next, in FIG. 20, a floor slab 45 is supported using an H-beam 44 in which only the lower flange 43 is made of the steel of the present invention, and a concrete filler 46 is attached to the H-beam 44.
This is a partial cross-sectional view of the space between the flanges of H.
Although it was necessary to wrap the entire section steel thickly with concrete, the present invention makes it possible to simplify the process as shown in the figure. FIG. 21 is a partial cross-sectional view of an example in which H-shaped steel is used as a pillar material for a building, and only the inner flange 47 supports an external wall material 49 using H-shaped steel 48, which is the steel material of the present invention. Although the space between both flanges is filled with a fibrous heat-resistant material 50 instead of the concrete shown in FIG. 20, there is no need to wrap the H-beam 48 thickly with the fibrous heat-resistant material or concrete as in the conventional case. Similarly, FIG. 22 shows an example in which H-shaped steel is used as a pillar material of a building, and only the inner flange 51 is made of H-shaped steel 52, which is the steel material of the present invention, and a block wall material 53 is used.
This is a partial cross-sectional view showing that the block wall material 53 and the inner flange 51 are filled with concrete or a fibrous heat-resistant material 54. Conventionally, the inner flange 51 was covered with thick concrete, but with the present invention, it is possible to create a simple fireproof structure as shown in the figure. Of course, even in this example, if the fire load is large,
It goes without saying that the inner flange 51 should be coated with a fireproof coating so as not to be exposed, but in that case as well, it may be made much thinner, for example, half as thick as before. Next, Figure 23a and b show general structural steel JIS G
This is a schematic cross-sectional view of an H-beam 55 made of 3101 and an H-beam 56 made of the steel of the present invention, in which the webs of each are cut into sawtooth shapes and the half-cut bodies 55a and 56a are welded together as shown in FIG. 57a, 5
7b and forming the honeycomb web shaped steel 58,
A useful beam material with excellent strength can be obtained. Unlike the conventional honeycomb web shaped steel 58, the lower side is made of the steel material of the present invention, so the fireproof coating can be reduced or eliminated as described above.
In addition, the through holes 59, 60, and 61 are often used for piping, and therefore, the space volume can be increased as structural materials for high-rise buildings, and the equipment costs for the various types of piping can be reduced, resulting in economic efficiency. As a good material, it can be used in a wide range of areas. FIG. 25 shows an example in which the honeycomb web shaped steel 58 is used as a beam material as in the example of FIG. 20, and when filling with concrete 62,
Because of the through holes 59, 60, and 61, concrete filling work can be carried out with extremely high efficiency. In this case, the fireproof coating on the honeycomb web shaped steel 58 can be reduced or eliminated as described above, so the economic effect is great. [Example] Steel plates (thickness 15 to 75 mm) of various steel compositions were manufactured using well-known converter, continuous casting, and thick plate processes, and their room temperature yield strength (yield strength), high temperature yield strength (yield strength), etc. were investigated. In Table 5, No. 1 to No. 19 are the steels of the present invention, and No. 20 to No. 2 are the steels of the present invention.
Figure 29 shows the chemical composition of comparative steel. Next, Table 6 shows the mechanical properties of the inventive steel and comparative steel under heating, rolling, and cooling conditions. Invention example No. 1 in Table 6
All of the examples No. 19 have good room temperature and high temperature proof strength. On the other hand, in Comparative Example No. 4, the water cooling start temperature after rolling is higher than the Ar3 temperature, so the room temperature proof stress is high, and the ratio with the proof stress at 600°C cannot satisfy 70%, and in No. 6, Because the heating temperature and rolling temperature are low, the yield strength at room temperature is high, and the ratio to the yield strength at 600℃ (hereinafter referred to as yield strength ratio) cannot satisfy 70%. Because it was rolled at a cutting temperature, the yield strength at room temperature was high, but the yield strength at 600°C was low, and the yield strength ratio could not be satisfied. In addition, similarly to No. 4, No. 9 could not satisfy the yield strength ratio because the water cooling start temperature was high, and the same could not be achieved with the quenching and tempering process of No. 10, and the yield strength ratio could not be satisfied with No. 15. In this case, the proof stress ratio could not be satisfied for the same reason as No. 6. Furthermore, Comparative Examples No. 20 to No. 29 were unable to satisfy the yield strength ratio because their chemical components were all out of the range of the steel of the present invention. In other words, in No. 20, Mo is low;
In No. 21, Mn is low, in No. 22, Mo is not added, in No. 23, the amount of Mo is too large and the water cooling start temperature is too high, and in No. 24 to No. 29, ,Mo
The yield strength ratio was not satisfactory.

【表】【table】

【表】【table】

【表】【table】

〔発明の効果〕〔Effect of the invention〕

本発明にかかる化学成分および製造法で製造し
た鋼材は、600℃の高温耐力（降伏強度）が常温
耐力（降伏強度）の70％（略々2/3）以上で、常
温の降伏比（降伏点／引張度）も低く、また圧延
終了後、Ar₃−20℃〜Ar₃−100℃まで空冷し、続
いてこの温度から３〜40℃／秒の冷却速度で550
℃以下の任意の温度まで水冷し、この後放冷する
方法により、低い炭素当量（C_eq）で強度を維持
することでき、また低い炭素当量にすることがで
きるために溶接性も良好である等の特徴を備えて
おり、無被覆もしく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ので、耐火施
工にかかるコストを大幅に引き下げることが可能
である。更に、本発明に於いては圧延後に所定温
度から水冷することにより、低いC_eqで高強度を
得ることができる。また低いC_eqとすることによ
り、溶接性を改善し、溶接熱影響部（HAZ）の
靭性を向上させることができる。また、大量生産
が可能で、しかも価格も安く、溶接など施工も用
意で、建設工期を短縮でき、 全体として建築費が低兼で済む。 また、製造方法についても、特に難しい操業の
必要がないので、経済的にも有利である。 Steel products manufactured using the chemical composition and manufacturing method according to the present invention have a high temperature yield strength (yield strength) at 600°C that is 70% (approximately 2/3) or more of the room temperature yield strength (yield strength), and a yield ratio (yield strength) at room temperature. After rolling, it is air cooled from Ar ₃ -20℃ to Ar ₃ -100℃, and then heated to 550℃ from this temperature at a cooling rate of 3 to 40℃/sec.
By water-cooling to any temperature below ℃ and then allowing it to cool, it is possible to maintain strength with a low carbon equivalent (C _eq ), and because the carbon equivalent can be kept low, weldability is also good. It has the following characteristics, and is 20 to 50% cheaper than uncoated or conventional fireproof coating.
Since the fireproofing objective can be achieved with a coating thickness of , it is possible to significantly reduce the cost of fireproofing construction. Furthermore, in the present invention, high strength can be obtained with low C _eq by water cooling from a predetermined temperature after rolling. Moreover, by setting a low C _eq , weldability can be improved and the toughness of the weld heat affected zone (HAZ) can be improved. In addition, mass production is possible, the price is low, and construction work such as welding is possible, shortening the construction period and reducing overall construction costs. Furthermore, the manufacturing method is also economically advantageous since it does not require particularly difficult operations.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は本発明鋼と比較鋼にかかる耐力の比較
グラフ、第２図は弾性係数の比較グラフ、第３図
は本発明鋼にかかるクリープ特性グラフ、第４図
は、比較鋼にかかるクリープ特性グラフ、第５図
は本発明にかかるＨ形鋼に吹き付けロツクウール
（湿式）を展着した柱の概略立面図ａおよびＡ−
Ａ断面図ｂ、第６図は前記柱の昇温曲線を示すグ
ラフ、第７図は前記柱の変形を示すグラフ、第８
図は本発明にかかるＨ形鋼に吹き付けロツクウー
ル（湿式）を展着したはりの概略立面図ａおよび
Ａ−Ａ断面図ｂ、第９図は前記はりの昇温曲線を
示すグラフ、第１０図は前記はりの変形を示すグ
ラフ、第１１図は防熱盾板を装着した鋼材の概略
横断面図、第１２図は、前記鋼材の昇温曲線を示
すグラフ、第１３図および第１４図はコンクリー
ト充填鋼管およびデツキプレートの昇温曲線を示
すグラフ、第１５図および第１６図は、それぞれ
放射率の異なつた無被覆鉄骨昇温曲線を示すグラ
フ、第１７図ａ〜ｆは本発明にかかるビルドアツ
プ耐熱形鋼の概略断面図、第１８図〜第２２図は
本発明にかかるビルドアツプ耐熱形鋼の実施例概
略断面図、第２３図ａ，ｂはＨ形鋼の概略断面
図、第２４図はハニカムウエブ耐熱形鋼の概略側
面図、第２５図は本発明にかかるハニカムウエブ
耐熱形鋼の実施例概略断面図である。 １…Ｈ形鋼、２…耐火材、３…Ｈ形鋼、４…耐
火材、５…はり上側フランジ、６…はり下側フラ
ンジ、７…ウエブ、８…Ｈ形鋼、９…薄鋼板、１
０…梁、１１…取付金具、１２…コンクリート
床、１３…Ｉ形鋼、１４…フランジ、１５ａ…フ
ランジ、１５ｂ…ウエブ、１６…溝形鋼、１７…
フランジ、１８ａ…フランジ、１８ｂ…ウエブ、
１９…山形鋼、２０…フランジ、２１…フラン
ジ、２２…角鋼管、２３…溝形鋼、２４…溝形
鋼、２５…柱材、２６…リツプ溝形鋼、２７…リ
ツプ溝形鋼、２８…Ｈ形鋼、２９ａ…フランジ、
２９ｂ…ウエブ、３０…フランジ、３１…コンク
リート床板、３２…耐火断熱層、３３…破線、３
６…外壁コンクリート、３７…内装ボード、３８
…支持梁、３９，４０…リツプ溝形鋼、４２…耐
火被覆材、４３…下側フランジ、４４…Ｈ形鋼、
４５…床版、４６…コンクリート充填材、４７…
内側フランジ、４８…Ｈ形鋼、４９…外壁材、５
０…繊維質耐熱材、５１…内側フランジ、５２…
Ｈ形鋼、５３…ブロツク壁材、５４…繊維質耐熱
材、５５…Ｈ形鋼、５５ａ…Ｈ形鋼半截材、５６
…Ｈ形鋼、５６ｂ…Ｈ形鋼半截材、５７ａ，５７
ｂ…溶接、５８…ハニカムウエブ形鋼、５９，６
０，６１…貫通孔、６２…コンクリート。 Figure 1 is a comparison graph of the yield strength of the inventive steel and comparison steel, Figure 2 is a comparison graph of elastic modulus, Figure 3 is a creep characteristic graph of the invention steel, and Figure 4 is the creep characteristic of the comparison steel. The characteristic graph, FIG. 5, is a schematic elevational view a and A- of a column in which sprayed rock wool (wet type) is spread on H-beam steel according to the present invention.
A sectional view b, FIG. 6 is a graph showing the temperature rise curve of the column, FIG. 7 is a graph showing the deformation of the column, and FIG.
The figures are a schematic elevational view a and an A-A sectional view b of a beam in which sprayed rock wool (wet type) is spread on H-section steel according to the present invention, FIG. 9 is a graph showing the temperature rise curve of the beam, and FIG. The figure is a graph showing the deformation of the beam, FIG. 11 is a schematic cross-sectional view of the steel material equipped with a heat shield plate, FIG. 12 is a graph showing the temperature rise curve of the steel material, and FIGS. 13 and 14 are Graphs showing temperature rise curves of concrete-filled steel pipes and deck plates, Figures 15 and 16 are graphs showing temperature rise curves of uncoated steel frames with different emissivities, respectively, and Figures 17 a to f are graphs showing temperature rise curves of concrete-filled steel pipes and deck plates. A schematic sectional view of a build-up heat-resistant section steel, FIGS. 18 to 22 are schematic sectional views of embodiments of a build-up heat-resistant section steel according to the present invention, FIGS. 23a and 23b are schematic sectional views of an H-section steel, and FIG. 24 25 is a schematic side view of a honeycomb web heat-resistant shaped steel, and FIG. 25 is a schematic cross-sectional view of an embodiment of the honeycomb web heat-resistant shaped steel according to the present invention. 1... H-beam steel, 2... Fireproof material, 3... H-beam steel, 4... Fireproof material, 5... Beam upper flange, 6... Beam lower flange, 7... Web, 8... H-beam steel, 9... Thin steel plate, 1
0... Beam, 11... Mounting bracket, 12... Concrete floor, 13... I-shaped steel, 14... Flange, 15a... Flange, 15b... Web, 16... Channel steel, 17...
Flange, 18a...flange, 18b...web,
19... angle iron, 20... flange, 21... flange, 22... square steel pipe, 23... channel steel, 24... channel steel, 25... column material, 26... lip channel steel, 27... lip channel steel, 28 ...H-shaped steel, 29a...flange,
29b...web, 30...flange, 31...concrete floor plate, 32...fireproof insulation layer, 33...dashed line, 3
6... Exterior wall concrete, 37... Interior board, 38
...Support beam, 39, 40...Rip channel steel, 42...Fireproof covering material, 43...Lower flange, 44...H section steel,
45... Floor slab, 46... Concrete filler, 47...
Inner flange, 48...H-shaped steel, 49...Outer wall material, 5
0...Fibrous heat-resistant material, 51...Inner flange, 52...
H-shaped steel, 53... Block wall material, 54... Fibrous heat-resistant material, 55... H-shaped steel, 55a... H-shaped steel half-cut material, 56
...H-shaped steel, 56b...H-shaped steel half-cut material, 57a, 57
b...Welding, 58...Honeycomb web shaped steel, 59,6
0, 61...Through hole, 62...Concrete.

Claims (1)

【特許請求の範囲】 １ 重量比でC0.04〜0.15％、Si0.6％以下、
Mn0.5〜1.6％、Mo0.2〜0.7％、Al0.1％以下及び
N0.006％以下を含有し、残部がFe及び不可避的
不純物からなり、かつミクロ組織が20〜50％のフ
エライトとベイナイトの混合組織からなることを
特徴とする耐火性の優れた建築用低降伏比鋼材。 ２ 重量比でC0.04〜0.15％、Si0.6％以下、
Mn0.5〜1.6％、Mo0.2〜0.7％、Al0.1％以下、
N0.006％以下に更にNb0.005〜0.04％、Ti0.005〜
0.10％、Zr0.005〜0.03％、V0.005〜0.10％、
Ni0.05〜0.5％、Cu0.05〜1.0％、B0.0003〜0.002
％、Ca0.0005〜0.005％、REM0.001〜0.02％のう
ち１種または２種以上を含有し、残部がFe及び
不可避的不純物からなり、かつミクロ組織が20〜
50％のフエライトとベイナイトの混合組織からな
ることを特徴とする耐火性の優れた建築用低降伏
比鋼材。 ３ 重量比でC0.04〜0.15％、Si0.6％以下、
Mn0.5〜1.6％、Mo0.2〜0.7％、Al0.1％以下及び
N0.006％以下を含有し、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
熱し、熱間圧延を800℃〜1000℃の温度範囲で終
了した後、得られた鋼板をAr₃−20℃〜Ar₃−100
℃まで空冷して該鋼板組織のフエライト分率を20
〜50％にし、続いてこの温度から３〜40℃／秒の
冷却速度で550℃以下の任意の温度まで水冷し、
その後放冷することを特徴とする耐火性の優れた
建築用低降伏比鋼材の製造方法。 ４ 重量比でC0.04〜0.15％、Si0.6％以下、
Mn0.5〜1.6％、Mo0.2〜0.7％、Al0.1％以下及び
N0.006％以下を含有するとともに、更にNb0.005
〜0.04％、Ti0.005〜0.10％、Zr0.005〜0.03％、
V0.005〜0.10％、Ni0.05〜0.5％、Cu0.05〜1.0％、
B0.0003〜0.002％、Ca0.0005〜0.005％、
REM0.001〜0.02％のうち１種又は２種以上を含
有し、残部がFe及び不可避的不純物からなる鋼
片を1100〜1300℃の温度域で加熱し、熱間圧延を
800℃〜1000℃の温度範囲で終了した後、得られ
た鋼板をAr₃−20℃〜Ar₃−100℃まで空冷して該
鋼板組織のフエライト分率を20〜50％とし、続い
てこの温度から３〜40℃／秒の冷却速度で550℃
以下の任意の温度まで水冷し、その後放冷するこ
とを特徴とする耐火性の優れた建築用低降伏比鋼
材の製造方法。 ５ 請求項３又は４記載の方法により得られた鋼
材をさらに熱間工程において塑性加工する耐火性
の優れた建築用低降伏比鋼材の製造方法。 ６ 請求項３又は４記載の方法により得られた鋼
材を冷間工程において塑性加工する耐火性の優れ
た建築用低降伏比鋼材の製造方法。 ７ 請求項１又は２記載の鋼材或いは５又は６記
載の方法により得られた鋼材の受熱表面に、無機
系繊維質耐火薄層材を展着せしめてなる耐火性の
優れた建築用低降伏比鋼材料。 ８ 請求項１又は２記載の鋼或いは５又は６記載
の方法により得られた鋼材の受熱表面に、高耐熱
性塗料を被着せしめてなる耐火性の優れた建築用
低降伏比鋼材料。 ９ 請求項１又は２記載の鋼材或いは５又は６記
載の方法により得られた鋼材の受熱表面に、防熱
盾板を装着せしめてなる耐火性の優れた建築用低
降伏比鋼材料。 １０ 請求項１又は２記載の鋼材或いは５又は６
記載の方法により得られた中空鋼材にコンクリー
トを充填してなる耐火性の優れた建築用低降伏比
鋼材料。 １１ 請求項１又は２記載の鋼材或いは５又は６
記載の方法により得られた鋼材の表面に、極薄金
属を展着してなる耐火性の優れた建築用低降伏比
鋼材料。 １２ 請求項１又は２記載の鋼材或いは５又は６
記載の方法により得られた鋼材と一般構造用鋼材
を所定形状に成形して溶接接合してなる建築用低
降伏比鋼材料。 １３ 一般構造用鋼材が、一般構造用圧延鋼材、
溶接構造用圧延鋼材、溶接構造用耐候性熱間圧延
鋼材、高耐候性圧延鋼材のうちの一種である請求
項１２記載の建築用低降伏比鋼材料。[Claims] 1. C0.04 to 0.15%, Si 0.6% or less by weight,
Mn0.5~1.6%, Mo0.2~0.7%, Al0.1% or less and
Low yield for construction with excellent fire resistance, characterized by containing 0.006% or less of N, the balance consisting of Fe and unavoidable impurities, and a microstructure consisting of a mixed structure of 20 to 50% ferrite and bainite. Specific steel material. 2 C0.04-0.15% by weight, Si 0.6% or less,
Mn0.5~1.6%, Mo0.2~0.7%, Al0.1% or less,
Below N0.006%, further Nb0.005~0.04%, Ti0.005~
0.10%, Zr0.005~0.03%, V0.005~0.10%,
Ni0.05~0.5%, Cu0.05~1.0%, B0.0003~0.002
%, Ca0.0005~0.005%, REM0.001~0.02%, the balance is Fe and unavoidable impurities, and the microstructure is 20 ~
A low yield ratio steel material for construction with excellent fire resistance, characterized by a mixed structure of 50% ferrite and bainite. 3 C0.04-0.15% by weight, Si 0.6% or less,
Mn0.5~1.6%, Mo0.2~0.7%, Al0.1% or less and
A steel billet containing 0.006% or less of N and the balance consisting of Fe and unavoidable impurities is heated in a temperature range of 1100 to 1300℃, and after hot rolling is completed in a temperature range of 800℃ to 1000℃, Ar ₃ −20℃～Ar ₃ −100
The ferrite fraction of the steel plate structure was reduced to 20℃ by air cooling to ℃.
~50%, followed by water cooling from this temperature to any temperature below 550°C at a cooling rate of 3 to 40°C/sec,
A method for producing a low yield ratio steel material for construction with excellent fire resistance, which is characterized in that it is then allowed to cool. 4 C0.04-0.15% by weight, Si 0.6% or less,
Mn0.5~1.6%, Mo0.2~0.7%, Al0.1% or less and
Contains N0.006% or less and additionally Nb0.005
~0.04%, Ti0.005~0.10%, Zr0.005~0.03%,
V0.005~0.10%, Ni0.05~0.5%, Cu0.05~1.0%,
B0.0003~0.002%, Ca0.0005~0.005%,
A steel billet containing one or more of 0.001 to 0.02% REM, with the remainder consisting of Fe and unavoidable impurities, is heated in a temperature range of 1100 to 1300°C and hot rolled.
After finishing in the temperature range of 800°C to 1000°C, the obtained steel plate is air-cooled to Ar ₃ -20°C to _{Ar 3} -100°C to make the ferrite fraction of the steel plate structure 20 to 50%. From temperature to 550℃ at a cooling rate of 3 to 40℃/sec
A method for producing a low yield ratio steel material for construction with excellent fire resistance, which comprises water-cooling to the following arbitrary temperature and then allowing it to cool. 5. A method for producing a low yield ratio steel material for construction with excellent fire resistance, which further comprises plastic working the steel material obtained by the method according to claim 3 or 4 in a hot process. 6. A method for producing a low yield ratio steel material for construction with excellent fire resistance, which comprises plastically working the steel material obtained by the method according to claim 3 or 4 in a cold process. 7. A low yield ratio for construction with excellent fire resistance, which is obtained by spreading an inorganic fibrous fire-resistant thin layer material on the heat-receiving surface of the steel material according to claim 1 or 2 or the steel material obtained by the method according to claim 5 or 6. steel material. 8. A low yield ratio steel material for construction with excellent fire resistance, which is obtained by coating the heat-receiving surface of the steel according to claim 1 or 2 or the steel material obtained by the method according to claim 5 or 6 with a highly heat-resistant paint. 9. A low yield ratio steel material for construction with excellent fire resistance, which is obtained by attaching a heat shield plate to the heat-receiving surface of the steel material according to claim 1 or 2 or the steel material obtained by the method according to claim 5 or 6. 10 Steel material according to claim 1 or 2 or 5 or 6
A low yield ratio steel material for construction with excellent fire resistance, which is obtained by filling a hollow steel material obtained by the method described above with concrete. 11 Steel material according to claim 1 or 2, or 5 or 6
A low yield ratio steel material for construction with excellent fire resistance, which is obtained by spreading an ultra-thin metal onto the surface of a steel material obtained by the method described above. 12 Steel material according to claim 1 or 2 or 5 or 6
A low yield ratio steel material for construction, which is obtained by forming a steel material obtained by the method described above and a general structural steel material into a predetermined shape and joining them by welding. 13 General structural steel materials include general structural rolled steel materials,
The low yield ratio steel material for construction according to claim 12, which is one of rolled steel materials for welded structures, weather resistant hot rolled steel materials for welded structures, and high weather resistant rolled steel materials.