JP6432607B2 - Structural steel with excellent weather resistance - Google Patents

Structural steel with excellent weather resistance Download PDF

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JP6432607B2
JP6432607B2 JP2016565368A JP2016565368A JP6432607B2 JP 6432607 B2 JP6432607 B2 JP 6432607B2 JP 2016565368 A JP2016565368 A JP 2016565368A JP 2016565368 A JP2016565368 A JP 2016565368A JP 6432607 B2 JP6432607 B2 JP 6432607B2
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weather resistance
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JPWO2017043021A1 (en
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進一 三浦
進一 三浦
村瀬　正次
正次 村瀬
力 上
力 上
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JFE Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
    • C22C38/105—Ferrous alloys, e.g. steel alloys containing cobalt containing Co and Ni
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
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  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)

Description

本発明は、主に橋梁などの屋外で用いられる構造用鋼材に関し、特に海岸近傍などの飛来塩分量が多い環境下での使用に供して好適な耐候性に優れた構造用鋼材に関するものである。   The present invention relates to a structural steel material mainly used outdoors such as a bridge, and more particularly to a structural steel material excellent in weather resistance suitable for use in an environment with a large amount of incoming salt such as the vicinity of a coast. .

従来から、橋梁などの屋外で用いられる鋼構造物には、耐候性鋼材が用いられている。耐候性鋼材は、大気暴露環境において、鋼材表面が、Ｃｕ，Ｐ，Ｃｒ，Ｎｉなどの合金元素が濃化した保護性の高いさび層で覆われることにより腐食速度が著しく低減する鋼材である。その優れた耐候性により、耐候性鋼を使用した橋梁は無塗装のまま数十年間の供用に耐えることが知られている。   Conventionally, weathering steel is used for steel structures used outdoors such as bridges. The weather-resistant steel material is a steel material in which the corrosion rate is remarkably reduced when the steel material surface is covered with a highly protective rust layer enriched with an alloy element such as Cu, P, Cr, or Ni in an air exposure environment. Due to its excellent weather resistance, it is known that bridges using weather-resistant steel can withstand service for several decades without being painted.

しかしながら、海岸近傍などの飛来塩分量が多い環境では、上記したような保護性の高いさび層は生成しにくく、実用的な耐候性が得難いことが知られている。   However, it is known that, in an environment with a large amount of incoming salt, such as the vicinity of the coast, it is difficult to form a rust layer with high protection as described above, and it is difficult to obtain practical weather resistance.

例えば、非特許文献１によれば、従来の耐候性鋼（JIS G 3114：溶接構造用耐候性熱間圧延鋼材）は、飛来塩分量が０．０５ｍｇ・ＮａＣｌ／ｄｍ2／ｄａｙ（以降、単位（ｍｇ・ＮａＣｌ／ｄｍ2／ｄａｙ）をｍｄｄにて表記する場合がある）以下の地域でのみ、無塗装での使用が可能となっている。For example, according to Non-Patent Document 1, the conventional weathering steel (JIS G 3114: weathering hot rolled steel for welded structure) has an incoming salt content of 0.05 mg · NaCl / dm 2 / day (hereinafter, unit) (There may be cases where mg · NaCl / dm 2 / day) is expressed in mdd.) It can be used without painting only in the following areas.

従って、海岸近傍などの飛来塩分量が多い環境では、普通鋼材（JIS G 3106：溶接構造用圧延鋼材）に塗装等の防食措置を施したものが使用されている。
しかしながら、塗装は、時間の経過とともに塗膜が劣化するため、定期的な補修が必要となる。加えて、人件費の高騰や、再塗装の困難さが加わる。このような理由から、現在、無塗装での使用が可能な鋼材の要望が高い。Therefore, in an environment with a large amount of incoming salt, such as near the coast, ordinary steel (JIS G 3106: rolled steel for welded structure) with anticorrosion measures such as painting is used.
However, since the coating deteriorates with the passage of time, periodic repairs are necessary. In addition, labor costs increase and repainting becomes difficult. For these reasons, there is a high demand for steel materials that can be used without painting.

これまで、鋼材の耐候性を向上させる手法として、種々の技術が提案されている。
例えば、特許文献１には、Ｃｕと１質量％以上のＮｉを添加した高耐候性鋼材が開示されている。
特許文献２には、１質量％以上のＮｉとＭｏを添加した耐候性に優れた鋼材が開示されている。
特許文献３には、Ｎｉに加え、Ｃｕ、Ｔｉを添加した耐候性に優れた鋼材が開示されている。
特許文献４には、Ｎｉを多量に含有し、加えてＰおよびＣｕ，Ｍｏ，Ｓｎ，Ｓｂ等を含有した溶接構造用鋼材が開示されている。
特許文献５には、Ｓｎを添加した耐食性に優れた鋼材が開示されている。Until now, various techniques have been proposed as a technique for improving the weather resistance of steel materials.
For example, Patent Document 1 discloses a highly weather-resistant steel material to which Cu and 1% by mass or more of Ni are added.
Patent Document 2 discloses a steel material excellent in weather resistance to which 1% by mass or more of Ni and Mo are added.
Patent Document 3 discloses a steel material excellent in weather resistance in which Cu and Ti are added in addition to Ni.
Patent Document 4 discloses a steel material for welded structure containing a large amount of Ni and additionally containing P, Cu, Mo, Sn, Sb and the like.
Patent Document 5 discloses a steel material excellent in corrosion resistance to which Sn is added.

特許第３７８５２７１号公報（特開平１１−１７２３７０号公報）Japanese Patent No. 3785271 (Japanese Patent Laid-Open No. 11-172370) 特許第３８４６２１８号公報（特開２００２−３０９３４０号公報）Japanese Patent No. 3846218 (Japanese Patent Laid-Open No. 2002-309340) 特許第３５６８７６０号公報（特開平１１−７１６３２号公報）Japanese Patent No. 3568760 (Japanese Patent Laid-Open No. 11-71632) 特開平１０−２５１７９７号公報Japanese Patent Laid-Open No. 10-251797 特開２０１２−２５５１８４号公報JP 2012-255184 A

建設省土木研究所，(社)鋼材倶楽部，(社)日本橋梁建設協会，耐候性鋼材の橋梁への適用に関する共同研究報告書（ＸＸ），平成５年３月Ministry of Construction, Public Works Research Institute, Steel Club, Japan Bridge Construction Association, Joint Research Report on the Application of Weathering Steel to Bridges (XX), March 1993

しかしながら、特許文献１，２および３のようにＮｉの含有量を増加させた場合、合金コストの上昇により鋼材の価格が上昇してしまうという問題があった。
また、特許文献４のようにＮｉおよびＰの含有量を増加させ、Ｃｕ，Ｍｏ，Ｓｎ，Ｓｂ等を含有した鋼材では、合金コストの上昇により鋼材の価格が上昇するだけでなく、Ｐの含有量が高いために溶接性の低下が避けられない。
さらに、特許文献５のようにＳｎの含有量を増加させた場合、合金コストの上昇により鋼材の価格が上昇してしまうという問題があった。However, when the Ni content is increased as in Patent Documents 1, 2, and 3, there is a problem that the price of the steel material increases due to an increase in alloy cost.
Moreover, in steel materials which increased the content of Ni and P as in Patent Document 4 and contained Cu, Mo, Sn, Sb, etc., not only the price of the steel materials increases due to an increase in alloy cost, but also the content of P Since the amount is high, a decrease in weldability is inevitable.
Further, when the Sn content is increased as in Patent Document 5, there is a problem that the price of the steel material increases due to an increase in alloy cost.

本発明は、上記の事情に鑑み開発されたもので、低コストで、しかも飛来塩分量が多い環境下においても優れた耐候性を示す構造用鋼材を提供することを目的とする。   The present invention has been developed in view of the above circumstances, and an object thereof is to provide a structural steel material that exhibits excellent weather resistance even in an environment that is low in cost and has a large amount of incoming salt.

さて、発明者らは、上記の課題を解決するために、耐候性の観点から鋼材の成分組成について鋭意検討を重ねた。
その結果、少量のＣｕ，Ｎｉ，Ｃｏに加え、さらに微量のＮｂおよびＳｎを複合含有させることによって、鋼材の耐候性が大幅に向上することを見出した。
さらに、Ｃｒを含有させることにより、耐候性の一層の向上効果が得られることを見出した。
本発明は、上記の新規知見に立脚するものである。Now, in order to solve the above-mentioned problems, the inventors have made extensive studies on the component composition of steel from the viewpoint of weather resistance.
As a result, it was found that the weather resistance of the steel material is significantly improved by adding a small amount of Nb and Sn in addition to a small amount of Cu, Ni, and Co.
Furthermore, it discovered that the further improvement effect of a weather resistance was acquired by containing Cr.
The present invention is based on the above-described novel findings.

すなわち、本発明の要旨構成は次のとおりである。
１．質量％で、
Ｃ：０．０２０％以上０．２００％未満、
Ｓｉ：０．１０％以上１．００％以下、
Ｍｎ：０．２０％以上２．００％以下、
Ｐ：０．００３％以上０．０３０％以下、
Ｓ：０．０００１％以上０．０２００％以下および
Ａｌ：０．００１％以上０．１００％以下
を含み、かつ
Ｃｕ：０．０１％以上１．００％以下、
Ｎｉ：０．０１％以上０．６５％以下
Ｃｏ：０．００２％以上０．２２０％未満、
Ｎｂ：０．００５％以上０．２００％以下および
Ｓｎ：０．００５％以上０．２００％以下
を含有し、残部はＦｅおよび不可避的不純物からなる耐候性に優れた構造用鋼材。That is, the gist configuration of the present invention is as follows.
1. % By mass
C: 0.020% or more and less than 0.200%,
Si: 0.10% or more and 1.00% or less,
Mn: 0.20% or more and 2.00% or less,
P: 0.003% or more and 0.030% or less,
S: 0.0001% or more and 0.0200% or less and Al: 0.001% or more and 0.100% or less, and Cu: 0.01% or more and 1.00% or less,
Ni: 0.01% or more and 0.65% or less Co: 0.002% or more and less than 0.220%,
Nb: 0.005% or more and 0.200% or less and Sn: 0.005% or more and 0.200% or less, and the balance is a structural steel material having excellent weather resistance composed of Fe and inevitable impurities.

２．Ｃｕ，Ｎｉ，Ｃｏ，ＮｂおよびＳｎ量が、次式（１）を満足する前記１に記載の耐候性に優れた構造用鋼材。
Ｌｏｇ（Ｃｕ×５００−１)×Ｌｏｇ（Ｎｉ×５００−１)×Ｌｏｇ（Ｃｏ×１０００−０．００１)×Ｌｏｇ（Ｎｂ×１０００−３)×Ｌｏｇ（Ｓｎ×１０００−３)＞０．０２・・・（１）2. The structural steel material excellent in weather resistance according to 1 above, wherein the amounts of Cu, Ni, Co, Nb and Sn satisfy the following formula (1).
Log (Cu × 500-1) × Log (Ni × 500-1) × Log (Co × 1000-0.001) × Log (Nb × 1000-3) × Log (Sn × 1000-3)> 0.02 ... (1)

３．さらに、質量％で、
Ｃｒ：０．０１％以上１．００％以下
を含有する前記１または２に記載の耐候性に優れた構造用鋼材。3. Furthermore, in mass%,
3. Structural steel material excellent in weather resistance according to 1 or 2 above, containing Cr: 0.01% or more and 1.00% or less.

４．さらに、質量％で、
Ｍｏ：０．００１％以上１．０００％以下、
Ｗ：０．００５％以上１．０００％以下および
Ｓｂ：０．００５％以上０．２００％以下
のうちから選ばれる一種以上を含有する前記１〜３のいずれかに記載の耐候性に優れた構造用鋼材。4). Furthermore, in mass%,
Mo: 0.001% or more and 1.000% or less,
W: 0.005% or more and 1.000% or less and Sb: 0.005% or more and 0.200% or less containing one or more kinds selected from the above, and excellent weather resistance according to any one of 1 to 3 above Structural steel.

５．さらに、質量％で、
Ｔｉ：０．００５％以上０．２００％以下、
Ｖ：０．００５％以上０．２００％以下、
Ｚｒ：０．００５％以上０．２００％以下および
Ｂ：０．０００１％以上０．００５０％以下
のうちから選ばれる一種以上を含有する前記１〜４のいずれかに記載の耐候性に優れた構造用鋼材。5). Furthermore, in mass%,
Ti: 0.005% or more and 0.200% or less,
V: 0.005% or more and 0.200% or less,
Zr: 0.005% or more and 0.200% or less and B: Excellent weather resistance according to any one of 1 to 4 containing one or more selected from 0.0001% and 0.0050% or less Structural steel.

６．さらに、質量％で、
ＲＥＭ：０．０００１％以上０．０１００％以下、
Ｃａ：０．０００１％以上０．０１００％以下および
Ｍｇ：０．０００１％以上０．０１００％以下
のうちから選ばれる一種以上を含有する前記１〜５のいずれかに記載の耐候性に優れた構造用鋼材。6). Furthermore, in mass%,
REM: 0.0001% or more and 0.0100% or less,
Ca: 0.0001% or more and 0.0100% or less and Mg: 0.0001% or more and 0.0100% or less containing one or more selected from the above, excellent weather resistance according to any one of 1 to 5 above Structural steel.

本発明によれば、耐候性向上に有効な元素を少量ずつ複合含有させることによって、低コストで、しかも飛来塩分量が多い環境下においても優れた耐候性を有する構造用鋼材を得ることができる。   According to the present invention, a structural steel material having excellent weather resistance can be obtained at low cost and in an environment with a large amount of incoming salt by compounding elements effective for improving weather resistance little by little. .

本発明に従う成分設計によって優れた耐候性が得られる理由については、まだ明確に解明されたわけではないが、発明者らは以下のように推定している。
Ｃｕ，Ｎｉ，Ｃｏは、さび層全体に分布し、さび粒子の表面に存在する、あるいはさび粒子中に取り込まれることでさび粒子を微細化させ、これによりさび層が緻密化する。その結果、腐食促進因子である酸素や塩化物イオンがさび層を透過して地鉄に到達するのを防止する。特にＣｏは腐食促進因子のさび層中の透過を抑制する効果が高く、本発明においては重要な元素である。また、Ｎｂは、地鉄表面近傍のさび中に濃化することで、腐食促進因子である塩化物イオンがさび層を透過して地鉄に到達することを防止し、鋼材のアノード反応、カソード反応を抑制する。Ｓｎは、地鉄表面近傍のさび中に濃化し、さび層を微細化することで腐食促進因子のさび層中の透過を抑制し、鋼材のアノード反応、カソード反応を抑制する。
ただし、これらの効果は、各成分の単独含有では不十分で、Ｃｕ，Ｎｉ，Ｃｏ，Ｎｂ，Ｓｎを複合含有させ、各々の添加効果を相乗的に作用させることによって、初めて耐食性の著しい向上が達成される。The reason why excellent weather resistance can be obtained by the component design according to the present invention has not yet been clearly clarified, but the inventors presume as follows.
Cu, Ni, and Co are distributed throughout the rust layer and are present on the surface of the rust particles, or are taken into the rust particles to make the rust particles finer, thereby densifying the rust layer. As a result, oxygen and chloride ions, which are corrosion promoting factors, are prevented from penetrating the rust layer and reaching the base iron. In particular, Co is highly effective in suppressing the penetration of corrosion promoting factors through the rust layer, and is an important element in the present invention. In addition, Nb is concentrated in the rust near the surface of the ground iron to prevent chloride ions, which are corrosion accelerating factors, from passing through the rust layer and reaching the ground iron. Suppresses the reaction. Sn is concentrated in the rust in the vicinity of the surface of the ground iron, and by making the rust layer finer, the permeation of the corrosion promoting factor through the rust layer is suppressed, and the anode reaction and cathode reaction of the steel material are suppressed.
However, these effects are not sufficient when each component is contained alone. By adding Cu, Ni, Co, Nb, and Sn in a composite manner and synergistically adding the respective effects, the corrosion resistance is significantly improved for the first time. Achieved.

以下、本発明を具体的に説明する。
まず、本発明において、鋼材の成分組成を前記の範囲に限定した理由について説明する。
Ｃ：０．０２０％以上０．２００％未満
Ｃは、構造用鋼材の強度を向上させる元素であり、所定の強度を確保するためには０．０２０％以上含有させる必要がある。一方、Ｃ含有量が０．２００％以上では溶接性および靭性の劣化を招く。従って、Ｃ量は０．０３０％以上０．２００％未満の範囲とした。好ましくは０．０３％以上、０．１８％以下、より好ましくは０．０６％以上、０．１６％以下である。Hereinafter, the present invention will be specifically described.
First, the reason why the component composition of the steel material is limited to the above range in the present invention will be described.
C: 0.020% or more and less than 0.200% C is an element that improves the strength of the structural steel material, and in order to ensure a predetermined strength, it is necessary to contain 0.020% or more. On the other hand, if the C content is 0.200% or more, the weldability and toughness are deteriorated. Therefore, the C content is in the range of 0.030% or more and less than 0.200%. Preferably they are 0.03% or more and 0.18% or less, More preferably, they are 0.06% or more and 0.16% or less.

Ｓｉ：０．１０％以上１．００％以下
Ｓｉは、本発明において重要な成分であり、さび層全体のさび粒を微細化させて緻密なさび層を形成し、鋼材の耐候性を向上させる効果を有する。また、熱間圧延時の鋼材表面の割れを防止する効果を有する。これらの効果を得るためには、０．１０％以上含有させる必要がある。一方、１．００％を超えて過剰に含有すると靭性および溶接性が著しく劣化する。従って、Ｓｉ量は０．１０％以上１．００％以下の範囲とした。好ましくは０．１５％以上０．７０％以下、より好ましくは０．４０％以上０．６０％以下である。Si: 0.10% or more and 1.00% or less Si is an important component in the present invention, and the rust grains of the entire rust layer are refined to form a dense rust layer, thereby improving the weather resistance of the steel material. Has an effect. Moreover, it has the effect of preventing cracks on the surface of the steel material during hot rolling. In order to acquire these effects, it is necessary to make it contain 0.10% or more. On the other hand, when it contains excessively exceeding 1.00%, toughness and weldability will deteriorate remarkably. Accordingly, the Si amount is set to a range of 0.10% to 1.00%. Preferably they are 0.15% or more and 0.70% or less, More preferably, they are 0.40% or more and 0.60% or less.

Ｍｎ：０．２０％以上２．００％以下
Ｍｎは、構造用鋼材の強度を向上させる元素であり、所定の強度を確保するためには０．２０％以上含有させる必要がある。一方、２．００％を超えて過剰に含有すると靭性および溶接性が劣化する。従って、Ｍｎ量は０．２０％以上２．００％以下の範囲とした。好ましくは０．４０％以上１．８％以下、より好ましくは０．６０％以上１．６５％以下である。Mn: 0.20% or more and 2.00% or less Mn is an element that improves the strength of the structural steel material, and in order to ensure a predetermined strength, it is necessary to contain 0.20% or more. On the other hand, when it contains excessively exceeding 2.00%, toughness and weldability will deteriorate. Accordingly, the amount of Mn is set in the range of 0.20% or more and 2.00% or less. Preferably they are 0.40% or more and 1.8% or less, More preferably, they are 0.60% or more and 1.65% or less.

Ｐ：０．００３％以上０．０３０％以下
Ｐは、構造用鋼材の耐候性を向上させる元素であり、この効果を得るためには０．００３％以上含有させる必要がある。一方、０．０３０％を超えて含有すると溶接性が劣化する。従って、Ｐ量は０．００３％以上０．０３０％以下とする。好ましくは０．０２０％以下である。P: 0.003% or more and 0.030% or less P is an element that improves the weather resistance of the structural steel material. In order to obtain this effect, it is necessary to contain 0.003% or more. On the other hand, if it exceeds 0.030%, weldability deteriorates. Therefore, the P content is 0.003% or more and 0.030% or less. Preferably it is 0.020% or less.

Ｓ：０．０００１％以上０．０２００％以下
Ｓは、０．０２００％を超えて含有すると溶接性および靭性が劣化する。一方、含有量を０．０００１％未満まで低下させると、生産コストが増大する。従って、Ｓ量は０．０００１％以上０．０２００％以下とした。S: 0.0001% to 0.0200% When S exceeds 0.0200%, weldability and toughness deteriorate. On the other hand, when the content is reduced to less than 0.0001%, the production cost increases. Therefore, the S content is set to 0.0001% or more and 0.0200% or less.

Ａｌ：０．００１％以上０．１００％以下
Ａｌは、製鋼時の脱酸に必要な元素であり、この効果を得るためはＡｌ量として０．００１％以上含有させる必要がある。一方、０．１００％を超えて含有すると溶接性に悪影響を及ぼす。従って、Ａｌ量は０．００１％以上０．１００％以下とする。好ましくは０．００５％以上０．０７％以下、より好ましくは０．０１０％以上０．０５％未満である。Al: 0.001% or more and 0.100% or less Al is an element necessary for deoxidation at the time of steelmaking. In order to obtain this effect, it is necessary to contain 0.001% or more as the amount of Al. On the other hand, if the content exceeds 0.100%, the weldability is adversely affected. Therefore, the Al amount is set to 0.001% or more and 0.100% or less. Preferably they are 0.005% or more and 0.07% or less, More preferably, they are 0.010% or more and less than 0.05%.

Ｃｕ：０．０１％以上１．００％以下
Ｃｕ、本発明において重要な成分であり、Ｎｉ，Ｃｏ，ＮｂおよびＳｎと共存させることにより、鋼材の耐候性を著しく向上させる効果を有する。Ｃｕは、さび層のさび粒を微細化することで緻密なさび層を形成し、腐食促進因子である塩化物イオンの地鉄への透過を抑制する効果を有する。この効果は、含有量が０．０１％以上で得られる。一方、含有量が１．００％を超えるとＣｕ消費量増加に伴うコスト上昇を招く。従って、Ｃｕ量は０．０１％以上１．００％以下の範囲とする。好ましくは０．０３％以上０．４５％以下、より好ましくは０．１０％以上０．３６％以下である。Cu: 0.01% or more and 1.00% or less Cu, which is an important component in the present invention, has the effect of remarkably improving the weather resistance of steel by coexisting with Ni, Co, Nb and Sn. Cu refines the rust grains of the rust layer to form a dense rust layer, and has an effect of suppressing transmission of chloride ions, which are corrosion promoting factors, to the ground iron. This effect is obtained when the content is 0.01% or more. On the other hand, if the content exceeds 1.00%, a cost increase associated with an increase in Cu consumption is caused. Therefore, the amount of Cu is made 0.01% or more and 1.00% or less. Preferably they are 0.03% or more and 0.45% or less, More preferably, they are 0.10% or more and 0.36% or less.

Ｎｉ：０．０１％以上０．６５％以下
Ｎｉは、本発明において重要な成分であり、Ｃｕ，Ｃｏ，ＮｂおよびＳｎと共存させることによって、鋼材の耐候性を著しく向上させる効果を有する。Ｎｉは、さび粒を微細化することで緻密なさび層を形成し、これにより鋼材の耐候性を向上させる効果を有する。この効果を十分に得るためには０．０１％以上含有させる必要がある。一方、０．６５％を超えて含有するとＮｉ消費量増加に伴うコスト上昇を招く。従って、Ｎｉ量は０．０１％以上０．６５％以下とする。好ましくは０．０３％以上０．５０％以下、より好ましくは０．２０％以上０．４０％以下である。Ni: 0.01% or more and 0.65% or less Ni is an important component in the present invention, and has the effect of remarkably improving the weather resistance of steel by coexisting with Cu, Co, Nb and Sn. Ni has an effect of forming a dense rust layer by refining rust grains, thereby improving the weather resistance of the steel material. In order to obtain this effect sufficiently, it is necessary to contain 0.01% or more. On the other hand, when it contains exceeding 0.65%, the cost rise accompanying Ni consumption increase will be caused. Therefore, the Ni content is set to 0.01% or more and 0.65% or less. Preferably they are 0.03% or more and 0.50% or less, More preferably, they are 0.20% or more and 0.40% or less.

Ｃｏ：０．００２％以上０．２２０％未満
Ｃｏは、本発明において重要な成分であり、Ｃｕ，Ｎｉ，ＮｂおよびＳｎと共存させることによって、鋼材の耐候性を著しく向上させる効果がある。Ｃｏは、さび層全体に分布し、さび粒を微細化することで緻密なさび層を形成し、これにより鋼材の耐候性を向上させる効果を有する。この効果を十分に得るためには、０．００２％以上含有させる必要がある。一方、０．２２０％以上含有するとＣｏ消費量増加に伴うコスト上昇を招く。従って、Ｃｏ量は０．００２％以上０．２２０％未満とする。好ましくは０．００３％以上０．１００％以下、より好ましくは０．０１０％以上０．０３０％以下である。Co: 0.002% or more and less than 0.220% Co is an important component in the present invention, and has the effect of remarkably improving the weather resistance of the steel material by coexisting with Cu, Ni, Nb and Sn. Co is distributed throughout the rust layer, and forms a fine rust layer by refining rust grains, thereby having an effect of improving the weather resistance of the steel material. In order to obtain this effect sufficiently, it is necessary to contain 0.002% or more. On the other hand, if the content is 0.220% or more, the cost increases with an increase in Co consumption. Therefore, the Co content is set to be 0.002% or more and less than 0.220%. Preferably they are 0.003% or more and 0.100% or less, More preferably, they are 0.010% or more and 0.030% or less.

Ｎｂ：０．００５％以上０．２００％以下
Ｎｂは、本発明において重要な成分であり、Ｃｕ，Ｎｉ，ＣｏおよびＳｎと共存させることにより、鋼材の耐候性を著しく向上させる効果がある。Ｎｂは、アノード部においてさび層と地鉄の界面付近に濃化し、アノード反応、カソード反応を抑制する。この効果を十分に得るためには、０．００５％以上含有させる必要がある。一方、０．２００％を超えて含有すると靭性の低下を招く。従って、Ｎｂ量は０．００５％以上０．２００％以下とする。好ましくは０．００８％以上０．１００％以下、より好ましくは０．０１０％以上０．０３０％以下である。Nb: 0.005% or more and 0.200% or less Nb is an important component in the present invention, and has the effect of remarkably improving the weather resistance of the steel by coexisting with Cu, Ni, Co and Sn. Nb is concentrated near the interface between the rust layer and the ground iron in the anode part to suppress the anode reaction and the cathode reaction. In order to obtain this effect sufficiently, it is necessary to contain 0.005% or more. On the other hand, if it exceeds 0.200%, toughness is reduced. Therefore, the Nb amount is set to be 0.005% or more and 0.200% or less. Preferably they are 0.008% or more and 0.100% or less, More preferably, they are 0.010% or more and 0.030% or less.

Ｓｎ：０．００５％以上０．２００％以下
Ｓｎは、本発明において重要な成分であり、Ｃｕ，Ｎｉ，ＣｏおよびＮｂと共存させることによって、鋼材の耐候性を著しく向上させる効果がある。Ｓｎは、鋼材表面にＳｎを含む酸化皮膜を形成し、鋼材のアノード反応、カソード反応を抑制することで鋼材の耐候性を向上させる。この効果を十分に得るためには、０．００５％以上含有させる必要がある。一方、０．２００％を超えて含有すると鋼の延性や靭性の劣化を招く。従って、Ｓｎ量は０．００５％以上０．２００％以下とする。好ましくは０．０１０％以上０．１００％以下、より好ましくは０．０２０％以上０．０５０％未満である。Sn: 0.005% or more and 0.200% or less Sn is an important component in the present invention, and has the effect of remarkably improving the weather resistance of the steel by coexisting with Cu, Ni, Co and Nb. Sn forms an oxide film containing Sn on the surface of the steel material, and improves the weather resistance of the steel material by suppressing the anode reaction and cathode reaction of the steel material. In order to obtain this effect sufficiently, it is necessary to contain 0.005% or more. On the other hand, if the content exceeds 0.200%, the ductility and toughness of the steel are deteriorated. Therefore, the Sn amount is set to 0.005% or more and 0.200% or less. Preferably they are 0.010% or more and 0.100% or less, More preferably, they are 0.020% or more and less than 0.050%.

残部はＦｅおよび不可避的不純物である。ここで、主な可避的不純物としてＮやＯが挙げられるが、それぞれＮ：０．０１００％以下、Ｏ：０．０１００％以下で許容できる。   The balance is Fe and inevitable impurities. Here, although N and O are mentioned as main unavoidable impurities, N is acceptable at 0.0100% or less and O: 0.0100% or less, respectively.

さらに、大気腐食環境下において十分な耐候性向上効果を得るためには、Ｃｕ，Ｎｉ，Ｃｏ，Ｎｂ，Ｓｎを次式（１）を満足する範囲で含有させることがより有利であり、この範囲で含有させることによって一層の耐候性向上効果を得ることができる。
この（１）式は大気環境下における耐候性の指標となるものであり、耐候性向上に有効なＣｕ、Ｎｉ、Ｃｏ、Ｎｂ、Ｓｎの含有量が多いほど、耐候性が向上し、０．０２より大きい値となることで目標の耐候性を得ることができる。好ましくは０．０５以上である。より好ましくは０．０８以上である。
また、各元素の添加量が増大すると、耐候性の向上効果は徐々に小さくなり、（１）式の値が２５．００を超えると耐候性の向上効果は飽和に達する。さらに、鋼材の溶接性や靱性の劣化、合金コストの増大を招く。したがって、（１）式の上限値は、２５．００が好ましい。より好ましくは、２２．００である。さらに好ましくは、１８．００である。
Ｌｏｇ（Ｃｕ×５００−１)×Ｌｏｇ（Ｎｉ×５００−１)×Ｌｏｇ（Ｃｏ×１０００−０．００１)×Ｌｏｇ（Ｎｂ×１０００−３)×Ｌｏｇ（Ｓｎ×１０００−３)＞０．０２・・・（１）Furthermore, in order to obtain a sufficient weather resistance improvement effect in an atmospheric corrosive environment, it is more advantageous to contain Cu, Ni, Co, Nb, and Sn in a range that satisfies the following formula (1). By further containing, it is possible to obtain a further effect of improving weather resistance.
This equation (1) serves as an indicator of weather resistance in an atmospheric environment, and as the content of Cu, Ni, Co, Nb, Sn effective for improving weather resistance increases, the weather resistance increases. The target weather resistance can be obtained when the value is larger than 02. Preferably it is 0.05 or more. More preferably, it is 0.08 or more.
Moreover, when the addition amount of each element increases, the effect of improving weather resistance gradually decreases, and when the value of formula (1) exceeds 25.00, the effect of improving weather resistance reaches saturation. Furthermore, the weldability and toughness of the steel material are deteriorated, and the alloy cost is increased. Therefore, the upper limit value of the formula (1) is preferably 25.00. More preferably, it is 22.00. More preferably, it is 18.00.
Log (Cu × 500-1) × Log (Ni × 500-1) × Log (Co × 1000-0.001) × Log (Nb × 1000-3) × Log (Sn × 1000-3)> 0.02 ... (1)

以上、必須成分について説明したが、本発明では、その他にも必要に応じて以下の元素を適宜含有させることができる。
Ｃｒ：０．０１％以上１．００％以下
Ｃｒは、さび粒を微細化することで緻密なさび層を形成し、耐侯性を向上させる元素である。この効果を得るためには、０．０１％以上含有させる必要がある。一方、Ｃｒを１．００％を超えて過剰に含有すると溶接性が低下する。従って、Ｃｒを含有させる場合、含有量は０．０１％以上１．００％以下とする。好ましくは０．０４％以上１．００％以下、より好ましくは０．１０％以上０．５０％以下である。As described above, the essential components have been described. However, in the present invention, the following elements can be appropriately contained as needed.
Cr: 0.01% or more and 1.00% or less Cr is an element that forms a dense rust layer by refining rust grains and improves weather resistance. In order to acquire this effect, it is necessary to make it contain 0.01% or more. On the other hand, when Cr is excessively contained exceeding 1.00%, weldability is deteriorated. Therefore, when Cr is contained, the content is set to 0.01% or more and 1.00% or less. Preferably they are 0.04% or more and 1.00% or less, More preferably, they are 0.10% or more and 0.50% or less.

Ｍｏ：０．００１％以上１．０００％以下
Ｍｏは、鋼材のアノード反応に伴ってＭｏＯ4 2-が溶出し、さび層中にＭｏＯ4 2-が分布することで、腐食促進因子の塩化物イオンがさび層を透過して地鉄に到達するのを防止する働きがある。また、鋼材表面にＭｏを含む化合物が沈殿することで、鋼材のアノード反応を抑制する作用もある。これらの効果を十分に得るためには、０．００１％以上の含有が必要である。一方、含有量が１．０００％を超えるとＭｏ消費量増加に伴うコスト上昇を招く。従って、Ｍｏを含有させる場合、Ｍｏ量は０．００１％以上１．０００％以下とする。好ましくは０．０１０％以上０．５００％以下、より好ましくは０．０５０％以上０．３００％以下である。Mo: 0.001% or more and 1.000% or less Mo is a corrosion-promoting factor chloride because MoO 4 2- is eluted with the anode reaction of steel and MoO 4 2- is distributed in the rust layer. It functions to prevent ions from passing through the rust layer and reaching the iron. Moreover, it has the effect | action which suppresses the anode reaction of steel materials because the compound containing Mo precipitates on the steel material surface. In order to obtain these effects sufficiently, a content of 0.001% or more is necessary. On the other hand, if the content exceeds 1.000%, a cost increase accompanying an increase in Mo consumption is caused. Therefore, when Mo is contained, the amount of Mo is set to 0.001% or more and 1.000% or less. Preferably they are 0.010% or more and 0.500% or less, More preferably, they are 0.050% or more and 0.300% or less.

Ｗ：０．００５％以上１．０００％以下
Ｗは、鋼材のアノード反応に伴ってＷＯ4 2-が溶出し、さび層中にＷＯ4 2-として分布することによって、腐食促進因子の塩化物イオンがさび層を透過して地鉄に到達するのを静電的に防止するはたきがある。また、鋼材表面にＷを含む化合物が沈殿することで、鋼材のアノード反応を抑制する作用もある。これらの効果を十分に得るためには、０．００５％以上の含有が必要である。一方、含有量が１．０００％を超えるとＷ消費量増加に伴うコスト上昇を招く。従って、Ｗを含有させる場合、Ｗ量は０．００５％以上１．０００％以下とする。好ましくは０．０１０％以上０．５００％以下、より好ましくは０．０３０％以上０．３００％以下である。W: 0.005% or more and 1.000% or less W is a corrosion-promoting factor chloride by elution of WO 4 2- with the anode reaction of the steel material and distribution as WO 4 2- in the rust layer. There is a firearm that electrostatically prevents ions from passing through the rust layer and reaching the base iron. Moreover, it has the effect | action which suppresses the anode reaction of steel materials because the compound containing W precipitates on the steel material surface. In order to obtain these effects sufficiently, a content of 0.005% or more is necessary. On the other hand, if the content exceeds 1.000%, a cost increase accompanying an increase in W consumption will be caused. Therefore, when W is contained, the W amount is set to 0.005% or more and 1.000% or less. Preferably they are 0.010% or more and 0.500% or less, More preferably, they are 0.030% or more and 0.300% or less.

Ｓｂ：０．００５％以上０．２００％以下
Ｓｂは、鋼材のアノード反応を抑制すると共に、カソード反応である水素発生反応を抑制することで鋼材の耐候性を向上させる元素である。このような効果を十分に得るためには、０．００５％以上含有させる必要がある。一方、０．２００％を超えてＳｂを過剰に含有すると靭性の劣化を招く。従って、Ｓｂを含有させる場合、Ｓｂ量は０．００５％以上０．２００％以下とする。好ましくは０．０１０％以上０．１００％以下、より好ましくは０．０２０％以上０．０５０％以下である。Sb: 0.005% or more and 0.200% or less Sb is an element that suppresses the anode reaction of the steel material and suppresses the hydrogen generation reaction that is the cathode reaction, thereby improving the weather resistance of the steel material. In order to sufficiently obtain such effects, it is necessary to contain 0.005% or more. On the other hand, when Sb is contained excessively exceeding 0.200%, toughness is deteriorated. Therefore, when Sb is contained, the amount of Sb is set to 0.005% or more and 0.200% or less. Preferably they are 0.010% or more and 0.100% or less, More preferably, they are 0.020% or more and 0.050% or less.

Ｔｉ：０．００５％以上０．２００％以下
Ｔｉは、強度を高める上で有用な元素である。この効果を十分に得るためには、０．００５％以上含有させる必要がある。一方、含有量が０．２００％を超えると靭性の劣化を招く。従って、Ｔｉを含有させる場合、Ｔｉ量は０．００５％以上０．２００％以下とする。好ましくは０．０１０％以上０．１０％以下、より好ましくは０．０２０％以上０．０５０％以下である。Ti: 0.005% or more and 0.200% or less Ti is an element useful for increasing the strength. In order to obtain this effect sufficiently, it is necessary to contain 0.005% or more. On the other hand, if the content exceeds 0.200%, the toughness is deteriorated. Therefore, when Ti is contained, the Ti amount is set to 0.005% or more and 0.200% or less. Preferably they are 0.010% or more and 0.10% or less, More preferably, they are 0.020% or more and 0.050% or less.

Ｖ：０．００５％以上０．２００％以下
Ｖは、強度を高める上で有用な元素である。この効果を十分に得るためには、０．００５％以上含有させる必要がある。一方、含有量が０．２００％を超えると効果が飽和する。従って、Ｖを含有させる場合、Ｖ量は０．００５％以上０．２００％以下とする。好ましくは０．０１０％以上０．１５％以下、より好ましくは０．０３０％以上０．１００％以下である。V: 0.005% or more and 0.200% or less V is an element useful for increasing the strength. In order to obtain this effect sufficiently, it is necessary to contain 0.005% or more. On the other hand, when the content exceeds 0.200%, the effect is saturated. Therefore, when V is contained, the amount of V is set to 0.005% or more and 0.200% or less. Preferably they are 0.010% or more and 0.15% or less, More preferably, they are 0.030% or more and 0.100% or less.

Ｚｒ：０．００５％以上０．２００％以下
Ｚｒは、強度を高める上で有用な元素である。この効果を十分に得るためには、０．００５％以上含有させる必要がある。一方、含有量が０．２００％を超えると効果が飽和する。従って、Ｚｒを含有させる場合、Ｚｒ量は０．００５％以上０．２００％以下とする。好ましくは０．０１０％以上０．１０％以下、より好ましくは０．０２０％以上０．０５０％以下である。Zr: 0.005% or more and 0.200% or less Zr is an element useful for increasing the strength. In order to obtain this effect sufficiently, it is necessary to contain 0.005% or more. On the other hand, when the content exceeds 0.200%, the effect is saturated. Therefore, when Zr is contained, the amount of Zr is set to 0.005% or more and 0.200% or less. Preferably they are 0.010% or more and 0.10% or less, More preferably, they are 0.020% or more and 0.050% or less.

Ｂ：０．０００１％以上０．００５０％以下
Ｂは、強度を高める上で有用な元素である。この効果を十分に得るためには、０．０００１％以上含有させる必要がある。一方、含有量が０．００５０％を超えると靭性の劣化を招く。従って、Ｂを含有させる場合、Ｂ量は０．０００１％以上０．００５０％以下とする。好ましくは、０．０００５％以上０．００４０％以下、より好ましくは、０．００１０％以上０．００２５％以下である。B: 0.0001% or more and 0.0050% or less B is an element useful for increasing the strength. In order to obtain this effect sufficiently, it is necessary to contain 0.0001% or more. On the other hand, if the content exceeds 0.0050%, the toughness is deteriorated. Therefore, when B is contained, the B content is set to 0.0001% or more and 0.0050% or less. Preferably, it is 0.0005% or more and 0.0040% or less, and more preferably 0.0010% or more and 0.0025% or less.

ＲＥＭ：０．０００１％以上０．０１００％以下
ＲＥＭは、さび層全体に分布し、さび粒を微細化することで緻密なさび層を形成し、鋼材の耐候性を向上させる効果を有する。この効果を十分に得るためには、０．０００１％以上含有させる必要があるが、０．０１００％を超えるとその効果は飽和する。従って、ＲＥＭを含有させる場合、ＲＥＭ量は０．０００１％以上０．０１００％以下とする。REM: 0.0001% or more and 0.0100% or less REM is distributed over the entire rust layer, and has an effect of forming a dense rust layer by refining rust grains and improving the weather resistance of the steel material. In order to obtain this effect sufficiently, it is necessary to contain 0.0001% or more, but when it exceeds 0.0100%, the effect is saturated. Therefore, when REM is contained, the REM content is 0.0001% or more and 0.0100% or less.

Ｃａ：０．０００１％以上０．０１００％以下
Ｃａは、鋼中のＳを固定して溶接熱影響部の靭性向上に有効な元素である。この効果を十分に得るためには０．０００１％以上含有させる必要がある。一方、含有量が０．０１００％を超えると鋼中の介在物の量が増加し、かえって靭性の劣化を招く。従って、Ｃａを含有させる場合、Ｃａ量は０．０００１％以上０．０１００％以下とする。Ca: 0.0001% or more and 0.0100% or less Ca is an element effective for fixing S in steel and improving the toughness of the weld heat affected zone. In order to obtain this effect sufficiently, it is necessary to contain 0.0001% or more. On the other hand, if the content exceeds 0.0100%, the amount of inclusions in the steel increases, which leads to deterioration of toughness. Therefore, when Ca is contained, the Ca content is set to 0.0001% or more and 0.0100% or less.

Ｍｇ：０．０００１％以上０．０１００％以下
Ｍｇは、鋼中のＳを固定して溶接熱影響部の靭性向上に有効な元素である。この効果を十分に得るためには０．０００１％以上含有させる必要がある。一方、含有量が０．０１００％を超えると鋼中の介在物の量が増加し、かえって靭性の劣化を招く。従って、Ｍｇを含有させる場合、Ｍｇ量は０．０００１％以上０．０１００％以下とする。Mg: 0.0001% or more and 0.0100% or less Mg is an element effective for fixing S in steel and improving the toughness of the weld heat affected zone. In order to obtain this effect sufficiently, it is necessary to contain 0.0001% or more. On the other hand, if the content exceeds 0.0100%, the amount of inclusions in the steel increases, which leads to deterioration of toughness. Therefore, when Mg is contained, the Mg amount is set to 0.0001% or more and 0.0100% or less.

本発明の耐候性に優れた構造用鋼材は、上記の成分組成に調製した溶鋼を、通常の連続鋳造や分塊法によってスラブとし、ついで得られたスラブを熱間圧延によって厚板や形鋼、薄鋼板、棒鋼等の鋼材とすることにより得られる。
熱間圧延における加熱条件や圧延条件は、要求される材質に応じて適宜決定すればよく、また制御圧延、加速冷却、あるいは再加熱熱処理等の組合せも可能である。
なお、各元素の含有量は、スパーク放電発光分光分析法、蛍光Ｘ線分析法、ＩＣＰ発光分光分析法およびＩＣＰ質量分析法、燃焼法等により求めることができる。The structural steel material having excellent weather resistance according to the present invention is a molten steel prepared in the above component composition, made into a slab by a normal continuous casting or a block method, and then the obtained slab is subjected to hot rolling to a thick plate or a shape steel. It is obtained by using steel materials such as thin steel plates and steel bars.
The heating conditions and rolling conditions in the hot rolling may be appropriately determined according to the required material, and a combination of controlled rolling, accelerated cooling, reheating heat treatment, or the like is also possible.
The content of each element can be determined by spark discharge emission spectrometry, fluorescent X-ray analysis, ICP emission spectroscopy, ICP mass spectrometry, combustion method, and the like.

表１に示す成分組成の鋼を溶製し、１１５０℃に加熱した後、熱間圧延し、ついで室温まで空冷して、厚さ１２ｍｍの鋼板を作製した。ついで、得られた鋼板から５０ｍｍ×５０ｍｍ×４ｍｍの試験片を採取した。試験片は、表面を表面粗さＲａが１．６μｍ以下となるよう研削加工し、端面、裏面をテープシールし、表面露出部の面積が４０ｍｍ×４０ｍｍとなるよう表面もテープシールした。
以上により得られた試験片について、乾湿繰り返し腐食試験を行い、耐候性を評価した。Steels having the composition shown in Table 1 were melted and heated to 1150 ° C., then hot-rolled, and then air-cooled to room temperature to produce a 12 mm thick steel plate. Subsequently, a test piece of 50 mm × 50 mm × 4 mm was collected from the obtained steel plate. The test piece was ground so that the surface roughness Ra was 1.6 μm or less, the end surface and the back surface were tape-sealed, and the surface was also tape-sealed so that the area of the exposed surface portion was 40 mm × 40 mm.
The test pieces obtained as described above were subjected to repeated wet and dry corrosion tests to evaluate the weather resistance.

腐食試験の条件は以下のとおりである。
温度６０℃、相対湿度３５％ＲＨの乾燥工程を３時間、その後、移行時間を１時間とった後、温度を４０℃、相対湿度を９５％ＲＨの湿潤工程を３時間として、その後１時間移行時間をとり、合計８時間で１サイクルとした。前記工程を８サイクル繰り返したのち、８時間の乾燥工程を実施した。さらに、前記工程を１１サイクル繰り返したのち、８時間の乾燥工程を実施した。また、８時間乾燥工程中に試験片表面に付着する塩分量が０．３０ｍｄｄとなるよう調整した人工海水溶液を試験片表面に噴霧した。この条件にて、１２週間で８４サイクルの試験を行った。The conditions of the corrosion test are as follows.
The drying process at a temperature of 60 ° C. and a relative humidity of 35% RH was performed for 3 hours, and then the transition time was set to 1 hour. Time was taken to make one cycle for a total of 8 hours. After repeating the said process 8 cycles, the drying process for 8 hours was implemented. Furthermore, after repeating the said process 11 cycles, the drying process for 8 hours was implemented. Moreover, the artificial seawater solution adjusted so that the amount of salt adhering to the test piece surface might be 0.30 mdd during the drying process for 8 hours was sprayed on the test piece surface. Under these conditions, 84 cycles of tests were conducted in 12 weeks.

上記の腐食試験終了後、試験片を塩酸にヘキサメチレンテトラミンを加えた水溶液に浸漬して脱錆してから重量を測定し、得られた重量と初期重量との差を求め、テープシール部を除く試験片の表面積と鉄の密度から、片面の平均板厚減少量を求め、腐食量とした。
表１−１および表１−２に腐食量（平均板厚減少量）について調べた結果および式（１）の値を併記する。なお、この腐食量（平均板厚減少量）が１５μｍ以下であれば、耐侯性が優れているといえる。After the above corrosion test is completed, the test piece is immersed in an aqueous solution of hexamethylenetetramine in hydrochloric acid and derusted, and then the weight is measured. The difference between the obtained weight and the initial weight is obtained, and the tape seal portion is removed. From the surface area of the test piece to be removed and the density of iron, the average reduction in thickness on one side was determined and used as the amount of corrosion.
In Table 1-1 and Table 1-2, the results of the investigation of the corrosion amount (average thickness reduction amount) and the value of the formula (1) are shown. In addition, if this corrosion amount (average thickness reduction amount) is 15 μm or less, it can be said that the weather resistance is excellent.

Figure 0006432607
Figure 0006432607

Figure 0006432607
Figure 0006432607

表１−１および表１−２から明らかなように、本発明の成分組成を満足する発明例はいずれも腐食量が１５μｍ以下であり、優れた耐侯性を有することが分かる。
これに対し、本発明でとくに重要とするＣｕ，Ｎｉ，Ｃｏ，ＮｂおよびＳｎの５元素のうち、一元素でも本発明の適正範囲を外れた比較例は、いずれも腐食量が１５μｍを超え、十分な耐侯性を得ることはできなかった。As is clear from Table 1-1 and Table 1-2, it can be seen that all of the inventive examples satisfying the component composition of the present invention have a corrosion amount of 15 μm or less and have excellent weather resistance.
In contrast, among the five elements of Cu, Ni, Co, Nb and Sn, which are particularly important in the present invention, any one of the comparative examples outside the proper range of the present invention has a corrosion amount exceeding 15 μm. Sufficient weather resistance could not be obtained.

Claims (6)

質量％で、
Ｃ：０．０２０％以上０．２００％未満、
Ｓｉ：０．１０％以上１．００％以下、
Ｍｎ：０．２０％以上２．００％以下、
Ｐ：０．００３％以上０．０３０％以下、
Ｓ：０．０００１％以上０．０２００％以下および
Ａｌ：０．００１％以上０．１００％以下
を含み、かつ
Ｃｕ：０．０１％以上１．００％以下、
Ｎｉ：０．０１％以上０．６５％以下
Ｃｏ：０．００２％以上０．２２０％未満、
Ｎｂ：０．００５％以上０．２００％以下および
Ｓｎ：０．００５％以上０．２００％以下
を含有し、残部はＦｅおよび不可避的不純物からなる耐候性に優れた構造用鋼材。 % By mass
C: 0.020% or more and less than 0.200%,
Si: 0.10% or more and 1.00% or less,
Mn: 0.20% or more and 2.00% or less,
P: 0.003% or more and 0.030% or less,
S: 0.0001% or more and 0.0200% or less and Al: 0.001% or more and 0.100% or less, and Cu: 0.01% or more and 1.00% or less,
Ni: 0.01% or more and 0.65% or less Co: 0.002% or more and less than 0.220%,
Nb: 0.005% or more and 0.200% or less and Sn: 0.005% or more and 0.200% or less, and the balance is a structural steel material having excellent weather resistance composed of Fe and inevitable impurities. Ｃｕ，Ｎｉ，Ｃｏ，ＮｂおよびＳｎ量が、次式（１）を満足する請求項１に記載の耐候性に優れた構造用鋼材。
Ｌｏｇ（Ｃｕ×５００−１)×Ｌｏｇ（Ｎｉ×５００−１)×Ｌｏｇ（Ｃｏ×１０００−０．００１)×Ｌｏｇ（Ｎｂ×１０００−３)×Ｌｏｇ（Ｓｎ×１０００−３)＞０．０２・・・（１） The structural steel material excellent in weather resistance according to claim 1, wherein the amounts of Cu, Ni, Co, Nb and Sn satisfy the following formula (1).
Log (Cu × 500-1) × Log (Ni × 500-1) × Log (Co × 1000-0.001) × Log (Nb × 1000-3) × Log (Sn × 1000-3)> 0.02 ... (1) さらに、質量％で、
Ｃｒ：０．０１％以上１．００％以下
を含有する請求項１または２に記載の耐候性に優れた構造用鋼材。 Furthermore, in mass%,
The structural steel material excellent in weather resistance according to claim 1 or 2, containing Cr: 0.01% or more and 1.00% or less. さらに、質量％で、
Ｓｂ：０．００５％以上０．２００％以下
を含有する請求項１〜３のいずれかに記載の耐候性に優れた構造用鋼材。 Furthermore, in mass% ,
S b: 0.200% or less under less than 0.005%
The structural steel material excellent in the weather resistance in any one of Claims 1-3 containing. さらに、質量％で、
Ｖ：０．００５％以上０．２００％以下、
Ｚｒ：０．００５％以上０．２００％以下および
Ｂ：０．０００１％以上０．００５０％以下
のうちから選ばれる一種以上を含有する請求項１〜４のいずれかに記載の耐候性に優れた構造用鋼材。 Furthermore, in mass%,
V: 0.005% or more and 0.200% or less,
Zr: 0.005% or more and 0.200% or less and B: one or more selected from 0.0001% or more and 0.0050% or less are excellent in weather resistance according to any one of claims 1 to 4. Structural steel. さらに、質量％で、
ＲＥＭ：０．０００１％以上０．０１００％以下および
Ｃａ：０．０００１％以上０．０１００％以下のうちから選ばれる一種以上を含有する請求項１〜５のいずれかに記載の耐候性に優れた構造用鋼材。
Furthermore, in mass%,
REM: 0.0001% or more 0.0100% or less and Ca: weather resistance according to claim 1 containing an inner shell least one selected 0.0100% or less than 0.0001% Excellent structural steel.
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