JP4677714B2 - Steel materials for bridges with excellent beach weather resistance and structures using the same - Google Patents
Steel materials for bridges with excellent beach weather resistance and structures using the same Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims description 85
- 239000010959 steel Substances 0.000 title claims description 85
- 239000000463 material Substances 0.000 title claims description 58
- 238000005260 corrosion Methods 0.000 claims description 51
- 229910052759 nickel Inorganic materials 0.000 claims description 12
- 229910052718 tin Inorganic materials 0.000 claims description 11
- 229910052804 chromium Inorganic materials 0.000 claims description 10
- 229910052802 copper Inorganic materials 0.000 claims description 10
- 229910052787 antimony Inorganic materials 0.000 claims description 8
- 229910052750 molybdenum Inorganic materials 0.000 claims description 7
- 229910052721 tungsten Inorganic materials 0.000 claims description 6
- 229910052791 calcium Inorganic materials 0.000 claims description 5
- 229910052749 magnesium Inorganic materials 0.000 claims description 5
- 229910052758 niobium Inorganic materials 0.000 claims description 5
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- 239000012535 impurity Substances 0.000 claims description 3
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- 229910052717 sulfur Inorganic materials 0.000 claims description 3
- 229910052799 carbon Inorganic materials 0.000 claims description 2
- 229910052748 manganese Inorganic materials 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims 1
- 230000007797 corrosion Effects 0.000 description 49
- 150000003839 salts Chemical class 0.000 description 46
- 230000000694 effects Effects 0.000 description 36
- 239000011651 chromium Substances 0.000 description 25
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 24
- 238000006243 chemical reaction Methods 0.000 description 21
- 238000012360 testing method Methods 0.000 description 21
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 20
- 229920006395 saturated elastomer Polymers 0.000 description 11
- 238000004090 dissolution Methods 0.000 description 10
- 238000002844 melting Methods 0.000 description 7
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- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 5
- 229910000870 Weathering steel Inorganic materials 0.000 description 5
- 229910045601 alloy Inorganic materials 0.000 description 5
- 239000000956 alloy Substances 0.000 description 5
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- 239000011248 coating agent Substances 0.000 description 4
- 238000010276 construction Methods 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
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- 230000001681 protective effect Effects 0.000 description 4
- 238000006722 reduction reaction Methods 0.000 description 4
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- 238000001035 drying Methods 0.000 description 3
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- 238000006460 hydrolysis reaction Methods 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 239000007800 oxidant agent Substances 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- 238000010422 painting Methods 0.000 description 3
- 238000005507 spraying Methods 0.000 description 3
- 229910006540 α-FeOOH Inorganic materials 0.000 description 3
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- 239000004593 Epoxy Substances 0.000 description 2
- 241000221535 Pucciniales Species 0.000 description 2
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- XNGIFLGASWRNHJ-UHFFFAOYSA-N phthalic acid Chemical compound OC(=O)C1=CC=CC=C1C(O)=O XNGIFLGASWRNHJ-UHFFFAOYSA-N 0.000 description 2
- 238000011160 research Methods 0.000 description 2
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910003153 β-FeOOH Inorganic materials 0.000 description 2
- CBECDWUDYQOTSW-UHFFFAOYSA-N 2-ethylbut-3-enal Chemical compound CCC(C=C)C=O CBECDWUDYQOTSW-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- JOYRKODLDBILNP-UHFFFAOYSA-N Ethyl urethane Chemical compound CCOC(N)=O JOYRKODLDBILNP-UHFFFAOYSA-N 0.000 description 1
- 229910002588 FeOOH Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- 229910007570 Zn-Al Inorganic materials 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000011088 calibration curve Methods 0.000 description 1
- -1 chromium carbides Chemical class 0.000 description 1
- GVEHJMMRQRRJPM-UHFFFAOYSA-N chromium(2+);methanidylidynechromium Chemical compound [Cr+2].[Cr]#[C-].[Cr]#[C-] GVEHJMMRQRRJPM-UHFFFAOYSA-N 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
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- JTHNLKXLWOXOQK-UHFFFAOYSA-N n-propyl vinyl ketone Natural products CCCC(=O)C=C JTHNLKXLWOXOQK-UHFFFAOYSA-N 0.000 description 1
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- 230000001737 promoting effect Effects 0.000 description 1
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- 239000005413 snowmelt Substances 0.000 description 1
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- 229910006299 γ-FeOOH Inorganic materials 0.000 description 1
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- Heat Treatment Of Steel (AREA)
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Description
本発明は、海浜地域や融雪塩が散布される地域等で飛来塩分量が多い環境下でもミニマムメンテナンス材料として使用することができる耐候性に優れた橋梁用鋼材（以下、単に「海浜耐候性に優れた鋼材」という）に関するものである。
The present invention is a steel material for bridges with excellent weather resistance that can be used as a minimum maintenance material even in an environment where the amount of incoming salt is high, such as in a beach area or an area where snow melting salt is sprayed (hereinafter simply referred to as “sea beach weather resistance”). Excellent steel materials).
通常、耐候性鋼材を大気腐食環境中に暴露すると、その表面に保護性のあるさび層が形成され、それ以降に鋼材表面に発生する腐食が抑制される。そのため、耐候性鋼材は、塗装せずに裸のまま使用できるミニマムメンテナンス鋼材として橋梁等の構造物に用いられている。 Usually, when a weather-resistant steel material is exposed to an atmospheric corrosive environment, a protective rust layer is formed on the surface, and thereafter, corrosion that occurs on the steel material surface is suppressed. For this reason, weathering steel is used for structures such as bridges as a minimum maintenance steel that can be used as it is without being painted.
ところが、海浜地域や、内陸部でも融雪塩が散布される地域等で飛来塩分量が多い地域では、鋼材表面に保護性のあるさび層が形成されず、腐食を抑制する効果はみられない。そのため、海浜部では、塗装なしで裸のままの耐候性鋼材を用いることができず、普通鋼に塗装を施して使用する普通鋼の塗装使用が一般的である。しかし、このような塗装使用の場合には、腐食による塗膜劣化のため約１０年毎に再塗装する必要があり、そのため維持管理に要する費用は莫大なものとなる。 However, in areas where the amount of incoming salt is high, such as in the coastal area or inland where snow melting salt is sprayed, a protective rust layer is not formed on the surface of the steel material, and the effect of suppressing corrosion is not observed. For this reason, it is not possible to use a bare weatherproof steel material without painting at the beach, and it is common to use plain steel that is coated with plain steel. However, in the case of such coating use, it is necessary to repaint every 10 years because of the deterioration of the coating film due to corrosion, and therefore the cost required for maintenance becomes enormous.
近年、日本工業規格（ＪＩＳ）で規格化された耐候性鋼（JIS G 3114 ：溶接構造用耐候性熱間圧延鋼材）は、飛来塩分量がＮａＣｌとして０．０５ｍｇ／ｄｍ2／ｄａｙ（０．０５ｍｄｄ）以上の地域、すなわち海浜地域では、ウロコ状錆や層状錆等の発生により腐食減量が大きいため、無塗装では使用できないことになっている（建設省土木研究所、（社）鋼材倶楽部、（社）日本橋梁建設協会：耐候性鋼の橋梁への適用に関する共同研究報告書（ＸＸ）−無塗耐候性橋梁の設計・施工要領（改訂版−1993.3））。 In recent years, weather resistant steel (JIS G 3114: weather resistant hot rolled steel for welded structures) standardized by Japanese Industrial Standards (JIS) has an incoming salt content of 0.05 mg / dm 2 / day (0. 05mdd) and above, that is, the beach area, the loss of corrosion is large due to the occurrence of scale-like rust, layered rust, etc., so it can not be used without painting (Ministry of Construction, Public Works Research Institute, Steel Club) Japan Bridge Construction Association: Joint Research Report on the Application of Weatherproof Steel to Bridges (XX)-Design and Construction Guidelines for Uncoated Weatherproof Bridges (Revised Version-1993.3)).
このため、海浜地域などの塩分の多い環境下では、普通鋼材に塗装を行って対処しているが、河口付近の海浜地域や融雪塩を撒く山間部等の道路に建設される橋梁は腐食が著しく、再塗装せざるを得ないのが現状である。これらの再塗装には多大な工数がかかることから、無塗装で使用できる鋼材への要望が強い。 For this reason, ordinary steel materials are coated in a salty environment such as in the coastal area, but the bridge constructed in the coastal area near the estuary and roads such as mountainous areas where snowmelt salt is eroded is corroded. At present, it is extremely difficult to repaint. Since these repainting takes a lot of man-hours, there is a strong demand for steel materials that can be used without painting.
鋼材の腐食は、飛来塩分量が多くなるにしたがって激しくなるため、耐食性と経済性の観点からは、飛来塩分量に応じた耐候性鋼材が必要になる。また、橋梁といっても、使用される場所や部位により鋼材の腐食環境は同じではない。例えば、桁外部では、降雨、結露水および日照に曝される。一方、桁内部では、結露水に曝されるが雨掛かりはない。一般に、飛来塩分量が多い環境では、桁外部より桁内部の方が腐食が激しいと言われている。 Since corrosion of steel materials increases as the amount of flying salt increases, weathering steel according to the amount of flying salt is required from the viewpoint of corrosion resistance and economy. Moreover, even if it is called a bridge, the corrosive environment of steel materials is not the same by the place and site | part used. For example, outside the girders, they are exposed to rainfall, condensed water and sunlight. On the other hand, inside the girder, it is exposed to condensed water, but there is no rain. In general, in an environment where the amount of incoming salt is large, it is said that the inside of the girders is more corrosive than the outside of the girders.
また、融雪塩を道路に撒く環境では、その塩が走行中の車に巻き上げられ、道路を支える鉄骨に付着し、厳しい腐食環境となる。また海岸から少し離れた軒下等でも厳しい塩害環境に晒され、このような地域では飛来塩分量が１ｍｄｄ以上の厳しい腐食環境になる。 In addition, in an environment where snow melting salt is sprinkled on the road, the salt is wound up on a running car and adheres to the steel frame that supports the road, creating a severe corrosive environment. Moreover, even under the eaves a little away from the coast, it is exposed to a severe salt damage environment, and in such an area, the amount of incoming salt becomes a severe corrosive environment of 1 mdd or more.
このような問題に対応するため、飛来塩分量が多い環境での腐食を防止する鋼材の開発が従来から進められており、特許文献１ではクロム（Ｃｒ）の含有量を増加させた耐候性鋼材、さらに特許文献２ではニッケル（Ｎｉ）含有量を増加させた耐候性鋼材等が提案されている。 In order to cope with such problems, the development of steel materials that prevent corrosion in an environment with a large amount of incoming salt has been developed, and in Patent Document 1, the weathering steel material with an increased chromium (Cr) content is proposed. Further, Patent Document 2 proposes a weather-resistant steel material having an increased nickel (Ni) content.
しかしながら、Ｃｒは、ある程度以下の飛来塩分量の領域においては耐候性を改善することができるものの、それを超える厳しい塩分環境においては逆に耐候性を劣化させる。 However, although Cr can improve the weather resistance in a region where the amount of incoming salt is below a certain level, Cr deteriorates the weather resistance in a severe salt environment exceeding that.
一方、Ｎｉ含有量を増加させた場合、耐候性はある程度改善されるが、鋼材自体のコストが高くなり、橋梁等の用途に使用される材料としては高価なものになる。これを避けるため、Ｎｉ含有量を少なくすると、耐候性はさほど改善されず、飛来塩分量が多い場合には、鋼材の表面に層状の剥離さびが生成し、長期間の使用に耐えられないという問題が生じる。 On the other hand, when the Ni content is increased, the weather resistance is improved to some extent, but the cost of the steel material itself becomes high, and the material used for applications such as bridges becomes expensive. In order to avoid this, if the Ni content is reduced, the weather resistance is not improved so much, and if the amount of incoming salt is large, layered peeling rust is generated on the surface of the steel material, and it cannot be used for a long period of time. Problems arise.
本発明者らは、先に特許文献３でＣｕ、ＮｉおよびＣｒを複合して含有させた海浜耐候性を有する鋼材を提案している。しかし、これらの元素を数％程度含有させるだけでは、ＪＩＳ耐候性鋼に比べて耐候性を改善することができるが、飛来塩分量が１ｍｄｄを超えるような非常に厳しい環境では十分な耐候性を発揮することができず、さらに改善が必要になる。 The inventors of the present invention have previously proposed a steel material having beach weather resistance in which Cu, Ni, and Cr are combined and contained in Patent Document 3. However, it is possible to improve the weather resistance as compared with JIS weather resistant steel only by adding about several percent of these elements, but sufficient weather resistance in a very severe environment where the amount of incoming salt exceeds 1 mdd. It cannot be demonstrated and further improvements are needed.
また、特許文献４にはＰ、Ｎｉ、Ｍｏ、ＳｂおよびＳｎ等を含有する溶接構造用鋼、特許文献５にはＣｕ、ＮｉおよびＳｂを含有させた高耐候性鋼材が提案されている。前者の溶接構造用鋼については、飛来塩分量の多い環境における耐候性を得るためにＰの含有量を多くしているため、溶接性が十分でないという問題がある。後者の高耐候性鋼材は、飛来塩分量０．８ｍｄｄの環境において耐候性が良好であるとしているが、１ｍｄｄを超えるような厳しい腐食環境においては耐候性が十分でないという問題がある。 Patent Document 4 proposes a welded structural steel containing P, Ni, Mo, Sb, Sn and the like, and Patent Document 5 proposes a highly weather-resistant steel material containing Cu, Ni and Sb. The former steel for welded structure has a problem that weldability is not sufficient because the P content is increased in order to obtain weather resistance in an environment with a large amount of incoming salt. The latter high weathering steel material is said to have good weather resistance in an environment with an incoming salt content of 0.8 mdd, but there is a problem that the weather resistance is not sufficient in a severe corrosive environment exceeding 1 mdd.
さらに、特許文献６にはＣｕ、Ｎｉ、Ｃｒ、ＳｎおよびＳｂ等を含有することにより耐食性を向上させた耐酸露点腐食鋼が提案されており、煙突や熱交換器等における酸露点腐食に対し優れた耐食性を発揮している。しかしながら、飛来塩分量が１ｍｄｄを超えるような大気腐食環境において、耐候性は十分でないという問題がある。 Furthermore, Patent Document 6 proposes an acid dew-point corrosion steel having improved corrosion resistance by containing Cu, Ni, Cr, Sn, Sb, etc., and is excellent against acid dew point corrosion in a chimney or a heat exchanger. Exhibits high corrosion resistance. However, there is a problem that the weather resistance is not sufficient in an atmospheric corrosive environment in which the amount of incoming salt exceeds 1 mdd.
本発明は、従来の耐候性鋼等が内包する問題に鑑みてなされたものであり、海浜地域や融雪塩が散布される地域等で飛来塩分量が多い環境下でも、優れた耐候性を発揮することができる鋼材およびこれを用いた構造物を提供することを目的としている。 The present invention has been made in view of the problems inherent in conventional weathering steel and the like, and exhibits excellent weather resistance even in an environment where the amount of flying salt is large in a beach area or an area where snow melting salt is dispersed. It aims at providing the steel material which can be performed, and a structure using the same.
本発明者らは、上記の課題を解決するため、Ｃｒ、ＣｕおよびＮｉの耐候性に及ぼす影響に着目し、Ｃｒ、ＣｕおよびＮｉの含有量を変化させた材料を用いて耐候性試験を行った。これは、本発明者らの一人が既に報告しているように（「材料と環境」第４３巻（1994）第１号２６頁）、さび層が保護性を有するのは、Ｆｅの一部がＣｒで置換された微細なα−（Ｆｅ1-XＣｒX）ＯＯＨからなるさび層の生成によるものであること、およびＣｕやＮｉを含有させることにより海浜地域での耐候性を向上できることを知見したことによる。上記の耐候性試験の結果、次の（ａ）、（ｂ）のことが判明した。
（ａ）Ｃｒは、飛来塩分量が比較的少ない環境では耐候性を向上させるが、飛来塩分量が多い環境では逆に耐候性を劣化させる。
（ｂ）ＣｕおよびＮｉは、飛来塩分量が多い環境においても耐候性改善に効果がある。
In order to solve the above-mentioned problems, the present inventors focused on the effect of Cr, Cu and Ni on the weather resistance, and conducted a weather resistance test using materials in which the content of Cr, Cu and Ni was changed. It was. This is because, as already reported by one of the present inventors ("Materials and Environment", Vol. 43 (1994), No. 1, p. 26), the rust layer has a protective part of Fe. Is due to the formation of a rust layer composed of fine α- (Fe 1-X Cr X ) OOH substituted with Cr, and the weather resistance in the beach area can be improved by containing Cu and Ni According to findings. As a result of the weather resistance test, the following (a) and (b) were found.
(A) Cr improves the weather resistance in an environment with a relatively small amount of flying salt, but conversely deteriorates the weather resistance in an environment with a large amount of flying salt.
(B) Cu and Ni are effective in improving weather resistance even in an environment where the amount of incoming salt is large.
上記の知見に基づいて、さらに検討を重ねた結果、飛来塩分量の多い環境ではＦｅＣｌ3溶液の乾湿繰り返しが本質的条件となり、Ｆｅ3+の加水分解によりｐＨが低下した状態で、かつＦｅ3+が酸化剤として作用し腐食を加速することを見出した。このときの腐食反応は、
カソード反応：Ｆｅ3+ ＋ ｅ → Ｆｅ2+ （Ｆｅ3+の還元反応）
アノード反応：Ｆｅ → Ｆｅ2+ ＋ ２ｅ （Ｆｅの溶解反応）
となり、総括反応としては、
２Ｆｅ3+ ＋ Ｆｅ → ３Ｆｅ2+ ・・・ 反応１
となる。
As a result of further studies based on the above findings, in an environment with a large amount of incoming salt, repeated drying and wetting of the FeCl 3 solution is an essential condition, and in a state where the pH is lowered by the hydrolysis of Fe 3+ , and Fe 3 We have found that + acts as an oxidant and accelerates corrosion. The corrosion reaction at this time is
Cathode reaction: Fe 3+ + e → Fe 2+ (Fe 3+ reduction reaction)
Anode reaction: Fe → Fe 2+ + 2e (Fe dissolution reaction)
As a summary reaction,
2Fe 3+ + Fe → 3Fe 2+ ... Reaction 1
It becomes.
上記反応１により生成したＦｅ2+は、空気酸化によりＦｅ3+に酸化され、生成したＦｅ3+は再び酸化剤として腐食を加速する。この際、Ｆｅ2+の空気酸化の反応速度は低ｐＨ環境では一般に遅いが、濃厚塩化物溶液中では加速され、Ｆｅ3+が生成され易くなる。このようなサイクリックな反応のため、飛来塩分量が非常に多い環境では鋼の耐食性が著しく劣化することが判明した。 The Fe 2+ produced by the reaction 1 is oxidized to Fe 3+ by air oxidation, and the produced Fe 3+ again accelerates corrosion as an oxidant. At this time, the reaction rate of air oxidation of Fe 2+ is generally slow in a low pH environment, but is accelerated in a concentrated chloride solution, and Fe 3+ is easily generated. Due to such a cyclic reaction, it has been found that the corrosion resistance of steel is significantly deteriorated in an environment where the amount of incoming salt is very large.
また、飛来塩分量が非常に多い環境ではさび層の保護性は期待できず、鋼自身のアノード溶解反応を遅くするのが有効である。すなわち、飛来塩分量が非常に多い環境では、Ｃｒを含有する鋼はアノード溶解反応が促進されるため、耐候性が劣化するのに対し、Ｎｉ等を含有する鋼はアノード溶解反応を遅延させるので耐候性が向上する。 In addition, in an environment where the amount of flying salt is very large, the protection of the rust layer cannot be expected, and it is effective to slow the anodic dissolution reaction of the steel itself. That is, in an environment where the amount of flying salt is very large, steel containing Cr accelerates the anodic dissolution reaction, so that weather resistance deteriorates, whereas steel containing Ni or the like delays the anodic dissolution reaction. Weather resistance is improved.
上述の塩分環境における腐食のメカニズムを基に、種々の合金元素の耐候性への影響について検討した結果、さらに下記（ｃ）〜（ｉ）の知見を得た。
（ｃ）ＳｎはＳｎ2+として溶解し、２Ｆｅ3+＋Ｓｎ2+→２Ｆｅ2+＋Ｓｎ4+なる反応により、Ｆｅ3+の濃度を低下させることにより反応１を抑制する。さらに、Ｓｎにはアノード溶解を抑制する作用もある。
（ｄ）Ｓｂは、Ｎｉ等と同様、鋼のアノード溶解反応を抑制するのに有効である。
（ｅ）飛来塩分量の多い環境において、単独添加では耐候性を劣化させるＣｒをＳｎやＳｂと複合して含有させることにより、Ｃｒは耐候性を向上させる効果を発揮する。
（ｆ）Ａｌを含有させると海浜耐候性が向上する。
（ｇ）Ｎはアンモニアとして溶解し、腐食界面のｐＨを上昇させる作用を有する。飛来塩分量の多い環境において上記Ｆｅ3+の加水分解によりｐＨが低下するが、Ｎを含有させることにより、腐食界面のｐＨ低下を抑制し海浜耐候性が向上する。
（ｈ）上記（ｃ）〜（ｇ）の材料に、さらにＴｉ、Ｎｂ、Ｍｏ、Ｗ、Ｖ、ＣａおよびＭｇ
よりなる群から選ばれた１種または２種以上を含有させても、海浜耐候性の改善に効果がある。
（ｉ）上記（ｃ）〜（ｈ）の材料に、さらに、ＲＥＭを含有させると鋼材の溶接性が改善される。
As a result of examining the influence of various alloy elements on the weather resistance based on the mechanism of corrosion in the above-mentioned salinity environment, the following findings (c) to (i) were obtained.
(C) Sn is dissolved as Sn 2+, by 2Fe 3+ + Sn 2+ → 2Fe 2+ + Sn 4+ comprising reaction, suppressing a reaction 1 by reducing the concentration of Fe 3+. Furthermore, Sn also has an action of suppressing anodic dissolution.
(D) Sb is effective in suppressing the anodic dissolution reaction of steel, like Ni and the like.
(E) In an environment where the amount of incoming salt is large, Cr alone has an effect of improving weather resistance by containing Cr in combination with Sn or Sb, which degrades weather resistance when added alone.
(F) When Al is contained, the beach weather resistance is improved.
(G) N dissolves as ammonia and has the effect of raising the pH of the corrosion interface. Although the pH decreases due to the hydrolysis of Fe 3+ in an environment with a large amount of flying salt, the inclusion of N suppresses the pH decrease at the corrosion interface and improves the beach weather resistance.
(H) In addition to the materials (c) to (g), Ti, Nb, Mo, W, V, Ca and Mg
Even if one or more selected from the group consisting of these are contained, there is an effect in improving beach weather resistance.
(I) When REM is further added to the materials (c) to (h), the weldability of the steel material is improved.
本発明は、このような知見に基づいて完成されたものであり、下記の（１）〜（５）の海浜耐候性に優れた鋼材、および（６）の構造物を要旨としている。
（１）質量％で、Ｃ：０．００１〜０．１５％、Ｓｉ：２．５％以下、Ｍｎ：５．０％以下、Ｐ：０．０３％以下、Ｓ：０．００５％以下、Ｃｕ：０．０５〜１．０％、Ｎｉ：０．１〜９．０％、Ｃｒ：０．５〜３．０％（ただし、０．５％を除く）、Ａｌ：０．００３〜２．５％、Ｎ：０．００１〜０．１％およびＳｎ：０．０３〜０．５０％を含有し、残部がＦｅおよび不純物からなることを特徴とする海浜耐候性に優れた鋼材である。
（２）上記（１）の海浜耐候性に優れた鋼材は、さらに、質量％で、Ｓｂ：０．０３〜０．５０％を含有させるのが望ましい。
（３）上記（１）または（２）の海浜耐候性に優れた鋼材は、さらに、質量％で、Ｔｉ：０．０１〜０．３％、Ｎｂ：０．０１〜０．１％、Ｍｏ：０．０１〜１．０％、Ｗ：０．０１〜１．０％、Ｖ：０．０１〜１．０％、Ｃａ：０．０００１〜０．１％およびＭｇ：０．０００１〜０．１％よりなる群から選ばれた１種または２種以上を含有させるのが望ましい。
（４）上記（１）〜（３）のいずれかの海浜耐候性に優れた鋼材は、さらに、質量％で、ＲＥＭを０．０００１％〜０．０２％含有させるのが望ましい。
（５）上記（１）〜（４）のいずれかに記載の鋼材の表面が防食皮膜で覆われるようにするのが望ましい。
（６）上記（１）〜（５）のいずれかに記載の鋼材を用いた構造物である。
The present invention has been completed on the basis of such findings, and the gist of the steel materials having excellent beach weather resistance (1) to ( 5 ) below and the structure ( 6 ) below.
(1) In mass%, C: 0.001 to 0.15%, Si: 2.5% or less, Mn: 5.0% or less, P: 0.03% or less, S: 0.005% or less, Cu: 0.05 to 1.0%, Ni: 0.1 to 9.0 %, Cr: 0.5 to 3.0% (excluding 0.5%) , Al: 0.003 to 2 .5% , N: 0.001 to 0.1% and Sn: 0.03 to 0.50% , and the balance is made of Fe and impurities, and is a steel material with excellent beach weather resistance. .
(2) The steel material excellent in beach weather resistance of (1) is further preferably contained in mass% and containing Sb: 0.03 to 0.50%.
( 3 ) The steel material excellent in beach weather resistance of the above (1) or (2) is further in mass%, Ti: 0.01 to 0.3 %, Nb: 0.01 to 0.1%, Mo : 0.01-1.0%, W: 0.01-1.0%, V: 0.01-1.0%, Ca: 0.0001-0.1% and Mg: 0.0001-0 It is desirable to contain one or more selected from the group consisting of 1%.
( 4 ) The steel material excellent in beach weather resistance of any one of the above (1) to ( 3 ) is further preferably contained in an amount of 0.0001% to 0.02% by mass of REM.
( 5 ) It is desirable that the surface of the steel material according to any one of (1) to ( 4 ) is covered with an anticorrosion film.
( 6 ) A structure using the steel material according to any one of (1) to ( 5 ) above.
本発明の鋼材は、飛来塩分量が多い環境下において十分な耐候性を有しており、海浜耐候性に優れた材料として最適であり、これにより、海浜地域や融雪塩が散布される地域における橋梁等の構造物に使用するミニマムメンテナンス材料として適用することができる。 The steel material of the present invention has sufficient weather resistance in an environment with a large amount of incoming salt, and is optimal as a material with excellent beach weather resistance. It can be applied as a minimum maintenance material used for structures such as bridges.
以下に、本発明の鋼材に含まれる合金元素の作用効果を、その含有量を上記のように限定した理由とあわせて説明する。以下の説明において、合金元素の含有量「％」は、いずれも「質量％」を意味する。 Below, the effect of the alloy element contained in the steel material of this invention is demonstrated with the reason which limited the content as mentioned above. In the following description, the alloy element content “%” means “mass%”.
Ｃ：０．００１〜０．１５％
Ｃは、鋼の強度を確保するために必要な合金元素であるが、多量に含有させると鋼材の溶接性が劣化する。したがって、Ｃ含有量は０．１５％を上限とする。また、０．００１％未満になると所定の強度が確保できないので、下限は０．００１％とする。なお、望ましい範囲は、０．００５％〜０．１５％である。
C: 0.001 to 0.15%
C is an alloying element necessary for ensuring the strength of steel, but if contained in a large amount, the weldability of the steel material deteriorates. Therefore, the upper limit of the C content is 0.15%. Moreover, since predetermined intensity | strength cannot be ensured if it becomes less than 0.001%, a minimum is made into 0.001%. A desirable range is 0.005% to 0.15%.
Ｓｉ：２．５％以下
Ｓｉは、製鋼時の脱酸に必要な合金元素であるとともに、耐候性を向上させる元素である。２．５％を超えて含有させると、鋼の靱性が損なわれる。したがって、その含有量は２．５％以下とする。下限は特に定めないが、含有量が少なすぎると脱酸が十分に行われないので、Ａｌを含有しない場合には、０．１％以上含有させるのが望ましい。
Si: 2.5% or less Si is an alloy element necessary for deoxidation at the time of steelmaking, and is an element that improves weather resistance. If the content exceeds 2.5%, the toughness of the steel is impaired. Therefore, the content is 2.5% or less. The lower limit is not particularly defined, but if the content is too small, deoxidation is not sufficiently performed. Therefore, when Al is not contained, it is desirable to contain 0.1% or more.
Ｍｎ：５．０％以下
Ｍｎは、低コストで鋼の強度を高める作用効果を有する元素であるが、Ｓと結合してＭｎＳを形成し、このＭｎＳが腐食の起点となり、耐食性、ひいては耐候性を劣化させる。鋼中Ｓ量が低い場合には、高飛来塩分環境における耐候性を向上させる作用を有するが、５．０％を超えると強度が高くなりすぎる。したがって、その含有量は５．０％以下とする。なお、海浜耐候性を向上させる効果を顕著に発揮させるためには、０．５％以上含有させるのが望ましい。
Mn: 5.0% or less Mn is an element having an effect of increasing the strength of steel at a low cost. However, it combines with S to form MnS, and this MnS becomes a starting point of corrosion, resulting in corrosion resistance and thus weather resistance. Deteriorate. When the amount of S in steel is low, it has the effect of improving the weather resistance in a high-flying salinity environment, but when it exceeds 5.0%, the strength becomes too high. Therefore, the content is 5.0% or less. In addition, in order to show the effect which improves a beach weather resistance notably, it is desirable to make it contain 0.5% or more.
Ｐ：０．０３％以下
Ｐは、耐候性を著しく向上させる元素である。しかし、過度に含有させると溶接性を劣化させる。したがって、その含有量は０．０３％以下とする。下限は特に定めないが、耐候性向上効果を発揮させるために、０．００５％以上含有させるのが望ましい。
P: 0.03% or less P is an element that significantly improves weather resistance. However, if it is excessively contained, the weldability is deteriorated. Therefore, the content is 0.03% or less. Although the lower limit is not particularly defined, it is desirable to contain 0.005% or more in order to exhibit the effect of improving weather resistance.
Ｓ：０．００５％以下
Ｓは、Ｍｎと結合して非金属介在物のＭｎＳを形成して腐食の起点となり易く、耐候性を劣化させるので、できるだけ少なくする必要がある。したがって、その上限は０．００５％とする。
S: 0.005% or less S is bonded to Mn to form MnS of non-metallic inclusions, which tends to be a starting point of corrosion and deteriorates weather resistance. Therefore, S needs to be reduced as much as possible. Therefore, the upper limit is made 0.005%.
Ｃｕ：０．０５〜１．０％
Ｃｕは、耐候性を向上させる基本元素であり、０．０５％以上含有させると耐候性が向上する。しかし、１．０％を超えて含有させても、その効果が飽和するだけでなく、脆化を起こす原因となる。したがって、その含有量は０．０５〜１．０％とする。
Cu: 0.05 to 1.0%
Cu is a basic element that improves the weather resistance, and when 0.05% or more is contained, the weather resistance is improved. However, even if the content exceeds 1.0%, the effect is not only saturated, but also causes embrittlement. Therefore, the content is made 0.05 to 1.0%.
Ｎｉ：０．１〜９．０％
Ｎｉを含有するＸ線的非晶質さびまたはα−ＦｅＯＯＨは、微細で、さび層の緻密性を向上させることにより物質の透過を抑制する性質を有しているので、飛来塩分量の多い環境で使用される鋼材の合金元素として有効な元素である。また、Ｎｉを含有することにより、鋼のアノード溶解が抑制され耐候性を向上させる効果もある。これらの効果は、０．１％以上含有させることにより得られるが、９．０％を超えると鋼材のコストが上昇する。したがって、その含有量は０．１〜９．０％とする。
Ni: 0.1-9.0%
X-ray amorphous rust or α-FeOOH containing Ni is fine and has the property of suppressing the permeation of substances by improving the denseness of the rust layer. It is an effective element as an alloying element of steel materials used in the above. In addition, the inclusion of Ni also has the effect of suppressing the anodic dissolution of steel and improving the weather resistance. These effects can be obtained by adding 0.1% or more, but if it exceeds 9.0%, the cost of the steel material increases. Therefore, the content is made 0.1 to 9.0%.
ここで、Ｘ線的非晶質さびとはＸ線回折によりピークを与えず、結晶として捉えられないさび成分を言う。通常の大気腐食環境中で生成するさびのうち、Ｘ線回折により検知可能なものはα−ＦｅＯＯＨ、β−ＦｅＯＯＨ、γ−ＦｅＯＯＨおよびＦｅ3Ｏ4であり、これらを結晶性さびとし、それ以外をＸ線的非晶質さびと称する。 Here, the X-ray amorphous rust refers to a rust component which does not give a peak by X-ray diffraction and cannot be grasped as a crystal. Of the rust generated in a normal atmospheric corrosive environment, those detectable by X-ray diffraction are α-FeOOH, β-FeOOH, γ-FeOOH, and Fe 3 O 4 , which are crystalline rusts, and others Is called X-ray amorphous rust.
Ｘ線的非晶質さびの有無は、例えば、下記のＸ線定量分析にて判断できる。すなわち、測定装置として理学電機（株）製ＲＵ２００型を用い、測定条件をターゲット：Ｃｏ、電圧−電流：３０ｋＶ−１００ｍＡ、および走査速度：２°／ｍｉｎとして、さび試料にＺｎＯ粉末をさびに対し２０％の割合で混合しＸ線回折を実施し、得られたＸ線回折パターンを予め人工さびを用いて作成した検量線で解析して、さび中のα−ＦｅＯＯＨ、β−ＦｅＯＯＨ、γ−ＦｅＯＯＨおよびＦｅ3Ｏ4の割合を定量し、これらの結晶性さびの合計を引いたものをＸ線的非晶質さびとする。 The presence or absence of X-ray amorphous rust can be determined by, for example, the following X-ray quantitative analysis. That is, RU200 type manufactured by Rigaku Corporation is used as a measuring device, the measurement conditions are target: Co, voltage-current: 30 kV-100 mA, and scanning speed: 2 ° / min. X-ray diffraction was performed by mixing at a ratio of 20%, and the obtained X-ray diffraction pattern was analyzed with a calibration curve prepared in advance using artificial rust, and α-FeOOH, β-FeOOH, γ- The proportion of FeOOH and Fe 3 O 4 is quantified, and the sum of these crystalline rusts is taken as the X-ray amorphous rust.
Ｃｒ：０．５〜３．０％（ただし、０．５％を除く）
Ｃｒは、飛来塩分量がそれほど多くない環境において保護性さびによる耐食性の向上が期待できるが、飛来塩分量が多い環境において鋼のアノード溶解反応を促進し耐候性を劣化させる。
Cr: 0.5 to 3.0% (excluding 0.5%)
Cr can be expected to improve the corrosion resistance due to protective rust in an environment where the amount of incoming salt is not so high, but it promotes the anodic dissolution reaction of steel in an environment where the amount of incoming salt is high and deteriorates the weather resistance.
ところが、後述するように、ＳｎやＳｂを含有する場合には、飛来塩分量が多い環境においてもＣｒ含有による耐候性の向上効果が発揮される。この効果は含有量０．５％以上（ただし、０．５％を除く）で発揮されるが、３．０％を超えると局部腐食感受性が高まるとともに溶接性が劣化する。したがって、Ｃｒ含有量は０．５〜３．０％（ただし、０．５％を除く）とする。 However, as will be described later, when Sn or Sb is contained, the effect of improving the weather resistance due to the Cr content is exhibited even in an environment with a large amount of incoming salt. This effect is exhibited when the content is 0.5 % or more (excluding 0.5%) , but if it exceeds 3.0%, the local corrosion sensitivity increases and the weldability deteriorates. Therefore, the Cr content is 0.5 to 3.0% (excluding 0.5%) .
Ａｌ：０．００３〜２．５％
Ａｌは、０．００３％以上含有させると耐候性が向上するが、含有量が２．５％を超えるとその効果は飽和する。したがって、Ａｌ含有量は０．００３〜２．５％とする。なお、多量に添加すると鋼が脆化し易くなるので、含有量の上限は２．０％とするのが望ましい。
Al: 0.003-2.5%
When Al is contained in an amount of 0.003% or more, the weather resistance is improved. However, when the content exceeds 2.5%, the effect is saturated. Therefore, the Al content is set to 0.003 to 2.5%. In addition, since it will become easy to embrittle steel when it adds abundantly, it is desirable that the upper limit of content is 2.0%.
Ｎ：０．００１〜０．１％
Ｎは、アンモニアとなって溶解し、飛来塩分量の多い環境におけるＦｅ3+の加水分解によるｐＨ低下を抑制することで、塩分環境における耐候性を向上させる効果を有する。この効果は０．００１％以上含有することにより得られ、０．１％を超えると飽和する。したがって、Ｎ含有量は０．００１〜０．１％とする。
N: 0.001 to 0.1%
N dissolves as ammonia and has the effect of improving the weather resistance in a salt environment by suppressing the pH drop due to the hydrolysis of Fe 3+ in an environment with a large amount of incoming salt. This effect is obtained by containing 0.001% or more, and when it exceeds 0.1%, it is saturated. Therefore, the N content is 0.001 to 0.1%.
ＳｎおよびＳｂ：０．０３〜０．５０％
Ｓｎは、Ｓｎ2+となって溶解し、酸性塩化物溶液中でのインヒビター作用により腐食を抑制する作用を有する。また、Ｆｅ3+を速やかに還元させ、酸化剤としてのＦｅ3+濃度を低減することにより、Ｆｅ3+の腐食促進作用を抑制するので、高飛来塩分環境における耐候性を向上させる。
Sn and S b: 0.03~0.50%
Sn dissolves as Sn 2+ and has an action of inhibiting corrosion by an inhibitor action in an acidic chloride solution. In addition, since Fe 3+ is rapidly reduced and the concentration of Fe 3+ as an oxidant is reduced, the corrosion promoting action of Fe 3+ is suppressed, thereby improving the weather resistance in a high-flying salinity environment.
また、Ｓｎには鋼のアノード溶解反応を抑制し耐食性を向上させる作用もある。さらに、Ｓｎを含有することにより、飛来塩分が多い環境においてもＣｒの耐候性を向上させる効果が発揮される。 Sn also has the effect of suppressing the anodic dissolution reaction of steel and improving the corrosion resistance. Furthermore, by containing Sn, the effect of improving the weather resistance of Cr is exhibited even in an environment with a large amount of incoming salt.
Ｓｎを添加することによる作用は０．０３％以上の含有で顕著になり、０．５％を超えると脆化を起こす原因となる。したがって、その含有量は０．０３％〜０．５％とする。なお、含有量の望ましい範囲は０．０３〜０．２％である。
Action due to added pressure to Sn becomes remarkable when the content is 0.03% or more, causing problems related to embrittlement exceeds 0.5%. Therefore, the content is 0.03% to 0.5%. In addition, the desirable range of content is 0.03 to 0.2%.
一方、Ｓｂは、鋼のアノード溶解反応を抑制するとともに、水素ガス発生反応やＦｅ3+の還元反応を抑制するので、高飛来塩分環境における耐候性を向上させる。さらに、Ｓｂを含有することにより、飛来塩分が多い環境においてもＣｒの耐候性を向上させる効果が発揮される。 On the other hand, Sb suppresses the anodic dissolution reaction of steel and suppresses the hydrogen gas generation reaction and the reduction reaction of Fe 3+ , thereby improving the weather resistance in a high flying salinity environment. Furthermore, by containing Sb, the effect of improving the weather resistance of Cr is exhibited even in an environment with a large amount of incoming salt.
Ｓｂを添加することによる作用は０．０３％以上の含有で顕著になり、０．５％を超えると靭性が著しく劣化する。したがって、その含有量は０．０３〜０．５％とする。 Action due to added pressure to the Sb becomes remarkable when the content is more than 0.03%, the toughness is remarkably deteriorated when it exceeds 0.5%. Therefore, the content is 0.03 to 0.5%.
ＳｎおよびＳｂを複合添加する場合には、その合計値が０．０３％未満の場合には、高飛来塩分環境における耐候性を向上させる作用が顕著に現れず、また、０．５０％を超えると鋼の靭性が劣化する。このため、ＳｎおよびＳｂの含有量の合計値は０．０３〜０．５％とする。
In the case where Sn and Sb are added in combination, if the total value is less than 0.03%, the effect of improving the weather resistance in a high-flying salinity environment does not appear remarkably, and exceeds 0.50%. And the toughness of steel deteriorates. For this reason, the total value of the contents of Sn and Sb is set to 0.03 to 0.5%.
本発明の鋼材は、上記の合金元素の他に、さらにＴｉ、Ｎｂ、Ｍｏ、Ｗ、Ｖ、ＣａおよびＭｇよりなる群から選ばれた１種または２種以上を含有してもよい。これらの元素の含有量を前記のように限定した理由は、次の通りである。 The steel material of the present invention may further contain one or more selected from the group consisting of Ti, Nb, Mo, W, V, Ca and Mg in addition to the above alloy elements. The reason why the contents of these elements are limited as described above is as follows.
Ｔｉ：０．０１〜０．３％
Ｔｉは、ＴｉＣを形成してＣを固定し、クロム炭化物の形成を抑制して耐候性を向上させるとともに、ＴｉＳの形成により腐食の起点となるＭｎＳの形成を抑える。この効果は含有量が０．０１％以上で現れ、０．３％を超えると、効果が飽和するだけでなく、鋼材のコストが上昇する。したがって、Ｔｉを含有させる場合、その含有量は０．０１〜０．３％とする。
Ti: 0.01 to 0.3%
Ti forms TiC to fix C, suppresses the formation of chromium carbide and improves the weather resistance, and suppresses the formation of MnS as a starting point of corrosion due to the formation of TiS. This effect appears when the content is 0.01% or more, and if it exceeds 0.3%, the effect is not only saturated, but the cost of the steel material increases. Therefore, when Ti is contained, the content is set to 0.01 to 0.3 % .
Ｎｂ：０．０１〜０．１％
Ｎｂには、Ｔｉと同様、ＮｂＣを形成してクロム炭化物の形成を抑制して耐候性を向上させる効果がある。この効果は含有量が０．０１％以上で現れ、０．１％を超えると飽和する。このため、Ｎｂを含有させる場合、その含有量は、０．０１〜０．１％以下とする。
Nb: 0.01 to 0.1%
Nb, like Ti, has the effect of improving weatherability by forming NbC and suppressing the formation of chromium carbides. This effect appears when the content is 0.01% or more, and is saturated when the content exceeds 0.1%. For this reason, when it contains Nb, the content shall be 0.01 to 0.1% or less.
Ｍｏ：０．０１〜１．０％
Ｍｏは、溶解して酸素酸イオンＭｏＯ4 2-の形でさびに吸着し、さび層中の塩化物イオンの透過を抑制し、耐食性を向上させる元素である。鋼中における含有量が０．０１％以上になるとこの効果が得られるが、１．０％を超えると効果が飽和するだけでなく、鋼材のコストが上昇する。したがって、Ｍｏを含有させる場合、その含有量は０．０１〜１．０％とする。
Mo: 0.01 to 1.0%
Mo is an element that dissolves and adsorbs to rust in the form of oxyacid ions MoO 4 2− , suppresses permeation of chloride ions in the rust layer, and improves corrosion resistance. This effect is obtained when the content in the steel is 0.01% or more. However, when the content exceeds 1.0%, the effect is not only saturated, but the cost of the steel material is increased. Therefore, when Mo is contained, the content is set to 0.01 to 1.0%.
Ｗ：０．０１〜１．０％
Ｗは、Ｍｏと同様、溶解して酸素酸イオンの形で存在し、さび層中の塩化物イオンの透過を抑制し、耐食性を向上させる。この効果は含有量が０．０１％以上で現れ、１．０％を超えると飽和するだけでなく、鋼材のコストが上昇する。したがって、Ｗを含有させる場合、その含有量は０．０１〜１．０％とする。
W: 0.01 to 1.0%
W, like Mo, dissolves and exists in the form of oxygenate ions, suppresses permeation of chloride ions in the rust layer, and improves corrosion resistance. This effect appears when the content is 0.01% or more, and when it exceeds 1.0%, not only is the content saturated, but the cost of the steel material increases. Therefore, when it contains W, the content shall be 0.01-1.0%.
Ｖ：０．０１〜１．０％
Ｖは、ＭｏやＷと同様、溶解して酸素酸イオンの形で存在し、さび層中の塩化物イオンの透過を抑制し、耐食性を向上させる。この効果は０．０１％以上含有させると現れ、１．０％を超えると飽和する。したがって、Ｖを含有させる場合、その含有量は０．０１〜１．０％とする。
V: 0.01 to 1.0%
V, like Mo and W, dissolves and exists in the form of oxyacid ions, suppresses permeation of chloride ions in the rust layer, and improves corrosion resistance. This effect appears when the content is 0.01% or more, and is saturated when the content exceeds 1.0%. Therefore, when V is contained, the content is set to 0.01 to 1.0%.
Ｃａ：０．０００１〜０．１％
Ｃａは、鋼中に酸化物の形で存在し、腐食反応部における界面のｐＨの低下を抑制して、腐食の促進を抑える作用を有している。この効果は０．０００１％以上含有させることにより得られるが、０．１％を超えると飽和する。したがって、Ｃａを含有させる場合、その含有量は０．０００１〜０．１％以下とする。
Ca: 0.0001 to 0.1%
Ca exists in the form of an oxide in steel, and has an effect of suppressing the promotion of corrosion by suppressing the decrease in pH at the interface in the corrosion reaction part. This effect can be obtained by adding 0.0001% or more, but when it exceeds 0.1%, it is saturated. Therefore, when Ca is contained, its content is set to 0.0001 to 0.1% or less.
Ｍｇ：０．０００１〜０．１％
Ｍｇは、Ｃａと同様、腐食反応部における界面のｐＨの低下を抑制し、耐食性を向上させる。この効果は０．０００１％以上含有させることにより得られるが、０．１％を超えると飽和する。したがって、Ｍｇを含有させる場合、その含有量は０．０００１〜０．１％とする。
Mg: 0.0001 to 0.1%
Mg, like Ca, suppresses the decrease in pH at the interface in the corrosion reaction part and improves the corrosion resistance. This effect can be obtained by adding 0.0001% or more, but when it exceeds 0.1%, it is saturated. Therefore, when it contains Mg, the content shall be 0.0001 to 0.1%.
ＲＥＭ：０．０００１〜０．０２％
ＲＥＭは、鋼の溶接性を向上させる目的で含有させる。含有量が０．０００１％以上でその効果を発揮し、０．０２％を超えると効果が飽和する。このため、ＲＥＭを含有させる場合には、その含有量は０．０００１〜０．０２％とする。
REM: 0.0001 to 0.02%
REM is contained for the purpose of improving the weldability of steel. When the content is 0.0001% or more, the effect is exhibited, and when it exceeds 0.02%, the effect is saturated. For this reason, when it contains REM, the content shall be 0.0001 to 0.02%.
本発明の鋼材は、上記の必須元素および任意元素を含有し、残部がＦｅおよび不純物からなる鋼材である。なお、鋼中にオキサイド等の介在物が微細分散されている鋼も本発明の鋼材に含まれる。 The steel material of the present invention is a steel material containing the above essential elements and optional elements, with the balance being Fe and impurities. Note that steel in which inclusions such as oxide are finely dispersed in the steel is also included in the steel material of the present invention.
本発明の鋼材は、さらに耐候性および耐食性を確保するため、その表面を防食皮膜で覆うのが望ましい。ここで規定する防食皮膜とは、さび安定化処理膜、Ｚｎめっき、Ａｌめっき、Ｚｎ−Ａｌめっき等のめっき、Ｚｎ溶射、Ａｌ溶射等の金属溶射皮膜、ビニルブチラール系、エポキシ系、ウレタン系、フタル酸系などの一般の防食塗装等、鋼材の防食目的で施される皮膜を意味する。いずれの防食皮膜を施した場合であっても、優れた耐候性を有し高い防食性能を発揮することができる。 In order to further ensure the weather resistance and corrosion resistance of the steel material of the present invention, it is desirable to cover the surface with an anticorrosion film. The anticorrosion film specified here is a rust stabilization treatment film, Zn plating, Al plating, plating such as Zn-Al plating, metal spraying film such as Zn spraying, Al spraying, vinyl butyral, epoxy, urethane, It means a coating applied for the purpose of corrosion protection of steel, such as general anti-corrosion coatings such as phthalic acid. Even if any anticorrosion film is applied, it has excellent weather resistance and can exhibit high anticorrosion performance.
上述の通り、本発明の鋼材は、飛来塩分量が多い環境下において優れた海浜耐候性を発揮するので、海浜地域や融雪塩が散布される地域における橋梁等の構造物に、塗装を必要としないミニマムメンテナンス材料として使用することができる。 As described above, the steel material of the present invention exhibits excellent beach weather resistance in an environment with a large amount of incoming salt, so it is necessary to paint structures such as bridges in the beach area and areas where snow melting salt is sprayed. Can not be used as minimum maintenance material.
（実施例１）
表１に示した化学組成を有するＮｏ．１〜Ｎｏ．２１の鋼について、１５０Ｋｇ真空溶解炉で溶製し、インゴットを鍛造した後、加熱、圧延を行い、厚さ４ｍｍ×幅１５０ｍｍ×長さ１０００ｍｍの寸法に加工して、次いで表裏面を機械研削し、厚さ３ｍｍ×幅６０ｍｍ×長さ１００ｍｍの試験片を切り出した。なお、本実施例では、酸素の含有量は０．０００１〜０．００５％の範囲であった。
Example 1
No. having the chemical composition shown in Table 1. 1-No. 21 steel was melted in a 150 kg vacuum melting furnace, ingots were forged, heated and rolled, processed to a size of 4 mm thickness x 150 mm width x 1000 mm length, and then the front and back surfaces were mechanically ground. A test piece having a thickness of 3 mm, a width of 60 mm, and a length of 100 mm was cut out. In this example, the oxygen content was in the range of 0.0001 to 0.005%.
得られた試験片で人工海水による乾湿繰り返し試験を行い、耐食性を評価した。具体的には、３５℃の人工海水（ASTM-D-1141-52 に準拠）を用いて、０．５時間の浸漬および２．５時間の乾燥を１サイクルとし、８００サイクルの試験での腐食減量を評価した。本試験は、飛来塩分量が１ｍｄｄを超えるような厳しい腐食環境を模擬する試験であった。 The obtained test piece was subjected to repeated wet and dry tests with artificial seawater to evaluate the corrosion resistance. Specifically, using artificial seawater at 35 ° C (according to ASTM-D-1141-52), 0.5 cycle immersion and 2.5 hour drying is one cycle, and corrosion in an 800 cycle test. Weight loss was evaluated. This test was a test that simulated a severe corrosive environment in which the amount of incoming salt exceeded 1 mdd.
試験終了後、各試験片の表面のさび層を除去し、板厚減少量を測定した。試験結果を表１に示す。同表における「腐食減量」は、試験片の平均の板厚減少量であり、試験前後の重量減少と試験片の表面積を用いて算出したものである。ここで、「腐食減量」の値は、比較例（Ｎｏ．１９）の「腐食減量」を１００とし、それとの比較で表したものである。 After the test was completed, the rust layer on the surface of each test piece was removed, and the thickness reduction amount was measured. The test results are shown in Table 1. “Corrosion weight loss” in the table is an average reduction in the thickness of the test piece, and is calculated using the weight reduction before and after the test and the surface area of the test piece. Here, the value of “corrosion weight loss” is expressed by comparison with “corrosion weight loss” of Comparative Example (No. 19) as 100.
表１の結果から明らかなように、比較例（Ｎｏ．１７）はＣｒ含有量が少ないため、比較例（Ｎｏ．１８、Ｎｏ．２１）はＳｎの含有量が少ないため、さらに、比較例（Ｎｏ．１９、Ｎｏ．２０）はＣｒおよびＳｎの含有量が少ないため、腐食量が大きくなった。 As apparent from the results in Table 1, because there is less Comparative Example (No.17) the Cr content, Comparative Example (No.18, No.21) has a small content of S n, further comparative examples (No. 19, No. 20) had a large amount of corrosion due to a small content of Cr and Sn.
本発明例では、いずれも本発明で規定する成分含有量を満足しているので、腐食減量は５４以下と小さくなっている。特に、Ｍｎ量が４．０２％と多い鋼（Ｎｏ．６）、Ｎｂ、Ｔｉ、Ｖ、Ｍｏ、Ｗ、ＣａまたはＭｇを含有する鋼（Ｎｏ．７〜Ｎｏ．１４）は、耐食性が向上している。上記の元素に加えてさらにＲＥＭを含有する鋼（Ｎｏ．１５）は、耐食性に加えて溶接性も向上することを確認した。また、Ｓｉ量およびＡｌ量が多い鋼（Ｎｏ．１６）は、一段と耐食性が向上することがわかる。
（実施例２）
次に、本発明例Ｎｏ．１と比較例Ｎｏ．１９とについて、上記実施例１と同様の方法で採取した試験片の表面にタールエポキシを約２００μｍ塗装し、カッターナイフを用いて試験片の中央を中心としてクロスカットを入れて、腐食試験片とした。
In all the examples of the present invention, the content of components specified in the present invention is satisfied, so the corrosion weight loss is as small as 54 or less. In particular, steel (No. 6) with a high Mn content of 4.02%, steel containing Nb, Ti, V, Mo, W, Ca or Mg (No. 7 to No. 14) has improved corrosion resistance. ing. It was confirmed that the steel (No. 15) containing REM in addition to the above elements also improved the weldability in addition to the corrosion resistance. Moreover, it turns out that steel (No. 16) with much Si amount and Al amount improves corrosion resistance further.
(Example 2)
Next, Invention Example No. 1 and Comparative Example No. 19 was coated with about 200 μm of tar epoxy on the surface of the test piece collected in the same manner as in Example 1 above, and a crosscut was made around the center of the test piece using a cutter knife. did.
上記実施例１と同様に、得られた試験片で人工海水による乾湿繰り返し試験を行い、耐食性を評価した。具体的には、３５℃の人工海水（ASTM-D-1141-52 に準拠）を用いて、０．５時間の浸漬および２．５時間の乾燥を１サイクルとし、８００サイクル試験後のクロスカット部からの塗膜の膨れ幅を測定し、耐食性を評価した。 In the same manner as in Example 1, the obtained test piece was subjected to repeated wet and dry tests using artificial seawater to evaluate the corrosion resistance. Specifically, using artificial seawater at 35 ° C (according to ASTM-D-1141-52), a cycle of 0.5 hours of immersion and 2.5 hours of drying is taken as one cycle, and a cross cut after 800 cycles of the test The swelling width of the coating film from the part was measured to evaluate the corrosion resistance.
評価結果は、比較例Ｎｏ．１９の試験片では膨れ幅が４．５ｍｍであったに対し、本発明例Ｎｏ．１の試験片では２．２ｍｍであり、本発明例Ｎｏ．１の鋼は耐食性が著しく向上していることが分かる。 The evaluation results are Comparative Example No. In the test piece of No. 19, the swollen width was 4.5 mm. In the test piece of No. 1, it is 2.2 mm. It can be seen that the steel No. 1 has significantly improved corrosion resistance.
本発明の鋼材は、Ｃｒ、ＣｕおよびＮｉは飛来塩分量が多い環境においても耐候性改善効果を有することを見出して完成された鋼材であり、飛来塩分量が多い環境下において十分な耐候性を有している。したがって、海浜耐候性に優れた材料として最適であり、これにより、海浜地域や融雪塩が散布される地域における橋梁等の構造物に使用するミニマムメンテナンス材料として土木および建築分野等において広く適用することができる。
The steel material of the present invention is a steel material which has been found by finding that Cr, Cu and Ni have an effect of improving weather resistance even in an environment where the amount of flying salt is large, and has sufficient weather resistance under an environment where the amount of flying salt is large. Have. Therefore, it is most suitable as a material with excellent weather resistance on the beach, and as a result, it is widely applied in the civil engineering and construction fields as a minimum maintenance material used for structures such as bridges in the beach area and areas where snow melting salt is spread. Can do.
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| CN115261714A (en) * | 2021-04-29 | 2022-11-01 | 宝山钢铁股份有限公司 | Steel for pressure container and preparation method thereof |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000297343A (en) * | 1999-04-09 | 2000-10-24 | Sumitomo Metal Ind Ltd | Steel product excellent in seaside weatherability |
| JP2001214236A (en) * | 2000-01-31 | 2001-08-07 | Nippon Steel Corp | Corrosion resistant steel for crude oil and heavy oil storage speed |
| JP2002053929A (en) * | 2000-08-03 | 2002-02-19 | Kawasaki Steel Corp | Highly weather resistance steel |
| JP2002180187A (en) * | 2000-10-06 | 2002-06-26 | Nippon Steel Corp | High strength and high toughness weather resistant steel having excellent shade weather resistance |
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2003
- 2003-12-02 JP JP2003402593A patent/JP4677714B2/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000297343A (en) * | 1999-04-09 | 2000-10-24 | Sumitomo Metal Ind Ltd | Steel product excellent in seaside weatherability |
| JP2001214236A (en) * | 2000-01-31 | 2001-08-07 | Nippon Steel Corp | Corrosion resistant steel for crude oil and heavy oil storage speed |
| JP2002053929A (en) * | 2000-08-03 | 2002-02-19 | Kawasaki Steel Corp | Highly weather resistance steel |
| JP2002180187A (en) * | 2000-10-06 | 2002-06-26 | Nippon Steel Corp | High strength and high toughness weather resistant steel having excellent shade weather resistance |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108950400A (en) * | 2018-08-10 | 2018-12-07 | 武汉钢铁集团鄂城钢铁有限责任公司 | A kind of low temperature marine steel and preparation method thereof |
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| JP2004360064A (en) | 2004-12-24 |
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