JP2002212682A - Cr-CONTAINING BAR STEEL FOR REINFORCING BAR HAVING EXCELLENT CORROSION RESISTANCE IN CONCRETE AND REINFORCING BAR CONCRETE STRUCTURE - Google Patents
Cr-CONTAINING BAR STEEL FOR REINFORCING BAR HAVING EXCELLENT CORROSION RESISTANCE IN CONCRETE AND REINFORCING BAR CONCRETE STRUCTUREInfo
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、コンクリート中で
の耐食性に優れた鉄筋用Cr含有棒鋼およびそれを用いた
鉄筋コンクリート構造物に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Cr-containing steel bar for reinforcing steel having excellent corrosion resistance in concrete and a reinforced concrete structure using the same.
【０００２】[0002]
【従来の技術】従来、鉄筋用鋼としては SD345鋼や SD3
90鋼などが用いられてきたが、このような普通鋼鉄筋
は、コンクリートが中性化した場合やコンクリート中に
塩素イオンが混入した場合には、容易に腐食するため、
コンクリート崩壊の危険性が指摘され、最近大きな問題
となっている。2. Description of the Related Art Conventionally, as steel for reinforcing steel, SD345 steel and SD3 steel have been used.
90 steel etc. has been used, but such ordinary steel bars are easily corroded when the concrete is neutralized or when chloride ions are mixed in the concrete,
The danger of concrete collapse has been pointed out and has recently become a major problem.
【０００３】その対策として、次に述べるような種々の
防食鉄筋が提案されている。例えば、特開昭60−92451
号公報には、Ｓ量を0.01mass％以下に低減した上で、0.
05〜3.00mass％のCrあるいはこのCrと共に0.03〜0.60ma
ss％のCuを複合添加し、さらに必要に応じてＶ, Mo, Ｐ
等を添加することによって、耐食性を向上させたコンク
リート用鉄筋が提案されている。また、特開昭62−1887
54号公報には、0.30〜5.00mass％のCrと0.50超〜1.50ma
ss％のCuを複合添加すると共に、Ni, Mo, Ｖを併せて添
加することによって、耐食性と曲げ加工性を向上させた
鉄筋が提案されている。さらに、特開昭62−274050号公
報には、Ｓ量を0.005 mass％以下に低減した上で、0.5
超〜5.5 mass％のCrと 7.0〜20.0mass％のAlを含有させ
ることによって、塩分に起因した鉄筋の腐食を防止した
耐海水鉄筋棒鋼が提案されている。As a countermeasure, various anticorrosion reinforcing bars as described below have been proposed. For example, JP-A-60-92451
The publication discloses that the amount of S is reduced to 0.01 mass% or less,
05 ~ 3.00mass% Cr or 0.03-0.60ma with this Cr
ss% of Cu is added in combination, and if necessary, V, Mo, P
There has been proposed a reinforcing steel bar for concrete in which corrosion resistance is improved by adding such elements. Also, JP-A-62-1887
No. 54 discloses that 0.30 to 5.00 mass% of Cr and more than 0.50 to 1.50 ma
There has been proposed a reinforcing bar having improved corrosion resistance and bending workability by adding ss% of Cu in combination and adding Ni, Mo, and V together. Further, Japanese Patent Application Laid-Open No. Sho 62-274050 discloses that after reducing the S content to 0.005 mass% or less,
There has been proposed a seawater-resistant reinforcing steel bar which contains super-5.5 mass% of Cr and 7.0-20.0 mass% of Al to prevent corrosion of reinforcing steel caused by salt.
【０００４】しかしながら、特開昭60−92451 号公報や
特開昭62−188754号公報などのように、Cr含有量が５ma
ss％以下の場合には、塩害地域等では十分な耐食性を得
ることができないという問題がある。また、特開昭62−
274050号公報のように、Al含有量が７mass％以上と高い
場合には、耐食性は良いものの、コストが高いという問
題がある。However, as disclosed in Japanese Patent Application Laid-Open Nos. 60-92451 and 62-188754, the Cr content is 5 ma.
If the content is less than ss%, there is a problem that sufficient corrosion resistance cannot be obtained in a salt damage area or the like. Also, Japanese Patent Application Laid-Open
When the Al content is as high as 7 mass% or more as in Japanese Patent No. 274050, there is a problem that the corrosion resistance is good but the cost is high.
【０００５】現在、ある程度有効であるとして使用され
ている防食鉄筋は、エポキシ被覆鉄筋である。しかしな
がら、このエポキシ被覆鉄筋も施工時に生じた庇や溶接
部については現地で補修する必要があり、また曲げ加工
の際に庇を生じない特殊な加工機が必要になるなど、問
題が多い。海外では、実際に施工する場合の問題の多さ
から、エポキシ被覆鉄筋の使用を中止したという報告も
ある。[0005] Anticorrosion rebars that are currently used to some extent are epoxy coated rebars. However, this epoxy-coated rebar has many problems, such as the need for on-site repair of eaves and welds generated during construction, and the need for a special processing machine that does not generate eaves during bending. Overseas, there are reports that the use of epoxy-coated steel bars has been discontinued due to the many problems involved in actual construction.
【０００６】そのため、海外では、塩害地域用防食鉄筋
としてステンレス鉄筋が部分的に使用されている。しか
しながら、それらは殆ど SUS 304や SUS 316といった高
価なオーステナイト系ステンレス鋼であり、これらは耐
食性には極めて優れているものの、高価であるため使用
範囲が限定されるという問題があった。[0006] For this reason, stainless steel bars are partially used overseas as anticorrosion bars for salt-damaged areas. However, most of them are expensive austenitic stainless steels such as SUS 304 and SUS 316, and although they are extremely excellent in corrosion resistance, there is a problem that the range of use is limited because they are expensive.
【０００７】[0007]
【発明が解決しようとする課題】本発明は、上記の実状
に鑑み開発されたもので、上述したような鉄筋腐食に起
因したコンクリート構造物の崩壊を防止できるのはいう
までもなく、エポキシ被覆鉄筋のように施工に厳しい制
約がなく、しかも海外で使用されている SUS 304や SUS
316等よりもはるかに安価な鉄筋用Cr含有棒鋼を提案す
ることを目的とする。また、本発明は、上記の鉄筋用Cr
含有棒鋼を利用することにより、塩害地域において用い
ても崩壊するおそれのない鉄筋コンクリート構造物を提
案することを目的とする。DISCLOSURE OF THE INVENTION The present invention has been developed in view of the above-mentioned situation, and it is needless to say that the collapse of a concrete structure caused by the corrosion of reinforcing steel as described above can be prevented. SUS 304 and SUS used overseas without strict restrictions on construction like rebar
The purpose is to propose a Cr-containing steel bar for reinforcing steel which is much cheaper than 316 etc. The present invention also relates to the above-described Cr for reinforcing steel.
An object of the present invention is to propose a reinforced concrete structure which does not collapse even when used in a salt-damaged area by using a contained steel bar.
【０００８】[0008]
【課題解決のための手段】さて、発明者らは、上記の目
的を達成すべく、多くの合金元素の影響について調査を
行った。その結果、Cr量が 5.0mass％超で、かつ少量の
Coを含有する鋼が、アルカリ性となり、溶存酸素による
カソード反応も制限されるコンクリート中での耐食性に
優れ、 コスト的にもSUS304やSUS316よりもはるかに安価
で、 防食鉄筋材料として極めて優れていることの知見を
得た。本発明は、上記の知見に立脚するものである。Means for Solving the Problems The present inventors have investigated the effects of many alloying elements in order to achieve the above object. As a result, the amount of Cr is over 5.0 mass%
Steel containing Co is alkaline and has excellent corrosion resistance in concrete where the cathodic reaction due to dissolved oxygen is limited.It is also much cheaper than SUS304 and SUS316 in terms of cost, and is extremely excellent as a corrosion-resistant reinforcing steel material. Was obtained. The present invention is based on the above findings.
【０００９】すなわち、本発明の要旨構成は次のとおり
である。 １．Ｃ：0.001 mass％超、0.3 mass％未満、Ｎ：0.001
mass％超、0.3 mass％未満、Si：0.1 mass％超、4.0 ma
ss％未満、Mn：0.1 mass％超、4.0 mass％未満、Cr：5.
0 mass％超、15.0mass％未満、Co：0.01mass％超、1.0
mass％未満、Al：0.04mass％未満、Ｐ：0.04mass％未満
およびＳ：0.03mass％未満を含有し、残部はFeおよび不
可避的不純物の組成になることを特徴とする、コンクリ
ート中での耐食性に優れた鉄筋用Cr含有棒鋼。That is, the gist of the present invention is as follows. 1. C: more than 0.001 mass%, less than 0.3 mass%, N: 0.001
More than mass%, less than 0.3 mass%, Si: more than 0.1 mass%, 4.0 ma
Less than ss%, Mn: more than 0.1 mass%, less than 4.0 mass%, Cr: 5.
More than 0 mass%, less than 15.0 mass%, Co: more than 0.01 mass%, 1.0
Corrosion resistance in concrete characterized by containing less than mass%, less than 0.04 mass% Al: less than 0.04 mass%, less than 0.04 mass% P: less than 0.03 mass%, the balance being Fe and inevitable impurities Excellent Cr-containing steel bar for reinforcing steel.
【００１０】２．上記１において、鋼が、さらにＶ：1.
0 mass％未満およびＷ：1.0 mass％未満のうちから選ん
だ一種または二種を含有する組成になることを特徴とす
る、コンクリート中での耐食性に優れた鉄筋用Cr含有棒
鋼。[0010] 2. In the above item 1, the steel further has V: 1.
A Cr-containing steel bar for reinforcing steel having excellent corrosion resistance in concrete, characterized by having a composition containing one or two selected from less than 0 mass% and W: less than 1.0 mass%.
【００１１】３．上記１または２において、鋼が、さら
にNi：3.0 mass％未満、Cu：3.0 mass％未満およびMo：
3.0 mass％未満のうちから選んだ一種または二種以上を
含有する組成になることを特徴とする、コンクリート中
での耐食性に優れた鉄筋用Cr含有棒鋼。3. In the above 1 or 2, the steel further contains Ni: less than 3.0 mass%, Cu: less than 3.0 mass%, and Mo:
A Cr-containing steel bar for reinforcing steel having excellent corrosion resistance in concrete, characterized by having a composition containing one or more selected from less than 3.0 mass%.
【００１２】４．上記１，２または３において、鋼が、
さらにNb：1.0 mass％未満、Ti：1.0 mass％未満、Ta：
1.0 mass％未満、Zr：1.0 mass％未満およびＢ：0.01ma
ss％未満のうちから選んだ少なくとも一種を含有する組
成になることを特徴とする、コンクリート中での耐食性
に優れた鉄筋用Cr含有棒鋼。4. In the above 1, 2 or 3, the steel is
Further, Nb: less than 1.0 mass%, Ti: less than 1.0 mass%, Ta:
Less than 1.0 mass%, Zr: less than 1.0 mass% and B: 0.01 ma
A Cr-containing steel bar for reinforcing steel having excellent corrosion resistance in concrete, characterized by having a composition containing at least one selected from less than ss%.
【００１３】５．上記１〜４のいずれかに記載の鉄筋用
Cr含有棒鋼を、鉄筋として内部に設置してなることを特
徴とする鉄筋コンクリート構造物。5. For rebar according to any one of the above 1 to 4
A reinforced concrete structure characterized in that a Cr-containing steel bar is installed inside as a reinforcing bar.
【００１４】[0014]
【発明の実施の形態】以下、本発明について具体的に説
明する。まず、本発明において、鋼材の成分組成を上記
の範囲に限定した理由について説明する。 Ｃ：0.001 mass％超、0.3 mass％未満 Ｃは、オーステナイト相および炭化物の生成元素であ
る。オーステナイト相は、溶接部において、マルテンサ
イト組織を生じて強度を向上させ、また微細炭化物も強
度の向上に寄与する。しかしながら、Ｃ含有量が 0.001
mass％以下ではオーステナイト相および炭化物の生成量
が少なすぎて強度不足となり、一方 0.3mass％以上では
硬くなり過ぎて靱性の劣化を招く。従って、Ｃ量は 0.0
01mass％超、0.3 mass％未満の範囲に限定した。BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. First, the reason why the composition of the steel material is limited to the above range in the present invention will be described. C: more than 0.001 mass% and less than 0.3 mass% C is an element forming austenitic phase and carbide. The austenite phase forms a martensitic structure in the weld to improve the strength, and fine carbides also contribute to the strength. However, if the C content is 0.001
If it is less than mass%, the amount of austenite phase and carbide generated is too small, resulting in insufficient strength, while if it is more than 0.3 mass%, it becomes too hard, resulting in deterioration of toughness. Therefore, the amount of C is 0.0
The range is limited to more than 01 mass% and less than 0.3 mass%.
【００１５】Ｎ：0.001 mass％超、0.3 mass％未満 Ｎも、オーステナイト相および窒化物の生成元素であ
り、オーステナイト相は溶接部において、マルテンサイ
ト組織を生じて強度を向上させ、また微細窒化物も強度
を向上させる。しかしながら、Ｎ含有量が 0.001mass％
以下ではオーステナイト相および窒化物の生成量が少な
過ぎて強度不足となり、一方 0.3mass％以上になると硬
くなり過ぎて靱性の劣化を招く。従って、Ｎ量は 0.001
mass％超、0.3 mass％未満の範囲に限定した。なお、特
に強度を高めたい場合には、Ｃ，Ｎをそれぞれ0.02mass
％以上、より好ましくは0.03mass％以上とすることが望
ましい。N: more than 0.001 mass% and less than 0.3 mass% N is also an element forming austenitic phase and nitride, and the austenitic phase forms a martensitic structure in the welded portion to improve the strength and to improve the fine nitride. Also improve strength. However, N content is 0.001mass%
Below, the amount of austenite phase and nitride generated is too small, resulting in insufficient strength. On the other hand, if it exceeds 0.3% by mass, the steel becomes too hard, resulting in deterioration of toughness. Therefore, the amount of N is 0.001
The range was more than mass% and less than 0.3 mass%. In particular, when it is desired to increase the strength, each of C and N is set to 0.02 mass.
% Or more, more preferably 0.03 mass% or more.
【００１６】Si：0.1 mass％超、4.0 mass％未満 Siは、脱酸剤として有用な元素であるが、含有量が 0.1
mass％以下では十分な脱酸効果が得られず、一方 4.0ma
ss％以上になると硬くなって機械的性質の劣化を招く。
従って、Si量は 0.1mass％超、4.0 mass％未満の範囲に
限定した。Si: more than 0.1% by mass and less than 4.0% by mass Si is a useful element as a deoxidizing agent.
If it is less than mass%, a sufficient deoxidizing effect cannot be obtained.
If it exceeds ss%, it becomes hard and causes deterioration of mechanical properties.
Therefore, the Si content is limited to a range of more than 0.1 mass% and less than 4.0 mass%.
【００１７】Mn：0.1 mass％超、4.0 mass％未満 Mnも、Ｃと同様、オーステナイト相生成元素であるが、
含有量が 0.1mass％以下ではオーステナイト相の生成が
不十分となるため、溶接部のマルテンサイト組織が少な
くなって、強度不足となる。一方、Mn含有量が 4.0mass
％以上になると鋼中に残存する介在物が多くなって耐食
性が劣化する。従って、Mn量は 0.1mass％超、4.0 mass
％未満の範囲に限定した。Mn: more than 0.1 mass% and less than 4.0 mass% Mn is also an austenite phase forming element like C,
When the content is 0.1 mass% or less, the generation of the austenite phase becomes insufficient, so that the martensite structure of the welded portion is reduced and the strength becomes insufficient. On the other hand, Mn content is 4.0mass
% Or more, the inclusions remaining in the steel increase and the corrosion resistance deteriorates. Therefore, the amount of Mn exceeds 0.1 mass% and 4.0 mass%.
%.
【００１８】Cr：5.0 mass％超、15.0mass％未満 Crは、本発明における耐食性の改善成分として重要な元
素である。本発明で対象にする鉄筋として、コンクリー
ト中において長期使用が可能となるレベルの耐食性を確
保するためには、少なくとも 5.0mass％超のCrが必要で
ある。一方、Cr量が15.0mass％以上になると、耐食性は
良くなるものの、コストアップになるだけでなく、フェ
ライト相の生成量が多くなって溶接部の靱性不足とな
る。従って、Cr量は5.0 mass％超、15.0mass％未満の範
囲に限定した。Cr: more than 5.0 mass%, less than 15.0 mass% Cr is an important element as a component for improving corrosion resistance in the present invention. In order to ensure a level of corrosion resistance that enables long-term use in concrete, at least 5.0 mass% of Cr is required as the reinforcing steel used in the present invention. On the other hand, when the Cr content is 15.0 mass% or more, the corrosion resistance is improved, but not only the cost is increased, but also the generation amount of the ferrite phase is increased and the toughness of the weld is insufficient. Therefore, the Cr content is limited to a range of more than 5.0 mass% and less than 15.0 mass%.
【００１９】Co：0.01mass％超、1.0 mass％未満 Coは、本発明の重要な成分であり、このCo添加によって
コンクリート中でのCr鋼素地の腐食速度を低減して耐食
性の向上を図ることができる。少量のCoによるこのよう
な耐食性の向上効果は、アルカリ環境で、しかも溶存酸
素によるカソード反応も制限されるコンクリート中にお
いて初めて見出されたものである。ここに、Co含有量が
0.01mass％以下では上記の効果を十分に得ることができ
ず、一方 1.0mass％以上になると上記の効果は飽和に達
し、むしろコストの上昇を招くので、Co量は0.01mass％
超、1.0mass ％未満の範囲に限定した。Co: more than 0.01 mass% and less than 1.0 mass% Co is an important component of the present invention. By adding Co, the corrosion rate of the Cr steel base in concrete is reduced to improve the corrosion resistance. Can be. Such an effect of improving the corrosion resistance by a small amount of Co was first found in concrete in which the cathode reaction due to dissolved oxygen is limited in an alkaline environment. Here, the Co content
If the content is less than 0.01 mass%, the above effect cannot be sufficiently obtained. On the other hand, if the content is more than 1.0 mass%, the above effect reaches saturation, and rather increases the cost.
It is limited to the range of super, less than 1.0 mass%.
【００２０】Al：0.04mass％未満 Alは、脱酸剤として有用な元素である。Siによる脱酸が
不十分な場合にはAlによる脱酸が行われるが、その含有
量が0.04mass％以上になると介在物が多くなって耐食性
が劣化する。従って、Alは0.04mass％未満で含有させる
こととした。Al: less than 0.04% by mass Al is an element useful as a deoxidizing agent. If the deoxidation by Si is insufficient, deoxidation by Al is performed. However, if the content is 0.04 mass% or more, the number of inclusions increases and the corrosion resistance deteriorates. Therefore, Al was determined to be contained at less than 0.04 mass%.
【００２１】Ｐ：0.04mass％未満 Ｐは、靱性等の機械的性質を劣化させるだけでなく、耐
食性に対しても有害な元素であり、特にＰ含有量が0.04
mass％以上になるとその悪影響が顕著になるので、Ｐ量
は0.04mass％未満に制限した。P: less than 0.04% by mass P not only deteriorates mechanical properties such as toughness, but also is harmful to corrosion resistance.
If the content is more than mass%, the adverse effect becomes remarkable. Therefore, the P content is limited to less than 0.04 mass%.
【００２２】Ｓ：0.03mass％未満 Ｓは、Mnと結合してMnＳを形成し、初期発銹起点とな
る。またＳは、結晶粒界に偏析して、粒界脆化を促進す
る有害元素でもあるので、極力低減することが好まし
い。特にＳ含有量が0.03mass％以上になるとその悪影響
が顕著になるので、Ｓ量は0.03mass％未満に制限した。S: less than 0.03 mass% S combines with Mn to form MnS, and serves as an initial rusting point. In addition, S is also a harmful element that segregates at crystal grain boundaries and promotes grain boundary embrittlement. Therefore, it is preferable to reduce S as much as possible. In particular, when the S content is 0.03 mass% or more, its adverse effect becomes remarkable, so the S content is limited to less than 0.03 mass%.
【００２３】以上、必須成分および抑制成分について説
明したが、本発明では、その他にも以下に述べる各種元
素を適宜含有させることができる。 Ｖ：1.0 mass％未満 Ｖを添加することにより、Cr炭窒化物の析出が少なくな
って、耐食性が向上する。また、Ｖは、Cr鋼素地の耐食
性の向上にも寄与する。特にコンクリート中という腐食
環境では、Ｖは少量の添加でも耐食性向上に有効に寄与
するという知見が得られた。しかしながら、含有量が
1.0mass％以上になると上記の効果は飽和に達し、むし
ろコストの上昇を招くことになる。従って、Ｖは 1.0ma
ss％未満で含有させることとした。The essential component and the inhibitory component have been described above. In the present invention, other various elements described below can be appropriately contained. V: less than 1.0 mass% By adding V, precipitation of Cr carbonitride is reduced and corrosion resistance is improved. V also contributes to improving the corrosion resistance of the Cr steel base. In particular, it was found that in a corrosive environment such as in concrete, even a small amount of V effectively contributes to the improvement of corrosion resistance. However, the content
When the content is 1.0 mass% or more, the above-described effect reaches saturation, which rather leads to an increase in cost. Therefore, V is 1.0ma
The content was determined to be less than ss%.
【００２４】Ｗ：1.0 mass％未満 Ｗは、Ｖと同様、Cr炭窒化物の析出を少なくして耐食性
を向上させるだけでなく、Cr鋼素地の耐食性の向上にも
寄与する。特にコンクリート中という腐食環境では、Ｗ
は、Ｖと同様、少量の添加でも耐食性向上に有効に寄与
するという知見が得られた。しかしながら、含有量が
1.0mass％以上にすると機械的性質の劣化を招くので、
Ｗは 1.0mass％未満で含有させることとした。W: less than 1.0 mass% W, like V, not only improves the corrosion resistance by reducing the precipitation of Cr carbonitrides, but also contributes to the improvement of the corrosion resistance of the Cr steel base. Especially in a corrosive environment such as in concrete, W
It was found that, like V, even a small amount effectively contributes to the improvement of corrosion resistance. However, the content
If it exceeds 1.0 mass%, the mechanical properties will deteriorate.
W is contained at less than 1.0 mass%.
【００２５】Ni：3.0 mass％未満 Niは、Cr鋼の活性溶解を低減して耐食性を向上させる有
用元素であるが、含有量が 3.0mass％以上にするとコス
トアップが大きくなるので、Niは 3.0mass％未満で含有
させることとした。Ni: less than 3.0 mass% Ni is a useful element that reduces the active dissolution of the Cr steel and improves the corrosion resistance. However, if the content is 3.0 mass% or more, the cost is greatly increased. It was determined to be contained at less than mass%.
【００２６】Cu：3.0 mass％未満 Cuも、Cr鋼の活性溶解を低減して耐食性を向上させる作
用があるが、含有量が3.0 mass％以上になると逆に耐食
性が劣化する傾向にあるので、Cuは 3.0mass％未満で含
有させることとした。Cu: less than 3.0 mass% Cu also has the effect of reducing the active dissolution of the Cr steel to improve corrosion resistance. However, when the content exceeds 3.0 mass%, the corrosion resistance tends to deteriorate. Cu was determined to be contained at less than 3.0 mass%.
【００２７】Mo：3.0 mass％未満 Moも、Cr鋼の耐食性を向上させる上で極めて有効な元素
であるが、3.0 mass％以上の添加はコストアップが大き
くなるため、Moは 3.0mass％未満で含有させることとし
た。Mo: less than 3.0 mass% Mo is also an extremely effective element for improving the corrosion resistance of Cr steel, but the addition of 3.0 mass% or more increases the cost, so that Mo is less than 3.0 mass%. It was decided to be contained.
【００２８】Nb：1.0 mass％、Ti：1.0 mass％未満、T
a：1.0 mass％未満、Zr：1.0 mass％未満 Nb, Ti，TaおよびZrはいずれも、Cr炭窒化物の析出を少
なくして耐食性を向上させる働きがある。しかしなが
ら、いずれも 1.0mass％以上では機械的性質を劣化させ
るので、これらの元素は単独添加、複合添加いずれの場
合にも 1.0mass％未満で含有させるものとした。Nb: 1.0 mass%, Ti: less than 1.0 mass%, T
a: less than 1.0 mass%, Zr: less than 1.0 mass% Nb, Ti, Ta and Zr all have the function of reducing the precipitation of Cr carbonitride and improving the corrosion resistance. However, in any case, the mechanical properties are deteriorated at 1.0 mass% or more. Therefore, these elements are contained at less than 1.0 mass% in both cases of single addition and composite addition.
【００２９】Ｂ：0.01mass％未満 Ｂは、Ｎと結合することにより、Cr窒化物の析出を少な
くして耐食性を向上させる作用がある。しかしながら、
含有量が0.01mass％以上だと、鋼材製造時の熱間加工性
が劣化するので、Ｂは0.01mass％未満で含有させるもの
とした。B: less than 0.01 mass% B has an effect of bonding with N to reduce precipitation of Cr nitride and improve corrosion resistance. However,
If the content is 0.01 mass% or more, the hot workability during the production of steel material deteriorates. Therefore, B is contained at less than 0.01 mass%.
【００３０】なお、本発明鋼の製造に際しては、特別な
制限はなく、常法に従って製造すれば良い。参考のた
め、代表的な製造条件を以下に示す。 (1) 精錬工程 高炉溶銑を転炉にてCrを添加しつつ脱炭したもの、また
はスクラップ等のFe，Cr原料を電気炉にて溶解した溶鋼
を、ＶＯＤ等により脱炭、成分調整したものを、連続鋳
造にてブルームとするか、または造塊によりインゴット
を製造する。 (2) 熱間圧延工程 ブルームまたはインゴットを、1100〜1200℃に加熱した
のち、熱間圧延または熱間鍛造により50mm角程度のビレ
ットとする。このビレットを、再び1100℃程度に加熱し
たのち、線棒圧延機により15mmφ程度の棒鋼とする。 (3) 仕上工程 熱間圧延により製造した棒鋼は、そのまま使用すること
が可能であるが、必要に応じて適当な熱処理により強度
を調整する。また、より耐食性を向上させる場合には、
熱間圧延後、場合によっては熱処理後の棒鋼に、ショッ
トブラスト、さらには硝酸＋ふっ酸等による脱スケール
処理を施す。In the production of the steel of the present invention, there is no particular limitation, and the steel may be produced according to a conventional method. Representative production conditions are shown below for reference. (1) Refining process Molten steel obtained by decarburizing molten iron from blast furnace molten iron in a converter while adding Cr, or molten steel obtained by melting Fe and Cr raw materials such as scrap in an electric furnace and decarburizing and adjusting the composition by VOD etc. Is made into a bloom by continuous casting, or an ingot is produced by ingot making. (2) Hot rolling step After heating the bloom or ingot to 1100 to 1200 ° C, a billet of about 50 mm square is formed by hot rolling or hot forging. After the billet is heated again to about 1100 ° C., it is made into a bar steel of about 15 mmφ by a wire rod rolling mill. (3) Finishing process The steel bars manufactured by hot rolling can be used as they are, but the strength is adjusted by appropriate heat treatment as needed. In order to further improve the corrosion resistance,
After hot rolling, if necessary, the steel bar after the heat treatment is subjected to shot blasting and further descaling treatment with nitric acid + hydrofluoric acid or the like.
【００３１】また、本発明の鉄筋コンクリート構造物
は、上記した本発明鋼を鉄筋として用いれば良い。この
時の施工方法には特に制限はなく、常法に従い、例えば
本発明鋼を鉄筋として配置すると共に、周囲に型枠を設
営して、この型枠の内部にコンクリートを打設すれば良
い。In the reinforced concrete structure of the present invention, the above-described steel of the present invention may be used as a reinforcing bar. The construction method at this time is not particularly limited, and the steel of the present invention may be arranged as a reinforcing bar, a formwork may be set up around the form, and concrete may be poured into the formwork in accordance with a conventional method.
【００３２】[0032]
【実施例】表１〜表４に示す成分組成になる鋼塊50kgを
真空溶解した。ついで、鋼塊の表面５mmを研削したの
ち、1200℃，１ｈの焼鈍を施し、熱間鍛造により50mm角
のビレットとした。このビレットに1100℃，１ｈの焼鈍
を施したのち、線棒圧延機により15mmφの棒鋼とした。
ついで、この棒鋼に、ショットブラストと３％ふっ酸−
12％硝酸の混合酸による脱スケール処理を施した。な
お、本実験では、熱間でのスケールを除去するためにシ
ョット−酸洗処理を行ったが、コンクリート中での腐食
環境が弱い場合には、ショットのみまたは脱スケールな
しでもよい。さらに、熱間鍛造−圧延により棒鋼を製造
した後に、強度を調整するための熱処理を施してもよ
い。このようにして製造したステンレス鉄筋と市販の S
D390，SUS304, SUS316鉄筋を用いて、以下に示す条件で
鉄筋コンクリートを作成した。EXAMPLE 50 kg of a steel ingot having the composition shown in Tables 1 to 4 was melted in vacuum. Next, after grinding the surface of the steel ingot 5 mm, the steel ingot was annealed at 1200 ° C. for 1 hour, and a billet of 50 mm square was formed by hot forging. After this billet was annealed at 1100 ° C. for 1 hour, it was turned into a bar of 15 mmφ by a wire rod rolling mill.
Then, shot blast and 3% hydrofluoric acid
A descaling treatment was performed with a mixed acid of 12% nitric acid. In this experiment, shot-pickling treatment was performed to remove hot scale. However, if the corrosive environment in concrete is weak, only shot or no descaling may be used. Further, after manufacturing the steel bar by hot forging-rolling, a heat treatment for adjusting the strength may be performed. The stainless steel bar produced in this way and commercial S
Using D390, SUS304 and SUS316 rebar, reinforced concrete was made under the following conditions.
【００３３】・鉄筋コンクリート製造条件 １．石骨材 約1200 kg/m3 ２．砂骨材 約800 kg/m3 ３．ポルトランドセメント 300 kg/m3 ４．水 200 kg/m3 ５．塩化物イオン添加量 0.6 kg/m3 の組成のコンクリートを用いて、表面から30mm位置に供
試用の鉄筋を埋め込み、30日間の養生を行って、鉄筋コ
ンクリート試験体を作製した。この鉄筋コンクリート試
験体に、海水を毎日６時間噴霧したのち、海岸で暴露す
る試験を１年間行った後に、コンクリートに生じた割れ
の程度と、取り出した鉄筋に生じた腐食面積率を測定す
ることによって耐食性を評価した。得られた結果を表
５，表６に示す。· Reinforced concrete production conditions Stone aggregate about 1200 kg / m 3 2. Sand aggregate approximately 800 kg / m 3 3. Portland cement 300 kg / m 3 4. Water 200 kg / m 3 5. Using concrete composition of the chloride ion amount 0.6 kg / m 3, embedded rebar of the test trial from the surface to 30mm position, performing curing for 30 days, to prepare a reinforced concrete test specimen. After spraying seawater on this reinforced concrete test specimen every day for 6 hours, and performing an exposure test on the shore for one year, the degree of cracks generated in the concrete and the corrosion area rate generated in the taken out reinforcing steel were measured. The corrosion resistance was evaluated. Tables 5 and 6 show the obtained results.
【００３４】[0034]
【表１】 [Table 1]
【００３５】[0035]
【表２】 [Table 2]
【００３６】[0036]
【表３】 [Table 3]
【００３７】[0037]
【表４】 [Table 4]
【００３８】[0038]
【表５】 [Table 5]
【００３９】[0039]
【表６】 [Table 6]
【００４０】表５，表６に示したように、本発明に従う
Cr含有棒鋼を鉄筋として用いた場合、コンクリートに割
れは生じず、また鉄筋の腐食も殆どが１％以下と良好で
あった。According to the present invention, as shown in Tables 5 and 6,
When a Cr-containing steel bar was used as a reinforcing bar, cracks did not occur in concrete, and corrosion of the reinforcing bar was almost 1% or less, which was good.
【００４１】[0041]
【発明の効果】かくして、本発明によれば、 SUS 304や
SUS 316といった高価なステンレス鋼を用いなくても、
コンクリート中における耐食性が従来の普通鋼鉄筋より
も遥かに優れた鉄筋用Cr含有棒鋼を得ることができる。
また、本発明の鉄筋コンクリート構造物によれば、塩化
物イオンが存在する環境においても、割れが生じず、崩
壊のおそれがない。Thus, according to the present invention, SUS 304 or
Even without using expensive stainless steel such as SUS 316,
It is possible to obtain a Cr-containing steel bar for reinforcing steel which has much better corrosion resistance in concrete than conventional ordinary steel reinforcing steel.
Further, according to the reinforced concrete structure of the present invention, even in an environment where chloride ions are present, cracks do not occur and there is no possibility of collapse.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 太田 裕樹 千葉県千葉市中央区川崎町１番地 川崎製 鉄株式会社技術研究所内 (72)発明者 古君 修 千葉県千葉市中央区川崎町１番地 川崎製 鉄株式会社技術研究所内 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroki Ota 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba In the Technical Research Institute of Kawasaki Steel Co., Ltd. (72) Inventor Osamu Furukun 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corp.
Claims (5)
ことを特徴とする、コンクリート中での耐食性に優れた
鉄筋用Cr含有棒鋼。C: more than 0.001 mass%, less than 0.3 mass%, N: more than 0.001 mass%, less than 0.3 mass%, Si: more than 0.1 mass%, less than 4.0 mass%, Mn: more than 0.1 mass%, 4.0 mass %, Cr: more than 5.0 mass%, less than 15.0 mass%, Co: more than 0.01 mass%, less than 1.0 mass%, Al: less than 0.04 mass%, P: less than 0.04 mass% and S: less than 0.03 mass% A Cr-containing steel bar for reinforcing steel having excellent corrosion resistance in concrete, characterized by the balance of Fe and inevitable impurities.
ことを特徴とする、コンクリート中での耐食性に優れた
鉄筋用Cr含有棒鋼。2. The concrete according to claim 1, wherein the steel further has a composition containing one or two selected from V: less than 1.0 mass% and W: less than 1.0 mass%. Cr-containing steel bar for reinforcing steel with excellent corrosion resistance in steel.
に Ni：3.0 mass％未満、 Cu：3.0 mass％未満および Mo：3.0 mass％未満 のうちから選んだ一種または二種以上を含有する組成に
なることを特徴とする、コンクリート中での耐食性に優
れた鉄筋用Cr含有棒鋼。3. The composition according to claim 1, wherein the steel further comprises one or more selected from the group consisting of Ni: less than 3.0 mass%, Cu: less than 3.0 mass%, and Mo: less than 3.0 mass%. Cr-containing steel bars for reinforcing steel with excellent corrosion resistance in concrete, characterized by becoming
さらに Nb：1.0 mass％未満、 Ti：1.0 mass％未満、 Ta：1.0 mass％未満、 Zr：1.0 mass％未満および Ｂ：0.01mass％未満 のうちから選んだ少なくとも一種を含有する組成になる
ことを特徴とする、コンクリート中での耐食性に優れた
鉄筋用Cr含有棒鋼。4. The steel according to claim 1, wherein the steel is
Further, the composition must include at least one selected from Nb: less than 1.0 mass%, Ti: less than 1.0 mass%, Ta: less than 1.0 mass%, Zr: less than 1.0 mass%, and B: less than 0.01 mass%. Characterized by Cr-containing steel bars for steel bars with excellent corrosion resistance in concrete.
Cr含有棒鋼を、鉄筋として内部に設置してなることを特
徴とする鉄筋コンクリート構造物。5. A reinforcing bar according to any one of claims 1 to 4.
A reinforced concrete structure characterized in that a Cr-containing steel bar is installed inside as a reinforcing bar.
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|---|---|---|---|---|
| JP2007107073A (en) * | 2005-10-17 | 2007-04-26 | Sanyo Special Steel Co Ltd | METHOD FOR PRODUCING Fe-Cr MARTENSITIC STAINLESS STEEL BAR |
| JP2007113079A (en) * | 2005-10-21 | 2007-05-10 | Nippon Steel & Sumikin Stainless Steel Corp | Deformed stainless steel bar having excellent durability in concrete structure |
| JP4624904B2 (en) * | 2005-10-21 | 2011-02-02 | 新日鐵住金ステンレス株式会社 | Stainless deformed steel bar with excellent durability in concrete structures |
| JP2007177259A (en) * | 2005-12-27 | 2007-07-12 | Sumitomo Metal Ind Ltd | Austenitic stainless steel for nuclear power use, and its manufacturing method |
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| JP2007269566A (en) * | 2006-03-31 | 2007-10-18 | Jfe Steel Kk | Hydrated hardened body having reinforcing rod excellent in neutralization resistance and salt damage resistance |
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| JP2013209804A (en) * | 2012-03-30 | 2013-10-10 | Nippon Steel & Sumikin Stainless Steel Corp | Chromium-containing deformed bar with superior corrosion resistance in concrete structure |
| JP2013209834A (en) * | 2012-03-30 | 2013-10-10 | Nippon Steel & Sumikin Stainless Steel Corp | Stainless deformed bar with superior corrosion resistance in concrete structure |
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