JP5408598B2 - Stainless steel rebar and manufacturing method thereof - Google Patents
Stainless steel rebar and manufacturing method thereof Download PDFInfo
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- JP5408598B2 JP5408598B2 JP2007110151A JP2007110151A JP5408598B2 JP 5408598 B2 JP5408598 B2 JP 5408598B2 JP 2007110151 A JP2007110151 A JP 2007110151A JP 2007110151 A JP2007110151 A JP 2007110151A JP 5408598 B2 JP5408598 B2 JP 5408598B2
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- 229910001220 stainless steel Inorganic materials 0.000 title claims description 21
- 239000010935 stainless steel Substances 0.000 title claims description 21
- 238000004519 manufacturing process Methods 0.000 title claims description 11
- 238000010438 heat treatment Methods 0.000 claims description 31
- 230000003014 reinforcing effect Effects 0.000 claims description 19
- 238000005098 hot rolling Methods 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 2
- 229910000831 Steel Inorganic materials 0.000 description 21
- 239000010959 steel Substances 0.000 description 21
- 230000007797 corrosion Effects 0.000 description 20
- 238000005260 corrosion Methods 0.000 description 20
- 239000011651 chromium Substances 0.000 description 17
- 239000004567 concrete Substances 0.000 description 11
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 7
- 229910052804 chromium Inorganic materials 0.000 description 7
- 229910001566 austenite Inorganic materials 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 3
- 238000005452 bending Methods 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 2
- 238000003483 aging Methods 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000003822 epoxy resin Substances 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000003973 paint Substances 0.000 description 2
- 229920000647 polyepoxide Polymers 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000037303 wrinkles Effects 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- 229910001294 Reinforcing steel Inorganic materials 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 210000003205 muscle Anatomy 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000011150 reinforced concrete Substances 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
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Description
本発明は、コンクリート構造物中での耐久性に優れた鉄筋に関するものである。 The present invention relates to a reinforcing bar having excellent durability in a concrete structure.
具体的には、弾性比例限の高いクロム系ステンレス鉄筋とその製造方法に関する。 Specifically, the present invention relates to a chromium-based stainless steel rebar having a high elastic proportional limit and a manufacturing method thereof.
従来、鉄筋用鋼としてはＳＤ２９５鋼、ＳＤ３４５鋼、ＳＤ３９０鋼などが用いられてきた。このような普通鋼鉄筋は、コンクリート中の塩化物イオンが侵入した場合や、コンクリートが中性化した場合に容易に発銹する。コンクリート中の鉄筋に錆が発生すると、この錆によって体積膨張するために、コンクリートにひびが入り崩落することや、鉄筋自身が減肉し強度を保てなくなるためコンクリート構造物の耐久性を大きく損なうことになる。 Conventionally, SD295 steel, SD345 steel, SD390 steel, etc. have been used as steel for reinforcing bars. Such ordinary steel bars are easily generated when chloride ions in concrete enter or when the concrete is neutralized. If rust occurs in the reinforcing steel bars in concrete, the rust expands, causing cracks in the concrete and collapsing, or the reinforcing bars themselves lose their thickness and lose their strength, greatly impairing the durability of the concrete structure. It will be.
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（特許文献１〜４）。
As countermeasures, various anticorrosion reinforcing bars as described below have been proposed (
特許文献１に記載された発明は非磁性（透磁率２０以下）、で高強度の鉄筋であることを特徴とするものである。
The invention described in
特許文献２に記載された発明は優れた耐食性と曲げ加工性を特徴とするものである。しかし、Ｃｒ含有量が５％以下の場合には海岸や融雪塩を多量に散布する塩害地域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。 The invention described in Patent Document 2 is characterized by excellent corrosion resistance and bending workability. However, when the Cr content is 5% or less, there is a problem that sufficient corrosion resistance cannot be obtained in a coastal area or a salt damage area where a large amount of snow melting salt is dispersed.
特許文献３に記載された文献は優れた耐食性、強度、延性を有する１３Ｃｒ系ステンレス鋼（SUS４１０系）を経済的に製造する方法に特徴を持つものである。 The document described in Patent Document 3 is characterized by a method for economically producing 13Cr stainless steel (SUS410 series) having excellent corrosion resistance, strength and ductility.
特許文献４に記載された文献はＣｒ量が５．０％以上で、かつ少量のＣｏを含有することで優れた耐食性をもつことを特徴とするものである。 The document described in Patent Document 4 is characterized in that the Cr content is 5.0% or more and has excellent corrosion resistance by containing a small amount of Co.
また、現在，塩化物イオンに対する耐食性を有すると考えられている鉄筋としては，エポキシ樹脂被覆鉄筋と亜鉛めっき鉄筋がある。エポキシ樹脂被覆鉄筋は，塗膜によって鉄筋を保護するものであるが，運搬や施工時において塗膜に疵が付きやすく，施工時に生じた疵や溶接部については現地で補修する必要がある。また曲げ加工の際に，疵を生じない特殊な加工機が必要になることや疵を防止するために鉄筋を曲げ加工した後に樹脂を被覆するなど多大な労力を要し，取扱いに問題が多い。また，塗膜表面は節やリフ゛においても素材表面に比べて滑らかであるため，コンクリートとの付着強度を高めるには限界がある。 In addition, as reinforcing bars currently considered to have corrosion resistance to chloride ions, there are epoxy resin-coated reinforcing bars and galvanized reinforcing bars. Epoxy resin-coated reinforcing bars protect the reinforcing bars with a paint film, but the paint film is likely to be damaged during transportation and construction. In addition, a special processing machine that does not generate wrinkles is required during bending, and it takes a lot of labor, such as coating the resin after bending the reinforcing bars to prevent wrinkles, and there are many problems in handling. . Also, since the coating surface is smoother at the nodes and ribs than the material surface, there is a limit to increasing the adhesion strength with concrete.
この他に、亜鉛めっきを施した鉄筋は，亜鉛の犠牲防食作用で下地の鉄筋の発錆を抑制するものであるが，下地の発錆までの時間が亜鉛の目付け量に依存するため 恒久的な防食性能は期待できない。また，亜鉛めっきの腐食生成物がコンクリート構造物の耐久性にどのような影響を与えるか不明な点も多い。 In addition, galvanized reinforcing bars suppress the rusting of the underlying reinforcing bars due to the sacrificial anticorrosive action of zinc. However, the time until the rusting of the underlying depends on the amount of zinc coated, so it is permanent. No anticorrosion performance can be expected. In addition, there are many unclear points on how galvanized corrosion products affect the durability of concrete structures.
このように、これまで優れた耐食性を持つ鉄筋は多く提案されている。しかし、クロム系のステンレス鋼は普通鋼のように降伏点を示さないために、弾性比例限（見かけ上のヤング率）が低い傾向を示す。このためクロム系ステンレス鋼では普通鋼と同じ構造計算が行えないという課題がある
本発明は、優れた耐食性を有し、かつ、高い弾性比例限、耐力を有するクロム系ステンレス鋼鉄筋およびその製造方法を提供することを課題とする。 An object of the present invention is to provide a chromium-based stainless steel rebar having excellent corrosion resistance and having a high elastic proportional limit and proof stress, and a method for producing the same.
本発明は前記課題を解決するためになされたもので、種々検討した結果、Ｃｒ量が８．０〜１３．５％のステンレス鋼で、熱間圧延にて製造後、３００〜５５０℃で熱処理を行うことにより、弾性比例限及び耐力が向上し、かつ耐食性や経済的にも優れたクロム系ステンレス鋼鉄筋が得られることを見出した。 The present invention has been made to solve the above-mentioned problems, and as a result of various studies, it is a stainless steel having a Cr content of 8.0 to 13.5%, manufactured by hot rolling, and then heat treated at 300 to 550 ° C. It has been found that a chromium-based stainless steel rebar having improved elastic proportional limit and yield strength, and excellent in corrosion resistance and economy can be obtained.
すなわち、本発明の要旨とするところは、特許請求の範囲に記載した通りの下記内容で
ある。
（１）質量％で、Ｃ≦０．１５％、Ｓｉ≦２．０％、Ｍｎ≦２．０％、Ｐ≦０．０５％、
Ｓ≦０．０３％、Ｃｒ：８．０〜１３．５％、０．００１≦Ｎ≦０．１５％を含有し、残部Ｆｅおよび不可避的不純物からなり、弾性比例限が２００ＭＰａ以上、０．２％耐力が２９５ＭＰａ
以上であることを特徴とするステンレス鉄筋。
（２）さらに、質量％で、Ｎｉ≦１．０％を含有することを特徴とする（１）に記載のス
テンレス鉄筋。
（３）さらに、質量％で、Ｍｏ≦１．０％を含有することを特徴とする（１）または（２
）に記載のステンレス鉄筋。
（４）表面が脱スケールされていることを特徴とする（１）及至（３）のいずれか一項に
記載のステンレス鉄筋。
（５）熱間圧延にて製造後、温度：３００〜５５０℃、時間：２分以上の熱処理を行うこ
とを特徴とする（１）及至（４）のいずれか一項に記載のステンレス鉄筋の製造方法。
That is, the gist of the present invention is the following contents as described in the claims.
(1)% by mass, C ≦ 0.15%, Si ≦ 2.0%, Mn ≦ 2.0%, P ≦ 0.05%,
S ≦ 0.03%, Cr: 8.0 to 13.5%, 0.001 ≦ N ≦ 0.15%, balance Fe and inevitable impurities, elastic proportionality limit of 200 MPa or more, 2% yield strength is 295 MPa
A stainless steel rebar characterized by the above.
(2) The stainless steel reinforcing bar according to (1), further containing Ni ≦ 1.0% by mass.
(3) Further, it contains Mo ≦ 1.0% by mass% (1) or (2
) Stainless steel rebar.
(4) The stainless steel rebar according to any one of (1) to (3), wherein the surface is descaled.
(5) After manufacturing by hot rolling, heat treatment is performed at a temperature of 300 to 550 ° C. and a time of 2 minutes or more. (1) to (4) The stainless steel rebar according to any one of (1) to (4) Production method.
以下に、先ず、本発明の請求項１記載の限定理由について説明する。
＜C：０．１５％以下＞
Ｃはオーステナイト安定化元素である。オーステナイト相は、熱間加工後にマルテンサイト組織を生じて強度を向上させる。しかしながら、０．１５％以上では硬くなりすぎ、靭性が劣化する。そのため、上限を０．１５％とした。また、Ｃは鋼の強度を確保させるため０．００１％以上が好ましい。好ましくは０．００２〜０．０３％である。
＜Ｓｉ：２．０％以下＞
Ｓｉは脱酸剤として作用し、耐酸化性を向上させるにも有効な元素であるので０．１％以上含有させるが、必要以上の含有は硬くなり靭性を劣化させることに加え、フェライト相の生成が多くなって溶接部の靭性が不足するなどがおこるため、２．０％を上限とした。好ましくは０．２〜０．４％である。
＜Mｎ：２．０％以下＞
ＭｎもＣと同様にオーステナイト相生成元素であるが、２．０％以上になると鋼中の介在物が多くなり、耐食性が劣化する。また、０．１％より少ないと強度不足となることがある。好ましくは０．２〜１．０％である。
＜P：０．０５％以下＞
Ｐは含有量が多いと熱間加工性を低下させるため０．０５％を上限とした。好ましくは０．０４％以下である。
＜S：０．０３％以下＞
ＳはＭｎと結合してＭｎＳを形成し、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、その上限を０．０３％とした。好ましくは０．０２％以下である。
＜Cr：８．０〜１３．５％＞
Ｃｒは本発明における耐食性発現成分として、重要な元素である。本発明で、コンクリート中において塩化物イオン濃度に対する耐食性を確保するためには少なくとも８．０％以上のＣｒが必要である。一方、Ｃｒ量が１３．５％以上となると耐食性は良好になるものの、フェライト相の生成が多くなって、溶接部の靭性が不足することや、コストアップに繋がる、好ましくは１０．５〜１３．５％である。
＜Ｎ：０．１５％以下＞
Ｎはオーストナイト相および窒化物の生成元素であり、強度を高めるが、耐食性や靭性を劣化させるために上限を０．１５％とした。また、鋼の強度を確保するために、０．００１％以上が好ましい。好ましくは０．００５〜０．０３％である。
＜弾性比例限：２００ＭＰa以上＞
弾性比例限は荷重を除荷後、もとの寸法に戻る限度（最大）の応力であり、かつ応力とひずみが直線的に上昇する限度（最大）の応力である。この弾性比例限が高くなると、鉄筋を使用する上で重要な因子である見かけ上のヤング率についても向上する。ここで「見かけ上のヤング率」とは、応力−ひずみ曲線において、耐力（降伏点、０．２％耐力）と原点を結んだ直線の傾きのことをいう。圧延ままのクロム系ステンレス鋼ではこの弾性比例限（見かけの上のヤング率）が低く、引張強度に達するまで荷重が徐々に増加していく。しかし、熱処理を行うことにより、弾性比例限及び見かけ上のヤング率が上昇する。弾性比例限（見かけ上のヤング率）が高いとコンクリート中の鉄筋に歪がかかる応力を計算する際により普通鋼と同様の計算方法で、明確かつ正確に構造計算を行うことができる。この値が低いコンクリート中の鉄筋が外部からの非常に大きな歪みを受けると変形しやすく、歪を受ける前の形状に戻りにくくなるという難点があるものの、その下限値は明確にされていない。そこで、下限値はＳＵＳ４１０L成分の圧延まま材の弾性比例限の上限を超える２００MPaとした。
＜０．２％耐力：２９５ＭＰa以上＞
０．２％耐力は構造物の強度を決める上で重要な値である。この値が低いと構造用（主筋サイス゛）の鉄筋として不適である。主筋用として使用可能な耐力は２９５MPa以上必要である。好ましくは３４５MPa以上である。
Below, the reason for limitation of
<C: 0.15% or less>
C is an austenite stabilizing element. The austenite phase produces a martensite structure after hot working and improves strength. However, at 0.15% or more, it becomes too hard and the toughness deteriorates. Therefore, the upper limit was made 0.15%. C is preferably 0.001% or more in order to ensure the strength of the steel. Preferably it is 0.002 to 0.03%.
<Si: 2.0% or less>
Si acts as a deoxidizer and is an effective element for improving oxidation resistance, so it is contained in an amount of 0.1% or more. However, if it is contained more than necessary, it hardens and deteriorates toughness. Since the generation increases and the toughness of the welded portion is insufficient, the upper limit is set to 2.0%. Preferably it is 0.2 to 0.4%.
<Mn: 2.0% or less>
Mn is an austenite phase-forming element like C, but if it is 2.0% or more, the inclusions in the steel increase and the corrosion resistance deteriorates. On the other hand, if it is less than 0.1%, the strength may be insufficient. Preferably it is 0.2 to 1.0%.
<P: 0.05% or less>
When P content is large, the hot workability is lowered, so 0.05% was made the upper limit. Preferably it is 0.04% or less.
<S: 0.03% or less>
S combines with Mn to form MnS and serves as a starting point. S is also a harmful element that segregates at the grain boundaries and promotes embrittlement of grain boundaries, so the upper limit was made 0.03%. Preferably it is 0.02% or less.
<Cr: 8.0 to 13.5%>
Cr is an important element as a corrosion resistance developing component in the present invention. In the present invention, at least 8.0% or more of Cr is necessary to ensure corrosion resistance against chloride ion concentration in concrete. On the other hand, when the Cr content is 13.5% or more, the corrosion resistance becomes good, but the generation of ferrite phase increases, leading to insufficient toughness of the welded part and an increase in cost, preferably 10.5 to 13 .5%.
<N: 0.15% or less>
N is an element forming the austenite phase and nitride, and increases the strength, but the upper limit was made 0.15% in order to deteriorate the corrosion resistance and toughness. Moreover, in order to ensure the intensity | strength of steel, 0.001% or more is preferable. Preferably it is 0.005 to 0.03%.
<Elastic proportional limit: 200 MPa or more>
The elastic proportional limit is the limit (maximum) stress that returns to the original dimension after unloading the load, and the limit (maximum) stress at which the stress and strain rise linearly. As this elastic proportional limit increases, the apparent Young's modulus, which is an important factor in using the reinforcing bar, also improves. Here, “apparent Young's modulus” refers to the slope of a straight line connecting the yield strength (yield point, 0.2% yield strength) and the origin in the stress-strain curve. The as-rolled chromium-based stainless steel has a low elastic proportional limit (apparent Young's modulus), and the load gradually increases until the tensile strength is reached. However, the heat treatment increases the elastic proportional limit and the apparent Young's modulus. When the elastic proportionality limit (apparent Young's modulus) is high, it is possible to calculate the structure clearly and accurately by the same calculation method as that for ordinary steel when calculating the stress that strains the reinforcing bars in the concrete. Although the rebar in concrete with this low value is easily deformed when it receives a very large strain from the outside, it is difficult to return to the shape before the strain, but the lower limit is not clarified. Therefore, the lower limit value is set to 200 MPa which exceeds the upper limit of the elastic proportional limit of the rolled SUS410L component.
<0.2% proof stress: 295 MPa or more>
The 0.2% yield strength is an important value in determining the strength of the structure. If this value is low, it is not suitable as a reinforcing bar for structural use (main reinforcement size). The proof stress that can be used for the main muscle is 295 MPa or more. Preferably it is 345 MPa or more.
本発明の請求鋼２に記載の限定理由について述べる。
＜Ni：１．０％以下＞
Ｎｉは耐食性を向上させるのに有用元素であるが、１．０％以上添加するとコストアップが大きくなる。また、靭性を高めるために０．０１％以上が好ましい。好ましくは０．０５〜０．６％である。
The reason for limitation described in claim steel 2 of the present invention will be described.
<Ni: 1.0% or less>
Ni is a useful element for improving the corrosion resistance, but if added at 1.0% or more, the cost increases. Moreover, 0.01% or more is preferable in order to improve toughness. Preferably it is 0.05 to 0.6%.
本発明の請求鋼３に記載の限定理由について述べる。
＜Ｍｏ：１．０％以下＞
ＭｏはＣｒと同様に耐食性を向上させるのに有効な元素であり０．０１％以上の添加により安定した効果が得られる。しかし、多量に添加させると、コストアップに繋がるために上限を1．０％とした。好ましくは０．０5〜１．０％である。
また、請求項４に記載のように、表面を、例えば塩酸水溶液や硫酸水溶液を用いて酸洗し、もしくは、機械的手段を用いて脱スケールすることにより、表面性状に優れたステンレス鉄筋を提供できる。
The reason for limitation described in claim steel 3 of the present invention will be described.
<Mo: 1.0% or less>
Mo is an element effective for improving the corrosion resistance like Cr, and a stable effect can be obtained by addition of 0.01% or more. However, if added in a large amount, the cost is increased, so the upper limit was made 1.0%. Preferably it is 0.05-1.0%.
In addition, as described in claim 4, the surface is pickled using, for example, an aqueous hydrochloric acid solution or an aqueous sulfuric acid solution, or descaled using mechanical means, thereby providing a stainless steel bar having excellent surface properties. it can.
本発明の請求項５に記載の限定理由について述べる。
＜熱処理条件：温度３００〜５５０℃ 時間２分以上＞
熱処理温度については３００℃未満で行うと、時効硬化によるＣ，Ｎによる転移の固着が起こらず、弾性比例限、０．２％耐力の向上が見られない。また５５０℃超であると鋼の軟化が起こり、熱処理を行っていないものと同程度の強度になることから５５０℃を上限の温度とした。好ましくは４００〜５００℃である。熱処理時間については２分未満であると、時効硬化による強度の上昇が見られない。また１００分を超えると、生産性が低下する。好ましくは２〜１００分である。
図１に熱処理温度と弾性比例限、耐力の関係を示す。試験片は成分（０．０１％Ｃ−０．３％Ｓｉ−０．４％Ｍｎ−０．０２％Ｐ−０．００３％Ｓ−１１．７％Ｃｒ−０．０１％Ｎ）、Φ１９、２５のものを用い、熱処理時間を２０分として熱処理を行った。３００〜５５０℃の温度範囲で弾性比例限、耐力の上昇が見られる。また６００℃で熱処理を行っても熱処理を行う前の強度と同程度になることがわかる。この結果から熱処理温度を３００〜５５０℃の範囲とした。
The reason for limitation according to claim 5 of the present invention will be described.
<Heat treatment conditions:
When the heat treatment temperature is less than 300 ° C., the fixing of the transition due to C and N due to age hardening does not occur, and the elastic proportional limit and 0.2% yield strength are not improved. The softens the steel to be 550 ° C. greater, and the 550 ° C. from becoming comparable strength to those not subjected to heat treatment to a temperature upper limit. Preferably it is 400-500 degreeC. If the heat treatment time is less than 2 minutes, no increase in strength due to age hardening is observed. Moreover, when it exceeds 100 minutes, productivity will fall. Preferably it is 2 to 100 minutes.
FIG. 1 shows the relationship between heat treatment temperature, elastic proportional limit, and yield strength. The test piece is composed of components (0.01% C-0.3% Si-0.4% Mn-0.02% P-0.003% S-11.7% Cr-0.01% N), Φ19, The heat treatment was performed using a heat treatment time of 25 minutes. In the temperature range of 300 to 550 ° C. , an elastic proportional limit and an increase in yield strength are observed. It can also be seen that even if heat treatment is performed at 600 ° C., the strength is the same as before the heat treatment. From this result, the heat treatment temperature was set in the range of 300 to 550 ° C.
図２に熱処理時間と弾性比例限、０．２％耐力の関係を示す。熱処理時間は設定温度に到達してからの時間である。図２の試験では成分（０．０１％C−０．３％Ｓｉ−０．４％Ｍｎ−０．０２％Ｐ−０．００３％Ｓ−１１．７％Ｃｒ−０．０１％Ｎ）、Φ２５の試験片を用い、熱処理温度４００℃で試験をおこなった。熱処理時間が１分と非常に短い時間であると、強度（弾性比例限、０．２％耐力）上昇は見られないが、２分以上の熱処理を行うと弾性比例限、耐力ともに４００ＭＰａ以上となり、大幅な上昇が見られた。しかし、その強度上昇は長時間側で飽和した状態になってくる。約１２０分の熱処理を行っても約３０分の値と比べて大きな強度上昇はなく、長時間の熱処理では製造コストの上昇や製造効率が悪化することから、上限は１００分が好ましい。 FIG. 2 shows the relationship between heat treatment time, elastic proportional limit, and 0.2% proof stress. The heat treatment time is the time after reaching the set temperature. In the test of FIG. 2, the components (0.01% C-0.3% Si-0.4% Mn-0.02% P-0.003% S-11.7% Cr-0.01% N), A test was performed at a heat treatment temperature of 400 ° C. using a test piece of Φ25. If the heat treatment time is as short as 1 minute, no increase in strength (elastic proportional limit, 0.2% yield strength) will be observed, but if heat treatment for 2 minutes or longer, both the elastic proportional limit and yield strength will be 400 MPa or more. There was a significant increase. However, the intensity increase becomes saturated on the long time side. Even if the heat treatment is performed for about 120 minutes, the strength is not significantly increased as compared with the value for about 30 minutes, and the heat treatment for a long time causes an increase in production cost and production efficiency. Therefore, the upper limit is preferably 100 minutes.
以下に本発明の実施例について説明する。 Examples of the present invention will be described below.
表1に本発明の実施例の化学成分と熱処理条件、熱処理後の弾性比例限、耐力の評価結果を示す。 Table 1 shows the evaluation results of the chemical components and heat treatment conditions, the elastic proportional limit after heat treatment, and the yield strength of the examples of the present invention.
したのち、１２００℃−１時間の焼鈍を施し、９００℃における熱間圧延によって１９Φ
と２５Φの異形棒鋼とした。
弾性比例限、０．２％耐力はＪＩＳＺ２２４１：１９９８により、鉄筋の引張試験を実施
し、弾性比例限、０．２％耐力を測定した。本発明鋼の弾性比例限は２００ＭＰa以上、
０．２％耐力は２９５ＭＰａ以上であった。
一方、比較例Ｎｏ．２１〜３５は本発明に比べ、以下に示す点が劣っていた。
Ｎｏ．２１はＣ量が高いために靭性が劣化した。
Ｎｏ．２２はＳｉが高いために素地の靭性が劣化するとともに、フェライト相の生成が多
くなって溶接部の靭性が劣化した。
Ｎｏ．２３はＭｎが高いため、鋼中の介在物が多くなり、耐食性が劣化した。
Ｎｏ．２４はＰが高いため、熱間加工性が劣化し、製造上問題があった。
Ｎｏ．２５はＣｒが低いため、十分な耐食性が得られなかった。
Ｎｏ．２６はＳが高いため、鋼中のＭｎと結合してＭｎＳとなり耐食性を劣化させた。
Ｎｏ．２７はＣｒが高いため、フェライト相の生成が多くなって、溶接部の靭性が不足す
ることや、コストアップに繋がる。
Ｎｏ．２８はＮが高いため、靭性、耐食性が劣化した。
Ｎｏ．２９はＮｉが高いため、コストアップに繋がる。
Ｎｏ．３０はＭｏが高いとコストアップに繋がるとともに、今回の試験では熱処理後の耐
力が下限を下回った。
Ｎｏ．３１は熱処理時間が短いために、熱処理による強度上昇を得られなかった。
Ｎｏ．３２は熱処理時間を長時間にしたものの、強度の上昇は短い時間と比べても大きく
変化はなく、製造効率を悪化させた。
Ｎｏ．３３は熱処理温度を行わなかったために、弾性比例限を満足しなかった。
Ｎｏ．３４は熱処理温度が低いために、熱処理による弾性比例限の上昇が得られなかった
。
Ｎｏ．３５は熱処理温度が高いために、熱処理により、鋼の軟化が起こり、弾性比例限の
上昇が得られなかった。
And 25Φ deformed steel bar.
The elastic proportional limit and 0.2% yield strength were measured in accordance with JIS Z2241: 1998 by conducting a tensile test of the reinforcing bar and measuring the elastic proportional limit and 0.2% yield strength. The elastic proportional limit of the steel of the present invention is 200 MPa or more,
The 0.2% proof stress was 295 MPa or more.
On the other hand, Comparative Example No. 21-35 were inferior to the present invention in the following points.
No. No. 21 had high toughness due to its high C content.
No. Since No. 22 was high in Si, the toughness of the substrate deteriorated, and the generation of ferrite phase increased and the toughness of the welded portion deteriorated.
No. Since No. 23 had high Mn, the inclusion in steel increased and corrosion resistance deteriorated.
No. Since No. 24 had high P, hot workability deteriorated and there was a problem in production.
No. Since No. 25 had low Cr, sufficient corrosion resistance was not obtained.
No. Since No. 26 has high S, it combined with Mn in steel and became MnS, which deteriorated the corrosion resistance.
No. Since No. 27 is high in Cr, the generation of ferrite phase increases, leading to insufficient toughness of the welded part and an increase in cost.
No. Since No. 28 had high N, toughness and corrosion resistance deteriorated.
No. Since 29 has high Ni, it leads to a cost increase.
No. When Mo was high, the cost increased when Mo was 30. In this test, the yield strength after heat treatment was below the lower limit.
No. No. 31 could not obtain an increase in strength due to the heat treatment because the heat treatment time was short.
No. In No. 32, although the heat treatment time was extended, the increase in strength was not significantly changed compared to the short time, and the production efficiency was deteriorated.
No. 33 did not satisfy the elastic proportionality limit because no heat treatment temperature was applied.
No. Since the heat treatment temperature of 34 was low, an increase in the elastic proportional limit due to the heat treatment could not be obtained.
No. Since No. 35 has a high heat treatment temperature, the heat treatment caused the softening of the steel, and the elastic proportional limit could not be increased.
以上の実施例から分かるように本発明例に優位性は明らかであり本発明の効果が確認された。 As can be seen from the above examples, the advantages of the present invention example are clear and the effects of the present invention were confirmed.
以上の説明から明らかなように、本発明により高い弾性比例限と耐力をもつクロム系ステンレス鉄筋の提供が可能であり、耐久性と強度に優れた鉄筋コンクリート建築構造物を設計・施工する上で極めて有用である。 As is clear from the above explanation, the present invention can provide a chromium-based stainless steel rebar having a high elastic proportional limit and proof strength, which is extremely important in designing and constructing a reinforced concrete building structure excellent in durability and strength. Useful.
Claims (5)
Ｃ≦０．１５％、
Ｓｉ≦２．０％、
Ｍｎ≦２．０％、
Ｐ≦０．０５％、
Ｓ≦０．０３％、
Ｃｒ：８．０〜１３．５％、
０．００１≦Ｎ≦０．１５％を含有し、残部Ｆｅおよび不可避的不純物からなり、弾性比例限が２００ＭＰａ以上、０．２％耐力が２９５ＭＰａ以上であることを特徴とするステンレス鉄筋。 % By mass
C ≦ 0.15%,
Si ≦ 2.0%,
Mn ≦ 2.0%,
P ≦ 0.05%,
S ≦ 0.03%,
Cr: 8.0 to 13.5%,
A stainless steel rebar comprising 0.001 ≦ N ≦ 0.15%, consisting of the balance Fe and inevitable impurities, having an elastic proportionality limit of 200 MPa or more and a 0.2% proof stress of 295 MPa or more.
ンレス鉄筋。 The stainless steel rebar according to claim 1, further comprising Ni ≦ 1.0% by mass.
２に記載のステンレス鉄筋。 The stainless steel reinforcing bar according to claim 1, further comprising Mo ≦ 1.0% by mass.
ステンレス鉄筋。 The stainless steel rebar according to any one of claims 1 to 3, wherein the surface is descaled.
特徴とする請求項１及至請求項４のいずれか一項に記載のステンレス鉄筋の製造方法。 The method for producing a stainless steel rebar according to any one of claims 1 to 4, wherein after the production by hot rolling, a heat treatment is performed at a temperature of 300 to 550 ° C and a time of 2 minutes or more.
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