JP5119595B2 - Corrosion resistant steel for shipbuilding - Google Patents
Corrosion resistant steel for shipbuilding Download PDFInfo
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本発明は，船舶用鋼材に関し，特に，海水腐食環境下で使用されるバラストタンク用鋼材について，補修塗装寿命延長および補修塗装作業軽減の観点から，その耐食性を向上させようとするものである。 The present invention relates to marine steel materials, and in particular, to improve the corrosion resistance of steel materials for ballast tanks used in seawater corrosive environments from the viewpoint of extending the repair coating life and reducing the repair coating work.
バラストタンクは、海水が出入りすることから、厳しい腐食環境下にあり、通常その防食はエポキシ系塗料と電気防食とが併用されている。しかし、それらの防食を講じていても、バラストタンクの腐食は激しい状態にある。すなわち、バラストタンクの海水充満時においては、海水に完全に浸されている部分は、電気防食が働き、腐食の進行を抑えられる。しかし、バラストタンクの最上部付近、特にアッパーデッキの裏側は海水に完全に漬からず、海水飛沫の状態にある。そのため、このような部位では、電気防食が働かず、さらに太陽光により、鋼板が高温に曝されるため、厳しい腐食環境となり、激しい腐食状態となる。また、バラストタンクに海水がない場合においては、海水の残留付着塩分の作用によって、激しい腐食状態となる。 The ballast tank is in a severe corrosive environment because seawater enters and exits. Usually, the anticorrosion is combined with epoxy paint and cathodic protection. However, even if these anticorrosion measures are taken, the corrosion of the ballast tank is in a severe state. That is, when the ballast tank is filled with seawater, the portion that is completely immersed in seawater acts as an anticorrosion, and the progress of corrosion can be suppressed. However, the vicinity of the uppermost part of the ballast tank, particularly the back side of the upper deck, is not completely immersed in seawater and is in a state of splashing seawater. Therefore, in such a part, since the anticorrosion does not work and the steel plate is exposed to high temperature by sunlight, it becomes a severe corrosive environment and a severe corrosive state. Moreover, when there is no seawater in a ballast tank, it will be in a severe corrosion state by the effect | action of the residual adhering salt content of seawater.
このように厳しい腐食環境下にあるバラストタンクの塗膜寿命は、約10年といわれており、船の寿命（20年）の半分である。従って、残りの10年は、補修塗装で安全性を維持しなければならない。バラストタンクでは、このような厳しい腐食環境による激しい腐食状態、そして、それに起因した狭い空間での補修再塗装という悪条件下での作業が重大な問題であるため、補修塗装寿命の延長、および補修塗装作業の軽減を達成できる耐食性鋼材の開発が望まれている。 Ballast tanks under such a severe corrosive environment have a coating film life of about 10 years, which is half the life of a ship (20 years). Therefore, for the remaining 10 years, safety must be maintained by repair painting. In ballast tanks, the severe corrosion caused by such a severe corrosive environment, and the work under adverse conditions of repainting in a narrow space resulting from this, is a serious problem. Development of corrosion-resistant steel that can achieve reduction in painting work is desired.
一方、バラストタンクの耐食化に関する鋼材側からの対策としては、以下のものが提案されている。 On the other hand, the following have been proposed as countermeasures from the steel side regarding the corrosion resistance of the ballast tank.
特許文献１には，P：0.03〜0.10％，Cu：0.1〜1.0％，Ni：0.1〜1.0％を添加した鋼材にエポキシ、ピュアエポキシ、ウレタン樹脂などを塗布したバラストタンクが提案されている。これは下地金属の耐食性が向上するため、樹脂皮膜の接着劣化寿命が延長し、バラストタンクの耐久化が図られるとしている。そして、20〜30年に渡って、メンテナンスを不要にすることが可能になるという提案がなされている。 Patent Document 1 proposes a ballast tank in which epoxy, pure epoxy, urethane resin, or the like is applied to a steel material added with P: 0.03-0.10%, Cu: 0.1-1.0%, and Ni: 0.1-1.0%. This is because the corrosion resistance of the base metal is improved, so that the adhesive deterioration life of the resin film is extended, and the ballast tank is made durable. And it has been proposed that maintenance can be made unnecessary for 20 to 30 years.
特許文献２には、Cr：0.2〜5％を添加することで、また、特許文献3には、Cr：0.5〜3.5％を添加することで、耐食性が向上し、船舶のメンテナンスフリー化に寄与できるという提案がなされている。 Addition of Cr: 0.2 to 5% to Patent Document 2 and Addition of Cr: 0.5 to 3.5% to Patent Document 3 improve corrosion resistance and contribute to a maintenance-free ship Proposals have been made.
特許文献４には、Ni：0.1〜4.0％を添加することで、耐塗膜損傷性が向上し、補修塗装などの保守費用を大幅に削減できるとという提案がなされている。
しかし、特許文献1の技術では、下地金属の耐食性を向上させるため、P含有量が0.03〜0.10％と比較的多く含有されており、溶接性および溶接部靭性に問題があると考えられる。また、特許文献2及び3の技術では、Cr含有量が比較的高く、特許文献4の技術ではNi含有量が比較的高く、いずれも製造コスト高となる問題がある。 However, in the technique of Patent Document 1, in order to improve the corrosion resistance of the base metal, the P content is relatively large as 0.03 to 0.10%, and it is considered that there is a problem in weldability and weld zone toughness. Further, in the techniques of Patent Documents 2 and 3, the Cr content is relatively high, and in the technique of Patent Document 4, the Ni content is relatively high.
そこで、本発明は、船舶バラストタンクの補修再塗装寿命の延長および補修再塗装作業の軽減に寄与すべく、上記した溶接性、溶接部靭性の劣化や製造コストの高騰を回避できる耐食性に優れた船舶バラストタンク用鋼材を提供することを目的とする。 Therefore, the present invention has excellent corrosion resistance capable of avoiding the above-described deterioration of weldability, welded portion toughness and increase in manufacturing cost in order to contribute to the extension of the repair repaint life of the ship ballast tank and the reduction of the repair repaint work. It aims at providing the steel materials for ship ballast tanks.
発明者らは，耐食性向上有効元素を見出すため、種々の合金を添加した鋼材を溶製して圧延し、それぞれの鋼板から5mm×100mm×200mmの暴露試験片を採取した。これら試験片に、ショットブラスト後、ジンクリッチプライマー（約15μm）、タールエポキシ樹脂塗料（約100μm）を塗布した。その後、カッターナイフで、試験片の地鉄表面まで達する80mm長さのスクラッチを付加した。これら試験片を、実船のバラストタンクアッパーデッキ裏を模擬した乾湿繰り返し試験を行い、スクラッチ周囲のさびによる塗膜膨れおよび剥離面積を測定した。試験期間は６ヶ月間である。 In order to find an effective element for improving corrosion resistance, the inventors melted and rolled steel materials to which various alloys were added, and collected 5 mm × 100 mm × 200 mm exposure test pieces from the respective steel plates. After shot blasting, zinc rich primer (about 15 μm) and tar epoxy resin paint (about 100 μm) were applied to these test pieces. Thereafter, a 80 mm long scratch reaching the surface of the test piece was added with a cutter knife. These test pieces were subjected to a dry and wet repeated test simulating the back of the upper deck of an actual ship's ballast tank, and the swelling of the coating film and the peeled area due to rust around the scratch were measured. The test period is 6 months.
その結果、鋼へのW添加が塗膜下でのさび生成を顕著に抑制し、塗膜膨れ、塗膜剥離に有効であることを見出した。さらに、Ni，Moの添加、また、Cu，Co，Sn，Sbの添加により、その効果をさらに高めることが可能であることが分かった。さらに、大入熱溶接において溶接部靱性の向上の観点からTi、N量の適正化が有効であることがわかった。そして、それぞれの合金元素の母材機械的特性、溶接部靭性を調査し、さらにコストを勘案し、本発明はなされた。 As a result, it has been found that the addition of W to steel significantly suppresses the formation of rust under the coating film, and is effective for coating film swelling and coating film peeling. Furthermore, it has been found that the effect can be further enhanced by addition of Ni, Mo and addition of Cu, Co, Sn, Sb. Furthermore, it was found that optimization of Ti and N contents is effective from the viewpoint of improving weld toughness in high heat input welding. The present invention was made by investigating the base metal mechanical properties and weld toughness of each alloy element, and further considering the cost.
１．第一の発明は、鋼の成分組成が、質量％でC：0.03〜0.25％、Si：0.05〜0.50％、Mn：0.1〜2.0％、P：0.025％以下、S：0.01％以下、Al：0.01〜0.10％、W：0.01〜1.0％、Sn：0.001〜0.3％を含み、残部Feおよび不可避的不純物からなることを特徴とする造船用耐食鋼である。 1. In the first invention, the component composition of the steel is, in mass%, C: 0.03-0.25%, Si: 0.05-0.50%, Mn: 0.1-2.0%, P: 0.025% or less, S: 0.01% or less, Al: It is a corrosion-resistant steel for shipbuilding characterized by containing 0.01 to 0.10%, W: 0.01 to 1.0%, Sn : 0.001 to 0.3%, and the balance being Fe and inevitable impurities.
２．第二の発明は、鋼の成分組成として、更に質量％でNi：0.01〜1.0％を含むことを特徴とする第一の発明に記載の造船用耐食鋼である。 2. The second invention is the corrosion-resistant steel for shipbuilding according to the first invention, further comprising Ni: 0.01 to 1.0% by mass% as a component composition of the steel.
３．第三の発明は、鋼の成分組成として、更に質量％でMo：0.01〜0.5％を含むことを特徴とする第一の発明又は第二の発明に記載の造船用耐食鋼である
４．第四の発明は、鋼の成分組成として、質量％でCu：0.02〜1.0％、Co：0.02〜1.0％、Sb:0.001〜0.3％のうちから選ばれた1種または２種以上を更に含むことを特徴とする第一の発明から第三の発明のいずれかに記載の造船用耐食鋼である。
3. 3. The third invention is the corrosion-resistant steel for shipbuilding according to the first invention or the second invention, characterized by further containing Mo: 0.01 to 0.5% by mass% as a component composition of the steel. According to a fourth aspect of the present invention, the composition of steel further includes one or more selected from Cu: 0.02 to 1.0%, Co: 0.02 to 1.0% , and Sb: 0.001 to 0.3% by mass%. It is a corrosion-resistant steel for shipbuilding according to any one of the first to third inventions, characterized in that it is included.
５．第五の発明は、鋼の成分組成として、質量％でB：0.0003〜0.003％を更に含むことを特徴とする第一の発明から第四の発明のいずれかに記載の造船用耐食鋼である。 5). The fifth invention is the corrosion-resistant steel for shipbuilding according to any one of the first to fourth inventions, further comprising B: 0.0003 to 0.003% by mass% as a component composition of the steel. .
本発明によれば、鋼材への比較的少ないW添加により、バラストタンクの腐食環境で優れた耐食性を示すので、製造コストの高騰を抑え、溶接性、溶接部靭性を確保しつつ、船舶バラストタンクの補修再塗装寿命の延長および補修再塗装作業の軽減に大きく寄与することができる。 According to the present invention, a relatively small amount of W added to the steel material exhibits excellent corrosion resistance in the corrosive environment of the ballast tank. This greatly contributes to the extension of the repair and repaint life and the reduction of repair and repaint operations.
本発明の鋼材の成分組成および製造方法について、以下に具体的に説明する。
１．成分組成について
成分組成の限定理由について説明する。なお、成分組成における各元素の含有％は全て質量％を意味する。
The component composition and manufacturing method of the steel material of the present invention will be specifically described below.
1. The reason why the component composition is limited will be described. In addition, all the content% of each element in a component composition means the mass%.
C：0.03-0.25％
Cは鋼材の強度を上昇させる元素であり、本発明では所望の強度を得るためには、0.03％以上の含有を必要とする。一方，0.25％を超える含有は、HAZ（：溶接熱影響部）の靭性を劣化させる。このため、Cは0.03〜0.25％の範囲に限定した。なお、強度、靭性の観点から、好ましくは0.05〜0.20％である。
C: 0.03-0.25%
C is an element that increases the strength of the steel material. In the present invention, the content of 0.03% or more is required to obtain a desired strength. On the other hand, the content exceeding 0.25% deteriorates the toughness of HAZ (: welding heat affected zone). For this reason, C was limited to the range of 0.03-0.25%. From the viewpoint of strength and toughness, it is preferably 0.05 to 0.20%.
Si：0.05〜0.50％
Siは、脱酸剤として作用するとともに、鋼材の強度を増加させる元素であり、本発明では、0.05％以上の含有が好ましいが、0.50％を超える含有は、鋼の靭性を劣化させる。このため、Siは0.50％以下の範囲に限定した。
Si: 0.05-0.50%
Si is an element that acts as a deoxidizing agent and increases the strength of the steel material. In the present invention, the content is preferably 0.05% or more, but the content exceeding 0.50% deteriorates the toughness of the steel. For this reason, Si was limited to the range of 0.50% or less.
Mn：0.1〜2.0％
Mnは、鋼材の強度を増加させる元素であるが、2.0％を超える含有は、鋼の靭性および溶接性を低下させる。このため、Mnは2.0％以下に限定した。好ましくは0.5〜1.6％である。
Mn: 0.1-2.0%
Mn is an element that increases the strength of the steel material, but inclusion exceeding 2.0% lowers the toughness and weldability of the steel. For this reason, Mn was limited to 2.0% or less. Preferably it is 0.5 to 1.6%.
P：0.025％以下
Pは鋼の母材靭性、さらに溶接性および溶接部靭性を劣化させる。したがって、出来るだけ低減するのが好ましいが、0.025％までは許容できる。0.025％を超えて含有すると母材靭性および溶接部靭性が顕著に低下する。このため，Pは0.025％以下に限定した。
P: 0.025% or less
P deteriorates the base metal toughness, weldability and weld toughness of steel. Therefore, it is preferable to reduce as much as possible, but it is acceptable up to 0.025%. If the content exceeds 0.025%, the base metal toughness and weld toughness are remarkably reduced. For this reason, P was limited to 0.025% or less.
S：0.01％以下
Sは靭性および溶接性を劣化させる有害な元素であることから、可能な限り低減する必要がある。従って、0.01％以下に限定した。
S: 0.01% or less
Since S is a harmful element that deteriorates toughness and weldability, it must be reduced as much as possible. Therefore, it was limited to 0.01% or less.
Al：0.01〜0.10％以下
Alは脱酸剤として添加し、0.01％以上を含有するが、0.10％を超えて含有すると、耐食性を顕著に劣化させる。従って、0.10％を上限とした。
Al: 0.01 to 0.10% or less
Al is added as a deoxidizer and contains 0.01% or more, but if it exceeds 0.10%, the corrosion resistance is remarkably deteriorated. Therefore, 0.10% was made the upper limit.
W：0.01〜1.0％
Wは塗膜下でのさび生成を顕著に抑制するため、本発明鋼材の中で、最も重要な元素である。その効果は、塗膜下での鋼板の腐食に伴い、さび中でWO4 2-を形成し、このWO4 2-の存在により、塩化物イオンの鋼板表面への侵入を抑制する。さらに、鋼板表面のアノード部などpHが下がった部位では難溶性のFeWO4を形成し、このFeWO4の存在により、塩化物イオンの鋼板表面への侵入を抑制する。塩化物イオンの鋼板表面への侵入抑制により、鋼板の腐食を抑制し、さび生成を抑制する。以上の効果は、W：0.01％以上の含有で顕著になり、1.0％以上では、効果が飽和する。このため、W含有量は0.01〜1.0％の範囲に限定した。
W: 0.01-1.0%
W is the most important element in the steel of the present invention because it significantly suppresses rust formation under the coating film. The effect is that WO 4 2- is formed in the rust as the steel sheet corrodes under the coating film, and the presence of this WO 4 2- suppresses the penetration of chloride ions to the steel sheet surface. Further, hardly soluble FeWO 4 is formed at a site where the pH is lowered, such as the anode part on the surface of the steel sheet, and the presence of this FeWO 4 suppresses the entry of chloride ions to the steel sheet surface. By suppressing the penetration of chloride ions into the steel sheet surface, corrosion of the steel sheet is suppressed and rust formation is suppressed. The above effect becomes remarkable when the content of W is 0.01% or more, and the effect is saturated when the content is 1.0% or more. For this reason, W content was limited to 0.01 to 1.0% of range.
Ni：0.01〜1.0％
Niは塗膜下でのさび生成を抑制するため、本発明鋼材の中で重要な元素である。
その効果は、さび粒子を緻密化し、地鉄への水、酸素、塩化物イオンの鋼板表面への侵入を抑制する。以上の腐食因子の鋼板表面への侵入抑制により、鋼板の腐食を抑制し、さび生成を抑制する。この効果はNi：0.0１％以上の含有で効果を発揮し、1.0％以上では、効果が飽和する。このため、Ni含有量は0.01〜1.0％の範囲に限定した。
Ni: 0.01-1.0%
Ni is an important element in the steel of the present invention because it suppresses the formation of rust under the coating film.
This effect densifies rust particles and suppresses the penetration of water, oxygen, and chloride ions into the steel plate surface. By suppressing the penetration of the above corrosion factors into the steel sheet surface, corrosion of the steel sheet is suppressed and rust formation is suppressed. This effect is exhibited when Ni is contained in an amount of 0.01% or more, and when 1.0% or more, the effect is saturated. For this reason, Ni content was limited to the range of 0.01 to 1.0%.
Mo：0.01〜0.5％
MoはWと同様の作用により、塗膜下でのさび生成をやや抑制するため、補助的に使用できる。その効果は、塗膜下での鋼板の腐食に伴い、さび中でMoO4 2-を形成し、このMoO4 2-の存在により、塩化物イオンの鋼板表面への侵入を抑制する。この効果は、Mo：0.01％以上の含有で発現し、0.5％以上では、効果が飽和する。このため、Mo含有量は0.01〜0.5％の範囲に限定した。
Mo: 0.01-0.5%
Mo can be used supplementarily because it has the same effect as W and slightly suppresses the formation of rust under the coating film. The effect is that MoO 4 2− is formed in the rust as the steel sheet corrodes under the coating film, and the presence of MoO 4 2− suppresses the entry of chloride ions to the steel sheet surface. This effect is manifested at a Mo content of 0.01% or more, and the effect is saturated at 0.5% or more. For this reason, Mo content was limited to 0.01 to 0.5% of range.
Cu：0.02〜1.0％、Co：0.02〜1.0％、Sn：0.001〜0.3％、Sb：0.001〜0.3％のうちの１種または2種以上
Cu、Co、Sn、Sbは、塗膜下でのさび生成を抑制するが、その効果は上記W、Ni、Moほど大きくない。しかし、さび生成抑制の観点から補助的に使用できる。
Cu、Coはさび粒微細化による塩化物イオン侵入抑制の作用から、0.02〜1.0％の範囲でさび生成抑制効果がある。Sn、Sbについては作用機構は定かではないが、それぞれ0.001％以上の添加で、さび生成を抑制するため、0.001％以上含有できる。しかし、0.3％を超えると母材靭性，HAZ靭性を顕著に劣化させる。そのため、それぞれ0.001〜0.3％の範囲とした。
One or more of Cu: 0.02-1.0%, Co: 0.02-1.0%, Sn: 0.001-0.3%, Sb: 0.001-0.3%
Cu, Co, Sn, and Sb suppress the formation of rust under the coating film, but the effect is not as great as that of W, Ni, and Mo. However, it can be used supplementarily from the viewpoint of suppressing rust formation.
Cu and Co have an effect of inhibiting rust formation in the range of 0.02 to 1.0% because of the action of inhibiting chloride ion intrusion due to rust grain refinement. Although the mechanism of action of Sn and Sb is not clear, 0.001% or more can be contained in order to suppress rust formation when 0.001% or more is added. However, if it exceeds 0.3%, the base metal toughness and HAZ toughness are significantly deteriorated. Therefore, it was set as 0.001 to 0.3% of range, respectively.
Nb：0.002〜0.05％、Ti：0.002〜0.05％、V：0.002〜0.2％のうちの１種または2種以上
Nb、Ti、Vはいずれも、鋼材の強度を増加させる元素であり、必要に応じて選択して含有できる。このような効果を得るためには、 Nb：0.002％、Ti：0.002％、V：0.002％以上をそれぞれ含有することが好ましい。一方，Nb：0.05％、Ti：0.05％、V：0.2％を超えてそれぞれ含有すると靭性が劣化する。このため、Nb：0.05％以下、Ti：0.05％以下、V：0.2％以下の範囲とするのがよい。
Nb: 0.002-0.05%, Ti: 0.002-0.05%, V: One or more of 0.002-0.2%
Nb, Ti, and V are all elements that increase the strength of the steel material, and can be selected and contained as necessary. In order to obtain such an effect, it is preferable to contain Nb: 0.002%, Ti: 0.002%, and V: 0.002% or more. On the other hand, if Nb: 0.05%, Ti: 0.05%, V: more than 0.2%, the toughness deteriorates. For this reason, it is good to set it as the range of Nb: 0.05% or less, Ti: 0.05% or less, and V: 0.2% or less.
B：0.0003〜0.003％
Bは鋼材の強度を増加させる元素であり、必要に応じて含有できる。このような効果を得るためには、0.0003％以上含有することが好ましい。一方，0.003％を超えて含有すると靭性が劣化する。このため、Bは0.0003〜0.003％とするのが好ましい。
B: 0.0003-0.003%
B is an element that increases the strength of the steel material and can be contained as required. In order to acquire such an effect, it is preferable to contain 0.0003% or more. On the other hand, if it exceeds 0.003%, the toughness deteriorates. For this reason, B is preferably 0.0003 to 0.003%.
Ca：0.0002〜0.01％、REM：0.001〜0.01％のうちの１種または2種以上
Ca、REMはいずれもHAZの靭性向上に寄与する元素であり、必要に応じて選択して含有できる。このような効果は、Ca：0.0002％、REM：0.001％以上の含有で顕著となるが，Ca：0.01％，REM：0.01％を超えて含有すると靭性が劣化する。このため、Ca：0.01％、REM：0.01％以下の範囲とするのがよい．
Ti:0.005〜0.025%、N:0.0030〜0.0065%
Ti、Nは溶鋼凝固時にTiNを形成する。そして、TiNは溶接時の加熱によるオーステナイト粒の粗大化を防止し、さらに微細フェライトを多量生成する。この作用により、大入熱溶接熱影響部の靱性を向上させる。Tiが0.005%未満、Nが0.0030%未満では、溶鋼凝固時でのTiNの形成量が少なく、また、大入熱溶接時の加熱により、TiNの多くが溶解するため、上記作用が得られない。一方、Tiが0.025%超えでは、母材靱性に悪影響を与える。また、N量が0.0065%を超えると、連続鋳造割れの発生、溶接熱影響部での島状マルテンサイトの生成による靱性劣化、母材より溶接金属部への希釈による溶接金属部の靱性劣化を引き起こす。従って、Ti:0.005〜0.025%、N:0.0030〜0.0065%の範囲とした。
本発明の鋼材では、上記した成分以外の残部はFeおよび不可避的不純物である。
Ca: 0.0002 to 0.01%, REM: One or more of 0.001 to 0.01%
Ca and REM are both elements that contribute to improving the toughness of HAZ, and can be selected and contained as necessary. Such an effect becomes remarkable when the content of Ca is 0.0002% and REM is 0.001% or more, but when the content exceeds Ca: 0.01% and REM: 0.01%, the toughness deteriorates. For this reason, it is good to set it as the range of Ca: 0.01% and REM: 0.01% or less.
Ti: 0.005-0.025%, N: 0.0030-0.0065%
Ti and N form TiN during solidification of molten steel. TiN prevents austenite grains from coarsening due to heating during welding, and generates a large amount of fine ferrite. This action improves the toughness of the high heat input weld heat affected zone. When Ti is less than 0.005% and N is less than 0.0030%, the amount of TiN formed during solidification of molten steel is small, and the TiN is dissolved by heating during high heat input welding, so the above effect cannot be obtained. . On the other hand, if Ti exceeds 0.025%, the toughness of the base metal is adversely affected. If the N content exceeds 0.0065%, continuous casting cracks occur, toughness deteriorates due to the formation of island martensite in the heat affected zone, and toughness deteriorates in the weld metal due to dilution from the base metal to the weld metal. cause. Therefore, Ti: 0.005 to 0.025%, N: 0.0030 to 0.0065% range.
In the steel material of the present invention, the balance other than the above components is Fe and inevitable impurities.
２．製造方法について
つぎに，本発明の鋼材の好ましい製造方法について説明する。まず、上記した成分組成の溶鋼を転炉、電気炉等の通常の溶製方法で溶製し、連続鋳造法、造塊法等の通常公知の鋳造方法で鋼素材とするのが好ましい。なお溶鋼で取鍋精錬、真空脱ガス等の処理を付加しても良いことは言うまでもない。
2. About a manufacturing method Below, the preferable manufacturing method of the steel materials of this invention is demonstrated. First, it is preferable that molten steel having the above-described component composition is melted by an ordinary melting method such as a converter or an electric furnace, and is made into a steel material by an ordinary known casting method such as a continuous casting method or an ingot-making method. It goes without saying that treatments such as ladle refining and vacuum degassing may be added to the molten steel.
ついで、得られた鋼素材を、結晶粒粗大化防止の観点から好ましくは1050〜1250℃の温度に加熱したのち、所望の寸法形状に熱間圧延するか、あるいは鋼素材の温度が熱間圧延可能な程度に高温である場合には、加熱することなく、あるいは均熱する程度で、ただちに所望の寸法形状の鋼材に熱間圧延することが出来る。 Next, the obtained steel material is preferably heated to a temperature of 1050 to 1250 ° C. from the viewpoint of preventing grain coarsening, and then hot rolled to a desired size or shape, or the temperature of the steel material is hot rolled. When the temperature is as high as possible, it can be immediately hot-rolled into a steel material having a desired size and shape without heating or with a level of soaking.
本発明では、強度確保の観点から、熱間圧延では、熱間仕上圧延終了温度および熱間仕上圧延終了後の冷却速度を適正範囲とすることが好ましい。ここで、熱間仕上圧延終了温度は700℃以上とするのが好ましく、また、熱間仕上圧延終了後は空冷、または冷却速度100℃/以下の加速冷却を行うことができる。また，冷却後，再加熱処理を行うこともできる。
In the present invention, from the viewpoint of securing strength, in hot rolling, it is preferable to set the hot finish rolling end temperature and the cooling rate after the hot finish rolling end to an appropriate range. Here, the finish temperature of hot finish rolling is preferably 700 ° C. or higher, and after the finish of hot finish rolling, air cooling or accelerated cooling at a cooling rate of 100 ° C./less can be performed. In addition, after cooling, reheating treatment can be performed.
表1に示す化学成分の鋼を転炉で溶製し、連続鋳造法でスラブとし、このスラブを加熱炉に挿入して1150℃に加熱したのち、熱間圧延し、厚鋼板（25mm厚×2500mm幅）とした。かくして得られた鋼板について、母材引張特性、衝撃特性を調査した。また、サブマージアーク溶接での入熱150kJ/cm相当の熱サイクルを付与して再現したHAZの衝撃特性（再現HAZ衝撃特性）を評価した。その結果、表２に示すとおり、P含有量が本発明範囲を超える鋼No.20では、母材衝撃特性および再現HAZ衝撃特性が劣化した。 Steel of the chemical composition shown in Table 1 was melted in a converter and made into a slab by a continuous casting method. This slab was inserted into a heating furnace and heated to 1150 ° C. 2500 mm width). The base material tensile characteristics and impact characteristics of the steel sheets thus obtained were investigated. In addition, the impact characteristics (reproduced HAZ impact characteristics) of HAZ reproduced by applying a heat cycle equivalent to 150 kJ / cm heat input in submerged arc welding were evaluated. As a result, as shown in Table 2, in steel No. 20 in which the P content exceeds the range of the present invention, the base metal impact characteristics and the reproduced HAZ impact characteristics deteriorated.
次に、それぞれの鋼板から5mm×100mm×200mmの暴露試験片を採取した。これら試験片にショットブラスト後、ジンクリッチプライマー（約15μm）、タールエポキシ樹脂塗料（約200μm）を塗布した。その後、カッターナイフで、試験片の地鉄表面まで達する80mm長さのスクラッチを付加した。これら試験片を、実船のバラストタンクアッパーデッキ裏に装着、暴露試験に供した。暴露期間は2年間であり、このバラストタンク内の環境は、バラストタンク内に海水が入っている期間：約20日、バラストタンク内に海水が入っていない期間：約20日を1サイクルとした環境であった。暴露試験後、スクラッチ周囲のさびによる塗膜膨れおよび剥離面積を測定した。そして，ベース鋼（鋼No.18）に対する比率を算出した。その結果を表２に示す。 Next, an exposure test piece of 5 mm × 100 mm × 200 mm was taken from each steel plate. After shot blasting to these test pieces, a zinc rich primer (about 15 μm) and a tar epoxy resin paint (about 200 μm) were applied. Thereafter, a 80 mm long scratch reaching the surface of the test piece was added with a cutter knife. These test pieces were mounted on the back of the ballast tank upper deck of an actual ship and subjected to an exposure test. The exposure period is 2 years, and the environment in this ballast tank is one cycle: the period when seawater is in the ballast tank: about 20 days, the period when seawater is not in the ballast tank: about 20 days It was an environment. After the exposure test, the swelling of the coating film and the peeled area due to rust around the scratch were measured. The ratio to the base steel (steel No. 18) was calculated. The results are shown in Table 2.
本発明鋼の（鋼No.1〜17）の面積率は60％以下であり、本発明の鋼材は優れた耐食性を有していることが分かる。一方、本発明の範囲を外れる比較例（鋼No.19，21,22）の面積率は、それぞれ本発明例に比べて大きくなっている。比較例（鋼No.20）はW量が本発明範囲内であるため、面積率は43％と小さな値を示すが、上記のとおり，母材衝撃特性および再現HAZ衝撃特性が劣化している。 The area ratio of (Steel No. 1 to 17) of the steel of the present invention is 60% or less, and it can be seen that the steel material of the present invention has excellent corrosion resistance. On the other hand, the area ratios of the comparative examples (steel Nos. 19, 21, and 22) outside the scope of the present invention are larger than those of the present invention examples. In the comparative example (steel No. 20), since the W amount is within the range of the present invention, the area ratio shows a small value of 43%. .
本発明の造船用耐食鋼は、優れた耐塗装損傷性を有するので過酷な腐食環境である船舶のバラストタンクへ適用することができる。又、バラストタンクと類似の湿潤環境の用途にも適用できる。
Since the corrosion-resistant steel for shipbuilding of the present invention has excellent paint damage resistance, it can be applied to a ballast tank of a ship which is a severe corrosive environment. It can also be used in wet environments similar to ballast tanks.
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| JP4687531B2 (en) * | 2006-03-27 | 2011-05-25 | Ｊｆｅスチール株式会社 | Steel for crude oil tank and method for producing the same |
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| JP4935579B2 (en) * | 2007-08-22 | 2012-05-23 | Ｊｆｅスチール株式会社 | Corrosion resistant steel for ships |
| JP5130828B2 (en) * | 2007-08-22 | 2013-01-30 | Ｊｆｅスチール株式会社 | High strength marine corrosion resistant steel and method for producing the same |
| JP5157518B2 (en) * | 2008-02-22 | 2013-03-06 | Ｊｆｅスチール株式会社 | Corrosion-resistant steel for marine vessels with excellent high heat input weld toughness and method for producing the same |
| JP5157519B2 (en) * | 2008-02-22 | 2013-03-06 | Ｊｆｅスチール株式会社 | Corrosion-resistant steel for marine vessels with excellent high heat input weld toughness and method for producing the same |
| JP5076961B2 (en) * | 2008-02-22 | 2012-11-21 | Ｊｆｅスチール株式会社 | High strength marine corrosion resistant steel with excellent high heat input weld toughness and method for producing the same |
| JP5669352B2 (en) * | 2008-12-19 | 2015-02-12 | 株式会社神戸製鋼所 | Dissimilar material joint with excellent corrosion resistance against contact corrosion of dissimilar metals |
| JP5353283B2 (en) * | 2009-02-12 | 2013-11-27 | Ｊｆｅスチール株式会社 | Corrosion-resistant steel for marine vessels and method for producing the same |
| JP5453840B2 (en) * | 2009-02-25 | 2014-03-26 | Ｊｆｅスチール株式会社 | Marine steel with excellent corrosion resistance |
| JP5481980B2 (en) * | 2009-07-16 | 2014-04-23 | Ｊｆｅスチール株式会社 | Marine steel with excellent film swell resistance |
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