JP2011058038A - Hot rolled shape steel for vessel having excellent corrosion resistance, and method for producing the same - Google Patents
Hot rolled shape steel for vessel having excellent corrosion resistance, and method for producing the same Download PDFInfo
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Abstract
Description
本発明は、石炭や鉱石の運搬船、原油タンカー、LPGやLNGの運搬船、ケミカルタンカー、コンテナ船、ばら積み船、木材専用船、チップ専用船、冷凍運搬船、自動車専用船、重量物船、RORO船、石灰石専用船、セメント専用船等の各種船舶に用いられる船舶用形鋼に関し、特に、厳しい海水による腐食環境下にあるバラストタンクの縦通材(ロンジ材)等に用いられる船舶用熱間圧延形鋼とその製造方法に関するものである。ここで、上記熱間圧延形鋼とは、具体的には、等辺山形鋼、不等辺山形鋼、不等辺不等厚山形鋼、溝形鋼、球平形鋼、T形鋼などの熱間圧延によって製造されたものを言う。 The present invention includes coal and ore carrier, crude oil tanker, LPG and LNG carrier, chemical tanker, container ship, bulk carrier, wood carrier, chip carrier, refrigerated carrier, automobile carrier, heavy ship, RORO ship, Hot-rolled form for ships used for longitudinal members (longi materials) of ballast tanks in corrosive environments with severe seawater, especially for ship shaped steels used in various ships such as limestone ships and cement ships The present invention relates to steel and its manufacturing method. Here, the hot-rolled section steel is specifically hot-rolled such as equilateral chevron, non-equal chevron, uneven unequal thick chevron, channel steel, spherical flat steel, T-shape steel, etc. Says what was manufactured by.
船舶のバラストタンクは、積荷がない時に、海水を注入して船舶の安定航行を可能とする役目を担うものであるため、海水による厳しい腐食を受ける環境下におかれている。そこで、バラストタンクに用いられる鋼材には、通常、防食のためにエポキシ樹脂塗膜形成による防食と電気防食とが施されている。 Since the ship's ballast tank plays a role of injecting seawater to enable stable navigation of the ship when there is no cargo, it is placed in an environment subject to severe corrosion by seawater. Therefore, the steel material used for the ballast tank is usually subjected to anticorrosion by forming an epoxy resin coating and cathodic protection for corrosion prevention.
しかし、それらの防食対策を講じても、バラストタンクの腐食環境は依然として厳しい状態にある。たとえば、バラストタンクに海水を注入しているときは、海水に完全に浸されている部分は、電気防食が機能するため、腐食を効果的に抑制することができる。しかし、バラストタンクの最上部付近、特に上甲板の裏側部分は、海水に漬かることがなく、海水の飛沫のみを浴びる状態におかれているため、この部位では、電気防食が機能しない。さらに、この部位は、太陽光によって鋼板温度が上昇するため、腐食環境はより厳しいものとなる。一方、バラストタンクに海水が注入されていないときは、電気防食が全く働かないため、残留付着した塩分によって、激しい腐食を受けることになる。 However, even if these anticorrosion measures are taken, the corrosive environment of the ballast tank is still severe. For example, when seawater is being injected into the ballast tank, the portion that is completely immersed in the seawater functions as an anticorrosion, so that corrosion can be effectively suppressed. However, the vicinity of the uppermost part of the ballast tank, particularly the backside portion of the upper deck, is not soaked in seawater and is in a state where it is exposed to only seawater splashes. Furthermore, since the steel plate temperature is increased by sunlight, the corrosive environment becomes more severe in this part. On the other hand, when seawater is not injected into the ballast tank, since the anti-corrosion does not work at all, it will be severely corroded by residual adhered salt.
そのため、上記のような激しい腐食環境下にあるバラストタンクの防食塗膜の寿命は、一般に約10年と言われており、船舶の寿命(約20年)の半分程度である。従って、残りの10年間は、補修塗装等の処理を施すことよって、耐食性を維持しているのが実情である。しかし、バラストタンクの腐食環境は非常に厳しいものがあるため、補修塗装を行ってもその効果を長時間持続させるのは難しい。また、補修塗装は、狭い空間での作業となるため、好ましい作業環境ではない。そこで、補修塗装までの期間をできる限り延長すると共に、作業負荷を軽減できる耐食性に優れた鋼材の開発が望まれている。 Therefore, it is generally said that the anticorrosive coating film of the ballast tank under the severe corrosive environment as described above has a life of about 10 years, which is about half the life of the ship (about 20 years). Therefore, in the remaining 10 years, the actual situation is that the corrosion resistance is maintained by performing a treatment such as repair painting. However, since the corrosive environment of the ballast tank is very severe, it is difficult to maintain the effect for a long time even if repair coating is performed. In addition, the repair coating is not a preferable working environment because it is performed in a narrow space. Therefore, it is desired to develop a steel material with excellent corrosion resistance that can extend the period until repair coating as much as possible and reduce the work load.
このような背景から、バラストタンク等、厳しい腐食環境下で用いられる鋼材自体の耐食性を向上する技術が幾つか提案されている。たとえば、特許文献1には、C:0.20mass%以下の鋼に、耐食性改善元素として、Cu:0.05〜0.50mass%、W:0.01〜0.05mass%未満を添加し、さらに、Ge,Sn,Pb,As,Sb,Bi,TeおよびBeのうちの1種または2種以上を0.01〜0.2mass%添加した耐食低合金鋼が開示されている。また、特許文献2には、C:0.20mass%以下の鋼材に、耐食性改善元素として、Cu:0.05〜0.50mass%、W:0.05〜0.5mass%を添加し、さらに、Ge,Sn,Pb,As,Sb,Bi,TeおよびBeのうちの1種もしくは2種以上を0.01〜0.2mass%添加した耐食性低合金鋼が開示されている。また、特許文献3には、C:0.15mass%以下の鋼に、Cu:0.05mass%以上0.15mass%未満、W:0.05〜0.5mass%を添加した耐食性低合金鋼が開示されている。 Against this background, several techniques for improving the corrosion resistance of steel materials themselves used in severe corrosive environments such as ballast tanks have been proposed. For example, in Patent Document 1, Cu: 0.05 to 0.50 mass%, W: 0.01 to less than 0.05 mass%, as a corrosion resistance improving element, is added to steel of C: 0.20 mass% or less, Furthermore, a corrosion-resistant low alloy steel is disclosed in which one or more of Ge, Sn, Pb, As, Sb, Bi, Te and Be are added in an amount of 0.01 to 0.2 mass%. Further, in Patent Document 2, Cu: 0.05 to 0.50 mass%, W: 0.05 to 0.5 mass%, as a corrosion resistance improving element, is added to a steel material having C: 0.20 mass% or less, and , Ge, Sn, Pb, As, Sb, Bi, Te, and Be are disclosed corrosion resistant low alloy steel added with 0.01 to 0.2 mass% of one or more of them. Patent Document 3 discloses a corrosion-resistant low alloy steel in which Cu: 0.05 mass% or more and less than 0.15 mass% and W: 0.05 to 0.5 mass% are added to steel of C: 0.15 mass% or less. It is disclosed.
また、特許文献4には、C:0.15mass%以下の鋼に、耐食性改善元素として、P:0.03〜0.10mass%、Cu:0.1〜1.0mass%、Ni:0.1〜1.0mass%を添加した低合金耐食鋼材に、タールエポキシ塗料、ピュアエポキシ塗料、無溶剤型エポキシ塗料、ウレタン塗料等の防食塗料を塗布して樹脂被覆したバラストタンクが開示されている。この技術は、鋼材自身の耐食性向上により防食塗装の寿命を延長し、船舶の使用期間である20〜30年に亘ってメンテナンスフリー化を実現しようとするものである。 In Patent Document 4, C: 0.15 mass% or less of steel, P: 0.03-0.10 mass%, Cu: 0.1-1.0 mass%, Ni: 0.0. A ballast tank is disclosed in which an anticorrosion paint such as a tar epoxy paint, a pure epoxy paint, a solventless epoxy paint, and a urethane paint is applied to a low alloy corrosion resistant steel material to which 1 to 1.0 mass% is added and is resin-coated. This technology intends to extend the life of the anticorrosion coating by improving the corrosion resistance of the steel material itself, and to realize maintenance-free over 20 to 30 years, which is the use period of the ship.
また、特許文献5には、C:0.15mass%以下の鋼に、耐食性改善元素として、Cr:0.2〜5mass%を添加して耐食性を向上し、船舶のメンテナンスフリー化を実現しようとする提案がなされている。さらに、特許文献6には、C:0.15mass%以下の鋼に、耐食性改善元素として、Cr:0.2〜5mass%を添加した鋼材を構成材料として使用すると共に、バラストタンク内部の酸素ガス濃度を大気中の値に対して0.5以下の比率とすることを特徴とするバラストタンクの防食方法が提案されている。 In Patent Document 5, an attempt is made to improve the corrosion resistance by adding 0.2% to 5% by mass as a corrosion resistance improving element to C: 0.15 mass% or less steel, thereby realizing a maintenance-free ship. Proposals have been made. Further, Patent Document 6 uses a steel material in which Cr: 0.2 to 5 mass% is added as a corrosion resistance improving element to steel of C: 0.15 mass% or less as a constituent material, and oxygen gas inside the ballast tank. An anticorrosion method for a ballast tank has been proposed in which the concentration is a ratio of 0.5 or less with respect to the value in the atmosphere.
また、特許文献7には、C:0.1mass%以下の鋼に、Cr:0.5〜3.5mass%を添加することで耐食性を向上し、船舶のメンテナンスフリー化を実現しようとする提案がなされている。さらに、特許文献8には、C:0.001〜0.025mass%の鋼に、Ni:0.1〜4.0mass%を添加することで、耐塗膜損傷性を向上し、補修塗装などの保守費用を軽減する船舶用鋼材が開示されている。 Further, Patent Document 7 proposes to improve corrosion resistance by adding Cr: 0.5 to 3.5 mass% to steel of C: 0.1 mass% or less, and to realize a maintenance-free ship. Has been made. Furthermore, in Patent Document 8, by adding Ni: 0.1-4.0 mass% to C: 0.001-0.025 mass% steel, coating film damage resistance is improved, repair coating, etc. Marine steel materials that reduce maintenance costs are disclosed.
また、特許文献9には、C:0.01〜0.25mass%の鋼に、Cu:0.01〜2.00mass%、Mg:0.0002〜0.0150mass%を添加することで、船舶外板、バラストタンク、カーゴオイルタンク、鉱炭石カーゴホールド等の使用環境においても耐食性を有する船舶用鋼が開示されている。さらに、特許文献10には、C:0.001〜0.2mass%の鋼において、Mo,WとCuとを複合添加し、不純物であるP,Sの含有量を低減することにより、原油油槽で生じる全面腐食、局部腐食を抑制する鋼が開示されている。 Moreover, in patent document 9, it is a ship by adding Cu: 0.01-2.00 mass% and Mg: 0.0002-0.0150 mass% to C: 0.01-0.25 mass% steel. Steel for ships having corrosion resistance is disclosed even in use environments such as an outer plate, a ballast tank, a cargo oil tank, and a coal ore cargo hold. Furthermore, Patent Document 10 discloses a crude oil tank by adding Mo, W and Cu in a steel of C: 0.001 to 0.2 mass% and reducing the contents of impurities P and S. Steel that suppresses general corrosion and local corrosion that occur in JIS is disclosed.
しかしながら、上記の特許文献1〜3では、バラストタンク等を構成する鋼材に通常塗布されているジンクエポキシ樹脂塗料等の塗膜存在下における耐食性については十分な検討がなされていない。また、特許文献4の鋼材は、下地金属の耐食性を向上させるために、Pを0.03〜0.10mass%と比較的多量に添加しており、溶接性および溶接部靭性の点で問題がある。また、特許文献5および特許文献6の鋼材は、Crを0.2〜5mass%含有し、また、特許文献7の鋼材は、Crを0.5〜3.5mass%と比較的多く含有しているため、いずれも溶接性および溶接部靭性に問題がある他、製造コストが高くなるという問題がある。 However, in the above Patent Documents 1 to 3, sufficient investigation has not been made on the corrosion resistance in the presence of a coating film such as a zinc epoxy resin paint that is normally applied to a steel material constituting a ballast tank or the like. Moreover, in order to improve the corrosion resistance of the base metal, the steel material of Patent Document 4 has a relatively large amount of P added, from 0.03 to 0.10 mass%, which is problematic in terms of weldability and weld toughness. is there. Moreover, the steel materials of Patent Literature 5 and Patent Literature 6 contain 0.2 to 5 mass% of Cr, and the steel material of Patent Literature 7 contains relatively large amount of Cr to 0.5 to 3.5 mass%. Therefore, both have problems in weldability and weld zone toughness, as well as the problem of increased manufacturing costs.
また、特許文献8の鋼材は、C含有量が低く、Ni含有量が高いため、製造コストが高くなるという問題がある。さらに、特許文献9の鋼材は、Mgの添加を必須としているため、製鋼歩留りが安定せず、鋼材の機械的特性も安定しないという問題がある。さらに、特許文献10の鋼材は、H2Sが存在する環境下で使用される原油油槽用の耐食鋼であり、H2Sが存在しないバラストタンクでの耐食性は不明である。さらに、バラストタンク用鋼材に一般的に使用されているジンクプライマー塗装が施された状態での耐食性については検討がなされていない。
したがって、バラストタンクに用いられる従来技術の鋼材には、塗膜存在下での耐食性を含めて、さらなる改善の余地が残されている。
Moreover, since the steel material of patent document 8 has low C content and high Ni content, there exists a problem that manufacturing cost becomes high. Furthermore, since the steel material of Patent Document 9 requires the addition of Mg, there is a problem that the steel making yield is not stable and the mechanical properties of the steel material are not stable. Furthermore, the steel material of patent document 10 is a corrosion resistant steel for a crude oil tank used in an environment where H 2 S exists, and the corrosion resistance in a ballast tank without H 2 S is unknown. Furthermore, the corrosion resistance in a state where a zinc primer coating generally used for steel for ballast tanks is applied has not been studied.
Therefore, there is still room for further improvement in the steel materials of the prior art used for the ballast tank, including the corrosion resistance in the presence of the coating film.
ところで、一般に、船舶は、厚鋼板や薄鋼板、形鋼、棒鋼等の各種鋼材を溶接して建造されているが、これらの鋼材、中でも厚鋼板や形鋼は、使用量低減によるコスト削減や安全性確保の観点から、高強度化が進められている。そこで、厚鋼板の熱間圧延による製造においては、炭素当量を低めて高い溶接性を付与した鋼素材を、制御圧延と制御冷却を組み合わせたTMCP(Thermo−mechanical control process)を採用して、第2相として硬質のベイナイト組織を導入することで、降伏応力YSが315MPa以上の高強度化を達成している。 By the way, in general, ships are constructed by welding various steel materials such as thick steel plates, thin steel plates, shaped steels, and bar steels. However, these steel materials, especially thick steel plates and shaped steels, can be reduced in cost due to reduced usage. Higher strength is being promoted from the viewpoint of ensuring safety. Therefore, in the production of thick steel plates by hot rolling, a steel material having a low carbon equivalent and imparted high weldability is adopted by adopting TMCP (Thermo-mechanical control process) that combines controlled rolling and controlled cooling. By introducing a hard bainite structure as two phases, the yield strength YS is increased to 315 MPa or more.
一方、バラストタンクのロンジ材等に使用される鋼材、中でも、不等辺不等厚山形鋼やT形鋼などの熱間圧延により製造される形鋼は、同じ船舶に用いられる厚鋼板などと比較して断面形状・寸法が複雑であり、製品に歪みや強度むらを発生しやすいという問題がある。そのため、形鋼の圧延においては、圧延途中での曲がりや反り等の歪を配慮しながら、製造する必要があるため、たとえば、降伏応力YSが235MPa以上で引張強さTS:400MPa以上のような高強度材の造り込み手段として、厚鋼板と同様の制御圧延・加速冷却プロセスするTMCPを採用するのは難しいという問題がある。 On the other hand, steel materials used for ballast tanks such as long steel, especially steels manufactured by hot rolling such as unequal unequal thick angle steels and T-shaped steels, are compared with thick steel plates used in the same ship. As a result, the cross-sectional shape and dimensions are complicated, and there is a problem that the product is likely to be distorted and uneven in strength. Therefore, in rolling the shape steel, it is necessary to manufacture while considering distortion such as bending and warping in the middle of rolling. For example, the yield stress YS is 235 MPa or more and the tensile strength TS is 400 MPa or more. There is a problem that it is difficult to adopt TMCP which performs a controlled rolling / accelerated cooling process similar to that of a thick steel plate as means for building a high-strength material.
この問題に対しては、例えば、特許文献11に開示されているように、鋼素材を熱間圧延して製造する際に、フランジ(短辺側)部の表面温度が800〜600℃となるように仕上圧延することが行なわれている。しかし、この方法では、仕上圧延時に、温度調整のための待機時間が発生し、圧延能率の低下や製造コストの上昇を招くため、上記待機時間の発生のない製造方法の開発が望まれている。 To solve this problem, for example, as disclosed in Patent Document 11, when manufacturing a steel material by hot rolling, the surface temperature of the flange (short side) portion becomes 800 to 600 ° C. Thus, finish rolling is performed. However, in this method, during finish rolling, a waiting time for temperature adjustment occurs, which causes a reduction in rolling efficiency and an increase in manufacturing cost. Therefore, development of a manufacturing method that does not generate the waiting time is desired. .
船舶に使用されている鋼材の表面には、普通、防食塗装が施されている。上記防食塗装は、一次防錆として、ジンクプライマーを塗布し、小組み後あるいは大組み後に、二次塗装(本塗装)として、エポキシ樹脂塗装が施されるのが一般的である。したがって、船舶の鋼材表面の大部分は、ジンクプライマーとエポキシ樹脂の2層構造の防食塗装が施されている。しかし、鋼材の溶接部は、溶接時の熱によってジングプライマーが焼失するため、溶接後から本塗装までの間の防錆対策として、ジンクプライマーによる補修塗装(タッチアップ)が施されることがあるが、本塗装までの期間が短い場合には、補修塗装が行われないこともある。また、建造後、長年に亘って使用された船舶では、上記塗膜が劣化し、防錆機能を十分に果たしていない部分があったり、塗膜が剥離して鋼材表面が裸状態になっていたりする部分が存在する。
つまり、就航している船舶の鋼材の表面には、ジンクプライマーとエポキシ樹脂の2層塗膜が存在している部分と、エポキシ樹脂の塗膜のみの部分と、裸状態の部分の3つの状態が存在する。したがって、船舶の耐食性を向上させるという目的を達成するためには、それらのいずれの状態においても優れた耐食性を示す船舶用鋼材であることが必要とされる。
The surface of steel used for ships is usually coated with anticorrosion. In the anticorrosion coating, a zinc primer is generally applied as a primary rust prevention, and after a small assembly or a large assembly, an epoxy resin coating is generally applied as a secondary coating (main coating). Accordingly, most of the steel surface of the ship is subjected to a two-layer anticorrosion coating of a zinc primer and an epoxy resin. However, since the ging primer is burned down by the heat during welding, the steel material welded part may be subjected to repair coating (touch-up) with a zinc primer as a rust prevention measure between welding and main coating. However, if the period until this painting is short, repair painting may not be performed. In addition, in ships that have been used for many years after construction, the above-mentioned coating film has deteriorated, there are parts that have not fulfilled the rust prevention function, or the coating film has peeled off and the steel surface has become bare There is a part to do.
In other words, on the surface of the steel material of the ship in service, there are three states: a part where a two-layer coating film of zinc primer and epoxy resin is present, a part where only an epoxy resin coating film is present, and a bare part Exists. Therefore, in order to achieve the object of improving the corrosion resistance of the ship, it is necessary to be a marine steel material that exhibits excellent corrosion resistance in any of these states.
さらに、前述したように、バラストタンクのロンジ材等に使用される鋼材、中でも、不等辺不等厚山形鋼やT形鋼などの熱間圧延により製造される形鋼では、高強度を達成する手段として、厚鋼板と同様のTMCPを採用するのは難しい。したがって、降伏応力YSが235MPa以上で、引張強さTSが400MPa以上のような高強度形鋼を熱間圧延で製造するためには、独自の製造方法を検討する必要がある。 Furthermore, as described above, high strength is achieved with steel materials used for ballast tanks, such as long steels, and in particular, shape steels manufactured by hot rolling such as unequal side unequal thick angle steel and T-shape steel. As a means, it is difficult to adopt the same TMCP as the thick steel plate. Therefore, in order to manufacture a high-strength steel having a yield stress YS of 235 MPa or more and a tensile strength TS of 400 MPa or more by hot rolling, it is necessary to study a unique manufacturing method.
そこで、本発明の目的は、船舶のバラストタンク等の厳しい腐食環境下において、塗膜の存在状態に左右されることなく優れた耐食性を発揮して、補修塗装までの期間の延長が可能となり、ひいては補修塗装の作業軽減を図ることができる耐食性に優れる船舶用熱間圧延形鋼を提供するとともに、熱間圧延における歪や強度むらを起こすことなく高い生産性をもって製造することができる船舶用熱間圧延形鋼の製造方法を提案することにある。 Therefore, the object of the present invention is to exhibit excellent corrosion resistance without being affected by the presence state of the coating film in a severe corrosive environment such as a ballast tank of a ship, and it is possible to extend the period until repair coating, As a result, it is possible to provide marine hot-rolled section steel with excellent corrosion resistance that can reduce the work of repair coating, and to produce marine heat that can be manufactured with high productivity without causing distortion and uneven strength in hot rolling. The purpose of this invention is to propose a method for producing hot rolled steel.
発明者らは、海水による厳しい腐食を受ける環境下でも表面状態(塗膜の存在状態)に左右されることなく優れた耐食性を発揮すると共に、降伏応力YSが235MPa以上の高強度を有する形鋼の開発に向けて鋭意研究を重ねた。その結果、耐食性向上のための必須元素として、W,CrおよびNbを複合添加することによって、ジンクプライマーとエポキシ樹脂の2層塗膜存在下のみならず、エポキシ樹脂塗膜存在下および無塗装の裸状態のいずれの状態においても優れた耐食性を発揮する船舶用形鋼が得られること、および、これにさらに、Sb,Sn等の耐食性向上元素を適正量添加することにより、より優れた耐食性を示す船舶用形鋼が得られること、そしてさらに、上記のようにNbを必須元素として添加したことによって、熱間圧延での仕上温度を800℃超としても、圧延後の鋼組織が加工フェライトを含まないフェライトとパーライトからなる組織でありながら、所期した高強度化を達成することができるので、生産性や溶接性等を阻害することなく、安価に船舶用形鋼を製造し得ることを見出し、本発明を完成させた。 The inventors exhibit excellent corrosion resistance without being influenced by the surface state (existing state of the coating film) even in an environment subject to severe corrosion by seawater, and have a high strength with a yield stress YS of 235 MPa or more. Intensive research for the development of. As a result, by adding W, Cr and Nb as essential elements for improving corrosion resistance, not only in the presence of a two-layer coating film of zinc primer and epoxy resin, but also in the presence or absence of an epoxy resin coating film Ship shape steel that exhibits excellent corrosion resistance in any state of the bare state can be obtained, and by adding an appropriate amount of corrosion resistance improving elements such as Sb and Sn to this, further excellent corrosion resistance can be obtained. The obtained steel shape steel can be obtained, and furthermore, by adding Nb as an essential element as described above, the steel structure after the rolling has processed ferrite even if the finishing temperature in hot rolling exceeds 800 ° C. Although it is a structure consisting of ferrite and pearlite not included, it can achieve the expected high strength, so without interfering with productivity and weldability, It found that it is possible to manufacture the marine section steel to the valence, and completed the present invention.
すなわち、本発明は、C:0.05〜0.20mass%、Si:0.05〜0.50mass%、Mn:0.1〜2.0mass%、P:0.025mass%以下、S:0.01mass%以下、Al:0.005〜0.10mass%、W:0.01〜1.0mass%、Cr:0.01mass%以上0.20mass%未満、Nb:0.001〜0.03mass%、N:0.001〜0.008mass%を含有し、残部がFeおよび不可避的不純物からなる成分組成を有し、加工フェライトを含まないフェライトとパーライト組織とからなるミクロ組織を有する船舶用熱間圧延形鋼である。 That is, the present invention is C: 0.05-0.20 mass%, Si: 0.05-0.50 mass%, Mn: 0.1-2.0 mass%, P: 0.025 mass% or less, S: 0 .01 mass% or less, Al: 0.005 to 0.10 mass%, W: 0.01 to 1.0 mass%, Cr: 0.01 mass% or more and less than 0.20 mass%, Nb: 0.001 to 0.03 mass% , N: 0.001 to 0.008 mass%, the remainder having a component composition composed of Fe and inevitable impurities, and having a microstructure composed of ferrite and pearlite structure not containing processed ferrite Rolled section steel.
また、本発明の船舶用熱間圧延形鋼は、上記成分組成に加えてさらに、下記A〜E群のうちの少なくとも1群の成分を含有することが好ましい。
記
A群;Sb:0.001〜0.3mass%およびSn:0.001〜0.3mass%のうちから選ばれる1種または2種
B群;Cu:0.005〜0.5mass%、Ni:0.005〜0.25mass%、Mo:0.01〜0.5mass%およびCo:0.01〜1.0mass%のうちから選ばれる1種または2種以上
C群;Ti:0.001〜0.1mass%、Zr:0.001〜0.1mass%およびV:0.002〜0.2mass%のうちから選ばれる1種または2種以上
D群;B:0.0002〜0.003mass%
E群;Ca:0.0002〜0.01mass%、REM:0.0002〜0.015mass%およびY:0.0001〜0.1mass%のうちから選ばれる1種または2種以上
Moreover, in addition to the said component composition, it is preferable that the hot rolled shape steel for ships of this invention contains the component of at least 1 group of the following AE group further.
Group A; Sb: 0.001 to 0.3 mass% and Sn: 0.001 to 0.3 mass% or one selected from Group B; Cu: 0.005 to 0.5 mass%, Ni : 0.005 to 0.25 mass%, Mo: 0.01 to 0.5 mass%, and Co: 0.01 to 1.0 mass%, one or more C groups; Ti: 0.001 ~ 0.1 mass%, Zr: 0.001 to 0.1 mass%, and V: 0.002 to 0.2 mass%, one or more selected from group D; B: 0.0002 to 0.003 mass %
Group E; Ca: 0.0002 to 0.01 mass%, REM: 0.0002 to 0.015 mass%, and Y: 0.0001 to 0.1 mass%, or one or more selected from the group
また、本発明の船舶用熱間圧延形鋼は、形鋼の表面に、エポキシ樹脂塗膜、ジンクプライマー塗膜、および、ジンクプライマー塗膜とエポキシ樹脂塗膜のいずれかの塗膜を形成してなることを特徴とする。 The marine hot-rolled section steel of the present invention forms an epoxy resin coating, a zinc primer coating, and any one of a zinc primer coating and an epoxy resin coating on the surface of the shape steel. It is characterized by.
また、本発明は、上記のいずれかに記載の成分組成を有する鋼素材を1000〜1350℃に加熱後、圧延仕上温度を800℃超とする熱間圧延し、放冷して、加工フェライトを含まないフェライトとパーライト組織とからなるミクロ組織とすることを特徴とする船舶用熱間圧延形鋼の製造方法を提案する。 In addition, the present invention is a method in which a steel material having any of the above-described component compositions is heated to 1000 to 1350 ° C. and then hot-rolled with a rolling finishing temperature exceeding 800 ° C. We propose a method for manufacturing a hot-rolled section steel for marine vessels, characterized by having a microstructure comprising no ferrite and a pearlite structure.
本発明によれば、高強度でかつ海水による厳しい腐食を受ける環境下でも優れた耐食性を発揮する船舶用熱間圧延形鋼を生産性よく安価に製造することができる。また、本発明の形鋼は、耐食性に優れるので、船舶の補修塗装までの期間の延長および補修塗装の作業負荷軽減にも大きく寄与することができる。 ADVANTAGE OF THE INVENTION According to this invention, the hot rolled shape steel for ships which exhibits the high corrosion resistance in the environment which receives high intensity | strength and severe corrosion by seawater can be manufactured with low productivity and low cost. In addition, since the shape steel of the present invention is excellent in corrosion resistance, it can greatly contribute to the extension of the period until repair painting of a ship and reduction of the work load of repair painting.
発明者らは、就航している船舶の鋼材に存在する3つの状態、即ち、ジンクプライマーとエポキシ樹脂の2層塗膜を有する状態、エポキシ樹脂塗膜のみを有する状態および保護被膜のない裸状態のいずれの状態においても優れた耐食性を示す船舶用熱間圧延形鋼を開発するために、以下の実験を行った。
種々の合金元素を添加した鋼を実験室的に溶製して鋼塊としたのち、熱間圧延して、板厚が5mmの熱延板とし、それらの熱延板から5mmt×100mmW×200mmLまたは5mmt×50mmW×150mmLの試験片を採取し、その試験片の表面にショットブラストを施して、表面のスケールや油分を除去した。
The inventors have three states existing in the steel materials of ships in service, namely, a state having a two-layer coating film of a zinc primer and an epoxy resin, a state having only an epoxy resin coating film, and a bare state without a protective coating film In order to develop a marine hot-rolled section steel exhibiting excellent corrosion resistance in any of these conditions, the following experiment was conducted.
Steels added with various alloy elements are melted in the laboratory to form steel ingots, and then hot rolled to form hot rolled sheets with a thickness of 5 mm. From these hot rolled sheets, 5 mmt x 100 mmW x 200 mmL Or the test piece of 5mmtx50mmWx150mmL was extract | collected, the surface of the test piece was shot-blasted, and the scale and oil component of the surface were removed.
次いで、上記試験片に、下記3種類の表面処理を施し、耐食試験用試験片を作製した。
・条件A:試験片表面に、ジンクプライマー(膜厚約15μm)とタールエポキシ樹脂(膜厚約100μm)を塗布し、2層被膜を形成
・条件B:試験片表面に、タールエポキシ樹脂(膜厚約100μm)を塗布し、単層被膜を形成
・条件C:試験片表面にショットブラストを施したままの裸状態(防食被膜なし)
なお、塗膜を形成した上記条件A,Bの試験片については、試験前に、塗膜の上からカッターナイフで地鉄表面まで達する80mm長さのスクラッチ疵を一文字状に付与した。
Next, the following three types of surface treatments were applied to the test piece to prepare a test piece for corrosion resistance test.
・ Condition A: Zinc primer (film thickness of about 15 μm) and tar epoxy resin (film thickness of about 100 μm) are applied to the surface of the test piece to form a two-layer film. ・ Condition B: Tar epoxy resin (film) on the surface of the test piece (Approx. 100 μm thick) to form a single layer coating ・ Condition C: Bare state with shot blasting on test piece surface (no anticorrosion coating)
In addition, about the test piece of the said conditions A and B in which the coating film was formed, 80 mm length scratch scissors which reach | attain to a ground-iron surface with a cutter knife from the top of the coating film were provided to the character shape before the test.
上記のようにして作製した耐食試験用試験片は、その後、実船のバラストタンクの上甲板裏側の腐食環境を模擬した、(35℃、5mass%NaCl溶液噴霧×2hr)→(60℃、相対湿度(RH)5%×4hr)→(50℃、RH95%×2hr)を1サイクルとし、これを132サイクル繰返して行う塩水噴霧乾湿繰返し腐食試験に供して、耐食性を評価した。なお、耐食性は、塗膜を形成した条件AおよびBの試験片については、試験後、スクラッチ疵の周囲に発生した塗膜膨れの面積を測定することで、また、塗膜を形成してない条件Cの試験片については、試験後、脱錆した試験片質量と腐食試験前の試験片質量との差(減少量)から平均板厚減少量を算出することで評価した。 The test piece for the corrosion resistance test prepared as described above simulated the corrosive environment on the back side of the upper deck of the ballast tank of the actual ship. (35 ° C., 5 mass% NaCl solution spray × 2 hr) → (60 ° C., relative Humidity (RH) 5% × 4 hr) → (50 ° C., RH 95% × 2 hr) was taken as one cycle, and this was subjected to a salt spray dry and wet repeated corrosion test repeated 132 cycles to evaluate the corrosion resistance. Corrosion resistance is determined by measuring the area of the swollen coating film generated around the scratch ridge after the test for the test pieces of conditions A and B on which the coating film was formed. About the test piece of condition C, after the test, it evaluated by calculating an average board thickness reduction | decrease amount from the difference (reduction | decrease amount) of the test piece mass derusted and the test piece mass before a corrosion test.
上記腐食試験の結果を基にして、各合金元素の耐食性向上効果を、試験片表面の塗膜条件ごとに纏めて示したのが表1である。この結果を簡単に述べると、以下のようになる。
1)条件A(ジンクプライマー+タールエポキシ樹脂の2層塗膜)の場合;耐食性の向上に最も有効な元素はCrであり、次いでW,Nb、次いでSbである。
2)条件B(タールエポキシ樹脂の1層塗膜)の場合;耐食性の向上に最も有効な元素はWであり、次いでNb、次いでSb,Snである。
3)条件C(裸状態)の場合;耐食性の向上に最も有効な元素はWであり、次いでNb、次いでSb,Snである。
4)W,CrおよびNbの複合添加は、単独添加より、条件Aにおける耐食性を向上し、さらにSb,Snを追加添加することにより、条件Aだけでなく、条件B,Cでも顕著な耐食性改善効果が得られる。
5)Moは、条件A,B,Cでの耐食性をやや向上し、Cu,Ni,Coは、条件A,Cでの耐食性をやや向上する。
Table 1 shows the effect of improving the corrosion resistance of each alloy element for each coating film condition on the surface of the test piece based on the results of the corrosion test. The result is briefly described as follows.
1) In the case of condition A (zinc primer + tar epoxy resin two-layer coating); the most effective element for improving corrosion resistance is Cr, then W, Nb, and then Sb.
2) In the case of condition B (one-layer coating film of tar epoxy resin); W is the most effective element for improving corrosion resistance, followed by Nb, then Sb, Sn.
3) In the case of condition C (bare state); the most effective element for improving the corrosion resistance is W, then Nb, then Sb, Sn.
4) The combined addition of W, Cr and Nb improves the corrosion resistance under condition A over the addition of a single addition, and by adding Sb and Sn further, the corrosion resistance significantly improves not only under condition A but also under conditions B and C. An effect is obtained.
5) Mo slightly improves the corrosion resistance under conditions A, B, and C, and Cu, Ni, and Co slightly improves the corrosion resistance under conditions A and C.
そこで、本発明では、上記表1に示した結果に基づいて、耐食性を向上する必須の基本元素としてW,CrならびにNbを複合添加し、さらに耐食性が要求される場合には、Sb,Snから選ばれる1種または2種を追加して添加する成分設計を採用することとした。そして、より優れた耐食性を要求される場合には、さらにCu,Ni,MoおよびCoから選ばれる1種または2種以上を添加することとした。 Therefore, in the present invention, based on the results shown in Table 1 above, W, Cr and Nb are added in combination as essential basic elements for improving the corrosion resistance, and when corrosion resistance is required, Sb and Sn are used. It was decided to adopt a component design in which one or two selected ones were additionally added. When more excellent corrosion resistance is required, one or more selected from Cu, Ni, Mo and Co are further added.
次に、本発明の耐食性に優れる船舶用形鋼が有すべき成分組成について説明する。
C:0.05〜0.20mass%
Cは、鋼の強度を高めるのに有効な元素であり、本発明では所望の強度を得るために0.05mass%以上含有させる必要がある。一方、0.20mass%を超える添加は、溶接熱影響部(HAZ)の靭性を低下させる。よって、Cは0.05〜0.20mass%の範囲とする。
Next, the component composition that the marine structural steel excellent in corrosion resistance of the present invention should have will be described.
C: 0.05-0.20 mass%
C is an element effective for increasing the strength of steel, and in the present invention, it is necessary to contain 0.05 mass% or more in order to obtain a desired strength. On the other hand, addition exceeding 0.20 mass% lowers the toughness of the weld heat affected zone (HAZ). Therefore, C is set to a range of 0.05 to 0.20 mass%.
Si:0.05〜0.50mass%
Siは、鋼の脱酸剤として、また、鋼の強度を高めるために添加される元素であり、本発明では、0.05mass%以上含有させる。しかし、0.50mass%を超える添加は、鋼の靭性を低下させるので、Siの上限は0.50mass%とする。
Si: 0.05-0.50 mass%
Si is an element added as a deoxidizer for steel and to increase the strength of steel. In the present invention, Si is contained in an amount of 0.05 mass% or more. However, since addition exceeding 0.50 mass% lowers the toughness of steel, the upper limit of Si is made 0.50 mass%.
Mn:0.1〜2.0mass%
Mnは、Sによる熱間脆性を防止すると共に、鋼の強度を高める効果がある元素であり、0.1mass%以上含有させる。しかし、2.0mass%を超える添加は、鋼の靭性および溶接性を低下させるため、Mnの上限は2.0mass%とする。好ましくは、0.5〜1.6mass%の範囲である。
Mn: 0.1 to 2.0 mass%
Mn is an element that has the effect of preventing hot brittleness due to S and increasing the strength of steel, and is contained in an amount of 0.1 mass% or more. However, since addition exceeding 2.0 mass% reduces the toughness and weldability of steel, the upper limit of Mn is set to 2.0 mass%. Preferably, it is in the range of 0.5 to 1.6 mass%.
P:0.025mass%以下
Pは、鋼の母材靭性、溶接性および溶接部靭性を低下させる有害な元素であり、できるかぎり低減するのが望ましい。特に、Pの含有量が0.025mass%を超えると、母材靭性および溶接部靭性の低下が大きくなる。よって、Pは0.025mass%以下とする。好ましくは、0.014mass%以下である。
P: 0.025 mass% or less P is a harmful element that lowers the base metal toughness, weldability, and weld toughness of steel, and is desirably reduced as much as possible. In particular, when the P content exceeds 0.025 mass%, the deterioration of the base metal toughness and the welded portion toughness increases. Therefore, P is set to 0.025 mass% or less. Preferably, it is 0.014 mass% or less.
S:0.01mass%以下
Sは、鋼の靭性および溶接性を低下させる有害な元素であり、できるかぎり低減するのが望ましく、本発明では、0.01mass%以下に制限する。
S: 0.01 mass% or less S is a harmful element that lowers the toughness and weldability of steel, and is desirably reduced as much as possible. In the present invention, it is limited to 0.01 mass% or less.
Al:0.005〜0.10mass%
Alは、鋼の脱酸剤として添加される元素であり、0.005mass%以上添加する必要がある。しかし、0.10mass%を超えて添加すると、地鉄の腐食により溶出したA13+によって地鉄表面のpHが低下し、耐食性が低下するので、Alの上限は0.10mass%とする必要がある。
Al: 0.005-0.10 mass%
Al is an element added as a deoxidizer for steel, and it is necessary to add 0.005 mass% or more. However, if it is added in excess of 0.10 mass%, the pH of the surface of the ground iron is lowered by A1 3+ eluted by corrosion of the ground iron, and the corrosion resistance is lowered. Therefore, the upper limit of Al needs to be 0.10 mass%. .
W:0.01〜1.0mass%
Wは、上述したように、ジングプライマーとエポキシ樹脂の2層塗膜の存在下での耐食性を向上し、さらに、エポキシ樹脂塗膜存在下および裸状態での耐食性を顕著に向上する効果があり、本発明では、耐食性向上元素として最も重要な元素の1つである。Wの上記効果は、0.01mass%以上の添加で発現する。しかし、添加量が1.0mass%超えると、上記効果は飽和してしまう。よって、Wは0.01〜1.0mass%の範囲とする。好ましくは0.02〜0.3mass%の範囲である。
W: 0.01-1.0 mass%
As described above, W has the effect of improving the corrosion resistance in the presence of the two-layer coating film of the ging primer and the epoxy resin, and further significantly improving the corrosion resistance in the presence of the epoxy resin coating film and in the bare state. In the present invention, it is one of the most important elements as an element for improving corrosion resistance. The above effect of W is manifested by the addition of 0.01 mass% or more. However, if the addition amount exceeds 1.0 mass%, the above effect is saturated. Therefore, W is in the range of 0.01 to 1.0 mass%. Preferably it is the range of 0.02-0.3 mass%.
なお、Wが上記のような耐食性向上効果を有する理由は、鋼板の腐食によって生成する錆の中にWO4 2−が生成され、このWO4 2−の存在によって塩化物イオンの鋼板表面からの侵入が阻止され、さらに、鋼板表面のアノード部など、pHが低下した部位に難溶性のFeWO4が生成され、このFeWO4の存在によっても、塩化物イオンの鋼板表面への侵入が阻止される結果、鋼の腐食が効果的に抑制されるからであると考えられる。また、WO4 2−のインヒビター作用によっても、鋼の腐食が抑制されると考えられる。 The reason why W has the above-described effect of improving the corrosion resistance is that WO 4 2− is generated in the rust generated by the corrosion of the steel plate, and the presence of this WO 4 2− causes chloride ions from the steel plate surface. Intrusion is prevented, and in addition, poorly soluble FeWO 4 is generated at sites where the pH is lowered, such as the anode portion of the steel sheet surface, and the presence of this FeWO 4 also prevents the penetration of chloride ions into the steel sheet surface. As a result, it is considered that corrosion of steel is effectively suppressed. Moreover, it is thought that corrosion of steel is also suppressed by the inhibitor action of WO 4 2− .
Cr:0.01mass%以上0.20mass%未満
Crは、ジンクプライマーとエポキシ樹脂の2層塗膜の存在下での耐食性を大きく向上する元素であり、本発明の船舶用熱間圧延形鋼においては重要元素の1つである。上記耐食性向上効果が得られる理由は、ジンクプライマー存在下での腐食では、ジンクプライマー中のZnが溶出して、ZnOやZnCl2・4Zn(OH)2等のZn系腐食生成物が生成されるが、Crは、このZn系腐食生成物に作用して、Zn系腐食生成物による地鉄の防食効果をより向上させるためと推定される。このような、ジンクプライマー存在下でのCrの耐食性向上効果は、0.01mass%以上の添加で得られる。しかし、0.20mass%以上添加すると、溶接部の靭性が低下する。よって、Crは、0.01mass%以上0.20mass%未満の範囲とする。好ましくは0.02〜0.15mass%の範囲である。
Cr: 0.01 mass% or more and less than 0.20 mass% Cr is an element that greatly improves the corrosion resistance in the presence of a two-layer coating film of a zinc primer and an epoxy resin. Is one of the important elements. The reason why the corrosion resistance improvement effect is obtained is that, in the corrosion in the presence of the zinc primer, Zn in the zinc primer is eluted and a Zn-based corrosion product such as ZnO or ZnCl 2 · 4Zn (OH) 2 is generated. However, it is presumed that Cr acts on this Zn-based corrosion product to further improve the anticorrosion effect of the ground iron by the Zn-based corrosion product. Such an effect of improving the corrosion resistance of Cr in the presence of the zinc primer can be obtained by addition of 0.01 mass% or more. However, when 0.20 mass% or more is added, the toughness of the welded portion decreases. Therefore, Cr is in a range of 0.01 mass% or more and less than 0.20 mass%. Preferably it is the range of 0.02-0.15 mass%.
Nb:0.001〜0.03mass%
Nbは、上述したように、鋼の存在状態にかかわらず耐食性を高める元素である。
また、Nbは、(フェライト+パーライト)組織中のフェライトの粒径を微細化し、鋼の強度を高める元素でもある。以下、Nbの強度特性に及ぼす影響を調査した基礎実験について説明する。
表2に示した成分組成を有するNo.1〜5の鋼を真空溶解炉または転炉で溶製してブルームとし、このブルームを加熱炉で再加熱後、表3に示した条件で熱間圧延して、同じく表3に示した断面寸法の不等辺不等厚山形鋼(NAB)を製造した。次いで、上記不等辺不等厚山形鋼の短辺から、JIS Z2201に規定された1A号引張試験片を採取して引張試験を行い、降伏応力YS、引張強さTSおよび伸びElを測定した。また、不等辺不等厚山形鋼の短辺を20kJ/cmの入熱で突合せ多層盛り溶接(GMAW)し、そのHAZ中央部から、シャルピー衝撃試験片(2mmVノッチ試験片)を採取し、−20℃でのシャルピー衝撃試験における吸収エネルギーを測定した。なお、不等辺不等厚山形鋼の短辺からは、別途、組織観察用の試料を採取し、光学顕微鏡を用いて、板厚1/4部におけるミクロ組織を倍率200倍で観察し、扁平化した加工フェライトが存在しないことを確認した。
Nb: 0.001 to 0.03 mass%
As described above, Nb is an element that enhances corrosion resistance regardless of the presence of steel.
Nb is also an element that refines the grain size of ferrite in the (ferrite + pearlite) structure and increases the strength of the steel. Hereinafter, a basic experiment for investigating the influence of Nb on the strength characteristics will be described.
No. having the component composition shown in Table 2. The steel of 1-5 was melted in a vacuum melting furnace or converter to form a bloom, and this bloom was reheated in a heating furnace, and then hot-rolled under the conditions shown in Table 3, and the cross section shown in Table 3 A non-uniform unequal thickness angle steel (NAB) was produced. Next, from the short side of the unequal side unequal thickness steel, a No. 1A tensile test piece defined in JIS Z2201 was sampled and subjected to a tensile test, and the yield stress YS, tensile strength TS, and elongation El were measured. In addition, the short sides of the unequal unequal thickness chevron are butt multi-layered (GMAW) with a heat input of 20 kJ / cm, and a Charpy impact test piece (2 mmV notch test piece) is taken from the center of the HAZ. The absorbed energy in a Charpy impact test at 20 ° C. was measured. In addition, from the short side of the unequal side unequal thickness angle steel, a sample for observing the structure is separately collected, and the microstructure at the ¼ part thickness is observed at a magnification of 200 times using an optical microscope. It was confirmed that the processed ferrite was not present.
上記の試験の結果を表4に示した。この結果から、Nbを0.001mass%以上添加した鋼素材を800℃超の仕上温度で熱間圧延することで、加工フェライトを含まないフェライトとパーライト組織とからなるミクロ組織でありながら、靭性の低下を伴うことなく高強度(TS≧400MPa)を達成できることを新規に見出した。ただし、Nbの添加量が0.03mass%を超えると、鋼の強度が上昇し過ぎて靭性が大きく低下する。よって、本発明では、Nbは0.001〜0.03mass%の範囲で添加する。好ましくは、0.005〜0.03mass%の範囲である。 The results of the above test are shown in Table 4. From this result, the steel material added with 0.001 mass% or more of Nb is hot-rolled at a finishing temperature of over 800 ° C., so that the toughness of the microstructure is composed of ferrite and pearlite structure not containing processed ferrite. It has been newly found that high strength (TS ≧ 400 MPa) can be achieved without a decrease. However, if the amount of Nb added exceeds 0.03 mass%, the strength of the steel increases too much and the toughness is greatly reduced. Therefore, in the present invention, Nb is added in the range of 0.001 to 0.03 mass%. Preferably, it is the range of 0.005-0.03 mass%.
N:0.001〜0.008mass%
Nは、鋼の靭性を低下する有害な成分である。したがって、靭性の向上を図るためには、Nはできるだけ低減することが望ましく、本発明では、上限を0.008mass%とする。しかし、工業的規模で、Nを0.001mass%未満に低減するのは難しい。よって、Nは0.001〜0.008mass%の範囲とする。
N: 0.001 to 0.008 mass%
N is a harmful component that lowers the toughness of steel. Therefore, in order to improve toughness, it is desirable to reduce N as much as possible. In the present invention, the upper limit is set to 0.008 mass%. However, it is difficult to reduce N to less than 0.001 mass% on an industrial scale. Therefore, N is set to a range of 0.001 to 0.008 mass%.
また、本発明の船舶用熱間圧延形鋼は、より優れた耐食性を得ることを目的として、上記成分に加えてさらに、Sb:0.001〜0.3mass%およびSn:0.001〜0.3mass%のうちの1種または2種を添加することができる。
Sbは、ジンクプライマーとエポキシ樹脂の2層塗膜存在下のみならず、エポキシ樹脂塗膜存在下および裸状態における耐食性を向上させる効果がある。また、Snは、エポキシ樹脂塗膜の存在下および裸状態における耐食性を向上させる効果がある。Sb,Snの上記効果は、鋼板表面のアノード部などのpHが低下した部位での腐食が抑制されるためと考えられる。上記効果は、Sn,Sbとも、0.001mass%以上の添加により発現する。しかし、それぞれ0.3mass%を超えて添加すると、母材靭性およびHAZ部靭性が低下する。よって、SbおよびSnはそれぞれ0.001〜0.3mass%の範囲で添加するのが好ましい。なお、添加効果をより高めるには、SbとSnを複合添加するのが好ましい。
Moreover, in addition to the said component, the hot-rolled shape steel for ships of this invention is Sb: 0.001-0.3mass% and Sn: 0.001-0 in addition to the said component for the purpose of obtaining the more outstanding corrosion resistance. One or two of 3 mass% can be added.
Sb has an effect of improving the corrosion resistance not only in the presence of a two-layer coating film of a zinc primer and an epoxy resin but also in the presence of an epoxy resin coating film and in a bare state. Moreover, Sn has an effect of improving the corrosion resistance in the presence of an epoxy resin coating film and in a bare state. The above effect of Sb and Sn is thought to be due to the suppression of corrosion at sites where the pH is lowered, such as the anode portion on the steel sheet surface. The above effects are manifested by adding 0.001 mass% or more for both Sn and Sb. However, if each exceeds 0.3 mass%, the base material toughness and the HAZ part toughness are lowered. Therefore, it is preferable to add Sb and Sn in the range of 0.001 to 0.3 mass%, respectively. In order to further enhance the effect of addition, it is preferable to add Sb and Sn in combination.
また、本発明の船舶用熱間圧延形鋼は、さらなる耐食性の向上を目的として、上記成分に加えてさらに、Cu:0.005〜0.5mass%、Ni:0.005〜0.25mass%、Mo:0.01〜0.5mass%およびCo:0.01〜1.0mass%のうちから選ばれる1種または2種以上を添加することができる。
Cu,Ni,MoおよびCoは、ジンクプライマーとエポキシ樹脂の2層塗膜存在下および裸状態における鋼の耐食性を向上し、さらに、Moは、エポキシ樹脂の塗膜存在下でも、耐食性を向上する効果がある。したがって、これらの元素は、耐食性をより向上させたいときに補助的に添加することができる。Cu,Ni,MoおよびCoの上記効果は、錆粒子の微細化作用によるものと考えられ、さらに、Moは、錆中にMoO4 2−を生成して、塩化物イオンの鋼板表面への侵入を抑制することも寄与していると考えられる。
これらの効果は、Cu,Niでは0.005mass%以上、Moでは0.01mass%以上、Coでは0.01mass%以上添加することで発現する。しかし、Cu:0.5mass%超、Ni:0.25mass%超、Mo:0.5mass%超、Co:1.0mass%超の添加は、上記耐食性向上効果が飽和し、原料コストの上昇を招くだけである。よって、Cu,Ni,MoおよびCoは、それぞれ上記範囲で添加するのが好ましい。
In addition to the above components, the hot-rolled section steel for marine vessels of the present invention further includes Cu: 0.005-0.5 mass%, Ni: 0.005-0.25 mass%, in addition to the above components. One or two or more selected from Mo: 0.01 to 0.5 mass% and Co: 0.01 to 1.0 mass% can be added.
Cu, Ni, Mo and Co improve the corrosion resistance of steel in the presence of a two-layer coating film of zinc primer and epoxy resin and in the bare state, and Mo improves the corrosion resistance even in the presence of an epoxy resin coating film. effective. Therefore, these elements can be supplementarily added when it is desired to further improve the corrosion resistance. The above-mentioned effects of Cu, Ni, Mo and Co are considered to be due to the refinement of rust particles. Furthermore, Mo generates MoO 4 2− in the rust, and chloride ions enter the steel sheet surface. It is thought that the suppression is also contributing.
These effects are manifested by adding 0.005 mass% or more for Cu and Ni, 0.01 mass% or more for Mo, and 0.01 mass% or more for Co. However, addition of Cu: more than 0.5 mass%, Ni: more than 0.25 mass%, Mo: more than 0.5 mass%, Co: more than 1.0 mass%, the above-mentioned corrosion resistance improvement effect is saturated, and the raw material cost is increased. It only invites. Therefore, Cu, Ni, Mo, and Co are preferably added in the above ranges.
さらに、本発明の熱間圧延形鋼は、強度を高めたり、靭性を向上させたりするため、上記成分に加えてさらに、下記の成分を添加することができる。
Ti:0.001〜0.1mass%、Zr:0.001〜0.1mass%およびV:0.002〜0.2mass%のうちの1種または2種以上
Ti,ZrおよびVは、いずれも鋼の強度を高める元素であり、要求される強度に応じて選択して添加することができる。上記効果を得るためには、Ti,Zrは、それぞれ0.001mass%以上、Vは0.002mass%以上添加するのが好ましい。一方、Ti,Zrは0.1mass%超、Vは0.2mass%超添加すると、却って靭性が低下する。よって、Ti,Zr,Vは、それぞれ上記範囲で添加するのが好ましい。
Furthermore, in order to increase the strength or improve the toughness of the hot rolled steel of the present invention, the following components can be added in addition to the above components.
One or more of Ti: 0.001 to 0.1 mass%, Zr: 0.001 to 0.1 mass% and V: 0.002 to 0.2 mass% Ti, Zr and V are all It is an element that increases the strength of steel and can be selected and added according to the required strength. In order to acquire the said effect, it is preferable to add Ti and Zr 0.001 mass% or more respectively, and V to add 0.002 mass% or more. On the other hand, when Ti and Zr are added in excess of 0.1 mass% and V is added in excess of 0.2 mass%, the toughness is lowered. Therefore, Ti, Zr, and V are preferably added within the above ranges.
B:0.0002〜0.003mass%
Bも、鋼の強度を高める元素であり、必要に応じて添加することができる。上記効果を得るためには、0.0002mass%以上添加するのが好ましい。しかし、0.003mass%を超えて添加すると、靭性が却って低下する。よって、Bは0.0002〜0.003mass%の範囲で添加するのが好ましい。
B: 0.0002 to 0.003 mass%
B is also an element that increases the strength of the steel and can be added as necessary. In order to acquire the said effect, adding 0.0002 mass% or more is preferable. However, if added over 0.003 mass%, the toughness is reduced instead. Therefore, it is preferable to add B in the range of 0.0002 to 0.003 mass%.
Ca:0.0002〜0.01mass%,REM:0.0002〜0.015mass%およびY:0.0001〜0.1mass%のうちの1種または2種以上
Ca,REMおよびYは、いずれも溶接熱影響部の靭性向上に効果のある元素であり、必要に応じて選択して添加することができる。この効果は、Ca:0.0002mass%以上、REM:0.0002mass%以上、Y:0.0001mass%以上の添加で得られる。しかし、Ca:0.01mass%、REM:0.015mass%、Y:0.1mass%を超えて添加すると、却って靭性の低下を招く。よって、Ca,REM,Yは、それぞれ上記範囲で添加するのが好ましい。
Ca: 0.0002 to 0.01 mass%, REM: 0.0002 to 0.015 mass%, and Y: 0.0001 to 0.1 mass%, or two or more of Ca, REM, and Y It is an element effective in improving the toughness of the weld heat affected zone, and can be selected and added as necessary. This effect can be obtained by adding Ca: 0.0002 mass% or more, REM: 0.0002 mass% or more, and Y: 0.0001 mass% or more. However, addition exceeding Ca: 0.01 mass%, REM: 0.015 mass%, and Y: 0.1 mass% causes a decrease in toughness. Therefore, Ca, REM, and Y are preferably added in the above ranges.
なお、本発明の熱間圧延形鋼においては、上記以外の成分は、Feおよび不可避的不純物である。ただし、本発明の効果を害さない範囲内であれば、上記以外の成分の含有を拒むものではない。 In the hot rolled steel of the present invention, the components other than the above are Fe and inevitable impurities. However, as long as the effects of the present invention are not impaired, the inclusion of components other than those described above is not rejected.
次に、本発明に係る高強度でかつ耐食性に優れる船舶用熱間圧延形鋼のミクロ組織について説明する。
前述したように、船舶用の厚鋼板、とりわけ、降伏応力YSが315MPa以上の高強度厚鋼板においては、一般に、炭素当量を低めて高い溶接性を付与した鋼素材を、制御圧延と制御冷却を組み合わせたTMCPを採用し、第2相として硬質のベイナイト組織を導入することで高強度化を達成している。そして、より低温靭性や厚肉化が求められる場合には、上記制御圧延および制御冷却の条件を制御し、最適化することで対応している。したがって、TMCPを採用した場合、通常、得られる鋼板のミクロ組織は、フェライトとベイナイトからなる組織である。
Next, the microstructure of the marine hot-rolled section steel having high strength and excellent corrosion resistance according to the present invention will be described.
As described above, in the case of marine steel plates, particularly high strength thick steel plates with a yield stress YS of 315 MPa or more, generally, steel materials with low carbon equivalent and high weldability are subjected to controlled rolling and controlled cooling. High strength is achieved by employing a combined TMCP and introducing a hard bainite structure as the second phase. And when lower temperature toughness and thickening are calculated | required, it respond | corresponds by controlling and optimizing the conditions of the said controlled rolling and controlled cooling. Therefore, when TMCP is adopted, the microstructure of the obtained steel sheet is usually a structure composed of ferrite and bainite.
一方、船舶用の熱間圧延形鋼、例えば、断面が矩形ではない不等辺不等厚山形鋼の場合等では、短辺と長辺の幅や厚さが異なるために、必然的に圧延時や冷却時に、形鋼の部位間で温度の不均一が発生する。そのため、制御冷却(加速冷却)を適用した強化手段では、残留応力が不均一となり、ねじれや曲がり、反りを誘発して、寸法精度や形状の低下を招くため、圧延後の形状矯正負荷が増大する。したがって、第2相として硬質のベイナイト組織を導入して高強度化を図るTMCPを、熱間圧延形鋼に適用することは難しい。この点については、T形鋼など他の熱間圧延形鋼においても、全く同様のことが言える。 On the other hand, in the case of a hot-rolled section steel for ships, for example, in the case of an unequal side unequal thick angle steel with a non-rectangular cross section, the width and thickness of the short side and the long side are different, so that inevitably during rolling. During cooling, temperature non-uniformity occurs between the sections of the shape steel. Therefore, in the strengthening means using controlled cooling (accelerated cooling), the residual stress becomes non-uniform, causing twisting, bending, and warping, leading to a decrease in dimensional accuracy and shape, resulting in increased shape correction load after rolling. To do. Therefore, it is difficult to apply TMCP for increasing strength by introducing a hard bainite structure as the second phase to a hot rolled steel. About this point, the same thing can be said also in other hot rolled steel shapes such as T-shape steel.
したがって、例えば、降伏応力YS:235MPa以上で引張強さTS:400MPa以上の高強度の船舶用熱間圧延形鋼を製造するには、圧延後の加速冷却を行うことなく、したがって、通常の熱間圧延組織であるフェライトとパーライトからなる鋼組織で高強度化を図ることが必要とされる。 Therefore, for example, in order to produce a high-strength hot-rolled steel for a marine vessel having a yield stress YS: 235 MPa or more and a tensile strength TS: 400 MPa or more, it is not necessary to perform accelerated cooling after rolling. It is necessary to increase the strength of a steel structure composed of ferrite and pearlite, which is a cold rolled structure.
ここで、(フェライト+パーライト)組織で高強度化を実現する手段としては、第2相のパーライト分率を増やしてやる方法、フェライト組織を微細化する方法、フェライト地を固溶強化や析出強化する方法、あるいは(γ+α)2相域で熱間圧延して、フェライトの一部を加工フェライト化(高転位密度化)する方法等が考えられる。 Here, as means to achieve high strength in the (ferrite + pearlite) structure, a method of increasing the pearlite fraction of the second phase, a method of refining the ferrite structure, solid solution strengthening and precipitation strengthening of the ferrite ground Or a method in which a part of the ferrite is processed into ferrite (high dislocation density) by hot rolling in the (γ + α) two-phase region.
上記方法のうち、パーライト分率を高める方法は、Cを多量に添加する必要があるが、Cの過度な添加は溶接性の低下を招くため好ましくない。また、固溶強化元素や析出強化元素を添加してフェライト地を強化する方法は、合金元素の多量添加による溶接性の低下や、原料コストの上昇を招いたりする。また、加工フェライトの活用は、Cや合金元素の添加を最小限に抑制し、溶接性を維持した状態で、高強度化を図れる点で好ましい方法であるが、圧延能率を低下させる必要があるため、製造コストが上昇する。 Of the above methods, the method for increasing the pearlite fraction requires the addition of a large amount of C, but excessive addition of C is not preferable because it causes a decrease in weldability. Moreover, the method of strengthening the ferrite ground by adding a solid solution strengthening element or a precipitation strengthening element causes a decrease in weldability and an increase in raw material cost due to the addition of a large amount of alloy elements. Further, the utilization of processed ferrite is a preferable method in that the addition of C and alloy elements is suppressed to a minimum and the weldability is maintained, so that high strength can be achieved, but it is necessary to reduce the rolling efficiency. Therefore, the manufacturing cost increases.
一方、フェライト組織を微細化して高強度化を図る方法には、Nbの添加が有効である。さいわい、本発明では、耐食性向上元素としてNbを必須として添加している。そこで、本発明では、Nb添加による耐食性向上効果とフェライト組織の微細化効果を有効活用し、加工フェライトを含まないフェライト+パーライト組織のままで、フェライト相を微細化し、高強度化を図ることとした。 On the other hand, the addition of Nb is effective for the method of increasing the strength by refining the ferrite structure. Fortunately, in the present invention, Nb is added as an essential element for improving corrosion resistance. Therefore, in the present invention, the effect of improving the corrosion resistance by adding Nb and the effect of refining the ferrite structure are effectively utilized, and the ferrite phase is refined and the strength is increased with the ferrite + pearlite structure not including the processed ferrite. did.
次に、加工フェライトを含まないフェライトと、パーライトとからなるミクロ組織を有する本発明の船舶用熱間圧延形鋼の製造方法について説明する。
本発明の船舶用熱間圧延形鋼を製造するに当たっては、先ず、上述した成分組成を有する鋼を、転炉や電気炉等、通常公知の方法で溶製し、連続鋳造法、造塊法等の通常公知の方法でスラブやビレット等の鋼素材とするのが好ましい。なお、鋼の溶製において、取鍋精錬や真空脱ガス等の処理を付加しても良いことはもちろんである。
Next, a method for producing the marine hot rolled section steel of the present invention having a microstructure composed of ferrite not containing processed ferrite and pearlite will be described.
In producing the marine hot-rolled section steel of the present invention, first, the steel having the above-described component composition is melted by a generally known method such as a converter or an electric furnace, and a continuous casting method or an ingot-making method. It is preferable to use a steel material such as a slab or billet by a generally known method. In addition, in the melting of steel, it goes without saying that treatment such as ladle refining or vacuum degassing may be added.
次いで、上記鋼素材を、加熱炉に装入して1000〜1350℃の温度に再加熱し、熱間圧延して所望の寸法、組織および特性を有する船舶用熱間圧延形鋼とする必要がある。加熱温度が1000℃未満では、熱間圧延における変形抵抗が大きくなり、圧延することが難しくなる。一方、1350℃を超える加熱は、表面疵の発生原因となったり、スケールロスの増大や燃料原単位の上昇を招いたりする。好ましくは、1100〜1300℃の範囲である。 Next, the steel material must be charged into a heating furnace, reheated to a temperature of 1000 to 1350 ° C., and hot-rolled to obtain a hot-rolled steel for ships having desired dimensions, structure and characteristics. is there. If heating temperature is less than 1000 degreeC, the deformation resistance in hot rolling will become large and it will become difficult to roll. On the other hand, heating exceeding 1350 ° C. causes surface flaws, increases scale loss, and increases fuel consumption. Preferably, it is the range of 1100-1300 degreeC.
続く熱間圧延は、圧延仕上温度を800℃超として仕上圧延を行う必要がある。圧延仕上温度が800℃以下になると、圧延後のミクロ組織が加工フェライトを含んだ組織となり、鋼の強度は上昇するが、圧延時に温度調整のための待ち時間が発生するため、圧延能率が低下し、コストアップを招く。
熱間圧延後の冷却は、放冷する必要がある。これにより、圧延後の急速冷却に伴う不均一冷却から生じる曲がりや反りよる形状不良を低減でき、圧延後の製品の形状矯正に要する負担を軽減することができる。
In the subsequent hot rolling, it is necessary to perform finish rolling with the rolling finishing temperature exceeding 800 ° C. When the rolling finishing temperature is 800 ° C. or lower, the microstructure after rolling becomes a structure containing processed ferrite, and the strength of the steel increases, but a waiting time for temperature adjustment occurs during rolling, so the rolling efficiency decreases. And cost increases.
The cooling after hot rolling needs to be allowed to cool. Thereby, the shape defect by the bending and the curvature which arises from the non-uniform cooling accompanying rapid cooling after rolling can be reduced, and the burden required for the shape correction of the product after rolling can be reduced.
表5に示した成分組成を有するNo.1〜19の鋼を真空溶解炉または転炉で溶製してブルームとし、これらのブルームを加熱炉に装入して表6に示した温度に加熱後、熱間圧延し、表6に示した断面寸法の不等辺不等厚山形鋼(NAB)およびT形鋼を製造した。次いで、下記の引張試験、靭性試験およびミクロ組織観察に供した。
<引張試験>
不等辺不等厚山形鋼については短辺から、T形鋼についてはフランジ部から、JIS 1A号引張試験片(JIS Z2201)を採取し、引張試験を行い、降伏応力YS、引張強さTSおよび伸びElを測定した。
<靭性試験>
不等辺不等厚山形鋼については短辺を、T形鋼についてはフランジ部を、20kJ/cmの入熱で突合せ多層盛り溶接(GMAW)し、そのHAZ中央部から、シャルピー衝撃試験片(2mmVノッチ試験片)を採取して、−20℃でのシャルピー衝撃試験における吸収エネルギーを測定し、上記吸収エネルギーの値が27J以上のものを、溶接部の衝撃特性が良好であると判定した。なお、不等辺不等厚山形鋼の短辺およびT形鋼のフランジ部の母材についても、同様の衝撃試験を行い、吸収エネルギーを測定した。
<ミクロ組織観察>
不等辺不等厚山形鋼については短辺から、T形鋼についてはフランジ部から組織観察用の試料を採取し、光学顕微鏡を用いて板厚1/4部のミクロ組織を倍率200倍で観察し、扁平化した加工フェライトが存在しないことを確認した。
No. having the component composition shown in Table 5. Steels 1 to 19 were melted in a vacuum melting furnace or converter to form blooms. These blooms were charged into a heating furnace and heated to the temperatures shown in Table 6 and hot-rolled. Unequal-sided unequal thickness angle steel (NAB) and T-shaped steel with different cross-sectional dimensions were produced. Then, it used for the following tensile test, toughness test, and microstructure observation.
<Tensile test>
JIS 1A tensile test specimen (JIS Z2201) is taken from the short side for unequal side unequal thickness angle steel, and from T flange for the T shape steel, and a tensile test is conducted to obtain a yield stress YS, tensile strength TS and The elongation El was measured.
<Toughness test>
A short side is used for unequal side unequal thick angle steels, and a flange part is used for T-shaped steels by butt multi-layer welding (GMAW) with a heat input of 20 kJ / cm, and Charpy impact test piece (2 mmV) A notch test piece) was collected and the absorbed energy in a Charpy impact test at −20 ° C. was measured, and those having an absorbed energy value of 27 J or more were determined to have good impact characteristics at the weld. In addition, the same impact test was done about the base material of the short side of an unequal side unequal thickness angle steel, and the flange part of T-shaped steel, and the absorbed energy was measured.
<Microstructure observation>
Samples for microstructure observation were taken from the short side for unequal side unequal thickness angle steel, and for T-section steel from the flange part, and the microstructure of the ¼ part thickness was observed at 200 times magnification using an optical microscope. It was confirmed that there was no flattened processed ferrite.
さらに、上記熱間圧延形鋼について、以下の耐食性試験に供した。
<耐食性試験>
不等辺不等厚山形鋼は短辺から、T形鋼はフランジ部から、5mmt×100mmW×200mmLまたは5mmt×50mmW×150mmLの試験片を採取し、試験片表面にショットブラストを施した後、下記A〜Cの条件の表面処理を施して、耐食性試験片とした。
・条件A:試験片表面に、ジングプライマー(膜厚約15μm)とタールエポキシ樹脂(約200μm)を塗布し、2層被膜を形成
・条件B:試験片表面に、タールエポキシ樹脂(膜厚約200μm)を塗布し、単層被膜を形成
・条件C:試験片表面にショットブラストを施したままの裸状態(防食被膜なし)
なお、塗膜を形成した上記AおよびBの試験片には、塗膜の上からカッターナイフで地鉄表面まで達する長さ80mmのスクラッチ疵を一文字状に付与した。
Furthermore, the hot rolled steel was subjected to the following corrosion resistance test.
<Corrosion resistance test>
Samples of 5 mmt x 100 mmW x 200 mmL or 5 mmt x 50 mmW x 150 mmL were sampled from the short side for the unequal side unequal thickness angle steel, and the T-shaped steel from the flange part. A surface treatment under conditions A to C was applied to obtain a corrosion resistance test piece.
・ Condition A: Jing primer (film thickness: about 15 μm) and tar epoxy resin (about 200 μm) are applied to the surface of the test piece to form a two-layer film. • Condition B: Tar epoxy resin (film thickness: about 200 μm) 200 μm) is applied to form a single layer film. Condition C: Bare state with no shot blasting on the surface of the test piece (no anticorrosion film)
In addition, the test piece of said A and B in which the coating film was formed was provided with the scratch scissors of length 80mm which reaches the surface of the iron bar with a cutter knife from the top of the coating film.
次いで、上記試験片を、実船のバラストタンク上甲板裏側に2年間装着する暴露試験に供した。なお、この暴露試験の腐食環境は、平均して、バラストタンク内に海水が入っている期間が約20日、海水が入っていない期間が約20日を1サイクルとし、これを繰り返すものであった。そして、暴露試験後の耐食性の評価は、塗膜を有する条件AおよびBの試験片については、スクラッチ疵の周囲に発生した塗膜膨れ面積を測定し、また、塗膜を有しない条件Cの試験片については、試験後、脱錆した後の試験片質量と試験前の試験片質量との差(減少量)から平均板厚減少量を算出し、これらの値を、耐食性向上元素を特に含有していないNo.12のベース鋼材の値を基準(100)として相対化し、50%超えの値のもの耐食性が劣ると判定した。 Next, the test piece was subjected to an exposure test that was mounted on the backside of the upper deck of a ballast tank of an actual ship for 2 years. The corrosive environment of this exposure test is, on average, about 20 days when seawater is in the ballast tank and about 20 days when seawater is not in one cycle. It was. And the corrosion resistance evaluation after the exposure test is as follows. For the test pieces of the conditions A and B having the coating film, the film swelling area generated around the scratch ridge is measured, and the condition C without the coating film is measured. For test pieces, calculate the average reduction in thickness from the difference (reduction amount) between the test piece mass after derusting and the test piece mass before the test, and use these values as the corrosion resistance improving element. No. The values of 12 base steel materials were relativized with reference (100), and those with a value exceeding 50% were judged to be inferior.
表7に上記引張試験、衝撃試験、ミクロ組織観察よび腐食試験の結果をまとめて示した。この表から、本発明の成分組成を満たすNo.1〜11および17〜18の鋼材(発明例)は、表面処理条件がA〜Cのいずれの場合でも、ベース鋼材(No.12)に対する塗膜膨れ面積および板厚減少量の比がいずれも50%以下であり、良好な耐食性を示していることがわかる。これに対して、本発明の成分組成を満たさないNo.12〜16の鋼材(比較例)は、ベース鋼材(No.12)より耐食性が向上していても、ベース鋼材に対する塗膜膨れ面積や板厚減少量の比が50%超えであったり、溶接部の靭性が大きく低下していたりしている。また、No.19の鋼材(比較例)は、本発明の成分組成を満たしているが、圧延仕上温度を700℃と低くしているため、圧延中に温度低下待ちのための待機時間が約150sec発生し、発明例と比較して圧延能率が低下している。 Table 7 summarizes the results of the tensile test, impact test, microstructure observation, and corrosion test. From this table, No. 1 satisfying the component composition of the present invention is obtained. The steel materials 1-11 and 17-18 (invention examples) have a ratio of the coating film swelling area and the plate thickness reduction amount to the base steel material (No. 12) in any case where the surface treatment conditions are AC. It can be seen that it is 50% or less, indicating good corrosion resistance. On the other hand, No. which does not satisfy the component composition of the present invention. Even though the steel materials 12 to 16 (comparative example) have improved corrosion resistance compared to the base steel material (No. 12), the ratio of the coating film swelling area and the plate thickness reduction amount to the base steel material exceeds 50%, or welding The toughness of the part is greatly reduced. No. Although 19 steel materials (comparative examples) satisfy the composition of the present invention, the rolling finishing temperature is as low as 700 ° C., so that a waiting time for waiting for the temperature to drop during rolling occurs for about 150 seconds, The rolling efficiency is reduced as compared with the inventive examples.
本発明の船舶用形鋼は、防食塗膜の存在状態にかかわらず、海水による腐食環境下において優れた耐食性を発現する。したがって、本発明の船舶用形鋼は、船舶のバラストタンク用としてだけでなく、海洋構造物や化学プラント等、類似の腐食環境下で使用される他の分野の形鋼としても好適に用いることができる。 The ship shaped steel of the present invention exhibits excellent corrosion resistance in a corrosive environment with seawater regardless of the presence of the anticorrosion coating film. Therefore, the ship shape steel of the present invention is preferably used not only for ship ballast tanks but also as shape steels for other fields used in similar corrosive environments such as offshore structures and chemical plants. Can do.
Claims (10)
Si:0.05〜0.50mass%、
Mn:0.1〜2.0mass%、
P:0.025mass%以下、
S:0.01mass%以下、
Al:0.005〜0.10mass%、
W:0.01〜1.0mass%、
Cr:0.01mass%以上0.20mass%未満、
Nb:0.001〜0.03mass%、
N:0.001〜0.008mass%を含有し、
残部がFeおよび不可避的不純物からなる成分組成を有し、加工フェライトを含まないフェライトとパーライト組織とからなるミクロ組織を有する船舶用熱間圧延形鋼。 C: 0.05-0.20 mass%,
Si: 0.05-0.50 mass%,
Mn: 0.1 to 2.0 mass%,
P: 0.025 mass% or less,
S: 0.01 mass% or less,
Al: 0.005 to 0.10 mass%,
W: 0.01 to 1.0 mass%,
Cr: 0.01 mass% or more and less than 0.20 mass%,
Nb: 0.001 to 0.03 mass%,
N: 0.001 to 0.008 mass%,
A marine hot-rolled section steel having a microstructure comprising a ferrite and a pearlite structure, the balance of which is composed of Fe and inevitable impurities, and which does not contain processed ferrite.
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JP2013227610A (en) * | 2012-04-25 | 2013-11-07 | Jfe Steel Corp | Corrosion resistant steel for hold of coal carrier or coal/ore carrier |
CN103526112A (en) * | 2013-10-18 | 2014-01-22 | 武汉钢铁(集团)公司 | Anti-corrosion steel for bridge tubular pile and production method of anti-corrosion steel |
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JP2019127639A (en) * | 2018-01-26 | 2019-08-01 | 日本製鉄株式会社 | Mooring chain steel and mooring chain |
JP2023507804A (en) * | 2019-12-20 | 2023-02-27 | ポスコホールディングス インコーポレーティッド | Steel plate excellent in wear resistance and combined corrosion resistance and its manufacturing method |
CN113444995A (en) * | 2021-05-20 | 2021-09-28 | 南通莱鑫运动用品有限公司 | Metal surface treatment method for improving wear-resisting and rust-resisting properties of sports equipment |
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