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WO2006080658A1 - Acier a excellente resistance aux intemperies dans une atmosphere marine, et son procede de fabrication - Google Patents

Acier a excellente resistance aux intemperies dans une atmosphere marine, et son procede de fabrication Download PDF

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Publication number
WO2006080658A1
WO2006080658A1 PCT/KR2005/003213 KR2005003213W WO2006080658A1 WO 2006080658 A1 WO2006080658 A1 WO 2006080658A1 KR 2005003213 W KR2005003213 W KR 2005003213W WO 2006080658 A1 WO2006080658 A1 WO 2006080658A1
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WIPO (PCT)
Prior art keywords
steel
inclusion
cas
weather resistance
inclusions
Prior art date
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Ceased
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PCT/KR2005/003213
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English (en)
Inventor
Hwan-Gyo Jung
Jang-Yong Yoo
Kyung-Keun Um
Eui-Gyeong Jung
Jong-Kyo Choi
Jae-Sang Lee
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Posco Holdings Inc
Original Assignee
Posco Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from KR1020040092554A external-priority patent/KR101115692B1/ko
Priority claimed from KR1020040098152A external-priority patent/KR101125895B1/ko
Priority claimed from KR1020040109217A external-priority patent/KR101125944B1/ko
Priority claimed from KR1020040109221A external-priority patent/KR101126019B1/ko
Priority claimed from KR1020040109647A external-priority patent/KR101125938B1/ko
Priority claimed from KR1020040109220A external-priority patent/KR101125874B1/ko
Priority claimed from KR1020040109218A external-priority patent/KR101126013B1/ko
Priority to AT05856389T priority Critical patent/ATE553225T1/de
Priority to CN2005800462457A priority patent/CN101133177B/zh
Priority to EP05856389A priority patent/EP1825014B1/fr
Application filed by Posco Co Ltd filed Critical Posco Co Ltd
Publication of WO2006080658A1 publication Critical patent/WO2006080658A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper

Definitions

  • the present invention relates to steel with excellent corrosion resistance against atmospheric exposure, and a manufacturing method therefor. More particularly, the present invention relates to steel with excellent corrosion resistance at the seaside where salinity is high and in an atmosphere with a high concentration of chlorine where calcium chloride is used as anti-freezing agent.
  • a conventional weather resistant steel contains a very small amount of Cu, Cr and
  • the weather resistant steel has corrosion resistance superior to general steel for the following reasons.
  • the weather resistant steel gathers rust, which falls off or becomes detached in a manner similar to general steel during an early period of atmospheric exposure. But with time passing, some of the rust slowly adheres to a base metal, forming a layer of dense stable rust, which subsequently serves as protective layers against corrosive environment.
  • Stable rust that can function as protections against corrosive environment is FeOOH or ⁇ -FeOOH having an amorphous structure.
  • the conventional weather resistant steel demonstrates superior corrosion resistance after a long period of at least 3 years in a general atmospheric corrosion environment such as a rural area or a factory area containing SO
  • the conventional weather resistant steel indicates little improvement from general steel even though time passes at the seashore having a relative high concentration of chlorine or in a region where anti-freezing agent is used. This is because chlorine ion adhered to the steel surface facilitates oxidation of a water film formed thereon, increasing overall corrosion rate of the steel, obstructing formation of stable rust and generating defective corrosive product such as ⁇ -FeOOH on the steel surface.
  • ⁇ -FeOOH formation should be inhibited but ⁇ - FeOOH with a dense structure should be formed to generate a complete passive film.
  • a structure of rust layer formed when steel is exposed to atmosphere is affected by corrosive environment. With higher pH of corrosive environment or the water film formed on the steel surface, ⁇ -FeOOH formation is inhibited and ⁇ -FeOOH formation is expedited. However, pH is hardly controllable via control of atmosphere, and thus attempts have been made to elevate pH of the water film formed on the steel surface by adding chlorine elements to the steel.
  • Japanese Laid-Open Patent Application Nos. 2-125839 and 5-51668 disclose conventional technologies in which weather resistance is heightened by adding chlorine elements such as Ca and Mg, and increasing pH of the steel surface.
  • the Patent Application No.2- 125839 teaches a method of improving weather resistance by adding Ca to steel to produce complex oxide of (Al, Ca)O.
  • the Patent Application No. 5-51668 teaches a method of increasing pH of the steel surface by adding pretreated powder that mixes CaO particles of up to ID average diameter and iron of up to 200D average diameter.
  • inclusion produced by addition of Ca is not CaO single oxide but Ca-based complex oxide.
  • CaO injected reacts easily with other oxides present in molten steel such as Al O and SiO and exists as liquid inclusion such as (Al, Si, Ca)O, CaO- 2Al O , CaO- 6Al O compounds.
  • Ca-based composite oxide is not dissolved in water, not elevating pH of the material surface significantly and accordingly having little effect on improving weather resistance.
  • No. 2002-25571 which teaches a technology for enhancing weather resistance by adding Ca-Si wire to molten steel, forming Ca-based composite sulfide and Ca-based composite oxide on steel, and increasing pH of the steel surface.
  • addition of Ca-Si wire enables formation of steel inclusion containing Ca-based composite oxide and Ca-based composite sulfide.
  • 95% thereof exist as Ca-based composite oxide, not contributing to pH increase of the steel surface and thus not enhancing weather resistance substantially.
  • the present invention has been made to solve the foregoing problems of the prior art and it is therefore an object of the present invention to provide steel with excellent weather resistance at the seaside and in a region having a high concentration of salinity where anti-freezing agent is used, and a method for manufacturing the same. This is made possible by increasing pH of the steel surface at the early stage of corrosion and generating stable rust in a short period without conducting painting or surface treatment by optimizing steel elements and properly controlling weight fraction of water-soluble CaS inclusion out of Ca-based non-metallic inclusions.
  • steel with excellent weather resistance consisting of:
  • the steel with excellent weather resistance may further comprise at least one selected from a group consisting of 0.005 to 0. lwt% Ti, 0.01 to 1.0wt% Mo and 0.01 to 1.0wt% W.
  • the steel with excellent weather resistance further comprises at least one selected from a group consisting of 0.02 to 0.07wt% Nb, up to 0.1wt% V, 0.003 wt% B, the steel may have its strength improved considerably.
  • the steel has 30 to 80wt% water-soluble CaS inclusion out of Ca non-metallic inclusions.
  • the steel preferably has Ca-based non-metallic inclusion containing CaS distributed therein by an area fraction of at least 0.04%, [31] wherein the area fraction is determined by dividing inclusion area by observation area. [32] [33] Further, the steel has Ca-based non-metallic inclusion containing CaS sized up to 3D distributed therein by an area fraction of at least 0.02%. [34] [35] A method for manufacturing steel with excellent weather resistance comprising steps of:
  • the molten steel further consists of at least one selected from a group consisting of 0.005 to 0.1wt% Ti, 0.01 to 1.0wt% Mo, 0.01 to 1.0wt% W.
  • the molten steel further consists of at least one selected from a group consisting of
  • the steel preferably has 30 to 80 wt% CaS inclusion out of Ca-based non-metallic inclusions.
  • the steel has Ca-based non-metallic inclusion containing CaS distributed therein by an area fraction of at least 0.04%, wherein the area fraction is determined by dividing inclusion area by observation area.
  • the steel preferably has Ca-based non-metallic inclusion containing CaS sized up to 3D distributed therein by an area fraction of 0.02%.
  • the present invention provides steel with excellent weather resistance at the seaside and in a region where salinity is high and where anti-freezing agent is used by optimizing steel compositions, properly controlling weight fraction of water-soluble
  • CaS inclusion out of Ca-based non-metallic inclusions increasing pH of the steel surface in the early stage of corrosion, and forming stable rust in a short period without conducting painting or surface treatment.
  • steel with excellent weather resistance having at least 300MPa yield strength and at least 480MPa tensile strength in an environment having a high concentration of salinity where anti- freezing agent is used.
  • Figure Ia is a view illustrating the shape of an inclusion and a composition analysis result of comparative steel C
  • Figure Ib is a view illustrating the shape of an inclusion and a composition analysis result of inventive steel C
  • Figure 2a shows composition analysis made by randomly selecting 10 out of inclusions distributed in comparative steel C
  • Figure 2b shows a composition analysis result produced by randomly selecting 10 out of inclusions distributed in inventive steel C
  • Figure 3a shows thermodynamic calculation of inclusion formation behavior in molten steel of comparative steel
  • Figure 3b shows thermodynamic calculation of inclusion formation behavior in molten steel of inventive steel
  • Figure 4 shows the distribution of inclusions in inventive steel A
  • Figure 5 is a graph illustrating temporal pH changes on the surface of comparative and inventive steels
  • Figure 6 is a graph illustrating temporal pH changes in Ca-based composite oxides observed in comparative steels.
  • Figure 7a is a view illustrating the shape of an inclusion and a composition analysis result of comparative steel D
  • Figure 7b is a view showing the shape of an inclusion and a composition analysis result of inventive steel B
  • Figure 8a shows a composition analysis result produced by randomly selecting 10 out of inclusions distributed in comparative steel D
  • Figure 8b shows a composition analysis result produced by randomly selecting 10 out of inclusions distributed in inventive steel B;
  • Figure 9 shows the distribution of inclusions in inventive steel A
  • Figure 10 is a graph illustrating pH changes on a surface of inventive and comparative steels; and [70] Figure 11 is a graph illustrating pH changes in Ca-based composite oxide observed in comparative steels. [71]
  • Ca was added to steel to increase pH of the surface thereof in the early stage.
  • Ca added does not form water-soluble CaO or CaS capable of increasing pH of an aqueous solution but reacts with Si, Al, O present in the steel to form complex oxide (at least 90%) such as (Al, Si, Ca)O.
  • the inclusions are sized at least 3D and distributed unevenly.
  • the complex oxide formed in this manner is not dissolved in water, thus not leading to higher pH of the steel surface.
  • C is added to boost strength, and greater contents thereof enhance hardenability and subsequently strength.
  • C content should be preferably lmited to 0.15 wt% or less because C at the amount exceeding this value impairs weldability.
  • Si serves as a deoxidant and also increases strength.
  • Si content should be preferably limited to 1.0 wt% or less since Si content exceeding this value degrades toughness and weldability, and also reacts with Ca, thereby producing insoluble complex oxide and hindering improvement in weather resistance.
  • Mn is effective for boosting strength without degrading toughness. Higher Mn content leads to improved hardneablity and then increased strength. But the Min content should be preferably limited to 2.0 wt% or less since Min at the amount exceeding this value deteriorates weldability.
  • Cu is effective for enhancing weather resistance of steel by inducing fineness and density of rust layer particles.
  • Cu content less than 0.2 wt% does not allow improvement in weather resistance, while the content in excess of 1.0 wt% rarely improves weather resistance and also causes Cu with a low melting point to infiltrate into steel grain in case of reheating slab for hot-rolling, causing cracks in a heat process. Therefore the Cu content should be preferably limited to 0.2 to 1.0 wt%.
  • Ni is one of important elements conducive to increasing weather resistance.
  • Ni allows fineness and density of amorphous rust layer or ⁇ -FeOOH rust layer so that permeation into materials through rust layer is inhibited, thus enhancing weather resistance. More particularly, Ni is effective for improving weather resistance at the seaside having a high concentration of salinity. The Ni content less than 0.2 wt% does not ensure the aforesaid effects. But the Ni content in excess of 5.0 wt% rarely improves weather resistance, and also increases manufacturing costs resulting from a great quantity of addition of high-priced Ni. Therefore, the Ni content should be preferably limited to 0.2 to 5.0 wt %.
  • Al is essentially added for deoxidation in a steel-making process. Al improves shock absorption energy, but like Si, reacts with Ca to form insoluble complex oxide, thus hindering improvement in weather resistance. Al content less than 0.001 wt% does not allow sufficient deoxidation but the content in excess of 0.1 wt% degrades impact toughness. Therefore the Al content should be preferably limited to 0.001 to 0.1 wt%.
  • S serves as a starting point of corrosion by reacting with Mn to form MnS.
  • Ca in the case where Ca is added as in the present invention, it reacts with Ca to be dissolved in an aqueous solution and forms CaS capable of increasing pH, thereby improving weather resistance.
  • To achieve pH increase by CaS requires addition of S with at least 0.002 wt% in content. But the S content in excess of 0.03 wt% deteriorates impact toughness and weldability. Therefore the S content should be preferably limited to 0.002 to 0.03 wt%.
  • Ca reacts with Al, Si, O out of molten steel to form complex oxide such as (Al, Si,
  • Ca Ca
  • the gross complex oxide does not result in pH increase, having no effect on improving weather resistance but deteriorating impact toughness.
  • fine CaS inclusion is dissolved in water, increasing pH of the steel surface so that stable rust formation is facilitated to enhance weather resistance.
  • at least 0.001 wt% should be added but the Ca content in excess of 0.01 wt% causes wear of refractory material in a steel-making process. Therefore the Ca content should be preferably limited to 0.001 to 0.01 wt%.
  • the balance contains Fe and unavoidable impurities.
  • Ti generates fine oxide and nitride in steel, which due to high melting points, are not dissolved even over a reheating temperature in the case of hot-rolling. Thereby Ti inhibits growth of austenite crystal grain by grain boundary pinning effects and enhances impact toughness. Also, fine Ti oxide serves as a starting point to react with Ca and thus induces fine distribution of inclusions. Ti content less than 0.005 wt% does not ensure the aforesaid effects while Ti content in excess of 0.1 wt% boosts Ti amount of solid solution, deteriorating toughness of the base metal and weld. Therefore the Ti content should be preferably limited to 0.005 to 0.1 wt%.
  • Mo content less than 0.01 wt% does not yield the aforesaid effects, while the content in excess of 1.0 wt% leads to insignificant improvement.
  • Mo content should be preferably limited to 0.01 to 1.0 wt%.
  • W is effective for improving weather resistance at the seaside by forming WO ion in an aqueous solution to restrain permeation of chlorine ion that passes rust layer.
  • W content less than 0.01 wt% does not yield the aforesaid effects while the content in excess of 1.0 wt% rarely improves weather resistance. Thereby the W content should be preferably limited to 0.01 to 1.0 wt%.
  • higher-strength steel with excellent weather resistance is obtainable by adding at least one selected from a group consisting of Nb, V and B in a content defined later.
  • Nb refines crystal grain effectively, and also improves strength significantly. Nb content less than 0.02 wt% does not yield the aforesaid effects, while the Nb content in excess of 0.07 wt% generates gross Nb precipitates, potentially causing cracks in steel and degrading impact properties. Therefore, the Nb content should be preferably limited to 0.02 to 0.07 wt%.
  • V forms carbide- nitride like Nb and thus is effective for boosting strength.
  • V content in excess of 0.1 wt% has little effect on improving strength, also impairing impact properties of steel. Therefore, the V content should be preferably limited to 0.1 wt%.
  • B content in excess of 0.003 wt% forms Fe B, causing red brittleness and impairing weldability. Therefore the B content should be preferably limited to 0.003 wt%.
  • Ca forms CaS that ensures improved weather resistance while forming complex oxide not contributing thereto. Accordingly, Ca, S, Al, and Si contents should be adequately controlled to inhibit complex oxide and boost CaS inclusion formation.
  • An Equation 1 below was set for restraining complex oxide and enhancing CaS inclusion formation, and derived from repeated experiments of the inventors.
  • such split injection of Ca and composition optimization allows at least 30% weight fraction of CaS inclusion out of Ca-based non-metallic inclusions in the final steel.
  • Steel with excellent weather resistance at the seaside is composed as set forth above.
  • the steel as explained earlier with regard to grounds for limited composition of the steel with excellent weather resistance, may further contain at least one selected from a group consisting of Ti, Mo and W or further contain at least one selected from a group consisting of Nb, V and B.
  • Ca-Si wire was split-injected at least twice instead of conventional one-time injection, and found a considerable increase in CaS inclusion in steel. That is, when Ca-Si wire is split- injected at least twice as just described, Ca injected initially reacts with oxides present in steel to form complex inclusion, and then is mixed into a slag layer via floatation in steel while waiting for the next Ca injection, thereby diminishing complex inclusion in steel. Therefore, Ca injected after first injcetion reacts with S in steel to effectively form CaS.
  • steel with excellent weather resistance having at least 30% of water-soluble CaS inclusion out of Ca-based non-metallic inclusions in the final product can be manufactured by carrying out continuous casting of molten steel having compositions as described above to fabricate a steel slab, and then hot- rolling the steel slab under a normal condition.
  • the steel has at least 30% CaS inclusion out of Ca-based non-metallic inclusions because weight fraction of less than 30% does not lead to improvement in pH of the steel surface. This will be explained in more detail hereunder.
  • Ca injected into molten steel reacts with oxygen, aluminum, silicon and sulfur present in the steel to form inclusions such as (Al, Si, Ca)O and CaS.
  • inclusions such as (Al, Si, Ca)O and CaS.
  • complex inclusions other than CaS are not dissolved in an aqueous solution, not increasing pH of the steel surface, but only CaS inclusion is dissolved in the aqueous solution to increase pH. Consequently, weight fraction of CaS out of total inclusions serves as a decisive factor for pH increase of a water film.
  • pH of water film is at least 7.0, a neutral level, it can contribute to enhancing weather resistance.
  • the weight fraction of CaS inclusion out of total inclusions should be at least 30%.
  • water-soluble CaS inclusion out of Ca-based non-metallic inclusions in steel is limited to 30 to 80% for the following reasons.
  • Addition of Ca produces oxide inclusion and sulfide inclusion at the same time.
  • Sulfide inclusion, i.e., CaS may cause nozzle clogging in a continuous casting process, while oxide inclusion may inflict wear on refractory in a continuous casting process. Therefore to enhance weather resistance and secure stability of the continuous casting process, the fraction of CaS inclusion out of total inclusions should be preferably limited to up to 80%.
  • Ca-based non-metallic inclusions are Ca-based inclusions formed by injecting Ca into molten steel, and are complex inclusions such as (Al, Si, Ca)O except for CaS.
  • complex inclusions such as (Al, Si, Ca)O are oxide consisting of at least 2 of Al, Si, Ca, and contain CaAl O , CaAl O , Ca SiO , and Ca Al SiO The inclusions are variously sized and distributed, and impact
  • steel in view of improved weather resistance, steel preferably should have CaS and Ca-based non-metallic inclusion including complex inclusion such as Al, Si, Ca)O distributed therein by an area fraction of at least 0.04% .
  • steel preferably should have Ca- based non-metallic inclusion containing CaS sized up to 3D distributed therein by an area fraction of 0.02%.
  • the invention provides steel with excellent weather resistance by optimizing steel compositions and adequately controlling weight fraction of CaS inclusion out of Ca-based non-metallic inclusions in the product.
  • Examples 1 to 4 have been made to confirm effects of steel with excellent weather resistance and a method for manufacturing the same.
  • Examples 5 to 8 have been made to confirm whether the steel has excellent weather resistance and improved strength if at least one selected from a group consisting of Nb, V and B is additionally added thereto to enhance strength.
  • Example 1 Molten steel having composition as in Table 1 has been prepared to fabricate a steel slab via continuous casting. Then the steel slab was hot-rolled under a normal condition to manufacture steel. At this time, in the case of inventive steels A to J and comparative steels A to F having Ca added, Ca was injected into molten steel as in Table 2 below. Meanwhile, conventional steel A and conventional steel B were prepared for comparison with inventive steels. Conventional steel A in Table 1 was a general weather resistant steel, and conventional steel B was a general structural steel.
  • a -F Comparative Steels A-F [178]
  • a and B Conventional Steels A and B
  • Figure l(a) and (b) illustrate the shape of inclusion and a composition analysis result of comparative steel C and comparative steel C.
  • inclusions in comparative steel C are variously sized and composed, and at least 95% of inclusions have Ca-based complex oxide with the size of at least 3D.
  • 60% of inclusions have fine Cas inclusion with the size of about ID.
  • Example 2 Size of inclusions and area fraction (inclusion area/observation area) with respect to inclusions present in each steel prepared in example 1 were measured. Then, by analyzing size and distribution of inclusions in steel as in Figure 4, measurement was conducted on average inclusion size, and area fraction of inclusion and fine inclusion, and the results are shown in Table 4. In Table 4, fine inclusion means an inclusion sized up to 3D.
  • inventive examples 1 to 10 in which compositions are optimized and Ca is split-injected in a steel-making process show results superior to co mparative examples 1 to 10 in terms of average inclusion size, and area fraction of inclusion and fine inclusion.
  • Example 3 To examine effects of inclusion produced by Ca addition on pH of the steel surface, steels of example 1 (inventive steels A,C,D and H, comparative steels A,C and E, conventional steel A) were thinly coated with a water film on the surface to measure pH thereof. The results are shown in FIG.5.
  • Example 4 [214] The steel of example 1 was exposed to a salt spray environment of lmdd to measure corrosion depth. The results are shown in Table 5.
  • inventive examples 1 to 10 in which compositions are optimized and Ca is split-injected at least twice in a steel-making process indicate superior weather resistance.
  • inventive examples 4 to 10 in which at least one selected from a group consisting of Ti, Mo and W is added inventive examples 4 to 10 showed weather resistance superior to inventive examples having no Ti, Mo and W.
  • Improved weather resistance according to the invention is achieved since CaS inclusion formed by Ca addition is dissolved in a water film condensed on the steel surface, increasing pH of the steel surface and thus forming stable rust in the early stage.
  • Example 5 Molten steel having composition as in Table 6 below was prepared and steel slab was fabricated via continuous casting. Then the fabricated steel slab was hot-rolled under a normal condition to manufacture steel. At this time, for inventive steels A to K and comparative steels A to I having Ca, Ca was injected into molten steel as in Table 7. Meanwhile, conventional steels A and B were prepared in the examples for comparison with inventive steels. Conventional steel A in Table 6 below was a general weather resistant steel and conventional steel B was a general structural steel.
  • Figure 7 (a) and (b) show the shape of inclusion and a composition analysis result of comparative steel D and inventive steel B. As shown in Figure 7 (a) and (b), inclusions in comparative steel D are variously sized an composed, and at least 95% of inclusions are sized at least 3D, while 60% of inclusions in inventive steel B are fine CaS inclusions sized about ID.
  • Example 6 With respect to inclusions present in the steel prepared in example 5, measurement was conducted on the size of inclusions and their area fraction (inclusion area/ observation area). In this case, by analyzing the size distribution of inclusions in the steel as in Figure 9, measurement was conducted on the average inclusion size and the area fraction of inclusion and fine inclusion in inventive and comparative steels. The results are shown in Table 9. Herein fine inclusion in Table 9 means an inclusion sized up to 3D.
  • inventive examples 1 to 11 in which compositions are optimized and Ca is split-injected in a steel-making process indicate results superior to comparative examples 1 to 14 in terms of average inclusion size and the area fraction of inclusion and fine inclusion.
  • Example 7 To examine effects of inclusion produced by Ca addition on pH of the steel surface, steels of example 1 (inventive steels B,F and H comparative steels B,F and G conventional steel A) were thinly coated with a water film to measure pH changes of the water film. The results are shown in Figure 10.
  • inventive steel F and comparative steel F are compared, pH changes thereof are different despite a similar amount of Ca added. This results from difference in the weight fraction of CaS.
  • Example 8 [263] The steel of example 5 was exposed to a salt spray environment of lmdd for 300 days of to measure corrosion depth thereof. The results are shown in Table 10.
  • inventive examples 1 to 11 in which compositions are optimized and Ca is split-injected at least twice in a steel-making process indicate superior weather resistance.
  • inventive examples 3 to 11 in which at least one selected from Ti, Mo and W is added show results superior to inventive examples having no Ti, Mo and W added.
  • weather resistance is enhanced because CaS inclusion produced by Ca addition is dissolved in a water film condensed on the steel surface so that pH of the steel surface is elevated to form stable rust.
  • inventive examples according to the invention can produce high strength steel having at least 307MPa of yield strength and at least 483MPa of tensile strength.

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
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  • Organic Chemistry (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Sheet Steel (AREA)

Abstract

La présente invention a trait à de l'acier à excellente résistance aux intempéries dans une atmosphère marine, et son procédé de fabrication. Selon l'invention, l'acier est constitué d'une quantité allant jusqu'à 0,15 en poids de C, 1,0 % en poids de Si, 2,0 % en poids de Mn, 0,2 à 1,0 % en poids de Cu, 0,2 à 5,0 % en poids de Ni, 0,001 à 0,01 % en poids d'Al, jusqu'à 0,03 % en poids de P, 0,002 à 0,03 % en poids de S, 0,001 à 0,1 % en poids de Ca. Le reste contient du Fe et des impuretés inévitables, et les teneurs en Ca, S, Al, Si sont déterminées par une équation 1 Ca(%)/S(%) > 1,5 Al(%)+2Si(%). En outre, l'acier comporte au moins 30 % en poids d'inclusion de CaS hydrosoluble sur des inclusions non métalliques à base de Ca. L'invention procure de l'acier à excellente résistance aux intempéries dans une atmosphère présentant une concentration élevée de salinité.
PCT/KR2005/003213 2004-11-12 2005-09-28 Acier a excellente resistance aux intemperies dans une atmosphere marine, et son procede de fabrication Ceased WO2006080658A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP05856389A EP1825014B1 (fr) 2004-11-12 2005-09-28 Procede de fabrication d'un acier a excellente resistance aux intemperies dans une atmosphere marine
CN2005800462457A CN101133177B (zh) 2004-11-12 2005-09-28 在海滨环境中具有优异耐候性的钢及其制造方法
AT05856389T ATE553225T1 (de) 2004-11-12 2005-09-28 Herstellungsverfahren für einen stahl mit hervorragender wetterbeständigkeit in meeresatmosphäre

Applications Claiming Priority (14)

Application Number Priority Date Filing Date Title
KR1020040092554A KR101115692B1 (ko) 2004-11-12 2004-11-12 해변 내후성이 우수한 고강도 강재 및 그 제조방법
KR10-2004-0092554 2004-11-12
KR1020040098152A KR101125895B1 (ko) 2004-11-26 2004-11-26 인성이 우수한 고강도 해변용 내후성강의 제조방법
KR10-2004-0109218 2004-12-01
KR10-2004-0098152 2004-12-01
KR10-2004-0109221 2004-12-01
KR10-2004-0109220 2004-12-01
KR10-2004-0109217 2004-12-01
KR1020040109221A KR101126019B1 (ko) 2004-12-21 2004-12-21 인성이 우수한 고강도 해변용 내후성강의 제조방법
KR10-2004-0109647 2004-12-21
KR1020040109647A KR101125938B1 (ko) 2004-12-21 2004-12-21 인성과 강도가 우수한 저항복비 해변용 내후성강의 제조방법
KR1020040109217A KR101125944B1 (ko) 2004-12-21 2004-12-21 인성이 우수한 고강도 해변용 내후성강의 제조방법
KR1020040109220A KR101125874B1 (ko) 2004-12-21 2004-12-21 인성이 우수한 고강도 해변용 내후성강의 제조방법
KR1020040109218A KR101126013B1 (ko) 2004-12-21 2004-12-21 인성과 강도가 우수한 저항복비 해변용 내후성강의 제조방법

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CN104002014A (zh) * 2014-05-19 2014-08-27 南京钢铁股份有限公司 一种耐滨海地区大气腐蚀用钢的焊条电弧焊焊接工艺
JP2015151571A (ja) * 2014-02-13 2015-08-24 株式会社神戸製鋼所 耐食性に優れる塗装鋼材

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JP2000017383A (ja) * 1998-07-03 2000-01-18 Nippon Steel Corp 高耐候性鋼
WO2000061829A1 (fr) * 1999-04-08 2000-10-19 Kawasaki Steel Corporation Produit en acier resistant a la corrosion atmospherique
KR20020041031A (ko) 2000-11-25 2002-06-01 이구택 인장강도가 우수한 해안 내후성강 및 그 제조방법
KR20030055534A (ko) 2001-12-27 2003-07-04 주식회사 포스코 해안용 내후성강 제조방법
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JPH06320234A (ja) * 1993-03-15 1994-11-22 Nippon Steel Corp 海岸高耐候性クラッド鋼板の製造方法
JP2000017383A (ja) * 1998-07-03 2000-01-18 Nippon Steel Corp 高耐候性鋼
WO2000061829A1 (fr) * 1999-04-08 2000-10-19 Kawasaki Steel Corporation Produit en acier resistant a la corrosion atmospherique
KR20020041031A (ko) 2000-11-25 2002-06-01 이구택 인장강도가 우수한 해안 내후성강 및 그 제조방법
KR20030055534A (ko) 2001-12-27 2003-07-04 주식회사 포스코 해안용 내후성강 제조방법
KR20040059176A (ko) * 2002-12-28 2004-07-05 주식회사 포스코 인장강도 50㎏ｆ/㎟급 해안 내후성 강의 제조방법
KR20050115079A (ko) * 2004-06-03 2005-12-07 주식회사 포스코 해변 내후성이 우수한 강재 및 그 제조방법

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015151571A (ja) * 2014-02-13 2015-08-24 株式会社神戸製鋼所 耐食性に優れる塗装鋼材
CN104002014A (zh) * 2014-05-19 2014-08-27 南京钢铁股份有限公司 一种耐滨海地区大气腐蚀用钢的焊条电弧焊焊接工艺

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