US20210388458A1 - High strength steel plate for structure with good seawater corrosion resistant property and method of manufacturing same - Google Patents

High strength steel plate for structure with good seawater corrosion resistant property and method of manufacturing same Download PDF

Info

Publication number
US20210388458A1
US20210388458A1 US17/291,823 US201917291823A US2021388458A1 US 20210388458 A1 US20210388458 A1 US 20210388458A1 US 201917291823 A US201917291823 A US 201917291823A US 2021388458 A1 US2021388458 A1 US 2021388458A1
Authority
US
United States
Prior art keywords
less
steel
steel plate
strength
content
Prior art date
Legal status (The legal status 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 status listed.)
Pending
Application number
US17/291,823
Other languages
English (en)
Inventor
Jin-ho Park
Ju-Yeon Yi
Seng-Ho YU
Bong-Ju Kim
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
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
Application filed by Posco Co Ltd filed Critical Posco Co Ltd
Assigned to POSCO reassignment POSCO ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: PARK, JIN-HO, YU, Seng-Ho, KIM, BONG-JU, YI, Ju-Yeon
Publication of US20210388458A1 publication Critical patent/US20210388458A1/en
Assigned to POSCO HOLDINGS INC. reassignment POSCO HOLDINGS INC. CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). Assignors: POSCO
Assigned to POSCO CO., LTD reassignment POSCO CO., LTD ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: POSCO HOLDINGS INC.
Pending legal-status Critical Current

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • 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
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite

Definitions

  • the present disclosure relates to a steel fora structure having excellent corrosion resistance in an environment in which corrosion is accelerated by seawater, such as a steel plate for building structures on the coast, a ballast tank in a ship and related appurtenant equipment, or the like, and a method of manufacturing the steel.
  • Chromium and copper may play different roles depending on corrosive environments, and may exhibit an excellent anti-corrosion effect even in an environment, in which corrosion is accelerated by seawater, when added in an appropriate ratio.
  • chromium does not have a significant effect in an acidic environment, and copper causes casting cracking to occur in a casting process, so that relatively expensive nickel should be added in a certain level or more.
  • chromium has an effect of improving corrosion resistance, and the minimum amount of nickel added to prevent casting defects of copper-added steel may be reduced due to the recent development in continuous casting technology. Accordingly, the amount of expensive nickel added may be reduced, so that the cost of a product may be reduced.
  • Patent Document 1 discloses that a composition system and manufacturing conditions are controlled to control a microstructure of a steel sheet, but it is difficult to secure strength when the content of a low-temperature structure is low (less than 20%).
  • the content of nickel (Ni) is specified as being 0.05% or less, so that many casting defects may occur during casting.
  • Patent Document 2 0.1% or more of Al is added to form coarse oxide inclusions in a steelmaking process, and inclusions are crushed and elongated during a rolling process to form elongated inclusions. Accordingly, void formation is promoted to reduce localized corrosion resistance.
  • An aspect of the present disclosure is to provide a steel plate, having excellent corrosion resistance to a seawater environment, in which corrosion characteristics and a microstructure of a surface of the steel plate are controlled through optimization of a composition system and manufacturing conditions to improve strength characteristics of the steel plate and to significantly reduce a corrosion rate.
  • a high-strength steel (or steel plate) for structure comprising, by weight, carbon (C): 0.03% or more to less than 0.1%, silicon (Si): 0.1% or more to less than 0.8%, manganese (Mn): 0.3% or more to less than 1.5%, chromium (Cr): 0.5% or more to less than 1.5%, copper (Cu): 0.1% or more to less than 0.5%, aluminum (Al): 0.01% or more to less than 0.08%, titanium (Ti): 0.01% or more to 0.1% or less, nickel (Ni): 0.05% or more to less than 0.1%, niobium (Nb): 0.002% or more to less than 0.07%, phosphorus (P): 0.03% or less, sulfur (S): 0.02% or less, and a balance of iron (Fe) and unavoidable impurities.
  • C carbon
  • Si silicon
  • Mn manganese
  • Cr chromium
  • Cu copper
  • Al aluminum
  • the high-strength steel has a microstructure comprising, by area fraction, 20% or more of bainite, less than 80% of polygonal ferrite and acicular ferrite in total, and less than 10% of pearlite and MA as the other phases.
  • the carbon (C) may be contained in an amount of 0.03% or more to less than 0.09%.
  • the silicon (Si) may be contained in an amount of 0.2% or more to less than 0.8%.
  • the copper (Cu) may be contained in an amount of 0.1% or more to less than 0.45%.
  • the high-strength steel (or steel plate) for a structure may have yield strength of 500 MPa and tensile strength of 600 MPa.
  • a method of manufacturing a high-strength steel (or steel plate) for a structure includes: reheating a slab to a temperature of 1000° C. or more to 1200° C. or less, the slab comprising, by weight, carbon (C): 0.03% or more to less than 0.1%, silicon (Si): 0.1% or more to less than 0.8%, manganese (Mn): 0.3% or more to less than 1.5%, chromium (Cr): 0.5% or more to less than 1.5%, copper (Cu): 0.1% or more to less than 0.5%, aluminum (Al): 0.01% or more to less than 0.08%, titanium (Ti): 0.01% or more to 0.1% or less, nickel (Ni): 0.05% or more to less than 0.1%, niobium (Nb): 0.002% or more to less than 0.07%, phosphorus (P): 0.03% or less, sulfur (S): 0.02% or less, and a balance of
  • cooling a rolled steel plate from a cooling initiation temperature of 750° C. or more to a cooling finish temperature of 400° C. to 700° C. at a cooling rate of 10° C./sec or more.
  • a steel (or steel plate) for a structure in which corrosion resistance of the steel itself is improved in seawater atmosphere, having excellent strength characteristics of yield strength of 500 MPa or more and tensile strength of 600 MPa or more may be provided.
  • FIG. 1 is an image of Inventive Steel 4 observed with a microscope, in which (a) is an image obtained by observing a surface, (b) is an image obtained by observing a 1 ⁇ 4t portion in a thickness direction, and (c) is an image obtained by observing a 1 ⁇ 2t portion in the thickness direction.
  • Example embodiments of the present disclosure may be modified in various forms, and the scope of the present disclosure should not be construed as being limited to the embodiments described below. These embodiments are provided to complete the present disclosure and to allow those skilled in the art to understand the scope of the disclosure.
  • the present inventors have conducted deep research into a method of improving corrosion resistance of a steel (or steel plate) for a structure itself. As a result, the inventors have found that when the contents of chromium and copper are appropriately controlled and manufacturing conditions such as a reheating temperature, a finish rolling temperature, a cooling end temperature, and the like, are optimized to control a microstructure, excellent seawater-resistant characteristics and strength characteristic may be secured. Based on this knowledge, the inventors have invented the present invention.
  • the high-strength steel (or steel plate) for a structure includes, by weight, carbon (C): 0.03% or more to less than 0.1%, silicon (Si): 0.1% or more to less than 0.8%, manganese (Mn): 0.3% or more to less than 1.5%, chromium (Cr): 0.5% or more to less than 1.5%, copper (Cu): 0.1% or more to less than 0.5%, aluminum (Al): 0.01% or more to less than 0.08%, titanium (Ti): 0.01% or more to 0.1% or less, nickel (Ni): 0.05% or more to less than 0.1%, niobium (Nb): 0.002% or more to less than 0.07%, phosphorus (P): 0.03% or less, sulfur (S): 0.02% or less, and a balance of iron (Fe) and unavoidable impurities
  • Carbon (C) is an element added to improve strength.
  • a content of carbon (C) is increased, hardenability may be increased to improve strength.
  • general corrosion resistance is reduced.
  • precipitation of carbide or the like is promoted, localized corrosion resistance is also affected.
  • the content of carbon (C) should be decreased to improve the general corrosion resistance and the localized corrosion resistance.
  • the content of carbon (C) is less than 0.03%, it is difficult to secure sufficient strength as a material for a steel (or steel plate) for a structure.
  • the content of carbon (C) is 0.1% or more, weldability is deteriorated to be inappropriate for the steel (or steel plate) for a structure.
  • the content of carbon (C) may be limited to 0.03% or more to less than 0.1%. From the viewpoint of corrosion resistance, the content of carbon (C) may be less than 0.09%. In some cases, the content of carbon (C) may be less than 0.08% to further prevent casting cracking and to reduce carbon equivalent.
  • a lower limit of the content of carbon (C) may be, in detail, 0.035%.
  • An upper limit of the content of carbon (C) may be, in detail, 0.06%. The upper limit of the content of carbon (C) may be, in further detail, 0.054%.
  • Silicon (Si) needs to be present in amount of 0.1% or more to serve as a deoxidizer and to serve to increase strength of steel.
  • silicon (Si) contributes to improvement in general corrosion resistance, it is advantageous to increase the content of silicon (Si).
  • the content of silicon (Si) may be limited to, in detail, 0.1% or more to less than 0.8%.
  • silicon (Si) is added in an amount of 0.2% or more to improve corrosion resistance.
  • a lower limit of the content of silicon (Si) may be, in detail, 0.2%, and, in further detail, 0.27%.
  • An upper limit of the content of silicon (Si) may be, in detail, 0.5% and, in further detail, 0.44%.
  • Manganese (Mn) is an element effect in increasing the strength through solid-solution strengthening without reducing toughness.
  • MN manganese
  • an electrochemical reaction rate of a steel surface may be increased during a corrosion reaction to reduce corrosion resistance.
  • manganese (Mn) is added in an amount of less than 0.3%, it may be difficult to secure durability of a steel plate for a structure. Meanwhile, when the content of manganese (Mn) is increased, hardenability may be increased to improve strength.
  • manganese (Mn) when manganese (Mn) is added in an amount of 1.5% or more, a segregation zone may b significantly developed in a central portion of thickness during slab casting in a steelmaking process, weldability may be reduced, and corrosion resistance of a surface of a steel plate may be reduced. Therefore, the content of manganese (Mn) may be limited to, in detail, 0.3% or more to less than 1.5%.
  • a lower limit of the content of manganese (Mn) may be, in detail, 0.4% and, in further detail, 0.5%.
  • An upper limit of the content of manganese (Mn) may be, in detail, 1.4% and, in further detail, 0.9%.
  • Chromium (Cr) is an element increasing the corrosion resistance by forming a chrome-containing oxide layer on a surface of the steel in a corrosive environment. Chromium (Cr) should be contained in an amount of 0.5 or more to exhibit a corrosion resistance effect depending on addition of chromium (Cr). However, when chromium (Cr) is contained in an amount of 1.5% or more, toughness and weldability are adversely affected. Therefore, the content of chromium (Cr) may be set to, in detail, be 0.5% or more to less than 1.5%. A lower limit of the content of chrome (Cr) may be, in detail, 0.6% and, in yet further detail, 1.2%.
  • An upper limit of content of chrome (Cr) may be, in detail, 1.4%. That is, in the steel (or steel plate) for a structure according to an example embodiment, the content of chrome (Cr) may be, in detail, 1.2% or more to 1.4% or less (that is, 1.2% to 1.4%).
  • copper (Cu) When copper (Cu) is contained in an amount of 0.05 wt % or more together with nickel (Ni), exudation of iron (Fe) is delayed, which is effective in improving general corrosion resistance and localized corrosion resistance.
  • the content of copper (Cu) when the content of copper (Cu) is 0.5% or more, copper (Cu) in a liquid state melts into a grain boundary during production of a slab. Thus, cracking occurs during hot working (“hot shortness”). Therefore, the content of copper (Cu) may be limited to, in detail, 0.1% or more to less than 0.5%. In particular, a lower limit of the content of copper (Cu) may be, in detail, 0.2% and, in yet further detail, 0.28%.
  • a frequency of occurrence of the surface cracking may vary depending on the content of each element, but the content of copper (Cu) may be set to be, in detail, less than 0.45% and, in yet further detail, 0.43% or less to significantly reduce possibility that surface cracking occurs, irrespective of the content of each element.
  • Aluminum (Al) is an element added for deoxidation, and reacts with nitrogen (N) in the steel in such a manner that an aluminum nitride (AlN) is formed and austenite grains are refined to improve toughness.
  • the content of aluminum (Al) in a dissolved state may be, in detail, 0.01% or more for sufficient deoxidation.
  • a lower limit of the content of aluminum (Al) may be, in detail, 0.02% and, in further detail, 0.022%.
  • the content of aluminum (Al) may be limited to, in detail, less than 0.08%.
  • An upper limit of aluminum (Al) may be, in detail, 0.05% and, in further detail, 0.034%.
  • Titanium (Ti) is bonded to carbon (C) in steel to form TiC when added in an amount of 0.01% or more, serving to improve strength due to a precipitation strengthening effect. Meanwhile, when the content of Ti is added in an amount of 0.1% or more, a strength improvement effect is not large, as compared with the increase in the content thereof. Accordingly, the content of titanium (Ti) may be limited to 0.01% or more to less than 0.1%. A lower limit of the content of titanium (Ti) may be, in detail, 0.015%. In addition, an upper limit of the content of titanium (Ti) may be, in further detail, 0.05%, and, in yet further detail, 0.028%.
  • nickel (Ni) when nickel (Ni) is contained in an amount of 0.05% or more, it is effective in improving general corrosion resistance and localized corrosion resistance. Meanwhile, a lower limit of the content of Nickel (Ni) may be, in detail, 0.07%.
  • nickel (Ni) when nickel (Ni) is added together with copper (Cu), nickel (Ni) reacts with copper (Cu) in such a manner that formation of a copper (Cu) phase is suppressed to prevent hot shortness from occurring. In most Cu-added steels, nickel (Ni) is generally added at one or more times of the content of copper (Cu).
  • an element related to carbon equivalent such as carbon (C) or manganese (Mn)
  • C carbon
  • Mn manganese
  • Cu copper
  • an upper limit of the content of nickel (Ni) may be limited to, in detail, 0.1% in consideration of a relative addition effect.
  • the upper limit of the content of nickel (Ni) may be, in further detail, 0.09%.
  • Niobium (Nb) is an element bonded to carbon in steel to form NbC such as titanium (Ti), serving to strengthen precipitation.
  • NbC such as titanium (Ti)
  • Ti titanium
  • the content of Nb may be limited to, in detail, 0.002% or more to less than 0.07%.
  • a lower limit of the content of niobium (Nb) may be, in further detail, 0.01% and, in yet further detail, 0.017%.
  • an upper limit of the content of niobium (Nb) may be, in further detail, 0.05% and, in yet further detail, 0.044%.
  • Phosphorus (P) is present as an impurity element in steel.
  • the phosphorous (P) is added in an amount greater than 0.03%, weldability is significantly reduced and toughness is deteriorated. Therefore, the content of phosphorous (P) is limited to, in detail, 0.03% or less.
  • An upper limit of the content of phosphorous (P) may be, in detail, 0.02% and, in further detail, 0.018%. Since phosphorous (P) is an impurity, it is advantageous as the content of phosphorous (P) is reduced. Therefore, a lower limit of the content of phosphorous (P) is not separately limited.
  • Sulfur (S) is present as an impurity in steel.
  • the content of sulfur (S) is greater than 0.02%, ductility, impact toughness, and weldability of steel are deteriorated. Accordingly, the content of sulfur (S) may be limited to, in detail, 0.02% or less.
  • Sulfur (S) is apt to react with manganese (Mn) to form an elongated inclusion such as manganese sulfide (MnS). And voids, formed on both ends of the elongated inclusion, may be an initiation point of localized corrosion. Therefore, an upper limit of the content of sulfur (S) may be limited to, in further detail, 0.01% and, in yet further detail, 0.008% or less.
  • sulfur (S) is an impurity, it is advantageous as the content of sulfur (S) is reduced. Therefore, a lower limit of the content of sulfur (S) is not separately limited.
  • a balance may be iron (Fe).
  • Fe iron
  • unintended impurities may be inevitably incorporated from raw materials or surrounding environments, so that they may not be excluded. Since these impurities are commonly known to those skilled in the art, and all contents thereof are not specifically mentioned in this specification.
  • the high-strength steel (or steel plate) for a structure may have a microstructure including, by area fraction, 20% or more of bainite, less than 80% of polygonal ferrite and acicular ferrite in total, and less than 10% of pearlite and martensite-austenite (MA) as the other phases.
  • a microstructure including, by area fraction, 20% or more of bainite, less than 80% of polygonal ferrite and acicular ferrite in total, and less than 10% of pearlite and martensite-austenite (MA) as the other phases.
  • an area fraction of bainite may be, in detail, 20% or more, in further detail, 30% or more, and, in yet further detail, 51% or more.
  • an area fraction of bainite may be 78% or less.
  • an area fraction of bainite may be 68% or more to 71% or less.
  • an area fraction of polygonal ferrite and acicular ferrite in total may be less than 80% and, in further detail, 45% or less.
  • an area fraction of polygonal ferrite and acicular ferrite in total may be 10% or more and, in further detail, 19% or more.
  • an area fraction of polygonal ferrite and acicular ferrite in total may be 25% or more to 30% or less and, in further detail, 27% or more to 30% or less.
  • an area fraction of pearlite and martensite-austenite (MA) as the other phases may be less than 10%, in detail, 5% or less, in further detail, 4% or less, and, in yet further detail, 2% or less.
  • thick steel plate strength of at least 500 MPa, in detail, 600 MPa or more should be secured to be used as a material of a high-strength steel plate for strength.
  • a microstructure mainly included 20% or more of bainite and other phases of polygonal and/or acicular ferrite.
  • pearlite and MA other phases, are contained in an amount of 10% or more, low-temperature toughness and corrosion resistance may be insufficient in an environment in which the steel (or steel plate) for a structure according to the present disclosure is used. Therefore, an upper limit of the area fraction of pearlite and MA may be less than 10%.
  • the high-strength steel (or steel plate) for a structure according to an example embodiment may satisfy the above-mentioned composition system and microstructure to have yield strength of 500 MPa or more and tensile strength of 600 MPa or more.
  • a method of manufacturing a high-strength steel (or steel plate) for a structure may include a slab reheating process, a hot rolling process, and a cooling process. Detailed conditions of each of the processes are as follows.
  • a slab having the above-mentioned composition system is prepared, and then heated within a temperature range of 1000° C. to 1200° C.
  • the reheating temperature may be set to 1000° C. or more to solid-solubilize carbonitride formed during casting.
  • the reheating temperature may be set to, in further detail, 1050° C. or more to fully solid-solubilize the carbonitride.
  • austenite may be formed to be coarse. Therefore, the reheating temperature may be, in detail, 1200° C. or less.
  • a hot rolling process including rough rolling and finish rolling, may be performed on the reheated slab.
  • the finish rolling may be completed, in detail, at 750° C. or more of finish rolling temperature.
  • the finish rolling temperature is less than 750° C., it may cause a problem of producing a large amount of ferrite by air-cooling.
  • the finish rolling temperature is more than 950 C, strength and toughness may be reduced due to structure coarseness. Therefore, the finish rolling temperature may be limited to, in detail, 750° C. to 950° C.
  • the hot-rolled steel material is cooled through water cooling.
  • a core technology is to secure high strength of even a thick steel plate through sufficient cooling, and it is necessary to perform a cooling process to a temperature of 700° C. or less at a cooling rate of 10° C. or more.
  • the cooling process may be started at a cooling initiation temperature of 750° C. or more.
  • micro-cracking may occur in a central portion due to a quenching process to cause deviation of material properties in a surface and a central portion of a product and a deviation of material properties in front/end portions of the product.
  • the cooling process may be finished at temperature of, in detail, 400° C. or more.
  • a steel plate rolled may be cooled, in detail, from the cooling initiation temperature of 750° C. or more to the cooling finish temperature of 400° C. to 700° C. at a cooling rate of 10° C./sec or more.
  • a range of the cooling finish temperature may be, in further detail, 500° C. to 650° C. and, in yet further detail, 522° C. to 614° C.
  • An upper limit of the cooling rate is mainly related to equipment capacity. When the cooling rate is 10° C./sec or more, a meaningful change in strength does not occur even with an increase in the cooling rate. Therefore, the upper limit of the cooling rate is not separately limited. On the other hand, a lower limit of the cooling rate may be, in detail, 20° C./sec, in further detail, 25° C./sec, and, in yet further detail, 30° C./sec.
  • a slab was produced by preparing molten steel having a composition system listed in Table 1 below and then performing a continuous casting process. The produced slab was reheated, hot-rolled, and cooled under manufacturing conditions of Table 2 below to manufacture a steel plate.
  • a microstructure of the manufactured steel plate was observed with optical and electron microscopes to measure an area fraction of each phase, and yield strength and tensile strength were measured through a tensile test and are listed in Table 3.
  • a specimen was immersed in a 3.5% NaCl solution, simulating seawater. The specimen was inserted into an ultrasonic cleaner together with a 50% HCl+0.1% hexamethylene tetramine solution to be cleaned, and weight loss was measured and then divided by a surface area of an initial specimen to calculate a corrosion rate.
  • a relative corrosion rate was evaluated based on the corrosion rate of Comparative Steel 1 as 100, and the results are listed in Table 3.
  • Inventive Steels 1 to 4 had a microstructure having a low-temperature structure including 20% or more of bainite based on ferrite, and thus, had high strength of yield strength of 500 MPa or more and tensile strength of 600 MPa or more, so that they had a sufficient material of a steel (or steel plate) for a structure.
  • Inventive Steels 1 to 4 satisfied the composition range specified in the present disclosure to exhibit a lower corrosion rate than Comparative Steel 1, and thus, may have sufficient lifespan in a seawater-resistant atmosphere.
  • Comparative Steels 1 to 3 a composition range of Cr, Cu, Ni or Mn was outside the range of the present disclosure. For this reason, although Comparative Steels 1 to 3 were manufactured using a manufacturing method satisfying manufacturing conditions of the present disclosure, they exhibited a high corrosion rate of 100 or more. As a result, Comparative Steels 1 to 3 did not have sufficient lifespan in a sea-resistant atmosphere.
  • a steel plate for a structure according to an example embodiment contained 1.2% or more to 1.4% or less of Cr to have most excellent lifespan characteristics in a seawater-resistant atmosphere.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
US17/291,823 2018-11-08 2019-11-08 High strength steel plate for structure with good seawater corrosion resistant property and method of manufacturing same Pending US20210388458A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
KR1020180136846A KR102142774B1 (ko) 2018-11-08 2018-11-08 내해수 특성이 우수한 고강도 구조용강 및 그 제조방법
KR10-2018-0136846 2018-11-08
PCT/KR2019/015124 WO2020096398A1 (fr) 2018-11-08 2019-11-08 Plaque d'acier à haute résistance pour structure possédant une bonne propriété de résistance à la corrosion par l'eau de mer et son procédé de fabrication

Publications (1)

Publication Number Publication Date
US20210388458A1 true US20210388458A1 (en) 2021-12-16

Family

ID=70612140

Family Applications (1)

Application Number Title Priority Date Filing Date
US17/291,823 Pending US20210388458A1 (en) 2018-11-08 2019-11-08 High strength steel plate for structure with good seawater corrosion resistant property and method of manufacturing same

Country Status (6)

Country Link
US (1) US20210388458A1 (fr)
EP (1) EP3878996A4 (fr)
JP (1) JP7332692B2 (fr)
KR (1) KR102142774B1 (fr)
CN (1) CN112969809B (fr)
WO (1) WO2020096398A1 (fr)

Family Cites Families (25)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06316723A (ja) * 1993-03-12 1994-11-15 Kobe Steel Ltd ガス切断性及び溶接性の優れた建築構造用耐候性耐火鋼材の製造方法
JPH07216500A (ja) * 1994-01-28 1995-08-15 Sumitomo Metal Ind Ltd 耐食性の優れた高強度鋼材及びその製造方法
KR100371960B1 (ko) * 2000-09-29 2003-02-14 주식회사 포스코 60킬로그램급 인장강도를 갖는 고내후성 및 고가공성열연강판 및 그 제조방법
KR20040054272A (ko) 2002-12-18 2004-06-25 주식회사 포스코 내해수 부식성이 우수한 선체내 강관재의 제조방법
KR100942088B1 (ko) * 2005-03-28 2010-02-12 가부시키가이샤 고베 세이코쇼 확공 가공성이 우수한 고강도 열연 강판 및 그의 제조방법
KR100815709B1 (ko) * 2006-12-12 2008-03-20 주식회사 포스코 내후성 및 가공성이 우수한 고강도 냉연강판과 그 제조방법
KR101018159B1 (ko) * 2008-05-15 2011-02-28 주식회사 포스코 저온인성이 우수한 고강도 강판 및 그 제조방법
CN101883875B (zh) * 2007-12-04 2012-10-10 Posco公司 具有出色低温韧性的高强度钢板及其制造方法
KR100951296B1 (ko) * 2007-12-04 2010-04-02 주식회사 포스코 저온인성이 우수한 고강도 라인파이프용 강판 및 그제조방법
KR101125886B1 (ko) * 2008-11-29 2012-03-21 주식회사 포스코 강산 염수용액 내에서 전면부식 및 국부부식 저항성과 용접열영향부 인성이 우수한 고강도 선박용 강재 및 그 제조방법
CA2756409C (fr) * 2009-10-28 2013-12-31 Nippon Steel Corporation Tole d'acier pour des tubes de canalisation presentant une excellente resistance et une excellente ductilite et procede de fabrication de cette derniere
KR101289124B1 (ko) 2009-12-10 2013-07-23 주식회사 포스코 해수 내식성이 우수한 선박용 강재
KR101289154B1 (ko) 2009-12-29 2013-07-23 주식회사 포스코 내식성 및 충격인성이 우수한 열연강판 및 그 제조방법
JP5573265B2 (ja) * 2010-03-19 2014-08-20 Ｊｆｅスチール株式会社 引張強度５９０ＭＰａ以上の延靭性に優れた高強度厚鋼板およびその製造方法
JP6194951B2 (ja) * 2013-04-15 2017-09-13 新日鐵住金株式会社 熱延鋼板
KR101536471B1 (ko) * 2013-12-24 2015-07-13 주식회사 포스코 용접열영향부 인성이 우수한 초고강도 용접구조용 강재 및 이의 제조방법
KR20150112517A (ko) * 2014-03-28 2015-10-07 현대제철 주식회사 라인파이프용 강판 및 그 제조 방법
CN106480374B (zh) * 2015-08-31 2018-04-24 鞍钢股份有限公司 一种耐寒管线用高韧性低屈强比热轧厚板及其生产方法
CN105441799B (zh) * 2015-11-25 2017-05-24 武汉钢铁(集团)公司 低温环境用高强韧低屈强比调质钢板及其制备方法
JP6766642B2 (ja) * 2016-02-25 2020-10-14 日本製鉄株式会社 脆性き裂伝播停止特性に優れた鋼板およびその製造方法
JP6911575B2 (ja) * 2016-06-30 2021-07-28 日本製鉄株式会社 脆性き裂伝播停止特性に優れた鋼板およびその製造方法
KR101889182B1 (ko) * 2016-12-20 2018-08-16 주식회사 포스코 길이방향 균일 연신율 및 저온 인성이 우수한 용접강관용 강재, 이의 제조방법 및 이를 이용한 강관
KR101899689B1 (ko) * 2016-12-23 2018-09-17 주식회사 포스코 길이방향 균일 연신율이 우수한 용접강관용 강재, 이의 제조방법 및 이를 이용한 강관
CN108728733A (zh) * 2017-04-24 2018-11-02 鞍钢股份有限公司 输送煤制天然气用x70管线钢板及其制造方法
CN108467993B (zh) * 2018-06-11 2020-02-18 鞍钢股份有限公司 一种低温管线用超宽高韧性热轧厚板及其生产方法

Also Published As

Publication number Publication date
KR20200053342A (ko) 2020-05-18
JP7332692B2 (ja) 2023-08-23
KR102142774B1 (ko) 2020-08-07
EP3878996A4 (fr) 2022-01-05
JP2022506661A (ja) 2022-01-17
CN112969809A (zh) 2021-06-15
EP3878996A1 (fr) 2021-09-15
CN112969809B (zh) 2023-12-15
WO2020096398A1 (fr) 2020-05-14

Similar Documents

Publication Publication Date Title
US20200087764A1 (en) High-strength steel sheet
KR101989726B1 (ko) 고강도 강판 및 그 제조 방법
JP5195413B2 (ja) 曲げ加工性及び靭性の異方性に優れた高強度熱延鋼板及びその製造方法
KR100371960B1 (ko) 60킬로그램급 인장강도를 갖는 고내후성 및 고가공성열연강판 및 그 제조방법
JP2017002332A (ja) 加工性に優れた高強度鋼板およびその製造方法
US20160199892A1 (en) High-strength hot-rolled plated steel sheet and method for manufacturing the same
US20210388458A1 (en) High strength steel plate for structure with good seawater corrosion resistant property and method of manufacturing same
KR20160025185A (ko) 고강도 열연도금강판 및 그 제조 방법
CN113227426B (zh) 具有优异的脆性断裂抗力的结构钢和用于制造其的方法
CN114761598B (zh) 具有优异的耐海水腐蚀性的结构用钢板及其制造方法
CN111349850A (zh) 一种高耐蚀耐候钢及其制造方法
CN114008232B (zh) 具有优异耐腐蚀性的结构用高强度钢及其制造方法
KR101185222B1 (ko) 고강도 ａｐｉ 열연강판 및 그 제조 방법
KR101185232B1 (ko) 고강도, 고인성을 갖는 ａｐｉ 열연강판 및 그 제조 방법
KR101467030B1 (ko) 고강도 강판 제조 방법
KR101546147B1 (ko) 고강도 후판 및 그 제조 방법
KR101505278B1 (ko) 원유탱크용 강재 및 그 제조방법
KR101443443B1 (ko) 고강도 강판 및 그 제조 방법
JP2023554299A (ja) 延性に優れた高強度鋼板及びその製造方法
KR20140119898A (ko) 열연강판 및 그 제조방법
KR20120044121A (ko) 저항복비를 갖는 고강도 ａｐｉ 열연강판 및 그 제조 방법
KR20110108787A (ko) 강도-연성 밸런스가 우수한 고강도 열연강판 및 그 제조 방법
KR20120044126A (ko) 도금성이 우수한 ａｐｉ 강판 및 그 제조 방법

Legal Events

Date Code Title Description
AS Assignment

Owner name: POSCO, KOREA, REPUBLIC OF

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:PARK, JIN-HO;YI, JU-YEON;YU, SENG-HO;AND OTHERS;SIGNING DATES FROM 20210413 TO 20210420;REEL/FRAME:057112/0983

STPP Information on status: patent application and granting procedure in general

Free format text: DOCKETED NEW CASE - READY FOR EXAMINATION

AS Assignment

Owner name: POSCO HOLDINGS INC., KOREA, REPUBLIC OF

Free format text: CHANGE OF NAME;ASSIGNOR:POSCO;REEL/FRAME:061561/0730

Effective date: 20220302

AS Assignment

Owner name: POSCO CO., LTD, KOREA, REPUBLIC OF

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:POSCO HOLDINGS INC.;REEL/FRAME:061777/0937

Effective date: 20221019

STPP Information on status: patent application and granting procedure in general

Free format text: NON FINAL ACTION MAILED

STPP Information on status: patent application and granting procedure in general

Free format text: NON FINAL ACTION MAILED

STPP Information on status: patent application and granting procedure in general

Free format text: RESPONSE TO NON-FINAL OFFICE ACTION ENTERED AND FORWARDED TO EXAMINER