US20170175236A1 - Induction heatable stainless steel sheet having excellent corrosion resistance and method of manufacturing the same - Google Patents

Induction heatable stainless steel sheet having excellent corrosion resistance and method of manufacturing the same Download PDF

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US20170175236A1
US20170175236A1 US15/372,800 US201615372800A US2017175236A1 US 20170175236 A1 US20170175236 A1 US 20170175236A1 US 201615372800 A US201615372800 A US 201615372800A US 2017175236 A1 US2017175236 A1 US 2017175236A1
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stainless steel
steel sheet
corrosion resistance
excellent corrosion
induction heatable
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Seong In Jeong
Sun Mi Kim
Man Jin HA
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Posco Holdings Inc
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Posco Co Ltd
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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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
    • B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, 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
    • 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
    • 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
    • C21D8/0236—Cold 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
    • 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
    • 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
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/18—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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B21B2001/225—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length by hot-rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • 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

Definitions

  • the present disclosure relates to a stainless steel sheet for cookware and a method of manufacturing the same and, more particularly, to a stainless steel sheet having excellent induction heating properties and corrosion resistance and a method of manufacturing an induction heatable stainless steel sheet having excellent corrosion resistance using a twin roll strip casting process.
  • austenitic stainless steel having good workability and corrosion resistance includes iron (Fe) as a base metal as well as chrome (Cr) and nickel (Ni) as main alloying ingredients.
  • Other alloying elements such as molybdenum (Mo) and copper (Cu) are commonly added thereto, and thus, various grades of steel have been developed for various uses.
  • Austenitic stainless steel has excellent corrosion resistance and workability, but is non-magnetic.
  • Austenitic stainless steel having excellent corrosion resistance and workability includes Ni, Mo, and the like, which are relatively costly raw materials.
  • SUS 400-series stainless steel a ferritic stainless steel, has been developed. 400-series stainless steels have the disadvantage that formability and corrosion resistance thereof are lower than those of SUS 300-series stainless steels, austenitic stainless steels, but have ferromagnetism.
  • Duplex stainless steel in which an austenite phase and a ferrite phase are mixed, has all of the advantages of austenitic and ferritic stainless steels, and various types of duplex stainless steel have been developed to date, having magnetic properties between the properties of austenitic and ferritic stainless steels.
  • the magnetism described above is properties effective for induction heating, however, ferritic stainless steels are vulnerable to corrosion. Therefore, an induction heatable material having excellent corrosion resistance is required for use in the manufacturing of cookware.
  • the stainless steel described above has been widely used as a material for various types of cookware. As the leisure culture has developed, in consideration of safety in resorts and other types of accommodation, cooking with induction heaters has become commonplace.
  • magnetism According to the content of ferrite in steel, magnetism may be present. According to a degree of magnetism, induction heating may be possible, and appropriate magnetism is required.
  • An example of a type of cookware using stainless steel may be a three ply pot, and the like.
  • an interior portion is formed of SUS 304 stainless steel, an outer cover portion is formed of SUS 430 stainless steel, and a middle portion is formed of aluminum (Al), bonded together.
  • a reason that cookware is formed using three kinds of material as described above is to secure corrosion resistance and induction heating properties.
  • An aspect of the present disclosure may provide an induction heatable stainless steel sheet having excellent corrosion resistance.
  • Another aspect of the present disclosure may provide a method of manufacturing an induction heatable stainless steel sheet having excellent corrosion resistance using a twin roll strip casting process.
  • an induction heatable stainless steel sheet having excellent corrosion resistance may include, by wt %, carbon (C): 0.1% or less (excepting 0%), silicon (Si): 0.2% to 3.0%, manganese (Mn): 1.0% to 4.0%, chromium (Cr): 19.0% to 23.0%, nickel (Ni): 0.3% to 2.5%, nitrogen (N): 0.18% to 0.3%, copper (Cu): 0.3% to 2.5%, iron (Fe) as a residual component thereof, and other unavoidable impurities.
  • a microstructure may include, by volume %, ferrite: 30% to 70% and austenite as a remainder thereof. Relative permeability of the stainless steel sheet may be 20 ⁇ r to 80 ⁇ r .
  • a method of manufacturing an induction heatable stainless steel sheet having excellent corrosion resistance and having relative permeability of 20 ⁇ r to 80 ⁇ r in which a microstructure may include, by volume %, ferrite: 30% to 70% and austenite as a remainder thereof, may include: preparing molten steel including, by wt %, carbon (C): 0.1% or less (excepting 0%), silicon (Si): 0.2% to 3.0%, manganese (Mn): 1.0% to 4.0%, chromium (Cr): 19.0% to 23.0%, nickel (Ni): 0.3% to 2.5%, nitrogen (N): 0.18% to 0.3%, copper (Cu): 0.3% to 2.5%, iron (Fe) as a residual component thereof, and other unavoidable impurities; and manufacturing a thin plate by supplying the molten steel to a space between twin rolls of a twin roll strip caster including the twin rolls rotating in opposite directions.
  • a single material is applied to smoothly perform induction heating, whereby induction heating properties may be easily applied to cookware.
  • an interior portion is formed of SUS 304 stainless steel
  • an outer cover portion is formed of SUS 430 stainless steel
  • a middle portion formed of Al or the like bonded together, and a process of manufacturing the same is very complex.
  • a stainless steel sheet solving a problem described above, may be provided.
  • a twin roll strip casting process is used to stably manufacture an induction heatable stainless steel sheet having excellent corrosion resistance.
  • FIG. 1 is a schematic diagram illustrating an example of a twin roll strip casting process preferably used to manufacture a stainless steel sheet according to an exemplary embodiment in the present disclosure.
  • FIGS. 2A and 2B are photographs of microstructures of an example of representative austenitic stainless steel and a conventional example of representative ferritic stainless steel.
  • FIG. 2A illustrates austenitic stainless steel (Austenite: FCC), and
  • FIG. 2B illustrates ferritic stainless steel (Ferrite: BCC).
  • FIG. 3 is a microstructure picture of Inventive example 1 in accordance with an exemplary embodiment in the present disclosure.
  • FIG. 4 is a graph illustrating relationship of relative permeability and pitting potential for each type of steel.
  • FIG. 5 is a graph illustrating induction heating properties of a conventional three ply pot (Conventional example) and a single ply pot according to Inventive example 1.
  • FIG. 6 is a graph illustrating relationship of the content of ferrite and relative permeability.
  • ferrite microstructures and austenite microstructures are properly mixed to provide an induction heatable stainless steel material having good corrosion resistance.
  • the stainless steel material may have appropriate magnetism to be used as a material for induction heatable cookware.
  • high nitrogen duplex stainless steel is appropriate for improving corrosion resistance, and is manufactured using a twin roll strip casting process to prevent bubbles or the like, caused by nitrogen gas in solidification in an exemplary embodiment in the present disclosure.
  • an induction heatable stainless steel sheet having excellent corrosion resistance may preferably include, by wt %, carbon (C): 0.1% or less (excepting 0%), silicon (Si): 0.2% to 3.0%, manganese (Mn): 1.0% to 4.0%, chromium (Cr): 19.0% to 23.0%, nickel (Ni): 0.3% to 2.5%, nitrogen (N): 0.18% to 0.3%, Cu: 0.3% to 2.5%, iron (Fe) as a residual component thereof, and other unavoidable impurities.
  • C an austenite phase forming element
  • C is an element effective for increasing strength of a material by solid solution strengthening.
  • C is easily combined with an element for forming carbides, such as Cr, effective for providing corrosion resistance at a ferrite-austenite phase boundary to lower the content of Cr around a grain boundary, thereby reducing corrosion resistance.
  • C in order to significantly increase corrosion resistance, it is preferable to add C within a range of 0.1% or less.
  • Si is partially added for a deoxidation effect.
  • Si a ferrite phase forming element
  • Si is an element concentrated in ferrite in an annealing heat treatment.
  • 0.2% or more of Si is required to be added.
  • Si is added in excess of 3.0%, hardness of a ferrite phase is sharply increased, to reduce elongation.
  • an austenite phase affecting securing of elongation may be difficult to secure.
  • Si is added excessively, slag fluidity is decreased in a steelmaking process, Si is combined with oxygen to form an inclusion, and corrosion resistance is decreased.
  • it is preferable to limit the content of Si to 0.2% to 3.0%.
  • N is an element greatly contributing to the stabilization of an austenite phase along with Ni in stainless steel, and an element concentrated in an austenite phase in an annealing heat treatment.
  • the content of N is increased to incidentally improve corrosion resistance and improve strength.
  • solid solubility of N may be changed according to the content of added Mn, and thus, controlling the content thereof may be required.
  • a blow hole, a pin hole or the like may be generated during casting due to excess of nitrogen solid solubility, thereby causing a surface defect of a product.
  • N and Mn which are different austenite stabilizing elements, are added in an amount equal to a reduced amount of Ni, an austenite stabilizing element, to adjust a ferrite phase fraction. Only when at least 0.15% or more of N is added, may an appropriate phase fraction be secured.
  • the content of N is required to be 0.18% or more. It is preferable to limit the content of N to 0.18% to 0.30%.
  • Mn is a deoxidizer and an element for increasing nitrogen solid solubility
  • Mn an austenite forming element
  • Ni an austenite forming element
  • Mn When the content of Mn is less than 1.0%, a proper austenite phase fraction is limited to being secured even by adjusting Ni, Cu, N or the like, an austenite forming element. In addition, as solid solubility of added N is low, a sufficient solid solution amount of nitrogen may not be obtained at atmospheric pressure. Thus, it is preferable to limit the content of Mn to 1.0% to 4.0%.
  • Cr a ferrite stabilizing element along with Si, mainly serves to secure a ferrite phase of stainless steel, and is an essential element for securing corrosion resistance.
  • the content of Cr is increased, corrosion resistance is increased.
  • the content of relatively expensive Ni or other austenite forming elements is required to be increased.
  • Ni an austenite stabilizing element along with Mn, Cu, and N, mainly serves to secure an austenite phase of stainless steel.
  • amounts of added Mn and N, different austenite phase forming elements are commonly increased to maintain sufficient phase fraction balance due to a reduction in Ni.
  • Ni should be added to secure sufficient stability of an austenite phase.
  • an austenite phase fraction is increased, and thus, there may be limitations in securing an appropriate austenite fraction.
  • the content of Ni is preferable to be limited to being 0.3% to 2.5%.
  • a residual component of the stainless steel sheet according to an exemplary embodiment in the present disclosure other than components described above may include iron (Fe) and other unavoidable impurities.
  • Other unavoidable impurities may include, for example, phosphorous (P), sulfur (S) or the like.
  • a stainless steel sheet according to an exemplary embodiment in the present disclosure may have a microstructure including, by volume %, ferrite: 30% to 70% and austenite as a remainder thereof.
  • Ferrite is a structure having magnetism, and thus may have induction heating properties. When a fraction thereof is less than 30%, the content of ferrite having magnetism is low, whereby induction heating efficiency may be low. When a fraction thereof exceeds 70%, the content of ferrite having magnetism is high, whereby induction heating efficiency may be excessively high. In this case, for example, when food is cooked, food may be stuck to a bottom of a cooking vessel.
  • a fraction of ferrite of a microstructure of a steel sheet according to an exemplary embodiment in the present disclosure to 30% to 70%.
  • relative permeability of a stainless steel sheet according to an exemplary embodiment in the present disclosure it is preferable to limit relative permeability of a stainless steel sheet according to an exemplary embodiment in the present disclosure to 20 ⁇ r to 80 ⁇ r .
  • relative permeability thereof is less than 20 ⁇ r , relative permeability is weak not to efficiently perform induction heating.
  • relative permeability thereof exceeds 80 ⁇ r relative permeability is too excessive, whereby food may be stuck to a bottom of a cooking vessel or may be easily burnt.
  • the steel sheet In order to improve pickling properties in a process of annealing and pickling a steel sheet, the steel sheet is bent before a pickling process. In this case, when bending severely occurs and a value of Md30 is great, an occurrence probability of strip breakage may be increased due to brittleness caused by martensite generation.
  • Md30 it is preferable to limit Md30 to 80 or less.
  • Elongation of a steel sheet according to an exemplary embodiment in the present disclosure may be 40% or more, and pitting potential thereof may be 280 mV or more.
  • a steel sheet according to an exemplary embodiment in the present disclosure may be used to manufacture cookware.
  • 500 cc of water at room temperature is heated by an induction heater, the water may be heated to boiling point within 10 minutes.
  • a molten steel including, by wt %, C: 0.1% or less (excepting 0%), Si: 0.2% to 3.0%, Mn: 1.0% to 4.0%, Cr: 19.0% to 23.0%, Ni: 0.3% to 2.5%, N: 0.18% to 0.3%, Cu: 0.3% to 2.5%, iron (Fe) as a residual component thereof, and other unavoidable impurities, is prepared.
  • the molten steel prepared as described above is supplied to a space between twin rolls of a twin roll strip caster, rotating in opposite directions, to manufacture a thin plate.
  • the twin roll strip caster is not particularly limited and may be, for example, a twin roll strip caster such as that illustrated in FIG. 1 or the like.
  • FIG. 1 illustrating an example of a twin roll strip manufacturing process preferably applied to manufacture a stainless steel sheet according to an exemplary embodiment in the present disclosure
  • FIG. 1 illustrating an example of a twin roll strip manufacturing process preferably applied to manufacture a stainless steel sheet according to an exemplary embodiment in the present disclosure
  • an example of a method of manufacturing a stainless steel sheet according to an exemplary embodiment in the present disclosure will be described in detail.
  • the molten steel prepared as described above is accommodated in a ladle 1 , and flows into a tundish 2 through a nozzle.
  • the molten steel flowing into the tundish 2 is supplied through a molten steel injection nozzle 3 between edge dams 6 installed in both ends of casting rolls 5 , in other words, between the casting rolls 5 , to be solidified.
  • a meniscus shield 7 protects a molten metal surface and an appropriate gas is injected inside the meniscus shield 7 to appropriately adjust an atmosphere.
  • an unexplained number 4 denotes a sump.
  • an induction heatable stainless steel sheet having relative permeability of 20 ⁇ r to 80 ⁇ r , in which a microstructure including, by volume %, ferrite: 30% to 70% and austenite as a remainder thereof, may be manufactured.
  • molten steel having a composition as described in Table 1 90 tons was prepared to be cast using a twin roll strip caster illustrated in FIG. 1 , thereby manufacturing a thin steel sheet.
  • a casting width was 1,300 mm
  • a casting thickness was 4.0 mm.
  • the thin steel sheet was hot-rolled at a high temperature to continuously manufacture a hot-rolled plate having a thickness of about 2.5 mm.
  • the hot-rolled plate was cold rolled at a reduction rate of 50% to 70% and was annealed at a temperature of 1150° C.
  • FIGS. 2A and 2B are pictures, in which microstructures of representative examples of conventional austenitic stainless steel (SUS 304 stainless steel) and ferritic stainless steel (SUS 430 stainless steel) are illustrated by way of example.
  • SUS 304 stainless steel conventional austenitic stainless steel
  • SUS 430 stainless steel ferritic stainless steel
  • FIG. 3 is a picture in which a microstructure of Inventive example 1 in Table 2 is visible
  • FIG. 4 illustrates investigated relative permeability and pitting potential with respect to Inventive example 1, along with SUS 304, SUS 430, and SUS 201 stainless steel.
  • a pot was manufactured using the stainless steel of Inventive example 1 in Table 2.
  • 500 cc of water at room temperature was heated by an induction heater, heating properties were investigated and results thereof are illustrated in FIG. 5 .
  • FIG. 5 also illustrates heating properties with respect to a conventional three ply pot (Conventional example).
  • the conventional three ply pot was manufactured, as an interior portion was formed of SUS 304 stainless steel, an outer cover portion was formed of SUS 430 stainless steel, and a middle portion was formed of aluminum (Al), bonded together.
  • a material has excellent corrosion resistance and induction heating properties.
  • corrosion resistance thereof was low.
  • strip breakage occurred when a heat treatment process was performed.
  • a cause of strip breakage occurrence was Md30 greater than 80. In this case, as martensite was easily generated in deformation, strip breakage occurred when a heat treatment process was performed.
  • Comparative example 1 was a complete ferrite structure. In this case, when a heat treatment process was performed, a martensite structure due to deformation did not occur. Thus, Comparative example 1 was determined not to be affected by a value of Md30.
  • a microstructure of austenitic stainless steel was formed of austenite, and ferrite was finely present therein.
  • a microstructure of ferritic stainless steel was formed of ferrite. Austenite was a nonmagnetic body, and ferrite was a ferromagnetic body and has strong magnetism.
  • Inventive example 1 in accordance with an exemplary embodiment in the present disclosure had structural properties in which an austenite structure and a ferrite structure were stacked to be complex composed, thereby having properties of austenite and ferrite at the same time.
  • magnetism thereof was between those of austenitic stainless steel (SUS 300-series stainless steel) and ferritic stainless steel (SUS 400-series stainless steel), and had magnetism, to allow for induction heatable properties.
  • an SUS 400-series material had a high degree of magnetism, but had significantly low pitting potential properties, a corrosion resistance index.
  • An SUS 200-series material had very little magnetism, but a value of pitting potential was significantly low to have poor corrosion resistance.
  • An SUS 300-series material had good corrosion resistance, but had no magnetism, thereby having properties without induction heating properties.
  • pitting potential of an SUS 304 steel grade is 280 mV or more, which may be a measure of good corrosion resistance.
  • Inventive example 1 in accordance with an exemplary embodiment in the present disclosure had corrosion resistance similar to that of an SUS 300-series material, had a median value of relative permeability indicating magnetism, and had proper induction heating properties. In other words, Inventive example 1 had good corrosion resistance and was induction heatable.
  • a conventional pot (Conventional example), formed to have a conventional three layer structure, had heating properties similar to those of a pot having a single layer structure formed using a material of Inventive example 1.
  • the conventional pot and the pot having a single layer structure formed using a material of Inventive example 1 allowed water to be boiled within 10 minutes.
  • the pot having a three layer structure formed using three kinds of material was manufactured with an interior portion formed of SUS 304 stainless steel, an outer cover portion formed of SUS 430 stainless steel, and a middle portion formed of Al, bonded together. A bonding process was added and a process using three kinds of material was complex, whereby process costs were high. According to an exemplary embodiment in the present disclosure, a material may be conveniently applied, thereby solving a conventional problem described above.

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US15/372,800 2015-12-21 2016-12-08 Induction heatable stainless steel sheet having excellent corrosion resistance and method of manufacturing the same Abandoned US20170175236A1 (en)

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KR101977492B1 (ko) * 2017-11-10 2019-08-28 주식회사 포스코 고질소 오스테나이트계 스테인리스 강 및 그 제조방법
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CN111575588B (zh) * 2020-06-08 2021-06-22 浦项(张家港)不锈钢股份有限公司 一种马氏体沉淀硬化不锈钢及其制备方法与应用
CN115062504B (zh) * 2022-05-24 2024-04-16 桂林理工大学 一种模拟计算任意双相不锈钢显微组织磁导率的方法

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US20150176108A1 (en) * 2013-12-24 2015-06-25 Nucor Corporation High strength high ductility high copper low alloy thin cast strip product and method for making the same

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US6096441A (en) * 1997-06-30 2000-08-01 Usinor Austenoferritic stainless steel having a very low nickel content and a high tensile elongation
KR20130060658A (ko) * 2011-11-30 2013-06-10 주식회사 포스코 린 듀플렉스 스테인리스강
US20150176108A1 (en) * 2013-12-24 2015-06-25 Nucor Corporation High strength high ductility high copper low alloy thin cast strip product and method for making the same

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