WO2023113535A1 - Feuille d'acier laminée à froid pour émail, ayant d'excellentes propriétés anti-écaillage et son procédé de fabrication - Google Patents

Feuille d'acier laminée à froid pour émail, ayant d'excellentes propriétés anti-écaillage et son procédé de fabrication Download PDF

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WO2023113535A1
WO2023113535A1 PCT/KR2022/020584 KR2022020584W WO2023113535A1 WO 2023113535 A1 WO2023113535 A1 WO 2023113535A1 KR 2022020584 W KR2022020584 W KR 2022020584W WO 2023113535 A1 WO2023113535 A1 WO 2023113535A1
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steel sheet
cold
rolled steel
equation
enamel
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PCT/KR2022/020584
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Korean (ko)
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김재익
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주식회사 포스코
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    • 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
    • C21D8/0221—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
    • C21D8/0273—Final recrystallisation annealing
    • 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
    • C21D8/0278—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular surface treatment
    • 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
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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 a steel sheet, and more particularly, to a cold-rolled steel sheet for vitreous enameling with excellent fishscale resistance and a manufacturing method thereof.
  • Enameled steel sheet is a surface-treated product in which corrosion resistance, weather resistance, heat resistance, and chemical resistance are improved by applying a glassy glaze on a base steel sheet such as a hot-rolled steel sheet or a cold-rolled steel sheet and then firing at a high temperature.
  • the enamel steel sheet is used as a material for building exteriors, home appliances, tableware, and various industrial uses.
  • rimmed steel was mainly used for the enamel steel sheet in the early stage, recently, as the continuous casting method is used to improve productivity, most of the materials are continuously cast by the continuous casting method.
  • Fishscale defects one of the problems of the enamel steel sheet, are supersaturated in the steel during the process of cooling after firing hydrogen dissolved in the steel during the manufacturing process of the enamel product, and then released to the surface of the steel over time. It is a defect that causes the enamel layer to fall off in the shape of meat vinyl.
  • OCA open coil annealing
  • the recently developed enamel steel sheet utilizes a continuous annealing process.
  • Enamel steel by the continuous annealing method using the continuous annealing process typically uses, for example, precipitates such as titanium (Ti) or inclusions secured by the non-deoxidation method as a hydrogen storage source based on ultra-low carbon steel.
  • precipitates such as titanium (Ti) or inclusions secured by the non-deoxidation method as a hydrogen storage source based on ultra-low carbon steel.
  • titanium nitride (TiN) titanium nitride
  • inclusions occurs in the continuous casting stage of the steelmaking process. This causes a decrease in workability and a direct problem in production load.
  • the titanium nitride mixed in the molten steel exists on the upper part of the steel plate and causes a blister defect, which is a typical bubble defect.
  • a large amount of added titanium forms a titanium-based oxide layer, which inhibits the adhesion between the steel plate and the glaze layer. cause problems
  • a technical problem to be solved by the present invention is to provide a high-strength cold-rolled steel sheet for vitreous enameling, which has a yield strength of 220 MPa or more after enameling, no bubble defects, and excellent enamel adhesion and fishscale resistance.
  • Another technical problem to be solved by the present invention is to provide a method for manufacturing a cold-rolled steel sheet having the above advantages.
  • the thickness of the oxide layer formed in an inward direction from the surface of the cold-rolled steel sheet may be 0.006 to 0.030 ⁇ m.
  • the cold-rolled steel sheet may satisfy Equation 1 below.
  • the cold-rolled steel sheet may satisfy Equation 2 below.
  • the cold-rolled steel sheet may satisfy Equation 3 below.
  • Equation 3 P c is the number of surface irregularities per unit centimeter (cm), R max is the maximum point roughness value ( ⁇ m), and S e is the temper reduction rate (%))
  • the cold-rolled steel sheet may have a yield strength of 220 MPa or more after enamel firing heat treatment. In one embodiment, the cold-rolled steel sheet may have enamel adhesion of 95% or more. In one embodiment, the hydrogen permeability ratio of the cold-rolled steel sheet may be 600 sec/mm 2 or more.
  • a method for manufacturing a cold-rolled steel sheet contains, by weight, C: 0.0003 to 0.003%, Mn: 0.25 to 0.55%, Si: 0.001 to 0.03%, Al: 0.0005 to 0.0015%, P: 0.01 to 0.03% S: 0.001 to 0.010%, Cu: 0.03 to 0.08%, N: 0.008 to 0.015%, Mo: 0.1 to 0.3%, O: 0.025 to 0.055% and the balance Fe and unavoidable impurities Reheating the slab to a temperature range of 1,150 to 1,280 ° C., hot rolling the heated slab to a finish hot rolling temperature range of 890 to 950 ° C., winding the hot-rolled hot-rolled steel sheet to a temperature range of 580 to 720 ° C.
  • Step cold-rolling the rolled hot-rolled steel sheet at a cold rolling reduction rate of 60 to 90%, annealing the cold-rolled cold-rolled steel sheet at an annealing temperature of 720 to 850 ° C. for 10 to 70 seconds, and a reduction rate of 2.5% or less It may include preparing an annealed sheet by temper rolling, and subjecting the annealed sheet to enamel firing heat treatment at a temperature range of 780 to 850 °C.
  • a method of manufacturing a cold-rolled steel sheet may satisfy Equation 1 below.
  • the method for manufacturing a cold-rolled steel sheet may satisfy Equation 2 below.
  • a method for manufacturing a cold-rolled steel sheet may satisfy Equation 3 below.
  • Equation 3 P c is the number of surface irregularities per unit centimeter (cm), R max is the maximum point roughness value ( ⁇ m), and S e is the temper reduction rate (%))
  • the cold-rolled steel sheet according to an embodiment of the present invention provides a cold-rolled steel sheet excellent in enamel adhesion and fishscale resistance by controlling the steel composition, and is used in various applications such as home appliances, chemical appliances, kitchen appliances, sanitary appliances, and interior and exterior materials for buildings. Can be used for absence.
  • a method for manufacturing a cold-rolled steel sheet according to another embodiment of the present invention may provide a method for manufacturing a cold-rolled steel sheet having the above advantages.
  • FIG. 1 is a schematic cross-sectional view of a cold-rolled steel sheet according to an embodiment.
  • first, second and third are used to describe, but are not limited to, various parts, components, regions, layers and/or sections. These terms are only used to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention.
  • % means weight%, and 1ppm is 0.0001 weight%.
  • the meaning of further including an additional element means replacing and including iron (Fe) as much as the additional amount of the additional element.
  • FIG. 1 is a schematic cross-sectional view of a cold-rolled steel sheet 100 according to an embodiment.
  • a cold-rolled steel sheet 100 includes a steel sheet base material 10 and an oxide layer 20. It is formed in an inward direction from both surfaces of the steel sheet base material 10 and the cold-rolled steel sheet 100, and includes an oxide layer 20 that is distinguished from the steel sheet base material 10.
  • C 0.0003 to 0.003%
  • Mn 0.25 to 0.55%
  • Si 0.001 to 0.03%
  • Al 0.0005 to 0.0015%
  • P 0.01 to 0.03%
  • S 0.001 to 0.010%
  • Cu 0.03 to 0.08%
  • N 0.008 to 0.015%
  • Mo 0.1 to 0.3%
  • O 0.025 to 0.055%
  • Fe and unavoidable impurities in weight%, C: 0.0003 to 0.003%, Mn: 0.25 to 0.55%, Si: 0.001 to 0.03%, Al: 0.0005 to 0.0015%
  • P 0.01 to 0.03%
  • S 0.001 to 0.010%
  • Cu 0.03 to 0.08%
  • N 0.008 to 0.015%
  • Mo 0.1 to 0.3%
  • O 0.025 to 0.055%
  • wt% may be expressed as %.
  • Carbon (C) is an element that affects steel sheet properties such as solid solution strengthening, aging, and cell defects.
  • the carbon content may be 0.0003 to 0.0030%. Specifically, the carbon content may range from 0.0005 to 0.0028%.
  • Manganese (Mn) is a typical solid solution strengthening element, which precipitates sulfur dissolved in steel in the form of manganese sulfide (MnS) to prevent hot shortness and promotes the precipitation of carbides.
  • the manganese content may be 0.25 to 0.55%. Specifically, the manganese content may range from 0.27 to 0.53%.
  • Silicon (Si) is an element that promotes the formation of precipitates that increase strength and act as a hydrogen storage source.
  • the silicon content may be 0.001 to 0.030%. Specifically, the silicon content may range from 0.002 to 0.028%.
  • Aluminum (Al) is used as a strong deoxidizer to remove oxygen from molten steel in the steelmaking stage, and is a representative element that fixes solid nitrogen.
  • the aluminum content may be 0.0005 to 0.0015%. Specifically, the aluminum content may range from 0.0006 to 0.0014%.
  • the fraction of inclusions acting as a hydrogen storage source is reduced to significantly increase the occurrence of fishscale, and the amount of dissolved nitrogen is lowered to secure a target material after firing. there is a problem.
  • the content of the aluminum is out of the lower limit of the range, it is used as the deoxidizer, and there is a problem in that the effect of fixing solid nitrogen is not expressed.
  • Phosphorus (P) is a solid solution strengthening element and an element that controls surface pickling.
  • the phosphorus content may be 0.01 to 0.03%. Specifically, the phosphorus content may range from 0.011 to 0.028%.
  • S is an element that causes red brittleness by combining with manganese (Mn).
  • the sulfur content may be 0.001 to 0.010%. Specifically, the sulfur content may range from 0.002 to 0.009%.
  • Copper (Cu) is an element added to improve solid solution strengthening and adhesion.
  • the copper content may be 0.03 to 0.08%. Specifically, the copper content may range from 0.032 to 0.078%.
  • the pickling speed is lowered in the acid treatment step, which is a pre-enamel process, so that the roughness characteristics suitable for the steel sheet cannot be obtained, resulting in a decrease in adhesion.
  • the content of copper is out of the lower limit of the range, there is a problem in that the effect such as the solid solution strengthening and the adhesion improvement is not expressed.
  • Nitrogen (N), along with carbon (C), is a representative interstitial solid solution strengthening element, and is an element for securing a target strength level after a firing process.
  • the nitrogen content may be 0.008 to 0.015%. Specifically, the nitrogen content may be 0.0083 to 0.0145%.
  • Molybdenum is an element that secures stable strength and provides a hydrogen storage source by forming various precipitates and oxides.
  • the molybdenum content may be 0.1 to 0.3%. Specifically, the molybdenum content may range from 0.11 to 0.29%.
  • Oxygen (O) is an essential element in forming inclusions that act as a hydrogen storage source for enamel steel.
  • the oxygen content may be 0.025 to 0.055%. Specifically, the oxygen content may range from 0.0255 to 0.0540%.
  • the unavoidable impurities refer to impurities that are unavoidably mixed in the manufacturing process of steelmaking and grain-oriented electrical steel sheets. Since unavoidable impurities are widely known, detailed descriptions are omitted.
  • the addition of elements other than the above-described alloy components is not excluded, and may be variously included within a range that does not impair the technical spirit of the present invention. When additional elements are included, they are included in place of Fe, which is the remainder.
  • the cold-rolled steel sheet 100 may include titanium (Ti), niobium (Nb), chromium (Cr), and vanadium (V).
  • the cold-rolled steel sheet for vitreous enameling with excellent fishscale resistance may optionally further contain at least one of Ti: 0.005% or less, Nb: 0.005% or less, Cr: 0.05% or less, and V: 0.003% or less.
  • the cold-rolled steel sheet 100 of the present invention not only does not arbitrarily add an element such as titanium (Ti), which has higher oxidizing properties than iron (Fe), but also controls the surface oxide layer, thereby improving the enamel adhesion between the steel sheet and the glaze. The same characteristics can be improved.
  • Ti titanium
  • Fe iron
  • the oxide layer 20 is formed in an inward direction from both surfaces of the cold-rolled steel sheet 100, which is the base material 10, and can be classified based on a point containing 5% of oxygen. Specifically, the thickness of the oxide layer was divided based on the point containing 5% of oxygen by analyzing the oxygen concentration from the surface to the inside of the cross section of the steel sheet. More specifically, the thickness of the oxide layer was measured using GDS (Glow Discharge Spectroscopy) starting from the point containing 5% of oxygen.
  • GDS Low Discharge Spectroscopy
  • the thickness of the oxide layer 20 may range from 0.006 to 0.030 ⁇ m. Specifically, the thickness of the oxide layer 20 may be 0.007 to 0.028 ⁇ m.
  • the thickness of the oxide layer 20 is out of the upper limit of the above range, there is a problem in that the surface properties of the steel sheet are deteriorated. If the thickness of the oxide layer 20 is outside the lower limit of the above range, the bonding force between the glaze layer and the steel sheet decreases, making it difficult to secure normal adhesion, resulting in a decrease in fishscale resistance.
  • an enamel product is a product in which an organic glaze is applied on a steel plate, and it is very important to secure adhesion between the steel plate and the glaze.
  • the main component of the glaze is composed of a silicon-oxide (SiO 2 ) system, and there is a problem of applying an expensive glaze such as NiO among the glaze components in order to prevent a decrease in adhesion to the steel plate.
  • the high-strength cold-rolled steel sheet for enamel having excellent enamel adhesion and fishscale resistance according to an embodiment of the present invention can improve enamel adhesion by controlling the thickness of the oxide layer on the surface of the steel sheet. Enamel adhesion can be improved by promoting covalent bonding with silicon (Si) atoms in the glaze layer by managing the thickness of the oxide layer composed of 90 wt% or more of iron oxide (FeO-based) within a certain range.
  • the cold-rolled steel sheet 100 satisfies Equation 1 below.
  • Equation 1 is a correlation between phosphorus (P) and copper (Cu) and silicon (Si). Equation 1 may range from 0.014 to 0.080. Specifically, Equation 1 may range from 0.0142 to 0.0798. By satisfying the above range, the cold-rolled steel sheet 100 can suppress enamel adhesion and surface bubble defects.
  • Equation 1 When the value of Equation 1 exceeds the upper limit of the range, gas inflow into the surface portion of the steel sheet increases, resulting in surface defects such as bubble defects, thereby reducing product reliability. When the value of Equation 1 is outside the lower limit of the range, there is a problem in that enamel properties such as enamel adhesion are deteriorated as the surface is not modified in the sulfuric acid pretreatment process.
  • the cold-rolled steel sheet 100 satisfies Equation 2 below.
  • Equation 2 is a correlation between aluminum (Al) and molybdenum (Mo) for carbon (C) and nitrogen (N).
  • Al aluminum
  • Mo molybdenum
  • Equation 2 above may be 0.0065 to 0.0310. Specifically, Equation 2 above may range from 0.0067 to 0.0305.
  • Equation 2 When the value of Equation 2 is outside the upper limit of the range, workability is good, but there is a problem in that the rolling and annealing sheetability is lowered and the manufacturing cost increases due to the increase in the amount of expensive alloy elements.
  • the value of Equation 2 When the value of Equation 2 is outside the lower limit of the range, there is a problem in that fishscale resistance is lowered as precipitation is not promoted, and workability is lowered as the amount of interstitial solid solution elements increases.
  • the cold-rolled steel sheet 100 satisfies Equation 3 below.
  • Equation 3 P c is the number of surface irregularities per unit centimeter (cm), R max is the maximum point roughness value ( ⁇ m), and S e is the temper reduction rate (%))
  • Equation 3 above may be 0.50 to 1.05. Specifically, Equation 3 above may range from 0.505 to 1.00. When the value of Equation 3 is outside the upper limit of the range, crystal grains of the steel sheet grow after the enamel firing process, resulting in a problem in securing target material and enamel characteristics. When the value of Equation 3 is out of the lower limit of the range, the wedge effect of the surface of the steel sheet is reduced, resulting in a decrease in adhesion to the glaze.
  • the cold-rolled steel sheet 100 may have a yield strength of 220 MPa or more after enamel firing heat treatment.
  • the yield strength of materials used for structural members is a physical property that determines dent resistance and shape freezing of members.
  • the yield strength after the enamel firing heat treatment is 220 MPa or more, there is an advantage in that the stability of the product is excellent in the heat treatment step for drying after the glaze treatment.
  • the cold-rolled steel sheet 100 may have enamel adhesion of 95% or more. Specifically, the enamel adhesion may be 96% or more. Within the above range, the cold-rolled steel sheet 100 can be used as a material for enamel even when an inexpensive glaze is used. When the enamel adhesion is lower than the above range, there is a problem in that the rate of occurrence of fish scale due to hydrogen in the steel increases.
  • the cold-rolled steel sheet 100 may have a hydrogen permeability ratio of 600 sec/mm 2 or more.
  • the hydrogen permeation rate may be 610 sec/mm 2 or more.
  • the upper limit of the hydrogen permeation ratio is not particularly limited, but may be, for example, 1,700 sec/mm 2 .
  • the hydrogen permeability ratio is a representative index for evaluating fishscale resistance indicating resistance to fishscale defects, which are fatal defects when enameled steel is applied, and means the ability to fix hydrogen into the cold-rolled steel sheet.
  • the hydrogen permeation ratio is a value expressed by dividing the time taken by generating hydrogen in one direction of the steel sheet and penetrating the hydrogen in the other direction opposite to one direction of the steel sheet, and dividing it by the square of the thickness of the material.
  • the hydrogen permeation ratio is excessively low, when the resistance of fishscale defects is evaluated by accelerated heat treatment at 200 ° C. for 24 hours after enamel treatment, the defect rate is more than 50%, so there is a problem in using it as a stable enamel product.
  • a method for manufacturing a cold-rolled steel sheet 100 includes, by weight, C: 0.0003 to 0.003%, Mn: 0.25 to 0.55%, Si: 0.001 to 0.03%, Al: 0.0005 to 0.0015%, P: 0.01 to 0.03%, S: 0.001 to 0.010%, Cu: 0.03 to 0.08%, N: 0.008 to 0.015%, Mo: 0.1 to 0.3%, O: 0.025 to 0.055%, with the balance Fe and unavoidable impurities Reheating the steel slab, hot-rolling the heated slab, winding the hot-rolled hot-rolled steel sheet, cold-rolling the coiled hot-rolled steel sheet, annealing and temper-rolling the cold-rolled cold-rolled steel sheet for annealing
  • a detailed description of the steel slab is the same as that of the cold-rolled steel sheet described above to the extent that it does not
  • Reheating the steel slab is a step for smoothly performing a subsequent hot rolling process and homogenizing the steel slab.
  • the heating may mean reheating.
  • the step of reheating the steel slab may be a step of hot rolling in the range of 1,150 to 1,280 °C.
  • the reheating temperature range may be 1,150 to 1,280 °C.
  • the upper limit of the temperature range is exceeded, the amount of surface scale increases at the slab heating temperature, resulting in increased material loss and increased energy costs due to the increase in heat source.
  • the temperature is outside the lower limit of the temperature range, the rolling load rapidly increases in the hot rolling process, resulting in deterioration in hot workability.
  • the step of reheating the steel slab may be performed at a finish hot rolling temperature in the range of 890 to 950 °C.
  • the finish hot rolling temperature may be carried out in a temperature range of 900 to 945 °C.
  • the step of winding the hot-rolled hot-rolled steel sheet may be performed at a temperature range of 580 to 720 °C. Specifically, the temperature range may be 590 to 700 °C.
  • the hot-rolled steel sheet may be cooled on a run-out table (ROT) before winding.
  • ROT run-out table
  • the step of pickling the hot-rolled steel sheet may be further included.
  • the pickling step may remove scale generated during hot rolling.
  • the step of cold rolling the coiled hot-rolled steel sheet may be performed at a cold rolling reduction ratio of 60 to 90%. Specifically, the cold rolling reduction may be performed in the range of 63 to 88%.
  • the step of preparing an annealed sheet by annealing and temper rolling the cold-rolled cold-rolled steel sheet may be performed at an annealing temperature range of 720 to 850 ° C. during the annealing, for 10 to 70 seconds in the annealing temperature range. can be performed
  • the steps of preparing an annealed sheet by annealing and temper rolling the cold-rolled cold-rolled steel sheet may be performed at a reduction ratio of 2.5% or less during the temper rolling.
  • the temper rolling it is possible to control the shape of the material and obtain a desired surface roughness.
  • the temper rolling may be performed in the range of a reduction ratio of 0.3 to 2.2%.
  • the step of enamel baking heat treatment of the annealed sheet may be a step of enamel firing heat treatment of the annealed sheet at a temperature range of 780 to 850 °C.
  • the enamel firing heat treatment may be a step for drying the enamel-treated glaze.
  • the temperature range may be 790 to 840 °C.
  • the temperature range When the temperature range is out of the upper limit, the surface defect rate increases due to the increase in the thickness of the oxide layer, and as the energy consumption increases, there is a problem that acts as a factor in increasing manufacturing cost.
  • the temperature range is outside the lower limit, the wettability of the glaze is lowered, and thus, adhesion to the enamel cannot be secured.
  • a detailed description of the steel slab is the same as that of the cold-rolled steel sheet described above to the extent that it does not contradict, and thus, duplicate descriptions will be omitted.
  • Heating the steel slab may be performed at 1,150 °C or higher.
  • a temperature of 1,150° C. or higher is required because the precipitate formed in the steel must be re-dissolved.
  • a hot-rolled steel sheet may be obtained by hot-rolling the heated slab.
  • hot finish rolling may be performed on the steel slab at a temperature of Ar3 or higher.
  • the temperature of Ar3 or higher may be 890 °C or higher.
  • rolling may be performed in the austenite single phase region.
  • the step of cooling the hot-rolled hot-rolled steel sheet is cooled so as to be maintained for a time range of 150 to 1,200 seconds. If it is out of the lower limit of the time range, there is a problem in that a large amount of pearlite phase is formed and carbide with a large size is generated in the final material. When the size of the carbide is large, there is a problem in that the carbide becomes a starting point of a crack and reduces a hole expansion rate.
  • the step of cooling the hot-rolled hot-rolled steel sheet may be cooled to 710 °C to be maintained at a temperature between 710 and 860 °C for 150 to 1,200 seconds.
  • the cooled hot-rolled steel sheet may be wound at 560 to 700 °C.
  • the step of winding the cooled hot-rolled steel sheet in order to secure a grain size suitable for strength and workability may be controlled within the winding temperature range.
  • the coiling temperature is excessively low, there is a problem in that crystal grains become excessively fine, and in case the coiling temperature is excessively high, there is a problem in that crystal grains become excessively coarse.
  • a cold-rolled steel sheet may be manufactured by cold rolling at a reduction ratio of 80 to 95%.
  • the thickness of the conventional hot-rolled steel sheet is 2 to 4 mm, and a reduction ratio of 80% or more is required to reduce the thickness of 0.4 mm.
  • the step of pickling may be further included prior to the step of cold rolling the coiled hot-rolled steel sheet.
  • the pickling step may remove scale generated during hot rolling.
  • the step of annealing the cold-rolled cold-rolled steel sheet is annealed at a temperature of 620 to 760 ° C. to prepare an annealed steel sheet.
  • a process of annealing at a sufficiently high temperature is required to allow recrystallization to occur.
  • a final steel sheet may be manufactured by secondary rolling the annealed cold-rolled steel sheet at a reduction ratio of 6 to 18%. If the reduction ratio is out of the upper limit, there is a problem in that the desired level of processability cannot be secured due to the decrease in elongation. If the reduction ratio is out of the lower limit value, there is a problem that it is not sufficient to obtain the target strength.
  • Equation 1 represents ([Cu] ⁇ [Si])/[P]
  • Equation 2 represents ([Al] ⁇ [Mo])/([C] + [N]).
  • [Cu], [Si], [P], [Al], [Mo], [C], and [N] in the above formulas 1 and 2 mean the respective weight%.
  • cold-rolled steel sheets were manufactured according to the manufacturing conditions disclosed in Table 2 below for the slab. Specifically, after maintaining the slab in a heating furnace for 2 hours, hot rolling was performed, and at this time, the thickness of the hot-rolled steel sheet was adjusted to 4.0 mm. The hot-rolled hot-rolled steel sheet was subjected to cold rolling at each reduction ratio after pickling and removing the oxide film on the surface.
  • Examples 1 to 9 use the slabs of inventive steels 1 to 5 included in the composition range of the present invention, the slab reheating temperature, finish hot rolling temperature, winding temperature, cold reduction rate, annealing of the present invention It was carried out within the range of temperature, holding time, temper rolling rate, and enamel firing temperature.
  • Comparative Examples 1 to 4 are controlled so that at least one of the manufacturing conditions in Table 2 does not correspond to the conditions of the present invention using the slabs of Inventive Steels 1 to 4 included in the composition range of the present invention.
  • comparative steels 1 to 5 of Table 1 were controlled so that the manufacturing conditions of Table 2 were included within the scope of the present invention.
  • Table 3 shows the thickness of the oxide layer, sheet permeability, yield strength, cell defect occurrence or not, The presence or absence of fish scale, enamel adhesion, and hydrogen permeability are shown.
  • the thickness of the oxide layer is determined by analyzing the oxygen concentration from the surface of the steel sheet to the inside using GDS (Glow Discharge Spectroscopy), and by dividing the oxide layer and the base material based on the point containing 5% oxygen, to the point containing 5% oxygen. The thickness was measured, measured three times, and the average value was displayed.
  • GDS Glow Discharge Spectroscopy
  • the sheet permeability when the operability is 90% or more compared to the productivity of ordinary materials in the casting, hot rolling, and cold rolling processes, it is good (indicated by “ ⁇ ”), and the productivity is less than 90% or the defect rate is 10% or more is marked as defective (marked with “ ⁇ ”).
  • tensile test specimens were prepared (standard ASTM 13B) for specimens subjected to firing and heat treatment for 15 minutes at each temperature in a firing furnace, and tensile tests were performed at a crosshead speed of 10 mm/min. It was measured by conducting a test.
  • Enamel treatment specimens were cut into appropriate sizes for each purpose to meet the purpose of the test, and after heat treatment was completely degreased, standard glaze (Check Frit), which was relatively vulnerable to fish scale defects, was applied and maintained at 300 ° C for 10 minutes. to remove moisture. After drying, the specimen was fired at each firing temperature for 15 minutes to highlight the difference in enamel characteristics such as adhesion, and then cooled to room temperature. Severe conditions that were easy to achieve were selected.
  • the specimens after the enamel treatment were subjected to a fishscale acceleration test in which they were kept in an oven at 200 °C for 24 hours. After the fishscale acceleration process, the presence or absence of fishscale defects is observed with the naked eye, and when no fishscale defects occur, it is marked as good (marked with “ ⁇ ”), and when the fishscale defects occur, it is marked as bad (“ ⁇ ”). ⁇ ”).
  • Enamel adhesion which evaluates the adhesion between the steel plate and the glaze, is evaluated by applying a certain load to the enamel layer with a steel ball as defined in ASTM C313-78, the American Society for Testing and Materials, and then evaluating the degree of conduction in this area. The degree was expressed as an index.
  • the enamel adhesion evaluation results set the goal of securing adhesion of 95% or more in terms of securing application stability in relatively inexpensive glazes.
  • the bubble defects are judged as excellent (marked as “ ⁇ ”) and poor (marked as “x”), respectively, by visually observing the enamel surface of the specimen kept in an oven at 200 ° C. for 24 hours after enamel treatment. did
  • the hydrogen permeation ratio is one of the indices for evaluating resistance to fishscale, a fatal defect of enamel.
  • EN10209-2013 European standard
  • hydrogen is generated in one direction of the steel sheet and hydrogen permeates to the other side.
  • Time (ts, unit: second) is measured, and this is a value expressed as the square of the material thickness (t, unit: mm), and is expressed as ts/t2 (unit: second/mm 2 ).
  • inventive Examples 1 to 9 satisfying various characteristics such as component composition, manufacturing conditions, surface characteristics, and oxidation layer thickness of the present invention not only have good sheet-permeability, but also have relevant properties such as the thickness of the oxide layer.
  • inventive examples 1 to 9 do not generate enamel defects such as fish scale and bubble defects, and have a hydrogen permeability ratio of 600 sec/mm2 or more, an enamel adhesion index of 95% or more, and a yield strength of 220 MPa after firing and heat treatment of the enamel.
  • Comparative Examples 5 to 9 which do not satisfy the composition of the present invention, the thickness of the surface oxide layer, the hydrogen permeation ratio, and enamel adhesion were not satisfied, and in most cases, fish scale or air bubble defects occurred even in visual observation after enamel treatment, resulting in a problem in applicability to the target use.
  • the composition of the present invention was satisfied, but , In Comparative Examples 1 to 4, in which manufacturing conditions in various annealing processes during hot rolling did not satisfy the management range of the present invention, the thickness of the surface oxide layer was outside the range suggested in the present invention, and the enamel adhesion was less than 95%.
  • the cold-rolled steel sheet for enamel having excellent enamel adhesion and fishscale resistance satisfies the above alloy composition and alloy range, thereby reducing the thickness of the oxide layer formed in the inward direction to an appropriate level. Through this, it is possible to provide a high-strength cold-rolled steel sheet for enamel with excellent fishscale resistance.
  • the cold-rolled steel sheet has significantly improved enamel characteristics even through high-speed continuous annealing operation, can maintain a high level of strength after enamel firing heat treatment, and optimizes surface roughness characteristics in the heat treatment and temper rolling step in a continuous annealing furnace to increase adhesion.
  • stable material properties can be secured even after high-temperature firing by suppressing crystal grain growth during enamel firing, such as residual nitrogen in the surface layer of the steel sheet.

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Abstract

La présente invention concerne une feuille d'acier laminée à froid et son procédé de fabrication, la feuille d'acier laminée à froid comprenant, en % en poids, 0,0003 à 0,003 % de C, 0,25 à 0,55 % de Mn, 0,001 à 0,03 % de Si, 0,0005 à 0,0015 % d'Al, 0,01 à 0,03 % de P, 0,001 à 0,010 % de S, 0,03 à 0,08 % de Cu, 0,008 à 0,015 % de N, 0,1 à 0,3 % de Mo, 0,025 à 0,055 % de O, et un reste de Fe et d'impuretés inévitables, et comprenant une couche d'oxyde, l'épaisseur de la couche d'oxyde, qui est formée à partir de la surface de la feuille d'acier laminée à froid vers l'intérieur de celle-ci, pouvant être de 0,006 à 0,030 µm.
PCT/KR2022/020584 2021-12-17 2022-12-16 Feuille d'acier laminée à froid pour émail, ayant d'excellentes propriétés anti-écaillage et son procédé de fabrication WO2023113535A1 (fr)

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KR1020210182136A KR20230092603A (ko) 2021-12-17 2021-12-17 내피쉬스케일성이 우수한 법랑용 냉연강판 및 이의 제조 방법
KR10-2021-0182136 2021-12-17

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20020027565A (ko) * 2000-06-23 2002-04-13 데라카도 료우지 가공성, 시효성 및 법랑 특성이 우수한 법랑(琺瑯)용 강판및 그 제조방법
KR20020049921A (ko) * 2000-12-20 2002-06-26 이구택 실금결함이 발생하지 않는 고가공용 법랑강판의 제조방법
JP2006037215A (ja) * 2004-07-30 2006-02-09 Nippon Steel Corp ホーロー密着性が良好なホーロー用鋼板およびその製造方法並びにホーロー製品
KR20090043570A (ko) * 2006-09-19 2009-05-06 신닛뽄세이테쯔 카부시키카이샤 법랑 시유용 가공품, 법랑 가공품
KR20210080723A (ko) * 2019-12-20 2021-07-01 주식회사 포스코 법랑용 강판 및 그 제조방법

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20020027565A (ko) * 2000-06-23 2002-04-13 데라카도 료우지 가공성, 시효성 및 법랑 특성이 우수한 법랑(琺瑯)용 강판및 그 제조방법
KR20020049921A (ko) * 2000-12-20 2002-06-26 이구택 실금결함이 발생하지 않는 고가공용 법랑강판의 제조방법
JP2006037215A (ja) * 2004-07-30 2006-02-09 Nippon Steel Corp ホーロー密着性が良好なホーロー用鋼板およびその製造方法並びにホーロー製品
KR20090043570A (ko) * 2006-09-19 2009-05-06 신닛뽄세이테쯔 카부시키카이샤 법랑 시유용 가공품, 법랑 가공품
KR20210080723A (ko) * 2019-12-20 2021-07-01 주식회사 포스코 법랑용 강판 및 그 제조방법

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