WO2019039824A1 - Tôle d'acier laminée à froid pour émaillage et son procédé de fabrication - Google Patents

Tôle d'acier laminée à froid pour émaillage et son procédé de fabrication Download PDF

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WO2019039824A1
WO2019039824A1 PCT/KR2018/009575 KR2018009575W WO2019039824A1 WO 2019039824 A1 WO2019039824 A1 WO 2019039824A1 KR 2018009575 W KR2018009575 W KR 2018009575W WO 2019039824 A1 WO2019039824 A1 WO 2019039824A1
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weight
steel sheet
steel
composite oxide
enamel
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Korean (ko)
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차우열
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주식회사 포스코
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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
    • C22C38/002—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
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006—Adding metallic additives
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing
    • 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
    • C21D8/0221—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
    • 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
    • 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
    • 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
    • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
    • 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
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum

Definitions

  • the present invention relates to a cold rolled steel sheet for enamel and a method of manufacturing the same, and more particularly, to a cold rolled steel sheet for enamel which can improve formability and fish scale resistance and a method for manufacturing the same.
  • the enamel steel sheet is a kind of surface treatment product which is improved in corrosion resistance, weather resistance and heat resistance by applying vitreous glaze on a cold-rolled steel sheet as a base steel sheet and firing at a high temperature.
  • Such an enamel steel sheet is mainly used for building exterior, home appliance, .
  • the conventional steel sheet for enamel has been known to prevent fish scale defects, which are known to be the most fatal defects in enamel products, through the decarburization annealing process or the like, or to improve the formability.
  • this method has resulted in an increase in the cost of the product.
  • Ti-based enamel steel has a limited number of castings due to the occurrence of TiN and intermetallic compounds during the casting process due to Ti addition, resulting in clogging of the nozzles, resulting in increased production cost and production load. Further, when a large amount of Ti is added, there is a problem that Ti adversely affects adhesion between the enamel steel sheet and the ceramic glaze layer.
  • a high acid content steel in which oxides are artificially produced in the steel by increasing the content of oxygen in the steel and the hydrogen absorption capacity is secured by using the oxide has been proposed.
  • the high acid content of the high-oxygen steel has a high oxygen content, so there is a risk that the refractory loss is extremely high and there is a risk of operation such as the leakage of molten steel, the performance is low, and the manufacturing cost of the molten steel is high.
  • the present invention provides a cold rolled steel sheet for an enamel capable of suppressing surface defects and improving moldability and a method for producing the same.
  • the present invention provides a cold rolled steel sheet for enamel which does not cause crack defects during processing by enhancing hydrogen absorption capability and a method for producing the same.
  • the cold rolled steel sheet for enamel according to the present invention contains, by weight%, C: more than 0 wt% to 0.0015 wt%, Mn: 0.2 to 0.4 wt%, Al: more than 0 wt% to 0.001 wt% 0.02 to 0.04% by weight, O: not more than 0.02% by weight, S: more than 0% by weight and not more than 0.02% by weight, Cr: 0.05 to 0.1% And the balance of Fe and other unavoidable impurities, and may include a Mn-Nb-Cr composite oxide.
  • the Mn-Nb-Cr composite oxide may have a size of 3 m or more and 100 / mm < 2 > or more.
  • the ratio (K1 / K2) of the Mn and Cr fraction (K1) to the Nb fraction (K2) in the Mn-Nb-Cr composite oxide may be 0.1 to 1.0.
  • the method for manufacturing a cold rolled steel sheet for enamel comprises the steps of: preparing a molten steel containing a Mn-Nb-Cr composite oxide; Casting a cast steel using the molten steel; A step of rolling the cast steel to produce a steel sheet; And annealing the steel sheet.
  • the process for producing the molten steel includes a process of deoxidizing molten steel for which the refining of the converter has been completed; Cr and Nb are added to the deoxidized molten steel to form a Mn-Nb-Cr composite oxide.
  • the process for forming the Mn-Nb-Cr composite oxide comprises sequentially forming the Mn, Cr, .
  • the process for producing the steel sheet may include the steps of hot rolling the cast steel and finishing the hot rolling at a temperature of 800 to 900 ° C; Rolling the hot-rolled steel sheet at a temperature of 550 to 700 ° C; And cold rolling the hot-rolled steel sheet at a reduction ratio of 75 to 80%.
  • the annealing may be performed at 800 to 900 ° C. for 20 seconds or more.
  • niobium (Nb) to solidify solid carbon (C) and solid nitrogen (N) in steel in the form of NbC and NbN
  • the workability of the cold rolled steel sheet for enamel can be improved.
  • carbon and nitrogen in the steel are removed as much as possible to minimize dislocation of potential movement in the base material, minimization of high-priced niobium input can be ensured, economical efficiency can be secured, and moldability can be improved.
  • the Mn-Nb-Cr composite oxide is formed in the base material to improve the fracture property, thereby forming a large amount of micropores.
  • 1 is a graph showing the relationship between the amount of Nb and the steel formability.
  • FIG. 2 is a graph showing the relationship between the amount of Nb and the fish scale.
  • FIG. 3 is a scanning electron micrograph of a Mn-Nb-Cr composite oxide according to an embodiment of the present invention.
  • FIG. 4 is an optical microscope photograph showing a state where the Mn-Nb-Cr composite oxide contained in the cold rolled steel sheet for enamel according to the embodiment of the present invention is broken.
  • FIG. 5 is a flow chart showing a method of forming a Mn-Nb-Cr composite oxide in a method of manufacturing a cold rolled steel sheet for enamel according to an embodiment of the present invention.
  • an extremely low carbon steel cold rolled steel sheet having a very low carbon (C) in the steel is used as a material.
  • the addition of a large amount of Ti in order to solidify the carbon (C) and nitrogen (N) remaining in the steelmaking process as the carbon / nitride of TiC and TiN in the base material It forms the main part of the enamel steel sheet to be used.
  • TiN mixed in the molten steel is exposed to the surface of the enamel steel sheet, bubble-like blister defects are caused on the surface of the enamel steel sheet.
  • Ti added in a large amount inhibits adhesion between the enamel steel sheet and the ceramic glaze layer.
  • the enamel steel system utilizing an oxide not containing Ti is poor in workability as it contains a large amount of oxygen in the material.
  • the present invention solves the problem that the solid solution C and the solid solution N in the steel sheet are dissolved in the form of NbC and NbN through addition of Nb using Nb and the Mn-Nb-Cr composite oxide is formed in the steel sheet, This excellent cold rolled steel sheet for enamel can be provided.
  • a cold rolled steel sheet for enamel according to an embodiment of the present invention includes C: not less than 0% by weight, not more than 0.0015% by weight, Mn: 0.2 to 0.4% by weight, Al: not less than 0% 0.05 to 0.1% by weight of Cr, 0.03 to 0.05% by weight of Nb, 0 to 0.002% by weight of N, 0.002 to 0% by weight of O, 0.02 to 50% by weight of O, 0.04% by weight, the balance Fe and other unavoidable impurities, and may include a Mn-Nb-Cr composite oxide.
  • the content of each component means weight%.
  • FIG. 1 is a graph showing the relationship between the Nb input amount and the formability of the steel material
  • FIG. 2 is a graph showing the relationship between the Nb input amount and the fish scale of the steel material.
  • Mn can be added to secure the strength of the steel sheet and to prevent hot shortness by precipitating solid sulfur in manganese sulfide in the steel. Therefore, when the content of manganese is less than 0.2% by weight, the possibility of occurrence of the heat-induced brittleness is high. Therefore, the lower limit is set to 0.2% by weight, and if the content of manganese exceeds 0.4% by weight, the moldability is greatly lowered, 0.4% by weight.
  • Mn is an element that forms an initial Mn oxide (MnO) at the time of forming the Mn-Nb-Cr composite oxide. When Mn is less than 0.2% by weight, Mn which contributes to Mn oxide formation is insufficient and Mn oxide is not formed smoothly. To 0.2% by weight.
  • Nb is the most important element in the present invention, and a large amount of NbC and NbN precipitates are precipitated to secure moldability and added for the purpose of Mn-Nb-Cr composite oxide formation.
  • Nb may be included at a minimum of 0.03 wt% so that the difference between Mn-Cr and Nb in the Mn-Nb-Cr composite oxide is reduced.
  • Nb is less than 0.03% by weight, the fish scale resistance can be ensured, but the formability may be deteriorated.
  • Nb is more than 0.05% by weight, workability is improved by adding Nb, And the fish scale property can be reduced.
  • the addition amount of Nb is limited to 0.03 to 0.05% by weight, which is a range in which moldability and fish scale resistance can be secured at the same time.
  • Cr is added next to Nb in the present invention as an important element for the purpose of improving the fish scale property. It is an essential element that binds with Mn-Nb oxide to form a large amount of Mn-Nb-Cr composite oxide. In order to secure the fish scale property, Cr should be added in an amount of 0.05 wt% or more, and when Cr is more than 0.1 wt%, the formability may be poor.
  • P is an element inhibiting the physical properties of steel. If it exceeds 0.02% by weight, the formability is significantly lowered, so the upper limit value is set to 0.02% by weight. However, since it is almost impossible to completely remove P from the steel, the lower limit is specified to be more than 0% by weight.
  • S is generally known as an element which hinders the physical properties of steel. When it exceeds 0.02% by weight, the ductility is greatly lowered and the upper limit value is limited to 0.02% by weight since it is likely to cause brittleness due to sulfur. Since the sulfide formed by S is formed by adhering to the composite oxide, it is preferable to reduce the content of S as much as possible because it inhibits the formation of micro-voids formed by crushing oxide after rolling and fills the micropores formed . However, since it is almost impossible to completely remove S in the steel, the lower limit is specified to be more than 0% by weight.
  • Al more than 0% by weight and not more than 0.001% by weight
  • the addition amount is limited to 0.001 wt% or less.
  • the Al content exceeds 0.001% by weight, the Al-Nb composite oxide is formed, which is not Mn-Nb-Cr composite oxide, and the amount of micro-voids is remarkably reduced, .
  • the lower limit is specified as 0% by weight or more.
  • N more than 0 wt% to less than 0.002 wt%
  • the upper limit value is limited to 0.002 wt%.
  • the lower limit is specified to be more than 0% by weight.
  • the fish scale property was better as the amount was larger, but the upper limit value was limited to 0.04% by weight because the moldability was deteriorated when the content exceeded 0.04% by weight.
  • O is less than 0.02% by weight, O for forming the Mn-Nb-Cr composite oxide is insufficient and the fish scale resistance is weakened to make the lower limit 0.02% by weight.
  • composition of the enamel steel sheet according to the present invention having the same is, hot and cold rolling, when Mn-Nb-Cr complex oxides are crushed as fine public (micro-void) to a quantity formed state of hydrogen than the atomic state of H + molecules H 2 gas to permanently store hydrogen, thereby making it possible to prevent fish scale defects.
  • Mn-Nb-Cr composite oxide stable at high temperature is used as a hydrogen storage source, it is hardly influenced by the conditions of hot and cold rolling control, and quality deviation can be reduced.
  • a multi-element complex oxide in order to increase the crushability of the composite oxide during hot rolling and cold rolling, a multi-element complex oxide can be formed by utilizing Mn, Nb and Cr in the steel.
  • an oxide having a multi-component composition it is excellent in the ability to be fractured under the same pressing force as compared with a single component oxide. This is because, when a multi-component system is formed, the composition is unevenly formed in the oxide due to the difference in affinity with oxygen. That is, the multi-component oxide is formed by the reduction reaction of the oxide at a high temperature of about 1600 ° C in a very short time, and thus the time for homogenizing the entire oxide is not sufficient.
  • oxides of heterogeneous composition formed in a multi-component state have different hardnesses depending on the composition of the oxides, so that they can be easily broken in hot and cold rolling compared to oxides uniformly formed in a single component system. A large amount of three-dimensional microvoids can be formed.
  • the difference of the constituents in the composite inclusion causes fracture of the ferrite and Mn-Nb-Cr composite oxide having different strengths during hot rolling and cold rolling, ) Is formed in large quantity and is utilized as a hydrogen occlusion source.
  • FIG. 3 is a scanning electron micrograph of a Mn-Nb-Cr composite oxide according to an embodiment of the present invention
  • FIG. 4 is a cross- In the same manner as in Example 1.
  • FIG. 3 shows the Mn-Nb-Cr composite oxide formed in the casting process, and the Mn-Nb-Cr composite oxide is formed in a lump shape.
  • the Mn-Nb-Cr composite oxide is crushed in the course of rolling the slab and is formed into a flat plate as shown in FIG.
  • the Mn-Nb-Cr composite oxide is broken and forms micropores around the micropores, and the micropores thus formed can be utilized as a space for storing hydrogen in the steel sheet.
  • the cold rolled steel sheet for enamel according to the embodiment of the present invention is characterized in that a nonmetallic inclusion having a particle size of 1 ⁇ or more, which is detected when an area of 500 mm 2 is observed with a scanning electron microscope, is determined by energy dispersive spectrometry (EDS)
  • EDS energy dispersive spectrometry
  • the Mn-Nb-Cr composite oxide inclusion was found to be a composite oxide containing Mn, Nb and Cr at the same time, and Mn and Cr and Nb fractions of inclusions having a particle diameter of 3 ⁇ or more, Can be calculated.
  • K1 / K2 is less than 0.1, the size of the composite oxide is relatively small and the composition of Nb in the composite oxide is mostly occupied, so that the fracture between the interface of the composite oxide and the iron oxide during rolling does not occur, Fish scale property can not be secured.
  • K1 / K2 is more than 1.0, the content of Nb in the composite oxide is decreased, and the fracture ability is decreased, so that the micropores can not be sufficiently secured.
  • the number of Mn-Nb-Cr composite oxides can be 100 or more per 1 mm < 2 > When the number of the Mn-Nb-Cr composite oxides is less than 100 per 1 mm 2, micro-pores can not be sufficiently secured, and the fish scale resistance is deteriorated.
  • FIG. 5 is a flowchart showing a method of forming a Mn-Nb-Cr composite oxide in a method of manufacturing a cold rolled steel sheet for enamel according to an embodiment of the present invention.
  • a method for manufacturing a rolled steel sheet for enamel comprises the steps of: preparing molten steel containing a Mn-Nb-Cr composite oxide; casting a cast steel; . ≪ / RTI >
  • the process of producing molten steel includes a process of deoxidizing molten steel that has been refined through decarburization using a vacuum degassing facility and a process of forming a Mn-Nb-Cr composite oxide by injecting Mn, Cr, and Nb into the deoxidized molten steel . ≪ / RTI >
  • Mn is first added to the deoxidized molten steel to react with oxygen remaining in the molten steel to form MnO (S10).
  • MnO can be wire-fed to form a large amount of MnO and be uniformly dispersed in molten steel.
  • Cr is added to reduce MnO to form Mn-Cr-O (S20).
  • Nb is added to form a Mn-Nb-Cr multi-component complex oxide (S30).
  • the reason for sequentially injecting Mn, Cr and Nb in this manner is to add a low oxygen-affinity component to form a large amount of Mn-Nb-Cr composite oxide.
  • the multi-component Mn-Nb-Cr composite oxide thus formed is heavier than the single-component oxide to be applied, it can not be separated by floating even if it is formed in the molten steel stage, so that it can be remained in molten steel in comparison with general oxide- Further, the present invention is characterized in that Al, which has a very high affinity with oxygen, is not added so that a large amount of the Mn-Nb-Cr composite oxide can be formed. In addition, since the amount of Ti can be omitted, it is possible to solve the problem caused by a large amount of Ti added to the known Ti based enamel steel.
  • C not more than 0.0015 wt%
  • Mn 0.2 to 0.4 wt%
  • Al more than 0 wt% to not more than 0.001 wt%
  • P not more than 0 wt% to not more than 0.02 wt%
  • S not more than 0 wt%, not more than 0.02 wt%
  • Cr not more than 0.05 wt%, not more than 0.1 wt%
  • Nb not more than 0.03 wt%
  • other unavoidable impurities are not more than 0.0015 wt%
  • Mn 0.2 to 0.4 wt%
  • Al more than 0 wt% to not more than 0.001 wt%
  • P not more than 0 wt% to not more than 0.02 wt%
  • S not more than 0 wt%, not more than 0.02 wt%
  • Cr not more than 0.05 wt%, not more than 0.1 wt%
  • Nb not more than
  • the molten steel may be transferred to a continuous casting facility to cast the cast.
  • the cast steel cast using the molten steel has the same composition as the molten steel.
  • the cast steel When the cast steel is cast, it is charged into a heating furnace and then heat-treated at a temperature of 1200 to 1300 ° C for 1 hour.
  • the steel sheet can be manufactured by rolling the cast steel.
  • the steel sheet can be manufactured by hot rolling the cast steel heated in the heating furnace.
  • the finishing temperature of the hot rolling may be about 800 to 900 ⁇ ⁇ .
  • the finishing rolling temperature is lower than 800 ° C, the rolling resistance becomes too large during rolling and productivity deteriorates.
  • the finish rolling temperature exceeds 900 ° C, the oxide layer of the thermal expansion material is excessively grown and the yield is lowered. Therefore, it is preferable to perform finish rolling at 800 to 900 ⁇ ⁇ .
  • the steel sheet produced by hot rolling the cast steel is rolled up using a winder, and the coiling temperature may be about 550 to 700 ° C. At this time, if the coiling temperature is lower than 550 ⁇ , the grain size formed in the steel sheet becomes small, and the formability may be deteriorated. On the other hand, when the temperature exceeds 700 ° C, an excessively hot-rolled oxide layer occurs. Therefore, the coiling temperature is preferably limited to 550 to 700 ⁇ ⁇ .
  • the hot-rolled steel sheet is subjected to pickling treatment to remove the oxide film formed on the surface thereof, and cold rolling is performed at a cold rolling reduction rate in the range of 75 to 80%.
  • cold rolling reduction is lower than the suggested range, the development of the recrystallized aggregate structure is low and the formability is lowered, and the Mn-Nb-Cr composite oxide is not properly crushed and the micropores in the steel sheet are reduced.
  • the cold reduction ratio is higher than the range suggested, the ductility is lowered, and the micropores formed by crushing the Mn-Nb-Cr composite oxide are squeezed to reduce the absolute amount of the micropores. .
  • the steel sheet After the steel sheet is manufactured through hot rolling and cold rolling, the steel sheet is charged into the annealing furnace and continuous annealing is performed at a temperature of about 800 to 900 DEG C for 20 seconds or more.
  • the continuous annealing process is for imparting ductility and formability to the cold-rolled steel sheet.
  • the temperature is set at less than 800 ° C, recrystallization is not completed and it is difficult to secure ductility and formability.
  • Requires too much heating equipment in the field it is hard to heat up realistically, and the durability of the roll due to excessive high temperature is deteriorated. Therefore, it is preferable that the annealing is performed in the range of 800 to 900 DEG C in the continuous annealing. Further, even if the annealing time is too short, recrystallization is not completed, so that it is difficult to secure ductility and moldability
  • a casting having the composition shown in Table 1 below was carried out by performing the converter-secondary refining-performance process.
  • deoxidation through decarburization was performed using a vacuum degassing facility, and then Mn, Cr and Nb were sequentially charged to form a Mn-Nb-Cr composite oxide.
  • the cast steel was maintained in a heating furnace at 1250 DEG C for 1 hour and then subjected to hot rolling at a finishing hot rolling temperature of 900 DEG C, a coiling temperature of 650 DEG C, and a final thickness of 3.2 mm.
  • the hot rolled steel sheet produced by hot rolling the cast steel was subjected to pickling treatment to remove the oxide film on the surface, and then cold rolling was performed. At this time, the cold reduction ratio was set to 78%, and a cold-rolled steel sheet having a thickness of 0.8 mm was produced.
  • Example 1 0.0013 0.35 ⁇ 0.0005> 0.0101 0.015 ⁇ 0.005> 0.031 0.07 17 373 Mn-Nb-Cr
  • Example 2 0.0012 0.26 ⁇ 0.0005> 0.0156 0.013 ⁇ 0.005> 0.039 0.08 16 320 Mn-Nb-Cr
  • Example 3 0.0010 0.23 ⁇ 0.0005> 0.0121 0.012 ⁇ 0.005> 0.042 0.10 15 281 Mn-Nb-Cr
  • Example 4 0.0009 0.26 ⁇ 0.0005> 0.0184 0.015 ⁇ 0.005> 0.047 0.06 17 345 Mn-Nb-Cr
  • Example 5 0.0010 0.27 ⁇ 0.0005> 0.0156 0.017 ⁇ 0.005> 0.034 0.09 18 292 Mn-Nb-Cr
  • Example 6 0.0012
  • the enamel treated specimens were cut into cold-rolled steel sheets with a size of 70 mm x 150 mm, and then subjected to continuous annealing at 830 ° C. After completion of the annealing, the substrate was thoroughly degreased, and then the lower oil glaze was applied and dried at 200 ° C for 10 minutes to completely remove water. The dried specimens were held at 830 ° C for 7 minutes, baked, and then cooled to room temperature. The specimens treated with Hae Yu enamel were again applied with an oily glaze, and then dried at 200 ° C for 10 minutes to completely remove moisture. The dried specimens were held at 800 ° C for 7 minutes, baked, and then air-cooled.
  • the atmospheric conditions of the firing furnace were set at a dew point temperature of 30 ⁇ ⁇ to apply harsh conditions in which fish scale defects were most likely to occur.
  • the specimen was maintained at 200 ° C for 20 hours to accelerate the fish scale.
  • the non-metallic inclusions having a particle diameter of 1 ⁇ or more were analyzed by EDS to determine the inclusion complex oxide containing Mn, Nb and Cr at the same time,
  • the distribution of the Mn-Nb-Cr composite oxide was analyzed by using inclusions having a particle diameter of 3 ⁇ or more when the diameter of the inclusions was converted into a circle.
  • the number of Mn-Nb-Cr composite oxides was measured by an electron microscope using a point counting method with an image of 5000 to 40 fields, and then converted into 1 mm 2 by using an image analyzer. Respectively.
  • Example 1 Mn-Nb-Cr oxide distribution (K1 / K2) Mn-Nb-Cr composite oxide (number / mm2) Formability Number of fish scale occurrences compatibility
  • Example 1 0.56 280 Very good 0 ⁇
  • Example 2 0.62 295 Very good 0 ⁇
  • Example 3 0.26
  • Example 4 0.43
  • Example 5 0.83 268 Great 0 ⁇
  • Example 6 0.39 324 Great 0 ⁇
  • Example 7 0 0 Great 93 or more ⁇
  • Example 8 9.19 158 Very bad 23 or more ⁇
  • Example 9 0.11 198 Very good 46 or more ⁇
  • Example 10 0.23 270 Bad 0 ⁇
  • Examples 1 to 6 were able to secure the fish scale property because the number and size of the Mn-Nb-Cr composite oxide were within the range limited by the present invention, Chengdu was also very good.
  • Example 7 Al 2 O 3 inclusions were formed due to a high Al content, and a part of Al-Nb, which is a microcrystalline inclusion containing Nb, was formed as shown in Table 1, And the fish scale was more than 93 in number.
  • Example 8 the number of Mn-Nb-Cr composite oxides falls within the range limited by the present invention. However, since the content of Nb is low and the K1 / K2 value indicating the distribution of Mn-Nb- Which is higher than the range. The formability was also very poor, and the fish ciches also occurred in 23 or more.
  • Example 9 Although the distribution and the number of the Mn-Nb-Cr composite oxide fall within the range limited by the present invention, the Nb content is relatively high, so that the Mn-Nb- And the number of fish scales was more than 46 because there were few micro - vacancies capable of absorbing hydrogen.
  • Example 10 although the content of Nb was 0.032% by weight, the content of C which deteriorates the formability was as high as 0.0042% by weight and the formability was poor.
  • the cold rolled steel sheet for enamel and the method of manufacturing the same according to the embodiment of the present invention are characterized in that niobium (Nb) is added to solidify solid carbon (C) and solid nitrogen (N) in steel in the form of NbC and NbN, A high-quality cold rolled steel sheet for an enamel improved in scaleability can be produced.
  • Nb niobium
  • C solid carbon
  • N solid nitrogen

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Abstract

La présente invention concerne une tôle d'acier laminée à froid pour émaillage et son procédé de fabrication, la tôle d'acier laminée à froid comprenant (en % en poids), C (plus de 0 % et pas plus de 0,0015 %), Mn (0,2 à 0,4 %), Al (plus de 0 % et pas plus de 0,001 %), P (plus de 0 % et pas plus de 0,02 %), S (plus de 0 % et pas plus de 0,02 %), Cr (0,05 à 0,1 %), Nb (0,03 à 0,05 %), N (plus de 0 % et pas plus de 0,002 %), O (0,02 à 0,04 %), le reste étant constitué de Fe et d'autres impuretés inévitables, la tôle d'acier laminée à froid comprenant un oxyde composite de Mn-Nb-Cr et pouvant améliorer l'aptitude au moulage et la résistance à l'écaillage.
PCT/KR2018/009575 2017-08-21 2018-08-21 Tôle d'acier laminée à froid pour émaillage et son procédé de fabrication WO2019039824A1 (fr)

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