EP4350017A1 - Metal sheet-quenching apparatus, continuous annealing facility, metal sheet-quenching method, cold-rolled steel sheet production method, and plated steel sheet production method - Google Patents

Metal sheet-quenching apparatus, continuous annealing facility, metal sheet-quenching method, cold-rolled steel sheet production method, and plated steel sheet production method Download PDF

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Publication number
EP4350017A1
EP4350017A1 EP22845679.4A EP22845679A EP4350017A1 EP 4350017 A1 EP4350017 A1 EP 4350017A1 EP 22845679 A EP22845679 A EP 22845679A EP 4350017 A1 EP4350017 A1 EP 4350017A1
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EP
European Patent Office
Prior art keywords
metal sheet
sheet
restraining
quenching
roll pairs
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Pending
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EP22845679.4A
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German (de)
English (en)
French (fr)
Inventor
Hideyuki Takahashi
Soshi YOSHIMOTO
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JFE Steel Corp
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JFE Steel Corp
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Publication of EP4350017A1 publication Critical patent/EP4350017A1/en
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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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/573—Continuous furnaces for strip or wire with cooling
    • C21D9/5735—Details
    • C21D9/5737—Rolls; Drums; Roll arrangements
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/62—Quenching devices
    • C21D1/63—Quenching devices for bath quenching
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/62—Quenching devices
    • C21D1/667—Quenching devices for spray quenching
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/60—Aqueous agents
    • 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
    • C21D9/0062—Heat-treating apparatus with a cooling or quenching zone
    • 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
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/22—Electroplating: Baths therefor from solutions of zinc
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • C25D7/06—Wires; Strips; Foils
    • C25D7/0614—Strips or foils
    • 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
    • C21D2211/008—Martensite
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • 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
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • 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
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of 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
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

Definitions

  • the present invention relates to a quenching apparatus for a metal sheet with which it is possible to inhibit shape defects from occurring in the metal sheet when quenching is performed by using continuous annealing equipment, in which annealing is performed while the metal sheet is continuously passed, and to continuous annealing equipment, a method for quenching a metal sheet, a method for manufacturing a cold rolled steel sheet, and a method for manufacturing a coated steel sheet.
  • Patent Literature 1 proposes a method in which, to inhibit wavelike deformation from occurring in a metal sheet when rapid-cooling quenching is performed in a continuous annealing furnace, bridle rolls are installed upstream and downstream of a rapid-cooling quenching region to change tension applied to a steel sheet which is subjected to a rapid-cooling quenching process.
  • Patent Literature 2 proposes a method in which, by focusing on the fact that a shape defect occurs due to buckling occurring in a metal sheet because of thermal compressive stress in the width direction of the metal sheet generated at a quenching start point (cooling start point), out-of-plane deformation is inhibited by restraining the metal sheet from both surface sides of the metal sheet in the region in which the compressive stress in the width direction of the metal sheet is generated by cooling or in the vicinity of such a region.
  • Patent Literature 3 proposes a method in which, when the Ms temperature, at which the martensite transformation of a metal sheet starts, is defined as TMs (°C) and the Mf temperature, at which the martensite transformation of the metal sheet finishes, is defined as TMf (°C), the metal sheet that is being subjected to rapid-cooling quenching is restrained by using a restraining roll pair placed in a coolant while the temperature of the metal sheet is in the temperature range of (TMs + 150°C) to (TMf - 150°C).
  • Patent Literature 4 proposes an apparatus having a water tank containing a liquid in which a metal sheet is immersed, an injection device having plural injection nozzles through which a liquid is injected onto the front and back surfaces of the metal sheet, and one or plural restraining roll pairs with which the metal sheet is restrained and a method in which the liquid is injected through all of the injection nozzles of the injection device in the direction toward the restraining rolls.
  • Patent Literature 1 to Patent Literature 4 since the sheet thickness of the metal sheet or the sheet passing speed of the metal sheet in the water tank is not taken into consideration when the metal sheet is restrained by using the restraining rolls, there is a problem in that it is not possible to restrain the metal sheet by using the restraining rolls while the temperature of the metal sheet is in the temperature range of (TMs + 150°C) to (TMf - 150°C). As a result, there is a problem in that shape defects occur after the metal sheet has been subjected to quenching.
  • the present invention has been completed in view of the situation described above, and an object of the present invention is to provide a quenching apparatus for a metal sheet with which it is possible to inhibit shape defects from occurring in the metal sheet when quenching is performed regardless of the sheet passing speed or the sheet thickness of the metal sheet, continuous annealing equipment, a method for quenching a metal sheet, a method for manufacturing a cold rolled steel sheet, and a method for manufacturing a coated steel sheet.
  • the quenching apparatus for a metal sheet the method for quenching a metal sheet, and the method for manufacturing a steel sheet according to the present invention, it is possible to inhibit shape defects from occurring in the metal sheet when quenching is performed regardless of the sheet passing speed or the sheet thickness of the metal sheet.
  • Fig. 1 is a diagram illustrating a quenching apparatus 1 for a metal sheet S according to an embodiment of the present invention.
  • the quenching apparatus 1 is used for a cooling apparatus which is placed on the exit side of the soaking zone of a continuous annealing furnace (continuous annealing equipment).
  • a water injection apparatus 3 is installed in a water tank 2 which contains water used for cooling in a manner such that some water injection nozzles 3a are exposed above the water surface (denoted by W in the figure).
  • plural water injection nozzles 3a are arranged in the sheet passing direction (denoted by an arrow P in the figure) of the metal sheet S, which is continuously passed in the water tank 2, on the front and back surface sides of the metal sheet S with a predetermined gap being provided between the nozzles and the metal sheet, and plural restraining roll pairs 4 are arranged in the sheet passing direction with the water injection nozzles being interposed between the pairs.
  • plural restraining roll pairs 4 may have controlling systems for adjusting the positions of the pairs with respect to the metal sheet S in accordance with operation conditions.
  • the metal sheet S is to be quenched on the exit side of a continuous annealing furnace to achieve desired material properties.
  • shape defects occur in the metal sheet S due to thermal shrinkage caused by rapid cooling for a quenching treatment.
  • TMs (°C) martensite start temperature
  • TMf (°C) martensite finish temperature
  • stress generated in the metal sheet S peaks, which results in a deterioration in the shape of the metal sheet S.
  • the temperature of the metal sheet S which is being subjected to rapid cooling for quenching is equal to or lower than (TMs + 150°C) and equal to or higher than (TMf - 150°C)
  • the temperature be equal to or lower than (TMs + 100°C) and equal to or higher than (TMf - 100°C).
  • the number of the restraining roll pairs 4 to be placed should be determined so that it is possible to restrain the metal sheet S by using at least two or more restraining roll pairs 4 in the temperature ranges of (TMs + 150°C) to (TMf - 150°C) when the sheet passing speed and sheet thickness of the metal sheet S vary.
  • cooling is promoted by using a water injection apparatus 3 having plural water injection nozzles 3a.
  • the water injection apparatus 3 which is composed of plural water injection nozzles 3a, is arranged so as to cover a region from a position immediately above the water surface W to a position below the water surface.
  • the water injection nozzles 3a are arranged at positions farther from the metal sheet S than those of the restraining roll pairs 4.
  • the distance between the water injection nozzles 3a and the metal sheet S there is a risk that the water injection nozzles 3a come into contact with the metal sheet S due to warpage or vibration of the steel sheet (metal sheet S) in the case where the distance is small and, conversely, that cooling ability decreases due to a decrease in jet flow speed when the coolant reaches the steel sheet (metal sheet S) in the case where the distance is large. Therefore, the distance is to be taken into consideration.
  • a position at which the coolant (denoted by 3b in the figure) injected through the water injection nozzle 3a located at the uppermost position of the water injection apparatus 3 impinges on the metal sheet S, that is, a jet flow impinging position, is at a distance A above the water surface W (as illustrated in Fig. 1 ), and it is preferable that the height be 10 mm.
  • the jet flow impinging position be excessively near to the water surface W because, since the jet flow impinging position is influenced by a variation in the position of the water surface W, a position at which a vapor film is removed is unstable, which results in the cooling capacity being largely influenced.
  • the jet flow impinging position be excessively far from the water surface W because, since there is an increase in the temperature of the injected water while flowing down, there is a decrease in the cooling capacity in the region in which the water flows down, which results in the occurrence of transition boiling. Therefore, it is preferable that the distance between the water surface W and the jet flow impinging position, which is denoted by A, be about 5 mm to 50 mm (or 10 mm).
  • the water injection nozzles 3a be arranged so as to tilt at the positions nearest the restraining roll pair 4 (refer to Fig. 5 ) to inject water toward positions at which the restraining roll pair 4 and the metal sheet S come into contact with each other (hereinafter, referred to as "roll side") for the purpose of inhibiting a decrease in the cooling rate of the metal sheet S.
  • a temperature range in which restraining is performed by using the restraining roll pairs 4 in a quenching process is about 150°C to 550°C.
  • a temperature range which corresponds to a range from a nucleate boiling range to a transition boiling range
  • a vapor film does not exist (nucleate boiling), or a vapor film is considerably unstable (transition boiling). Therefore, since it is possible to break the vapor film by using a small amount of water injection, it is not necessary to arrange the nozzles so as to tilt toward the restraining roll pair, and water injected onto the metal sheet S at a right angle does not pose a problem.
  • the quenched material is a metal sheet S having a martensite start temperature (TMs (°C)) of 450°C or lower or preferably 400°C or lower.
  • TMs (°C) martensite start temperature
  • the present invention by providing a moving system with which the restraining roll pairs 4 move independently from each other in a direction for the restraining rolls 4a to push the metal sheet S or to draw away from the metal sheet S, it is possible to achieve a stable cooling state, even in the case where the water injection nozzles 3a are arranged in a manner such that cooling water is injected in facing directions from the front and back surface sides of the metal sheet S. To inject the cooling water through the water injection nozzles 3a in facing directions across the metal sheet S, it is necessary to arrange the water injection nozzles 3a almost perpendicularly to the sheet passing direction of the metal sheet S.
  • the expression "almost perpendicularly” denotes a case where ⁇ is 80° or more and 100° or less, preferably 82° or more and 98° or less, or more preferably 87° or more and 93° or less.
  • each of the restraining roll pairs 4 may have a system with which the pair moves independently from other pairs, and instead each of the rolls (restraining roll 4a) constituting the pair may have a system with which the roll moves independently from the other roll.
  • operation conditions denotes heat treatment conditions and cooling conditions; and, in particular, the sheet passing speed, the sheet thickness, the quenching start temperature, and the warpage of the metal sheet are items having large influences.
  • operation conditions denotes heat treatment conditions and cooling conditions; and, in particular, the sheet passing speed, the sheet thickness, the quenching start temperature, and the warpage of the metal sheet are items having large influences.
  • the heat treatment conditions before quenching is performed and a distance between a position at which the heat treatment is finished and a position at which cooling is started are identical, it is preferable that such a determination be made in accordance with the sheet passing speed and the sheet thickness.
  • Examples of a method for determining restraining roll pairs to be used include the method described above (the restraining roll pairs to be used are determined in accordance with positions corresponding to the preferable temperature range described in paragraph 0018 which are derived in accordance with the sheet passing speed and the sheet thickness) and a method in which preferable restraining roll pairs are selected to be used on the basis of accumulated data regarding the relationship between the combination of operation conditions and restraining roll pairs used and shape stability.
  • the metal sheet S when the metal sheet S is quenched, by adjusting the positions of the plural restraining roll pairs 4 with respect to the metal sheet S in accordance with operation conditions, that is, in accordance with the sheet passing speed and the sheet thickness, it is possible to restrain the metal sheet S with certainty while the temperature of the metal sheet S is equal to or lower than (TMs + 150°C) and equal to or higher than (TMf - 150°C), that is, in the preferable temperature range.
  • the sheet passing speed and the sheet thickness may be used as the operation conditions, the product of the sheet passing speed and the sheet thickness (hereinafter, referred to as "LSD") may also be used.
  • the upper limit of Rz is set to be 50 um or less.
  • the maximum height roughness Rz is prescribed in Japanese Industrial Standards "JIS B 0601 Surface Roughness (2001)" and derived in accordance with "JIS B 0633" from a profile in the width direction of the metal sheet S, that is, the longitudinal direction of the restraining rolls 4a, obtained by using a two-dimensional roughness meter.
  • the measurement method adopted by a measurement device may be of a contact type or a non-contact type as long as the obtained measurement results satisfy the prescription in "JIS B 0601 surface roughness".
  • the diameter (D (mm)) of the restraining rolls 4a there is also a preferable range for the diameter (D (mm)) of the restraining rolls 4a for the reasons described below.
  • D (mm) diameter of the restraining rolls 4a
  • the diameter of the restraining rolls 4a is large, since the water flow becomes unstable due to an increase in the degree of interference with the water flow, the state of the removal of a vapor film becomes unstable, which results in the shape of the metal sheet S becoming unstable.
  • the roll diameter is excessively small, since deflection occurs in the rolls when restraining the metal sheet S, there is a decrease in force for restraining the metal sheet S, which results in the effect of correcting shape not being realized. Therefore, it is preferable that the roll diameter be 50 mm or more.
  • Fig. 2 and Fig. 3 illustrate an example of the arrangement constitution of the restraining roll pairs 4.
  • the restraining roll pair 4 which is composed of two restraining rolls 4a that are arranged respectively on the front and back surface sides of the metal sheet S so as to face each other across the metal sheet S, it is preferable that a distance in the sheet passing direction P of the metal sheet S be provided between the central axes of the restraining rolls 4a (offset) constituting the pair.
  • the directions of the movement of the central axes be the same in all the restraining roll pairs 4; that is, the movement direction of the restraining roll 4a on one side may be upward in one pair while the movement direction of the restraining roll 4a on the same side is downward in another pair. It is not possible to push the metal sheet S in the case where such a distance is not provided, and, in the case where such a distance is provided, since the pushing-in distances are variable, there is an increase in restraining force.
  • the distance in the sheet passing direction of the metal sheet provided between the central axes of the restraining rolls 4a constituting each pair that is, an offset value (denoted by B in the figure)
  • an offset value denoted by B in the figure
  • D denotes the diameter (mm) of the restraining roll 4a as described above.
  • the offset value is more than D (mm)
  • the offset value is less than (D ⁇ 1/4) (mm)
  • the effect of roll restraining is large, there is an insufficient effect of correcting shape due to a sufficient push-in distance in the metal sheet pushing-in direction not being achieved, and it is not possible for a thick metal sheet to pass through a gap between the rolls.
  • the movement of the restraining roll pair 4 in the metal sheet S-pushing-in direction be -t (mm) to (+10 ⁇ t) (mm).
  • the movement I of the restraining rolls 4a in the metal sheet S pushing-in direction is less than -t (mm) (refer to Fig. 3(a) )
  • the position of the restraining roll pair 4 may be adjusted in accordance with information about the warpage of the metal sheet S.
  • information about the warpage of the metal sheet S there is no particular limitation on the information about the warpage of the metal sheet S, and such information may be based on predicted values or measured values.
  • examples of the measurement position of the warpage include three positions, that is, a position upstream of the water tank 2, a position downstream of the water tank 2, and an offline position, and a combination thereof may be used.
  • the measurement of the warpage of the metal sheet S may be performed by using a laser-type distance meter or the like.
  • the measurement is performed before the metal sheet S is cooled because this makes it possible to determine the conditions applied for the restraining roll pairs 4 (restraining roll pairs to be used, distances between the restraining roll pairs, intermesh values, offset values, and the like), without delay.
  • the measurement is performed after the metal sheet S has been cooled, although it is not possible to avoid a delay in determining the conditions due to a time lag, since the determination is made on the basis of information about the practical warpage of the metal sheet S, it is possible to appropriately adjust the restraining roll pairs 4.
  • the warpage of the metal sheet S is measured offline, there is an increased delay in determining the conditions applied for the restraining roll pairs 4, but there is an advantage in that, for example, it is possible to perform manual measurement.
  • the positions of the plural restraining roll pairs 4 with respect to the metal sheet S may be adjusted in accordance with operation conditions including not only the sheet passing speed and the sheet thickness but also the information about warpage of the metal sheet S.
  • the restraining roll pairs to be used, the distances between the restraining roll pairs, the intermesh values, the offset values, and the like may be adjusted as in the case of the restraining roll pair 4.
  • the expression "distance between restrain roll pairs 4" denotes the distance between the center of the lower restraining roll 4a of the upper restraining roll pair 4 and the center of the upper restraining roll 4a of the lower restraining roll pair 4.
  • the appropriate range of the distance C is set to be D (mm) or more and 10 ⁇ D (mm) or less. It is not preferable that the distance C between the restraining roll pairs 4 be less than D (mm) because, in this case, since water which is injected through the water injection nozzles 3a is disturbed by the restraining roll pairs 4 before the water reaches the metal sheet S, sufficient cooling capacity is not achieved, which results in an increase in the size of the equipment due to an increase in distance necessary for shape correction. In addition, since there is an increase in the number of points at which the metal sheet S and the restraining roll pairs 4 come into contact, there is an increased risk of the occurrence of surface defects such as pressing flaws, slip flaws, and the like.
  • the restraining rolls 4a should be made of a material having excellent thermal conductivity and strength sufficient to endure a load placed on the rolls when the rolls compress the metal sheet.
  • a material having excellent thermal conductivity and strength sufficient to endure a load placed on the rolls when the rolls compress the metal sheet.
  • Examples of such a material include heat-resistant steel (for example, KHR12C), stainless steel (SUS304, SUS310), ceramics, and the like, but CFRP easily realizes the effect of roll restraining and is advantageous especially for achieving satisfactory cooling capacity because the deflection of a roll made of CFRP is small even in the case where the roll diameter is small.
  • the present invention is intended to reduce complex and nonuniform, wavy shape which occurs due to microstructure volume expansion caused by martensite transformation occurring when the metal sheet S is rapidly cooled, it is preferable that the present invention be used in a method for manufacturing a cold rolled steel sheet.
  • the relevant cold rolled steel sheet may be subjected to a coating treatment.
  • the coating treatment which may be performed include an electro-galvanizing treatment, a hot-dip galvanizing treatment, and a hot-dip galvannealing treatment.
  • the present invention be used for manufacturing a high strength steel sheet (high tensile strength steel sheet) having a tensile strength of 580 MPa or higher.
  • a high strength steel sheet high tensile strength steel sheet
  • the upper limit of the tensile strength as long as the roll material or the like withstands high strength, and, in the case where stainless steel (SUS304, SUS310), ceramics, or the like is used for the rolls, it is expected for the effects to be realized even when the tensile strength is about 3000 MPa.
  • Examples of the high strength steel sheet (high tensile strength steel sheet) described above include a high strength cold rolled steel sheet and steel sheets which are manufactured by performing a surface treatment on the high strength cold rolled steel sheet, that is, a hot-dip galvanized steel sheet, an electro-galvanized steel sheet, a hot-dip galvannealed steel sheet, and the like. That is, it is preferable that a high strength cold rolled steel sheet, a hot-dip galvanized steel sheet, an electro-galvanized steel sheet, and a hot-dip galvannealed steel sheet be manufactured by performing continuous annealing utilizing the quenching apparatus for the metal sheet S and the method for quenching the metal sheet S according to the present invention.
  • the high strength steel sheet include one having a chemical composition containing, by mass%, C: 0.04% or more and 0.25% or less, Si: 0.01% or more and 2.50% or less, Mn: 0.80% or more and 3.70% or less, P: 0.001% or more and 0.090% or less, S: 0.0001% or more and 0.0050% or less, sol.Al: 0.005% or more and 0.065% or less, optionally at least one of Cr, Mo, Nb, V, Ni, Cu, and Ti in an amount of 0.5% or less each, optionally at least one of B and Sb in an amount of 0.01% or less each, and a balance of Fe and incidental impurities.
  • the present invention for rapidly cooling metal sheets in general.
  • the present invention is not limited to the embodiment which is described as an example and in which cooling is performed by using a water immersion method, and it is possible to use the present invention as a method for preventing deformation from occurring in a steel sheet due to transformation by physically restraining the steel in processes in general regardless of whether the relevant process is a heating process or a cooling process.
  • the quenching apparatus 1 illustrated in Fig. 1 basically, high tensile strength cold rolled steel sheets (metal sheets S) having a sheet thickness of 1.0 mm to 2.3 mm, a width of 1000 mm, a tensile strength of 1470 MPa class were manufactured under the conditions of a sheet passing speed (refer to "LS" in Table 1) of 60 mpm to 108 mpm, a quenching start temperature of 800°C, a cooling water injection flow rate of 1000 T/hr, and a water temperature of 30°C.
  • LS sheet passing speed
  • the quenching apparatus 1 illustrated in Fig. 1 has four restraining roll pairs 4 which are vertically arranged, one to three restraining roll pairs were vertically arranged in the present examples.
  • the representative chemical composition of the high tension cold rolled steel sheet having a tensile strength of 1470 MPa class contained, by mass%, C: 0.20%, Si: 1.0%, Mn: 2.3%, P: 0.005%, and S: 0.002%.
  • the Ms temperature (TMs (°C)) of such a high tension cold rolled steel sheet is 400°C
  • the Mf temperature (TMf (°C)) of the steel sheet is 300°C.
  • the temperature range of the steel sheet in which restraining utilizing the restraining roll pairs 4 is effective is 150°C to 550°C.
  • the roll diameter (D) of the restraining rolls 4a was 150 mm.
  • the restraining roll pairs 4 were placed at a position located 0.3 m (first restraining roll pair) and a position located 0.75 m (second restraining roll pair) from the water surface W whose position was set to be 0 m, the distance was measured in the sheet passing direction P.
  • C in Fig. 2 was 0.45 m.
  • Examples 15 and 16 are examples in which one more restraining roll pair was added at a position located 1.05 m (third restraining roll pair) from the water surface.
  • the base condition was set to be a case where movement of restraining rolls in metal sheet S pushing-in direction was 0 mm. That is, in the case where "0.0 mm" in the column “I.M” in Table 1 denotes a state in which the restraining roll pair 4 pushed the metal sheet S. In more detail, in the case where I.M is "0.0 mm", the surfaces of the restraining rolls 4a in the restraining roll pair 4 reach the central position of the metal sheet S.
  • the evaluations of the examples were conducted from the viewpoint of the warpage quantity (mm) and surface quality of the metal sheet S which had been cooled.
  • the warpage quantity (denoted by K in Fig. 4 ) of the metal sheet S was measured in the width direction of the metal sheet S.
  • the surface quality of the metal sheet S was evaluated by performing surface-appearance observation on three samples in total having the same width as that of the metal sheet S and a length of 1 m which were taken from the front end, central position, and tail end in the sheet passing direction of the metal sheet S.
  • Example LS [mpm] Sheet Thickness [mm] LSD [mpm ⁇ mm] Maximum Height Roughness [ ⁇ m] Offset Value in Restraining Roll Pair (8) [mm] Injection Direction of Water Injection Nozzle (with Respect to Metal Sheet) First Restraining Roll Pair Second Restraining Roll Pair Third Restraining Roll Pair Warpage Quantity [mm] Surface Quality Distance [m] I.M (I) [mm] Distance [m] I.M (I) [mm] Distance [m] I.M (I) [mm] Rz min Rz max Comparative Example 1 60 1.0 60 - - - 90° - - - - - - 34.5 ⁇ Comparative Example 2 60 1.0 60 25.3 29.6 75 90° - - 0.75 0.0 - - 15.2 ⁇ Comparative Example 3 60 1.8 108 25.3 29.6 75 90° - - 0.75 0.0 - - 2.1 ⁇ Comparative Example 4 100 1.8 180 25.3 29.6 75 90° - - 0.75 0.0
  • the restraining roll pair 4 was not placed, and the metal sheet S was cooled by injecting water through the water injection nozzles 3a in the direction perpendicular to the sheet passing direction P of the metal sheet S.
  • the warpage quantity of the metal sheet S was 34.5 mm, which means a shape defect occurred.
  • examples 1 to 6 show the results of the cases where two restraining roll pairs 4 were placed.
  • the restraining roll pair 4 to be used was selected (the movement conditions of the restraining roll pairs 4 were selected) in accordance with LSD, and, as a result, it was clarified that it is possible to respond a wide range of a change in LSD.
  • a metal sheet for which the present invention is mainly intended is a steel sheet, and it is possible to organize the sheet cooling state in accordance with LSD. Therefore, the larger the LSD, the more difficult it is to cool the metal sheet, and the larger the distances from the cooling start position to the martensite start position and the martensite finish position.
  • the restraining roll pairs 4 placed at lower positions in Fig. 1 it is preferable to select the restraining roll pairs 4 placed at lower positions in Fig. 1 .
  • the smaller the LSD the easier it is to cool the metal sheet, and the smaller the distance from the cooling start position to the martensite start position and the martensite finish position. Therefore, it is preferable to select the restraining roll pairs 4 placed at upper positions in Fig. 1 .
  • Example 15 is an example in which quenching was performed with reference to examples 4 to 6.
  • the plural restraining roll pairs 4 By using the plural restraining roll pairs 4, it was possible to realize the effect of correcting shape of the metal sheet S to some extent.
  • example 16 by selecting roll pairs to be used from the plural restraining roll pairs 4 in accordance with the product of the sheet passing speed and sheet thickness of the metal sheet S (LSD) and the measurement results of the warpage of the metal sheet S to thereby adjust the positions at which the metal sheet S was restrained and the distance between the restraining roll pairs, it is possible to suppress the warpage quantity of the metal sheet S to be 3.1 mm.
  • restraining roll pairs to be used were selected to thereby adjust the distance between the restraining roll pairs
  • the items to be adjusted may be the intermesh values and offset values.
  • various kinds of conditions applied for the plural restraining roll pairs 4 may be determined.
  • the present inventors diligently conducted investigations to solve the problems described above and to thereby complete the quenching apparatus for a metal sheet, a method for quenching a metal sheet, and a method for manufacturing a steel sheet according to the present invention and, as a result, the following knowledge was obtained.
  • the destabilization of the shape of the metal sheet S is caused by the unstableness of the cooling capacity, and this was presumed to be because of the destabilization of the vapor film-removing capability due to a water flow.
  • the contact state between the metal sheet S and water varies in accordance with the temperature range of the metal sheet S in the cooling process; that is, film boiling, transition boiling, and nucleate boiling occur in this order as the temperature decreases, which results in a variation in cooling rate and cooling uniformity.
  • scratch occurring in the surface of the metal sheet S is a defect caused by the slip of the restraining rolls 4a and that such a defect is caused by a hydroplaning phenomenon occurring in the case where a water film is formed between the restraining rolls 4a and the metal sheet S.

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EP22845679.4A 2021-07-19 2022-05-11 Metal sheet-quenching apparatus, continuous annealing facility, metal sheet-quenching method, cold-rolled steel sheet production method, and plated steel sheet production method Pending EP4350017A1 (en)

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PCT/JP2022/019933 WO2023002741A1 (ja) 2021-07-19 2022-05-11 金属板の焼入装置、連続焼鈍設備、金属板の焼入方法、冷延鋼板の製造方法及びめっき鋼板の製造方法

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JP2011184773A (ja) 2010-03-10 2011-09-22 Kobe Steel Ltd 連続焼鈍設備およびその設備における急冷焼入時の金属板の波状変形抑制方法
MX2017006870A (es) 2014-11-28 2017-08-14 Jfe Steel Corp Metodo para la fabricacion de lamina de metal y unidad de temple rapido.
JP6308287B2 (ja) 2015-12-28 2018-04-11 Ｊｆｅスチール株式会社 急冷焼入れ装置及び急冷焼入れ方法
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