WO2017072989A1 - Method for manufacturing hot-dip galvanized steel sheet - Google Patents
Method for manufacturing hot-dip galvanized steel sheet Download PDFInfo
- Publication number
- WO2017072989A1 WO2017072989A1 PCT/JP2016/003631 JP2016003631W WO2017072989A1 WO 2017072989 A1 WO2017072989 A1 WO 2017072989A1 JP 2016003631 W JP2016003631 W JP 2016003631W WO 2017072989 A1 WO2017072989 A1 WO 2017072989A1
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- Prior art keywords
- zone
- gas
- soaking zone
- steel strip
- hot
- Prior art date
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- 229910001335 Galvanized steel Inorganic materials 0.000 title claims abstract description 22
- 239000008397 galvanized steel Substances 0.000 title claims abstract description 22
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 20
- 238000000034 method Methods 0.000 title abstract description 16
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 96
- 239000010959 steel Substances 0.000 claims abstract description 96
- 238000002791 soaking Methods 0.000 claims abstract description 94
- 238000010438 heat treatment Methods 0.000 claims abstract description 59
- 238000001816 cooling Methods 0.000 claims abstract description 46
- 238000000137 annealing Methods 0.000 claims abstract description 33
- 230000001590 oxidative effect Effects 0.000 claims abstract description 12
- 238000005246 galvanizing Methods 0.000 claims description 38
- 238000005275 alloying Methods 0.000 claims description 36
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 31
- 238000002844 melting Methods 0.000 claims 1
- 230000008018 melting Effects 0.000 claims 1
- 238000007747 plating Methods 0.000 abstract description 30
- 239000007789 gas Substances 0.000 description 146
- 230000003647 oxidation Effects 0.000 description 14
- 238000007254 oxidation reaction Methods 0.000 description 14
- 239000012528 membrane Substances 0.000 description 10
- 238000002485 combustion reaction Methods 0.000 description 9
- 230000007423 decrease Effects 0.000 description 8
- 238000001035 drying Methods 0.000 description 8
- 230000007547 defect Effects 0.000 description 5
- 238000009826 distribution Methods 0.000 description 4
- 239000012510 hollow fiber Substances 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 239000002436 steel type Substances 0.000 description 4
- 238000011144 upstream manufacturing Methods 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000002737 fuel gas Substances 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 2
- 239000004642 Polyimide Substances 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000012141 concentrate Substances 0.000 description 2
- 238000009833 condensation Methods 0.000 description 2
- 230000005494 condensation Effects 0.000 description 2
- 238000007598 dipping method Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 229910052731 fluorine Inorganic materials 0.000 description 2
- 239000011737 fluorine Substances 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229920001721 polyimide Polymers 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 210000004894 snout Anatomy 0.000 description 2
- 230000037303 wrinkles Effects 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 239000003014 ion exchange membrane Substances 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
Images
Classifications
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
- C21D1/76—Adjusting the composition of the atmosphere
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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
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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
- C21D9/561—Continuous furnaces for strip or wire with a controlled atmosphere or vacuum
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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
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- 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
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- C—CHEMISTRY; METALLURGY
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- 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
- C23C2/003—Apparatus
- C23C2/0038—Apparatus characterised by the pre-treatment chambers located immediately upstream of the bath or occurring locally before the dipping process
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- C—CHEMISTRY; METALLURGY
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- 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
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- C23C2/004—Snouts
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- C—CHEMISTRY; METALLURGY
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- 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
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- 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
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- C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
- C23C2/0222—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating in a reactive atmosphere, e.g. oxidising or reducing atmosphere
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- 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
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- C23C2/0224—Two or more thermal pretreatments
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- C—CHEMISTRY; METALLURGY
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- 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
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- C—CHEMISTRY; METALLURGY
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- 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
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- C23C2/261—After-treatment in a gas atmosphere, e.g. inert or reducing atmosphere
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- C—CHEMISTRY; METALLURGY
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- 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
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- C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
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- C—CHEMISTRY; METALLURGY
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- 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
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- C23C2/29—Cooling or quenching
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- C—CHEMISTRY; METALLURGY
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- 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
- C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
- C23C2/36—Elongated material
- C23C2/40—Plates; Strips
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- C—CHEMISTRY; METALLURGY
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- 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
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- C23C2/50—Controlling or regulating the coating processes
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- 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
Definitions
- the present invention provides a hot-dip galvanized steel sheet using a continuous hot-dip galvanizing apparatus having an annealing furnace in which a heating zone, a soaking zone and a cooling zone are juxtaposed in this order, and a hot-dip galvanizing facility adjacent to the cooling zone Regarding the method.
- high-tensile steel plates that contribute to weight reduction of structures.
- a high-tensile steel material for example, it has been found that a steel plate with good hole expansibility by containing Si in the steel, and a steel plate with good ductility can be produced by easily containing residual ⁇ by containing Si or Al. Yes.
- An alloyed hot-dip galvanized steel sheet is obtained by heat-annealing a base steel sheet in a reducing or non-oxidizing atmosphere at a temperature of about 600 to 900 ° C., then subjecting the steel sheet to hot-dip galvanizing treatment, and further heating the galvanizing Manufactured by alloying.
- Si in the steel is an easily oxidizable element and is selectively oxidized even in a generally used reducing atmosphere or non-oxidizing atmosphere to concentrate on the surface of the steel sheet to form an oxide.
- This oxide reduces wettability with molten zinc during the plating process and causes non-plating. Therefore, as the Si concentration in the steel increases, the wettability decreases sharply and non-plating occurs frequently. In addition, even when non-plating does not occur, there is a problem that the plating adhesion is poor. Further, when Si in the steel is selectively oxidized and concentrated on the surface of the steel sheet, there is a problem that a remarkable alloying delay occurs in the alloying process after hot dip galvanizing, and the productivity is remarkably hindered.
- Patent Document 1 discloses that by directly oxidizing the surface of the steel sheet using a direct-fired heating furnace (DFF), the steel sheet is annealed in a reducing atmosphere, thereby obtaining Si.
- DFF direct-fired heating furnace
- the reduction annealing after heating may be performed by a conventional method (dew point -30 to -40 ° C).
- Patent Document 2 discloses a steel plate in a region where the steel plate temperature is at least 300 ° C. in a continuous annealing hot dipping method using an annealing furnace and a hot dipping bath having a heating zone first stage, a heating zone latter stage, a heat retention zone, and a cooling zone in this order.
- the in-furnace atmosphere of each zone is 1 to 10% by volume of hydrogen, the balance is nitrogen and inevitable impurities, and the temperature reached by the steel plate during heating in the preceding stage of the heating zone is 550 ° C. 750 ° C. or less, dew point less than ⁇ 25 ° C., and subsequent dew point of the heating zone and the retentive zone to be ⁇ 30 ° C.
- Patent Document 3 while measuring the dew point of the in-furnace gas and changing the position of supply and discharge of the in-furnace gas according to the measured value, the dew point of the reducing furnace gas exceeds 0 ° C. over ⁇ 30 ° C.
- a technique is described in which Si is concentrated on the surface of a steel sheet by controlling the temperature to be within a range of ° C or less.
- the heating furnace may be any of DFF (direct flame heating furnace), NOF (non-oxidation furnace), and radiant tube type, but there is a description that it is preferable because the invention effect can be remarkably exhibited in the radiant tube type.
- the present invention provides a hot dip galvanized steel sheet that has a high plating adhesion and can provide a good plating appearance even when hot dip galvanizing is applied to a steel strip containing 0.2 mass% or more of Si. It aims at providing the manufacturing method of.
- the gist of the present invention is as follows.
- a hot-dip galvanized steel sheet using a continuous hot-dip galvanizing apparatus having an annealing furnace in which a heating zone, a soaking zone, and a cooling zone are juxtaposed in this order, and a hot-dip galvanizing facility adjacent to the cooling zone
- a manufacturing method of Conveying the steel strip in the annealing furnace in the order of the heating zone, the soaking zone, and the cooling zone, and annealing the steel strip and Using the hot dip galvanizing equipment, applying hot dip galvanizing to the steel strip discharged from the cooling zone;
- the reducing gas or non-oxidizing gas supplied to the soaking zone is a humidified gas humidified by a humidifier, and a dry gas not humidified by the humidifier, While the width of the steel strip passing through the soaking zone and the plate passing speed are constant, the humidified gas is controlled against the fluctuation of the pressure in the annealing furnace by adjusting the flow rate of the dry gas.
- the heating zone includes a direct-fired heating furnace, and the continuous hot dip galvanizing apparatus has an alloying equipment adjacent to the hot dip galvanizing equipment,
- the continuous hot dip galvanizing apparatus 100 includes an annealing furnace 20 in which a heating zone 10, a soaking zone 12, and cooling zones 14 and 16 are arranged in this order, and a hot dip galvanizing bath 22 as a hot dip galvanizing facility adjacent to the cooling zone 16.
- the hot-dip galvanizing bath 22 and the adjacent alloying equipment 23 are provided.
- the heating zone 10 includes a first heating zone 10A (a heating zone upstream) and a second heating zone 10B (a heating zone downstream).
- the cooling zone includes a first cooling zone 14 (quenching zone) and a second cooling zone 16 (cooling zone).
- the tip of the snout 18 connected to the second cooling zone 16 is immersed in a hot dip galvanizing bath 22, and the annealing furnace 20 and the hot dip galvanizing bath 22 are connected.
- the steel strip P is introduced into the first heating zone 10A from the steel strip inlet at the bottom of the first heating zone 10A.
- one or more hearth rolls are disposed at the upper and lower portions.
- the steel strip P is conveyed a plurality of times in the vertical direction inside a predetermined strip of the annealing furnace 20 to form a plurality of passes.
- FIG. 1 an example of 10 passes in the soaking zone 12, 2 passes in the first cooling zone 14, and 2 passes in the second cooling zone 16 is shown.
- the number of passes is not limited to this, and it depends on the processing conditions. It can be set as appropriate.
- the steel strip P is changed to a right angle without turning back, and the steel strip P is moved to the next strip.
- the steel strip P can be transported in the annealing furnace 20 in the order of the heating zone 10, the soaking zone 12, and the cooling zones 14 and 16, and the steel strip P can be annealed.
- adjacent bands communicate with each other via a communication portion that connects the upper parts or the lower parts of each band.
- the first heating zone 10 ⁇ / b> A and the second heating zone 10 ⁇ / b> B communicate with each other via a throat (throttle portion) that connects the upper portions of the respective zones.
- the second heating zone 10B and the soaking zone 12 communicate with each other via a throat that connects the lower portions of each zone.
- the soaking zone 12 and the first cooling zone 14 communicate with each other via a throat connecting the lower portions of the respective zones.
- the 1st cooling zone 14 and the 2nd cooling zone 16 are connected via the throat which connects the lower parts of each zone.
- each throat may be set as appropriate, but it is preferable that the height of each throat is as low as possible from the viewpoint of increasing the independence of the atmosphere of each band.
- the gas in the annealing furnace 20 flows from the downstream to the upstream of the furnace and is discharged from the steel strip inlet at the bottom of the first heating zone 10A.
- the second heating zone 10B is a direct-fired heating furnace (DFF).
- DFF direct-fired heating furnace
- a well-known DFF can be used.
- a plurality of burners are arranged in a distributed manner facing the steel strip P on the inner wall of the direct-fired heating furnace in the second heating zone 10B.
- the plurality of burners are preferably divided into a plurality of groups, and the fuel ratio and the air ratio can be independently controlled for each group.
- the combustion exhaust gas from the second heating zone 10B is supplied into the first heating zone 10A, and the steel strip P is preheated by the heat.
- Combustion rate is a value obtained by dividing the amount of fuel gas actually introduced into the burner by the amount of fuel gas in the burner at the maximum combustion load. When the burner is burned at the maximum combustion load, the burning rate is 100%. The burner cannot obtain a stable combustion state when the combustion load becomes low. Therefore, it is preferable that the combustion rate is usually 30% or more.
- the air ratio is a value obtained by dividing the amount of air actually introduced into the burner by the amount of air necessary for complete combustion of the fuel gas.
- the heating burner of the second heating zone 10B is divided into four groups (# 1 to # 4), and the three groups (# 1 to # 3) on the upstream side in the steel plate moving direction are oxidation burners,
- the final zone (# 4) is a reduction burner, and the air ratio of the oxidation burner and the reduction burner can be individually controlled.
- the air ratio is preferably 0.95 or more and 1.5 or less.
- the air ratio is preferably 0.5 or more and less than 0.95.
- the temperature inside the second heating zone 10B is preferably set to 800 to 1200 ° C.
- the steel strip P in the soaking zone 12, can be indirectly heated using a radiant tube (RT) (not shown) as a heating means.
- RT radiant tube
- the average temperature Tr (° C.) inside the soaking zone 12 is measured by inserting a thermocouple into the soaking zone, but is preferably 700 to 900 ° C.
- the soaking zone 12 is supplied with reducing gas or non-oxidizing gas.
- reducing gas a H 2 —N 2 mixed gas is usually used, for example, H 2 : 1 to 20% by volume, and the balance is composed of N 2 and inevitable impurities (dew point: about ⁇ 60 ° C.) Is mentioned.
- non-oxidizing gas include a gas having a composition composed of N 2 and inevitable impurities (dew point: about ⁇ 60 ° C.).
- the reducing gas or non-oxidizing gas supplied to the soaking zone 12 is in two forms: humidified gas and dry gas.
- the “dry gas” is the reducing gas or non-oxidizing gas having a dew point of about ⁇ 60 ° C. to ⁇ 50 ° C., and is not humidified by a humidifier.
- “humidified gas” is a gas that has been dehumidified to 0 to 30 ° C. by a humidifier.
- a humidified gas is supplied to the soaking zone 12 in addition to the dry gas.
- FIG. 2 is a schematic diagram showing a supply system of humidified gas and dry gas to the soaking zone 12.
- the humidified gas is supplied in three systems: humidified gas supply ports 42A, 42B, 42C, humidified gas supply ports 44A, 44B, 44C, and humidified gas supply ports 46A, 46B, 46C.
- the reducing gas or non-oxidizing gas dry gas
- the dry gas supply ports 48A, 48B, 48C, 48D is supplied into the soaking zone 12 through the dry gas supply ports 48A, 48B, 48C, 48D.
- the position and number of the drying gas supply ports are not particularly limited, and may be appropriately determined in consideration of various conditions. However, it is preferable that a plurality of the drying gas supply ports be arranged at the same height position, and it is preferable that the drying gas supply ports are arranged uniformly in the steel strip traveling direction.
- the gas humidified by the humidifying device 26 is distributed to the three systems by the humidifying gas distribution device 30 and is supplied to the humidified gas supply ports 42A, 42B, 42C and the humidified gas supply ports via the humidified gas pipes 36, respectively.
- 44A, 44B, 44C and humidified gas supply ports 46A, 46B, 46C are supplied into the soaking zone 12.
- the position and number of humidified gas supply ports are not particularly limited, and may be determined as appropriate in consideration of various conditions. However, it is preferable to provide one or more humidified gas supply ports in each of the four zones divided into two in the vertical direction of the soaking zone 12 and two in the entrance / exit direction. This is because the dew point can be uniformly controlled throughout the soaking zone 12.
- Reference numeral 38 denotes a humidified gas flow meter
- reference numeral 40 denotes a humidified gas dew point meter. Since the dew point of the humidified gas may change due to slight dew condensation in the humidified gas pipes 34, 36, the dew point meter 40 is desirably installed immediately before the humidified gas supply ports 42, 44, 46.
- a humidification module having a fluorine-based or polyimide-based hollow fiber membrane or a flat membrane, and a dry gas is allowed to flow inside the membrane, and the outside of the membrane is brought to a predetermined temperature in a circulating constant temperature water bath 28. Circulate adjusted pure water.
- a fluorine-based or polyimide-based hollow fiber membrane or a flat membrane is a kind of ion exchange membrane having an affinity for water molecules.
- the dry gas temperature changes according to the season and daily temperature change, but this humidifier can also exchange heat by taking sufficient contact area between the gas and water through the water vapor permeable membrane. Regardless of whether the temperature is higher or lower than the circulating water temperature, the dry gas becomes a gas humidified to the same dew point as the set water temperature, and high-precision dew point control is possible.
- the dew point of the humidified gas can be arbitrarily controlled in the range of 5 to 50 ° C. If the dew point of the humidified gas is higher than the piping temperature, condensation may occur in the piping, and the condensed water may directly enter the furnace.Therefore, the humidifying gas piping should be above the humidifying gas dew point and above the ambient temperature. It is heated and insulated.
- the pressure in the annealing furnace varies depending on the combustion conditions of the heating zone 10 and the operating conditions of the cooling fans in the cooling zones 14 and 16.
- the furnace pressure is too high, an excessive force is applied to the furnace wall, which may damage the annealing furnace.
- the furnace pressure is too low, oxygen outside the annealing furnace may be mixed in the soaking zone 12.
- the combustion gas in the heating zone 10 may flow in and adversely affect the steel plate quality. Therefore, in general, control is performed to increase or decrease the gas flow rate supplied to the soaking zone 12 so as to suppress fluctuations in the furnace pressure, and preferably keep the furnace pressure constant.
- the conventional control method varies not only the flow rate of the dry gas but also the flow rate of the humidified gas.
- the amount of water supplied to the tropics also fluctuated.
- the soaking zone 12 it is necessary to always supply the soaking zone 12 with a necessary amount of water from the viewpoint of internal oxidation of Si and Mn in the steel strip.
- the flow rate of the humidified gas is decreased to suppress fluctuations in the furnace pressure, the amount of water supplied to the soaking zone 12 is insufficient, and the dew point in the soaking zone 12 falls below the lower limit of the appropriate range, resulting in partial Non-plating occurred, and the appearance of plating sometimes deteriorated.
- the alloying temperature increases, and as a result, a desired tensile strength may not be obtained.
- the flow rate of the humidifying gas is increased in order to suppress fluctuations in the furnace pressure, the amount of water supplied to the soaking zone 12 becomes excessive, resulting in roll pick-up, and the steel strip surface is also caused by the roll pick-up. In some cases, the plating appearance deteriorates and the plating appearance deteriorates.
- annealing is performed by adjusting the flow rate of the dry gas. While suppressing fluctuations in the pressure in the furnace, the amount of water supplied to the soaking zone 12 by the humidified gas should be kept as constant as possible, specifically, the fluctuation range of the moisture amount should be 20% or less. It is essential. Thereby, a favorable plating appearance can be obtained, and in an operation in which alloying treatment is also performed, a decrease in tensile strength can be suppressed by lowering the alloying temperature.
- the “variation width of the amount of water” supplied to the soaking zone is (M max ⁇ M min ) / M max , where M max is the maximum amount of water and M min is the minimum amount under the same operating conditions.
- M max is the maximum amount of water
- M min is the minimum amount under the same operating conditions.
- the amount of water can be calculated by the following formula (2).
- the mode of suppressing the fluctuation range of the moisture amount to 20% or less is not particularly limited.
- the dew point of the humidified gas is made constant and the fluctuation range of the flow rate is controlled to 20% or less.
- the humidified gas flow rate from each supply port and the total humidified gas flow rate should be as constant as possible (specifically, 20% or less). Is preferred.
- the amount of water M (g / min) introduced into the soaking zone 12 by the humidified gas needs to be adjusted by the soaking zone volume, the width of the steel strip P passing through the soaking zone 12, and the plate passing speed.
- the inventors set the flow rate and dew point of the humidified gas so that the amount of water M (g / min) supplied to the soaking zone 12 by the humidified gas satisfies the following formula (1). Has been found to be effective for obtaining a good plating appearance.
- Vf is the volume of the soaking zone 12 (m 3 )
- W is the width (m) of the steel strip P passing through the soaking zone 12
- S is the plate speed (m / s) of the steel strip P.
- the flow rate of the humidified gas so that the water content M (g / min) satisfies the formula (1). It is also effective to change the dew point.
- the volume Vf of the soaking zone 12 is practically a constant.
- the width W of the steel strip P passing through the soaking zone 12 and the passing plate speed S increase, or when one of the width W and the passing plate speed S is constant and the other increases, the inside of the soaking zone 12 per unit time. Since the steel strip area in contact with the gas increases, the amount of moisture by the humidified gas is increased based on the formula (1).
- the width W and the sheet passing speed S of the steel strip P passing through the soaking zone 12 decrease, or when one of the width W and the sheet passing speed S is constant and the other decreases, on the contrary, based on the formula (1) Therefore, it is necessary to reduce the amount of moisture by the humidified gas.
- the amount of moisture by the humidified gas is adjusted based on the formula (1).
- the amount of moisture M (g / min) can be calculated by the formula (2) from the dew point Tw (° C.) of the humidified gas and the total flow rate Vm (Nm 3 / hr).
- the flow rate Vm of the humidified gas supplied into the soaking zone 12 is not particularly limited as long as it is controlled as described above, but is generally maintained within a range of 100 to 400 (Nm 3 / hr).
- the flow rate of the dry gas supplied into the soaking zone 12 is not particularly limited, but is generally maintained within a range of 10 to 300 (Nm 3 / hr).
- the dew point measuring port 50 is arranged in the upper half region in the height direction of the soaking zone 12. Moreover, since the vicinity of the humidified gas supply port has a locally high dew point, it is an unsuitable region for dew point measurement. Therefore, the dew point measurement port 50 is preferably disposed at a position 1 m or more away from the position of each humidified gas supply port, and at a position 1 m or more away from the inner wall position of the soaking zone facing each supply port. .
- the flow rate of the humidified gas so that the dew point in the soaking zone 12 measured at the dew point measuring port 50 is maintained at ⁇ 25 ° C. or more and 0 ° C. or less.
- the steel strip P is cooled in the cooling zones 14 and 16.
- the steel strip P is cooled to about 480 to 530 ° C. in the first cooling zone 14 and is cooled to about 470 to 500 ° C. in the second cooling zone 16.
- the supply of the drying gas to the cooling zones 14 and 16 is not particularly limited, but it is preferable to supply the drying gas from two or more inlets in the height direction and two or more inlets in the longitudinal direction so as to be uniformly introduced into the cooling zone. .
- the total gas flow rate Qcd of the dry gas supplied to the cooling zones 14 and 16 is measured by a gas flow meter (not shown) provided in the pipe and is not particularly limited, but is about 200 to 1000 (Nm 3 / hr).
- the pressure fluctuation in the annealing furnace may be suppressed by adjusting only the flow rate of the dry gas supplied to the soaking zone, but also adjusting the flow rate of the dry gas supplied to the cooling zone. Preferably it is done.
- Hot dip galvanization bath Using the hot dip galvanizing bath 22, hot dip galvanization can be performed on the steel strip P discharged from the second cooling zone 16. Hot dip galvanization may be performed according to a conventional method.
- the galvanization applied to the steel strip P can be heated and alloyed using the alloying equipment 23.
- the alloying process may be performed according to a conventional method. According to this embodiment, since alloying temperature does not become high temperature, the fall of the tensile strength of the manufactured galvannealed steel plate can be suppressed.
- the alloying equipment 23 and the alloying treatment using it are not essential. This is because the effect of obtaining a good plating appearance can be obtained even when the alloying treatment is not performed.
- the steel strip P to be subjected to annealing and hot dip galvanizing treatment is not particularly limited, but in the case of a steel strip having a component composition containing 0.2% by mass or more of Si, that is, a high-strength steel, the effect of the present invention is advantageously obtained. be able to.
- the second heating zone was DFF.
- the heating burner is divided into four groups (# 1 to # 4).
- the three groups (# 1 to # 3) on the upstream side in the direction of moving the steel plate are oxidation burners, and the final zone (# 4) is a reduction burner.
- the air ratio of the oxidation burner and the reduction burner was set to the values shown in Table 2.
- the length of the steel plate conveyance direction of each group is 4 m.
- the soaking zone was an RT furnace with a volume Vf of 700 m 3 .
- the average temperature Tr in the soaking zone was set as shown in Table 2.
- the drying gas the gas having the balance consisting of N 2 and unavoidable impurities in 15% by volume of H 2 (dew point: -50 ° C.) was used.
- Part of this dry gas was humidified by a humidifier having 10 hollow fiber membrane humidification modules to prepare a humidified gas.
- Each module was supplied with a maximum of 500 L / min of dry gas and a maximum of 20 L / min of circulating water.
- the circulating water bath is common to each module and can supply a total of 200 L / min of pure water.
- the dry gas supply port and the humidified gas supply port were arranged at the positions shown in FIG.
- the first half (time 0:00 to 0:55) is a comparative example
- the second half (time 0:55 to 1:50) is an invention example. That is, in the first half plate, the flow rate of the dry gas supplied to the soaking zone, the flow rate of the humidified gas, and the flow rate of the dry gas supplied to the cooling zone are varied as shown in Table 2 to keep the furnace pressure constant. I tried to keep it.
- the dew point of the humidifying gas is constant and the fluctuation range of the flow rate of the humidifying gas is constant while the type, width, and plate passing speed of the steel strip passing through the soaking zone are constant.
- the furnace pressure was kept constant by adjusting the flow rate of the dry gas supplied to the soaking zone and the cooling zone.
- the dew point in the soaking tropics measured at the position of the dew point measuring port 50 in FIG. 2 is shown.
- the “dew point near the humidified gas supply port” indicates the dew point in the soaking zone measured at a position 80 cm away from the humidified gas supply port 40B in FIG.
- the “humidified gas dew point” indicates the dew point measured by the humidified gas dew point meter 40 of FIG.
- the dry gas (dew point: ⁇ 50 ° C.) was supplied at the flow rate shown in Table 2 from the bottom of each zone.
- the plating bath temperature was 460 ° C.
- the Al concentration in the plating bath was 0.130%
- the adhesion amount was adjusted to 50 g / m 2 per side by gas wiping.
- the line speed was set to 1.0 to 2.0 m / s along with the change of the plate thickness.
- alloying treatment was performed in an induction heating type alloying furnace so that the degree of film alloying (Fe content) was within 10 to 13%.
- the alloying temperature at that time is shown in Table 2.
- the steel type A of high-tensile steel passed 590 MPa or more, and the steel type B of high-tensile steel passed 980 MPa or more. The results are shown in Table 2.
- the predetermined moisture amount can be stably supplied, so that a good surface appearance is obtained over the entire length of the coil, and desired tensile characteristics are obtained.
- the tensile strength and surface appearance are particularly high in the time range of 1:20 to 2:00 when the fluctuation of the water content is within 20% and the dew point is controlled to -25 to 0 ° C while satisfying the formula (1). Stable.
- the method for manufacturing a hot dip galvanized steel sheet of the present invention even when hot dip galvanizing is applied to a steel strip containing 0.2 mass% or more of Si, it is possible to obtain a good plating appearance with high plating adhesion. is there. Moreover, according to the manufacturing method of the hot dip galvanizing of the present invention, when the alloying process is further performed, the alloying temperature does not become high, so that the decrease in the tensile strength of the manufactured hot galvanized steel sheet is suppressed. be able to.
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Abstract
Description
[1]加熱帯と、均熱帯と、冷却帯とがこの順に並置された焼鈍炉と、前記冷却帯に隣接した溶融亜鉛めっき設備と、を有する連続溶融亜鉛めっき装置を用いた溶融亜鉛めっき鋼板の製造方法であって、
鋼帯を前記焼鈍炉の内部で、前記加熱帯、前記均熱帯及び前記冷却帯の順に搬送して、前記鋼帯に対して焼鈍を行う工程と、
前記溶融亜鉛めっき設備を用いて、前記冷却帯から排出される鋼帯に溶融亜鉛めっきを施す工程と、
を有し、
前記均熱帯に供給される還元性ガス又は非酸化性ガスは、加湿装置により加湿された加湿ガス、及び前記加湿装置により加湿されていない乾燥ガスであり、
前記均熱帯を通過する鋼帯の幅及び通板速度が一定である間は、前記乾燥ガスの流量を調節することで前記焼鈍炉内の圧力の変動を抑制するのに対して、前記加湿ガスによって前記均熱帯に供給される水分量の変動幅を20%以下とすることを特徴とする溶融亜鉛めっき鋼板の製造方法。 The gist of the present invention is as follows.
[1] A hot-dip galvanized steel sheet using a continuous hot-dip galvanizing apparatus having an annealing furnace in which a heating zone, a soaking zone, and a cooling zone are juxtaposed in this order, and a hot-dip galvanizing facility adjacent to the cooling zone A manufacturing method of
Conveying the steel strip in the annealing furnace in the order of the heating zone, the soaking zone, and the cooling zone, and annealing the steel strip; and
Using the hot dip galvanizing equipment, applying hot dip galvanizing to the steel strip discharged from the cooling zone;
Have
The reducing gas or non-oxidizing gas supplied to the soaking zone is a humidified gas humidified by a humidifier, and a dry gas not humidified by the humidifier,
While the width of the steel strip passing through the soaking zone and the plate passing speed are constant, the humidified gas is controlled against the fluctuation of the pressure in the annealing furnace by adjusting the flow rate of the dry gas. The method for producing a hot-dip galvanized steel sheet, characterized in that the fluctuation range of the amount of water supplied to the soaking zone is 20% or less.
40+Vf(W-0.9)(S+4)/90 < M < 60+Vf(W-0.9)(S+4)/90 ・・・(1)
ここで、Vfは前記均熱帯の容積(m3)、Wは前記均熱帯を通過する鋼帯の幅(m)、Sは前記鋼帯の通板速度(m/s)である。 [2] The flow rate and dew point of the humidified gas are set so that the amount of moisture M (g / min) supplied to the soaking zone by the humidified gas satisfies the following formula (1): [1] The manufacturing method of the hot-dip galvanized steel sheet as described in 2.
40 + Vf (W−0.9) (S + 4) / 90 <M <60 + Vf (W−0.9) (S + 4) / 90 (1)
Here, Vf is the volume of the soaking zone (m 3), W is the width of the steel strip passing through the soaking (m), S is a sheet passing speed of the steel strip (m / s).
前記合金化設備を用いて、前記鋼帯に施された亜鉛めっきを加熱合金化する工程をさらに有する、上記[1]~[4]のいずれか一項に記載の溶融亜鉛めっき鋼板の製造方法。 [5] The heating zone includes a direct-fired heating furnace, and the continuous hot dip galvanizing apparatus has an alloying equipment adjacent to the hot dip galvanizing equipment,
The method for producing a hot-dip galvanized steel sheet according to any one of the above [1] to [4], further comprising a step of heat-alloying the zinc plating applied to the steel strip using the alloying equipment .
本実施形態において、第2加熱帯10Bは、直火型加熱炉(DFF)である。DFFは公知のものを用いることができる。図1においては図示しないが、第2加熱帯10Bにおける直火型加熱炉の内壁には、複数のバーナが鋼帯Pに対向して分散配置される。複数のバーナは複数のグループに分けられ、グループごとに燃料率及び空気比を独立に制御可能とすることが好ましい。第1加熱帯10Aの内部には、第2加熱帯10Bの燃焼排ガスが供給され、その熱で鋼帯Pを予熱する。 (Heating zone)
In the present embodiment, the
本実施形態において均熱帯12では、加熱手段としてラジアントチューブ(RT)(図示せず)を用いて、鋼帯Pを間接加熱することができる。均熱帯12の内部の平均温度Tr(℃)は、均熱帯内に熱電対を挿入することによりにより測定されるが、700~900℃とすることが好ましい。 (Soaking)
In this embodiment, in the soaking
40+Vf(W-0.9)(S+4)/90 < M < 60+Vf(W-0.9)(S+4)/90 ・・・(1)
ここで、Vfは均熱帯12の容積(m3)、Wは均熱帯12を通過する鋼帯Pの幅(m)、Sは鋼帯Pの通板速度(m/s)である。 The amount of water M (g / min) introduced into the soaking
40 + Vf (W−0.9) (S + 4) / 90 <M <60 + Vf (W−0.9) (S + 4) / 90 (1)
Here, Vf is the volume of the soaking zone 12 (m 3 ), W is the width (m) of the steel strip P passing through the soaking
本実施形態において冷却帯14,16では、鋼帯Pが冷却される。鋼帯Pは、第1冷却帯14では480~530℃程度にまで冷却され、第2冷却帯16では470~500℃程度にまで冷却される。 (Cooling zone)
In the present embodiment, the steel strip P is cooled in the
溶融亜鉛めっき浴22を用いて、第2冷却帯16から排出される鋼帯Pに溶融亜鉛めっきを施すことができる。溶融亜鉛めっきは定法に従って行えばよい。 (Hot galvanizing bath)
Using the hot
合金化設備23を用いて、鋼帯Pに施された亜鉛めっきを加熱合金化することができる。合金化処理は定法に従って行えばよい。本実施形態によれば、合金化温度が高温にならないため、製造された合金化溶融亜鉛めっき鋼板の引張強度の低下を抑制することができる。ただし、本発明において合金化設備23や、それによる合金化処理は必須ではない。良好なめっき外観を得るとの効果は、合金化処理をしない場合にも得ることができるからである。 (Alloying equipment)
The galvanization applied to the steel strip P can be heated and alloyed using the alloying
図1及び図2に示す連続溶融亜鉛めっき装置を用いて、表1に示す成分組成の鋼帯を表2に示す各種焼鈍条件で焼鈍し、その後溶融亜鉛めっき及び合金化処理を施した。鋼種A、鋼種Bともに高張力鋼である。表2に記載の「時間」は操業開始からの経過時間を意味し、時間の経過とともに、表2のとおりに通板する鋼帯の種類、板厚、板幅、及び連続溶融亜鉛めっき装置の操業条件を変更した。 (Experimental conditions)
Using the continuous hot dip galvanizing apparatus shown in FIGS. 1 and 2, the steel strip having the composition shown in Table 1 was annealed under various annealing conditions shown in Table 2, and then hot dip galvanized and alloyed. Both steel types A and B are high-tensile steels. “Time” shown in Table 2 means the elapsed time from the start of operation, and with the passage of time, the type, thickness, width, and continuous hot-dip galvanizing device The operating conditions were changed.
めっき外観の評価は、光学式の表面欠陥計による検査(φ0.5以上の不めっき欠陥やロールピックアップによる疵を検出)および目視による合金化ムラ判定を行い、全ての項目が合格で○、軽度の合金化ムラがある場合は△、一つでも不合格があれば×とした。結果を表2に示す。 (Evaluation methods)
The appearance of the plating is evaluated by optical surface defect meter inspection (detection of unplating defects of φ0.5 or more and wrinkles by roll pick-up) and visual judgment of alloying unevenness. △ when there was an alloying unevenness, and × if there was any failure. The results are shown in Table 2.
比較例では、均熱帯内の露点が-25℃を下回った場合は、部分的な不めっきによりめっき外観が劣化し、また、合金化温度の上昇に伴って引張強度が不合格となった。また、均熱帯露点が0℃を上回った場合には、ロールピックアップが発生し、鋼帯表面にもロールピックアップに起因する疵が発生した結果、めっき外観が劣化した。また、0:20、0:35、0:45の時間帯では、水分量も式(1)を満たしていたが、前後の時間帯との水分量の変動が大きく、露点も-25~0℃の範囲に入っていなかったため、軽度の合金化ムラが見られた。 (Evaluation results)
In the comparative example, when the dew point in the soaking zone was below −25 ° C., the appearance of plating deteriorated due to partial non-plating, and the tensile strength failed as the alloying temperature increased. Moreover, when the soaking zone dew point exceeded 0 degreeC, roll pick-up generate | occur | produced and the plating external appearance deteriorated as a result of the wrinkles resulting from roll pick-up also having occurred on the steel strip surface. In addition, in the time zones of 0:20, 0:35, and 0:45, the water content also satisfied the equation (1), but the water content fluctuated greatly between the previous and next time zones, and the dew point was -25 to 0. Since it was not in the range of ° C., mild uneven alloying was observed.
10 加熱帯
10A 第1加熱帯(前段)
10B 第2加熱帯(後段、直火型加熱炉)
12 均熱帯
14 第1冷却帯(急冷帯)
16 第2冷却帯(除冷帯)
18 スナウト
20 焼鈍炉
22 溶融亜鉛めっき浴
23 合金化設備
24 乾燥ガス分配装置
26 加湿装置
28 循環恒温水槽
30 加湿ガス分配装置
32 乾燥ガス用配管
34,36 加湿ガス用配管
38 加湿ガス用流量計
40 加湿ガス用露点計
42A,42B,42C 加湿ガス供給口
44A,44B,44C 加湿ガス供給口
46A,46B,46C 加湿ガス供給口
48A,48B,48C,48D 乾燥ガス供給口
50 露点測定口
52A 上部ハースロール
52B 下部ハースロール
P 鋼帯 100 Continuous hot
10B Second heating zone (later, direct-fired heating furnace)
12 Soaking
16 Second cooling zone (cooling zone)
18
Claims (5)
- 加熱帯と、均熱帯と、冷却帯とがこの順に並置された焼鈍炉と、前記冷却帯に隣接した溶融亜鉛めっき設備と、を有する連続溶融亜鉛めっき装置を用いた溶融亜鉛めっき鋼板の製造方法であって、
鋼帯を前記焼鈍炉の内部で、前記加熱帯、前記均熱帯及び前記冷却帯の順に搬送して、前記鋼帯に対して焼鈍を行う工程と、
前記溶融亜鉛めっき設備を用いて、前記冷却帯から排出される鋼帯に溶融亜鉛めっきを施す工程と、
を有し、
前記均熱帯に供給される還元性ガス又は非酸化性ガスは、加湿装置により加湿された加湿ガス、及び前記加湿装置により加湿されていない乾燥ガスであり、
前記均熱帯を通過する鋼帯の幅及び通板速度が一定である間は、前記乾燥ガスの流量を調節することで前記焼鈍炉内の圧力の変動を抑制するのに対して、前記加湿ガスによって前記均熱帯に供給される水分量の変動幅を20%以下とすることを特徴とする溶融亜鉛めっき鋼板の製造方法。 A method for producing a hot-dip galvanized steel sheet using a continuous hot-dip galvanizing apparatus, comprising: an annealing furnace in which a heating zone, a soaking zone, and a cooling zone are arranged in this order; and a hot-dip galvanizing facility adjacent to the cooling zone Because
Conveying the steel strip in the annealing furnace in the order of the heating zone, the soaking zone, and the cooling zone, and annealing the steel strip; and
Using the hot dip galvanizing equipment, applying hot dip galvanizing to the steel strip discharged from the cooling zone;
Have
The reducing gas or non-oxidizing gas supplied to the soaking zone is a humidified gas humidified by a humidifier, and a dry gas not humidified by the humidifier,
While the width of the steel strip passing through the soaking zone and the plate passing speed are constant, the humidified gas is controlled against the fluctuation of the pressure in the annealing furnace by adjusting the flow rate of the dry gas. The method for producing a hot-dip galvanized steel sheet, characterized in that the fluctuation range of the amount of water supplied to the soaking zone is 20% or less. - 前記加湿ガスによって前記均熱帯に供給される水分量M(g/min)が、以下の式(1)を満たすように、前記加湿ガスの流量及び露点を設定する、請求項1に記載の溶融亜鉛めっき鋼板の製造方法。
40+Vf(W-0.9)(S+4)/90 < M < 60+Vf(W-0.9)(S+4)/90 ・・・(1)
ここで、Vfは前記均熱帯の容積(m3)、Wは前記均熱帯を通過する鋼帯の幅(m)、Sは前記鋼帯の通板速度(m/s)である。 The melting according to claim 1, wherein the flow rate and dew point of the humidified gas are set so that the amount of moisture M (g / min) supplied to the soaking zone by the humidified gas satisfies the following formula (1). Manufacturing method of galvanized steel sheet.
40 + Vf (W−0.9) (S + 4) / 90 <M <60 + Vf (W−0.9) (S + 4) / 90 (1)
Here, Vf is the soaking zone volume (m 3 ), W is the width (m) of the steel strip that passes through the soaking zone, and S is the plate passing speed (m / s) of the steel strip. - 前記均熱帯を通過する鋼帯の幅及び通板速度の少なくとも一方が変動したとき、前記水分量M(g/min)が前記式(1)を満たすように、前記加湿ガスの流量及び露点を変更する、請求項2に記載の溶融亜鉛めっき鋼板の製造方法。 When at least one of the width of the steel strip passing through the soaking zone and the plate passing speed fluctuates, the flow rate and dew point of the humidified gas are set so that the water content M (g / min) satisfies the equation (1). The manufacturing method of the hot dip galvanized steel plate of Claim 2 to change.
- 前記均熱帯の高さ方向の上部1/2の領域内で、前記均熱帯に設けられた前記加湿ガスの供給口の位置から1m以上離れた位置で、かつ、前記供給口に対向する前記均熱帯の内壁位置から1m以上離れた位置で、前記均熱帯に設けられた露点測定口において測定される前記均熱帯内の露点を-25℃以上0℃以下に制御する、請求項1~3のいずれか一項に記載の溶融亜鉛めっき鋼板の製造方法。 Within the upper half area of the soaking zone, the soaking zone facing the feeding port at a position 1 m or more away from the humidifying gas feeding port provided in the soaking zone. The dew point in the soaking zone measured at a dew point measuring port provided in the soaking zone is controlled to -25 ° C or more and 0 ° C or less at a position 1 m or more away from the tropical inner wall position. The manufacturing method of the hot dip galvanized steel plate as described in any one of Claims.
- 前記加熱帯は直火型加熱炉を含み、前記連続溶融亜鉛めっき装置は前記溶融亜鉛めっき設備に隣接した合金化設備を有し、
前記合金化設備を用いて、前記鋼帯に施された亜鉛めっきを加熱合金化する工程をさらに有する、請求項1~4のいずれか一項に記載の溶融亜鉛めっき鋼板の製造方法。 The heating zone includes a direct-fired heating furnace, and the continuous hot dip galvanizing apparatus has an alloying equipment adjacent to the hot dip galvanizing equipment,
The method for producing a hot-dip galvanized steel sheet according to any one of claims 1 to 4, further comprising a step of heat-alloying the galvanizing applied to the steel strip using the alloying equipment.
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