WO2014119263A1 - HOT-DIP Al-Zn GALVANIZED STEEL PLATE AND METHOD FOR PRODUCING SAME - Google Patents
HOT-DIP Al-Zn GALVANIZED STEEL PLATE AND METHOD FOR PRODUCING SAME Download PDFInfo
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- WO2014119263A1 WO2014119263A1 PCT/JP2014/000341 JP2014000341W WO2014119263A1 WO 2014119263 A1 WO2014119263 A1 WO 2014119263A1 JP 2014000341 W JP2014000341 W JP 2014000341W WO 2014119263 A1 WO2014119263 A1 WO 2014119263A1
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- steel sheet
- plated steel
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- 229910018137 Al-Zn Inorganic materials 0.000 title claims abstract description 53
- 229910018573 Al—Zn Inorganic materials 0.000 title claims abstract description 53
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 35
- 229910001335 Galvanized steel Inorganic materials 0.000 title abstract description 4
- 239000008397 galvanized steel Substances 0.000 title abstract description 4
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 126
- 239000010959 steel Substances 0.000 claims abstract description 126
- 238000007747 plating Methods 0.000 claims description 127
- 229910045601 alloy Inorganic materials 0.000 claims description 22
- 239000000956 alloy Substances 0.000 claims description 22
- 238000001816 cooling Methods 0.000 claims description 18
- 229910052804 chromium Inorganic materials 0.000 claims description 9
- 229910052748 manganese Inorganic materials 0.000 claims description 9
- 229910052750 molybdenum Inorganic materials 0.000 claims description 9
- 229910052759 nickel Inorganic materials 0.000 claims description 9
- 229910052712 strontium Inorganic materials 0.000 claims description 9
- 229910052719 titanium Inorganic materials 0.000 claims description 9
- 229910052720 vanadium Inorganic materials 0.000 claims description 9
- 239000012535 impurity Substances 0.000 claims description 4
- 238000005260 corrosion Methods 0.000 abstract description 44
- 230000007797 corrosion Effects 0.000 abstract description 44
- 238000000034 method Methods 0.000 abstract description 27
- 238000005246 galvanizing Methods 0.000 abstract 2
- 239000010410 layer Substances 0.000 description 57
- 239000011248 coating agent Substances 0.000 description 18
- 238000000576 coating method Methods 0.000 description 18
- 239000011701 zinc Substances 0.000 description 18
- 238000011282 treatment Methods 0.000 description 12
- 239000000203 mixture Substances 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 9
- 238000005452 bending Methods 0.000 description 8
- 229910000765 intermetallic Inorganic materials 0.000 description 8
- 239000000126 substance Substances 0.000 description 8
- 238000000137 annealing Methods 0.000 description 7
- 210000001787 dendrite Anatomy 0.000 description 6
- 238000011156 evaluation Methods 0.000 description 6
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 238000007598 dipping method Methods 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- 238000007711 solidification Methods 0.000 description 4
- 230000008023 solidification Effects 0.000 description 4
- 229910018125 Al-Si Inorganic materials 0.000 description 3
- 229910018520 Al—Si Inorganic materials 0.000 description 3
- 239000004566 building material Substances 0.000 description 3
- 239000010960 cold rolled steel Substances 0.000 description 3
- 238000007796 conventional method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000007781 pre-processing Methods 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 230000001629 suppression Effects 0.000 description 3
- 229910052725 zinc Inorganic materials 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 2
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 2
- 238000005097 cold rolling Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000003618 dip coating Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000005498 polishing Methods 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000005238 degreasing Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000002003 electron diffraction Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000007602 hot air drying Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- RYZCLUQMCYZBJQ-UHFFFAOYSA-H lead(2+);dicarbonate;dihydroxide Chemical compound [OH-].[OH-].[Pb+2].[Pb+2].[Pb+2].[O-]C([O-])=O.[O-]C([O-])=O RYZCLUQMCYZBJQ-UHFFFAOYSA-H 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000010731 rolling oil Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 210000004894 snout Anatomy 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
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- 238000011077 uniformity evaluation Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000004736 wide-angle X-ray diffraction Methods 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C18/00—Alloys based on zinc
- C22C18/04—Alloys based on zinc with aluminium as the next major constituent
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/02—Alloys based on aluminium with silicon as the next major constituent
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/10—Alloys based on aluminium with zinc as the next major constituent
-
- 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
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
-
- 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
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
- C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
- C23C2/0224—Two or more thermal pretreatments
-
- 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
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
- C23C2/024—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by cleaning or etching
-
- 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
- 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
- C23C2/26—After-treatment
- C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
-
- 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
- C23C2/26—After-treatment
- C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
- C23C2/29—Cooling or quenching
-
- 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
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
- C23C28/021—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material including at least one metal alloy layer
Definitions
- the present invention relates to a molten Al—Zn-plated steel sheet having good flat plate portion corrosion resistance and excellent workability due to excellent workability, and a method for producing the same.
- Patent Document 1 discloses a molten Al—Zn-based plated steel sheet containing 25 to 70% by mass of Al in the plating film. Due to its excellent corrosion resistance, the demand for molten Al-Zn-plated steel sheets has increased in recent years, especially in the field of building materials such as roofs and walls that have been exposed to the outdoors for long periods of time, and civil engineering and construction fields such as guardrails, wiring piping, and soundproof walls. ing.
- the plating film formed on the molten Al-Zn-based plated steel sheet is composed of an alloy layer present at the interface with the underlying steel sheet and an upper layer present thereon, the upper layer mainly containing Zn in supersaturation and Al being a dendrite. It is composed of a solidified portion (Al-rich phase) and a remaining dendrite gap portion (Zn-rich phase), and has a structure in which a plurality of Al-rich phases are laminated in the film thickness direction of the plating film. Such a characteristic coating structure complicates the corrosion path from the surface, making it difficult for corrosion to reach the underlying steel sheet.
- the molten Al-Zn plated steel sheet is a molten zinc with the same coating thickness. Excellent corrosion resistance compared to plated steel sheet.
- a spangle pattern derived from the solidification of the plating exists on the surface of the molten Al—Zn-based plated steel sheet.
- this spangle there are fine irregularities corresponding to the Al-rich phase and Zn-rich phase, and this irregularly reflects light, so that the surface of the molten Al-Zn-based plated steel sheet has a beautiful silver-white appearance. .
- hot-dip Al-Zn plated steel sheets pickled and descaled hot rolled steel sheets, or cold rolled steel sheets obtained by cold rolling the hot rolled steel sheets as base steel sheets, It is common to be manufactured. Specifically, first, the base steel sheet is heated to a specific temperature in an annealing furnace maintained in a reducing atmosphere, and along with annealing, the rolling oil adhering to the steel sheet surface is removed and the oxide film is reduced and removed. Next, the base steel sheet is immersed in the molten Al—Zn plating bath by passing the inside of the snout whose lower end is immersed in the plating bath.
- the steel plate immersed in the plating bath is pulled up to the upper part of the plating bath via the sink roll, and a pressurized gas is sprayed from the gas wiping nozzle arranged on the plating bath toward the surface of the steel plate.
- a molten Al—Zn-based plated steel sheet on which a desired plating film is formed is obtained.
- the composition of the plating bath and the cooling rate after plating in the above-described continuous hot-dip plating equipment Is done.
- the thinner the alloy layer the thicker the upper layer that is effective in improving the corrosion resistance. Therefore, suppressing the growth of the alloy layer contributes to the improvement of the corrosion resistance.
- the alloy layer is harder than the upper layer and becomes the starting point of cracks during processing, the suppression of the growth of the alloy layer also reduces the occurrence of cracks and brings about the effect of improving the bending workability.
- the base steel plate is exposed and the generated crack part is inferior in corrosion resistance, reducing the occurrence of cracks improves the corrosion resistance of the bent part.
- the molten Al—Zn-based plated steel sheet is often used in the field of building materials such as roofs and walls exposed to the outdoors for a long period of time due to its excellent corrosion resistance.
- the hot-dip Al-Zn-plated steel sheet manufactured in a continuous hot-dip plating facility is plated when it is bent because the plating layer solidifies in a non-equilibrium state due to rapid cooling and the plating upper layer is hardened.
- the film was cracked to cause cracks, and as a result, the corrosion resistance of the processed part was inferior. Therefore, it has been desired to improve the corrosion resistance of the processed part by improving the workability.
- the present invention provides a method for producing a hot-dip Al-Zn plated steel sheet having good flat plate portion corrosion resistance and excellent workability due to good workability by a continuous hot dipping equipment.
- an object of the present invention is to provide a molten Al—Zn-based plated steel sheet obtained by the method.
- the present inventors As a result of intensive research to solve the above-mentioned problems, the present inventors, as a result of maintaining a certain time in a specific temperature range for a plated steel sheet after hot-dip plating in a continuous hot-dip plating facility, As a result, the present inventors have found that a molten Al—Zn-based plated steel sheet having good flat plate portion corrosion resistance and excellent workability and excellent corrosion resistance of the processed portion can be obtained. Moreover, it discovered that the formation of a spangle was suppressed and the outstanding external appearance uniformity was realizable by rapidly cooling to the specific temperature about the plated steel plate after the said hot dipping.
- the present invention has been made based on the above findings, and the gist thereof is as follows. 1.
- a method for producing a hot-dip Al-Zn-plated steel sheet characterized in that, in a continuous hot-dip coating facility, the hot-plated steel sheet is held at a temperature of 250 to 375 ° C for 5 to 60 seconds.
- the upper layer further contains one or more selected from Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B in a total amount of 0.01 to 10% by mass. 8.
- a hot-dip Al-Zn-plated steel sheet having excellent flat plate portion corrosion resistance and excellent workability due to excellent workability can be produced by a continuous hot-dip plating apparatus.
- FIG. 3 is a process diagram showing one embodiment of a method for producing a hot-dip Al—Zn-based plated steel sheet according to the present invention.
- FIG. 1 is a diagram showing a rough flow of a method for producing a molten Al—Zn-based plated steel sheet according to the present invention.
- the method for producing a hot-dip Al—Zn-based plated steel sheet according to the present invention is a method for producing in a continuous hot-dip plating facility. Production by a continuous hot dip plating facility makes it possible to produce an Al-Zn-based plated steel sheet more efficiently than when the hot dip plating equipment is further combined with a batch heating equipment. And as shown in FIG. 1, this invention performs pre-processing (pre-processing process), such as degreasing and pickling, and annealing (annealing process) with respect to a to-be-processed steel plate (base steel plate) as needed.
- pre-processing process such as degreasing and pickling
- annealing annealing process
- hot-dip plating (plating process) is performed, and preferably the steel sheet after hot-dip plating is cooled within 5 seconds from the bath temperature of the plating bath to ⁇ 20 ° C. (rapid cooling step).
- the plated steel sheet is held at a temperature of 250 to 375 ° C. for 5 to 60 seconds (temperature holding step).
- base steel sheet used in the hot-dip Al—Zn-based plated steel sheet of the present invention there are no particular restrictions on the type of base steel sheet used in the hot-dip Al—Zn-based plated steel sheet of the present invention.
- a hot-rolled steel plate or steel strip that has been pickled and descaled, or a cold-rolled steel plate or steel strip obtained by cold rolling them can be used.
- it does not specifically limit about the conditions of the said pre-processing process and annealing process Arbitrary methods are employable.
- the conditions for the hot dipping are not particularly limited as long as an Al—Zn plating film can be formed on the base steel plate, and can be performed according to a conventional method.
- the plating film having a desired film thickness can be formed by cooling to the vicinity of the plating bath temperature, immersing in the plating bath, and then performing wiping.
- the Al concentration in the hot dip plating bath is 20 to 95% by mass.
- the plating bath contains Si with an Al content of 10% or less, and the balance is made of Zn and inevitable impurities. Further, the plating bath contains 0.01 to 10% by mass in total of one or more selected from Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B. Is preferred.
- the plating film formed by the Al—Zn plating bath is composed of an interface alloy layer present at the interface with the underlying steel plate and an upper layer present on the interface alloy layer.
- the composition of the upper layer is almost the same as the composition of the plating bath as a whole, although Al and Si are slightly lower on the interface alloy layer side. Therefore, the composition of the plating upper layer can be accurately controlled by controlling the plating bath composition.
- the steel sheet after the hot dipping is cooled within 5 seconds from a bath temperature of the plating bath of ⁇ 20 ° C. to a bath temperature of the plating bath of ⁇ 80 ° C.
- a rapid cooling step is preferred.
- the average size of spangles formed on the plating film is 0.5 mm or less, a coating film (particularly a high gloss coating film that requires a smooth and uniform appearance) is formed on the molten Al-Zn plated steel sheet of the present application.
- the boundary of spangles is particularly preferred because it does not rise up to the surface of the coating film and is not visually recognized.
- the cooling time of the rapid cooling is preferably within 3 seconds, and more preferably within 1 second. When the cooling time to the plating bath temperature of ⁇ 80 ° C. exceeds 5 seconds, there is no sufficient spangle suppression effect, and the average size cannot be reduced to 0.5 mm or less.
- this rapid cooling step may not necessarily be performed, and the manufacturing method in that case is not limited.
- the “top roll” means a roll in which the plated steel sheet first comes into contact with the base steel sheet after hot-dip plating.
- the plating film obtained by the manufacturing method of the present invention can improve the corrosion resistance of the processed part by reducing the number and width of cracks generated during processing compared to the plating film obtained by the conventional manufacturing method. It becomes.
- the holding temperature is less than 250 ° C. or when the holding time is less than 5 seconds, the hot dip coating film is quickly cured, and sufficient strain release and separation of the Al-rich phase and the Zn-rich phase can be achieved. Since it does not progress, the desired processability cannot be obtained.
- the holding temperature exceeds 375 ° C. because of the relationship with the metal pickup described above, and when the holding time exceeds 60 seconds, the holding time is too long, so that the manufacturing is performed in a continuous hot dip plating facility. Not suitable for.
- the holding temperature of the plated steel sheet in the temperature holding step is preferably 300 to 375 ° C., more preferably 350 to 375 ° C.
- the holding time of the hot-dip galvanized steel sheet is preferably 5 to 30 seconds, and more preferably 5 to 20 seconds.
- the temperature holding step is not particularly limited, and a molten Al—Zn-based plated steel sheet can be produced according to a conventional method.
- a chemical conversion treatment film is formed on the surface of the molten Al-Zn-plated steel sheet after the temperature holding step (chemical conversion treatment step), or a coating film is formed in a separate coating facility (coating). Film forming step).
- the chemical conversion treatment film is formed by, for example, a chromate treatment or a chromium-free chemical conversion treatment in which a chromate treatment solution or a chromium-free chemical conversion treatment solution is applied, and a drying treatment is performed at a temperature of 80 to 300 ° C. without washing with water. It is possible. These chemical conversion treatment films may be a single layer or multiple layers, and in the case of multiple layers, a plurality of chemical conversion treatments may be performed sequentially. Examples of the method for forming the coating film include roll coater coating, curtain flow coating, and spray coating. After coating a coating material containing an organic resin, it is possible to form a coating film by heating and drying by means of hot air drying, infrared heating, induction heating or the like.
- the hot-dip Al—Zn-plated steel sheet that is the subject of the present invention is a hot-dip Al—Zn-plated steel sheet having a plating film obtained by the above-described manufacturing method.
- the plating film is composed of an interface alloy layer present at the interface with the base steel plate and an upper layer present thereon.
- the upper layer contains 20 to 95% by mass of Al and Si of 10% or less of the Al content, with the balance being composed of Zn and inevitable impurities.
- the plating film has a Vickers hardness of 50 to 100 Hv on average. Furthermore, the average size of spangles of the plating film is preferably 0.5 mm or less.
- the Al content in the upper layer is 20 to 95% by mass, preferably 45 to 85% by mass, from the balance between corrosion resistance and operational aspects. If the Al content of the plating upper layer is 20% by mass or more, dendritic solidification of Al occurs. As a result, the upper layer mainly contains Zn in a supersaturated state, and consists of a portion where Al is dendrite solidified and a portion of the remaining dendrite gap, and the dendrite solidified portion has a structure with excellent corrosion resistance laminated in the film thickness direction of the plating film. . The more Al dendrites are laminated, the more complicated the corrosion progressing path becomes, and corrosion becomes difficult to reach the base steel sheet, so that the corrosion resistance is improved.
- the Al content in the upper layer is more preferably 45% by mass or more.
- the Al content in the upper layer exceeds 95% by mass, the content of Zn having a sacrificial anticorrosive action with respect to Fe decreases, and the corrosion resistance deteriorates.
- Al content of an upper layer shall be 95 mass% or less.
- the Al content of the upper layer is 85% by mass or less, the amount of adhesion of plating is reduced, and even when the steel substrate is easily exposed, it has a sacrificial anticorrosive action against Fe and has sufficient corrosion resistance. can get. Therefore, the Al content of the plating upper layer is preferably 85% by mass or less.
- Si is added to the plating bath for the purpose of suppressing the growth of the interfacial alloy layer formed at the interface with the base steel sheet and improving the corrosion resistance and workability, and is necessarily contained in the upper plating layer.
- Si is added to the plating bath for the purpose of suppressing the growth of the interfacial alloy layer formed at the interface with the base steel sheet and improving the corrosion resistance and workability, and is necessarily contained in the upper plating layer.
- the steel sheet is immersed in the plating bath and at the same time the Fe on the steel sheet surface and Al or Si in the bath. React with each other to form Fe-Al and / or Fe-Al-Si compounds.
- the formation of the Fe—Al—Si interface alloy layer suppresses the growth of the interface alloy layer.
- the Si content of the plating bath is 3% or more of the Al content because the growth of the interface alloy layer can be sufficiently suppressed.
- Si content of the plating bath exceeds 10% of the Al content of the plating bath, a Si phase that becomes a propagation path of cracks and lowers the workability easily precipitates on the upper layer of the formed plating film.
- Si content in a plating bath shall be 10% or less of Al content in a plating bath. Therefore, as described above, since the composition of the plating upper layer is substantially the same as the plating bath composition, the Si content of the plating upper layer is set to 10% or less of the Al content of the plating upper layer.
- the plating upper layer may contain 0.01 to 10% by mass in total of one or more selected from Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B. preferable. This is because the stability of the corrosion product can be improved and the effect of delaying the progress of corrosion can be exhibited.
- the interfacial alloy layer is present at the interface with the base steel plate, and as described above, the Fe—Al system that is inevitably formed by an alloying reaction between Fe on the steel plate surface and Al or Si in the bath. And / or Fe-Al-Si compounds. Since this interface alloy layer is hard and brittle, if it grows thick, it becomes the starting point of crack generation during processing, and therefore it is preferably as thin as possible.
- the interface alloy layer and the upper layer can be observed by using a scanning electron microscope or the like for the cross section of the polished and / or etched plating film.
- a scanning electron microscope There are several types of methods for polishing and etching the cross section, but there is no particular limitation as long as it is a method generally used for observing the cross section of the plating film.
- the observation conditions with a scanning electron microscope are, for example, an acceleration voltage of 15 kV and a magnification of 1000 times or more in a reflected electron image, the alloy layer and the upper layer can be clearly observed.
- a glow discharge emission spectrometer This can be confirmed by performing a penetration analysis on the plating film.
- a glow discharge emission analyzer is merely an example, and it is a method that can check the presence / distribution of Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B in the plating upper layer. Other methods can be used if present.
- one or more selected from the above-mentioned Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B are selected from Zn, Al and Si in the plating upper layer. It is preferable to form an intermetallic compound with one kind or two or more kinds. In the process of forming the plating film, the Al-rich phase solidifies before the Zn-rich phase, and therefore, intermetallic compounds are discharged from the Al-rich phase in the solidification process and gather in the Zn-rich phase.
- the corrosion products contain Mn, V, Cr, Mo, Ti, Sr, Ni, Co , One or more selected from Sb and B will be incorporated. As a result, it is possible to stabilize the corrosion product in the initial stage of corrosion more effectively.
- the intermetallic compound contains Si
- the intermetallic compound absorbs Si in the plating film, and as a result, the excess Si in the plating upper layer is reduced. As a result, insoluble Si (Si phase) is formed in the plating upper layer. Since it can prevent the bending workability fall by forming in, it is further more preferable.
- one or more selected from among Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B are one or more selected from Zn, Al and Si.
- a method for confirming whether or not an intermetallic compound is formed there is the following method. A method of detecting these intermetallic compounds from the surface of the plated steel sheet by wide-angle X-ray diffraction or a method of detecting the cross section of the plating film by electron diffraction in a transmission electron microscope is used. In addition, any method other than these may be used as long as the method can detect the intermetallic compound.
- the average size of spangles formed on the plating film is preferably 0.5 mm or less. This is because by making the spangle fine, the visibility of the spangle is lowered and the appearance uniformity is improved. In particular, when a highly glossy coating film is formed on a plated steel sheet, an effect of suppressing spangle protrusion is brought about.
- the average size of the spangles a plated surface of the sample is photographed using an optical microscope or the like, an arbitrary straight line is drawn on the photograph (image) photographed, and the number of spangles crossing the straight line is counted. By dividing the length of the straight line by the number of spangles (the length of the straight line / the number of spangles), the average spangle size can be obtained.
- the molten Al—Zn-based plated steel sheet of the present invention has an average Vickers hardness of 50 to 100 Hv in the plating film.
- the Vickers hardness of the plating film is the Vickers hardness of the plating upper layer.
- the lower limit of the Vickers hardness is set to 50 Hv in order to prevent the plating film from adhering to the mold or the like during the molding process.
- the coating amount of the molten Al—Zn-based plated steel sheet of the present invention is 35 to 150 g / m 2 per side. If it is 35 g / m 2 or more, excellent corrosion resistance is obtained, and if it is 150 g / m 2 or less, excellent workability is obtained.
- the plated steel sheet can be a surface-treated steel sheet further having a chemical conversion treatment film and / or a coating film on the surface thereof.
- a cold-rolled steel sheet having a thickness of 0.35 mm manufactured by a conventional method was used as a base steel sheet, and a hot-dip Al—Zn-based plated steel sheet as a sample was manufactured in a continuous hot-dip plating facility.
- Table 1 shows the composition of the plating bath, the cooling time of the steel sheet after plating, the holding temperature and time conditions of the plated steel sheet after passing through the top roll, and the composition of the plating upper layer.
- the bath temperature of the plating bath was 600 ° C.
- the amount of plating was 75 g / m 2 per side, that is, 150 g / m 2 on both sides.
- each sample of the present invention example has a softer plating film than each sample of the comparative example. Moreover, although there is no big difference about the corrosion resistance of a flat plate part, it turns out that each sample of this invention example is excellent in the corrosion resistance of a bending process part compared with each sample of a comparative example. Furthermore, it can be seen that among the samples of the present invention example, the sample 1 that has not been subjected to rapid cooling after plating has a larger spangle size than the other samples of the present invention example.
- a molten Al—Zn-plated steel sheet having excellent flat plate portion corrosion resistance and excellent workability due to excellent workability can be obtained, and can be applied in a wide range of fields mainly in the field of building materials. can do.
Abstract
The problem addressed by the present invention is to provide a method for producing, on a continuous hot-dip galvanizing line, hot-dip Al-Zn galvanized steel plate having outstanding corrosion resistance in the flat part and excellent corrosion resistance in worked parts by virtue of good workability, and hot-dip Al-Zn plated steel plate obtained using said method. In order to address the aforementioned problem, the present invention is a continuous hot-dip galvanizing facility, wherein the steel plate after hot-dip galvanization is maintained for 5-60 seconds at a temperature of 250-375°C.
Description
本発明は、良好な平板部の耐食性を有するとともに、良好な加工性により加工部の耐食性にも優れた溶融Al－Zn系めっき鋼板及びその製造方法に関するものである。
The present invention relates to a molten Al—Zn-plated steel sheet having good flat plate portion corrosion resistance and excellent workability due to excellent workability, and a method for producing the same.
溶融Al－Zn系めっき鋼板は、Znの犠牲防食性とAlの高い耐食性とが両立できているため、他の溶融亜鉛めっき鋼板に比べて優れた耐食性を示す。例えば、特許文献１には、めっき皮膜中にAlを25～70質量％含有する溶融Al－Zn系めっき鋼板が開示されている。そして、溶融Al－Znめっき鋼板は、その優れた耐食性から、長期間屋外に曝される屋根や壁等の建材分野、ガードレール、配線配管、防音壁等の土木建築分野を中心に近年需要が伸びている。
The hot-dip Al-Zn-plated steel sheet exhibits both excellent corrosion resistance compared to other hot-dip galvanized steel sheets because both the sacrificial corrosion resistance of Zn and the high corrosion resistance of Al are compatible. For example, Patent Document 1 discloses a molten Al—Zn-based plated steel sheet containing 25 to 70% by mass of Al in the plating film. Due to its excellent corrosion resistance, the demand for molten Al-Zn-plated steel sheets has increased in recent years, especially in the field of building materials such as roofs and walls that have been exposed to the outdoors for long periods of time, and civil engineering and construction fields such as guardrails, wiring piping, and soundproof walls. ing.
溶融Al－Zn系めっき鋼板に形成されためっき皮膜は、下地鋼板との界面に存在する合金層と、その上に存在する上層とからなり、上層は、主としてZnを過飽和に含有しAlがデンドライト凝固した部分（Alリッチ相）と、残りのデンドライト間隙の部分（Znリッチ相）とから構成され、Alリッチ相がめっき皮膜の膜厚方向に複数積層した構造を有する。このような特徴的な皮膜構造により、表面からの腐食進行経路が複雑になるため、腐食が容易に下地鋼板に到達しにくくなり、溶融Al－Zn系めっき鋼板はめっき皮膜厚が同一の溶融亜鉛めっき鋼板に比べ優れた耐食性を実現できる。
The plating film formed on the molten Al-Zn-based plated steel sheet is composed of an alloy layer present at the interface with the underlying steel sheet and an upper layer present thereon, the upper layer mainly containing Zn in supersaturation and Al being a dendrite. It is composed of a solidified portion (Al-rich phase) and a remaining dendrite gap portion (Zn-rich phase), and has a structure in which a plurality of Al-rich phases are laminated in the film thickness direction of the plating film. Such a characteristic coating structure complicates the corrosion path from the surface, making it difficult for corrosion to reach the underlying steel sheet. The molten Al-Zn plated steel sheet is a molten zinc with the same coating thickness. Excellent corrosion resistance compared to plated steel sheet.
また、溶融Al－Zn系めっき鋼板の表面には、めっきの凝固に由来したスパングル模様が存在する。このスパングルの中には、前記Alリッチ相とZnリッチ相に対応した微細な凸凹があり、これが光を乱反射するため、溶融Al－Zn系めっき鋼板の表面は銀白色に輝く美麗な外観を呈する。
Also, a spangle pattern derived from the solidification of the plating exists on the surface of the molten Al—Zn-based plated steel sheet. In this spangle, there are fine irregularities corresponding to the Al-rich phase and Zn-rich phase, and this irregularly reflects light, so that the surface of the molten Al-Zn-based plated steel sheet has a beautiful silver-white appearance. .
このような溶融Al－Zn系めっき鋼板については、酸洗脱スケールした熱延鋼板、又はその熱延鋼板を冷間圧延して得られた冷延鋼板を下地鋼板とし、連続式溶融めっき設備において製造されることが一般的である。
具体的には、まず還元性雰囲気に保持された焼鈍炉内で下地鋼板を特定の温度まで加熱し、焼鈍とともに、鋼板表面に付着する圧延油等の除去及び酸化膜の還元除去を行う。次いで、下端がめっき浴に浸漬したスナウト内を通板させることによって、溶融Al－Zn系めっき浴中に下地鋼板を浸漬させる。その後、めっき浴に浸漬させた鋼板を、シンクロールを経由してめっき浴の上方へと引き上げ、めっき浴上に配置されたガスワイピングノズルから鋼板の表面に向けて加圧した気体を噴射してめっき付着量を調整し、冷却装置により冷却することで、所望のめっき皮膜が形成された溶融Al－Zn系めっき鋼板を得る。 For such hot-dip Al-Zn plated steel sheets, pickled and descaled hot rolled steel sheets, or cold rolled steel sheets obtained by cold rolling the hot rolled steel sheets as base steel sheets, It is common to be manufactured.
Specifically, first, the base steel sheet is heated to a specific temperature in an annealing furnace maintained in a reducing atmosphere, and along with annealing, the rolling oil adhering to the steel sheet surface is removed and the oxide film is reduced and removed. Next, the base steel sheet is immersed in the molten Al—Zn plating bath by passing the inside of the snout whose lower end is immersed in the plating bath. Then, the steel plate immersed in the plating bath is pulled up to the upper part of the plating bath via the sink roll, and a pressurized gas is sprayed from the gas wiping nozzle arranged on the plating bath toward the surface of the steel plate. By adjusting the plating adhesion amount and cooling with a cooling device, a molten Al—Zn-based plated steel sheet on which a desired plating film is formed is obtained.
具体的には、まず還元性雰囲気に保持された焼鈍炉内で下地鋼板を特定の温度まで加熱し、焼鈍とともに、鋼板表面に付着する圧延油等の除去及び酸化膜の還元除去を行う。次いで、下端がめっき浴に浸漬したスナウト内を通板させることによって、溶融Al－Zn系めっき浴中に下地鋼板を浸漬させる。その後、めっき浴に浸漬させた鋼板を、シンクロールを経由してめっき浴の上方へと引き上げ、めっき浴上に配置されたガスワイピングノズルから鋼板の表面に向けて加圧した気体を噴射してめっき付着量を調整し、冷却装置により冷却することで、所望のめっき皮膜が形成された溶融Al－Zn系めっき鋼板を得る。 For such hot-dip Al-Zn plated steel sheets, pickled and descaled hot rolled steel sheets, or cold rolled steel sheets obtained by cold rolling the hot rolled steel sheets as base steel sheets, It is common to be manufactured.
Specifically, first, the base steel sheet is heated to a specific temperature in an annealing furnace maintained in a reducing atmosphere, and along with annealing, the rolling oil adhering to the steel sheet surface is removed and the oxide film is reduced and removed. Next, the base steel sheet is immersed in the molten Al—Zn plating bath by passing the inside of the snout whose lower end is immersed in the plating bath. Then, the steel plate immersed in the plating bath is pulled up to the upper part of the plating bath via the sink roll, and a pressurized gas is sprayed from the gas wiping nozzle arranged on the plating bath toward the surface of the steel plate. By adjusting the plating adhesion amount and cooling with a cooling device, a molten Al—Zn-based plated steel sheet on which a desired plating film is formed is obtained.
そして、所望のめっき品質や材質を確保するため、上述した連続式溶融めっき設備における焼鈍炉の熱処理条件や雰囲気条件、めっき浴の組成やめっき後の冷却速度等の操業条件についての、調整や管理が行われる。
And in order to ensure the desired plating quality and material, adjustment and management of the operating conditions such as heat treatment conditions and atmosphere conditions of the annealing furnace, the composition of the plating bath and the cooling rate after plating in the above-described continuous hot-dip plating equipment Is done.
一般的に、めっき皮膜厚が同一ならば、合金層が薄いほど耐食性向上に効果のある上層が厚くなるため、合金層の成長を抑制することは耐食性の向上に寄与することになる。また、合金層は上層よりも固く、加工時にクラックの起点となることから、合金層の成長抑制はクラックの発生を減少させ、曲げ加工性を向上させる効果をもたらすことにもなる。そして、発生したクラック部は、下地鋼板が露出しており耐食性に劣るため、クラックの発生を減じることは曲げ加工部耐食性を向上させることになる。
Generally, if the plating film thickness is the same, the thinner the alloy layer, the thicker the upper layer that is effective in improving the corrosion resistance. Therefore, suppressing the growth of the alloy layer contributes to the improvement of the corrosion resistance. In addition, since the alloy layer is harder than the upper layer and becomes the starting point of cracks during processing, the suppression of the growth of the alloy layer also reduces the occurrence of cracks and brings about the effect of improving the bending workability. And since the base steel plate is exposed and the generated crack part is inferior in corrosion resistance, reducing the occurrence of cracks improves the corrosion resistance of the bent part.
上述したように、溶融Al－Zn系めっき鋼板は、その優れた耐食性から長期間屋外に曝される屋根や壁などの建材分野に使用されることが多い。
As described above, the molten Al—Zn-based plated steel sheet is often used in the field of building materials such as roofs and walls exposed to the outdoors for a long period of time due to its excellent corrosion resistance.
また、連続式溶融めっき設備で製造された溶融Al－Zn系めっき鋼板は、めっき皮膜が急冷により非平衡に凝固することで、めっき上層が硬質化しているため、曲げ加工を行った際にめっき皮膜が割れてクラックを生じ、結果として加工部耐食性が劣ることがあった。そのため、加工性の向上による加工部耐食性の改善が望まれていた。
In addition, the hot-dip Al-Zn-plated steel sheet manufactured in a continuous hot-dip plating facility is plated when it is bent because the plating layer solidifies in a non-equilibrium state due to rapid cooling and the plating upper layer is hardened. The film was cracked to cause cracks, and as a result, the corrosion resistance of the processed part was inferior. Therefore, it has been desired to improve the corrosion resistance of the processed part by improving the workability.
本発明は、かかる事情に鑑み、良好な平板部の耐食性を有するとともに、良好な加工性により加工部の耐食性にも優れた溶融Al－Zn系めっき鋼板を、連続式溶融めっき設備によって製造できる方法、並びに、その方法によって得られた溶融Al－Zn系めっき鋼板を提供することを目的としている。
In view of such circumstances, the present invention provides a method for producing a hot-dip Al-Zn plated steel sheet having good flat plate portion corrosion resistance and excellent workability due to good workability by a continuous hot dipping equipment. In addition, an object of the present invention is to provide a molten Al—Zn-based plated steel sheet obtained by the method.
本発明者らは、上記の課題を解決すべく、鋭意研究を重ねた結果、連続式溶融めっき設備において、溶融めっき後のめっき鋼板について、特定の温度範囲で一定時間保持することによって、めっき皮膜を軟質化できる結果、良好な平板部の耐食性を有するとともに、良好な加工性により加工部の耐食性にも優れた溶融Al－Zn系めっき鋼板が得られることを見出した。また、前記溶融めっき後のめっき鋼板について、特定の温度まで急速に冷却することによって、スパングルの形成を抑制し、優れた外観均一性を実現できることを見出した。
As a result of intensive research to solve the above-mentioned problems, the present inventors, as a result of maintaining a certain time in a specific temperature range for a plated steel sheet after hot-dip plating in a continuous hot-dip plating facility, As a result, the present inventors have found that a molten Al—Zn-based plated steel sheet having good flat plate portion corrosion resistance and excellent workability and excellent corrosion resistance of the processed portion can be obtained. Moreover, it discovered that the formation of a spangle was suppressed and the outstanding external appearance uniformity was realizable by rapidly cooling to the specific temperature about the plated steel plate after the said hot dipping.
本発明は、以上の知見に基づきなされたものであり、その要旨は以下の通りである。
１．連続式溶融めっき設備において、溶融めっき後の鋼板を250～375℃の温度で5～60秒間保持することを特徴とする溶融Al－Zn系めっき鋼板の製造方法。 The present invention has been made based on the above findings, and the gist thereof is as follows.
1. A method for producing a hot-dip Al-Zn-plated steel sheet, characterized in that, in a continuous hot-dip coating facility, the hot-plated steel sheet is held at a temperature of 250 to 375 ° C for 5 to 60 seconds.
１．連続式溶融めっき設備において、溶融めっき後の鋼板を250～375℃の温度で5～60秒間保持することを特徴とする溶融Al－Zn系めっき鋼板の製造方法。 The present invention has been made based on the above findings, and the gist thereof is as follows.
1. A method for producing a hot-dip Al-Zn-plated steel sheet, characterized in that, in a continuous hot-dip coating facility, the hot-plated steel sheet is held at a temperature of 250 to 375 ° C for 5 to 60 seconds.
２．前記溶融めっき後の鋼板を、めっき浴の浴温－20℃からめっき浴の浴温－80℃まで5秒以内に冷却することを特徴とする前記１に記載の溶融Al－Zn系めっき鋼板の製造方法。
2. 2. The molten Al—Zn plated steel sheet according to 1 above, wherein the hot-dip steel sheet is cooled within 5 seconds from a bath temperature of a plating bath of −20 ° C. to a bath temperature of a plating bath of −80 ° C. Production method.
３．前記めっき鋼板の冷却時間を3秒以内とすることを特徴とする前記２に記載の溶融Al－Zn系めっき鋼板の製造方法。
3. 3. The method for producing a molten Al—Zn-based plated steel sheet as described in 2 above, wherein the cooling time of the plated steel sheet is 3 seconds or less.
４．前記めっき鋼板の保持温度が300～375℃であることを特徴とする前記１～３のいずれかに記載の溶融Al－Zn系めっき鋼板の製造方法。
4). 4. The method for producing a hot-dip Al—Zn-plated steel sheet according to any one of items 1 to 3, wherein the holding temperature of the plated steel sheet is 300 to 375 ° C.
５．前記めっき鋼板の保持時間が5～30秒であることを特徴とする前記１～４のいずれかに記載の溶融Al－Zn系めっき鋼板の製造方法。
5. 5. The method for producing a hot-dip Al—Zn-plated steel sheet according to any one of 1 to 4, wherein the holding time of the plated steel sheet is 5 to 30 seconds.
６．前記めっき鋼板をトップロールと接触する前に375℃以下までさらに冷却することを特徴とする前記１～５のいずれかに記載の溶融Al－Zn系めっき鋼板の製造方法。
6). 6. The method for producing a molten Al—Zn-based plated steel sheet according to any one of 1 to 5, wherein the plated steel sheet is further cooled to 375 ° C. or less before contacting the top roll.
７．前記１～６のいずれかに記載の製造方法によって得られためっき皮膜を有する溶融Al－Zn系めっき鋼板であって、前記めっき皮膜は下地鋼板との界面に存在する界面合金層と該界面合金層の上に存在する上層からなり、該上層は、20～95質量％のAl及び該Al含有量の10％以下のSiを含有し、残部がZn及び不可避的不純物からなる組成を有し、前記めっき皮膜のビッカース硬度が平均で50～100Hvであることを特徴とする溶融Al－Zn系めっき鋼板。
7). 7. A molten Al—Zn-based plated steel sheet having a plating film obtained by the manufacturing method according to any one of 1 to 6, wherein the plating film is an interface alloy layer present at an interface with a base steel sheet and the interface alloy. Comprising an upper layer present on the layer, the upper layer containing 20 to 95% by mass of Al and Si of 10% or less of the Al content, the balance being composed of Zn and inevitable impurities, A molten Al—Zn-based plated steel sheet, wherein the plating film has an average Vickers hardness of 50 to 100 Hv.
８．前記上層中に、さらにMn、V、Cr、Mo、Ti、Sr、Ni、Co、Sb及びBのうちから選択される１種又は２種以上を、合計で0.01～10質量％含有することを特徴とする前記７に記載の溶融Al－Zn系めっき鋼板。
8). The upper layer further contains one or more selected from Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B in a total amount of 0.01 to 10% by mass. 8. The molten Al—Zn-based plated steel sheet as described in 7 above.
９．前記めっき皮膜のスパングルの平均サイズが0.5mm以下であることを特徴とする前記７又は８に記載の溶融Al－Zn系めっき鋼板。
9. 9. The molten Al—Zn-based plated steel sheet as described in 7 or 8 above, wherein an average size of spangles of the plating film is 0.5 mm or less.
本発明により、良好な平板部の耐食性を有するとともに、良好な加工性により加工部の耐食性にも優れた溶融Al－Zn系めっき鋼板を、連続式溶融めっき設備によって製造できる。
According to the present invention, a hot-dip Al-Zn-plated steel sheet having excellent flat plate portion corrosion resistance and excellent workability due to excellent workability can be produced by a continuous hot-dip plating apparatus.
本発明の溶融Al－Zn系めっき鋼板の製造方法について、図面を参照しながら説明する。
図１は、本発明の溶融Al－Zn系めっき鋼板の製造方法についての大まかな流れを示した図である。 The manufacturing method of the hot-dip Al—Zn-based plated steel sheet of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a rough flow of a method for producing a molten Al—Zn-based plated steel sheet according to the present invention.
図１は、本発明の溶融Al－Zn系めっき鋼板の製造方法についての大まかな流れを示した図である。 The manufacturing method of the hot-dip Al—Zn-based plated steel sheet of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a rough flow of a method for producing a molten Al—Zn-based plated steel sheet according to the present invention.
（溶融Al－Zn系めっき鋼板の製造方法）
本発明の溶融Al－Zn系めっき鋼板の製造方法は、連続式溶融めっき設備において製造を行う方法である。連続式溶融めっき設備によって製造を行うことで、溶融めっき設備にさらにバッチ式加熱設備を組み合わせて製造する場合に比べて、効率的なAl－Zn系めっき鋼板の製造が可能となる。
そして本発明は、図１に示すように、被処理鋼板（下地鋼板）に対して、必要に応じて、脱脂、酸洗などの前処理（前処理工程）、及び焼鈍（焼鈍工程）を行った後、溶融めっき（めっき工程）を施し、好ましくは溶融めっき後の鋼板をめっき浴の浴温－20℃からめっき浴の浴温－80℃まで5秒以内に冷却（急速冷却工程）した後、該めっき鋼板を250～375℃の温度で5～60秒間保持（温度保持工程）することを特徴とする。 (Manufacturing method of molten Al-Zn plated steel sheet)
The method for producing a hot-dip Al—Zn-based plated steel sheet according to the present invention is a method for producing in a continuous hot-dip plating facility. Production by a continuous hot dip plating facility makes it possible to produce an Al-Zn-based plated steel sheet more efficiently than when the hot dip plating equipment is further combined with a batch heating equipment.
And as shown in FIG. 1, this invention performs pre-processing (pre-processing process), such as degreasing and pickling, and annealing (annealing process) with respect to a to-be-processed steel plate (base steel plate) as needed. Then, hot-dip plating (plating process) is performed, and preferably the steel sheet after hot-dip plating is cooled within 5 seconds from the bath temperature of the plating bath to −20 ° C. (rapid cooling step). The plated steel sheet is held at a temperature of 250 to 375 ° C. for 5 to 60 seconds (temperature holding step).
本発明の溶融Al－Zn系めっき鋼板の製造方法は、連続式溶融めっき設備において製造を行う方法である。連続式溶融めっき設備によって製造を行うことで、溶融めっき設備にさらにバッチ式加熱設備を組み合わせて製造する場合に比べて、効率的なAl－Zn系めっき鋼板の製造が可能となる。
そして本発明は、図１に示すように、被処理鋼板（下地鋼板）に対して、必要に応じて、脱脂、酸洗などの前処理（前処理工程）、及び焼鈍（焼鈍工程）を行った後、溶融めっき（めっき工程）を施し、好ましくは溶融めっき後の鋼板をめっき浴の浴温－20℃からめっき浴の浴温－80℃まで5秒以内に冷却（急速冷却工程）した後、該めっき鋼板を250～375℃の温度で5～60秒間保持（温度保持工程）することを特徴とする。 (Manufacturing method of molten Al-Zn plated steel sheet)
The method for producing a hot-dip Al—Zn-based plated steel sheet according to the present invention is a method for producing in a continuous hot-dip plating facility. Production by a continuous hot dip plating facility makes it possible to produce an Al-Zn-based plated steel sheet more efficiently than when the hot dip plating equipment is further combined with a batch heating equipment.
And as shown in FIG. 1, this invention performs pre-processing (pre-processing process), such as degreasing and pickling, and annealing (annealing process) with respect to a to-be-processed steel plate (base steel plate) as needed. Then, hot-dip plating (plating process) is performed, and preferably the steel sheet after hot-dip plating is cooled within 5 seconds from the bath temperature of the plating bath to −20 ° C. (rapid cooling step). The plated steel sheet is held at a temperature of 250 to 375 ° C. for 5 to 60 seconds (temperature holding step).
本発明の溶融Al－Zn系めっき鋼板に用いられる下地鋼板の種類については、特に限定はされない。例えば、酸洗脱スケールした熱延鋼板若しくは鋼帯、又は、それらを冷間圧延して得られた冷延鋼板若しくは鋼帯を用いることができる。
また、前記前処理工程及び焼鈍工程の条件についても特に限定はされず、任意の方法を採用することができる。 There are no particular restrictions on the type of base steel sheet used in the hot-dip Al—Zn-based plated steel sheet of the present invention. For example, a hot-rolled steel plate or steel strip that has been pickled and descaled, or a cold-rolled steel plate or steel strip obtained by cold rolling them can be used.
Moreover, it does not specifically limit about the conditions of the said pre-processing process and annealing process, Arbitrary methods are employable.
また、前記前処理工程及び焼鈍工程の条件についても特に限定はされず、任意の方法を採用することができる。 There are no particular restrictions on the type of base steel sheet used in the hot-dip Al—Zn-based plated steel sheet of the present invention. For example, a hot-rolled steel plate or steel strip that has been pickled and descaled, or a cold-rolled steel plate or steel strip obtained by cold rolling them can be used.
Moreover, it does not specifically limit about the conditions of the said pre-processing process and annealing process, Arbitrary methods are employable.
前記溶融めっきの条件については、前記下地鋼板にAl－Zn系めっき皮膜を形成できれば特に限定はされず、常法に従って行うことができる。例えば、前記下地鋼板を還元焼鈍した後、めっき浴温近傍まで冷却し、めっき浴に浸漬させ、その後、ワイピングを行うことによって所望の膜厚のめっき皮膜を形成することができる。
The conditions for the hot dipping are not particularly limited as long as an Al—Zn plating film can be formed on the base steel plate, and can be performed according to a conventional method. For example, after the base steel sheet is subjected to reduction annealing, the plating film having a desired film thickness can be formed by cooling to the vicinity of the plating bath temperature, immersing in the plating bath, and then performing wiping.
前記溶融めっきのめっき浴におけるAl濃度は20～95質量％とする。また、過度の合金層成長を抑制するため、めっき浴にはAl含有量の10％以下のSiを含み、残部がZn及び不可避的不純物からなる。さらに、前記めっき浴には、Mn、V、Cr、Mo、Ti、Sr、Ni、Co、Sb及びBのうちから選択される一種又は二種以上を、合計で0.01～10質量％含有することが好ましい。このような組成のめっき浴とすることにより、後述するめっき皮膜を形成することが可能となる。
なお、後述するとおり、上記したAl－Zn系めっき浴により形成されるめっき皮膜は下地鋼板との界面に存在する界面合金層と該界面合金層の上に存在する上層からなる。該上層の組成は界面合金層側でAlとSiがやや低くなるものの、全体としてはめっき浴の組成とほぼ同等となる。よって、めっき上層の組成の制御は、めっき浴組成を制御することにより精度良く行うことができる。 The Al concentration in the hot dip plating bath is 20 to 95% by mass. In order to suppress excessive alloy layer growth, the plating bath contains Si with an Al content of 10% or less, and the balance is made of Zn and inevitable impurities. Further, the plating bath contains 0.01 to 10% by mass in total of one or more selected from Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B. Is preferred. By setting it as the plating bath of such a composition, it becomes possible to form the plating film mentioned later.
As will be described later, the plating film formed by the Al—Zn plating bath is composed of an interface alloy layer present at the interface with the underlying steel plate and an upper layer present on the interface alloy layer. The composition of the upper layer is almost the same as the composition of the plating bath as a whole, although Al and Si are slightly lower on the interface alloy layer side. Therefore, the composition of the plating upper layer can be accurately controlled by controlling the plating bath composition.
なお、後述するとおり、上記したAl－Zn系めっき浴により形成されるめっき皮膜は下地鋼板との界面に存在する界面合金層と該界面合金層の上に存在する上層からなる。該上層の組成は界面合金層側でAlとSiがやや低くなるものの、全体としてはめっき浴の組成とほぼ同等となる。よって、めっき上層の組成の制御は、めっき浴組成を制御することにより精度良く行うことができる。 The Al concentration in the hot dip plating bath is 20 to 95% by mass. In order to suppress excessive alloy layer growth, the plating bath contains Si with an Al content of 10% or less, and the balance is made of Zn and inevitable impurities. Further, the plating bath contains 0.01 to 10% by mass in total of one or more selected from Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B. Is preferred. By setting it as the plating bath of such a composition, it becomes possible to form the plating film mentioned later.
As will be described later, the plating film formed by the Al—Zn plating bath is composed of an interface alloy layer present at the interface with the underlying steel plate and an upper layer present on the interface alloy layer. The composition of the upper layer is almost the same as the composition of the plating bath as a whole, although Al and Si are slightly lower on the interface alloy layer side. Therefore, the composition of the plating upper layer can be accurately controlled by controlling the plating bath composition.
そして、本発明の製造方法は、図１に示すように、前記溶融めっき後の鋼板について、めっき浴の浴温－20℃からめっき浴の浴温－80℃まで5秒以内に冷却すること（急速冷却工程）が好ましい。この急速冷却工程によって、スパングルの形成を抑制でき、特に塗膜を形成した場合の優れた外観均一性を得ることが可能となる。具体的には、スパングルの平均サイズを0.5mm以下に抑えることができる。
めっき皮膜に形成されるスパングルの平均サイズが0.5mm以下であれば、本願の溶融Al－Zn系めっき鋼板に塗膜（特に平滑で均一な外観が求められる高光沢の塗膜）を形成して使用する場合にスパングルの境界が塗膜表面まで浮き出して視認されることがなく、表面外観を損ねることがないので特に好ましい。
また、より高いスパングル抑制効果を得る点からは、前記急速冷却の冷却時間は、3秒以内であることが好ましく、1秒以内であることがより好ましい。なお、前記めっき浴温－80℃までの冷却時間が5秒を超える場合には、十分なスパングルの抑制効果がなく、平均サイズを0.5mm以下にすることはできない。
ただし、スパングル形成が問題とならない、又はスパングル形成を必要とする用途向けに製造を行う場合、必ずしもこの急速冷却工程を行わなくても構わず、その場合における製造方法を限定するものでない。 In the production method of the present invention, as shown in FIG. 1, the steel sheet after the hot dipping is cooled within 5 seconds from a bath temperature of the plating bath of −20 ° C. to a bath temperature of the plating bath of −80 ° C. A rapid cooling step) is preferred. By this rapid cooling process, formation of spangles can be suppressed, and excellent appearance uniformity can be obtained particularly when a coating film is formed. Specifically, the average size of spangles can be suppressed to 0.5 mm or less.
If the average size of spangles formed on the plating film is 0.5 mm or less, a coating film (particularly a high gloss coating film that requires a smooth and uniform appearance) is formed on the molten Al-Zn plated steel sheet of the present application. When used, the boundary of spangles is particularly preferred because it does not rise up to the surface of the coating film and is not visually recognized.
Further, from the viewpoint of obtaining a higher spangle suppression effect, the cooling time of the rapid cooling is preferably within 3 seconds, and more preferably within 1 second. When the cooling time to the plating bath temperature of −80 ° C. exceeds 5 seconds, there is no sufficient spangle suppression effect, and the average size cannot be reduced to 0.5 mm or less.
However, when manufacturing for an application where spangle formation does not become a problem or requires spangle formation, this rapid cooling step may not necessarily be performed, and the manufacturing method in that case is not limited.
めっき皮膜に形成されるスパングルの平均サイズが0.5mm以下であれば、本願の溶融Al－Zn系めっき鋼板に塗膜（特に平滑で均一な外観が求められる高光沢の塗膜）を形成して使用する場合にスパングルの境界が塗膜表面まで浮き出して視認されることがなく、表面外観を損ねることがないので特に好ましい。
また、より高いスパングル抑制効果を得る点からは、前記急速冷却の冷却時間は、3秒以内であることが好ましく、1秒以内であることがより好ましい。なお、前記めっき浴温－80℃までの冷却時間が5秒を超える場合には、十分なスパングルの抑制効果がなく、平均サイズを0.5mm以下にすることはできない。
ただし、スパングル形成が問題とならない、又はスパングル形成を必要とする用途向けに製造を行う場合、必ずしもこの急速冷却工程を行わなくても構わず、その場合における製造方法を限定するものでない。 In the production method of the present invention, as shown in FIG. 1, the steel sheet after the hot dipping is cooled within 5 seconds from a bath temperature of the plating bath of −20 ° C. to a bath temperature of the plating bath of −80 ° C. A rapid cooling step) is preferred. By this rapid cooling process, formation of spangles can be suppressed, and excellent appearance uniformity can be obtained particularly when a coating film is formed. Specifically, the average size of spangles can be suppressed to 0.5 mm or less.
If the average size of spangles formed on the plating film is 0.5 mm or less, a coating film (particularly a high gloss coating film that requires a smooth and uniform appearance) is formed on the molten Al-Zn plated steel sheet of the present application. When used, the boundary of spangles is particularly preferred because it does not rise up to the surface of the coating film and is not visually recognized.
Further, from the viewpoint of obtaining a higher spangle suppression effect, the cooling time of the rapid cooling is preferably within 3 seconds, and more preferably within 1 second. When the cooling time to the plating bath temperature of −80 ° C. exceeds 5 seconds, there is no sufficient spangle suppression effect, and the average size cannot be reduced to 0.5 mm or less.
However, when manufacturing for an application where spangle formation does not become a problem or requires spangle formation, this rapid cooling step may not necessarily be performed, and the manufacturing method in that case is not limited.
また、図１に示すように、めっき浴に浸漬した後のめっきの施されためっき鋼板をトップロールと接触する前に375℃以下までさらに冷却すること（トップロール直前冷却）が好ましい。トップロールと接触する前のめっきの施されためっき鋼板の温度が375℃を超える場合、トップロールへ接触した際、めっき皮膜がトップロールに付着し、めっき皮膜の一部が剥がれる（メタルピックアップ）おそれがあるためである。
ここで、「トップロール」とは、前記下地鋼板に溶融めっきを施した後、めっきの施された鋼板が最初に接触するロールのことを意味する。 Moreover, as shown in FIG. 1, it is preferable to further cool the plated steel sheet that has been plated after being immersed in the plating bath to 375 ° C. or less before contacting the top roll (cooling immediately before the top roll). If the temperature of the plated steel sheet that has been plated before coming into contact with the top roll exceeds 375 ° C, when it comes into contact with the top roll, the plating film adheres to the top roll and a part of the plating film peels off (metal pickup) This is because there is a fear.
Here, the “top roll” means a roll in which the plated steel sheet first comes into contact with the base steel sheet after hot-dip plating.
ここで、「トップロール」とは、前記下地鋼板に溶融めっきを施した後、めっきの施された鋼板が最初に接触するロールのことを意味する。 Moreover, as shown in FIG. 1, it is preferable to further cool the plated steel sheet that has been plated after being immersed in the plating bath to 375 ° C. or less before contacting the top roll (cooling immediately before the top roll). If the temperature of the plated steel sheet that has been plated before coming into contact with the top roll exceeds 375 ° C, when it comes into contact with the top roll, the plating film adheres to the top roll and a part of the plating film peels off (metal pickup) This is because there is a fear.
Here, the “top roll” means a roll in which the plated steel sheet first comes into contact with the base steel sheet after hot-dip plating.
次に、本発明で最も重要となるめっき皮膜の加工性の向上方法について示す。本発明の製造方法では、溶融めっき後の鋼板を250～375℃の温度で5～60秒間保持すること（温度保持工程）が重要である。この温度保持工程によって、上述しためっき皮膜の硬質化の原因となる非平衡な凝固により、めっき皮膜中に導入された歪が解放されるとともに、Al－Zn系めっきにおいてAlリッチ相とZnリッチ相の二相分離が促進されるため、めっき皮膜の軟質化を実現できる。その結果、加工性の向上が可能となる。また、本発明の製造方法で得られためっき皮膜は従来の製造方法で得られためっき皮膜に比べ、加工時に発生するクラックの数や幅が減少することで、加工部の耐食性の改善が可能となる。
なお、前記保持温度が250℃未満の場合や、前記保持時間が5秒未満の場合には、溶融めっき皮膜の硬化が早く、十分に歪の解放や、Alリッチ相とZnリッチ相の分離が進まないため、所望の加工性が得られない。一方、前記保持温度が375℃を超えることは、上述したメタルピックアップとの関係から好ましくなく、前記保持時間が60秒を超える場合は、保持時間が長すぎるため、連続式溶融めっき設備での製造に適さない。 Next, a method for improving the workability of the plating film which is most important in the present invention will be described. In the production method of the present invention, it is important to hold the hot-dip plated steel sheet at a temperature of 250 to 375 ° C. for 5 to 60 seconds (temperature holding step). This temperature holding process releases strain introduced into the plating film due to the non-equilibrium solidification that causes the above-described hardening of the plating film to be hardened. Also, in the Al-Zn plating, the Al-rich phase and the Zn-rich phase Since the two-phase separation is promoted, softening of the plating film can be realized. As a result, workability can be improved. In addition, the plating film obtained by the manufacturing method of the present invention can improve the corrosion resistance of the processed part by reducing the number and width of cracks generated during processing compared to the plating film obtained by the conventional manufacturing method. It becomes.
In addition, when the holding temperature is less than 250 ° C. or when the holding time is less than 5 seconds, the hot dip coating film is quickly cured, and sufficient strain release and separation of the Al-rich phase and the Zn-rich phase can be achieved. Since it does not progress, the desired processability cannot be obtained. On the other hand, it is not preferable that the holding temperature exceeds 375 ° C. because of the relationship with the metal pickup described above, and when the holding time exceeds 60 seconds, the holding time is too long, so that the manufacturing is performed in a continuous hot dip plating facility. Not suitable for.
なお、前記保持温度が250℃未満の場合や、前記保持時間が5秒未満の場合には、溶融めっき皮膜の硬化が早く、十分に歪の解放や、Alリッチ相とZnリッチ相の分離が進まないため、所望の加工性が得られない。一方、前記保持温度が375℃を超えることは、上述したメタルピックアップとの関係から好ましくなく、前記保持時間が60秒を超える場合は、保持時間が長すぎるため、連続式溶融めっき設備での製造に適さない。 Next, a method for improving the workability of the plating film which is most important in the present invention will be described. In the production method of the present invention, it is important to hold the hot-dip plated steel sheet at a temperature of 250 to 375 ° C. for 5 to 60 seconds (temperature holding step). This temperature holding process releases strain introduced into the plating film due to the non-equilibrium solidification that causes the above-described hardening of the plating film to be hardened. Also, in the Al-Zn plating, the Al-rich phase and the Zn-rich phase Since the two-phase separation is promoted, softening of the plating film can be realized. As a result, workability can be improved. In addition, the plating film obtained by the manufacturing method of the present invention can improve the corrosion resistance of the processed part by reducing the number and width of cracks generated during processing compared to the plating film obtained by the conventional manufacturing method. It becomes.
In addition, when the holding temperature is less than 250 ° C. or when the holding time is less than 5 seconds, the hot dip coating film is quickly cured, and sufficient strain release and separation of the Al-rich phase and the Zn-rich phase can be achieved. Since it does not progress, the desired processability cannot be obtained. On the other hand, it is not preferable that the holding temperature exceeds 375 ° C. because of the relationship with the metal pickup described above, and when the holding time exceeds 60 seconds, the holding time is too long, so that the manufacturing is performed in a continuous hot dip plating facility. Not suitable for.
また、より優れた加工性を実現する点からは、前記温度保持工程におけるめっき鋼板の保持温度は、300～375℃であることが好ましく、350～375℃であることがより好ましい。
同様に、前記溶融めっき鋼板の保持時間は、5～30秒であることが好ましく、5～20秒であることがより好ましい。 In order to achieve better workability, the holding temperature of the plated steel sheet in the temperature holding step is preferably 300 to 375 ° C., more preferably 350 to 375 ° C.
Similarly, the holding time of the hot-dip galvanized steel sheet is preferably 5 to 30 seconds, and more preferably 5 to 20 seconds.
同様に、前記溶融めっき鋼板の保持時間は、5～30秒であることが好ましく、5～20秒であることがより好ましい。 In order to achieve better workability, the holding temperature of the plated steel sheet in the temperature holding step is preferably 300 to 375 ° C., more preferably 350 to 375 ° C.
Similarly, the holding time of the hot-dip galvanized steel sheet is preferably 5 to 30 seconds, and more preferably 5 to 20 seconds.
なお、本発明の製造方法において前記温度保持工程後については、特に限定はされず、常法に従って溶融Al－Zn系めっき鋼板を製造することができる。例えば、図１に示すように、温度保持工程後の溶融Al－Zn系めっき鋼板表面に、化成処理皮膜を形成すること（化成処理工程）や、別途塗装設備において塗膜を形成すること（塗膜形成工程）ができる。
In the production method of the present invention, the temperature holding step is not particularly limited, and a molten Al—Zn-based plated steel sheet can be produced according to a conventional method. For example, as shown in FIG. 1, a chemical conversion treatment film is formed on the surface of the molten Al-Zn-plated steel sheet after the temperature holding step (chemical conversion treatment step), or a coating film is formed in a separate coating facility (coating). Film forming step).
前記化成処理皮膜については、例えば、クロメート処理液又はクロムフリー化成処理液を塗布し、水洗することなく、鋼板温度として80～300℃となる乾燥処理を行うクロメート処理又はクロムフリー化成処理により形成することが可能である。これら化成処理皮膜は単層でも複層でもよく、複層の場合には複数の化成処理を順次行えばよい。
また、前記塗膜の形成方法としては、ロールコーター塗装、カーテンフロー塗装、スプレー塗装等が挙げられる。有機樹脂を含有する塗料を塗装した後、熱風乾燥、赤外線加熱、誘導過熱等の手段により加熱乾燥して塗膜を形成することが可能である。 The chemical conversion treatment film is formed by, for example, a chromate treatment or a chromium-free chemical conversion treatment in which a chromate treatment solution or a chromium-free chemical conversion treatment solution is applied, and a drying treatment is performed at a temperature of 80 to 300 ° C. without washing with water. It is possible. These chemical conversion treatment films may be a single layer or multiple layers, and in the case of multiple layers, a plurality of chemical conversion treatments may be performed sequentially.
Examples of the method for forming the coating film include roll coater coating, curtain flow coating, and spray coating. After coating a coating material containing an organic resin, it is possible to form a coating film by heating and drying by means of hot air drying, infrared heating, induction heating or the like.
また、前記塗膜の形成方法としては、ロールコーター塗装、カーテンフロー塗装、スプレー塗装等が挙げられる。有機樹脂を含有する塗料を塗装した後、熱風乾燥、赤外線加熱、誘導過熱等の手段により加熱乾燥して塗膜を形成することが可能である。 The chemical conversion treatment film is formed by, for example, a chromate treatment or a chromium-free chemical conversion treatment in which a chromate treatment solution or a chromium-free chemical conversion treatment solution is applied, and a drying treatment is performed at a temperature of 80 to 300 ° C. without washing with water. It is possible. These chemical conversion treatment films may be a single layer or multiple layers, and in the case of multiple layers, a plurality of chemical conversion treatments may be performed sequentially.
Examples of the method for forming the coating film include roll coater coating, curtain flow coating, and spray coating. After coating a coating material containing an organic resin, it is possible to form a coating film by heating and drying by means of hot air drying, infrared heating, induction heating or the like.
（溶融Al－Zn系めっき鋼板）
次に、本発明の溶融Al－Zn系めっき鋼板について説明する。
本発明の対象とする溶融Al－Zn系めっき鋼板は、上述した製造方法によって得られためっき皮膜を有する溶融Al－Zn系めっき鋼板である。該めっき皮膜は、下地鋼板との界面に存在する界面合金層とその上に存在する上層からなる。該上層は、20～95質量％のAl及び該Al含有量の10％以下のSiを含有し、残部がZn及び不可避的不純物からなる組成を有する。また、前記めっき皮膜のビッカース硬度が平均で50～100Hvであることを特徴とする。さらに前記めっき皮膜のスパングルの平均サイズは0.5mm以下であることが好ましい。 (Fused Al-Zn plated steel sheet)
Next, the molten Al—Zn-based plated steel sheet of the present invention will be described.
The hot-dip Al—Zn-plated steel sheet that is the subject of the present invention is a hot-dip Al—Zn-plated steel sheet having a plating film obtained by the above-described manufacturing method. The plating film is composed of an interface alloy layer present at the interface with the base steel plate and an upper layer present thereon. The upper layer contains 20 to 95% by mass of Al and Si of 10% or less of the Al content, with the balance being composed of Zn and inevitable impurities. The plating film has a Vickers hardness of 50 to 100 Hv on average. Furthermore, the average size of spangles of the plating film is preferably 0.5 mm or less.
次に、本発明の溶融Al－Zn系めっき鋼板について説明する。
本発明の対象とする溶融Al－Zn系めっき鋼板は、上述した製造方法によって得られためっき皮膜を有する溶融Al－Zn系めっき鋼板である。該めっき皮膜は、下地鋼板との界面に存在する界面合金層とその上に存在する上層からなる。該上層は、20～95質量％のAl及び該Al含有量の10％以下のSiを含有し、残部がZn及び不可避的不純物からなる組成を有する。また、前記めっき皮膜のビッカース硬度が平均で50～100Hvであることを特徴とする。さらに前記めっき皮膜のスパングルの平均サイズは0.5mm以下であることが好ましい。 (Fused Al-Zn plated steel sheet)
Next, the molten Al—Zn-based plated steel sheet of the present invention will be described.
The hot-dip Al—Zn-plated steel sheet that is the subject of the present invention is a hot-dip Al—Zn-plated steel sheet having a plating film obtained by the above-described manufacturing method. The plating film is composed of an interface alloy layer present at the interface with the base steel plate and an upper layer present thereon. The upper layer contains 20 to 95% by mass of Al and Si of 10% or less of the Al content, with the balance being composed of Zn and inevitable impurities. The plating film has a Vickers hardness of 50 to 100 Hv on average. Furthermore, the average size of spangles of the plating film is preferably 0.5 mm or less.
前記上層のAl含有量は、耐食性と操業面のバランスから、20～95質量％であり、好ましくは45～85質量％である。めっき上層のAl含有量が20質量％以上であれば、Alのデンドライト凝固が起こる。これにより、上層は主としてZnを過飽和に含有し、Alがデンドライト凝固した部分と残りのデンドライト間隙の部分からなり、且つ該デンドライト凝固部分がめっき皮膜の膜厚方向に積層した耐食性に優れる構造をとる。またこのAlのデンドライトが、多く積層するほど、腐食進行経路が複雑になり、腐食が容易に下地鋼板に到達しにくくなるので、耐食性が向上する。極めて高い耐食性を得るためには、上層のAl含有量を45質量％以上とすることがより好ましい。一方、上層のAl含有量が95質量％を超えると、Feに対して犠牲防食作用をもつZnの含有量が少なくなり、耐食性が劣化する。このため、上層のAl含有量は95質量％以下とする。また、上層のAl含有量が85質量％以下であれば、めっきの付着量が少なくなり、鋼素地が露出しやすくなった場合にもFeに対して犠牲防食作用を有し、十分な耐食性が得られる。よって、めっき上層のAl含有量は85質量％以下とすることが好ましい。
The Al content in the upper layer is 20 to 95% by mass, preferably 45 to 85% by mass, from the balance between corrosion resistance and operational aspects. If the Al content of the plating upper layer is 20% by mass or more, dendritic solidification of Al occurs. As a result, the upper layer mainly contains Zn in a supersaturated state, and consists of a portion where Al is dendrite solidified and a portion of the remaining dendrite gap, and the dendrite solidified portion has a structure with excellent corrosion resistance laminated in the film thickness direction of the plating film. . The more Al dendrites are laminated, the more complicated the corrosion progressing path becomes, and corrosion becomes difficult to reach the base steel sheet, so that the corrosion resistance is improved. In order to obtain extremely high corrosion resistance, the Al content in the upper layer is more preferably 45% by mass or more. On the other hand, when the Al content in the upper layer exceeds 95% by mass, the content of Zn having a sacrificial anticorrosive action with respect to Fe decreases, and the corrosion resistance deteriorates. For this reason, Al content of an upper layer shall be 95 mass% or less. In addition, if the Al content of the upper layer is 85% by mass or less, the amount of adhesion of plating is reduced, and even when the steel substrate is easily exposed, it has a sacrificial anticorrosive action against Fe and has sufficient corrosion resistance. can get. Therefore, the Al content of the plating upper layer is preferably 85% by mass or less.
また、Siは下地鋼板との界面に形成する界面合金層の成長を抑制し、耐食性や加工性の向上を目的にめっき浴中に添加され、必然的にめっき上層に含有される。具体的には、Al－Zn系めっき鋼板の場合、めっき浴中にSiを含有させめっき処理を行うと、鋼板がめっき浴中に浸漬されると同時に鋼板表面のFeと浴中のAlやSiが合金化反応し、Fe-Al系及び／又はFe-Al-Si系の化合物を形成する。このFe－Al－Si系界面合金層の形成により、界面合金層の成長が抑制される。めっき浴のSi含有量がAl含有量の3％以上であれば界面合金層の十分な成長抑制が可能となるので、好ましい。一方、めっき浴のSi含有量が、めっき浴のAl含有量の10％を超えた場合、形成しためっき皮膜の上層にクラックの伝播経路となり加工性を低下させるSi相が析出し易くなる。このため、めっき浴中のSi含有量はめっき浴中のAl含有量の10％以下とする。よって、前述に示した通り、めっき上層の組成は、めっき浴組成とほぼ同等であることから、めっき上層のSi含有量はめっき上層のAl含有量の10％以下とする。
Also, Si is added to the plating bath for the purpose of suppressing the growth of the interfacial alloy layer formed at the interface with the base steel sheet and improving the corrosion resistance and workability, and is necessarily contained in the upper plating layer. Specifically, in the case of an Al-Zn plated steel sheet, when the plating treatment is performed with Si contained in the plating bath, the steel sheet is immersed in the plating bath and at the same time the Fe on the steel sheet surface and Al or Si in the bath. React with each other to form Fe-Al and / or Fe-Al-Si compounds. The formation of the Fe—Al—Si interface alloy layer suppresses the growth of the interface alloy layer. It is preferable that the Si content of the plating bath is 3% or more of the Al content because the growth of the interface alloy layer can be sufficiently suppressed. On the other hand, when the Si content of the plating bath exceeds 10% of the Al content of the plating bath, a Si phase that becomes a propagation path of cracks and lowers the workability easily precipitates on the upper layer of the formed plating film. For this reason, Si content in a plating bath shall be 10% or less of Al content in a plating bath. Therefore, as described above, since the composition of the plating upper layer is substantially the same as the plating bath composition, the Si content of the plating upper layer is set to 10% or less of the Al content of the plating upper layer.
また、前記めっき上層は、Mn、V、Cr、Mo、Ti、Sr、Ni、Co、Sb及びBのうちから選択される一種又は二種以上を、合計で0.01～10質量％含有することが好ましい。腐食生成物の安定性を向上させ、腐食の進行を遅延させる効果を発揮できるためである。
The plating upper layer may contain 0.01 to 10% by mass in total of one or more selected from Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B. preferable. This is because the stability of the corrosion product can be improved and the effect of delaying the progress of corrosion can be exhibited.
なお、前記界面合金層は、下地鋼板との界面に存在するものであり、前述の通り、鋼板表面のFeと浴中のAlやSiが合金化反応して必然的に形成するFe－Al系及び／又はFe－Al－Si系の化合物である。この界面合金層は、硬くて脆いため、厚く成長すると加工時のクラック発生の起点となることから可能な限り薄いことが好ましい。
The interfacial alloy layer is present at the interface with the base steel plate, and as described above, the Fe—Al system that is inevitably formed by an alloying reaction between Fe on the steel plate surface and Al or Si in the bath. And / or Fe-Al-Si compounds. Since this interface alloy layer is hard and brittle, if it grows thick, it becomes the starting point of crack generation during processing, and therefore it is preferably as thin as possible.
ここで、界面合金層及び上層は、研磨及び／又はエッチングしためっき皮膜の断面を、走査型電子顕微鏡等を用いることによって観察できる。断面の研磨方法やエッチング方法はいくつか種類があるが、一般的にめっき皮膜断面を観察する際に用いられる方法であれば特に限定はされない。また、走査型電子顕微鏡での観察条件は、例えば加速電圧15kVで、反射電子像にて1000倍以上の倍率であれば、合金層及び上層を明確に観察することが可能である。
また、上層中にMn、V、Cr、Mo、Ti、Sr、Ni、Co、Sb及びBのうちから選択される一種又は二種以上が存在するか否かについては、例えばグロー放電発光分析装置でめっき皮膜を貫通分析することにより確認することができる。ただし、グロー放電発光分析装置を用いるのはあくまでも一例であり、めっき上層中のMn、V、Cr、Mo、Ti、Sr、Ni、Co、Sb及びBの有無・分布を調べることができる方法であれば、他の方法を用いることも可能である。 Here, the interface alloy layer and the upper layer can be observed by using a scanning electron microscope or the like for the cross section of the polished and / or etched plating film. There are several types of methods for polishing and etching the cross section, but there is no particular limitation as long as it is a method generally used for observing the cross section of the plating film. Moreover, if the observation conditions with a scanning electron microscope are, for example, an acceleration voltage of 15 kV and a magnification of 1000 times or more in a reflected electron image, the alloy layer and the upper layer can be clearly observed.
Whether or not one or more selected from Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B is present in the upper layer is, for example, a glow discharge emission spectrometer This can be confirmed by performing a penetration analysis on the plating film. However, the use of a glow discharge emission analyzer is merely an example, and it is a method that can check the presence / distribution of Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B in the plating upper layer. Other methods can be used if present.
また、上層中にMn、V、Cr、Mo、Ti、Sr、Ni、Co、Sb及びBのうちから選択される一種又は二種以上が存在するか否かについては、例えばグロー放電発光分析装置でめっき皮膜を貫通分析することにより確認することができる。ただし、グロー放電発光分析装置を用いるのはあくまでも一例であり、めっき上層中のMn、V、Cr、Mo、Ti、Sr、Ni、Co、Sb及びBの有無・分布を調べることができる方法であれば、他の方法を用いることも可能である。 Here, the interface alloy layer and the upper layer can be observed by using a scanning electron microscope or the like for the cross section of the polished and / or etched plating film. There are several types of methods for polishing and etching the cross section, but there is no particular limitation as long as it is a method generally used for observing the cross section of the plating film. Moreover, if the observation conditions with a scanning electron microscope are, for example, an acceleration voltage of 15 kV and a magnification of 1000 times or more in a reflected electron image, the alloy layer and the upper layer can be clearly observed.
Whether or not one or more selected from Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B is present in the upper layer is, for example, a glow discharge emission spectrometer This can be confirmed by performing a penetration analysis on the plating film. However, the use of a glow discharge emission analyzer is merely an example, and it is a method that can check the presence / distribution of Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B in the plating upper layer. Other methods can be used if present.
また、上述したMn、V、Cr、Mo、Ti、Sr、Ni、Co、Sb及びBのうちから選択される一種又は二種以上は、前記めっき上層中において、Zn、Al及びSiから選択される一種又は二種以上と金属間化合物を形成していることが好ましい。めっき皮膜を形成する過程において、Alリッチ相がZnリッチ相より先に凝固するため、めっき上層において金属間化合物は凝固過程でAlリッチ相から排出されてZnリッチ相に集まる。Znリッチ相はAlリッチ相より先に腐食するため、この金属間化合物が形成しているZnリッチ相が腐食すると、腐食生成物中にMn、V、Cr、Mo、Ti、Sr、Ni、Co、Sb及びBのうちから選択される一種又は二種以上が取り込まれることになる。この結果、より効果的に腐食の初期段階における腐食生成物の安定化を図れる。また、前記金属間化合物がSiを含む場合には、金属間化合物がめっき皮膜中のSiを吸収して、めっき上層中の余剰Siが減少する結果、非固溶Si（Si相）がめっき上層に形成することによる曲げ加工性の低下を防止できるため、さらに好ましい。
Further, one or more selected from the above-mentioned Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B are selected from Zn, Al and Si in the plating upper layer. It is preferable to form an intermetallic compound with one kind or two or more kinds. In the process of forming the plating film, the Al-rich phase solidifies before the Zn-rich phase, and therefore, intermetallic compounds are discharged from the Al-rich phase in the solidification process and gather in the Zn-rich phase. Since the Zn-rich phase corrodes before the Al-rich phase, if the Zn-rich phase formed by this intermetallic compound is corroded, the corrosion products contain Mn, V, Cr, Mo, Ti, Sr, Ni, Co , One or more selected from Sb and B will be incorporated. As a result, it is possible to stabilize the corrosion product in the initial stage of corrosion more effectively. Further, when the intermetallic compound contains Si, the intermetallic compound absorbs Si in the plating film, and as a result, the excess Si in the plating upper layer is reduced. As a result, insoluble Si (Si phase) is formed in the plating upper layer. Since it can prevent the bending workability fall by forming in, it is further more preferable.
なお、前記Mn、V、Cr、Mo、Ti、Sr、Ni、Co、Sb及びBのうちから選択される一種又は二種以上が、Zn、Al及びSiから選択される一種又は二種以上と金属間化合物を形成しているか否かを確認する方法としては、次の方法がある。めっき鋼板の表面から広角Ｘ線回折によってこれらの金属間化合物を検出する方法、若しくは、めっき皮膜の断面を透過電子顕微鏡中で電子線回折によって検出するなどの方法等が用いられる。また、これら以外の方法でも、前記金属間化合物を検出できる方法であれば、いずれの方法を用いても構わない。
In addition, one or more selected from among Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B are one or more selected from Zn, Al and Si. As a method for confirming whether or not an intermetallic compound is formed, there is the following method. A method of detecting these intermetallic compounds from the surface of the plated steel sheet by wide-angle X-ray diffraction or a method of detecting the cross section of the plating film by electron diffraction in a transmission electron microscope is used. In addition, any method other than these may be used as long as the method can detect the intermetallic compound.
さらに、本発明の溶融Al－Zn系めっき鋼板は、めっき皮膜に形成されたスパングルの平均サイズが0.5mm以下であることが好ましい。これは、スパングルを微細にすることで、スパングルの視認性を低下させ、外観均一性を向上するためである。特に、めっき鋼板上に高光沢の塗膜を形成する場合には、スパングルの浮き出しを抑制する効果をもたらす。
ここで、前記スパングルの平均サイズについては、光学顕微鏡等を用いてサンプルのめっき表面を撮影し、撮影された写真（画像）上に任意の直線を引いて、その直線を横切るスパングルの数を数え、直線の長さをスパングルの数で除すること（直線の長さ／スパングルの数）により、平均スパングルサイズを得ることができる。 Furthermore, in the molten Al—Zn-based plated steel sheet of the present invention, the average size of spangles formed on the plating film is preferably 0.5 mm or less. This is because by making the spangle fine, the visibility of the spangle is lowered and the appearance uniformity is improved. In particular, when a highly glossy coating film is formed on a plated steel sheet, an effect of suppressing spangle protrusion is brought about.
Here, regarding the average size of the spangles, a plated surface of the sample is photographed using an optical microscope or the like, an arbitrary straight line is drawn on the photograph (image) photographed, and the number of spangles crossing the straight line is counted. By dividing the length of the straight line by the number of spangles (the length of the straight line / the number of spangles), the average spangle size can be obtained.
ここで、前記スパングルの平均サイズについては、光学顕微鏡等を用いてサンプルのめっき表面を撮影し、撮影された写真（画像）上に任意の直線を引いて、その直線を横切るスパングルの数を数え、直線の長さをスパングルの数で除すること（直線の長さ／スパングルの数）により、平均スパングルサイズを得ることができる。 Furthermore, in the molten Al—Zn-based plated steel sheet of the present invention, the average size of spangles formed on the plating film is preferably 0.5 mm or less. This is because by making the spangle fine, the visibility of the spangle is lowered and the appearance uniformity is improved. In particular, when a highly glossy coating film is formed on a plated steel sheet, an effect of suppressing spangle protrusion is brought about.
Here, regarding the average size of the spangles, a plated surface of the sample is photographed using an optical microscope or the like, an arbitrary straight line is drawn on the photograph (image) photographed, and the number of spangles crossing the straight line is counted. By dividing the length of the straight line by the number of spangles (the length of the straight line / the number of spangles), the average spangle size can be obtained.
加えて、本発明の溶融Al－Zn系めっき鋼板は、めっき皮膜のビッカース硬度が平均で50～100Hvである。ここで、めっき皮膜のビッカース硬度とはめっき上層のビッカース硬度である。
前記めっき皮膜のビッカース硬度を平均で100Hv以下と軟質にすることで、曲げなどの加工を行った際、めっき皮膜が下地鋼板に追従し、クラックの発生を抑制でき、その結果として、曲げ加工部においても平板部と同程度の耐食性を確保できる。また、前記ビッカース硬度の下限を50Hvとしたのは、成形加工時にめっき皮膜が金型等に凝着するのを防止するためである。
さらに、本発明の溶融Al－Zn系めっき鋼板のめっき皮膜の付着量は片面あたり３５～１５０g／m2であることが好ましい。３５g／m2以上であれば優れた耐食性が得られ、１５０g／m2以下であれば優れた加工性が得られる。 In addition, the molten Al—Zn-based plated steel sheet of the present invention has an average Vickers hardness of 50 to 100 Hv in the plating film. Here, the Vickers hardness of the plating film is the Vickers hardness of the plating upper layer.
By making the Vickers hardness of the plating film as soft as 100 Hv or less on average, when processing such as bending, the plating film follows the base steel plate and can suppress the occurrence of cracks, resulting in bending parts The same corrosion resistance as that of the flat plate portion can be secured. The lower limit of the Vickers hardness is set to 50 Hv in order to prevent the plating film from adhering to the mold or the like during the molding process.
Furthermore, it is preferable that the coating amount of the molten Al—Zn-based plated steel sheet of the present invention is 35 to 150 g / m 2 per side. If it is 35 g / m 2 or more, excellent corrosion resistance is obtained, and if it is 150 g / m 2 or less, excellent workability is obtained.
前記めっき皮膜のビッカース硬度を平均で100Hv以下と軟質にすることで、曲げなどの加工を行った際、めっき皮膜が下地鋼板に追従し、クラックの発生を抑制でき、その結果として、曲げ加工部においても平板部と同程度の耐食性を確保できる。また、前記ビッカース硬度の下限を50Hvとしたのは、成形加工時にめっき皮膜が金型等に凝着するのを防止するためである。
さらに、本発明の溶融Al－Zn系めっき鋼板のめっき皮膜の付着量は片面あたり３５～１５０g／m2であることが好ましい。３５g／m2以上であれば優れた耐食性が得られ、１５０g／m2以下であれば優れた加工性が得られる。 In addition, the molten Al—Zn-based plated steel sheet of the present invention has an average Vickers hardness of 50 to 100 Hv in the plating film. Here, the Vickers hardness of the plating film is the Vickers hardness of the plating upper layer.
By making the Vickers hardness of the plating film as soft as 100 Hv or less on average, when processing such as bending, the plating film follows the base steel plate and can suppress the occurrence of cracks, resulting in bending parts The same corrosion resistance as that of the flat plate portion can be secured. The lower limit of the Vickers hardness is set to 50 Hv in order to prevent the plating film from adhering to the mold or the like during the molding process.
Furthermore, it is preferable that the coating amount of the molten Al—Zn-based plated steel sheet of the present invention is 35 to 150 g / m 2 per side. If it is 35 g / m 2 or more, excellent corrosion resistance is obtained, and if it is 150 g / m 2 or less, excellent workability is obtained.
さらに、前記めっき鋼板は、その表面に、化成処理皮膜及び／又は塗膜をさらに有する表面処理鋼板とすることができる。
Furthermore, the plated steel sheet can be a surface-treated steel sheet further having a chemical conversion treatment film and / or a coating film on the surface thereof.
次に、本発明の実施例を説明する。
常法で製造した板厚0.35mmの冷延鋼板を下地鋼板として用い、連続式溶融めっき設備において、サンプルとなる溶融Al－Zn系めっき鋼板の製造を行った。めっき浴の組成及びめっき後の鋼板の冷却時間、トップロール通過後のめっき鋼板の保持温度及び時間の条件、さらにめっき上層の組成については表１に示す。
なお、サンプルとなる全ての溶融Al－Zn系めっき鋼板の製造を、めっき浴の浴温は600℃とし、めっき付着量は片面あたり75g／m2、すなわち両面で150g／m2とした。 Next, examples of the present invention will be described.
A cold-rolled steel sheet having a thickness of 0.35 mm manufactured by a conventional method was used as a base steel sheet, and a hot-dip Al—Zn-based plated steel sheet as a sample was manufactured in a continuous hot-dip plating facility. Table 1 shows the composition of the plating bath, the cooling time of the steel sheet after plating, the holding temperature and time conditions of the plated steel sheet after passing through the top roll, and the composition of the plating upper layer.
In addition, in the manufacture of all the molten Al—Zn-based plated steel sheets as samples, the bath temperature of the plating bath was 600 ° C., and the amount of plating was 75 g / m 2 per side, that is, 150 g / m 2 on both sides.
常法で製造した板厚0.35mmの冷延鋼板を下地鋼板として用い、連続式溶融めっき設備において、サンプルとなる溶融Al－Zn系めっき鋼板の製造を行った。めっき浴の組成及びめっき後の鋼板の冷却時間、トップロール通過後のめっき鋼板の保持温度及び時間の条件、さらにめっき上層の組成については表１に示す。
なお、サンプルとなる全ての溶融Al－Zn系めっき鋼板の製造を、めっき浴の浴温は600℃とし、めっき付着量は片面あたり75g／m2、すなわち両面で150g／m2とした。 Next, examples of the present invention will be described.
A cold-rolled steel sheet having a thickness of 0.35 mm manufactured by a conventional method was used as a base steel sheet, and a hot-dip Al—Zn-based plated steel sheet as a sample was manufactured in a continuous hot-dip plating facility. Table 1 shows the composition of the plating bath, the cooling time of the steel sheet after plating, the holding temperature and time conditions of the plated steel sheet after passing through the top roll, and the composition of the plating upper layer.
In addition, in the manufacture of all the molten Al—Zn-based plated steel sheets as samples, the bath temperature of the plating bath was 600 ° C., and the amount of plating was 75 g / m 2 per side, that is, 150 g / m 2 on both sides.
（めっき皮膜のスパングルの平均サイズ）
溶融Al－Zn系めっき鋼板の各サンプルについて、光学顕微鏡でめっき表面を撮影し、写真上に任意に10mmの直線を10本引いて、その直線を横切るスパングルの数を数え、スパングル１個あたりの長さ＝スパングルサイズを計算する。計算結果を表１に示す。 (Average size of spangles on plating film)
For each sample of hot-dip Al-Zn-plated steel sheet, photograph the surface of the plating with an optical microscope, draw 10 10mm straight lines on the photo, count the number of spangles across the straight line, and measure the number of spangles per spangle. Calculate length = spangle size. The calculation results are shown in Table 1.
溶融Al－Zn系めっき鋼板の各サンプルについて、光学顕微鏡でめっき表面を撮影し、写真上に任意に10mmの直線を10本引いて、その直線を横切るスパングルの数を数え、スパングル１個あたりの長さ＝スパングルサイズを計算する。計算結果を表１に示す。 (Average size of spangles on plating film)
For each sample of hot-dip Al-Zn-plated steel sheet, photograph the surface of the plating with an optical microscope, draw 10 10mm straight lines on the photo, count the number of spangles across the straight line, and measure the number of spangles per spangle. Calculate length = spangle size. The calculation results are shown in Table 1.
（めっき皮膜のビッカース硬度）
溶融Al－Zn系めっき鋼板の各サンプルについて、めっき皮膜断面を研磨した後、マイクロビッカース硬度計を用いて、めっき皮膜の上層側の任意の箇所を断面方向から荷重5ｇで各20点ずつビッカース硬度を測定した。測定した20点の平均値をめっき皮膜の硬度として算出した。算出結果を表１に示す。
(Vickers hardness of plating film)
For each sample of molten Al-Zn plated steel sheet, after polishing the plating film cross section, using a micro Vickers hardness tester, Vickers hardness 20 points each at a load of 5 g from the cross-sectional direction at any point on the upper side of the plating film Was measured. The average value of the measured 20 points was calculated as the hardness of the plating film. The calculation results are shown in Table 1.
溶融Al－Zn系めっき鋼板の各サンプルについて、めっき皮膜断面を研磨した後、マイクロビッカース硬度計を用いて、めっき皮膜の上層側の任意の箇所を断面方向から荷重5ｇで各20点ずつビッカース硬度を測定した。測定した20点の平均値をめっき皮膜の硬度として算出した。算出結果を表１に示す。
(Vickers hardness of plating film)
For each sample of molten Al-Zn plated steel sheet, after polishing the plating film cross section, using a micro Vickers hardness tester, Vickers hardness 20 points each at a load of 5 g from the cross-sectional direction at any point on the upper side of the plating film Was measured. The average value of the measured 20 points was calculated as the hardness of the plating film. The calculation results are shown in Table 1.
（耐食性評価）
（１）平板部耐食性評価
溶融Al－Zn系めっき鋼板の各サンプルについて、JIS Z2371-2000に準拠した塩水噴霧試験を行った。各サンプルの赤錆が発生するまでの時間を測定し、以下の基準により評価した。評価結果を表２に示す。
○：赤錆発生時間≧2500時間
×：赤錆発生時間＜2500時間
（２）曲げ加工部耐食性評価
溶融Al－Zn系めっき鋼板の各サンプルについて、同板厚の板を内側に4枚挟んで180°曲げの加工（4T曲げ）を施した後、曲げの外側にJIS Z2371-2000に準拠した塩水噴霧試験を行った。各サンプルの赤錆が発生するまでの時間を測定し、以下の基準により評価した。評価結果を表２に示す。
○：赤錆発生時間≧2500時間
×：赤錆発生時間＜2500時間 (Corrosion resistance evaluation)
(1) Evaluation of corrosion resistance of flat plate portion A salt spray test based on JIS Z2371-2000 was performed on each sample of the molten Al—Zn-based plated steel sheet. The time until red rust occurred in each sample was measured and evaluated according to the following criteria. The evaluation results are shown in Table 2.
○: Red rust occurrence time ≧ 2500 hours ×: Red rust occurrence time <2500 hours (2) Bending part corrosion resistance evaluation For each sample of molten Al-Zn plated steel sheet, 4 sheets of the same thickness are sandwiched inside 180 ° After bending (4T bending), a salt spray test in accordance with JIS Z2371-2000 was performed on the outside of the bend. The time until red rust occurred in each sample was measured and evaluated according to the following criteria. The evaluation results are shown in Table 2.
○: Red rust occurrence time ≥ 2500 hours ×: Red rust occurrence time <2500 hours
（１）平板部耐食性評価
溶融Al－Zn系めっき鋼板の各サンプルについて、JIS Z2371-2000に準拠した塩水噴霧試験を行った。各サンプルの赤錆が発生するまでの時間を測定し、以下の基準により評価した。評価結果を表２に示す。
○：赤錆発生時間≧2500時間
×：赤錆発生時間＜2500時間
（２）曲げ加工部耐食性評価
溶融Al－Zn系めっき鋼板の各サンプルについて、同板厚の板を内側に4枚挟んで180°曲げの加工（4T曲げ）を施した後、曲げの外側にJIS Z2371-2000に準拠した塩水噴霧試験を行った。各サンプルの赤錆が発生するまでの時間を測定し、以下の基準により評価した。評価結果を表２に示す。
○：赤錆発生時間≧2500時間
×：赤錆発生時間＜2500時間 (Corrosion resistance evaluation)
(1) Evaluation of corrosion resistance of flat plate portion A salt spray test based on JIS Z2371-2000 was performed on each sample of the molten Al—Zn-based plated steel sheet. The time until red rust occurred in each sample was measured and evaluated according to the following criteria. The evaluation results are shown in Table 2.
○: Red rust occurrence time ≧ 2500 hours ×: Red rust occurrence time <2500 hours (2) Bending part corrosion resistance evaluation For each sample of molten Al-Zn plated steel sheet, 4 sheets of the same thickness are sandwiched inside 180 ° After bending (4T bending), a salt spray test in accordance with JIS Z2371-2000 was performed on the outside of the bend. The time until red rust occurred in each sample was measured and evaluated according to the following criteria. The evaluation results are shown in Table 2.
○: Red rust occurrence time ≥ 2500 hours ×: Red rust occurrence time <2500 hours
（外観均一性評価）
溶融Al－Zn系めっき鋼板の各サンプルのスパングルの平均サイズを以下の基準により評価した。評価結果を表２に示す。
○：スパングルの平均サイズ≦0.5ｍｍ
△：スパングル平均サイズ＞0.5ｍｍ (Appearance uniformity evaluation)
The average spangle size of each sample of the molten Al-Zn plated steel sheet was evaluated according to the following criteria. The evaluation results are shown in Table 2.
○: Average size of spangle ≦ 0.5mm
Δ: Spangle average size> 0.5 mm
溶融Al－Zn系めっき鋼板の各サンプルのスパングルの平均サイズを以下の基準により評価した。評価結果を表２に示す。
○：スパングルの平均サイズ≦0.5ｍｍ
△：スパングル平均サイズ＞0.5ｍｍ (Appearance uniformity evaluation)
The average spangle size of each sample of the molten Al-Zn plated steel sheet was evaluated according to the following criteria. The evaluation results are shown in Table 2.
○: Average size of spangle ≦ 0.5mm
Δ: Spangle average size> 0.5 mm
表１及び２の結果から、本発明例の各サンプルは、比較例の各サンプルに比べて、めっき皮膜が軟質であることがわかる。
また、平板部の耐食性については大きな差がないが、本発明例の各サンプルは、比較例の各サンプルに比べて、曲げ加工部の耐食性に優れることがわかる。
さらに、本発明例の各サンプルのうち、めっき後の急速冷却を行っていないサンプル１は、その他の本発明例サンプルに比べてスパングルサイズが大きいことがわかる。 From the results of Tables 1 and 2, it can be seen that each sample of the present invention example has a softer plating film than each sample of the comparative example.
Moreover, although there is no big difference about the corrosion resistance of a flat plate part, it turns out that each sample of this invention example is excellent in the corrosion resistance of a bending process part compared with each sample of a comparative example.
Furthermore, it can be seen that among the samples of the present invention example, the sample 1 that has not been subjected to rapid cooling after plating has a larger spangle size than the other samples of the present invention example.
また、平板部の耐食性については大きな差がないが、本発明例の各サンプルは、比較例の各サンプルに比べて、曲げ加工部の耐食性に優れることがわかる。
さらに、本発明例の各サンプルのうち、めっき後の急速冷却を行っていないサンプル１は、その他の本発明例サンプルに比べてスパングルサイズが大きいことがわかる。 From the results of Tables 1 and 2, it can be seen that each sample of the present invention example has a softer plating film than each sample of the comparative example.
Moreover, although there is no big difference about the corrosion resistance of a flat plate part, it turns out that each sample of this invention example is excellent in the corrosion resistance of a bending process part compared with each sample of a comparative example.
Furthermore, it can be seen that among the samples of the present invention example, the sample 1 that has not been subjected to rapid cooling after plating has a larger spangle size than the other samples of the present invention example.
本発明によれば、良好な平板部の耐食性を有するとともに、良好な加工性により加工部の耐食性にも優れた溶融Al－Zn系めっき鋼板が得られ、建材分野を中心に広範な分野で適用することができる。
According to the present invention, a molten Al—Zn-plated steel sheet having excellent flat plate portion corrosion resistance and excellent workability due to excellent workability can be obtained, and can be applied in a wide range of fields mainly in the field of building materials. can do.
Claims (9)
- 連続式溶融めっき設備において、溶融めっき後の鋼板を250～375℃の温度で5～60秒間保持することを特徴とする溶融Al－Zn系めっき鋼板の製造方法。 A method for producing a hot-dip Al-Zn-plated steel sheet, characterized by holding the hot-dip steel sheet at a temperature of 250 to 375 ° C for 5 to 60 seconds in a continuous hot-dip plating facility.
- 前記溶融めっき後の鋼板を、めっき浴の浴温－20℃からめっき浴の浴温－80℃まで5秒以内に冷却することを特徴とする請求項１に記載の溶融Al－Zn系めっき鋼板の製造方法。 2. The hot-dip Al—Zn-based plated steel sheet according to claim 1, wherein the hot-dip plated steel sheet is cooled within 5 seconds from a bath temperature of a plating bath of −20 ° C. to a bath temperature of a plating bath of −80 ° C. Manufacturing method.
- 前記めっき鋼板の冷却時間を3秒以内とすることを特徴とする請求項２に記載の溶融Al－Zn系めっき鋼板の製造方法。 The method for producing a molten Al-Zn-based plated steel sheet according to claim 2, wherein the cooling time of the plated steel sheet is 3 seconds or less.
- 前記めっき鋼板の保持温度が300～375℃であることを特徴とする請求項１～３のいずれか一項に記載の溶融Al－Zn系めっき鋼板の製造方法。 The method for producing a hot-dip Al-Zn-plated steel sheet according to any one of claims 1 to 3, wherein the holding temperature of the plated steel sheet is 300 to 375 ° C.
- 前記めっき鋼板の保持時間が5～30秒であることを特徴とする請求項１～４のいずれか一項に記載の溶融Al－Zn系めっき鋼板の製造方法。 The method for producing a hot-dip Al-Zn-plated steel sheet according to any one of claims 1 to 4, wherein a holding time of the plated steel sheet is 5 to 30 seconds.
- 前記めっき鋼板をトップロールと接触する前に375℃以下までさらに冷却することを特徴とする請求項１～５のいずれか一項に記載の溶融Al－Zn系めっき鋼板の製造方法。 6. The method for producing a hot-dip Al—Zn-based plated steel sheet according to claim 1, wherein the plated steel sheet is further cooled to 375 ° C. or lower before contacting with the top roll.
- 請求項１～６のいずれか一項に記載の製造方法によって得られためっき皮膜を有する溶融Al－Zn系めっき鋼板であって、
前記めっき皮膜は下地鋼板との界面に存在する界面合金層と該合金層の上に存在する上層からなり、該上層は、20～95質量％のAl及び該Al含有量の10％以下のSiを含有し、残部がZn及び不可避的不純物からなる組成を有し、前記めっき皮膜のビッカース硬度が平均で50～100Hvであることを特徴とする溶融Al－Zn系めっき鋼板。 A hot-dip Al-Zn plated steel sheet having a plating film obtained by the production method according to any one of claims 1 to 6,
The plating film comprises an interface alloy layer present at the interface with the underlying steel plate and an upper layer present on the alloy layer, the upper layer comprising 20 to 95% by mass of Al and 10% or less of the Al content of Si. A molten Al—Zn-based plated steel sheet, wherein the balance is composed of Zn and inevitable impurities, and the plating film has an average Vickers hardness of 50 to 100 Hv. - 前記上層中に、さらにMn、V、Cr、Mo、Ti、Sr、Ni、Co、Sb及びBのうちから選択される１種又は２種以上を、合計で0.01～10質量％含有することを特徴とする請求項７に記載の溶融Al－Zn系めっき鋼板。 The upper layer further contains one or more selected from Mn, V, Cr, Mo, Ti, Sr, Ni, Co, Sb and B in a total amount of 0.01 to 10% by mass. The molten Al-Zn-based plated steel sheet according to claim 7,
- 前記めっき皮膜のスパングルの平均サイズが0.5mm以下であることを特徴とする請求項７又は請求項８に記載の溶融Al－Zn系めっき鋼板。 The molten Al-Zn-based plated steel sheet according to claim 7 or 8, wherein an average size of spangles of the plating film is 0.5 mm or less.
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| CN201480006168.1A CN104955976A (en) | 2013-01-31 | 2014-01-23 | HOT-DIP Al-Zn GALVANIZED STEEL PLATE AND METHOD FOR PRODUCING SAME |
| AU2014212962A AU2014212962B2 (en) | 2013-01-31 | 2014-01-23 | Hot-dip Al-Zn galvanized steel plate and method for producing same |
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| CN105483591B (en) * | 2015-12-23 | 2018-12-07 | 常州大学 | Zn-Al-Si-Ni alloy layer and hot dip coating method used for hot dip galvanizing |
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| CN111655894B (en) | 2017-12-26 | 2022-09-27 | 日本制铁株式会社 | Hot-dip aluminized steel strip and method for producing same |
| CN109402452A (en) * | 2018-12-07 | 2019-03-01 | 株洲冶炼集团股份有限公司 | A kind of hot dip kirsite |
| KR102311503B1 (en) * | 2019-12-20 | 2021-10-13 | 주식회사 포스코 | Aluminium alloy plate steel sheet having excellent formability and corrosion resistance and method for manufacturing the same |
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| CN101805881A (en) * | 2010-05-18 | 2010-08-18 | 梁士臣 | Method and device for producing zinc-based alloy hot-dip steel strip by advanced air cooling method |
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| JPS6128748B2 (en) * | 1979-11-08 | 1986-07-02 | Bethlehem Steel Corp | |
| JP2001164350A (en) * | 1999-12-09 | 2001-06-19 | Daido Steel Sheet Corp | Method for manufacturing aluminum-zinc alloy plated steel sheet |
| JP2004323932A (en) * | 2003-04-25 | 2004-11-18 | Sumitomo Metal Ind Ltd | Coated steel sheet, base material plated steel sheet thereof and their production methods |
| JP2007162087A (en) * | 2005-12-15 | 2007-06-28 | Nippon Steel Corp | Method for cleaning steel strip in pickling line |
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