WO2019131563A1 - Procédé de galvanisation par immersion à chaud, procédé de production d'une tôle d'acier allié galvanisée par immersion à chaud à l'aide dudit procédé de galvanisation par immersion à chaud, et procédé de production d'une tôle d'acier galvanisée par immersion à chaud à l'aide dudit procédé de galvanisation par immersion à chaud - Google Patents

Procédé de galvanisation par immersion à chaud, procédé de production d'une tôle d'acier allié galvanisée par immersion à chaud à l'aide dudit procédé de galvanisation par immersion à chaud, et procédé de production d'une tôle d'acier galvanisée par immersion à chaud à l'aide dudit procédé de galvanisation par immersion à chaud Download PDF

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WO2019131563A1
WO2019131563A1 PCT/JP2018/047396 JP2018047396W WO2019131563A1 WO 2019131563 A1 WO2019131563 A1 WO 2019131563A1 JP 2018047396 W JP2018047396 W JP 2018047396W WO 2019131563 A1 WO2019131563 A1 WO 2019131563A1
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Prior art keywords
hot
dross
dip galvanizing
phase
bath
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PCT/JP2018/047396
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English (en)
Japanese (ja)
Inventor
剛嗣 小西
秀生 西村
晃一 西沢
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日本製鉄株式会社
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Priority to JP2019561678A priority Critical patent/JP6919724B2/ja
Priority to CN201880083471.XA priority patent/CN111615566B/zh
Publication of WO2019131563A1 publication Critical patent/WO2019131563A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • 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
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/40—Plates; Strips
    • 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
    • C23C2/50—Controlling or regulating the coating processes
    • C23C2/52—Controlling or regulating the coating processes with means for measuring or sensing
    • C23C2/521—Composition of the bath

Definitions

  • the present invention relates to a hot-dip galvanizing method, a method for producing an alloyed galvanized steel sheet using the hot-dip galvanizing method, and a method for producing a hot-dip galvanized steel sheet using the hot-dip galvanizing method.
  • Hot-dip galvanized steel sheets (hereinafter also referred to as GI) and alloyed hot-dip galvanized steel sheets (hereinafter also referred to as GA) are manufactured by the following manufacturing process.
  • a steel plate (base steel plate) to be subjected to hot-dip galvanizing treatment is prepared.
  • the base steel plate may be a hot rolled steel plate or a cold rolled steel plate.
  • a pickled hot-rolled steel plate is prepared.
  • the pickled hot rolled steel sheet may be subjected to Ni pre-plating treatment as necessary to prepare a hot rolled steel sheet having a Ni layer formed on the surface.
  • the hot rolled sheet steel in which the process other than the above-mentioned was given.
  • the base material steel plate is a cold rolled steel plate
  • a cold rolled steel plate subjected to an annealing treatment is prepared.
  • the cold-rolled steel plate having the Ni layer formed on the surface may be prepared by performing Ni pre-plating treatment on the annealed cold-rolled steel plate as necessary.
  • the prepared base steel plate (the above-described hot-rolled steel plate or cold-rolled steel plate) is immersed in a hot-dip galvanizing bath to carry out a hot-dip galvanizing treatment to produce a hot-dip galvanized steel plate.
  • the galvanized steel sheet is further heat-treated in an alloying furnace to produce an alloyed galvanized steel sheet.
  • a hot dip galvanization facility used for hot dip galvanization processing includes a hot dip galvanizing pot containing a hot dip galvanization bath, a sink roll disposed in the hot dip galvanization bath, and a gas wiping device.
  • a steel plate (base steel plate) is immersed in a hot dip galvanizing bath. Then, the traveling direction of the steel plate is changed upward by a sink roll disposed in the hot dip galvanization bath, and the steel plate is pulled up from the hot dip galvanization bath. For a steel sheet pulled up and moving upward, a wiping gas is blown from the gas wiping apparatus onto the surface of the steel sheet, excess molten zinc is scraped off, and the amount of plating on the surface of the steel sheet is adjusted.
  • the hot dip galvanizing treatment process is carried out by the above method.
  • the steel plate in which the amount of plating adhesion is adjusted is inserted into an alloying furnace to carry out an alloying treatment.
  • Bottom dross is an intermetallic compound having a specific gravity greater than that of a hot-dip galvanizing bath, and is dross deposited at the bottom of a molten zinc pot.
  • bottom dross in particular, is wound up from the bottom of the deposited molten zinc pot by the accompanying flow generated by the progress of the steel plate in the hot dip galvanizing bath during the hot dip galvanizing treatment, It floats in the plating bath.
  • Such floating bottom dross may adhere to the surface of the steel sheet during the hot dip galvanization treatment. Bottom dross adhering to the surface of the steel sheet may become point-like defects on the surface of the alloyed galvanized steel sheet or the galvanized steel sheet.
  • dross defects Such bottom dross-induced surface defects are referred to herein as "dross defects".
  • the dross defect degrades the appearance of the alloyed galvanized steel sheet and the galvanized steel sheet, and reduces the corrosion resistance. Therefore, it is preferable to be able to suppress the occurrence of dross defects.
  • Patent Document 1 Japanese Patent Application Laid-Open Nos. 11-350096 (Patent Document 1) and 11-350097 (Patent Document 2).
  • the molten zinc bath temperature T is in the range of 435 to 500 ° C.
  • the Al concentration in the bath is maintained in the range of Cz ⁇ 0.01 wt%.
  • Patent Document 1 describes as follows.
  • the composition of dross changes according to the Al concentration in the bath. Specifically, in the molten zinc bath maintained at 465 ° C., the dross becomes Fe—Al-based (top dross) when the Al concentration in the bath is 0.14% or more. When the Al concentration in the bath is lower than 0.14%, the dross becomes a delta 1 phase ( ⁇ 1 phase) of the Fe—Zn system (bottom dross). When the Al concentration in the bath is further lowered, the dross becomes a Fe-Zn based (bottom dross) zeta phase ( ⁇ phase).
  • the boundary of phase transformation of the ⁇ 1 phase and the ⁇ phase is defined as “boundary Al concentration Cz”.
  • the Al concentration in the bath is controlled at the boundary Al concentration Cz ⁇ 0.01 wt%. In this case, if the Al concentration in the bath exceeds the boundary Al concentration Cz, the dross becomes a ⁇ 1 phase, and if it becomes less than the boundary Al concentration Cz, the dross becomes a drier phase.
  • Patent Document 1 describes that the dross can be miniaturized and the occurrence of dross defects can be suppressed.
  • Patent Document 2 Al concentration in a bath is hold
  • Patent Document 2 describes as follows. In a bath Al concentration 0.15 wt% or more, dross becomes Fe-Al phase, in the 0.15 percent bath Al concentration, the dross becomes [delta] 1 phase. If the dross repeats phase transformation between the Fe-Al phase and the ⁇ 1 phase, the dross becomes finer.
  • the object of the present disclosure is a hot dip galvanization treatment method capable of suppressing the generation of dross defects, a method of manufacturing a galvannealed steel sheet using the hot dip galvanization treatment method, and a hot dip galvanization treatment method thereof It is providing the manufacturing method of a hot dip galvanized steel plate.
  • the hot-dip galvanizing method is a hot-dip galvanizing method used for manufacturing a hot-dip galvanized steel sheet or an alloyed hot-dip galvanized steel sheet, A sample collecting step of collecting a sample from a galvanizing bath containing Al; Using samples taken, and gamma 2 phase dross amount determining step of determining the gamma 2 phase dross content in molten zinc plating bath, And an operation condition adjusting step of adjusting an operation condition of the hot dip galvanizing treatment based on the obtained two- phase dross amount.
  • a method of manufacturing an alloyed galvanized steel sheet according to the present disclosure is A hot-dip galvanizing process step of carrying out the above-mentioned hot-dip galvanizing treatment method on a steel plate to form a hot-dip galvanized layer on the surface of the steel plate; An alloying process is performed on the steel sheet having a hot-dip galvanized layer formed on the surface to produce an alloyed hot-dip galvanized steel sheet.
  • the method for producing a hot-dip galvanized steel sheet according to the present disclosure is The steel sheet is provided with a hot-dip galvanization process step of performing the above-described hot-dip galvanization treatment method to form a hot-dip galvanized layer on the surface of the steel sheet.
  • the hot dip galvanization processing method according to the present disclosure can suppress the occurrence of dross defects. Moreover, the manufacturing method of the alloying hot-dip galvanized steel sheet by this indication can manufacture the alloying hot-dip galvanized steel sheet in which generation
  • FIG. 1 is a functional block diagram showing an entire configuration of a hot dip galvanizing line facility used for manufacturing an alloyed galvanized steel sheet and a galvanized steel sheet.
  • FIG. 2 is a side view of the hot dip galvanizing equipment in FIG.
  • FIG. 3 is a side view of the hot-dip galvanizing equipment having a configuration different from that of FIG.
  • FIG. 4 is a side view of the hot-dip galvanizing equipment having a configuration different from FIGS. 2 and 3.
  • FIG. 5 is a functional block diagram showing an overall configuration of a hot-dip galvanizing line facility having a configuration different from that of FIG.
  • FIG. 6 is a flow chart showing steps of the hot-dip galvanizing method of the present embodiment.
  • FIG. 1 is a functional block diagram showing an entire configuration of a hot dip galvanizing line facility used for manufacturing an alloyed galvanized steel sheet and a galvanized steel sheet.
  • FIG. 2 is a side view of the hot dip galvanizing equipment in FIG.
  • FIG. 7 is a view showing an example of a photographic image in a part of the observation visual field of the sample collected in the sample collecting step of the hot-dip galvanizing treatment method of the present embodiment.
  • FIG. 8 is a view showing the relationship between the Al concentration X (mass%) in the hot-dip galvanizing bath, the bath temperature T (° C.) of the hot-dip galvanizing bath, and the dross stabilized in the hot-dip galvanizing bath .
  • top dross Fe 2 Al 5 is called top dross.
  • Top dross has a specific gravity smaller than that of a hot dip galvanizing bath. Therefore, the top dross tends to rise to the surface of the hot dip galvanizing bath.
  • the crystal structure of Fe 2 Al 5 is orthorhombic, and its chemical composition consists of 45% Al, 38% Fe, and 17% Zn by mass. Since top dross is soft, it is known that it is difficult to cause dross defects.
  • Bottom dross has a higher specific gravity than a hot dip galvanizing bath. Therefore, bottom dross tends to deposit on the bottom of the molten zinc pot in which the hot dip galvanizing bath is stored.
  • the crystal structure of ⁇ 1 -phase dross is hexagonal, and its chemical composition consists of, in mass%, 1% or less of Al, 9% or more of Fe, and 90% or more of Zn.
  • the crystal structure of the first phase dross is face-centered cubic, and its chemical composition consists of 20% of Fe and about 80% of Zn in mass%.
  • the crystal structure of zeta phase dross is monoclinic, and its chemical composition is composed of, in mass%, 1% or less of Al, approximately 6% of Fe, and approximately 94% of Zn.
  • the present inventors considered that the dross defect is not caused by ⁇ 1 -phase dross but by other dross. Therefore, the present inventors re-analyzed the chemical composition and the crystal structure of the dross defect portion using the alloyed galvanized steel sheet in which the dross defect is generated. The inventors further analyzed the type of dross generated in the hot-dip galvanizing bath again. As a result, the present inventors obtained the following findings regarding the dross defect, which are different from the conventional research results.
  • the chemical composition of the dross defect portion on the surface of the alloyed galvanized steel sheet was analyzed using an EPMA (Electron Probe Micro Analyzer: electron beam micro analyzer). Furthermore, the crystal structure of the dross defect part was analyzed using TEM (Transmission Electron Microscope: transmission electron microscope). As a result, the chemical composition of the dross defect portion was composed of 2% Al, 8% Fe and 90% Zn by mass%, and the crystal structure was face-centered cubic.
  • ⁇ 1 -phase dross Al by 1% or less by mass, 1% by mass or more by Fe, and 90% by mass or more by Zn
  • the crystal structure of the ⁇ 1 -phase dross is hexagonal, and is not a face-centered cubic crystal identified in the dross defect portion. Therefore, the present inventors have, [delta] 1 phase dross was considered the main factor of the conventional dross defects, in fact, were not considered to be the main cause of dross defects.
  • the present inventors have identified a dross which causes dross defects.
  • the chemical composition of Fe 2 Al 5 top dross
  • the chemical composition of the dross defect portion As for the 1- phase dross, although the crystal structure is the same face-centered cubic crystal as the dross defect part, the chemical composition (20% of Fe and 80% of Zn by mass%) is large with the chemical composition of the dross defect part It is different.
  • the chemical composition Al by mass% or less of Al, approximately 6% of Fe, and approximately 94% of Zn
  • the crystal structure monoclinic crystal
  • the crystal structure face-centered cubic
  • the present inventors considered that the dross defect was not caused by the dross described in (1) to (4) above. Then, the present inventors considered that the dross defect is attributable to other types of dross other than the above (1) to (4).
  • the inventors further analyzed the dross in the hot dip galvanization bath.
  • the above-mentioned EPMA and TEM were used.
  • the present inventors have newly found that a gamma two- phase ( ⁇ two- phase) dross exists as a dross generated in the hot-dip galvanizing bath.
  • the chemical composition of the gamma 2 phase dross, in mass%, and 2% of Al, 8% Fe, consists of 90% of Zn, consistent with the chemical composition of the analyzed dross defect portion above. Further, the crystal structure of the gamma 2 phase dross is face-centered cubic, consistent with the crystal structure of the dross defect. Accordingly, the present inventors have, gamma 2 phase dross thought that it is the main factor of dross defects. Since the specific gravity of the gamma 2 phase dross is greater than the specific gravity of the molten zinc plating bath, gamma 2 phase dross was true dross which may deposit on the bottom of the molten zinc pot.
  • the present inventors have further investigated the phase 2 dross and the other drosses (1) to (4). As a result, the following matters were found.
  • dross defects are caused by dross having a large particle diameter, and dross having a small particle diameter is less likely to form dross defects.
  • the present inventors mainly use the d 1 phase dross as a main factor of the dross defect generated on the surface of the galvanized steel sheet subjected to the hot dip galvanizing treatment and the galvanized steel sheet. Rather, I concluded that ⁇ 2 phase dross. Furthermore, the present inventors have found that dross classified as dross, the gamma 2 phase dross, [delta] 1 phase dross, zeta phase dross, and, although either of the gamma 1-phase dross in a molten zinc plating bath, gamma We found that there was almost no single- phase dross.
  • the galvanizing treatment determine the gamma 2 phase dross content in molten zinc plating bath, on the basis of the gamma 2 phase dross content in molten zinc plating bath, by adjusting the operating conditions of the galvanizing treatment, the alloy In the galvannealed steel sheet and the galvanized steel sheet, it has been found that the generation of dross defects can be suppressed.
  • the hot dip galvanization processing method of this embodiment completed based on the above knowledge is as follows.
  • the hot-dip galvanizing method of [1] is It is a hot dip galvanization processing method used for manufacture of a hot dip galvanized steel sheet or an alloyed hot dip galvanized steel sheet, A sample collecting step of collecting a sample from a galvanizing bath containing Al; Using samples taken, and gamma 2 phase dross amount determining step of determining the gamma 2 phase dross content in molten zinc plating bath, And an operation condition adjusting step of adjusting an operation condition of the hot dip galvanizing treatment based on the obtained two- phase dross amount.
  • adjusting the operating conditions of the hot dip galvanizing treatment means adjusting the operating conditions of the hot dip galvanizing treatment capable of adjusting the amount of the two- phase dross in the hot dip galvanizing bath.
  • adjusting the operation conditions of the hot dip galvanization treatment includes not only the act of changing the operation conditions of the hot dip galvanization treatment but also the action of maintaining the operation conditions as it is.
  • the hot-dip galvanizing method of [2] is the hot-dip galvanizing method according to [1], and In the two- phase dross determination process, Using samples taken, the number of gamma 2 phase dross per predetermined area, obtains a gamma 2 phase dross amount.
  • Predetermined area is not particularly limited.
  • Predetermined area for example, may be the area of the whole observed field of view in the case of observing the gamma 2 phase dross at predetermined observation field with a sample may be a unit area (mm 2).
  • the hot-dip galvanizing method of [3] is the hot-dip galvanizing method according to [1] and [2], and In the operating condition adjustment process, Based on the obtained gamma 2 phase dross amount, to reduce (A) ⁇ at least one implemented gamma 2 phase dross amount of (C).
  • C Adjust the conveyance speed of the steel plate in the hot dip galvanization facility which carries out the hot dip galvanization process.
  • the (A) ⁇ (C) are both, or by phase transformation to gamma 2 phase dross dross other phase is an effective operating conditions for it suppresses the production of gamma 2 phase dross. Therefore, by implementing at least one of (A) ⁇ (C), it is possible to reduce the gamma 2 phase dross amount.
  • the hot-dip galvanizing method of [4] is the hot-dip galvanizing method according to any one of [1] to [3], and In the operating condition adjustment process, When the calculated amount of two- phase dross exceeds the threshold value, the operation condition of the hot dip galvanizing treatment is adjusted to reduce the amount of two- phase dross.
  • the hot-dip galvanizing method of [5] is the hot-dip galvanizing method according to [4], and In the two- phase dross determination process, Using samples taken, determine the number of gamma 2 phase dross per predetermined area as gamma 2 phase dross amount, In the operating condition adjustment process, If the calculated amount of two- phase dross is more than 0.045 pieces / mm 2 when converted to unit area (1 mm 2 ), adjust the operation conditions of the hot-dip galvanizing treatment and calculate the amount of two- phase dross Reduce.
  • the hot-dip galvanizing method of [6] is the hot-dip galvanizing method according to any one of [1] to [5], and In the operating condition adjustment process, The Al concentration X in the hot dip galvanizing bath is adjusted in the range of 0.100 to 0.159 mass%.
  • the hot-dip galvanizing method of [7] is the hot-dip galvanizing method according to [6], and In the operating condition adjustment process, When the Al concentration X is 0.100 to 0.140 mass%, adjustment is made so that the Al concentration X and the bath temperature T (° C.) of the hot dip galvanizing bath satisfy the formula (1), When the Al concentration X is greater than 0.140 to 0.159 mass%, the bath temperature T of the hot dip galvanizing bath is adjusted to 469 ° C. or higher. X ⁇ 0.002488 ⁇ T-1.0266 (1)
  • the Al concentration X is 0.100 to 0.140 wt%, satisfies the equation (1), [delta] 1 phase dross easily generated in place of the gamma 2 phase dross, stable production of gamma 2 phase dross Can be suppressed. Also, when the Al concentration X is more than 0.140 to 0.159 mass%, if the bath temperature T of the hot dip galvanizing bath is made 469 ° C. or more, almost no two- phase dross is generated, and the top dross or , ⁇ 1 phase dross is generated. Therefore, the generation of a dross defect caused by the ⁇ two- phase dross can be stably suppressed.
  • the hot-dip galvanizing method of [8] is the hot-dip galvanizing method according to any one of [1] to [7], and In the hot-dip galvanizing pot in which the hot-dip galvanizing bath is stored, a sink roll for contacting the steel plate immersed in the hot-dip galvanizing bath and changing the traveling direction of the steel plate upward is disposed. In the sample collection process, A sample is taken from a depth range in the range from the upper end to the lower end of the sink roll in the hot dip galvanizing bath in the hot dip galvanizing pot.
  • the sample is taken from the same depth range as the sink roll. Therefore, it is possible to further improve the correlation between gamma 2 phase dross amount and dross defects.
  • the manufacturing method of the galvannealed steel sheet of [9] is A hot dip galvanizing process step of forming a hot dip galvanizing layer on the surface of the steel plate by performing the hot dip galvanizing treatment method according to any one of [1] to [8] on the steel plate; An alloying process is performed on the steel sheet having a hot-dip galvanized layer formed on the surface to produce an alloyed hot-dip galvanized steel sheet.
  • the method of manufacturing the galvannealed steel sheet according to the present embodiment applies the hot-dip galvanizing method according to the present embodiment described above. Therefore, it is possible to manufacture an alloyed hot-dip galvanized steel sheet in which a dross defect is suppressed.
  • the method of manufacturing the galvanized steel sheet of [10] is The steel sheet is subjected to the hot dip galvanization process step of forming the hot dip galvanizing layer on the surface of the steel sheet by carrying out the hot dip galvanization treatment method according to any one of [1] to [8].
  • the method for manufacturing the hot-dip galvanized steel sheet of the present embodiment applies the hot-dip galvanizing method of the present embodiment described above. Therefore, a hot-dip galvanized steel sheet in which a dross defect is suppressed can be manufactured.
  • FIG. 1 is a functional block diagram showing an example of an entire configuration of a hot dip galvanizing line facility used for manufacturing an alloyed hot-dip galvanized steel sheet and a hot-dip galvanized steel sheet.
  • the hot-dip galvanizing line facility 1 includes an annealing furnace 20, a hot-dip galvanizing facility 10, and a temper rolling mill (skin pass mill) 30.
  • Annealing furnace 20 includes one or more heating zones (not shown) and one or more cooling zones disposed downstream of the heating zone.
  • a steel plate is supplied to the heating zone of the annealing furnace 20, and annealing is implemented with respect to a steel plate.
  • the annealed steel sheet is cooled by the cooling zone and conveyed to the hot dip galvanizing facility 10.
  • the hot dip galvanization facility 10 is disposed downstream of the annealing furnace 20.
  • hot-dip galvanizing equipment 10 hot-dip galvanizing treatment is performed on the steel plate to produce an alloyed hot-dip galvanized steel plate or a hot-dip galvanized steel plate.
  • the temper rolling mill 30 is disposed downstream of the hot dip galvanizing facility 10.
  • the alloyed galvanized steel sheet or the molten galvanized steel sheet or the galvanized steel sheet manufactured in the hot dip galvanization facility 10 is lightly reduced as necessary, and the galvanized steel sheet or the molten galvanized steel sheet or the galvanized steel sheet is Adjust the surface of galvanized steel sheet.
  • FIG. 2 is a side view of the hot dip galvanizing equipment 10 in FIG.
  • the galvanizing facility 10 includes a hot-dip galvanizing pot 101, a sink roll 107, a support roll 113, a gas wiping apparatus 109, and an alloying furnace 111.
  • Annealing furnace 20 heats steel plate S conveyed continuously as mentioned above in a heating zone. Thereby, the surface of the steel plate S is activated, and the mechanical properties of the steel plate S are adjusted.
  • the downstream end of the annealing furnace 20 corresponding to the outlet side of the annealing furnace 20 has a space in which the turndown roll 201 is disposed.
  • the downstream end of the annealing furnace 20 is connected to the upstream end of the snout 202.
  • the downstream end of the snout 202 is immersed in the hot dip galvanizing bath 103.
  • the interior of the snout 202 is isolated from the atmosphere and is maintained in a reducing atmosphere.
  • the steel sheet S whose transport direction has been changed downward by the turn down roll 201 passes through the snout 202 and is continuously immersed in the hot dip galvanizing bath 103 stored in the molten zinc pot 101.
  • a sink roll 107 is disposed inside the molten zinc pot 101.
  • the sink roll 107 has a rotation axis parallel to the width direction of the steel plate S.
  • the axial width of the sink roll 107 is larger than the width of the steel plate S.
  • the sink roll 107 is in contact with the steel plate S and switches the traveling direction of the steel plate S to the upper side of the galvanizing facility 10.
  • the support roll 113 is disposed in the hot dip galvanizing bath 103 and above the sink roll 107.
  • the support roll 113 comprises a pair of rolls.
  • a pair of rolls of the support roll 113 has a rotation axis parallel to the width direction of the steel plate S.
  • the support roll 113 supports the steel sheet S conveyed upward, sandwiching the steel sheet S whose traveling direction has been converted upward by the sink roll 107.
  • the gas wiping device 109 is disposed above the sink roll 107 and the support roll 113 and above the liquid surface of the hot dip galvanizing bath 103.
  • the gas wiping device 109 includes a pair of gas injection devices.
  • the pair of gas injection devices have gas injection nozzles opposed to each other.
  • the steel plate S passes between the pair of gas injection nozzles of the gas wiping device 109.
  • the pair of gas injection nozzles face the surface of the steel plate S.
  • the gas wiping apparatus 109 scrapes off a part of the hot-dip galvanization deposited on both surfaces of the steel plate S by blowing gas against both surfaces of the steel plate S pulled up from the hot-dip galvanizing bath 103. Adjust the amount of hot-dip galvanization on the surface.
  • the alloying furnace 111 is disposed above the gas wiping device 109.
  • the alloying furnace 111 performs an alloying process on the steel sheet S by passing the steel sheet S conveyed upward through the gas wiping device 109 inside.
  • the alloying furnace 111 includes, in order from the inlet side to the outlet side, a heating zone, a holding zone, and a cooling zone.
  • the heating zone is heated so that the temperature of the steel plate S (plate temperature) becomes substantially uniform.
  • the honing zone keeps the plate temperature of the steel plate S.
  • the hot-dip galvanized layer formed on the surface of the steel sheet S is alloyed to be an alloyed layer.
  • the cooling zone cools the steel plate S on which the alloyed layer is formed.
  • the alloying furnace 111 performs the alloying process using the heating zone, the water retaining zone, and the cooling zone.
  • the alloying furnace 111 implements the above-mentioned alloying process, when manufacturing an alloying hot-dip galvanized steel sheet.
  • the alloying furnace 111 does not carry out the alloying process.
  • the steel sheet S passes through the non-operational alloying furnace 111.
  • not operating means, for example, that the power supply is in a stopped state (not started) while the alloying furnace 111 is placed online.
  • the steel sheet S having passed through the alloying furnace 111 is conveyed by the top roll 115 to the next process.
  • the alloying furnace 111 may move off-line. In this case, the steel plate S is conveyed to the next step by the top roll 115 without passing through the alloying furnace 111.
  • the hot dip galvanization installation 10 is an installation for exclusive use of a hot dip galvanized steel plate, the hot dip galvanization installation 10 does not need to be equipped with the alloying furnace 111, as shown in FIG.
  • the hot-dip galvanizing line facility 1 is not limited to the configuration of FIG. 1.
  • Ni pre-plating treatment is performed on a steel plate before hot-dip galvanizing treatment to form a Ni layer on the steel plate
  • Ni is interposed between annealing furnace 20 and galvanizing facility 10 as shown in FIG.
  • Pre-plating equipment 40 may be arranged.
  • the Ni pre-plating facility 40 includes a Ni plating cell that stores a Ni plating bath.
  • the Ni plating process is carried out by electroplating.
  • the hot-dip galvanizing line facility 1 of FIGS. 1 and 5 includes an annealing furnace 20 and a temper rolling mill 30.
  • the hot-dip galvanizing line facility 1 may not include the annealing furnace 20. Further, the hot-dip galvanizing line facility 1 may not have the temper rolling mill 30. The hot-dip galvanizing line facility 1 only needs to include at least the hot-dip galvanizing facility 10. The annealing furnace 20 and the temper rolling mill 30 may be disposed as needed. Moreover, the hot dip galvanization line installation 1 may be equipped with the pickling installation for pickling a steel plate upstream from the hot dip galvanization installation 10, and other facilities other than the annealing furnace 20 and the pickling installation. May be provided. The hot dip galvanizing line facility 1 may further include other facilities other than the temper rolling mill 30 downstream of the hot dip galvanizing facility 10.
  • Fe dissolves from the steel sheet S immersed in the hot dip galvanizing bath 103 into the hot dip galvanizing bath 103.
  • the dissolved Fe reacts with Al and / or Zn in the hot-dip galvanizing bath 103 to form dross.
  • top dross floats on the liquid surface in the hot dip galvanizing bath 103.
  • the bottom dross of the generated dross sinks to the bottom of the molten zinc pot 101 and deposits.
  • bottom dross deposits on the bottom of the molten zinc pot 101.
  • the bottom dross deposited on the bottom of the molten zinc pot 101 is wound up in the hot dip galvanizing bath 103 by the accompanying flow of the steel plate S generated near the lower part of the sink roll 107 and floats in the hot dip galvanization bath 103.
  • Bottom dross floating in the hot-dip galvanizing bath 103 adheres to the surface of the steel plate S in the vicinity of the sink roll 107. There may be a dross defect where a bottom dross adheres to the surface of the steel plate S.
  • a dross defect occurs, uneven plating occurs on the plating surface, and the quality of the appearance of the alloyed galvanized steel sheet or the galvanized steel sheet is degraded. Furthermore, a local battery is likely to be formed in the dross defect portion of the steel sheet surface, and the corrosion resistance of the alloyed galvanized steel sheet or the galvanized steel sheet is reduced.
  • the galvanizing treatment method of this embodiment sequentially determined with the lapse of the 2-phase dross amount ⁇ of dross in the molten zinc plating bath 103 times. Then, the operation conditions of the hot-dip galvanizing treatment are adjusted based on the amount of ⁇ two- phase dross in the hot-dip galvanizing bath 103 to reduce the amount of ⁇ two- phase dross in the hot-dip galvanizing bath.
  • gamma 2 phase dross content in molten zinc plating bath 103 by adjusting the operating conditions of the galvanizing treatment to reduce the gamma 2 phase dross, gamma 2 phase dross in the molten zinc plating bath Reduce the amount below a certain amount (threshold). This suppresses the occurrence of dross defects in the alloyed galvanized steel sheet or the galvanized steel sheet.
  • the hot-dip galvanizing method of the present embodiment can also be applied to a method of producing a galvannealed steel sheet (GA), and can also be applied to a method of producing a hot-dip galvanized steel sheet (GI).
  • GA galvannealed steel sheet
  • GI hot-dip galvanized steel sheet
  • hot dip galvanization line equipment is used.
  • the hot-dip galvanizing line equipment has, for example, the configuration shown in FIG. 1 and FIG.
  • the hot-dip galvanizing line equipment used for the hot-dip galvanizing treatment method of the present embodiment may be the equipment shown in FIG. 1 or 5 or may be further added to the equipment shown in FIG. Other configurations may be added.
  • the steel type and size (plate thickness, plate width, etc.) of the steel plate (base steel plate) used for the hot dip galvanizing treatment of the present embodiment are not particularly limited.
  • the steel sheet is an alloyed galvanized steel sheet or a galvanized steel sheet according to the alloyed galvanized steel sheet to be manufactured or each mechanical property (for example, tensile strength, workability, etc.) required for the galvanized steel sheet.
  • a well-known steel plate applied to the above may be used. You may utilize the steel plate used for a car outer plate as a steel plate (base material steel plate) used for a hot dip galvanization process.
  • the steel plate (base steel plate) used for the hot-dip galvanizing treatment of the present embodiment may be a hot-rolled steel plate or a cold-rolled steel plate.
  • the following steel plates are used as base steel plates.
  • (A) Hot-rolled steel sheet that has been pickled (b) Hot-rolled steel sheet that has been subjected to Ni pre-plating treatment and has a Ni layer formed on the surface after being pickled (c) Cold-rolled that has been annealed Steel sheet (d) Cold-rolled steel sheet which has been subjected to Ni pre-plating treatment and then Ni layer is formed on the surface after annealing treatment.
  • the above (a) to (d) are used for the hot-dip galvanization treatment of this embodiment.
  • the steel plates used for the hot-dip galvanizing treatment of the present embodiment are not limited to the above (a) to (d).
  • the hot-rolled steel plate or the cold-rolled steel plate subjected to the treatment other than the above (a) to (d) may be a steel plate used for the hot dip galvanization treatment.
  • the main component of the hot dip galvanizing bath is Zn.
  • the hot-dip galvanizing bath further contains Al in addition to Zn. That is, the hot dip galvanization bath utilized for the hot dip galvanization processing method of this embodiment is a plating solution which contains Al of specific concentration, and remainder becomes from Zn and impurities. If the hot-dip galvanizing bath contains a specific concentration of Al, excessive reaction between Fe and Zn in the bath can be suppressed, and the steel plate immersed in the hot-dip galvanizing bath and non-uniform Zn The progress of the alloy reaction can be suppressed.
  • the preferred Al concentration (more specifically, the Free-Al concentration) in the hot dip galvanization bath is 0.100 to 0.159% by mass.
  • the Al concentration in the hot-dip galvanizing bath means the Al concentration (mass%) dissolved in the hot-dip galvanizing solution, and means the so-called Free-Al concentration. If the Al concentration in the hot-dip galvanizing bath is in the range of 0.100 to 0.159% by mass, generation of other pattern defects different from dross defects can be suppressed, and further, alloyed molten zinc In the alloying process in the manufacturing process of a plated steel plate, it can suppress that an unalloyed thing generate
  • the hot-dip galvanizing bath according to the present embodiment is a plating bath which contains Zn as a main component and further contains Al.
  • the hot-dip galvanizing bath may further contain 0.020 to 0.100% by mass of Fe eluted from equipment in the bath and a steel plate. That is, the Fe concentration (mass%) dissolved in the hot dip galvanizing bath is, for example, 0.020 to 0.100 mass%.
  • the concentration of Fe dissolved in the hot dip galvanization bath is not limited to the above numerical range.
  • FIG. 6 is a flow chart showing steps of the hot-dip galvanizing method of the present embodiment.
  • the hot-dip galvanizing treatment method of the present embodiment includes a sampling step (S1), a two- phase dross amount determination step (S2), and an operation condition adjustment step (S3). Each step will be described in detail below.
  • sample collection process (S1) In the sampling step (S1), a part of the plating solution is sampled as a sample from the hot dip galvanizing bath. In the sample collecting step (S1), samples are collected over time. “To take samples over time” means to take samples each time a specific time has elapsed. The specific time (the period between the time a sample is taken and the time the next sample is taken) may or may not be constant. For example, samples may be taken every hour. In addition, one sample may be taken one hour after the next sample is taken, and another sample may be taken after another 30 minutes. The specific time is not particularly limited.
  • the amount of sampling from the hot dip galvanizing bath is not particularly limited.
  • the sample collection volume is not particularly limited.
  • the sampled amount is, for example, 100 to 400 g.
  • the collected sample may be brought into contact with a metal having a high thermal conductivity at room temperature, and the sample may be rapidly cooled to room temperature and solidified.
  • the metal at normal temperature with high thermal conductivity is, for example, copper.
  • the sampling position in the hot dip galvanization bath is not particularly limited.
  • a sample is taken at the uppermost region D1 in hot dip galvanizing bath 103.
  • the sample may be taken in the middle region D2 or in the lowermost region D3.
  • Gamma 2 phase dross content in samples taken in each area D1 ⁇ D3 are different.
  • the collection position of the sample is not particularly limited. As shown in FIGS.
  • a direction parallel to the width direction of the steel plate S is defined as a width direction W
  • a depth direction of the hot-dip galvanizing bath 103 is a depth direction D
  • a direction perpendicular to the width direction W and the depth direction D is defined as a length direction L.
  • samples are taken over time from a specific width range in the width direction W, a specific depth range in the depth direction D, and a specific region partitioned by a specific length range in the length direction L. Collect In short, samples are taken over time from the same position (within a specific area) in the hot dip galvanizing bath 103.
  • a sample is taken from the area as close to the sink roll 107 as possible.
  • a sample is taken from within a specific depth range D 107 from the upper end to the lower end of the sink roll 107.
  • the specific depth range D1 is set as the range D107 from the upper end to the lower end of the sink roll 107.
  • the two- phase dross is likely to adhere to the surface of the steel sheet S in the vicinity of the sink roll 107. Therefore, gamma 2 phase dross of the sink roll 107 near, as an index of suppressing dross defects are most effective.
  • a sample is taken from depth range D107.
  • most steel sheets based on the samples taken from easily range adhered to the surface of S for determining the gamma 2 phase dross amount it is possible to further enhance the correlation between gamma 2 phase dross phase and dross defects.
  • a test piece for two- phase dross observation is prepared from the sample collected in the sample collection step (S1).
  • An example of a two- phase dross observation test piece is a rectangular solid (platelet shape) having a surface (test surface) capable of securing an observation field of view of 15 mm ⁇ 15 mm and a thickness of 0.5 mm.
  • a full field of view is observed in the above observation field of view (15 mm ⁇ 15 mm) using an optical microscope with a predetermined magnification or a scanning electron microscope (SEM) to identify dross in the entire field of view.
  • the contrast in the field of view can identify the dross, and the contrast can distinguish between top dross and bottom dross.
  • FIG. 7 shows an example of a photographic image of a part of the observation field of the sample collected in the sample collecting step (S1).
  • a hot-dip galvanized mother phase 200, top dross 100T, and bottom dross 100B are observed.
  • Top dross 100T has lower brightness (darker) than the mother phase 200 and bottom dross 100B.
  • bottom dross 100 B has lower brightness (darker) than parent phase 200 and higher brightness (brighter) than top dross 100 T.
  • top dross and bottom dross can be distinguished based on the contrast.
  • the dross that has been identified in the observation field of view (15 mm ⁇ 15 mm)
  • the bottom dross conducted composition analysis using EPMA, specifying the gamma 2 phase dross.
  • the types of dross in the observation field of view may be specified.
  • Gamma 2 phase dross content in molten zinc plating bath can be determined in a variety of indicators.
  • the number of gamma 2 phase dross per predetermined area may be a gamma 2 phase dross amount.
  • the predetermined area is not particularly limited, and may be, for example, the entire area of the observation field of view or a unit area (mm 2 ).
  • the observation field of view was set to 15 mm ⁇ 15 mm
  • the number of gamma 2 phase dross in the (number / 225 mm 2) may be gamma 2 phase dross amount.
  • the following methods obtaining the number of gamma 2 phase dross in the observation field.
  • the circle equivalent diameter ( ⁇ m) of the specified 2 phase dross is determined.
  • the diameter when the area of each ⁇ 2 phase dross in the above-mentioned observation visual field is converted into a circle is defined as a circle equivalent diameter ( ⁇ m).
  • the equivalent circle diameter ( ⁇ m) of the specified 2 phase dross is determined by known image processing. As described above, fine dross less than 10 ⁇ m is less likely to form a dross defect. Therefore, among the gamma 2 phase dross in the above-mentioned observation field, equivalent circle diameter determined the number of the above gamma 2 phase dross 10 [mu] m. Then, the number of gamma 2 phase dross amount equivalent circle diameter 10 ⁇ m or more gamma 2 phase dross in the observation field and (pieces / 225 mm 2) to.
  • the circle number of equivalent diameter 10 ⁇ m or more gamma 2 phase dross in the observation field may be defined as gamma 2 phase dross amount.
  • an observation visual field is not limited to said area
  • region (15 mm x 15 mm 225 mm ⁇ 2 >).
  • gamma 2 phase dross amount is not limited to the number of gamma 2 phase dross in the observation field.
  • the number of gamma 2 phase dross in the observation field the field area in divided by unit area (1 mm 2) number per (pieces / mm 2) may be gamma 2 phase dross amount.
  • Another index may be used as the amount of ⁇ two- phase dross in the hot-dip galvanizing solution.
  • the bottom dross (the gamma 2 phase dross, the [delta] 1 phase dross, and each ⁇ phase dross) determining the area of, the area of each gamma 2 phase dross.
  • the ratio of the total area of the gamma 2 phase dross to the total area of the bottom dross may be gamma 2 phase dross amount.
  • the ratio of the total area of the gamma 2 phase dross may be gamma 2 phase dross amount.
  • the total area of the gamma 2 phase dross in the above field may be gamma 2 phase dross amount.
  • the bottom-dross (gamma 2 phase dross, [delta] 1 phase dross, and, zeta phase dross) measuring the peak intensity of.
  • the ratio of the peak intensity of each bottom dross of the sum of the peak intensities (that is, peak intensity of gamma 2 phase dross, the peak intensity of the [delta] 1 phase dross, and, zeta sum of the peak amplitude of the phase dross) for, gamma 2 phase dross It may be a two- phase dross amount.
  • the peak intensity itself of the gamma 2 phase dross obtained by carrying out the X-ray diffraction measurement with respect to the test surface may be gamma 2 phase dross amount.
  • the two-phase dross gamma by X-ray diffraction measurement and gamma 1-phase dross is not easy to be clearly distinguished.
  • gamma 1-phase dross is considered hardly existent.
  • the target at the time of X-ray diffraction measurement utilizes Co dry bulb, for example. By other methods than those described above, it may be determined gamma 2 phase dross amount.
  • the amount of ⁇ two- phase dross in the hot dip galvanizing bath is determined using the sample collected in the sample collection step (S1).
  • the samples were taken by determining the gamma 2 phase dross amount each time taking samples, it is possible to grasp temporal changes in the gamma 2 phase dross content in molten zinc plating bath .
  • the operation conditions of the hot dip galvanizing treatment are adjusted based on the amount of the two- phase dross in the hot dip galvanizing bath. Specifically, when the obtained gamma 2 phase dross amount is excessively large, so as to reduce the gamma 2 phase dross amount of the molten galvanizing bath is adjusted (changed) the operating conditions. If the amount of 2 phase dross obtained is appropriate, the operating conditions may be maintained as it is.
  • Method of adjusting operating conditions if adjustment is gamma 2 phase dross content in molten zinc plating bath is not particularly limited. Specifically, the method of adjusting the operating conditions is not particularly limited as long as the amount of ⁇ two- phase dross in the hot dip galvanizing bath can be reduced.
  • At least one of the following (A) to (C) is carried out as a method of adjusting the operating conditions.
  • A) Adjust the bath temperature of the hot dip galvanizing bath.
  • B) Adjust the Al concentration of the hot dip galvanizing bath.
  • C) Adjust the conveyance speed of the steel plate in the hot dip galvanization facility.
  • the bath temperature of the hot dip galvanization bath may be raised.
  • gamma 2 phase dross phase transformation to a fine [delta] 1 phase dross.
  • fine [delta] 1 phase dross although increased, gamma 2 phase dross is reduced. Therefore, the occurrence of dross defects is suppressed.
  • raising the bath temperature raises the energy consumption rate. Therefore, it is not necessary to excessively increase the bath temperature if the amount of dross phase 2 phase is small.
  • the amount of ⁇ two- phase dross in the hot dip galvanization bath can be adjusted. Specifically, by raising the bath temperature of the hot dip galvanizing bath, the amount of ⁇ two- phase dross in the hot dip galvanizing bath can be reduced.
  • the gamma 2 phase dross content in molten zinc plating bath is excessively high, by adjusting the Al concentration in molten zinc plating bath be higher than 0.140%, gamma 2 phase dross in the molten zinc plating bath The amount can be reduced.
  • the Al concentration in the hot dip galvanizing bath is 0.140% or less, if the Al concentration is lowered, there is a high possibility that the 2 phase dross transforms into the ⁇ 1 phase dross. Therefore, when the Al concentration is 0.140% or less, the amount of ⁇ two- phase dross can be reduced by adjusting to reduce the Al concentration in the hot dip galvanizing bath.
  • only one of the operating conditions may be adjusted based on the determined amount of 2 phase dross, or two or more of the operating conditions may be adjusted. May be For example, if the amount of 2 phase dross is excessively high, the operating conditions of (A) and (B) may be adjusted. Specifically, even if the amount of 2 phase dross is excessively large, the bath temperature of the hot dip galvanization bath is increased, and if the Al concentration of the hot dip galvanization bath is 0.140% or less, the Al concentration is lowered. Good. In addition, when the amount of 2 phase dross is excessively large, the operating conditions of (A) and (C) may be adjusted.
  • the bath temperature of the hot dip galvanizing bath may be increased, and the conveyance speed of the steel plate in the hot dip galvanization facility may be reduced.
  • the operating conditions of (B) and (C) may be adjusted. Specifically, when the amount of 2 phase dross is excessively large, the Al concentration is lowered when the Al concentration of the hot dip galvanizing bath is 0.140% or less, and the conveyance speed of the steel plate in the hot dip galvanization facility is May be late. Further, when the amount of 2 phase dross is excessively large, all the operating conditions of (A) to (C) may be adjusted.
  • the temperature of the hot-dip galvanizing bath is increased when the amount of the two- phase dross is excessively large, and the Al concentration is decreased when the Al concentration of the hot-dip galvanizing bath is 0.140% or less,
  • the conveyance speed of the steel plate in the hot dip galvanization facility may be reduced.
  • Two- phase dross amount is not excessive, and if appropriate, the operating conditions (A) to (C) may be maintained as they are.
  • a threshold may be provided as a judgment index as to whether or not the two- phase dross amount obtained in the two- phase dross amount determining step (S2) is appropriate.
  • the operating conditions may be adjusted by comparing the obtained amount of 2 phase dross with the threshold value. For example, the operating conditions may be changed or may be maintained without change depending on whether or not the calculated amount of two- phase dross exceeds a threshold value.
  • the obtained gamma 2 phase dross amount exceeds the threshold value, it is judged that the gamma is excessively large biphasic dross amount, to change the operating conditions, gamma 2 phase dross content in molten zinc plating bath from the present time Adjust operating conditions to reduce Preferably, if obtained gamma 2 phase dross amount exceeds the threshold, gamma 2 phase dross amount to be equal to or less than the threshold value, to change the operating conditions. On the other hand, the obtained gamma 2 phase dross amount may not exceed the threshold, gamma 2 phase dross content in molten zinc plating bath, it is determined that the sufficiently low to maintain the operating condition as is.
  • Gamma 2 phase number of dross per predetermined area for example, as described above, when the number of gamma 2 phase dross amount of gamma 2 phase dross in the observation field, when converted to the number per unit area (1 mm 2)
  • gamma 2 phase dross amount determining step (S2) by the determined gamma 2 phase dross weight threshold (10) greater number than, i.e., 0.045 in the case of converted unit area (1 mm 2) If a number exceeding pieces / mm 2, it is determined that the gamma is excessively large biphasic dross amount, gamma 2 phase dross content in molten zinc plating bath to reduce and adjust the operating conditions.
  • the gamma 2 phase dross amount obtained by gamma 2 phase dross amount determining step (S2) is greater than the threshold value (10), i.e., 2-phase dross amount gamma obtained is converted in a unit area
  • the threshold value (10 pieces) that is, 0.045 pieces / mm 2 when converted to unit area
  • the above-mentioned (A) ⁇ (C at least one by implementing the operating conditions), reducing the gamma 2 phase dross amount.
  • the temperature of the hot dip galvanizing bath is increased to reduce the amount of double- phase dross.
  • to reduce the two-phase dross amount ⁇ enhances than 0.140% of Al content of molten zinc plating bath.
  • the Al content of the galvanizing bath is below 0.140%, to reduce the Al content to reduce the gamma 2 phase dross amount. Further, for example, to reduce late to gamma 2 phase dross amount the conveying speed of the steel sheet in the galvanizing.
  • the number of gamma 2 phase dross per predetermined area may the less does not particularly define the lower limit.
  • the Al concentration X in the hot-dip galvanizing bath is preferably 0% by mass, based on the amount of 2 phase dross obtained in the 2 phase dross amount determining step (S2).
  • the Al concentration X and the bath temperature T of the hot-dip galvanizing bath are expressed by the formula (1) when adjusted in the range of 100 to 0.159% and the Al concentration X is 0.100 to 0.140 mass%.
  • the hot-dip galvanizing bath is adjusted to 469.degree. C. or more when the Al concentration X is in the range of 0.140 to 0.159 mass%.
  • FIG. 8 is a view showing the relationship between the Al concentration X (mass%) in the hot-dip galvanizing bath, the bath temperature T (° C.) of the hot-dip galvanizing bath, and the dross stabilized in the hot-dip galvanizing bath .
  • the vertical axis in FIG. 8 indicates the Al concentration X (mass%), and the horizontal axis indicates the bath temperature T (° C.).
  • FIG. 8 corresponds to a metastable phase diagram of top dross, ⁇ two- phase dross, and ⁇ one- phase dross in a hot-dip galvanizing bath.
  • X 0.002488 ⁇ T- 1.0266 is when Al concentration X in the molten zinc plating bath of 0.100 ⁇ 0.140%, ⁇ 2 phase dross [delta] 1-phase It corresponds to the boundary (phase transformation line) that is transformed to dross. If the Al concentration X in the hot dip galvanization bath is 0.100 to 0.140% and the Al concentration X is higher than the right side of the formula (1), the chemical composition of the hot dip galvanization bath is ⁇ 1 -phase dross Two- phase dross is more stable than ⁇ two- phase dross.
  • the chemical composition of the hot-dip galvanizing bath falls within the ⁇ two- phase dross stable region in FIG.
  • the Al concentration X in the hot dip galvanizing bath is 0.100 to 0.140%
  • the ⁇ 1 phase dross in the hot dip galvanizing bath is likely to be transformed to the hot 2 phase dross. Therefore, in the hot-dip galvanizing bath, a two- phase dross tends to be generated.
  • the Al concentration X in the hot dip galvanizing bath is 0.100 to 0.140%
  • the Al concentration X and the bath temperature T are as long as the Al concentration X is not more than the right side of the equation (1).
  • the chemical composition of the hot-dip galvanizing bath is more ⁇ 1 phase than the two- phase dross.
  • the dross is in a more stable state.
  • the ⁇ two- phase dross in the hot-dip galvanizing bath tends to be transformed into the ⁇ 1 phase dross. Accordingly, the galvanizing bath, and gamma 2 phase dross reduction can stably suppress the gamma 2 phase dross.
  • the chemical composition of the hot-dip galvanizing bath completely separates from the inside of the two- phase dross stability region and falls within the top dross stability region. Therefore, when the Al concentration X in the galvanizing bath is 0.140 ultra-0.159%, if the bath temperature T of the molten zinc plating bath and 469 ° C. or higher, gamma 2 phase in the molten zinc plating bath dross is reduced, it can be stably suppressed gamma 2 phase dross.
  • the Al concentration in the hot-dip galvanizing bath is adjusted in the range of 0.100 to 0.159% by mass%, and the Al concentration
  • the Al concentration X and the bath temperature T of the hot dip galvanizing bath are adjusted to satisfy the formula (1), and the Al concentration X is more than 0.140 to 0.1.
  • the bath temperature T of the hot dip galvanizing bath is adjusted to 469 ° C. or more when it is 159% by mass, the amount of ⁇ two- phase dross can be stably reduced in the hot dip galvanization bath.
  • the above-described adjustment of the Al concentration X and the bath temperature T may be performed when the amount of dross phase 2 loss exceeds the threshold value.
  • the Al concentration X in the hot dip galvanizing bath is adjusted in the range of 0.100 to 0.159% by mass%, and the Al concentration X is 0
  • the concentration is 100 to 0.140 mass%
  • the Al concentration X and the bath temperature T of the hot-dip galvanizing bath are adjusted to satisfy the formula (1), and the Al concentration X is more than 0.140 to 0.159 mass% If, for example, the bath temperature T of the hot-dip galvanizing bath is adjusted to 469 ° C. or more, the amount of dross two- phase dross can be stably reduced.
  • the temperature (bath temperature) of the hot-dip galvanizing bath in the above-described hot-dip galvanizing method is preferably 440 to 500 ° C.
  • the dross in the hot-dip galvanizing bath mainly phase-transforms into top dross (Fe 2 Al 5 ), ⁇ two- phase dross, and ⁇ one- phase dross according to the bath temperature and the Al concentration.
  • gamma 2 phase dross tends to generate at low bath temperature region.
  • [delta] 1 phase dross is likely to generate at a bath temperature is higher region than generation region of the gamma 2 phase dross.
  • the bath temperature of the hot dip galvanizing bath is 500 ° C. or less, it can be suppressed that Zn evaporates and becomes fume. When fumes are generated, the fumes adhere to the steel plate and easily become surface defects (fumed soot).
  • the preferable lower limit of the hot dip galvanization bath is 460 ° C, more preferably 465 ° C, and still more preferably 469 ° C.
  • the upper limit of the hot-dip galvanizing bath is preferably 490 ° C, more preferably 480 ° C, and still more preferably 475 ° C.
  • top dross is likely to be generated in a region where the Al concentration is higher than the formation region of ⁇ 2 -phase dross and the generation region of ⁇ 1 -phase dross.
  • a sample is taken from the hot-dip galvanizing bath (sampling step (S1)) to determine the amount of ⁇ two- phase dross in the hot-dip galvanizing bath ( ⁇ 2 Phase dross amount determination step (S2)). Then, the operation conditions of the hot-dip galvanizing process are adjusted based on the amount of ⁇ two- phase dross in the hot-dip galvanizing bath (operation condition adjusting step (S3)).
  • the hot dip galvanization processing method of the above-mentioned this embodiment is applicable to the manufacturing method of a galvannealed steel plate (GA).
  • the manufacturing method of the galvannealed steel plate according to the present embodiment includes a galvanizing process and an alloying process.
  • the hot dip galvanizing treatment step the hot dip galvanizing treatment method described above is performed on the steel plate to form a hot dip galvanizing layer on the surface of the steel plate.
  • the alloying treatment step the alloying treatment is performed using the alloying furnace 111 shown in FIG. 2 on the steel plate having the hot-dip galvanized layer formed on the surface in the hot-dip galvanizing treatment step. It is sufficient to apply a known method for the alloying treatment.
  • An alloyed galvanized steel sheet can be manufactured by the above manufacturing process.
  • the hot-dip galvanizing method of the present embodiment described above is adopted. That is, based on the gamma 2 phase dross amount, reducing the gamma 2 phase dross by adjusting the operating conditions of the galvanizing process. Therefore, it can suppress that a dross defect generate
  • the manufacturing method of the alloying hot-dip galvanized steel sheet of this embodiment may also include a hot-dip galvanization treatment process and other manufacturing processes other than the alloying treatment process.
  • the manufacturing method of the alloyed hot-dip galvanized steel sheet of the present embodiment may include a temper rolling process of performing temper rolling using a temper rolling mill 30 shown in FIG. 1 after the alloying process. .
  • the appearance quality of the surface of the alloyed galvanized steel sheet can be further enhanced.
  • the hot dip galvanization processing method of the above-mentioned this embodiment is also applicable to the manufacturing method of a hot dip galvanized steel plate (GI).
  • the method of manufacturing a hot-dip galvanized steel sheet according to the present embodiment includes a hot-dip galvanizing process step.
  • the hot dip galvanizing treatment step the hot dip galvanizing treatment method described above is performed on the steel plate to form a hot dip galvanizing layer on the surface of the steel plate.
  • the hot-dip galvanizing method of the present embodiment described above is employed. That is, based on the gamma 2 phase dross amount, reducing the gamma 2 phase dross by adjusting the operating conditions of the galvanizing process. Therefore, it can suppress that a dross defect generate
  • the manufacturing method of the hot-dip galvanized steel sheet of this embodiment may also contain other manufacturing processes other than a hot dip galvanization process process.
  • the method for manufacturing a hot-dip galvanized steel sheet of the present embodiment may include a temper rolling process of performing temper rolling using a temper rolling mill 30 shown in FIG. 1 after the hot dip galvanizing process step. In this case, the appearance quality of the surface of the hot-dip galvanized steel sheet can be further enhanced.
  • the hot-dip galvanizing method of the present embodiment will be more specifically described by way of examples.
  • the conditions in the examples are an example of conditions adopted to confirm the feasibility and effect of the present invention. Therefore, the hot dip galvanization processing method of this embodiment is not limited to this one example of conditions.
  • the hot-dip galvanizing method was carried out using a hot-dip galvanizing facility having the same configuration as that shown in FIG. Specifically, the Al concentration X (mass%) and the bath temperature T (° C.) of the hot-dip galvanizing bath were adjusted as described in Table 1.
  • a steel plate a steel plate for a car outer plate (cold rolled steel plate) was used.
  • a sample was taken from within a specific depth range D107 from the upper end to the lower end of the sink roll 107. More specifically, in the hot-dip galvanizing bath 103 of FIG. 2, the specific depth range D107 in the depth D direction, the specific width range in the width direction W, and the specific length range in the length direction L A sample was taken from within a specific area (hereinafter referred to as a sampling area) to be partitioned. About 400 g of samples were taken from the same sampling area as described above for any test number. The collected sample was cooled to normal temperature.
  • the chemical composition of the hot-dip galvanizing bath of each test number was measured using an ICP emission spectrometer using the sample after cooling.
  • the Fe concentration in the hot-dip galvanizing bath was in the range of 0.020 to 0.050% by mass in any of the test numbers.
  • the bath temperature T of the hot-dip galvanizing bath should be constant at the value shown in Table 1, and the Al concentration X of the hot-dip galvanizing bath be the concentration shown in Table 1 It adjusted by adding Al suitably to.
  • the conveyance speed of the steel plate in the hot dip galvanization process was made constant in any test number.
  • Table 1 also shows the value of the right side of Formula (1).
  • the value on the right side of Formula (1) is not relevant because it is not relevant, and is described as "-" in the "Formula (1) Right Side” column in Table 1.
  • the Al concentration X is less than 0.100% (Test No. 31) or 0.160% or more (Test No. 32), as described above, the pattern defect (Test No. 31) or unalloyed Since (Test No. 32) was confirmed, the value on the right side of Formula (1) was regarded as unimportant, and was described as “-” in the “Formula (1) Right side” column of Table 1.
  • samples were taken from the hot dip galvanizing bath at the operating conditions shown in Table 1. Specifically, a sample of about 400 g was collected from the above-described sample collection area. From the collected samples were produced gamma 2 phase dross test piece for observation. The test surface of the test piece for two- phase dross observation was 15 mm ⁇ 15 mm, and the thickness was 0.5 mm. A full field of view was observed with the field of view (15 mm ⁇ 15 mm) of the test surface using a 100 ⁇ SEM, and a dross (top dross, bottom dross) was identified based on the contrast.
  • Circle equivalent diameter 10 ⁇ m or more gamma 2 phase number of dross in the observation field of view (number / 225 mm 2), and the gamma 2 phase dross amount.
  • the resulting gamma 2 phase dross amounts shown in Table 1. In the present example, no first- phase dross was observed in any of the test numbers.
  • the alloying treatment was performed under the same conditions as each of the test numbers to produce an alloyed galvanized steel sheet.
  • the surface of the manufactured alloyed galvanized steel sheet was visually observed, and the presence or absence of a dross defect was investigated to evaluate the dross defect.
  • the criteria for dross defect evaluation were as follows.
  • the dross defect can be suppressed by adjusting the operation conditions based on the amount of the second phase dross. And, preferably, when the number of gamma 2 phase dross amount of gamma 2 phase dross per predetermined area, 0.045 in the case where the obtained gamma 2 phase dross amount is converted in the unit area (1 mm 2) pieces / mm It was found that the dross defect can be remarkably suppressed by adjusting the operation conditions in the hot dip galvanizing treatment so that the number becomes 2 or less.
  • the total number of bottom dross of test numbers 16 to 19 and the dross defect evaluation is not correlated with the number of dross defects, and the amount of two- phase dross amount and the number of dross defects Showed higher correlation. Therefore, in order to suppress dross defects, as an index for adjusting the operating conditions, rather than the total number of bottom dross, is better to adopt a gamma 2 phase dross weight it was found to be suitable.
  • the Al concentration in the hot dip galvanization bath is 0.100 to 0.140 mass% (Test Nos. 1 to 23)
  • the Al concentration and the bath temperature of the hot dip galvanization bath satisfy the formula (1) (Test Nos. 2, 5, 6, 9, 10, 14, 15, 19, 20, 23)
  • the evaluation of dross defect was A or B, and the dross defect could be stably suppressed.
  • the Al concentration in the hot-dip galvanizing bath is greater than 0.140 to 0.159% (Test Nos. 24 to 30)
  • the bath temperature is 469 ° C. or higher (Test Nos. 27 and 30)
  • dross The defect evaluation was “A”, and the dross defect could be stably suppressed.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Coating With Molten Metal (AREA)

Abstract

L'invention concerne un procédé de galvanisation par immersion à chaud apte à limiter l'apparition de défauts d'écume. Le procédé de galvanisation par immersion à chaud selon le présent mode de réalisation est utilisé pour la production de tôles d'acier galvanisées par immersion à chaud ou de tôles d'acier allié galvanisées par immersion à chaud. Le procédé de galvanisation par immersion à chaud est pourvu d'une étape de collecte d'échantillon (S1), d'une étape de détermination de quantité d'écume de phase gamma Γ2 (S2), et d'une étape de réglage de condition de fonctionnement (S3). Dans l'étape de collecte d'échantillon (S1), un échantillon est collecté à partir d'un bain de galvanisation par immersion à chaud contenant de l'Al. Dans l'étape de détermination de quantité d'écume de phase gamma Γ2 (S2), la quantité d'écume de phase gamma Γ2 dans l'échantillon collecté est déterminée. Dans l'étape d'ajustement de condition de fonctionnement (S3), les conditions de fonctionnement pour la galvanisation par immersion à chaud sont ajustées sur la base de la quantité d'écume de phase gamma Γ2 déterminée.
PCT/JP2018/047396 2017-12-25 2018-12-21 Procédé de galvanisation par immersion à chaud, procédé de production d'une tôle d'acier allié galvanisée par immersion à chaud à l'aide dudit procédé de galvanisation par immersion à chaud, et procédé de production d'une tôle d'acier galvanisée par immersion à chaud à l'aide dudit procédé de galvanisation par immersion à chaud WO2019131563A1 (fr)

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JP2021042452A (ja) * 2019-09-13 2021-03-18 日本製鉄株式会社 溶融亜鉛めっき鋼板の製造方法、及び、合金化溶融亜鉛めっき鋼板の製造方法
JP2021042450A (ja) * 2019-09-13 2021-03-18 日本製鉄株式会社 溶融亜鉛めっき浴、溶融亜鉛めっき鋼板の製造方法、及び、その溶融亜鉛めっき鋼板の製造方法を用いた合金化溶融亜鉛めっき鋼板の製造方法

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JPH11350096A (ja) * 1998-06-03 1999-12-21 Nkk Corp 表面外観に優れた合金化溶融亜鉛メッキ鋼板の製造方法
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JPH11350096A (ja) * 1998-06-03 1999-12-21 Nkk Corp 表面外観に優れた合金化溶融亜鉛メッキ鋼板の製造方法
JP2010084214A (ja) * 2008-10-02 2010-04-15 Nippon Steel Corp 外観品位に優れた合金化溶融亜鉛めっき鋼板の製造方法

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JP2021042452A (ja) * 2019-09-13 2021-03-18 日本製鉄株式会社 溶融亜鉛めっき鋼板の製造方法、及び、合金化溶融亜鉛めっき鋼板の製造方法
JP2021042450A (ja) * 2019-09-13 2021-03-18 日本製鉄株式会社 溶融亜鉛めっき浴、溶融亜鉛めっき鋼板の製造方法、及び、その溶融亜鉛めっき鋼板の製造方法を用いた合金化溶融亜鉛めっき鋼板の製造方法
JP7252463B2 (ja) 2019-09-13 2023-04-05 日本製鉄株式会社 溶融亜鉛めっき鋼板の製造方法、及び、合金化溶融亜鉛めっき鋼板の製造方法

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