WO2019131562A1 - Procédé de galvanisation par immersion à chaud, procédé de production de tôle d'acier allié galvanisée par immersion à chaud à l'aide d'un procédé de galvanisation par immersion à chaud, et procédé de production de tôle d'acier galvanisée par immersion à chaud à l'aide d'un procédé de galvanisation par immersion à chaud - Google Patents

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

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WO2019131562A1
WO2019131562A1 PCT/JP2018/047395 JP2018047395W WO2019131562A1 WO 2019131562 A1 WO2019131562 A1 WO 2019131562A1 JP 2018047395 W JP2018047395 W JP 2018047395W WO 2019131562 A1 WO2019131562 A1 WO 2019131562A1
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Prior art keywords
hot
dross
dip galvanizing
phase
bath
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PCT/JP2018/047395
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English (en)
Japanese (ja)
Inventor
剛嗣 小西
直人 古川
拓朗 福原
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 CN201880083483.2A priority Critical patent/CN111566251A/zh
Priority to JP2019561677A priority patent/JP6919723B2/ja
Publication of WO2019131562A1 publication Critical patent/WO2019131562A1/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.
  • Such bottom dross-induced surface defects are referred to herein as "dross defects”. Dross defects reduce the appearance of the steel sheet and lower 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 producing an alloyed hot dip galvanized 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 [delta] 1-phase dross amount determining step of determining the [delta] 1 phase dross content in molten zinc plating bath, And an operation condition adjusting step of adjusting the operation condition of the hot dip galvanizing treatment based on the determined ⁇ 1 phase dross amount.
  • the manufacturing method of the alloyed hot-dip galvanized steel sheet according to the present disclosure is a hot-dip galvanization processing step of forming a hot-dip galvanized layer on the surface of the steel sheet by performing the above-described hot-dip galvanization processing method on the steel sheet.
  • 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 a hot-dip galvanized steel sheet according to the present disclosure comprises a hot-dip galvanizing process step of performing the above-described hot-dip galvanizing method on a steel sheet 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. 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.
  • 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 composition and 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 specified 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 ⁇ 2 phase grows faster than the 11 phase in the hot-dip galvanizing bath and tends to have a particle size of more than 10 ⁇ m which causes dross defects. Furthermore, since ⁇ 1 -phase dross is softer than ⁇ 2- phase dross, even if ⁇ 1 -phase dross is coarsened, dross defects are unlikely to occur.
  • 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. Then, [delta] 1 phase dross has been said that the main cause of the conventional dross defects were found to be difficult to form a dross defects.
  • 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
  • dross classified as dross the gamma 2 phase dross
  • [delta] 1 phase dross the gamma 1 phase dross
  • zeta phase dross zeta phase dross
  • the inventors further obtained the following findings.
  • the ⁇ two- phase dross and the ⁇ one- phase dross undergo phase transformation with each other. That is, the condition of the galvanizing treatment, gamma 2 phase dross or phase transformation [delta] 1 phase dross, [delta] 1 phase dross or phase transformation in gamma 2 phase dross. Therefore, among the bottom dross in the molten zinc plating bath, the larger the proportion of [delta] 1 phase dross, relatively, meaning that fewer gamma 2 phase dross content in molten zinc plating bath.
  • the present inventors is conventionally considered the main cause of dross defects, the [delta] 1 phase dross which has been a target to be reduced, unlike the conventional galvanizing treatment to increase dare It has been found that by adjusting the operation conditions of the above, it is possible to reduce the amount of ⁇ two- phase dross in the hot dip galvanizing bath, and as a result, it is possible to suppress the dross defect. And in the hot dip galvanization processing method, it was thought that the above-mentioned operation was practicable by controlling the amount of delta 1 phase dross in a hot dip galvanization bath.
  • the hot-dip galvanizing method of the present embodiment is completed based on an idea reverse to the conventional technical idea, and specifically, it 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 [delta] 1-phase dross amount determining step of determining the [delta] 1 phase dross content in molten zinc plating bath, And an operation condition adjusting step of adjusting the operation condition of the hot dip galvanizing treatment based on the determined ⁇ 1 phase dross amount.
  • 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 samples were obtained using, based on the [delta] 1 phase dross content in molten zinc plating bath, so as to increase the [delta] 1 phase dross amount, galvanized Adjust the operating conditions of the treatment method.
  • the galvanized has a negative correlation with the galvanizing bath, [delta] 1 phase dross amount and gamma 2 phase dross amount. Specifically, if the amount of? 1 phase dross in the hot dip galvanizing bath is large, it means that the amount of? 2 phase dross in the hot dip galvanizing bath is relatively small.
  • the ⁇ 1 phase dross amount in the hot dip galvanizing bath is determined, and the operating conditions are adjusted based on the determined ⁇ 1 phase dross amount to increase the ⁇ 1 phase dross, thereby increasing ⁇ 2 in the hot dip galvanizing bath.
  • the amount of phase dross can be reduced. As a result, the occurrence of dross defects can be suppressed.
  • the above-mentioned ⁇ 1 -phase dross amount is, for example, a ratio of the total amount of ⁇ 1 -phase dross to the total amount of bottom dross.
  • the total amount may be the total number or the total area.
  • the total amount of bottom dross is, gamma 2 phase dross, [delta] 1 phase dross, and means the total amount of the ⁇ phase dross.
  • ⁇ 1- phase dross is considered not to exist as mentioned above, so it is not included in the total amount (total number or total area) of bottom dross.
  • the hot-dip galvanizing method of [2] is the hot-dip galvanizing method according to [1], and In the ⁇ 1 phase dross determination process, Using the collected samples, the number ratio of ⁇ 1 -phase dross to the total number of bottom dross is determined as ⁇ 1 -phase dross amount.
  • the hot-dip galvanizing method of [3] is the hot-dip galvanizing method according to [1] or [2], and In the operating condition adjustment process, Based on the [delta] 1 phase dross amount calculated to increase at least one to implement, [delta] 1 phase dross amount of (A) and (B).
  • any of the above (A) and (B) is an effective operating conditions to cause phase transformation of the gamma 2 phase dross [delta] 1 phase dross. Therefore, by increasing the at least one implemented [delta] 1 phase dross based on [delta] 1 phase dross amount determined (A) and (B), reduce the gamma 2 phase dross content in molten zinc plating bath And can suppress dross defects.
  • 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 obtained ⁇ 1 -phase dross amount is less than the threshold value, the operation conditions of the hot dip galvanizing treatment are adjusted to increase the ⁇ 1 -phase dross.
  • whether to change the operating conditions can be readily determined based on the [delta] 1-phase dross amount and the threshold value. For example, when the obtained ⁇ 1 -phase dross amount is less than the threshold value, the operating conditions can be adjusted so that the ⁇ 1 -phase dross amount increases. More preferably, the obtained [delta] 1 phase dross amount when less than the threshold, [delta] 1 phase dross amount so that the above threshold value, adjusting the operating conditions of the galvanizing process.
  • the hot-dip galvanizing method of [5] is the hot-dip galvanizing method according to [4], and In the ⁇ 1 phase dross determination process, Using the collected sample, the number ratio of ⁇ 1 -phase dross to the total number of bottom dross is determined as ⁇ 1 -phase dross amount, In the operating condition adjustment process, When the determined ⁇ 1 -phase dross amount is less than 95.00%, the operation conditions of the hot dip galvanizing treatment are adjusted to increase the ⁇ 1 -phase dross.
  • 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, Adjust the Al concentration in the hot-dip galvanizing bath within the range of 0.100 to 0.150 mass%, and When the Al concentration in the hot dip galvanization bath is defined as X (mass%) and the bath temperature in the hot dip galvanization bath is defined as T (° C.), the Al concentration and the bath temperature satisfy the equation (1) Adjust to X ⁇ 0.002488 ⁇ T-1.0266 (1)
  • the galvanizing method of [7] is It is the hot dip galvanization processing method of any one of [1]-[6], Comprising: In the hot-dip galvanizing pot in which the hot-dip galvanizing bath is stored, a sink roll is arranged to contact the steel strip immersed in the hot-dip galvanizing bath to turn the traveling direction of the steel strip upward, In the sample collection process, A sample is taken from the depth range from the upper end to the lower end of the sink roll in the hot dip galvanizing bath in the hot dip zinc pot.
  • the sample is taken from the same depth area as the sink roll. Therefore, the correlation between the ⁇ 1 -phase dross amount and the dross defect can be further enhanced.
  • the manufacturing method of the galvannealed steel sheet of [8] 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 [7] 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 manufacturing method of the hot-dip galvanized steel sheet of [9] is The method according to any one of [1] to [7] is carried out on a steel plate to form a hot dip galvanizing layer on the surface of the steel plate.
  • 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 entrance side to the exit side of the steel plate S, 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 ⁇ 1 -phase dross and the ⁇ 2- phase dross undergo phase transformation with each other. That, [delta] 1 phase dross is phase transformation gamma 2 phase dross, gamma 2 phase dross is phase transformation [delta] 1 phase dross. Therefore, in the hot dip galvanizing bath, the ⁇ 1 phase dross amount and the negative 2 phase dross amount have a negative correlation, and if the ⁇ 1 phase dross amount in the hot dip galvanizing bath is large, it is in the hot dip galvanization bath ⁇ 2 phase means that the amount of dross is relatively small.
  • the amount of ⁇ 1 -phase dross of the dross in the hot-dip galvanizing bath 103 is determined. Then, based on the ⁇ 1 phase dross amount in the hot dip galvanizing bath 103, the operation conditions of the hot dip galvanization treatment are adjusted to increase the ⁇ 1 phase dross amount.
  • the [delta] 1 phase dross content in molten zinc plating bath as a result, it is possible to suppress the relatively gamma 2 phase dross amount. As a result, it is possible to suppress 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 the equipment shown in FIG. 1 or 5 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 0.150% 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 0.150% 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 is generated.
  • 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.
  • galvanizing treatment method of this embodiment comprises a sampling step (S1), and [delta] 1 phase dross amount determining step (S2), and operating conditions adjusting 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 sampling amount is not particularly limited as long as the ⁇ 1 -phase dross amount in the hot-dip galvanizing bath can be determined in the ⁇ 1 -phase dross amount determining step (S2) of the next step.
  • 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.
  • the amount of ⁇ 1 -phase dross in the samples collected in each of the regions D1 to D3 is 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 is defined as a 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, the ⁇ 1 -phase dross amount in the vicinity of the sink roll 107 is most effective as an index for suppressing the dross defect.
  • a sample is taken from depth range D107.
  • the amount of ⁇ 1 -phase dross is determined based on a sample collected from a range that is most likely to adhere to the surface of the steel sheet S, so the correlation between the ⁇ 1 -phase dross phase and the dross defect can be further enhanced.
  • [ ⁇ 1- phase dross determination process (S2)] In [delta] 1-phase dross amount determining step (S2), with samples taken to determine the [delta] 1 phase dross content in molten zinc plating bath.
  • the method of determining the ⁇ 1 -phase dross amount using a sample is not particularly limited, and various methods can be considered.
  • a test piece for ⁇ 1 -phase dross observation is prepared from the sample collected in the sample collection step (S1).
  • An example of the ⁇ 1 -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.
  • composition analysis using EPMA is performed on each bottom dross to specify ⁇ 1 -phase dross.
  • the crystal structure analysis using a TEM may be further performed on each bottom dross to identify ⁇ 1 -phase dross in the observation field of view.
  • the type of each dross in the field of view can be determined by performing compositional analysis and / or crystal structure analysis using TEM for each dross without distinguishing top dross and bottom dross by contrast.
  • dross, gamma 2 phase dross, [delta] 1 phase dross and may identify the ⁇ phase dross).
  • [Delta] 1 Phase dross content in molten zinc plating bath can be determined in a variety of indicators. For example, the ratio (%) of the number of ⁇ 1 -phase dross to the total number of bottom dross obtained by the above observation may be set as the ⁇ 1 -phase dross amount. In this case, the ⁇ 1 -phase dross amount (%) in the hot-dip galvanizing bath is represented by the following formula ( ⁇ ).
  • phase dross amount ⁇ 1- phase dross number / total number of bottom dross ⁇ 100 ( ⁇ )
  • gamma 2 phase dross, [delta] 1 phase dross, and the number of ⁇ phase dross is determined by the following method.
  • each bottom-dross identified (gamma 2 phase dross, [delta] 1 phase dross, and, zeta phase dross) obtaining the circle-equivalent diameter of.
  • the diameter when the area of each bottom dross in the above-mentioned visual field is converted to a circle is defined as a circle equivalent diameter ( ⁇ m).
  • the equivalent circle diameter ( ⁇ m) of each bottom dross specified is determined by known image processing using the photographic image of the above-mentioned visual field.
  • total number of phase dross and phase dross is defined as the total number of bottom dross (piece / 225 mm 2 ).
  • the number of ⁇ 1 -phase dross with a circle equivalent diameter of 1 ⁇ m or more is defined as the number of ⁇ 1 -phase dross (number / 225 mm 2 ).
  • the resulting [delta] 1 phase number of dross by using the (pieces / 225 mm 2) the total number of bottom dross (pieces / 225 mm 2), obtaining the [delta] 1 phase dross amount by formula (alpha) (%).
  • the upper limit of the circle equivalent diameter of each dross is not particularly limited. The upper limit of the circle equivalent diameter of each dross is, for example, 1000 ⁇ m.
  • the ⁇ 1 -phase dross amount in the hot-dip galvanizing solution may be used as the ⁇ 1 -phase dross amount 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 [delta] 1 phase dross.
  • the ratio of the total area of the [delta] 1-phase dross to the total area of the bottom dross may be [delta] 1 phase dross amount.
  • the ratio of the total area of the ⁇ 1 -phase dross to the observation visual field area may be set as the ⁇ 1 -phase dross amount.
  • the total area of the [delta] 1 Phase dross during the above field may be [delta] 1 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, [delta] 1 phase dross)
  • [delta] 1 phase dross May be used as the ⁇ 1 -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. However, as described above, gamma 1-phase dross is considered hardly existent.
  • the target at the time of X-ray diffraction measurement utilizes Co dry bulb, for example.
  • the ⁇ 1 -phase dross amount may be determined by another method other than the above.
  • [delta] 1 phase dross amount is defined by the ratio of the total amount of [delta] 1-phase dross against bottom dross total amount of the molten zinc plating bath.
  • the total amount referred to here may be the total number, the total area, or the total volume.
  • the total number may be per unit area or total number per unit volume.
  • the ⁇ 1 -phase dross amount determining step (S2) is preferably performed each time a sample is collected in the sample collecting step (S1).
  • the ⁇ 1 -phase dross amount may be determined over time based on samples taken over time.
  • operating condition adjusting step (S3) based on the [delta] 1 phase dross content in molten zinc plating bath to adjust the operating conditions of the galvanizing process. Specifically, when the obtained ⁇ 1 -phase dross amount is small, the operating conditions are adjusted (changed) so as to increase the ⁇ 1 -phase dross amount in the hot-dip galvanizing bath. The operating conditions may be maintained as they are if the obtained ⁇ 1 -phase dross amount is appropriate.
  • Method of adjusting operating conditions if adjustment is [delta] 1 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 ⁇ 1 -phase dross in the hot dip galvanizing bath can be increased.
  • At least one of the following (A) or (B) is carried out as a method of adjusting the operating conditions.
  • the amount of ⁇ 1 -phase dross in the hot dip galvanization bath can be adjusted.
  • the bath temperature of molten zinc plating bath it is possible to increase the [delta] 1 phase dross amount, as a result, it is possible to reduce the gamma 2 phase dross content in molten zinc plating bath.
  • only one of the operating conditions may be adjusted based on the determined ⁇ 1 phase dross amount, and the operations of (A) and (B) The conditions may be adjusted. For example, when the amount of ⁇ 1 phase dross is excessively small, the bath temperature of the hot dip galvanizing bath may be increased and the Al concentration of the hot dip galvanization bath may be lowered. If the ⁇ 1 -phase dross amount is appropriate, the operating conditions of (A) and (B) may be maintained as they are.
  • [delta] a [delta] 1 phase dross weight properly determine whether or not the index determined by the one-phase dross amount determining step (S2), may be provided a threshold.
  • the obtained [delta] 1 phase dross weight depending on whether it is less than the threshold value may be adjusted operation conditions. Specifically, depending on whether or not the obtained [delta] 1 phase dross amount is less than the threshold value, to change the operating conditions, it may be or maintained unchanged.
  • the operation conditions are changed, and the ⁇ 1 phase dross amount in the hot dip galvanizing bath is Adjust operating conditions to increase more than at present.
  • the obtained ⁇ 1 -phase dross amount is less than the threshold, the operating conditions are changed so that the ⁇ 1 -phase dross amount becomes equal to or more than the threshold.
  • the obtained [delta] 1 phase dross amount is greater than or equal to the threshold value, and [delta] 1 phase dross content in molten zinc plating bath is determined to be sufficiently large, to maintain the operating condition as is.
  • the observation field of view (15 mm ⁇ 15 mm) total number (pieces / 225 mm 2) number of [delta] 1 phase dross for the bottom dross in (number / 225 mm 2) the ratio, [delta] 1 phase dross
  • the threshold value of the ⁇ 1 -phase dross amount is 95.00%.
  • [delta] 1 phase dross amount determined by the [delta] 1 phase dross amount determining step (S2) is less than 95.00%
  • [delta] 1 phase dross amount is determined to excessively small, and change the operating conditions
  • the operating conditions are adjusted so that the amount of ⁇ 1 phase dross in the hot dip galvanizing bath is increased compared to the present time.
  • [delta] 1 phase dross amount determined by the [delta] 1 phase dross amount determining step (S2) is less than the threshold value, [delta] 1 phase dross amount such that the above threshold value, changes the operating conditions .
  • X ⁇ 0.002488 ⁇ T-1.0266
  • Equation (1) in the galvanizing bath, gamma 2 phase dross corresponds to the boundary (phase transformation line) for phase transformation [delta] 1 phase dross. If the Al concentration X in the hot-dip galvanizing bath is higher than the right side of the formula (1), the chemical composition of the hot-dip galvanizing bath can more stably exist in the 2 phase dross than the ⁇ 1 phase dross It has become. In this case, assuming that the Al concentration in the hot-dip galvanizing bath is 0.100 to 0.150%, the ⁇ 1 -phase dross is likely to be transformed to the d-phase 2 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 not more than the right side of the formula (1), that is, if the Al concentration X and the bath temperature T satisfy the formula (1), the Al concentration in the hot dip galvanizing bath is Given that it is from 0.100 to 0.150 percent, the chemical composition of the molten zinc plating bath, towards [delta] 1-phase dross than gamma 2 phase dross is in a state that can exist stably. Therefore, ⁇ two- phase dross in the hot-dip galvanizing bath is likely to be transformed to ⁇ one- phase dross. Accordingly, the galvanizing bath, gamma 2 phase dross is state easily reduced.
  • the Al concentration in the hot dip galvanizing bath is adjusted in the range of 0.100 to 0.150% by mass%, and the Al concentration in the hot dip galvanizing bath X If (mass%) and the bath temperature T (° C.) in the hot dip galvanizing bath are adjusted to satisfy (1), the formation of ⁇ 1 phase dross is promoted in the hot dip galvanization bath, and ⁇ 1 phase It is possible to reduce the amount of 2 phase dross which has a negative correlation with the amount of dross.
  • the Al concentration in the hot-dip galvanizing bath is adjusted in the range of 0.100 to 0.150% by mass%, and the Al concentration and the bath temperature satisfy the formula (1)
  • the ⁇ 1 -phase dross amount defined by the equation ( ⁇ ) is likely to become 95.00% or more of the threshold value.
  • 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 is mainly phase-changed to top dross (Fe 2 Al 5 ), ⁇ two- phase dross, ⁇ 1 -phase dross depending on the temperature of the hot-dip galvanizing bath and the Al concentration in the hot-dip galvanizing bath.
  • To metamorphose. ⁇ Two- phase dross tends to form in the region where the bath temperature is low.
  • [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.
  • samples were taken from the hot-dip galvanizing bath (sampling step (S1)), obtaining the [delta] 1 phase dross amount of the molten zinc plating bath (.delta.1 phase Dross amount determination step (S2)). Then, based on the [delta] 1 phase dross content in molten zinc plating bath to adjust the operating conditions of the galvanizing treatment (operation conditions adjusting step (S3)).
  • operation conditions adjusting step (S3) By controlling the amount of ⁇ 1 -phase dross having a negative correlation with the amount of 2- phase dross, the operating conditions can be adjusted to suppress the occurrence of dross defects.
  • 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 ⁇ 1 phase dross amount, the operation condition of the hot dip galvanization treatment is adjusted to increase the ⁇ 1 phase dross amount. Therefore, the ⁇ two- phase dross in the hot dip galvanizing bath is relatively reduced, and as a result, the occurrence of dross defects in the manufactured alloyed galvanized steel sheet can be suppressed.
  • 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 implemented using the hot dip galvanization installation which has the same structure as 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. As a steel plate, a steel plate for automobile outer 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 0.02 to 0.05% by mass in any of the test numbers.
  • the bath temperature of the hot-dip galvanizing bath is kept constant at the value shown in Table 1, and the Al concentration of the hot-dip galvanizing bath becomes the concentration shown in Table 1 as appropriate.
  • the adjustment was made by adding Al.
  • 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). However, when the Al concentration X is less than 0.100% or more than 0.150%, as described above, pattern defects (Test No. 27) or unalloyed (Test No. 28) were confirmed, so The value on the right side of (1) was not questioned, and “-” was described in the “Formula (1) Right side” column in 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 prepared [delta] 1 phase dross test piece for observation. The test surface of the ⁇ 1 -phase dross observation test piece 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.
  • composition analysis using EPMA was performed, and each dross was classified into top dross, bottom dross ( ⁇ 2 phase dross, ⁇ 1 phase dross, and n phase dross). Furthermore, the identified bottom dross (gamma 2 phase dross, [delta] 1 phase dross, and, zeta phase dross) was determined circle equivalent diameter of. In the field of view of 15 mm ⁇ 15 mm described above, the number (number / 225 mm 2 ) of ⁇ 1 -phase dross with a circle equivalent diameter of 1 ⁇ m or more was determined.
  • the circle equivalent diameter was determined 1 ⁇ m or more bottom dross (gamma 2 phase dross, [delta] 1 phase dross, and, zeta phase dross) of the (number / 225 mm 2).
  • the obtained ⁇ 1 -phase dross amounts are shown in Table 1. In the present example, no first- phase dross was observed in any of the test numbers.
  • bottom dross (gamma 2 phase dross, [delta] 1 phase dross, and, zeta phase dross) the total number of (pieces / 225 mm 2) were as follows.
  • Test No. 16 495/225 mm 2
  • Test No. 17 990/225 mm 2
  • Test No. 18 990 pcs / 225 mm 2
  • Test No. 19 2993 pieces / 225 mm 2
  • 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 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 ⁇ 1 phase dross amount and the number of dross defects Showed higher correlation (negative correlation). Therefore, as an index for adjusting the operating conditions, rather than the bottom dross total number, it is better to adopt a [delta] 1 phase dross weight was found to be suitable.
  • the dross defect evaluation was “A”, but due to the reaction between Fe and Al present in the bath, the steel plate On the other hand, a pattern defect different from the dross defect has occurred.
  • the dross defect evaluation was “A”, but unalloying occurred in the subsequent stage alloying furnace. Therefore, it has become clear that the Al concentration in the hot dip galvanizing bath is more preferably in the range of 0.100 to 0.150% by mass.
  • the Al concentration in the hot dip galvanizing bath is 0.100 to 0.150 mass% (Test Nos. 1 to 26)
  • the Al concentration and the bath temperature of the hot dip galvanizing bath satisfy the formula (1) (Test No. 2, 5, 6, 9, 9, 10, 14, 15, 19, 20, and 23)
  • ⁇ 1 phase dross amount is 95.00% or more
  • dross defect evaluation can be made A or B Met. Therefore, it was found that adjusting the operation conditions so as to satisfy the equation (1) is effective for suppressing the dross defect.

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Abstract

L'invention concerne un procédé de galvanisation par immersion à chaud apte à supprimer l'apparition de défauts d'écume. Le procédé de galvanisation par immersion à chaud selon ce mode de réalisation est utilisé pour fabriquer une tôle d'acier galvanisée par immersion à chaud ou une tôle d'acier allié galvanisée par immersion à chaud. Le procédé de galvanisation par immersion à chaud comprend une étape d'échantillonnage (S1), une étape de détermination de quantité d'écume de phase δ1 (S2), et une étape de réglage de condition de fonctionnement (S3). Dans l'étape d'échantillonnage, un échantillon est prélevé à partir d'un bain de galvanisation par immersion à chaud comprenant de l'Al. Dans l'étape de détermination de quantité d'écume de phase δ1, la quantité d'écume de phase δ1 dans le bain de galvanisation par immersion à chaud est déterminée à l'aide de l'échantillon collecté. Dans l'étape de réglage de condition de fonctionnement, les conditions de fonctionnement de la galvanisation par immersion à chaud sont réglées sur la base de la quantité obtenue d'écume de phase δ1.
PCT/JP2018/047395 2017-12-25 2018-12-21 Procédé de galvanisation par immersion à chaud, procédé de production de tôle d'acier allié galvanisée par immersion à chaud à l'aide d'un procédé de galvanisation par immersion à chaud, et procédé de production de tôle d'acier galvanisée par immersion à chaud à l'aide d'un procédé de galvanisation par immersion à chaud WO2019131562A1 (fr)

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JP2019561677A JP6919723B2 (ja) 2017-12-25 2018-12-21 溶融亜鉛めっき処理方法、その溶融亜鉛めっき処理方法を用いた合金化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処理方法を用いた溶融亜鉛めっき鋼板の製造方法

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