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WO2016170720A1 - Procédé et appareil de placage de métal en continu par immersion à chaud - Google Patents

Procédé et appareil de placage de métal en continu par immersion à chaud Download PDF

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Publication number
WO2016170720A1
WO2016170720A1 PCT/JP2016/001013 JP2016001013W WO2016170720A1 WO 2016170720 A1 WO2016170720 A1 WO 2016170720A1 JP 2016001013 W JP2016001013 W JP 2016001013W WO 2016170720 A1 WO2016170720 A1 WO 2016170720A1
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WO
WIPO (PCT)
Prior art keywords
snout
molten metal
steel strip
bath
temperature
Prior art date
Application number
PCT/JP2016/001013
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English (en)
Japanese (ja)
Inventor
高橋　秀行
Original Assignee
Ｊｆｅスチール株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP2015166199A external-priority patent/JP6361606B2/ja
Application filed by Ｊｆｅスチール株式会社 filed Critical Ｊｆｅスチール株式会社
Priority to US15/565,986 priority Critical patent/US20180105916A1/en
Priority to AU2016252162A priority patent/AU2016252162B2/en
Priority to KR1020177030349A priority patent/KR101953506B1/ko
Priority to CN201680022565.7A priority patent/CN107532269B/zh
Priority to MX2017013461A priority patent/MX2017013461A/es
Publication of WO2016170720A1 publication Critical patent/WO2016170720A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • 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

Definitions

  • the present invention relates to a continuous molten metal plating method and a continuous molten metal plating facility used for, for example, continuously producing a hot dip galvanized steel sheet.
  • the steel strips whose surfaces have been cleaned are usually annealed continuously in an annealing furnace, cooled to a predetermined temperature, and then entered into a hot dip zinc bath to apply hot dip galvanization to the steel strips. .
  • the annealing / cooling process in the annealing furnace is performed in a reducing atmosphere.
  • the steel strip passage is cut off from the atmosphere, and the steel strip can pass through the reducing atmosphere.
  • a snout is provided between the plating tank in which the molten zinc bath is formed.
  • a sink roll is installed in the molten zinc bath, and the steel strip that has entered the molten zinc bath changes its traveling direction by the sink roll and rises in the vertical direction.
  • the steel strip pulled up from the molten zinc bath is adjusted to a predetermined plating thickness by a gas wiping nozzle, then cooled and guided to a subsequent process.
  • the snout Since the snout is connected to the cooling zone (steel strip exit side) of the annealing furnace, the inside is usually a reducing atmosphere. Therefore, an oxide film is hardly formed on the molten zinc bath surface in the snout, and only a thin oxide film is formed. Since the oxide film formed on the molten zinc bath surface in the snout is not strong as described above, when the steel strip enters the molten zinc bath, the molten zinc is exposed to the bath surface due to vibrations, etc. Zinc evaporates inside. In this case, the molten zinc evaporates to a saturated vapor pressure at the ambient temperature inside the snout.
  • Zinc vapor reacts with a small amount of oxygen in the reducing atmosphere gas to form an oxide. Even when the zinc vapor is not oxidized, when the vapor pressure of the zinc vapor becomes equal to or higher than the saturated vapor pressure, a part of the zinc vapor changes into a liquid phase or solid phase zinc. In particular, since the snout is only composed of a thin heat-resistant material, the temperature of the inner wall surface of the snout is easily affected by the outside air and is likely to be below the saturation temperature of the vapor pressure of zinc vapor. Zinc vapor turns into zinc powder and adheres to the inner surface of the snout.
  • defects due to ash When such oxides and deposits (so-called ash) adhere to the steel strip, quality defects such as unplated parts occur.
  • quality defects such as non-plated portions caused by ash generated due to zinc vapor in the snout are hereinafter referred to as “defects due to ash” in the present specification.
  • Patent Document 1 There are the following technologies for suppressing defects caused by ash.
  • the snout is heated with a heater, the outside of the heater is further insulated with a heat insulating material, and the temperature difference between the atmospheric temperature in the snout and the inner wall temperature and the plating bath temperature is set to 150 ° C. or less.
  • a technique for preventing ash adhesion to the inner wall of the snout is described.
  • Patent Document 2 a suction blower is installed in the plating bath, and a suction pipe having a suction port at a position higher than the bath surface in the snout is connected to the suction side of the suction blower, so that zinc vapor in the snout is used as a system.
  • Patent Document 3 describes a technique for suppressing the generation of fume (zinc vapor) by making the atmosphere in the snout non-oxidizing gas for the steel sheet and oxidizing gas for the molten zinc. .
  • Patent Document 1 can suppress crystallization of zinc vapor on the inner wall of the snout, that is, generation of ash to some extent by heating the snout.
  • generation of zinc vapor from the molten zinc bath surface itself cannot be prevented, the generation of ash in an unheated place is unavoidable, and the potential danger of ash adhering to the steel strip cannot be excluded.
  • Patent Documents 1 to 3 have the following problems. That is, the suitable oxidizing power of the atmosphere in the snout (particularly in the vicinity of the bath surface) varies depending on the operating conditions such as the composition of the steel strip, the annealing conditions in the annealing process, and the components of the molten metal bath. For this reason, when operating conditions are switched, the oxidizing power of the atmosphere in the snout is also required to be switched quickly.
  • the techniques of Patent Documents 1 to 3 have a problem that the oxidizing power of the atmosphere in the snout cannot be changed stably and quickly. In particular, in Patent Document 3, since large natural convection exists in the snout, the oxidizing power of the atmosphere in the snout cannot be changed stably and quickly.
  • An object of the present invention is to provide a continuous molten metal plating method and a continuous molten metal plating facility capable of stably and quickly changing the oxidizing power of the atmosphere in the snout.
  • the present invention has been completed based on the above findings, and the gist of the present invention is as follows. (1) a step of continuously annealing a steel strip in an annealing furnace; A method of continuously supplying the steel strip after annealing to a plating tank containing a molten metal and forming a molten metal bath, and performing metal plating on the steel strip.
  • the operation condition is any one of the above (3) to (6), wherein the operation condition is at least one of a component composition of the steel strip, an annealing condition in the annealing step, and a component of the molten metal bath. Continuous molten metal plating method.
  • An annealing furnace for continuously annealing the steel strip A plating tank containing molten metal and forming a molten metal bath; Provided on the steel strip exit side of the annealing furnace, the end is positioned so as to be immersed in the molten metal bath, and defines a space through which the steel strip continuously supplied from the annealing furnace into the molten metal bath passes Snout to do, A heating body provided on an outer wall of the snout and an upper portion in the snout; A gas supply mechanism connected to the snout; The heating body and the gas supply mechanism are controlled to supply an oxidizing gas into the snout, and the temperature of the inner wall surface of the snout is not less than (plating bath temperature ⁇ 150 ° C.) and the inside of the snout A control unit that makes the upper atmosphere temperature (plating bath temperature –100 ° C) or higher, A continuous molten metal plating facility characterized by comprising:
  • both non-plating caused by metal vapor generated in the snout and non-plating caused by the oxide film on the molten metal bath surface in the snout are suppressed.
  • the oxidizing power of the atmosphere in the snout can be changed stably and quickly.
  • FIG. 1 It is a schematic diagram of the continuous hot dip galvanizing equipment 100 by one Embodiment of this invention. It is the figure which showed only the half from the width direction center of the steel strip P among the insides of the snout 14 in FIG. It is an expansion schematic diagram of the snout 14 in FIG. It is a graph which shows the relationship between the oxidizing power of a bath surface atmosphere, and a defect rate.
  • A is a graph which shows the relationship between the oxidizing power of a bath surface atmosphere and a defect rate about high Si content steel and low Si content steel
  • (B) is about high Al content bath and low Al content bath
  • (A) and (B) are graphs showing the relationship between the dew point in the snout and the defect rate in steel types A and B, respectively.
  • 6 is a graph showing the dew point fluctuation in the snout in Invention Examples 1 to 3 and Comparative Examples 1 and 2.
  • the continuous hot dip galvanizing equipment 100 includes an annealing furnace 10, a plating tank 12, and a snout 14.
  • the annealing furnace 10 is an apparatus for continuously annealing the steel strip P passing through the inside thereof, and is arranged in the order of the heating zone, the soaking zone, and the cooling zone.
  • FIG. 1 shows only the cooling zone.
  • a well-known or arbitrary thing can be used as an annealing furnace.
  • a reducing gas or a non-oxidizing gas is supplied into the annealing furnace.
  • a mixed gas of H 2 —N 2 is usually used, for example, H 2 : 1 to 20% by volume, and the balance is composed of N 2 and inevitable impurities (dew point: about ⁇ 60 ° C.) Is mentioned.
  • non-oxidizing gas examples include a gas having a composition composed of N 2 and inevitable impurities (dew point: about ⁇ 60 ° C.).
  • the annealed steel strip P is cooled to about 470-500 ° C. in the cooling zone.
  • the plating tank 12 contains molten zinc, and a molten zinc bath 12A is formed.
  • the snout 14 is provided on the steel strip exit side of the annealing furnace 10 in connection with the cooling zone in this embodiment.
  • the snout end 14A is positioned so as to be immersed in the molten zinc bath 12A.
  • the snout 14 is a member that partitions a space through which the steel strip P continuously supplied from the annealing furnace 10 into the molten zinc bath 12A passes.
  • a turn-down roll 26 that changes the traveling direction of the steel strip P from the horizontal direction to an obliquely downward direction is disposed on the upper part of the snout 14.
  • a portion that divides the space through which the steel strip P after passing through the turn-down roll 26 passes is rectangular in a sectional view perpendicular to the traveling direction of the steel strip P.
  • the steel strip P passes through the inside of the snout 14 and continuously enters the molten zinc bath 12A.
  • a sink roll 28 and a support roll 30 are installed in the molten zinc bath 12A, and the steel strip P that has entered the molten zinc bath 12A is changed in the sheet passing direction upward by the sink roll 28. It is guided to the support roll 30 and leaves the molten zinc bath 12A. In this way, hot dip galvanization is applied to the steel strip P.
  • the continuous galvanizing equipment 100 has a gas supply mechanism 20 connected to the snout 14.
  • the gas supply mechanism 20 is attached to the first pipe 22A through which hydrogen gas passes, the second pipe 22B through which nitrogen gas passes, the third pipe 22C through which water vapor as an oxidizing gas passes, and these pipes.
  • a valve 24 for adjusting the flow rate, a fourth pipe 22D through which a mixed gas obtained by mixing gases supplied from these pipes passes, and the fourth pipe 22D are connected to each other, and the tip is located inside the snout 14. 5th piping 22E.
  • the first piping 22A and the third piping 22C are connected to the second piping 22B, and by adjusting the valve 24, hydrogen, nitrogen, and water vapor can be mixed at an arbitrary flow rate ratio.
  • the oxidizing gas examples include gas containing water vapor, oxygen, carbon dioxide, and the like, and are not particularly limited. However, since the oxidizing power is not too high, it is easy to manage, the cost is low, and the oxidizing power can be easily measured with a dew point meter.
  • a heater 16 as a heating body is disposed on the outer wall of the snout 14, and the heater 16 is further covered with a heat insulating material 18.
  • the heater 16 covers the entire outer wall except for the tip of the snout 14 (near the bath surface).
  • a heater 17 as a heating body is also arranged in the upper part in the snout. Since the upper part of the snout has a great influence on the generation of thermal convection as will be described later, the ambient temperature of the upper part of the snout can be reliably increased by providing the heater 17.
  • the heaters 16 and 17 and the gas supply mechanism 20 are controlled by a control unit (not shown) to supply the oxidizing gas into the snout 14 and to set the temperature of the inner wall surface of the snout 14 (plating bath temperature ⁇ 150). It is important that the temperature of the atmosphere in the upper part of the snout 14 is controlled to (plating bath temperature ⁇ 100 ° C.) or higher. The technical significance will be described in detail below.
  • FIG. 4 is a diagram showing the concept. If the oxidization property is low, an oxide film is not formed on the bath surface, or even if it is formed, it is very thin, so defects due to the oxide film are difficult to occur, but zinc evaporation occurs actively, so defects due to ash increase. . On the other hand, when the oxidizing property is high, since the thick oxide film becomes a protective film and the evaporation of zinc hardly occurs, defects due to ash hardly occur, but many defects due to the oxide film occur.
  • the oxidizing power of the atmosphere near the bath surface is controlled by supplying a gas containing water vapor into the snout
  • the dew point of the atmosphere near the bath surface is strictly limited to a predetermined point (target dew point) ⁇ 4 ° C.
  • target dew point can be determined by the method described later if operating conditions other than the target dew point are determined.
  • the convection in the snout mainly includes the accompanying flow generated by the movement of the steel strip, the thermal convection due to the temperature difference in the snout, and the pressure flow due to the pressure difference in the snout. Then, the influence of thermal convection is dominant. For example, when the steel strip temperature is 500 ° C. and the plating bath temperature is 450 ° C., the inside of the snout has a temperature difference of 400 ° C. or more from the outside of the snout.
  • the upper part of the snout is connected to the cooling zone, so the atmospheric temperature of the upper part of the snout is often 200 to 300 ° C.
  • the wind speed due to thermal convection is about 4-5 m / s, which is considerably higher than 1 m / s, which is the typical value of the steel strip wake.
  • the present inventor is most likely to suppress zinc evaporation itself in order to strictly control the dew point near the bath surface and suppress both defects due to ash and defects due to oxide films. In order to achieve this, it was concluded that it is best to supply the minimum amount of oxidizing gas into the snout while suppressing thermal convection in the snout.
  • the present inventor aimed to reduce the temperature difference in the snout, which is the cause of such heat convection.
  • the steel strip has the highest temperature inside the snout, the normal steel strip is only about 10 ° C. higher than the bath temperature. Therefore, in the present invention, the temperature standard is the plating bath temperature. Further, since the thermal convection and the steel strip accompanying flow are in opposite directions, the convection in the snout can be greatly suppressed if the size of the thermal convection can be made twice or less the size of the steel strip accompanying flow.
  • the temperature of the inner wall surface of the snout is set to (plating bath temperature -150 ° C) or higher, the convection of the atmosphere in the snout can be suppressed to a fluid state that ignores the temperature effect.
  • the atmosphere temperature in the upper part of the snout has a larger influence on the heat convection, so it is necessary to set it to (plating bath temperature ⁇ 100 ° C.) or higher. This is because the density flow has a higher flow velocity when a gas having a high density exists at a high position. (The flow resulting from the density is proportional to ⁇ gh. H is the difference in height position, and if there is a high density at a high position, the flow velocity will be faster.)
  • the atmosphere temperature of the upper part in a snout shall be below (plating bath temperature +100 degreeC).
  • the higher the ambient temperature of the upper part the more the convection in the snout is stabilized (the state where there is a low-density substance in the upper part is stable), but the stabilizing effect exceeds (plating bath temperature + 100 ° C) This is because it becomes a peak.
  • the temperature of the inner wall surface of a snout shall be (plating bath temperature +0 degreeC) or less.
  • the “upper part in the snout” is defined as an area within the snout within 1 m from the surface of the turndown roll. In FIG. 3, the distance is within 1 m from the surface of the turndown roll 26 in the snout 14.
  • the oxidation state of the bath surface in the snout can be ideally maintained, both defects due to ash and defects due to the oxide film can be almost eliminated. Furthermore, the effect that the oxidizing power of the atmosphere in the snout can be changed stably and quickly can also be obtained. Therefore, when switching the operating conditions, the oxidizing power of the atmosphere in the snout can be switched quickly according to the changed operating conditions.
  • the oxidizing gas supplied into the snout is preferably nitrogen gas containing water vapor or a nitrogen / hydrogen mixed gas containing water vapor, and the dew point is appropriately determined depending on the components of the plating bath, the type of steel to be produced, and other operating conditions. It may be set, but in many cases it becomes good in the range of -20 to -35 ° C.
  • the supply amount of the oxidizing gas is affected by various operating conditions, but when the same conditions other than the temperature of the inner wall surface of the snout and the atmospheric temperature of the upper part of the snout are compared with the conditions outside the present invention, The same dew point can be achieved with a supply amount of about 1/4. Therefore, the supply amount of the oxidizing gas can be set to a minimum amount necessary for forming an appropriate oxide film.
  • the oxidizing gas is preferably supplied into the snout 14 from both ends of the snout in the steel strip width direction.
  • the reason why the fifth pipe 22E having the gas inlet is installed on the side surface of the snout 12 is that the temperature in the vicinity of the side surface in the snout often decreases. This is because the oxidizing gas can be efficiently reached.
  • the height of the gas inlet from the bath surface can be about 100 to 3000 mm. If it is less than 100 mm, there is a high possibility that the gas directly reaches the bath surface, and as a result, the concentration distribution of the oxidizing gas in the vicinity of the bath surface becomes large. On the other hand, if the distance exceeds 3000 mm, the distance from the bath surface is large, so that the gas concentration decreases, and as a result, a large amount of gas is required.
  • the suitable oxidizing power of the atmosphere in the vicinity of the bath surface in the snout varies depending on the operating conditions such as the composition of the steel strip, the annealing conditions in the annealing process, the components of the molten zinc bath, and the like. That is, the two curves shown in FIG. 4 can be shifted left and right depending on the operating conditions. This will be described below with reference to FIGS. 5A and 5B.
  • both the defect due to ash and the defect due to the oxide film correlate with the oxide film thickness formed on the bath surface.
  • the ash defect is related to the ash generation amount and its adhesion rate, and the oxide film defect depends on the oxide film amount and its adhesion rate.
  • FIG. 5 (A) shows an example of the influence of the composition of the steel strip on the suitable oxidizing power of the atmosphere in the vicinity of the bath surface in the snout.
  • the steel strip contains a large amount of so-called oxidizable elements such as Si, Mn, and Al
  • a large amount of surface concentrate is generated on the surface of the steel strip immediately before entering the plating bath.
  • the oxide film is likely to adhere to the steel strip, that is, the deposition rate of the oxide film is increased, and defects due to the oxide film are likely to occur.
  • the component composition of the steel strip has little effect on defects due to ash.
  • the annealing conditions also affect the probability of defects due to oxide films, but the ash defects are almost affected. do not do.
  • FIG. 5 (B) shows an example of the influence of the components of the molten zinc bath on the suitable oxidizing power of the atmosphere in the vicinity of the bath surface in the snout.
  • the higher the Al concentration in the bath the easier the oxide film is formed on the bath surface. Therefore, the higher the Al-containing bath, the less likely the defects due to ash occur, and the more likely the defects due to the oxide film occur. That is, the two curves in FIG. 4 shift to the left.
  • the oxidizing power of the oxidizing gas it is preferable to change the oxidizing power of the oxidizing gas according to the operating conditions. That is, when the oxidizing gas contains water vapor, the suitable dew point of the atmosphere in the vicinity of the bath surface, that is, the target dew point varies depending on the operating conditions, so the amount of water vapor in the oxidizing gas can be changed according to the operating conditions. That's fine.
  • the amount of water vapor in the oxidizing gas is usually 100 ppm or more.
  • the relationship between the dew point in the snout and the defect rate of defects due to ash and defects due to oxide films (that is, the information in FIG. 4) is investigated in advance, and within the snout under the operating conditions.
  • a target dew point can be determined.
  • steam in oxidizing gas can be determined based on the target dew point determined for every operating condition.
  • the amount of water vapor in the oxidizing gas may be changed based on the target dew point corresponding to the changed operating conditions.
  • the relationship between the dew point in the snout and the defect rate of defects due to ash and oxides is as follows. It can be obtained by grasping the trend of rates in advance. The presence or absence of each defect can be determined visually. The size of the defect that can be visually identified is about 100 ⁇ m or more. Then, the defect mixture rate per 0.5 m length is defined as “defect rate”. A defect rate of 1% is equivalent to 1 piece / 50m.
  • the dew point in the above-mentioned snout needs to be a dew point directly above the bath surface (near the bath surface). If the location where the dew point is actually measured is not directly above the bath surface, consider the following. First, if the present invention is applied and the thermal convection in the snout is eliminated, the measured dew point may be used as it is because there is almost no dew point distribution in the snout. However, when there is thermal convection in the snout, the measured dew point is corrected to the dew point near the bath surface. This correction can be performed using the dew point distribution predicted from the flow analysis.
  • the difference between the two is + 5 ° C and the difference in the water ratio is 150 ppm. . Therefore, a dew point obtained by always adding 150 ppm to the actually measured dew point value at a height of 500 mm can be adopted as the bath surface dew point.
  • the operating conditions that affect the suitable oxidizing power of the atmosphere near the bath surface in the snout are steel grades (component composition of the steel strip) ), Annealing conditions in the annealing step and components of the molten zinc bath. Therefore, it is preferable to obtain the information of FIG. 4 in advance in consideration of at least one of these. For example, in a specific continuous hot dip galvanizing facility, if it is known that the annealing conditions and the components of the hot dip zinc bath are not changed, the information in FIG. 4 is investigated in advance for each steel type to be passed through the facility, The target dew point should be determined. And when switching a steel type, what is necessary is just to change the water vapor
  • the present invention is not limited to the above embodiment, and the same applies to the case where a steel strip is continuously subjected to molten metal plating.
  • Example 1> Using the continuous hot dip galvanizing equipment shown in FIGS. 1 to 3, the component composition is mass%, C: 0.001%, Si: 0.01%, Mn: 0.1%, P: 0.003%, S: 0.005%, Al: A steel strip (hereinafter referred to as “steel type A”) containing 0.03% and the balance of Fe and inevitable impurities, having a thickness of 0.6 to 1.2 mm, a width of 900 to 1250 mm, and a tensile strength of 270 MPa is referred to as a steel plate speed 60 to A hot dip galvanized steel sheet was manufactured by entering the hot dip galvanized bath at 100 mpm. As shown in FIG.
  • the 5th piping which has a gas inlet was installed in the side surface of the snout, and the height from the bath surface of the gas inlet was 500 mm.
  • the relationship between the dew point in the snout and the defect rate of defects due to ash and defects due to oxide films was investigated in advance. The results are shown in FIG. Based on FIG. 6 (A), the target dew point in the snout was determined to be ⁇ 30 ° C. Then, it was found that if the dew point in the snout can be controlled within a range of about ⁇ 30 ° C. ⁇ 4 ° C., both defects due to ash and defects due to oxide films can be suppressed to a low level.
  • Test Examples No. 1 to 5 When the steel strip passes through the snout, in Test Examples No. 1 to 5, a nitrogen / hydrogen mixed gas containing water vapor is supplied (indicated as “water vapor supply available” in Table 1). In Nos. 6 and 7, a nitrogen / hydrogen mixed gas that does not contain water vapor (indicated as “water vapor supply, none” in Table 1) was supplied from the gas inlet.
  • the dew points of the input gases in Test Examples No. 1 to 5 were measured with a dew point meter provided in the dew point measurement hole 32A in the fifth pipe in FIG.
  • the temperature of the inner wall surface of the snout and the atmospheric temperature of the upper part of the snout when the steel strip passes through the snout were controlled as shown in Table 1.
  • Heating by a heater provided on the outer wall of the snout and the upper part in the snout was not performed.
  • the dew point of the atmosphere in the snout was measured over time with a dew point meter provided in the dew point measurement hole 32B at the center of the back surface of the snout and at a height of 500 mm shown in FIG.
  • the input gas flow rate was changed so that the measured dew point approached the target dew point based on the difference between the measured dew point and the target dew point ( ⁇ 30 ° C.).
  • This control was performed by general PID control logic.
  • Table 2 shows the histograms of measured dew points in each of Test Examples No. 1 to No. 7.
  • Test Examples No. 1 to 5 the ratio of the volume of water vapor to the total volume of the input gas under test is shown as “Moisture content” in Table 1, and the total input flow rate of the gas under test is No. 5
  • Table 1 shows the index as 1.
  • the dew point to be managed is the dew point directly above the bath surface
  • the position of the dew point meter should be close to the lower bath surface, but according to the present invention, almost no dew point is present in the snout. Since the distribution cannot be obtained, even if the dew point is measured at a height of 500 mm, the dew point near the bath surface can be grasped with high accuracy.
  • the dew point meter may not be installed under the snout. Many.
  • water vapor is used as the oxidizing gas
  • the gas measuring device is a dew point meter.
  • an oxidizing gas other than water vapor it is naturally necessary to install a measuring device for detecting the gas. There is.
  • defect rate evaluation The defect rates of the ash defects and the oxide film defects were evaluated by the following methods. The presence or absence of each defect was determined visually. The size of the defect that can be visually identified is about 100 ⁇ m or more. The defect mixing rate per 0.5 m length was defined as “defect rate” and shown in Table 1. A defect rate of 1% is equivalent to 1 piece / 50m.
  • No. 1 (invention example) is an example in which there is no temperature difference between the bath temperature, wall surface temperature, and top temperature, and there is almost no dew point fluctuation. As a result, almost no defects due to ash and no defects due to oxide films have occurred.
  • No.2 (invention example) is an example where the wall temperature is low
  • No.3 (invention example) is an example where the atmosphere temperature at the top of the snout is low, but the dew point of the atmosphere inside the snout is within the control range (-30 ° C ⁇ 4 ° C) )
  • the defect rate is also kept low.
  • the gas input flow rate could be made sufficiently lower than No. 5.
  • No. 4 is an example in which the wall surface temperature is outside the scope of the present invention
  • No. 5 is an example in which the ambient temperature at the top of the snout is outside the scope of the present invention.
  • the dew point could not be kept within the control range (-30 ° C ⁇ 4 ° C).
  • No. 6 is an example in which no steam was added and no heating with a heater was performed. In this case, since the dew point was low around -40 ° C., defects due to the oxide film did not occur, but very many defects due to ash occurred.
  • No. 7 (comparative example), the temperature difference was not applied, so the dew point was stable, but since it was low around -40 ° C, defects due to ash were still generated.
  • Example 2 In place of the steel strip of steel type A, the composition is C: 0.12%, Si: 1.0%, Mn: 1.7%, P: 0.006%, S: 0.006%, Al: 0.03%, with the balance being Fe.
  • steel type B a steel strip having a plate thickness of 0.6 to 1.2 mm, a plate width of 900 to 1250 mm, and a tensile strength of 780 MPa was used. The relationship between the dew point in the snout and the defect rate of defects due to ash and defects due to oxide films was determined. The results are shown in FIG.
  • both steel types A and B have dew points that can sufficiently suppress both defects due to ash and defects due to oxide films, but steel type B has an optimum value, that is, a target dew point. It can be seen that the dew point range in which both defect rates are sufficiently low is also narrow. From this, it can be seen that, for example, when switching from steel type A to B, it is necessary to change the atmospheric dew point accurately in a short time.
  • Example 3 Switching the dew point of the nitrogen / hydrogen mixed gas containing water vapor when the bath temperature, wall surface temperature and top temperature are No. 1 to 5 (Invention Examples 1 to 3 and Comparative Examples 1 and 2) shown in Table 1. Investigated the speed. As shown in FIG. 7, the input dew point was switched from ⁇ 35 ° C. to ⁇ 20 ° C. at 50 minutes.
  • both non-plating caused by metal vapor generated in the snout and non-plating caused by the oxide film on the molten metal bath surface in the snout are suppressed. can do.

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Abstract

La présente invention concerne un procédé de placage de métal en continu par immersion à chaud qui permet d'empêcher à la fois le non-placage attribuable à la vapeur générée à l'intérieur de la busette de coulée et le non-placage attribuable à un film d'oxyde sur la surface de bain de métal fondu à l'intérieur de la busette de coulée, et de modifier de manière stable et rapide la capacité d'oxydation de l'atmosphère à l'intérieur de la busette de coulée. Le procédé de placage de métal en continu par immersion à chaud selon la présente invention est caractérisé par la fourniture d'un gaz oxydant à l'intérieur d'une busette de coulée (14), la régulation de la température de la paroi intérieure de la busette de coulée à une température non inférieure à (température de bain de placage) -150 °C et la régulation de la température de l'atmosphère supérieure à l'intérieur de la busette de coulée à une température non inférieure à (température du bain de placage) -100 °C.
PCT/JP2016/001013 2015-04-21 2016-02-25 Procédé et appareil de placage de métal en continu par immersion à chaud WO2016170720A1 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US15/565,986 US20180105916A1 (en) 2015-04-21 2016-02-25 Continuous hot-dip metal coating method and continuous hot-dip metal coating line
AU2016252162A AU2016252162B2 (en) 2015-04-21 2016-02-25 Continuous hot-dip metal coating method and continuous hot-dip metal coating line
KR1020177030349A KR101953506B1 (ko) 2015-04-21 2016-02-25 연속 용융 금속 도금 방법 및 연속 용융 금속 도금 설비
CN201680022565.7A CN107532269B (zh) 2015-04-21 2016-02-25 连续熔融金属镀敷方法及连续熔融金属镀敷设备
MX2017013461A MX2017013461A (es) 2015-04-21 2016-02-25 Metodo de recubrimiento metalico por inmersion en caliente continuo y linea de recubrimiento metalico por inmersion en caliente continuo.

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JP2015086992 2015-04-21
JP2015-086992 2015-04-21
JP2015-166199 2015-08-25
JP2015166199A JP6361606B2 (ja) 2015-04-21 2015-08-25 連続溶融金属めっき方法及び連続溶融金属めっき設備

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WO2018181091A1 (fr) * 2017-03-31 2018-10-04 Ｊｆｅスチール株式会社 Procédé de production d'une bande d'acier plaquée par immersion à chaud
CN113046668A (zh) * 2019-12-28 2021-06-29 上海东新冶金技术工程有限公司 用于热镀锌炉鼻的电加热装置及其使用方法
CN114250430A (zh) * 2020-09-21 2022-03-29 宝山钢铁股份有限公司 利于抑制锌灰的炉鼻子内气氛温度控制方法和加热装置
WO2023286501A1 (fr) * 2021-07-14 2023-01-19 Ｊｆｅスチール株式会社 Procédé de production d'une tôle d'acier galvanisée à chaud
CN115836140A (zh) * 2020-07-29 2023-03-21 杰富意钢铁株式会社 渣滓缺陷预测方法、渣滓缺陷减少方法、热浸镀锌钢板的制造方法、合金化热浸镀锌钢板的制造方法、渣滓缺陷预测模型的生成方法、渣滓缺陷预测装置以及渣滓缺陷预测终端系统

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JPH11286762A (ja) * 1998-04-01 1999-10-19 Nippon Steel Corp 連続溶融めっき方法及びその装置
JP2002327256A (ja) * 2001-04-26 2002-11-15 Nkk Corp 連続溶融金属めっき方法および装置
JP2014043633A (ja) * 2012-08-29 2014-03-13 Jfe Steel Corp 連続溶融亜鉛めっき方法

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JPH0925550A (ja) * 1995-07-12 1997-01-28 Nkk Corp Ａｌ含有溶融亜鉛めっき鋼板及びその製造方法
JPH11286762A (ja) * 1998-04-01 1999-10-19 Nippon Steel Corp 連続溶融めっき方法及びその装置
JP2002327256A (ja) * 2001-04-26 2002-11-15 Nkk Corp 連続溶融金属めっき方法および装置
JP2014043633A (ja) * 2012-08-29 2014-03-13 Jfe Steel Corp 連続溶融亜鉛めっき方法

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018181091A1 (fr) * 2017-03-31 2018-10-04 Ｊｆｅスチール株式会社 Procédé de production d'une bande d'acier plaquée par immersion à chaud
JPWO2018181091A1 (ja) * 2017-03-31 2019-04-04 Ｊｆｅスチール株式会社 溶融めっき鋼帯の製造方法
CN113046668A (zh) * 2019-12-28 2021-06-29 上海东新冶金技术工程有限公司 用于热镀锌炉鼻的电加热装置及其使用方法
CN115836140A (zh) * 2020-07-29 2023-03-21 杰富意钢铁株式会社 渣滓缺陷预测方法、渣滓缺陷减少方法、热浸镀锌钢板的制造方法、合金化热浸镀锌钢板的制造方法、渣滓缺陷预测模型的生成方法、渣滓缺陷预测装置以及渣滓缺陷预测终端系统
CN114250430A (zh) * 2020-09-21 2022-03-29 宝山钢铁股份有限公司 利于抑制锌灰的炉鼻子内气氛温度控制方法和加热装置
CN114250430B (zh) * 2020-09-21 2024-01-09 宝山钢铁股份有限公司 利于抑制锌灰的炉鼻子内气氛温度控制方法和加热装置
WO2023286501A1 (fr) * 2021-07-14 2023-01-19 Ｊｆｅスチール株式会社 Procédé de production d'une tôle d'acier galvanisée à chaud
JPWO2023286501A1 (fr) * 2021-07-14 2023-01-19
JP7364092B2 (ja) 2021-07-14 2023-10-18 Ｊｆｅスチール株式会社 溶融亜鉛めっき鋼板の製造方法

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