EP2166124A1 - Verfahren und Vorrichtung zur kontinuierlichen Schmelztauchbeschichtung von Metallbändern - Google Patents

Verfahren und Vorrichtung zur kontinuierlichen Schmelztauchbeschichtung von Metallbändern Download PDF

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Publication number
EP2166124A1
EP2166124A1 EP08017991A EP08017991A EP2166124A1 EP 2166124 A1 EP2166124 A1 EP 2166124A1 EP 08017991 A EP08017991 A EP 08017991A EP 08017991 A EP08017991 A EP 08017991A EP 2166124 A1 EP2166124 A1 EP 2166124A1
Authority
EP
European Patent Office
Prior art keywords
gas
coating
metal product
metal
nitrogen
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP08017991A
Other languages
English (en)
French (fr)
Inventor
John J. Jr. Dwyer
Howard Robert Miller
Edward K. Chang
Timothy D. Olexa
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Linde GmbH
Original Assignee
Linde GmbH
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
Application filed by Linde GmbH filed Critical Linde GmbH
Publication of EP2166124A1 publication Critical patent/EP2166124A1/de
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • C23C2/14—Removing excess of molten coatings; Controlling or regulating the coating thickness
    • C23C2/16—Removing excess of molten coatings; Controlling or regulating the coating thickness using fluids under pressure, e.g. air knives
    • C23C2/18—Removing excess of molten coatings from elongated material
    • C23C2/20—Strips; Plates
    • 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
    • C23C2/003—Apparatus
    • C23C2/0034—Details related to elements immersed in bath
    • C23C2/00342—Moving elements, e.g. pumps or mixers
    • C23C2/00344—Means for moving substrates, e.g. immersed rollers or immersed bearings
    • 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
    • C23C2/14—Removing excess of molten coatings; Controlling or regulating the coating thickness
    • C23C2/16—Removing excess of molten coatings; Controlling or regulating the coating thickness using fluids under pressure, e.g. air knives
    • C23C2/18—Removing excess of molten coatings from elongated material
    • C23C2/185—Tubes; Wires
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05C3/00—Apparatus in which the work is brought into contact with a bulk quantity of liquid or other fluent material
    • B05C3/02—Apparatus in which the work is brought into contact with a bulk quantity of liquid or other fluent material the work being immersed in the liquid or other fluent material
    • B05C3/12—Apparatus in which the work is brought into contact with a bulk quantity of liquid or other fluent material the work being immersed in the liquid or other fluent material for treating work of indefinite length
    • B05C3/125—Apparatus in which the work is brought into contact with a bulk quantity of liquid or other fluent material the work being immersed in the liquid or other fluent material for treating work of indefinite length the work being a web, band, strip or the like

Definitions

  • the invention relates to a method for coating a metal product wherein a molten coating is applied to a surface of said metal product and wherein part of said molten coating is wiped off said metal product by a gas flow directed to said metal product. Further, the invention relates to an apparatus for coating a metal product comprising a coating section wherein a molten coating is applied to a surface of said metal product and a control section wherein said control section comprises a gas knife for wiping off part of said molten coating from said metal product.
  • Continuous hot-dip galvanizing of metal sheets is a well-known technique. This method involves the application of a molten coating onto the surface of a metal sheet in a continuous process.
  • the metal sheet is passed through a bath of a molten metal.
  • the surface of the metal sheet reacts with the molten metal to bond the coating onto the sheet surface.
  • excess liquid metal is bond to the surface, too.
  • the coating thickness is controlled.
  • This thickness control is achieved by a gas wiping process.
  • Gas nozzles deliver low-pressure, high-volume air streams on the surface of the metal sheet to wipe off surplus molten metal pulled from the molten metal bath. Since the gas nozzles "cut off' excess coating material they are often referred to as "gas knives".
  • gas knife shall mean a device for delivering a gas onto or along the surface, in order to wipe off surplus coating material.
  • air knife and “nitrogen knife” accordingly refer to devices for delivering air or nitrogen for gas wiping purposes.
  • Some of the steel manufacturers use nitrogen instead of air as the wiping gas in the steel galvanizing process.
  • the use of nitrogen has the advantage that a coating with improved surface quality is achieved due to the inertness of nitrogen.
  • heated shall mean that the temperature of the gas flow is increased in any manner, in particular by direct or indirect heat exchange, by heating with a burner or another conventional heater or by blending with another warm or hot fluid.
  • air and/or nitrogen as the wiping gas.
  • the air and / or nitrogen flows are pre-heated and then directed to the metal product for wiping off excess molten coating. It is especially preferred to use nitrogen as wiping gas.
  • nitrogen instead of air are reduced dross formation and improved surface quality.
  • the nitrogen consumption is between 1% and 99%, preferably between 1% and 60%, more preferred between 30% and 60%, of the nitrogen consumption of a pure nitrogen knife system.
  • the air to nitrogen ratio used in the inventive method is preferably between 1 to 99 and 99 to 1.
  • Said second gas flow is preferably obtained by means of a plasma generator.
  • a plasma torch is used to create a hot plasma gas which is then mixed with the main gas flow to create the desired gas flow for the gas knives. It is especially preferred to use a nitrogen plasma generator.
  • the second gas flow is obtained by combustion of a fuel gas and an oxygen-containing gas.
  • the product of in-line combustion of a liquid or gaseous fuel with an oxygen-containing gas, such as air or air enriched with oxygen, is added to the main gas flow in order to obtain the desired hot gas flow for wiping.
  • This alternative is especially advantageous when small amounts of CO 2 , H 2 O and oxygen do not cause any adverse effects on coating quality.
  • Pre-heating of the wiping gas flow has the advantage of increased surface quality of the metal product.
  • the cooling rate is decreased since the temperature difference between the metal product and the wiping gas is lower.
  • the gas flow is preferably heated to a temperature between 50°C to 10°C over the temperature of the coating metal bath (pot temperature), more preferably between 300°C and 600°C.
  • the invention is preferably aimed at coating elongated metal products, in particular metal strips, metal sheets or metal wires, for example steel sheets or steel strips, which are continuously passed through a coating section where a molten coating, in particular a metal coating, is applied to a surface of the metal product.
  • the metal strip or metal sheet or in general the elongated metal product is transported through a coating bath where coating material from the coating bath is bond to the surface of the metal product.
  • a heated gas flow is blown onto the surface to wipe off excess coating material and to achieve the desired thickness.
  • a metal coating is applied to said metal product.
  • the coating which is applied to the metal product comprises one or more metals or composites of the group of zinc, aluminium, silicon.
  • the invention is directed to galvanizing a metal product, and even more preferred to galvanizing metal sheets or metal strips, in particular steel sheets or steel strips.
  • inventive method can also be used for the application of other coating materials to a metal product by hot-dip coating, that is by dipping the metal product into a bath of coating material.
  • the amount of excess coating material which is dragged out of the coating bath depends on the speed the metal product exits the bath. The higher the speed, the more coating material is dragged out of the bath.
  • the inventive method works well at speeds of the metal product between 1 m/min and 300 m/min that is it fits quite well into the speed range of standard hot-dip coating systems.
  • the inventive apparatus for coating a metal product comprises a coating section wherein a molten coating is applied to a surface of said metal product and a control section wherein said control section comprises a gas knife for wiping off part of said molten coating from said metal product wherein a gas pre-heater is connected to said gas knife.
  • the gas knife is connected to a first gas supply line supplying a large flow of a wiping gas at low temperature, for example ambient temperature, and to a second gas supply line for supplying a smaller gas flow at high temperature.
  • the second gas supply line is provided with a gas pre-heater to heat up the gas.
  • the gas pre-heater can either comprise any means for heating the gas flow directed to the gas knife by indirect or direct heat exchange.
  • the gas pre-heater comprises a plasma generator for heating at least part of said gas supplied to said gas knife.
  • the gas pre-heater comprises a burner for heating at least part of said gas supplied to said gas knife.
  • the invention provides an apparatus and a method for economically heating large gas flows, in particular nitrogen flows, used for wiping excess molten coating, such as zinc, off a surface of a metal product.
  • the invention further provides a simple control over temperature and concentrations of various oxidants of the atmosphere.
  • a heated nitrogen wiping gas flow is generated by mixing a minor flow of nitrogen at high temperature with a major flow of nitrogen at low temperature, for example ambient temperature.
  • FIG. 1 schematically shows an arrangement for coating a steel sheet according to the invention.
  • the figure shows an apparatus for galvanizing a steel strip 1.
  • the steel strip 1 is transported through a snout 2 into a coating or galvanising bath 3 of molten zinc. Within the bath 3 molten zinc is bond to the steel surface.
  • the steel strip 1 is deflected by a sink roll 4 and exits the coating bath 3 in a vertical direction.
  • the coating bath 3 there is a control section which comprises a gas knife 6.
  • the gas knife 6 comprises a chamber 8 with a slot opening 9. Chamber 8 is connected to a gas inlet 10.
  • the steel strip 1 is passed at a high speed of for example about 150 m/min through the coating bath 3 and through the control section.
  • a high speed for example about 150 m/min
  • any excess zinc 14 which has been dragged off the coating bath 3 is blown off the steel strip 1 by pre-heated gas as described below.
  • Gas knife 6 is supplied with pressurized gas which is then blown out through the slot opening 9 onto the surface of the coated steel strip 1.
  • the resulting gas jet 18 acts as a knife and wipes off excess molten zinc from the surface of the steel strip 1.
  • the molten zinc which has been stripped off the steel strip 1 flows back into the coating bath 3.
  • the coating thickness has been reduced to the desired thickness 15.
  • the pressurised gas essentially consists of nitrogen. Since nitrogen is an inert gas a coating 15 with a high quality surface is produced.
  • Pressure and volume of the gas supplied to the gas knife 6 are controlled depending on the speed of the steel strip, the desired thickness and quality of the coating, and/or the type of coating material. Further parameters which might be used to control pressure and volume of the gas are the height of the gas knife 6 above the bath 3, the distance of the gas knife 6 from the passing steel strip 1, the angle of gas knife 6, or the size of slot opening 9.
  • a pre-heated gas is supplied to the gas knives 6 and then directed to both sides of steel strip 1.
  • the wiping process is preferably carried out with nitrogen as wiping gas. Therefore, pressurised nitrogen 19 is supplied via conduits 22, 23 to gas inlet 10.
  • Heating of the nitrogen stream 19 is achieved by mixing the main nitrogen stream 19 with a relatively smaller flow of a hot gas stream 20.
  • the hot gas stream 20 is obtained by means of a nitrogen plasma torch 21.
  • the nitrogen plasma is preferably produced within an annular enclosure 24.
  • Annular enclosure 24 and nitrogen supply conduit 22 are concentrically arranged and both have a flow connection to supply conduit 23.
  • One or more plasma torches 21 produce a small volume of hot nitrogen plasma 20 which is then passed to the nitrogen supply conduit 23 and blended with a relative large flow of nitrogen gas 19 at ambient temperature.
  • the temperature of the resulting pre-heated nitrogen gas stream can be set to the desired value.
  • the hot nitrogen gas stream 20 by means of a plasma generator 21 it is also possible to mix the main nitrogen gas stream 19 with the combustion product of air and fuel. In that case an air-fuel burner would be used instead of plasma torch 21. However, the resulting mixture of nitrogen stream 19 and the stream of combustion products 20 will contain small amounts of CO2, H 2 O and oxygen. Therefore, this embodiment will only be used if the CO2, H 2 O and oxygen do not adversely effect the coating quality. If zinc vapour presents an environmental problem the inventive pre-heating of the nitrogen gas stream by blending with air-fuel combustion products may even be a welcome feature.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Coating With Molten Metal (AREA)
EP08017991A 2008-09-12 2008-10-14 Verfahren und Vorrichtung zur kontinuierlichen Schmelztauchbeschichtung von Metallbändern Withdrawn EP2166124A1 (de)

Applications Claiming Priority (1)

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US9632308A 2008-09-12 2008-09-12

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EP2166124A1 true EP2166124A1 (de) 2010-03-24

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2514849A1 (de) * 2011-04-21 2012-10-24 Air Products and Chemicals, Inc. Verfahren und Vorrichtung zur Galvanisierung eines länglichen Objekts
EP2859980A4 (de) * 2012-06-11 2015-11-25 Senju Metal Industry Co Vorrichtung zur beschichtung eines dünnen geschmolzenen lotfilms, mit dünnem geschmolzenem lotfilm beschichtete komponente und herstellungsverfahren dafür
CN112853248A (zh) * 2021-01-19 2021-05-28 李先举 一种手持式镀锌高压截击枪

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4083323A (en) * 1975-08-07 1978-04-11 Xerox Corporation Pneumatic system for solder leveling apparatus
EP0039422A2 (de) * 1980-04-11 1981-11-11 Bethlehem Steel Corporation Verfahren zum Verhindern von Fehlern in Überzügen aus einer Al-Zn-Legierung, die durch ein Schmelztauchverfahren erhalten wurden, und dazu verwendete Vorrichtung
US4612215A (en) * 1983-04-13 1986-09-16 Ziegler S.A. Process and installation for the continuous application of an oxidizable coating to a strip
US6562412B1 (en) * 1999-04-28 2003-05-13 Fontaine Engineering Und Maschinen Method and apparatus for coating strip shaped materials

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4083323A (en) * 1975-08-07 1978-04-11 Xerox Corporation Pneumatic system for solder leveling apparatus
EP0039422A2 (de) * 1980-04-11 1981-11-11 Bethlehem Steel Corporation Verfahren zum Verhindern von Fehlern in Überzügen aus einer Al-Zn-Legierung, die durch ein Schmelztauchverfahren erhalten wurden, und dazu verwendete Vorrichtung
US4612215A (en) * 1983-04-13 1986-09-16 Ziegler S.A. Process and installation for the continuous application of an oxidizable coating to a strip
US6562412B1 (en) * 1999-04-28 2003-05-13 Fontaine Engineering Und Maschinen Method and apparatus for coating strip shaped materials

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2514849A1 (de) * 2011-04-21 2012-10-24 Air Products and Chemicals, Inc. Verfahren und Vorrichtung zur Galvanisierung eines länglichen Objekts
CN102758165A (zh) * 2011-04-21 2012-10-31 气体产品与化学公司 用于对细长物体镀锌的方法和装置
CN102758165B (zh) * 2011-04-21 2014-10-08 气体产品与化学公司 用于对细长物体镀锌的方法和装置
EP2859980A4 (de) * 2012-06-11 2015-11-25 Senju Metal Industry Co Vorrichtung zur beschichtung eines dünnen geschmolzenen lotfilms, mit dünnem geschmolzenem lotfilm beschichtete komponente und herstellungsverfahren dafür
US9956634B2 (en) 2012-06-11 2018-05-01 Senju Metal Industry Co., Ltd. Device for coating thin molten solder film, thin solder film-covered component and manufacturing method therefor
CN112853248A (zh) * 2021-01-19 2021-05-28 李先举 一种手持式镀锌高压截击枪

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