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
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F17/00—Multi-step processes for surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by subclass C21D or C22F or class C25
• • 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
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
  • C23G1/10—Other heavy metals
• • 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
  • C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
• • 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
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
  • C23G1/20—Other heavy metals

Definitions

• the invention relates to a method for producing corrosion-protected flat steel products which are provided with at least a first zinc-containing coating layer and an overlying second coating layer which is based on pure magnesium or a magnesium alloy. Such methods are used for example for the production of steel sheets, which are particularly suitable for use in the field of construction, the household appliance or the automotive industry due to their optimized corrosion resistance.
• hot-dip galvanized steel sheets are distinguished by high corrosion protection in unpainted steel such as by hot-dip coating painted state off.
• electrolytically galvanized steel sheets generally have a further improved surface quality compared to hot-dip galvanized steel sheets and also an improved phosphatability for preparing a coating. It must, however, be accepted that the production of electrolytically galvanized steel sheets by the higher energy input and the disposal measures, which entail the wet-chemical process, is more cost-intensive than the hot-dip galvanizing.
• An improvement in the service properties of galvanized steel sheets can be achieved by applying to the first finishing layer formed by the galvanizing a second layer based on pure magnesium or a magnesium alloy.
• a second magnesium-containing layer By applying this second magnesium-containing layer, a combination of properties is achieved in which the properties of the first zinc-containing layer and the second magnesium-based layer complement each other optimally.
• the coating process is preferably carried out in such a way that alloying through the layers is avoided.
• a diffusion or convection layer is formed between the zinc-containing and the magnesium-based layer, which ensures the connection of the magnesium-containing layer to the zinc layer.
• a method which allows the application of a second layer to a previously provided with a corrosion protective coating steel sheet is for example from the DE 195 27 515 C1 or the corresponding one EP 0 756 022 B1 known.
• the corrosion-protected steel sheets produced by this process have improved forming and spot weldability.
• the thus coated strip undergoes a heat treatment for at least ten seconds, which is carried out in the temperature range of 300 ° C to 400 ° C in an inert gas or oxygen-poor atmosphere.
• a heat treatment for at least ten seconds, which is carried out in the temperature range of 300 ° C to 400 ° C in an inert gas or oxygen-poor atmosphere.
• the metal of the coating diffuses into the first zinc-containing anticorrosion layer on the steel substrate.
• the steel sheet is subjected to a vacuum pretreatment by ion bombardment or a plasma treatment when carrying out the known method before the vacuum coating.
• a vacuum pretreatment by ion bombardment or a plasma treatment when carrying out the known method before the vacuum coating.
• the galvanized steel substrate to be covered with the second metal layer is finely cleaned and conditioned in such a way that the metal deposited in the subsequent PVD coating is distributed in a thin layer across the entire surface and close to the zinc layer.
• a corresponding fine cleaning is according to the findings of the art in particular required if to improve its adhesion and paintability on a galvanized steel sheet as Outside layer, a magnesium-based layer is applied.
• the object of the invention was to provide a method which allows the cost-effective production of corrosion-protected steel sheets with good performance for certain applications.
• a zinc-containing coating layer is applied to a flat steel product by hot-dip galvanizing in which the flat steel product is mechanically and / or chemically finished if necessary, in which a second magnesium-based coating layer is applied directly to the finished-cleaned zinciferous coating layer by means of vapor phase deposition, and in which after the application of the second coating layer under normal atmosphere, a thermal aftertreatment of the coated flat steel product to form a diffusion or convection layer between the zinc-containing and the magnesium-based coating layer is carried out at a treatment temperature which is 335 ° C to 359 ° C.
• the steel substrate which is a flat product, such as strip or sheet, of low carbon steel is first galvanized in a conventional manner and cleaned in a likewise conventional manner by mechanical or chemical means.
• the mechanical or chemical cleaning can be used alternatively or in combination, to ensure a largely fat-free and freed from loose zinc material and other residues surface of the zinc coating.
• the galvanized flat steel product is finally cleaned at the end of this cleaning.
• an intermediate step is indispensable, in the method according to the invention before the deposition of the magnesium-containing coating layer on the Zn layer there is no further one Fine cleaning more instead.
• the steel flat product provided with the zinc layer runs into the vapor deposition in the only mechanically and / or chemically finished state in which it is coated with the magnesium-containing outer layer.
• a test introduced in the automotive and steel industry to assess the suitability of a coated steel sheet for adhesion is the so-called "adhesive bead test".
• a commercial structural adhesive suitable for bonding body parts is applied to the previously degreased surface to be tested.
• the adhesive is applied in the form of two parallel adhesive beads, the width of which is about 10 mm at a height of 4 - 5 mm.
• the geometry of the bead is then adjusted by means of a template. After the curing of the adhesive, if necessary supported by the application of heat, the sheet is bent by an angle of approx. 100 °.
• the adhesive bead breaks as a rule first perpendicular to the sample surface and then peels off along the sample surface.
• peeling takes place in the transition region between the individual coating layers or between the lowermost coating layer and the steel substrate.
• the peeling process if it occurs at all, is limited to the boundary between the free surface of the outer coating layer or to the region of the adhesive bead itself. That is, despite the procedural simplification achieved by the present invention, in a steel sheet provided with a zinc-magnesium coating system according to the invention, the applied coating layers adhere to each other and to the steel substrate so strongly that in the adhesive bead bending test, the demolition of the adhesive does not occur in the coating layers or between the coating layers and the steel substrate takes place, but at most between the adhesive and the coating or only in the adhesive itself.
• the quality of an adhesive bond produced with a flat product according to the invention is thus dependent only on the adhesion of the adhesive to the surface of the coating. Spalling or splitting of the coating system applied to the steel substrate is certainly prevented despite the omission of a fine cleaning according to the invention before the vapor deposition of the magnesium layer by the heat treatment carried out according to the invention following application of the Mg coating.
• the stone chip resistance of coated steel flat products according to the invention is also found in practice Requirements.
• stone impact resistances corresponding to those of conventionally coated sheets can be ensured, in particular when the temperature window of the heat treatment below is preferred.
• flat products produced according to the invention are particularly suitable for the production of vehicle body components, which are formed by individual sheet metal parts glued together.
• the temperatures of the heat treatment are preferably selected specifically with a view to the best possible adhesive property of the finished processed flat steel product, so that they each lie in the upper section of the optimum temperature range for the respective application.
• the thermal aftertreatment according to the invention can be carried out in air. Also this contributes to the fact that the expenditure on equipment and, associated therewith, the costs associated with carrying out the method according to the invention are reduced to a minimum.
• the thermal aftertreatment is preferably carried out in such a way that the coated strip is held in the range of the optimum treatment temperature given by the invention for a period of up to 15 seconds, in particular 5-10 seconds, so that it leaves the heat treatment oven its surface has the relevant treatment temperature.
• the respective treatment temperature can be customary measuring devices, such as abrasive on the tape surface patch temperature sensor used, which are positioned, for example, in the outlet region of the furnace at a location where their signals and function are no longer disturbed by the operation of the furnace and on the other hand it is ensured that no significant cooling of the tape leaving the oven has occurred yet.
• a suitable positioning of the measuring device is particularly important if an induction furnace with correspondingly scattering electromagnetic fields is used for the thermal aftertreatment.
• the zinc coating can be applied to the steel substrate in a conventional manner by hot-dip galvanizing.
• the dry cleaning includes, for example, a pickling of the steel substrate by rinsing with an acid, in particular hydrochloric acid. Then a rinsing with demineralized water can follow the decaping in order to completely remove remaining acid residues on the galvanized sheet after decaping.
• a further optimization of the coating result can be achieved in that the steel substrate provided with the zinc-containing coating has a roughness Ra of at least 1.4 ⁇ m, in particular 1.4-1.6 ⁇ m, when entering the vapor deposition on its free surface roughness values higher than 1.4 ⁇ m are advantageous.
• the zinc-coated steel flat product when entering the vapor deposition has a peak number RPC of at least 60 / cm.
• the peak number RPC and the center roughness Ra are determined in the profile-cutting method, with the determination of the average roughness Ra using the procedures given in the StahlEisen-Prüfblatt SEP 1940 in DIN EN ISO 4287: 1998 and in determining the peak number RPC.
• the steel flat product provided with the zinc-containing coating is heated to or maintained at a temperature above room temperature but below the alloying temperature before it enters the vapor deposition.
• the temperatures which are particularly suitable for this purpose are in the range from 230 ° C to 250 ° C, in particular at about 240 ° C.
• the invention thus provides a method which can be carried out particularly economically in a continuously executed workflow and provides a product which, due to its surface properties and adhesive properties, is particularly well suited for the production of components for vehicle bodies using modern joining techniques such as gluing , suitable.
• a sheet metal strip is produced in a conventional manner, which is then coated in both conventional manner in a conventional continuous hot dip galvanizing process with a zinc coating of 35 gm -2 .
• the thus coated and brought to a suitable width steel strip is then provided in a continuous line for narrow strip (300mm) at a belt speed of 30 m / min in the run with a magnesium coating.
• the steel strip undergoes a final cleaning, in which first the corrosion protection oil adhering to the strip is removed by alkaline cleaning.
• a final cleaning in which first the corrosion protection oil adhering to the strip is removed by alkaline cleaning.
• a high-pressure cleaning is carried out, in which a commercial alkaline cleaning agent with a pressure of about 100 bar and a temperature of 80 ° C is applied to the strip surface.
• the steel strip passes through an ultrasonic bath, which is likewise formed from a conventional cleaning agent, whereupon it is then rinsed in a triple cascade rinse with demineralized water in order to safely remove residues of cleaning agent adhering to the surface of the belt.
• the steel strip is dried by means of hot air.
• the thus finished-cleaned steel strip is then passed through several pressure stages in a vacuum chamber. There, the steel strip is heated to a temperature of 240 ° before the actual vapor deposition by means of an induction heater, before it passes through the vapor deposition source. Without further treatment step acting directly on the strip surface, in particular without intermediate plasma cleaning, the magnesium vapor deposition takes place in a PVD process by means of a commercially available JET evaporator.
• an evaporation rate of 18 ⁇ m * m / min is set at a residual gas pressure of 2 * 10 -2 mbar, so that a magnesium deposit of 600 nm results on the steel strip already coated with the zinc coating.
• the galvanized steel strip coated with the Mg layer is subsequently returned to the normal atmosphere via a further series of pressure stages. Then it is passed through an induction furnace where it is heated under normal atmosphere within 4s to a temperature of 345 ° C ⁇ 5K, with which it leaves the induction furnace again.
• the temperature is monitored by means of grinding elements placed on the surface of the strip at the end of the induction furnace. Since the exactness of the temperature determination and the temperature control derived therefrom is of particular importance, it is important in the temperature detection that influences of the measurement by the induction furnace are largely excluded. Accordingly, the arrangement of the measuring devices is chosen so that they is not disturbed by the electromagnetic field generated by the furnace, but that the measurement can take place as close as possible to the exit of the furnace in order to obtain a timely and unaffected by a cooling detection of the actual temperature of the finished heat-treated steel strip.
• the steel strip After a free tape run of 4 m over a period of about 8 s and thereby entering cooling to ambient air by about 10 ° C, the steel strip is passed over cooling rollers and cooled to a temperature below 100 ° C.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Coating With Molten Metal (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Physical Vapour Deposition (AREA)
• Electroplating Methods And Accessories (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Laminated Bodies (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Applications Claiming Priority (1)

Publications (1)

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Cited By (5)

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Citations (3)

• 2005
  • 2005-09-23 DE DE102005045780A patent/DE102005045780A1/de not_active Withdrawn
• 2006
  • 2006-09-22 CN CNA2006800349016A patent/CN101268216A/zh active Pending
  • 2006-09-22 JP JP2008531712A patent/JP2010504420A/ja active Pending
  • 2006-09-22 BR BRPI0616110-3A patent/BRPI0616110A2/pt not_active IP Right Cessation
  • 2006-09-22 CA CA002622817A patent/CA2622817A1/en not_active Abandoned
  • 2006-09-22 RU RU2008115945/02A patent/RU2008115945A/ru unknown
  • 2006-09-22 KR KR1020087008616A patent/KR20080058369A/ko not_active Application Discontinuation
  • 2006-09-22 US US12/066,962 patent/US20090139872A1/en not_active Abandoned
  • 2006-09-22 AU AU2006293917A patent/AU2006293917A1/en not_active Abandoned
  • 2006-09-22 EP EP06121111A patent/EP1767670A1/de not_active Withdrawn
  • 2006-09-22 WO PCT/EP2006/066632 patent/WO2007033992A2/de active Application Filing
  • 2006-09-22 EP EP06793750A patent/EP1934386A2/de not_active Withdrawn
• 2008
  • 2008-03-20 ZA ZA200802606A patent/ZA200802606B/xx unknown

Patent Citations (3)

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