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.
• the further processing of the galvanized steel sheets to articles of daily use is usually carried out by forming, joints, organic coating (eg painting) or similar processes.
• organic coating eg painting
• the bonding of preformed sheet-metal parts to entire assemblies of the body is gaining in importance, in particular in the field of automobile body construction.
• Another important feature is the formability of the coatings, d. H. their ability to withstand severe deformation stresses, such as those occurring during deep drawing, without serious damage.
• Each of these requirements can not be met to the same extent with conventional, fully galvanized products.
• conventionally coated steel sheets generally have particularly good properties in the area of a specific requirement feature, while smears have to be accepted in the area of the other requirement features.
• Hot dip galvanized steel sheets are coated with a high level of corrosion protection in the unpainted and painted state.
• electrolytically galvanized steel sheets generally have a further improved surface quality as compared to hot-dip galvanized steel sheets, as well improved phosphatability to prepare for painting. 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 known for example from DE 195 27 515 Cl and the corresponding EP 0 756 022 Bl.
• the corrosion-protected steel sheets produced by this process have improved forming and spot weldability. That by hot-dip galvanizing or electrolytic galvanizing with the Zinc-coated steel sheet is first mechanically or chemically cleaned. Then, by means of a suitable method of physical
• Vapor deposition Physical Vapor Deposition
• PVD Physical Vapor Deposition
• the thus coated strip undergoes a heat treatment for at least ten seconds, which is carried out in the temperature range of 300 0 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 a magnesium-based layer is applied to improve its adhesion and paintability on a galvanized steel sheet as the outer layer.
• 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.
• This object has been achieved on the basis of the above-described prior art by a method for producing a corrosion-protected flat steel product, wherein according to the invention on a flat steel product, a zinc-containing coating layer is applied by electrodeposition, in which the flat steel product is, if necessary, mechanically and / or chemically finished in which immediate a second magnesium-based coating layer is applied to the finished-cleaned zinc-containing coating layer by means of vapor phase deposition, and after the second coating layer has been applied 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 320 0 C to 335 0 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 in order to ensure a largely fat-free surface of the zinc coating which is free of loose zinc material and other residue.
• the galvanized flat steel product is finally cleaned at the end of this cleaning.
• an intermediate step is indispensable, in the inventive method before depositing the magnesium-containing coating layer on the Zn layer no further fine cleaning takes place.
• the flat steel product provided with the zinc layer runs in only mechanically and / or chemically finished cleaned state the vapor deposition, in which it is covered with the magnesium-containing outer layer.
• a previously galvanized steel sheet or strip which is provided with a magnesium layer and dispenses with an upstream plasma cleaning, has an adhesive suitability in addition to an optimized surface appearance with respect to its optical appearance, which satisfies all the requirements imposed in the practical use of such metal sheets ,
• a test for assessing the suitability of a coated steel sheet for use in the automotive and steel-producing industries is the so-called "adhesive bead test".
• a commercially available structural adhesive suitable for bonding body components is applied to the previously degreased surface to be tested.
• the adhesive is applied in the form of two parallel adhesive beads whose width 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, assisted by heat supply, the sheet is bent by an angle of approx. 100 °.
• the adhesive bead first breaks perpendicularly to the sample surface and then peels off along the sample surface.
• the shuttering process if it occurs at all, is limited to the boundary between the free surface of the outer coating layer or to the area of the adhesive bead itself. That is, despite the procedural simplification achieved by the invention adhere to a coated in accordance with the invention with a zinc-magnesium coating system steel sheet applied coating layers so strong to each other and on the steel substrate that in Kleberaupen bending test of the demolition of the adhesive is not in the coating layers or between the Kochberzugs legien 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 connection 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 inventive waiver of a fine cleaning before the vapor deposition of the magnesium layer by the heat treatment carried out according to the invention following the application of the Mg coating.
• the rockfall resistance of flat steel products coated in accordance with the invention also meets the requirements that arise in practice.
• the rockfall resistance of flat steel products coated in accordance with the invention also meets the requirements that arise in practice.
• 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. This also 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 for a period of up to 15 seconds, in particular 5-10 seconds, in the region of the optimum treatment temperature given by the invention, so that it exits the heat treatment oven its surface has the relevant treatment temperature.
• To measure 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 is carried out by electrolytic galvanizing, so result in the inventively processed flat products optimized property combinations when the treatment temperature selected during the thermal treatment is 320 0 C to 335 0 C. By observing this temperature range, it can be ensured with particular certainty that no Fe-Zn-rich phases are formed in the coating layer, by which the adhesive properties of a sheet coated according to the invention could be impaired.
• all PVD methods can be used, which have already been preserved in practice for this purpose.
• the work results achieved by the method according to the invention can be further improved by preconditioning the steel sheet provided with the zinc-containing coating wet-chemically in the course of its final cleaning by winding with a suitable preconditioning agent.
• the galvanized steel strip can be wound with an alkaline solution in the course of the chemical final cleaning.
• the dry cleaning includes, for example, a pickling of the steel substrate by coils with an acid, especially hydrochloric acid.
• an acid especially hydrochloric acid.
• On the Dekapieren can then follow a rinse with demineralized water to remove on the galvanized sheet after picking still existing Saurereste largely completely.
• 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 .mu.m, in particular 1.4-1.6 .mu.m, when entering the vapor deposition on its free surface higher than 1.4 microns roughness values are advantageous.
• the zinc-coated steel flat product upon its entry into 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 center roughness Ra using the procedures specified in the Steel Iron Test Sheet SEP 1940 in DIN EN ISO 4287: 1998 and in determining the peak number RPC.
• the invention thus provides a method which can be carried out particularly economically in a continuously executed workflow and which delivers a product which, due to its
• Embodiment 1 The invention will be explained in more detail with reference to two embodiments. Embodiment 1
• PVD deposition and thermal aftertreatment module has been integrated behind the conventional gensets used for galvanizing and before the finishing equipment for the finished coated steel strip.
• electrolytically galvanized steel strip is passed to the galvanizing and a completed also in the conventional system finished cleaning in the module for PVD deposition and thermal aftertreatment in which it PVD-coated and is thermally treated. Subsequently, the steel strip is returned back to the conventional plant, where it is phosphated and oiled during the final treatment, for example.
• customary dimensions steel strips are typical steel grades in question. It has proved to be particularly advantageous if the average roughness value of the cold-rolled sheet used for the electrolytically galvanized thin sheet is at the upper limit of the automotive specification for outer parts of 1.1-1.6 ⁇ m Ra. A further increase in the Ra value above 2 ⁇ m would be advantageous in view of the adhesion of the coating and the consequent adhesive suitability, but at the moment it does not prove to be economical makes sense, since such a product today would not meet the specifications of automotive customers.
• a value of RPC> 60 / cm is preferred. Both values can also be positively influenced in the electrolytic galvanizing process. Another option for setting these values is to use a cementation process as the last step of the final cleaning.
• the steel strip is first conventionally provided in vertically arranged electrolytic cells by means of soluble anodes by electrolytic means with a two-sided zinc coating of 3 .mu.m. After rinsing and drying the now galvanized steel strip, the galvanized substrate is basically finished and prepared for the application of the magnesium-containing coating.
• the thus finished steel strip passes through several pressure stages in a vacuum chamber, in which without further treatment step, the magnesium vapor deposition by means of a PVD process using a commercial JET evaporator is performed.
• the JET Evaporator by means of suitable thermal or mechanical measures capable of providing evaporation rates between 6 microns * m / min and 54 microns * m / min.
• a treatment by means of NIR emitter is used in this case.
• the heating time is dependent on the belt speed, but can be adjusted by switching off individual modules.
• the peak temperature of the heat treatment is according to the invention 327 ° C ⁇ 7K.
• a special pyrometric imaging method is used which makes it possible to control the temperature treatment according to the invention precisely in terms of location and time. Different steel substrates and coating conditions can cause deviating emissivities, so that a detailed calibration must be carried out.
• the steel strip After a free tape run of 10 m, the steel strip is cooled by means of water. The heat remaining in the belt is adjusted so that the belt dries automatically.
• FE-SEM image is a
• Querschliffpraparation a coated according to the invention and at a temperature of 332 0 C heat treated steel strip reproduced in an inverted representation.
• the advantageous layer structure with the steel substrate S, which applied thereto by electrolytic coating zinc layer Z and on the Z zinc layer lie lying magnesium-containing ZnMg coating M.
• the layer which can be seen above the coating M is the investment material E which has been required for the preparation of the transverse cut.
• Evaporator realized to 96 microns * m / min at a belt speed of 64 m / min Mg runs of 1500 nm and thermally alloyed according to the invention. Also in these studies, the advantageous formation of the Zn-Mg alloying coating was detected.

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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)
• Physical Vapour Deposition (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Electroplating Methods And Accessories (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Laminated Bodies (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

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

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