Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/08—Anti-corrosive paints
  • C09D5/10—Anti-corrosive paints containing metal dust
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D1/00—Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
  • C09D7/40—Additives
  • C09D7/48—Stabilisers against degradation by oxygen, light or heat
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
  • C09D7/40—Additives
  • C09D7/60—Additives non-macromolecular
  • C09D7/61—Additives non-macromolecular inorganic
• • 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
  • C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D2202/00—Metallic substrate
  • B05D2202/10—Metallic substrate based on Fe
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D2701/00—Coatings being able to withstand changes in the shape of the substrate or to withstand welding
  • B05D2701/40—Coatings being able to withstand changes in the shape of the substrate or to withstand welding withstanding welding
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/02—Elements
  • C08K3/08—Metals
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T50/00—Aeronautics or air transport
  • Y02T50/60—Efficient propulsion technologies, e.g. for aircraft

Definitions

• the invention relates to a process for producing an active anti-corrosion coating on steel components.
• Hot-forming processes are being used increasingly to manufacture high-strength steel components of the sort required, for example, as structural body components for vehicle construction.
• One particular type of hot forming is the process referred to as press hardening, during which specialty steels (usually manganese-boron steels) are heated to austenizing temperature, hot-formed and quench-hardened in the forming tool.
• a martensitic microstructure of high mechanical strength is obtained, which makes it possible to manufacture components that are thin and therefore light in weight, yet high in strength.
• Austenizing takes place at temperatures above 850° C. At this temperature, pronounced scale formation occurs at the steel surface. The scale forms so quickly that even parts which are heated in an atmosphere of protective gas, e.g.
• the scale is apt to flake off, and is rough and brittle. It therefore damages components as well as forming tools, and has to be removed at high cost from the component following press hardening, for example by blasting.
• the regular cleaning of the forming tools which is necessary substantially increases cycle times, and the material removed by blasting has to be compensated for by using thicker metal sheet.
• For press hardening therefore, it is usual to use steel sheet which has been provided with a coating that protects against scaling.
• the EP 1 013 785 A1 describes the use of hot-dip aluminized steel types. These are coated with an approximately 20-30 ⁇ m thick layer of an Al—Si alloy, which is applied by hot-dip coating.
• This Al—Si coating does indeed offer a certain degree of corrosion protection for hot-dip aluminized sheet steel while it is in storage, which means that sheets and coils need not be oiled for storage and transport purposes; however, after the annealing process employed during hot-forming, the anti-corrosive effect of the coating is very much reduced. This becomes evident when, for example, hot-dip aluminized steel sheet that has been annealed at 950° C. is examined using the salt spray test according to German standard DIN 50021.
• a refined form of the wet-chemical antiscaling coating described which is the subject of the WO 2007/076766 A2, does possess the required electrical conductivity for resistance spot welding and cataphoretic dip-coating and can thus remain on the component after it has been press-hardened. Under normal conditions of press-hardening, the electrical resistance of these sheets is in the region of ⁇ 5 mOhm following the hardening process. If the component is subsequently to be subjected to a welding process, in particular a resistance spot welding process, or to cataphoretic hot-dip coating, the observance of process parameters that will lead to the formation of electrically conductive reaction layers when the steel sheet with its antiscaling coating is annealed is particularly important.
• the use a protective-gas atmosphere e.g.
• a general advantage of the wet-chemical antiscaling coatings described over hot-dip aluminizing is that on heating to austenizing temperature, no diffusion layer needs to be formed and therefore cycle times are shorter. Besides, on heating, there is no danger in this case of any melting, meaning that inductive or conductive heating methods may be used during press-hardening.
• WO 2005/021820 A1, WO 2005/021821 A1 and WO 2005/021822 A1 describe methods of manufacturing various hardened steel parts.
• a protective coating consisting of zinc combined with another element having an affinity for oxygen (especially aluminium) is applied to the steel.
• this protective coating is applied by means of a hot-dip process, in the WO 2005/021820 A1 and WO 2005/021822 A1 by means of a hot-dip or an electroplating process.
• these coatings which contain zinc as the main element, are extremely susceptible to oxidisation and vaporisation at the austenizing temperatures required for a press-hardening process. Even traces of dirt (e.g.
• the object of the invention is to develop an active anti-corrosion coating that can be applied on an industrial scale using conventional means (e.g. dipping, spraying, flooding or rolling) and is intended for hot-formed and, in particular, press-hardened steel parts provided with antiscaling means.
• conventional means e.g. dipping, spraying, flooding or rolling
• the invention is thus based on using a special antiscaling coating on steel in order to prevent scale formation during hot-forming and particularly during press-hardening at temperatures above 600° C.
• An embodiment of the invention consists in that annealing is effected at a temperature above 850° C.
• hardenable steels are annealed conductively or inductively in gas-operated or electrically-operated annealing furnaces.
• An advantageous embodiment of the invention consists in that the oxygen content in the annealing-furnace atmosphere is 0-10%.
• the antiscaling layer consists of an aluminium alloy, aluminium pigments, a coating containing an aluminium pigment, a magnesium alloy, magnesium pigments, a coating containing a magnesium pigment, a zinc alloy, zinc pigments or a coating containing a zinc pigment;
• the antiscaling layer has a maximum electrical resistance of 10 mOhm, preferably a maximum of 5 mOhm.
• the finished component has a maximum electrical resistance of 10 mOhm, preferably a maximum of 5 mOhm.
• the two preceding measures ensure that resistance spot welding is possible.
• the anti-corrosion layer is applied to the annealed reaction layer from the liquid phase in a wet-chemical process, in particular in a spraying, flooding, rolling or dipping process.
• the layer thickness of the anti-corrosion layer is less than 50 ⁇ m, preferably less than 20 ⁇ m and best of all less than 10 ⁇ m.
• the anti-corrosion layer is diluted with solvents prior to application.
• the anti-corrosion layer once applied, is dried at a temperature between room temperature and 400° C., preferably between room temperature and 250° C.
• the anti-corrosion layer contains a binder and metallic pigment.
• the anti-corrosion layer contains between 10 and 100 wt. %, preferably between 50 and 100 wt. % and best of all between 70 and 95 wt. % metallic zinc pigment and/or magnesium pigment.
• the anti-corrosion layer contains up to 50 wt. % metallic aluminium pigment.
• a preferred embodiment of the invention consists in that the binder used in the anti-corrosion layer contains 5 to 100 wt. % metal oxides, in particular titanium, aluminium or zirconium oxides.
• the binder used in the anti-corrosion layer contains up to 50 wt. % binder produced by the sol-gel process, silicones, siloxanes or waxes.
• the anti-corrosion layer contains solid-state lubricants, in particular graphite or boron nitride.
• the invention consists in that the steel element is in the form of sheet, coil, component or other solid body.
• a special embodiment of the invention consists in that the coated substrate is a steel element that has undergone a hardening process.
• the steel element was shaped in a hydroforming process.
• coated substrate is a steel element that has been provided with an antiscaling layer which is of a kind customary for the hardening process and which remains on the component.
• the steel element consists of an assembly of components made of diverse alloy steels—with or without metallic coatings such as aluminium or zinc coatings or coatings containing metal pigments—and joined together by way of standard joining processes, such as welding, bonding, bolting or riveting.
• a preferred embodiment of the invention consists in that, prior to being annealed, the steel element is provided wholly or partially with a coating that influences the heating-up behaviour of the steel part or of parts thereof.
• the steel element with a homogeneous, heat-absorbing coating, for example a black one, in order to reduce the heating-up time, the furnace time and/or the diffusion time, or with an inhomogeneous coating with heat-absorbing and heat-reflecting areas distributed over the surface of the steel element, for example a partial black coating and a partial silver coating so that, by way of this variation in the absorption of infrared rays at the surface, the energy input may be selectively controlled from area to area, allowing, for example, the formation of different hardening zones.
• This measure may of course be combined with the previously described assembly, where the steel element comprises diverse components joined together.
• An embodiment of the invention consists in that the components or assemblies of components provided with the anti-corrosion layer can be welded with each other, with customarily weldable alloy steels or with steel grades provided with metallic coatings.
• a special embodiment of the invention consists in that the electrical resistance of the steel element used is not influenced significantly by the anti-corrosion layer.
• the scope of the invention extends to use of the process according to the invention for producing anti-corrosive components or assemblies for machine construction, in particular for vehicle construction, building, in particular steelwork, for process engineering, aerospace, power plants and power-plant engineering, electrical engineering, medical engineering, sports equipment, horticulture and landscape gardening, toolmaking, agricultural machinery, furniture, kitchens, household appliances, toys, sports articles, camping equipment, caravans, window and door frames, heating installations, heat exchangers, air conditioners, escalators, conveyors, oil platforms, jewellery, locomotives, rails, transport systems, cranes, furnaces, engines and engine attachments, pistons, sealing rings, exhaust systems, ABS and braking systems, brake discs, chassis components, wheels, rims, sanitary articles, lamps and design articles.
• Degreased 22MnB5A steel strip moving at 60 m/min is roll-coated in a coil coating line with a coating material according to WO 2007/076766 A2.
• the coating material is hardened at a PMT (Peak Metal Temperature) of 200-250° C.
• PMT Peak Metal Temperature
• the coated steel strip is cut into tailored blanks and pre-drawn in a cold-forming process to a preform.
• the preform is heated in a nitrogen atmosphere having a maximum oxygen content of 10 vol. % to a temperature of 950° C. in an electrically operated continuous furnace for 4 minutes, transferred to the forming tool and hot-formed there, and then quench-hardened by cooling to 200° C. within 20 s.
• a suitable anti-corrosion coating for the press-hardened parts described is produced as follows:
• the coating solution is applied to the entire surface of the press-hardened part using a paint spray gun (e.g. Sata Jet, 1.2 mm nozzle) such as to produce a layer thickness of 3-10 ⁇ m after drying and hardening.
• a paint spray gun e.g. Sata Jet, 1.2 mm nozzle
• the coating solution hardens at room temperature within an hour of application, or within 20 minutes at 180° C.
• a component provided with an aluminium antiscaling coating (e.g. Usibor) is subjected as in Example 1 to a press-hardening process.
• a suitable anti-corrosion coating for this component is produced as follows:
• a mixture of 40 g methyltriethoxysilane (from Fluka) and 10 g tetraethoxysilane (from Fluka) is hydrolysed by stirring 15 g of 1% orthophosphoric acid into it. After 5 hours of stirring, the reaction mixture is single-phase and is stirred into the aforementioned dispersion to produce a homogeneous solution.
• the coating solution is prepared in a quantity sufficient to fill a suitably controlled dip tank.
• the component is lowered by means of a crane into the dip tank filled with coating solution, and after its entire surface has been homogeneously wetted, is lifted out again. After any excess coating solution has dripped off, the component is transferred to a furnace where the coating is hardened for 20 minutes at 180° C.
• the composite entity comprisng steel, aluminium and anti-corrosion layer has a resistance of ⁇ 10 mOhm and can be joined readily with other sheets by means of resistance spot welding.
• Body components are produced by means of press-hardening from steel blanks with an Al—Si dip-coating and from steel blanks coated according to the WO 2007/076766 A2. These are joined with uncoated steel components by means of resistance spot welding to form an assembly.
• a suitable anti-corrosion coating for this assembly is produced as follows:
• an aluminium oxide powder e.g. Aeroxide Alu C from Degussa
• a zinc powder e.g. Standart Zink Flake AT from Eckart
• Aerosil R 972 from Degussa
• 20 g of a suitable powdered wax e.g. Licowax C from Clariant
• a suitable powdered wax e.g. Licowax C from Clariant
• the coating solution is applied to the entire surface of the press-hardened assembly using spray painting equipment (e.g. HVLP pressurized-air nozzles with a diameter of 1.2 mm) such as to produce a layer thickness of 3-10 ⁇ m after drying and hardening.
• the solution is also sprayed particularly into cavities, gaps and joints. Hardening is effected for 20 minutes at a temperature of 180° C.
• the components and assemblies from the examples 1-3 are each coated with a 3-10 ⁇ m thick silver-grey anti-corrosion layer that adheres firmly to the substrate. After being exposed in a salt-spray test as per DIN EN ISO 9227 for 1000 h, the coatings showed no red-rust formation, neither on the surface nor at the cruciform injury site.
• the coated components and assemblies have an electrical resistance of ⁇ 10 mOhm and can be welded to other steel parts, for example to assemble a vehicle body.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Inorganic Chemistry (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Heat Treatment Of Articles (AREA)
• Coating By Spraying Or Casting (AREA)

Applications Claiming Priority (3)

Publications (1)

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Cited By (10)

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Citations (16)

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• 2007
  • 2007-08-13 DE DE102007038215A patent/DE102007038215A1/de not_active Withdrawn
• 2008
  • 2008-08-12 EP EP08801131A patent/EP2191030A2/de not_active Withdrawn
  • 2008-08-12 CN CN2008801032322A patent/CN101815805B/zh not_active Expired - Fee Related
  • 2008-08-12 WO PCT/DE2008/001298 patent/WO2009021489A2/de active Application Filing
  • 2008-08-12 JP JP2010520418A patent/JP2010535944A/ja active Pending
  • 2008-08-12 US US12/733,140 patent/US20100175794A1/en not_active Abandoned
  • 2008-08-12 KR KR1020107005510A patent/KR20100052534A/ko not_active Application Discontinuation

Patent Citations (18)

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