EP3872230A1 - Verfahren zum herstellen gehärteter stahlbauteile mit einer konditionierten zinklegierungskorrosionsschutzschicht - Google Patents

Verfahren zum herstellen gehärteter stahlbauteile mit einer konditionierten zinklegierungskorrosionsschutzschicht Download PDF

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Publication number
EP3872230A1
EP3872230A1 EP20160202.6A EP20160202A EP3872230A1 EP 3872230 A1 EP3872230 A1 EP 3872230A1 EP 20160202 A EP20160202 A EP 20160202A EP 3872230 A1 EP3872230 A1 EP 3872230A1
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EP
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Prior art keywords
tin
steel
solution
component blank
zinc
Prior art date
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EP20160202.6A
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German (de)
English (en)
French (fr)
Inventor
Dr. Dipl.-Ing. Martin Fleischanderl
Dipl.-Ing. Ernst Schachinger
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Voestalpine Stahl GmbH
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Voestalpine Stahl GmbH
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Publication date
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Priority to EP20160202.6A priority Critical patent/EP3872230A1/de
Priority to PCT/EP2021/054962 priority patent/WO2021170860A1/de
Priority to US17/802,576 priority patent/US20230145863A1/en
Priority to EP21707718.9A priority patent/EP4110970B1/de
Priority to CN202180017429.XA priority patent/CN115485415B/zh
Publication of EP3872230A1 publication Critical patent/EP3872230A1/de
Withdrawn legal-status Critical Current

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    • 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
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/60—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using alkaline aqueous solutions with pH greater than 8
    • C23C22/62—Treatment of iron or alloys based thereon
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0278—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular surface treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
    • B21D22/20—Deep-drawing
    • B21D22/208—Deep-drawing by heating the blank or deep-drawing associated with heat treatment
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0242—Flattening; Dressing; Flexing
    • 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
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/48—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates
    • C23C22/50—Treatment of iron 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
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/82—After-treatment
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
    • C23C28/023—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite
    • 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
    • C21D2261/00—Machining or cutting being involved

Definitions

  • the invention relates to a method for producing hardened steel components with a conditioned zinc alloy corrosion protection layer.
  • anti-corrosion layers on metal strips can be organic coatings, for example paints, although these paints can also contain anti-corrosive agents.
  • metal coatings can consist of an electrochemically more noble metal or of an electrochemically less noble metal.
  • barrier protective layer In the case of a coating made of an electrochemically more noble metal or a metal that passivates itself, such as aluminum, one speaks of a barrier protective layer, whereby, for example, when aluminum is applied to steel, the steel material suffers corrosion if this barrier protective layer is no longer present in places is, for example due to mechanical damage.
  • a common barrier protective layer of steel is the aforementioned aluminum layer, which is usually applied by hot-dip coating.
  • an electrochemically less noble metal is applied as a protective layer, one speaks of a cathodic corrosion coating, because if the corrosion protection coating is mechanically damaged down to the steel material, the electrochemically less noble metal is first corroded before the steel material itself is exposed to corrosion.
  • cathodic protective coating on steel is a zinc coating or an alloy based on zinc.
  • hot-dip galvanizing also known as hot-dip galvanizing
  • Steel is immersed continuously (e.g. strip or wire) or piece by piece (e.g. components or circuit boards) at temperatures of around 450 ° C to 600 ° C in a melt of liquid zinc (the melting point of zinc is 419.5 ° C).
  • the zinc melt conventionally has a zinc content of at least 98.0% by weight in accordance with DIN EN ISO 1461.
  • a resistant alloy layer of iron and zinc is formed on the steel surface and above it is a firmly adhering pure zinc layer, the composition of which corresponds to the zinc melt.
  • the zinc layer has a thickness of 5 ⁇ m to 40 ⁇ m.
  • the zinc layer can have a thickness of 50 ⁇ m to 150 ⁇ m.
  • electrolytic galvanizing galvanic galvanizing
  • steel strips or steel plates are not immersed in a zinc melt, but in a zinc electrolyte.
  • the steel to be galvanized is introduced into the solution as a cathode and an electrode made from the purest possible zinc or an electrolyte with a high amount of dissolved zinc is used as the anode. Electricity is passed through the electrolyte solution.
  • the zinc present in ionic form (oxidation level + II) is reduced to metallic zinc and deposited on the steel surface.
  • electrolytic galvanizing can apply thinner layers of zinc.
  • the zinc layer thickness is proportional to the strength and duration of the current flow, whereby - depending on the workpiece and anode geometry - a layer thickness distribution is created over the entire workpiece.
  • Careful surface pretreatment is required to ensure adhesion to the zinc layer. This can be, for example, degreasing, alkaline cleaning, rinsing and / or pickling.
  • one or more post-treatments can be carried out, such as phosphating, oiling, application of organic coatings (e.g. cataphoretic dip painting, KTL for short).
  • quench hardening means that a cooling rate above the critical cooling rate is selected to adjust the structure. This critical cooling rate is around 15 to 20 Kelvin per second, but can also be lower depending on the alloy composition.
  • a common type of steel that can be hardened by quench hardening are the so-called boron-manganese steels, such as the most commonly used 22MnB5, but also variants of this steel, such as 20MnB8, 30MnB8.
  • Non-hardenable steels such as micro-alloyed steel can also be hot-formed in a direct or indirect process.
  • Such steel grades can be easily deformed and cut to size in the unhardened state.
  • the first and somewhat older method is the so-called press hardening.
  • press hardening a flat plate is cut out of a steel strip made of a quench-hardenable steel alloy, for example a 22MnB5 or a similar manganese-boron steel.
  • This flat blank is then heated to such an extent that the steel structure has the appearance of gamma iron or austenite.
  • austenitizing temperature Ac 3 In order to achieve this structure, thus the so-called austenitizing temperature Ac 3 must be exceeded, at least if complete austenitizing is desired.
  • this temperature can be between 820 ° C. and 900 ° C., such steel blanks, for example, being heated to about 900 ° C. to 930 ° C. and held at this temperature until the structure changes completely. Then such a steel blank is transferred in the hot state in a press, in which the hot steel blank is brought into the desired shape with a single press stroke by means of an upper tool and a lower tool, each of which is correspondingly shaped.
  • press tools that is to say forming tools, energy is withdrawn from the steel very quickly.
  • the heat must be extracted so quickly that the so-called critical hardening speed is exceeded, which is usually between 20 ° and 25 ° Kelvin per second.
  • the structure of the austenite does not change back into a ferritic initial structure, but a martensitic structure is achieved. Due to the fact that austenite can dissolve considerably more carbon in its lattice than martensite, the carbon precipitates cause lattice distortion, which leads to the high hardness of the end product. As a result of the rapid cooling, the martensitic state is stabilized, so to speak. As a result, hardnesses or tensile strengths R m of more than 1500 MPa can be achieved. Hardness profiles can also be set by means of suitable measures, which will not be discussed in more detail, such as complete or partial rewarming.
  • press hardening developed by the applicant.
  • press hardening a flat steel plate is cut out of a steel strip and this flat steel plate is then formed in the cold state.
  • this reshaping does not take place with a single press stroke, but rather, as is customary in conventional press lines, for example in a five-stage process.
  • This process allows considerably more complex shapes, so that in the end a complex-shaped component, such as the B-pillar or a longitudinal member of a motor vehicle, can be produced.
  • this component is also austenitized in a furnace and transferred in the austenitized state to a molding tool, the molding tool having the contour of the final component.
  • the preformed component is preferably shaped before heating in such a way that after heating and thus even a thermal expansion of this component already largely corresponds to the final dimensions of the hardened component.
  • This austenitized blank is inserted into the mold in the austenitized state and the mold is closed.
  • the component is preferably touched on all sides by the molding tool and held in a clamping manner, and the contact with the molding tool also removes the heat in such a way that a martensitic structure is generated. In the clamped state, shrinkage cannot take place, so that the hardened end component with the corresponding final dimensions can be removed from the mold after hardening and cooling.
  • Corrosion protection coatings for components to be hardened are, however, exposed to different requirements than corrosion protection coatings for components that are not hardened.
  • the high temperatures that arise during hardening must be withstood by the anti-corrosion coatings. Since it has been known for a long time that hot-dip aluminized coatings can withstand high temperatures, press hardening steels were first developed, which have a protective layer made of aluminum. Such coatings are able to withstand not only the high temperatures, but also the deformation in the hot state.
  • the disadvantage is that hot-dip galvanizing is not usually used in motor vehicles, but hot-dip galvanizing, and it is fundamentally problematic to use different corrosion protection systems, especially when there is a risk of contact corrosion.
  • zinc coatings are considerably less complicated than aluminum coatings when it comes to cold forming, since aluminum coatings tend to peel off or crack at conventional forming temperatures. This does not happen with zinc.
  • the sheet steel being a sheet steel coated with a metallic coating and being heated and quenched for hardening.
  • the oxides present on the anti-corrosion coating due to the heating are removed, the component being subjected to vibratory grinding to condition the surface of the metallic coating, i.e. the anti-corrosion layer, the anti-corrosion coating being a zinc-based coating and the surface conditioning so it is carried out that oxides lying or adhering to the corrosion protection layer are ground off and, in particular, a microporosity is exposed.
  • Another alternative for removing or conditioning the oxide layer is what is known as wheel blasting, in which abrasive particles are blasted onto the belt, the oxide layer being blasted off or leveled by the particles.
  • wheel blasting in which abrasive particles are blasted onto the belt, the oxide layer being blasted off or leveled by the particles.
  • An example of this is the EP 1 630 244 B1 or EP 2 233 508 B1 .
  • Such protective layers usually only occur in zinc alloy coatings, while aluminum coatings often do not have to be cleaned or only have to be subjected to less complex cleaning.
  • a sol-gel preconditioning of the layer to reduce oxide layer formation and increase weldability is known.
  • the aim is to create an anti-oxidation coating for press-hardening steel materials on the basis of binders containing silane and titanium and oxidic pigments, which are apparently applied in the sol-gel process.
  • solvents such as methanol are used here, which cannot be used on steel production plants.
  • the coating is said to fall off by itself after press hardening, although attempts were made with titanium and silicon-based coatings and were not successful with either a thick or a thin wet film. The coating does not fall off by itself, nor is it suitable for industrial applications.
  • the object of the invention is to create a method for producing hardened steel components in which an existing zinc alloy corrosion protection layer is conditioned in such a way that blast cleaning (conditioning of the component surface using blasting material, vibratory grinding or the like) after hardening can be dispensed with.
  • Another object is to create a galvanized steel strip which is designed in such a way that the oxide layer does not need to be cleaned off.
  • a cleaning post-treatment is a manageable and well-established process, but a higher workload is generated.
  • the dimensional accuracy of the components can be restricted.
  • the cycle time may have to be adapted.
  • the oxide growth during the hardening process can be designed in such a way that subsequent mechanical surface conditioning, such as, for example, wheel blasting, vibratory grinding or dry ice blasting, is unnecessary.
  • metallic tin and in particular tin-containing salt solutions such as salt solutions of the preferred stannates, but also oxalates, zirconates and titanates, apparently modify the surface in such a way that any type of cleaning is unnecessary.
  • sheet metal coated with zinc alloy can usually be insufficiently phosphatizable in the annealed state.
  • stannate comprises the salts of tin acids (II) and - (IV).
  • an aqueous alkaline solution is bsp. applied by means of a roll coater or by a spray squeeze treatment or another treatment to a galvanized surface after skin passaging and before cold forming or annealing and hardening process.
  • very thin layers are used, which are 1-5 ⁇ m in water and 50-250 nm thick when dried.
  • the tin coverage when using stannates is 30-90 mg tin per m 2 in the form of K 2 [SnO 3 ].
  • the surface resistance is very low and even in a cyclic corrosion test according to VDA 233-102 climate change test, only a very low tendency to infiltration of paint could be determined.
  • Significantly fewer oxides can be seen visually, which is revealed by the silvery color of the annealed sheet.
  • Such a silvery appearance usually poses a problem, since it indicates a lack of thorough reaction or a stable Al 2 O 3 layer.
  • Investigations have shown that the zinc-iron crystals of the zinc layer have reacted completely.
  • a good formation of the phosphate crystals during the phosphating could be determined. This was not to be expected in this form.
  • stannates that can be used have already been listed; a potassium stannate solution is particularly suitable, with the application of stannate or tin in ionic form to the surface being one way in principle.
  • Both basic and acidic solutions can be used here and, in particular, solutions in which the tin is complexed can be used.
  • an aqueous layer thickness of 1-5 ⁇ m is aimed for, with a dried layer thickness of 50-250 nm, preferably 50-150 nm and a tin coating of 30-90 mg tin / m 2 in the form of K 2 [SnO 3 ].
  • the Figures 4 and 5 show a hot-dip galvanizing plant or an electrolytic galvanizing plant.
  • the stannate can preferably be applied in the area of chemical passivation (in Figure 4 ) or the "Passivation" station (in Figure 5 ) can be made.
  • Figure 3 shows a variant for this, the so-called phs-multiform process, in which after austenitization and an optional pre-cooling to 450 ° C to 650 ° C in particular, a multi-stage process with several forming steps or cutting and punching processes are subsumed under the term "hot forming steps, After hardening, the sheets heat-treated in this way have a layer on the surface, in particular of aluminum oxide and zinc oxide, which is preferably cleaned off.
  • the conditioning of the surface with very small amounts of tin obviously affects the formation of the oxide layer to such an extent that it does not arise in this form or is conditioned to such an extent that it does not have to be cleaned off.
  • a conventionally produced hardened steel plate shows a greenish-beige appearance on the surface, which is caused by the increased formation of zinc and manganese oxides. This is in Figure 6 shown.
  • the sheet When conditioned with a stannate solution, the sheet shows a silvery surface ( Figure 7 ) consisting mainly of zinc oxides or tin oxides.
  • Figure 8 shows again a comparison of a hardened galvanized steel sheet according to the prior art with one treated according to the invention.
  • Both sheets of quality 22MnB5 with a zinc layer of 140 g / m 2 (on both sides) were annealed for 45 seconds at a temperature above Ac3.
  • the appearance of the prior art sheet is much darker.
  • a surface formed and conditioned according to the invention can be seen in an electron microscopic sectional view, a basic solution of potassium stannate with potassium hydroxide being applied with a roll coater before the heat treatment.
  • the steel grade 340LAD with a zinc coating of 180 g / m 2 was annealed at 870 ° C. for 200 seconds.
  • the layers above measuring point 7 are preparation-related CSP redeposits and are therefore of no significance. It can be clearly seen that the lighter layer in the plane of the MP7 represents the Sn / Zn oxide; this is also confirmed by the components of the MP7, which show significantly high values for Sn.
  • the layer is very thin and almost completely over the entire surface of the belt. Underneath there is a darker layer of Al oxide (MP6) which is also present over the entire surface of the strip. Again underneath is the reacted Zn / Fe layer, which partially slightly oxidized areas (but not in MP4 in Figure 9 shown).
  • the concentration of the solution which is used for conditioning by means of roll coating, is chosen so that with a wet film of 1 ⁇ m 50-60 mg tin / m 2 are deposited.
  • a layer applied in this way causes a modification of the oxide layer that forms during annealing, so that mechanical cleaning by means of a centrifugal wheel or other mechanical processes is no longer necessary.
  • a solution which effects conditioning according to the invention has a solution concentration of 180-220 g / l K 2 SnO 3 * 3H 2 O.
  • 15-25 g / l KOH can be added to the solution so that a pH value of approx. 13, i.e. 12.5-13.5 is established.
  • the tin can be suitably complexed as an alternative to KOH to such an extent that it becomes clear Precipitation-free solution is obtained by adding citric acid in an amount of 30-50 g / l, which leads to a pH of about 4.8.
  • the surface conditioning according to the invention also provides an advantage in terms of the infiltration of the paint, because as the results in Figure 13 show, the paint infiltration results are so good that obviously a cathodic dip paint applied to the metal sheets without mechanical cleaning is only infiltrated very slightly and not to a greater extent than with other metal sheets.
  • the VDA 233-102 climate change test was carried out and the paint infiltration in mm as well as the respective cross-cut value in the cross section according to DIN EN ISO 16276-2 before and after the aforementioned corrosion test according to VDA 233-102 was determined.
  • the scale ranges from 0 (very good) to 5 (total release). You can see that mostly the value before and after the test 0 was excellent. Sometimes small areas have flaked off which led to values of 1 and sometimes 2.
  • the conditioning according to the invention was presented in particular on the basis of the stannates, but the titanates, oxalates and zirconates also react essentially in the same way. Accordingly, it can be assumed that these are equally effective, in particular the corresponding tin compounds.
  • the tin seems to be particularly effective, which is why the surface conditioning is also successful when the tin is metallic.
  • the deposition of the tin on the surface with the aid of the stannates, ie in ionic form, has the advantage, however, that the application can be carried out in a comparatively simple manner in a roll coating or dip-squeeze process.
  • the application can be done inline on the belt before it is cut into individual blanks.
  • the blanks cut out of the strip can be coated accordingly.
  • the blanks are then formed into a component blank, in particular in a multi-stage process. Coating only the component blank with the tin compound or the tin is also conceivable. However, it has been shown that the tin or tin salt coating surprisingly also tolerates the forming processes very well. Due to the soft tin layer, the person skilled in the art would have expected that during cold forming there could be severe abrasion at the areas subject to the forming load, but such abrasion or removal of the layer could only be ascertained to a small extent. This can certainly be a consequence of the advantageous low layer thickness.
  • a component blank obtained in this way is heated to a temperature that causes a structural change towards austenite.
  • the austenitized component blank is then fed to a form hardening tool in which the component blank is hardened in one stroke by means of the contact of an upper and lower tool, which essentially have the shape of the blank or correspond to it. Because the material of the component blank is in contact with the, in particular, cooled tools, the heat is withdrawn from the steel material so quickly that martensitic hardening occurs.
  • the advantage of the invention is that it is possible to condition the surface of a steel sheet provided for form hardening or press hardening in such a way that mechanical final cleaning to remove oxidic surface layers can be dispensed with, so that such sheets can be produced in the same way as, for example, hot-dip aluminized sheets , can be processed, but with the advantage that a high cathodic corrosion protection effect is achieved compared to hot-dip aluminized sheets.

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EP20160202.6A 2020-02-28 2020-02-28 Verfahren zum herstellen gehärteter stahlbauteile mit einer konditionierten zinklegierungskorrosionsschutzschicht Withdrawn EP3872230A1 (de)

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PCT/EP2021/054962 WO2021170860A1 (de) 2020-02-28 2021-03-01 Verfahren zum herstellen gehärteter stahlbauteile mit einer konditionierten zinkkorrosionsschutzschicht
US17/802,576 US20230145863A1 (en) 2020-02-28 2021-03-01 Method for producing hardened steel components with a conditioned zinc anti-corrosive layer
EP21707718.9A EP4110970B1 (de) 2020-02-28 2021-03-01 Verfahren zum herstellen gehärteter stahlbauteile mit einer konditionierten zinkkorrosionsschutzschicht
CN202180017429.XA CN115485415B (zh) 2020-02-28 2021-03-01 一种生产具有防腐蚀锌处理层的硬化钢构件的方法

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CN116810601A (zh) * 2023-08-10 2023-09-29 天津华源线材制品有限公司 一种镀锌丝表面覆膜用的处理装置及其处理方法

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EP1630244B1 (en) 2003-04-23 2009-07-01 Sumitomo Metal Industries, Ltd. Hot press formed product and method for production thereof
DE102007022174B3 (de) 2007-05-11 2008-09-18 Voestalpine Stahl Gmbh Verfahren zum Erzeugen und Entfernen einer temporären Schutzschicht für eine kathodische Beschichtung
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CN116810601B (zh) * 2023-08-10 2024-01-09 天津华源线材制品有限公司 一种镀锌丝表面覆膜用的处理装置及其处理方法

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EP4110970B1 (de) 2023-10-04
EP4110970A1 (de) 2023-01-04
EP4110970C0 (de) 2023-10-04
CN115485415B (zh) 2023-11-21
CN115485415A (zh) 2022-12-16
WO2021170860A1 (de) 2021-09-02

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