Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C18/00—Alloys based on zinc
  • C22C18/04—Alloys based on zinc with aluminium as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C18/00—Alloys based on zinc
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
  • C23C2/06—Zinc or cadmium or alloys based thereon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
  • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
  • B21B1/227—Surface roughening or texturing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
  • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
  • B21B2001/228—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length skin pass rolling or temper rolling

Definitions

• the invention relates to a steel sheet which is hot-dip refined and skin-passed, the steel sheet comprising a steel substrate made of a carbon-containing alloy and a metallic coating arranged on one or both sides of the steel substrate, which, in addition to zinc and unavoidable impurities, contains additional elements such as aluminum with a content of 0.5 to 8.0 wt.% and magnesium with a content of 0.5 to 8.0 wt.% in the coating, with an oxide layer formed on the side facing away from the steel substrate within the coating.
• the invention further relates to a method for producing a hot-dip refined and skin-passed steel sheet and to a use.
• Coatings made of zinc, aluminum and magnesium oxidize in air and form a covering oxide layer on the surface, which is predominantly rich in magnesium.
• This oxide layer has different chemical properties than established pure zinc or zinc-aluminum coatings. It is chemically inert and passivates the underlying (coating) surface. It is precisely because of these properties that the magnesium-rich oxide layer can interfere with known post-treatment processes and lead to wetting and adhesion problems, e.g. during activation and phosphating and/or in coil coating, so it can be useful to remove the magnesium-rich oxide layer, especially mechanically, before further treatment, cf. for example EP 2 841 614 B1 .
• Textured skin-pass rollers transfer their texture to the surface of the steel sheets to be processed as a negative during a skin-pass process, i.e. elevations on the roller surface result in depressions in the steel sheet surface and vice versa.
• the skin-pass impressions (depressions) introduced into the steel sheet surface in this way so-called closed empty volumes, generally serve as lubricant pockets that hold a lubricant applied to the steel sheet surface and can carry it along during the forming process.
• steel sheets skin-passed with a stochastic surface structure are known as examples from the patent specification EP 2 006 037 B1 and steel sheets with a deterministic surface structure, for example from the patent specification EP 2 892 663 B1 known.
• hot-dip coated coatings are constructed in such a way that that a layer of alloying elements with a higher affinity for oxygen forms on the zinc that is primarily in the coating.
• the mechanical stress during skin-passing can ensure that the zinc is exposed at the contact points between the skin-pass roller and the steel sheet instead of the alloying elements such as magnesium and/or aluminum.
• Hot-dip coated steel sheets that have been skin-passed with a stochastic surface structure have a different surface chemistry in the skin-pass impressions of the coated steel sheet than on the raised areas of the coated steel sheet. While the chemical composition in the skin-pass impressions is richer in zinc, the raised areas have high proportions of the oxygen-affine alloying elements (Al, Mg, etc.), cf. EN 10 2019 215 051 A1 .
• the task is therefore to essentially retain the surface of the hot-dip coated and tempered steel sheet in order to provide excellent corrosion protection.
• the object is achieved with respect to a steel sheet having the features of claim 1 and with respect to a method for producing a steel sheet having the features of claim 8.
• the oxide layer and thus the advantageous properties in terms of corrosion protection can be retained if the surface or surface chemistry is only slightly or insignificantly changed during skin-passing after hot-dip coating.
• the contact of shaping elements of the skin-passing roller with the surface of the hot-dip coated steel sheet should only exert a low mechanical stress in order to essentially maintain or only slightly change the oxide layer, which is predominantly rich in magnesium.
• the magnesium concentration should not fall below the minimum value of 65% in order to essentially maintain the inert and passivated magnesium-rich oxide layer and thus ensure excellent corrosion protection.
• the relative concentration of zinc, magnesium and aluminium is determined by determining the absolute concentration of these elements and then normalising to 100%.
• the sum of the concentration of zinc, magnesium and aluminium is equal to 100 and the proportion of the respective element in this 100% is evaluated or weighted as a relative concentration, i.e. related to 100%.
• the relative concentration of an element Al, Mg, Zn
• Al, Mg, Zn therefore refers to the sum of the concentrations or the sum of the signal intensities of the elements Mg, Zn and Al, with this sum representing 100%. Since the absolute concentration of the elements Zn, Mg and Al can vary from coating to coating, the information is given as a relative concentration in percentage points in order to define changes precisely.
• the relative concentration differences are determined for magnesium, aluminum and zinc on the surface of the coating, i.e. on the "native" (magnesium-rich) oxide layer, by recording the local distribution of the signals for these alloying elements using a time -of - flight secondary ion mass spectrometer (ToF-SIMS) in imaging mode or in a similar way using Auger electron or photoelectron spectroscopy.
• ToF-SIMS is an analytical method for determining the chemical surface composition of the top 1-3 monolayers.
• ToF-SIMS is used to measure certain relative concentration differences by scanning the surface to be analyzed within a representative measuring area. A spectrum in positive polarity is recorded at each position of the grid and the raw signals for the main components (alloying elements) are recorded.
• the relative concentration of element X which in this case represents one of the alloying elements in the hot-dip coated and tempered coating, is calculated from the quotient [X raw signal integral / (Zn raw signal integral + Mg raw signal integral + Al raw signal integral)], with the denominator of the quotient being the sum of the raw signal integrals of all alloying elements in the coating.
• Raw signal of element X in this definition is the intensity or peak area of element X in the mass spectrum or "raw signal integral" of element X is the integrated intensity, which is represented over a defined connected area of grid positions and assigned to the respective element X.
• the internal ToF-SIMS measurements were carried out using a TOF.SIMS 5 device from ION-TOF GmbH.
• the surface of the hot-dip coated and skin-rolled steel sheet has a standardized Mg content of at least 65%.
• the standardized Mg content can in particular be at least 66%, 67%, 68%, preferably at least 69%, 70%, 71%, 72%, preferably at least 73%, 74%, 75%.
• the standardized content corresponds in particular to the determined mean value, although fluctuations may occur within the scope of measurement tolerances (standard deviation). The sum of the standardized content of magnesium, aluminum and zinc is always 100%.
• Steel sheet is generally understood to mean a hot-rolled flat steel product which can be provided in sheet form, in blank form or in strip form.
• the thickness of the steel sheet can be between 0.45 and 8.0 mm, in particular at least 0.5 mm, preferably at least 1.0 mm and in particular a maximum of 7.0 mm, preferably a maximum of 6.0 mm.
• the metallic coating has magnesium with a content of at least 0.5% by weight, in particular of at least 0.8% by weight, preferably of at least 1.1% by weight.
• aluminum is also present with a content of at least 0.5% by weight, in particular of at least 0.8% by weight, preferably of at least 1.1% by weight, in order to improve the bonding of the coating to the steel sheet and in particular to essentially prevent the diffusion of iron from the steel sheet into the coating during heat treatment of the coated steel sheet, so that the positive corrosion properties are retained.
• the magnesium and aluminum contents can each be limited to a maximum of 8.0% by weight, in particular to a maximum of 6.5% by weight, preferably to a maximum of 5.0% by weight, preferably to a maximum of 4.0% by weight.
• the thickness of the coating can be between 5 and 50 ⁇ m, in particular between 10 and 45 ⁇ m, preferably between 15 and 40 ⁇ m per side.
• the steel sheet according to the invention is preferably intended for so-called blank applications, i.e. applications in which no paint or similar is applied. This produces a hot-dip coated and tempered steel sheet with the highest possible intact native oxide layer acts as an additional barrier and thus provides additional corrosion protection.
• the steel sheet can also be stretched (additionally). Stretched means that the steel sheet is drawn off during the skin-passing process with a higher strip tension than in the conventional process.
• the steel substrates in question here are carbon-containing steel alloys, which can be, for example, structural steels in accordance with DIN EN 10025.
• Structural steels are used in steel and mechanical engineering. Structural steel can be unalloyed, see DIN EN 10025-2, normalized, see DIN EN 10025, or low-alloyed fine-grain structural steel, see DIN EN 10025-4, depending on the intended use. Examples of steels of this type are available under the standard designation S235, S275, S355(N), S420(N), S460MC. These are hot-rolled steels.
• the surface of the steel sheet can have a stochastic surface structure. This is created using skin-pass rollers, the surfaces of which are textured in a so-called EDT process.
• the surface of the steel sheet can have a deterministic surface structure. This is created using skin-pass rollers whose surfaces are textured with a laser.
• a surface with a pseudo-stochastic surface structure would also be conceivable. These surface structures have a (quasi-)stochastic appearance, consisting of stochastic elements with a recurring structure.
• the invention relates to a method for producing a hot-dip coated and skin-passed steel sheet, comprising the following steps: - providing a steel substrate made of a carbon-containing alloy, - hot-dip coating the steel substrate on one or both sides with a metallic coating which, in addition to zinc and unavoidable impurities, contains additional elements such as aluminum with a content of 0.5 to 8.0 wt.% and magnesium with a content of 0.5 to 8.0 wt.% in the coating, - skin-passing the hot-dip coated steel sheet, wherein the skin-passing is carried out in such a way that a standardized Mg content of at least 65% remains on the surface of the hot-dip coated and skin-passed steel sheet.
• the surface (positive form) of the skin-pass roller forms a surface structure by applying force to the surface of the steel sheet, which defines depressions (negative form) and essentially corresponds to the surface with elevations (positive form) of the skin-pass roller.
• the mechanical and possibly optical properties of the steel sheet can be influenced, but usually also the surface chemistry.
• magnesium has a higher affinity for oxygen than aluminum, a magnesium-rich oxide layer forms on or near the surface of the coating during hot-dip finishing or after solidification and cooling.
• the skin-passing process must essentially be designed in such a way that mechanical and optical properties can be adjusted while the oxide layer is damaged as little as possible.
• a stochastic surface structure can be skin-passed according to one embodiment, with the skin-pass degree being selected between 0.2% and less than 1.0%.
• the skin-pass degree can in particular be less than or equal to 0.90%, preferably less than or equal to 0.80%, preferably less than or equal to 0.70%.
• the skin-pass degree expresses the ratio of the thickness reduction (input thickness to output thickness in the skin-pass stand) of the skin-passed steel sheet to the input thickness, in particular the thickness reduction is taken into account.
• a deterministic surface structure can be skin-passed, using a skin-pass roller or a pair of skin-pass rollers with a smooth surface texture, the surface texture having an arithmetic mean roughness R a of less than 1.0 ⁇ m.
• a smooth surface texture with an arithmetic mean roughness R a of less than 1.0 ⁇ m, in particular less than 0.950 ⁇ m, preferably less than 0.90 ⁇ m, preferably less than 0.850 ⁇ m, particularly preferably less than 0.80 ⁇ m, more preferably less than 0.750 ⁇ m, but greater than 0 ⁇ m, can preferably be provided, wherein the design of the texture can be represented individually, in particular taking into account the arithmetic mean roughness.
• the method for determining the R a value is specified in DIN ISO EN 4287. If a skin-pass roll or a pair of skin-pass rolls with a smooth surface texture is used, the degree of skin-passing plays only a minor role compared to the stochastic surface texture.
• the invention relates to a use of the steel sheet according to the invention, in particular produced according to the method according to the invention, as a frame and/or as a support for a solar panel, a facade, a silo, a wheelbarrow.
• Other applications, in particular in which no painting is required, are also conceivable.
• Samples 1 to 12 were skin-passed with a pair of skin-pass rolls with a stochastic surface texture
• samples 13 to 16 were skin-passed with a pair of skin-pass rolls with a deterministic surface texture, whereby the arithmetic mean roughness value R a was less than 1.0 ⁇ m
• sample 17 was skin-passed with a pair of skin-pass rolls with a pseudo-deterministic surface texture.
• the determination of the chemical composition close to the surface is carried out, for example, by means of X-ray photoelectron spectroscopy (XPS), whereby the procedure for determining the individual chemical compositions is familiar from the state of the art.
• XPS X-ray photoelectron spectroscopy
• the measurement can be carried out, for example, with the Phi Quantera II SXM Scanning XPS Microprobe device from Physical Electronics GmbH.
• the values measured by means of XPS Element concentrations can be taken from overview spectra that are recorded at, for example, a transmission energy of 280 eV over at least 7 cycles and can refer to a measuring area of 100 ⁇ 100 ⁇ m 2 .
• the determination of the standardized concentrations using ToF-SIMS has already been described.
• Table 1 sample Dressing degree [%] Coating [wt.%], balance Zn and impurities.

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Citations (10)

• 2022
  • 2022-10-19 DE DE102022127491.8A patent/DE102022127491A1/de active Pending
• 2023
  • 2023-10-13 EP EP23203496.7A patent/EP4357472A1/fr active Pending

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