EP3856936B1 - Procédé pour la préparation d'un produit plat en acier revêtu et produit plat en acier revêtu - Google Patents

Procédé pour la préparation d'un produit plat en acier revêtu et produit plat en acier revêtu Download PDF

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Publication number
EP3856936B1
EP3856936B1 EP18789005.8A EP18789005A EP3856936B1 EP 3856936 B1 EP3856936 B1 EP 3856936B1 EP 18789005 A EP18789005 A EP 18789005A EP 3856936 B1 EP3856936 B1 EP 3856936B1
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EP
European Patent Office
Prior art keywords
flat steel
steel product
weight
temperature
content
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EP18789005.8A
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German (de)
English (en)
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EP3856936A1 (fr
Inventor
Richard Georg THIESSEN
Manuela Irnich
Jan-hendrik RUDOLPH
Bernd Linke
Rainer FECHTE-HEINEN
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ThyssenKrupp Steel Europe AG
ThyssenKrupp AG
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ThyssenKrupp Steel Europe AG
ThyssenKrupp AG
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Priority to EP22177189.2A priority Critical patent/EP4083236A1/fr
Priority to PL18789005.8T priority patent/PL3856936T3/pl
Publication of EP3856936A1 publication Critical patent/EP3856936A1/fr
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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
    • 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
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/76—Adjusting the composition of the atmosphere
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/561—Continuous furnaces for strip or wire with a controlled atmosphere or vacuum
    • 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
    • C23C2/26—After-treatment
    • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
    • 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
    • C23C2/26—After-treatment
    • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
    • C23C2/29—Cooling or quenching
    • 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
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/40—Plates; Strips

Definitions

  • the present application relates to a method for producing a high-strength flat steel product provided with a metallic coating and a coated flat steel product.
  • High-strength steels are characterized by a high proportion of alloying elements that increase the strength of the material, such as silicon, manganese and chromium.
  • a surface-refining layer is often required to prevent material corrosion.
  • a surface-finishing layer can be applied, for example, electrolytically or by means of hot-dip coating, which is also referred to as hot-dip coating.
  • Zinc-based coatings, which are applied by hot-dip coating are of particular technical importance for corrosion protection.
  • the boundary layer between the anti-corrosion layer and the steel substrate or the base material is understood to be the layer that begins with the layer between the anti-corrosion layer and the base material, in which the zinc and iron content have the same value in % by weight, down to a depth of 300 nm into the base material.
  • An accumulation of one or more of the elements silicon, manganese and chromium in the boundary layer has a negative effect on the service properties of the coated flat steel product. For example, the adhesion of the anti-corrosion layer on the base material deteriorates. However, the formability of the coated flat steel product is also limited.
  • EP2540854B1 is known an ultra-high-strength cold-rolled steel sheet containing in % by mass 0.15-0.30% C, 0.01-1.8% Si, 1.5-3.0% Mn, not more than 0.05% P, not more than 0.005% S, 0.005-0.05% Al and not more than 0.005% N, optionally further one or more elements of 0.001-0.10% Ti, 0.001-0.10% Nb, 0, 01-0.50% V, 0.0001-0.005% B, 0.01-0.50% Cu, 0.01-0.50% Ni, 0.01-0.50% Mo and 0.01- 0.50% Cr and having a soft surface portion containing at least 90% tempered martensite.
  • the steel sheet has a tensile strength of not less than 1270 MPa.
  • the steel sheet is decarburized in an atmosphere having a high dew point of 30°C at 700-800°C for 15-60 minutes. Decarburizing annealing in an atmosphere with a high dew point for a relatively long period of time results in a decarburized, ductile surface layer, which is then subjected to a coating treatment.
  • This oxide layer which consists only of iron, manganese and silicon, is that due to the lack of chromium and a thickness of the oxide layer of up to 5 ⁇ m, the adhesion of metallic coatings can be impaired. In addition, a deterioration in local formability is to be expected between the soft, decarburized and easily formable ferrite layer and the harder and brittle oxide layer.
  • EP2524970A1 discloses a hot-dip galvanized (with Zn, ZnAl, ZnMg) high-strength complex-phase steel and its manufacturing process.
  • the object of the invention was to provide a method for producing a high-strength flat steel product coated by means of a hot-dip coating system, which ensures good adhesion of the metallic coating on the steel substrate and good formability of the coated flat steel product.
  • a high-strength, coated steel flat product should be specified, which has good adhesion of the metallic coating on the steel substrate and good forming properties.
  • the object was achieved in that at least the method steps specified in claim 1 are completed in the production of a high-strength, coated steel flat product.
  • the invention is based on the finding that the distribution of the main alloying elements silicon, manganese and chromium in the boundary layer has a significant influence on the adhesion of the anti-corrosion coating. This applies in particular to zinc-based anti-corrosion coatings.
  • Silicon, manganese and chromium are strong oxide formers. In theory, silicon has a higher affinity for oxygen than manganese, manganese has a higher affinity for oxygen than chromium, and chromium has a higher affinity for oxygen than iron. It would therefore be expected that, depending on the respective proportion of the element under consideration, silicon oxides form first in the boundary layer before manganese oxides and before chromium oxides. This applies under the assumption of equilibrium states that can only be reached theoretically and under ideal conditions, according to which all phases are present as pure phases and the formation of mixed phases is excluded, while the reaction kinetics and diffusion processes are not taken into account.
  • the distribution of silicon, manganese and chromium in the boundary layer can vary greatly and that the distribution can be influenced by the production parameters, such as the set temperatures and gas atmosphere.
  • the method according to the invention for producing a high-strength steel flat product provided with a metallic protective coating comprises at least the following work steps: a) Providing a hot-rolled flat steel product comprising a steel composed of (in % by weight) 0.1 - 0.5% C, 1.0-3.0% Mn, 0.7 - 2.5% Si, 0.05 - 1% Cr, up to 0.020% P, up to 0.005% S, up to 0.008% N, and optionally one or more of the following 0.01-1.5% Al, 0.05 - 0.5% Mo, 0.0004 - 0.001% B and optionally a total of 0.001-0.3% V, Ti and Nb, and the remainder consists of iron and unavoidable impurities; b) pickling and cold rolling the hot-rolled flat steel product, wherein the hot-rolled flat steel product undergoes a thickness reduction of at least 37%; c) two-stage heating of the cold-rolled flat steel product to a holding zone temperature THZ, which is above the A3 temperature of the
  • step a) a hot-rolled flat steel product produced by means of conventional casting and hot-rolling processes is made available.
  • the hot-rolled flat steel product provided in step a) is uncoated, ie it has no metallic anti-corrosion coating.
  • the uncoated flat steel product forms the steel substrate or the base material for the metallic anti-corrosion coating that is applied in step i).
  • the uncoated flat steel product comprises a steel, in particular it consists of a steel, of the composition explained in more detail below.
  • the carbon content of the steel of a flat steel product according to the invention is 0.1-0.5% by weight.
  • Carbon (C) influences the formation and stabilization of austenite. During the quenching, which is carried out to form martensite, and during the subsequent annealing treatment, any retained austenite is stabilized by C.
  • the C content has a strong influence on the strength of the martensite formed during the cooling in step f) with a cooling rate ThetaQ, as well as on the strength of the martensite formed during the last cooling step in step k) with a cooling rate ThetaB2 is formed.
  • the C content should be at least 0.1% by weight in order to ensure the austenite-stabilizing and strength-increasing effect.
  • the carbon content is at least 0.12% by weight in order to be able to use the austenite-stabilizing and strength-increasing effect of carbon particularly effectively.
  • the martensite start temperature is shifted to lower and lower temperatures, so that at a high C content, possibly no or only too little martensite can be formed.
  • the weldability of the flat steel product deteriorates.
  • the carbon content of the steel of a steel flat product according to the invention is limited to at most 0.5% by weight, preferably at most 0.4% by weight.
  • the steel of a steel flat product according to the invention contains both manganese and silicon.
  • the manganese content in the steel of a flat steel product according to the invention with manganese and silicon is 1.0-3.0% by weight.
  • Manganese (Mn) influences the hardenability of the steel and helps to avoid unwanted pearlite formation during cooling. These prerequisites enable the formation of a suitable structure of martensite and retained austenite after quenching in step f) with cooling rates of less than 100 K/s.
  • the steel of a flat steel product according to the invention contains at least 1.0% by weight, preferably at least 1.9% by weight, of Mn.
  • the Mn content is limited to a maximum of 3 0.0% by weight, preferably at most 2.7% by weight. Excessively high manganese contents also cause excessive manganese enrichment in the boundary layer between the anti-corrosion coating and the steel substrate and thus lead to poor adhesion. For this reason too, the Mn content is limited to at most 3.0% by weight, preferably at most 2.7% by weight.
  • the silicon content in the steel of a flat steel product according to the invention with silicon and manganese is 0.7-2.5% by weight, preferably at least 0.9% by weight.
  • Silicon (Si) contributes to the suppression of cementite formation. During the formation of cementite, carbon is bound in the form of carbides. By suppressing the formation of cementite, free carbon is available, which contributes to the stabilization of the retained austenite and thus to an improvement in elongation. This effect can also be partially achieved by alloying aluminum. If the Si content is too high, silicon can accumulate in the boundary layer between the anti-corrosion coating and the base material, which leads to poor adhesion of the anti-corrosion coating.
  • the Si content is limited to at most 2.5% by weight, in particular to less than 2.5% by weight. In a preferred embodiment, the Si content is limited to at most 1.5% by weight limited in order to additionally reduce the risk of the formation of red scale, which can occur during hot strip production.
  • the chromium content of the steel of a flat steel product according to the invention is 0.05-1% by weight.
  • Chromium (Cr) helps increase strength and is an effective inhibitor of pearlite.
  • the accumulation of Cr in the boundary layer between the anti-corrosion coating and the base material leads to improved adhesion.
  • the Cr content is at least 0.05% by weight, preferably at least 0.1% by weight.
  • Cr increases the risk of severe grain boundary oxidation, which adversely affects weldability and surface quality.
  • the Cr content is limited to at most 1.0% by weight. In a preferred embodiment, the Cr content is limited to a maximum of 0.6% by weight for cost reasons, which also contributes to further minimizing the risk of grain boundary oxidation.
  • Aluminum (Al) can optionally be contained in the steel of a flat steel product according to the invention with 0.01-1.5% by weight. Al can be used for deoxidation and for binding any nitrogen present. Al can also be used to suppress cementite. The addition of Al increases the austenitization temperature of the steel. If higher annealing temperatures can be set, Al can be alloyed with up to 1.5% by weight. Since aluminum increases the annealing temperature required for complete austenitization and complete austenitization is only possible with difficulty at Al contents above 1.5% by weight, the Al content of the steel of a steel flat product according to the invention is limited to a maximum of 1.5% by weight. -%, preferably at most 1.0% by weight. In a preferred embodiment, the Al content is limited to at most 0.1% by weight, in particular to 0.01-0.1% by weight, in order to limit the austenitization temperature.
  • Phosphorus (P), sulfur (S) and nitrogen (N) have a negative effect on the mechanical-technological properties of flat steel products according to the invention, which is why their presence in flat steel products according to the invention should be avoided if possible.
  • Phosphorus (P) has an unfavorable effect on weldability, which is why the P content should be at most 0.02% by weight, preferably less than 0.02% by weight.
  • sulfur (S) leads to the formation of MnS or to the formation of (Mn,Fe)S, which has a negative effect on elongation. Therefore, the S content is limited to values of at most 0.005% by weight, preferably less than 0.005% by weight.
  • N Nitrogen (N), both in interstitially dissolved form and as nitride, for example in combination with titanium, niobium or vanadium, leads to embrittlement of the steel, which can have a negative effect on formability, which is why the N content is limited to a maximum of 0.008 % by weight, preferably to less than 0.008% by weight.
  • Steels of flat steel products according to the invention can optionally contain molybdenum (Mo) in amounts of 0.05-0.5% by weight.
  • Mo molybdenum
  • Mo promotes the suppression of pearlite formation, and for this purpose it can be contained in the steel in an amount of at least 0.05% by weight.
  • the Mo content is limited to at most 0.5% by weight, in particular less than 0.5% by weight.
  • Steels of flat steel products according to the invention can optionally contain boron (B) in amounts of 0.0004-0.001% by weight. Boron segregates onto the phase boundaries and blocks their movement. This supports the formation of a fine-grain structure, which improves the mechanical properties of the steel flat product. In order to bring about an improvement in the mechanical properties, boron can be added in amounts of at least 0.0004% by weight. When alloying boron, sufficient Ti or Nb should preferably be available to bind N, which prevents the formation of harmful boron nitrides.
  • a titanium content is selected which is greater than 3.42 times the N content, or if a niobium content is selected which is greater than 3 .42 times the N content.
  • the positive effect of B is saturated at a content of around 0.001% by weight, which is why the steel contains no more than 0.001% by weight of B.
  • steels of flat steel products according to the invention can contain one or more micro-alloying elements in total contents of 0.001 to 0.3% by weight.
  • micro-alloy elements are understood to mean the elements titanium (Ti), niobium (Nb) and vanadium (V). Titanium or niobium or a combination of both are preferably used.
  • the micro-alloying elements can form carbides with carbon, which in the form of very finely divided precipitates contribute to greater strength. With a total content of microalloying elements of at least 0.001% by weight, preferably at least 0.005% by weight, precipitates can form which lead to the freezing of grain and phase boundaries during austenitizing.
  • the total concentration of the microalloying elements should be at most 0.3% by weight, preferably at most 0.2% by weight.
  • the hot-rolled flat steel product is first pickled in a conventional manner and then subjected to cold rolling.
  • the cold rolling reduces the thickness of the flat steel product by at least 37%, in particular by more than 37%.
  • the reduction in thickness refers to the difference between the initial thickness of the flat steel product before the first cold rolling pass and the final thickness of the flat steel product after the last cold rolling pass.
  • Cold rolling with a thickness reduction of at least 37% causes mechanical homogenization of the material and leads to a particularly fine-grained structure with an average grain size of less than 30 ⁇ m in the cold-rolled state.
  • the very fine-grained structure created by cold rolling provides many nucleation sites for the formation of austenite grains for the following austenitizing annealing, which consequently also leads to very fine-grained austenite.
  • the grain-refining effect can be intensified if a thickness reduction of preferably at least 42% is set during cold rolling.
  • the mechanical homogenization of the material during cold rolling facilitates the setting of the targeted ratio of Si, Mn and Cr in the boundary layer between the anti-corrosion coating and the steel substrate in the further course of the work.
  • step c) the cold-rolled flat steel product is heated to an annealing temperature THZ above the Ar temperature of the steel, which can also be referred to as the holding zone temperature, in order to enable a complete transformation of the microstructure into austenite.
  • the soak zone temperature THZ can be limited to a maximum of 950°C to save on operating costs.
  • the heating to THZ takes place in two stages.
  • the flat steel product is first heated at a heating rate Theta_H1 of 5 - 50 K/s until a turning temperature TW of 200 - 400 °C is reached. Above the turning temperature T_W, the heating takes place at a heating rate Theta_H2 of 2 - 10 K/s until the holding zone temperature THZ is reached.
  • the first heating rate Theta_H1 is not equal to the second heating rate Theta_H2.
  • Theta_H2 is less than Theta_H1.
  • the flat steel product is heated in a continuous furnace.
  • the flat steel product is heated in a furnace equipped with ceramic radiant tubes, which is particularly advantageous for reaching strip temperatures above 900°C.
  • the indirect heating avoids undesirably strong oxidation of the steel surface combined with the formation of an oxide layer, since the oxygen components required for combustion do not come into contact with the material.
  • a gas mixture is burned in a closed burner and the heat is transferred in this case by radiation.
  • a furnace is also known as a Radiant Tube Furnace or RTF.
  • step d) the flat steel product is held at the holding zone temperature THZ for a holding time tHZ of 5-15 s.
  • the holding time tHZ should not exceed 15 seconds in order to avoid the formation of a coarse austenite grain and irregular austenite grain growth and thus negative effects on the formability of the steel flat product.
  • the holding time should last at least 5 s in order to achieve complete transformation into austenite and a homogeneous C distribution in the austenite.
  • the atmosphere in which the flat steel product is kept contains 3-7% by volume of hydrogen.
  • the rest of the atmosphere is made up of nitrogen moistened with water vapor and unavoidable impurities, with a nitrogen content of 93 - 97% by volume being aimed at and the sum of all components being 100% by volume.
  • the information on the furnace atmosphere composition relates to atmosphere compositions resulting in a total of 100% by volume.
  • the atmosphere during holding consists in particular of 3-7% by volume of hydrogen and the remainder of nitrogen moistened with water vapor and avoidable ones impurities.
  • the amount of water vapor in the atmosphere is controlled by the dew point.
  • the dew point is reduced to values of -22°C to 0°C, preferably to values of at most -5°C, in particular to values of -22°C to -5°C, and particularly preferably to values of at least -20°C and/or at most -15 °C, in particular adjusted to values from -20 °C to -15 °C.
  • the concentration profile of the elements Si, Mn and Cr in the boundary layer can be controlled by the dew point and concentration profiles of the elements Si, Mn and Cr in the boundary layer can be obtained.
  • the proportion of water vapor is described using the dew point.
  • the dew point corresponds to the temperature at which the water condenses in a volume of gas. If the dew point values are low, the proportion of water in the gas mixture is low. As the dew point rises, the proportion of water in the gas mixture increases.
  • the moistened gas mixture in the furnace atmosphere in combination with the facilitated diffusion during annealing, initially leads to an enrichment of the elements Mn, Si and Cr, which have a higher oxygen affinity than iron, on the surface of the base material. Due to the small size difference between manganese and iron, Mn diffuses faster in the iron lattice than Cr or Si. Chromium exhibits slightly slower diffusion than Mn, while silicon diffuses significantly more slowly.
  • the enrichment is counteracted by the out-diffusion of the elements from the base material during the annealing in step d). Outdiffusion is particularly pronounced for Mn, but can also be observed for Si. Cr, on the other hand, passivates near the surface through the formation of oxides. Cr is therefore enriched in the range of up to 300 nm below the surface of the base material. However, if the dew point of the gas mixture is below -22°C, or if the oversupply of the elements Mn and Si, which have a higher oxygen affinity than Cr, is too high in the range of up to 300 nm below the surface of the base material, Cr also diffuses through the surface, which has a negative effect on the adhesion of the anti-corrosion coating and on the formability.
  • the proportion of water vapor in the furnace atmosphere in particular during holding in step d), is more than 0.070% by volume, particularly preferably at least 0.080% by volume.
  • the proportion of water vapor in the furnace atmosphere is at most 1.0% by volume, preferably at most 0.8% by volume.
  • the gas composition can be controlled, for example, with the aid of an automated system.
  • dry and moist gas components can be mixed with one another, with nitrogen being used as the carrier gas for the water vapor.
  • the feeding of the moistened with steam Nitrogen in the annealing furnace can be done, for example, below the deflection roller.
  • the annealing furnaces in which the flat steel product is subjected to an annealing treatment can be designed vertically or horizontally. During the annealing process, the strip is passed through the furnace. For example, the direction of movement of the steel flat product in a vertical furnace is changed from downwards to upwards and vice versa via so-called deflection rollers.
  • the elements Si, Mn and Cr in the after step i) have been carried out coated steel flat product have the following ratio of the sum of Si and Mn to Cr in the boundary layer between the anti-corrosion coating and the steel substrate: 1.7 ⁇ si + Mn / Cr _ GS ⁇ 15 with Si: Si content in % by weight in the boundary layer; Mn: Mn content in wt% in the boundary layer; Cr: Cr content in wt% in the boundary layer.
  • One finding of the present invention is that high Si and Mn contents in the boundary layer impair coatability, whereas Cr has no negative influence, but even a positive influence on the adhesion of the anti-corrosion coating if the abovementioned ratio is maintained. Maintaining the ratio of the oxide-forming elements Si, Mn and Cr in the boundary layer leads not only to excellent adhesion of the anti-corrosion coating but also to good formability of the coated flat steel product.
  • the elements Si, Mn and Cr have the following concentration gradient in the boundary layer: si + Mn / Cr _ GS ⁇ si + Mn / Cr _ GW with [(Si+Mn)/Cr]_GS: ratio of the sum of the Si content in % by weight and the Mn content in % by weight to the Cr content in % by weight in the boundary layer; [(Sl + Mn) / Cr]_GW: Ratio of the sum of the Si content in % by weight and the Mn content in % by weight to the Cr content in % by weight in the base material.
  • the element content of the base material typically refers to a layer that is one third of the thickness of the steel substrate.
  • the flat steel product is heated in step c) and/or held in step d) in a radiant tube furnace.
  • the combustion gases containing oxygen do not come into contact with the flat steel product, since the gas mixture to be burned is burned in a closed burner and the heat is transferred by radiation.
  • decarburization of the surface and severe oxidation of the surface of the uncoated steel flat product and the formation of a covering oxide layer can be reduced and preferably avoided.
  • step e the flat steel product is cooled to a temperature TLK.
  • the cooling starts after the end of the holding in step d). In particular, cooling starts immediately after holding, and thus at the latest after the maximum holding time of 15 s has expired.
  • the temperature TLK is no more than 150 °C below the A3 temperature of the steel of the steel flat product in order to avoid the formation of ferrite.
  • the duration for cooling from THZ to TLK is at least 50 s and at most 300 s.
  • the cooling carried out in step e) can also be referred to as controlled and slow cooling.
  • the flat steel product is further cooled from temperature TLK to a cooling stop temperature TAB.
  • the TLK is cooled down to TAB at a cooling rate ThetaQ, which is at least 30 K/s. Cooling can also be referred to as rapid cooling.
  • ThetaQ cooling rate is at least 30 K/s to avoid the formation of ferrite and the formation of bainite. Cooling can preferably be carried out at up to 120 K/s, which can be achieved, for example, by using modern gas jet cooling.
  • the cooling stop temperature TAB lies between the martensite start temperature TMS, ie the temperature at which a martensitic transformation begins, and a temperature which is up to 175°C lower than TMS. The following applies: TMS ⁇ 175 ° C ⁇ TAB ⁇ TMS .
  • the flat steel product is held at the cooling stop temperature TAB for a holding time tQ, which is between 10 and 60 seconds.
  • tQ is used as a parameter for adjusting the microstructure, in particular the martensite content.
  • step h) the steel flat product is heated at a maximum heating rate ThetaBI of 80 K/s to a treatment temperature TB of 450-500°C in order to enrich residual austenite with carbon from the supersaturated martensite.
  • the formation of carbides and the decomposition of retained austenite are avoided by observing a total treatment time for this operation of 10-1000 s.
  • the treatment temperature TB is matched to the subsequent hot-dip coating treatment.
  • TB is also a suitable temperature for immersion in a zinc-based molten bath.
  • the heating takes place at a heating rate of at most 80 K/s, in particular less than 80 K/s, in order to ensure sufficient redistribution of the carbon to guarantee.
  • the heating can be implemented, for example, by using radiant tubes or by using a booster.
  • the total treatment time tBT is at least 10 and at most 1000 s to ensure sufficient carbon redistribution.
  • the total treatment time tBT is made up of the time tBR required for heating and the time tBI during which the steel flat product is optionally held isothermally.
  • step i) the flat steel product is subjected to a coating treatment, in particular a hot dip coating.
  • the steel flat product runs through a coating bath with a zinc-based molten bath composition.
  • the temperature of the molten bath is preferably 450-500.degree.
  • a suitable molten bath composition can contain, for example, up to 2% by weight Al, up to 2% by weight Mg, the remainder zinc and unavoidable impurities, in particular from up to 2% by weight Al, up to 2% by weight Mg, The rest consists of zinc and unavoidable impurities.
  • a suitable molten bath composition can contain, for example, up to 1% by weight of Al, remainder zinc and unavoidable impurities, in particular consist of up to 1% by weight Al, remainder zinc and unavoidable impurities.
  • a melt bath composition can contain 1-2% by weight Al, 1-2% by weight Mg, the remainder zinc and unavoidable impurities, in particular 1-2% by weight Al, 1-2% by weight % Mg, balance zinc and unavoidable impurities.
  • the flat steel product can be subjected to a galvannealing treatment in an optional step j). To do this, it is tempered for a duration tGA of 10 s - 60 s at a temperature TGA of 500 - 565 °C.
  • step k the coated flat steel product is cooled to room temperature at a cooling rate ThetaB2 of at least 5 K/s, preferably more than 5 K/s.
  • the martensite formed in the course of the method according to the invention by the second quenching in step k) is referred to as untempered martensite.
  • the martensite created by the first quenching after austenitizing, which is subjected to heating in step h), is also referred to as tempered martensite.
  • Furnace atmosphere of the holding process of step d) are adjusted.
  • an atmosphere is preferably set in at least one further step, the 3 - 7 vol .-% hydrogen and as Rest with water vapor, preferably with at least 0.070% by volume, particularly preferably with at least 0.080% by volume, more preferably with at most 1.0% by volume, particularly preferably with at most 0.8% by volume, nitrogen humidified and contains unavoidable impurities.
  • the method according to the invention for producing a high-strength flat steel product provided with a metallic anti-corrosion coating comprises no further work steps and thus exclusively the work steps mentioned under a) - k).
  • a product according to the invention comprises a steel substrate which comprises a steel, preferably consists of a steel, which consists of (in % by weight): 0.1-0.5% C, 1.0-3.0% Mn, 0. 7 - 2.5% Si, 0.05 -1% Cr, up to 0.020% P, up to 0.005% S, up to 0.008% N, and optionally one or more of the following elements 0.01 -1.5 % Al, 0.05 - 0.5% Mo, 0.0004 - 0.001% B and optionally a total of 0.001 - 0.3% V, Ti and Nb, and the remainder consists of iron and unavoidable impurities.
  • a steel substrate which comprises a steel, preferably consists of a steel, which consists of (in % by weight): 0.1-0.5% C, 1.0-3.0% Mn, 0. 7 - 2.5% Si, 0.05 -1% Cr, up to 0.020% P, up to 0.005% S, up to 0.008% N, and optionally one or more of the following elements
  • the steel substrate has a microstructure containing 5-20% by volume retained austenite, less than 5% by area bainite, less than 10% by area ferrite and at least 80% by area martensite, of which at least 75% by area is tempered martensite and less than 25% by area is untempered martensite.
  • the structure of the product according to the invention consists of 5-20 vol. % of which at least 75% by area is tempered martensite and less than 25% by area is untempered martensite.
  • a high proportion of martensite is used to achieve the desired strength.
  • the ductility can be influenced by the proportion of tempered martensite. All of the martensite present in the structure is composed of tempered and untempered martensite, with the possibility that there is no untempered martensite.
  • microstructural proportions for retained austenite is based on vol. % and for other microstructural components such as martensite, ferrite and bainite, on area %.
  • the structure is particularly fine-grained and preferably has an average grain size of less than 30 ⁇ m. Due to the fineness of the microstructure, it is advisable to carry out the microstructure investigations using a scanning electron microscope (SEM) with a magnification of at least 5000x. An examination using X-ray diffraction (XRD) according to ASTM E975 is recommended as a suitable method for the quantitative determination of retained austenite.
  • SEM scanning electron microscope
  • XRD X-ray diffraction
  • the product according to the invention also includes a metallic protective coating, preferably a Zn-based anti-corrosion coating.
  • a suitable anti-corrosion coating contains up to 2% by weight Al, up to 2% by weight Mg, the remainder zinc and unavoidable impurities, in particular the anti-corrosion coating consists of up to 2% by weight Al and up to 2% by weight Mg , remainder Zn and unavoidable impurities.
  • the anti-corrosion coating has 1-2% by weight Al, 1-2% by weight Mg, the remainder zinc and unavoidable impurities, in particular it consists of 1-2% by weight Al, 1-2% by weight % Mg, remainder zinc and unavoidable impurities.
  • the anti-corrosion coating has up to 1% by weight Al, remainder zinc and unavoidable impurities, in particular it consists of up to 1% by weight Al, remainder zinc and unavoidable impurities.
  • the coated steel flat product according to the invention has a ratio of the sum of Si and Mn to Cr of at least 1.7 and at most 15 in the boundary layer between the anti-corrosion coating and the steel substrate according to the following relationship: 1.7 ⁇ si + Mn / Cr _ GS ⁇ 1 5 with Si: Si wt% content in the boundary layer, Mn: Mn wt% content in the boundary layer, Cr: Cr wt% content in the boundary layer.
  • Anti-corrosion coating deteriorates with an enrichment of Si and Mn in the boundary layer, whereas the adhesion is significantly improved when chromium is also enriched.
  • the Addition of Cr limited to at most 1.0 wt%, preferably at most 0.6 wt%, by its negative effect on grain boundary oxidation as well as by economic considerations, while minimum levels of Si and/or Mn to achieve the desired mechanical properties required are.
  • a relatively strong accumulation of Si and/or Mn in the boundary layer locally leads to pronounced oxide formation. These oxides lead to problems with hot-dip coating and result in insufficient adhesion of the anti-corrosion coating to the base material.
  • the risk of adhesion failure is low if the ratio of the sum of Si+Mn to Cr is 15 at most, preferably 13 at most.
  • the risk of adhesion failure is also low when the ratio of the sum of Si+Mn to Cr is at least 1.7, preferably at least 2.5.
  • the ratio of the sum of Si+Mn to Cr in the boundary layer is smaller than in the base material.
  • the coated steel flat product shows a concentration gradient between the boundary layer and the steel substrate or the base material, which can be represented by the following relationship: si + Mn / Cr _ GS ⁇ si + Mn / Cr _ GW with [(Si + Mn) / Cr]_GS: ratio of the sum of the Si content in % by weight and the Mn content in % by weight to the Cr content in % by weight in the boundary layer, [(Si + Mn) / Cr]_GW: Ratio of the sum of the Si content in % by weight and the Mn content in % by weight to the Cr content in % by weight in the base material.
  • the specification of the element content of the base material typically refers to the composition at one third of the thickness of the steel substrate.
  • [(Si + Mn) / Cr]_GS is smaller than [(Si + Mn) / Cr]_GW ensures that the steel flat product has good adhesion of the metallic coating on the steel substrate and good forming properties. This effect can be achieved particularly reliably if [(Si+Mn)/Cr]_GS is preferably less than 0.9*[(Si+Mn)/Cr]_GW, particularly preferably less than 0.6*[(Si+Mn ) / Cr]_GW is.
  • the coated flat steel products preferably have a tensile strength Rm of at least 600 MPa, a yield point Rp02 of at least 400 MPa and an elongation A80 of at least 7%, in particular more than 7%.
  • Tensile strengths of 950 to 1500 MPa are typically achieved. Yield strength values are typically at least 700 MPa. The yield point is below the achieved tensile strength. The yield point is typically below 950 MPa.
  • the coated flat steel products have excellent adhesion of the anti-corrosion coating, preferably level 1 adhesion determined by the ball impact test in accordance with SEP 1931, on the steel substrate, and very good formability.
  • Hole expansion for example, can be used as a measure of formability. The hole expansion is typically at least 25%.
  • the product of tensile strength and hole expansion can also be used as a measure of formability. In a preferred embodiment, the product of tensile strength and hole expansion is at least 20,000 MPa*%, preferably at least 25,000 MPa*%
  • the tensile strength, yield point and elongation were determined according to DIN EN ISO 6892, sample form 2, the adhesion was determined using a ball impact test KST according to SEP 1931 and the hole expansion was determined according to ISO 16630.
  • the element distribution in the boundary layer and in the areas adjacent to the boundary layer can be carried out using the glow discharge spectroscopy method (Glow Discharge Optical Emission Spectroscopy, GDOES for short).
  • GDOES glow discharge spectroscopy
  • a GDOES measuring device from Leco can be used for this. With GDOES it is possible to carry out the quantitative determination of elements in layer structures along the layer thickness.
  • the beginning of the boundary layer can be determined using GDOES by using the intersection of the curves of the Zn content and the Fe content as the starting point of the boundary layer, which extends 300 nm from this intersection into the base material.
  • the flat steel product according to the invention is produced by the method according to the invention explained above.
  • melts A-G of the compositions given in Table 1 were produced, from which 11 hot strips with a thickness of 1.8 to 2.5 mm were produced in a conventional manner.
  • the melts C, E, F and G correspond to the specifications according to the invention for the steel composition, whereas the melts A and B have too low Si contents and the melt D has too low a Si content and too high an Al content.
  • the hot strips were pickled in a conventional manner and further processed with the production parameters given in Table 2.
  • the hot strips were each rolled into cold strips with the degree of cold rolling “KWG” specified in Table 2, the cold strips were each heated to a turning temperature “TW” at a first, faster heating rate “ThetaHI” and then at a second, slower heating rate “ThetaH2” brought to the holding zone temperature "THZ”, at which they were held for the duration "tHZ" of 5 to 15s in an atmosphere with a dew point "TP".
  • the cold strips were first slowly cooled to an intermediate temperature "TLK” within a period of time “tLK” of 50 to 300 s, then quickly quenched from the intermediate temperature “TLK” at a cooling rate "ThetaQ” to a cooling stop temperature "TAB”, at which they were held for a duration "tQ” of 10 to 60s.
  • the flat steel products were then heated to a treatment temperature "TB” at a heating rate "ThetaBI” of at most 80K/s. The steel flat products were not kept at the treatment temperature.
  • the flat steel products were then subjected to hot dip coating, carried out in an otherwise conventional manner, in a melt bath with the following composition: up to 2% by weight Al, up to 2% by weight Mg, the remainder zinc and unavoidable impurities.
  • the steel flat products of melts A - F were finally quenched to room temperature at a cooling rate "ThetaB2" of at least 5 K/s.
  • the flat steel products of melt G were first tempered at a temperature TGA for a duration tGA and only after tempering were they quenched to room temperature at a cooling rate of at least 5 K/s.
  • the structural investigations were carried out on cross-sections at 1/3t layer, i.e. on sections which were taken from a third of the sheet thickness of the steel substrate.
  • the sections were prepared for scanning electron microscopy (SEM) examination and treated with a 3% Nital etch. Due to the fineness of the microstructure, the microstructure was characterized by means of REM observation at a magnification of 5000x.
  • the quantitative determination of the retained austenite was carried out by means of X-ray diffraction (XRD) according to ASTM E975.
  • XRD X-ray diffraction
  • the element content of the base material was determined using the combustion analysis ICP-OES (inductively coupled plasma optical emission spectrometry) in a 1/3t layer.
  • the mechanical properties yield strength "Rp02”, tensile strength “Rm” and elongation "A80" were tested according to DIN EN ISO 6892:2009, specimen form 2, on longitudinal specimens which were taken from the middle of the steel flat products.
  • the adhesion of the zinc-based anti-corrosion coating was determined as KST according to SEP 1931 and the hole expansion was determined according to IS016630.
  • samples C4, C5, E8 and F10 produced according to the invention have very low values for the [(Si+Mn)/CLGS ratio, of at most 15. At the same time, these samples show excellent adhesion of the anti-corrosion coating of less than 1.5 and very good hole expansion of over 25%. In comparison, samples of steels of the same strength class but with a [(Si+Mn)/CLGS value higher than 15 show poorer formability and poorer coating adhesion. Sample E9 shows that it is possible to achieve adequate values for the product of tensile strength and hole expansion (tensile strength*hole expansion) if the nitrogen in the gas mixture is not sufficiently moistened with water vapor and the dew point is therefore too low Adhesion of the anti-corrosion coating impaired.

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Claims (13)

  1. Procédé de fabrication d'un produit plat en acier à très haute résistance et pourvu d'un revêtement protecteur métallique, comprenant au moins les étapes de travail suivantes :
    a) pour la mise à disposition d'un produit plat en acier laminé à chaud comprenant un acier composé de (en % en poids)
    0,1 à 0,5 % de C,
    1,0 à 3,0 % de Mn,
    0,7 à 2,5 % de Si,
    0,05 à 1 % de Cr,
    jusqu'à 0,020 % de P,
    jusqu'à 0,005 % de S,
    jusqu'à 0,008 % de N,
    et éventuellement d'un ou de plusieurs des éléments suivants
    0,01 à 1,5 % d'AI,
    0,05 à 0,5 % de Mo,
    0,0004 à 0,001 % de B
    et éventuellement d'un total de 0,001 à 0,3 % de V, de Ti et de Nb, et le reste étant constitué de fer et d'impuretés inévitables ;
    b) décapage et laminage à froid du produit plat en acier laminé à chaud, le produit plat en acier laminé à chaud subissant une réduction d'épaisseur d'au moins 37 % ;
    c) chauffage en deux étapes du produit plat en acier laminé à froid à une température de zone de maintien THZ supérieure à la température A3 de l'acier, le chauffage étant d'abord effectué à une première vitesse de chauffage Theta_H1 de 5 à 50 K/s jusqu'à une température de changement TW comprise entre 200 et 400 °C, et au-delà de la température de changement TW, à une seconde vitesse de chauffage Theta_H2 de 2 à 10 K/s jusqu'à la température de zone de maintien THZ;
    d) maintien du produit plat en acier à la température de zone de maintien THZ pour une durée tHZ de 5 à 15 s dans une atmosphère de four qui contient 3 à 7 % en volume d'hydrogène, et le reste contenant de l'azote humidifié avec de la vapeur d'eau et des impuretés inévitables, le point de condensation de l'atmosphère de four se situant entre -22 °C et 0 °C ;
    e) refroidissement du produit plat en acier de la température de zone de maintien THZ à une température TLK qui n'est pas plus basse que 150 °C en dessous de la température A3 de l'acier du produit plat en acier, la durée pour le refroidissement de THZ à TLK étant d'au moins 50 s et d'au plus 300 s ;
    f) refroidissement du produit plat en acier de la température TLK à une vitesse de refroidissement ThetaQ d'au moins 30 K/s jusqu'à une température d'arrêt de refroidissement TAB se situant entre la température de démarrage de la martensite TMS et une température inférieure jusqu'à 175 °C à la TMS ;
    g) maintien du produit plat en acier à la température d'arrêt de refroidissement TAB pour une durée de 10 à 60 s ;
    h) chauffage du produit plat en acier à une vitesse de chauffage ThetaB1 d'au plus 80 K/s à une température de traitement TB comprise entre 450 et 500 °C et éventuellement maintien isotherme du produit plat en acier à la température de traitement TB, le temps de traitement tBT total pour le chauffage et le maintien isotherme éventuel étant de 10 à 1 000 s ;
    i) revêtement par immersion à chaud du produit plat en acier avec un revêtement anticorrosion à base de zinc ;
    j) éventuellement recuit du produit plat en acier revêtu à une température de 500 à 565°C pour une durée de 10 s à 60 s ;
    k) refroidissement du produit plat en acier revêtu à la température ambiante à une vitesse de refroidissement ThetaB2 d'au moins 5 K/s.
  2. Procédé selon la revendication 1, caractérisé en ce que le revêtement par immersion à chaud est effectué dans un bain de fusion contenant jusqu'à 2 % en poids d'AI, jusqu'à 2 % en poids de Mg et un reste de zinc et d'impuretés inévitables.
  3. Procédé selon la revendication 1 ou 2, caractérisé en ce que le point de condensation de l'atmosphère de four se situe entre -22 °C et -5 °C.
  4. Procédé selon l'une des revendications précédentes, caractérisé en ce que le chauffage du produit plat en acier dans l'étape de travail c) et/ou le maintien dans l'étape de travail d) sont effectués dans un four à tubes radiants.
  5. Produit plat en acier à très haute résistance et pourvu d'un revêtement protecteur métallique, caractérisé en ce qu'il comprend un substrat en acier comprenant un acier constitué de (en % en poids) :
    0,1 à 0,5 % de C,
    1,0 à 3,0 % de Mn,
    0,7 à 2,5 % de Si,
    0,05 à 1 % de Cr,
    jusqu'à 0,020 % de P,
    jusqu'à 0,005 % de S,
    jusqu'à 0,008 % de N,
    et éventuellement d'un ou de plusieurs des éléments suivants
    0,01 à 1,5 % d'AI,
    0,05 à 0,5 % de Mo
    0,0004 à 0,001 % de B
    et éventuellement d'un total de 0,001 à 0,3 % de V, de Ti et de Nb, et le reste étant constitué de fer et
    d'impuretés inévitables,
    dans lequel le produit plat en acier présente une structure contenant
    - 5 à 20 % en volume d'austénite résiduelle,
    - moins de 5 % en surface de bainite,
    - moins de 10 % en surface de ferrite,
    - au moins 80 % en surface de martensite, dont au moins 75 % en surface est de la martensite recuite,
    dans lequel le produit plat en acier présente, dans la couche de délimitation entre le revêtement anticorrosion et le substrat en acier, un rapport de la somme de Si et de Mn à Cr selon la relation suivante : 1,7 ≤ Si + Mn / Cr _ GS ≤ 15
    Figure imgb0014
    et le rapport de la somme de Si + Mn à Cr dans la couche de délimitation est inférieur à celui dans le matériau de base, de sorte que : Si + Mn / Cr _ GS < Si + Mn / Cr _ GW
    Figure imgb0015
    avec [(Si + Mn)/Cr]_GS : rapport de la somme de la teneur en Si en % en poids et de la teneur en Mn en % en poids à la teneur en Cr en % en poids dans la couche de délimitation,
    [(Si + Mn)/Cr]_GW : rapport de la somme de la teneur en Si en % en poids et de la teneur en Mn en % en poids à la teneur en Cr en % en poids dans le matériau de base,
    dans lequel la couche de délimitation est une couche qui commence avec la couche entre la couche anticorrosion et le matériau de base, dans laquelle la teneur en zinc et la teneur en fer ont la même valeur en % en poids, et qui atteint jusqu'à une profondeur de 300 nm dans le matériau de base,
    dans lequel le produit plat en acier présente, entre le matériau de base et la couche de délimitation, un gradient de concentration de Si + Mn / Cr _ GS < 0,6 * Si + Mn / Cr _ GW
    Figure imgb0016
    et dans lequel le revêtement anticorrosion est un revêtement anticorrosion à base de zinc.
  6. Produit plat en acier selon la revendication 5, caractérisé en ce qu'il présente une résistance à la traction Rm d'au moins 600 MPa, une limite élastique Rp02 d'au moins 400 MPa et un allongement A80 d'au moins 7 %.
  7. Produit plat en acier selon la revendication 5 ou 6, caractérisé en ce qu'il présente un élargissement de trou d'au moins 25 %, un produit de la résistance à la traction et de l'élargissement de trou d'au moins 20 000 MPa*% et/ou une très bonne adhérence du revêtement anticorrosion sur le substrat en acier.
  8. Produit plat en acier selon l'une des revendications 5 à 7, caractérisé en ce que le revêtement protecteur métallique contient jusqu'à 2 % en poids d'Al, jusqu'à 2 % en poids de Mg et un reste de zinc et d'impuretés inévitables.
  9. Produit plat en acier selon la revendication 8, caractérisé en ce que le revêtement protecteur métallique contient de 1 à 2 % en poids d'Al, de 1 à 2 % en poids de Mg et un reste de zinc et d'impuretés inévitables.
  10. Produit plat en acier selon l'une des revendications 5 à 7, caractérisé en ce que le revêtement protecteur métallique contient jusqu'à 1 % en poids d'AI et un reste de zinc et d'impuretés inévitables.
  11. Produit plat en acier selon l'une des revendications 5 à 10, caractérisé en ce que la teneur en Ti du substrat en acier est supérieure à 3,42 fois la teneur en N du substrat en acier ou en ce que la teneur en Nb du substrat en acier est supérieure à 3,42 fois la teneur en N du substrat en acier.
  12. Produit plat en acier selon l'une des revendications 5 à 11, caractérisé en ce que le produit plat en acier présente, dans la couche de délimitation entre le revêtement anticorrosion et le substrat en acier, un rapport de la somme de Si et de Mn à Cr [(Si + Mn)/Cr]_GS d'au plus 13.
  13. Produit plat en acier selon l'une des revendications 5 à 12, caractérisé en ce que le produit plat en acier présente, dans la couche de délimitation entre le revêtement anticorrosion et le substrat en acier, un rapport de la somme de Si et de Mn à Cr [(Si + Mn)/Cr]_GS d'au moins 2,5.
EP18789005.8A 2018-09-26 2018-09-26 Procédé pour la préparation d'un produit plat en acier revêtu et produit plat en acier revêtu Active EP3856936B1 (fr)

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WO2024033721A1 (fr) 2023-06-30 2024-02-15 Arcelormittal Pièce d'acier revêtue estampée à chaud contenant des fissures présentant une excellente soudabilité par points et une excellente adhérence de peinture
EP4592409A1 (fr) 2024-01-26 2025-07-30 ThyssenKrupp Steel Europe AG Acier réfractaire au maximum ayant de bonnes propriétés de surface et de déformation avec un revêtement à base de fer de zinc
EP4592407A1 (fr) * 2024-01-26 2025-07-30 ThyssenKrupp Steel Europe AG Acier à haute résistance mécanique présentant de bonnes propriétés de déformation et de surface
EP4592406A1 (fr) 2024-01-26 2025-07-30 ThyssenKrupp Steel Europe AG Acier réfractaire au maximum ayant de bonnes propriétés de surface et de déformation avec un revêtement à base de zinc
DE102024123439A1 (de) * 2024-08-16 2026-02-19 Thyssenkrupp Steel Europe Ag Verfahren zum Herstellen eines mit einem Korrosionsschutzüberzug auf Zn-Basis versehenen Stahlflachprodukts und Stahlflachprodukt

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EP2524970A1 (fr) * 2011-05-18 2012-11-21 ThyssenKrupp Steel Europe AG Produit plat en acier hautement résistant et son procédé de fabrication
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EP2924141B1 (fr) * 2014-03-25 2017-11-15 ThyssenKrupp Steel Europe AG Produit plat en acier laminé à froid et son procédé de fabrication
WO2016177420A1 (fr) * 2015-05-06 2016-11-10 Thyssenkrupp Steel Europe Ag Produit laminé plat en acier et son procédé de fabrication

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PL3856936T3 (pl) 2023-01-02
CN112789358B (zh) 2022-03-25
ES2927204T3 (es) 2022-11-03
CN112789358A (zh) 2021-05-11
JP2021530624A (ja) 2021-11-11
EP3856936A1 (fr) 2021-08-04
EP4083236A1 (fr) 2022-11-02
WO2020064096A1 (fr) 2020-04-02

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