EP3186401B1 - Method of manufacturing of a nitrided packaging steel - Google Patents

Method of manufacturing of a nitrided packaging steel Download PDF

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Publication number
EP3186401B1
EP3186401B1 EP15732735.4A EP15732735A EP3186401B1 EP 3186401 B1 EP3186401 B1 EP 3186401B1 EP 15732735 A EP15732735 A EP 15732735A EP 3186401 B1 EP3186401 B1 EP 3186401B1
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Prior art keywords
nitrogen
steel
ppm
annealing furnace
gas
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EP15732735.4A
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German (de)
French (fr)
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EP3186401A1 (en
Inventor
Burkhard KAUP
Blaise Massicot
Dirk Matusch
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ThyssenKrupp AG
ThyssenKrupp Rasselstein GmbH
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ThyssenKrupp AG
ThyssenKrupp Rasselstein GmbH
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    • 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
    • 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
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces
    • 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
    • C21D8/0236—Cold rolling
    • 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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0257—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment with diffusion of elements, e.g. decarburising, nitriding
    • 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
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • 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
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0405—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing 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
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
    • C21D8/0436—Cold rolling
    • 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
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
    • C21D8/0457—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment with diffusion of elements, e.g. decarburising, nitriding
    • 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
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
    • C21D8/0473—Final recrystallisation annealing
    • 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
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • 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
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/80—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
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F17/00—Multi-step processes for surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by subclass C21D or C22F or class C25

Definitions

  • the invention relates to a method for producing an embroidered packaging steel having the features of claim 1.
  • packaging steel flat steel products such as steel sheets or steel strips, which are intended for the production of packaging (hereinafter referred to as packaging steel), is known from the prior art.
  • packaging steel flat steel products
  • EP 0 216 399 B1 a steel sheet for packaging and a method for its production is described, which was prepared from an aluminum-killed, continuously cast carbon-manganese steel and obtained by picking up a lot of unbound, dissolved nitrogen, the minimum amount of unbound nitrogen depending on a desired hardness category of the steel sheet is defined and (for example for the hardness category T61 of the European standard 145-78) has an amount of unbound nitrogen of at least 5 ppm.
  • the chemical composition of the steel sheet disclosed therein corresponds to the usual soft steels in terms of carbon and manganese content and has, for example, a carbon content in the range of 0.03 to 0.1 wt .-% and a manganese content of 0.15 to 0.5 wt. -% on.
  • the steel sheet is characterized by a high yield strength in the range of 350-550 N / mm 2 .
  • a maximum value of 100 ppm is given, stating that the steel sheet at a higher content of unbound nitrogen due to the associated increase in strength no longer cold-rollable and thus not for the intended use as cold-rolled packaging steel suitable is.
  • a steel is first cast continuously, then hot rolled, cold rolled, recrystallized annealed and finally re-rolled. After re-rolling takes place a thermal Aftertreatment in which free dislocations formed in the steel by the temper rolling are fixed by the unbonded nitrogen introduced by the sticking to increase the hardness and yield strength over the post-rolling values.
  • the thermal aftertreatment can be suitably combined with another thermal treatment of the post-rolled steel, which is to be carried out anyway in the context of the production of a packaging steel, such as, for example, melting a layer of tin electrolytically applied to the surface of the steel sheet or baking a paint layer applied to the steel sheet surface ,
  • a low aluminum steel strip for the manufacture of containers which produce a hot rolled steel strip containing between 0.050% and 0.080% by weight of carbon, between 0.25% and 0.40% by weight of manganese, less than 0.020 %
  • the nitrogen content of the Stahlabnds is ensured by the addition of calcium cyanamide in the ladle during steel extraction or by blowing gaseous nitrogen into the steel bath.
  • JP 11315343-A is a steel strip with a carbon content of ⁇ 0.06%, a silicon content of ⁇ 0.03%, a manganese content of 0.05% to 0.5%, a phosphorus content of ⁇ 0.02%, a sulfur content of ⁇ 0, 02%, an aluminum content of 0.02% to 0.10% and a nitrogen content of 0.005% to 0.015% for the Production of cans known in the production of a hot steel rolled slab to a hot strip and the hot strip is first cold rolled, then annealed and finally re-rolled.
  • WO 2013/183274 A1 is a three-piece can and a process for its manufacture from a steel sheet having a carbon content of at least 0.02 and up to 0.10%, a silicon content of ⁇ 0.10%, a manganese content of 0.1% to 0.8% , a phosphorus content of 0.001% to 0.10%, a sulfur content of 0.001% to 0.02%, an aluminum content of 0.005 to 0.10% and a nitrogen content of 0.013 to 0.020%.
  • the steel strip has tensile strengths of 440 MPa or more and an elongation at break of 12% or more.
  • the embroidering of a steel can be introduced in the manufacturing process of the steel by introducing nitrogen into the molten steel, for example by blowing nitrogen gas N 2 .
  • a method of embossing steel melts in steelmaking in the oxygen inflation method is, for example, in US Pat DE 2 237 498 described.
  • Flat steel products, in particular steel strips, can be embroidered by a surface conditioning, for example by diffusion of nitrogen into the steel sheet surface, which can be done for example by gas nitriding in an ammonia atmosphere with slight overpressure, by bath nitriding in nitrogen-containing salt baths or by plasma nitriding.
  • By diffusion of nitrogen forms on the steel sheet surface while a hard, superficial bonding layer and an underlying diffusion zone in which the nitrogen is embedded to a certain depth in the (ferritic) steel matrix.
  • the object of the invention is to show a flat steel product (sheet steel or steel strip) for the production of packaging, which has the highest possible strength combined with good elongation at break and good forming properties.
  • a packaging steel with strengths of at least 600 MPa with an elongation at break of at least 5% should be made available.
  • the higher-strength packaging steel must at the same time have sufficient formability for the intended use as packaging steel, for example in deep-drawing or ironing process, so that from the flat steel product intended packaging, such. Canned or beverage cans can be produced.
  • the present as flat steel product packaging steel should have the usual thicknesses in the fine and Feinstblech Scheme, which are regularly produced by cold rolling.
  • the process of the present invention can produce an embroidered packaging steel having a carbon content of 10 to 1000 ppm and an amount of unbound steel dissolved nitrogen of greater than 100 ppm and preferably greater than 150 ppm, with the steel being upset in two stages ,
  • a molten steel is nitrided to a maximum nitrogen content of 160 ppm by feeding nitrogen to the molten steel, for example in the form of a nitrogen-containing gas and / or a nitrogen-containing solid.
  • a slab is poured and hot rolled into a hot strip.
  • the hot strip is subsequently pickled (after cooling to ambient temperature), if necessary, and cold rolled to a flat steel product (steel sheet or steel strip).
  • the cold-rolled steel flat product is then recrystallized in an annealing furnace.
  • the second step of the nitrogenizing step is carried out by introducing a nitrogen-containing gas into the annealing furnace and directing it to the flat steel product to increase the amount of unbound nitrogen in the steel beyond the amount of nitrogen introduced into the molten steel in the first stage of the nitrogenizing step continue to increase.
  • the two-stage embroidering of the packaging steel ensures that the hot-rolled strip is used with those commonly used for the production of packaging steels Cold rolling devices (rolling mills) easily to a flat steel product, in particular to a steel strip, can be cold rolled. This is made possible by the fact that in the first stage of the Aufstickens a content of unbound nitrogen of at most 160 ppm is introduced into the molten steel.
  • the hot strip produced from the embroidered molten steel by hot rolling remains cold-rolled at these nitrogen contents, so that a fine or very fine sheet can be produced in the standard thickness for packaging purposes from the hot strip by cold rolling. Higher nitrogen contents in the molten steel also lead to undesirable defects in the slab cast from the molten steel.
  • the desired strength of the packaging steel preferably greater than 600 MPa, is achieved during cold rolling and in the second stage of the nitrogen blanketing of the flat steel product during its recrystallizing annealing.
  • flat steel products, in particular steel strips, with thicknesses in the fine and Feinstblech Scheme for use as packaging steel with very high tensile strengths at the same time high elongation at break of preferably at least 5% can be produced without suffering a restriction in the forming properties.
  • the steel melt is embossed in the first stage by introducing nitrogen gas (N 2 ) and / or lime nitrogen (CaCN 2 ) and / or manganese nitrogen (MnN) into the molten steel.
  • the embroidering of the flat steel product in the second stage is preferably carried out by introducing ammonia gas (NH 3 ) into the annealing furnace, in which the steel flat product is annealed in a recrystallizing manner.
  • the ammonia gas is thereby gassed by means of spray nozzles on the surface of the flat steel product.
  • the amount of ammonia gas introduced into the annealing furnace is preferably adjusted so that an ammonia equilibrium with an ammonia concentration in the range of 0.05 to 1.5% is established in the annealing furnace.
  • the ammonia concentration in the annealing furnace is preferably detected by means of an ammonia sensor, and the detected value of the ammonia equilibrium concentration is used for controlling the amount of ammonia gas introduced into the annealing furnace per unit time.
  • an inert gas is preferably introduced into the annealing furnace during the recrystallizing annealing in the annealing furnace in the second stage of the addition of nitrogen, for example nitrogen gas and / or hydrogen gas or a mixture thereof, for example in a composition of 95% by weight. Nitrogen gas and 5% by weight of hydrogen gas.
  • the total amounts of unbound nitrogen introduced by the two-stage embroidering of the packaging steel are between 100 and 500 ppm, preferably above 150 ppm and more preferably in the range between 200 and 350 ppm.
  • a maximum nitrogen content of 160 ppm is introduced into the molten steel. Maintaining an upper limit of about 160 ppm for the content of unbound nitrogen in the molten steel ensures that no defects occur on the slab produced from the molten steel, for example in the form of pores and cracks, which can oxidise by ambient oxygen.
  • the hot strip produced from the slab remains cold-rolled at a nitrogen content of at most 160 ppm.
  • the amount of unbound nitrogen which can additionally be introduced in the second stage when the steel flat product is being embroidered is preferably in the range from 180 to 350 ppm.
  • a total amount of unbound nitrogen in the packaging steel according to the invention of up to 500 ppm can be introduced by the two stages of the embroidering.
  • tensile strengths of more than 650 MPa and up to 1000 Mpa can be achieved, whereby a linear relationship has been established between the content of unbound nitrogen and the tensile strength and, for example for tensile strengths of about 650 MPa, a content of unbound nitrogen of approx 200 ppm is required.
  • the cold-rolled steel flat product For recrystallizing annealing of the cold-rolled steel flat product, it is preferably heated in the annealing furnace to temperatures of more than 600 ° C. and in particular of more than 620 ° C.
  • the recrystallizing annealing restores the formability of the cold-rolled steel flat product.
  • heating of the flat steel product to a temperature of 620 ° C. to 660 ° C. and more preferably of approximately 640 ° C. has proven to be preferred.
  • a plurality of spray nozzles is preferably used, with which a nitrogen-containing gas, such. Ammonia gas can be uniformly applied to the surface of the flat steel product.
  • the plurality of spray nozzles for example transversely to the strip running direction, are preferably arranged equidistant from each other. As a result, a homogeneous nitriding of the flat steel product over the entire surface is possible.
  • an embroidered molten steel is initially produced in a converter and / or in a subsequent ladle treatment, which has a content of free, unbound (ie dissolved in steel) nitrogen of up to 160 ppm.
  • the carbon content of the steel produced is preferably in the range from 10 to 1000 ppm and more preferably between 100 and 900 ppm and usually between 400 and 900 ppm.
  • the converter is filled with scrap and pig iron and the melt is blown with oxygen gas and nitrogen gas, whereby the oxygen gas (O2) from above and nitrogen gas (N2) is injected from below into the converter by means of bottom nozzles.
  • O2 oxygen gas
  • N2 nitrogen gas
  • a nitrogen content in the molten steel of 70 to 120 ppm sets, whereby it comes to a saturation.
  • the composition and esp. The nitrogen content of the melt is detected. If the given analysis has not been made (for example, if the level of phosphorus is too high) oxygen gas is bubbled through an oxygen lance and argon gas (Ar) through the bottom nozzles. Since hardly any more carbon (C) is present in the steel, no overpressure arises and the nitrogen of the air is pulled in with, whereby it can come to an additional nitriding.
  • lime-nitrogen calcium cyanamide, CaCN2
  • the lime nitrogen is added, for example, in the form of granules (5-20 mm).
  • the pan comes to the first Argon capitae, where with a refractory immersed lance with argon for about 3 minutes is rinsed. After a control analysis, if necessary, rinse a second time in a second argon rinse for about 3 minutes. The pan then comes to a third argon sink. This represents the last stage before casting.
  • manganese nitride for example in the form of a wire of MnN powder in a steel sheath, may be added to the third argon sink.
  • the amount of possibly missing nitrogen is converted into a required amount of MnN (for example, into a required length of the MnN wire), which is added to the melt.
  • the MnN is added until the predetermined target nitrogen content or Mn upper limit of the steel is reached.
  • the melt is placed in a distributor trough to pour a slab from the molten steel. Due to leaks and diffusion of atmospheric nitrogen, the nitrogen content may rise by about 10 ppm. An upper limit of the amount of dissolved nitrogen in the cast steel slab of about 160 ppm should not be exceeded, because at higher nitrogen contents, defects can form on the slab such as cracks or pores, which lead to undesired oxidation.
  • the slab cast from the molten steel is then hot rolled and cooled to room temperature.
  • the hot strip produced has thicknesses in the range of 1 to 4 mm and is possibly wound up into a roll (coil).
  • the hot strip must be cold rolled, with a reduction in thickness ranging from 50 to more than 90%.
  • Thin sheet is understood to mean a sheet with a thickness of less than 3 mm and a fine sheet has a thickness of less than 0.5 mm.
  • the hot strip which may have been wound up as a roll, is unwound from the roll, pickled and introduced into a cold rolling device, for example a cold rolling mill.
  • the cold-rolled steel strip In order to restore the crystal structure of the steel, which has been destroyed during cold rolling, the cold-rolled steel strip must be recrystallized. This is done by passing the cold-rolled steel strip through a continuous annealing furnace in which the steel strip is heated to temperatures above the recrystallization point of the steel and in particular to temperatures above 600 ° C. In the process according to the invention, a further embroidering of the steel strip in a second stage takes place simultaneously with the recrystallization annealing. This is carried out in the annealing furnace by introducing into the annealing furnace a nitrogen-containing gas, preferably ammonia (NH 3 ).
  • a nitrogen-containing gas preferably ammonia (NH 3 ).
  • FIG. 1 schematically a continuous annealing furnace for carrying out the recrystallization and the second stage of the Aufstickens is shown.
  • different zones are formed, which are in the direction of passage (tape running direction V, in FIG. 1 from right to left) of the guided through the continuous annealing furnace steel strip are arranged one behind the other.
  • a heating zone 1 arranged on the input side of the continuous annealing furnace, the steel strip S is heated to temperatures in the range from 600 ° C. to 750 ° C.
  • a temperature range of 620 ° C to 700 ° C and has proven to be particularly preferred from 620 ° C to 660 ° C. The best results were achieved at temperatures of about 640 ° C. These temperatures are above the recrystallization temperature of the steel, which is why in the heating zone 1, the steel strip S is annealed recrystallizing.
  • the heating zone 1 is followed by a holding zone 2, in which the temperature of the steel strip S is maintained in the above-mentioned temperature range.
  • a plurality of cascades 3a, 3b, 3c of spray nozzles in the strip running direction are arranged one behind the other.
  • Each cascade 3a, 3b, 3c comprises a plurality of nozzles 3, which are arranged transversely to the strip running direction at a distance from each other.
  • the nozzles 3 are coupled to a gas supply line via which they are charged with a nitrogen-containing gas.
  • a nitrogen-containing gas As the gas particularly suitable for the second stage of the gasification, ammonia gas has been found.
  • nozzles 3 of the cascades are in the German patent application DE 102014106135 from 30.4. 2014, the disclosure of which is hereby incorporated by reference.
  • a nozzle device for treating a flat steel product is described, wherein the nozzle device comprises an outer tube and an inner tube disposed therein with a primary opening for feeding a gas flowing through the nozzle device in the outer tube and the outer tube is provided with a secondary opening through which the gas escape can.
  • the primary opening of the inner tube and the secondary opening of the outer tube are offset from each other. This allows a very homogeneous flow of gas to the surface of the flat steel product.
  • a homogeneous fumigation of the surface of the steel strip in the holding zone 2 of the continuous annealing furnace with the nitrogen-containing gas (ammonia) can be achieved, whereby over the surface of the steel strip, in particular across its width, a homogeneous diffusion of nitrogen and thereby the formation of a homogeneous, nitrogen-enriched and cured surface layer can be achieved.
  • the nitrogen-containing gas ammonia
  • the method of direct loading of the steel strip (gassing) with a nitrogen-containing gas by means of nozzles has two major advantages: Firstly, only a low concentration of nitrogen (NH 3 concentration) in the protective gas is required, resulting in a low consumption of nitrogen-containing gas (eg NH 3 consumption). On the other hand, there is no formation of a nitride layer due to a very short reaction time. Following gassing with a nitrogen-containing gas (eg NH 3 treatment), the steel strip is annealed even further (expediently more than 5 seconds) at unchanged temperatures, before it is cooled. This results in a homogenization of the nitrogen distribution over the cross section of the steel strip and consequently to improved forming properties. In particular, this can be used to avoid expansion loss due to paint aging (see page 6, lines 14 - 20).
  • a nitrogen-containing atmosphere with a nitrogen equilibrium concentration which is as constant as possible must be maintained during the passage of the steel strip S through the holding zone 2 of the continuous annealing furnace.
  • a nitrogen-containing atmosphere with a nitrogen equilibrium concentration which is as constant as possible is in the range of cascades 3a, 3b, 3c with the Nozzles 3 detects the nitrogen concentration formed.
  • ammonia is used as the nitrogen-containing gas
  • the ammonia concentration formed in the holding zone 2 by gassing with ammonia is measured for this purpose.
  • a concentration sensor arranged outside the continuous annealing furnace is provided, which may, for example, be a laser spectroscopy sensor.
  • This is fed to a gas sample taken from the holding zone 2 in order to detect the ammonia concentration and from this the nitrogen concentration of the gas atmosphere in the holding zone 2.
  • the gas sample is, for example, at the in FIG. 1 taken from the point indicated by reference numeral 4.
  • the concentration of the nitrogen in the gas atmosphere of the holding zone 2 detected by the concentration sensor is supplied to and used by a controller to keep the amount of nitrogen-containing gas (ammonia) sprayed into the holding zone 2 via the nozzles 3 constant at a predetermined target value.
  • Target values for the equilibrium concentration of the ammonia in the range of 0.05 to 1.5%, and preferably of less than 1%, in particular less than 0.2%, have proven particularly expedient when ammonia is used as the nitrogen-containing gas.
  • the equilibrium concentration of the ammonia is in the range of 0.1 to 1.0%, and more preferably between 0.1 and 0.2%.
  • an inert gas is expediently introduced into the annealing furnace in the holding zone 2 in addition to the nitrogen-containing gas (ammonia).
  • This may, for example, be nitrogen gas and / or hydrogen gas.
  • a mixture of about Vol. 95% nitrogen and about Vol. 5% hydrogen gas is used.
  • a plurality of cooling zones 5, 6 adjoin the holding zone 2 in the strip running direction V, with a faster cooling of the steel strip S in a first cooling zone 5 and a slower cooling in a subsequent second cooling zone 6.
  • the steel strip S After cooling in the cooling zones 5 and 6, the steel strip S leaves the continuous annealing furnace and is dry-rolled (dressed) in order to give the strip the forming properties required for the production of packaging.
  • the degree of rolling varies between 0.4 and 2%, depending on the intended use of the packaging steel.
  • the steel strip can also be wet rolled to another Thickness reduction by up to 43% (double reduced steel strip, "double reduced DR").
  • the steel strip S is fed to a coating installation in which the surface of the steel strip, for example, is electrolytically provided with a tin or a chromium / chromium dioxide coating (ECCS) or a coating in order to increase the corrosion resistance.
  • ECCS chromium / chromium dioxide coating
  • embroidered steel strips can be produced, which are characterized by a very high strength of more than 600 MPa with simultaneously good elongation at break of more than 5% and good forming properties.
  • the increased through the two-stage Aufsticken strength and elongation at break are very homogeneous over the cross section of the steel strip both in and across the rolling direction of the cold-rolled steel strip. This results from the very homogeneous introduction of unbound nitrogen into the steel, especially in the second stage of the stitching.
  • the recrystallizing annealing and the second step of the embossing can be carried out in a continuous annealing furnace instead of in a continuous annealing furnace.
  • the cold rolled and wound as a roll steel strip S is placed in a crucible annealing furnace and annealed there under a protective gas atmosphere at the required for a recrystallizing annealing annealing temperatures of more than 520 ° C.
  • the annealing process takes place in the "open-coil" process. In this case, spacers are inserted between the layers of rolled into a roll steel strip to keep the surface of the steel strip for the diffusion of nitrogen accessible.

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Description

Die Erfindung betrifft ein Verfahren zur Herstellung eines aufgestickten Verpackungsstahls mit den Merkmalen des Anspruchs 1.The invention relates to a method for producing an embroidered packaging steel having the features of claim 1.

Aus dem Stand der Technik ist es bekannt, die Festigkeit von Stählen durch Einbringen von ungebundenem, im Stahl gelösten Stickstoff zu erhöhen. Das Einbringen von ungebundenem Stickstoff in den Stahl wird als Aufsticken bzw. Nitrieren oder Nitridieren bezeichnet und stellt ein bekanntes Verfahren zum Härten von Stahl und Stahlprodukten dar.From the prior art, it is known to increase the strength of steels by introducing unbound, dissolved in the steel nitrogen. The incorporation of unbound nitrogen into the steel is referred to as nitriding or nitriding, and is a known method for hardening steel and steel products.

Auch das Aufsticken von Stahlflachprodukten wie Stahlbleche oder Stahlbänder, welche für die Herstellung von Verpackungen vorgesehen sind (im Folgenden als Verpackungsstahl bezeichnet), ist aus dem Stand der Technik bekannt. In der EP 0 216 399 B1 wird beispielsweise ein Stahlblech für Verpackungszwecke sowie ein Verfahren zu dessen Herstellung beschrieben, welches aus einem aluminiumberuhigten, kontinuierlich gegossenen Kohlenstoff-Mangan-Stahl hergestellt wurde und durch Aufsticken eine Menge an ungebundenem, gelösten Stickstoff erhalten hat, wobei die Mindestmenge an ungebundenem Stickstoff in Abhängigkeit einer gewünschten Härtekategorie des Stahlblechs definiert ist und (beispielsweise für die Härtekategorie T61 des europäischen Standards 145-78) eine Menge an ungebundenem Stickstoff von wenigstens 5 ppm aufweist. Die chemische Zusammensetzung des dort offenbarten Stahlblechs entspricht bezüglich des Kohlenstoff- und Mangangehalts den üblichen weichen Stählen und weist beispielsweise einen Kohlenstoffgehalt im Bereich von 0,03 - 0,1 Gew.-% und einen Mangangehalt von 0,15 - 0,5 Gew.-% auf. Das Stahlblech zeichnet sich dabei durch eine hohe Streckgrenze im Bereich von 350 - 550 N/mm2 aus. Für die Menge an ungebundenem, im Stahl gelösten Stickstoff wird dabei ein Maximalwert von 100 ppm angegeben und damit begründet, dass das Stahlblech bei einem höheren Gehalt an ungebundenem Stickstoff aufgrund der damit verbundenen Festigkeitserhöhung nicht mehr kaltwalzbar und damit nicht für die vorgesehene Verwendung als kaltgewalzter Verpackungsstahl geeignet ist.Also, the embroidering of flat steel products such as steel sheets or steel strips, which are intended for the production of packaging (hereinafter referred to as packaging steel), is known from the prior art. In the EP 0 216 399 B1 For example, a steel sheet for packaging and a method for its production is described, which was prepared from an aluminum-killed, continuously cast carbon-manganese steel and obtained by picking up a lot of unbound, dissolved nitrogen, the minimum amount of unbound nitrogen depending on a desired hardness category of the steel sheet is defined and (for example for the hardness category T61 of the European standard 145-78) has an amount of unbound nitrogen of at least 5 ppm. The chemical composition of the steel sheet disclosed therein corresponds to the usual soft steels in terms of carbon and manganese content and has, for example, a carbon content in the range of 0.03 to 0.1 wt .-% and a manganese content of 0.15 to 0.5 wt. -% on. The steel sheet is characterized by a high yield strength in the range of 350-550 N / mm 2 . For the amount of unbound, dissolved in steel nitrogen, a maximum value of 100 ppm is given, stating that the steel sheet at a higher content of unbound nitrogen due to the associated increase in strength no longer cold-rollable and thus not for the intended use as cold-rolled packaging steel suitable is.

In dem Verfahren zur Herstellung dieses bekannten Verpackungsstahls wird zunächst ein Stahl kontinuierlich gegossen, anschließend warmgewalzt, kaltgewalzt, rekristallisierend geglüht und schließlich nachgewalzt. Nach dem Nachwalzen erfolgt eine thermische Nachbehandlung, bei der freie Versetzungen, die in dem Stahl durch das Nachwalzen gebildet werden, durch den durch das Aufsticken eingebrachten ungebundenen Stickstoff fixiert werden, um die Härte und Streckgrenze über die Werte nach dem Nachwalzen zu erhöhen. Die thermische Nachbehandlung kann dabei zweckmäßig mit einer anderen thermischen Behandlung des nachgewalzten Stahls kombiniert werden, welche im Rahmen der Herstellung eines Verpackungsstahls ohnehin durchzuführen ist, wie z.B. beim Aufschmelzen einer auf die Oberfläche des Stahlblechs elektrolytisch aufgebrachten Zinnschicht oder beim Einbrennen einer auf die Stahlblechoberfläche aufgebrachten Lackschicht.In the process for producing this known packaging steel, a steel is first cast continuously, then hot rolled, cold rolled, recrystallized annealed and finally re-rolled. After re-rolling takes place a thermal Aftertreatment in which free dislocations formed in the steel by the temper rolling are fixed by the unbonded nitrogen introduced by the sticking to increase the hardness and yield strength over the post-rolling values. The thermal aftertreatment can be suitably combined with another thermal treatment of the post-rolled steel, which is to be carried out anyway in the context of the production of a packaging steel, such as, for example, melting a layer of tin electrolytically applied to the surface of the steel sheet or baking a paint layer applied to the steel sheet surface ,

Wegen der in der EP 0 216 399 B1 vorgeschlagenen Obergrenze für die Menge des ungebundenen und im Stahl gelösten Stickstoff von 100 ppm sind die Festigkeiten dieses bekannten Verpackungsstahls limitiert. Es erscheint grundsätzlich möglich, Stahlbleche mit noch höherem Gehalt an ungebundenem Stickstoff im Stahl herzustellen, um dadurch Zugfestigkeiten oberhalb von 600 MPa zu erzielen. So sind beispielsweise in der EP 1 342 798 B1 und der DE 1 433 690 A1 aufgestickte Stähle mit einem Stickstoffgehalt von bis zu 250 ppm bzw. bis zu 400 ppm beschrieben. Allerdings haben sich derart hohe Gehalte an ungebundenem Stickstoff im Stahl in der Praxis nicht realisieren lassen.Because of in the EP 0 216 399 B1 The proposed upper limit for the amount of unbound and dissolved in steel nitrogen of 100 ppm, the strengths of this known packaging steel are limited. It seems possible in principle to produce steel sheets with an even higher content of unbound nitrogen in the steel in order to achieve tensile strengths above 600 MPa. For example, in the EP 1 342 798 B1 and the DE 1 433 690 A1 embroidered steels with a nitrogen content of up to 250 ppm or up to 400 ppm. However, such high levels of unbound nitrogen in the steel have not been realized in practice.

Aus der EP 1065286 B1 ist ein Stahlband mit geringem Aluminiumgehalt für die Herstellung von Behältern bekannt, bei dessen Herstellung ein warmgewalztes Stahlband, das zwischen 0,050 % und 0,080 Gew.-% Kohlenstoff, zwischen 0,25 % und 0,40 Gew.-% Mangan, weniger als 0,020 Gew.-% Aluminium und zwischen 0,010 % und 0,014 Gew.-% Stickstoff sowie Rest Eisen und unvermeidliche Restverunreinigungen enthält, zunächst kalt gewalzt und danach kontinuierlich auf Temperaturen oberhalb des Beginns der perlitischen Umwandlung Ac1 geglüht, gegebenenfalls eine zweite Kaltwalzung durchgeführt und das Band abschließend bis auf Umgebungstemperatur abgekühlt wird. Der Stickstoffgehalt des Stahlabnds wird dabei durch Zugabe von Calciumcyanamid in die Gießpfanne bei der Stahlgewinnung oder durch Einblasen von gasförmigem Stickstoff in das Stahlbad gewährleistet.From the EP 1065286 B1 For example, a low aluminum steel strip is known for the manufacture of containers which produce a hot rolled steel strip containing between 0.050% and 0.080% by weight of carbon, between 0.25% and 0.40% by weight of manganese, less than 0.020 % By weight of aluminum and between 0.010% and 0.014% by weight of nitrogen and the remainder containing iron and unavoidable residual impurities, first cold-rolled and then continuously annealed to temperatures above the beginning of the pearlitic transformation Ac1, if appropriate a second cold-rolling and finally the strip cooled to ambient temperature. The nitrogen content of the Stahlabnds is ensured by the addition of calcium cyanamide in the ladle during steel extraction or by blowing gaseous nitrogen into the steel bath.

Aus der JP 11315343-A ist ein Stahlband mit einem Kohlenstoffgehalt von ≤ 0,06 %, einem Siliziumgehalt von ≤ 0,03 %, einem Mangangehalt von 0,05 % bis 0,5 %, einem Phosphorgehalt von ≤ 0,02 %, einem Schwefelgehalt von ≤ 0,02 %, einem Aluminiumgehalt von 0,02 % bis 0,10 % und einem einem Stickstoffgehalt von 0,005 % bis 0,015 % für die Herstellung von Dosen bekannt, bei dessen Herstellung eine Stahlbramme zu einem Warmband warmgewalzt und das Warmband zunächst kaltgewalzt, danach geglüht und schließlich nachgewalzt wird.From the JP 11315343-A is a steel strip with a carbon content of ≤ 0.06%, a silicon content of ≤ 0.03%, a manganese content of 0.05% to 0.5%, a phosphorus content of ≤ 0.02%, a sulfur content of ≤ 0, 02%, an aluminum content of 0.02% to 0.10% and a nitrogen content of 0.005% to 0.015% for the Production of cans known in the production of a hot steel rolled slab to a hot strip and the hot strip is first cold rolled, then annealed and finally re-rolled.

Aus der WO 2013/183274 A1 ist eine dreiteilige Dose und ein Verfahren zu dessen Herstellung aus einem Stahlblech mit einem Kohlenstoffgehalt von mindestens 0,02 und bis zu 0,10%, einem Siliziumgehalt von ≤ 0,10 %, einem Mangangehalt von 0,1 % bis 0,8 %, einem Phosphorgehalt von 0,001 % bis 0,10 %, einem Schwefelgehalt von 0,001 % bis 0,02 %, einem Aluminiumgehalt von 0,005 bis 0,10 % und einem einem Stickstoffgehalt von 0,013 bis 0,020 % bekannt. Das Stahlband weist dabei Zugfestigkeiten vom 440 MPa oder mehr und eine Bruchdehnung von 12 % oder mehr auf.From the WO 2013/183274 A1 is a three-piece can and a process for its manufacture from a steel sheet having a carbon content of at least 0.02 and up to 0.10%, a silicon content of ≤ 0.10%, a manganese content of 0.1% to 0.8% , a phosphorus content of 0.001% to 0.10%, a sulfur content of 0.001% to 0.02%, an aluminum content of 0.005 to 0.10% and a nitrogen content of 0.013 to 0.020%. The steel strip has tensile strengths of 440 MPa or more and an elongation at break of 12% or more.

Aus der US 3 219 494 - B ist ein Verfahren zum Aufsticken von Stahlbändern für die Herstellung von Weißblech und anderen Verpackungsstählen bekannt, in dem ein zu einem Coil aufgewickeltes Stahlband in einem Haubenglühofen aufgestickt wird, um zunächst eine stickstoffreiche äußere Schale in dem Stahlband zu erzielen, wobei das Aufsticken in dem Haubenglühofen durch Einleiten von Ammoniakgas erfolgt und das Stahlband dabei auf Temperaturen oberhalb der Rekristallisationstemperatur in einer Inertgasatmosphäre erhitzt wird, wodurch der Stickstoff aus der stickstoffreichen äußeren Schale durch das Stahlband diffundieren kann.From the US 3,219,494 B is a method for embossing steel strips for the production of tinplate and other packaging steels is known in which a wound into a coil steel strip is embroidered in a crucible annealing furnace to first obtain a nitrogen-rich outer shell in the steel strip, wherein the embroidering in the Annealing annealing furnace is carried out by introducing ammonia gas and the steel strip is heated to temperatures above the recrystallization temperature in an inert gas atmosphere, whereby the nitrogen from the nitrogen-rich outer shell can diffuse through the steel strip.

Das Aufsticken eines Stahls kann beim Herstellungsprozess des Stahls durch Einbringen von Stickstoff in die Stahlschmelze, beispielsweise durch Einblasen von Stickstoffgas N2, eingebracht werden. Ein Verfahren zum Aufsticken von Stahlschmelzen bei der Stahlherstellung im Sauerstoffaufblasverfahren ist beispielsweise in der DE 2 237 498 beschrieben. Stahlflachprodukte, insbesondere Stahlbänder, können durch eine Oberflächenkonditionierung aufgestickt werden, beispielsweise durch Eindiffusion von Stickstoff in die Stahlblechoberfläche, was beispielsweise durch Gasnitrieren in einer Ammoniak-Atmosphäre bei leichtem Überdruck, durch Badnitrieren in stickstoffhaltigen Salzbädern oder durch Plasmanitrieren erfolgen kann. Durch Eindiffusion von Stickstoff bildet sich an der Stahlblechoberfläche dabei eine harte, oberflächliche Verbindungsschicht sowie eine darunter liegende Diffusionszone aus, in welcher der Stickstoff bis zu einer bestimmten Tiefe in der (ferritischen) Stahlmatrix eingelagert ist.The embroidering of a steel can be introduced in the manufacturing process of the steel by introducing nitrogen into the molten steel, for example by blowing nitrogen gas N 2 . A method of embossing steel melts in steelmaking in the oxygen inflation method is, for example, in US Pat DE 2 237 498 described. Flat steel products, in particular steel strips, can be embroidered by a surface conditioning, for example by diffusion of nitrogen into the steel sheet surface, which can be done for example by gas nitriding in an ammonia atmosphere with slight overpressure, by bath nitriding in nitrogen-containing salt baths or by plasma nitriding. By diffusion of nitrogen forms on the steel sheet surface while a hard, superficial bonding layer and an underlying diffusion zone in which the nitrogen is embedded to a certain depth in the (ferritic) steel matrix.

Die Aufgabe der Erfindung besteht darin, ein Stahlflachprodukt (Stahlblech oder Stahlband) für die Herstellung von Verpackungen aufzuzeigen, welches eine möglichst hohe Festigkeit bei gleichzeitig guter Bruchdehnung und guten Umformeigenschaften aufweist. Insbesondere soll ein Verpackungsstahl mit Festigkeiten von wenigstens 600 MPa bei einer Bruchdehnung von wenigstens 5 % zur Verfügung gestellt werden. Der höherfeste Verpackungsstahl muss dabei für den vorgesehenen Verwendungszweck als Verpackungsstahl gleichzeitig eine ausreichende Umformfähigkeit aufweisen, beispielsweise in Tiefzieh- oder Abstreckziehverfahren, damit aus dem Stahlflachprodukt bestimmungsgemäß Verpackungen, wie z.B. Konserven- oder Getränkedosen, hergestellt werden können. Der als Stahlflachprodukt vorliegende Verpackungsstahl soll dabei die üblichen Dicken im Fein- und Feinstblechbereich aufweisen, welche regelmäßig durch Kaltwalzen erzeugt werden.The object of the invention is to show a flat steel product (sheet steel or steel strip) for the production of packaging, which has the highest possible strength combined with good elongation at break and good forming properties. In particular, a packaging steel with strengths of at least 600 MPa with an elongation at break of at least 5% should be made available. The higher-strength packaging steel must at the same time have sufficient formability for the intended use as packaging steel, for example in deep-drawing or ironing process, so that from the flat steel product intended packaging, such. Canned or beverage cans can be produced. The present as flat steel product packaging steel should have the usual thicknesses in the fine and Feinstblechbereich, which are regularly produced by cold rolling.

Diese Aufgaben werden mit einem Verfahren mit den Merkmalen des Anspruchs 1 gelöst. Bevorzugte Ausführungsformen des erfindungsgemäßen Verfahrens sind in den abhängigen Ansprüchen aufgezeigt.These objects are achieved by a method having the features of claim 1. Preferred embodiments of the method according to the invention are shown in the dependent claims.

Mit dem erfindungsgemäßen Verfahren kann ein aufgestickter Verpackungsstahl mit einem Kohlenstoffgehalt von 10 bis 1000 ppm und einer Menge von ungebundenem, im Stahl gelösten Stickstoff von mehr als 100 ppm und bevorzugt von mehr als 150 ppm hergestellt werden, wobei das Aufsticken des Stahls in zwei Stufen erfolgt. In einer ersten Stufe wird eine Stahlschmelze auf einen Stickstoffgehalt von maximal 160 ppm nitriert, indem der Stahlschmelze Stickstoff, beispielsweise in Form eines stickstoffhaltigen Gas und/oder eines stickstoffhaltigen Feststoffs, zugeführt wird. Aus der so aufgestickten Stahlschmelze wird eine Bramme gegossen und zu einem Warmband warmgewalzt. Das Warmband wird anschließend (nach Abkühlung auf Umgebungstemperatur) erforderlichenfalls gebeizt und zu einem Stahlflachprodukt (Stahlblech oder Stahlband) kaltgewalzt. Das kaltgewalzte Stahlflachprodukt wird danach in einem Glühofen rekristallisierend geglüht. In dem Glühofen wird dabei die zweite Stufe des Aufstickens durchgeführt, indem in den Glühofen ein stickstoffhaltiges Gas eingeleitet und auf das Stahlflachprodukt gerichtet wird, um die Menge an ungebundenem Stickstoff im Stahl über die bereits in der ersten Stufe des Aufstickens in die Stahlschmelze eingebrachte Stickstoffmenge hinaus weiter zu erhöhen.The process of the present invention can produce an embroidered packaging steel having a carbon content of 10 to 1000 ppm and an amount of unbound steel dissolved nitrogen of greater than 100 ppm and preferably greater than 150 ppm, with the steel being upset in two stages , In a first stage, a molten steel is nitrided to a maximum nitrogen content of 160 ppm by feeding nitrogen to the molten steel, for example in the form of a nitrogen-containing gas and / or a nitrogen-containing solid. From the thus embroidered molten steel, a slab is poured and hot rolled into a hot strip. The hot strip is subsequently pickled (after cooling to ambient temperature), if necessary, and cold rolled to a flat steel product (steel sheet or steel strip). The cold-rolled steel flat product is then recrystallized in an annealing furnace. In the annealing furnace, the second step of the nitrogenizing step is carried out by introducing a nitrogen-containing gas into the annealing furnace and directing it to the flat steel product to increase the amount of unbound nitrogen in the steel beyond the amount of nitrogen introduced into the molten steel in the first stage of the nitrogenizing step continue to increase.

Durch das zweistufige Aufsticken des Verpackungsstahls wird gewährleistet, dass das Warmband mit den üblicherweise für die Herstellung von Verpackungsstählen verwendeten Kaltwalzvorrichtungen (Walzstraßen) problemlos zu einem Stahlflachprodukt, insbesondere zu einem Stahlband, kaltgewalzt werden kann. Dies wird dadurch ermöglicht, dass in der ersten Stufe des Aufstickens ein Gehalt an ungebundenem Stickstoff von höchstens 160 ppm in die Stahlschmelze eingebracht wird. Das aus der aufgestickten Stahlschmelze durch Warmwalzen erzeugte Warmband bleibt bei diesen Stickstoffgehalten kaltwalzbar, so dass aus dem Warmband durch Kaltwalzen ein Fein- oder Feinstblech in den für Verpackungszwecke üblichen Dicken herstellbar ist. Höhere Stickstoffgehalte in der Stahlschmelze führen darüber hinaus auch zu unerwünschten Defekten in der aus der Stahlschmelze gegossenen Bramme. Die gewünschte Festigkeit des Verpackungsstahls von bevorzugt mehr als 600 MPa wird beim Kaltwalzen und in der zweiten Stufe des Aufstickens des Stahlflachprodukts während seines rekristallisierenden Glühens erzielt. Dadurch können Stahlflachprodukte, insbesondere Stahlbänder, mit Dicken im Fein- und Feinstblechbereich zur Verwendung als Verpackungsstahl mit sehr hohen Zugfestigkeiten bei gleichzeitig hoher Bruchdehnung von bevorzugt wenigstens 5 % hergestellt werden, ohne eine Beschränkung in den Umformeigenschaften zu erleiden.The two-stage embroidering of the packaging steel ensures that the hot-rolled strip is used with those commonly used for the production of packaging steels Cold rolling devices (rolling mills) easily to a flat steel product, in particular to a steel strip, can be cold rolled. This is made possible by the fact that in the first stage of the Aufstickens a content of unbound nitrogen of at most 160 ppm is introduced into the molten steel. The hot strip produced from the embroidered molten steel by hot rolling remains cold-rolled at these nitrogen contents, so that a fine or very fine sheet can be produced in the standard thickness for packaging purposes from the hot strip by cold rolling. Higher nitrogen contents in the molten steel also lead to undesirable defects in the slab cast from the molten steel. The desired strength of the packaging steel, preferably greater than 600 MPa, is achieved during cold rolling and in the second stage of the nitrogen blanketing of the flat steel product during its recrystallizing annealing. As a result, flat steel products, in particular steel strips, with thicknesses in the fine and Feinstblechbereich for use as packaging steel with very high tensile strengths at the same time high elongation at break of preferably at least 5% can be produced without suffering a restriction in the forming properties.

In bevorzugten Ausführungsbeispielen des erfindungsgemäßen Verfahrens erfolgt das Aufsticken der Stahlschmelze in der ersten Stufe durch Einleiten von Stickstoffgas (N2) und/oder Kalkstickstoff (CaCN2) und/oder Manganstickstoff (MnN) in die Stahlschmelze.In preferred embodiments of the method according to the invention, the steel melt is embossed in the first stage by introducing nitrogen gas (N 2 ) and / or lime nitrogen (CaCN 2 ) and / or manganese nitrogen (MnN) into the molten steel.

Das Aufsticken des Stahlflachprodukts in der zweiten Stufe erfolgt bevorzugt durch Einleiten von Ammoniakgas (NH3) in den Glühofen, in dem das Stahlflachprodukt rekristallisierend geglüht wird. Zweckmäßig wird das Ammoniakgas dabei mittels Sprühdüsen auf die Oberfläche des Stahlflachprodukts aufgegast. Die Menge an Ammoniakgas, die in den Glühofen eingebracht wird, wird bevorzugt so eingestellt, dass sich in dem Glühofen ein Ammoniakgleichgewicht mit einer Ammoniakkonzentration im Bereich von 0,05 bis 1,5 % einstellt. Die Ammoniakkonzentration in dem Glühofen wird bevorzugt mittels eines Ammoniaksensors erfasst und der erfasste Messwert der Ammoniak-Gleichgewichtskonzentration wird für eine Regelung der pro Zeiteinheit in den Glühofen eingeleiteten Menge an Ammoniakgas verwendet. Dadurch kann eine gleichbleibende Ammoniakgas-Konzentration in dem Glühofen und damit eine homogene Aufstickung des Stahlflachprodukts mit über die Produktionszeit eines Stahlbands gleichbleibender Qualität und homogener Stickstoffkonzentration über die Länge des Stahlbands gewährleistet werden.The embroidering of the flat steel product in the second stage is preferably carried out by introducing ammonia gas (NH 3 ) into the annealing furnace, in which the steel flat product is annealed in a recrystallizing manner. Appropriately, the ammonia gas is thereby gassed by means of spray nozzles on the surface of the flat steel product. The amount of ammonia gas introduced into the annealing furnace is preferably adjusted so that an ammonia equilibrium with an ammonia concentration in the range of 0.05 to 1.5% is established in the annealing furnace. The ammonia concentration in the annealing furnace is preferably detected by means of an ammonia sensor, and the detected value of the ammonia equilibrium concentration is used for controlling the amount of ammonia gas introduced into the annealing furnace per unit time. As a result, it is possible to ensure a constant ammonia gas concentration in the annealing furnace and thus homogeneous nitriding of the flat steel product with consistent quality and homogeneous nitrogen concentration over the length of the steel strip over the production time of a steel strip.

Zur Vermeidung von Oxidationsprozessen wird beim rekristallisierenden Glühen in dem Glühofen in der zweiten Stufe des Aufstickens neben dem Ammoniakgas bevorzugt noch ein Inertgas in den Glühofen eingeleitet, beispielsweise Stickstoffgas und/oder Wasserstoffgas oder ein Gemisch davon, beispielsweise in einer Zusammensetzung von 95 Gew.-% Stickstoffgas und 5 Gew.-% Wasserstoffgas.In order to avoid oxidation processes, an inert gas is preferably introduced into the annealing furnace during the recrystallizing annealing in the annealing furnace in the second stage of the addition of nitrogen, for example nitrogen gas and / or hydrogen gas or a mixture thereof, for example in a composition of 95% by weight. Nitrogen gas and 5% by weight of hydrogen gas.

Die durch das zweistufige Aufsticken des Verpackungsstahls eingebrachten Gesamtmengen an ungebundenem Stickstoff liegen zwischen 100 und 500 ppm, bevorzugt oberhalb von 150 ppm und besonders bevorzugt im Bereich zwischen 200 und 350 ppm. Dabei wird in der ersten Stufe beim Aufsticken der Stahlschmelze ein Stickstoffgehalt von maximal 160 ppm in die Stahlschmelze eingebracht. Das Einhalten einer Obergrenze von ca. 160 ppm für den Gehalt an ungebundenem Stickstoff in der Stahlschmelze stellt sicher, dass an der aus der Stahlschmelze erzeugten Bramme keine Defekte entstehen, beispielsweise in Form von Poren und Risse, welche durch Umgebungssauerstoff oxidieren können. Weiterhin bleibt das aus der Bramme erzeugte Warmband bei einem Stickstoffgehalt von höchstens 160 ppm kaltwalzbar.The total amounts of unbound nitrogen introduced by the two-stage embroidering of the packaging steel are between 100 and 500 ppm, preferably above 150 ppm and more preferably in the range between 200 and 350 ppm. In the first stage, when embedding the molten steel, a maximum nitrogen content of 160 ppm is introduced into the molten steel. Maintaining an upper limit of about 160 ppm for the content of unbound nitrogen in the molten steel ensures that no defects occur on the slab produced from the molten steel, for example in the form of pores and cracks, which can oxidise by ambient oxygen. Furthermore, the hot strip produced from the slab remains cold-rolled at a nitrogen content of at most 160 ppm.

Die in der zweiten Stufe beim Aufsticken des Stahlflachprodukts zusätzlich einbringbare Menge an ungebundenem Stickstoff liegt bevorzugt im Bereich von 180 bis 350 ppm. Damit kann durch die beiden Stufen des Aufstickens eine Gesamtmenge an ungebundenem Stickstoff in den erfindungsgemäß hergestellten Verpackungsstahl von bis zu 500 ppm eingebracht werden. Dadurch lassen sich Zugfestigkeiten von mehr als 650 MPa und bis zu 1000 Mpa erzielen, wobei zwischen dem Gehalt an ungebundenem Stickstoff und der Zugfestigkeit ein linearer Zusammenhang fest gestellt worden ist und bspw. für Zugfestigkeiten von ca. 650 MPa ein Gehalt an ungebundenem Stickstoff von ca. 200 ppm erforderlich ist.The amount of unbound nitrogen which can additionally be introduced in the second stage when the steel flat product is being embroidered is preferably in the range from 180 to 350 ppm. Thus, a total amount of unbound nitrogen in the packaging steel according to the invention of up to 500 ppm can be introduced by the two stages of the embroidering. As a result, tensile strengths of more than 650 MPa and up to 1000 Mpa can be achieved, whereby a linear relationship has been established between the content of unbound nitrogen and the tensile strength and, for example for tensile strengths of about 650 MPa, a content of unbound nitrogen of approx 200 ppm is required.

Zum rekristallisierenden Glühen des kaltgewalzten Stahlflachprodukts wird dieses in dem Glühofen bevorzugt auf Temperaturen von mehr als 600°C und insbesondere von mehr als 620°C erhitzt. Durch das rekristallisierende Glühen wird die Umformfähigkeit des kaltgewalzten Stahlflachprodukts wieder hergestellt. Als bevorzugt hat sich dabei eine Erhitzung des Stahlflachprodukts auf eine Temperatur von 620°C bis 660 °C und besonders bevorzugt von ca. 640°C erwiesen.For recrystallizing annealing of the cold-rolled steel flat product, it is preferably heated in the annealing furnace to temperatures of more than 600 ° C. and in particular of more than 620 ° C. The recrystallizing annealing restores the formability of the cold-rolled steel flat product. In this case, heating of the flat steel product to a temperature of 620 ° C. to 660 ° C. and more preferably of approximately 640 ° C. has proven to be preferred.

Beim Aufsticken des Stahlflachprodukts in der zweiten Stufe, die in dem Glühofen durchgeführt wird, wird bevorzugt eine Mehrzahl von Sprühdüsen verwendet, mit denen ein stickstoffhaltiges Gas, wie z.B. Ammoniakgas, gleichförmig auf die Oberfläche des Stahlflachprodukts aufgebracht werden kann. Bei Herstellung eines Stahlbands, welches mit einer Bandgeschwindigkeit von wenigstens 200 m/min durch den Glühofen geleitet wird, werden die mehreren Sprühdüsen bspw. quer zur Bandlaufrichtung bevorzugt in äquidistantem Abstand zueinander angeordnet. Dadurch ist eine homogene Aufstickung des Stahlflachprodukts über die gesamte Oberfläche möglich.When piecing the steel flat product in the second stage, which is carried out in the annealing furnace, a plurality of spray nozzles is preferably used, with which a nitrogen-containing gas, such. Ammonia gas can be uniformly applied to the surface of the flat steel product. When producing a steel strip, which is passed through the annealing furnace at a belt speed of at least 200 m / min, the plurality of spray nozzles, for example transversely to the strip running direction, are preferably arranged equidistant from each other. As a result, a homogeneous nitriding of the flat steel product over the entire surface is possible.

Durch die Erfassung der Konzentration des in den Glühofen eingebrachten stickstoffhaltigen Gases kann sichergestellt werden, dass während des Durchlaufens des Stahlbands durch den Glühofen eine gleichbleibende Stickstoffatmosphäre im Glühofen aufrechterhalten wird. Dies ermöglicht ein homogenes Aufsticken des Stahlbands über dessen Länge.By detecting the concentration of nitrogen-containing gas introduced into the annealing furnace, it can be ensured that during the passage of the steel strip through the annealing furnace, a constant nitrogen atmosphere is maintained in the annealing furnace. This allows a homogeneous embroidering of the steel strip over its length.

Durch Vergleichsversuche konnte festgestellt werden, dass durch das Aufsticken des erfindungsgemäß hergestellten Verpackungsstahls nicht nur dessen Festigkeit erhöht werden kann, sondern dass zusätzlich durch den höheren Gehalt an ungebundenem Stickstoff in dem Stahl eine verbesserte Umformbarkeit zu beobachten ist. Dies zeigt sich insbesondere bei erfindungsgemäß hergestellten Verpackungsstählen, welche mit einem Lack beschichtet werden. Bei herkömmlich lackbeschichteten Verpackungsstählen ist nach einer beim Lackieren zum Einbrennen erforderlichen Wärmebehandlung eine sprunghafte Reduzierung der Bruchdehnung des Stahlflachprodukts bei höheren Festigkeiten zu beobachten. Dieses Phänomen kann bei den erfindungsgemäß hergestellten aufgestickten Stahlflachprodukten nicht beobachtet werden. Hier wird auch bei sehr hohen Festigkeiten von mehr als 650 MPa nach einer Wärmebehandlung beim Lackieren (Lackalterung) keine Reduktion der Bruchdehnung beobachtet. Dies kann möglicherweise dadurch erklärt werden, dass der durch das zweistufige Aufsticken vorhandene hohe Gehalt an ungebundenem Stickstoff und die sehr homogene Verteilung des Stickstoffs in dem Stahl vorhandene Versetzungen zunächst blockiert und diese durch freie Stickstoffatome blockierten Versetzungen bei einer Verformung des Stahlflachprodukts plötzlich in großer Zahl gelöst werden, sobald eine angelegte Zugspannung über einen Grenzwert hinaus erhöht wird. Dadurch können die vielen, durch die Verformung von einer Stickstoffblockade freigesetzten Versetzungen im Stahl wandern, wodurch die Umformbarkeit verbessert wird.By comparison experiments it was found that not only its strength can be increased by the embroidering of the packaging steel according to the invention, but that in addition by the higher content of unbound nitrogen in the steel improved formability is observed. This manifests itself in particular in packaging steels produced according to the invention, which are coated with a lacquer. In conventionally lacquer-coated packaging steels, a sudden reduction in the elongation at break of the flat steel product at higher strengths is to be observed after a heat treatment required for painting for stoving. This phenomenon can not be observed in the embroidered flat steel products produced according to the invention. Here, even at very high strengths of more than 650 MPa after a heat treatment during painting (paint aging), no reduction of the elongation at break is observed. This may possibly be explained by the fact that the high content of unbound nitrogen present by the two-stage Aufsticken and the very homogeneous distribution of nitrogen in the steel existing dislocations initially blocked and solved by free nitrogen atoms dislocations suddenly dissolved in a large number of deformation of the steel flat product as soon as an applied tensile stress is increased beyond a limit. This allows the many dislocations released by the deformation from nitrogen blockade to migrate in the steel, thereby improving the formability.

Diese und weitere Vorteile des erfindungsgemäß hergestellten Verpackungsstahls ergeben sich aus dem nachfolgend unter Bezugnahme auf die begleitenden Zeichnungen näher beschriebenen Ausführungsbeispiel. Die Zeichnungen zeigen:

Figur 1:
schematische Darstellung eines Glühofens, in dem die zweite Stufe des erfindungsgemäßen Verfahrens durchgeführt wird;
These and other advantages of the packaging steel produced according to the invention will become apparent from the embodiment described in more detail below with reference to the accompanying drawings. The drawings show:
FIG. 1:
schematic representation of an annealing furnace, in which the second stage of the method according to the invention is carried out;

In einem Ausführungsbeispiel des erfindungsgemäßen Verfahrens wird zunächst in einem Konverter und/oder in einer folgenden Pfannenbehandlung eine aufgestickte Stahlschmelze erzeugt, welche einen Gehalt an freiem, ungebundenem (d.h. im Stahl gelösten) Stickstoff von bis zu 160 ppm aufweist. Die Legierungszusammensetzung des Stahls erfüllt dabei zweckmäßig die durch Normen für Verpackungsstahl vorgegebenen Grenzwerte (wie z.B. in der Norm ASTM A623-11 "Standard Specification for Tin Mill Products" oder im "European Standard EN 10202" definiert), mit Ausnahme des oberen Grenzwerts für den Stickstoffgehalt (der in der Norm EN10202 bei Nmax=80 ppm und in dem AST-Standard ASTM 623 bei_Nmax=200 ppm liegt), der aufgrund der Aufstickung in dem erfindungsgemäßen Verfahren überschritten werden kann. Der Kohlenstoffanteil des erzeugten Stahls liegt dabei bevorzugt im Bereich von 10 bis 1000 ppm und besonders bevorzugt zwischen 100 und 900 ppm und in der Regel zwischen 400 und 900 ppm.In one embodiment of the method according to the invention, an embroidered molten steel is initially produced in a converter and / or in a subsequent ladle treatment, which has a content of free, unbound (ie dissolved in steel) nitrogen of up to 160 ppm. The alloy composition of the steel suitably meets the limits prescribed by standards for packaging steel (as defined, for example, in the ASTM A623-11 Standard Specification for Tin Mill Products or the European Standard EN 10202), with the exception of the upper limit value for the steel Nitrogen content (which is in the standard EN10202 at N max = 80 ppm and in the AST standard ASTM 623 bei_N max = 200 ppm), which can be exceeded due to the nitrification in the process according to the invention. The carbon content of the steel produced is preferably in the range from 10 to 1000 ppm and more preferably between 100 and 900 ppm and usually between 400 and 900 ppm.

Zur Erzeugung der Stahlschmelze wird der Konverter mit Schrott und Roheisen gefüllt und die Schmelze wird mit Sauerstoffgas und Stickstoffgas geblasen, wobei das Sauerstoffgas (O2) von oben und Stickstoffgas (N2) mittels Bodendüsen von unten in den Konverter eingeblasen wird. Dadurch stellt sich ein Stickstoffgehalt in der Stahlschmelze von 70 bis 120 ppm ein, wobei es zu einer Sättigung kommt. Während der Herstellung der Stahlschmelze wird die Zusammensetzung und insb. der Stickstoffgehalt der Schmelze erfasst. Falls die vorgegebene Analyse nicht getroffen wurde (z.B. wenn der Anteil an Phosphor zu hoch ist) wird durch eine Sauerstofflanze Sauerstoffgas und durch die Bodendüsen Argongas (Ar) nachgeblasen. Da im Stahl kaum mehr Kohlenstoff (C) vorhanden ist, entsteht kein Überdruck und der Stickstoff der Luft wird mit eingezogen, wodurch es zu einer zusätzlichen Aufstickung kommen kann.To produce the molten steel, the converter is filled with scrap and pig iron and the melt is blown with oxygen gas and nitrogen gas, whereby the oxygen gas (O2) from above and nitrogen gas (N2) is injected from below into the converter by means of bottom nozzles. As a result, a nitrogen content in the molten steel of 70 to 120 ppm sets, whereby it comes to a saturation. During the production of the molten steel, the composition and esp. The nitrogen content of the melt is detected. If the given analysis has not been made (for example, if the level of phosphorus is too high) oxygen gas is bubbled through an oxygen lance and argon gas (Ar) through the bottom nozzles. Since hardly any more carbon (C) is present in the steel, no overpressure arises and the nitrogen of the air is pulled in with, whereby it can come to an additional nitriding.

Falls die gewünschte Menge an (gelöstem) Stickstoff in der Stahlschmelze (welche regelmäßig bei ca. 120 ppm liegt) durch das Einblasen des Stickstoffgas noch nicht erreicht ist, kann beim Entleeren des Konverters (Abstich), zusätzlich noch Kalk-Stickstoff (Calcium Cyanamid, CaCN2) in den aus dem Konverter austretenden Stahlstrahl gegeben werden. Der Kalk-Stickstoff wird dabei bspw. in Form eines Granulats (5-20 mm) zugegeben.If the desired amount of (dissolved) nitrogen in the molten steel (which is regularly at about 120 ppm) by blowing the nitrogen gas is not yet reached is, when emptying the converter (tapping), additionally lime-nitrogen (calcium cyanamide, CaCN2) are added to the emerging from the converter steel jet. The lime nitrogen is added, for example, in the form of granules (5-20 mm).

Anschließend kommt die Pfanne zur ersten Argonspüle, wo mit einer feuerfesten, eingetauchten Lanze mit Argon für ca. 3 Minuten gespült wird. Nach einer Kontrollanalyse wird ggf. ein zweites Mal in einer zweiten Argonspüle für ca. 3 Minuten gespült. Die Pfanne kommt dann zu einer dritten Argon-Spüle. Dies stellt die letzte Stufe vor dem Gießen dar. Falls der Stickstoffgehalt nicht im vorgegebenen Zielbereich liegt, kann in der dritten Argon-Spüle Mangannitrid (MnN), bspw. in Form eines Drahts von MnN-Pulver in einer Stahlhülle), hinzugefügt werden. Die Menge an ggf. fehlendem Stickstoff wird dabei in eine erforderliche Menge an MnN umgerechnet (bspw. in ein erforderliche Länge des MnN-Draht), die in die Schmelze gegeben wird. Das MnN wird solange zugegebenen, bis der vorgegebene Stickstoff-Zielgehalt oder eine Mn-Obergrenze des Stahls erreicht wird.Then the pan comes to the first Argonspüle, where with a refractory immersed lance with argon for about 3 minutes is rinsed. After a control analysis, if necessary, rinse a second time in a second argon rinse for about 3 minutes. The pan then comes to a third argon sink. This represents the last stage before casting. If the nitrogen content is not within the specified target range, manganese nitride (MnN), for example in the form of a wire of MnN powder in a steel sheath, may be added to the third argon sink. The amount of possibly missing nitrogen is converted into a required amount of MnN (for example, into a required length of the MnN wire), which is added to the melt. The MnN is added until the predetermined target nitrogen content or Mn upper limit of the steel is reached.

Schließlich wird die Schmelze in eine Verteilerrinne gegeben, um aus der Stahlschmelze eine Bramme zu gießen. Bedingt durch Undichtigkeiten und Eindiffusion von Luftstickstoff kann der Stickstoffgehalt dabei um ca. 10 ppm ansteigen. Eine Obergrenze der Menge an gelöstem Stickstoff in der gegossenen Stahlbramme von ca. 160 ppm sollte nicht überschritten werden, weil sich bei höheren Stickstoffgehalten Defekte an der Bramme wie Risse oder Poren bilden können, welche zu einer unerwünschten Oxidation führen.Finally, the melt is placed in a distributor trough to pour a slab from the molten steel. Due to leaks and diffusion of atmospheric nitrogen, the nitrogen content may rise by about 10 ppm. An upper limit of the amount of dissolved nitrogen in the cast steel slab of about 160 ppm should not be exceeded, because at higher nitrogen contents, defects can form on the slab such as cracks or pores, which lead to undesired oxidation.

Die aus der Stahlschmelze gegossene Bramme wird danach warmgewalzt und auf Raumtemperatur abgekühlt. Das erzeugte Warmband weist dabei Dicken im Bereich von 1 bis 4 mm auf und wird ggf. zu einer Rolle (Coil) aufgewickelt. Zur Herstellung eines Verpackungsstahls in Form eines Stahlflachprodukts in den üblichen Fein- und Feinstblechdicken muss das Warmband kaltgewalzt werden, wobei eine Dickenreduktion im Bereich von 50 bis über 90 % erfolgt. Unter Feinblech wird dabei ein Blech mit einer Dicke von weniger als 3 mm verstanden und ein Feinstblech weist eine Dicke von weniger als 0,5 mm auf. Für die Durchführung des Kaltwalzens wird das ggf. als Rolle aufgewickelte Warmband von der Rolle abgewickelt, gebeizt und in eine Kaltwalzvorrichtung, bspw. eine Kaltwalzstraße, eingeführt.The slab cast from the molten steel is then hot rolled and cooled to room temperature. The hot strip produced has thicknesses in the range of 1 to 4 mm and is possibly wound up into a roll (coil). To produce a packaging steel in the form of a flat steel product in the usual fine and fine plate thicknesses, the hot strip must be cold rolled, with a reduction in thickness ranging from 50 to more than 90%. Thin sheet is understood to mean a sheet with a thickness of less than 3 mm and a fine sheet has a thickness of less than 0.5 mm. For carrying out the cold rolling, the hot strip, which may have been wound up as a roll, is unwound from the roll, pickled and introduced into a cold rolling device, for example a cold rolling mill.

Zur Wiederherstellung des beim Kaltwalzen zerstörten Kristallgefüges des Stahls muss das kaltgewalzte Stahlband rekristallisierend geglüht werden. Dies erfolgt durch Durchleiten des kaltgewalzten Stahlbands durch einen Durchlaufglühofen, in dem das Stahlband auf Temperaturen oberhalb des Rekristallisationspunkts des Stahls und insbesondere auf Temperaturen oberhalb von 600 °C erhitzt wird. In dem erfindungsgemäßen Verfahren erfolgt gleichzeitig mit dem Rekristallisationsglühen ein weiteres Aufsticken des Stahlbands in einer zweiten Stufe. Diese wird in dem Glühofen durchgeführt, indem in den Glühofen ein stickstoffhaltiges Gas, bevorzugt Ammoniak (NH3) eingebracht wird.In order to restore the crystal structure of the steel, which has been destroyed during cold rolling, the cold-rolled steel strip must be recrystallized. This is done by passing the cold-rolled steel strip through a continuous annealing furnace in which the steel strip is heated to temperatures above the recrystallization point of the steel and in particular to temperatures above 600 ° C. In the process according to the invention, a further embroidering of the steel strip in a second stage takes place simultaneously with the recrystallization annealing. This is carried out in the annealing furnace by introducing into the annealing furnace a nitrogen-containing gas, preferably ammonia (NH 3 ).

In Figur 1 ist schematisch ein Durchlaufglühofen zur Durchführung der Rekristallisation und der zweiten Stufe des Aufstickens gezeigt. Darin sind verschiedene Zonen ausgebildet, die sich in Durchlaufrichtung (Bandlaufrichtung V, in Figur 1 von rechts nach links) des durch den Durchlaufglühofen geführten Stahlbands hintereinander angeordnet sind. In einer eingangsseitig des Durchlaufglühofens angeordneten Heizzone 1 wird das Stahlband S auf Temperaturen im Bereich von 600°C bis 750°C erhitzt. Als für die zweite Stufe des Aufstickens besonders günstig hat sich dabei ein Temperaturbereich von 620°C bis 700°C und als besonders bevorzugt von 620°C bis 660°C erwiesen. Die besten Ergebnisse wurden bei Temperaturen von ca. 640°C erzielt. Diese Temperaturen liegen oberhalb der Rekristallisationstemperatur des Stahls, weshalb in der Heizzone 1 das Stahlband S rekristallisierend geglüht wird.In FIG. 1 schematically a continuous annealing furnace for carrying out the recrystallization and the second stage of the Aufstickens is shown. Therein, different zones are formed, which are in the direction of passage (tape running direction V, in FIG. 1 from right to left) of the guided through the continuous annealing furnace steel strip are arranged one behind the other. In a heating zone 1 arranged on the input side of the continuous annealing furnace, the steel strip S is heated to temperatures in the range from 600 ° C. to 750 ° C. As for the second stage of the embossing particularly favorable, a temperature range of 620 ° C to 700 ° C and has proven to be particularly preferred from 620 ° C to 660 ° C. The best results were achieved at temperatures of about 640 ° C. These temperatures are above the recrystallization temperature of the steel, which is why in the heating zone 1, the steel strip S is annealed recrystallizing.

An die Heizzone 1 schließt sich eine Haltezone 2 an, in der die Temperatur des Stahlbands S im o.g. Temperaturbereich gehalten wird. In der Haltezone 2 sind mehrere Kaskaden 3a, 3b, 3c von Sprühdüsen in Bandlaufrichtung hintereinander angeordnet. Jede Kaskade 3a, 3b, 3c umfasst dabei eine Mehrzahl von Düsen 3, die quer zur Bandlaufrichtung im Abstand zueinander angeordnet sind. Die Düsen 3 sind mit einer Gaszufuhrleitung gekoppelt, über welche sie mit einem stickstoffhaltigen Gas beaufschlagt werden. Als für die zweite Stufe des Aufstickens besonders geeignetes Gas hat sich Ammoniakgas erwiesen. Dieses wird über die Düsen 3 der Kaskaden auf die Oberflächen des durchlaufenden Stahlbands S aufgegast, wo es in den oberflächennahen Bereich des Stahlbands eindringt und dort gleichmäßig in die Tiefe des Stahlbands diffundiert. Es bildet sich über die Dicke des Stahlbands eine gleichmäßig homogene Stickstoffverteilung aus, deren Konzentrationsverteilung über die Blechdicke bei Stahlblechen mit einer Dicke von weniger als 0,4 mm um höchstens ± 10 ppm und regelmäßig um lediglich ± 5 ppm um den Mittelwert schwankt.The heating zone 1 is followed by a holding zone 2, in which the temperature of the steel strip S is maintained in the above-mentioned temperature range. In the holding zone 2 a plurality of cascades 3a, 3b, 3c of spray nozzles in the strip running direction are arranged one behind the other. Each cascade 3a, 3b, 3c comprises a plurality of nozzles 3, which are arranged transversely to the strip running direction at a distance from each other. The nozzles 3 are coupled to a gas supply line via which they are charged with a nitrogen-containing gas. As the gas particularly suitable for the second stage of the gasification, ammonia gas has been found. This is filled via the nozzles 3 of the cascade on the surfaces of the continuous steel strip S, where it penetrates into the near-surface region of the steel strip and diffused evenly into the depth of the steel strip. A uniformly homogeneous nitrogen distribution is formed over the thickness of the steel strip whose concentration distribution over the sheet thickness for steel sheets with a thickness of less than 0.4 mm fluctuates by at most ± 10 ppm and regularly by only ± 5 ppm around the mean value.

Die Ausbildung von bevorzugt verwendeten Düsen 3 der Kaskaden ist in der deutschen Patentanmeldung DE 102014106135 vom 30.4. 2014 beschrieben, deren Offenbarungsgehalt diesbezüglich hiermit einbezogen wird. In dieser Patentanmeldung ist eine Düseneinrichtung zur Behandlung eines Stahlflachprodukts beschrieben, wobei die Düseneinrichtung ein Außenrohr und ein darin angeordnetes Innenrohr mit einer Primäröffnung zum Einspeisen eines die Düseneinrichtung durchströmenden Gases in das Außenrohr umfasst und das Außenrohr mit einer Sekundäröffnung versehen ist, durch die das Gas austreten kann. Die Primäröffnung des Innenrohrs und die Sekundäröffnung des Außenrohrs sind dabei versetzt zueinander angeordnet. Dadurch wird ein sehr homogener Gasfluss auf die Oberfläche des Stahlflachprodukts ermöglicht. Bei der Verwendung einer solchen Düseneinrichtung in dem erfindungsgemäßen Verfahren kann eine homogene Begasung der Oberfläche des Stahlbands in der Haltezone 2 des Durchlaufglühofens mit dem stickstoffhaltigen Gas (Ammoniak) erzielt werden, wodurch über die Oberfläche des Stahlbands, insbesondere über dessen Breite hinweg, eine homogene Eindiffusion von Stickstoff und dadurch die Ausbildung einer homogenen, stickstoffangereicherten und gehärteten Oberflächenschicht erzielt werden kann.The formation of preferably used nozzles 3 of the cascades is in the German patent application DE 102014106135 from 30.4. 2014, the disclosure of which is hereby incorporated by reference. In this patent application, a nozzle device for treating a flat steel product is described, wherein the nozzle device comprises an outer tube and an inner tube disposed therein with a primary opening for feeding a gas flowing through the nozzle device in the outer tube and the outer tube is provided with a secondary opening through which the gas escape can. The primary opening of the inner tube and the secondary opening of the outer tube are offset from each other. This allows a very homogeneous flow of gas to the surface of the flat steel product. When using such a nozzle device in the method according to the invention, a homogeneous fumigation of the surface of the steel strip in the holding zone 2 of the continuous annealing furnace with the nitrogen-containing gas (ammonia) can be achieved, whereby over the surface of the steel strip, in particular across its width, a homogeneous diffusion of nitrogen and thereby the formation of a homogeneous, nitrogen-enriched and cured surface layer can be achieved.

Das Verfahren der Direktbeaufschlagung des Stahlbandes (Begasung) mit einem stickstoffhaltigen Gas mittels Düsen hat dabei zwei wesentliche Vorteile: Zum einen wird nur eine geringe Stickstoffkonzentration (NH3-Konzentration) im Schutzgas benötigt, was zu einem geringen Verbrauch an stickstoffhaltigem Gas (bspw. NH3-Verbrauch) führt. Zum anderen erfolgt durch eine sehr kurze Einwirkungszeit keine Bildung einer Nitridschicht. Im Anschluss an die Begasung mit einem stickstoffhaltigen Gas (bspw. NH3-Behandlung) wird das Stahlband noch weiter (zweckmäßig mehr als 5 Sekunden) bei unveränderten Temperaturen geglüht, bevor es abgekühlt wird. Dadurch kommt es zu einer Homogenisierung der Stickstoffverteilung über den Querschnitt des Stahlbands und folglich zu verbesserten Umformeigenschaften. Insbesondere kann dadurch ein Dehnungsabfall durch Lackalterung vermieden werden (s. Seite 6, Zeilen 14 - 20).The method of direct loading of the steel strip (gassing) with a nitrogen-containing gas by means of nozzles has two major advantages: Firstly, only a low concentration of nitrogen (NH 3 concentration) in the protective gas is required, resulting in a low consumption of nitrogen-containing gas (eg NH 3 consumption). On the other hand, there is no formation of a nitride layer due to a very short reaction time. Following gassing with a nitrogen-containing gas (eg NH 3 treatment), the steel strip is annealed even further (expediently more than 5 seconds) at unchanged temperatures, before it is cooled. This results in a homogenization of the nitrogen distribution over the cross section of the steel strip and consequently to improved forming properties. In particular, this can be used to avoid expansion loss due to paint aging (see page 6, lines 14 - 20).

Um auch über die Länge des Stahlbands S eine möglichst homogene Ausbildung einer stickstoffangereicherten Oberflächenschicht zu gewährleisten, ist während der Durchführung des Stahlbands S durch die Haltezone 2 des Durchlaufglühofens eine stickstoffhaltige Atmosphäre mit einer möglichst gleichbleibenden Stickstoff-Gleichgewichtskonzentration einzuhalten. Um dies sicher zu stellen, wird im Bereich der Kaskaden 3a, 3b, 3c mit den Düsen 3 die ausgebildete Stickstoffkonzentration erfasst. Bei Verwendung von Ammoniak als stickstoffhaltiges Gas wird hierzu die in der Haltezone 2 durch das Begasen mit Ammoniak ausgebildete Ammoniakkonzentration gemessen. Hierfür ist ein außerhalb des Durchlaufglühofens angeordneter Konzentrationssensor vorgesehen, bei dem es sich bspw. um einen Laserspektroskopie-Sensor handeln kann. Diesem wird eine aus der Haltezone 2 entnommene Gasprobe zugeführt, um die Ammoniakkonzentration und daraus die Stickstoffkonzentration der Gasatmosphäre in der Haltezone 2 zu erfassen. Die Gasprobe wird bspw. an der in Figur 1 mit Bezugszeichen 4 gekennzeichneten Stelle entnommen. Die vom Konzentrationssensor erfasste Konzentration des Stickstoffs in der Gasatmosphäre der Haltezone 2 wird einer Steuereinrichtung zugeführt und von dieser verwendet, um die Menge des über die Düsen 3 in die Haltezone 2 eingesprühten stickstoffhaltigen Gases (Ammoniak) konstant auf einem vorgegebenen Zielwert zu halten.In order to ensure as homogeneous a formation of a nitrogen-enriched surface layer as possible over the length of the steel strip S, a nitrogen-containing atmosphere with a nitrogen equilibrium concentration which is as constant as possible must be maintained during the passage of the steel strip S through the holding zone 2 of the continuous annealing furnace. To ensure this, is in the range of cascades 3a, 3b, 3c with the Nozzles 3 detects the nitrogen concentration formed. When ammonia is used as the nitrogen-containing gas, the ammonia concentration formed in the holding zone 2 by gassing with ammonia is measured for this purpose. For this purpose, a concentration sensor arranged outside the continuous annealing furnace is provided, which may, for example, be a laser spectroscopy sensor. This is fed to a gas sample taken from the holding zone 2 in order to detect the ammonia concentration and from this the nitrogen concentration of the gas atmosphere in the holding zone 2. The gas sample is, for example, at the in FIG. 1 taken from the point indicated by reference numeral 4. The concentration of the nitrogen in the gas atmosphere of the holding zone 2 detected by the concentration sensor is supplied to and used by a controller to keep the amount of nitrogen-containing gas (ammonia) sprayed into the holding zone 2 via the nozzles 3 constant at a predetermined target value.

Als besonders zweckmäßig haben sich bei Verwendung von Ammoniak als stickstoffhaltigem Gas Zielwerte für die Gleichgewichtskonzentration des Ammoniak im Bereich von 0,05 bis 1,5 % und bevorzugt von unter 1 %, insbesondere unter 0,2 % erwiesen. Bevorzugt liegt die Gleichgewichtskonzentration des Ammoniak im Bereich von 0,1 bis 1,0 % und besonders bevorzugt zwischen 0,1 und 0,2 %.Target values for the equilibrium concentration of the ammonia in the range of 0.05 to 1.5%, and preferably of less than 1%, in particular less than 0.2%, have proven particularly expedient when ammonia is used as the nitrogen-containing gas. Preferably, the equilibrium concentration of the ammonia is in the range of 0.1 to 1.0%, and more preferably between 0.1 and 0.2%.

Zur Vermeidung von Oxidationsprozessen an der Oberfläche des Stahlbands S wird zweckmäßig in der Haltezone 2 neben dem stickstoffhaltigen Gas (Ammoniak) noch ein Inertgas in den Glühofen eingebracht. Dabei kann es sich bspw. um Stickstoffgas oder/oder Wasserstoffgas handeln. Bevorzugt wird ein Gemisch von ca. Vol. 95% Stickstoff- und ca. Vol. 5% Wasserstoffgas verwendet.To avoid oxidation processes on the surface of the steel strip S, an inert gas is expediently introduced into the annealing furnace in the holding zone 2 in addition to the nitrogen-containing gas (ammonia). This may, for example, be nitrogen gas and / or hydrogen gas. Preferably, a mixture of about Vol. 95% nitrogen and about Vol. 5% hydrogen gas is used.

An die Haltezone 2 schließen sich in Bandlaufrichtung V mehrere Kühlzonen 5, 6 an, wobei in einer ersten Kühlzone 5 zunächst eine schnellere Abkühlung des Stahlbands S und in einer nachfolgenden zweiten Kühlzone 6 eine langsamere Abkühlung erfolgt.A plurality of cooling zones 5, 6 adjoin the holding zone 2 in the strip running direction V, with a faster cooling of the steel strip S in a first cooling zone 5 and a slower cooling in a subsequent second cooling zone 6.

Nach dem Abkühlen in den Kühlzonen 5 und 6 verlässt das Stahlband S den Durchlaufglühofen und wird trocken nachgewalzt (dressiert), um dem Band die für die Herstellung von Verpackungen erforderlichen Umformeigenschaften zu verleihen. Der Nachwalzgrad variiert je nach Verwendungszweck des Verpackungsstahls zwischen 0,4 und 2 %. Erforderlichenfalls kann das Stahlband auch nass nachgewalzt werden, um eine weitere Dickenreduktion um bis zu 43% zu erzeugen (doppelt reduziertes Stahlband, "double reduced DR"). Anschließend wird das Stahlband S ggf. einer Beschichtungsanlage zugeführt, in der die Oberfläche des Stahlbands zur Erhöhung der Korrosionsbeständigkeit bspw. elektrolytisch mit einer Zinn- oder einer Chrom/Chromdioxidbeschichtung (ECCS) oder einer Lackierung versehen wird. Es hat sich gezeigt, dass mit dem erfindungsgemäßen Verfahren hergestellte Verpackungsstähle auch in Bezug auf ihre Korrosionsbeständigkeit bessere Eigenschaften aufweisen als die bekannten Stahlflachprodukte.After cooling in the cooling zones 5 and 6, the steel strip S leaves the continuous annealing furnace and is dry-rolled (dressed) in order to give the strip the forming properties required for the production of packaging. The degree of rolling varies between 0.4 and 2%, depending on the intended use of the packaging steel. If necessary, the steel strip can also be wet rolled to another Thickness reduction by up to 43% (double reduced steel strip, "double reduced DR"). Subsequently, if necessary, the steel strip S is fed to a coating installation in which the surface of the steel strip, for example, is electrolytically provided with a tin or a chromium / chromium dioxide coating (ECCS) or a coating in order to increase the corrosion resistance. It has been found that packaging steels produced by the process according to the invention also have better properties in terms of their corrosion resistance than the known flat steel products.

Mit dem erfindungsgemäßen Verfahren lassen sich aufgestickte Stahlbänder herstellen, die sich durch eine sehr hohe Festigkeit von mehr als 600 MPa bei gleichzeitig guter Bruchdehnung von mehr als 5% und guten Umformeigenschaften auszeichnen. Die durch das zweistufige Aufsticken erhöhte Festigkeit und die Bruchdehnung sind dabei sehr homogen über den Querschnitt des Stahlbands und zwar sowohl in als auch quer zur Walzrichtung des kaltgewalzten Stahlbands. Dies resultiert aus dem sehr homogenen Einbringen von ungebundenem Stickstoff in den Stahl, insbesondere in der zweiten Stufe des Aufstickens. Schmelzanalysen an erfindungsgemäß hergestellten Stahlflachprodukten haben ferner gezeigt, dass die durch das Aufsticken eingebrachte Stickstoffkonzentration über die Dicke des Stahlflachprodukts jedenfalls bei Feinstblechen nur in einem schmalen Band von höchstens ± 10 ppm und regelmäßig nur um ± 5 ppm um die mittlere Konzentration schwankt.With the method according to the invention, embroidered steel strips can be produced, which are characterized by a very high strength of more than 600 MPa with simultaneously good elongation at break of more than 5% and good forming properties. The increased through the two-stage Aufsticken strength and elongation at break are very homogeneous over the cross section of the steel strip both in and across the rolling direction of the cold-rolled steel strip. This results from the very homogeneous introduction of unbound nitrogen into the steel, especially in the second stage of the stitching. Melt analyzes of flat steel products produced according to the invention have furthermore shown that the nitrogen concentration introduced by the pickling varies at least in a narrow band of at most ± 10 ppm and regularly only by ± 5 ppm over the average concentration over the thickness of the flat steel product.

Das rekristallisierende Glühen und die zweite Stufe des Aufstickens können statt in einem Durchlaufglühofen auch in einem Haubenglühofen durchgeführt werden. Hierfür wird das kaltgewalzte und als Rolle aufgewickelte Stahlband S in einen Haubenglühofen eingebracht und dort unter einer Schutzgasatmosphäre bei den für ein rekristallisierendes Glühen erforderlichen Glühtemperaturen von mehr als 520°C geglüht. Um auch im Haubenglühofen gleichzeitig mit dem rekristallisierenden Glühen die zweite Stufe des Aufstickens durchführen zu können, erfolgt das Haubenglühen im "open-coil"-Verfahren. Dabei werden zwischen den Lagen des zu einer Rolle aufgerollten Stahlbands Abstandshalter eingelegt, um die Oberfläche des Stahlbands für die Eindiffusion von Stickstoff zugänglich zu halten.The recrystallizing annealing and the second step of the embossing can be carried out in a continuous annealing furnace instead of in a continuous annealing furnace. For this purpose, the cold rolled and wound as a roll steel strip S is placed in a crucible annealing furnace and annealed there under a protective gas atmosphere at the required for a recrystallizing annealing annealing temperatures of more than 520 ° C. In order to be able to carry out the second stage of the embossing process also in the annealing furnace at the same time as the recrystallizing annealing, the annealing process takes place in the "open-coil" process. In this case, spacers are inserted between the layers of rolled into a roll steel strip to keep the surface of the steel strip for the diffusion of nitrogen accessible.

In den nachfolgenden Tabellen sind bevorzugte Ausführungsbeispiele von erfindungsgemäß hergestellten Stahlflachprodukten in verschiedenen Varianten (jew. mit "Variante" bezeichnet) und für verschiedene Anwendungsfälle für die Herstellung von Verpackungen bzw. Teilen davon (Aufreißdeckel für eine Dose bzw. tiefgezogene Drehverschlüsse) aufgeführt und mit herkömmlich erzeugten Stahlflachprodukten (ohne zweistufiges Aufsticken, jew. mit "Standard" bezeichnet) mit gleicher oder ähnlicher Stahlanalyse (Legierungsbestandteile) verglichen. Tabelle 1 Ausführungs beispiel eines Verpackungsstahls für Herst tellung von Vollaufreißdeckeln (Standardgüte mit C = 600 - 900 ppm, N = 80-140 ppm) Standard Einstufige Aufstickung der Stahlschmelze Variante 1 Zweistufige Aufstickung gem. der Erfindung Chemische Analyse C [ppm] 740 750 N [ppm] 122 187 Mn [ppm] 3100 3100 Al [ppm] 150 150 Si [ppm] 90 110 Cr [ppm] 290 270 Ni [ppm] 130 120 Cu [ppm] 130 70 P [ppm] 140 150 S [ppm] 50 40 Warmband Dicke [mm] 2,0 2,0 TEndwalz [°C] 861 854 THaspel [°C] 571 570 Kaltband TGlühe [°C] 670 640 Nachwalzgrad [%] 8 11 Enddicke [mm] 0,160 0,160 Kennwerte Streckgrenze (Reh) (200°C, 20 min) [MPa] 560 640 Zugfestigkeit (200°C, 20 min) [MPa] 540 644 Zipfelhöhe (ß=1,8, Napf=33mm) [mm] - - Bruchdehnung [%] 4,2 8,5 Tabelle 2 Ausführungsbeispiel eines Verpackungsstahls für Herstellung tiefgezogener Drehverschlüsse (Standardgüte mit C = 10- 40 ppm, N < 40 ppm) Standard 1 Standard 2 Variante 1 Zweistufige Aufstickung gem. der Erfindung Variante 2 Zweistufige Aufstickung gem. der Erfindung Variante 3 Zweistufige Aufstickung gem. der Erfindung Chemische Analyse C [ppm] 23 25 28 20 17 N [ppm] 15 30 110 170 180 Mn [ppm] 2100 2100 2200 2300 2300 Al [ppm] 20 20 20 180 10 Si [ppm] 220 200 190 100 230 Cr [ppm] 250 210 200 180 210 Ni [ppm] 130 110 110 150 120 Cu [ppm] 80 60 70 60 70 P [ppm] 100 90 80 90 70 S [ppm] 70 70 60 70 80 Warmband Dicke [mm] 2,5 2,5 2,5 2,5 2,5 TEndwalz [°C] 870 877 880 871 862 THaspel [°C] 631 621 620 601 618 Kaltband TGlühe [°C] 690 690 690 690 690 Nachwalzgrad [%] 40 40 40 40 32 Enddicke [mm] 0,140 0,154 0,140 0,140 0,140 Kennwerte Streckgrenze (Reh) (200°C, 20 min) [MPa] 633 598 680 685 690 Zugfestigkeit (200°C, 20 min) [MPa] 633 599 680 685 690 Zipfelhöhe (ß=1,8, Napf=33mm) [mm] 0,70 0,75 0,65 0,71 0,68 Bruchdehnung [%] 0,35 1,59 1,01 0,85 1,89 In the following tables preferred embodiments of flat steel products according to the invention are produced in different variants (in each case with "variant") and for different applications for the production of packaging or parts thereof (tear-open lid for a can or deep-drawn screw caps) and compared with conventionally produced flat steel products (without two-step embossing, each referred to as "standard") with the same or similar steel analysis (alloy constituents). <b> Table 1 </ b> Example of a packing steel for the production of full-open lids (standard grade with C = 600 - 900 ppm, N = 80-140 ppm) Standard single-stage nitriding of molten steel Variant 1 Two-stage nitrification acc. the invention Chemical Analysis C [Ppm] 740 750 N [Ppm] 122 187 Mn [Ppm] 3100 3100 al [Ppm] 150 150 Si [Ppm] 90 110 Cr [Ppm] 290 270 Ni [Ppm] 130 120 Cu [Ppm] 130 70 P [Ppm] 140 150 S [Ppm] 50 40 hot strip thickness [Mm] 2.0 2.0 T finish roll [° C] 861 854 T reel [° C] 571 570 cold strip T annealing [° C] 670 640 Nachwalzgrad [%] 8th 11 final thickness [Mm] 0,160 0,160 characteristics Yield point (R eh ) (200 ° C, 20 min) [MPa] 560 640 Tensile strength (200 ° C, 20 min) [MPa] 540 644 Tip height (ß = 1.8, cup = 33mm) [Mm] - - elongation [%] 4.2 8.5 Exemplary embodiment of a packaging steel for producing deep-drawn screw caps (standard quality with C = 10-40 ppm, N <40 ppm) Standard 1 Standard 2 Variant 1 Two-stage nitrification acc. the invention Variant 2 Two-stage nitrification acc. the invention Variant 3 Two-stage nitrification acc. the invention Chemical Analysis C [Ppm] 23 25 28 20 17 N [Ppm] 15 30 110 170 180 Mn [Ppm] 2100 2100 2200 2300 2300 al [Ppm] 20 20 20 180 10 Si [Ppm] 220 200 190 100 230 Cr [Ppm] 250 210 200 180 210 Ni [Ppm] 130 110 110 150 120 Cu [Ppm] 80 60 70 60 70 P [Ppm] 100 90 80 90 70 S [Ppm] 70 70 60 70 80 hot strip thickness [Mm] 2.5 2.5 2.5 2.5 2.5 T finish roll [° C] 870 877 880 871 862 T reel [° C] 631 621 620 601 618 cold strip T annealing [° C] 690 690 690 690 690 Nachwalzgrad [%] 40 40 40 40 32 final thickness [Mm] 0.140 0.154 0.140 0.140 0.140 characteristics Yield point (R eh ) (200 ° C, 20 min) [MPa] 633 598 680 685 690 Tensile strength (200 ° C, 20 min) [MPa] 633 599 680 685 690 Tip height (ß = 1.8, cup = 33mm) [Mm] 0.70 0.75 0.65 0.71 0.68 elongation [%] 0.35 1.59 1.01 0.85 1.89

Claims (15)

  1. Method for producing a nitrided packaging steel with a carbon content of 10 to 1,000 ppm relative to the weight and a content of uncombined nitrogen dissolved in the steel of more than 100 ppm relative to the weight, characterised by the following steps:
    a) nitriding a steel melt to a nitrogen content of maximum 160 ppm relative to the weight by introducing a nitrogen-containing gas and/or a nitrogen-containing solid into the steel melt;
    b) casting a slab from the steel melt and hot-rolling the slab to form a hot strip;
    c) cold-rolling the hot strip to form a flat steel product;
    d) recrystallizing annealing of the cold-rolled flat steel product in an annealing furnace, in particular a continuous annealing furnace, wherein a nitrogen-containing gas is introduced into the annealing furnace and directed onto the flat steel product in order to increase the quantity of uncombined nitrogen in the flat steel product above the nitrogen content already present in the steel melt.
  2. Method according to claim 1, characterised in that in step a), the nitriding of the steel melt is effected by introducing nitrogen gas (N2) and/or calcium cyanamide (CaCN2) and/or manganese nitride (MnN) into the steel melt.
  3. Method according to claim 1 or 2, characterised in that in step d), ammonia gas (NH3) is introduced into the annealing furnace.
  4. Method according to claim 3, characterised in that the ammonia gas (NH3) in the annealing furnace is directed onto the flat steel product by means of one or more spray nozzles.
  5. Method according to claim 3 or 4, characterised in that an ammonia equilibrium with a concentration in the range from 0.05 to 1.5 volume% is set in the annealing furnace by introducing ammonia gas (NH3).
  6. Method according to one of claims 3 to 5, characterised in that the equilibrium concentration of ammonia being set in the annealing furnace by introducing ammonia gas (NH3) is recorded using an ammonia sensor.
  7. Method according to claim 6, characterised in that the recorded measured value of equilibrium concentration of ammonia is used for regulating the quantity of ammonia gas introduced into the annealing furnace per unit of time.
  8. Method according to one of claims 3 to 7, characterised in that an inert gas, in particular nitrogen gas (N2) and/or hydrogen gas (H2) is also introduced into the annealing furnace in addition to ammonia gas (NH3), preferably a mixture of 95 volume% of nitrogen gas (N2) and 5 volume% of hydrogen gas (H2).
  9. Method according to one of the preceding claims, characterised in that the weight proportion of uncombined nitrogen, after nitriding the cold-rolled flat steel product in the annealing furnace, lies between 100 and 500 ppm, preferably between 200 and 350 ppm.
  10. Method according to one of the preceding claims, characterised in that the recrystallizing annealing of the cold-rolled flat steel product in step d) is effected by means of passing the flat steel product through a continuous annealing furnace, in which the flat steel product is heated at temperatures of more than 600°C and preferably at a temperature of 620°C to 660°C.
  11. Method according to one of the preceding claims, characterised in that the carbon content of the steel, relative to the weight, lies between 100 and 1,000 ppm and preferably between 500 and 900 ppm.
  12. Method according to one of the preceding claims, characterised in that the thickness of the flat steel product is less than 0.5 mm and the concentration distribution of the uncombined nitrogen varies over the thickness of the flat steel product by less than ± 10 ppm about the average value of the nitrogen content relative to the mass.
  13. Method according to claim 12, characterised in that the concentration distribution of the uncombined nitrogen varies over the thickness of the flat steel product by less than ± 5 ppm about the average value of the nitrogen content relative to the mass.
  14. Method according to claim 12, characterised in that the tensile strength of the packaging steel produced by the method is more than 600 MPa.
  15. Method according to claim 12, characterised in that the average value of the nitrogen content of uncombined nitrogen relative to the mass is more than 150 ppm.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102014116929B3 (en) 2014-11-19 2015-11-05 Thyssenkrupp Ag Method for producing an embroidered packaging steel, cold rolled flat steel product and apparatus for recrystallizing annealing and embroidering a flat steel product
DE102020106164A1 (en) * 2020-03-06 2021-09-09 Thyssenkrupp Rasselstein Gmbh Cold rolled flat steel product for packaging
DE102020112485B3 (en) 2020-05-08 2021-08-12 Thyssenkrupp Rasselstein Gmbh Steel sheet and method of manufacturing a steel sheet for packaging

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3219494A (en) 1962-06-28 1965-11-23 United States Steel Corp Method of making high-strength tin plate
JPS5827930A (en) 1981-08-13 1983-02-18 Kawasaki Steel Corp Production of black plate for tin plate and tin-free steel plate
EP0216399A1 (en) 1985-07-29 1987-04-01 Hoogovens Groep B.V. Hard steel sheet manufactured from aluminium-killed continuous-cast carbon-manganese steel, and a method for the manufacture of such sheet
JPH08260059A (en) 1995-03-17 1996-10-08 Nippon Steel Corp Continuous annealing furnace excellent in atmosphere control ability
EP0764725A1 (en) 1995-09-21 1997-03-26 Sollac S.A. Process for making a metallic strip for packages and metallic packages made by this process
JPH1121627A (en) 1997-06-30 1999-01-26 Nippon Steel Corp Nitrificating treatment of grain oriented electrical steel sheet having small deviation in longitudinal and width directions and apparatus therefor
EP1065286A1 (en) 1999-07-01 2001-01-03 Sollac S.A. Low aluminum steel sheet for cans
WO2005056841A1 (en) 2003-12-09 2005-06-23 Nippon Steel Corporation Steel sheet for containers, and manufacturing method therefor
EP2330223A1 (en) 2008-09-10 2011-06-08 Nippon Steel Corporation Directional electromagnetic steel plate manufacturing method
KR20130055916A (en) 2011-11-21 2013-05-29 주식회사 포스코 Apparatus for uniform nitriding with decarburizing and nitriding annealing of grain-oriented electrical steel sheet
WO2013183274A1 (en) * 2012-06-06 2013-12-12 Ｊｆｅスチール株式会社 Three-piece can and method for producing same

Family Cites Families (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1132168B (en) * 1960-07-18 1962-06-28 Mannesmann Ag Process for the production of nitrogen-containing unalloyed or low-alloy steels
US3139359A (en) 1961-06-12 1964-06-30 Jones & Laughlin Steel Corp Method of producing high strength thin steel
GB1013190A (en) 1961-08-12 1965-12-15 Yawata Iron & Steel Co Process for producing a low-temperature tough steel
AU2433671A (en) 1970-02-06 1972-07-20 Armco Steel Corporation Product and method for making drawing quality enameling stock
GB1358177A (en) 1970-07-08 1974-06-26 Brush Co Ltd Carpet sweepers
DE2237498B2 (en) 1972-07-31 1974-07-25 Stahlwerke Peine-Salzgitter Ag, 3150 Peine Method for embroidering molten steel
JPS6059981B2 (en) * 1981-07-08 1985-12-27 日新製鋼株式会社 High-strength stainless steel with excellent intergranular corrosion cracking properties and workability
DE69015817T2 (en) * 1990-10-17 1995-06-08 Daido Oxygen Process for nitriding steel.
FR2723964B1 (en) 1994-08-29 1997-03-14 Lorraine Laminage PROCESS FOR PREPARING STEEL FOR PACKAGING SUITABLE FOR DEEP STAMPING AND STEEL OBTAINED BY THIS PROCESS
JP3970323B2 (en) * 1996-06-05 2007-09-05 デュラセル、インコーポレーテッド Improved production of lithiated lithium manganese oxide spinel.
IT1284268B1 (en) * 1996-08-30 1998-05-14 Acciai Speciali Terni Spa PROCEDURE FOR THE PRODUCTION OF GRAIN ORIENTED MAGNETIC SHEETS, WITH HIGH MAGNETIC CHARACTERISTICS, STARTING FROM
IT1285153B1 (en) * 1996-09-05 1998-06-03 Acciai Speciali Terni Spa PROCEDURE FOR THE PRODUCTION OF GRAIN ORIENTED MAGNETIC SHEET, STARTING FROM THIN SHEET.
FR2761081B1 (en) * 1997-03-21 1999-04-30 Usinor METHOD FOR MANUFACTURING AN ELECTRIC STEEL SHEET WITH ORIENTED GRAINS FOR THE MANUFACTURE, IN PARTICULAR OF MAGNETIC CIRCUITS OF TRANSFORMERS
JPH11315343A (en) * 1998-03-06 1999-11-16 Kawasaki Steel Corp Slit steel strip for welded can, its manufacture, and cold rolled steel strip coil for slit steel strip
FR2795743B1 (en) * 1999-07-01 2001-08-03 Lorraine Laminage LOW ALUMINUM STEEL SHEET FOR PACKAGING
CN1318612C (en) * 2000-12-13 2007-05-30 杰富意钢铁株式会社 Process for producing high-nitrogen ultra low-carbon steel
DE10117118C1 (en) * 2001-04-06 2002-07-11 Thyssenkrupp Stahl Ag Production of fine sheet metal used in the production of cans comprises casting a steel to slabs or thin slabs, cooling, re-heating, hot rolling in several passes
JP4328124B2 (en) * 2003-04-24 2009-09-09 新日本製鐵株式会社 Steel sheet for ultra-thin containers with extremely good can characteristics and manufacturing method thereof
WO2005068667A1 (en) * 2004-01-19 2005-07-28 Nippon Steel Corporation Steel sheet for use in containers and manufacturing method therefor
CN101294268B (en) * 2007-04-24 2010-12-08 宝山钢铁股份有限公司 Nitrogen case hardening method of orientation silicon steel
CN101775548B (en) * 2009-12-31 2011-05-25 武汉钢铁(集团)公司 Method for producing low nitriding amount and high magnetic induction oriented silicon steel strip
DE102014106135A1 (en) 2014-04-30 2015-11-05 Thyssenkrupp Ag Nozzle device and method for treating a flat steel product

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3219494A (en) 1962-06-28 1965-11-23 United States Steel Corp Method of making high-strength tin plate
JPS5827930A (en) 1981-08-13 1983-02-18 Kawasaki Steel Corp Production of black plate for tin plate and tin-free steel plate
EP0216399A1 (en) 1985-07-29 1987-04-01 Hoogovens Groep B.V. Hard steel sheet manufactured from aluminium-killed continuous-cast carbon-manganese steel, and a method for the manufacture of such sheet
JPH08260059A (en) 1995-03-17 1996-10-08 Nippon Steel Corp Continuous annealing furnace excellent in atmosphere control ability
EP0764725A1 (en) 1995-09-21 1997-03-26 Sollac S.A. Process for making a metallic strip for packages and metallic packages made by this process
JPH1121627A (en) 1997-06-30 1999-01-26 Nippon Steel Corp Nitrificating treatment of grain oriented electrical steel sheet having small deviation in longitudinal and width directions and apparatus therefor
EP1065286A1 (en) 1999-07-01 2001-01-03 Sollac S.A. Low aluminum steel sheet for cans
WO2005056841A1 (en) 2003-12-09 2005-06-23 Nippon Steel Corporation Steel sheet for containers, and manufacturing method therefor
EP2330223A1 (en) 2008-09-10 2011-06-08 Nippon Steel Corporation Directional electromagnetic steel plate manufacturing method
KR20130055916A (en) 2011-11-21 2013-05-29 주식회사 포스코 Apparatus for uniform nitriding with decarburizing and nitriding annealing of grain-oriented electrical steel sheet
WO2013183274A1 (en) * 2012-06-06 2013-12-12 Ｊｆｅスチール株式会社 Three-piece can and method for producing same
EP2860124A1 (en) * 2012-06-06 2015-04-15 JFE Steel Corporation Three-piece can and method for producing same

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PAUL JOHNSON: "ASM Handbook. 10th ed.", 1991, article "Furnace atmospheres", pages: 542 - 567, XP055711737

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US20170253957A1 (en) 2017-09-07
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CN106661655A (en) 2017-05-10
JP6357274B2 (en) 2018-07-11
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CA2954713A1 (en) 2016-03-03
WO2016030056A1 (en) 2016-03-03
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CN106661655B (en) 2018-09-28
BR112017002172A2 (en) 2017-11-21

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