EP3692178A1 - Acier multiphase à haute résistance et procédé de fabrication d'une bande d'acier composée de cet acier multiphase - Google Patents

Acier multiphase à haute résistance et procédé de fabrication d'une bande d'acier composée de cet acier multiphase

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Publication number
EP3692178A1
EP3692178A1 EP18779642.0A EP18779642A EP3692178A1 EP 3692178 A1 EP3692178 A1 EP 3692178A1 EP 18779642 A EP18779642 A EP 18779642A EP 3692178 A1 EP3692178 A1 EP 3692178A1
Authority
EP
European Patent Office
Prior art keywords
steel
strip
content
final thickness
weight
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP18779642.0A
Other languages
German (de)
English (en)
Other versions
EP3692178B1 (fr
Inventor
Thomas Schulz
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Salzgitter Flachstahl GmbH
Original Assignee
Salzgitter Flachstahl GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Salzgitter Flachstahl GmbH filed Critical Salzgitter Flachstahl GmbH
Publication of EP3692178A1 publication Critical patent/EP3692178A1/fr
Application granted granted Critical
Publication of EP3692178B1 publication Critical patent/EP3692178B1/fr
Active legal-status Critical Current
Anticipated expiration legal-status Critical

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    • 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
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • 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
    • C21D8/0226—Hot 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
    • C21D8/0221—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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0242—Flattening; Dressing; Flexing
    • C—CHEMISTRY; METALLURGY
    • 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
    • C21D8/0273—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
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/561—Continuous furnaces for strip or wire with a controlled atmosphere or vacuum
    • C—CHEMISTRY; METALLURGY
    • 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
    • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
    • 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
    • C22C38/06—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
    • 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
    • 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
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • 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
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • 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
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
    • C23C2/0222—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating in a reactive atmosphere, e.g. oxidising or reducing atmosphere
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
    • C23C2/0224—Two or more thermal pretreatments
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/024—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by cleaning or etching
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/40—Plates; Strips
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B21B2001/221—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length by cold-rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B21B2001/225—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length by hot-rolling
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    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C21D1/32—Soft annealing, e.g. spheroidising
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    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
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    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
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    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
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    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite

Definitions

  • the invention relates to a high-strength multi-phase steel with dual-phase structure or complex phase structure and small amounts of retained austenite with
  • the invention further relates to a method for producing steel strips from such a steel according to claim 25 and to steel strips produced therewith according to claim 38. More particularly, the invention relates to steels with a tensile strength in the range of at least 980 MPa, in the un-tempered state, for the production of components which have an improved formability, such as with regard to a hole widening and improved joining suitability, such as, for example, welding properties.
  • the steel suppliers contribute by providing high strength steels. Task invoice. In addition, by providing
  • Welding and / or surface post-treatment such as phosphating and cathodic dip painting, as well as the manufacturing processes of the primary supplier, such as surface finishing by metallic or organic coating.
  • Hole expanding capability is a material property that describes the resistance of the material to crack initiation and crack propagation during forming operations in near edge areas, such as collaring.
  • the Lochetzweite pulp is normatively regulated, for example, in ISO 16630. Thereafter, prefabricated, for example punched in a sheet holes are widened by means of a mandrel.
  • the measured quantity is the change in the diameter of the hole in relation to the initial diameter at which the first crack occurs through the sheet at the edge of the hole.
  • An improved edge crack resistance means an increased formability of the sheet edges and can be described by an increased Lochetzweit43. This fact is under the synonyms “Low Edge Crack” (LEC) or known as “High Hole Expansion” (HHE) and xpand®.
  • LOC Low Edge Crack
  • HHE High Hole Expansion
  • the bending angle describes a material property, which gives conclusions on the material behavior in forming operations with dominant bending components (for example, when folding) or in crash loads. Increased bending angles thus increase passenger compartment safety.
  • the determination of the bending angle (a) is normatively regulated, for example, via the platelet bending test in VDA 238-100.
  • the failure behavior or the fracture pattern of the weld can be improved by a clear alloying with micro-alloying elements, in low-carbon steels with lowered carbon equivalent.
  • High-strength components must be sufficiently resistant to hydrogen
  • AHSS Advanced High Strength Steels
  • dual-phase steels consist of a ferritic basic structure in which a martensitic second phase is incorporated. It has been found that in low-carbon, micro-alloyed steels shares further phases such as bainite and retained austenite advantageous for example the Lochetzweit , the bending behavior and the hydrogen-induced
  • the bainite can here in different
  • multi-phase steels are also used in the automotive industry, such as complex-phase steels, ferritic-bainitic steels, bainitic steels and martensitic steels which have different structural compositions.
  • Complex-phase steels are, according to EN 10346, steels which contain small amounts of martensite, retained austenite and / or pearlite in a ferritic / bainitic matrix, whereby a pronounced grain refining is effected by delayed recrystallization or by precipitation of micro-alloying elements.
  • Ferritic-bainitic steels are according to EN 10346 steels containing bainite or solidified bainite in a matrix of ferrite and / or solidified ferrite. The strength of the matrix is brought about by a high dislocation density, grain refining and the excretion of micro-alloying elements.
  • Dual-phase steels are, according to EN 10346, steels with a ferritic basic structure, in which a martensitic second phase is insular, occasionally also with proportions of bainite as second phase.
  • TRIP steels are according to EN 10346 steels with a predominantly ferritic Basic structure in which bainite and retained austenite is embedded, which can transform to martensite during transformation (TRIP effect). Because of its strong work hardening, the steel achieves high levels of uniform elongation and
  • the high-strength steels with single-phase structure include, for example, bainitic and martensitic steels.
  • Bainitic steels are according to EN 10346 steels, which are characterized by a very high
  • the microstructure typically consists of bainite. Occasionally small fractions of other phases, such as, for example, martensite and ferrite, may be present in the microstructure.
  • Martensitic steels are, according to EN 10346, steels which contain small amounts of ferrite and / or bainite in a matrix of martensite due to thermomechanical rolling. This steel grade is characterized by a very high yield strength and tensile strength at a sufficiently high elongation for cold forming processes. Within the group of multiphase steels, the martensitic steels have the highest tensile strength values. The suitability for thermoforming is limited.
  • the martensitic steels are mainly suitable for bending forming processes, such as roll forming.
  • air hardening Hardening in air to bainite or martensite, the process is called "air hardening.” A tempering after hardening can have a specific effect on the strength / toughness ratio.
  • Multi-phase structure is not possible without restrictions, such as for the heat treatment before cold rolling. In areas with different sheet thicknesses, a homogeneous multi-phase microstructure in cold- as well as hot-rolled steel strips can not be set due to a temperature gradient occurring in the common process windows.
  • the cold-rolled steel strips are usually, for economic reasons, re-annealed in a continuous annealing process to form a thin sheet that can be readily formed.
  • the process parameters such as throughput speed, annealing temperatures and cooling rate, are set according to the required mechanical and technological properties with the necessary structure.
  • the above-mentioned properties are significantly influenced by, for example, the steel compositions, the process parameters during hot rolling, the process parameters during pickling (for example, the stretch bend density) and the process parameters during cold rolling even before the continuous annealing.
  • the steel composition is determined by analytical rules defining MIN and MAX ranges.
  • the process parameters during hot rolling such as standard slab thickness, slab lay time, slab discharge temperature, pre-strip rolling pass schedule, standard pre-strip thickness, hot strip line entry temperature, hot rolling pass schedule, final roll temperature, hot strip cooling pattern, coiler temperature, are set.
  • an optional stretch bending (stretching) affects the subsequent process step.
  • the hot strip thickness for the presentation of a cold rolling thickness by a standard Kaltabwalzgrad already during the order conversion in the technical specifications (process parameters) are determined.
  • the thickness of the pre-strip in the hot rolling process describes the initial thickness prior to entering the multi-stand hot strip mill, wherein the pre-strip was reversibly made in several passes (passes) from a slab with a defined standard thickness.
  • Typical slab thicknesses are between 250 mm and 300 mm (standard 250 mm, further considered here), the pre-strip thicknesses usually range between 40 mm to 60 mm for the multiphase steels.
  • the pre-strip thicknesses for the subsequent hot rolling are relatively constant, depending on the material composition, for example at 45 mm (called standard here).
  • the rolling degree during cold rolling (cold rolling degree) describes the percentage ratio of the difference between the hot strip starting thickness and the finished cold strip thickness based on the hot strip exit thickness.
  • Kaltabwalzgrade are relatively constant, they are in thicker cold tapes of about 2 mm up to about 40% and up to about 60% for cold tapes up to 1 mm thickness.
  • the critical threshold for recrystallization can not be overcome, so that a fine-grained and relatively uniform structure can not be achieved. Due to different particle sizes in the cold strip, even after recrystallization, different grain sizes appear in the final microstructure, which leads to characteristic fluctuations. Different sized grains may increase upon cooling from the oven temperature
  • the cold strip is heated in a continuous annealing furnace to a temperature at which the required microstructure formation (for example dual or complex phase structure) is established during cooling.
  • the required microstructure formation for example dual or complex phase structure
  • the annealing treatment is usually carried out in a continuous hot-dip galvanizing plant, in which the heat treatment or Annealing and the downstream galvanizing take place in a continuous process.
  • the decisive process parameter for material with a relatively constant degree of cold rolling is therefore the adjustment of the speed during continuous annealing, since the phase transformation takes place in a temperature- and time-dependent manner. ever
  • a method for producing a steel strip with different thickness over the strip length is described for example in DE 100 37 867 A1.
  • Complex-phase steels also have an even narrower process window than dual-phase steels.
  • Cold strip thickness determines the thickness of the hot strip and thus the hot strip production parameters.
  • Cold strip thickness determines the thickness of the hot strip and thus the hot strip production parameters.
  • the known alloy concepts for multiphase steels are characterized by a too narrow process window and therefore especially for cold-rolled strip production variable pre-strip thicknesses and variable Kaltabwalzgraden, as well as for flexibly rolled strips, unsuitable.
  • German Offenlegungsschrift DE 10 2012 002 079 A1 discloses a high-strength, multi-phase steel with minimum tensile strengths of 950 MPa, which indeed already has a very wide process window for the continuous annealing of hot or cold strips, but it has been shown that even with this steel neither variable pre-strip thicknesses, nor variable Kaltabwalzgrade be achieved with a single hot strip thickness (Masterwarmbanddicke) under realization of uniform material properties.
  • German Offenlegungsschrift DE 10 2015 1 1 177 A1 discloses a high-strength multiphase steel with minimum tensile strengths of 980 MPa, which already has a very wide process window for continuous annealing of hot or cold strips, as well as, for example, a single hot strip thickness (master hot strip thickness) Variable Kaltabwalzgrade, pass annealed cold strips with different thicknesses and with uniform material properties can achieve.
  • German Offenlegungsschrift DE 10 2014 017 274 A1 discloses a high-strength air-hardenable multiphase steel with minimum tensile strengths in the non-air-cured state of 950 MPa, which already has a very wide process window for the continuous annealing of hot or cold strips, as well as, for example, with a single hot strip thickness (US Pat. Masterwarmbanddicke) under realization of variable Kaltabwalzgrade, pass annealed cold strips, with different thicknesses and with uniform material properties can be achieved and is suitable for the subsequent air hardening process.
  • the goal of achieving the resulting mechanical and technological properties in a narrow range over bandwidth and strip length by the controlled adjustment of the volume fractions of the structural components has top priority and is only possible through an enlarged process window.
  • the known alloy concepts are characterized by too narrow a process window and therefore unsuitable for solving the present problem, in particular in flexibly rolled strips. With the known alloying concepts, only steels of a strength class with defined cross-sectional areas (strip thickness and strip width) can currently be represented, see above that for different strength classes and / or cross-sectional areas changed alloy concepts are necessary.
  • CEV (IIW) C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo + V) / 5
  • CET C + (Mn + Mo) / 10 + (Cr + Cu) / 20 + Ni / 40
  • PCM C + (Mn + Cu + Cr) / 20 + Ni / 60 + Mo / 15 + V / 10 + 5 B
  • the characteristic standard elements such as carbon and manganese, and chromium or molybdenum and vanadium considered (contents in wt .-%).
  • the prior art is also that an increase in the strength by the quantitative increase of carbon and / or silicon and / or manganese and a
  • Carbon and / or manganese content for improved cold working and performance.
  • Ratio of yield strength (Re) or yield strength (Rp0.2) to tensile strength This leads to steel developments with a comparatively large yield point interval at a normative tensile strength interval.
  • a low yield ratio (Re / Rm) is typical for a dual-phase steel and is used primarily for formability in drawing and deep drawing operations.
  • Re / Rm A higher yield ratio (Re / Rm), which is typical for complex phase steels, is also distinguished by resistance to edge cracks. This is due to the smaller differences in the strengths of each
  • Microstructure components lead back, which has a favorable effect on a homogeneous deformation in the area of the cutting edge.
  • the analytical landscape for achieving multiphase steels with minimum tensile strengths of 980 MPa is very diverse and shows very large alloy ranges in the strength-increasing elements carbon, manganese, phosphorus, aluminum and chromium and / or molybdenum, as well as in the addition of micro-alloys individually or in combinations, as well as in the material characterizing special properties, such as hole widening and lowered carbon equivalent, etc.
  • the range of dimensions is broad and lies in the thickness range from 0.50 to 3.00 mm, whereby the range between 0.80 to 2.10 mm is relevant in terms of quantity.
  • Thickness ranges below 0.50 and over 3.00 mm are conceivable.
  • Recrystallization after continuous annealing at a given Vorbanddicke for producing a Masterwarmbanddicke after hot rolling no manufacturing flexibility (s. Figure 1, process steps 6,8 and 9 are then necessary) is more in terms of achievable different cold strip thicknesses.
  • the production of different cold strip thicknesses at a constant master heat Thickness with comparable material properties on the produced cold strip due to a too small process window not possible.
  • the specification of a constant pre-strip thickness for producing a predetermined constant master hot-strip thickness additionally limits the manufacturing flexibility.
  • the invention is therefore based on the object of specifying a new alloy concept for a high-strength multiphase steel, a method for producing a steel strip from this high-strength multiphase steel and a steel strip produced by this method, with which the process window for the continuous annealing of cold strips can be expanded that from different
  • Vorbanddicken a predetermined hot strip thickness (Masterwarmbanddicke) different cold strip thicknesses or from different hot strip thicknesses a cold strip thickness (Masterkaltbanddicke) can be made.
  • variable pre-strip thicknesses before hot rolling should be used instead of constant pre-strip thicknesses.
  • the process window for the annealing, in particular continuous annealing, of cold rolled steel strip to be extended so that in addition to bands with different cross sections (jump in cross section) and steel bands over band length and possibly bandwidth varying thickness (TRB®) with the most homogeneous mechanical and technological Properties can be generated.
  • this object is achieved by a high-strength multiphase steel having a minimum tensile strength of 980 MPa with the following contents in% by weight:
  • the mechanical properties are reliably achieved in a narrow range for cold strips with variable pre-strip thickness before hot rolling, as well as variable cold rolling degrees during cold rolling.
  • variable pre-strip thicknesses the cold rolling process can be positively influenced that the steps annealing of hot strip before cold rolling, double cold rolling, annealing the cold rolled strip before the next cold rolling step, without negative consequences on the production of the above-described Masterwarmbanddicke or Masterkaltbanddicke.
  • final thickness determines the necessary hot strip thickness and a standard pre-strip thickness is necessary
  • a cold strip thickness it is also advantageously possible to produce a cold strip thickness to be achieved from different hot strip thicknesses analogously. This significantly increases flexibility in manufacturing and also reduces production costs.
  • Heat treatment can be adjusted.
  • the steel according to the invention also offers the advantage of a significantly enlarged process window compared to the known steels. This results in increased process reliability in the continuous annealing of cold strip with multi-phase structure.
  • more homogeneous mechanical and technological properties can be achieved for strips with variable degrees of cold rolling as well as in the Band or in the transition region of two bands even at different
  • a steel strip can be produced from the inventive multiphase steel in which a hot strip is produced from the multiphase steel, from the hot strip the steel strip is cold rolled with the final thickness to be achieved and then the steel strip is annealed, in particular continuously annealed.
  • the properties of the multiphase steel make it possible to cold-roll steel strips of the final thickness to be achieved, starting from a variable pre-strip thickness, a selected master hot strip with a particular thickness or selected hot strips of different thicknesses in a wide range of cold rolling degrees of 10% to 70%.
  • the chemical composition of the multi-phase steel is selected according to the invention depending on the final thickness of the cold strip to be achieved. It is thus possible, within selectable thickness graduations of the cold strip to be achieved, to produce a master cold strip with a uniform thickness from a master heat strip having a thickness corresponding cold strips with one or more end thicknesses or else from different hot strip thicknesses.
  • the steel strip is cold rolled to a final thickness of 0.50 to 3.00 mm and, depending on the final thickness to be achieved, the chemical composition of the multiphase steel is chosen as follows, even if find variable Vorbanddicken application.
  • the sum amount of Mn-Si + Cr is chosen as a function of the final thickness of the cold strip to be obtained as follows:
  • the sum amount of Mn-Si + Cr + Mo is selected as a function of the final thickness of the cold strip to be obtained as follows:
  • the carbon equivalent CEV (NW) is chosen as follows, depending on the final thickness of the cold strip to be achieved:
  • Cold strips produced from multiphase steel with varying sheet thicknesses can be made of this material advantageous stress-optimized components forming technology.
  • the material produced can be produced as a cold strip via a hot-dip galvanizing line or a pure continuous annealing plant in the dressed and undressed and also in the heat-treated state (overaging) and in the stretched and unstretched state (stretch bending strains).
  • microstructural fractions by selective variation of the process parameters so that steels in different strength classes, for example with yield strengths between 550 MPa and 950 MPa, as well as Tensile strengths between 980 MPa and 1 140 MPa are displayed.
  • steel strips can be produced by an intercritical annealing between Ac1 and Ac3 or in an austenitizing annealing over Ac3 with final controlled cooling, which leads to a dual or multi-phase structure.
  • Annealing temperatures of about 700 to 950 ° C have proved to be advantageous. Depending on the overall process (only continuous annealing or with additional
  • Hot dipping there are according to the invention different approaches for a heat treatment.
  • the cold rolled steel strip is cooled to an intermediate temperature of about 160 to 250 ° C starting from the annealing temperature at a cooling rate of about 15 to 100 ° C / s.
  • the cooling to room temperature is finally carried out at a cooling rate of about 2 to 30 ° C / s (see method 1, Figure 8a).
  • it may be cooled to room temperature at a cooling rate between about 15 and 100 ° C / s from the intermediate temperature of 300 to 500 ° C.
  • the second variant of the temperature control in the hot dip finishing includes holding the temperature for about 1 to 20 seconds at the intermediate temperature of about 200 to 350 ° C and then reheating to the
  • the ribbon is cooled to approx. 200 to 250 ° C after refining.
  • the cooling to room temperature takes place again at a cooling rate of about 2 to 30 ° C / s (see method 3, Figure 8c).
  • besides carbon, manganese, chromium and silicon are also responsible for the transformation of austenite to martensite.
  • Material characteristic is also that the addition of manganese with increasing weight percent of the ferrite is shifted to longer times and lower temperatures during cooling, similar effect also the elements carbon, chromium, molybdenum and boron.
  • the proportions of ferrite are thereby increased levels of Bainite more or less reduced depending on the process parameters.
  • the carbon equivalent can be reduced, thereby improving weldability and avoiding excessive weld hardening. In resistance spot welding, moreover, the electrode life can be significantly increased.
  • Hydrogen (H) can be the only element without creating lattice strains diffuse through the iron grid. This causes the hydrogen in the
  • Iron grating is relatively mobile and can be relatively easily absorbed during the processing of the steel. Hydrogen can only be taken up in atomic (ionic) form in the iron lattice.
  • Hydrogen has a strong embrittlement and preferably diffuses to energy-favorable sites (defects, grain boundaries, etc.). In this case, defects act as hydrogen traps and can significantly increase the residence time of the hydrogen in the material.
  • the hydrogen content in the steel according to the invention is limited to ⁇ 0.0010% by weight (10 ppm) or advantageously to ⁇ 0.0008% by weight, optimally to ⁇ 0.0005% by weight.
  • a more uniform structure also reduces the susceptibility to hydrogen embrittlement.
  • Oxygen (O) In the molten state, the steel has a relatively high absorption capacity for gases. At room temperature, however, oxygen is only soluble in very small quantities. Similar to hydrogen, oxygen can only diffuse into the material in atomic form. Due to the strong embrittling effect and the negative effects on the aging resistance, as much as possible is attempted during production to reduce the oxygen content.
  • the oxygen content in the steel should be as low as possible.
  • Phosphorus (P) is a trace element from iron ore and is dissolved in the iron lattice as a substitution atom. Phosphorus increases hardness by solid solution strengthening and improves hardenability. However, it is generally attempted to lower the phosphorus content as much as possible, since it is highly prone to segregation, among other things due to its low solubility in the solidifying medium, and greatly reduces the toughness. Due to the addition of phosphorus at the grain boundaries, grain boundary fractures occur. In addition, phosphorus increases the transition temperature from tough to brittle behavior up to 300 ° C. During hot rolling, near-surface phosphorus oxides at the grain boundaries can lead to breakage cracks.
  • phosphorus is used as a micro-alloying element in small quantities ( ⁇ 0.1% by weight) due to its low cost and high strength enhancement, for example, in higher-strength IF (interstitial free) steels, bake hardening steels or some alloy concepts for dual-phase steels.
  • the steel according to the invention differs from known analysis concepts, which use phosphorus as a mixed-crystal former, inter alia by the fact that phosphorus is not alloyed but is adjusted as low as possible.
  • the phosphorus content in the steel according to the invention is limited to unavoidable amounts in steelmaking.
  • P should be ⁇ 0.020 wt%.
  • S sulfur
  • MnS manganese sulfide
  • the manganese sulfides are often rolled in rows during the rolling process and act as nucleation sites for the transformation. This leads, especially in the case of diffusion-controlled transformation, to a line-shaped structure and can lead to impaired mechanical properties in the case of pronounced bristleness, for example to pronounced Martensitzeilen instead of distributed Martensitinseln, anisotropic
  • the sulfur content of the steel according to the invention is limited to ⁇ 0.0020% by weight or advantageously to ⁇ 0.0015% by weight, optimally to ⁇ 0.0010% by weight.
  • Alloying elements are usually added to the steel in order to specifically influence certain properties.
  • An alloying element in different steels can influence different properties. The effect generally depends strongly on the amount and the solution state in the material. The connections can therefore be quite varied and complex. In the following, the effect of the alloying elements will be discussed in greater detail.
  • Carbon (C) is considered the most important alloying element in steel. Through its targeted introduction of up to 2.06 wt .-% iron is only for steel. Often the carbon content is drastically lowered during steelmaking. at
  • Dual-phase steels for a continuous hot-dip finishing is its proportion according to EN 10346 or VDA 239-100 maximum 0.230 wt .-%, a minimum value is not specified. Due to its comparatively small atomic radius, carbon is interstitially dissolved in the iron lattice. The solubility is 0.02% maximum in ⁇ -iron and 2.06% maximum in iron. Carbon in solute significantly increases the hardenability of steel and is therefore essential for the formation of a sufficient amount of martensite. However, excessive carbon contents increase the hardness difference between ferrite and martensite and limit weldability. In order to meet the requirements for, for example, high hole widening and bending angles as well as improved weldability, the steel according to the invention contains
  • Structural phase is the cementite (FesC).
  • FesC cementite
  • significantly harder special carbides with other metals such as chromium, titanium, niobium but also vanadium can form.
  • the minimum C content is set at 0.075% by weight and the maximum C- Content determined to 0.1 15 wt .-%, advantageous are contents with a cross-sectional differentiation, such as:
  • Silicon (Si) binds oxygen during casting and is therefore used to calm down during the deoxidation of the steel.
  • the Seigerungskostory is significantly lower than, for example, that of manganese (0.16 compared to 0.87). Seingings generally result in a line arrangement of the structural components that degrade the forming properties, such as hole widening and bending capability.
  • silicon causes strong solid solution hardening.
  • 0.1% silicon causes an increase in tensile strength of about 10 MPa, with elongation only slightly deteriorating when added up to 2.2% silicon.
  • the increase from 0.2 to 0.5% silicon caused an increase in strength of about 20 MPa in the yield strength and about 70 MPa in the tensile strength.
  • the elongation at break decreases by about 2%.
  • the latter is partly due to the fact that silicon reduces the solubility of carbon in the ferrite and increases the activity of carbon in the ferrite, thus preventing the formation of carbides, which reduce the ductility as brittle phases, which in turn improves the formability. Due to the low strength-increasing effect of silicon within the range of the steel according to the invention, the basis for a broad process window is created.
  • the atmospheric conditions during the annealing treatment in a continuous hot-dip coating plant cause a reduction of iron oxide, which can form, for example, during cold rolling or as a result of storage at room temperature on the surface.
  • oxygen-affinity alloy components such as
  • Silicon, manganese, chromium, boron, the gas atmosphere is oxidizing with the result that segregation and selective oxidation of these elements can occur.
  • the selective oxidation can take place both externally, that is on the substrate surface, and internally within the metallic matrix. It is known in particular that silicon diffuses during the annealing to the surface and forms oxides on the steel surface alone or together with manganese. These oxides can prevent contact between the substrate and the melt and prevent or worsen the wetting reaction. As a result, undiluted spots, so-called "bare spots", or even large areas without coating may occur
  • the strip surface is free from scale residues, pickling or rolling oil or other dirt particles by a chemical-mechanical or thermal-hydro-mechanical pre-cleaning.
  • a chemical-mechanical or thermal-hydro-mechanical pre-cleaning In order to prevent silicon oxides from reaching the strip surface, further methods are to be taken which promote the internal oxidation of the alloying elements below the surface of the material.
  • different measures are used here.
  • the internal oxidation of the alloying elements can be targeted by adjusting the oxygen partial pressure of the furnace atmosphere (N2-H2 shielding gas atmosphere) to be influenced.
  • the set oxygen partial pressure must satisfy the following equation, with the furnace temperature between 700 and 950 ° C.
  • Si, Mn, Cr, B denote the corresponding alloying proportions in the steel in wt .-% and p02 the oxygen partial pressure in mbar.
  • DFF direct fired furnace
  • a subsequent radiant tube furnace see process 2 in Figure 8b
  • selective oxidation can be used also influence the alloying elements via the gas atmospheres of the furnace areas.
  • the combustion reaction in the NOF can be used to adjust the oxygen partial pressure and thus the oxidation potential for iron and the alloying elements. This should be adjusted so that the oxidation of the alloying elements takes place internally below the steel surface and, if necessary, a thin iron oxide layer is formed on the steel surface after passing through the NOF region. This is achieved, for example, by reducing the CO value below 4% by volume.
  • the optionally formed iron oxide layer is reduced under Isb-F protective gas atmosphere and likewise the alloying elements are further internally oxidized.
  • the set oxygen partial pressure in this furnace area must satisfy the following equation, with the furnace temperature between 700 and 950 ° C.
  • Si, Mn, Cr, B denote the corresponding alloying proportions in the steel in wt .-% and p0 2 the oxygen partial pressure in mbar.
  • the minimum silicon content is set at 0.400% by weight and the maximum silicon content at 0.500% by weight.
  • Manganese (Mn) is added to almost all steels for desulfurization to convert the harmful sulfur into manganese sulphides.
  • manganese increases the strength of the ferrite by solid solution strengthening and shifts the ⁇ / ⁇ conversion to lower temperatures.
  • manganese increases the hardness ratio between martensite and ferrite.
  • the line of the structure is reinforced.
  • a high hardness difference between the phases and the formation of Martensitzeilen result in a lower Lochaufweitstory, which is equivalent to an increased edge crack sensitivity.
  • manganese tends to form oxides on the steel surface during the annealing treatment.
  • manganese oxides for example MnO
  • Mn mixed oxides for example Mn2SiC> 4
  • manganese is considered to be less critical, since giobuare oxides rather than oxide films are formed.
  • high levels of manganese can negatively affect the appearance of the zinc layer and zinc adhesion.
  • the manganese content is determined for the reasons mentioned to 1, 900 wt .-% to 2.350 wt .-%. In order to achieve the required minimum strengths, it is advantageous to adhere to a band-thickness-dependent differentiation of the manganese content.
  • the manganese content is preferably in a range between> 1.900% by weight and ⁇ 2.200% by weight, with final thicknesses of 1.00 to 2.00 inclusive mm between> 2.050 wt .-% to ⁇ 2.250 wt .-% and at final thicknesses of 2.00 to 3.00 mm inclusive between> 2.100 wt .-% to ⁇ 2.350 wt .-%.
  • Another peculiarity of the invention is that the variation of the manganese content can be compensated by simultaneously changing the silicon content.
  • the increase in strength (here the yield strength, YS) by manganese and silicon is generally well described by the Pickering equation:
  • chromium causes particle hardening with appropriate temperature control in the form of chromium carbides.
  • the associated increase in the number of seed sites with simultaneously reduced content of carbon leads to a reduction in the hardenability.
  • chromium increases the tempering resistance significantly, so that there is almost no loss of strength in the hot dip.
  • Chromium is also a carbide former. If chromium-iron mixed carbides are present, the austenitizing temperature must be high enough before curing to dissolve the chromium carbides. Otherwise, the increased germ count may lead to a deterioration of the hardenability.
  • Chromium also tends to form oxides on the steel surface during the annealing treatment, which may degrade the hot dipping quality.
  • measures for adjusting the furnace areas in continuous hot-dip coating reduce the formation of Cr oxides or Cr mixed oxides on the steel surface after annealing.
  • the chromium content is therefore set at levels of 0.250 wt .-% to 0.400 wt .-%.
  • the chromium content is preferably in a range between> 0.260 wt .-% to ⁇ 0.330 wt .-%, with final thicknesses of 1.00 to 2.00 mm inclusive between > 0.290 wt .-% to ⁇ 0.360 wt .-% and at final thicknesses of 2.00 to 3.00 mm inclusive between> 0.320 wt .-% to ⁇ 0.370 wt .-%.
  • Carbon equivalent CEV (IIW), also here especially for the processing with variable pre-strip thicknesses.
  • the chromium content is preferably in a range between> 0.260 wt .-% to ⁇ 0.330 wt .-% with a carbon equivalent CEV (IIW) of ⁇ 0.62%, at final thicknesses of 1.00 to 2.00 mm including between 0.290 wt .-% to ⁇ 0.360 wt .-% at a
  • Molybdenum (Mo) The addition of molybdenum is similar to that of chromium and Manganese to improve hardenability. The pearlite and bainite transformation is postponed to longer times and the martensite start temperature is lowered. At the same time, molybdenum is a strong carbide former that gives rise to finely divided mixed carbides, including titanium. Molybdenum also increases the tempering resistance significantly, so that in the hot dip no strength losses are expected. Molybdenum also works by solid solution hardening, but is less effective than manganese and silicon.
  • the content of molybdenum is therefore set between more than 0.200 wt .-% to 0.300 wt .-%.
  • the Mo content is advantageously adjusted to a range between more than 0.200 wt .-% to 0.250 wt .-%.
  • Hot-dip dipability has proved to be advantageous for the alloy concept according to the invention a sum content of Mo + Cr of ⁇ 0.650% by weight.
  • Copper (Cu): The addition of copper can increase the tensile strength and hardenability. In conjunction with nickel, chromium and phosphorus, copper can be a
  • copper When combined with oxygen, copper can form harmful oxides at the grain boundaries, which can be detrimental to hot working processes can.
  • the content of copper is therefore fixed at ⁇ 0.050% by weight and thus limited to quantities that are unavoidable in steel production.
  • V Vanadium (V): In the present alloy concept, the content of
  • Tin (Sn) Since addition of tin is not necessary with the present alloy concept, the content of tin is determined to ⁇ 0.040% by weight, thus limiting unavoidable steel-accompanying amounts.
  • Aluminum (AI) is usually added to the steel to bind the dissolved oxygen in the iron and nitrogen. Oxygen and nitrogen become so in
  • Converted aluminum oxides and aluminum nitrides can cause a grain refining by increasing the germination sites and thus increase the toughness properties and strength values.
  • Titanium nitrides have a lower formation enthalpy and are formed at higher temperatures.
  • Niobium has different effects in steel. During hot rolling in the finishing train, it retards recrystallization by forming finely divided precipitates, increasing the nucleation density and producing a finer grain after conversion. The proportion of dissolved niobium also works
  • TiN Mixed carbide on.
  • the precipitates have a high temperature stability, so that they exist in contrast to the mixed carbides at 1200 ° C largely as particles that impede grain growth. Titanium also retards recrystallization during hot rolling, but is less effective than niobium. Titanium works by precipitation hardening. The larger TiN particles are less effective than the finely divided mixed carbides. The best effectiveness is achieved in the range of 0.005 wt .-% to 0.060 wt .-% titanium, therefore, this represents the alloy span according to the invention. For this, contents of 0.025 wt .-% to 0.045 wt .-% have been found to be advantageous.
  • Boron is an extremely effective alloying agent for realizing variable degrees of cold rolling.
  • the very narrow range for the addition of boron according to the invention has a pronounced effect on the uniformity of the mechanical properties of the cold-rolled strips with variable degree of cold rolling produced in the subsequent processing. This pronounced effect first leads to the possibility of defining characteristic ranges according to the process variables instead of a relatively constant degree of cold rolling. Steps ( Figures 8a, 8b and 8c) also for the material with variable Kaltabwalzgraden based on a Masterwarmbanddicke or based on a Masterkaltbanddicke adjust.
  • boron is an effective hardening enhancer that is effective in very small quantities.
  • the martensite start temperature remains unaffected.
  • boron must be in solid solution. Since it has a high affinity for nitrogen, the nitrogen must first be set, preferably by the stoichiometrically necessary amount of titanium. Due to its low solubility in iron, the dissolved boron prefers to attach to the
  • Austenite grain boundaries There it partially forms Fe-B carbides, which are coherent and reduce the grain boundary energy. Both effects have a retarding effect on ferrite and pearlite formation and thus increase the hardenability of the steel. Excessive levels of boron, however, are detrimental as iron boride can form, adversely affecting the hardenability, formability and toughness of the material. Boron also tends to form oxides or mixed oxides during annealing during the continuous hot-dip coating, which deteriorate the quality of galvanizing. The above measures for adjusting the furnace areas in continuous hot dip coating reduce the formation of oxides on the steel surface.
  • Alloy concept set to values of more than 0.0005 wt .-% to 0.0010 wt .-%, advantageously to values ⁇ 0.0009 wt .-% or optimally to> 0.0006 wt .-% to ⁇ 0, 0009% by weight
  • Nitrogen (N) can be both an alloying element and a companion element from steelmaking. Excessive levels of nitrogen cause an increase in strength associated with rapid loss of toughness and aging effects.
  • the N content is therefore to values of> 0.0020 wt .-% to ⁇ 0.0120 wt .-% set.
  • niobium and titanium contents of ⁇ 0.100% by weight have been found to be advantageous and, owing to the principal interchangeability of niobium and titanium, to a minimum niobium content of 0.005% by weight and, for cost reasons, particularly advantageously ⁇ 0.090% by weight. % proved.
  • Masterswarmband of 2.30 mm was produced, but also in the thickness range 0.50 to 3.00 mm can be generated, which is characterized by a sufficient tolerance to process variations.
  • the annealing temperatures for the dual-phase structure to be achieved are between about 700 and 950 ° C. for the steel according to the invention, so that depending on
  • Temperature range reaches a partially austenitic (two-phase area) or a fully austenitic structure (austenitic area).
  • the continuous annealed and occasionally hot-dip refined material can be in the dressed (cold rolled) or undressed state and / or in the stretch bent or non-stretch bent state and also in the
  • the steel strips of the alloy composition according to the invention are also characterized in the further processing by a high Kantenrissuna- speed and a high bending angle.
  • steel strips can thus be produced which have a minimum product value Rm x ⁇ (tensile strength x [bending angle according to VDA 238-100]) of 100,000 MPa x °, in particular of 120000 MPa x °.
  • the steel strips according to the invention have a delayed fracture-free state for at least 6 months, while meeting the requirements of SEP 1970 for hole pull and iron-on samples made available by the steel manufacturer.
  • the very small differences in the characteristic of the steel strip along and across its rolling direction are advantageous for later material use.
  • the cutting of blanks from a strip regardless of the rolling direction (for example, transversely, longitudinally and diagonally or at an angle to the rolling direction) take place and so the waste can be minimized.
  • a board is cut from a steel strip according to the invention, which is then heated to a temperature above Ac3.
  • the heated board is formed into a component and then cured in a forming tool or in air, with optional subsequent tempering.
  • the steel according to the invention has the property that the hardening takes place already on cooling at still air, so that a separate cooling of the forming tool can be omitted.
  • the structure of the steel is converted by heating into the austenitic region, preferably to temperatures above 950 ° C. under a protective gas atmosphere. During subsequent cooling in air or inert gas takes place Formation of a martensitic microstructure for a high-strength component.
  • a subsequent tempering makes it possible to reduce residual stresses in the hardened component. At the same time, the hardness of the component is reduced so that the required toughness values are achieved.
  • FIG. 1 process chain (schematic) for the production of a strip from the steel according to the invention
  • FIG. 2 time-temperature curve (schematically) of the process steps hot rolling and cold rolling and continuous annealing (with optional hot-dip finishing), as well as component production, optional tempering (air hardening) and optional tempering by way of example for the steel according to the invention,
  • FIG. 3 chemical composition (examples 1 to 4) of the steel according to the invention
  • FIG. 4 a shows mechanical characteristic values (transverse to the rolling direction) of the steel according to the invention in the hot rolled state (HR),
  • FIG. 4b shows mechanical characteristics (transverse to the rolling direction) of the steel according to the invention in the cold-rolled state (CR),
  • FIG. 5a hardening behavior during cold rolling of the steel according to the invention, characteristic values transverse to the rolling direction, FIG.
  • FIG. 5b hardening behavior during cold rolling of the steel according to the invention, cold flow curve
  • FIG. 6 a shows mechanical characteristics (transverse to the rolling direction) of the steel according to the invention, in the state of sheet metal (HDG),
  • FIG. 6b Results of the hole expansion tests according to ISO 16630 and of the
  • FIG. 8a method 1, temperature-time curves (annealing variants schematically),
  • FIG. 8b method 2, temperature-time curves (annealing variants schematically),
  • FIG. 8c method temperature-time curves (annealing variants schematically),
  • Figure 1 shows schematically the process chain for the production of a strip of the steel according to the invention. Shown are the possible process routes in the invention. Until pickling, the process route is the same for all steels according to the invention, after which deviating process routes take place, depending on the desired results.
  • the pickled hot strip may be cold rolled and hot dip refined with varying degrees of rolling. Also soft annealed hot strip or annealed cold strip can be cold rolled and
  • Material can also be optionally processed without hot dip finishing, ie only in the context of continuous annealing with and without subsequent electrolytic galvanizing. From the optionally coated material, a complex component can now be produced. Following this can optionally be
  • Annealing process such as the air hardening, where the heat-treated component is cooled in air.
  • a tempering stage can complete the thermal treatment of the component.
  • FIG. 2 shows schematically the time-temperature profile of the process steps
  • Hot rolling and continuous annealing of strips of the invention Alloy composition Shown are the time- and temperature-dependent transformation for the hot rolling process as well as for post-cold-rolled heat treatment, component fabrication and optional tempering with optional tempering.
  • FIG. 3 shows in examples 1 to 4, which originate from a melt, in order to exclude the analytical influence, the alloy compositions of the steel according to the invention, depending on the produced pre-strip thickness. From a hot strip nominal thickness of 2.30 mm, cold strips with a cold strip nominal thickness of 1.50 mm were produced. Depending on the pre-strip thickness to be produced before hot rolling, Example 1 shows the alloy composition for a
  • Vorbanddicke of 40 mm Example 2 for a pre-strip thickness of 45 mm, Example 3 for a pre-strip thickness of 50, Example 4 for a Vorband with a thickness of 55 mm.
  • FIG. 4 shows the mechanical characteristic values (transverse to the rolling direction) of the steel according to the invention in the hot rolled state (HR, Hot Rolled) in FIG. 4a and in the cold rolled state (CR, Cold Rolled) in FIG. 4b.
  • FIG. 5 shows the solidification behavior, via the mechanical characteristics transverse to the rolling direction, during cold rolling of the steel according to the invention, in tabular form in FIG. 5a and graphically as cold flow curve in FIG. 5b.
  • FIG. 6 shows the mechanical characteristics (transverse to the rolling direction) of the steel according to the invention in the thin sheet state (HDG, Hot Dipped Galvanized) in FIG. 6a and the results of the hole expansion tests according to ISO 16630 and the platelet bending test according to VDA 238-100 in the thin sheet state (HDG). along and across the rolling direction, as well as the corresponding products with the tensile strength, in Figure 6b.
  • FIG. 7 shows the mechanical characteristic values (transverse to the rolling direction) of the steel according to the invention in the state HR, CR and HDG using a pre-strip thickness of 40 mm in FIG. 7a, 45 mm in FIG. 7b, 50 mm in FIG. 7c, 55 mm in FIG. 7d and FIG in Figure 7e as a summary graphical overview.
  • FIG. 8 schematically shows three variants of the temperature Time courses during the annealing treatment and cooling and in each case different austenitizing conditions.
  • Process 1 shows the annealing and cooling of the steel strip produced and cold-rolled to final thickness in a continuous annealing plant.
  • the tape is heated to a temperature in the range of about 700 to 950 ° C (Ac1 to Ac3).
  • the annealed steel strip is then cooled from the annealing temperature at a cooling rate between about 15 and 100 ° C / s up to an intermediate temperature (ZT) of about 200 to 250 ° C.
  • ZT intermediate temperature
  • a second intermediate temperature about 300 to 500 ° C
  • the steel strip is cooled at a cooling rate between about 2 and 30 ° C / s until reaching room temperature (RT) in air or the
  • Cooling at a cooling rate between about 15 and 100 ° C / s is maintained to room temperature.
  • the process 2 ( Figure 8b) shows the process according to method 1, but the cooling of the steel strip for the purpose of a hot dip finishing briefly interrupted when passing through the hot dipping vessel, then the cooling at a cooling rate between about 15 and 100 ° C / s up to an intermediate temperature of about 200 to 250 ° C continue. Subsequently, the steel strip is cooled at a cooling rate between about 2 and 30 ° C / s until it reaches room temperature in air.
  • Process 2 corresponds to annealing, for example hot dip galvanizing with a combined direct fired furnace and radiant tube furnace, as described in FIG. 8b.
  • the method 3 ( Figure 8c) also shows the process according to method 1 in a hot dipping refinement, however, the cooling of the steel strip by a short Break (about 1 to 20 s) at an intermediate temperature in the range of about 200 to 400 ° C interrupted and heated up to the temperature (ST), which is necessary for hot dip refining (about 400 to 470 ° C), reheated. Subsequently, the steel strip is again cooled to an intermediate temperature of about 200 to 250 ° C. With a cooling rate of about 2 and 30 ° C / s takes place until reaching the
  • the method 3 corresponds for example to a process control in a continuous annealing plant, as described in Figure 8c.
  • the method 3 corresponds for example to a process control in a continuous annealing plant, as described in Figure 8c.
  • a reheating of the steel can be achieved optionally directly in front of the zinc bath.
  • the decreases from slab to sliver vary in the examples below from 78% to 84% for subsequent hot rolling to one
  • Hot strip thickness of 2.30 mm with corresponding decreases of 94% to 96%.
  • variable pre-strip thicknesses can significantly influence the cold rollability, such as the necessary rolling forces, without causing any problems the higher hot strip strength (HR) and higher cold strip strength (CR), with decreasing pre-strip thickness, would lead to significant fluctuations in the thin sheet (HDG):
  • the slab material of 250 mm was hot rolled in the roughing mill to a pre-strip of 40 mm reversing rolled with a percentage decrease of 84% and then in the hot strip mill at a final target roll temperature of 910 Hot rolled at a reduction of 94% and unwound at a coiler temperature of 650 ° C with a master heat-treated thickness of 2.30 mm and after pickling without additional
  • the yield ratio Re / Rm in the transverse direction was 66%.
  • the yield ratio Re / Rm in the transverse direction was 77%.
  • the slab material of 250 mm was reversibly rolled before hot rolling in the roughing train to a preliminary strip of 45 mm with a percentage decrease of 82% and then in the hot strip mill at a final rolling target temperature from 910 ° C with a decrease of 95% hot rolled and at a reel target temperature of 650 ° C with a master hot strip thickness of 2.30 mm and cold after pickling without additional heat treatment (such as bell annealing) to 1.50 mm in one pass (Cold rolling degree 35%).
  • the yield ratio Re / Rm in the transverse direction was 67%.
  • the material characteristics transverse to the rolling direction would correspond for example to a HC660XD.
  • the yield ratio Re / Rm in the transverse direction was 70%.
  • alloy composition A 0.104% C steel of the invention; 0.443% Si; 2.178% Mn; 0.012% P;
  • the 250 mm slab material was reversibly rolled in a roughing mill in the roughing train to a 50 mm pitch of 80% percent reduction and then in the hot strip mill at 910 final rolling target temperature ° C with a decrease of 96% hot rolled and at a reel target temperature of 650 ° C with a master hot strip thickness of 2.30 mm and after pickling without additional heat treatment (such as bell annealing) to 1.50 mm cold rolled in one pass (Kaltabwalzgrad 35%).
  • the yield ratio Re / Rm in the transverse direction was 65%.
  • the material characteristics transverse to the rolling direction would correspond for example to a HC660XD.
  • the yield ratio Re / Rm in the transverse direction was 69%.
  • the yield ratio Re / Rm in the transverse direction was 66%.
  • the yield ratio Re / Rm in the transverse direction was 70%.
  • the invention has been described with reference to sheet steel plates with a final thickness of 1, 50 mm to be achieved in the thickness range 0.50 to 3.00 mm. It is also possible, if necessary, to produce final thicknesses in the range of 0.10 to 4.00 mm.

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Abstract

L'invention concerne un acier multiphase à haute résistance, présentant une résistance à la traction minimale de 980 MPa, contenant (en % en poids) : C ≥ 0,075 à ≤ 0,115 ; Si ≥ 0,400 à ≤ 0,500 ; Mn ≥ 1,900 à ≤ 2,350 ; Cr ≥ 0,250 à ≤ 0,400 ; Al ≥ 0,010 à ≤ 0,060 ; N ≥ 0,0020 à ≤ 0,0120 ; P ≤ 0,020 ; S ≤ 0,0020 ; Ti ≥ 0,005 à ≤ 0,060 ; Nb ≥ 0,005 à ≤ 0,060 ; V ≥ 0,005 à ≤ 0,020 ; B ≥ 0,0005 à ≤ 0,0010 ; Mo ≥ 0,200 à ≤ 0,300 ; Ca ≥ 0,0010 à ≤ 0,0060 ; Cu ≤ 0,050 ; Ni ≤ 0,050 ; Sn ≤ 0,040 ; H ≤ 0,0010, le reste étant composé de fer, y compris les impuretés usuelles accompagnant l'acier, dues à la fusion, dans lequel la somme des teneurs Mn-Si+Cr est ≥ 1,750 % en poids à ≤ 2,250 % en poids, eu égard à la fenêtre de procédé la plus large possible lors de la calcination, en particulier lors de la calcination continue, de bandes à froid composées de cet acier.
EP18779642.0A 2017-10-06 2018-09-27 Procede de fabrication d'une bande d'acier a partir d'un acier multiphase a tres haute resistance Active EP3692178B1 (fr)

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DE102017123236.2A DE102017123236A1 (de) 2017-10-06 2017-10-06 Höchstfester Mehrphasenstahl und Verfahren zur Herstellung eines Stahlbandes aus diesem Mehrphasenstahl
PCT/EP2018/076307 WO2019068560A1 (fr) 2017-10-06 2018-09-27 Acier multiphase à haute résistance et procédé de fabrication d'une bande d'acier composée de cet acier multiphase

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DE202022100637U1 (de) * 2022-02-03 2023-05-05 STG Stanztechnik GmbH & Co. KG Verstärkungsband für einen Formkörper aus einer spritzfähigen Formmasse sowie Formkörper mit einem derartigen Verstärkungsband
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WO2024105428A1 (fr) * 2022-11-14 2024-05-23 Arcelormittal Pièce en acier durcie à la presse à ténacité élevée et son procédé de fabrication

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EP3692178B1 (fr) 2022-06-08
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