Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES, PROFILES OR LIKE SEMI-MANUFACTURED PRODUCTS OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
  • B21C47/00—Winding-up, coiling or winding-off metal wire, metal band or other flexible metal material characterised by features relevant to metal processing only
  • B21C47/02—Winding-up or coiling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/62—Quenching devices
  • C21D1/673—Quenching devices for die quenching
• • 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
  • C21D6/00—Heat treatment 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys 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
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0278—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular surface treatment 
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for drawing, e.g. for deep-drawing
  • C21D8/0421—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for drawing, e.g. 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/40—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rings; for bearing races
• • 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
  • 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
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium 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
  • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
• • C—CHEMISTRY; METALLURGY
  • 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
  • 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
  • C23C2/0224—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
  • C23C2/12—Aluminium 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
  • C23C2/26—After-treatment
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/26—After-treatment
  • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/26—After-treatment
  • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
  • C23C2/29—Cooling or quenching
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
  • C23C2/36—Elongated material
  • C23C2/40—Plates; Strips
• • 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
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
  • C23G1/08—Iron or steel
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/002—Bainite
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/005—Ferrite
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/008—Martensite

Definitions

• the present invention relates to coated steel sheets and to high strength press hardened steel parts having good bendability properties.
• This weight reduction can be achieved in particular thanks to the use of steel parts with a martensitic or bainitic/martensitic microstructure.
• the publication WO2016104881 relates to a hot press forming part used as a structural part of a vehicle or the like, requiring impact resistance characteristics, and more particularly, having a tensile strength of 1300 MPa or greater and a method for manufacturing the same by heating a steel material to a temperature at which an austenite single phase may be formed, and quenching and hot forming thereof using a mold.
• the base steel sheet comprises a thin ferrite layer lower than 50 ⁇ m at the surface, and the carbides size and density should be controlled. This ferrite layer in the substrate allow to inhibit the propagation of the fine cracks formed on the plating layer to the base but leads to a low bendability with bending angle lower than 70°.
• the publication WO2018179839 relates to a hot-pressed part obtained by hot pressing a steel sheet having a microstructure changing in the thickness direction, with a soft layer made of at least 90% of ferrite, a transition layer made of ferrite and martensite and a hard layer mainly martensitic and has both high strength and high bendability.
• the cold rolled steel sheet is annealed in an atmosphere with a dew point temperature comprises from 50°C to 90°C, which could be harmful to aluminium alloy coating.
• US2017/260599A1 and WO2018/220540A1 is described in US2017/260599A1 and WO2018/220540A1 .
• the purpose of the invention therefore is to solve the above-mentioned problem and to provide a press hardened steel part having a combination of high mechanical properties with the tensile strength TS above or equal to 1500 MPa and bending angle higher than 70°.
• the press hardened steel part according to the invention has yield strength YS above or equal to 1250 MPa.
• Another purpose of the invention is to obtain a coated steel sheet that can be transformed by hot forming into such a press hardened steel part.
• composition of the steel according to the invention will now be described, the content being expressed in weight percent.
• the manganese content is comprised from 0.5% to 1.8 %. Above 1.8% of addition, the risk of central segregation increases to the detriment of the bendability. Below 0.5% the hardenability of the steel sheet is reduced. Preferably the manganese content is comprised from 0.5% to 1.3%.
• silicon content is comprised from 0.1% to 1.25%.
• Silicon is an element participating in the hardening in solid solution. Silicon is added to limit carbides formation. Above 1.25%, silicon oxides form at the surface, which impairs the coatability of the steel. Moreover, the weldability of the steel sheet may be reduced.
• the silicon content is from 0.2% to 1.25%. More preferably the silicon content is from 0.3% to 1.25%. More preferably, the silicon content is from 0.3% to 1%.
• the aluminium content is comprised from 0.01% and 0.1% as it is a very effective element for deoxidizing the steel in the liquid phase during elaboration. Aluminium can protect boron if titanium content is not enough.
• the aluminium content is lower than 0.1% to avoid oxidation problems and ferrite formation during press hardening. Preferably the aluminium content is comprised from 0.01% to 0.05%.
• the chromium content is comprised from 0.1% to 1.0 %. Chromium is an element participating in the hardening in solid solution and must be higher than 0.1%. The chromium content is below 1.0% to limit processability issues and cost.
• the titanium content is comprised from 0.01% to 0.1% in order to protect boron from formation of BN. Titanium content is limited to 0.1% to avoid TiN formation.
• the boron content is comprised from 0.001% to 0.004%. Boron improves the hardenability of the steel.
• the boron content is not higher than 0.004% to avoid a risk of breaking the slab during continuous casting.
• Nickel may be added as an optional element up to 0.5% as it can substantially reduce the sensitivity to delayed fracture.
• Molybdenum content can optionally be added up to 0.40%. As boron, molybdenum improves the hardenability of the steel. Molybdenum is not higher than 0.40% to limit cost.
• niobium can optionally be added up to 0.08% to improve ductility of the steel. Above 0.08% of addition, the risk of formation of NbC or Nb(C,N) carbides increases to the detriment of the bendability.
• the niobium content is below or equal to 0.05%.
• Calcium may be also added as an optional element up to 0.1%. Addition of Ca at the liquid stage makes it possible to create fine oxides which promote castability of continuous casting.
• the remainder of the composition of the steel is iron and impurities resulting from the smelting.
• P, S and N at least are considered as residual elements which are unavoidable impurities.
• Their content is less than 0.010 % for S, less than 0.020 % for P and less than 0.010 % for N.
• a section of a coated steel sheet of the invention is schematically represented on Fig 3a and Fig 4a .
• the coated steel sheet comprises a bulk (2) topped by a decarburized layer (3) comprising in upper part a ferrite layer having a thickness from 1 ⁇ m to 100 ⁇ m (4), and a coating layer (1).
• the thickness of the ferrite layer is comprised from 20 ⁇ m to 100 ⁇ m. More preferably, the thickness of the ferrite layer is from 25 ⁇ m to 100 ⁇ m. More preferably the thickness of the ferrite layer is from 30 ⁇ m to 80 ⁇ m.
• the bulk of the coated steel sheet (2) has a microstructure comprising, in surface fraction, from 60% to 90% of ferrite, the rest being martensite-austenite islands, pearlite or bainite.
• This ferrite is formed during the intercritical annealing of the cold rolled steel sheet.
• the rest of the microstructure is austenite at the end of the soaking, which transform into martensite-austenite islands, pearlite or bainite during the cooling of the steel sheet.
• the decarburized layer present on top of the bulk is obtained during the annealing of the cold rolled steel sheet thanks to the control of the atmosphere in the furnace to set a dew point temperature strictly higher than -10°C and below or equal to 20°C.
• the coated steel sheet according to the invention can be produced by any appropriate manufacturing method and the man skilled in the art can define one. It is however preferred to use the method according to the invention comprising the following steps: A semi-product able to be further hot-rolled, is provided with the steel composition described above. The semi product is reheated at a temperature comprised from 1150°C to 1300°C.
• the steel sheet is then hot rolled at a finish hot rolling temperature comprised from 800°C to 950°C.
• the hot-rolled steel is then cooled and coiled at a temperature T coil lower than 670°C, and optionally pickled to remove oxidation.
• the ratio between the ferritic grain width in the interdiffusion layer GW int over prior austenite grain size in the bulk PAGS bulk satisfies following equation: GW int / PAGS bulk -1 ⁇ 30 % in order to improve bendability of the steel sheet, without deteriorating mechanical properties.
• the ferritic grain width is the average distance between two parallel grain boundaries of the interdiffusion layer, grain boundaries being oriented in the direction of the thickness of the sheet.
• the combination of annealing temperature T A , annealing time t A and dew point temperature T DP1 promotes the formation of large grain width GW int in the interdiffusion layer.
• the thermal treatment of the steel blank before the press forming rules the austenitic grain growth and so the PAGS in the bulk.
• the press hardened steel part may further comprise a martensite layer with a carbon gradient between the bulk and the interdiffusion layer, as represented by (8) in Fig 4b .
• a martensite layer with a carbon gradient between the bulk and the interdiffusion layer, as represented by (8) in Fig 4b .
• carbon diffuses from the bulk to the surface.
• the ferrite upper part of the decarburized layer is then transformed in a layer of austenite with a gradient of carbon.
• this layer of austenite with a gradient of carbon is transformed in a layer of martensite with a carbon gradient.
• the press hardened steel part according to the invention can be produced by any appropriate manufacturing method and the man skilled in the art can define one. It is however preferred to use the method according to the invention comprising the following steps: A coated steel sheet according to the invention is cut to a predetermined shape to obtain a steel blank. The steel blank is then heated to a temperature comprised from 880°C to 950°C during 10s to 900s to obtain a heated steel blank. The heated blank is then transferred to a forming press before being hot formed and die-quenched.
• Samples 1,2,5 and 6 did undergo a second annealing at a temperature T 2 before coating, the steel sheet being maintained at said T 2 temperature for a holding time t 2 , in an HNx atmosphere with 5% of H 2 and a controlled dew point.
• the following specific conditions were applied: Trial Steel Soaking Second soaking t A (s) T A (°C) T DP1 (°C) t 2 (s) T 2 (°C) T DP2 (°C) 1 A 135 850 10 70 800 0 2 B 135 850 10 70 800 0 3 C 240 755 -10 - - - 4 D 30 730 -40 - - - 5 E 10800 700 0 70 750 0 6 F 135 850 10 70 800 0
• the coated steel sheets were then cut to obtain a steel blank, heated at 900°C during 6 minutes and hot-formed.
• the steel parts were analyzed and the corresponding microstructure, ferritic grain width in interdiffusion layer GW int , and prior austenite grain size in the bulk PAGS bulk are gathered in table 4.
• Mechanical properties are gathered in Table 5.
• the surface fractions, ferritic grain width in the interdiffusion layer and PAGS are determined through the following method: a specimen is cut from the press hardened steel part, polished and etched with a reagent known per se, to reveal the microstructure. The section is afterwards examined through optical or scanning electron microscope, for example with a Scanning Electron Microscope with a Field Emission Gun ("FEG-SEM”) at a magnification greater than 5000x, coupled to a BSE (Back Scattered Electron) device.
• FEG-SEM Field Emission Gun
• Figure 3a represents a schematic section of the coated steel sheet of trial 2.
• the combination of process parameters of the invention, annealing temperature T A , annealing time t A and dew point temperature T DP1 allow to obtain a decarburized layer (3), in which a layer of ferrite is formed in the upper part (4).
• Fig 3b represents a schematic section of the press hardened steel part of trial 2.
• the grain width of ferrite formed in the interdiffusion layer (5) is a heritage of the pure ferrite layer in which austenite formation takes place during heating, with larger grain size.
• the interdiffusion layer grows on this large austenite grain size.
• the grain width of ferrite in the interdiffusion layer (6) is then larger than prior austenite grain size in the bulk (7), leading to good bendability with bending angle higher than 70°.
• Figure 4a represents a schematic section of the coated steel sheet of trial 1.
• annealing temperature T A annealing time t A and dew point temperature T DP1 allow to obtain a decarburized layer (3), in which a layer of ferrite is formed in the upper part (4), thicker than in trial 1 due to the higher C content.
• Fig 4b represents a schematic section of the press hardened steel part of trial 1.
• the grain width of ferrite formed in the interdiffusion layer (6) is a heritage of the pure ferrite layer in which austenite formation takes place during heating, with larger grain size.
• the interdiffusion layer grows on this large austenite grain size .
• the grain width of ferrite in the interdiffusion layer (6) is then larger than prior austenite grain size in the bulk (7), leading to good bendability with bending angle higher than 70°.
• a layer of martensite with a carbon gradient is formed between the bulk and the interdiffusion layer in the press hardened steel part, leading to tensile strength higher than 1500 MPa.
• the coated steel sheet has a decarburized layer, without ferrite layer in its upper part, as represented schematically in Fig 2a .
• the absence of ferrite layer is due to the low dew point temperature T DP1 of -10°C, which slow down the kinetics of the decarburization.
• Figure 2b represents a schematic section of the press hardened steel part from trial 3. Due to the absence of the ferrite layer, the ferritic grain width in the interdiffusion layer (6) is then equivalent to prior austenite grain size in the bulk (7), leading to a low bending angle below 70°.
• the low dew point temperature T DP1 of -40°C implies an absence of the decarburized layer and ferrite layer in the coated steel sheet.
• Fig 1a represents a schematic section of the coated steel sheet of this trial, with the coating layer (1) and the bulk (2).
• Figure 1b represents a schematic section of the press hardened steel part from trial 4. Due to the absence of the ferrite layer, the ferritic grain width in the interdiffusion layer (6) is then equivalent to prior austenite grain size in the bulk (7), leading to a low bending angle below 70°.
• Fig 5a represents a schematic section of the coated steel sheet of trial 5, with the coating layer (1) the decarburized layer (3), the thicker ferrite layer (4) with coarser grain size, and the bulk (2).
• Fig 5b represents a schematic section of the press hardened steel part from trial 5.
• the microstructure of the bulk is austenitic, and the thick ferrite layer is transformed in a layer of austenite with gradient of carbon. But due to the thickness of the ferrite layer higher than 100 ⁇ m, a layer of ferrite remains present between the interdiffusion layer and the layer of austenite with gradient of carbon.
• the ferrite layer is still present and the layer of austenite with carbon gradient transforms into a martensite layer with gradient of carbon, leading to a multi-phased layer. This triggers a decrease of yield strength.
• the steel sheet has a low carbon level of 0.21%. This low carbon content combined to the process parameters, leads to a decarburized layer in the coated steel sheet with the ferrite layer. Nevertheless, the yield strength and tensile strength of the press hardened steel part are not achieved because of the low level of carbon.

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