Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/041—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing involving a particular fabrication or treatment of ingot or slab
  • C21D8/0415—Rapid solidification; Thin strip casting
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
  • C21D8/0426—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
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
  • C21D8/0473—Final recrystallisation annealing
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
• • C—CHEMISTRY; METALLURGY
  • 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
  • C21D2211/008—Martensite

Definitions

• the invention relates to a method for producing steel flat products, such as strips or sheet metal blanks, from high-strength, aluminum-alloyed steels.
• steels belong to the group of multiphase steels. These are usually steels whose properties are determined by the type, amount and arrangement of the phases of the structure.
• the structure therefore has at least two phases (eg ferrite, martensite, bainite). This gives them a strength / formability combination that is superior to conventional steels.
• This preparation route presents problems in particular when casting peritectically solidifying compositions.
• These steel grades there is the danger of the formation of longitudinal cracks during continuous casting.
• the formation of such longitudinal cracks can reduce the quality of the hot strips produced from the cast slabs or thin slabs so much that they become unusable.
• extensive measures such as increased insulation costs, are required, which can go so far that the processing of such steel grades becomes uneconomical.
• multiphase steels are of particular interest for the automotive industry because of their high strength, they allow the use of lower material thicknesses and concomitantly a reduction in vehicle weight and, secondly, the safety of the vehicle body in the event of a collision (crash behavior) ,
• multiphase steels with at least constant strength of the overall body allow a reduction in the sheet thickness of a component produced from such multiphase steels compared to a body produced from conventional steels.
• multiphase steels are melted in the converter steelworks and cast on a continuous casting plant into slabs or thin slabs, which are then hot rolled into hot strip and coiled.
• the mechanical properties of the hot strip can be varied.
• the hot strips can be cold-rolled to cold-rolled strip in order to provide thinner sheet-metal thicknesses (EP 0 910 675 B1, EP 0 966 547 B1, EP 1 169 486 B1, EP 1 319 725 B1, EP 1 398 390 A1).
• the cast strip is then hot rolled in-line in one or more passes of between 25% and 70% strain to a hot strip.
• the final temperature of hot rolling is above the Ar 3 temperature.
• the hot strip obtained is then cooled in two stages. In the first stage of this cooling, a cooling rate of 5 -
• the object of the invention was therefore to provide a method by means of which high-strength steel flat products can be produced over a wide range of geometric dimensions with reduced manufacturing outlay.
• this object has been achieved by a method for producing steel flat products, in which a multiphase structure forming steel, the (in wt .-%) 0.10 - 0.14% C, 1 , 30 - 1.70% Mn, up to 0.030% P, up to 0.004% S, 0.10 - 0.30% Si, 0.90 - 1.2% Al, up to 0.0070% N, 0.070 0.130% Ti, 0.040-0.060% Nb, 0.140-0.260% Mo and the remainder contains iron and unavoidable impurities, is cast into a cast strip with a thickness of 1-4 mm, in which the cast strip in a continuous operation a degree of deformation of more than 20% in-line at a lying in the range of 850 - 1000 0 C hot rolling end temperature is hot rolled to a hot strip with a thickness of 0.5 - 3.2 mm and the
• the hot strip at a 350 - 480 0 C forming amount coiling temperature is coiled, so that a hot strip is obtained, the tensile strength R m of at least 800 MPa at an elongation at break A 8 o of at least 5%.
• the invention uses the possibility of strip casting to process a particularly high-strength, peritectically solidifying multiphase steel into a hot strip. Since the cast strip itself already has a small thickness, in the course of hot rolling of this strip only relatively low degrees of deformation must be maintained in order to produce flat products with small thicknesses, as are required in particular in the automotive industry. Thus, by specifying a corresponding output thickness of the cast strip, it is easily possible to produce hot strips with the method according to the invention, which have a maximum property distribution of at most 1.5 mm and from which, for example, elements for the support structure of an automobile can be produced.
• the invention makes it possible to manufacture high-strength hot strips consisting of a martensitic steel of the specified composition processed according to the invention, whose width is more than 1,200 mm, in particular more than 1,600 mm.
• a further particular advantage of the procedure according to the invention is that hot strip produced according to the invention has high strengths of at least 800 MPa, without having to observe a special cooling cycle of the hot strip between the end of the hot rolling and the hasp, as described in EP 1 072 689 Bl is required by the need for a cooling break.
• it merely has to be ensured that the hot rolling ends in a relatively narrow temperature window and that the reeling is also carried out in a precisely defined temperature range. In between there is a one-stage cooling down.
• Hot strips produced according to the invention are particularly suitable for further processing into cold rolled strip. Accordingly, a practice-oriented embodiment of the invention provides that the hot strip is cold rolled to a cold strip having a thickness of 0.5-1.4 mm, in particular 0.7 mm to 1.3 mm, as is required for the construction of automobile bodies. In order to eliminate arising during cold hardening, the cold strip is at an annealing temperature from 750 to 850 0 C to be annealed. For cold rolled strip produced in this way from the hot strip produced according to the invention, tensile strengths of at least 800 MPa can be reliably ensured. The breaking elongation A 50 of the cold strip is just as safe at least 10%.
• the flat product produced according to the invention is characterized by a particularly good coatability.
• the cold strip is provided in a conventional manner with a metallic coating, which may be, for example, a galvanizing.
• the strength and elongation values according to the invention produced hot strips can be adjusted over a wide range by an appropriate vote of the hot rolling and reel temperatures.
• R m tensile strength
• the tapes cast from steels A and B were hot rolled into a hot strip whose thickness was 1.25 mm in four different trials immediately after in-line strip casting at a hot rolling end temperature WET. Subsequently, each hot strip obtained has been cooled directly in a cooling step to a coiler temperature HT and coiled. After coiling, the hot strips produced from steels A and B each had a tensile strength R m and an elongation at break A 80 , which, like the hot rolling end temperature WET and reel temperature HT, respectively, maintained in their preparation, are given in Table 2.
• the tensile strength R m of the cold strip thus obtained was 985 MPa.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Coating With Molten Metal (AREA)
• Metal Rolling (AREA)
• Heat Treatment Of Steel (AREA)
• Treatment Of Steel In Its Molten State (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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Citations (6)

Family Cites Families (7)

• 2006
  • 2006-10-30 PL PL06123140T patent/PL1918404T3/pl unknown
  • 2006-10-30 DE DE502006003832T patent/DE502006003832D1/de active Active
  • 2006-10-30 ES ES06123140T patent/ES2325963T3/es active Active
  • 2006-10-30 AT AT06123140T patent/ATE432374T1/de active
  • 2006-10-30 EP EP06123140A patent/EP1918404B1/de not_active Not-in-force
• 2007
  • 2007-10-24 KR KR1020097007486A patent/KR101461584B1/ko active IP Right Grant
  • 2007-10-24 CN CN2007800393899A patent/CN101528966B/zh not_active Expired - Fee Related
  • 2007-10-24 WO PCT/EP2007/061391 patent/WO2008052920A1/de active Application Filing
  • 2007-10-24 US US12/447,627 patent/US20100065162A1/en not_active Abandoned
  • 2007-10-24 JP JP2009533823A patent/JP5350254B2/ja not_active Expired - Fee Related

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Non-Patent Citations (2)

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