Classifications

• • 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
  • C22C38/02—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
  • C22C38/14—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
  • C21D2211/001—Austenite
• • 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
• • 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
  • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, 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 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

Definitions

• the invention relates to a high-strength and very deep-drawable duplex or triplex lightweight steel and its use.
• High-strength steel is developed for the automotive industry, construction industry and in aerospace applications with different properties and is already used in production.
• the desire to reduce the weight of the vehicle through new materials is becoming increasingly important.
• the aim is to manufacture lighter steel alloys, which otherwise maintain or further improve the previous favorable properties.
• high-strength lightweight steels which have a higher proportion of aluminum, chromium and nickel and manganese and as a result which have a lower density than iron.
• the steel alloy is characterized by good corrosion and stress corrosion cracking resistance as well as high strength.
• Such steels have aluminum contents of up to 10% by weight.
• the austenitic or austenitic / ferritic lightweight steel has a composition with 7-27% by weight Mn, 1-10% by weight Al, less than 10% by weight Cr, less than 10% by weight Ni, more than 0.7-4% by weight of Si, less than 3% by weight of Cu, less than 0.5% by weight of C and a remaining composition of iron and melting-related impurities.
• the other alloy components can consist of small amounts of nitrogen, niobium, titanium, vanadium and phosphorus.
• the known lightweight steels listed above have important advantageous properties for use in the mentioned technology areas, but these are associated with significant disadvantages. Further weight savings, for example in the automotive industry, can only be achieved with the known steels by further reducing the sheet thickness or by additional design measures. Well-formable, ie deep-draw and stretch-drawable, cold-rollable and recrystallized annealed deep-drawing steels with a higher aluminum content, such as are required in particular for use in automotive engineering, are not known in this form due to the still too high specific density from the prior art.
• the object of the invention is to create a highly stable lightweight steel which is easy to form, in particular deeply and extensible, the density of which is below the specific density of previously known steels.
• the solution according to the invention relates to a high-strength ⁇ / ⁇ -
• the proportions of the elements Mg, Ga and Be, if present, are each greater than 0.3%.
• the elements N, Nb, V and possibly Ti with the following proportions are preferably used as further alloy elements:
• the lightweight steel according to the invention is formed from a multi-phase structure in the case of duplex steel from ⁇ -ferrite and ⁇ -austenite mixed crystals. In the case of triplex steel, an artensitic ⁇ phase and / or K phase is added to the first two phases.
• the specific weight of the steel according to the invention is reduced to low values by the high proportions of the light alloy elements Al, Si, C and Mn and at least one of the elements Mg, Ga, Be and possibly Ti.
• a density below 7 g / cm 3 is achieved with both alloys, which is significantly reduced by up to 15% compared to conventional steels with values between 7.3 and 7.5 g / cm 3 .
• the solution according to the invention also has a further reduction in density compared to the lightweight steels known from the literature with up to 8% aluminum content.
• the lightweight steel according to the invention achieves one through the element Mg, insofar as it is present in the alloy further lowering of its density due to the very low specific weight of Mg.
• Be insofar as it is present in the alloy, an additional increase in strength being achieved here, which can be achieved while maintaining the ductility.
• the element Ti is present in the alloy, a further increase in strength is achieved through grain refinement and mixed crystal hardening.
• the element Ga if present in the alloy, also serves to increase strength and hardness. In addition, it increases the castability of the alloy, since the proportion of Ga makes it more liquid at comparable temperature conditions.
• duplex or triplex lightweight steel according to the invention is characterized in the cold-rolled and recrystallized state by a fine-grained two- or three-phase structure with an equiaxial i.e. isotropic morphology of the ⁇ -ferrite, ⁇ -austenite or ⁇ -martensite grains.
• the respective fine-grained two-phase or three-phase structure increases the energy absorption - the dissipative energy - of this steel when subjected to stress at high expansion speeds, such as occurs due to impact loads or in the event of a crash.
• the lightweight steel is characterized by yield stresses of over 400 MPa. Due to a high degree of solidification due to strong interaction of the dislocations of the coexisting / ⁇ - or ⁇ / ⁇ / ⁇ (K) phases, tensile strengths on the hot strip of up to 1000 MPa are achieved and uniform strains up to 40% and maximum strains up to 50%.
• the recrystallizing annealed cold strip has strengths in the range of 900 MPa with maximum elongations of 70%.
• the significantly lower density than conventional steels is particularly advantageous.
• the lightweight steel according to the invention also has a previously unknown density reduction compared to the lightweight steel with aluminum components known from the prior art.
• Another advantage of the solution according to the invention is that, despite its high strength, the material has very good formability. These properties had previously only been achieved with high-alloy stainless steel. Particularly noteworthy is its pourability during processing, which, as already mentioned, is further improved in the presence of Ga.
• the ⁇ / ⁇ duplex or ⁇ / ⁇ / ⁇ (K) triplex lightweight steel according to the invention thus results in a further improvement in the combination of previously unknown advantageous properties.
• the lightweight steel Due to the high proportion of alloy components with a specific weight below the specific weight of iron and previously known lightweight steels, one for the Auto industry achieved advantageous weight reduction while maintaining the previous design. Furthermore, the lightweight steel has excellent ductility, high strength and an extremely high hardening rate. The property of a high loading speed in the crash behavior in the event of an accident should be emphasized, so that this steel alloy is particularly suitable for motor vehicle construction. Furthermore, there is an increased resistance to corrosion and, in particular, stress crack corrosion, so that this steel alloy is also suitable for use in other technological areas, for example in construction.
• the lightweight steels according to the invention can be used excellently, in particular as prestressed concrete steels and reinforcing bars (steel) or guard rails and sheet piling.
• the corrosion resistance can further be improved by chemical, electrochemical, organic, non-metallic or metallic coatings.
• a protective cover layer can be achieved by enriching and / or coating the surface with aluminum.
• the deep- and stretch-drawable aluminum-containing steel is melted in the manufacturing process, cast in the continuous casting process, rolled in the temperature range above the recrystallization temperature or preferably by casting rolling, thin strip casting, cast as a strip close to the final dimension.
• the steel can either be directly processed as hot strip or can be cold rolled after hot rolling.
• the lightweight steel according to the invention is particularly suitable for component production for body-in-white components / body, integral beams, chassis structures and space frames.
• Other lightweight components in motor vehicles are steering, axles and axle components, add-on parts, seat rails, fastening parts and systems for passive safety, wheel suspensions, drive train and fuel tanks.
• the area of application also extends to rail and water vehicles as well as in aerospace, there preferably in thin-walled components relevant to rigidity.
• the material is also suitable for conveyor systems, conveyor belts and in metallurgy.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
• Body Structure For Vehicles (AREA)
• Treatment Of Steel In Its Molten State (AREA)
• Heat Treatment Of Sheet Steel (AREA)

Applications Claiming Priority (5)

Publications (2)

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• 2002
  • 2002-09-25 EP EP02800111A patent/EP1430161B1/fr not_active Expired - Lifetime
  • 2002-09-25 JP JP2003532715A patent/JP2005504175A/ja active Pending
  • 2002-09-25 WO PCT/EP2002/010679 patent/WO2003029504A2/fr active Application Filing
  • 2002-09-25 ES ES02800111T patent/ES2242899T3/es not_active Expired - Lifetime
  • 2002-09-25 US US10/491,055 patent/US20070125454A1/en not_active Abandoned
  • 2002-09-25 AT AT02800111T patent/ATE298009T1/de not_active IP Right Cessation

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