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
  • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous 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
  • B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
• • 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
  • B22D11/12—Accessories for subsequent treating or working cast stock in situ
  • B22D11/1213—Accessories for subsequent treating or working cast stock in situ for heating or insulating strands
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
• • C—CHEMISTRY; METALLURGY
  • 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
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
• • 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
  • 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

Definitions

• the invention relates to a method for producing a hot-rolled steel flat product from a high-strength, high-ductile manganese steel, which in addition to a high Mn content has a 5.9-11.5 wt .-% amount of Al content.
• Vehicle construction in particular the construction of automobile body or chassis parts are suitable.
• Recrystallization inertia of the cooler band edges can form cracks.
• the steels counteract hot and cold rolling with extremely high hot or cold rolling resistances, which are significantly higher than with other high-alloy steels, such as RSH steels or conventional high-alloy Mn steels.
• US Pat. No. 7,794,552 B2 discloses a method for producing a flat steel product from such a conventionally composed, austenitic, high manganese-containing hot rolled steel, which, in addition to iron and unavoidable impurities (in% by weight), has a content of 0.85-1.05% C, 16.
• the strength of the known steel made in this way should be more than 1200 MPa and the product of strength and strength
• a correspondingly composed molten steel is poured into a preliminary product, which may be a slab, thin slab or a cast strip.
• the precursor is heated to a temperature of 1100-1300 ° C and hot rolled at a hot rolling end temperature of at least 900 ° C to a hot strip. If necessary, then sufficient for the desired complete recrystallization of the strip surface
• the resulting hot strip is then at least 20 ° C / s amount
• the hot strip thus produced can then in one or more cold rolling steps if necessary intermediate annealing be rolled into a cold strip.
• Deoxidation can be used, however, the Al content is limited to at most 0.05 wt .-% in order to avoid the precipitation of A1N. Accordingly, the presence of AIN precipitates is expected to entail the risk of cracking during deformation of the steel strip produced in the known manner.
• the object of the invention was a
• hot-rolled steel flat product first melted a steel, in addition to iron and unavoidable
• Impurities (in% by weight) C: 0.5-1.3%, Mn: 18-26%, Al: 5.9-11.5%, Si: less than 1%, Cr: less than 8% , Ni: less than 3%, Mo: less than 2%, N: less than 0.1%, B: less than 0.1%, Cu: less than 5%, Nb: less than 1%, Ti: less than 1%, V: less than 1%, Ca: less than 0.05%, Zr: less than 0.1%, P: less than 0.04%, S: less than 0.04%.
• the contents of the alloying elements Si, Cr, Ni, Mo, N, B, Cu, Nb, Ti, V, Ca, Zr, P and S are in each case alone or in combination with one another as follows
• Composite molten steel is then cast in a conventional two-roll casting machine in a conventional manner to a cast strip, for example.
• Horizontal feed direction is redirected, so the cast strip on its way from the casting machine to the heating device typically with a cools
• Cooling rate of 10 - 20 K / s to a usually not less than 700 ° C amounts Intermediate temperature. According to the invention this
• Hot rolling start temperature is carried out according to the invention with a minimum of 20 K / s amounts
• the cast strip heated so rapidly to the hot rolling start temperature is then hot rolled in one or more passes to form a hot strip.
• a cooling in which the hot strip obtained is cooled at a cooling rate of at least 100 K / s to ⁇ 400 ° C. Due to this rapid cooling, the formation of embrittling constituents, such as carbides or
• the invention is based on the recognition that the
• Steel flat product made of a steel having high contents of C, Mn and Al succeeds when a thin, not more than 5 mm, in particular 3 - 5 mm thick strip is cast from a correspondingly composed melt.
• the thickness of the cast strip is thus already in the range of thickness, which should have the finished hot-rolled product.
• Cross cracks and star cracks do not occur when casting the cast strip and longitudinal cracks only in greatly reduced numbers.
• the occurrence of core segregations can be controlled by varying the casting roll force.
• the thin, according to the invention only max.
• the cast tape can be
• Peripheral zones and globulitic nucleus Peripheral zones and globulitic nucleus.
• the cast strip is heated to the required, 1100 - 1300 ° C hot rolling start temperature while making maximum use of the inherent in leaving the casting machine casting heat.
• the heating takes place as quickly as possible, especially with a
• the temperature distribution across the width of the band can be adjusted.
• the heating may also be carried out that is across the width of the cast strip
• Hot rolling start temperature is particularly suitable for an inductively operating heating device, as they
• Contact time can be heated to a relatively precise predetermined temperature can.
• Hot rolling start temperature is chosen so that the
• Hot rolling carried out according to the invention is typically in the range from 1000 to 1050 ° C. This proviso is based on the finding that the steels processed according to the invention, due to their high
• the hot rolling of the cast strip in-line on strip casting reduces the process and material-specific core porosity of the cast strip, promotes the homogeneity of the microstructure and thus improves the overall ribbon properties.
• Hot rolling only comparatively low degrees of deformation must be achieved. These are typically at least 10%, in particular 10-20%. Such low degrees of deformation can be achieved in one pass, which helps to optimize the economy of the machine
• the rapid cooling carried out after hot rolling at a cooling rate of at least 100 K / s ensures that no grain growth takes place in the hot-rolled strip after leaving the last hot-rolling mill.
• the cooling rates achieved with the cooling performed after hot rolling are in the range of 100 to 250 K / s.
• cooling should take place as close as possible to the end of hot rolling, but no later than within 10 seconds.
• Protective gas atmosphere can be performed.
• An inerting of the molten metal region of the molten steel which is to be cast there in the respective strip casting device reduces the formation of oxide deposits on the surfaces.
• the hot strip obtained according to the invention has a
• austenitic-ferritic structure with a ferrite content which is typically 5 - 50%.
• Carbon can in a steel according to the invention in
• the C content is above 0.5 wt .-%.
• the C content is significant for austenite formation and strength due to solid solution hardening, increase in stacking fault energy, and formation of carbides. If the hot strip produced according to the invention is cold rolled to form a cold strip, an extremely fine carbide can be precipitated on the cold strip to improve the yield strength of the cold strip by a specific overaging treatment after a final recrystallization annealing. At above 1.2 wt .-% lying C levels, there is a risk that carbides are produced in embrittlement effective amounts.
• Manganese is present in a steel processed according to the invention in contents of 18-26% by weight. Manganese is
• a steel processed according to the invention has 5.9-11.5% by weight, in particular> 6-11.5% by weight, Al.
• Aluminum reduces the density, acts as a solid solution and increases the stacking fault energy. Aluminum also has a passivating effect and increases the
• Si can be present in a steel processed according to the invention in amounts of less than 1% by weight, in particular 0.1-0.4% by weight, in order to obtain a
• Cr, Ni and Mo likewise have a solid-solution hardening effect and improve the oxidation and corrosion resistance of the steel processed according to the invention.
• Cr leads to the formation of special carbides which can be highly embrittling if the contents are too high.
• Optimally usable are the positive effects of Cr, Ni and Mo, if, as predetermined by the invention, in an inventive processed the Cr content to less than
• Nitrogen forms nitrides with aluminum and acts
• the N content of a steel according to the invention is N ⁇ 0.1% by weight, in particular 0.005-0.04% by weight,
• the B content of a steel according to the invention is up
• the Cu content is one according to the invention
• micro-alloying elements Nb, Ti and V lead to it
• Processed steel non-metallic materials such as A1 2 0 3 and FeS and improves the ductility.
• the formation of Ca aluminates transfers clay to the slag and improves the degree of purity.
• Zr acts in accordance with the invention processed steel microcrystalline. Because Zr but due to
• Grain boundary segregations also has an embrittling effect, the content of a steel processed according to the invention is limited to this element.
• Annealing 1100 - 1200 ° C annealing temperature is annealed. If the hot strip annealing takes place in a continuous annealing furnace, annealing times of 60 - 300 s are required. Such a hot strip annealing is particularly useful when the Al content of the steel processed according to the invention
• At least 10 wt .-% is.
• Cooling rate of at least 40 K / s expire.
• the hot strip obtained according to the invention can optionally pickled in the usual manner after coiling and in
• a cold rolling and a final recrystallization annealing condenses and homogenizes, for example, the microstructure in the core region.
• the hot strip produced according to the invention can accordingly be processed in a manner known per se in one or more passes to form a cold strip. This may turn, if necessary
• the high hot rolling and cold rolling resistance inherent in the steel according to the invention has only insignificant effects on hot and cold rolling due to the already close to final cast strip and the concomitantly small deformations required. This makes it possible, even from the problematic in terms of their rolling processing steels according to the invention
• the invention is based on
• the figure shows schematically a production line 1 for producing a hot strip W.
• the production line 1 set up for a continuous production process comprises a conventional two-roll casting device 1, in which a melt S in between two counter-rotating Casting 2.3 limited pouring gap is cast into a cast strip G whose thickness is typically
• exiting cast strip G is in a conventional manner via a strand guide in a
• deflected horizontal conveying direction F in which it arranged by means of a at the end of the strand guide
• the casting belt G which is oriented in the conveying direction F, enters a heating device 5. On its way to the heating device 5, the cast strip G cools to an intermediate temperature at a cooling rate of 10 - 20 K / s.
• Inductors 6 inductively heated to a hot rolling start temperature, which is typically in the range of 1100 - 1300 ° C, in particular at least 1150 ° C.
• the temperature increase of the cast strip G as it passes through the heating device as a result of the action of the electromagnetic field generated by the inductors 6 is up to 300 ° C, typically 50-150 ° C.
• the inductors 6 can, as
• the two-roll caster 1, the strand guide, the conveyor 4 and the heating device 5 are kept under a protective gas atmosphere S.
• the cast strip G enters a roll stand 9, where it is hot rolled in one pass to a hot strip W having a thickness of typically 2.4 to 4.5 mm.
• the conveying direction F leaves the last rolling stand 9, in this case is regularly in the range of 1000 - 1050 ° C.
• the degrees of deformation achieved over the one rolling pass are regularly in the range of 10 to 30%.
• the hot strip W obtained is cooled in a cooling device 10 at a cooling rate, which is typically 100-200 K / s, to a coiler temperature lying in the range of 300-400 ° C., with the the hot strip W is then wound in a coiler 11 to a coil C.
• At the reeling can join a hot strip annealing in a heat treatment device, not shown here.
• the strips G cast from the slits Sl-S3 are cooled on the way to the heating device 5 at a cooling rate of approximately 15 K / s each and heated in the heating device 5 by a temperature increase ⁇ to the respective hot rolling start temperature WAT and in the hot rolling mill 9 in FIG three stitches at one
• the hot strip produced from the steel S3 is after the
• Reels were additionally subjected to hot strip annealing at 1100 ° C. in a continuous annealing furnace for 120 s. In this way, even with the hot strip produced from this steel S3, despite its particularly high C, Mn and Al content, surface defects could be reliably prevented.
• Table 3 shows the microstructure as well as the mechanical

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Metallurgy (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Physics & Mathematics (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Heat Treatment Of Steel (AREA)
• Metal Rolling (AREA)
• Continuous Casting (AREA)

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• 2011
  • 2011-01-11 DE DE102011000089A patent/DE102011000089A1/de not_active Withdrawn
  • 2011-12-14 EP EP11794191.4A patent/EP2663411B1/de not_active Not-in-force
  • 2011-12-14 MX MX2013007874A patent/MX345374B/es active IP Right Grant
  • 2011-12-14 WO PCT/EP2011/072671 patent/WO2012095232A1/de active Application Filing
  • 2011-12-14 CA CA2823095A patent/CA2823095C/en not_active Expired - Fee Related
  • 2011-12-14 ES ES11794191.4T patent/ES2625281T3/es active Active
  • 2011-12-14 CN CN201180064797.6A patent/CN103328120B/zh not_active Expired - Fee Related
  • 2011-12-14 BR BR112013017753A patent/BR112013017753A2/pt not_active Application Discontinuation
  • 2011-12-14 JP JP2013548768A patent/JP2014505172A/ja active Pending
  • 2011-12-14 US US13/978,969 patent/US20140007992A1/en not_active Abandoned
  • 2011-12-14 RU RU2013137456/02A patent/RU2554265C2/ru active
  • 2011-12-14 KR KR1020137021027A patent/KR20130100215A/ko active Search and Examination

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