Global Patent Index - EP 2690183 A1

EP 2690183 A1 20140129 - Hot-rolled steel flat product and method for its production

Title (en)

Hot-rolled steel flat product and method for its production

Title (de)

Warmgewalztes Stahlflachprodukt und Verfahren zu seiner Herstellung

Title (fr)

Produit plat en acier laminé à chaud et son procédé de fabrication

Publication

EP 2690183 A1 20140129 (DE)

Application

EP 12178330 A 20120727

Priority

EP 12178330 A 20120727

Abstract (en)

Hot-rolled flat steel product comprises 0.1-0.6 wt.% carbon, 0.4-2 wt.% silicon, up to 2 wt.% aluminum, 0.4-2.5 wt.% manganese, up to 1 wt.% nickel, up to 2 wt.% copper, up to 0.4 wt.% molybdenum, up to 2 wt.% chromium, up to 0.2 wt.% titanium, up to 0.2 wt.% niobium, up to 0.5% vanadium, iron and unavoidable impurities. The structure of the flat steel product comprises optionally up to 5 vol.% ferrite, up to 10 vol.% martensite, at least 60 vol.% bainite and balance of residual austenite. At least a part of the residual austenite is present in block form. Hot-rolled flat steel product comprises 0.1-0.6 wt.% carbon, 0.4-2 wt.% silicon, up to 2 wt.% aluminum, 0.4-2.5 wt.% manganese, up to 1 wt.% nickel, up to 2 wt.% copper, up to 0.4 wt.% molybdenum, up to 2 wt.% chromium, up to 0.2 wt.% titanium, up to 0.2 wt.% niobium, up to 0.5% vanadium, iron and unavoidable impurities. The structure of the flat steel product comprises optionally up to 5 vol.% ferrite, up to 10 vol.% martensite, at least 60 vol.% bainite and balance of residual austenite. At least a part of the residual austenite in block form and blocks of the austenite present in block form to at least 98% exhibits an average diameter of less than 5 mu m. The flat steel product exhibits a product of tensile strength and elongation of at least 18000 Mpa.%. An independent claim is also included for producing the flat steel product, comprising providing an intermediate product in the form of a slab, thin slab or cast strip, which comprises 0.1-0.6 wt.% carbon, 0.4-2 wt.% silicon, up to 2 wt.% aluminum, 0.4-2.5 wt.% manganese, up to 1 wt.% nickel, up to 2 wt.% copper, up to 0.4 wt.% molybdenum, up to 2 wt.% chromium, up to 0.2 wt.% titanium, up to 0.2 wt.% niobium, up to 0.5% vanadium, iron and unavoidable impurities, hot rolling the intermediate product to form a hot strip in at least one roll stitch, accelerating cooling of the resulting hot strip at a cooling rate of at least 5[deg] C/second to a coiling temperature, which lies in the region between the martensite starting temperature and 600[deg] C, coiling the hot strip to form a coil, and cooling the coils, where (a) the temperature of the coil during cooling to form bainite is maintained at a temperature range with upper limit and lower limit until at least 60 vol.% structure of the hot strip is made of bainite, (b) the upper limit is equal to the bainite starting temperature for producing bainite in the structure of the hot strip, and lower limit is equal to the martensite starting temperature for producing martensite in the structure of the hot strip, and (c) the resulting hot strip on leaving the last roll stitch, exhibits a final hot-rolling of at least 880[deg] C.

Abstract (de)

Die Erfindung betrifft ein warmgewalztes Stahlflachprodukt mit einem Produkt aus Rm und A80 ‰¥ 18000 MPa*%, einer Zusammensetzung, die aus (in Gew.-%) C: 0,10 - 0,60 %, Si: 0, 4 - 2,0 %, Al: ‰¤ 2,0 %, Mn: 0,4 - 2,5 %, Ni: ‰¤ 1 %, Cu: ‰¤ 2,0 %, Mo: ‰¤ 0,4 %, Cr: ‰¤ 2 %, Ti: ‰¤ 0,2 %, Nb: ‰¤ 0,2 %, V: ‰¤ 0,5 %, Rest Fe und unvermeidbaren Verunreinigungen besteht, und einem Gefüge, das (in Vol.-%) aus ‰¤ 5 % Ferrit, ‰¤ 10 % Martensit, ‰¥ 60 % Bainit und als Rest aus Restaustenit besteht, wobei zumindest ein Teil des Restaustenits blockigförmig ist und ‰¥ 98 % der Restaustenit-Blöcke ‰¤ 5 µm groß sind. Zur Herstellung des Stahlflachprodukts wird eine Bramme, Dünnbramme oder ein gegossenes Bands mit der genannten Zusammensetzung bereitgestellt, das Vorprodukt mit einer Warmwalzendtemperatur ‰¥ 880 °C zu einem Warmband warmgewalzt, das erhaltene Warmband mit einer Abkühlrate ‰¥ 5 °C/s auf eine zwischen der Martensitstarttemperatur MS und 600 °C liegende Haspeltemperatur abgekühlt, das Warmband zu einem Coil gehaspelt und im Coil abgekühlt, wobei die Temperatur des Coils solange zwischen der Bainitstarttemperatur BS und der Martensitstarttemperatur MS gehalten wird, bis ‰¥ 60 Vol.-% des Warmbandgefüges aus Bainit bestehen.

IPC 8 full level

C21D 1/20 (2006.01); C22C 38/04 (2006.01); C22C 38/28 (2006.01); C22C 38/50 (2006.01)

CPC (source: CN EP KR US)

C21D 1/20 (2013.01 - CN EP KR US); C21D 6/004 (2013.01 - CN EP US); C21D 6/005 (2013.01 - CN EP US); C21D 6/008 (2013.01 - CN EP US); C21D 8/0226 (2013.01 - CN EP US); C21D 8/0263 (2013.01 - CN EP US); C21D 8/0463 (2013.01 - CN EP KR US); C22C 38/00 (2013.01 - EP US); C22C 38/02 (2013.01 - CN KR US); C22C 38/04 (2013.01 - CN EP KR US); C22C 38/06 (2013.01 - CN EP US); C22C 38/16 (2013.01 - CN EP US); C22C 38/18 (2013.01 - CN EP US); C22C 38/22 (2013.01 - CN EP US); C22C 38/28 (2013.01 - CN EP KR US); C22C 38/34 (2013.01 - CN US); C22C 38/42 (2013.01 - CN US); C22C 38/46 (2013.01 - CN US); C22C 38/50 (2013.01 - CN US); C22C 38/58 (2013.01 - CN KR US); C21D 2211/001 (2013.01 - CN EP US); C21D 2211/002 (2013.01 - CN EP US)

Citation (applicant)

  • EP 1466024 B1 20070725 - ARCELOR FRANCE [FR]
  • DE 60315129 T2 20080410 - ARCELOR FRANCE [FR]
  • US 2009107588 A1 20090430 - ALLAIN SEBASTIEN [FR], et al
  • US 6190469 B1 20010220 - KOH HYANG JIN [KR], et al
  • H.K.D.H. BHADESHIA; D.V. EDMONDS: "Bainite in silicon steels: new composition-property approach", METAL SCIENCE, vol. 17, September 1983 (1983-09-01), pages 411 - 419,420-425
  • H. BHADESHIA: "Thermodynamic Exatrapolation and Martensite-Start-Temperature of Substitutionally Alloyed Steels", METAL SCIENCE, vol. 15, 1981, pages 178 - 180

Citation (search report)

  • [X] US 6364968 B1 20020402 - YASUHARA EIKO [JP], et al
  • [AD] US 2009107588 A1 20090430 - ALLAIN SEBASTIEN [FR], et al
  • [A] JP H01159317 A 19890622 - NIPPON STEEL CORP
  • [A] CABALLERO F G ET AL: "Theoretical design and advanced microstructure in super high strength steels", MATERIALS AND DESIGN, LONDON, GB, vol. 30, no. 6, 1 June 2009 (2009-06-01), pages 2077 - 2083, XP026079028, ISSN: 0261-3069, [retrieved on 20080912], DOI: 10.1016/J.MATDES.2008.08.042

Designated contracting state (EPC)

AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

Designated extension state (EPC)

BA ME

DOCDB simple family (publication)

EP 2690183 A1 20140129; EP 2690183 B1 20170628; BR 112015001456 A2 20170704; CN 104662179 A 20150527; CN 104662179 B 20180112; JP 2015528064 A 20150924; JP 6154010 B2 20170628; KR 20150038426 A 20150408; US 2015203946 A1 20150723; WO 2014016420 A1 20140130

DOCDB simple family (application)

EP 12178330 A 20120727; BR 112015001456 A 20130726; CN 201380049258 A 20130726; EP 2013065836 W 20130726; JP 2015523568 A 20130726; KR 20157005074 A 20130726; US 201314417685 A 20130726