Thyssenkrupp Steel Europe Ag

Jfe Steel Corporation

Thyssenkrupp Steel Ag

Jian Bian

Thomas Heller

Hiroshi Matsuda

Yasushi Tanaka

Yasunobu Nagataki

Kohei Hasegawa

Akio Kobayashi

Shusaku Takagi

Kenji Kawamura

Jens-Ulrik Becker

Taro Kizu

Brigitte Hammer

Rudolf Schoenenberg

Harald Hofmann

Sabine Zeizinger

Richard Georg Thiessen

Rolf Bode

Günter Stich

Evgeny Balichev

Thomas Rieger

Brigitte Bode, Legal Representative

Giovanni Sabatino

Axel Grafen

Rudolf Schönenberg

Oliver Bulters

Oliver Bülters

A flat steel product having a tensile strength of at least 1200 MPa and consists of steel containing (wt %) C: 0.10-0.50%, Si: 0.1-2.5%, Mn: 1.0-3.5%, Al: up to 2.5%, P: up to 0.020%, S: up to 0.003%, N: up to 0.02%, and optionally one or more of the elements 'Cr, Mo, V, Ti, Nb, B and Ca' in the quantities: Cr: 0.1-0.5%, Mo: 0.1-0.3%, V: 0.01-0.1%, Ti: 0.001-0.15%, Nb: 0.02-0.05%, wherein &#x3a3;(V, Ti, Nb)&#x2266;0.2% for the sum of the quantities of V, Ti and Nb, B: 0.0005-0.005%, and Ca: up to 0.01% in addition to Fe and unavoidable impurities. The flat steel product has a microstructure with (in surface percent) less than 5% ferrite, less than 10% bainite, 5-70% untempered martensite, 5-30% residual austenite, and 25-80% tempered martensite, at least 99% of the iron carbide contained in the tempered martensite having a size of less than 500 nm.

High-strength flat steel product and method for producing same

In a method to produce formed steel parts a primary steel material is provided, which (in % by weight) comprises C: 0.02-0.6%, Mn: 0.5-2.0%, Al: 0.01-0.06%, Si: max. 0.4%, Cr: max. 1.2%, P: max. 0.035%, S: max. 0.035%, and optionally one or more of the elements of the 'Ti, Cu, B, Mo, Ni, N' group, with the proviso that Ti: max. 0.05%, Cu: max. 0.01%, B: 0.0008-0.005%, Mo: max. 0.3%, Ni: max. 0.4%, N: max. 0.01%, and the remainder as iron and unavoidable impurities. The primary material is heated through at a heating temperature (TA) lying between the Ac1 and the Ac3 temperature, such that at best incomplete austenitising of the primary material takes place, is placed into a press-form tool and formed therein into the formed steel part. The formed steel part is then heated to a bainite forming temperature (TB), which is above the martensite starting temperature (MS), however below the pearlite transformation temperature of the steel. After cooling, it is maintained for an austernpering period (tB) at the bainite forming temperature (TB) in a substantially isothermic manner, until the foamed steel part has produced a structure consisting predominantly of ferrite and bainite, the martensite content thereof being &#x3c;5%, wherein residual austenite contents of &#x3c;10% may be present. The formed part is then cooled to room temperature.

Method for producing a formed steel part having a predominantly ferritic-bainitic structure

Disclosed is a method which allows steel strip to be produced in which high hardness and good formability are combined. The following steps of operation are followed:

Method for producing a surface-decarburised hot-rolled strip

A high strength steel sheet and a method for manufacturing the same has superior phosphatability properties and hot-dip galvannealed properties besides a tensile strength of 950 MPa or more and a high ductility, and also having a small variation in mechanical properties with the change in annealing conditions.

High strength steel sheet having superior ductility

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Moers, Germany

Jian Bian