Outokumpu Oyj

Erik Schedin

James Oliver

Jan-Olof Andersson

Mats Liljas

Rachel Pettersson

Peter Samuelsson

Simon Lille

Pelle Johansson

Disclosed is a duplex ferritic austenitic stainless steel of 40-60 volume % ferrite and 40-60 volume % austenite, with improved cold workability and impact toughness. It contains less than 0.07% carbon (C), 0.1-2.0% silicon (Si), 3-5% manganese (Mn), 19-23% chromium (Cr), 1.1-1.9% nickel (Ni), 1.1-3.5% copper (Cu), 0.18-0.30% nitrogen (N), optionally molybdenum (Mo) and/or tungsten (W) according to the formula (Mo+&#xbd;W)&#x3c;1.0%. It optionally contains 0.001-0.005% boron (B), up to 0.03% of each of cerium (Ce) and/or calcium (Ca), with the balance being iron (Fe) and impurities where the chromium equivalent (Cr) and the nickel equivalent (Ni): 20&#x3c;Cr&#x3c;24.5 and Ni&#x3e;10, where Cr=Cr+1.5Si+Mo+2Ti+0.5Nb Ni=Ni+0.5Mn+30(C+N)+0.5(Cu+Co).

Duplex ferritic austenitic stainless steel

The invention relates to a method for producing a high-strength ferritic austenitic duplex stainless steel with the TRIP (Transformation induced plasticity) effect with deformation. After the heat treatment on the temperature range of 950-1150&#xb0; C. in order to have high tensile strength level of at least 1000 MPa with retained formability the ferritic austenitic duplex stainless steel is deformed with a reduction degree of at least 10%, preferably at least 20% so that with a reduction degree of 20% the elongation (A) is at least 15%.

Method for producing high-strength duplex stainless steel

The invention relates to a duplex stainless steel having austenitic-ferritic microstructure of 35-65% by volume, preferably 40-60% by volume of ferrite and having good weldability, good corrosion resistance and good hot workability. The steel contains 0.005-0.04% by weight carbon, 0.2-0.7% by weight silicon, 2.5-5% by weight manganese, 23-27% by weight chromium, 2.5-5% by weight nickel, 0.5-2.5% by weight molybdenum, 0.2-0.35% by weight nitrogen, 0.1-1.0% by weight copper, optionally less than 1% by weight tungsten, less than 0.0030% by weight one or more elements of the group containing boron and calcium, less than 0.1% by weight cerium, less than 0.04% by weight aluminium, less than 0.010% by weight sulphur and the rest iron with incidental impurities.

Ferritic-austenitic stainless steel

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Uppsala, Sweden

Erik Schedin