Outokumpu Oyj

James Oliver

Jan Y Jonsson

Jan-Olof Andersson

Juho Talonen

Erik Schedin

Rachel Pettersson

Alexander Thulin

Rachel Petersson

A duplex ferritic austenitic stainless steel having high formability utilizing the TRIP effect and high corrosion resistance with the high pitting resistance equivalent. The duplex stainless steel contains less than 0.04 weight % carbon, 0.2-0.8 weight % silicon, 0.3-2.0 weight % manganese, 14.0-19.0 weight % chromium, 2.0-5.0 weight % nickel, 4.0-7.0 weight % molybdenum, less than 4.5 weight % tungsten, 0.1-1.5 weight % copper, 0.14-0.23 weight % nitrogen, the rest being iron and inevitable impurities occurring in stainless steels. Further, the co-effect of the chromium, molybdenum and tungsten contents in weight % is in the range of 20<(Cr+Mo+0.5W)<23.5, where the ratio Cr/(Mo+0.5W) is in the range of 2-4.75.

Duplex ferritic austenitic stainless steel composition

A duplex ferritic austenitic stainless steel having high formability utilizing the TRIP effect and high corrosion resistance with the balanced pitting resistance equivalent is formed with less than 0.04 weight % carbon, 0.2-0.8 weight % silicon, less than 2.0 weight % manganese, 16.5-19.5 weight % chromium, 3.0-4.7 weight % nickel, 1.5-4.0 weight % molybdenum, less than 3.5 weight % tungsten, less than 1 weight % copper, 0.13-0.26 weight % nitrogen, the rest being iron and inevitable impurities occurring in stainless steels.

Duplex stainless steel

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 a duplex ferritic austenitic stainless steel having high formability utilizing the TRIP effect and high corrosion resistance with the balanced pitting resistance equivalent. The duplex stainless steel contains less than 0.04 weight % carbon, less than 0.7 weight % silicon, less than 2.5 weight % manganese, 18.5-22.5 weight % chromium, 0.8-4.5 weight % nickel, 0.6-1.4 weight % molybdenum, less than 1 weight % copper, 0.10-0.24 weight % nitrogen, the rest being iron and inevitable impurities occurring in stainless steels.

The invention relates to a method for manufacturing a ferritic-austenitic stainless steel having good formability and high elongation. The stainless steel is heat treated so that the microstructure of the stainless steel contains 45-75% austenite in the heat treated condition, the remaining microstructure being ferrite, and the measured Mtemperature of the stainless steel is adjusted between 0 and 50&#xb0; C. in order to utilize the transformation induced plasticity (TRIP) for improving the formability of the stainless steel.

Method for manufacturing and utilizing ferritic-austenitic stainless steel with high formability

The invention relates to a method for manufacturing a ferritic-austenitic stainless steel having good formability, good weldability and high elongation. The stainless steel containing the sum of carbon and nitrogen C+N in the range 0.17-0.295 in weight % in which sum C+N a lower carbon content to avoid sensitisation during welding is compensated by an increased nitrogen content to maintain formability is heat treated so that the microstructure of the stainless steel contains 45-75% austenite in the heat treated condition, the remaining microstructure being ferrite, and the measured Mtemperature of the stainless steel is adjusted between 0 and 50&#xb0; C. in order to utilize the transformation induced plasticity (TRIP) for improving the formability of the stainless steel.

Method for manufacturing and utilizing 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%.

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Fjärdhundra, Sweden

James Oliver