DUPLEX STAINLESS STEELS AND THEIR USE Russian patent published in 2022 - IPC C22C38/58 C22C38/52 C07C273/00 

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy, namely to the use of duplex stainless steel as material for at least part of equipment in a urea production installation and/or a method for production of urea, wherein equipment is in contact with fluid containing ammonium carbamate. Stainless steel contains, wt.%: C 0.03 or less, Si 0.5 or less, Mn 2.5 or less, Cr from more than 30.0 to 35.0, Ni from 5.5 to 8.0, Co from 0.01 to 0.8, Mo from 2.0 to 2.5, W 2.5 or less, N from 0.3 to 0.6, Cu 1.0 or less, one or more of the following: Ca 0.0040 or less, Mg 0.0040 or less, and one or more of rear earth elements in the total amount of 0.1 or less, the rest is Fe and impurities. Stainless steel is characterized by a compositional parameter (Z) in the range from 14.95 to 19.80, which is total contents of Ni, Co, Mo, determined by the equation: Z=1.062×(Ni+Co)+4.185×Mo, where Ni, Co, Mo are weight percent of Ni, Co, and Mo respectively.

EFFECT: high corrosion resistance of steel, possibility of use in media containing ammonium carbamate, at high pressures and temperatures.

29 cl, 2 dwg