CORROSION-RESISTANT TWO-PHASE STAINLESS STEEL Russian patent published in 2023 - IPC C22C38/58 C22C38/52 C07C273/00 

FIELD: metallurgy.

SUBSTANCE: invention is related to two-phase stainless alloy steel used for manufacturing of technological equipment for synthesis of urea. Steel contains the following elements, expressed in wt.%: C from 0.001 to 0.03, Si from 0.001 to 0.5, Mn from 0.001 to 2.5, Cr more than 30.0 up to 35.0, Ni from 6.0 to 7.5, Mo from 2, 0 to 2.5, W from 0.001 to 2.5, Co from 0.01 to 0.8, N from 0.3 to 0.6, Cu from 0.001 to 1.0, at least one element selected from the group including: Ca 0.0040 or less, Mg 0.0040 or less, and one or more rare earth elements in a total amount of 0.1% or less, wherein the rare earth element is selected from the group of La, Ce, Pr and mixtures thereof, the rest of the mass comprise Fe and inevitable impurities. The steel components satisfy the following relationship: CRC=1.062×(Ni+Co)+4.185×Mo, ranging from 14.95 to 18.00. Steel has a corrosion rate (CR) of no more than 0.12 mm/year for 13 days or 1 month, measured gravimetrically by immersing a steel sample in a solution containing urea, ammonia and water in an autoclave at a temperature of 180-210°C and pressure 140-200 bar.

EFFECT: steel has high corrosion resistance in environments containing urea.

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