Method of making a duplex stainless steel and a duplex stainless steel product with improved mechanical properties

摘要

There is disclosed a method of making a duplex stainless steel for an alloy having the following composition:Carbon 0.001 to 0.08 Wt.%Manganese 0.001 to 2.00 Wt.%Silicon 0.001 to 1.50 Wt.%Chromium 20.00 to 27.50 Wt.%Nickel 8.00 to 11.00 Wt.%Molybdenum 3.00 to 4.50 Wt.% .Sulfur 0.0001 to 0.050 Wt.%Phosphorus 0.0001 to 0.050 Wt.%Nitrogen 0.10 to 0.30 Wt.%Iron Balanceby selecting a heat treating temperature in the range of about 2050 F to about 2350°F to provide a desired impact toughness and a desired yield strength. There is also disclosed a duplex stainless steel having austenite pools in a ferrite matrix resulting from heating to a temperature in the range of 2050°F -2350°F and cooling rapidly thereafter, said steel having essentially the above-mentioned composition with the proviso thatwhere:Creq = 1.5 (%Cr+%Si+%Mo)Nieq = %Ni+0,3 (_%Mn) +_%Cu+₂₂(%C) +5_%Nand having greater impact toughness values in the cast form than Ferralium Alloy 225 and SAF 2205, theimpact toughness in Charpy V-notch testing at -100°F being above 75 ft.-Ibs. when tested from keel blocks per ASTM E23-82, the HAZ impact toughness at -100° F being above about 50 ft.-Ibs. and having a yield strength of at least 65 KSI.