Austenitic steel with improved high-temperature strength and corrosion resistance

Abstract

Austenitic steel with improved high-temperature strength and corrosion resistance, characterized by the simultaneous presence, in defined quantities, of Nb, Mo and V and by the presence of C and N in a specific ratio with said three elements.

We claim: 
     
       1. Austenitic steel with improved and long-term constant high-temperature strength and resistance to aggressive agents, .[.comprising.]. .Iadd.consisting essentially of .Iaddend.the following elements in % by weight: 0.40-0.65 carbon   0.35-0.60 nitrogen   .[.2.0-3.0 manganese.].   .Iadd.about 2.30 manganese .Iaddend.   22.0-24.0 chromium   7.5-8.5 nickel   
     
     
       0. 7-1.3 molybdenum 0.6-1.2 vanadium   0.7-1.5 niobium   up to 0.3 silicon   up to 0.03 sulphur   up to 0.025 phosphorus   balance essentially iron, carbon, nitrogen, vanadium, molybdenum and niobium being intercorrelated by specific ratios, said specific ratios being expressed in atomic fractions through the following mathematical relations: (A) Nb+V/C+N=0.25-0.45   (B) N/C=0.60-1.10   (C) V/Nb=0.50-2.0   (D) Mo/C=0.15-0.25. .Iadd.     
     
     
       2.  Austenitic steel with improved and long-term constant high-temperature strength and resistance to aggressive agents, comprising the following elements in % by weight: 0.40-0.65 carbon   0.35-0.60 nitrogen   about 2.39 manganese   22.0-24.0 chromium   7.5-8.5 nickel   0.7-1.3 molybdenum   0.6-1.2 vanadium   0.7-1.5 niobium   up to 0.3 silicon   up to 0.03 sulphur   up to 0.025 phosphorus   balance essentially iron, carbon, nitrogen, vanadium, molybdenum and niobium being intercorrelated by specific ratios, said specific ratios being expressed in atomic fractions through the following mathematical relations: (A) Nb+V/C+N=0.25-0.45   (B) N/C=0.60-1.10   (C) V/Nb=0.50-2.0   (D) Mo/C=0.15-0.25. .Iaddend.