Austenitic heat-resistant alloy and welded structure

Abstract

An austenitic heat-resistant alloy has a chemical composition of, in mass %: 0.04 to 0.14% C; 0.05 to 1% Si; 0.5 to 2.5% Mn; up to 0.03% P; less than 0.001% S; 23 to 32% Ni; 20 to 25% Cr 1 to 5% W; 0.1 to 0.6% Nb; 0.1 to 0.6% V; 0.1 to 0.3% N; 0.0005 to 0.01% B; 0.001 to 0.02% Sn; up to 0.03% AI; up to 0.02% 0; 0 to 0.5% Ti; 0 to 2% Co; 0 to 4% Cu; 0 to 4% Mo; 0 to 0.02% Ca; 0 to 0.02% Mg; 0 to 0.2% REM; and the balance being Fe and impurities. The alloy microstructure has a grain size number in accordance with ASTM E112 of 2.0 or more and less than 7.0.

1 . An austenitic heat-resistant alloy having a chemical composition of, in mass %:
 0.04 to 0.14% C;   0.05 to 1% Si;   0.5 to 2.5% Mn;   up to 0.03% P;   less than 0.001% S;   23 to 32% Ni;   20 to 25% Cr;   1 to 5% W;   0.1 to 0.6% Nb;   0.1 to 0.6% V;   0.1 to 0.3% N;   0.0005 to 0.01% B;   0.001 to 0.02% Sn;   up to 0.03% Al;   up to 0.02% O;   0 to 0.5% T;   0 to 2% Co;   0 to 4% Cu;   0 to 4% Mo;   0 to 0.02% Ca;   0 to 0.02% Mg;   0 to 0.2% REM; and   the balance being Fe and impurities,   the alloy having a microstructure with a grain size represented by a grain size number in accordance with ASTM E112 of 2.0 or more and less than 7.0.   
     
     
         2 . The austenitic heat-resistant alloy according to  claim 1 , wherein the chemical composition contains one or more elements selected from one of the first to third groups provided below, in mass %:
 first group: 0.01 to 0.5% Ti;   second group: 0.01 to 2% Co, 0.01 to 4% Cu, and 0.01 to 4% Mo; and   third group: 0.0005 to 0.02% Ca; 0.0005 to 0.02% Mg; and 0.0005 to 0.2% REM.   
     
     
         3 . A welded structure including the austenitic heat-resistant alloy according to  claim 1 . 
     
     
         4 . A welded structure including the austenitic heat-resistant alloy according to  claim 2 .