Austenitic Stainless Steel

1 . An austenitic stainless steel comprising a chemical composition consisting of, in mass %:

C: 0.030% or less;

Si: 0.10 to 1.00%;

Mn: 0.20 to 2.00%;

P: 0.040% or less;

S: 0.010% or less;

Cr: 16.0 to 25.0%;

Ni: 10.0 to 30.0%;

Mo: 0.1 to 5.0%;

Nb: 0.20 to 1.00%;

N: 0.050 to 0.300%;

sol.Al: 0.0005 to 0.100%;

B: 0.0010 to 0.0080%;

Cu: 0 to 5.0%;

W: 0 to 5.0%;

Co: 0 to 1.0%;

V: 0 to 1.00%;

Ta: 0 to 0.2%;

Hf: 0 to 0.20%;

Ca: 0 to 0.010%;

Mg: 0 to 0.010%; and

rare earth metals: 0 to 0.10%,

with the balance being Fe and impurities,

and satisfying Formula (1):

B+0.004−0.9C+0.017Mo 2 ≥0  (1)

where symbols of elements in Formula (1) are to be substituted by contents of corresponding elements (mass %).

2 . The austenitic stainless steel according to claim 1 , wherein the chemical composition contains one or more elements selected from the group consisting of:

Cu: 0.1 to 5.0%;

W: 0.1 to 5.0%; and

Co: 0.1 to 1.0%.

3 . The austenitic stainless steel according to claim 1 , wherein the chemical composition contains one or more elements selected from the group consisting of:

V: 0.1 to 1.00%;

Ta: 0.01 to 0.2%; and

Hf: 0.01 to 0.20%.

4 . The austenitic stainless steel according claim 1 , wherein the chemical composition contains one or more elements selected from the group consisting of:

Ca: 0.0005 to 0.010%;

Mg: 0.0005 to 0.010%; and

rare earth metals: 0.001 to 0.10%.

5 . The austenitic stainless steel according to claim 1 , wherein the chemical composition contains

Cu: 0 to 1.9%.

6 . The austenitic stainless steel according to claim 2 , wherein the chemical composition contains one or more elements selected from the group consisting of:

V: 0.1 to 1.00%;

Ta: 0.01 to 0.2%; and

Hf: 0.01 to 0.20%.

7 . The austenitic stainless steel according to claim 2 , wherein the chemical composition contains one or more elements selected from the group consisting of:

Ca: 0.0005 to 0.010%;

Mg: 0.0005 to 0.010%; and

rare earth metals: 0.001 to 0.10%.

8 . The austenitic stainless steel according to claim 3 , wherein the chemical composition contains one or more elements selected from the group consisting of:

Ca: 0.0005 to 0.010%;

Mg: 0.0005 to 0.010%; and

rare earth metals: 0.001 to 0.10%.

9 . The austenitic stainless steel according to claim 6 , wherein the chemical composition contains one or more elements selected from the group consisting of:

Ca: 0.0005 to 0.010%;

Mg: 0.0005 to 0.010%; and

rare earth metals: 0.001 to 0.10%.