Duplex stainless steel

1. A duplex stainless steel comprising, by mass %:

C: 0.005% to 0.03%;

Si: 0.05% to 1.0%;

Mn: 0.1% to 4.0%;

Ni: 3% to 8%;

Cr: 20% to 35%;

Mo: 0.01% to 4.0%;

Al: 0.001% to 0.30%;

N: 0.05% to 0.60%;

one or more selected from Re: 0.01% to 2.0% and Ge: 0.01% to 2.0%;

optionally Ga: 0.01% to 2.0%; and

a balance consisting of Fe and impurities.

2. The duplex stainless steel according to claim 1 , further comprising, by mass %:

one or more elements selected from the following first group and second group in place of a part of the Fe,

First group: W: 6.0% or less and Cu: 4.0% or less

Second group: Ca: 0.01% or less, Mg: 0.01% or less, and REM: 0.2% or less.