Duplex stainless steel material

A duplex stainless steel material consisting of, in mass %,

• C:
• 0.030% or less,
• Si:
• 0.20 to 1.00%,
• Mn:
• 0.5 to 7.0%,
• P:
• 0.040% or less,
• S:
• 0.0200% or less,
• Al:
• 0.100% or less,
• Ni:
• 4.0 to 9.0%,
• Cr:
• 20.0 to 30.0%,
• Mo:
• 0.5 to 2.0%,
• Cu:
• 1.5 to 3.0%,
• N:
• 0.15 to 0.30%,
• V:
• 0.01 to 0.50%,
• Co:
• 0.05 to 1.00%,
• Sn:
• 0.001 to 0.050%,
• Nb:
• 0 to 0.300%,
• Ta:
• 0 to 0.100%,
• Ti:
• 0 to 0.100%,
• Zr:
• 0 to 0.100%,
• Hf:
• 0 to 0.100%,
• W:
• 0 to 0.200%,
• Sb:
• 0 to 0.100%,
• Ca:
• 0 to 0.020%,
• Mg:
• 0 to 0.020%,
• B:
• 0 to 0.020%, and
• rare earth metal:
• 0 to 0.200%,
• with the balance being Fe and impurities,
• wherein:
• a yield strength is 758 MPa or more;
• the microstructure is composed of, in volume ratio, ferrite in an amount of 35 to 65%, with the balance being austenite;
• and
• a dislocation density ρ(α) in the ferrite and a dislocation density ρ(γ) in the austenite satisfy Formula (1):
• 0.3
• <
• ρ
• ⁡
• (
• γ
• )
• /
• ρ
• ⁡
• (
• α
• )
• <
• 4.
• (
• 1
• )
• where, in Formula (1), a dislocation density in the austenite in m−2 is substituted for ρ(γ), and a dislocation density in the ferrite in m−2 is substituted for ρ(α).