Air conditioner

An air conditioner comprising:

• an outdoor unit comprising a compressor, an outdoor heat exchanger, and a main expansion device, wherein a refrigerant is circulated by a refrigerant pipe configured to connect the compressor, the outdoor heat exchanger, and the main expansion device,
• an indoor unit comprising an indoor heat exchanger;
• and
• a connection pipe configured to connect the outdoor unit and the indoor unit,
• wherein the air conditioner has a cooling capability between 23 kW and 35 kW,
• wherein a mixed refrigerant containing R32 of 50% or more is used as the refrigerant, and
• wherein the refrigerant pipe comprises a ductile stainless steel pipe having a delta ferrite matrix structure of 1% or less on a basis of a grain area,
• wherein the ductile stainless steel material comprises:
• percent by weight, C:
• exceeding 0 to 0.03% or less, Si:
• exceeding 0 to 1.7% or less, Mn:
• 1.5 to 3.5%, Cr:
• 15.0 to 18.0%, Ni:
• 7.0 to 9.0%, Cu:
• 1.0 to 4.0%, Mo:
• exceeding 0 to 0.03% or less, P:
• exceeding 0 to 0.04% or less, S:
• exceeding 0 to 0.04% or less and N:
• exceeding 0 to 0.03% or less,
• and wherein the stainless steel has 160 MPa of yield strength, 480 MPa of tensile strength, 120 Hv of hardness, and 60% or more of elongation.