Fe-cr-ni alloys with excellent surface properties and their production methods

A Fe—Cr—Ni alloy having excellent surface properties consisting of:

• in mass %, C:
• 0.020 to 0.150%, Si:
• 0.05 to 0.80%, Mn:
• 0.10 to 1.50%, P:
• not greater than 0.035%, S:
• not greater than 0.0050%, Ni:
• 34.0 to 48.0%, Cr:
• 22.0 to 29.0%, Mo:
• 0.20 to 1.20%, Al:
• 0.005 to 0.180%, Mg:
• 0.0001 to 0.0100%, Ca:
• 0.0001 to 0.0100%, Nb:
• 0.20 to 0.80%, N:
• 0.050 to 0.500%, O:
• 0.0001 to 0.0060%, Cu:
• not greater than 0.80%, Ti:
• not greater than 0.100%, Co:
• not greater than 0.50%, and Fe and inevitable impurities as the remainder, wherein
• non-metallic inclusions contain at least one of MgO and CaO—Al2O3—MgO type oxide as an essential component and contain optionally selected from CaO, CaO—MgO type oxide and MgO·Al2O3 as an optional component,
• number ratio of the MgO·Al2O3 with respect to the total oxide type non-metallic inclusions is not greater than 50%, and number ratio of total of the CaO and CaO—MgO type oxide with respect to the total oxide type non-metallic inclusions is not greater than 50%.