Faulted condition determination device and faulted condition determination method

A faulted condition determination method adapted to a welded joint in which a ferrite steel and another steel are welded together using a weld material containing nickel, comprising:

• detecting a chromium content and a nickel content in a predetermined boundary region, which are measured in the ferrite steel of the welded joint;
• and
• determining a faulted condition as a replacement standby state to standby regarding replacement of a replacement part when the chromium content is equal to a first lower threshold or more while the nickel content is less than a second lower threshold, the replacement part being a part that is made of the ferrite steel or the another steel;
• and
• determining the faulted condition as a replacement consideration state to consider replacement of the replacement part when the chromium content is less than the first lower threshold while the nickel content is equal to the second lower threshold or more.