Iron casting and method of manufacturing it

A method of manufacturing an iron casting by executing a heat treatment for a heat treatment object that is provided by using and casting an austenite-type material for casting, wherein

• the material for casting includes 26.0 mass % or more and 50.0 mass % or less of Ni, 0.1 mass % or more and 3.5 mass % or less of C, 0.1 mass % or more and 3.5 mass % or less of Si, 0 mass % or more and 8.0 mass % or less of Co, 0 mass % or more and 3.0 mass % or less of Mn, 0 mass % or more and 0.2 mass % or less of Mg, and a balance that is Fe and an inevitable element(s),
• the heat treatment includes
• a first holding step of holding the heat treatment object at a first holding temperature of 850° C. or higher and 1250° C. or lower, and
• a first cooling step of cooling the heat treatment object to a first cooling end temperature of −150° C. or higher and 150° C. or lower after the first holding step, and
• the first holding step includes holding the heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less.