Patent ID: 9657383
Date: 2017-05-23
CPC Classifications: C21D,C22C,C23C,F24S,Y02E

Claim:
1. A heat resistant ferritic steel comprising: a base material comprising, by mass percent, C: 0.01 to 0.3%, Si: 0.01 to 2%, Mn: 0.01 to 2%, P: at most 0.10%, S: at most 0.03%, Cr: 7.5 to 14.0%, sol. Al: at most 0.3%, and N: 0.005 to 0.15%, the balance being Fe and impurities, and an oxide film which is formed on the base material and whose chemical composition excluding oxygen and carbon contains 25 to 97% of Fe and 3 to 75% of Cr, wherein the oxide film contains spinel-type oxides and Cr 2 O 3 , wherein the following Formulas (1) and (2) are satisfied: where the maximum diffraction peak intensity of Cr wherein the oxide film on the base material is formed by oxidizing the base material at a temperature of 500 to 1150° C. in a gas atmosphere in which an oxygen partial pressure Po where R is a gas constant whose unit is J·K −1 ·mol −1 , and T is a temperature whose unit is K.