Ferritic heat-resisting steel

Abstract

A ferritic heat-resisting steel that shows a slight decrease in creep strength at the heat affected zone of the welded joint. The steel is characterized by consisting of, by mass %, C: less than 0.05%, Si: not more than 1.0%, Mn: not more than 2.0%, P: not more than 0.030%, S: not more than 0.015%, Cr: 7-14%, V: 0.05-0.40%, Nb: 0.01-0.10%, N: not less than 0.001% but less than 0.050%, sol. Al: not more than 0.010%, and O (oxygen): not more than 0.010%, with the balance being Fe and impurities, and further characterized in that the density of carbide and carbonitride precipitates contained with a grain diameter of not less than 0.3 μm is not more than 1×106/mm2. This steel may further contain one or more of the following elements: a total of 0.1-5.0% of Mo and W; a total of 0.02-5.00% of Cu, Ni and Co; a total of 0.01-0.20 of Ta, Hf, Nd and Ti; a total of 0.0005-0.0100% of Ca and Mg; and 0.0005-0.0100% of B.

Dependencies are inferred from the claim text.