Chromoum heat-resistant steel excellent in toughness and having high cracking resistance and high creep strength in welded joint

摘要

A chromium heat-resistant steel excellent in toughness and having a high cracking resistance and a high creep strength when said steel is utilized to form a welded joint, said steel consisting essentially of: PP______________________________________ PP carbon: from 0.04 to 0.09 wt. %, PP silicon: from 0.01 to 0.50 wt. %, PPmanganese: from 0.25 to 1.50 wt. %, PPchromium: from 7.0 to 9.2 wt. %, PP molybdenum: from 0.50 to 1.50 wt. %, PP soluble aluminum: PP from 0.005 to 0.060 wt. %, P Pnitrogen: from 0.001 to 0.060 wt. %, PP ______________________________________ PPP Pwhere, the total amount of nitrogen and carbon being up to 0.13 wt. %, at least one element selected from the group consisting of:______________________________________ PPvanadium: from 0.01 to 0.30 wt. %, PPand PPniobium: from 0.005 to 0.200 wt. %, PP ______________________________________ PPP Pwhere, the total amount of vanadium and 1.5 times niobium being up to 0.30 wt. %, and the balance being iron and incidental impurities; and the amount of ferrite as represented by the ferrite number (&dgr;.sub.F) in the above-mentioned chromium heat-resistant steel being -5 or lower, as calculated by the following formula:PP&dgr;.sub.F=- 104-555 (C+6/7N)+32.9Si-49.5Mn+12.1Cr+39.1Mo+46.1V+83.5Nb.