from the conferences organized by TANGER Ltd.
The temperature of the hot bending of creep resistant steels is usually performed above the transition temperature Ac3. The steel thus undergoes a short-term austenitization followed by martensitic and/or bainitic transformation during subsequent fast cooling. Especially in the case of alloyed steels the austenitization is too short to allow dissolution of special carbides and/or nitrides, which results in the bimodal distribution of these secondary phases after bending. In order to guarantee the required material properties as well as homogeneous final microstructure after bending, it is necessary to perform the complete post bend heat treatment (PBHT) comprising of normalizing and tempering.In order to verify the influence of omitted normalization after bending on the material properties of a pipe bend made of 0.5Cr-0.5Mo-0.3V heat resistant steel, two different heat treatment modes were applied after a heat cycle simulating hot bending, the first inclusive normalizing and tempering and the second where the material was only tempered. Comprehensive analysis of mechanical properties, microstructure, substructure and creep resistance was then performed to confirm the effect of PBHT regime on material behaviour.
Keywords: 0.5Cr-0.5Mo-0.3V steel, hot bending, post bend heat treatment, microstructure, stress rupture test© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.