Microstructure in Unbent and As-Hot Bent Segments of Thick-Walled P92 Steel Pipe

• Published in: Key Engineering Materials Vol. 651-653; pp. 53 - 58
• Main Authors: Sklenička, Vaclav, Král, Petr, Kuchařová, Květa, Kvapilová, Marie, Svobodová, Marie, Horvath, Ladislav
• Format: Journal Article
• Language: English
• Published: Zurich Trans Tech Publications Ltd 10.07.2015
• Subjects: Chromium molybdenum vanadium steels; Detectors; Electric potential; Heat resistant steels; Heat treatment; High strength steels; Hot bending; Microstructure; Pipe; Scanning electron microscopy; Steels; Hot Bending; Creep Behavior; Microstructure; P92 Steel Pipe; EBSD
• ISBN: 3038354716; 9783038354710
• ISSN: 1013-9826; 1662-9795; 1662-9795
• DOI: 10.4028/www.scientific.net/KEM.651-653.53

The microstructure of P92 steel pipe processed by hot bending was evaluated in order to characterize the influence of hot bending on microstructure changes in extrados and intrados of bend. The straight pipes, with an outer diameter 350 mm and wall thickness of 39 mm (Productos Tubulares, s.a.u. Spain), were normalized at 1050°C/60min/air and tempered at 740°C/140min/air.The thick-walled P92 pipe was hot bended at 920-960 °C using bending rate 7 mm/min. The bends were normalized at 1050°C/60min/air and tempered at 775°C/140min/air after hot bending. The selected specimens, machined from different locations of pipe, were additionally thermal ageing at 650 °C to simulate microstructure degradation typical for long-term service conditions.Microstructure was investigated by scanning electron microscope Tescan Lyra 3 equipped with NordlysNano EBSD detector operating at an accelerating voltage of 20 kV with specimen tilted at 70° and by transmission el. microscope JEM-2100F.Microstructure investigation revealed that different processing history influenced distribution and size of secondary phases and caused changes in interboundary spacing in straight pipe and bends. It was found that microstructure changes induced during hot bending and subsequent post-bending heat treatment caused deterioration in creep properties of bends in comparison with those of straight pipe.