Effect of PWHT cycles on fatigue crack growth and toughness of quenched and tempered pressure vessel steels

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 391; no. 1; pp. 256 - 263
• Main Authors: Sterjovski, Z., Carr, D.G., Dunne, D.P., Ambrose, S.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 25.01.2005; Elsevier
• Subjects: Applied sciences; CTOD; Exact sciences and technology; Fatigue crack growth; Fractures; Impact toughness; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Postweld heat treatment; Quenched and tempered steel; Transportable pressure vessels; Void coalescence; Fatigue crack growth; Transportable pressure vessels; Void coalescence; CTOD; Impact toughness; Postweld heat treatment; Quenched and tempered steel; Heat treatment; Thermal cycle; Pressure vessel; Steel; Crack propagation resistance; Fatigue crack; Crack propagation; Weld; Fracture toughness; Thickness; Tempering; Microstructure
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2004.09.002

Transportable pressure vessels, commonly manufactured from quenched and tempered (QT) steels, require mandatory postweld heat treatment (PWHT) regardless of plate thickness. During their life, transportable pressure vessels may have up to 4 PWHT cycles at temperatures between 540 and 590 °C, and concerns have emerged about possible effects on the mechanical properties of the base (parent) plate. This paper reports work on the resistance to fatigue crack growth, impact toughness and CTOD fracture toughness of two types of QT steels. The parent metal region was examined for both steels, and then exposed to temperatures and times in the PWHT range. Although there was a marginal decrease in the resistance to fatigue crack growth for up to four postweld heat treatment cycles, there was a significant decrease in impact toughness and CTOD fracture toughness.