SYMPOSIA PAPER Published: 01 January 1997

Effects of Composition and Heat Treatment on the Toughness of ASTM A508 Grade 3 Class 1 Material for Pressure Vessels


A laboratory study was conducted to evaluate the effects of composition and heat treatment on the toughness of ASTM A508 Grade 3 Class 1 material for pressure vessels. Five steels were vacuum induction melted and cast as ingots in the laboratory. These heats included a base steel representing the specification mid-range analysis, a steel containing higher levels of Si, Ni, and Cr (high-side composition) as compared to the base steel, and three steels derived from the high-side composition by adding Al, Al/N, and Nb, respectively. The ingots were rolled to plate, heat treated, and evaluated. Among these steels, the high-side composition with additions of Al and N displays the best strength/toughness combination. For example, a 75 mm-thick plate of this steel has acceptable strength and a reference nil ductility transition temperature (RTNDT) of ≤ -29‡C after austenitizing at 875‡C, air cooling, and tempering at 660‡C for up to 20 hours. Upper-nose temper embrittlement (UNTE) occurs in all these steels. This UNTE is attributed to the precipitation of needle-like Mo-rich carbides during tempering, and is significantly reduced by increasing the cooling rate after austenitizing.

Author Information

Lin, M
Bethlehem Steel Corporation, Bethlehem, PA
Hansen, SS
Bethlehem Steel Corporation, Bethlehem, PA
Nelson, TD
BethForge, Inc., Bethlehem Steel Corporation, Bethlehem, PA
Focht, RB
BethForge, Inc., Bethlehem Steel Corporation, Bethlehem, PA
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Developed by Committee: A01
Pages: 33–55
DOI: 10.1520/STP16591S
ISBN-EB: 978-0-8031-5349-3
ISBN-13: 978-0-8031-2423-3