Effects of extrusion-billet preheating on the microstructure and properties of Zr-2.5Nb pressure tube materials

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:479458

Choubey, R; Cann, C D ^[1]; Aldridge, S A ^[2]; Theaker, J R; Coleman, C E ^[3]

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1. Atomic Energy of Canada Limited, Pinawa, Manitoba (Canada). Whiteshell Labs.
2. Nu-Tech Precision Metals, Inc., Arnprior, Ontario (Canada)
3. Atomic Energy of Canada Ltd., Chalk River, Ontario (Canada). Chalk River Labs.

The effects of extrusion temperature and pre-heat soak time for billets on the mechanical properties of Zr-2.5Nb pressure tubes for CANDU reactors have been examined. The {beta}-quenched billets from a quadruple-melted ingot containing approximately 1,200 ppm of oxygen were extruded at 780, 815, and 850 C with pre-heat soak times of 15 to 300 min. The extruded hollows were finished by cold drawing (with a 28% reduction in area) and then stress relieving at 400 C. The {alpha}-phase grain structure, tensile strength, and fracture toughness properties were found to vary with the pre-heat temperature and soak time. All the materials were tough because embrittling impurities were absent. The tubes with 780 C preheat had a very fine and uniform {alpha}-grain structure, giving high strength and toughness at all soak times. The opposite was true for the 850 C soaks; the grain structure was coarse and inhomogeneous and the materials tended to be less strong and less touch. The tubes with the 815 C soaks showed intermediate values of strength and toughness. These variations in mechanical properties are discussed in terms of {alpha}-grain refinement and oxygen enrichment.

• Sponsoring Organization: Organization of CANDU Industries, Toronto, ON (Canada)
• OSTI ID: 479458
• Report Number(s): CONF-950926--
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
36 MATERIALS SCIENCE
ALLOY-ZR97NB3
CANDU TYPE REACTORS
FABRICATION
FRACTURE PROPERTIES
GRAIN REFINEMENT
MECHANICAL PROPERTIES
MICROSTRUCTURE
PRESSURE TUBES
TENSILE PROPERTIES