The Effects of Repeated Weld Repairs on the Mechanical Properties of Copper-Nickel Pipe Joints

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Authors
  1. Munro, C.
Corporate Authors
Defence R&D Canada - Atlantic, Dartmouth NS (CAN)
Abstract
Copper-nickel pipe (nominally 70% copper, 30% nickel) was subjected to repeated welding operations in order to physically simulate the mechanical and metallurgical effects of multiple weld repairs being conducted on the same pipe location. This work was undertaken in order to provide guidance on how many times this material can be repaired by welding in service. In this study pipe sections were fabricated that were welded a total of one, three, and five times. Multiple welding operations had the tendency to increase the degree of distortion, as pipes became pinched inwards at the location of the weld. Analysis of these sections showed that repeated welding led to moderate increases in heat affected zone hardness and yield strength, but also to significant decreases in impact energy absorption (27% reduction between samples welded once and five times). This decrease in impact energy could however be reversed through annealing, suggesting that work hardening associated with the welding distortion was its cause. Copper-nickel pipe used in naval applications has no impact energy requirement, therefore up to five welding operations are recommended as safe for use based on the findings of this work.

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Report Number
DRDC-ATLANTIC-TM-2013-100 — Technical Memorandum
Date of publication
01 Aug 2013
Number of Pages
48
DSTKIM No
CA039873
CANDIS No
800939
Format(s):
Electronic Document(PDF)

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