Fig. 1
Brittle forced fracture in the heat-affected zone of the weld seam
Fig. 2
Fig. 2 Parent metal showing numerous Cu₂O precipitations at the grain boundaries as cause for an embrittlement of the material
Fig. 3
Fractographic characteristic of hydrogen brittleness or respectively gassing of copper

Description:
Rectangular copper profile sections are welded together and formed to rings having various different radii. In these processing steps, brittle fractures will occur within the heat affected zone of the weld seams (Fig. 1).  

Failure cause:
Offensichtlich ist während des Verschweißens der Kupferprofile infolge von Sauerstoffaufnahme Kupferoxidul im Werkstoff entstanden, was zu seiner örtlichen Versprödung (Abb. 2) und somit zur Bildung von spröden Brüchen (Abb. 3) bei der mechanischen Belastung der Schweißverbindung führte (Wasserstoffkrankheit von Kupfer).

Remedy:
The use of SE copper grades is absolutely necessary for such welding work. In addition, the bevel edges should be cleaned from adhering oxide constituents before beginning with the welding work. Moreover, an optimally shielded inert gas atmosphere should be ensured in case of tungsten inert-gas welding (WIG) or MIG welding.

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