Zirconium alloys are the go-to material for handling highly corrosive media in nuclear fuel reprocessing and chemical processing plants. But welding zirconium demands extreme cleanliness and a precise Welding Procedure Specification (WPS).
Oxygen, nitrogen, and hydrogen contamination at welding temperatures embrittle the weld metal and heat-affected zone. That is why gas shielding must cover not only the torch nozzle but also the entire hot zone with a trailing shield and backup purge. ASME Section IX and AWS D10.6 both require tensile and bend tests on production-representative coupons.
Key variables in a zirconium WPS include:
• Argon purity of 99.998% minimum, with dew point below -50°C.
• Interpass temperature capped at 120°C to avoid excessive grain growth.
• Color check after each pass: a silver or straw tint is acceptable; blue or gray indicates contamination and requires removal.
A properly qualified WPS for zirconium piping is not just a paperwork exercise. It is the only way to ensure that field welds meet the corrosion resistance and mechanical properties the design demands.
Source: AWS D10
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