An aluminum fabrication shop built a 6061-T6 structural frame for an overhead conveyor support system. 10 groove welds on 1/4″ and 3/8″ wall rectangular tubing, GMAW-P, ER5356 filler, AWS D1.2. All 10 welds were accepted. The inspector focused on weld profile — aluminum commonly shows higher convexity due to lower surface tension — and on fusion quality, since low heat input on 6061 can cause LOF at toes.
Frequently Asked Questions
Why is AWS D1.2 used instead of D1.1 for aluminum?
AWS D1.1 applies specifically to structural carbon and low-alloy steel. Aluminum structural welding is governed by AWS D1.2, which has different visual acceptance criteria, filler classifications, and essential variables.
What is the main visual inspection risk on 6061-T6 aluminum welds?
HAZ liquation cracking at grain boundaries near the fusion line, particularly on 6061-T6 in the T6 temper. It appears as fine cracks parallel to the weld in the HAZ. Most common on thin sections with high heat input or in the T6 temper where the alloy is most susceptible.