I had a few questions on keyhole plasma (semi-automatic) welding half inch thick 6-4 Ti by the Plasma Keyhole process. If anyone has experience with anything close to this, advice would be well-recieved. Right now I am having a big contamination problem (in addition to a penetration issue) and the purge box is not doing the job consistent enough. Are there conditions beyond oxygen inside the purge box that could cause severe discoloration? Also, I have been trying to determine a correct AWS test coupon for my procedure qualification/welding operators. My project falls into the realm of AWS D17.1 which calls for AWS B2.1 for qualification. If I am reading the code correctly, I will need a test coupon 28" X 14" minimum for testing. It may be a beginner question, but is this correct? It seems a bit excessive...would it be possible to use multiple welds for procedure qualification testing? Any input would be greatly appreciated.

osu45

(PS the variables for my process are similar to those for Ti PAW in the Welding Handbook: approx: 260Amps, 3/16inch standoff, 0.125" orifice diam., 9.5"/min travel speed, and orifice gas flow about 6.5L/min)