when you get your 1.6 mm collet use that with some 0.9 mm filler wire should be alright, same amps 30-40A. wont need to purge inside, unless your doing a weld test that has to pass x-ray. always add filler, not too much but enough so it keeps the finished weld above the material your welding. Thats called reinforcement. critical for a long lasting crack free weld.