Hi there,
These are MIG welds using C25 Argon-Co2 gas. It requires no purging to get full penetration. Important is that you are welding healthy material. I have decent welding equipment, you just set the wire size (I am using 0.023, 0.03, 0.035" depending on material thickness), metal type and material thickness and you get a base line. You tweak from there and will get a feel and hearing for a good weld after some time. Some welders are self-learning these days.
Good luck with your project.