1 part prep, 1 part pre heat, 1 part proper consumables(filler/gas).
Yes it was machined with a proper bevel on both surfaces. I have a large kiln to preheat engine blocks/heads/manifolds like this to properly weld on them. You cannot weld it right w/o preheating the material fully and evenly especially large chunks of cast steel/iron or aluminum. Then the consumables, in this case 625 and an argon/helium mix, to fuse the dissimilar metals for an extreme heat environment.
Welding used cast steel is a MOFO, because you have a shit ton of carbon precipitates in the base metal that you cannot remove, which contaminate the weld pool and result in inclusion. Takes skill to make sure it’s to the surface of the puddle before moving on. Exhaust manifolds are the worst of the worst in this case.
Not my best welding there. I should start taking more pics of my stuff. I’ll post some pictures of the tube chassis for the kit cars as they progress more, or cossey’s 321 996 exhaust when I get to it. I always forget to bring the camera, and get bitched at by my wife when I do and leave it at the shop for weeks on end 