Hey there guys. I got a question i want to throw out your way. So i need to fillet weld a 4"x.5" aluminum flat bar to another 4"X.5" flat bar. The alloy is 6061t and my filler is 1/16th 5356. Ill be using a miller aluma pro with a miller deltaweld. Now the question...should i preheat this or can i just weld. The peices are about 19 feet in length. So there you go..if you need more information about this project let me know.