You can weld, Hobart machines are great m welders, so weld it.
If you worry about porosity & piping in welds there are two solutions:
Take a propane torch to the suspect welds on the day you plan to start the ferment. Heat 'em to about 300F & that'll do it every time. OR use a high flow rate high silver content ( zink & lead free) solder over the welds.
Or get a silver with the least tin you can.
Silver with Zink will melt and flow easier but Zink is not the best in a food app.
Gold would be better but it's pricey stuff for the small amoutn you'll need .
Seriously the propane torch trick is the easiest and most direct.
If you will be using threaded fittings instead of sanitary you'll be taking them apart for cleaning on every brew day anyway. Clean the threads and heat the thing up and poof you are golden. If you use sanitary trt clover fittings you'll have 'em clean and ready for the torch anyway.