I Would agree with a few people here...silicon bronze is not meant for anything structural. The only time it should be used on a header is on the out side of the flange. Everything else should be ER70S for mild steel or 308L for SS.

I have 045" silicon bronze tig rod. I've never tried it in a wire feed welder, but I couldn't imagine the results would be very good. Pretty solf to push through the liner for starters.