Mild steel should do it- Rocketman is right- brazing is at a higher temperature than soldering, and any case in the parent metal would be annealed. Only "bad news" TIG job I ever heard of on a fine shotgun- years ago a Grand Rapids area Gunsmith(?) with a fair reputation as a pistolsmith- attempted to rebuild apparently worn sears on a friend's Parker ejector grade 20- his father-in-law owned a machine shop and had a TIG welder- a Miller 300 GoldStar if memory serves, and he did just that- BUT- forgot that sears are hardened- forgot to check hardness, anneal, weld at controlled temperature and then have the sears re-hardened- the shotgun ended up with Mr. DelGrego- I won't repeat his reported remarks to my friend who inherited that Parker about "rookie gunsmiths"- but any form of welding goes to the old saying "90 percent of a successful weld job is in the preparation"!! I suggested 1/16 mild steel silicon killed (S-3) and 100% Argon shielding gas for a more fluid puddle, and lower open arc amperage for the 1/16th" dia. filler rod- possible 3/32" dia. would work too-using the rod dia. to thousands theorm for amperage (as a starting point) 1/16th DC straight polarity start on your scrap piece to test- 65 to 70 amps- 3/32" 85 to 90, and use a 2% thoria tungsten and grind to a blunt tip- not a sharp pencil tip- TIG tips for your buddy, who most likely knows all this. TIG welding is to SMAW- stick welding, say a farmer welding a rusty drag tooth with 6013- as brain surgery is to trimming your toenails- there isn't any known metal that can't be properly welded with TIG- now I have to get involved with this spray welding process and learn the ins and outs of that- just as the compressed air plasma arc cutting torch is replacing the old tried and true "gas axe" aka- oxy-acetylene- RWTF
