Yes, welded is OK. So is high-temperature solder. I like the way ArmaLite does it - They drill a blind hole that cuts into the barrel, drive in a pin, then weld the hole closed and grind it smooth.
The brake (not "break" BTW) cannot be 22 mm in diameter like a standard military muzzle device 'cause that's a standard size for Grenade Launchers of Doom. BATF has approved specific kinds for use on post-bans. See your friendly parts supplier for details.