By joint restraint I meant the restraint that the welded part is under after welding. Example is when a fixture and clamp is used to hold a part for welding to prevent the part from moving during the welding process. Once that part is welded and it is removed from the fixture or unclamped, the joint has been restrained and heating it up as with heat treat will help the part relax, allowing it to move. Pre-heat makes a big difference and you will be fine. I think there is another post about distortion control in the "Tricks of the Trade" section that might also have some pointers for you.