Preliminary studies indicate that appreciably more iron can be tolerated in the welds of nickel-ciad vessels to be used in caustic soda service than has been permitted heretofore in most specifications.
Conventional welding of nickel-ciad equipment calls for the use of an appropriate steel electrode with the steel side being welded first. The root bead should fuse to the base of the steel but should not penetrate into the nickel. Penetration of the steel root bead into the nickel may form a hard, brittle alloy which is difficult to back chip and may later result in cracking of the weld. Accurate fitting of the plate edges and proper bevelling are important in controlling this penetration.
After the steel side is welded, the clad side is chipped or ground to clean, sound weld metal. For caustic service, the clad side welding is done entirely with a straight nickel electrode. To reduce...
