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18/8 Mo 221

Unitor 18/8 Mo 221 is a rod for welding stainless and acid resistant steel. Application areas are similar to those for the coated electrode 18/8 321 N, but with the advantages TIG can offer. When welding thin sheets and pipes (less than 2 mm) it is always an advantage to use TIG. This filler rod may also be used as a root bead when welding thicker sheets with prepared V-grooves. The groove can subsequently be filled, using coated electrodes. Burn-through is difficult to avoid when using coated electrodes on thin sheets. As 18/8 Mo may be used on both stainless and acid resistant sheet and pipes, it is a very useful filler rod on board chemical tankers. For TIG welding DC negative polarity welding current is used, combined with a pointed tungsten electrode alloyed with rare earth metals. The Leftward welding technique is used.

Note: The hot surface of the back of the weld will be attacked by air unless it is shielded. In piping this can be done by introducing argon gas and blocking the pipe ends. When welding sheets, a suitable grooved back-up sheet underneath the weld will prevent oxidization.

TIG welding thin sheets and pipes ­­. . .

3.02

­­. . . or used as root bead in V-grooves.

Remember there is considerably more shrinkage in stainless steel than in mild steel and the tacks should therefore be placed as closely as possible.

Argon hose

Small hole to let the gas escape Argon backing gas used to prevent oxidization inside pipes.

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