“Burn-off” is the reduction in length of a weld stud, which occurs during the arc stud welding process.
STUDs – Before and after weld:
The Process
- Place stud & ferrule to work surface.
- When the trigger is pulled, the stud lifts, and draws a pilot arc.
- Pilot arc turns to sustained arc while stud remains lifted
- In a split second the stud plunges to base material, a fillet solidifies around base and the ferrule is removed.
Determining Proper Length Stud – Formula:
(After weld length + “burn off” = Stud Purchase length)
*EXAMPLE of a ¾” x 4.00” Shear Connector welded thru decking:
4.00” (after weld length) + 3/8” (burn off) = ¾ x 4-3/8” (stud purchase length)
Stud Reductions per Diameter:
| Stud Diameter | Approximate Reduction |
|---|---|
| 3/16”-1/2” | 1/8” |
| 5/8”-7/8” | 3/16” |
| 1” and over | 1/4” |
| 3/4″ thru-deck | 3/8” |
Examples of After Weld Lengths Bare Steel vs. Thru Deck:
Example 1
| Approx. after weld length when welding to bare steel. | Approx. after weld length when welding thru metal decking. | |
|---|---|---|
| 4-3/16″ | 4.00″ | 3.813″ |
| 4-3/8″ | 4.188″ | 4.0″ |
| 4-7/8″ | 4.688″ | 4.50″ |
Example 2
| Approx. after weld length when welding to bare steel. | Approx. after weld length when welding thru metal decking. | |
|---|---|---|
| 5-3/16″ | 5.00″ | 5-7/8″ |
| 5-3/8″ | 5.188″ | 5.688″ |
| 5-7/8″ | 5.0″ | 5.50″ |