The pulse schedule is brief, but due to the increased resistance between the consumable and the product at the interface, increasing work (joules), and having a small contact area (power per square inch), a generous amount of energy is released. This causes the contact area of the product to arrive close to a semisolid, or plastic state, and therefore reduces the vertical strength of the surface material. This material reduces the amount of oxygen that comes in contact with the aluminum on the consumable as the product’s surface deforms to form a dimple. Tie this into the amount of energy released and is radiated away from the weld area due to the shape of the surrounding contact area. If you have excessive expulsion, you will need to reduce your baseline weld setting for the current variable but keep the spread between the pulse and the new baseline weld parameters. Once the pulse is set, simply go into your weld schedule with the increased weld force and weld time. The full dome will act as a natural control on the growth of the weld nugget as the power per square inch decreases exponentially with the increase in deformation of the weld area as the nugget arrives at a semiliquid state. If this is being performed on an AC/SCR resistance welding system, you may need to reduce the current from the original baseline weld schedule due to excessive expulsion. Since the pulse is now set up properly, you do not need to modify the weld schedule variables on the pulse to maintain the rules. Now that you have completed the run of the aluminum product line, all you have to do is dress the full dome consumable to produce the contact geometry and weld face required for the steel product. This can be done with a variety of tools and automation, but the main rule to keep in mind is you want to keep the contact surface generated between a 32- and 16- micron finish no matter what method you apply. The dressing required will remove any aluminum oxide buildup on the consumable, and you are down to using only one style of consumable. There is no need for the pulse scenario to be applied for the steel product run unless there is an exotic coating on the steel. Simply apply your baseline weld schedule for the steel product, along with the consumables dressed to the geometry from the steel baseline, and run the production run for that product. The full-dome consumable gives you tremendous flexibility to change the weld face while only having to stock a single consumable. In conclusion, to change a system between an aluminum product run and a steel run, it is as simple as 1-2-3 and a dressing operation. Really it is as easy as 10-20-30 for a pulse addition on the aluminum weld schedule. 22 WELDING JOURNAL / MARCH 2016 WJ MICHAEL S. SIMMONS is director, BF Entron, Ltd., and HAMILTON TERRELL is sales representative, TuffControl (Entron) group of companies. Send your comments and questions to them c/o Welding Journal, 8669 NW 36 St., # 130, Miami, FL 33166, or via email at simmons@entroncontrols.com. For info, go to www.aws.org/adindex
Welding Journal | March 2016
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