| Abstract Scope |
This presentation reviews the physics of burnoff rate in arc welding with a consumable electrode; common processes that fall in this category include GMAW, MCAW, FCAW, SAW, SMAW, EGW. Some aspects of this model are also helpful to understand related processes such as ESW and how-wire additions. Deposition rate is one of the essential factors in calculation of welding costs and times to completion in practical applications. The relationship of deposition rate with current is also determinant of dilution of deposited material (essential concept in overlays), and is a tool of diagnostic of the welding process. For some common materials such as aluminum alloys, the variations in deposition rate with current are not well understood, and common explanations might be misleading. The physical foundations burnoff are mass and energy balances together with the mass and heat transfer mechanisms involved. Heat transfer mechanisms considered include the energy deposited by the fall voltage of the arc against the consumable, Joule heating of the electrode extension, evaporation losses, and heat exchange with the contact tip. The calculation of Joule heating considers the amount and shape of electrical resistivity variation with temperature. |