Frequently Asked Questions
All attempts at raising productivity should begin with a thorough appraisal of the whole manufacturing process, both before and after the welding stage. Factors such as material and work flow and the amount of rework should be examined and particular note taken of any bottlenecks in production. Only when this has been done should attention be turned to the details of the welding process.
In attempting to increase the effectiveness of the submerged-arc process itself fabricators have turned to high welding currents and multiple arc systems However, although use of high currents or multiple arcs may increase deposition rate, it sometimes does so at the expense of weld metal and/or HAZ toughness, or at the risk of solidification cracking or poor slag detachability. Additionally, multiple arc systems require high capital cost equipments. Accuracy requirements for joint preparations and fit-up are often more demanding for high heat input welding applications.
Increasing metal deposition rates without an appreciable increase in energy input is possible by means of several deposition efficient process variants including:
- fine wire diameters
- hot or cold wire additions
- tubular flux and metal cored electrode wires
- metal powder additions
- increased electrode extension
- DCEN (Direct Current Electrode Negative) polarity
A major advantage of the process variants is that they can be applied with modest modifications to conventional equipment and are relatively simple to operate. Although many successful applications can be cited, some limitations also apply. These methods may increase the risk of fusion faults if they are incorrectly applied, and in some cases, arc starting can be more problematic. Training of shopfloor personnel in their proper use is a key requirement for successful application.
Back gouging, an expensive procedure, can be eliminated sometimes by using the 'punch through' method. After superficial cleaning of the second side of a butt joint, a deeply penetrating bead fuses into the root run on the first side. There is high dilution, however, and where weld metal toughness is a crucial factor special consumables, e.g. titanium-boron (Ti-B) containing wires and fluxes, may be necessary.