Specialists at the Andritz Hydro Ravensburg site have been using the CMT (Cold Metal Transfer) welding process to finish the surfaces of impellers and ship propellers and have achieved significant benefits in terms of quality and efficiency. The welders clad the parts that come into contact with water, plus any sealing and sliding surfaces. Cladding means applying a finish coating to a base material using welding as the thermal joining process. The coating material is usually a high alloy and the base material a low alloy. During cladding, the low and high alloys mix metallurgically within the melting range. Rather than the conventional GMAW (gas metal arc welding) process, the welders at Ravensburg employ the CMT process from Fronius and the TransPuls Synergic 5000 CMT power source. CMT achieves an identical deposition rate, but with heat input reduced to a minimum. At 0.3 to 0.5mm, the fusion penetration (the dilution zone) is just deep enough.
