Recycling welding rod residuals based on development of a top-down nanomanufacturing system employing indexing equal channel angular pressing

Fusion welding processes such as shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW) are used extensively and economically in fabrication of critical engineering structures and components across varied industries and applications throughout the world. By-product inherent with these welding processes consists of varied discrete lengths of unused welding rod remaining at the end of the weld thermal cycle. These residuals are typically considered spent or scrap material with minimal engineering value. This paper, however, presents an experimental investigation to further process such materials into commodities and components of enhanced economic and engineering value. A novel prototype system identified as indexing equal channel angular pressing (IX-ECAP) was developed using modifications to traditional equal channel angular pressing (ECAP) to transform welding residuals into nanostructured or ultra-fine grained materials. Such materials with significantly enhanced performance characteristics can then be used as feed stock for potential uses as composite matrix reinforcements, micro-machine elements, and micro-fasteners. Micro-hardness conversions from processed material allowed theoretical determination of grain sizes employing Hall-Petch relationships. Analysis of variance (ANOVA) using a five-factor two-level fractional factorial split plot design (FFSP) studied significance of number of passes, pressing speed, temperature, back pressure, and vibration on material properties. IX-ECAP provided significant improvements in mechanical properties and offered a viable solution whereby processing of discrete variable length aluminum 4043 welding rod residuals proved very successful.