Microstructural and hardness modeling: Effect of multiple bead deposition in temper bead welding technique

Flux Cored Arc Welding (FCAW) process is often employed in industry where multiple welding sequences are used to produce stronger fastening between mating parts. Post Weld Heat Treatment (PWHT) is almost always recommended for relieving residual stresses and tempering the microstructural properties in order to prolong the fatigue and fracture life; however, it is often done away with due to the high costs involved, time constraints, infeasibility or sometime deleterious effects of the tempering process. This paper investigates whether the sequence of the initial deposition of the weld material itself can temper the microstructural properties and reduce the size of the Heat Affected Zone (HAZ) in the weld and parent metal. Four weld beads are deposited on a mild steel plate, with each being tempered by an overlapping bead using the Temper Bead Welding (TBW) technique. Numerical simulation is performed using FEA software VrWeld to evaluate the microstructure, hardness and size of the HAZ. It is concluded that there are significant improvements in the microstructure, hardness and size of the HAZ as a result of the deposition of the overlapping, tempering beads

Surface Evaluation of a Multi-Pass Flexible Magnetic Burnishing Brush for Rough and Soft Ground 60/40 Brass

Burnishing is an advanced finishing process that produces higher-quality surfaces with better hardness and roughness than conventional finishing processes. Herein, a flexible magnetic burnishing brush comprising stainless steel pins under permanent magnet poles was used to investigate the influence of multiple passes and directions on the produced surface of soft and rough ground prepared brass. In total, five different samples were burnished on each of the two brass samples prepared. Four samples were processed in the same direction for up to four passes and the fifth sample was processed with two passes in the opposite direction. Results indicate that there was approximately a 30% increase in hardness and an 83% increase in microroughness for rougher-surface brass samples. For smoothly prepared surfaces, there was approximately a 14% increase in hardness and a 35% increase in microroughness. In the same direction of multi-pass burnishing, increasing the number of passes negatively affected surface roughness; for rougher surfaces, the surface hardness reduced and process uniformity increased owing to surface over-hardening and flaking mechanisms, and for smoother surfaces, the hardness, roughness, and process non-uniformity increased with the number of passes owing to repeated surface deformation at some locations and high flaking at other locations. Compared to single-pass burnishing, wherein the surface roughness and microhardness showed almost no change with high process uniformity, in burnishing with two opposite-direction passes, the produced surface exhibited better surface roughness, process uniformity, and microhardness improvements owing to a reverse strain mechanism. Hence, opposite burnishing passes are recommended