Avaliação das técnicas de soldagem com e sem tecimento aplicadas no reparo de trincas em escavadeiras hidráulicas

Abstract

Welding is a joining process of materials of great versatility and easy operation. It is used in most industrial sectors, for both equipment fabrication and their maintenance. Welding processes in the maintenance of hydraulic excavators allow increasing equipment’s life, avoiding stops and saving costs. Some producers recommend the use of weaved beads while others prefer stringer beads for maintenance of excavators, creating doubts about which operation is the best considering productivity, costs, and final properties. In this work, ASTM A36 plates used in excavators’ arms were welded using different procedures (waving and not-waving) to fill V-grooves. The microstructure of the weld and the hardness profile of the joints were similar for both techniques. Both the fusion (FZ) and the heat-affected (HAZ) zones presented a higher hardness than the base metal due to the high cooling rate and the presence of acicular ferrite. Weaving allowed shorter welding times than stringer beads since that technique required less welding passes to fill the groove. This implied in different weld regions sizes with weaving producing thicker HAZ and larger FZ. The comparison between welds extension was simulated by Rosenthal equation and confirmed by measurements in weld macrographs. In multi-pass welding, the as-welded zone of the weld metal of a previous pass undergoes reheating during a succeeding pass. Hence, an extended HAZ implies in greater stress relief of the weld, what is beneficial for the process. Therefore, it is concluded that the more appropriate practice is filling the groove weaving and using stringer beads for the final passes.