Effect of vibration on weld metal hardness and toughness

Abstract

Vibration of welded parts is usually applied to achieve effects similar to thermal stress relief. With vibration, it is not only residual stresses that are affected. Using two different welding processes, the influence of vibration on hardness and toughness of the weld was measured. For each welding process, two series of Charpy specimens were made over the temperature range from 260 to z20uC. The only difference between the two series was in performing welding with or without vibration. Slight differences in weld metal hardness were observed. Toughness measurements show an increase in impact toughness and a significant increase in fracture toughness in samples which were vibrated during welding.

Charpy toughness and microstructure of vibrated weld metal

“…Because of the higher degree of aligned microstructures in the unvibrated weld, lower toughness would be expected. This premise is supported by the results of previous investigations, 2 where fracture toughness was measured.…”

“…Greater differences could be obtained with fracture toughness testing. It suggests that the authors' expectations are correct and are results of previous research work, 2 where changes of multipass weld impact toughness owing to the vibration were negligible in comparison with those obtained with fracture toughness testing on the same weld.…”

“…The vibrated specimen expresses tough fracture when A v 559 J, but in the unvibrated specimen (A v 536 J) brittle tearing prevails at the same hardness. 2 According to the results it seems that vibration during welding inhibits changes of the weld metal transformation, resulting in loss of weld metal toughness at elevated or reheated temperature. Further research is needed to understand what or why this phenomenon happens.…”

“…Cyclic load at less than half yield strain has negligible effect on the fatigue life of all specimens. 22 Previous research work 2 shows an increase in notch and fracture toughness of multipass welds made with submerged arc welding (SAW) and gas metal arc welding (GMAW) procedures compared with as welded condition. Fracture toughness was increased by 80%.…”

“…Vibration during welding affects weld metal microstructure and toughness. 1,2 When vibrating during multipass welding a part of the weld is vibrated in the liquid condition. Parameters of the vibration must be suitable so as not to cause undulation of the weld pool, which would result in excessive spattering and instability of the arc.…”