Vibratory Stress Relief and Vibratory Weld Conditioning of Flux cored arc welded CA6NM steel

Abstract

ASTM A743 CA6NM steel is used in the manufacturing of hydraulic turbines components. Multipass welding is commonly used for their fabrication or repairing. In this work, two different vibratory welding procedures were studied: vibration applied during welding (VWC) and vibration applied after welding (VSR). Results have shown that in both conditions, CA6NM steel presented a martensitic microstructure, in which the VSR welded joint presented column-shaped packets and fine martensite delineating the individual beads, while VWC joint presented grain refinement. Heat affected zones (HAZ) presented δ-phase in small amounts for both conditions in the regions which reached higher temperatures. VSR and VWC conditions presented similar behavior in terms of hardness, HAZ hardness values being close to those of the weld metal, except for the root regions, where higher values were obtained. Charpy-V results showed that HAZs presented higher impact values than those of the weld metal. The low impact values of the weld metal were attributed to presence of inclusions from the welding electrode.

Welding and Thermal Spray Processes for Maintenance of Hydraulic Turbine Runners: Case Studies

“…Porosity, cracks, deformations, and microstructural or mechanical inappropriate properties in the materials are examples of defects or discontinuities of casting [6,13] or welding [14]. Normally, after the welding procedures, post heat treatments are applied for stress relief, the most common is the thermal treatment of tempering [10,15], however, other processes were studied, such vibration during and after the welding [16]. After manufacturing the component needs to be inspected, some NDT (Non-Destructive Testing) is used.…”