Metallurgical Characteristics and Performance Experience of Spiral Overlay Tubes inBlack Liquor Recovery Boilers

摘要

Spiral overlay tubes produced by a patented process involving a tandem gas-metal-arc welding (GMAW) and gastungstenarc welding (GTAW) process are discussed in terms of the microstructure and mechanical properties.rnThese overlay tubes offer a potential alternative material for mitigating the cracking problems encountered by thernwidely used co-extruded 304L/carbon steel composite tubes in recovery boilers. Alloy 625 overlay tubes have beenrninstalled in recovery boilers since 1997. Performance of these tubes has so far been excellent. Cases of overlayrntubes installed in different boilers are presented.