Abstract
Welding processes and fabrication techniques are being developed for Advanced USC boilers. Advanced 9Cr steels, Nickel base alloys (HR6W, HR35, Alloy 617, Alloy 263 and Alloy 740H) have been selected as candidate materials for the boilers. The GTAW and SMAW welding processes were developed for plates, small-diameter tubes and large-diameter pipes, and welding procedure tests were performed by GTAW; maximum creep rupture tests of these weld joints are expected to take over 100,000 hours. In fabrication techniques, methods for hot bending tests by high-frequency induction heating for large-diameter pipes and cold/hot bending tests for small-diameter tubes have been established. Mock-ups of SH-header and RH-header adequately confirmed the ability of tubes to be fabricated and cold bent, the weldability of pipes, the ability to fabricate at the stub weld joints and the weldability of stub joints. Mock-up tube loops were also produced to confirm the ability of tubes to be cold and hot bent, the weldability at the slide spacer and the weldability of dissimilar weld joints between HR6W and stainless steels. With test-loop fabrication finished, the loop test in the plant has been in progress for two years.
