Takashi Daikoku

Experience of High Chromium Ferritic Steel Tubes in Power Plant

A new steel low C-9Cr-2Mo steel has been developed for use as superheater and reheater tubes in power boilers. The steel has higher strength than 21/4Cr-1Mo or 9Cr-1Mo steel and fills the gap in elevated temperature strength between these ferritic grades and the austenitic stainless grades. Because of the steel’s strength and its good oxidation resistance up to 1202 °F (650 °C), it may provide an economic alternative for austenitic stainless tubes. The steel has been installed in a number of power boilers. This paper reports on the examination of 9Cr-2Mo reheater and superheater tubes removed from the oil and blast furnace gas fired 156 MW power boiler.

Development of 12Cr-1Mo-1W-V-Nb Steel for Elevated Temperature Applications

The 12Cr steels have attracted attention for high temperature application due to their resistance to corrosive environments and good elevated temperature strength.

Service Experiences of 12Cr-1Mo-1W-V-Nb Steel and 9Cr-2Mo Steel in a Power Boiler

Both newly developed duplex structure low C-12Cr-1Mo-1W-V-Nb steel (HCM12)[1] and low C-9Cr-2Mo steel (HCM9M)[2] have a practical capability to be used for steam generator tubing from the aspect of oxidation resistance and elevated temperature strength as well as weldability and formability.

Fabrication and formability evaluation of thick-wall chromized and coextruded superheater tubings for advanced cycle power applications

Chromized and coextruded superheater tubings were welded and bent to construct the ultrasupercritical (USC) steam generator. Prior to the fabrication of the USC steam generator, welding and formability tests were performed to establish the fabrication procedures. In addition, mechanical and metallurgical investigations were also carried out. Welding of the chromized and coextruded tubings was satisfactorily accomplished and the joint showed sound structures and good strength properties, so that the established procedures were applied to the fabrication of the USC superheater. Bending formability for the chromized and coextruded thick wall tubings was evaluated, and the nocrackbending procedures for chromized tubing were developed.