Development of clad boiler tubes extruded from bimetallic centrifugal castings

Journal Article · Wed Apr 01 04:00:00 EST 1998 · Journal of Materials Engineering and Performance

DOI:https://doi.org/10.1361/105994998770347963· OSTI ID:616474

Sponseller, D L ^[1]; Bakker, W T ^[2]; Timmons, G A

---

1. ERIM Transportation and Energy Materials Lab., Ann Arbor, MI (United States)
2. EPRI, Palo Alto, CA (United States)

Wrought tubes of T-11 steel, externally clad with SS310, have been produced by a new method. The alloys were united directly from the molten state by centrifugal casting. In the optimum process, temperatures were controlled to prevent meltback of the SS310 outer layer by the higher melting T-11 stream. Hollow extrusion billets were prepared from the heavy-walled cast bimetallic tubes and successfully hot extruded to 84-mm OD x 64-mm ID tubes, and to 51-mm OD x 38-mm ID tubes. For the most part, thicknesses of the cladding and of the tube wall are rather uniform around the circumference and from end to end of the tubes. Hardness and tensile properties of annealed 51-mm tubes are uniform from end to end of a tube, and between tubes, and readily conform to ASTM A 213; tubes satisfy the flattening and flaring requirements of ASTM A 450. The cladding is metallurgically bonded to be base metal, as revealed by metallography, and by two tests developed for this study: a bond shear strength test and a twist test. In the latter test, rings 3.1 mm in thickness are slotted and severely twisted with a special tool. In tubes made by the optimum process, minute fissures that form adjacent to some of the pressure points during twist testing occupy just 3% of the bond-line length. Cost estimates for commercial production of 51-mm tubes via the centrifugal casting route suggest that such tubes should be considerably less expensive than conventionally clad tubes (extruded from composite billets assembled from heavy-walled wrought tubes). Such tubes should be attractive for the following applications in utility boilers: high-corrosion areas of existing coal-fired boilers, in both steam-generating tubes and superheaters; water walls, screen tubes, and superheater tubes of municipal waste-incineration boilers; future ultra super-critical boilers operating a higher temperatures and pressures; and steam-generating tubes of Syngas coolers of integrated coal gasification power plants.

• OSTI ID: 616474
• Journal Information: Journal of Materials Engineering and Performance, Journal Name: Journal of Materials Engineering and Performance Journal Issue: 2 Vol. 7; ISSN JMEPEG; ISSN 1059-9495
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
09 BIOMASS FUELS
20 FOSSIL-FUELED POWER PLANTS
36 MATERIALS SCIENCE
BOILERS
CASTING
CORROSION RESISTANCE
CORROSION RESISTANT ALLOYS
EXTRUSION
MECHANICAL PROPERTIES
PROTECTIVE COATINGS
STAINLESS STEEL-310
STEEL-CRMO
TUBES