Development of clad boiler tubes extruded from bimetallic centrifugal castings

Book · Sun Dec 31 04:00:00 EST 1995

OSTI ID:233918

Sponseller, D L ^[1]; Timmons, G A ^[2]; Bakker, W T ^[3]

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1. ERIM Transportation and Energy Materials Lab., Ann Arbor, MI (United States)
2. Timmons (G.A.), Ann Arbor, MI (United States)
3. Electric Power Research Inst., 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 are 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 (at a ratio of 13.4) to 3.3-inch OD x 2.5-inch ID tubes, and (at a ratio of 37.6) to 2-inch OD x 1.5-inch ID tubes. In all, ten castings were produced, and 12 billets were extruded to tubes. For the most part, thicknesses of the cladding and tube wall are rather uniform around the circumference and from end to end of the tubes. Hardness and tensile Properties of annealed 2-inch tubes are uniform from end to 6nd 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 the base metal, as revealed by metallography, and by two tests developed for this study: a bond hear-strength test and a twist test. In the latter test, rings 0.125 inch 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 just 2.7 percent of the bond-line length. Cost estimates OCCUPY for commercial production of 2-inch 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).

• OSTI ID: 233918
• Report Number(s): CONF-950908--; ISBN 0-87170-539-7
• Country of Publication: United States
• Language: English

Related Subjects

20 FOSSIL-FUELED POWER PLANTS
36 MATERIALS SCIENCE
BOILERS
CASTING
CHEMICAL COMPOSITION
COMPOSITE MATERIALS
COST
EXPERIMENTAL DATA
EXTRUSION
FABRICATION
FOSSIL-FUEL POWER PLANTS
HARDNESS
MECHANICAL PROPERTIES
MICROSTRUCTURE
SCANNING ELECTRON MICROSCOPY
STAINLESS STEEL-310
STEELS
TENSILE PROPERTIES