Creep and rupture properties of longitudinal seam welded hot reheat piping

Book · Fri Dec 01 04:00:00 EST 1995

OSTI ID:131861

Ellis, F V ^[1]; Steakley, M F; Roberts, B W ^[2]

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1. Tordonato Energy Consultants, Inc., Chattanooga, TN (United States)
2. Tennessee Valley Authority, Chattanooga, TN (United States)

Post exposure creep rupture testing was performed on two longitudinal seam welded hot reheat piping samples. The first pipe was 2-1/4Cr-1Mo steel with a large inside surface repair weld that had been given a subcritical postweld heat treatment. The weld had a shallow lack of fusion defect at the root pass. Weldment rupture specimens oriented in the hoop direction of the pipe were tested at 41.4 MPa and 665 C, 650 C and 635 C. The failure path was through the fine-grained region of the heat-affected-zone. The measured rupture time of the longitudinal seam weldment was approximately 2/3 of that for minimum strength unexposed base metal. The complete creep curve was fit to a power law primary plus an exponential softening tertiary with explicit rupture time. The second pipe was 1-1/4Cr-1/2Mo steel and the weld had been given a renormalizing and tempering heat treatment. All weld metal creep rupture specimens were used. Creep and tensile tests were performed to develop constitutive equations for creep crack growth analysis. The emphasis was on primary and secondary creep with test stresses of 41.4 MPa and 68.6 MPa and temperatures from 550 C to 650 C. The maximum test duration was approximately one year. The measured rupture time for the weld metal was approximately equal to that for minimum strength base material. Exponential and rational polynomial primary plus steady state creep equations were fit to the data. The minimum creep rate was fit to a Dorn parameter with stress dependent activation energy. At 540 C, the power for the stress dependence of the minimum creep rate was 6.2. The primary creep coefficients corresponding to time constants were shown to have good correlations with rupture time and minimum creep rate. The product of the primary creep coefficients (initial creep rate) had good correlation with the minimum creep rate for each stress.

• OSTI ID: 131861
• Report Number(s): CONF-950740--; ISBN 0-7918-1334-7
• Country of Publication: United States
• Language: English

Related Subjects

20 FOSSIL-FUELED POWER PLANTS
36 MATERIALS SCIENCE
CHROMIUM STEELS
CREEP
DESTRUCTIVE TESTING
EQUATIONS
EXPERIMENTAL DATA
FOSSIL-FUEL POWER PLANTS
KINGSTON STEAM PLANT
METALLOGRAPHY
MOLYBDENUM ADDITIONS
RUPTURES
STEAM LINES
STEEL-CR2MO
TENNESSEE VALLEY AUTHORITY
TENSILE PROPERTIES
WELDED JOINTS