Product Number:
51300-03103-SG
ISBN:
03103 2003 CP
Author:
D.L. Sponseller, C.J. Padfield, B.E. Urband
Member Price:
$0.00
Non Member Price:
$20.00
Price:
$20.00
Twenty-three pipe samples of casing and coupling stock were evaluated to identify and study factors affecting the SSC rating when tested by the double-cantilever-beam (DCB) test. All samples had been tested under standard conditions defined by NACE TM0177-96(D). Tested specimens, along with some full-thickness samples of pipe wall, were specially prepared to determine the patterns of chemical segregation inherited from the solidification process, and affected by the tubemaking method, that existed in the pipe walls. Remarkable variations in segregation pattern are observed within individual pipes, and among the many pipes evaluated. Dendrite patterns persist in the heavy walls of coupling stock. The SSC cracks tend to follow segregation lines and thus be guided away from midplane. Edge cracks then initiate at the root of the side groove and serve to maintain the general crack surface at or near midplane. Because they impede and delay crack growth to a time of weaker acidity, large and/or numerous edge cracks give false high values of sulfide fracture toughness, KIssc. A correlation is presented between the incidence of serious edge cracking and both hardness and the amount of hot reduction during tubemaking. Shallower side cracks do not eliminate edge cracks; some changes in profile of side grooves, and in aqueous solution chemistry are suggested. Reducing chemical segregation by a homogenization treatment does give flatter crack surfaces and lowers the incidence of edge cracking. The significance of the chemical segregation patterns with regard to SSC testing, and to field service, is discussed.
Key Words: Casting segregation, ingot segregation, chemical segregation, dendrites, dendritic segregation, segregation pattern, segregation lines, banding, grain flow, rotary piercing, Mannesmann mill, twist angle, homogenization, casing, coupling stock, modified 4130 steel, C-90, T-95, C-100, C-110, C-125, Q-125, hydrogen sulfide, sour gas, deep sour-gas wells, corrosion, fracture mechanics, double-cantilever-beam test, DCB test, corrosion, sulfide stress cracking, SSC, sulfide fracture toughness, KIssc, TM0177-96, TM0177-03, NACE, HIC cracking, deep etching, edge cracking, shark's teeth, stress grooves, ribbon cracks, side grooves, fracture, fracture surface, fracture topology, reduction parameter.