Abstract
The transverse yield strengths of hot-rolled seamless linepipes were studied with respect to the different test methods, including the tensile tests with cold-flattened strap and unflattened round specimens. These results were compared with the longitudinal yield strength and the yield strength obtained by the ring ex pansion test, and were discussed in relation to yielding of a pipe under triaxial stress state. The following conclusions are reached from the experimental results and discussion.
(1) There is little difference between the longitudinal and transverse tensile properties of hot-rolled seamless linepipe.
(2) The cold-flattened strap specimen does not represent the true material properties, because of the pipe-size effect on the yield strength.
(3) The transverse yield strength, which is obtained with the cold-flattened strap specimen, can be well explained with the combination of work-hardening and the Bauschinger effect.
(4) As for the hot-rolled seamless linepipe, the use of longitudinal tensile specimens should be recommended as the most reliable practical method for the purpose of quality control.
